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10CaH4(P04)2 '
2HF
After mixing, the slurry is directed to a "den" where
solidification occurs. Like mixers, there are a number of den
designs, one of the most popular continuous ones being the Broadfield.
This den is a linear horizontal slat belt conveyor mounted on rollers
with a long stationary box mounted over it and a revolving cutter at
the end. The sides of the stationary box serve as retainers for the
slurry until it sets up.
FIGURE 4-11. TVA CONE MIXER
4-23
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The solidified slurry which exits fro* the dert is not a •
finished product. It must be cured - usually for 3 weeks or more - •
to allow the reactions to approach completion. The final curing stage
is depicted in Figure 4-10 fay the conveying of product to the sheltered I
storage pile.
4.5.2 Granular Triple Superphosphate Manufacture and Storage
Two processes for the direct production of granular triple J
superphosphate will be briefly presented, A third process uses
cured run-of-pile triple superphosphate, treats it with water and Jp
steam in a rotary drum, then dries and screens the product. A •
large amount of granulated triple superphosphate is produced by
this method but product properties are not as good as that •
produced by other processes.
The TVA one-step granular process 1s shown in Figure 4-12, In •
this process, phosphate rock, ground to 75 percent below 200 mesh, •
and recycled process fines are fed into the acidulation drum along
with concentrated pfeosphoric acid and stea». The use of steen helps I
accelerate the reaction and ensure an even distribution of moisture in
the mix. The mixture is discharged into the granulator where solidifi- |
cation occurs, passes tfcrougtt a rotary cooler, and is screened. Over- _
sized material 1s crushed and returned with undersized material to "
the process. The reaction for the process is the same as that of •
S 9
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4-24 1
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MMPMATC
yV^
t ,.,77 ,,,T7,. >
r— i
STEAM -J| L:
II AC
PHOSPHORIC HEATER
ACID I 1
Lit"™
PUMP
S
* 4
1 RECYCLED FINES I
[ STEAM |
L 1 1
trW : r
T , , n nf I
— --J \ n
IOUIATION 1 1 | L1
GRANULATOR ll
1 1 r-",
COOLER
*A/ 1 OVERSIZE
WEENS [: 1 1,
~T 1 CAGE
FINES J-j MILL
ROLL 1__P
CRUSHER S1F4, PARTICULATE
PRODUCT
STORACE
FIGURE 4-12. TVA ONE-STEP PROCESS FOR
GRANULAR TRIPLE SUPERPHOSPHATE
4-25
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The Dorr-Oliver slurry granulation process is shown in
Figure 4-13. In this process, phosphate rock, ground to an •
appropriate fineness 1s mixed with phosphoric »cid (39% P205) in a •
series of mixing tanks. A thin slurry is continuously removed, mixed
with a large quantity of dried, recycled fines in a pugmill mixer •
(blunger), where it coats out on the granule surfaces and builds up
the granule size. The granules are dried, screened, and mostly (about |
86 percent) recycled back into the process. Emissions from the drier _
and screening operations art sent to separate cyclones for dust removal *
and collected material is returned to the process. B
After manufacture, granular triple superphosphate is
sent to storage for a short curing period. Figure 4-14 illustrates J
the activities in the storage building. After 3 to 5 days,* during _
which some fluorides evolve from the storage pile, the product is ™
considered cured and ready for shipping. Front-end loaders move the •
GTSP to elevators or hoppers where it is conveyed to screens for size
separation. Oversize material is rejected, pulverized, and returned |
to the screen. Under size material is returned to the GTSP production
plant. Material within specification is shipped as product. •
* Many plants observe a shorter curing time. |
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4.6 REFERENCES
1. Blue, T.A. Phosphate Rock. In: Chemical Economics Hand-
| book. Menlo Park, Stanford Research Institute, 1967.
_ p. 760.2011 F.
2. Slack, A.V. Fertilizers. In: Kirk-Othmer Encyclopedia of
• Chemical Technology, Vol. 9^ Standen, A. (ed). New York,
• John Wiley & Sons, Inc., 1966. p. 100, 106, 125.
_ 3. Slack, A.V. Dihydrate Processes - Prayon. In: Phosphoric Acid,
" Vol. 1, Slack, A.V. (ed). New York, Marcel Dekker, Inc.,
I
1968. p. 254.
4. Noyes, R. Phosphoric Acid by the Wet Process. Park Ridge,
Noyes Developaent Corporation, 1967. p. 10-11.
™ 5. Roos, J.T. Commercial Filters - Bird-Prayon. In: Phosphoric
• Acid, Vol. I, Slack, A.V. (ed.). New York, Marcel Dekker,
Inc., 1968. p. 446.
6. Atmospheric Emissions from Wet Process Phosphoric Acid Manufacture.
V National Air Pollution Control Administration. Raleigh, N.C.
Publication Number AP-57. April 1970. p. 13-14.
7. Reference 6, p. 11.
" 8. Reference 4, p. 174.
• 9. Striplin, M.M., Jr. Production by Furnace Method. In:
g Phosphoric Acid, Vol. r,, Slack, A.V. (ed.). New York,
Marcel Dekker, Inc., 1968. p. 1008.
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10. Reference 4, p. 222.
11. Harre, E.A. Fertilizer Trends 1973. Tennessee Valley
Authority. Muscle Shoals, Alabama. 1974. p. 22. £
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5. EMISSIONS
" 5.1 NATURE OF EMISSIONS.
ft In assessing the environmental effect of the emissions from
the various phosphate fertilizer processes, fluorides - which are largely
I— •
emitted in gaseous form, were considered to be the most significant
_ and were chosen for regulation as discussed in Section 1.2.
Gaseous fluorides emitted from phosphate fertilizer processes
I are primarily silicon tetra fluoride (S1F.) and hydrogen fluoride
•
(HP) . The origin of these gases may be traced to the reaction
between phosphate rock and sulfurlc acid represented by equation 4-1.
30H2S04 + Si°2 + 58H2° * (4"])
18 «P0 + HSiF
•
Under the existing conditions of temperature and acidity,
• excess fluosilicic acid decomposes as follows:
I H2S1F6(1) *S1F4(g) +2HF(g) (5-1)
I Actually, the mole ratio of hydrogen fluoride to silicon tetra-
fluoride in the gases emitted during the decomposition of phosphate
B rock change with conditions {e.g., the amountfof excess silica*
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5-1
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1n the reaction mixture) and is seldom equal to the stoichto- •
metric value. At high levels of excess silica, the hydrogen
fluoride evolved will react to form silicon tetrafluorlde according §
to equation 5-2: •
4HF + Si02 * S1F4 + 2H20 (5-2)
At low concentrations of silica, emissions will be rich in
hydrogen fluoride. 1
Not all of the fluorides are driven off during the digestion _
of the phosphate rock. A certain amount 1s retained 1n the product *
acid depending upon the type of rock treated and the process used. •
These fluorides can be emitted during the manufacture of super-
phosphoric acid, d1ammonium phosphate, or triple superphosphate. £
Fluoride jM$«rtons from superphosphoric acid and diammonium
phosphate processes depend solely on the fluoride content of the ™
feed acid. In the manufacture of triple superphosphate, fluoride •
emissions can also be attributed to the release of fluorides from
the phosphate rock. Calcium fluoride and silica in the rock react •
with phosphoric acid to form silicon tetrafluoride according to the
following reaction : m
ZCaF,, + 4H,PO. + S10w * S1FA + 2CaHj(P(h)0 • 2H-0 (5-3) •
234 Z 4 4 42 2 •
Scrubbing with water is an effective fluoride control technique I
because of the high water solubility of most gaseous fluorides.
1
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I This straight- forward approach is somewhat complicated, however,
— by the presence of silicon tetrafluoride. Silicon tetrafluoride will
^ react with water to form hydrated silica (S1(OH)4) and fluosilicic
• acid (H2 SiFg) as indicated by equation 5-4:
. 3SiF4 + 4 H20 -»• 2H2SiF6 + Si(OH)4 (5-4)
Hydrated silica precipitates forming deposits on control equipment
• surfaces which plug passageways and tend to absorb additional
• silicon tetrafluoride. The nature of the precipitate, in the
presence of hydrogen fluoride, is temperature dependent. Below
temperature, it is a solid. Control systems should be designed
• 125°F, the precipitate is in the form of a gel. Above this
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to minimize plugging and to allow removal of silica deposits.
Entrainment of scrubbing liquid must be kept to a minimum to
prevent the escape of absorbed fluorides. Fluorides can also
• be eaitted as . participate from some fertilizer processes.
emissions can be effectively controlled by using
in combination with water scrubbers.
5.2 UNCONTROLLED FLUORIDE EMISSIONS.
• 5.2.1 Emissions from Wet-Process Phosphoric Acid Manufacture
Fluoride emissions from w*t-pnae«ss acid manufacture are
| gaseous silicon tetrafluoride and !*ydrogen fluoride. The reactor
is the major source of fluoride emissions from the process accounting
• for as much as 90 percent of the fluorides emitted from an uncontrolled
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5-3
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plant. Additional sources are the filter, the filtrate feed and •
seal tanks, the flash cooler seal tank, the evaporator system
hotwell , and the acid storage tanks. Table 5-1 lists reported
1
emission factors for the various sources. Fluoride emissions will vary •
depending upon the type of rock treated and the process used.
Table "5-1 Fluoride Emissions fro» an Uncontrolled
Wet-Process Phosphoric Acid Plant4
Source Evolution Factor
(IbTF/ton P00,r)
Reactor 0.04 - 2.2
Filter 0.01 - 0.06
Miscellaneous (filtrate feed and up to 0.26
seal tanks, hotwells, etc.)
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Modern reactors emit fluorides from two sources; the reaction V
vessel and the vacuum flash cooler. The primary source 1s the
reactor tank, where silicon tetrafluoride and hydrogen fluoride are £
evolved during the digestion of the phosphate rock.
M
To prevent an excessive temperature "rise in the reactor, the ™
heat of reaction 1s removed by cycling a portion of the reaction •
slurry iftroyfii a vacuum flash cooler. Vapors from the cooler are
condensed in a barometric condenser and sent to a hot well while I
the non-condensables are removed by a steam ejector and also
vented
to the hot well. This arrangement is illustrated in Figure 4-2. V
The majority of the fluorides evolved in the flash cooler are •
absorbed by the cooling water in the barometric condenser. If air
cooling is utilized, fluoride evolution can be considerably areater •
titan Indicated in Table 5-1.
5-4
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The filter Is the second largest source of fluoride emissions.
" Most of the fluorides are evolved at the points where feed add
• and wash liquor are Introduced to the filter. These locations
are usually hooded and vented to the digester scrubber.
• A third source of fluoride emissions Is the multiple effect
evaporator used to concentrate the phosphoric acid from 30 percent
• PgOj- to 54 percent P205. It has been estimated that 20 to 40 percent
• of the fluorine originally Introduced Into the process with the rock
1s vaporized during this operation. Most of these fluorides are
• collected In the system's barometric condensers. The remainder
exit with the non-condensables and are sent to the hot well
• which becomes the emission source for this operation.
« In the plant design Illustrated in Figure 4-2, the vapor stream
from the evaporator 1s scrubbed with a 15 to 25 percent solution
M of f1uos111c1c add at a temperature at which water vapor, which would
dilute the solution, Is not condensed. The water vapor 1s then
B removed by a barometric condenser before the non-condensables are
« ejected from the system. Almost all of the fluoride Is recovered
as by-product fluosllidc add.
• In addition to the preceding sources of fluoride emissions,
there are several minor sources. These Include the vents from such
f points as sumps, clariflers, and acid tanks. Collectively, these
sources of fluoride emissions can be significant and are often
" ducted to a scrulinr.
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Table 5-2 illustrates a typical material balance for the
fluorine originally present in ohosphate rock. It should be
noted that the results in any given wet-process acid plant may differ
considerably from those shown in the table. Fluorine distribution
will depend upon the type of rock treated, process used, and kind of
operation prevailing.
TABLE 5-2
TYPICAL MATERIAL BALANCE OF FLUORIDE IN MANUFACTURE
OF WET-PROCESS PHOSPHORIC ACID
Fluoride Input # F/100 # Feed Rock
Feed
Fluoride Output #
Product acid
Gypsum
Barometric condensers
Air*
Total
*
Typical emission from an uncontrolled plant.
Fluoride-bearing water from the barometri
the gypsum slurry is sent to the gypsum pond.
3.9
F/10C # Feed Rock
1.0
1.2
1.67
0.03
3.9
c condensers as well as
In the gypsum pond,
silica present in the soil converts hydrogen fluoride to fluosilicates.
Limestone or lime may be added to ponds to raise the pH and convert
fluoride to insoluble calcium fluoride. Fluoride associated with the
gypsum slurry ->s already in the insoluble fonn
the pond.
5-6
before being sent to
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£ 5.2.2 iiissions from Superphosphoric Acid I'.anufacture
« 5.2.2.1 Submerged combustion process
The direct contact evaporator is the major source of fluoride
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emissions from the submerged combustion process. Fluoride
evolution is in the form of silicon tetrafluoride and hydrogen fluo-
ride with a substantial portion as the latter. The amount of
B- fluorides evolved v/ill depend on the fluoride content of the feed
acid and the final concentration of phosphoric acid produced. Feed
• acid containing 54 percent P?CV has a typical fluoride content (as F)
I
of from 0.4 to 0.8 percent.
Control of evaporator off-gases is complicated by the presence of
I large amounts of entrained phosphoric acid - amounting to as much as
o
5 percent of the P00- input to the concentrator. An entrainment
r d. j>
I separator is used to recover acid and recycle it to the process. Some
entrained acid exits the separator, however, and tends to form a diffi-
• cult to control acid aerosol. The formation of this aerosol can be
I
they contact the acid.
• The acid sump and product holding tank are secondary sources of
fluoride emissions from the submerged combustion process. These
minimized by reducing the temperature of the combustion gases before
9
emission points are identified in Figure 4-6. Uncontrolled emissions
from the submerged combustion process range fro?" 13 to 22 pounds of
10
2 o
I
fluoride oer ton of PO^- input.
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5.2.2.2 Vacuun evaporation nrocess |[
The jaromatric condenser hctwell , the evaporator recycle tank,
and the product coolinci tank are the three sources of fluoride "•
emissions from the vacuum evaooration orocess. These emission noints •
are identified in Pi cures 4-7 and A-8. "lost of the fluorides
evolved during evaporation are absorbed by the coolino water in the •
barometric condensers resultino in a negligible emission to the
atmosphere from this source. !\!oncondensables are e.iected from the •
condenser system and sent to the hotwell alone? with the :ondenser •
water. This results in the hotwell beconinq the ma.ior source of
emissions from the process. The evaporator recycle tank and the £
oroduct cooling tank are lesser sources of fluoride emissions. _
•
Total emissions from an uncontrolled lant are estimated at 0.005 nounds m
per ton PO input.
5.2.3 Emissions from Diammonium Phosphate Manufacture.
witli filter acid - is usual lv used in the DAD Trocess. Filter acid
is used for annonia recoverv.
5-8
•
•
Fluorides are introduced into the DAp process with the wet nrocess
* ' •
phosphoric acid feed and are also evolved froir the pliosohoric acid •
scrubbing solution used to recover ammonia. Wet process acid which
has been concentrated to 54 oercent V-f-c typically contains 0.4 to 0.8 m
percent fluorides (as F) while filter acid (26-30% P?^) vn^ contain M
from 1.8 to 2.0 percent. ' Dhosphoric acid ccntaininn about 40
percent P?0r - obtained by mixinn 54 percent acid from the evgnoratcrs •
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• ^lajor sources of fluoride emissions fron dian^oniuf nhosnhate
" olants include the reactor. nranulatcr, dryer, cooler, scraens and
•* mills. The locations of these emission points are depicted in
• Fiaure 4-9. Ventilation streams ,from these sources are combined
for purposes of control accordin0 to the foil wine scheme: 1)
• reactor-granulator oases. 2) drysr qases, and 3) cooler and screening
qases.
• Fluorides and amronia are the major emissions from both the
• reactor and the granulator. Reactor-granulator rases are treated
for ammonia recovery in a scrubber that uses ohosohoric acid as
I the scrubber liquid. The phosphoric acid reacts with the ammonia and
the resulting product is recycled back to the process. Fluorides
™ can be stripped from, the nhos^horic acid and a secondary scrubber is
• usually required for fluoride control. Removal of evolved ^lunrides
can be comolicated by their reaction v/ith ammonia to form a narticu-
| , late.
Drier emissions consist of amronia, fluoridas, and oarticulate.
~ Gases are sent through a cyclone for oroduct recovery before beinq
• treated for ammonia or fluoride removal, "edition?! fluorides can
be stripped from the ohosphoric acid scrubbing if ammonia recovery is
• practiced.
Emissions from the screens, mills, and cooler consist orirarily
• of oarticulate and aaseous fluorides. A,ll qasss are treated fnr
• product recovery before entering •Huoride control enui^ment. Tvolutinn
of fluorides from the oroduction of diamnoniu1" ^iiosoh^te is about 0.3
I rounds of fluorides ner ton of p r fron the reactor ard nranulator,
2 ^
5-9
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and screens.
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and 0.3 pounds of fluoride ner ton of D«(V ^rom the drver, cooler
14
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5.2.4 Emissions from Triple Sunerohosohate Manufacture and Storaoe
5.2.4.1 Run-of-nile triple sunernhosnhate
Huorides can be released from both the nhosnhoric acid and the* |
phosphate rock durino the acidulation reaction. Maior sources o* «
fluoride emissions include the mixino cone, curino belt (den),
transfer convevors. and storaoe niles. These emission nrints *re •
shown in ^iqure 4-"i9.
The rrixino cone, curina belt, and transfer convevors are t.vnicallv £
hooded with ventilation streams sent to a common -fluoride control ^
system. Storane buildinos are usually sealed and ventilated bv *
aooroximately five air chanoes oer hour. The ventilation stream •
from the storaoe facilitv may either be combined with the mixer
and den oases for treatment or sent tn separate controls. f
Fluoride emissions are nrimarilv silicon tetrafluoride - *rom _
•
35 to 55 oercent of the total fluoride content of the acid and rock •
is volatilized as silicon tetrafluoride. ^a^or sources o* fluoride •
are the mixing cone, curino belt, ^roduct convevors, and storage
facilities. Distribution of emissions amonn these sources vill varv •
denendinn on the reactivitv n^ the rock and the sneci^ic ooeratin^ con-
ditions employed. Emissions from the cone, curinn belt, and con- •
vevors can account for as much as 90 nercent «f toe t^tjl ^lu^rides
released. Converse!*/, it has been claimed that annroxi^tel" °°
5-10
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• percent e^ ihe fluoride emissions from certain ROP plants are from
the storage area. Emissions from the storage area depend on such
» factors as the turnover rate and the age and quantity of POP-TSP
• in storage.
Evolution of fluorides from ROP-TSP production and storage has
I been estimated at 31 to 48 pounds per ton of P2^5- T!l1's
is based on the following assumptions: 1) silicon tetrafluoride is
m the only fluoride emitted in appreciable quantities and 2) the feed
m acid and rock contain typical amounts of fluorine.
5.2.4.2 Granular triple superphosphate
» Manufacture
• The major sources of fluoride emissions from granular trinle
superphosphate plants using the TVA one step process are the
I acidulation drum, the granulator, the cooler, and the screening and
crushing operations. Major sources of emissions for the Dorr-Oliver
• process include the mixing tanks, the blunger, the drier, and the
• screens. These emission ooints are indicated in Figures 4-12 and
4-13. In addition to gaseous forms, fluorides are emitted as
• parti cul ate from the granulator, blunger, dryer, screens, and mills.
The acidulation drum and granulator (TVA process) and the
• mixing tanks and blunger (Dorr-Oliver process) account for about 38
•percent of the fluoride emissions, the drier and screens account for
1 8
50 percent, and the storage facilities account for the remainder.
I" It has been estimated that an uncontrolled production facility would
1R
emit approximately 21 powufel of fluorides per ton of PpOr input.
s-n
• ••"•> '*•,,_
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assumed to h»¥« installed spray-crossflow packed bed scrubbers or their
equivalent at a part of the original design.
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Storage
GTSP storage facilities can emit both particulate and aaseous
fluorides. Uncontrolled emissions are estimated to be three oounds
10 •
per ton of P20g input. |
5.3 TYPICAL CONTROLLED FLUORIDE EMISSIONS •
5.3.1 Emissions from Wet-Process Phosphoric Acid Manufacture .
Almost all existing wet-process phosphoric acid plants are equipped
to treat the reactor and filter gases. A large number of install a- •
tlons also vent sumps, hotwells, and storage tanks to controls.
Typical emissions range from 0.02 to 0.07 pounds of fluoride per ton £
of P205 input, however, emission factors as high as 0.60 pounds fluoride _
19 20 •
per ton P205 have been reported for a few poorly controlled plants. ' m
It is believed that approximately 53 percent of the wet-process •
acid plants - accounting for 74 percent of the production caoacity -
are either sufficiently controlled at present to meet the SPNSS £
emission level of 0.02 pounds of total fluorides (as F) per ton of
P^Ot input to the process or will be required to attain that level •
by July 1975 to satisfy existing State regulations. This estimate is •
based on the following: 1) a41 wet-process acid plants located in
Florida are required to meet an emission standard equivalent to the SPNSS I
as of July 1975 and 2) all wet process plants built since 1967 are
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5.3.2 Emissions from Superphosphoric Acid Manufacture
I Two types of processes are used for superphosphoric acid
manufacture; the vacuum evaporation (VE) process and the direct
m contact evaporation (DCE) or submerged combustion process. Emissions
• from the VE process are very low in comparison to the DCE process.
