FINAL REPORT



                          ON



           SULFUR DIOXIDE SCRUBBERS



       STONE & WEBSTER - IONICS PROCESS



              CONTRACT NO. CPA 22-69-8O



                          FOR



      DIVISION OF PROCESS CONTROL ENGINEERING



  NATIONAL AIR POLLUTION CONTROL ADMINISTRATION



U. S. DEPARTMENT OF HEALTH, EDUCATION AND WELFARE
                     JANUARY 197O

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                  FINAL REPORT
                      ON
            SULFUR DIOXIDE SCRUBBERS
         STONE & WEBSTER/IONICS PROCESS
            CONTRACT NO. CPA 22-69-80

                      FOR

     DIVISION OF PROCESS CONTROL ENGINEERING
 NATIONAL AIR POLLUTION CONTROL ADMINISTRATION
U. S. DEPARTMENT OF HEALTH, EDUCATION AND WELFARE
                  JANUARY 1970
       STONE & WEBSTER ENGINEERING CORPORATION

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       STONE 8 WEBSTER ENGINEERING CORPORATION
             225 FRANKLIN STREET. BOSTON, MASSACHUSETTS  O21O7
 NEW YORK
 BOSTON
                                January 30, 1970
                                                                      ENGINEERING
Mr. Jonathan P. Earhart
New Process Development Unit
Process Control Engineering Division
National Air Pollution Control Administration
5710WoosterPike
Cincinnati, Ohio 45227

Dear Mr. Earhart:

     In accordance with the  authorization contained in  Contract No. 22-69-80, dated
May 1, 1969, we have made a study to determine the most economical scrubber for use in
the removal of sulfur dioxide from flue gas produced by a coal burning power plant.

     The  scrubber would be specifically designed to operate as part of a system using the
Stone & Webster/Ionics  sulfur dioxide recovery process as described  in the proprietary
Stone & Webster proposal dated July 22, 1968, previously presented to NAPCA.

     The  design described in the S&W proposal was based on removing sulfur dioxide from
the flue gases produced in a coal-fired power station rated 1 ,200 Mw and consisting of four
boilers. The flue gas from one boiler amounts to 880,000 actual cfm at 300 F and contains
0.3 mole  percent  sulfur  dioxide.  Fly ash loading is 0.05 grains per cu ft. The electrolytic
regeneration system will  produce a feed stream to the scrubber system which contains about
4.4 moles of NaOH plus 2.7  moles of Na2SO4 per 100 moles of water.

     The  equipment provided consisted of a tower with water sprays for cooling the flue gas
and  removing some residual fly  ash,  a sulfur dioxide removal section comprised of two
packed sections of Johnstone wood slat packing, an induced draft blower, scrubbing liquor
circulation pumps, and necessary connecting duct work, piping and instruments.

     To determine whether  any other type of scrubber is superior to the Johnstone packed
tower, quotations were requested from 23 manufacturers of various types of gas scrubbers.
Of the quotations received, one in each of the following classes of scrubbers was selected for
estimation:

                          Stone & Webster Ripple Tray tower
                          Floating ball contactor
                          Intalox Saddle packed tower
                          Impingement grid packed tower
                          Venturi contactor
                          Cyclonic contactor

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     An attempt was made to determine the percentage oxidation of sulfites to sulfate for
each type of scrubber. Values from the literature and quoted values from vendors were used.
No positive conclusions regarding degree of oxidation for each type could be reached.

     Investment and  operating costs were estimated for each type  of  scrubber  system
studied. The conclusions reached can be summarized as follows:

         1.   Large  single scrubber installations are  least  expensive to
              install and overall least costly to operate.

         2.   Proprietory  equipment such as venturi, cyclonic and floating
              ball scrubbers is impractical in the S&W/Ionics process at the
              present time. Equipment manufacturers will have to produce
              units with much larger throughput to be competitive with
              packed towers.

         3.   The differences  in large single scrubbers such as packed and
              Ripple Tray towers  are  not  great, although the Johnstone
              wood grid packed  towers showed some advantages over the
              other types.

     For further details, we refer you to the following pages of this report.

                                       Yours very truly,
                                              __
                                       E. G. Lowrance
                                       Project Director

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                        TABLE OF CONTENTS

INTRODUCTION	  1
  SCOPE OF WORK	  1
  DESIGN BASIS	  2
  TYPES OF SCRUBBERS STUDIED	  2
  VENDORS CONTACTED AND REPLIES	  3
DISCUSSION	  4
  PREQUENCH AND FLY ASH REMOVAL	  .  4
  SULFUR DIOXIDE ABSORPTION	  4
    Efficiency of Sulfur Dioxide Removal	  4
    Utilization of Caustic	  5
  OXIDATION	  6
    Literature Search	  7
    Application of Literature Information	10
    Estimated Oxidation for Scrubbers Studied	11
  MATERIALS OF CONSTRUCTION	11
ECONOMIC COMPARISON OF VARIOUS SCRUBBERS
 FOR THE STONE & WEBSTER/IONICS PROCESS	13
  INVESTMENT	13
  SCRUBBER SYSTEM OPERATING COST	14
SULFUR DIOXIDE SCRUBBER SYSTEM COST EVALUATION	15

APPENDIX A - VAPOR PRESSURE OF SO2 OVER SULFITE SOLUTIONS
APPENDIX B - DERIVATION OF ECONOMIC FACTORS

Table 1    LIST OF VENDORS CONTACTED
Table 2    VENDORS QUOTING ON FLY ASH REMOVAL AND QUENCH EQUIPMENT
Table 3    VENDORS QUOTING ON S02 SCRUBBERS
Table 4    SUMMARY OF VENDORS' QUOTATIONS
Table 5    INVESTMENT COMPARISON
Table6    OPERATING COST COMPARISON
Table 7    COST EVALUATION

FIGURE 1  SCHEMATIC FLOW DIAGRAM

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                                  INTRODUCTION
 SCOPE OF WORK

     The National Air Pollution Control Administration (NAPCA) of the U. S. Department
 of Health,  Education and Welfare (HEW) engaged Stone & Webster Engineering Corporation
 to make a study to determine the most economical scrubber for  the removal of sulfur
 dioxide  from flue gas produced by a coal burning power plant. The scrubber would be
 specifically designed to operate as part of a system, using the Stone & Webster/Ionics sulfur
 dioxide  recovery process as described in the proprietary Stone & Webster (S&W) Proposal,
 dated July 22, 1968, which was presented to NAPCA.

     The S&W/Ionics sulfur dioxide recovery process includes a sulfur dioxide scrubber in
 which sulfur dioxide is  absorbed  in a  sodium hydroxide  solution to form  a  sodium
 sulfite/sodium bisulfite solution which is sent to a neutralization stage.* The economics of
 the process are such that a high bisulfite-to-sulfite ratio and a minimum oxidation to sulfate
 are desired.  The installed and  operating costs included in  the  S&W Proposal of July 22,
 1968, were based on using a sulfur dioxide scrubber provided with Johnstone type wood
 slat packing as described in the paper by Johnstone & Singh of March 1937,1.E.C., Vol. 29.

     Since it seemed probable  that an  improved means of scrubbing  might have been
 developed  since  Johnstone's  work  of 1937, this study  was authorized to accumulate,
 organize and report pertinent engineering information on various types of scrubbers which
 would be  technically feasible  for  use as a chemical contactor in the S&W/Ionics sulfur
. dioxide removal and recovery process.

