EPA-650/2-73-012
August 1973
Environmental Protection Technology Series
-------
EPA-650/2-73-012
PROPERTIES OF
AMMONIUM SULFATE,
AMMONIUM BISULFATE,
AND SULFUR DIOXIDE SOLUTIONS
IN AMMONIA SCRUBBING PROCESSES
by
J.E. Boone and J.H. Turner
Research Branch
Control Systems Laboratory
National Environmental Research Center
Research Triangle Park, North Carolina 27711
ROAP 21ACX, Task No. 62
Program Element No. 1A2013
Prepared for
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, N.C. 27711
August 1973
-------
This report has been reviewed by the Environmental Protection Agency and
approved for publication. Approval does not signify that the contents
necessarily reflect the views and policies of the Agency, nor does
mention of trade names or commercial products constitute endorsement
or recommendation for use.
11
-------
ABSTRACT
The report gives the results of a study that involved the
collection of data that should be useful in evaluating pilot plant
operation of an ammonia scrubber with an ammonium bisulfate regeneration
system. The study determined: (1) the density, pH, and composition
of saturated (NH4)2$04 solutions at 50, 65, and 80°C; (2) the effects
on density, pH, and composition of NH.HSCL addition to the solutions in
(1); and (3) the solubility and the stripping rates of SO^ in saturated
solutions of ammonium sulfate containing ammonium bisulfate at 65°C
and 80°C.
The solubility of (NH^LSO. in water was determined and compared
with accepted values: good agreement was found. Addition of NH.HSO.
to the saturated solutions lowered the solubility of (NH.LSCL, decreased
the pH, and increased the density. The solubility of SCL in saturated
(NH.LSO. decreased with increasing temperature and with increasing
concentration of NH.HSCL. For the system and conditions used in this
experiment, SCL stripping rates were found to be first order with
respect to concentration of SCL except when the pH rose above 2.6. The
stripping rate is dependent on temperature, NH.HSO. concentration, and
almost certainly on sweep gas rate and agitation rate.
111
-------
CONTENTS
Section Page
I Conclusions 1
II Recommendations 2
III Introduction 3
Background 3
Objectives 4
IV Procedure 5
Equipment 5
Materials 5
Experimental Methods 5
V Discussion 8
VI Acknowledgements 13
VII References .14
VIII Appendices 34
Appendix A - Lot Analysis of Chemicals Used 35
Appendix B - The Effects of NH4HS04 on Density, 36
pH, and Composition of Saturated
Solutions of (NH4)2S04 at 80°C,
Using Procedure A
-------
FIGURES
No. Page
1 NH,, Scrubbing — NH.HSO, Regeneration Process 15
2 Effect of NH4HS04 on Concentration of (NH4)2$04 in a 16
Saturated Solution—Grams Per Liter
3 Effect of NH4HS04 on Concentration of (NH4)2S04 in a 17
Saturated Solution—Moles Per 100 Moles hLO
4 Effect of NH4HS04 on pH Reading of a Saturated (NH4)2S04 18
Solution
5 Effect of NH4HS04 on Density of a Saturated (NH4)2S04 19
Solution
6 Absorption of S02 in Saturated (NH4)2S04 Solutions 20
Containing NH4HS04 at 65°C
7 Abosrption of S02 in Saturated (NH4)2S04 Solutions 21
Containing NH4HS04 at 80°C
8 S02 Solubility in Saturated (NH4)2S04 Solutions Containing 22
NH4HS04
9 Stripping Rates for S02 in Saturated (NH4)2S04 Solutions 23
Containing NH4HS04 at 65°C
10 Stripping Rates for S02 in Saturated (NH4)2S04 Solutions 24
Containing NH4HS04 at 80°C
11 S0? Stripping as a Function of S0? Concentration at 65°C 25
12 S02 Stripping as a Function of S02 Concentration at 80°C 26
VI
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TABLES
No. Page
1 Density, pH, and Composition of Saturated Ammonium 27
Sulfate Solutions at 50, 65, and 80°C
2 Effects of NH4HS04 on Density, pH, and Composition 28
of Saturated (NH4)2S04 Solutions at 50, 65, and 80°C
3 Absorption of S02 in Saturated (NH4)2S04 Solutions . 29
Containing NH4HSO. at 65°C
4 Absorption of S02 in Saturated (NH4)2S04 Solutions 30
Containing NH4HS04 at 80°C
5 Stripping Rates for S02 in a Saturated (NH4)2S04 Solution 31
Containing NH4HS04 at 65°C
6 Stripping Rates for S02 in a Saturated (NHJ2S04 Solution 32
Containing NH4HS04 at 80°C
7 Stripping Rate Constants 33
vn
-------
Section I
CONCLUSIONS
For the experimental conditions used:
1. The pH, density, and composition of saturated ammonium
sulfate solutions determined at 50, 65, and 80°C are consistent
with literature values.
