Ind. Eng. Chem. Process Des. Dev. 1982, 21, 539-544
539
Solubility of H2S and C02 in Aqueous Methyldiethanolamine Solutions Fang-yuan Jou, Alan E. Mather, and Frederlck D. Otto' Department of Chemical Engineedng, The Univers@ of Alberta, Edmonton, Alberta. Canade T6G 2G6
The solubilities of H2S and C02 in 1.0, ,2.0, and 4.28 kmol/m3 aqueous solutions of methyldiethanolamine have been measured for temperatures and acid gas partial pressures ranging from 40 to 120 O C and 0.001 to 6600 kPa, respectively. The procedure presented by Kent and Eisenberg has been used to correlate the solubili data and enthalpies of solution have been calculated from the experimental results.
sizing the absorber to give a residence time that permits most of the H2S to be absorbed but is insufficient for significant reaction with C02 to occur. The MDEA process is capable of treating acid gas streams to remove HzS to the 4 ppm (l/., grain) level; however, greater selectivity is achieved as the specification on HzS in the purified gas is relaxed [Pearce (1978); Vidaurri and Kahre (1977)l. An optimum combination of selectivity and H2S removal can be established by proper selection of absorber height, solution strength, and circulation rate. Information on the equilibrium solubility of H2S and C02 in aqueous MDEA solutions is required for the design and analysis of MDEA treating units. To date, no solubility data have been published. Experimental Section Amine solutions were prepared from distilled water and N-methyldiethanolamine having a purity of 99+% obtained from Aldrich Chemical Co. Carbon dioxide and hydrogen sulfide were obtained from Linde and Matheson, respectively, and were of high purity. The equipment used for the solubility measurements was essentially the same as that used previously in this laboratory for studies of the solubility of H2S and COz in amine solutions [Lee et al. (1973); La1 et al. (1980)l. Solubility data measured at higher partial pressures were obtained using a closed system where the gas of interest was circulated and bubbled through an amine solution contained in a windowed equilibrium cell. The equilibrium cell consisted of a Jerguson liquid level gauge with a 250-cm3 tubular gas reservoir mounted on the top. A magnetically driven piston pump was used to circulate the gas phase. The cell and pump were housed in an air bath controlled to within *0.5 "C. The pressure in the cell was measured by a calibrated Heise Bourdon tube gauge. The MDEA solution was made to the desired strength and charged to the cell. Hydrogen sulfide or carbon dioxide was then added in an amount determined by observation of the pressure. If necessary, nitrogen was added so that the total pressure was always greater than atmospheric. Generally no nitrogen was added at pressures above about 200 kPa. To ensure that equilibrium had been reached, vapor was bubbled through the liquid for at least 8 h prior to sampling the liquid and vapor phases. It was possible to measure solubility data with this apparatus at acid gas partial pressures down to 0.1 kPa. Samples of vapor were analyzed using gas chromatography. The chromatograph has a 3 m long, 6.35 mm 0.d. column packed with Chromosorb 104. It was operated at temperatures between 80 and 120 "C. Response factors were measured in our laboratory and were N2: 1.17, C 0 2 : 1.00, and H2S: 1-01.