     The S&W/Ionics Process  underwent  pilot plant  tests during  1967  at  the Gannon
 Station  of Tampa  Electric Co.  in  Tampa, Florida, where the operation as a whole and
 critical components were  evaluated, using actual flue gas from a boiler fired by pulverized
 coal. The pilot unit was sized to process about 200 cfm of flue gas containing approximately
 0.25 volume percent sulfur dioxide.  The equipment included a flue gas quench which cooled
 the gas  to about 120 F and removed most of the fly  ash and which was followed by an
 absorber. Since our primary purpose was to evaluate the electrolytic cell, only a  Venturi
 type scrubber and later a spray type  scrubber were tested. Figure 1 illustrates the flow.

     The scope of the study  which  is described in this report did  not allow time or money
 for any  experimental work.  It is anticipated that the results of the study will narrow the
 selection of scrubber types to  one or two  and that  some  experimental work  may be
 necessary before the detailed design  of a prototype begins.
 *The neutralized spent liquor is then regenerated in an electrolytic cell for reclamation of
  the caustic for reuse in the process.

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DESIGN BASIS

    The design described in the S&W proposal was based on removing sulfur dioxide from
the flue gases  produced in a coal-fired power station rated  at 1,200 Mw and consisting of
four boilers. The  flue gas from each boiler amounts to 880,000 actual cfm at 300 F and
contains 0.3 mole  percent sulfur  dioxide. Fly ash loading is 0.05 grains per cu ft. The
electrolytic regeneration system will produce a feed stream to the scrubber system which
contains about 4.4 moles of NaOH plus 2.7 moles of Na2 SO4 per 100 moles of water.

     The equipment provided consisted of a tower with water sprays for cooling the flue gas
and removing  some  residual fly  ash, a sulfur dioxide removal section comprised of two
packed sections of Johnstone wood slat packing, an induced draft blower, scrubbing liquor
circulation pumps, and necessary connecting duct work, piping and instruments. Because of
the low gas pressure drop in the system, the induced draft fan was placed at the outlet of
the sulfur dioxide scrubber.

TYPES OF SCRUBBERS STUDIED

     For the present study  of sulfur dioxide scrubbers,  the same general arrangement of
equipment has been retained except that the fan is located  upstream of the quench and fly
ash removal  equipment because of the  higher pressure drop  associated with most of the
other scrubbers studied. This requires handling a larger volume of gas at 300 F, but avoids
corrosion problems since the flue gas is above its water dew point.

     To determine whether  any other type of scrubber is superior to the Johnstone packed
tower, quotations were requested from 23 manufacturers of various types of gas scrubbers.
Of the quotations received, one in each of the following classes of scrubbers was selected for
estimation:

                           Stone & Webster Ripple Tray tower
                           Floating ball contactor
                           Intalox Saddle packed tower
                           Impingement grid packed tower
                           Venturi contactor
                           Cyclonic contactor

     In some cases, the quench section  and  the  absorption section use the same type of
scrubber, but occasionally a combination was used. In one case, for example, a spray quench
followed by a Stone & Webster Ripple Tray tower was used.

     An attempt  was made to select equipment which would achieve  90 percent sulfur
dioxide removal. Since no supporting data were supplied by the vendors, at least two actual
contact stages are provided in all cases.

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VENDORS CONTACTED AND REPLIES

     Table  1 lists the vendors contacted and indicates those who declined to quote for one
reason or another. Generally, those who declined to quote stated that the gas volume to be
handled was too large for their equipment. Of the 23 companies contacted, nine declined to
quote and one (Research-Cottrell, Inc.) quoted on the fly ash removal stage only. Thus, 13
quotations plus the S&W Ripple Tray design were left for consideration.

     Since  a 90 percent  sulfur dioxide removal was a necessary requirement of this
evaluation,  only those vendors offering a minimum of two contact stages were considered as
being  acceptable even  though  no supporting data  were  supplied by the  vendors to
substantiate this selection.

     Table  2 shows the type of equipment quoted for the quench/fly ash removal section.
The type of equipment quoted for the sulfur dioxide absorption section is shown in Table 3.

     The UOP Air Correction Division declined to quote because they believe that low
liquid velocities and  very high retention times are required in producing a liquor high in
bisulfite. This is in  opposition  to the operating principle of  their Turbulent Contact
Absorber (TCA) scrubber.

     Most of the vendors offered to test their equipment  or to  cooperate in test work
preliminary to a design of a prototype unit.

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                                   DISCUSSION
PREQUENCH AND FLY ASH REMOVAL

     Flue gas leaving the electrostatic precipitators will normally be at about 300 F and
about 0 psi gage. Fly ash loading is expected to be about 0.05 grains per cu ft. Expected size
distribution of the fly ash is as follows:

                         Size, Microns             Wt %
                              0-10                 45
                             11-20                 23
                             21-45                 20
                          45 and over               12

     An inspection  of the proposals received shows that quenching of the flue gas from
300 F to about 130 F can be accomplished. However, only one vendor offered a guarantee
on the extent of cooling.

     The extent of  fly ash removal is less clear. Claims of the vendors varied from 90 to
99 percent  removal  of the  contained fly ash to  no estimate at all.  The vendor with the
highest rate offered  removal of 99 percent of the fly ash over  1 micron in size. Supporting
data were not submitted by  any vendor. We believe some ash will pass through the quench
section and will be captured in the sodium sulfite/sodium bisulfite solution. Thus, filtration
will be required before the  solution can be sent to the electrolytic cells. Therefore, some
incremental increase in investment and operating costs will result if fly ash removal  in the
quench section is lower than expected. However, due to the indefinite nature of the claims,
this factor was not included in our estimated costs for this study.

SULFUR DIOXIDE  ABSORPTION

Efficiency of  Sulfur  Dioxide Removal

     To meet local air pollution standards that are being proposed, it is necessary to reduce
the sulfur  dioxide  concentration in flue gas to a value equivalent to firing coal with
1 percent sulfur. For a 4 percent sulfur content coal, this would be equivalent to removing
75 percent  of the sulfur dioxide produced. Since the  S&W/Ionics process recovers sulfur
dioxide as a salable  product, we have based  our designs on a recovery of 90 percent of the
sulfur dioxide in the flue gas. Based on a sulfur dioxide concentration at the outlet  of the
electrostatic  precipitators  of  0.3 volume percent or 3,000 ppm, this would result in a
reduction to  300 ppm by  volume. This  high  recovery not only adds to the salable sulfur
dioxide but also permits the utility to meet more rigid standards which may be imposed in
the future by  local or Federal authorities.

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     Calculations based on data developed by Johnstone and Singh22 indicated that about
8 ft of slat packing would be required for this service. Since there is insufficient fresh
caustic solution to wet the packing adequately, recirculation of scrubbing liquor is required.
Thus, we have divided the packing into two stages of 6 ft each, with trap-out trays and
recirculation pumps for each stage. Johnstone and Singh data indicated that, for the wood
slat packing configuration used, the height of a transfer unit was approximately 1.6 ft in this
service.  We have  provided 7.4 transfer units as compared with  5.0 units which we have
calculated as the required amount.

     We do not  have a method for comparing  the performance of Johnstone wood slat
packing and the  other types of contactors offered by the vendors solicited. None of the
vendors supplied  information  to substantiate  the  claims  for  the  performance  of  his
equipment. Most vendors believed that one or, at most, two stages would be adequate. Our
own calculations indicate that two packed sections would be required to obtain 90 percent
removal, with  three packed sections needed for 95 percent removal.  One contacting stage
would  not  be adequate because  of the high vapor pressure of sulfur  dioxide above bi-
sulfite  solutions.  Most vendors have  offered  to do test work or to  cooperate in test
work to determine the number of contacting  stages required. Such test work could be
carried out at vendors' laboratories or in cooperation with a utility. Discussion of a testing
program has been deferred until a prototype unit  is under consideration.