2. Ammonium bisulfate addition to the above solutions lowered
(NHjpSO, solubility, decreased pH, increased density, and lowered
S02 solubility.
3. The stripping rate of S02 from (NH^SO. solutions, -dSO^/dt,
was found to be a linear function of S02 -concentration for pH values
below 2.6.
-------
Section II
RECOMMENDATIONS
A valuable addition to the accomplishments listed in this
report would be an investigation of the effects of agitation and
gas flow rate on S02 stripping rates. It would be useful to know
the effects of these variables on the first order stripping rate
constant. Without these data, scale up is difficult. The usefulness
of the rate data which are contained in this report is limited to
qualitative work only.
Another area requiring investigation is the effect of ammonium
bisulfate on the release rates from ammonium sulfite-sulfate solutions,
These data would be of great benefit in studying acidifier kinetics
in the ammonia scrubbing process.
-------
Section III
INTRODUCTION
Background
The problem of stack gas desulfurization has received much
attention in the past few years". As a result, modifications of NH«
scrubbing of S02 with an NH.HSO. regeneration cycle are being
investigated. The original work is described in Hixon and Miller
patent No. 2,405,747* .
This process essentially consists of scrubbing the flue gas
stream with an NH- and (NH,)SO. solution. The scrubber effluent is then
acidified with NH.HSO, to release the greater portion of SOp, stripped
of the remaining SOp in a stripper, neutralized with NH.,, and crystallized
to yield solid (NH^SO^. The solid (NH^SO^ is thermally decomposed
to yield NH^HSO^ and NH., which are recycled back into the process
(see Figure 1).
The reactions below describe the chemistry of the system.
Scrubber Reactions
NH3 + H20 + S02 + NH4HS03
NH4HS03 + NH3 - (NH4)2S03
(NH4)2S03 + S02 + H20 •*• 2 NH4HS04
Regeneration Reactions
. (NH4)2S03 + 2 NH4HS04
NH4HSQ3 + NH4HS04 ->•
(NH4)2S04 -v NH4HS04
Heat
-------
Objectives
This study will be used as a basis to evaluate the results
of the pilot plant operation. In particular, basic S02 release
rate data are needed to evaluate the effectiveness of the stripper
and acidifier.
There were three objectives that this work was to meet in order
to satisfy the need of the pilot plant project. First, measurements
of the density, pH, and composition of saturated (NH.LSO. solutions
were to be determined at 50, 65, and 80°C. Since the solutions
throughout the process would be nearly saturated it is important
to know these values. Also some of these data were available in the
literature as a check on accuracy of the measurements. Second,
the effects of addition of NH.HSO, on density, pH, and composition of
these solutions were to be studied. These effects are important in
the operation of the acidifier. Finally, the solubility and the
stripping rates of S02 in saturated solutions of (NHJ^SO. containing
incremental amounts of NH.HSO. were to be studied at 65 and 80°C.
These data would yield the characteristics of the release of SO^ in
the acidifier and in the stripper.
-------
Section IV
PROCEDURE
Equipment
The reaction vessels in this experiment were 500 and 1000 ml,
three-necked, round-bottom flasks. Agitation was supplied by a 6.25 cm.
Teflon blade on a 0.95 cm. diameter glass rod powered by a Fisher
Dyna Mix. The SOp and N~ gas flow rates were measured by Brooks Rotameters.
An Instrumentation Laboratories Model 245 pH meter (with a Beckman 39183
Combination Electrode) was used to measure pH. Density was measured by
weighing the sample with a Sartorius analytical balance.
Materials
(NHJ-SO, was obtained from two suppliers: Matheson, Coleman, and
Bell and Fisher Scientific. The latter was used for all S0? absorption
and stripping rates; the former was used for the 50 and 65°C solubility
data only. A comparison made between the salts failed to show a difference.