Emissions from a VE process using a water actuated venturi to treat
• hotwell and product cooler vent gases have been reported to range
from 4.VX 10"4 to 15 X 10~4 pounds fluoride per ton P90c input.
However, uncontrolled emissions from this process are also less than
u the 0.01 pound per ton of P90r input emission guideline .
I
Since most of the existing superphosphoric acid plants use the VE
Jj process, approximately 78 percent of these plants are currently
meeting the emission guideline,
• Since the DCE process has much higher emissions, the emission
« guideline was established at 0.01 Ib. F/ton P205 input.
This guideline is consistent with the level of emission control
• achievable by application of best control equipment to a DCE process.
Typical controls used are a primary scrubber for removal of entrained
fluorldt per ton
• 5.3.3 Emissions from Dlamwnium Phosphate Manufacture
• Most existing plants are equipped with ammonia recovery
scrubbers (venturi or cyclonic) on the reactor-granulator and
I drier streams and particulate controls (cyclones or wet scrubbers)
on the cooler streaw. Additional scrubbers for fluoride removal are
I comoa, btrt not typical. Only about 15-20 percent of the instal-
_ lations contacted by EPA durinq the development of the SPNSS were
5-13
22
acid and one «r more additional scrubbers for fluoride control.
Emission from an existing facility weee reported at 0.12 pounds
23
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equipoed with spray-crossflow packed bed scrubbers or their eauiva- •
lent for fluoride removal. Fluoride erissions ranoe from 0.0? to 0.5
?^ •
oounds per ton P^V deoendina uoon the dearee of control orovided." •
5.3.4 Emissions from Triple Superphosphate Manufacture and Storage •
5.3.4.1 ROP triple superphosphate (manufacture and storaqe) _
All run-of-pile triple superphosphate oroduction facilities and
70 percent of the storaqe facilities are eauipped v.'ith so^e form of |
25
control. Emissions from those olants '-.'hich control bo^h ^reduction —
and storage areas .an ranqe from 0.2 to 3.1 pounds of fluoride oer •
ton of PoPr input depending upon the dearee of control orovided. ~°" •
* •
Plants with uncontrolled storaae -facilities could emit as much as 12.7
pounds of fluoride per ton of PJ^c. inout. ".t least 60 oercent O-P the |
industry will be required to meet State emission standards eouivalent _
to the SPNSS by July 1975. . •
5.3.4.2 Granular triple superphosphate (manufacture) •
Existing State regulations will require 75 oercent of the industn> •
to meet an emission standard of 0.20 pound fluoride ner ton P^C ^
July 1975. Emission factors for the industry ranne from 0.20 to 0.60 •
oounds per ton PnCv.
I
5.3.4.3 Granular triple suoerohosphate (storaqe)
Aooroximately 75 aercent of the TTSP storace facilities are •
2°
thouqht to be equipped vnth some form of control. J Poorlv con-
trolled buildinns can release as nuch as 15 x 1C" oounds of •
^u
fluoride per hour per ton of P?' ^ in storsce. ' K'ell-controlled •
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storaqe facilities can reduce emissions to less than 5 x 10 oounds
5-14
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30
- fluoride per hour per ton of P205 in storage. It is estimated
• that 33 percent of the controlled buildings could reet rDKSS er is si on
« -
• 29
•* level.
• »^*
V 5.4 GYPSUM POND EMISSIONS
A wet process phosphoric acid plant produces gypsum in slurry
I form, according to the chemical reaction indicated in equation 4-1.
• The reaction also volatilizes fluorides which are largely absorbed
in scrubber and condenser water and is then sent with the gvpsum to
I large storage ponds, known as aypsun ponds or "gyp" ponds. nver 70
percent of the fluorine content c~? the rock used in the wet-acid
1 process may pass over to the gyp pond. If the same plant also pro-
• - duces DAP or TSP, a large part of the fluorine content of the phosphoric
acid will also pass to the gyp pond through the use of water scrubbers
I in tiiese additional processes. Thus, 85 percent or more of the fluo-
rine originally present in the phosphate rock may find its way to the
• gyp pond.
/(•
• T;:-2 water of the gyp pond is normally acic1, having a pH amr.ic
1.5. This acidity is. probably due to inclusion of phosphoric acid in
• the './ashed gypsum from the gypsum filter. It is impractical to remove
all of the acid from the filter cake by washing. For this reason,
• gyp ponds around the country have bee.i found to have a fluoride concen-
• tration of 2000-12,500 ppm. ~ The fluoride concentration of a given
oond does not continue rising, rut tends to stabilize. Tin's nay '32
• due to precipitation cf cor-lir. calcium silicofluoridcs in the pond
•
,/ater. There would oe an equilibrium involving these cor:)! exes,
hydrogen ion, and soluble or volatile dissolved fluorides.
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It has been observed that the above concentrations of fluoride
or more.
pyp ponds. These factors vary from about 0.2 to 10 Ibs F/acre dav. ~s '
5-16
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exert a partial pressure out o* oyp oond water and that volatile
fluorides tend to evolve fror pyp ponds. Based on wet orocess I
ohosphoric acid production, plants have gyp oonds of surface areas
in the range of 0.1-0.4 acres per daily ton of 'Vc- Tflis »"eans •
that a large plant may have a qyo pond with surface area of 200 acres •
Emission factors have been estimated, measured and calculated for I
•
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The most comprehensive work on gvp pond emission ^actors is that
recently done in EPA Grant Mo. R-8^0950. The experimental and
mathematical procedures are quite detailed and the entire report should
be examined by those needinn to understand the methods used. The •
partial pressure of fluorides out of actual pond water was determined
in the laboratory. The evaporation rates of dilute fluoride solutions •
were derived from known data for flat water surfaces, usino established •
mass transfer principles. Also, ambient air fluorides were measured
downwind of the same pyp oonds which furnished the above water samples I
for fluoride partial pressure measurements. Finally, the contribution
of the gyp pond to the fluoride measurement at the downwind sensor »
v/as calculated, usina a variant of the Pasquill diffusion eauation. •
The source strength in this eouation was, of course, calculated
with the partial pressure data and mass transfer coefficient previouslv I
developed. There were a total of 95 useable downwind measurements for
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• two pond sites, and the estimated and the measured downwind fluoride
•concentrations showed pood aoree^ent. The calculated value <^ the
I ambient air fluorine concentration downv.'ind of the oonri v/a.s found
to be statistically the sane as the neasured value.
• Some emission factors fro*71 the above investigation ?re niven in
• Table 5-3. Data at other temoeratures mav be found in the orioinal
reference.
Table 5-3. FLUORIDE EMISSION FACTORS FOR SELECTED GY&SUM pONDS fT
90°F; Ibs/acre day.34
velocity
at 16 ft elevation,
m/sec
1 2
pond 10 0.8 1.3
6,400 ppm F
Pond 20 0.8 1.3
12,000 pom F
4 ' 6
2.3
2.3 3.2
• For the two plants studied, the emission rates were nearly
identical. There nay be significant differences if other sonds are
| considered, but more measurements would be reouired to establish this.
_ The most effective v;ay to reduce fluoride evolution from nvn nonds
'• would be to reduce their fluoride oartial pressure in some wa". The
most effective method now knov/n would be liming, to raise the nP.
Liming to a pH of 6.1 has reduced the oartial oressure of fluoride 30-
31
fold. The indicated li>e cost would be hi oh for the case described,
si*'- but this cost can be reduced i* a method can b
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5.5 REFERENCES
Contract EHSD 71-14. January 1972. p. 3-152.
5. Atmospheric Emissions from Met-Process Dhosnhoric ^cid Manufacture.
I
I
1. Teller, A.J. Control of Gaseous Fluoride Emissions. Chemical I
Engineerinn Proqress. 63: 75-79. March 1967. _
~ ' - I
2. Lutz. W.A. and C.J. Pratt, f'ianufacture of Triple Superphosphate.
In: Chemistry and Technology of Fertilizers. Sauchelli, V. (ed.). 1
Hew York, Reinhold Publishing Corporation, 1960. D. 175. •
3. Teller, A.J. and D. Reeve. Scrubbing of Gaseous Effluents.
In: Phosphoric acid, Vol. I, Slack, A.V. (ed.). Hew York, •
Marcel Dekker, Inc., 1968. p. 752. •
4. Engineering and Cost Effectiveness Study of Fluoride Enissions •
Control. Resources Research, Ire. McLean, Viroinia. FDA
I
I
National Air Pollution Control Administration. Paleiqh, north
4.
Carolina. Publication Number AP-57. April 1970. p. 18. |
6. Control Techniques for Fluoride Emissions. Environmental Health I
Service. Second Draft. September 1970. p. 4-71. (Unpublished).
7. Noyes, R. Phosphoric Acid by the Wet Process. park Ridge,
New Jersey. Noyes Development Corporation, 1967. p. 224, I
231.
•
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• R. Scott, W.C. Jr. Droduction by Wet Process. In:
Phosphoric Acid, Vol. I, Slack. A.V. (ed). flew York,
I Parcel Dekker, Inc., 1968. D. 1080.
I 9. Reference 7, p. 191 .
• 10. Reference 5, p. 4-71.
• 11. Air Pollution Control Technology and Costs in Seven Selected
Areas, Phase I. Industrial ^as Cleaninq Institute. Stanford,
• Connecticut. EPA Contract 68-02-0289. flarch 1973. D. 86.
• 12. Reference 7, p. 256.
• - 13. Reference 6, p. 4-106.
14. Reference 4, p. 3-161.
15. Tirpberlake, R.C. Fluorine Scrubber. Southern Engineer.
I June 1967. p. 62-64.
st
I 16. Jacob, K.D. et al. Composition and Prooerties of Suoerohosphete,
_ Ind. and Enq. Chem. 34: 7^7. June 1942.
I
17. Reference 2, D. 180.
I
18. Reference 4, p. 3-167.
19. Reference' 5, p. 3.
I
• 5-19
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I
20. Technical Report: Phosphate Fertilizer Industry. In: An •
Investigation of the Pest Systens of Erissior. Deduction *er ^i/.
Phosphate Fertilizer Processes. Environmental Protection *oencv. I
Research Triangle Park, North Carolina. April 197-1. n. 2?.
21. Reference 20, p. 33.
22. Reference 6. p. 4-74.
23. Goodwin, D. Written communication from ?V. R.D. Srith, Ccci- •
dental Chemical Company. Houston, Texas. April 3"), 1973. •
24. Reference 20., p. 36, 38. •
25. Beck, L.L. Recommendations for F.mission Tests of Phosohate _
Fertilizer Facilities. Environmental Protection Aqencv. *
Durham. North Carolina. September 28, 1972. p. 14-16. •
26. Reference 20, p. 47. •
27. P.eferente 4, p. 3-1C7. _
28. Reference 20, o. 52, 53.
29. Reference 25, D. 10-13.
30. Reference 20. o. 57.
31. Reference 5, on. 15-16. *
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5-20 •
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32. Tatera, B.J. Parameters which Influence Fluoride Emissions from
Gypsun Donds. PhD Thesis. University of Florida, ??inisvill2.
• 1970. (University 'licrofilrs, ~'.nn /rbor, "den., !;u~ber 71-275.)
• 33. Elfers, L.A., J'.APC:., to ^\ -J.J. and Crane, 6.S. d&ted
Decsnbsr 31, 1368. Fluoride Analyses of Gyp Pond Hater from
| Texas Gulf Sulfur Corporation.
• 34. Kino. W.R. Fluorine ."-ir Pollution from Wet-Process Phosphoric
;".cid Plant Process - u'ater Ponds. PhD Thesis. !'orth Carolina
B State University. Rsleinh, !'.C. 1°74, supported bv EPA Research
• Grant i\o. R-800950.
« . 35. Teller, A.J. Communication at f'APCTAC meeting ir. Raleigh, "!.C.
on Februarv 21, 1973.
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_ 6. CONTROL TECHNIQUES FOR FLUORIDES FROM PHOSPHATE FERTILIZER PROCESSES
6.1 SPRAY-CROSSFLOW PACKED BED SCRUBBtR
6.1.1 Description
| The spray-crossflow packed bed scrubber nas been accepted for
_ several years as the r.'iost sat if. factory fluoride control device available
™ for wet-process phosphoric acid plants.' Most wet-process acid plants
• built since 1967 probably have Installed this scrubber as part of the
original design. During this same time, however, the spray-crossflow
| packed bed design has seen less general use in processes other than wet
_ acid manufacture. The reluctance of the fertilizer industry to fully
• adopt the spray-crossflow packed bed scrubber can be traced primarily
• to concern about its operational dependability when treating effluent
streams with a high solids loading. Such effluent streams can be
I*-
handled by placing a venturi scrubber in series with and before a spray-
crossflow packed bed scrubber; the EPA has tested a number of DAP and GTSP
• plants having this dual scrubber arrangement. Also, improvements in spfay-
• crossflow packed scrubber design have alleviated the initial problem of
plugging and allow a greater solids handling capacity. The development
• of stricter fluoride emission standards should provide incentive for more
widespread use of this scrubber design.
I Figure 6-1 is a diagrammatic representation of the spray-crossflow
• packed bed scrubber. It consists of two sections - a spray chamber and
a packed bed - separated by a series of irrigated baffles. Scrubber
• size will depend primarily upon the volume of gas treated. A typical
unit treating the effluent streams from a wet acid plant (20,000 scfm)
I is 9 feet wide, 10 feet high, and 30 feet long.2
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6-2
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_ All internal parts of the scrubber are constructed of
™ corrosion resistant plastics or rubber-lined steel. Teflon can be
• used for high temperature service. General maintenance consists
of replacement of the packing once or twice a year. Expected life
J of the scrubber is 20 years.
Both the spray and the packed section is equipped with a qas
™ inlet. Effluent streams with relatively high fluoride concentrations -
• particularly those rich in silicon tetrafluoride - are treated in the
spray chamber before entering the packing. This preliminary scrubbing
I removes silicon tetrafluoride thereby reducing the danger of plugginq
the bed. At the same time, it reduces the loading on the packed stage
I and provides some solids handling capacity. Gases low in, silicon tetra-
• fluoride can be introduced directly to the packed section.
The spray section accounts for approximately 40 to 50 percent
• of the total length of the scrubber. It consists of a series of
countercurrent spray manifolds with each pair of spray manifolds followed
I by a system of irrigated baffles. The irrigated baffles remove pre-
M cipitated silica and prevent the formation of scale in the spray chamber.
Packed beds of both cocurrent and crossflow design have been
I tried with the crossflow design proving to be the more dependable,
The crossflow design operates with the qas stream moving horizontally
| through the bed while the scrubbing liquid flows vertically through
— the packing. Solids tend to deposit near the front of the bed where
• they can be washed off by a cleaning spray. This design also allows the
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use of a higher irrigation rate at the front of the bed to aid in
solids removal. The back portion of the bed is usually operated dry —
to provide mist elimination. "
The bed is seldom more than 3 or 4 feet in length, but this can •
1 B
be increased if necessary with little change in capital or operatinq cost.
Several types of ceramic and polyethylene packing are in use with I
Tellerettes probably the most common. Pressure loss through the scrubber
ranges from 1 to 8 inches of water with 4 to 6 being average. ' •
Recycled pond water is normally used as the scrubbing liquid •
in both the spray and packed sections. Filters are located in the
water lines ahead of the spray nozzles to prevent plugging by suspended •
solids. The ratio of scrubbing liquid to gas ranges from 0.02 to 0.07
gpm/acfm depending upon the fluoride content - especially the silicon |
tetrafluoride content - of the gas stream. » Approximately one-third IK
of this water is used in the spray section while the remaining two-thirds
is used in the packing. •
The packed bed is designed for a scrubbing liquid inlet pressure
of about 4 or 5 pounds-per-square-inch (gauge). Water at this pressure ||
is available from the pond water recycle ¥yi**Bte The spray section •
requires an inlet pressure of 20 to 30 pounds-per-square inch (gauge). ~
This normally necessitates the use of a booster pump. Spent scrubbing •
water is collected in a sump at the bottom of the scrubber and pumped
to the gypsum pond.
6-4
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6.1.2 Emission Reduction
The use of gypsum pond water as the scrubbing solution con-
pi icates the task of fluoride removal regardless of the scrubber
design. Gypsum pond water can be expected to contain from 0.2 to 1.5
percent fluosilicic acid (2000-12,500 ppm F) or most often, 5000-
6000 ppm F. Decomposition of fluosilicic acid to silicon tetrafluoride
and hydrogen fluoride results in the formation or a vapor-liquid
equilibrium that establishes a lower limit for the fluoride concentra-
tion of the gas stream leaving the scrubber. This limit will vary
with the temperature, pressure, and fluosillcic acid concentration of
the water. Table 6-1 presents equilibrium concentrations (y1) calcu-
lated from experimentally obtained vapor pressure data at three
temperatures and several fluosilicic acid.concentrations.
Table 6-1. CALCULATED EQUILIBRIUM CONCENTRATIONS OF FLUORINE IN
THE VAPOR PHASE OVER AQUEOUS SOLUTIONS OF FLUOSILICIC
ACID6
Fluosilicic acid
content of solution (wt %}
0.105'
Total fluorine concentration
in vapor phase (ppm F)
50°C
2.4
0.550 3.8
1.000
2.610
2.640
5.050
7.470
9.550
11.715
14.480
*- ,
4.4
S.6
8.2R
12.45
13.5
19.1
_
60°C
3.8
4.4a
7.1
9.8a
...
H.2f
19«4d
25.6
34.6
83.5
70°C
10. 5a
15.4
20. 7a
_.
54. la
208.5
_
_
-
^Average based on several vapor pressure measurements,
5-5
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Providing that the solids loading of the effluent stream has
been reduced sufficiently to prevent plugging, the fluoride removal
efficiency of the spray-crossflow packed bed scrubber is limited
only by the amount of packing used and the scrubbing liquid. Efficiencies
as high as 98.5 and 99.9 percent have been measured for scrubbers
installed at separate wet-process acid plants. ' Table 6-2 lists the
levels of fluoride control reached by several wet acid plants tested
by the Environmental Protection Agency during the development of
SPMSS. All plants used a sprav-packed bed type scrubber to control
the combined emissions from the reactor, the filter, and several
miscellaneous sources and were felt to represent the best controlled
segment of the industry. Gypsum pond water was used as the scrubbing
liquid. Emission rates ranged from 0.002 to 0.015 pounds fluoride
(as F) per ton P0 input to the process.
Table 6-2. SCRUBBER PERFORMANCE IN WET-PROCESS PHOSPHORIC ACID
PLANTS8
Plant
A
B
C
D
Scrubber design
spray-cocurrent packed bed
spray-crossflow packed bed
spray-crossflow packed bed
spray-crossflow packed bed
Fluoride emissions3
(Ib F/ton P205)
0.015
0.006
0.002, 0.012b
0.011
Average of testing results
Second series of tests
6-6
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• Spray-packed bed type scrubbers have seen only limited service in
• diammonium phosphate and granular triple superphosphate plants and none
.. at all in run-of-pile triple superphosphate plants. Table 6-3 oresents
I performance data, collected during the development of SPNSS, for
soray-crossflow packed bed scrubbers treating effluent streams from
• diammonium phosphate, granular triple superphosphate production, and
• granular triple superphosphate storage facilities. In most cases, a
preliminary scrubber (venturi or cyclonic) was used to reduce the
• loading of other pollutants (ammonia or solids) prior to treatment in
the spray-crossflow packed bed scrubber. Gyosum nond water was used as
• the scrubbing solution except where indicated. Fluoride emission rates
• from diammonium phosphate plants ranged from 0.029 to 0.039 nounds ner
ton P?0r input, while emissions from granular triple superphosphate pro-
• • duction facilities ranged from 0.06 to 0.18 pounds oer ton PoOc- Pranular
triple superphosphate storage facility emissions were measured at 0.00036
• pounds per hour per ton of P?05 in storage.
| 6.1.3 Retrofit Costs for Spra.y-Crcssflcw Packed Bed Scrubbers
_ This section discusses the costs associated with retrofitting spray-
crossflow packed bed scrubbers in wet-process ohosohoric acid, suoer-
• phosphoric acid, diammonium phosphate, run-of-pile triple superohosphate,
and granular triple superphosphate plants. Two separate approaches -
| retrofit models and retrofit cases - are used to present cost information.
— Tne retrofit model approach is meant to estimate costs for an averaqe or
* typical installation. No specific plant is expected to conform exactly
fl to the description presented in these models. Hhere oossible, the retrofit
—
I
model treatment is supplemented by retrofit cases - descriotions of soecific
plants which have added spray-crossflow packed bed scrubbers to uonrade
their orioinal control systems.
6-7
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• 6.1.3.1 Retrofit Models
General Procedure
H | . Each retrofit model provides the following information:
g "i . A brief description of the process in USGS
2. A description of existing Huoride controls and the sources
• treated .
3. A description of the retrofit project (including the reduction
| If fluoride emissions achieved) s and
» 4. A breakdown of estimated retrofit custs.
Items 1 and 2 are self-explanatory, however, items 3 and 4 will require
I some discussion. In the case of item 3, al", retrofit systems are designed
to meet SPNSS emission levels. A scaled plot pi an of a model phosphate
| fertilizer complex was used \,o estimate piping, ductwork, pumps, and fan
•j raquirements.
The procedure used for development of costs is a module approach,
• starting with the purchase cost of an vcern - ruch as a pump, scrubber,
fan, etc. - and building up to a field installed cost by using an
•
appropriate factor to account for ancillary materials and labor. For
• example, a pump of mild steel construction costing $10,000 is projected
to $17,600 field installed. The installation cost index in this case
8 Is ".76 arid tha installation cost is $7,6G00 If the pump were built
of stainlass steel, the purchase cost, would be $19,300 but the installa-
1 tion cost would remain at $7,600 since it is calculated for the element
of base construction - mild steel.
