- Email: [email protected]
potassium carbonate
Greenhouse Gas Control Technologies, Volume n M. Wilson, T. Morris, J. Gale, K. Thambimuthu (Eds.) © 2005 Elsevier Ltd. All rights reserved
1821
PILOT PLANT FOR CO2 CAPTURE USING AQUEOUS PIPERAZINE/POTASSIUM CARBONATE Eric Chen and Gary T. Rochelle* Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78712 ABSTRACT The removal of CO2 typically uses an absorption/stripping system with an amine solvent, such as monoethanolamine (MEA). A new solvent, piperazine promoted potassium carbonate, has been developed. A solution of 2.5m piperazine (PZ) and 5m potassium bicarbonate (K"^) has a CO2 absorption rate 1 to 3 times faster than 7m MEA (30 wt%). The solvent also has a lower heat of CO2 absorption, which should reduce the heat requirement for stripping. A rigorous model absorber model has been developed to estimate absorber performance. The model predicts an equilibrium pinch in the absorber near the point of maximum liquid temperature. Experiments have been conducted on a pilot plant with solvent compositions containing 4.2 m KV 2.1 m PZ and 5 m K"^/ 2.5 m PZ. The CO2 concentration was varied from 3 to 13%. The gas and liquid rates were varied from 120800 cfm and 2.4-10 gpm, respectively. The C02 removal rates ranged from 85 to 99.8 percent. INTRODUCTION A number of CO2 capture technologies have been developed and applied to ammonia production and synthesis gas purification. The majority of these commercial CO2 capture plants typically utilize an absorber/stripper system with an amine solvent. Monoethanolamine (MEA) is currently the most widely used solvent for CO2 capture from flue gas. It was developed over 60 years ago and has been modified to reduce solvent degradation and equipment corrosion [1]. A number of amine-promoted potassium carbonate systems have been developed for CO2 removal in absorber/stripper systems. Previous studies have shown that a good carbon dioxide removal rate was obtained with piperazine-promoted potassium carbonate [2, 3]. Preliminary bench-scale experiments have shown that the absorption rate of CO2 is 1 to 3 times faster than 7m MEA. The heat of absorption is also approximately 25% less than MEA and the capacity is comparable to that of 7m MEA. The heat required for stripping should be about 25% less than that for MEA. This paper presents experimental and absorber modeling results for the pilot plant with the potassium carbonate/piperazine solvent. The absorber and stripper performance has been characterized with Flexipac lY structured packing and sieve trays, respectively. PILOT PLANT TESTING The absorption of CO2 in piperazine-promoted potassium carbonate was measured in a pilot scale absorber/stripper system. The experiments were conducted using solvent concentrations with IC/PZ approximately equal to 2. An existing pilot plant facility was converted into an integrated absorber/stripper system. The pilot plant is maintained by the Separations Research Program (SRP) at the University of Texas at Austin, which uses the facility to test and characterize trays and packing in distillation, absorption, and extraction processes. The pilot plant consists of two 16.8-inch ID carbon steel columns with multiple penetrations and a number of observation windows. The columns are 30 feet in height and have spool pieces in the middle that swing out to expedite the change out of column internals. A schematic of the pilot plant is shown in Figure 1. All of the existing carbon steel piping was replaced with 304L stainless steel. Stainless steel solvent feed heater and a cooler were added to control temperature to the stripper column and absorber feed tank, respectively. A
Corresponding author: Tel. (512) 471-7230, Fax. (512) 475-7824, Email: [email protected]
1822