The comparison results can be seen in Figures 2 through 5. The 65°C
data in these figures were determined using each salt. Material from
Matheson, Coleman, and Bell was used in procedure A and from Fisher
Scientific in procedure B. NH.HSO. was purchased from Fisher Scientific.
N2 and pure anhydrous S02 were supplied by Matheson Gas Products.
Appendix A is a lot analysis of the solid chemicals used in these experiments.
Experimental Methods
The properties of (NH4)2S04 and NH4HS04 solutions at 50 and 65°C were
determined by a different method than the one used for the 80°C data.
The change in procedure resulted from several factors, the most important
of which was the inadequacy of the sampling technique used in the original
method for temperatures above 65°C. A change in the determination of
solution composition was made to increase the accuracy of readings at
lower bisulfate concentrations. The change in suppliers of
was due to a greater than anticipated usage of the chemical.
-------
For simplicity, procedure A for the 50 and 65°C data will be described
in detail; changes made for the 80°C data, procedure B, will follow.
For procedure A (used for 50 and 65°C data), saturated (NH.LSO.
solutions were prepared by placing 400 g of the reagent grade crystals
and 320 ml of deoxygenated, deionized water into a three-necked flask.
The solution was heated for 2 hours at 95°C and cooled to the desired
temperature by adding ice to the bath as needed. After 20 minutes a
sample of the solution was withdrawn with a standard 5 ml transfer pipet
and drained into a tared vessel. The sample was weighed to determine
o =
density and analyzed by a barium perchlorate titration for SO. and the
Kjeldal analysis for NH.. The pH was recorded at the time the sample
was taken. The measurements made above were repeated on (NH.KSO.
Saturated solutions containing NH.HSO, which had been added incrementally.
Twenty minutes was allowed for each portion of bisulfate to dissolve,
and complete solution was verified by a non-changing pH response.
For procedure B (used for the 80°C data), an insulated and heated
automatic pipet replaced the standard pipet. An NaOH titration using
formaldehyde to tie up NH- ions was used for the (NH.)?SO. determination.
Solubility of S02 and the S02 stripping rates were determined in
procedure B by preparing 1 liter of saturated (NH.KSO. in the same
manner as for procedure A. Pure S09 was bubbled into the flask at a rate
3
of 600 cm' /min through a fritted glass impinger immersed in the solution.
Agitation was constant at 200 rpm. In order to take a liquid sample,
agitation had to be stopped to allow settling of excess (NH,)?SO,
crystals. Thus, for this period gas flow was stopped, and the sample
period was not included in the time measurement. Initially, and at
each sample period, the pH, composition, and density were measured. The
saturated S09 solution produced above was then stripped with N? gas at
3
1000 cm /min and 200 rpm agitation. Samples were taken and analyzed using
procedure B, and SO- concentrations were determined iodimetrically.
-------
The effects of NH.HSO. on stripping and solubility of S02 were
determined by making the same measurements on saturated sulfate solutions
containing incremental amounts of NH/ISO,.
A discussion of measurement accuracy follows. First the reading
on the pH meter was accurate to - 0.01 pH unit when tested against known
standards. Density measurements were found to be within 0.005 g/ml of
the correct value. This deviation was the maximum error found in several
determinations of the density of distilled water. The accuracy of the
analytical methods for composition was. for the most part good. Both
of the methods for sulfate and sulfite analysis were found to be within
1% accuracy. The bisulfate analyses were accurate to within 1% except
when SOp analyses were also performed. In these cases the tests were
only accurate to within 10 g/1. This effect is explained in the
discussion.
-------
Section V
DISCUSSION
Table 1 contains the properties of saturated (NH4),,S04 solutions.
The composition of the solutions agrees to within 1% of the values listed
in the literature. Linke and Seidell list the solubility of (NHjpSO.
in weight percent rather than grams per liter. Thus, to compare the
Table 1 values with Linke and Seidell values, both the density and the
concentration in Table 1 must be used. This situation indicates that
the experimental values of both concentration and density are reliable.
There is a question, however, as to the reliability of the pH reading.