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6-?
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The purchase cost of the various items on an equipment specifica-
tion list drawn up for each model plant were derived from literature, •
manufacturer's bulletins, telephone quotations from suppliers, and
a report prepared by the Industrial Gas Cleaning Institute. Scrubber •
costs were obtained by combining designer, manufacturer and user estimates.
Purchase costs were scaled up to field installed costs by using an
appropriate installed cost index. Table 6-4 is a list of the cost indices •
assumed for this analysis.
Table 6-4. INSTALLED COST INDICES
Item Installed cost index
Pumps 1.76
Piping (except valves) 2.00 I
Scrubbers 1.20 •
Centrifugal fans 1.60
A-
Stack 1.50 •
Ductwork 1.40
The sum of the field installed equipment cost is the direct m
cost billed to a particular project. Other costs such as general
engineering, procurement of goods and services, equipmental rentals, I
field supervision, labor burdens, contractor fees, freights, insurance,
sales taxes, and interest on funds used in construction are included |
in the catch-all category of indirect costs. In this study, the indirect ^
cost is assumed to be 35 percent of the direct cost. In addition, a
6-10
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• contingency factor is included in a capital project to account for
unforeseen expenditures. Due to the nature of the type retrofit
I projects studied in this document, a factor of 25 percent of direct
— costs has been incorporated in the capital estimates. The total
™ capital requirement of a project therefore is equal to the sum of
• the direct cost, the indirect cost, and the contingency cost, as
indicated in equation 6-1:
I I = D+0.35D+0.25D
— where I = total capital
™ D = total direct cost
• The following assumptions were used in the development of cost
estimates:
• 1. The purchase costs of scrubbers were determined from the most
_ recent manufacturer quotations, users wherever possible,
™ and the Industrial Gas Cleaning Institute. The purchase
cost of ductwork, stacks, and centrifugal fans were derived
12
"' from a manufacturer's published list prices. The costs
I
| are 1974 estimates based, for the most part, on the use of
_ corrosion resistent fiber reinforced plastics (FRP) as the
™ material of construction.
• 2. Installed costs for scrubbers, ductwork, stacks, and centri-
fugal fans (including drivers) were derived by multiplying
|| the purchase costs by the appropriate cost index from
Table 6-4. An inherent assumption is that FRP is a base
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6-11
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construction material suitable for application of the g
listed indices.
3. Demolition costs were estimated from contractor Quotations to be •
$2500/8-hour day. •
4. Piping costs were derived for a corrosion resistant material
called Permastrand. I
5. Pumps were assumed to be of stainless steel construction.
13 I
Cost estimates were obtained from the literature. These •
costs, originally published in 1968, were increased 54 percent
•
(7.5% per year) to update to 1974 costs.
6. Costs for pump motors were obtained from the literature and I
adjusted for inflation usir.g the same procedure described for
pumps . ' •
7. Special compensatory factors for construction costs were •
incorporated into the ROP-TSP and GTSP storage facilities.
Such factors appear under the headings of "sealing of storage I
building", "curing belt hooding", and "structural steel sunnorts/
bldg." The costs for these items were pro-rated on the basis •
14
of a recent engineering project study for a fertilizer producer. •
8. Cost for performance tests were based on a telephone survey of
independent contractors. •
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6-12
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1
• 9. Annualized Costs
a. Capital charges are 16.3 percent of tlie toto.1 capital
I outlay. This was derived from the capital recovery
• factor equation,,
i 0 + On
R = jr— i5 (6-2)
• (1 + i)n - 1
where: P = capital outlay ^principal),
• R - periodic capital cnarge,
•' - annual interest race (10%), and
• n •-; number ci payments (10)
• b. Maintenance and repair charge. vvat a assumed to be 3
percent of the original investment.
• c. Taxes, insurance, and administrative costs were assumed
to be 4 percent of tht on'ginai investment.
• d. Operating labor1 costs were estimated at $2,000 per
• year for the simple operation (phosphoric acid plant
*. and GTS storage) $4000 for the mere difficult operations
| (DAP, ROPS and GTSP processing).15
e. Utilities (electricity only) were based on a rate of
• $0.015 per kw-hr and 7,900 hours operation per year.
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* 6-13
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Wet Process Phosphoric Acid Plant |
The model plant uses the Prayon process for the manufacture of
wet process phosphoric acid. Figure 6-2 presents a basic flow dia- •
gram of the operation. The reactor is a multicompartment unit (9 •
compartments) with a designed production rate of 500 tons per day
PoOr. Temperature control for the reactor is provided by a vacuum •
flash cooler. Under normal conditions, the reactor is maintained
at a temperature of 160-180°F and produces an acid containing 30 •
percent ?2®5" •
Filtering and washing of the by-product gypsum is accomplished
with a Bird-Prayon tilting pan filter. The separated gypsum is re- •
moved from the filter, slurried with water, and pumped to a settling
pond. Product acid from the reactor (30% P205) is stored before
I
being sent to the concentration system. Three vacuum evaporators in •
series are used to concentrate the acid to 54 percent P^O,.. Evaporator
off gases are treated in barometric condensers for removal of conden- I
sables: a large percentage of the fluorides are also collected.
Retrofit costs for some wet-process phosphoric acid plants |
could be substantially greater than those estimated for this plant. _
The retrofit model is of moderate complexity and includes all of the *
activities with which most installations are expected to become •
involved; however, increases in the gas volume being treated, additions
to the scope 6f work, and space limitations are all factors caoable I
of inflating the project cost above that estimated. Modifications
to the plant drainage system and installation of a ventilation system •
6-14
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for the filter are two items which have not been included within
the scope of the model but which could be encountered by some plants. •
Costs will be estimated for two effluent stream sizes - 25,000
and 35,000 scfm. The effluent stream from an actual 500 ton per day |
plant could range from about 20,000 to 40,000 scfm depending primarily •
on the digester design.
Existing Controls (Case A) I
Existing controls consist of a cyclonic spray tower used to treat
the digester and the filter ventilation streams. Gypsum pond water J|
is used as the scrubbing liquid. This scrubber has been in operation —
for eight years. Figure 6-3 shows the location of the unit. *
Volumetric flow rates and fluoride concentrations associated •
with the various emission sources are listed in Table 6-5. The flow
rates are based on a combination of literature data, source test g
information, and control equipment design data. Fluoride removal
efficiency of the cyclonic spray tower is 81 percent. Total emissions •
to the atmosphere from the sources listed in Table 6-5 are 7.3 pounds •
of fluoride per hour with existing controls. Several miscellaneous
sources of fluoride such as the flash cooler seal tank, the evaporator I
hotwell , the filtrate sump, the filtrate seal tank, and the filter
acid storage tanks are uncontrolled. Emission rates from these •
sources are unknown.
6-16
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T?KlQ fi_5. , FLOW RATES AND FLUORIDE CONCENTRATIONS OF '.JPPA PLANT
EFFL'JENT STREAMS SINT TC EXISTING CCNTR?LS (CASE .-)
Emission source
Digester vent gas
Filter vent gas
Flow rate
(SCR'')
10,000
7,500
14
Fluoride concentration
(mg/SPF) (pom)
25
5.5
1050
23"
Retrofit Controls (Case A)
The retrofit consists of the replacement of the cyclonic spray
tower v/ith a crosstlow packed bed scrubber. Limitations imposed
by the arrangement of existing equipment require the nev.1 scrubber
to be installed at a site 50 feet from the one previously occupied
by the tower. Gypsum pond v/ater will be used as the scrubbing liquid.
Several miscellaneous sources (flash cooler seal tank, evaporator
hot well,-filtrate sump, filtrate seal tank, and acid storage tanks)
will be vented to the new unit which is designed to meet SPNSS
requirements for v/et-process phosphoric acid plants (0.02 pounds
fluoride per ton P205 input). This corresponds to an emission rate
of 0.42 pounds fluoride per hour. Table 6-6 summarizes the volumetric
flow rates and the fluoride concentrations associated with the
emission sources to be treated.
6-18
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Table 6-5. FLOli RATES ".:;? FL'.'OniL'E CONCENTRATIONS OF '.-IPPA PLANT
ppc| iipwr qjopAMC CFMT ~[ n prrrno - j^ ye n rnw^Drti c; (P/lSF A)
Ep"issicn source
Digester vent gas
Filter vent gas
Miscellaneous
i-l OK rate ,
(SCFf'i)
10,003
7,500
7,5'yi
Fl uoride
(ng/SCF
25
5.5
0.3
14
concentration
) (DOHI)
105"
230
13
Figure 6-4 provides a view of tne plant layout following tHe ccrn-
oletion of the retrofit croiect. Installation o* the new scrubber
requires the rearrangement of the existing ductworK and the addition
of a new ventilation systen to handle the miscellaneous sources. />
new fan vili be required for the digester-filter ventilation system
because of the higher pressure drop of the crossflow- oacked bed scrub-
ber. Treated gases will be exhausted from a newly installed 75-foot
tall stack.
/i
Scrubbing water will be obtained from existing plant water lines.
A booster pump is required to provide 40 psig v:ater for the spray
section. Pond water is assumed to have the oroperties shown in
Table 6-7. All scrubbing water will be recycled to the gyosum pond in
the existing plant drainage system.
6-19
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Table 6-7. POND WATER SPECIFICATIONS
15
Pond Hater ph
Temp. , °F
SO., wt %
f\ *
Pr* \ !+• °l
oV.;c 5 " *- '°
H2SiF6, wt %
Fluoride, wt %
resign
2.0
80.0
0.15
0.1
0.63
0.5
Min.
1.2
55
-
-
0.25
0.2
Max.
2.2
88
-
-
1.0
0.8
F'ajor retrofit items are listed in Table 6-8. All ducting, piping,
and motors are specified in terms of the nearest aporooriate standard
size. Table 6-9 oresents typical operating conditions for the new
scrubber and the estimated number of transfer units (NTli) necessary
to meet emission requirements. The NTU were calculated
by using equation 6-3.
NTU required = In
(6-3)
-vl
where: y~ = fluoride concentration of gas stream at the
scrubber inlet
y, = fluoride concentration of gas stream at the
scrubber outlet
y1 = fluoride concentration cf gas stream in
equilibrium with entering liquid stream
Table 6-10 lists the estimated capital and annualized costs of the
project.
6-21
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Table 6-8. MAJOR RETROFIT ITEMS FOR MODEL WPPA PLANT (CASE A) I
1. Ductwork required to connect existing digester-filter ventilation •
system with retrofit scrubber - 50 feet of 36-inch duct. New
ventilation system connecting miscellaneous sources with control I
system. Requirements are - 175 feet of 9-inch duct, 50 feet of _
10-inch duct, 125 feet of 12-inch duct, 75 feet of 16-inch duct, "
100 feet of 20-inch duct, and 50 feet of 24-inch duct. •
2. Pipe connecting spray-crossflow packed bed scrubber with existing •
plant water "line - 150 feet of 6-inch pipe.
I
3. Booster pump for spray section - 190 gpm, 81 feet total dynamic
head (TDH), 7.5 horsepower motor. •
4. Centrifugal fan for digester - filter ventilation system - £
17,500 scfm, 620 feet TDH, 50 horsepower motor. Fan for miscel-
laneous sources - 7,500 scfm, 660 feet TDH, 20 horseoower motor. 8
si
5. Removal of cyclonic spray to^'er and existing stack. •
6. Spray-crossflow packed bed scrubber. Unit will be reouired to •
reduce the fluoride concentration to C.I3 mc/SCF (5.6 ppm)
when using the pond water specified in Table 6-7 and treatina •
the gases listed in Table 6-6.
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7. Stack - 75-foot tall, 4-foot diameter.
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6-22
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Table 6-9. OPERATING CONDITIONS FOR SPPAY-CRCSSFLO',' PACKED
BED SC'':~BF.P F'"D "fDEL MPPA PL A: IT, CASE A
n tons/da" P~°5)
-0 Gas to Scrubber
m Flow, SCFM 25,000
" Flow, DSCFM 22,725
Flow, ACFK 27,150
Temp., °F 116
Moisture, Vol . % 9.1
Fluoride (as F), Ib/hr 38.7
Fluoride (as F), ppm 492
Gas from Scrubber
ft ' Flow, SCFI1 24,400
Flow. DSCFM 22,725
Flow, ACFM 25,700
Temo., °F 100
• ^ Moisture, Vol. % 6.5
• Fluoride (as F), Ib/hr 0.42
Fluoride (as F), ppm 5.6
J| Fluoride Removal, wt % 99
Estimated y1, ppm (see 0.85
• page 6-5)
Estimated NTU required 4.7
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E. Annualized Costs
6-24
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Table 6-10. RETROFIT COSTS FOR MODEL WPPA PLANT, CASE A •
(500 tons/day P205) November 1974 m
Cost ($) |
A. Direct Items (installed) a
1. Spray-crossflow packed bed scrubber 58,900 "
2. Ductwork 18,600
3. Piping 2,400 •
4. Pumps and motor 4,200 m
5. Centrifugal fan and motor 14,300
6. Removal of old equipment 12,500 •
7. Stack 15,800 §
8. Performance test 4,000
Total Direct Items 130,700 I
B. Indirect Items
Engineering construction expense, fee,interest on m
loans during construction, sales tax, freight insurance.
(»0% of A) 65,400 m
C. Contingency
(25% of A) 32,700 _
D. Total Capital Investment 228,800 *
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1. Capital charges 37,300
2. Maintenance 6,200 •
3. Operating labor 2,000 §
4. Utilities 6,900
5. Taxes, insurance, administrative 9,100 «
Total Annualized Costs 61,500
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Existing Controls (Case B)
The existing control system is the same as describee! in case A:
a cyclonic spray tov;er is used to treat the digester and filter
ventilation streams. Fluoride collection efficiency of the tov;er is
81 percent, f'inor miscellaneous sources of fluoride are uncontrolled.
Volumetric flow rates and fluoride concentrations of the various
effluent streams being controlled are listed in Table 6-11. Emissions
from the sources listed are currently 11.0 pounds of fluoride per
hour.
Table 6-11. FLOW RATES AND FLUORIDE CONCENTRATIONS OF WPPA PLANT
EFFLUENT STREAMS SENT TO EXISTING CONTROLS (C/*SE B)
Emission Source
'Digester vent gas
(Filter vent gas
i
i
Flow Rate
(SCFM)
20,000
7,500
Fluoride Concentration
(mg/SCF) (ppm)
20 840
5.5 230
4.
Retrofit Controls (Case B)
Details of the retrofit oroject remain the same as in the initial
case. The cyclonic spray tower treating the digester-filter gases
will be replaced with a spray crossflow packed bed scrubber de-
signed to handle the sources listed in Table 6-12.
6-25
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Table 6-12 FLOW RATES awn njinpipE CONCENTRATIONS OF HPPA PLANT
EFFLUENT STREAMS S:::T T? P.ET.n?FITTEn CONTROLS (ffiSE R)
Emission Source
Digester vent gas
:ilter vent gas
Miscellaneous
Flow Pate ; Fluoride Concentration i
(SCR') | (mg/SCF) (pom)
i
! 20,000 20 840
! 1
'• 7,500 \ 5.5 230
i 7,500 i 0.3 13
1 | i
| i
A list of major retrofit items is presented in Table fi-13 while
operating condit1'
Estimated capital
ons for the new scrubber are provided in Table 6-14.
and annualized costs of the program is listed in
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Table 6-15. Increasing the capacity of the system by T\noo SCF^
has resulted in a
program and a 21
20 percent increase in the capital cost of the
percent increase in the annual i zed cost.
1
Table 6-13. MAJOR RETROFIT ITEMS FOR MODEL WPPA PLANT (CAbE C)
1. Ductwork required to connect existing digester-filter ventilation
system with retrofit scrubber - 50 feet of "8-inch duct, flew •
ventilation system connecting miscellaneous sources with control
system - 175 feet of 9-inch duct, 50 feet of 10-inch duct, 125 §
feet of 12-inch duct, 75 feet of 16-inch duct, 100 *eet of 2^- —
inch duct, and 50 feet of 2Mnch duct.
2. Pipe connecting spray-crossflow packed bed scrubber with existinq m
plant water line - 150 feet of 8-inch pine. £
3. Booster pump for spray section - 269 apn, 81 feet total dynamic ~
head (TDH), 10 horsepower motor.
6-26
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• a. Centrifugal fan for digester - filter ventilation system -
27,500 scfm, 604 feet TPH, 75 horsepower wtor. Fan for
g miscellaneous sources - 7,500 scfm, 660 feet TDH, 20 horsenover
motor.
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5. Removal of cyclonic soray tov/er and existino stack.
6. Soray-crossflow packed bed scrubber. Unit will be required
to reduce the fluoride concentration to 0.09 mci/scf (3.9 ppm)
when using the pond water specified in Table 6-7 and treating
the gases listed in Table 5-11.
7. Stack - 75 foot tell, 5 foot diameter.
Table 5-14. OPERATING CONDITIONS FOR SPRAY-CPOSSFLOW PACKED BED
SCRUBBER FOR i'.ODEL UPPA PLANT, CASE 3
(500 tons/day P90c)
Gas to Scrubber
Flow, SCFM 35,000
I Flow, DSCFM 31,800
Flow, ACFfl 37,600
* Temp., °F 109
a f^cisture, vol. % 9.1
• Fluoride (as F), Ib/hr 58.1
* Fluoride (as F), ppm 529
«Gas from Scrubber
Flow, SCFM 34,000
Flov, DSCF!' 31 ,800
I Flow, ACFr* 35,600
Temo., °F 95
''oisture, vol. % 6.5
Fluoride, Ib/hr 0.42
Fluoride, ppm 3.9
Fluoride removal, wt % 9Q.3
Estimated y1 , ODHI 0.85
Estimated NTU required 5.2
6-27
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Taole 6-15. r^TROFIT COSTS FO* MODi*. &PPA PLACT, CASE 3
(500 tons/day P9Cr] November 1974 • m
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Cost ($)
A. Direct Items (install ea) M
1. Spray-cross low packed bed scrubber 78,800 •
2. DuctworK 20,000 |
3. Piping 3,300
4. Pump ana rnotor 5,300 —
5. Centrifugal fans and no tors 16,000 •
6. Removal of old equipment 12,500 *
7. Slack 15,800
8. Performance test 4,000 •
Total Direct items 155,700
B. Indirect Items £
i nee ring construction expense, fee, interest on
g-i rng , , ^
loans during construction, sales tax, freight insurance. •
(bO% of A) 77,900 •
C. Contingency
(25% of A) 38,900
D. Total Capital Investment 272,500
E. Annual i zed Costs
6-28
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1. Capital charges 44,400 I
2. Maintenance 7,500 ™
3. Operating labor 2,000
4. Utilities 9,300 •
5. Taxes, insurance, administrative 10,900 m
Total Annual i zed Costs 74,100 •
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Superphosphoric Acid
I Two processes are currently available for the manufacture of
superphosphoric acid - vacuum evaporation and submerged combustion.
m All but two of the existing U.S. production facilities use the vacuum
• evaporation process and it is believed that new facilities will
favor vacuum evaporation. No retrofit model will be presented for vacuum
fl evaporation plants because the low level of fluori.de emissions from
these facilities do not require control equipment in order to meet the
• emission guidelines.
B Existing submerged combustion plants are expected to continue
* operation with some expansion in capacity possible. Retrofitted control
ft equipment may be needed to meet the emission guidelines for this type
of process. A retrofit model is presented for a plant using the
| submerged combustion process in order to estimate the costs of applying
^ control equipment. The costs are developed based upon control equip-
• ment designed to meet the fluoride emission guideline of 0.01 pounds per
• ton of P20g input.
m The model plant uses the Occidental Agricultural Chemicals process
for the production of superphosphoric acid. Desianed production capacity
| is 300 tons per day P205. Figure 4-6 is a basic flow diaqram of the
process.
• Wet-process acid containing 54 percent PgCL is fed to the
- evaporator and concentrated product acid containino 72 percent P 0
is withdrawn. The acid is maintained at its boiling point by Trtrc-
| ducing a stream of hot combustion gases into the acid pool. Gaseous
™ 6-29
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effluent from the evaporator is cooled by direct contact with weak
phosphoric acid feed in the evaporator vapor outlet duct, treated for
phosphoric acid recovery, given additional coolinq, and treated for fluoride •
removal .
Existing Controls *
Exhaust gases from the evaporator are treated for the recovery M
of entrained acid before being sent to fluoride controls. The phosphoric
acid recovery system consists of an initial cyclonic separator followed f
by a baffled spray duct and a second cyclonic separator. Weak phosohoric _
acid (30% P2°5) i? used as the scrubbing liquid in the soray duct. *
Fluoride controls consist of 3 spray chambers in series followed ft
by an impingement scrubber. The spray chambers are baffled and each
is followed by an entrainment separator. Pond water is used as the |
scrubbing liquid in all cases. Emissions to the atmosphere are 1.56 ^
pounds of fluoride per hour with existing controls.
Retrofit Controls
•
The retrofit cost projection is based on reolacement of the A
impingement scrubber with a spray-crossflow packed bed scruhber.. Since •
available space is usually limited, the new unit is assumed to be •
installed at the site previously occupied by the impingement scrubber.
Figure 6-5 provides a schematic diagram of the plant following j|
completion of the retrofit project. _
Gypsum pond water will be used as the scrubbinq liquid. Pond water
characteristics are listed in Table 6-7. Retrofitted controls are •
designed to reduce fluoride emissions to 0.01 pounds fluoride/ton P205.