Utilization  of Caustic

     The electrolytic  regeneration system  will  produce a feed to the absorption system
which will  contain about 2N or 8 wt % sodium  hydroxide (pH of about 14). Since all the
scrubbers  being  studied  require  recirculation  of absorption liquor  in  order to  provide
adequate liquid loading, this caustic feed will be added to recirculated liquid at  the top
stage. The amount  of free caustic in the combined liquid to the top stage is a function of the
amount of recirculation to the stage and the amount of sulfur dioxide absorption in the
stage.

     The principal reactions that occur in the absorber are as follows:

                      SO2 + H2O  -  H2SO3
                      CO2 +H2O  -  H2CO3
                      2 NaOH + H2CO3 *? Na2CO3 + 2 H2O
                      Na2CO3 +H2CO3  ^ 2NaHCO3
                      2 NaOH + H2 SO3 - Na2 SO3 + 2 H2 O
                      Na2 SO3 + H2 SO3 ^ 2 NaHSO3
                      Na2CO3 +H2SO3 -»• Na2SO3 +CO2t + H2O
                      NaOH + NaHSO3 ->•  Na2 SO3  + H2 O

     It is expected that there will be little or no free caustic in the combined feed to the top
section. This stream  will  contain  mostly Na2CO3 and Na2SO3. As the liquid flows down
through the tower, CO2 will be displaced by SO2 and Na2SO3  will be partially converted to
NaHSO3.

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     The vapor pressure of sulfur dioxide over neutral sodium sulfite is essentially zero,
while over mixtures  of sulfite/bisulfite the vapor pressure is a  function  of the sodium
bisulfite  concentration. Johnstone23  found it  convenient to  characterize the relative
amounts of sulfite and bisulfite in a solution by using the ratio of S/C or moles of dissolved
SO2 per mole of available sodium ion (S/C = 0.5  for Na2SO3 ; S/C = 1.0 for NaHSO3). The
relationships  between the  vapor pressure  of sulfur  dioxide  and  S/C  are discussed in
Appendix A.

     The absorption system should have sufficient contact stages to produce a liquor which
contains a  high ratio of S/C and should have adequate contacting in each stage to approach
equilibrium between gas and  liquid.  It  is also  essential  to  provide a system  in which
entrainment from stage to stage is minimized. A ratio of S/C of 0.9 or higher in the scrubber
product is  required to achieve the most economical cell operation. The pH of this solution
leaving the final stage should be about 3.5.

     None  of the vendors who submitted proposals offered any data that would be useful in
determining the extent of conversion to sodium bisulfite. Actually, not much information
could be  expected  from the vendors  since  caustic or sodium  carbonate has  not  been
reported in commercial use to extract sulfur dioxide from flue gas. Recovery of sulfur
dioxide from gases produced by combustion of sulfur is practiced in  the paper industry as
part of a magnesium sulfite pulping process, but magnesium hydroxide, rather than sodium
hydroxide, is used as  the absorbent. In other sulfite pulping processes, either water or an
alkaline  solution is  used to absorb sulfur  dioxide  from  the gases.  In these cases sulfur
dioxide is present in much higher concentrations than those appearing in  a flue  gas from a
coal burning power plant.

     If vendors could have provided data supporting the claimed sulfur dioxide removal, the
ratio of S/C could be calculated.  It is our opinion that none of the claimed figures can be
used in a system where separate recirculation to each contact stage is used.

     Since  many of the vendors have test facilities, it should be possible to determine the
maximum  concentration of bisulfite during  the design stage for a prototype unit, but until
this is done we will not be able to  evaluate this factor.

OXIDATION

     The contract requires that an estimate  of the percentage of sulfur dioxide transferred
from gas to liquid which is  oxidized shall be made for each scrubber type being considered.
Oxidation  is defined as the percentage of net sulfur dioxide absorbed that is converted from
sulfite  or bisulfite to  sulfate. Oxidation is  an important  factor in the economics of any
scrubber type being  considered,  since  increased oxidation results in  increased electrical
energy  requirements.  Consequently, a  scrubber with excessive  oxidation, by  virtue of
oxidation alone, could be economically unattractive.

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     To predict or estimate oxidation percentages, the relationship between scrubber design
parameters and oxidation must be known. The best but most expensive way to obtain this
information would  be to run tests on various scrubber types.  However,  due to time and
expense,  testing  was not   possible for  this  study;  thus,  our  inquiries  to  scrubber
manufacturers requested that they supply us with any data they had on oxidation. We also
made an extensive literature search for such information. None of the vendors was able to
give  us any specific information on oxidation, although one, The Norton Company, stated
that  oxidation would not exceed 2 percent.

Literature Search

     Our  literature  search had  two objectives. The first  objective  was to  search  for
information  concerning  the  mechanism  of absorption of  oxygen  into sodium sulfite
solutions and those factors affecting that absorption. The second objective  was to relate the
absorption mechanism to  the chemical  reaction and  to see how factors  which affect  the
reaction also affect the absorption into the liquid. Once this information had been collected,
the task of relating it to absorber types could be done.

     Absorption  Mechanism   and Chemical Reaction.  The  literature  appears to be  in
agreement on the mechanisms of  absorptions of oxygen into sodium sulfite solutions. It has
been proved  that the gas film resistance in this  transfer is negligible.4'6 Thus, the oxygen
transfer mechanism can be separated into two individual rate processes:

          1.   Transfer of gas from gas-liquid interface to the bulk of the
              liquid

          2.   Chemical reaction of O2 with sulfite

     However, it  has also been shown by Wartman18 that the oxidation of solutions of
normal sulfites is limited by  the .rate at which solutions will absorb oxygen. In Wartman's
tests, all  carried out at 25 C,  25 cc of distilled water were saturated with pure oxygen and
then 2 cc of 3 molar ammonium sulfite were added, mixed, and allowed to  stand for a given
period of time. HC1 was then added to stop further oxidation and the solution was analyzed
for sulfates. The test was repeated for different time intervals varying from 7 sec to 3 min.
Bisulfite  solutions were also tested in this manner. All dissolved oxygen was consumed by
normal  sulfite within  7 sec,  whereas with  bisulfites  the reaction proceeded  much more
slowly. Wartman also measured the amount  of oxidation occurring when pure  oxygen was
bubbled through a solution of normal sulfite. By increasing the contact surface between gas
and  liquid, Wartman  found  that  the rate of oxidation could be greatly increased. It then
follows from  this work  that the rate-limiting oxygen  transfer mechanism becomes  the
transfer of gas from gas-liquid interface to the bulk of the liquid.

     Qualitatively, there are certain variables which affect the diffusional transfer or rate of
absorption of oxygen.4>6-9 These  are:

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          1.   Area of contact
          2.   Time of contact
          3.   Turbulence
          4.   Concentration gradient (magnitude of driving force)
          5.   Temperature

     Even if there were no chemical reaction in the overall mechanism, the following factors
which   would   affect   chemical   reaction   also  would  affect  the  rate  of
absorption:2'3'5'6-8'10'14'17

          6.   Solute concentration
          7.   pH
          8.   Light intensity
          9.   Catalysis

     Our  literature search resulted in information showing how the above variables affect
direction and intensity in the oxidation of sodium sulfite to  sodium sulfate.

