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Comparison of rotating packed bed and packed bed absorber in pilot plant and model simulation for CO2 capture
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Comparison of rotating packed bed and packed bed absorber in pilot plant and model simulation for CO2 capture Nipon Chamchan a, Jia-Yu Chang a, Hsiao-Ching Hsu a, Jia-Lin Kang a, David Shan Hill Wong a,∗, Shi-Shang Jang a, Jui-Fu Shen b a b
Department of Chemical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan, ROC New Materials Research & Development Department, China Steel Corporation, Kaohsiung, Taiwan, ROC
a r t i c l e
i n f o
Article history: Received 1 May 2016 Revised 30 July 2016 Accepted 16 August 2016 Available online xxx Keywords: Rotating packed bed Packed bed Pilot plant Carbon dioxide capture Chemical absorption Simulation
a b s t r a c t In this study, both packed-bed (PB) and rotating PB (RPB) absorbers with a packed-bed stripper were used in a pilot plant for the removal of carbon dioxide (CO2 ) with 30 wt% monoethanolamine (MEA) as the solvent. The flue gas feed is the combustion product of the blast furnace gas from a steel mill containing approximately 30% of CO2 . Both PB and RPB exhibit the same performance for the capture of CO2 with the same amount of energy consumption, but the RPB has a volume of approximately one-third that of PB absorber. The results obtained from experiments using ∼20 wt% MEA showed good agreement with those obtained from simulation using an Aspen rate-based model for PB and an Aspen custom modeler for RPB. These results demonstrated the feasibility of using a RPB for decreasing the size of absorber under relevant process conditions for capturing CO2 . © 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
1. Introduction Emissions of carbon dioxide (CO2 ) are considered to be the most important anthropogenic greenhouse gas (GHG), which contributes to global warming. Several methods are available for mitigating anthropogenic CO2 . The International Energy Administration (IEA) have stipulated as the capture, storage, and utilization of CO2 (CCSU) as one of the important options for reducing GHG emissions [1]. Three main methods are available for the capture of CO2 : post-combustion, pre-combustion, and oxy-fuel combustion. Postcombustion capture involves chemical absorption for separating CO2 for further storage and utilization. On the other hand, with the use of pre-combustion for the capture of CO2 , increased CO2 concentration could decrease the apparatus and equipment costs. Also, the hydrogen produced by the above-mentioned process can be used as fuel as well as for other purposes. Oxy-fuel combustion involves the separation of oxygen from air for producing flue gases, mainly consisting of CO2 and water, with the aim of producing a more concentrated CO2 stream. Among the aforementioned processes, post-combustion carbon capture technology is emerging as a commercially viable process. The main advantage is that ∗
Corresponding authors. Fax: +886 35715408. E-mail addresses: [email protected] (D.S.H. Wong), [email protected] (S.-S. Jang).
this method can be easily applied to existing power plants without significant change in the process of power generation. However, chemical absorption processes exhibit main drawbacks of requirements of PB absorbers with enormous volume and high energy for regenerating solvents. As developed by Ramshaw and Mallinson [2], RPB or Higee absorbers are well known to enhance the mass transfer rate between liquid and vapor phases, thereby considerably decreasing equipment size. Several authors have investigated the application of RPB for CO2 absorption [3–8]. Most of these studies were conducted using laboratory-size absorbers. In our studies, by using a pilot plant with RPB and packed-bed stripper, the height transfer unit (HTU) is substantially reduced comparing with PB and packed-bed stripper in pilot scale. Monoethanolamine (MEA) is the most commonly used amine, and typically, 30 wt% MEA is used as a benchmark absorbent, found that the advantage of RPB will only be significant when the kinetic rates of chemical reaction is fast. Notably, in a capture plant, the absorber is always operated in conjunction with the stripper, and the input of the lean solvent is not free of CO2 . For an MEA process, lean and rich loading should range between 0.35 and 0.49 [9, 10] for minimizing energy consumption during regeneration. Furthermore, numerous pilot-scale studies consisting of a full absorber stripper have been reported, with more previous studies reviewed by Llano-Restrepo [11]. On the other hand, studies using an RPB absorber are relatively scarce.