6-30
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Installation of the spray-crossflow packed bed scrubber will •
require moderate alteration of existing ductwork and construction of a
new pipe line connecting the scrubber to the existing water supply. No £
additional fans will be required. Treated oases will be exhausted from ^
the existing stack. Scrubbing water is to be recvcled to the oyosum pond
in the existing drainage system. II
A list of major items required for the retrofit project is
presented in Table C-16. Table 6-17 provides operating conditions for £
the new scrubber. Retrofit cost estimates are listed in Table 6-18. —
Table 6-16. MAJOR RETROFIT ITEMS FOR MODEL SPA PLANT
1. Ductwork - modification of existing ducting to connect new soray-
crossflow packed bed scrubber. Requirements are 100 feet of 30-inch |
duct. —
2. Line connecting scrubber to main pond water supply system - 150
feet of 4-inch pipe. V
3. Centrifugal pump - 130 gpm,113 feet total dynamic head (TDH), 7.5 I
si IHr
horsepower motor. ^
4. Removal of impingement scrubber.
5. Supports and foundations.
6. Spray-crossflow packed bed scrubber. Unit is required to reduce
the fluoride concentration to 0.09 mg/SCF (4 npm) when usinq pond •
water specified in Table 6-7 and treatinq qas stream described in
Table 6-12. I
6-32 I
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Table 6-17. OPERATING CONDITIONS FOR SPRAY-CROSSFLOW PACKED
BED SCRUBBER FOR MODEL SPA PLANT
(300 Tons/DayP20g)
Gas to Scrubber
Flow, SCFM 9,800
Flow, DSCFM 9,110
Flow, ACFM 10,600
Temp., °F 115
Moisture, vol. % 7.0
Fluoride (as F), Ib/hr 3.9
Fluoride (as F), ppm 126
Gas from Scrubber
Flow, SCFM 9,400
Flow, DSCFM 9,110
Flow, ACFM 9,760
Temp., °F 90
Moisture, vol. % 3.0
Fluoride (as F), Ib/hr 0.12
Fluoride (as F), ppm 4.0
Fluoride removal, wt % 96.7
Estimated y', ppn 0.85
Estimated NTU required 3.7
6-33
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Table 6-18. RETROFIT COSTS FOR MODEL SPA PLANT
(300 tons/day P205) November 1974
A. Direct Items (installed)
1. Spray-crossflow packed bed scrubber
2. Ductwork
3. Piping
4. Pump and motor
5. Removal of old equipment
6. Performance test
Total Direct Items
B. Indirect Items
Engineering construction expense, fee, interest on
loans durinq construction, sales tax, freight insurance.
(50% of A)
C. Contingency
(25% of A)
D. Total Capital Investment
E. Annualized Costs
1. Capital charges
2. Maintenance
3. Operating labor
4. Utilities
5. Taxes, jnsurance, administrative
Total Annualized Costs
6-34
Cost ($)
37,500
5,000
1,900
4,200
12,500
4,000
64,300
32,600
16,300
114,000
18,600
3,000
2,000
700
4,400
28,700
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I
• Piammoniurn Phosphate
This plant uses the TVA process for the production, of diamnonium
I phosnhate. A flou diagram of the operation is provided in Figure 4-9.
• The model plant has a designed production capacity of approximately
1080 tons per day diammonium phosphate (500 T/D P?^) •
• A preneutralization reactor is used for the initial contacting
of the anhydrous ammonia and the phosphoric acid. Completion of
•- the reaction and solidification of the product occurs in the granula-
• tor. Effluent gases from the preneutralization reactor and the granu-
lator are treated for ammonia recovery and fluoride control before
• being vented to the atmosphere.
A gas-fired rotary drier is used to remove excess moisture from
• the product. Drier flue gases are vented through dry cyclones for
• product recovery before being treated for ammonia removal. Air
streams vented from accessory cooling and screening equipment are
1 treated for particulate removal in dry cyclones before being exhausted.
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A.
Existing Controls
Exhaust gases from the preneutralization reactor and the granula-
tor are combined and vented to a venturi scrubber for ammonia re-
covery. Weak phosphoric acid (30% PpOc) serves as the scrubbing
• liquid. Approximately 95 percent of the anmonia is recovered and
recycled to the reactor. Fluorides stripped from the phosphoric
m acid in the venturi are removed by a cyclonic spray tower using
m gypsum pond water as tlio Sur.orbinq solution. Fluoride removal
efficiency is 74 percent.
6-35
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The drier flue gases are treated for product recovery before .
being- sent to additional controls. Collected particulate is re-
cycled to the granulator. A venturi scrubber using weak phosphoric •
acid is used for ammonia recovery. Ammonia removal efficiency is
approximately 94 percent. No additional scrubbing is practiced. |
Air streams vented from product cooling and screening equip- _
ment are sent through dry cyclones for product recovery, combined,
and treated in a venturi scrubber for particulate removal. Weak |
phosphoric acid serves as the scrubbing solution. Collected DAP is
recycled to the reactor. Diammonium phosphate particulate collected £
in dry cyclqjjgs is recycled to the granulator; that collected in the ^
scrubber is-recycled to the reactor.
Volumetric flow rates and fluoride concentrations associated with •
the three major emission sources are presented in Table 6-19. The
values listed are estimates based on source test results and data ob- |
tained from a recent contract study of control equipment costs (5).
Fluoride concentrations presented for the reactor-granulator and the •
drier gas streams are values at the outlet of the ammonia recovery •
scrubbers.4 Total fluoride emissions from the sources identified in
Table 6-19 are 4.95 pounds per hour with existing controls. £
Table 6-19. FLOW RATES AND FLUORIDE CONCENTRATIONS FOR •
DAP PLANT EMISSION SOURCES'/.18 |
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6-36 •
Emission source Flow rate
(SCR)
Combined reactor-granula-
tor vent gases
Drier oases
Cooler and screening equip-
ment vent gases
30 ,000
45 ,000
45,000
Fluoride concentration
(mg/SCF) (ppm)
0.65
0.36
0.36
27
15
. 15
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Retrofit Controls
The retrofit consists of the replacement of the cyclonic spray
to'./er or, the reactcr-cranulator stream with a spray-crossflov.f packed
bed scrubber and the addition of spray-crossflov; packed bed scrubbers
as tail gas units to the drier and cooler streams. Gypsum pond
water v;ill be used as the scrubbing liquid. Pond water is available
at 80°F v;ith the properties listed in Table 6-7. The control system
is designed to conform with the fluoride emission guideline of 0.06
pounds cf fluoride per tor, P^vV input - 1.25 pounds fluoride per hour.
Existing controls are located as depicted in Figure 6-6. The
arrangement of equipment is such that the spray-crossflov/ packed bed
Gcrul'j^rs can be installed adjacent to the venturi scrubbers after
moderate alteration of the ductv/ork. A nev: v/ater line must be in-
stalled to satisfy the increased demand caused by the retrofitted scrub-
bers. A nev/ fan vrill also be required for both the drier and the cooler
stream to compensate for the pressure drop of the secondary scrubber.
Treated gases will be exhausted from the existing stack. Spent scrub-
bing v/ater is to be recycled in the existing drainage system.
Figure 6-7 provides a view of the plant layout after the instal-
lation of nev.1 controls, A list of major retrofit items is provided
in Table 5-20. Table 6-21 presents operating conditions for the spre.y-
crossflov/ packed bed scrubbers. Total capital cost and annualized
cost estimates for the project are presented in Table 6-22.
R-37
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6-39
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Table 6-20. MAJOR RETROFIT ITEMS FOR MODEL DAP PLANT §
1. Ductwork -• removal of cyclonic spray tower from service and B
connection of three spray-crossflow packed bed scrubbers.
Requirements are 100 feet of 60-inch duct and 50 feet of 54- •
inch duct. m
2. Water line connecting gypsum pond with spray-crossflow packed
bed scrubbers - 1200 feet of 16-inch pipe with a 200-foot branch "-
of 14-inch pipe and a 150-foot branch of 6-inch pipe. •
3. Two centrifugal pumps (one spare) - 2550 gpm, 105 feet _.
total dynamic head (TDK), 125 horsepower motor. Booster pump *
for spray section of both the drier and the cooler stream scrubber - •
345 gpm, 89 feet TDH, 7.5 horsepower motor.
4. Two centrifugal fans - 45,000 scfm, 285 feet TDH, 50 horsepower
motor. •
5. Removal of cyclonic spray tower. •
6. Supports and foundations. •
7. Three spray-crossflow packed bed scrubbers. When using specified
pond water and treating gases described in Table 6-19, scrubbers ™
are required to obtain performance indicated in Table 6-21. •
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6-40 •
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Table 6-21. OPERATING CONDITIONS FOR SPRAY-CROSSFLOW PACKED
BED SCRUBBERS FOR MODEL DAP PLANT
(500 Tons/Day P0)
Gas to scrubber
Flow, SCFM
Flow, DSCFM
Flow, ACFM
Temp. , °F
Moisture, vol . %
Fluoride (as F) , Ib/hr
Fluoride (as F), ppm
Gas from scrubber
Flow, SCFM
Flow, DSCFM
Flow, ACFM
Temp., °F
Moisture, vol . %
Fluoride (as F), Ib/hr
Fluoride (as F), ppm
Fluoride removal , wt %
Estimated y1 , ppm
Estimated NTU required
Reactor-
granulator
stream
30,000
18,000
34,000
140
40
2.58
27.1
19,400
18,000
23,600
100
7
0.44
5.9
83
1.05
1.69
Dryer
stream
45,000
29,200
52,700
160
35
2.14
15.0
31,500
29,200
38,400
100
7
0.36
3.0
83.5
1.25
2.06
Cooler
stream
45,000
43 ,600
49,600
125
3
2.14
15.0
45,400
43,600
48,000
100
4
0.45
3.0
79
1.05
1.94
•6-41
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Table 6-22. RETROFIT COSTS FOR MODEL DAP PLANT
(500 tons/day P205) November 1974 ft
Costs ($) •
A. Direct Items (installed)
1. Spray-crossflow packed bed scrubbers (3) 285,000 I
2. Ductwork 16,700 "
3. Piping 26,200
4. Pumps and motors 41,500 ft
5. Centrifugal fans and motors 33,000 W
6. Removal of old equipment 12,500
7. Performance test 4,000 •
Total Direct Items 418,900
B. Indirect Items ft
Engineering construction expense, fee, interest on
loans during construction, sales tax, freight insurance. ft
(50% of A) 209,500 ft
C. Contingency •
(25% of A) 104,700 §
D. Total Capital Investment 733,100 »
E. Annualized Costs *
1. Cptital Charges 119,500
2. Maintenance 20,000 •
3. Operating labor 4,000 ft
4. Utilities 21,200
5. Taxes, insurance, administrative 29,400 m
Total Annualized Costs 194,100
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6-42 •
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I
I Pun-of-Pile Triple Superphosphate
The plant uses the conventional TVA cone process for the pro-
| duction of run-of-pile triple superphosphate. Rated production
— capacity is approximately 1200 tons of triple superphosphate per day
™ (550 T/D Pp^)- Actual production averages approximately 800 tons
• of triple superphosphate per day.
Figure 4-10 provides a flow diagram of the operation. Ground
• phosphate rock is contacted with phosphoric acid (54 percent PpOr)
in a TVA cone mixer. The resultant slurry is discharged to the den
H where solidification of the product occurs. Cutters are used to
• break up the product before it is sent to storage. A curing period of
approximately thirty days is required to allow the reaction to ao to
• completion.
Two initial levels of control will be assumed for the model P.np
• triple superphosphate plant and retrofit costs estimated for each
• case. Most actual costs should fall somewhere between the two estimates,
Existing Controls ("Cise A)
It In this case, it is assumed that the plant is in a relatively
good state of repair, that necessary ducting and piping changes are
£ moderate, and that the existing ventilation system does not require
_ modification. Replacement of an existing scrubber is assumed to be
* the major item in the retrofit program.
• Gases vented from the cone mixer and the den are currently treated
in a 20,000 cfm venturi, combined with the storage building ventila-
£ tion stream, and sent to a spray tower. The storage building ventila-
| 6-43
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tion air is sent directly to the spray tower. This control system
has been in'operation for approximately five years.
Gypsum pond water serves as the scrubbing liquid for both the
venturi and the spray tower. Hater is available at 80°F with a fluo-
ride content (as F) of 0.5 weight percent. Additional information
regarding the scrubbing liquid is provided in Table 6-7.
Ventilation flow rates and fluoride concentrations for the
various sources are listed in Table 6-23. The values listed in this
table are estimates based on source test results and CDntrol equip-
ment design data. Fluoride removal efficiencies are 86 percent for
the venturi treating the combined cone mixer - den gases arid 71 percent
for the spray tcwer. Total fluoride emissions from the production
and storage facilities are 127 pounds per hour.
Table 6-23. FLOW RATES AND FLUORIDE CONCENTRATIONS FOR ROP-TSP
PLANT EMISSION' SOURCES!9-21
Emission Source
Cone mixer vent gases
Curing belt (den) vent
gases
Storage building vent
gases
Flow Rate
(SCR')
500
24,500
125,000
Fluoride Concentration
(mg/SCF) (pom)
0.71
95
24
30
4000
1000
Retrofit Controls
The proposed retrofit involves the replacement of the spray tower
with a spray-crossflow packed bed scrubber designed for 9P percent
fluoride removal. Installation of the new scrubber will reduce
6-44
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m fluoride emissions to 4.6 pounds per hour. This emission level is
§ equivalent to the emission guideline of 0.2 pounds fluoride per ton P
input.
fl Moderate rearrangement of the ductv.'ork will be reouired to
install the new scrubber. Existing controls are located as deoicted
| in Figure 6-8. The spray tov.-er will be removed and the spray-cross -
« flow packed bed scrubber installed in the vacated area. A new fan
will be required to compensate for the higher pressure drop of the
fl spray-crossflow packed bed scrubber. Existing water lines and pumps
will be used to supply gypsum pond water at 40 psiq to the spray
1 section. A 16-inch line will be required to supply 2400 qom of water
« at 5 psig for the packed bed. Spent scrubbing water is to be re-
cycled to the gypsum pond in the existing drainage system. Treated
I • gases will be emitted from a newly installed 75 foot stack.
Table 6-24 lists the major cost items involved in the retrofit
| project. Operating conditions for the spray-crossflow packed bed
_ scrubber are presented in Table 6-25. A breakdown of the estimated
cost of the project is orovided by Table 6-26.
A
m
Table 5-24. MAJOP RETROFIT ITEMS FOP »W£L ROP-TSP PLANT (CASE A)
£ 1 Rearrangement of ductwork - removal of spray tower from service
— and connection of spray-crossflow packed bed scrubber and stack
™ Requirements are 50 feet of 96 -inch* duct.
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*Not necessarily circular, but of equivalent cross-section:;! area.
I
2. Water line connecting gypsum pond with spray-crossflow oacked
bed scrubber - 1600 feet of 16-inch pipe.
I
6-45
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3. Two centrifugal pumps (one spare) - 2400 gpm, 76 feet total
dynamic head (TDK), 100-horsepower motor. |
4. Removal of spray tower. •
5. Centrifugal fan - 150,000 SCFM, 355 feet TDH, 200-horsepower fl
motor.
I
6. Spray-crossflow packed bed scrubber. Unit is designed to
handle 158,000 acfm. Using pond water at specified conditions, B
scrubber must reduce fluoride concentration to 0.23 mg/scf
(9.7 ppm) when treating streams listed in Table 6-23. •
7. Stack - 75 fviet tall, 9 feet diameter. |
8. Supports and foundations. I
Table 6-25. OPERATING CONDITIONS FOR SPRAY-CP.OSSFLOW PACKED
BED SCRUBBER FOP MODEL PHP-ISP PLANT, C^FF A
(550 Tons/Day P0)
Gas to scrubber
Flow, SCFM 150,000 _
Flow, DSCFM 145,500 •
Flow, ACFM 158,000 m
Temp., °F 100
Moisture, Vol . % 3.0 •
Fluoride (as F), Ib/hr 439 *
Fluoride (as F), pom 928
Gas from scrubber p
Flow. SCFM 150,000
Flow, DSCFM 145,500 _
Flow, ACFK 156.000 •
Temp., °F 90 *
Moisture, Vol . % 3.0
Fluoride (as F), Ib/hr 4.6 •
Fluoride (as F), ppm Q.7 M
Fluoride removal, wt % 99.^
Estimated y1 , ppm • 0.8 »
Estimated NTU required 4.7 •
6-^6
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6-47
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Table 6-26. RETROFIT COSTS FOR MODEL ROP-TSP PLANT, CASE A
(550 tons/day P205) November 1974
A. Direct Items (installed)
1. Spray-crossflow packed bed scrubber
2. Ductwork
3. Piping
4. Pumps and motors
5. Centrifugal fan and motor
6. Removal of old equipment
7. Stack
8. Performance test
Total Direct Items
B. Indirect Items
Engineering construction expense, fee,interest on
loans during construction, sales tax, freight insurance.
(502 of A)
C.- Contingency
(25% of A)
D. Total Capital Investment
E. Annualized Costs
1. Capital charges
2. Maintenance
3. Operating labor
4. Utilities
5. Taxes, insurance administrative
Total Annualized Costs
6-48
Cost ($)
294,000
9,800
33,300
31 ,900
28,800
12,500
44,000
4,000
458,300
229,200
114,600
802,100
130,700
21 ,700
4,000
26^500
32,000
214,900
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Existing Controls (Case B)
In this case, it is assumed that only the production area is
originally equipped v.'i th controls. A Doyle scrubber is used to
treat the combined ventilation streams from the nixing coni er-1
the den. Ventilation flow rates and fluoride concentrations for
these sources are presented in Table 6-27. Fluoride removal efficiency
of the Doyle scrubber is approximately 59 percent. Emissions from the
production area are 95.2 pounds of fluoride per hour with existing
controls.
The RQP-TSP storage area is currently uncontrolled. Estimated
fluoride emissions from this source are 198 pounds per hour.
Table 6-27. FLOVi RATES AND FLUORIDE CONCENTRATIONS OF EFFLUENT
STREAMS SENT TO EXISTING CONTROLS.
r ! ;
{Emission Source \ Flow Pate Fluoride Concentration !
! ; (SCFM) (mg/scf) (pom) !
i
i ' ' !
jCojne mixer vent gases 500 0.71 30 1
; , 1
(Curing belt vent gases > 14,500 ! 160 '. 68nn
i i
i i . • . i
Retrofit Controls (Case B)
The hooding on the curing belt is in a poor state of reoair and
will be replaced. A new hooding arrangement utilizing a flat
stationary air tight top and plastic side curtains v/ill be used.
The ventilation rate for the belt will be increased to 24,500 SCFM.
This higher flow rate will necessitate the replacement of existing
6-49
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ductwork and fans. The mixing cone will continue to be ventilated •
at a rate of 500 SCFK.
Control of emissions from the storage area requires the £
sealing of the building (roof monitor and sides) and the installation _
of a ventilation system designed to handle 125,000 SCFM. All ^
associated fans, pumps, piping, and ductwork must be installed. The •
ventilation stream from the storage area will be combined with the
effluent stream from the production area and sent to controls. Flow £
rates and fluoride concentrations associated with the various emission
sources are the sime as listed in Table 6-23. »
Fluoride emissions must be reduced to 4.6 pounds per hour in •
order to meet the emission guideline of 0.2 pounds fluoride per ton
P205 input. This will be accomplished by removing the Doyle Scrubber £
and installing a spray-crossflow packed bed scrubber designed for
99.3 percent fluoride removal. Figure 6-9 indicates the placement " -^ - "
of the retrofit scrubber. Treated gases will be emitted from a newly ft
installed 75-foot stack.
*• •
Gypsum pond water will be used as the scrubbing liquid. Pond •
water characteristics are listed in Table 6-7. An 18-inch line will
be installed to supply the required 3450 gpm of pond water. Spent ™
scrubbing water is to be recycled to the gypsum pond in an existing •
drainage system.
Table 6-28 identifies the major cost items involved in the •
retrofit project. Operating conditions for the new scrubber are
listed in Table 6-2° Estimated costs are provided in Table *>-3°. 9f
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6-50
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Table 6-28. KAJOR RETROFIT ITEMS FOR MODEL RCP-TSP PLANT (CASE B)
6-52
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1. Cuctwork - replacement of the curing belt ventilation system
and installation of a storage building ventilation system.
Curing belt ventilation system - 175 feet of 42-inch duct
with a 50 foot branch of 6-inch duct connecting the mixing •
cone. Storage building ventilation system - 150 feet of 96-
inch duct with two 160-foot branches of 66-inch duct. (,
2. Water line connecting gypsum pond with spray-cro.>sflo',j packed B
bed scrubber - 1700 feet of 18-inch pipe.
3. - Two centrifugal pumps (one spare) - 3450 gom, 74 feet
total dynamic head (TDH), 125-horsepower motor. Booster pump |,
for spray section - 1150 gpm, 81-feet TDH, 4Q-horsepower motor. •
m
4. Centrifugal fan for curing belt ventilation system - 25,000
SCFM, 760 feet TDH, 75-horsepower motor. Fan for storage M-
building ventilation system - 125,000 SCFM, 725 feet TDH, •
350 horsepower motor.
1
5. Removal cf - 1) old hooding system from curing belt and
2) Doyla scrubber. I
6. Installation of a new hooding system consisting of a wooden air- 9
tight top and plastic side curtains on the curinc belt.
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7. Sealing of the storage building - roof monitor and sides of
building.