     Area of Contact.  The  literature18 states that oxidation increases as the area of contact
increases.  The oxygen transfer  mechanism is a function of the transfer of gas from the
gas-liquid  interface to  the bulk of the liquid and can be expressed as:

                                 rd=kL(A)(Ci-cL)                              (1)

where

     rd        =    rate of oxygen absorption, grams O2 absorbed/(hr) (liter)

     kL       =    liquid-film mass transfer coefficient, grams O2 transferred/(hr) (sq cm)
                   (unit concentration difference)

     A        =    transfer area, (sq cm)

     (Cj — CL ) =    driving force of gas across interface into bulk of liquid, (grams/liter)

     We have estimated that 5 percent oxidation would be  expected from a Johnstone type
scrubber,  and the contract states that this figure should be used as a base case. On this basis,
the effect of gas-liquid contact area on other types of scrubbers can be expressed as follows:

_         .,  ..      ,_,           ., ..   J  Contact area  of new scrubber   \
Percent oxidation = (Base case oxidation)!-^—-—	^7—	——r-r— )       (2)
                                       \ Contact area of base case scrubber /

     It  must be kept in mind, however, that this estimate will be accurate only to the extent
that the base case figure and the  determination of the area of contact are exact.

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     Time  of Contact.  The literature made  no definitive  statements on time of contact.
However, it did imply that as time of contact increased, oxidation increased. Unfortunately,
there was no basis in the literature to show a quantitative relationship between the two.

     Turbulence (Agitation). Since absorption is controlled by liquid film resistance, it can
be inferred4'6'9'15  that agitation of the liquid phase enhances the rate of mass transfer and
increases oxidation. However, as in the case of time of contact, there was no basis in the
literature for the development of a quantitative relationship.

     Concentration Gradient (Magnitude of Driving Force).  Referring to Equation 1 :

         rd    =    kL(A)(Cj-cL)

         Cj    =    concentration of oxygen at the interface, (grams/liter)

         CL   =    concentration of oxygen in the bulk of the liquid, (grams/liter)

     The literature4'9'15  defines the term (c; —  CL)  as the driving force for absorption.
Since oxygen solubility follows Henry's Law very closely and since the gas film coefficient is
negligible, the partial pressure of oxygen at the interface is the same as that in the bulk of
the gas.
          PQ   =    partial pressure of solute in gas phase
          HO  =    Henry's law constant


     Also,  since  the chemical  reaction is very  rapid, CL =* 0  and the  driving force is
approximately  equal to the concentration of oxygen at the interface. It can be seen from
the above that  by decreasing the oxygen content in the flue gas,  oxidation should decrease
proportionately.

     It should be emphasized  that operators of boiler plants using any process affected by
oxidation should try to maintain excess air at the minimum consistent with good boiler
operation. The exact values of excess air will depend on the type of .coal and the design of
the boiler system.

     Temperature. Although published data on the solubility of oxygen  in various solvents
indicate  that, as temperature  increases, solubility  of oxygen decreases, Cooper et al6 state
that the oxidation rate of sodium sulfite solutions increases by a factor of 2  when  the
temperature is  increased from 32 F to 50 F. He also found that  in the range of  68-104 F,
the rate  increases  more slowly with increasing temperature. Our pilot plant data indicate
that as temperature was increased in the range of  100-132 F, oxidation increased, although
we found  very little  change in oxidation with  temperature  from  132 F  to  140F. A
quantitative explanation for these findings is not available.

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                                          10
     Solute Concentration.  The  literature  is not  very  clear on this subject.  Several
sources10'18 contend that oxidation rate decreases as solute concentration increases. Other
sources6'8'19  indicate that  oxidation proceeds  at  a  rate independent  of sulfite-ion
concentration over concentration ranges as wide as 0.35-1.0 normal.

     pH. One literature source1 ° stated that oxidation apparently increased as acidity of the
solution increased. This position is contested by several sources5'6'8'13  who contend that
oxidation is greatest in a neutral or slightly alkaline solution. We are inclined to accept the
views of the latter since Wartman18 noted that the oxidation of bisulfite, which has a pH of
about 3.5, was slower than for neutral sulfite.

     Light Intensity.  It has been established that  oxidation of sodium sulfite solutions to
sodium sulfate  is a  chain reaction which  is  highly  light  sensitive.2'8'14 However, the
literature  fails to  provide  an  insight as to relative increases  in oxidation rates due to the
extreme light sensitivity  of the reaction. This is not a factor  in our process  since our
equipment is all metal. However, since light is a factor, laboratory tests done in glass might
have shown higher oxidation than should be expected in a commercial plant.

     Catalysis. It has also been shown that oxidation of sodium  sulfite solutions is highly
susceptible to both positive and negative catalysis. The heavy, variable-valence metal ions,
such as Fe, Cu, Co, Ni and Mn have a powerful positive catalytic effect.2'3 >5 ;8>14 ]17 There
are inhibitors which  tend to  reduce activity of  these metal catalysts. Organic alcohols,
phenols and potassium cyanide  have a very  strong  negative effect.2'8'10'14 However, if
trace amounts of NOX are present  in the gas, oxidation becomes very difficult to inhibit.14
A mechanism1 has been  proposed to explain both positive and negative catalysis, but has
not been proved. The literature on catalysis as it affects oxidation yields little information
which is quantitatively applicable.

Application of Literature Information

     Of the nine  identifiable  factors affecting  oxidation of sodium  sulfite solutions to
sodium sulfate,  six are  independent  of scrubber  design  parameters. Temperature, solute
concentration, pH, and light intensity will be common to all scrubber types. Concentration
gradient and catalysis (positive) will be a function of boiler operations. Negative catalysis, if
applicable, could be used in any scrubber, regardless of its type. This leaves only the factors
of area of contact, time  of contact, and turbulence as variables in the various scrubber
designs.

     Time of contact and  turbulence, while unique  to each scrubber type,  were not
determinable from the information provided. Therefore, only area of contact has been used
in this report to estimate oxidation  rates for various scrubber types.

     As shown  in Equation 2. these estimates will  be only as accurate as  the  base case
oxidation percentage and the determinations  of area  of contact. Even in pilot plant testing,
Johnstone experienced wide ranging oxidation percentages. Because of this, oxidation rates
shown in  this  report may be very inaccurate.  It would seem, then, that  testing programs are

-------
                                        11
justified  to generate good design information on  various scrubber types. This cannot  be
done within the scope of this report but could be  a prerequisite to the final selection of a
scrubber design for application in a commercial plant.

Estimated Oxidation for Scrubbers Studied

     The results of pilot  plant work and studies of Johnstone's work suggest that oxidation
of sulfite to sulfate over  Johnstone wood slat packing will be approximately 5 percent. We
have attempted  to  make  predictions of the  percentage of sulfite oxidized in each of the
several types of scrubbers studied. The  figures are shown in Table 4. Using the wood slat
packing  as a  base, with  5 percent oxidation expected, we estimate the  other types  of
scrubber would produce the following results:

                                                            Percent
                  Type of Scrubber                         Oxidation
              Wood slat packing                                5
              Intalox Saddle packed tower                    10-15
              Stone & Webster Ripple Tray                     8-10
              Glitsch grid impingement packing                 3-5
              Cyclonic contactor                               2-5
              Floating ball contactor                           2-5
              Venturi contactor                               10-15

     All  except the venturi  scrubber  are  based  on a contact area relative to  wood slat
packing.  Since no  suitable method was found  to determine  the  surface area of liquid
droplets  for the venturi  contactor, we  have  used  a value reported for  a venturi unit not
quoted (private communication).