It should be pointed out that all pH's reported are instrument readings:
no corrections were made for electrode processes as the correction factor
was assumed negligible for the present work. For saturated solutions the
pH drifted with time to lower values. Raising the temperature of the
solution accelerated the pH drop. Information available from the lot
analysis of the chemical indicated that the pH of a 5% solution would be
in the range of 5.0 to 6.0 pH units. Freshly made saturated and 5%
solutions fell into this pH range, but in both cases pH drifted to lower
values according to the time-temperature history of the solution. It
is thought that this drop in pH was due to thermal decomposition of
(NH4)2S04 to NH-HSO,. However, this has not been confirmed because the
analysis for NH^HSO^ is not sensitive to such low concentrations.
The effects of NH.HSO* addition can be noted from Table 2 and
Figures 2-5. Figures 2 and 3 show that the addition of NH.HSO, to
saturated (NH.LSO. solutions lowers the solubility of the latter salt
in that solution. Figure 3 shows the data on a constant water basis.
The major source of error in these data is the determination of low NH.HSO,
concentrations. In the 50 and 65°C data, this error resulted from taking
a small difference between two large titrations. The 80°C readings using
procedure B should be somewhat more reliable because they were determined
by direct titration. The work for 50 and 65°C had already been completed
when the analysis in procedure B was initiated.
-------
A second effect, the pH lowering due to the acid nature of NH.HSO,,
is shown in Figure 4. The pH lowering is independent of temperature.
There are no data in the available literature with which a comparison
can be made. The pH reading did not suffer from the same drift as noted
above in the pure saturated solutions.
A third effect of NH4HS04 on (NH4)2S04 solutions is the increase in
density of the solution with the increase of NH4HS04. It appears from
Figure 5 that the density of the saturated solutions is independent of
temperature. One explanation of this is that the increase of salt concen-
tration offsets the increase in volume.
Absorption rates for S02 in (NH4)2S04 and NH4HS04 solutions were
measured to indicate when the solutions were reaching saturation. Thus,
the end points of the curves in Figures 6 and 7 show solutions which are
approximately saturated in SCL. Figure 8 shows the decrease of the
solubility of SCL in solution as the concentration of NH4HS04 increases.
Tables 3 through 6 show that the density measurements were unaffected by
the concentration of SCL. Although there is scatter in the data, these
tables indicate that concentration of SCL has no effect on the concentration
of (NH4)2S04 and NH4HS04. The scatter was produced by an analytical method
which required taking differences among large numbers when SCL was present
in the sample. For solutions having no SCL (those at zero time in Tables 3
through 6), the (NHJ2S04 and NH4HS04 values were found from direct
titrations and are more accurate. Stopping agitation and sweep gas apparently had
no effect on the results. The pH did not change during the delay period,
indicating no SCL evolution, and the experimental stripping curves matched
derived, first-order curves closely enough to indicate absences of SCL
evolution.
The stripping curves in Figures 9 and 10 were analyzed in greater
detail than the absorption curves. The instantaneous rate was found at
various points on the curves and plotted against the concentration of S02
10
-------
as shown in Figures 11 and 12. The plots, which appear linear except
at low concentrations of SCL and NH.HSO. (pH values above 2.6), indicate
that the first order differential equation below applies:
• kC H)
Where C is concentration of S09, g/1; k is the proportionality constant,
_] <•
min ; and t is time, min. This equation can be integrated to find the
concentration at any time which is given by
C = CQ e'kt (2)
where C is the initial concentration of S02, g/1; and e is the natural
logarithm base. The rate constant k, which is the slope of the lines in
Figures 11 and 12, is listed in Table 7 for various concentrations of
NH^HSO. and temperatures. Using equation 2 and obtaining the constants
from Figure 8 and Table 7, curves of concentration verus time can be
generated and compared with curves in Figures 9 and 10. The agreement is
good for all portions of the curve where equation 1 was valid or for portions
below a pH of 2.6.
Equation 2 cannot be used in the general case because the dependency
of k on temperature, NH.HSO. concentration, sweep gas rate, and agitation
is not known.
The deviation in first order behavior above a 2.6 pH is not fully
understood. One possible explanation of this phenomenon is that the
dissolved S02 exists in several forms as described by the following:
S02 * H20 — * H2S03 - — * H+ + HSO~ - — * 2H+ + SO^
According to this hypothesis the mass transfer of S02 from the liquid
phase to the gas phase is proportional to the concentration of S0? * H?0,
+
the driving force. At low pH readings: the H concentration is high,
11
-------
the equilibrium is shifted to the left, and the SCL present is almost
exclusively in the hydrated form. Accordingly, the concentration of
total S0? which is determined analytically is an accurate measure of the
^ +
true driving force. However, at higher pH values: the H concentration
is lower, the equilibrium is shifted to the right, and the'SCL present
is distributed among the several forms. In this case the total *SCL
which is measured analytically is larger than the true driving force, the
S02 " H20. It is postulated that if only the S02 * H^O were measured
at any time the first order behavior would be observed over the whole pH
range.