Aqueous solutions of methyldiethanolamine (MDEA) are attractive solvents for the selective removal of H2Sfrom process streams containing C02and hydrocarbons. The first description of the use of MDEA in a process to selectively remove H2S in the presence of C02 is given in publications of Frazier and Kohl (1950) and Miller and Kohl (1953) which describe the results of laboratory, pilot plant, and commercial plant studies carried out by the Fluor Corporation during the late 1940's and early 1950's. Commercial implementation of MDEA as a treating solution did not follow immediately because of the high cost of MDEA relative to the cost of either MEA or DEA. However, it is now used in a number of treating plants and it is apparent that MDEA processing technology will find increasing application for enriching the H@ content of the acid gas feed to Claus sulfur recovery plants and the feed to processes used for the synthesis of sulfur derivatives; for removal of H2Sfor recycling to the sulfur plant in the Scot process; for recovery of C02 for use in enhanced recovery processes and in general for removal of H2S from gases rich in COP The removal of H2S from gases produced from gasifying coke and coal is a probable area of application. Here the removal of large quantities of COz present may not be economically justified. Recently, a number of companies have reported the results of pilot plant and commercial scale testing [Pearce and Brownlie (1976);Pearce (1978); Vidaurri and Kahre (1977);Johnson and Say (1979); Blanc et al. (1980)l. Suggestions for processing schemes that employ the use of MDEA treating have been presented by Goar (1980). MDEA is a tertiary amine and is more selective for H2S than conventional amines such as MEA, DEA, and DIPA. Thii selectivity arises because MDEA, which does not have a hydrogen atom attached to the nitrogen, cannot react directly with C02to form carbamate. However, it reacts directly with H2S via the same instantaneous proton transfer mechanism that occurs when H2S reacts with primary and secondary amines, i.e. H2S + R2NCH3 e RZNCH3' HS(1) The COPmust first react with water to form bicarbonate. C02 + H 2 0 HC03- H+ (2) The bicarbonate then combines with the amine via an acid-base neutralization reaction so that the overall reaction is COz + HzO + R2NCH3 e HC03- RzNHCH3+ (3) The formation of HC03- is slow and controls the rate of reaction of COP The rate of absorption of COz in MDEA solution is thus much slower than the rate of absorption of H2S and selective removal of H2S can be achieved by
+
+
+
0196-4305/82/1121-0539$01.25/0
0
1982 American Chemical Society
540
Ind. Eng. Chem. Process Des. Dev., Vol. 21, No. 4, 1982
Table I. Solubility of H,S in 1.0 kmol m - 3 MDEA Solution ( a ,Mole Ratio in Liquid, H,S/MDEA)
25 1960.0 1380.0 830.0 413.0 182.0 38.9 8.37 1.10 0.170 0.0273 0.00674 40 2730.0 1800.0 1290.0 417.0 102.0 43.3 10.9 1.99 0.513
2.935 70 0.0391 0.0232 2.364 0.0110 1.850 1.424 0.00810 1.183 0.00336 0.911 0.00210 0.658 100 5890.0 0.315 4920.0 0.137 3930.0 0.0539 2090.0 0.0293 994.0 2.902 414.0 2.250 113.0 1.917 35.8 1.308 4.22 0.994 1.03 0.866 0.236 0.604 0.090 0.297 120 5230.0 0.149 3730.0 0.0910 0.0613 2710.0 0.0109 0.0225 1290.0 0.00409 0.0144 496.0 0.00230 0.0111 129.0 70 5030.0 3.229 11.5 3690.0 2.591 1.70 2420.0 2.085 0.52 1650.0 1.751 0.050 925.0 1.405 511.0 1.185 146.0 0.886 14.3 0.384 11.0 0.354 0.269 0.0537 0.0836 0.0300
0.0225 0.0183 0.0130 0.0109 0.00661 0.00540 3.000 2.665 2.298 1.641 1.251 0.936 0.593 0.358 0.118 0.0561 0.0283 0.0179 2.627 2.078 1.750 1.233 0.871 0.495 0.145 0.0566 0.0324 0.0098
Table 11. Solubility of H,S in 2.0 kmol m - 3 MDEA Solution (a, Mole Ratio in Liquid, H,S/MDEA) T,"C 40
PH,s,kPa 2260.0 1010.0 258.0 107.0 27.3 8.98 5.76 1.20 0.370 0.171 0.0308 0.00871 0.00260
~H,S
1.906 1.489 1.063 0.965 0.674 0.443 0.368 0.162 0.0871 0.0576 0.0238 0.0127 0.00725
T , " C P H ~ s , ~ ~P H~, S 100 1550 1020 483.3 266.3 146.9 72.53 29.07 16.43 0.745
1.256 1.076 0.846 0.660 0.474 0.357 0.203 0.156 0.029
Liquid samples were injected into 40 mL of 1 N NaOH solution and then analyzed. Absorption into NaOH quantitatively converts the acid gases into ionic species. The amount of amine solution was determined by weighing. The COz in the liquid was precipitated as BaC03 and then tritrated with 0.1 N HCl using a modified methyl orange indicator. The H2S in the liquid was determined by using the iodinethiosulfate titration with starch as an indicator. The amine concentration was determined by direct titration of an aliquot of the liquid sample with 1.0 N H2S04solution using methyl red indicator. A flow apparatus was used to measure solubility data for acid gas partial pressures in the range 0.001 kPa to 100 kPa. In this apparatus, gas was bubbled through amine solutions contained in several stainless steel cylinders connected in series. The method permits the use of large vapor phase samples for analysis without disturbing
c.21
0301
001
01
2
r?