http://dx.doi.org/10.1016/j.jtice.2016.08.046 1876-1070/© 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Please cite this article as: N. Chamchan et al., Comparison of rotating packed bed and packed bed absorber in pilot plant and model simulation for CO2 capture, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.08.046
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Fig. 1. Experimental apparatus for the capture of CO2 using the PB and RPB. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
In addition, not only experiments, but also simulation, of the capture of CO2 by chemical absorption is widely investigated. A rate-based model has been successfully developed by a commercial platform, Aspen plus, using solvent of 30 wt% MEA; it has already validated results with a number of experimental data [12– 14]. However, the RPB model is not available in the commercial software; Kang [15] has developed this model based on a twofilm theory for mass transfer, which was successfully validated and showed good agreement with the results obtained from laboratoryscale experiments. In this study, pilot-scale results are reported using the PB and RPB absorber operating with a PB stripper results using 30 wt% MEA as the solvent. In addition, the results obtained from the experiments conducted using 30 wt% MEA are compared to those obtained from simulation using the rate-based model developed by Aspen Plus and Advanced Customer Modeler (ACM). 2. Experiment 2.1. Pilot plant setup The combustion product of a blast furnace gas was used as the inlet flue gas stream: 68 vol% of N2 , 30 vol% of CO2 , 1.5 vol% of O2 , water, SOx , and NOx . The pilot plant is designed to have a nominal capacity 0.1 ton/day of the flue gas. Fig. 1 shows the process flow diagram of the facility used in this study. The gas reacts with the recycled lean solvent in the absorber, and leaves the top of the absorber. Rich solution stream
containing the absorbed CO2 leaves the bottom of the absorber, and heat exchange with the hot lean solvent before entering the stripper. The desorbed CO2 leaving in the top of stripper, while the lean solvent stream is recycled back to the absorber after cooling. The PB column had a diameter of 0.1 m and a height of 2 m, which was packed with 16 mm SUS pall ring. The volume of the PB absorber was 15,707 cm3 . The RPB absorber had an inner diameter of 0.12 m, an outer diameter 0.36 m, and a height of 0.06 m, which was packed with a wire mesh packing; the packing volume was 5428 cm3 , approximately 1/3 of the PB column.
2.2. Operating procedure The operating procedures for the absorption of CO2 over PB are detailed below, and the flowsheet showed in Fig. 1 (green and blue solid lines represent the gas in and out and liquid in and out, respectively) (1) Open the valve 101 (V101) for the input of exhaust gas in the experiments. (2) Open cool water to the absorber (A101) and stripper (A102). (3) Open the valves 106, 108, 109, and 110 (V106, V108, V109, and V110) for recycling the exhaust gas to A101 and A102. (4) Open the exit valve (KSV-102) of cooling water of the columns for releasing the cooling wastewater. (5) Open the instrumentation glass panel, unscrew the emergency bottom, and start the power switch.