12
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Section VI
ACKNOWLEDGEMENTS
Assistance is gratefully acknowledge to L. I. Griffin
for the original concept of this work, to J. H. Abbott for providing
much helpful criticism and analysis, and to R. Grote for assistance
with laboratory requirements.
13
-------
Section VII
REFERENCES
1. Linke, William F. and A. Seidell. Solubilities of Inorganic
and Metal-Organic Compounds, Volume II. Washington, D. C., American
Chemical Society, 1965.
2. Fritz, J. S. and S. S. Yamamura. Rapid Microtitration of
Sulfate. Anal. Chem. 27, 9:1461-1464, September 1955.
3. Van Peursem, R. L. and H. C. Imes. Elementary Quantitative
Analysis. New York, McGraw Hill, 1953. p. 267-269.
4. Official and Tentative Methods of Analysis of the Association
of Official Agricultural Chemists, 8th edition. AOAC, 1955. p. 13.
5. Laitinen, H. A. Chemical Analysis. New York, McGraw Hill, 1960.
p. 394, 395, 400, 401 and 410.
14
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SCRUBBING LIQUOR
(NH4)2S04 AND NH3
ri-UL.
GAS
•
SCRUBBER
FLUE GAS
CONTAINING
S02
S02
EFFLUENT
SCRUBBING
LIQUOR
(NH4)2S04
(NH4)2S03
NH4HS04
ACIDIFIER
;
STRIPPING GAS/S02
STRIPPING
G
AS
»
STRIPPER
STRIPPED
SCRUBBER
EFFLUENT
»•
(NH4)2S04
NH4HS04
REMAINING
REGENERATION
PROCESSES
f
SOLID NH4HS04 . HEAT
MAKEUP
NH3
Figure 1. Ammonia scrubbing-ammonia bisulfate regeneration process.
-------
«=c
oc
o
o
o
in
Csl
O 80° C (PROCEDURE B)
D 65 °C (PROCEDURE A)
A 65°C (PROCEDURES)
• 50°C (PROCEDURE A)
200 300
NH4HS04 CONCENTRATION, g/liter
Figure 2. Effect of NH4HS04 on concentration of (NH4)2S04 in a saturated solution.
-------
o
CM
o
o
O 80°C (PROCEDURES)
D 65° C (PROCEDURE A)
A 65 °C (PROCEDURE B)
• 50°C (PROCEDURE A)
Figure 3. Effect of
10 15
NH4HS04 CONCENTRATION, moles/102 moles H20
on concentration of (NHSC in a saturated solution.
-------
O 80°C (PROCEDURES)
D 65°C (PROCEDURE A)
A 65°C (PROCEDURES)
• 50 °C (PROCEDURE A)
200 300
NH4HS04 CONCENTRATION, g/liter
Figure 4. Effect of NH4HSC>4 on pH reading of a saturated
solution.
-------
1.36
1.32
>-
h;
c/»
1.28
O 80° C (PROCEDURE B)
D 65°C (PROCEDURE A)
A 65°C (PROCEDURES)
• 50°C (PROCEDURE A)
100
400
200 300
NH4HS04 CONCENTRATION, g/liter
Figure 5. Effect of NH4HS04 on the density of a saturated (NH4)2S04 solution.
-------
to
o
10
20 30 40
TIME, minutes
50
60
Figure 6. Absorption of S02 in saturated (NH4)2SO4 solutions containing NH4HS04 at 65° C.
-------
to
10
40
50
60
20 30
TIME, minutes
Figure 7. Absorption of SO2 in saturated (NH4)2S04 solutions containing NH4HS04 at 80° C.
-------
100 200 300
NH4HS04 CONCENTRATION, g/liter
Figure 8. 862 solubility in saturated (NH^SC^ solutions containing
500
-------
to
CO
et
cc
o
§
o
CM
O
10
20 30
TIME, minutes
40
60
Figure 9. Stripping rates for S02 in saturated (NH4)2S04 solutions containing NH4HS04 at 65°
-------
to
10
60
20 30 40
TIME, minutes
Figure 10. Stripping rates for S02 in saturated (NH4)2S04 solutions containing NH4HSO4 at 80° C.