Mole Ratio in Liquid ( H2S/MDEA)
Figure 1. Effect of temperature on the solubility of H2S in 4.28 kmol/m3 MDEA solution. Table 111. Solubility of H,S in 4.28 kmol m - 3 MDEA Solution (a, Mole Ratio in Liquid, H,S/MDEA)
T,
"c
T,
PH2S, kPa
25 1960.0' 1830.0 1670.0 1370.0 1060.0 765.0 476.0 296.0 88.8 36.9 0.603 0.464 0.195 0.114 0.0180 0.00593 40 2800.0' 2360.0 2140.0 1540.0 949.0 500.0 107.0 28.5 8.71 1.42 0.271 0.0387 0.0102 0.00714 0.00502 0.00314
aH,S
"c
PH,S,kPa
1.699 7 0 4990.0' 1.686 4120.0 1.588 3460.0 1.506 2530.0 1.373 1420.0 1.273 528.0 1.173 132.0 1.088 23.7 0.921 16.8 0.780 0.353 0.106 0.00985 0.0972 0.00714 0.0611 0.00451 0.0446 0.00274 0.0171 0.00130 0.00960 100 5680.0 1.723 4720.0 1.576 3630.0 1.520 2300.0 1.369 1690.0 1.210 765.0 1.083 240.0 0.849 26.1 0.499 1.66 0.268 0.383 0.103 0.133 0.0446 0.0417 0.0165 120 5840.0 0.00805 5390.0 0.00734 4690.0 0.00580 3400.0 0.00508 2510.0 1130.0 252.0 25.1 0.342
aH,S
1.727 1.616 1.521 1.355 1.163 0.953 0.549 0.233 0.188 0.0253 0.00367 0.00311 0.00258 0.00177 0.00129 1.518 1.409 1.272 1.104 1.004 0.763 0.435 0.130 0.0305 0.0142 0.00763 0.00434 1.328 1.285 1.221 1.084 0.969 0.677 0.303 0.0895 0.00950
' Liquid H,S phase exists. equilibrium but is more difficult to operate, particularly at the higher temperatures. Solubility Data Experimental solubility data for HzS in 1.0 and 4.28 kmol/m3 MDEA solutions were measured at 25, 40, 70, 100, and 120 "C and in 2.0 kmol/m3 MDEA solution at 40 and 100 OC. The results are presented in Figures 1,2, and 3 and in Tables 1-111. Figure 3 also gives a comparison
Ind. Eng. Chem. Process Des. Dev., Vol. 21, No. 4, 1982
541
1 0 kmol/m3 MDEA Solution
0001
ni
001
in "
? _n"
Mole Ratio in Liquid [ C02/MDEA) Mole Ratio in Liquid (H$/MDEA)
Figure 2. Effect of temperature on the solubility of H2S in 1.0 kmol/m3 MDEA solution.