Please cite this article as: N. Chamchan et al., Comparison of rotating packed bed and packed bed absorber in pilot plant and model simulation for CO2 capture, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.08.046
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N. Chamchan et al. / Journal of the Taiwan Institute of Chemical Engineers 000 (2016) 1–7 Table 1 Experimental data for PB and RPB absorber at CSC pilot plant with 30 wt% MEA. PB Liquid flow rate (kg/h) Energy consumption (GJ/ton CO2 ) Gas inlet flowrate (mol/h) Gas outlet flowrate (mol/h) CO2 gas inlet flowrate (mol/h) CO2 gas outlet flowrate (mol/h)
3
Table 2 Mass balance data for PB and RPB absorber at CSC pilot plant with 30 wt% MEA absorbent. PB
110 8.21 244.32 174.44 80.14 10.26
120 8.08 264.63 188.78 86.32 10.48
130 7.48 287.23 202.39 94.53 9.69
110 8.70 0.164 241.11 176.07 77.28 12.24
120 8.04 0.150 263.61 170.63 85.41 12.43
130 7.99 0.125 285.37 204.99 93.31 12.93
Liquid flow rate (kg/h) Actual MEA concentration (wt%) Rich loading (molCO2 /molMEA ) Lean loading (molCO2 /molMEA ) Liquid obtained (molCO2 /h) Gas loss (molCO2 /h) Mass balance error (%)
RPB
110 20.77 0.57 0.36 78.57 69.88 −12.43
120 20.06 0.57 0.36 84.35 75.84 −11.22
130 21.23 0.57 0.37 87.67 84.84 −3.34
110 20.27 0.55 0.37 65.72 65.04 −1.05
120 20.27 0.55 0.35 76.46 72.98 −4.77
130 20.00 0.54 0.36 76.64 72.21 −6.13
RPB Liquid flow rate (kg/h) Energy consumption (GJ/ton CO2 ) Rotation energy (GJ/ton CO2 ) Gas inlet flowrate (mol/h) Gas outlet flowrate (mol/h) CO2 gas inlet flowrate (mol/h) CO2 gas outlet flowrate (mol/h)
(6) Open the KSV-101 valve and KSP-101 pump for increasing the pressure in A101 and switch to automatic control. (7) Regulate the CO2 analyzer. (8) Set the opening degree for changing the input rate to 11.2 m3 /h. (9) Set the KSV-101 and V106 to automatic control and set the recycle pressure to 1.14 kg/cm2 and 0.1 kg/cm2 . (10) Set a small output stream in KSV-102 for releasing some wastewater. (11) Ensure that valves 111, 112, and 113 (V111, V112, and V113) are closed and place the absorbent solvent into storage tank 1. (12) Open V113 after storage tank 1 through pump 103 (P103) for pumping MEA to storage tank 2, and after overbrimming the absorbent solvent, close V113. (13) Open V111, close V109, V110, and pump 102 (P102), as well as set the recycle rate. After filling the absorbent in A102, close V111, and open V109 and V110. (14) Through P102, the absorbent recycles to A101. (15) The exhaust gas (gas in) contacts with the absorbent, and the vent gas (gas out) emits at the top of A101. (16) When P101 is opened, the rich-CO2 solvent (liquid out) will pump back to A102, and the recycle is being built. (17) Wait for the absorbent to attain saturation: the CO2 concentration in the liquid in is same as the liquid out. Open the reboiler for heating the solvent. (18) Wait until the system is stabilized, then sample the lean solvent (liquid in) and rich solution (liquid out) and record the temperature, pressure, flow rate, and CO2 concentrations. (19) After step 18, set a new recycle rate and return to step 13. The procedures for the absorption of CO2 using the RPB are listed below, and only few the differences between with procedures for the absorption of CO2 over PB (dotted line represent flows when operated in RPB mode, solid line represents flow when operated in PB mode). (1) Open valve 102 (V102) for inputting gas into the RPB; (2) open the cool water to the RPB and stripper (A102); (3) open valves 105, 108, 109, and 110 (V105, V108, V109, and V110) for recycling exhaust gas to A101 and A102; (6) open the KSV-103 valve and KSP-101 pump for increasing the pressure in the RPB and switch to automatic control; (9) set the KSV-103 and V105 to automatic control; (10) set a small output stream in KSV-104 for the timely release of some wastewater; and (15) the exhaust gas (gas in) contacts with the absorbent, and the vent gas (gas out) is emitted at the top of the RPB. Table 1 list the results obtained from the experiments using 30 wt% MEA with PB and RPB. In each set of experiments, absorp-
Liquid flow rate (kg/h) Actual MEA concentration (wt%) Rich loading (molCO2 /molMEA ) Lean loading (molCO2 /molMEA ) Liquid obtained (molCO2 /h) Gas loss (molCO2 /h) Mass balance error (%)