-------
1.5
1.0
to
os
C3
(^
ec
CM
o
0.5
NH4HS04
O 0
D 9.2
A 72
• 425
liter
NOTE:
ALL SOLUTIONS
SATURATED WITH (NH4)2S04
10
15
20
25
S02 CONCENTRATION, g/liter
Figure 11. SO2 stripping as a function of SC>2 concentration at 65° C.
-------
1.5
to
1.0
Q.
&
cc
fe
0.5
0
NH.HSO
NOTE:
ALL SOLUTIONS
SATURATED WITH (NH4)2S04
20
5 10 15
S02 CONCENTRATION, g/liter
Figure 12. S02 stripping as a function of SC>2 concentration at 80° C.
-------
Table 1. DENSITY, pH, AND COMPOSITION OF SATURATED
(NH4)2S04 SOLUTIONS AT 50, 65, AND 80°C
Temperature
°C
50
65
80
Cone (NH4)2S04
9/1
570
596
616
moles/100 moles H,,0
11.4
12.4
13.1
Density
g/cm
1.254
1.251
1.256
pH
Reading
5.18
5.10
5.17
27
-------
Table 2. EFFECTS OF NH4HS04 ON DENSITY, pH, AND COMPOSITION
OF SATURATED (NH4)2$04 SOLUTIONS AT 50, 65, and 80°C
Cone (NH4)2S04
grams
TTHF
moles
100 moles H^O
Cone NH4HS04
grams
fvte?
moles
. 100 moles H20
PH
Reading
Density
grams
cm3
Results at 50°C (Procedure A)
570
561
547
509
442
402
358
11.4
11.1
10.9
10.5
9.2
9.4
9.1
0
6
20
85
185
332
441
0
0.14
0.46
2.01
4.37
8.87
12.9
5.18
3.51
3.05
2.00
1.39
0.82
0.64
1.254
1.255
1.250
1.255
1.276
1.320
1.334
Results at 65°C (Procedure A)
596
590
579
562
548
498
414
12.4
12.3
12.0
11.7
11.6
11.0
10.5
0
5
10
35
60
160
352
0
0.12
0.24
0.84
1.45
4.07
9.91
5.10
3.85
3.50
2.66
2.09
1.50
0.74
1.251
1.248
1.247
1.250
1.255
1.273
1.322
Results at 65°C (Procedure B)
596
584
544
394
616
597
565
430
12.5
12.1
11.6
10.1
13.1
12.7
12.4
11.1
0
9.6
72.0
425.0
0
0.23
1.76
12.55
5.18
3.11
2.00
0.98
1.245
1.251
1.251
1.349
Results at 80°C (Procedure B)
0
9.9
80.0
375.0
0
0.25
2.0
11.1
5.17
3.11
2.13
1.05
1.255
1.254
1.261
1.331
28
-------
Table 3. ABSORPTION OF S02 IN SATURATED (NH4)2S04
SOLUTIONS CONTAINING NH4HS04 AT 65°C
Time
min
0
3
21
45
60
0
19
35
60
0
10
30
60
0
10
35
60
PH
Reading
5.18
3.25
2.62
2.53
2.52
3.11
2.64
2.37
2.31
2.00
1.91
1,87
1.87
0.98
0.95
0.94
0.93
Density
g/cm3
Concentration
1.245
1.246
1.244
1.247
10250
Concentration
1.251
1.250
1.256
1.255
Concentration
1.256
1.257
1.257
1.260
Concentration
1.349
1.350
1.352
1.351
so2
g/i
NH4HS04 = 0 grams /liter
0
2.5
21.2
26.0
26.4
NH4HS04 =9.6 grams/liter
0
12.1
22.6
24.8
NH4HS04 = 72 grams/liter
0
. 10.2
15.7
16.5
NH4HS04 = 425 grams/liter
0
4.6
9.6
10.9
(NH4)2S04
9/1
586
580
586
590
583
584
582
593
586
544
543
547
554
394
394
391
396
NH4HS04
g/i