1.000
Table IV. Solubility of CO, in 2.0 kmol m - 3 MDEA Solution (a.Mole Ratio in Liauid. CO-IMDEA)
1
T, "C
L
001
0001
01
001
20
IO
Mole Ratio in Liquid ( H2S/Amine)
Figure 3. Comparison of the solubility of H2S in 2.0 kmol/m3 MDEA and 2.5 kmol/m3 MEA solutions at 40 and 100 OC. 10,000
, ,
' ' ' I l l
I
,
I
'
1 1 1 1
, , ,
I " I , ,
I
,
/ 1,000
Figure 5. Effect of temperature on the solubility of C02 in 2.0 kmol/m3 MDEA solution and comparison with the solubility in 2.5 kmol/m3 MEA solution.
k
25 6380.0" 5260.0 4570.0 3550.0 2040.0 698.0 181.0 9.26 4.22 1.55 0.0295 0.0218 0.00688 0.00100 40 6630.0 6330.0 4800.0 3200.0 2360.0 640.0 294.0 101.0 11.2 2.38 0.184 0.0132 0.00369 0.00306 0.00217 a
001 L 1 l 1 , I I l
0001
0 01
01
1
1
, I , . , /
I
IO
, 40
Mole Ratio in Liquid ( H * S / M D E A ) Figure. 4. Effect of concentration on the solubility of Ha in MDEA solutions at 40 and 100 O C .
of the solubility of HzS in 2.0 kmol/m3 MDEA with that in a 2.5 km01/m3 MEA solution. Figure 4 depicts the effect
of MDEA solution strength on H2S solubility. The results
T, P~o,~kPa
QCO,
"C
Pco,,kPa
=CO,
1.833 70 6020.0 1.397 1.676 4230.0 1.235 1.587 2730.0 1.182 1.479 2320.0 1.147 1.308 993.0 1.011 1.146 447.0 0.841 1.025 40.9 0.369 0.638 0.951 0.0439 0.452 0.305 0.0208 0.334 0.0480 0.00560 0.0402 0.00335 0.00129 0.0329 0.00208 0.00090 0.0166 100 5530.0 1.218 0.0050 4200.0 1.161 1.682 2600.0 1.009 1.639 573.0 0.564 1.467 373.0 0.502 1.268 30.8 0.130 1.204 0.128 0.00376 1.083 0.0468 0.00218 0.990 120 5490.0 1.152 0.866 4660.0 1.043 0.441 3380.0 0.910 0.224 1930.0 0.689 0.0676 493.0 0.336 0.0120 57.7 0.0973 0.00504 3.84 0.0133 0.00429 0.116 0.00166 0.00300 0.0725 0.00124
Liquid CO, phase exists.
cover HzS partial pressures ranging from 0.001 kPa to about 6000 kPa. A plot of the solubility data obtained for C 0 2 in a 2.0 kmol/m3 MDEA solution at 25,40,70,100, and 120 "C and at partial pressures ranging from 0.001 kPa to 6600 kPa is given as Figure 5. The raw data are presented in Table IV. Lines representing the solubility of COz in 2.5 kmol/m3 MEA solution at 40 and 100 "C are plotted for comparison purposes. It can be noted that the partial pressures of COzand HzS are larger over MDEA solutions than MEA solutions at acid gas loading less than about 1.0 for HzS and 0.6 for COP,and that the difference between C 0 2partial pressures for MDEA and MEA solutions at a given loading is considerably greater than the similar difference between H2S partial pressures. Solubility data
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Ind. Eng. Chem. Process Des. Dev., Vol. 21, No. 4, 1982
Table V. Solubility of CO, in 4.28 kmol m - 3MDEA Solution ( a , Mole Ratio in Liquid, CO,/MDEA)
5430.0 3939.0 1190.0 235.0 111.0 48.1 5.30 0.384 0.0857 0.0341 0.00859 0.00385 40 6570.0 5550.0 4070.0 2800.0 1420.0 413.0 106.0 83.4 13.3 2.67 0.703 0.0301 0.0109 0.00767 0.00231
a
1.370 5590.0 1.300 4300.0 1.115 2890.0 0.996 1620.0 0.930 705.0 0.784 40.3 0.318 0.918 0.0720 0.17 0.0306 0.0183 0.0191 0.00963 0.0103 0.00485 0.00621 0.00161 1.290 100 5590.0 1.272 4010.0 1.218 2680.0 1.170 1310.0 1.100 331.0 0.936 63.1 0.710 7.69 0.700 0.277 0.2845 0.174 0.136 0.0712 0.0609 0.0554 0.0104 0.0401 0.0057 120 5290.0 0.00381 2920.0 0.00202 857.0 248.0 69.1 14.3 0.479 0.183 0.143