tion was performed at three rates of recycling liquid: 110, 120, and 130 kg/h. 2.3. Mass balance Although a nominal solution concentration of 30 wt% MEA was used, this solution was used for a period of time in other experiments. Hence, these concentrations may change because of loss of vaporization or degradation. As a result, the concentrations of amine in the recycled lean solvent and rich solutions were titrated, as well as CO2 loading. Table 2 lists the results obtained from titration as well as mass balances calculated by these results. The concentration of MEA in the 30 wt% MEA solution is approximately 20 wt%. Given the rich and lean loading as well as the amine concentration, the increased CO2 in the liquid can be calculated as follows:
CO2 Captured in liquid (Rich loading − Lean loading )wt% of Amines = (Molecular weight of Amines) × Liquid flowrate × Liquid flowrate
(1)
CO2 Extracted in gas = CO2 Inlet flowrate − CO2 Outlet flowrate (2) Mass balance (MB) errors are defined as follows:
MB Error% = 1 −
CO2 Captured in liquid CO2 Extracted in gas
× 100%
(3)
The MB errors were found to range between 1% and 13%. The accuracy of mass balance can be rechecked in systems. 2.4. Experimental results Fig. 2a compares the %CO2 removal between PB and RPB obtained using MEA. In all cases, as compared to PRB, PB exhibits a slightly higher capture ratio as the flow rate of the liquid is between 110 and 130 kg/h. These results indicate that absorption performance is more or less the same in an RPB with one-third the packing volume of PB. For measuring the performance of mass transfer, the HTU of a PB can be expressed as the height of packed column divided by the log mean of inlet and outlet of CO2 concentration.
HTUPB =
HPB yCO , inlet ln y 2 CO , outlet
(4)
2
Please cite this article as: N. Chamchan et al., Comparison of rotating packed bed and packed bed absorber in pilot plant and model simulation for CO2 capture, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.08.046
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Fig. 2c shows the estimated energy consumption (GJ/ton CO2 ) of the captured CO2 . However, energy consumption using RPB is similar to, albeit slightly higher than, that of the PB; the values were higher in comparison to the standard values reported in literature because of undersized heat exchanger used, attributed to leakage during the experimental period. In the RPB operation, electrical power is required to rotate the RPB. The powers required for each experiments were logged and given in Table 2 and Fig. 2c. They were small compared to the energy consumption of the reboiler. 3. Modeling studies 3.1. Model development The implementation model in ACM is based on the RPB model introduced by Kang [15]. The following assumptions were utilized for model development with respect to the adopted absorber based on the assumptions made by Kvamsdal et al. [16]. For the chemical reaction which occurs only in the liquid phase, the equilibrium reaction parameters was taken from Austgen et al. [17]. On the other hand, the kinetic reaction used the Aspen plus databanks [18]. Moreover, Onda et al. [19] and Tung and Mah [20] were used as gas and liquid mass transfer correlation, respectively on model of RPB. However, in case of PB model, Billet and Schultes [21] mass-transfer correlation was applied in both ACM and Aspen Plus rate based simulation. As compared to the plant operation, the advanced mathematical model can describe the behavior of the RPB absorber. Dependent variables in this model can possibly vary with the radial position in the absorber. The explanation of this behavior involves a partial differential equation and an algebraic equation. However, the PB model was also developed on the basis of the same assumption, as well as the RPB model, albeit considering a different flow direction. 3.2. Model validation The in-house model for PB were validated using pilot plant data from literature using PB [22– 24]. Furthermore, the PB simulations were also compared with the Aspen plus platform for ensuring the reliability of the result. In case of Sulzer structured packing, such as Mellapak 250Y, CV and CL constants are not available for the Billet and Schultes masstransfer correlation; hence, this validation uses previously reported values [25] of 0.983 and 0.270 for CL and CV , respectively. On the other hand, no previous study has reported the use of not only Mellapak 250Y but also pall ring metal 16 mm [21]; hence, in general, a constant number of pall ring 25 mm is used instead, as 1.440 and 0.336 for CL and CV , respectively. Fig. 2. Comparison of the MEA absorbent in PB and RPB (a) %CO2 removal (b) HTU and (c) energy consumption.