8. Spray-crossflow packed bed scrubber. Unit is designed to
handle 158,000 acfrn. Using pond water at specified conditions,
scrubber must reduce fluoride concentration to 0.23 mg/scf
(9.7 ppm) when treating streams listed in Table 6-23.
9. Stack - 75 feet tall, 9 foot diameter.
10. Supports and foundations.
Table 6-29 OPERATING CONDITIONS FOR SPRAY-CROSSFLOW PACKED BED
SCRUBBER FOR MODEL ROP-TSP PLANT, CASE B
(550 Tons/Day P0)
Gas to Scrubber
Flow, SCR1 150,000
Flow, DSCR1 145,500
Flow, ACFM 158,000
Temp., °F 100
Moisture, Vol . % 3.0
Fluoride (as F), Ib/hr 703
* Fluoride (as F), ppm 1490
Gas from Scrubber
Flow, SCFK 150,000
Flow, DSCFM 145,500
Flow, ACFM 156,000
Temp., °F 90
Moisture, Vol. % 3.0
Fluoride (as F) , Ib/hr 4.6
Fluoride (as F) , ppm 9.7
Fluoride removal, wt % 99.3
Estimated y1 , ppm 0.8
Estimated MTU required 5.1
6-53
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Table 6-30. RETROFIT COSTS FOR MODEL ROP-TSP PLANT, CASE B* •
(550 tons/day P205) November 1974 m
cost ($) m
A. Direct Items (installed)
1. Spray-crossflow packed bed scrubber 294,000 g
2. Ductwork 89,200
3. Piping 39,800 —
4. Pumps and motors 48,200 •
5. Centrifugal fans and motors 40,800 *
6. Curing belt hooding 26,700
7. Sealing of storage building 80,000 •
8. Removal of old equipment 20,000 m
9. Stack 44,000
10. Performance test 4,000 •
11. Structural ste*l supports/bldg. 100,000 |
Total Direct Items 786,700 m
B. Indirect Items *
Engineering constiuction expense, fee, interest on
loans during construction, sales tax, freight insurance. •
of A) 393,400 »
C. Contingency •
(25% of A) 196,700 I
D. Total Capital Investment 1,376,800 ^
E. Annual i zed Costs *
1. Capitarcharges 224,400 •
2. Maintenance 37,100 V
3. Operating labor 4,000
4. Utilities 48,200 m
5. Taxes, insurance, administrative 55,700 Jg
Total Annual i zed Costs 369,400 .
*In costing this model, extensive use was made of a project report dated
June 27, 1974, prepared by Jacobs Engineering company for 0. R. Simplot g
Co. , Pocatello, Idaho.
6-54
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j'anuler Triple Superphosphate Production and Storace
The ••.odel plant uses the. "crr-Oliver process ••"or the production
of granular triple superphosphate. Designed production capacity is
870 tons of triple superphosphate per clay (400 T/D ?9Cr). Figure
_
4-13 orcvides a schematic diagram of the operation.
Ground phosphate rock and phosphoric acid (39 percent PO-C) are
contacted in a series of reactors. The reaction mixture is then
pumped to the granulator v.t.ere it is mixed v;ith recycled material
from the cyclone dust collectors and the screening operations to pro
duce product sized granules of triple superphosphate. A rotary
drier is used to reduce the product moisture content to about 3 per-
cent.
Dried triple superphosphate is cooled and screened before being
sent to storage. A curing period of 3 to 5 days is provided before
the product is considered ready for shipping. Shipping cf GTSP
is on a seasonal basis, therefore, a large storage capacity is re-
/I
quired. The storage facility has a capacity of 25,000 tons of a
triple superphosphate (11,500 tons PO^C)- This building is venti-
lated at a rate of 75,000 scfm using a roof monitor.
Existing Controls
Sases vented from the reactors and the granulator are combined
and treated in a t.:o-stage system consisting of a venturi and a
cyclonic spray tov.;er. C-ypsu^ pond v/ater serves as the scrubbing
liquid in both units. Pond v/ater is available at 80° F with a fluo-
6-55
-------
ride content of 0.5 percent. Additional properties srs listed in •
Table 6-7. . Fluoride removal efficiency is 8S parcant for tha v?n-
turi scrubber and 82 percent for the cyclonic spray to\;ar. •
The drier gases are passed through cyclones for product «
recovery and then treated for fluoride removal by a tv/o-stage
scrubbing system (venturi-cyclonic spray tov:er) similar to that de- •
scribed for the reactor-granulator cases. Fluoride collection is 85
percent in the venturi and 86 percent in the cyclonic scrubber. m
Gypsum pond water is used as the scrubbing liquid. •
Miscellaneous gas streams vented from the product cooling and
screening operations are a third source of emissions from tha GTSP •
production facility. These streams are combined and treated for
product recovery (dry cyclone) and fluoride removal (cyclonic spray m
tower). Fluoride collection efficiency of the cyclonic spray tov.'er •
is 87 percent.
Existing controls have been in operation for five years. Flow •
rates and fluoride concentrations for the various emission sources
1
are listed in Table 6-31. All values are estimates based on a com- m
bination of source test results and published data. Total fluoride •
emissions from the production facilities are 31.0 pounds per hour.
Ventilation air from the storage building is presently emitted I
uncontrolled. Table 6-31 lists the estimated volumetric flov/ rate
and fluoride concentration based on source test data. Fluoride •
emissions from the storage building are 13.2 pounds per hour. •
I
6-56
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Table 6-31. FLOV: RATES AND FLUORIDE CONCENTRATIONS FOR GTSP PLA.^T
El'ISSIQ''! SCURCES22-24
-mission source Flow rate Fluoride concentration
(SCR'O (ng/SCF) (oor-)
.
Reactor-granulator gases 18,000 84
Drier vent gases 485000 84
Cooler « screening equip- 51.000 16.8
ment gases
Storage building ventilation 75,000 1.3
3500
3500
700
54
Retrofit Controls
The retrofit project for the GTSP production facility involves
tlia replacement of the cyclonic spray tov/er on the reactor-granula-
tor stream and on the drier stream with a spray-crossflov; packed bed
scrubber. A third spray-crossflovi packed bed unit vill be installed
on the miscellaneous stream to provide secondary scrubbing. The
A
new control system is designed to reduce fluoride emissions from the
production operation to 3.34 pounds per hour. This emission rate is
equivalent to the emission guideline of 0.2 pounds fluoride per ton P
input.
Figure 6-10 shows the position of existing controls. Retrofit
plans call for the removal of the cyclonic spray towers treating the
reactor-granulator and the drier gases and the installation of spray-
crossflow packed bed scrubbers in the vacated arees. The soray-
crossflow packed bad scrubber for the miscellaneous stream vill -_isr
oe located adjacent to the preliminary scrubber as indicated in
Fiqure 6-11. 6-5;
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Existing pumps, fans, piping and ductwork will be utilized •
wherever possible. The existing piping system will be used to
supply water to the three preliminary scrubbers and the spray w
sections of the secondary (spray-crossflow packed) scrubbers on the m
reactor-granulator and the drier streams. Some minor alteration in
the piping arrangement will be required because of changes in the •
scrubber geometry. A 16-inch line will be installed to provide 2160
gpm of water at 5 psig for the spray-crossflow packed bed unit on the
miscellaneous stream and the packed sections of the secondary scrub- •
bers on the reactor-granulator and the drier streams. Duplicate
pumps, one on stand-by, will be provided for this service. In all •
cases, the spent scrubbing liquid will be recycled to the gypsum
pond using the existing plant drainage system.
Some alteration of existing ductwork will be required to install
the retrofit scrubbers. A new fan will be installed on the miscellaneous
stream to compensate for the pressure loss caused by the secondary
scrubber.
Control of emissions from the 6TSP storage facility requires
the sealing of the roof monitor and the installation of 350 feet of _
ventilation ducting. Ventilation air will be treated in a spray- *
cross 'flow packed bed scrubber before being emitted. The unit is •
designed to reduce fluoride emissions to 1.25 pounds per hour; a rate
equivalent to emission guideline under most conditions. All associated '•
fans, pumps, piping, and ductwork must be installed. The existing plant
§
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drainage system will be used to recycle gypsiw oond v:ater.
Fiaure 6-11 provides a view of the equipment layout.
All major retrofit items are tabulated in Table S-37.
Table 6-33 provides a list of operating conditions for the four
retrofitted spray-crossflow packed bed scrubbers. Table 6-34 pre-
sents the retrofit project costs.
Table 6-32. i-'AOOR RETROFIT ITEMS FOR MODEL GTSP PLANT
GTSP Production
1. Rearrangement of ductwork - removal of existing cyclonic scrubbers
on reactor-granulator and drier streams and connection of
replacement spray-crossflow packed bed scrubbers. Installation
of third spray-crossflov: packed bed unit on miscellaneous
stream. Requirements are 150 feet of 60-inch diameter duct and
50 feet of 42-inch duct.
2. Nev: water line connecting gypsum pond with retrofitted scrubbers -
* 1200 feet of 16-inch pips with 200-foot branch of 14-inch pipe
to scrubbers treating the drier and miscellaneous streams and 150
foot branch of 5-inch pine to the reactor-granulator scrubber.
•
3. Two centrifugal pumps, each 2160 gpm, 105 feet total dynamic
head (TDK), 100-horsepower motor. Booster pump for spray
section of spray-crossflow packed bed scrubber on miscellaneous
stream - 374 gpm, 89 feet TDK, IC-horsepower motor.
6-61
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1 .,?;
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Table 6-32. MAJOR RETROFIT ITEMS FOR MODEL GTSP PLANT (cont.)
4. Centrifugal fan for miscellaneous stream - 51,000 scfm, *
1
356 feet TDH, 75-horsepower motor.
5. Removal of cyclonic scrubbers on reactor-granulator and f|
miscellaneous streams.
6. Three spray-crossflow packed bed scrubbers. Design parameters *
are provided in Table 6-33. Using pond water at specified •
conditions, the scrubbers are required to meet the indicated
emission levels when treating the gases described in Table 6-31. £
7. Supports and foundations. •
GTSP Storage •
1. Sealing of roof monitor and installation of ducting - 350 feet of
78-inch ducting for ventilation of building and connection of •
scrubber.
•
2. Water line connecting gypsum pond with spray-crossflow packed
bed scrubber - 1700 feet of 12-inch pipe. •
3. Centrifugal pump - 1730 gpm, 81 feet TDH, 60-horsepower motor. £
Booster oumo for sorav section - 580 oom, 89 feet TDH, 15-
r .
•&,,.>. .
4. Centrifugal fan - 75,000 scfm, 630 feet TDH, 200 horsepower
motor.
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I Table 6-32. MAJOR RETROFIT ITEMS FOR MODEL GTSP PLANT (cont).
V 5. Spray-crossflow packed bed scrubber. Using specified pond
water, scrubber must reduce fluoride concentration of venti-
B lation stream to 0.13 mg/scf (5.1) when treating the gases
_ described in Table 6-31.
6. Supports and foundations.
m
7. Stack - 50 feet tall, 6 foot diameter.
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Table 6-33. OPE.RATING CONDITIONS FOP SP?AY-CROSSFLOU
PACKED BED SCP'JBBERS F^P i'.QPEL GTSP PLANT
(400 Tons/Day P°)
'•3 to Scrubber
Flow, SCF.M
Plow, HSCF"
Flov/, f-Cf'.'.
Ter.p., °F
Moisture, vol. %
Fluoride (as F), Ib/hr
Fluoride (as F)5 ppn
Gas from Scrubber
Flow, SCFM
Floy;, DSCFF'
Flow, ACFf^
Temp., °F
Moisture, vol. %
Fluoride (as F), Ib/hr
Fluoride,(as F), ppm
Fluoride removal, wt %
Estimated y', ppm
Estimated MTU required
Product!
Reactor
18,000
16,560
19,400
Tin
8.0
28
490
16,850
16,560
17,500
DO
2.0
1.00
17.5
96.5
n •"'c
• i *J
3.38
on
Drier
48,000
44,160
52,500
120
8.0
79.8
525
45,050
44,160
46,800
90
2.0
1.76
11.5
97.8
0.95
3.90
Cooler
51 ,000
48,450
54,900
110
5.0
14.8
92
49,400
48,450
51,200
?0
2.0
0.63
3.9
96.0
°.85
3.39
Storaae
wentilation
75,000
74,480
77,10P
87
0.7
13.2
5^.1
76,nOO
74 ,480
78,100
85
2.0
1.25
5.1
90.5
0.7
?. .4°
6-64
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Table 6-34. RETROFIT COSTS FOR MODEL
GTSP PLANT (400 tons/day P90r) November 1974
C- \)
Cost ($)
A. Direct Items (installed)
1. GTSP Production
a. Spray-crossflow packed bed scrubbers (3) 261,000
b. Ductwork 22,800
c. Piping 26,200
d. Pumps and motors 35,900
e. Removal of old equipment 18,000
f. Performance test 4,000
g. Centrifugal fan and motor 14,400
2. GTSP Storage
a. Cross flow packed scrubber 150,000
b. Ductwork 56,600
c. Piping . 27,800
d. Pumps and motors 19,400
e. Centrifugal fan and motor 23,'000
f. Structural steel supports/bldg. 50,000
g. Sealing of storage building 10,000
h. Performance test . 4,000
Total Direct Items 723,100
B. Indirect Items
Engineering construction expense, fee, interest on
loans during construction, sales tax, freight insurance.
(50% of A) 361,600
C. Contingency
(25% of A) 180,800
D. Total Capital Investment 1,265,500
E. Annualized Costs
1. Capital charges 206,300
2. Maintenance 33,800
3. Operating labor 6,000
4. Utilities 40,600
5. Taxes, insurance, administrative 50 5QQ
Total Annualized Costs 337,200
6-65
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6.1.3.2 Retrofit Case Descriptions I
General Procedure •
This' section describes two actual cases in which control
systems containing spray-crossflow oacked bed scrubbers were added to £
existing production facilities. Each case description provides the _
following information: ™
1. A description of the process in use, •
2. Identification of the oriainal fluoride controls and sources
treated , |
3. A description of the retrofit project, and
4. Retrofit costs. •
Case A I
Case A involves the retrofitting of controls to a oranular triple •
superphosphate plant. This facility was built in 1953 using the Dorr-
Oliver slurry granulation process. Annual production capacity was oriainallv •
100,000 tons triple suoerphosphate but improvements in olant desicm have
almost doubled,, this value. •
The production equipment is housed in a structure which also contains «
a second granular triple superphosphate olant and a run-of-pile triple
superphosphate plant. All available soace within the buildina is in use and •
any rearrangement of equioment or ducting would require major modifications.
Space limitations also exist in the area immediately surroundinn the build- |
ing and would affect any retrofit project.
6-66
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• Original Controls
Fluoride control was initially orovided by a spray tower installed
I in 1953 as part of the orioinal plant design. Gypsum oond water was used
as the scrubbing liquid. Ventilation streams from the drier and the
I product screens were sent to the spray tower while both reactor and
• granulator gases were vented directly to the atmosphere. The sprav
tower was improved in 1954 by the addition of more sprays and a mist
I elimination section. Performance data for this system is not available.
• Retrofit Controls
The spray tower was removed in 1966 as part of a retrofit project
I and replaced by a three stage scrubbina system. Gases vented from the drier
(60,000 acfm) and the screens (40,000 acfm) are now treated in senarate venturi
• - scrubbers, combined, passed through a cyclonic scrubber, and final!"
• treated in a spray-crossflow packed bed scrubber. Operating characteristics
of these units are listed in Table 6-35. pond water serves as the
I scrubbing liquid for the entire system. Controls for the reactor and the
granulator were not added at this time.
• All associated fans, pumps, piping, ductwork, and stacks were installed
• as part of the retrofit project. New pond water supply and drainage svstems
were also required.
• Designed fluoride removal efficiency is 99+ oercent. Tests
conducted by the Environmental Protection Aqency in June 1972 measured
™ fluoride removal efficiencies ranqing uo to 99.6 nercent.
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Table
1
6-35. OPERATING CHARACTERISTICS OF SCRUBBERS IN RETROFIT CASE A
Scrubber type Scrubbing liquid
to gas ratio (gal/SCF)
Drier
venturi 0.008
Screen venturi 0.006
Cyclonic scrubber 0.007
Spray-crossflow 0.002
packed bed scrubber
Retrofit Costs
1
Gas stream 1
pressure drop (in. H20 *
12-15 1
8-13 |
4-6 •
2-6 |
•
Total installed cost of the retrofit control equipment was $368,000, ™
however, this does not include the cost of removing old eouipment or of I
adding new pond water supply and drainage systems. The annual operating
cost
Case
is reported to be $51,000.
B
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ft ™
Case B is similar to Case A in most respects. The facility involved _
is a
uses
granular triple superphosphate plant built
... ...-„ „ r -.-*.
the Dorr-Oliver process for GTSP. Annual capacity is approximately •
200,000 tons triple superphosphate. Space limitations aro similar to those
described in Case A.
6-68
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Original Controls
Emissions from the drier and the screening area were controlled bv
I a spray tower which had been installed as part of the original olant
design. Fluoride removal efficiency data is not available for this system.
| Reactor and granulator gases were vented to the atmosphere without treatment.
Retrofit Controls
I
Tne retrofit project consisted of the removal of the spray tower and
• its replacement by a system similar to that described in Case A. Controls
• are in tnree stages - 3 Venturis in oarallel followed by a cyclonic scrubber
and a spray-crossflow packed bed scrubber. Effluent streams from the drier
• and the screens are treated in separate Venturis, combined with the gases
from the third venturi, and sent to the remaining controls. The third
• • venturi treats gases from either an adjacent wet acid plant or a nearby
• run-of-pile triple superphosphate plant. Designed capacity of the control
system is 115,000 acfm. Gypsum pond water serves as the scrubbina liquid.
I Controls for the reactor ar.d the granulator were not installed as a part of
this project.
I
• The retrofit controls were added in 1972. All associated fans, pumps,
• piping, and ducting were installed as part of this project. Fluoride removal
efficiency of the system is reported to be 99+ percent.
Retrofit Costs
• Total installed cost for the retrofit controls was reported to be
5)760,000. Table 6-36 lists a breakdown of the cost. Demolition costs
| and the cost of adding new pond water supplv and drainage systems ar-';
m not included, ilo ooeratinn costs ware provided.
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Table 6-36. CASE B RETROFIT PROJECT COSTS
Item
Foundations
Structural steel
Blowers and motors
Wet scrubbers
Pumps, sumps and piping
Ducts and stack
Electrical and instruments
Installed Cost
(dollars)
6-70
81,000
52,000
85,000
218,000
175,000
102,000
47,000
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6.1 VEiiTURI SCRUBBER
I 6.2.1 inscription
Venturi scruboers are primarily particulate collection devices,
| however, tnsy are also applicable to gas absorption work and are in
• widespread use throughout the phosphate fertilizer industry. They are
particularly well suited for treating effluent streams containing large
I amounts Of solids or silicon tetrafluoride because of thair high solids
handling capacity and self-cleaninn characteristics. Operational reliability
I and low maintenance requirements are major reasons for the popularity of
this scrubber design.
A venturi provides a high degree of gas-liauid nixing but the
ft relatively short contact time and the cocurrent flow of the scrubbing
liquid tend to limit its absorption capabilities. When treating effluent
I streams requiring a high degree of fluoride removal, Venturis are often
• used as the initial component in a multiple-scrubber system.
Two types of venturi scrubbers, gas actuated and water actuated, are
I in general use. In both cases, the necessary gas-liquid contacting is
obtained from velocity differences between the two phases and turbulence
| in the venturi throat. Both types also reouire the use of a mist elimination
_ section for removal of entrained scrubbing liquid. The major difference
between the designs is the source of motive power for oneratina the scrubber.
In the case of the gas actuated venturi, the velocity of the gas stream
provides the energy required for gas-liauid contacting. The scrubbino
liquid is introduced into the qas stream at t'ie throat of the venturi
-------
and is broken into fire droplets by the acceleratinn aas |
stream. Pressure drop across the scrubber is generally hi oh - from •
8 to 20 inches of water. A fan is reauired to conpsnsate for this
loss in gas stream pressure. Figure 6-12 provides a schematic •
diagram of a gas actuated venturi.
A water acutated venturi is pictured in Fiaure 6-13. In this |
case, the scrubbing liquid is introduced at a high velocity through «
a nozzle located upstream of the venturi throat. The velocitv of the
water streams is used to pump the effluent gases through the venturi. I
Drafts of up tu 8 inches of water can be developed at hiah liouid
flow rates. |
The removal of the fan from the system makes the water actuated _
venturi mechanically simpler, more reliable, and less costly
than the qas actuated type. An additional advantaqe is its relative Ij
?fi
insensitivity to variations in the gas stream flow rate. Gas
actuated Venturis rely upon the gas stream velocity for the enerqy |
for gas-liquid contacting, therefore, variations in the aas flow can _
greatly affject scrubber efficiency. The performance of the water- *
actuated venturi depends mainly on the liquid stream velocity.
Water actuated Venturis find application princioally as aas
25
absorption units. Their use is usually linited, however, to small
5-72
•
gas streams with moderate scrubbing requirements. The water-actuated _
venturi is seldom used for gas flows greater than 5,000 acfm because •
?fi
of the large water requirements. I
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AIR
INLET
WATER
INLET
VENTURI
AIR
OUTLET
CYCLONIC
MIST ELIMINATION
SECTION
WATER
OUTLET
FIGURE 6
-12. GAS ACTUATED VENTURI SCRUBBER WITH CYCLONIC MIST ELIMINATOR.
WATER
INLET
&
SPRAY !>-T
NOZZLE L
\
t •
n
'!