1.187 1.159 1.110 0.941 0.740 0.189 0.021 0.0078 0.00228 0.00128 0.00088 0.00037 1.096 0.941 0.784 0.532 0.256 0.0947 0.0276 0.00376 0.00291 0.00151 0.00135 0.00100 0.743 0.525 0.279 0.128 0.0553 0.0186 0.00225 0.00129 0.00105
Liquid CO, phase exists.
for C 0 2 in a 4.28 kmol/m3 MDEA solution at 25, 40, 70, 100, and 120 "C are given in Table V, and plotted in Figure 6. In general, the solubility of either C02 or H a per mole of MDEA decreases with increasing temperature and with increasing solution strength. Correlation of Solubility Data The approach used by Kent and Eisenberg (1976) was used to correlate the solubility data. In accordance with their model and after the elimination of the carbamate equilibrium reaction, the equilibria between species in solution for the C02-H2S-MDEA-H20 system may be described by the following reactions R2NCH3H' F? H+ + R2NCH3 (4) HzO + C 0 2 G H+ + HC03-
(5)
H2O G H+ + OH-
(6)
HC03- 2 H+ + C032(7) H2S s H+ + HS(8) HS- F? H+ + S2(9) The associated stoichiometric equilibrium constant expressions are K1 = [H+] [RzNCH3]/[R2NCH3H+] (10) K3 = [H+l [HCO,-I/[C021 (11) K4 = [H+] [OH-] (12)
K5
= [H+] [C032-]/[HC03-]
K6
= [H+l [HS-I/[H,Sl
K7 = [H+] [S2-]/[HS-]
(13) (14) (15)
COI
._z
- & L L , , , , ., 000' 001 01 Mole Ratio in Liquid ( C02/MDEA)
b/ 0 001 LA-_-
000Cl
-
A
2
10'5
Figure 6. Effect of temperature on the solubility of C02 in a 4.28 kmol/m3 MDEA solution.
The equilibrium constants are numbered so as to conform with the numbering system used by Kent and Eisenberg. The vapor pressures of the acid gas components are related to the free acid gas concentrations in the liquid through Henry's law, i.e. HCO, = Pco,/[C02l (16) HH$3
= P H g / LH2S1
(17)
In addition, the following charge and mass balances apply m = [RzNCH3]+ [R2NCH3H+] (18)
+ [HC03-] + [C032-] mCYH2s= [HS-] + [S2-] + [H,S] [R2NCH3H+]+ [H+] = [HS-] + 2[S2-] + [OH-]+ 2[C032-] + [HCO,-] macoz = [CO,]
(19) (20) (21)
where R represents C2H40H,CY is the solution loading, mol acid gas/mol MDEA, m is the amine concentration, kmol/m3, and the quantities in brackets are the molarities of the various species. Equations 10 through 21 can be arranged to provide expressions which relate the partial pressures of H2S and C 0 2 over a MDEA solution to the solution loading at a particular temperature P ~ f =i (ff~,s[H+]~A/K&7) (1/(1 +[H+I/K,)) (22)
The equilibrium constants and Henry's law coefficients that appear in these expressions vary markedly with ionic strength, solution composition, and temperature [Danckwerts and Sharma (1966)l. Although values are available in the literature (pK1 for MDEA at 25 "C is 8.52), they usually only apply at the condition of infiiite dilution, and satisfactory information on the effect of ionic strength is lacking. Thus, if published values for ionization constants and Henry's coefficients are used in the model, the partial pressures calculated are not in good agreement with measured values. Kent and Eisenberg developed a predictive model for MEA and DEA solutions by using published values for Henry's coefficients and for all ionization constants except
Ind. Eng. Chem. Process Des. Dev., Vol. 21,
No. 4, 1982 543
i
4.28 kmol/m3MDEA Solution
0
1
I
1
1
1
I
I
20
40
60
80
100
120
140
lo-loO
0 20
40
I
I
10'61
I
I
100
I20
140
Figure 9. K 1for COPin a 4.28 kmol/m3 MDEA solution.