For an RPB, HTU can be defined as the volume of the packing divided by the log mean of inlet and outlet of CO2 concentration multiply with the log mean of the inner and outer areas.
HTURPB =
VRPB
yCO
ln y
2 , inlet
CO2 , outlet
×
(5)
Aouter −Ainner ln
Areaouter Areainner
As can be observed in Fig. 2b, the HTU of the RPB is only 1/10 that of the PB for MEA. Hence, the performance of an RPB absorber is substantially better than that of a PB absorber.
3.2.1. Pilot plant in Newcastle, Australia [22] The pilot plant located at the CSIRO Centre to test the solvent and process improvements at a pilot-scale. This process was designed to operate with a CO2 capacity of 25 kg/h and maximum inlet gas flowrate of 72 nm3 /h. The absorber is packed bed column which has 8 packed section with the 16 mm metal pall ring with 0.308 m of height per section and 0.148 m of diameter. The column has a total height of 5.7 m. The stripper was designed with the same number of packing and size of column. The outlet gas from the stripper passes through a condenser to remove water and then releases to the atmosphere. 3.2.2. Pilot plant in Lyngby, Denmark [23] This process of CO2 capture is a standalone packed bed column located at Center for Energy Resources Engineering (CERE)
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Fig. 3. Agreement of %CO2 removal between simulation and experimental results (a) published PB pilot-plant (b) CSC pilot-plant.
which can be used for model development and test their ratedbased model. The absorber is designed with 10.5 m which can vary the height of the packing from 1.6 to 8.2 m. with a packing diameter of 0.084 m. The absorber was made from pyrex glass with the structured packing of Sulzer Mellapak 250Y which is separated into 10 sections. A steady state of this process is received when the process variables varied less than 4%. Therefore, this pilot-plant experiment has a good reliable mass balance with an important factor to validate the model with the experimental data.
Furthermore, the RPB model is validated by the data obtained from China Steel Corporation (CSC) pilot plant; however, only one pilot plant is operated using the RPB absorber; nevertheless, the same assumption can be made for the PB model compared to experiment and Aspen plus, demonstrating that this model predicts accurate results with this assumption, so this model can be used in RPB as well as in PB. Table 4 shows the characteristics of the RPB absorber.
3.2.3. Pilot plant in Kaiserslautern, Germany [24] This pilot plant located at the Laboratory of Engineering Thermodynamics (LTD) with the full cycle of CO2 capture process with the typical flowsheet. This experimental data was used to validate theirs in-house model for designing the suitable scale-up process. The absorber is designed with 5 packing sections, in each contain structured packing Sulzer Mellapak 250Y with 0.84 m of height per section. The diameter of the absorber is 0.125 m. Furthermore, the stripper with the same diameter as well as in absorber but with the total height of 2.52 m. For the summary process descriptions of each pilot plant are listed in Table 3. Therefore, the in-house PB model is compared with the commercial software, Aspen plus, to validate the assumption of the pilot-scale model.