stainless steel cooler was added to control gas temperature into the absorber. The pilot facility has the ability to operate with gas rates from 100 to 1000 scfm and liquid rates up to 40 gpm. The flow rate, temperature, and density of the solvent streams were measured by MicroMotion® coriolis flowmeters. The density measurements were used to maintain the water balance in the system. Gas flow rates were measured using an annubar. Liquid levels in the two columns were maintained by differential pressure transmitters. Temperature measurements were taken using RTD's. Steam flow was metered using an orifice plate and differential pressure transmitters. A Delta V process control computer unit was used to log the data and control the operations of the absorber/stripper system. Two Vaisala CO2 monitors were used to measure online gas concentrations at the inlet and outlet of the absorber column. A Horiba PIR-2000 CO2 analyzer was used to measure CO2 concentration at the middle of the absorber. Three major campaigns will be undertaken with the piperazine-promoted potassium carbonate system. A fourth campaign will be conducted using MEA to establish a baseline. During each campaign, the pilot plant will be operated for approximately 4 weeks, 5 days per week, and 24 hours per day. The first campaign established the base case scenario for the piperazine/potassium carbonate solvent. A major portion of Campaign 1 was devoted to the setup and troubleshooting of the pilot plant. Experiments were conducted with two solvent compositions, 4.2 m K"*^ / 2.1 m piperazine and 5.0 m IC / 2.5 m piperazine. The synthetic flue gas contained 3 and 13 % CO2 in air at 25 to 50 °C. The temperature of the solvent to the absorber variedfi-om35 to 45 °C. The absorber pressure was operated at 1 atm. The stripper pressure was varied from 1 to 1.7 atm. The absorber contained 20 ft of Flexipac lY structured packing and the stripper contained 13 sieves trays with 18-inch tray spacing. The values of the effecUve contact area and liquid film mass transfer coefficients will be extracted. In the second campaign, another type of random packing will be installed in the stripper. The gas velocity in the absorber will be varied from 20-90% of flooding. The flue gas will contain 12% CO2 at 55 °C. The solvent composition will be the same as the base case and will be operated at the near-optimum flow rate. The stripper pressure will be varied from 0.1 to 2 atm. The objective of the campaign will be to optimize the stripper pressure for isothermal operation and to quantify the feasibility of vacuum stripping with non-isothermal operation. The MEA baseline case will be established during the third campaign. The same packing and operating conditions will be used for the 30 wt% MEA experiments. The results will permit direct comparisons of the piperazine/potassium carbonate system to the MEA system. During the fourth campaign, an optimized configuration for the absorber/system will be demonstrated based on modeling results. The two columns will be operated over a wide range of gas, solvent, and steam flow rates. The experiments will be used to characterize the gas and liquid contact area and liquid film mass transfer coefficients. CAMPAIGN RESULTS As part of campaign 1, the effective interfacial area of the absorber column was first measured by absorbing CO2 from air into a 0.1 N solution of potassium hydroxide. The effecfive wetted area of the Flexipac lY packing was calculated from the known kinetics of CO2 absorption into hydroxide soluUons [4, 5]. Figure 2 shows that the wetted area varies from 135 to 202 m^/m^. The maximum area is achieved at moderate and high gas and liquid rates and is about 49% of the dry area of the packing (410 m^/m^ for Flexipac 1Y). This is typical of the performance of high area structured packing [4]. The results from selected runs using the piperazine promoted potassium carbonate solvent are shown in Table 1. The absorber was operated in a way to avoid any pinches. In some cases, the CO2 removal rates exceeded 96%. The pilot plant was operated to give a solvent capacity from 0.7 to 1.0 mol CO2 /kg solvent. The liquid capacity of the solvent was determined by taking the difference between the lean and rich loading of the absorber. The gas capacity was determined by performing a CO2 material balance across the absorber column. The CO2 loading was determined by performing an inorganic carbon (IC) analysis. Titration with a 2N solution of hydrochloric acid to a methyl orange endpoint was used to determine total alkalinity. Several absorber temperature profiles were generated by scanning the column surface every 6 inches with an infrared camera.