     The Norton Company 'had stated that oxidation would not exceed  2 percent, whereas
calculations based  on surface area indicate  15 percent. Since Norton's value  is based  on
different operating conditions, it would  require testing under our conditions to  determine
what the true value would be.

MATERIALS OF CONSTRUCTION

     The sulfur  dioxide  recovery pilot  plant in Tampa was constructed of materials that
were available and thought to be  suitable from a corrosion standpoint. The quench tower,
the quench water pump casing, impeller shafts and wearing rings were 316 stainless steel.
The scrubber  recirculation pumps were also stainless steel. The absorption  section was
resin-impregnated fiberglass. Piping was stainless steel or polyvinyl chloride. The blower was
resin-coated carbon steel. After several months of  operation, the fiberglass venturi scrubber
was replaced,  because of high oxidation rates, with a 3 stage plexiglass tower using plastic
spray  nozzles  for  atomization   of the  recirculated  sulfite  solutions.  The  scrubber
recirculation pumps were replaced with polyethylene pumps at the same time.

-------
                                        12
     Operation of the pilot plant over a four month period showed that stainless steel was
attacked slightly in the quench system.  Thus, a better choice would be a nonmetallic
material or rubber lined steel. As long as there is no carryover from the quench zone, mild
corrosion  would  not affect  the operability of the system. However,  carryover would add
metallic products of corrosion and dissolved metal ions from the fly ash to the absorption
circuit and would eventually form metal hydroxides which must be removed from the feed
stream before  it enters  the  electrolytic cells. Because  of problems associated  with this
possibility, lined equipment is  a  virtual  necessity.  The absorption section and internals
should also  be constructed of or lined with nonmetallic material. This arrangement would
favor designs using nonmetallic packings assuming that nonmetallic or coated supports and
distributors  could  be  fabricated.  Designs with large exposed  metal  surfaces,  such as
multivane cyclonic contactors, would be more difficult to coat and would experience more
erosion from particulate matter and subsequently more corrosion.

     We have relocated  the blower  to the  inlet side of the quench tower where hot gas will
be handled and special materials for the blower are not required. This will require a larger
blower, but will eliminate the structure previously required to support the blower and will
make maintenance easier and less expensive.

     Piping  should also  be  constructed of or lined  with  nonmetallic material. Polyvinyl
chloride piping was satisfactory for the pilot plant. Epoxy resin fiberglass should be suitable
for very large piping.

     Duct work for the hot gases would be of carbon steel but should be lined or coated
with nonmetallic coating after the quench section.

-------
                                       13
               ECONOMIC COMPARISON OF VARIOUS SCRUBBERS
                  FOR THE STONE & WEBSTER/IONICS PROCESS
INVESTMENT

    The cost of a scrubber system based on the work of Johnstone was estimated, to serve
as the  base  cost of the scrubber system in the S&W/Ionics sulfur dioxide removal and
recovery process. The estimate was made for a four boiler 1,200 Mw station. It included:

         1.    Duct  work required  to take  hot  flue gas from  existing
              precipitators to  quench devices,  which would  also act as
              solids scrubbers

         2.    Four gas quenchers

         3.    Four two stage sulfur dioxide scrubbers

         4.    Fans to provide a pressure boost equal to the overall system
              pressure loss

         5.    Duct  work  to carry the flue gas from the scrubbers back to
              the stack

         6.    All necessary pumps for quencher and absorption sections to
              provide liquid  flows as required for each unit

         7.    Fired reheaters in the quenched, sulfur dioxide cleaned gas to
              provide enough reheat to prevent condensation in  the stack

         8.    Construction costs and  Contractor's field costs,  engineering
              burdens, and fees

    Investment costs were estimated for each of the other six types of scrubbers for which
manufacturers supplied information.  Each  estimate  considered the  same  eight  cost
categories shown above. In addition to these items, the effect of oxidation on the number of
cells required to process sodium  sulfate was estimated and, depending on whether the new
design  was more or  less prone to oxidation as compared to the Johnstone type, a capital
adjustment was made to the estimate for each type of scrubber.

    Where oxidation is shown as a range, the lowest estimated  level was used to compute
the investment penalty or credit.

    The estimates for  the seven types of scrubbers are shown in Table 5. All six of the
scrubber systems  have  been estimated to cost  more than the Johnstone based system

-------
                                       14
originally used by S&W in its proposal  to NAPCA. The Johnstone, Glitsch 'grid, Intalox
Saddle and S&W Ripple Tray systems can be scaled up to the point where only one dual
purpose, quench, two stage scrubber tower need  be built for each boiler. Since only one
tower is required for each boiler, the cost of duct work for these systems is significantly
smaller than the cost of duct work in the more complex venturi, cyclonic, and floating ball
systems.  ;

SCRUBBER SYSTEM OPERATING COST

     One of the  major operating costs in the scrubber systems is the cost  of power for the
flue gas fans which are used to overcome the sulfur dioxide scrubber system pressure drops.
The venturi system, while it has a lower AP in the gas stream  than the Johnstone system, uses
the quench and absorption fluids as drivers to boost pressure through the scrubbing device.
In spite of this interesting operational characteristic, the total energy required for fans and
fluid pumps in the venturi system is slightly higher than  that required by the Johnstone
unit. All of the  other systems studied also have a higher  energy cost  than the Johnstone
system.

     While the oxidation levels in all of the scrubber types studied can only be estimated at
this time, it would appear that the cyclonic (Pulverizing Machinery) and floating ball (Buell)
could well generate lower  oxidation levels than the Johnstone type.  The Glitsch system
might also offer slight reductions as compared to the  Johnstone unit. In addition to the
operating cost associated with pressure drop in the scrubber system, a sum would be needed
to cover the operating cost of an additional (or reduced) number of cells  required to cope
with estimated increases (or decreases) in the oxidation level characteristic of each type.

     Maintenance costs were assumed to be 2 percent of the installed cost.

     A summary of the operating costs is shown in Table 6.

-------
                                       15
            SULFUR DIOXIDE SCRUBBER SYSTEM COST EVALUATION
     The basis of evaluation  for this study was the net present value of the cash flows for
each type of scrubber over a 15 yr period, using a discount factor of 6 percent. The capital
return  factor used  was 17.50 percent. This includes bonded debt cost, depreciation on a
5 percent straight-line basis,  local taxes and insurance,  and utility return on equity after
taxes (see Appendix B).

     Since the construction period for recovery plants will be short,  we have assumed that
the total differential investment will be made in the first year of operation. This assumption
will tend to decrease the effect of capital cost and overemphasize the value of operating cost
savings. The formula used,  10.288 (0.1750 A Investment + A Operating) equals the  15 yr
evaluated cost of the scrubber. The Johnstone unit  15 yr evaluated cost is zero. All of the
other units are considerably more expensive than the Johnstone unit. Based on the estimates
made,  it  would  appear  that  only  the  Glitsch grid  packed  tower would  offer any
competition to the Johnstone system proposed by S&W for inclusion  in an add-on sulfur
dioxide recovery situation suggested in our proposal to NAPCA.

     The evaluated  comparative costs of  the six  types  of scrubbers studied are shown in
Table 7.

     Until the manufacturers of venturi, cyclonic, and floating ball units  can produce very
large single units, the evaluated cost of such units makes their use in the S&W/Ionics process
impractical.