Fig. 3a shows the agreement of %CO2 removal between the experimental and simulation data obtained from the pilot plants with different process condition and characteristics of PB, flue gas, and solvent. It should be pointed out that the pilot results selected cover a large range of capture efficiencies achieved by different means. The pilot plant results of Newcastle achieved variations between 70 and 100% by varying the L/G ratio which the increasing of L/G ratio. Furthermore, the pilot plant in Lyngby adjusted the height of packing from 1.6 and 8.2 m. and L/G ratios but vary the operating conditions. The data selected are in the range of 90–100%, and had been validated by Llano-Restrepo et al.[11]. The pilot plant in Kaiserslautern, provided data in the lower range of 40–60% for model validation. The in-house ACM PB model simulation results
3.3. Model results
Please cite this article as: N. Chamchan et al., Comparison of rotating packed bed and packed bed absorber in pilot plant and model simulation for CO2 capture, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.08.046
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N. Chamchan et al. / Journal of the Taiwan Institute of Chemical Engineers 000 (2016) 1–7 Table 3 Characteristics of the pilot-scale PB absorber and stripper. Parameters
unit
Sønderby et al. [23]
Notz et al. [24]
Saimpert et al. [22]
CSC (2015)
Absorber Diameter Packing height Packing type Pressure Gas inlet Gas in temp. molCO2 frac. in Liquid inlet Liquid in temp. MEA conc. Lean loading
m m – atm mol/min °C – kg/h °C wt% molCO2 /molMEA
0.1 4.9–8.2 Mellapak 250Y 1 24.5–26.7 24.8–28.2 0.094–0.104 260–564 20.0–27.9 30 0.112–0.300
0.125 4.2 Mellapak 250Y 1 2.56–2.74 47.1–48.7 0.054–0.132 125–275 46.3–48.5 30 0.260–0.353
0.148 2.46 Pall ring 16 1 13.8–25.4 35.4–40.4 0.087–0.089 120–222 39.3–41.5 32.4–36.2 0.182–0.210
0.1 2.0 Pall ring 16 1 4.07–4.41 24.8–26.6 0.326–0.329 110–130 35.1–35.6 30 0.357–0.365
Stripper Diameter Packing height Packing type
m m –
– – –
0.125 2.52 Mellapak 250Y
0.148 2.46 Pall ring 16
0.1 2.0 Pall ring 16
Table 4 Characteristics of the RPB absorber at CSC pilot plant. Parameters
Unit
Value
Inside diameter Outside diameter Packing height Motor speed Packing type Total surface area Porosity
m m m RPM – m2 /m3 –
0.12 0.36 0.06 1600 Stainless wire mesh 246.1 0.9832
agreed well with the experimental results. They are also similar to Aspen Plus Rate-based model predictions. With the model validated, the ACM-PB and ACM-RPB models were applied to experimental runs obtained from our pilot plant in CSC. There are in general good agreement as show in Fig. 3b. The ASPEN Plus Rate-based model also agrees well with the experiments. The stripper energy consumption was also compared in Fig. 4. They were obtained using the ASPEN Plus Rate-Based model for the stripper. The simulated rich solution streams were heat exchanged with the bottom stream coming out of the stripper, so that the stream reached temperature of the rich solution going into stripper, or heated by the exchange duty provided by experimenters. The reboiler duty was adjusted so that regenerated solvent recovered lean loading used in the absorption. The simulated results obtained for the Newcastle plant and the Kaiserslautern plant were higher than the experimental values. No data was provided by the Lygnby plant. For the CSC plant, model predictions agree well with experiments in Fig. 4b. It should be pointed out that in the CSC plant, the heat was provided by electricity and the amount of heat generated can be recorded with accuracy. In addition, the average absolute average deviation (%AAD) of CO2 removal efficiency as 5.72% for PB using Aspen plus, 5.84% for PB using ACM, and 4.18% for RPB using ACM. For energy consumption, predicts the simulation result of 11.19%AAD for PB using Aspen plus, 11.44%AAD for PB using ACM, and 2.19%AAD for RPB using ACM. The good agreement between the simulation of both commercial platform and the in-house model demonstrates reliable results. 4. Conclusions In this study, the performance of PB and RPB absorber were compared in absorption–regeneration process using MEA solvents.