1823
A concentration of approximately 1000 ppm of vanadium was maintained in the solvent to reduce potential corrosion issues. Corrosion coupons were inserted for over a week long period and preliminary results suggest that little corrosion occurred during the time period. The coupons that were used included 316L, 304L, 317L, 2205, CIOIO, and FRP. In the future, experiments will need to be conducted over an extended period. Ovhd Gas Ace
JStripper
220 _
Vacuum Pump
CD
Ovhd Liq Ace
Reflux Heater
'^
>
^
a
n
n
n
180
o o o
1
160
ISOacfm 300acfm 450 acfm
>
' Makeup Air Makeup CO,
0
C3
Solvent/^ Heater V V /
L^ f
o
200 E
0
3
I 140
\PJ T _
3 ,^
^
Absorber Middle i
120
25
10 Absorber Feed Tank
_ Makeup Water
100 Liquid Flow (gpm/ff)
Figure 2: Effective area of absorber by CO2 absorption into 0.1 N KOH
Figure 1: Pilot Plant Schematic
TABLE]I: PILOT PLANT ABSORBER PERFORMANCE WITH AQUEOUS PIPERAZINE/POTASSIUM CARBONATE USING FLEXDPAC 1Y (20 FT) Capacity ACO2 TMax Run K^/PZ L Total Alk. mol G C02,,n C02,0ut Lean Ldg T c j n T G , Out T L J O (Skin) pLean C02/kg solvent (gpm) (acfm) (%) 8.1 4.2/2.1 5.0
601
3.29
mol CO2/
(%)
kg solvent
(K)
(K)
(K)
0.22
2.5
38
44
41
(K) (kg/m^)
-
1206
mol/ kg solvent
Gas
Liquid
5.6
0.89
-
11.1 4.3/2.2 2.5
300
2.67
0.22
2.6
24
36
35
-
1213
5.7
0.74
16.2 4.3/2.2 7.8
300
11.97
1.66
2.8
29
50
43
64
1213
-
0.99
0.86
18.2 5.0/2.5 7.7
250
12.04
0.43
3.0
34
53
46
-
1228
6.3
0.91
0.85
ABSORBER PERFORMANCE Model An adiabatic absorber model was completed and simulations were performed using the Flexipac 1Y packing to predict the performance of the absorber column. The model is based on the rigorous adiabatic absorption model developed by Treybal [6]. The absorber model was implemented in Microsoft Excel using Visual Basic. The model uses the Gualito-Rocha-Bravo-Fair model to calculate mass transfer parameters and pressure drop [7]. The GualitoRocha-Bravo-Fair model tends to over-predict the effective area by up to 100%. However, it was assumed that the kga and kia calculated by the model were correct. Air-Water tests conducted by the SRP showed that a similar structured packing only had an effective area approximately 45% of the specific area at our operating conditions. Therefore, in the model, the calculated effective area was multiplied by 0.45 and the calculated kg and ki were divided by 0.45. The kg' was calculated from a model that was fitted to the data generated in the wetted wall column by Cullinane et al. [3]. Vapor-liquid equilibrium (VLE) data was obtained from a model that was fitted to data that was generated by the VLE Fortran program written by Cullinane [3]. For 12% CO2, the model shows that with 20 ft of packing, removal of CO2 can be achieved with a CO2 loading of 0.61 mol/ (mol K"^ + mol PZ), a gas rate of 12.25
1824
kmol/hr (185 acfm), and a liquid rate of 150 kmol/hr (15 gpm). A pinch occurs towards the bottom of the column (Figure 2) near the maximum temperature point of 59 °C. The calculated rich loading was 0.68 mol/ (mol K^ + mol PZ). For the 3% case, when the column is operated at the same conditions, a pinch occurs towards the top of the column (Figure 3). 335
0.14 0.12 0.1 c 0.08 o >* 0.06
o
-;/C-- •«. "N^ jf
'
325 -I
1 2 3 4 5 Height from Tower Bottom (m)
•
0.615 a. •
•
—»- Eq. Line
(D
0.01
•
«4.