Figure 7. K1 for HzS in a 4.28 kmol/m3 MDEA solution. I
80
Temperature ('C)
Temperature ("C)
10.'
60
I
I
I
1
I
I
4
t
i
1 .O kmol/m3MDEA Solution
t
2.0 kmollm3MDEA Solution
1 10-'Ob
io
a0
do
io
1bo
I20
la0
Temperature ("C)
Figure 8. K , for HzS in a 1.0 kmol/m3 MDEA solution.
Figure 10. K1for COz in a 2.0 kmol/m3 MDEA solution.
the two constanta used to describe amine equilibria. They determined these by a best fit to experimental solubility data. In this way, an attempt is made to lump all nonidealities into two adjustable parameters. The model described here for the H2S-C02-MDEAH 2 0 system contains one equilibrium constant, K1, which describes amine equilibrium. Values of K1for the H2SMDEA-H20 system were determined by accepting published values for K6, K,, and HHlsand fitting experimental solubility data to eq 4 , 6 , 8 , and 9. The values determined for 1.0 and 4.28 kmol/m3 MDEA solutions are plotted in Figures 7 and 8. Values of K1 for C02 in 2.0 and 4.28 kmol/m3 MDEA solutions were determined in a similar
way by using published values for K3,K4,Ks, and Hcsand solving eq 4 , 5 , 6 , and 7. They are plotted in Figures 9 and 10. As one would expect, the K:s, which have been derived from experimental data, are a function of temperature, acid gas loading, and amine concentration. However, the information provided can be used with eq 22,23, and 24 to predict solubility values outside the range of the experimental data for the H2S-C02-MDEA-H20 system. Enthalpies of Solution Approximate values of the differential enthalpy of solution of H2S and C 0 2 in the MDEA solutions were cal-
Ind. Eng. Chem. Process Des. Dev., Vol. 21, No. 4, 1982
544
Table VI. Enthalpy of Solution of H,S in MDEA Solutions (-AH,, kJ/mol H,S) soln concn QH,S (mole ratio in liquid, H,S/MDEA) 0.01 41.2 41.4
1.O kmol/m3 4.28 kmol/m3
0.3 40.3 41.0
0.1 41.2 41.4
0.5 38.7 39.2
0.9 28.7 32.8
1.0 24.3 27.8
1.2 18.5 20.8
1.5 15.0 16.3
Table VII. Enthalpy of Solution of CO, in MDEA Solutions (-AHs, kJ/mol CO,) soln concn
aCO,
0.01 65.0 62.4
0.003
2.0 kmol/m3 4.28 kmol/m3
65.0
.