-------
                                  APPENDIX A
              VAPOR PRESSURE OF SO2 OVER SULFITE SOLUTIONS
     Johnstone22 found that his  experimentally determined values for the equilibrium
vapor pressure of sulfur dioxide over solutions of sodium sulfite/sodium bisulfite were well
correlated by an equation of the following form:

                              p    _„     (2S-C)2
                               so2
(C-S)
where
     P        =   vapor pressure of SO2 (mm. Hg.)
      o \j 2

     S        =   total concentration of dissolved SO2 in the form of sulfite and bisulfite
                  (moles per 100 moles of water)

     C        =   total concentration of "available" Na+, moles per 100 moles of water

     M        =   constant which depends only on temperature

Sodium  ions which are in the form of Na2SO4 are not "available" to react with SO2. For a
solution which  contains  4.4 moles of NaOH plus 2.7 moles of Na2SO4 per 100 moles of
water, S = 0 and C = 4.4. As sulfur dioxide is added to such a solution, S increases and C
does not change.

     Johnstone,  Read and  Blankmeyer12  give  the  following relationship  between  the
constant M, and the absolute temperature in degrees Kelvin:

                             log,0 M = 4.519- 1987/T

If it  is  assumed that the scrubbing liquor  which is  in contact with the  flue gas has a
temperature of 130 F, then M = 0.0452. Exhibit 1 is a plot of Pso  versus the ratio S/C (for
NaOH, S/C = 0; for Na2SO3, S/C - 0.5; and for NaHS03, S/C = LO). The relative positions
of the lines for C = 4.4 and for C = 8.0 (near saturation) show why the attainment of a ratio
of S/C of 0.9 or higher requires that a relatively dilute solution of NaOH be used.

-------
                      VAPOR PRESSURE OF SO2 OVER NaHSO3 - ^803 SOLUTIONS
                          asm
4000
3500
Temperature..= 130 F
C = moles Na+/100 moles H20
S = moles SO2/100 moles H20
                                                                                                    m
                                                                                                    X
                                                                                                    CD

-------
    CALCULATED VALUES OF Pg0  USED FOR EXHIBIT 1
        so
                         MC
                       7.6 x 1CT4
                  (2S/C- I)2
                   (1 - S/C)
                  At 130 F, M = 0.0452
S/C
(AtC=4.4)Pso  (ppm)
(AtC=8.0)Pso  (ppm)
0.60
0.65
0.70
0.75
0.78
0.80
0.82
0.84
0,86
0.88
0.89
0.90
0.91
0.92
0.93
0.94
26
67
140
262
373
471
595
756
969
1260
1447
1675
1955
2308
2765
3377
48
122
254
476
678
856
1083
1375
1762
2290
2632
3045
3555
—
—
	

-------
                                  APPENDIX B

                     DERIVATION OF ECONOMIC FACTORS
1.    Annual Capital Return Factors

     Bonded Debt, 60% 1 at 6%                                            (3.6%) (I)
     Depreciation, 20 yr Straight Line                                       (5.0%) (I)
     Local Taxes and  Insurance                                            (3.0%) (I)
     Utility Return on Investment
      40% equity at 7% allowable after tax                                  (2.8%) (I)
     Federal Tax (52.2% rate)                                              (3.1%) (I)
         Total Return on Annual Basis                                    (17.50%)(I)

2.    Annual Cost Differential of Any Process — Johnstone as Base

     Annual cost of operation will have two components:

     A.   Return factor which will be 17.50 percent of differential
         investment between Johnstone and other types

     B.   Operating Cost Component which will be differential
         between Johnstone and  other types

     If it is assumed that the load  factor on the recovery plant in later years, i.e., 10 through
15, is equal to the early years, i.e.,  1 through  5, the present worth of any alternate is equal
to   the  discounted sum of (0.1750AI + A Operating)  over  a 15yr  period when the
expression is calculated for the first year. The discount factors when summed equal  10.288.

-------
                                REFERENCES

                          STUDY OF SO2 SCRUBBERS
            NATIONAL AIR POLLUTION CONTROL ADMINISTRATION
 1.  Aerojet-General Corp.. "Applicability of Aqueous  Solutions  to the Removal of SO2
    from Flue Gases" (Report S-4850-01-2), Contract PH86-68-77

 2.  Backstrom, H. L. J., "The  Chain-Reaction Theory of Negative Catalysis," Journal of
    the American Chemical Society, 49, 1460, 1927

 3.  Barren, C. H., and O'Hern, H. A., "Reaction Kinetics of Sodium Sulfite Oxidation  by
    the Rapid-Mixing Method," Chemical Engineering Science, 21, 397, 1966

 4.  Bartholomew, W. H., Karow, E. O., Sfat M. R., and Whilhelm, R. H., "Oxygen Transfer
    and Agitation  in Submerged  Fermentations," Industrial and Engineering Chemistry,
    42,1801,1950

 5.  Betz, W. H., and  Betz, L. D., "Oxygen Removal  with  Na2SO3,"  Technical  Paper
    No. 114

 6.  Cooper. C. M.,   Fernstrom, G. A.,  and  Miller, S. A.,  "Performance  of  Agitated
    Gas-Liquid Contactors," Industrial and Engineering Chemistry, 36, 504, 1944

 7.  Frankenberg, T. T., "Removal of Sulfur from Products of Combustion," API Preprint
    No. 53-65, May 12, 1965

 8.  Fuller, E. C., and Crist, R. H., "The Rate of Oxidation of Sulfite Ions by Oxygen,"
    Journal of the American Chemical Society, 63, 1644, 1941

 9.  Hixson, A. W.,  and Gaden, E.  L., Jr., "Oxygen Transfer in Submerged Fermentation,"
    Industrial and Engineering Chemistry, 42, 1792,  1950

10.  Johnstone, H. F., and Singh, A. D., "Recovery of Sulfur Dioxide from Waste Gases,"
    Industrial and Engineering Chemistry, 32, 1037,  1940

1 1.  Johnstone, H. F., and Kleinschmidt, R. V., "The Absorption of Gases in Wet Cyclone
    Scrubbers," Transactions of the American  Institute of Chemical Engineers, 34, 181,
    1938

12.  Johnstone, H. F.,  Read, H. J., and Blankmeyer, H. C.,  "Recovery  of Sulfur Dioxide
    from Waste Gases," Industrial and Engineering Chemistry, 30,  101, 1938

13.  Mallette. F. S.,  Problems  and  Control of Air  Pollution,  Chapter 15,  Reinhold
    Publishing Corp., New York, 1955

-------
14.  Manvelyan, M. G.,  Grigoryan, G. O., et al,  "Effect  of Inhibitors on  Oxidation  of
    Magnesium  Sulfite  to  Sulfate  by Atmospheric  Oxygen  in  Presence  of Traces  of
    Nitrogen Oxides," translated from Zhurnal Prikladnoi Khimii, 34, 896, 1961

15.  Maxon,W. D.,  and Johnson, M. J., "Aeration  Studies on Propagation  of Baker's
    Yeast," Industrial and Engineering  Chemistry, 45, 2554, 1953

16.  Phillips, D. H., and Johnson, M. J., "Oxygen Transfer in Agitated  Vessels," Industrial
    and Engineering Chemistry, 51, 83, 1959

17.  Srivastana, R. D.,  McMillan, A. F., and Harris, I. J.,  "The  Kinetics  of  Oxidation  of
    Sodium Sulphite,"  Canadian Journal of Chemical Engineering, 46, 181, 1968