'^
\ '
>^ 0.015
315
t 0
\
-
(D
320 ^ V J
0.62
0.025
' \
-»-Eq. Line -"- Op. Line
0.03 :^^ 1 ^-Ldg[
H 330
"
0.04 0.02
-*-Tgas -«-Tliq
0 625
0.035
^ 6
310
Figure 3: Calculated Absorber Composition Profile, 12% CO2, 5m KV2.5m PZ, G= 12.25 kmol/hr (185 acfm), L=150 kmol/hr (15 gpm)
0.61
•^- Op. Line 0.005 0
^^"'*-~^»*-_,^ 3
1
"^^~*' -- : 2
3
4
!___ 5
(
^ 0.605
( Height from Tower Bottom (m) Figure 4: Calculated Absorber Composition Profile, 3% CO2, 5m lC/2.5m PZ, 0=12.25 kmol/hr (185 acfm), L=150 kmol/hr ( 15 gpm)
FUTURE WORK The three remaining pilot plant campaigns will be completed by next July. The absorber model will be modified to fit the pilot plant data. ACKNOWLEDGEMENTS This work was supported by DOE Cooperative Agreement DE-FC26-02NT41440, by an EPA Star Fellowship, by the Separations Research Program at the University of Texas, and by the a number of industrial sponsors. However, any opinions, findings, conclusions, or recommendations expressed herein are those of the authors and do not necessarily reflect the views of the DOE or other sponsors. REFERENCES Herzog, H., 1999. An Introduction to C02 Separation and Capture Technologies. In Energy Laboratory Working Paper. Cullinane, J. T., 2(X)2. Carbon Dioxide Absorption in Aqueous Mixtures of Potassium Carbonate and Piperazine, M.S. Thesis, The University of Texas at Austin. Cullinane, J. T., Oyenekan, B.; Lu, J.; Rochelle, G. T., 2004. Aqueous Piperazine/Potassium Carbonate for Enhance C02 Capture (Peer-reviewed paper for GHGT-7 Conference). Wilson, I., 2004. Gas-Liquid Contact Area of Random and Structured Packing, M.S. Thesis, The University of Texas at Austin. Pohorecki, R. and Moniuk, W., 1988. Kinetics of Reaction between CO2 and Hydroxyl Ions in Aqueous Electrolyte Solutions. Chem. Eng. Sci, Vol. 43, No. 7: 1677. Treybal, R. E., 1969. Adiabatic Gas Absorption and Stripping in Packed Towers. Ind. Eng. Chem. Vol. 61, No. 7:36-41. Gualito, J. J., Cerino, F. J., Cardenas, J. C, and Rocha, J. A., 1997. Design Method for Distillation Columns Filled with Metallic, Ceramic, or Plastic Structured Packing. Ind. Eng. Chem. Res., Vol. 36: 1747-1757.
1821
PILOT PLANT FOR CO2 CAPTURE USING AQUEOUS PIPERAZINE/POTASSIUM CARBONATE Eric Chen and Gary T. Rochelle* Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78712 ABSTRACT The removal of CO2 typically uses an absorption/stripping system with an amine solvent, such as monoethanolamine (MEA). A new solvent, piperazine promoted potassium carbonate, has been developed. A solution of 2.5m piperazine (PZ) and 5m potassium bicarbonate (K"^) has a CO2 absorption rate 1 to 3 times faster than 7m MEA (30 wt%). The solvent also has a lower heat of CO2 absorption, which should reduce the heat requirement for stripping. A rigorous model absorber model has been developed to estimate absorber performance. The model predicts an equilibrium pinch in the absorber near the point of maximum liquid temperature. Experiments have been conducted on a pilot plant with solvent compositions containing 4.2 m KV 2.1 m PZ and 5 m K"^/ 2.5 m PZ. The CO2 concentration was varied from 3 to 13%. The gas and liquid rates were varied from 120800 cfm and 2.4-10 gpm, respectively. The C02 removal rates ranged from 85 to 99.8 percent. INTRODUCTION A number of CO2 capture technologies have been developed and applied to ammonia production and synthesis gas purification. The majority of these commercial CO2 capture plants typically utilize an absorber/stripper system with an amine solvent. Monoethanolamine (MEA) is currently the most widely used solvent for CO2 capture from flue gas. It was developed over 60 years ago and has been modified to reduce solvent degradation and equipment corrosion [1]. A number of amine-promoted potassium carbonate systems have been developed for CO2 removal in absorber/stripper systems. Previous studies have shown that a good carbon dioxide removal rate was obtained with piperazine-promoted potassium carbonate [2, 3]. Preliminary bench-scale experiments have shown that the absorption rate of CO2 is 1 to 3 times faster than 7m MEA. The heat of absorption is also approximately 25% less than MEA and the capacity is comparable to that of 7m MEA. The heat required for stripping should be about 25% less than that for MEA. This paper presents experimental and absorber modeling results for the pilot plant with the potassium carbonate/piperazine solvent. The absorber and stripper performance has been characterized with Flexipac lY structured packing and sieve trays, respectively. PILOT PLANT TESTING The absorption of CO2 in piperazine-promoted potassium carbonate was measured in a pilot scale absorber/stripper system. The experiments were conducted using solvent concentrations with IC/PZ approximately equal to 2. An existing pilot plant facility was converted into an integrated absorber/stripper system. The pilot plant is maintained by the Separations Research Program (SRP) at the University of Texas at Austin, which uses the facility to test and characterize trays and packing in distillation, absorption, and extraction processes. The pilot plant consists of two 16.8-inch ID carbon steel columns with multiple penetrations and a number of observation windows. The columns are 30 feet in height and have spool pieces in the middle that swing out to expedite the change out of column internals. A schematic of the pilot plant is shown in Figure 1. All of the existing carbon steel piping was replaced with 304L stainless steel. Stainless steel solvent feed heater and a cooler were added to control temperature to the stripper column and absorber feed tank, respectively. A
Corresponding author: Tel. (512) 471-7230, Fax. (512) 475-7824, Email: [email protected]
1822
stainless steel cooler was added to control gas temperature into the absorber. The pilot facility has the ability to operate with gas rates from 100 to 1000 scfm and liquid rates up to 40 gpm. The flow rate, temperature, and density of the solvent streams were measured by MicroMotion® coriolis flowmeters. The density measurements were used to maintain the water balance in the system. Gas flow rates were measured using an annubar. Liquid levels in the two columns were maintained by differential pressure transmitters. Temperature measurements were taken using RTD's. Steam flow was metered using an orifice plate and differential pressure transmitters. A Delta V process control computer unit was used to log the data and control the operations of the absorber/stripper system. Two Vaisala CO2 monitors were used to measure online gas concentrations at the inlet and outlet of the absorber column. A Horiba PIR-2000 CO2 analyzer was used to measure CO2 concentration at the middle of the absorber. Three major campaigns will be undertaken with the piperazine-promoted potassium carbonate system. A fourth campaign will be conducted using MEA to establish a baseline. During each campaign, the pilot plant will be operated for approximately 4 weeks, 5 days per week, and 24 hours per day. The first campaign established the base case scenario for the piperazine/potassium carbonate solvent. A major portion of Campaign 1 was devoted to the setup and troubleshooting of the pilot plant. Experiments were conducted with two solvent compositions, 4.2 m K"*^ / 2.1 m piperazine and 5.0 m IC / 2.5 m piperazine. The synthetic flue gas contained 3 and 13 % CO2 in air at 25 to 50 °C. The temperature of the solvent to the absorber variedfi-om35 to 45 °C. The absorber pressure was operated at 1 atm. The stripper pressure was varied from 1 to 1.7 atm. The absorber contained 20 ft of Flexipac lY structured packing and the stripper contained 13 sieves trays with 18-inch tray spacing. The values of the effecUve contact area and liquid film mass transfer coefficients will be extracted. In the second campaign, another type of random packing will be installed in the stripper. The gas velocity in the