Fig. 4. Agreement of energy consumption between simulation and experimental results (a) published PB pilot-plant (b) CSC pilot-plant.
Better separation efficiency is observed by using an RPB absorber, proven by the significant decrease in the HTU, and the use of only 35% of PB absorber volume, while the energy consumption is almost the same. The experimental results are also consistent with in-house ACM PB and RPB model predictions integrated into an ASPEN plus flowsheet.
Acknowledgment This work was supported by the Ministry of Science and Technology, Republic of China, under Grant 105-3113-E-0 07-0 01, China Steel Corporation under Grant RE-1046-3-9, and National Tsing Hua University under Grant 105N508CE1.
Please cite this article as: N. Chamchan et al., Comparison of rotating packed bed and packed bed absorber in pilot plant and model simulation for CO2 capture, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.08.046
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[14] Zhang LL, Wang JX, Xiang Y, Zeng XF, Chen JF. Absorption of carbon dioxide with ionic liquid in a rotating packed bed contactor: mass transfer study. Ind Eng Chem Res 2011;50:6957–64. [15] Kang JL, Sun K, Wong DSH, Janga SS, Tan CS. Modeling studies on absorption of CO2 by monoethanolamine in rotating packed bed. Int J Greenh Gas Control 2014;25:141–50. [16] Kvamsdal HM, Jakobsen JP, Hoff KA. Dynamic modeling and simulation of a CO2 absorber column for post-combustion CO2 capture. Chem Eng Process Process Intensif 2009;48:135–44. [17] Austgen DM, Rochelle GT, Peng X, Chen CC. Model of vapor liquid equilibria for aqueous acid gas alkanolamine systems using the electrolyte nrtl equation. Ind Eng Chem Res 1989;28:1060–73. [18] Aspen, 2008. Rate-based model of the CO2 capture process by MEA using aspen plus. [19] Onda K, Takeuchi H, Okumoto Y. Mass transfer coefficients between gas and liquid phases in packed columns. J Chem Eng Japan 1968;1:56–62. [20] Tung HH, Mah RSH. Modeling liquid mass-transfer in higee separation process. Chem Eng Commun 1985;39:147–53. [21] Billet R, Schultes M. Prediction of mass transfer columns with dumped and arranged packings – updated summary of the calculation method of Billet and Schultes. Chem Eng Res Des 1999;77:498–504. [22] Saimpert M, Puxty G, Qureshi S, Wardhaugh L, Cousins A. A new rate based absorber and desorber modelling tool. Chem Eng Sci 2013;96:10–25. [23] Sønderby TL, Carlsen KB, Fosbøl PL, Kiørboeb LG, von Solms N. A new pilot absorber for CO2 capture from flue gases: measuring and modelling capture with MEA solution. Int J Greenh Gas Control 2013;12:181–92. [24] Notz R, Mangalapally HP, Hasse H. Post combustion CO2 capture by reactive absorption: pilot plant description and results of systematic studies with MEA. Int J Greenh Gas Control 2012;6:84–112. [25] Razi N, Svendsen HF, Bolland O. Validation of mass transfer correlations for CO2 absorption with MEA using pilot data. Int J Greenh Gas Control 2013;19:478–91.