'/
i
,\
;
r
si
\
-^ AIR
-1-"\-fr^- INLET
/r .-
SEPARATOR
/ BOX
AIR
OUTLET
WATER
OUTLET
FIGURE' 6^1 3.
WATER ACTUATED VENTURI.
" 6^73
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6.2.2 Emission Reduction
No wet-acid plant using a venturi scrubber was tested by the
Environmental Protection Agency, however, fluoride absorption efficiency
ranging from 84 to 96 percent have been reported for water-actuated
27
Venturis treating wet-acid plant effluent gases. Performance data was
obtained for venturi scrubbers installed in superphosphoric acid and
diammonium phosphate plants. This infornation is presented in Table 6-37.
Several additional plants (DAP, GTSP, ROP-TSP) were tested at which venturi
scrubbers were used as the preliminary scrubber in a two or three stage
system. Performance data for the overall systems are presented in Tables
6-3 and 6-40.
Table 6-37. VENTURI SCRUBBER PERFORMANCE IN SUPERPHOSPHORIC ACID AND
DIAMMONIU'1. PHOSPHATE PLANTS 28
Type of plant
Vacuum evapora-
tion SPA
DAP
Sources controlled
barometric conden-
ser, hotwell, and
' product cooling tank
reactor, granula-
tor, drier, and
cooler
Control
system
water
actuated
venturi
3 gas
actuated
Venturis
in para-
llel
Scrubbing
liquid
pond
water
weak acid
(20-22%
Fluoride emissions
(Ib F/ton P205)
0.0009
i
0.129
Average of testing results
6-74
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6.2.3 Retrofit Costs for Venturi Scrubbers
This section evaluates the costs involved \'it', retrofitlvip.r
venturi scrubbers in a diammonium chosohste plant. Venturis
night be used to provide fluoride control for this source because
of their high solids handling capability. Cnlv the rej:r?fv'. code!
approach will be used to orovide costs.
The nodel plant is the saire as described in section 6.1.3.1.
To avoid repetition, only a summary of retrofit controls, e. list
of major retrofit items, and a breakdov/n of costs rill he oresented
here.
The general aspects of the retrofit project are the same as
described in Section 6.1.3.1. Sas-actuated Venturis will be used
as fluoride scrubbers on the reactor-granulator, the drier, ?nd
the cooler streams. Pumping and fan requirements differ fro^ those
presented in section 6.1.3.1. An existing line will be used to
supply part of the water requirement. Table 6-38 provides a list
*
of major retrofit items required. Costs are presented, in Table
6-39.
Table 6-3S. NAJOR RETROFIT ITEMS FOR MODEL DAP PLA'IT
1. Ductwork - removal of cyclonic spray tower from service and
connection of three gas-actuated venturi scrubbers. Reouire-
ments are 100 feet of 60-inch duct and 50 feet of ?£-inch duct.
2. Hater line connecting gypsum nond with venturi scrubbers -
1200 feet of 15-inch pipe with 200-foot branch of H-inch
6-75
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pipe and 150-foot branch of 6-inch nips.
3. Two centrifugal ounos (one spare) - 2550 gnr., 195 *
I
feet total dynanic head (TDH), 150 horsenower rotor.
4. ihree centrifugal fans: one for the reactor-oranulator •
stream, one for the dri^r stream, and one for the cooler
stream. Peactor-granulator fan - 30,000 scfrn, 713 feet TDH, I
75 horsepower motor. Drier stream fan and cooler stream
fan - 45,000 scfm, 713 feet TDH, 125 horsepower motor. I
5. Removal of cyclonic spray tower. |
6. Three venturi scrubbers equipped with mist eliminator •
sections. When using specified pond water and treatino
gases described in Table 6-19, scrubbers are reouired to obtain •
performance indicated in Table 6-21. •
7. Supports and foundations. m
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1
1
1
•
1
1
1
1
1
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1
1
1
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1
1
1
1
Table 6-39. RETROFIT COSTS FOR MODEL DAP
(500 Tons/Day P205) November
A. Direct Items (installed)
1. Venturi scrubbers (3)
2. Ductwork
3. Piping
4. Pumps and motors
5. Centrifugal fans and motors
6. Removal of old equipment
7. Performance test
Total Direct Items
B. Indirect Items
Engineering construction expense,
fee, interest on loans during
construction, sales tax, freight
insurance (50% of A«)
C. Contingency (25% of A.)
D. Total Capital Investment
E. Annual i zed Costs
4
1 . Capital charges
2. Maintenance
3. Operating labor
4. Utilities
5. Taxes, insurance, administrative
Total Annual i zed Costs
6-77
PLANT
1974
Cost ($)
181,700
17,000
26,500
39,200
38,400
12,500
4,000
319,300
159,700
79,800
558,800
91,100
15,000
4,000
31 ,000
22,400
163,500
-------
5.3 SPRAY TOVIER SCRUBBER
6.3.1 Descriction
I
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Spray towers provide the interpnase contacting necessary for
gas absorption by dispersing the scrubbing liquid in the gas phase I
in the form of a fine spray. Several types of spray towers are in
general use. The simplest consists of an empty tower equipped with •
liquid sprays at the top and a gas inlet at the bottom. Scrubbing •
liquid is sprayed into the gas stream and droplets fall by 'iravity
through a upward flow of gas. This design has the advantages of a •
very low pressure drop and an inexpensive construction cost but it can
29 I
provide only about ona transfer unit for absorption. " Entrainment of •
scrubbing liquid is also a problem. flj
Cyclonic sp^ay towers eliminate the excessive entrainnent of
scrubbing liquid by utilizing, centrifugal force to remove entrained •
' . •.;;: ;•'•" -* ;.Ss*« . "
droolets. Finure 6-14 is a schematic diagram of a tvpical desicm.
~* - . - ~. vV I
In this case, a tangential inlet is.'used to impart" the spinning •
motion to the gas stream. Water sprays are directed parallel to the •
gas flow providing crossflow contacting of the gas and liquid streams.
Pressure drops across the scrubber ranges from 2 to 8 inches of water. •
Solids handling capacity is high, however, a'.sootier: caoacit" is
29 30 I
limited to about two transfer units. ' •
6.3.2 Emission Reduction |
Fluoride removal efficiencies ranging from 84 to 95 percent have ^
bsen reported for cyclonic spray tov/ers treating wet acid plant ™
6-78 |
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CORE BUSTER DISK
SPRAY MASlrOLD'
GAS IN
FIGURE 6-14. CYCLONIC SPRAY TOWER SCRUBBER.
31
effluent oases. Table 6-40 presents nerfonnance <1ata obtained b"
the Environnental Protection Aneno/ ^or cvclonic snrav tov/ers installed
in vjet-process ohosohoric acid, diannoniun Dliosohate, and run-o^-nile
trinle suoernhosphate plants. In nost cases, the control system con-
sisted of a primary venturi scrubber or cyclonic s^rav tower followed
by a secondary cvclonic sprav tower. Gvosun oond v/ater was used as
the scrubbinp solution except where indicated.
6.3.3 Retrofit Costs for Cvclonic ^rav Towers
This section will use the retrofit rndel anpro^ch to estimate
the costs involved with the installation of cyclonic snrav towers in
? "0D-TSP nlant. Control svstens utilizinn c'/clonic snrav towers are
caoable of orovidinn the collection efficiencv necessarv tn reet
the emission guideline of 0.2 pounds fluoride per ton P?0r input.
f-79
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~fl • Ti.e rodal plant is t.ie sane as described in section ^.l.?.l
(Case /'•). Flow rates and fluoride concentrations of the various
I effluent streams are listed in Table 6-23. -ases vented from the
. cone irixer and den are presently treated in a 20,000 cfm venturi,
™ combined with the storage buildino ventilation stream and sent to a
I spray tov;er. The storaqe buildino ventilation air is sent directly
to the spray tower. Total fluoride emissions are 127 nounds oer
jj hour with axistino controls.
^ The retrofit project involves the removal of the existinn scrubbers
and the installation of a new control system consisting of orelimina^v
l| cyclonic spray towers on the ventilation streams ^ron the production
and storaqe areas followed by a secondary cvclonic sprav tower treatino
| the combined effluent streams. This system will reduce fluoride
_ emissions to 4.6 oounds per hour which is eouivalent to the emission
™ guideline.
ft -Retrofit controls will be located as shovin in Ficure 6-15. ''od-
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erate rearrangement of the ductwork is necessary to install the
cyclonic spray towers. Two new fans will be required because of the
hiciher oressure dron associated with the retrofit svstem. txistino
* water lines and numps will be user! to supply the nrelirinarv scrubbers.
A 14-inch line will be installed to orovide 1725 gpn nf oond water
for the secondary scrubber. Scent scrubbino water v/ill be recvcleri
to the nyosum pond in the existino drainage svsterr. Treated cases
<-.'ill be emitted from a newly installed 75 foot stacK
-------
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6-82
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Table 6-41 lists the major cost items involved in this retrofit
project. Operating conditions for the three cyclonic snray tov/ers are
I provided in Table 6-42. Retrofit costs are estimated in Table 6-43.
• Table 6-41. MAJOR RETROFIT ITEMS FOR MODEL ROP-TSP PLANT
. 1. Rearrangement of ductwork - removal of venturi and spray tower
from service and connection of three cyclonic spray towers and
• stack. Requirements are 50 feet of 42-inch duct and 125 feet
of 96-inch duct.
2. Water line connecting gypsum pond with cyclonic spray tower
• treating the combined effluent streams from the production and
the storage area - 1600 feet of 14-inch pipe.
I
3. Centrifugal pump - 1725 qpm, 167 feet total dynamic head (TDH),
• 125-horsepower motor.
4. Removal of venturi and spray tower.
5. Centrifugal fan for the storage building ventilation system -
125,000 SCFM, 514 feet TDH, 250 horsepower motor. Centrifuqal
I fan for the combined effluent streams - 150,000 SCFM, 461 feet
TDH, 175 horsepower motor.
6. Three cyclonic spray tower scrubbers. When using pond water
I specified in Table 6-7 and treating the effluent streams described
in Table 6-23, scrubbers are required to obtain the performance
indicated in Table 6-42.
6-83
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7. Stack - 75 feet tall, 9 feet diameter.
8. Supports and foundations.
Table 6-42.
Gas to scrubber
Flow, SCFM
Flow, DSCFM
Flow, ACFM
Temp., °F
Moisture, Vol. !
Fluoride (as F)
Fluoride (as F)
Gas from scrubber
Flow, SCFM
Flow, DSCFM
Flow, ACFM
Temp., °F
Moisture, vol. %
Fluoride (as F),
Fluoride (as F),
Fluoride removal
FOR MODEL ROD-TSP PLANT
(550 Tons/Dav P Og)
Mixing cone and den
ventilation stream
25,000
24,500
28,400
140
2
307
4,000
Ib/hr
ppm
Ib/hr
ppm
, wt %
Estimated y', ppm
Estimated NTU required
25,300
24,500
27,500
115
3
20.5
260
93
0.8
2.7
6-84
PRAY TOWER SCRUBBERS
Storage
building
ventilation stream
125
122
128
1
126
122
128
,000
,500
,200
85
2
396
,000
,000
,500
,500
80
3
30
76
92.5
0.8
2.6
Combined
streams
150,000
145,500
154,000
85
50.5
107
150,000
145,500
153,000
PO
3
4.6
9.7
91
O.P.
2.5
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Table 6-43. RETROFIT COSTS FOR MODEL ROP-TSP PLANT
(550 Tons/Dav PoOc) November
A. Direct Items (installed)
1. Centrifugal spray tower scrubbers (3)
2. Ductwork
3. Piping
4. Pump and motor
5. Centrifugal fans and motors
6. Removal of old equipment
7. Stack
8. Performance test
Total Direct Items
B. Indirect Items
Engineering construction expense,
fee, interest on loans during
construction, sales tax, freight
insurance (50% of A.)
C. Contingency (25% of A.)
D. Total Capital Investment
E. Annual i zed Costs
1. Capital charges
2. Maintenance
3. Operating labor
4. Utilities
5. Taxes, insurance, administrative
Total Annual i zed Costs
6-85
1974
Cost ($)
300,000
25,000
29,100
22,200
54,400
12,500
44,000
4,000
491 ,200
245,600
122,800
859,600
140,100
23,400
6,000
48 ',600
34,500
252,600
-------
6.4 IMPINGEMENT SCRUBBER
Impingement scrubbers are primarily particulate collection
devices but they also possess some absorption capability and have
been used with limited success to treat effluent streams from wet-
process acid and diammonium phosphate plants. The Doyle scrubber
pictured in Figure 6-16 is the type most commonly used by the
fertilizer industry.
OOWNCOMEft DUCT
FIGURE 6-16. DOYLE SCRUBBER.
Effluent gases are introduced into the scrubber as shown in
Figure t»tt. The lower section of the inlet duct is equipped with a
axially located coi>e that causes an increase in gas stream velocity
prior to its impingement on the surface of the pond. The effluent
gases contact the pool of scrubbing liquid at a hiqh velocity-and under-
go a reversal in direction. Solids impinge on the liquid surface and
are retained while absorption of gaseous fluorides is promoted by the
interphase mixing generated by impact. Solids handling capacity is
33
high, however, absorption capability is very limited.
6-86
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6.5 SUMMARY OF CONTROL OPTIONS
Sections 6.1 through 6.4 have examined the operational charac-
teristics of several scrubber designs commonly used in the phosphate
fertilizer industry. Only the spray-crossflow packed bed scrubber is
capable of providing the degree of fluoride control required to meet
SPNSS emission levels in all cases. In certain cases, cyclonic spray
tower scrubbers will meet the standards, but only at a higher cost as the
ROP-fSP retrofit example illustrates (Table 6-44). Although retrofit
costs for installing venturi scrubbers in a DAP plant were lower than
those for spray-crossflow packed bed scrubbers, there is no data
available which substantiates that a venturi scrubber alone can achieve
SPNSS emission levels. The primary value of venturi scrubbers in
fluoride control is their higher solids handling capacity. This feature
is exploited in several spray-crossflow packed bed scrubber designs
which incorporate a preliminary venturi scrubber.
Table 6-44. ESTIMATED TOTAL CAPITAL INVESTMENT AND ANNUALIZED COST
FOR DAP AND ROP-TSP RETROFIT MODELS USING SPRAY-CROSS-
FLOW PACKED BED AND ALTERNATIVE SCRUBBERS.
November 1974.
Facility Type of Scrubber Capacity Total Capital Annual i zed
(tons/day Investment Cost
PA)
DAP Spray-crossflow 500 $733,100 $194,100
packed bed
DAP Venturi 500 558,800 163,500
j *
ROP-TSP Spray-crossflow 550 802,100 214,900
packed bed
ROP-TSP Cyclonic spray 550 859,600 252,600
tower
6-87
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6.6 DESIGN, INSTALLATION, AND STARTUP TIMES
This section discusses the time required to procure and install
a wet scrubber on a phosphate fertilizer operation. Actual time •
requirements can vary tremendously depending upon such factors as
space limitations, weather conditions, lack of available utilities,
in equipment delivery, and lack of engineering data. The
_
information presented in this section f- has to a limited extent, *
attempted to take such factors into consideration. Since these •
estimates are general, however, they should be used primarily as a guide-
line and may be modified as dictated by specific circumstances. |
Figure 6-17 identifies the various steps involved in the procurement and I
installation of a wet scrubber on a wet-process phosphoric acid plant. It
also provides an estimate of the total time requirement of the pro.iect. In p
estimating this time requirement, it was assumed that those activities leadinn «
up to the final ization of control equipment plans and specifications had been
completed prior to the initiation of the retrofit project. The individual fl
steps shown in Figure 6-17 are explained in more detail in Table 6-45.
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6.7 REFERENCES
1. Atmospheric Emissions'from Wet-Process Phosphoric Acid
Q Manufacture. National Air Pollution Control Administration.
— Raleigh, North Carolina. Publication Number AP-57. April 1970.
* p. 25-26.
• 2. Reference 1, p. 31.
II 3. Technical Report: Phosphate Fertilizer Industry. In: Group III
Background Document. Environmental Protection Agency. Research
• Triangle Park.
I 4. Reference 1, p. 30-32, 49, 51-52.
• 5. Air Pollution Control Technology and Costs in Seven Selected
Areas; Phase I. Industrial Gas Cleaning Institute. Stanford,
I Connecticut. EPA Contract 68-02-0289. March 1973. p. 52.
| 6. Reference 5, p. 41, 43.
V 7. Test No. 73-PSA-2; Texas Gulf, Inc.; Wet Process Phosphoric Acid;
Aurora, North Carolina; August 31-September 1, 1972. Environmental
£ Engineering, Inc. Gainesville, Florida. Contract No. 68-02-0232.
. p. 4.
8. Technical Report: Phosphate Fertilizer Industry. In: An
• Investigation of the Best Systems of Emission Reduction for Six
m Phosphate Fertilizer Processes. Environmental Protection Agency.
Research Triangle Park, North Carolina. April 1974. p. 25.
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9. Reference 3.
6-95
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10. Guthrie, K.M. Capital Cost Estimating. In: Modern Cost- *
Engineering Techniques, Popper, H. (ed). New York, McGraw-Hill I
Book Co., 1970. p. 80-108.
11. Reference 5, p. 192.
12. Standards and Costs; Gas Absorption-and Pollution Control Equip- *
ment. Ceilcote Company. Berea, Ohio. Bulletin 1200. 19 p. •
13. Guthrie, K. Piping, Pumps, and Valves. In: Modern Cost- m
Engineering Techniques, Popper, H. (ed). New York, McGraw-Hill
Book Co., 1970. p. 161-176. I
14. Reference 5, p. 39. •
15. Reference 5, p. 57. ^
16. Goodwin, D.R. Written communication from Mr. R.D. Smith,
Occidental Chemical Company. Houston, Texas. April 30, 1973. •
17. Reference 5, p. 148. |
18. Test No. 72-CI-25; Royster Company; Diammonium Phosphate; •
Mulberry, Florida; May 17-18, 1972. Contract No. 68-02-0232.
p. 8. 1
19. Test No. 72-CI-18; Royster Company; Run-of-Pile Triple |
Superphosphate; Mulberry, Florida; February 29-March 1, 1972. _
Environmental Engineering, Inc. Gainesville. Florida. Contract *
No. 68-02-0232. p. 4-5. •
6-96 •
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• 20. Reference 3.
21. Reference 20, p. 4-95.
22. Reference 5, p. 114.
23. Control Techniques for Fluoride Emissions. Environmental Health
I Service. Second Draft, September 1970. p. 4-95 (unpublished).
I 24. Reference 3.
m 25. Chatfield, H.E. and R.M. Ingels. Gas Absorption Equipment. In:
Air Pollution Engineering Manual, Danielson, J.A. (ed). Research
• Triangle Park, Ncrth Carolina. Environmental Protection Agency.
1973. p. 229.
I
26. Reference 5, p. 80.
27. Reference 1, p. 26.
* 28. Reference 3.
I 29. Reference 25, p. 228.
M 30. Emmert, R.E. and R.L. Pigford. Gas Absorption and Solvent
Extraction. In: Chemical Engineers' Handbook, Perry, R.H.,
• C.H. Chilton, and S.D. Kirkpatrick (ed). New York. McGraw-
• Hill, Inc. 1963. p. 14-37 to 14-39.
31. Reference 1, p. 27.
32. Reference 3.
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33. Reference 1, p. 27. ™
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34. Technical Guide for Review and Evaluation of Compliance
Schedules for Air Pollution Sources. The Research Triangle
Institute and PEDCo - Environmental Specialists, Inc. Pre-
liminary Draft. June 1973. p. 3-39. (unpublished). I
35. Reference 34, p. 2-4 to 2-8. •
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7. ECONOMIC IMPACT
7.1 INTRODUCTION
ff This section describes the economic impact of adopting regulations
that require control of fluoride emissions from existing wet-process
| phosphoric acid, superphosphoric acid, diammonium phosphate, run-of-pile
•m triple superphosphate, and granular triple superphosphate facilities.
The costs shown in Table 7-1 are based upon the installation and
• operation of control equipment described in chapter 6.1.3. Installation
of other, less efficient control equipment is not expected to result
• in any significant reduction in the economic impact incurred. The
_ capital costs and annualized costs of installing control equipment
•* represent expenditures needed to achieve the emission guidelines shown
• in Table 1-2, but would also apply to the adoption of less stringent
fluoride emission regulations.
• The economic impacts have been developed on a nrocess-by-process
basis since the national or industry-wide impact will be dependent
• upon the collective actions of the states. To provide a perspective
• on the significance of the costs incurred by adopting fluoride
emission regulations, they are related to unit production and product
• sales price (Table 7-1). Additional insight on potential impacts
related to costs are given by a discussion on potential plant closures.
m Criteria are presented that describe circumstances that could result
m in plant closures, and the number of closures within the industry
that would result if all states adopted fluoride emission regulations
• is estimated.
The information presented in this chapter is intended to assist
J| states in deciding on the advisability of adopting fluoride regulations.
7-1
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It is not expected that these emission guidelines would be •
appropriate for all existing facilities. _
7.2 IMPACT ON MODEL PLANTS
The total capital investment and annualized control cost ob- I
tained from section 6.1.3.1 for each of the model facilities is
presented in Table 7-1 on a plant basis, on a unit product basis, and •
as a percentage of the product sales price. For purposes of this •*
analysis, it is assumed that the wet-process acid plant sells all
acid production at prevailing merchant acid prices. The estimated •
control costs for superphosphoric acid, diammonium phosphate, and
triple superphosphate plants reflect the retrofit requirements of y
both the individual production facility and an associated wet-process ^
acid plant which produces the required intermediate phosphoric acid. *
The captive acid plants are assumed to be sufficiently sized to flj
supply the needs of the various production units. For example, the
SPA plant is associated with a 300 ton P^Or/day acid plant while the •
DAP plant requires a 500 ton/day unit. Control costs for the captive •
units were obtained by prorating the costs developed for the model acid
plants. I
A more detailed analysis of the potential financial effects of
control costs upon the phosphate industry could be obtained by cal- •
culating the changes in profits and cash incomes for all plants or m
firms in the industry if the necessary information were available.