absorber will be varied from 20-90% of flooding. The flue gas will contain 12% CO2 at 55 °C. The solvent composition will be the same as the base case and will be operated at the near-optimum flow rate. The stripper pressure will be varied from 0.1 to 2 atm. The objective of the campaign will be to optimize the stripper pressure for isothermal operation and to quantify the feasibility of vacuum stripping with non-isothermal operation. The MEA baseline case will be established during the third campaign. The same packing and operating conditions will be used for the 30 wt% MEA experiments. The results will permit direct comparisons of the piperazine/potassium carbonate system to the MEA system. During the fourth campaign, an optimized configuration for the absorber/system will be demonstrated based on modeling results. The two columns will be operated over a wide range of gas, solvent, and steam flow rates. The experiments will be used to characterize the gas and liquid contact area and liquid film mass transfer coefficients. CAMPAIGN RESULTS As part of campaign 1, the effective interfacial area of the absorber column was first measured by absorbing CO2 from air into a 0.1 N solution of potassium hydroxide. The effecfive wetted area of the Flexipac lY packing was calculated from the known kinetics of CO2 absorption into hydroxide soluUons [4, 5]. Figure 2 shows that the wetted area varies from 135 to 202 m^/m^. The maximum area is achieved at moderate and high gas and liquid rates and is about 49% of the dry area of the packing (410 m^/m^ for Flexipac 1Y). This is typical of the performance of high area structured packing [4]. The results from selected runs using the piperazine promoted potassium carbonate solvent are shown in Table 1. The absorber was operated in a way to avoid any pinches. In some cases, the CO2 removal rates exceeded 96%. The pilot plant was operated to give a solvent capacity from 0.7 to 1.0 mol CO2 /kg solvent. The liquid capacity of the solvent was determined by taking the difference between the lean and rich loading of the absorber. The gas capacity was determined by performing a CO2 material balance across the absorber column. The CO2 loading was determined by performing an inorganic carbon (IC) analysis. Titration with a 2N solution of hydrochloric acid to a methyl orange endpoint was used to determine total alkalinity. Several absorber temperature profiles were generated by scanning the column surface every 6 inches with an infrared camera.
1823
A concentration of approximately 1000 ppm of vanadium was maintained in the solvent to reduce potential corrosion issues. Corrosion coupons were inserted for over a week long period and preliminary results suggest that little corrosion occurred during the time period. The coupons that were used included 316L, 304L, 317L, 2205, CIOIO, and FRP. In the future, experiments will need to be conducted over an extended period. Ovhd Gas Ace
JStripper
220 _
Vacuum Pump
CD
Ovhd Liq Ace
Reflux Heater
'^
>
^
a
n
n
n
180
o o o
1
160
ISOacfm 300acfm 450 acfm
>
' Makeup Air Makeup CO,
0
C3
Solvent/^ Heater V V /
L^ f
o
200 E
0
3
I 140
\PJ T _
3 ,^
^
Absorber Middle i
120
25
10 Absorber Feed Tank
_ Makeup Water
100 Liquid Flow (gpm/ff)
Figure 2: Effective area of absorber by CO2 absorption into 0.1 N KOH
Figure 1: Pilot Plant Schematic
TABLE]I: PILOT PLANT ABSORBER PERFORMANCE WITH AQUEOUS PIPERAZINE/POTASSIUM CARBONATE USING FLEXDPAC 1Y (20 FT) Capacity ACO2 TMax Run K^/PZ L Total Alk. mol G C02,,n C02,0ut Lean Ldg T c j n T G , Out T L J O (Skin) pLean C02/kg solvent (gpm) (acfm) (%) 8.1 4.2/2.1 5.0
601
3.29
mol CO2/
(%)
kg solvent
(K)
(K)
(K)
0.22
2.5
38
44
41
(K) (kg/m^)
-
1206
mol/ kg solvent
Gas
Liquid
5.6
0.89
-
11.1 4.3/2.2 2.5
300
2.67
0.22
2.6
24
36
35
-
1213
5.7
0.74
16.2 4.3/2.2 7.8
300
11.97
1.66
2.8
29
50
43
64
1213
-
0.99
0.86
18.2 5.0/2.5 7.7
250
12.04
0.43
3.0
34
53
46
-
1228
6.3
0.91
0.85