18.  Wartman, F. S., "Oxidation of Ammonium  Sulphite Solution," United  States Bureau
    of Mines, Progress Reports - R.I. 3339 Metallurgical Division, No. 17, May  1937

19.  Yagi, S., and Inoue, H., "The Absorption of Oxygen into Sodium  Sulphite Solution,"
    Chemical Engineering Science, 17,411, 1962

20.  Johnstone, H. F.,  "Recovery of Sulfur Dioxide  from Waste  Gases," Industrial and
    Engineering  Chemistry, 27, 587, 1935

21.  Johnstone, H. F., and Keyes, D. B., "Recovery of Sulfur Dioxide from Waste Gases,"
    Industrial and Engineering Chemistry, 27, 659, 1935

22.  Johnstone, H. F.,   and Singh, A. D., "Recovery of Sulfur Dioxide  from  Waste Gases,"
    Industrial and Engineering Chemistry, 29, 286, 1937

23.  Johnstone, H. F.,  "Recovery of Sulfur Dioxide  from Waste  Gases," Industrial and
    Engineering  Chemistry, 29, 1396, 1937

24.  Johnstone, H. F.,  and  Williams, G. C.,  "Absorption of Gases by Liquid Droplets,"
    Industrial and Engineering Chemistry, 31,993, 1939

25.  Johnstone, H. F., and Silcox, H. E., "Gas Absorption and Humidification in Cyclone
    Spray Towers," Industrial and Engineering Chemistry, 39, 808, 1947

26.  Pigford, R. L.  and  Pyle,C., "Performance Characteristics of Spray Type  Absorption
    Equipment," Industrial and Engineering Chemistry, 43, 1649, 1951

27.  Whitney, R. P., et  al,  "On the Mechanism of Sulfur Dioxide  Absorption  in Aqueous
    Media," TAPPI, 36, 172, 1953

28.  Parkinson, R. V.,   "The  Absorption   of   Sulfur  Dioxide  from  Gases  of  Low
    Concentration," TAPPI, 39, 522, 1956

29.  Pollock, W. A., et  al, "Removal of Sulfur Dioxide and Fly Ash  from  Coal Burning
    Power Plant Flue Gases," ASME Preprint, August 5, 1966

-------
30.  Katell, S., "Removal of Sulfur Dioxide from Flue Gas," Chemical Engineering Progress,
     62,67, 1966

31.  Reiss, L. P., "Cocurrent Contacting in  Packed Towers," Industrial and Engineering
     Chemistry, Process Design and Development, Vol. 6, 486, 1967

32.  Kopita, R.,  and Gleason, T. G., "Wet  Scrubbing of  Boiler  Flue Gas,"  Chemical
     Engineering Progress, 64, 74, 1968

33.  Blosser, R. O.,  and Cooper, H. B. H.,  "Trends  in Atmospheric  Participate  Matter
     Reduction in the Kraft Industry," TAPPI, 51, 73A, 1968

34.  Danckwerts, P. V.,  "Gas   Absorption  with  Instantaneous  Reaction,"   Chemical
     Engineering Science, 23, 1045, 1968

-------
                                                                         Table 1
                              FLY ASH REMOVAL
                        LIST OF VENDORS CONTACTED
                          STUDY  OF SO2 SCRUBBERS
            NATIONAL AIR POLLUTION CONTROL ADMINISTRATION
Pulverizing Machinery Company
 (Formerly Aireton Eng. Co.)
Buell Engineering Company, Inc.
Buffalo Forge Company
Burgess-Manning Company
The Ceilcote Company, Inc.
Chemical Construction Corporation
Clermont Engineering Co.
Corning Glass Works
Croll-Reynolds Company, Inc.
Dorr-Oliver
The Ducon Company, Inc.
Fuller Company

Fritz W. Glitsch & Sons, Inc.
Heil Process Equipment Corporation
Maurice A. Knight Co.
Koch Engineering Company, Inc.
National Dust Collector Corporation

Nooter Corporation

Peabody Engineering Corporation
Research-Cottrell, Inc.
U.O.P. Air Correction Division
Claude B. Schneible Co.
Norton Company
 (Formerly U. S. Stoneware, Inc.)
Quoted

8-22-69
9-11-69


9-19-69
                                                  Reason for Declining to Quote
8-27-69

9-18-69
9-17-69
8-25-69
7-18-69
9-10-69
9-16-69
7-19-69

8-11-69

9-15-69
Equipment too small
Do not have suitable equipment

Will not quote without fee
Do not have equipment this size
Equipment too small

Declined to quote

Do not offer this type of
 equipment
Can quote only in connection
 with Combustion Engineering
Can offer no information on
 flue gas treating

Quote on fly ash removal only
See Note below
Note:  The UOP Air Correction Division declined to quote because they believe that low
      liquid velocities and very high retention times are required  in producing a liquor
      high in bisulfite. This is in opposition to the operating principle of their Turbulent
      Contact Absorber (TCA)  scrubber.

-------
              VENDORS QUOTING ON FLY ASH REMOVAL AND QUENCH EQUIPMENT
                                  STUDY OF SO2 SCRUBBERS
                     NATIONAL AIR POLLUTION CONTROL ADMINISTRATION
                                                   Type of Fly Ash Removal Section
       Manufacturer

Pulverizing Machinery Company
 (Formerly Aireton Eng. Co.)
Buell Engineering Company, Inc.
The Ceilcote Company, Inc.
Croll-Reynolds Co., Inc.
Fritz W. Glitsch & Sons, Inc.
Heil Process Equipment Corporation
Maurice A. Knight Co.
Koch Engineering Company, Inc.
Peabody Engineering Corporation
Research-Cottrell, Inc.
Claude B. Schneible Co.
Norton Company
 (Formerly U. S. Stoneware, Inc.)
Tray
Venturi
            X
            X

            X
            X
            X
          Impinge-
Cyclone    merit
Packed
 Bed
Other
                                                      X
                                           X
                       X
                                 X
                                                      X
                      X
                                           X
                                                                                                               Q]
                                                                                                               CD
                                                                                                               NJ

-------
                            VENDORS QUOTING ON SO2 SCRUBBERS
                                   STUDY OF SO2 SCRUBBERS
                     NATIONAL AIR POLLUTION CONTROL ADMINISTRATION
       Manufacturer

Pulverizing Machinery Company
 (Formerly Aireton Eng. Co.)
Buell Engineering Company, Inc.
The Ceilcote Company, Inc.
Croll-Reynolds Company, Inc.
Fritz W. Glitsch & Sons, Inc.
Heil Process Equipment Corporation
Maurice A. Knight Co.
Koch Engineering Company, Inc.
Peabody Engineering Corporation
Claude B. Schneible Co.
Norton Company
 (Formerly U. S. Stoneware, Inc.)
                                                    Type of SO2 Absorption Section
Tray
Venturi    Cyclone
Impinge-
  ment
Packed
  Bed
Other
                      X
 X
  X

  X
                                           X
                                           X
                                 X
                      X
                                                                                                               Q>
                                                                                                               0>
                                                                                                               W

-------
                                                                                               SUMMARY OF VENDORS' QUOTATIONS'1'
                                                                                                     STUDY OF SO2 SCRUBBERS
                                                                                      NATIONAL AIR POLLUTION CONTROL ADMINISTRATION
                                                                                                                                                                                                                        Table 4

Vendor
Quench Section
Type of Quench
Number of Units in Parallel
Size of Unit

Materials of Construction

Fly Ash Removed, %
Pressure Drop, In. H20
Water Circ. Rate, Gpm
(Total)
S02 Scrubbing Section
Type of Scrubber
Number of Units in Parallel
Total Number o* Units
Size of Unit

Materials of Construction

Total Packed Height, Ft
Stages S02 Removal
SO 2 Removed, %
Pressure Drop, In. H20
Liq. Recirc. Rate, Gpm
Pulverizing
Machinery Co.
Venturi
7
6'-6"diam
xlT
Steel-Coated
Emersite
97 >1
10
725


Cyclonic
7
14
12'-6" diam
x44'
Steel -
Rubber Lined
-
2
95
12
14,700

Buell Eng. Co.
Floating Ball
9
14'-0"diam
x27'
Fiberglass

95
4
1,760


Floating Ball
9
9
.14' diam
x35'
316S.S.