Diammonium phosphate and granular triple superphosphate are the more •
popular products sold and their processing will incur the higher
control costs on a unit basis. Industry statistics, representative •
of 1973 performance, indicate that after-tax profit margins ranged
7-2
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from 5 to 6 percent of sales and approximately doubled these per-
centages in 1974. Against this level of profitability, control costs •
as shown in Table 7-1 appear to have minimal impact on a nlant typical
of this profit performance. As long as product prices are unrestricted tt
(the Cost of Living Council removed price ceilings on domestic ferti-
lizers on October 25, 1973) and plant utilization remains at the cur- |
rent level of approximately 90 percent, control costs could be ab- —
sorbed by the industry without any price increases. On the other hand, ™
price increases to pay for the costs would be minimal. •
An objective of this analysis is to highlight where the implemen-
tation of the emission guidelines might impose an economic £
burden upon plants. A scenario for possible plant closures eould be
presented in this fashion: overcapacity in spite of growing demand ••
develops in a particular segment of the industry resulting in under- •
utilization at rates near 75 and 80 percent of capacity. Prices
and profits subsequently decline. In such a situation, plants •
would probably close; however, the question is to what extent would
the impact of retrofit controls be responsible for plant closures. . •
In section 7.3, criteria are presented which can be used to pinpoint •
the extent of plant closures.
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7.3 CRITERIA FOR PLANT CLOSURES
Reasons for closing a facility are usually traced to the absence
of profitability for a specific site or facility. Managers of existing
plants faced with increased capital requirements for continuity of •
operations will have to decide whether the incremental investment will
"save" future cash income that otherwise would be lost by ceasing ™
operations. Plant managers will have the following options in such a m
situation;
7-4
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• 1. Undergo increased capital expenditures on the existing plant.
2. Shut down the plant and discontinue business.
£ 3. Shut down the plant and replace it with a new plant.
The selection of an option is based on an interest or opportunity
• cost for employing the required capital. There is usually a minimum
• return that a plant manager will accept for employing funds—interest
cost for borrowing money or the interest cost of investing in short
I term obligations. Since there is a risk with employment of capital,
businesses will require a higher rate of return for investing of
» funds. A familiar tool for analyzing investments involves the deter-
• mination of the sum of all future cash flow (income) streams over a
projected time span discounted (with the appropriate interest rate) to
• the present. If .the sum of these discounted residuals exceeds intended
cash outlay for investment, resulting in a positive term for net
• present value, than the investment will be a good choice. Conversely,
m if the discounted present value of projected cash flow streams results
in a negative value, then the proposed investment will be rejected.
• The managerial tool of discounted cash flow analysis can be
applied to the retrofitting of control equipment to existing plants
m in this manner. If the existing operations can only be continued in
•| the future by meeting a standard, then the investing of the control
capital has to be evaluated on the basis of the value of the future
• income derived from continuing the operation of the present plant.
The merit of continuing operations after retrofitting a plant must be
£ evaluated in retrospect with the alternatives of discontinuing operations
and building a new plant.
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Guidelines for pinpointing plants as candidates for closure are m
presented as follows. First, new plants to replace existing plants
of the comparable model size described in Table 7-1 v/ould require some •
$10 to $20 million. In no instance could the construction of a new
plant be a better alternative than retrofitting controls requiring 9
the magnitude of capital, or even tv/ice the values, shown in Table 7-1. •
On the other hand, plants that have small or negative cash incomes
prior to retrofitting would certainly close. Plants that have small or •
negative profits (after deducting depreciation charges) would eventually
become candidates for closure upon termination of their depreciation
schedules and subsequent increased tax liability. I
The type of plants that would most likely face these circum-
stances are the following: £
1. Small plants which generally suffer from the usual economies ^
of scale of production—less than 170,000 tons-per-year cap- *
acity. •
2. Old plants which generally have outlived their useful or
|J
3. Plants isolated fron raw materials—particularly diammonium ^
phosphate plants that purchase merchant phosphoric acid and
ammonia. ft
4. Plants likely to suffer from a shift in the overall market
structure as a result of external forces. B
Financial data on an individual plant basis necessary to evaluate .
the impact of retrofit controls are unfortunately unavailable. Hence,
plant closures can be estimated only from a categorical approach, which W
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classifies plants that possess characteristics of the nature of those
£ discussed above. Any estimate of plant closures has to be presented
_ with the usual qualifications.
7.4 IMPACT ON THE INDUSTRY
I At the present time, the condition of the fertilizer industry is
• healthy. Prices and profits in 1974 were the highest they have been
in years. The U.S. industry has become a leader in phosphate processing
• technology and benefits from world trade in both rock and concentrated
• phosphates. This position became more pronounced recently, in spite
of the fracture in the international monetary structure and con-
B current high inflation. When the Cost of Living Council lifted
price ceilings on October 25, 1973, domestic prices heretofore con-
I strained by CLC immediately arose 60 percent on the average reflecting
M the foreign demand for domestic phosphate products. Demand for
fertilizers to increase agricultural production and yields has been
ft strong and will continue to be so, in spite of fluctuating international
currency values. Projected long-term demand for phosphate nutrients
12
is expected to grow at an annual rate of 5-6 percent.
M Historically, the fertilizer industry has experienced cyclic
patterns of overexpansion followed by plant shutdowns and product price
II cutting. New phosphoric acid plant expansion scheduled to come on
stream in 1975-1976 may result in short term price declines until in-
£ creases in consumer demand restores equilibrium with capacity. In
A anticipation of overexpansion, producers will probably curtail con-
struction activity in the period beginning in 1976-1977. However,
flj during this slack period, retrofitting of existing plants for
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controls will be required in accordance with implementation plans.
Therefore, these retrofit projects should not hinder new construction. M
Rather than resulting in plant closures, requirements for retro-
fitting fluoride emission control systems will probably encourage some w
improvements of marginal plants. •
The nature of the impact of the lll(d) regulations for the
fertilizer industry will be geographical in scope. The state of m
Florida, where most of the industry is located, has adopted regula- •
tions for the existing industry that are equivalent m most instances
to the emission guidelines. Most of the remainina states with phos- •
phate process facilities have no emission standards.
The greatest control cost - on a unit basis - for any process m>
subject to standards is for the combination of processing anc' storage •
of granular triple superphosphate. However, 75 percent of the industry
capability in GTSP production will be required to meet the •
emission guideline by July 1975 regardless of Federal action. Since
a large portion of the production facilities will not require additional •
retrofit controls, the impact upon the industry doesn't appear severe. m
For run-of-pile triple superphosphate, the conclusion would be similar
to the GTSP as some 60 percent of the industry will be adequately con- •
trolled because Of state standards.
The one segment of the industry where a wide-scale effort in •
retrofitting would be required is for diammoniurn phosphate plants.
Some 60 percent of industry capacity would be expected to retrofit as a •
result of Federal regulations. Control costs for this process, •
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• however, would amount to only 0.5 percent of sales. These costs alone
are not sufficient to close any plants.
Ji Diammonium phosphate plants which incur water abatement costs as
I great or greater than fluoride emission control costs would be likely
o
candidates for plant closures. There is no specific information
f concerning plants which may fall into this category. The only
definitive statement that can be made is that those affected will
• be outside the state of Florida and may amount to 3 to 5
• plants, or approximately 10 percent of the total DAP manufacturing
capacity.
• With regard to triple superphosphate plants, 1 to 3 plants (out-
side Florida) may close as a result of implementing the recommended emission
• guidelines for control of aaseous fTunnHP. This is likply to occur
m in a geographical region where there is an oversupply of phosphate
processing capacity. An abundant supply of low-cost sulfuric acid
ft derived from non-ferrous smelters in the Rocky Mountains area could be
an incentive for construction of new phosphate facilities, ultimately
| resulting in oversupply and price-cutting. Triple superphosphate capacity
« does appear to be expanding rapidly in this area with a new 340,000
ton-per-year plant coming on-stream in 1975-1976.
ft Most of the control costs associated with a TSP complex are for
the solids manufacture and storage. Therefore, the closure of a TSP
j[ facility as implied above does not mean that the entire complex
_ will be shut down. The plant manager has several options--(l) sell
ft merchant acid, (2) convert to mixed fertilizers, or (3) produce
• diammonium phosphate. However, if the same plant manager is faced
with installing water abatement facilities, the overall abatement costs
ft will affect the entire facility.
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7.5 IMPACT ON EMPLOYMENT AND COMMUNITIES
The fertilizer industry is generally recognized as a capital £
intensive industry; in other words, labor requirements for production _
work and plant supervision are small, relative to plant sales. *
Usually, those plants that may be affected by implementation of the •
emission guidelines are widely dispersed throughout the
United States. Only in central Florida does the fertilizer industry £
represent a substantial portion of overall community economic activity
and employment. ™
For purposes of illustrating the effects of plant closures on •
employment, the shutdown of 1 to 3 triple superphosphate plants cited
in Section 7.4 might result in the loss of 10 to 50 jobs. Onlv those •
jobs directly associated with the triple superphosphate plants would
be affected. Employment in supporting activities such as rock mining, •
phosphoric acid production, and transportation services would remain m
unaffected.
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7.6 SUMMARY
An optimistic outlook for the phosphate fertilizer industry in
the next few years has been presented, but such an appraisal must be
cautionary after reviewing the historical chronic cyclic patterns £
of product shortages and oversupply. Assuming that oversupplv con-
ditions may occur in the next few years, some estimates of plant •
closures have been made. In the triple superphosphate sector of m
the industry, as many as three plants could close as a direct result
of the states adopting the emission guidelines. In the diammonium phosphate £
a combination of expenditures for retrofitting both fluoride emission
7-10 §
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• controls and water effluent controls may result in as many as five
plant closures, or 10 percent of industry capacity.
J However, fluoride emission controls alone would not cause these
_ closures. Associated costs for fluoride emission controls for wet-
' process phosphoric acid plants that do not have attendant DAP or TSP
• processes will not warrant plant closures. Similarly, costs for
superphosphoric acid plants do not present any apparent problems.
B The number of predicted closures reflects the adoption of the
emission guidelines by all states; therefore, it reflects the maximum
• number of closures that may occur.
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7.7 REFERENCES _
1. David, Milton L., J.M. Malk, and C.C. Jones. Economic Analysis
of Proposed Effluent Guidelines for the Fertilizer Industry. M
Development Planning and Research Associates, Inc. Washington,
D.C. Publication Number EPA 230-1-73-010. November 1973. |
p. VI-12 to VI-15. _
2. U.S. Industrial Outlook 1972 - With Projections to 1980. U.S.
Department of Commerce. Washington, D.C. Publication Number m
BOC-704-08-72-005. p. 174-175. •
3. Reference 4, p. V-13 to V-18. —
4. Reference 4, p. VI-26.
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1
8. EMISSION GUIDELINES FOR EXISTING
PHOSPHATE FERTILIZER PLANTS
• 8.1 GENERAL RATIONALE
These ennssion guidelines represent the same degree of control
• as is required by the standards of performance promulgated for new
plants [wet-process phosphoric acid, superphosphoric acid, diammonium
™ phosphate, run-of-pile triple superphosphate (production and storage),
• and granular triple superphosphate (production and storage)]. The
emission guidelines were developed after consideration of the
• following factors:
1. The degree of emission reduction achievable through the
• application of the best adequately demonstrated svstem of
m emission reduction (considering cost).
2. The technical and economic feasibility of applying the
• best demonstrated technology to existing sources.
3. The impact of adopting the emission guidelines on annual
V U. S. fluoride emissions.
• 4. The environmental, energy and economic costs of the
emission guidelines.
• Identification of the best demonstrated control technology was
accomplished first. During the development of standards of
( performance for new facilities in the phosphate fertilizer industry,
^ the spray-crossflow packed bed scrubber was found to represent the
best demonstrated control for total fluoride emissions. Historically,
8 the spray-crossflow packed bed scrubber was developed to control
fluoride emissions from the phosphate fertilizer industry. From this
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viewpoint, it is not unusual that this scrubber design is the best •
demonstrated control technology. Many of the spray-crossflow packed •
bed scrubbers tested by EPA were retrofitted. For this reason,
spray-crossflow packed bed scrubbers are recognized as the best •
demonstrated control technology for both new and existing plants.
Alternative fluoride control technologies, such as the venturi *
and cyclonic spray tower scrubbers, can only provide approximately •
two transfer units for fluoride absorption unless two or more are used
in series, at multiplied costs. Spray-crossflow packed bed scrubbers I
are not limited by the number of transfer units which they can provide;
in practice, five to nine transfer units per scrubber are provided. Con- •
trol of gas streams with high particulate loadings has caused a plugging A
problem for spray-crossflow packed bed scrubbers in the past. However,
use of a built-in venturi scrubber and other improvements in spray- •
crossflow packed bed scrubber design have eliminated this problem. In
addition, all current fluoride control technologies involve some type of m
scrubbing system, and consequently, they share any plugging tendencies, m
as well as similar costs and energy requirements. With these considera-
tions in mind, it is not unreasonable to base fluoride emission guide- •
lines on the one clearly superior scrubbing technology.
Evaluation of the problems and costs associated with a retrofit |
project is complicated by the lack of actual data. Some of the —
facilities equipped with spray-crossflow packed bed scrubbers installed ™
8-2
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Jl the units as part of the original plant design. Retrofit information
that is available is usually incomplete because of changes in plant
• management and lack of cost breakdowns. Retrofit models were therefore
• developed to evaluate the technical and economic feasibility of in-
stalling spray-crossflow packed bed scrubbers on existing WPPA, SPA,
I DAP, ROP-TSP, GTSP processing, and GTSP storage facilities. The retro-
fit model approach was meant to estimate costs for an average plant and
m to clarify the technical problems involved in a typical retrofit pro-
• ject. No technical problems, other than space limitations, were
foreseen for the average plant. In all cases, the mannitude of the
• estimated retrofit costs is minimal as is discussed in Section 7.
Table 9-1 indicates the impact of the emission nuidelinei.
• ' on annual U.S. fluoride emissions. Adoption of the emission guidelines
• would result in emission reductions ranging from 50 percent for GTSP
storage facilities to 90 percent for ROP-TSP plants. Overall emissions
P from the affected facilities would be renuced by 75 percent.
_ Environmental and energy costs associated with the
™ emission guidelines are minimal. With current spray-crossflow packed
• bed scrubber designs, gypsum pond water can be used as the scrubbing
medium to meet the emission guidelines in practically all cases.
£ In the rare case where the partial pressure of fluoride out of pond water
is high, the emission guidelines can still be met. The aliquot of water
* sent to the final section of scrubber packing may be fresh or limed water.
• This aliquot will only be a small fraction of the total water to the scruober
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and will contain only a small fraction of the total fluoride absorbed
in the scrubber. This implies that no additional effluent need be m
created. Any solids generated by fluoride scrubbing (e.g., in the WPPA m
process) would go to the gypsum pond and cause no more than a 0.06 *
percent increase in the amount of solids normally produced. W
The estimated total annual incremental electrical energy demand
which would be created by fluoride control to meet the |
emission guidelines is only 38,7 X 10 KWH/yr. This is equivalent A
to the amount of energy required to operate only one 300 tons/day
P?0r SPA plant by the submerged combustion process 115 days/yr. I
8.2 EVALUATION OF INDIVIDUAL EMISSION GUIDELINES
8.2.1 Wet-Process Phosphoric Acid Plants
Fluoride Emission Guideline
process.
Discussion
8-4
•
0.01 grams of fluoride (as F~) per kilogram of P00^ input to the •
I
The emission guideline is equal to the standard of performance fl|
for new plants. Control to the level of the guideline would require
removal of 99 percent of the fluorides evolved from the wet-acid |
process. A spray-crossflow packed bed scrubber is capable of providing _
this collection efficiency. •
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• Rationale
M The economic impact of the emission Guideline on the
industry is negligible. Approximately 53 percent of the
fl existing wet process acid plants, ^ccountin^ for 74 percent of the
production capacity, *re either sufficiently controlled at present
| to meet an emission level of 0.01 grams F/kilogram P?05 or will be
f required to attain that level of control regardless of the proposed
emission guideline. This estimate is based on the assumption that
• all wet-process acid plants built since 1967 have installed controls
capable of meeting an emission level of 0.01 grams of fluoride
I par Lilogran1, P^Gb input as part of the original plant Josi^n.
m ' ~~the retrofit costs for those plants that are affected, approximately
$230,000 for a 500 ton P^O^/day facility, can be successfully absorbed
• within the existing cost structure. Annualized control costs for an
average sized plant, including capital charges, amount to approximately
0.2 percent of sales.
Relaxation of the guideline to allow emission increases of 50 to
100 percent would not a!3<*• .additional control options or appreciably
reduce retrofit costs for the following reasons:
• a. Only a packed bed scrubber is capable of providing the re-
quired fluoride removal efficiency - 99 percent. A tenfold
£ increase in the emission guideline would be required
8-5
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to allow the use of other commonly used scrubber designs -
Venturis, cyclonic spray towers, etc. with 85-90 percent •
collection efficiency.
b. Packed bed scrubber cost will not vary significantly with m
moderate changes in packing depth. The cost of additional
packing to increase scrubber efficiency is minor compared •
to overall control costs.
1
Estimated impact of the emission guideline on annual fluoride
emissions is significant - 73 percent reduction. I
8.2.2 Superphosphoric Acid Plants
Fluoride Emission Guideline
8-6
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0.005 grams of fluoride (as F") per kilogram of P20,- input to the
process. •
Discussion
The emission guideline for existing SPA plants is equal to the m
standard of performance for new facilities. Control to the level of «
the guideline would require removal of approximately 90 percent of the
fluorides now being emitted from SPA plants using the submerged •
combustion process. A spray-crossflow packed bed scrubber is capable
of providing this performance. Three designers of control equipment J§
have submitted proposals to one operator for control to the level of ^
the emission guideline; venturi and other designs were quoted, *
including the spray-crossflow packed bed scrubber (1). Plants using •
the vacuum evaporation process (79 percent of the SPA industry) will
require no additional control. £
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Rationale
• Impact on the industry is negligible. The two existing plants
• using the submerged combustion process could be required to add
retrofit controls.
• Existing submerged combustion plants are capable of meeting
the emission guideline by treating the exhaust stream from controls
• with a spray-crossflow packed bed scrubber. This scrubber can be
ft added to any existing mist separators, baffles, and spray chambers,
as was assumed in the SPA retrofit model, Figure 6-5.
• Retrofit costs are expected to be acceptable ($114,000 for a 300
ton per day plant). Annualized control costs, including capital
• charges, amount to only 0.3 percent of sales.
•| Relaxing the emission guideline to allow a three-fold increase
in emissions (0.015 grams F/kilogram P205) would be required to
• accommodate the use of Venturis and cyclonic spray towers, if the
retrofit costs are to remain about the same.
I
8.2.3 Diammonium Phosphate Plants
I Fluoride Emission Guideline
^ 0.03 grams of fluoride (as F~) per kilogram of P90c input to the
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•
m.
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process.
Discussion
The emission guideline for existing DAP plants is equal to the
• standard of performance for new facilities. Control to the level
of the guideline would require removal of approximately 85 percent
9 of the fluorides evolved from the DAP process. Spray-crossflow
packed bed scrubbers, added to any existing Venturis, are capable of
8-7
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»
providing the required collection efficiency. As pointed out in section
8.1, new designs for these scrubbers are available and are expected to •
overcome problems formerly associated with plugging by excessive parti cu-
lates (2). f
Rationale I
Relaxing the emission guideline to allow the use of alternative
scrubber technologies would increase fluoride emissions to the atmosphere |
by 49 tons per year, a 50 percent increase. ^
Retrofit costs (733,000 for a 500 ton P -Or/day plant) are not
I
considered excessive. Annual ized cost, including capital charges, £
would amount to 0.5 percent of sales. A
Impact of applying the emission guideline on fluoride emissions
from U. S. DAP plants is significant - a 65 percent reduction (160 ^
tons/year. •
8.2.4 Run-of-Pile Triple Superphosphate Production and Storage Facilities «
Fluoride Emission Guideline
0.1 gram of fluoride (as F") per kilogram of P205 input to the process. 9
Discussion
I
The emission guideline is equal to the standard of performance for _
1
new facilities. Only 40 percent of the industry is directly affected by m
the emission guideline. •
8-8
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V Compliance with a 0.1 gram F per kilogram P205 emission level
would require collection of about 99.2 percent of the fluorides evolved
Ji from the process. This efficiency can be obtained by a two stage
« system using Venturis and a spray-crossflow packed bed scrubber.
Rationale
I Economic impact on the industry is moderate. Only 40 percent
of the industry is directly affected by the emission guideline.
I The remaining 60 percent will be required to meet more stringent
_ State regulations.
No additional control options would be made available by relaxing
I the emission guideline by 50 to 100 percent. It would be necessary to
H. triple the emission guideline to allow the use of a venturi or cyclonic
spray tower as the secondary scrubber.
• Retrofit costs ($800,000 for a typical 550 ton P205/day plant
• to $1,371,000 for the extreme case) are not considered excessive.
Annualized control costs, including capital charges, amount to 0.50
I to 0.80 percent of sales. Although these costs are more severe
than retrofit costs for most other sources, they are expected to be
* manageable.