0
0
0
0
0
9.6
5.7
4.5
3.5
72.0
70.0
63.0
61.0
425.0
418.0
405.0
415.0
29
-------
Table 40 ABSORPTION OF S02 IN SATURATED (NH4)2S04 SOLUTIONS
CONTAINING NH.HSO, at 80°C
Time
m1n
0
10
30
60
0
10
30
60
0
15
35
55
0
5
15
60
PH
Reading
5.17
2.91
2.68
2.66
3.11
2.66
2.54
2.50
2.13
2.10
2.09
2008
1.05
1.06
1.05
1.04
Density
3
g/cm
Concentration
1.255
1.256
1.259
1.258
Concentration
1.254
1.260
1.258
1.259
Concentration
1.261
1.267
1.266
1.270
Concentration
1.331
1.329
1.335
1.333
so2
9/1
NH4HS04 = 0 grams/liter
0
11.4
19.'7
21.3
NH4HS04 = 9.9 grams/liter
0
10.3
16.8
18.4
NH4HS04 = 80 grams/liter
0
8.6
9.4
9.4
NH4HS04 = 375 grams/liter
0
2.2
5.0
5.9
(NH4)2S04
9/1
616
608
611
610
585
582
609
598
565
562
564
566
430
436
440
435
NH4HS04
9/1
0
0
0
0
9.9
3.7
11.5
8.1
80.0
76.0
84.0
80.0
375.0
372.0
364.0
382.0
30
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Table 5. STRIPPING RATES FOR S02 IN A SATURATED (NH4)2S04 SOLUTION
CONTAINING NH4HS04 AT 65°C
Time
min
0
10
40
0
10
28
52
0
10
30
60
0
10
50
pH
Reading
2.52
2.70
3.10
2.31
2.54
2.76
2.94
1.87
1.93
1.95
1.97
0.93
0.95
0.96
Density
g/cm3
Concentration
1.250
1.274
1.244
Concentration
1.255
1.253
1.253
1.251
Concentration
1.260
1.258
1.255
1.256
Concentration
1.348
1.350
1.347
so2 (r
g/i
NH4HS04 = 0 grams/ liter
26.4
15.8
4.2
NH4HS04 =9.6 grams /liter
24.8
14.6
5.8
3.0
NH4HS04 = 72 grams/liter
16.5
5.9
0.9
0.5
NH4HS04 = 425 grams/liter
10.9
4.5
0.5
-------
Table 6. STRIPPING RATES FOR S02 IN SATURATED (NH4)2S04 SOLUTIONS CONTAINING
" AT 80°C
Time
min
0
10
30
60
0
10
30
60
0
10
30
60
0
5
20
60
pH
Reading
2.66
2.96
3.27
3.54
2.50
2.71
2.86
2.99
2.08
2.11
2.12
2.12
1.04
1.05
1.06
1.08
Density
g/cm3
Concentration
1.258
1.258
1.255
1.255
Concentration
1.259
1.258
1.254
1.254
Concentration
1.270
1.267
1.267
1.267
Concentration
1.351
1.355
1.360
1.359
so2
q/1
NH4HS04 = 0
21.3
10.9
4.5
2.9
NH4HS04 = 9.
18.4
9.5
4.2
2.5
NH4HS04 = 80
9.4
2.3
0.3
0.3
(NH4)2S04
g/1
grams/liter
610
610
613
611
9 grams/liter
598
580
607
600
grams/liter
566
563
564
568
NH4HS04
g/1
0
0
0
0
8.1
5.3
11.3
7.5
80.0
80.0
86.0
83.0
NH4HS04 = 375 grams/liter
5.9
2.6
0.7
0.4
435
425
434
430
382.0
386.9
372.0
372.0
32
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Table 7. STRIPPING RATE CONSTANTS
Temperature
C°
65
65
65
65
80
80
80
80
Cone NH4HS04
9/1
0
9.6
72
425
0
9.9
80
375
Rate Constant
rnin"