-
2
Not stated
7.5
3,520
The Ceilcote
Co., Inc.
Tellerette
Packing
8
20'x14'
x18'
Reinforced
Plastic
98-99 >5/u +
1
6,800


Tellerette
Packing
8
8
Included in
Quench Sec.
Reinforced
Plastic
-
2
95-97
5
4,000
Croll-Reynolds
Co., Inc.
Venturi
3
10' diam
x40'
Steel with
Amercoat
Most
0
7,500


Venturi
3
6
10' diam
x40'
Fiberglass
Dyne) Liner
-
2
Not stated
0
10,000
The Oucon
Co., Inc.
Venturi
12
9'-2"diam x
13'-6"
316S.S.

99+
10
9,600


Cyclonic
Multivane
12
12
12' diam x
28'-3"
Steel-Epoxy
Lined
-
1
90-92
3
6,000
Fritz W. Glitsch
& Sons, Inc.
Spray
1
38' diam
x20'
Steel -
Rubber Lined
Not stated
-
1,600


Impingement
Grids-410S.S.
1
1
38' diam
x34'
Steel -
Amercoat
16
2
Not stated
7.0
3,400
Heil Process
Equipment Corp.
Water-Jet
8
Not stated

316 S.S.

Most-Over 5/Lt
3
Not stated


Packed
Section
8
8
Not stated

Plastic

Not stated
Not stated
99
Not stated
Not stated
Maurice A. Knight Koch Engineering
Co.
Venturi
6
Not stated

Steel- Lined

95
20
6,600


Packed 2"
Saddles
1
1
Not stated

Steel -
Plastic Lined
Not stated
Not stated
Not stated
4
3.5 Gpm/S.F.
Co., Inc.
Venturi
4
12' diam
x20'
Steel -
Rubber Lined
90
30
6,000


Packed 31/*"
P.P. Rings
2
2
30' diam
x56'
31 6 S.S.& Steel-
Rubber Lined
14
1
Not stated
8
5,000
Peabody Eng.
Corp.
Impingement
Baffle Plate
4
12'x3G'
x25'
31€ S.S.

Not stated
-
3,040


Impingement
Baffle Plate
4
4
Included
Above
316S.S.

-
3
Not stated
11 (Total)
4,080
Research-Cottrell,
Inc.
Flooded Disc
4
8'diam x 13'-9"&
21'diamx33'
Steel - PVC
Lined
98
6
4,400


No Quote
No Quote
No Quote
No Quote

No Quote

No Quote
No Quote
No Quote
No Quote
No Quote
Claude B.
Schneible
Multiwash
Cyclonic
14
10'-9"diam
x26'
304 S.S.

99 >1
-
3,400


Multiwash
Cyclonic
14
14
10'-9"diam
x22'
304 S.S.

-
1
95
6.8 (Total)
3,400

Norton Co.
Packed
3" Intalox
Saddles
1
43' diam
x20'
Steel -
Amercoat
99+
0.5
4,350


Packed
3" Intalox
Saddles
1
1
43' diam
x42'
Steel -
Amercoat
24
2
Not stated
8.5
8,700

S&W Eng. Corp.
Spray
1
37'-6" diam
x20'
Steel -
Amercoat
90+
-
1,600


Ripple Trays
1
1
37'-6" diam
x40'
Steel -
Amercoat
(10 trays)
2
Est.90
18
4,600

S&W Eng. Corp.
Spray
1
37' diam
x20'
Steel -
Amercoat
90+
-
1,600


Johnstone
Slat Packing
1
1
37' diam
x28'
Steel -
Amercoat
10
2
Est.90
4 (Total)
3,400
(Total)
Estimated Oxidation, %
2-5
2-5
(2)            10-15          (2)            3-5           (2)           (2)

Notes: (1) Quotations based on equipment required for one boiler for 300 megawatt unit; (U) Not Estimated
                                                                                                                                  (2)
(2)
No Quote
(2)
                                                                                                                                                    10-15
                                                                                                                                                                               8-10

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                                                                       Table 5
                          INVESTMENT COMPARISON
        SO2 SCRUBBERS FOR THE STONE & WEBSTER/IONICS PROCESS
            NATIONAL AIR POLLUTION CONTROL ADMINISTRATION
     Type of Absorber

Johnstons wood slat packing
GIitsci^/id impingement packing
Intalox Saddle packing
Venturi scrubbers
Stone & Webster Ripple Tray
Cyclonic scrubbers
Floating ball
System Cost,1
 1,200 Mw

 $6,040,000
  6,720,000
  7,920,000
  8,960,000
  9,500,000
 11,920,000
 12,800,000
  Differential from
Johnstone Base Cost
              0
      +$680,000
      +1,880,000
      +2,920,000
      +3,460,000
      +5,880,000
      +6,760,000
' Cost includes quench, sulfur dioxide scrubber, pumps for two stages, blowers, ducts, piping,
  instrumentation,  dampers, civil accounts, investment in  cells for oxidation  differential
  from  Johnstone base for four 300 Mw boilers.

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                             OPERATING COST COMPARISON
                SO2 SCRUBBERS FOR THE STONE & WEBSTER/IONICS PROCESS
                  NATIONAL AIR POLLUTION CONTROL ADMINISTRATION
Scrubber System
Type of Differential Power
Scrubber Cost, $/Year
Johnstone
Glitsch grid
Intalox Saddle
Venturi
Ripple Tray
Cyclonic
Floating ball
_
+$18,800
+42,800
+20,400
+138,800
+212,000
+109,000
Oxidation
Differential Power
Cost, $/Year
	
-$84,200
+ 100,500
+ 110,500
+126,300
-126,300
-126,300
Maintenance
Differential
$/Year (2%AI)
	
+$13,600
+37,600
+58,400
+69,200
+117,600
+135,200
Total Operating
Cost Differential,
$/Year
	
-$41,800
+ 190,900
+ 189,300
+334,300
+203,300
+117,900
Note:  The annual operating cost of a Johnstone-based system will be on the order of $2,500,000.
                                                                                                   0)
                                                                                                   CT
                                                                                                   CD

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                                                                    Table 7
                            COST EVALUATION
                          SO2 SCRUBBER SYSTEM
           NATIONAL AIR POLLUTION CONTROL ADMINISTRATION
                                                               Comparative
                                                              Present Worth,
                                                              Johnstone Type
     Type of Scrubber                                              as Base
Johnstone wood slat packing                                          Base (Zero)
Glitsch grid impingement packing                                      +$794,000
IntaloxSaddle packing                                               +5,350,000
Venturi scrubbers                                                   +7,200,000
Stone & Webster R ipple Tray                                          +9,670,000
Cyclonic scrubbers                                                 +12,680,000
Floating ball                                                      +13,380,000

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AVAILABLE
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