ABSORBER PERFORMANCE Model An adiabatic absorber model was completed and simulations were performed using the Flexipac 1Y packing to predict the performance of the absorber column. The model is based on the rigorous adiabatic absorption model developed by Treybal [6]. The absorber model was implemented in Microsoft Excel using Visual Basic. The model uses the Gualito-Rocha-Bravo-Fair model to calculate mass transfer parameters and pressure drop [7]. The GualitoRocha-Bravo-Fair model tends to over-predict the effective area by up to 100%. However, it was assumed that the kga and kia calculated by the model were correct. Air-Water tests conducted by the SRP showed that a similar structured packing only had an effective area approximately 45% of the specific area at our operating conditions. Therefore, in the model, the calculated effective area was multiplied by 0.45 and the calculated kg and ki were divided by 0.45. The kg' was calculated from a model that was fitted to the data generated in the wetted wall column by Cullinane et al. [3]. Vapor-liquid equilibrium (VLE) data was obtained from a model that was fitted to data that was generated by the VLE Fortran program written by Cullinane [3]. For 12% CO2, the model shows that with 20 ft of packing, removal of CO2 can be achieved with a CO2 loading of 0.61 mol/ (mol K"^ + mol PZ), a gas rate of 12.25
1824
kmol/hr (185 acfm), and a liquid rate of 150 kmol/hr (15 gpm). A pinch occurs towards the bottom of the column (Figure 2) near the maximum temperature point of 59 °C. The calculated rich loading was 0.68 mol/ (mol K^ + mol PZ). For the 3% case, when the column is operated at the same conditions, a pinch occurs towards the top of the column (Figure 3). 335
0.14 0.12 0.1 c 0.08 o >* 0.06
o
-;/C-- •«. "N^ jf
'
325 -I
1 2 3 4 5 Height from Tower Bottom (m)
•
0.615 a. •
•
—»- Eq. Line
(D
0.01
•
«4.
'^
\ '
>^ 0.015
315
t 0
\
-
(D
320 ^ V J
0.62
0.025
' \
-»-Eq. Line -"- Op. Line
0.03 :^^ 1 ^-Ldg[
H 330
"
0.04 0.02
-*-Tgas -«-Tliq
0 625
0.035
^ 6
310
Figure 3: Calculated Absorber Composition Profile, 12% CO2, 5m KV2.5m PZ, G= 12.25 kmol/hr (185 acfm), L=150 kmol/hr (15 gpm)
0.61
•^- Op. Line 0.005 0
^^"'*-~^»*-_,^ 3
1
"^^~*' -- : 2
3
4
!___ 5
(
^ 0.605
( Height from Tower Bottom (m) Figure 4: Calculated Absorber Composition Profile, 3% CO2, 5m lC/2.5m PZ, 0=12.25 kmol/hr (185 acfm), L=150 kmol/hr ( 15 gpm)
FUTURE WORK The three remaining pilot plant campaigns will be completed by next July. The absorber model will be modified to fit the pilot plant data. ACKNOWLEDGEMENTS This work was supported by DOE Cooperative Agreement DE-FC26-02NT41440, by an EPA Star Fellowship, by the Separations Research Program at the University of Texas, and by the a number of industrial sponsors. However, any opinions, findings, conclusions, or recommendations expressed herein are those of the authors and do not necessarily reflect the views of the DOE or other sponsors. REFERENCES Herzog, H., 1999. An Introduction to C02 Separation and Capture Technologies. In Energy Laboratory Working Paper. Cullinane, J. T., 2(X)2. Carbon Dioxide Absorption in Aqueous Mixtures of Potassium Carbonate and Piperazine, M.S. Thesis, The University of Texas at Austin. Cullinane, J. T., Oyenekan, B.; Lu, J.; Rochelle, G. T., 2004. Aqueous Piperazine/Potassium Carbonate for Enhance C02 Capture (Peer-reviewed paper for GHGT-7 Conference). Wilson, I., 2004. Gas-Liquid Contact Area of Random and Structured Packing, M.S. Thesis, The University of Texas at Austin. Pohorecki, R. and Moniuk, W., 1988. Kinetics of Reaction between CO2 and Hydroxyl Ions in Aqueous Electrolyte Solutions. Chem. Eng. Sci, Vol. 43, No. 7: 1677. Treybal, R. E., 1969. Adiabatic Gas Absorption and Stripping in Packed Towers. Ind. Eng. Chem. Vol. 61, No. 7:36-41. Gualito, J. J., Cerino, F. J., Cardenas, J. C, and Rocha, J. A., 1997. Design Method for Distillation Columns Filled with Metallic, Ceramic, or Plastic Structured Packing. Ind. Eng. Chem. Res., Vol. 36: 1747-1757.