0.049
0.053
0.110
0.110
0.070
0.070
0.180
0.180
33
-------
Section VIII
APPENDICES
Appendix Page
A Lot Analysis of Chemicals Used 30
B The Effects of NH4HS04 on Density, pH, and 31
Composition of Saturated Solutions of
(NH4)2S04 at 80°C Using Procedure A
34
-------
Appendix A
LOT ANALYSIS OF CHEMICALS USED
A. Ammonium Sulfate, (NH^LSO.
Manufacturer - Matheson, Coleman, and Bell
Maximum Impurities & Specifications
Arsenic .......................... 0.00002%
Chloride . . ....................... 0.0005%
Heavy metals (as Pb) ................... 0.0005%
Insoluble matter ..................... 0.005%
Iron ........................... 0.0005%
Nitrate ..... , .................... 0.001%
pH of a 5% solution .................... 5.0 - 6.0
Phosphate ................ „ ........ 0.0005%
Residue after ignition .................. 0.005%
B. Ammonium Bisulfate, N
Manufacturer - Fisher Scientific Company
Maximum Impurities
Chloride ......................... 0.0003%
Iron ......................... 0.0004%
Non-volatile matter .................... 0.003%
Other heavy metals (as Pb) ................ 0.001%
35
-------
Appendix B
THE EFFECTS OF NH4HS04 ON DENSITY, pH, AND COMPOSITION OF
SATURATED SOLUTIONS OF (NH4)2S04 AT 80°C
USING PROCEDURE Ac
Cone (NH4)2S04
grams
liter
moles
100 moles H20
Cone NHjHSOj
grams
liter
Moles
100 moles H20
PH
Density
g/cm
Run Number 1
610
396
565
530
535
423
13.0
12.6
11.6
10.7
11.44
9.69
0
6
18
44
80
252
0
0.15
0.42
1.00
1.96
6.62
4.00
3.86
3.55
2.95
2.22
1.50
1.249
1.248
1.250
1.252
1.253
1.270
Run Number 2
607
530
495
366
310
13.0
10.6
9.91
9.90
9.05
0
40
78
407
538
0
0.92
1.79
12.6
18.0
4.02
2.91
2.61
1.47
0.98
1.250
1.249
1.254
1.277
1.314
These data are believed incorrect but are included for completeness,
36
-------
"BIBLIOGRAPHIC DATA
SHEET
1. Report No. . . .,
EPA- 650/2- 73-012
3,r-.P<;eipi.ent>s:Aceesaion1No.'•
4. Title and Subtitle
Properties of Ammonium Sulfate, Ammonium Bisulfate, and
Sulfur Dioxide Solutions in Ammonia Scrubbing
Processes •
5. Report Date
August 1973-
6.
7. Author(s)
J.E. BooneandJ.H. Turner
8. Performing Organization Kept.
No.
9. Performing Organization Name and Address
EPA, Office of Research and Development
NERC-RTP, Control Systems Laboratory
^Research Triangle Park. North Carolina
10. Project/Task/Work Unit No.
21ACX (Task 62)
11. Contract/Grant No.
In-House Report
12. Sponsoring Organization Name and Address
NA
13. Type of Report & Period
Covered
Final
14.
15. Supplementary Notes
16. Abstracts Tne report giveg results of a study involving data that can be used to evaluate
pilot-plant operation of an NH3 scrubber with NH4HSO4 regeneration. It determined
the density, pH, and composition of saturated (NH4)2SO4 solutions at 50, 65, and
80°C; effects on density, pH, and composition of adding NH4HSO4 to the above sol-
utions; and the solubility and,stripping rates of SO2 in saturated solutions of (NH4)2SO4
containing NH4HSO4 at 65 and 80°C. (NH4)2SO4 solubility in water compared favor-
ably with accepted values. Adding NH4HSO4 to the saturated solutions lowered (NH4)2-
SO4 solubility, decreased pH, and increased density. SO2 solubility in saturated
(NH4)2SO4 decreased with both increasing temperature and increasing NH4HSO4
concentration. SO2 stripping rates were found to be first order with respect to SO2
concentration except when the pH rose above 2.6. Stripping rate depends on temper-
ature, NH4HSO4 concentration, and almost certainly on sweep gas and agitation rates
17. Key Words and Document Analysis. 17o. IVsrripmrs
Air Pollution Liquid Saturation
Washing Desorption
Sulfur Dioxide
Ammonium Compounds
Ammonia
Flue Gases
Solubility
Density (Mass/Volume)
pH
17b. Identifiers/Opcn-Iinded Terms
Air Pollution Control
Ammonia Scrubbing
Gas Stripping
17e. COSATI Fie Id/Group 7D, 7 A , 13 B
18. Availability Statement
Unlimited
19. Security Class (This
Report)
UNCLASSIFIED
20. Security Class (This"
Page
XINC UASS1F1 ED
21- No. of Pages
42
22. Price
ROOM NTIS-89 (REV. 3-72)
37
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