4
(mole ratio in liquid, CO,/MDEA) 0.1 62.0 59.8
i
28 kmol/m3 1 0 kmoI/m3
v)
I
20F
I
I
\--
,
,
,
, , l , l
,
40,
I
I
01
I
I
1
40
IO
Mole Ratio in Liquid ( H2S/MDEA)
Figure 11. Enthalpy of solution of H2S in MDEA solution. 100
1
1
MEA 80
,I 0,Oi
1 I
I
1
1
1
1
1
1
l
I
1
I
,
01
,
,
,
,
'C
20
Mole Ratio in Liquid (Con/MDEA)
Figure 12. Enthalpy of solution of COz in MDEA solution. culated by use of the following form of the Gibbs-Helmholtz equation AHs/R = [e In P l / ~ ( l / n l x l where the subscript 1 refers to the acid gas component being considered and x is the mole fraction of the acid gas in the liquid. The plots of In pl vs. 1/T were linear within the accuracy of the data, and this indicates that AHs is independent of temperature. The values of AHs calculated for H2S are presented in Table VI and plotted in Figure 11and those for C02are given in Table VI1 and in Figure 12. The calculated values depend strongly on the loading of the solution at loadings greater than about 0.3 mol/mol MDEA and approach the enthalpies of solution in water
0.5 55.4 53.2
0.9 41.6
1.0 33.7
1.5 12.1
at loadings greater than 1.0mol/mol MDEA. The average values of 41.2 kJ/mol H2S and 61.0 kJ/mol COz, for loadings less than about 0.3, agree well with values of 41.8 kJ/mol H2S and 62.7 kJ/mol COPreported by Blanc et al. (1980). As also shown in Figures 11and 12, the enthalpies of solution of H2Sand C02 in MDEA are about 20% and 32% lower, respectively, than in MEA.
Acknowledgment Financial support was provided by the Canadian Gas Processors Association and the National Research Council of Canada. Nomenclature A = maH,s- PH+/HH,s,kmol m-3 B = maco, - Pco /Hcol, kmol m-3 H = Henry's c o e h e n t , kPa/kmol m-3 AH,= enthalpy of solution, k J mol-' K1...K, = stoichiometric equilibrium constants K ' = 1 + [H+]/K, m = concentration of amine, kmol m-3 p = partial pressure of acid gas kPa T = temperature, K x = mole fraction in the liquid phase a = mole ratio in the liquid phase, mol acid gas/mol amine [ ] = molarity of a species, kmol m-3, mol/L Subscripts 1 = solute species COz,H2S = individual acid gas
Literature Cited Blanc, C.; Elgue, J.; Lallemand, F. "Proceedings of the 30th Canadian Chemical Engineering Conference", Edmonton, Canada, 1980; vol. 3, pp 743-755. Danckwerts, P. V.; Sharma, M. M. The Chem. Eng. 1966, (202), CE 244-280. Frazier, H. H.; Kohl, A. L. Ind. f n g . Chem. 1950, 42, 2288-2292. Goar, B. G. Oil Gas J . 1960. 76(18), 239-242. Johnson, R. R.; Say, G. R. Proceedings of the 3rd International Conference on Control of Sulfur and other Gaseous Emissions, University of Salford, England 1979. Kent, R. L.; Eisenberg, B. hp3ocarbon Process. 1976, 55(2), 87-90. h i , D.; Isaacs, E. E.; Mather, A. E.; Otto, F. D. Proceedings of the Gas Conditioning Conference, Norman, OK, 1980; pp 11-118. Lee, J. I.; Otto, F. D.; Mather, A. E. Gas Processing/Canada 1973, 65(4), 26-34. Miller, F. E.; Kohl, A. L. O i / G a s J . 1953, 51(51), 175-183. Pearce, R. L.; Brownlle, T . J. Proceedings of the Gas Condltionlng Conference, Norman, OK, 1978, pp Kl-K24. Pearce, R. L. R o c . Ann. Conv., Gas Process. Assoc., Tech. Papers 1970, 57, 139-144. Vldaurri. F. C.: Kahre, L. C. Hydrocarbon Process. 1977, 56(11), 333-337.
Received for review June 17, 1981 Revised manuscript received February 26, 1982 Accepted March 29, 1982