(/ The emission guideline would reduce annual fluoride emissions
_ from existing ROP-TSP plants by 88 percent.
t
8.2.5 Granular Triple Superphosphate Production Facilities
j| Fluoride Emission Guideline
10.1 gram fluoride (as F~) per kilogram of PJDr input to the process.
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Discussion
I
The fluoride emission guideline is equal to the standard of performance
for new facilities. Compliance with the emission guideline would require
collection of about 99.6 percent of the fluoride evolved from the GTSP •
production process. This efficiency can be obtained by a two-stage system
consisting of a venturi and a spray-crossflow packed bed scrubber. m
Rationale •
Economic impact of the emission guideline is moderate. Only 25
percent of the industry is directly affected by the emission guideline. ft
The remaining 75 percent will be required to meet more stringent State
regulations. £
Relaxing the emission guideline by 50 percent would provide greater ^
flexibility with regard to the development of a control strategy, *
however, it would also allow the emission of an additional 66 tons of •
fluoride per year. A five-fold increase in the emission guideline would
be necessary to allow the use of a venturi or a cyclonic spray tower as £
the secondary scrubber in all effluent streams.
The estimated retrofit costs ($666,000 for a 400 ton P205/day ™
plant) are not considered excessive. Annualized control costs amount ft
to 0.52 percent of sales.
The emission guideline would reduce annnual fluoride emissions from 1
GTSP production facilities by 51 percent.
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8-10 |
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8.2.6 Granular Triple Superphosphate Storage Facilities
Fluoride Emission Guideline
2.5 X 10~ gram fluoride (as F~) per hour per kilogram of P^Or in
storage.
Discussion
The fluoride emission guideline for existinq granular triple
superphosphate storage facilities is equal to the SPNSS. In order
to meet this emission level, a typical facility would be required to
remove approximately 90 percent of the fluorides evolved. Only 25
to 35 percent of the industry currently has this degree of control.
Twenty-five percent of the existing facilities are presently uncon-
trolled.
Rationale
It is estimated that 50 percent of the industry would still be
required to add retrofit scrubbers even if the allowable emissions
were increased by 50 percent.
The cost of retrofitting uncontrolled facilities would not vary
significantly with moderate (50 percent) relaxation of the emission
guideline. The major portion of the costs is associated with
refurbishing the building and is exclusive of the control device
itself.
8-11
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I
3. Retrofit costs for uncontrolled facilities ($596,000 for a 25,000
ton storage building) are not considered to be excessive. Such a *
facility would accompany a 400 ton P^Or/day GTSP production facility. •
Annualized control costs, including capital charges, would equal 0.4
percent of sales. •
4. The emission guideline would reduce annual fluoride emissions I'
from GTSP storage facilities by 67 percent.
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8-12 »
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8.3 REFERENCES
• 1. Atwood, W. W., Occidental Chemical Company to Goodwin, D. dated
June 27, 1973. Fluorine Emissions from Submerged Combustion
»
Evaporation of Phosphoric Acid.
2. Crane, George B. Private communication with Teller Environmental
Systems, Inc. New York, N.Y. December 13, 1974.
8-13
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9. ENVIRONMENTAL ASSESSMENT
9.1 ENVIRONMENTAL ASSESSMENT OF THE EMISSION GUIDELINES
I t
' ' 9.1.1 Air
* Installation of retrofit controls similar to those described
<•> in section 6.1.3.1 could reduce fluoride emissions from existing sources
by the amounts indicated in Table 9-1. Emission reductions range
• from 50 percent for granular triple superphosphate production facilities
to 88 percent for run-of-pile triple superphosphate plants. All estimates
m are based on information presented in chapters 3, 5, and 6 of this study.
* The following procedure was used to arrive at the estimates listed
in Tables 9-1 and 9-2. The percentage of existing facilities (or capacity)
R attaining emission levels equivalent to SPNSS was estimated in Chapter 5.
The remainder of the existing facilities were assumed to emit at a rate
I midway between the SPNSS level and a level characteristic of a poorly
m controlled plant. The retrofit models were used as a source of
information regarding poorly controlled plants.
ft Total emissions following the installation of retrofit controls
were estimated by applying the SPNSS level to the entire industry
I which is identical to the lll(d) emission guidelines contained herein.
— All estimates assume a 90 percent utilization of production capacity.
This general approach was altered in certain instances (SPA, DAP,
jj GISP storfge) either to make use of additional information or to com-
pensate for the lack of necessary data.
9-1
-------
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1
As indicated in Table 9-1, an overall fluoride emission reduction of nearly
w
75 percent can be achieved by installation of retrofit controls capable of
meeting the emission guidelines. The correspondinq reduction in
typical fluoride emission source strengths is illustrated by Table 9-2.
I
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9.1.1.1 Atmospheric Dispersion of Fluoride Emissions
A dispersion analysis was made to compare around-level fluoride
concentrations downwind of a phosphate fertilizer complex, before and
after retrofit of controls. The diffusion estimates were based on 30- I
day average fluoride concentrations and extended to distances from the
plant where fluoride concentrations were less than 0.5 pg/m . A 30- £
3
day average ground-level fluoride concentration of 0.5 yg/m causes an _
accumulation of more than 40 ppm fluoride in cattle forage, and this *
concentration in their feed is a damage threshold for cattle. •
The fertilizer complex being investigated represents no actual plant,
but contains all of the units discussed in Section 6.1.3.1 - Retrofit ^|
Models - except the submerged combustion-superphosphoric acid plant.
The model used to calculate emissions from an existing complex after ™
retrofit was assumed to contain an additional new and well-controlled •
UPPA plant. A railroad spur and WPPA storage facilities were also
assumed with which acid could be shipped in or out of the complex. •
Emissions from this complex are not necessarily typical of the
emissions used in the retrofit models of section 6, nor are they the •
same as the source strengths listed in Table 9-2. However, these emis- *»
sions fall within the range of emissions from actual plants. Specific
9-4 §
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fertilizer manufacturing units are pictured in Figures 6.3, 6.4, and
V elsewhere. All of these units were assembled to scale on a plot plan
of the entire complex. From this plot plan the meteorologist could
• measure the distance relationships of sources and of interferences such
H as buildings and phosphate rock piles. The heights of these inter-
ferences were also tabulated. Additional information used is shown in
I Tables 9-3 and 9-4. The former table indicates emissions from the
fertilizer complex having existing mediocre emission controls. The
|| latter table shows the emissions from the same sources after installation
_ of good controls. Since the new WPPA facility of the retrofitted complex
was considered to meet the emission guidelines, its effect is ignored
• in Table 9-4.
The source data indicated that aerodynamic downwash was a problem
I at the facility modeled, particularly for wind speeds in excess of 3 or
H 4 meters per second. At lower wind speeds, plume rise from some of the
stacks could be significant. Plume rise factors were consequently
^ developed, which accounted for the plume rise at low wind speeds and
downwash at higher speeds. Those factors were then incorporated into the
B dispersion estimates.
— The dispersion estimates were made through application of the
' Climatological Dispersion Model (COM). The COM provides estimates of
A long-term pollutant concentrations at selected ground-level receptors.
The model uses average emission rates from point and area sources and a
• joint frequency distribution of wind direction, wind speed, and stability.
I
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One year of monthly stability-wind data from Orlando, Florida were
utilized in the COM dispersion estimates. The climatology of that lo-
cation is representative of that at facilities of concern in this docu-
ment. The COM estimates are typical high 30-day average ambient fluo-
ride concentrations. The results of the analysis are presented in
Table 9-5. A more general review of 5-year summaries of monthly stability-
wind data from the same location verified that the values presented in
Table 9-5 are representative of typical high 30-day average concentrations
for any given year.
Table 9-5 shows that the best technology retrofit controls made a large
reduction in the ground-level fluoride concentrations which had existed when
the mediocre controls were used on the four sources shown. At distances
greater than about 1-1/2 mile, the concentrations do not exceed 0.5 i>g/m3,
even in the most unfavorable months when the emission guidelines herein are
applied.
Table 9-5. ESTIMATED 30-DAY AVERAGE AMBIENT FLUORIDE CONCENTRATIONS
DOWNWIND OF A PHOSPHATE FERTILIZER COMPLEX
Fluoride Sources
Existing Controls
WPPA DAP TSP GTSP
After Retrofit
WPPA DAP TSP GTSP
Estimated 30-Day Average
Fluoride Concentration
1
6
0.8
2
4
0.6
3
3
0.4
5
1.9
0.3
10
1.0
0.1
• 3
yg/m )
15 km
0.5
0.1
9-8
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• 9.1.1.2 Emission Guidelines vs. a Typical Standard
Ten states presently have regulations covering fluoride emissions
| from fertilizer plants in particular and fluoride emissions in
general. Two states, Iowa and Mississippi, limit emissions to 0.4# F/ton
• Pp05 with Montana setting a 0.3# F/ton P205 limit. Iowa also has a
m 100 # F/day maximum emission rate. Virginia and North Carolina have
variable rates based upon production levels. Four states have regula-
• tions based upon ambient concentrations and best control technology.
Florida, the state having the most plants, also has the most thorough
m standard. Table 9-6 gives a comparison of the emission guidelines
m with the Florida standards. In all cases, the typical standard is as
strict or more so than the emission guidelines.
I 9.1.2 Water Pollution
_ Increased or decreased control of gaseous water-soluble fluorides
™ will not change the amount of liquid waste generated by the phosphate
A industry. Most control systems now in use utilize recycled process
(gypsum pond) water as the scrubbing medium thereby eliminating the
| creation of additional effluent. Phosphate fertilizer plants do not need
_ to discharge gypsum pond water continuously. The pond water is re-used in
™ the process, and a discharge is needed only when there is rainfall in excess
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of evaporation. For thi
s reason, the volume of effluent from phosphate
fertilizer plants is almost exclusively a function of rainfall conditions.
|
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EPA effluent limitations
guidelines require that any gypsum pond water
discharged to navigable waters when rainfall exceeds evaporation meet
the limitations in Table 9-7. A two-stage lime neutralization procedure
combined with settling is
Table 9-7. EPA EFFLUENT
Aqueous
Waste
Constituent
Phosphorus as (P)
Fluoride as (F)
Total Suspended
nonfilterable solids
sufficient control to meet these limitations.
LIMITATIONS GUIDELINES FOR GYPSUM POND WATER1
Maximum Daily Maximum Average of Daily
Concentration Values for Periods of
(mg/1) Discharge Covering 30
Consecutive Days
(mg/1)
105 35
75 25
150 50
The pH of the water discharged shall be within the range of 8.0 to 9.5
at all times.
The phosphate industry has voiced concern that the partial pressure
f
• of fluoride out of pond water makes it infeasible in some cases to reach
* SPNSS fluoride limitations with a scrubber using pond water. An equili-
brium fluoride concentration between 5000-6000 ppm seems to be estab-
• Ushed in gypsum ponds - possibly because of a slow reaction between
234
gypsum and soluble fluosilicates. ' ' Even a pond with an apparent fluo-
• ride concentration of 12,500 ppm has fallen within this equilibrium range
• when the water was passed through a millipore filter. The excess fluoride
can be attributed to suspended solids. Pond water containing about 6000
I
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9-11
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I
ppm of fluoride has a low enough partial pressure of fluoride to
allow scrubber vendors to design to meet emission guidelines. In all I
cases, emission guidelines can be achieved with pond water
if a well-designed spray-crossflow packed bed scrubber is used as the |
control device. _
9.1.3 Solid Waste Disposal m
Any solid waste generated by scrubbing fluorides would be in the
form of CaFp or similar precipitates in the gypsum ponds. The amount I
of precipitate formed is negligible in comparison to the amount of
gypsum generated in producing wet process phosphoric acid, a required £
intermediate throughout the phosphate fertilizer industry. An example •
of the relative amounts of each of the solids produced in normal processing
with scrubbers which meet emission guidelires for a 500 Ij
tons/day P90,- WPPA plant.is presented below:
•
Assumptions: |
1. 6427# phosphate rock = 1 ton P90i-. m
I
2. Phosphate rock is 35 weight percent Ca. m
3. Uncontrolled emissions of 58.1 #F/hr are reduced to 0.42 #F/hr Jj
by a scrubber, (See retrofit model WPPA plant, case B).
4. All of the F absorbed by the scrubber precipitates in the |
gypsum pond as CaFg. (See Section 5.2.1, page 5-6).
5. The plant capacity is 500 tons/day P2°5*
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9-12 •
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3Ca1Q (P04)g F2 + 30H2S04 + Si02 + 58H20 + 30 CaS04 • 2H20 (4-1)
. + 18H3P04 + H2SiF6.
This reaction implies: 40#Ca -> 172# gypsum.
I
1500 x 6427 x 0.35 x 172
gypsum produced = _ = 201,510
# gypsum/hr
• 24 x 40
From assumptions 3 and 4:
• F absorbed in scrubber = 58.1 - 0.42 # F/hr
= 57.68 # F/hr
I Ca++ + 2F" + CaF2 I (5-1)
_ CaF, 4- = 57.68 x 78 = 118.4 # CaF9/hr
I ^ ~~38 *
1% increase in solids = 118.4 x 100 = 0.06
201,510
_ This exaaple illustrates that the Increase in solids due only to
• scrubbing fluorides is negligible (0.06X). The disposal of the
9. large volume of gypsum is by depositing in mined-out areas, and by
lagoon ing, followed fry drying and piling techniques. Such piles are
f as iuch as 100 feet above grade in some areas.
I 9.1.4 Energy
Changes in fluoride control electrical power requirements for the
I spray-crossflow packed bed scrubber retrofit models in Section 6 are
_ presented in Table 9-8. Existing fluoride control power requirements
" were estimated from the pump and fan requirements for the assumed existing
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9-13
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I controls in the retrofit models. Power requirements for the retrofit
controls were obtained by adding the power ratings of the specified
™ retrofit fans and pumps to the existing power requirements and sub-
• tracting the power for any fans or pumps removed in retrofitting.
The largest incremental power requirement for fluoride control
• is for GTSP. This can be attributed to installing a spray-crossflow
packed bed scrubber for GTSP storage, a previously uncontrolled source
I in the retrofit model which generates a very large volume of air having
• a small concentration of fluoride. Raising the standard to allow larger
emissions from GTSP storage would not greatly reduce these power require-
K ments. It would only allow the use of a scrubber with a fewer number of
transfer units. A less efficient scrubber would not reduce the volume
| of gas to be scrubbed nor would it greatly reduce the amount of oond
« water required for scrubbing. Only the pressure drop through the scrubber
would be reduced by raising the standard. In other words, raising the
• GTSP storage standard by a factor of two would not reduce the power require-
ments proportionately.
| Incremental increases in phosphate fertilizer processing energy
_ requirements are given in Table 9-9; such increases will vary from
I
m plant to plant. Volumetric flow rates of fluoride-contaminated air
• sent to the scrubbers can vary by a factor of two or three for the same
size and type of plant. Existing control schemes will also influence
• incremental power requirements by the extent to which their pumping
and fan systems can be adapted. Therefore, the numbers presented in
K Tables 9-8 and 9-9 should be considered approximate.
" 9-15
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Fertilizer processing energy requirements presented in Table 9-9
are primarily based upon material in reference (6). The types of
energy utilized by the various processes vary. For example, approximately
50 percent of the energy required in 6TSP processing can be attributed to
the 3 gallons of fuel oil used per ton PpO^ processed while nearly all
the energy used in the submerged combustion process for SPA comes from
natural gas. All processing energy requirements listed in Table 9-9
include electrical power required for rock crushing and pumping.
Table 9-9. INCREASE IN PHOSPHATE INDUSTRY ENERGY REQUIREMENTS RESULTING
FROM INSTALLATION OF RETROFIT CONTROLS TO MEET EMISSION GUIDELINES
Fertilizer process
WPPA
DAP*
SPA*
ROP-TSP*
GTSP*
Existing energy
requirements
(KWH/Ton P205)
225
236
782
152
305
Fluoride control
incremental
energy require-
ments
(KWH/Ton P205)
1.8
8.4
0.4
6.5
25
Percent
increase in
energy re-
quirements
0.8
3.6
0.05
4.3
8.2
*Existing energy requirements figures include energy needed to process WPPA
feed for process.
Annual incremental electrical energy demand for fluoride control is
presented in Table 9-10. These figures are based upon Tables 9-6 and
9-8 along with production statistics in section 3. The total incremental
9-16
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9-17
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electrical energy demand resulting from installation of retrofit con- m
trols- to w>pf pnuss-t™. "ut^el tries; ts- emitvalent to the energy required to
operate one 300 ton/day P205 SPA plant 115 days/yr. It should be em- •
phasized that these numbers can be only approximations. As mentioned
in the discussion of Tables 9-8 and 9-9, individual plant fluoride control |i
energy and power requirements will vary. This variability necessarily •
constrains the accuracy of projections based upon single retrofit models.
I
9.1.5 Other Environmental Concerns
Due to the proposed method of fluoride control, namely, utilization I
of a spray-crossflow packed bed scrubber with pond water as the scrubbing
medium, no other environmental concerns are anticipated. Scrubbing |
fluorides with gypsum pond water produces a closed system effect for •
phosphate fertilizer complexes. Although radioactive materials have been
detected in the wastewater at fertilizer complexes, recycling of the pond I
water to the scrubber is not expected to contribute to this potential problem.
•
9.2 ENVIRONMENTAL IMPACT UNDER ALTERNATIVE EMISSION CONTROL SYSTEMS
Analysis of the data t ase on which the emission guidelines are based |
indicates that only the spray-crossflow packed bed scrubber can meet •
emission guideTinesTrTaTFcases. ROP-TSP plants can use cyclonic
spray tower scrubbers to meet the emission guidelines, but at a higher •
cost than for a spray-crossflow packed bed scrubber (Table 6-44).
Tables 6-37 and 6-40 show that the ROP-TSP standard is the only one I
substantiated by data which allows use of an alternative scrubber design. •
Use of either scrubber design for controlling ROP-TSP plants would result
in similar environmental impacts. Except for ROP-TSP plants, raising •
the emission guidelines to allow use of alternative scrubber designs
would result in a 50 percent to 1000 percent increase in fluoride |
emissions without causing any beneficial environmental impacts. .
"9-18
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I 9.3 SOCIO-ECONOMIC IMPACTS
The phosphate fertilizer industry is generally recognized as a
I capital intensive industry, labor requirements for production work and
• plant supervision are small, compared to plant sales. Usually, those
fertilizer facilities which may be affected by the emission
• guidelines are widely dispersed throughout the United States. Only in
central Florida does the fertilizer industry represent a substantial
<| portion of overall community economic activity and employment, and
M Flor-ida enacted emission standards effective July 1, 1975 which are
at least as strict as the enission guidelines. Therefore, any potential
• plant closures as a result of the implementation of lll(d) regulations
will produce minimal community effects in terms of job losses and sales
fl revenues.
M Retrofitting existing plants for controls should not impede new
plant construction programs. During the years 1973 through 1974, the
• phosphate industry entered an expansionary D';ase with the construction
of several new fertilizer manufacturing complexes. The construction
m rate i3* expected to decrease after 1976 as these new plants come on-
m stream. Installation of retrofit controls will consequently occur during
a period of slack construction activity and should not interruot the
I long-term availability of phosphate fertilizers.
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9-19
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9.5 REFERENCES
1. FEDERAL REGISTER, (41 FR 20582), May 19, 1976, p. 20582. "
2. Teller, A.J. Control of Gaseous Fluoride Emissions. Chemical j§
Engineering Progress. 63:75-79, March 1967. m
I
3. Huffstutler, K.K. Pollution Problems in Phosphoric Acid
Production. In: Phosphoric Acid, Vol. I., Slack, A.V. (ed). M
New York, Marcel Dekker, Inc., 1968. p. 728. •
4. Weber, W.C. and C.J. Pratt. Wet-Process Phosphoric Acid Manu- •
facture. In: Chemistry and Technology of Fertilizers,
Sauchelli, V. (ed). New York, Reinhold Publishing Corporation, I
196U. p. 224.
I
5. Crane, George B. Telephone Conversation with Dr. Aaron Teller,
Teller Environmental Systems, Inc. New York, N.Y. December 13, •
1974. '
6. Bixby, David W., Delbert L. Rucker, and Samuel L. Tisdale.
Phosphatic Fertilizers. The Sulphur Institute. Washington, D.C. |
February 1964. _
7. Rouse, J. V. Letter. In: Environmental Science and Technology.
Easton, Pa. October 1974. I
I
9-20
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
1 REPORT NO.
EPA-450/2-77-005
3. RECIPIENT'S ACCESSION-NO.
'4. TITLE AND SUBTITLE
, Final Guideline Document: Control of Fluoride
j Emissions from Existing Phosphate Fertilizer Plants
5. REPORT DATE
March, 1977 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7 AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
1.2-070
9. PERFORMING ORGANIZATION NAME AND ADDRESS
U. S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The document serves as a text to state agencies in the development of their gaseous
fluoride emission regulations from existing phosphate fertilizer plants. Recommended
emission units are suggested for five production facilities: wet-process phosphoric
acid, diammonium phosphate, superphosphoric acid, triple superphosphate, granular
triple superphosphate production and storage. Information contained within includes
data on the phosphate fertilizer industry and control technology, a discussion of the
guideline emission limitations and the supporting data, and analyses of the environ-
mental and economic impacts of the guideline limits.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
Phosphate Fertilizer Plants
Fluorides
Standards of Performance
Air Pollution Control
c. COSATl Field/Group
I
8. DISTRIBUTION STATEMENT
Unlimited. Available from Public
Information Center (PM-215), EPA
Washington, D. C. 20460
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
274
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
9-21
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