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Comparison of rotating packed bed and packed bed absorber in pilot plant and model simulation for CO2 capture Nipon Chamchan a, Jia-Yu Chang a, Hsiao-Ching Hsu a, Jia-Lin Kang a, David Shan Hill Wong a,∗, Shi-Shang Jang a, Jui-Fu Shen b a b
Department of Chemical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan, ROC New Materials Research & Development Department, China Steel Corporation, Kaohsiung, Taiwan, ROC
a r t i c l e
i n f o
Article history: Received 1 May 2016 Revised 30 July 2016 Accepted 16 August 2016 Available online xxx Keywords: Rotating packed bed Packed bed Pilot plant Carbon dioxide capture Chemical absorption Simulation
a b s t r a c t In this study, both packed-bed (PB) and rotating PB (RPB) absorbers with a packed-bed stripper were used in a pilot plant for the removal of carbon dioxide (CO2 ) with 30 wt% monoethanolamine (MEA) as the solvent. The flue gas feed is the combustion product of the blast furnace gas from a steel mill containing approximately 30% of CO2 . Both PB and RPB exhibit the same performance for the capture of CO2 with the same amount of energy consumption, but the RPB has a volume of approximately one-third that of PB absorber. The results obtained from experiments using ∼20 wt% MEA showed good agreement with those obtained from simulation using an Aspen rate-based model for PB and an Aspen custom modeler for RPB. These results demonstrated the feasibility of using a RPB for decreasing the size of absorber under relevant process conditions for capturing CO2 . © 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
1. Introduction Emissions of carbon dioxide (CO2 ) are considered to be the most important anthropogenic greenhouse gas (GHG), which contributes to global warming. Several methods are available for mitigating anthropogenic CO2 . The International Energy Administration (IEA) have stipulated as the capture, storage, and utilization of CO2 (CCSU) as one of the important options for reducing GHG emissions [1]. Three main methods are available for the capture of CO2 : post-combustion, pre-combustion, and oxy-fuel combustion. Postcombustion capture involves chemical absorption for separating CO2 for further storage and utilization. On the other hand, with the use of pre-combustion for the capture of CO2 , increased CO2 concentration could decrease the apparatus and equipment costs. Also, the hydrogen produced by the above-mentioned process can be used as fuel as well as for other purposes. Oxy-fuel combustion involves the separation of oxygen from air for producing flue gases, mainly consisting of CO2 and water, with the aim of producing a more concentrated CO2 stream. Among the aforementioned processes, post-combustion carbon capture technology is emerging as a commercially viable process. The main advantage is that ∗
Corresponding authors. Fax: +886 35715408. E-mail addresses: [email protected] (D.S.H. Wong), [email protected] (S.-S. Jang).
this method can be easily applied to existing power plants without significant change in the process of power generation. However, chemical absorption processes exhibit main drawbacks of requirements of PB absorbers with enormous volume and high energy for regenerating solvents. As developed by Ramshaw and Mallinson [2], RPB or Higee absorbers are well known to enhance the mass transfer rate between liquid and vapor phases, thereby considerably decreasing equipment size. Several authors have investigated the application of RPB for CO2 absorption [3–8]. Most of these studies were conducted using laboratory-size absorbers. In our studies, by using a pilot plant with RPB and packed-bed stripper, the height transfer unit (HTU) is substantially reduced comparing with PB and packed-bed stripper in pilot scale. Monoethanolamine (MEA) is the most commonly used amine, and typically, 30 wt% MEA is used as a benchmark absorbent, found that the advantage of RPB will only be significant when the kinetic rates of chemical reaction is fast. Notably, in a capture plant, the absorber is always operated in conjunction with the stripper, and the input of the lean solvent is not free of CO2 . For an MEA process, lean and rich loading should range between 0.35 and 0.49 [9, 10] for minimizing energy consumption during regeneration. Furthermore, numerous pilot-scale studies consisting of a full absorber stripper have been reported, with more previous studies reviewed by Llano-Restrepo [11]. On the other hand, studies using an RPB absorber are relatively scarce.
http://dx.doi.org/10.1016/j.jtice.2016.08.046 1876-1070/© 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Please cite this article as: N. Chamchan et al., Comparison of rotating packed bed and packed bed absorber in pilot plant and model simulation for CO2 capture, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.08.046
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Fig. 1. Experimental apparatus for the capture of CO2 using the PB and RPB. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
In addition, not only experiments, but also simulation, of the capture of CO2 by chemical absorption is widely investigated. A rate-based model has been successfully developed by a commercial platform, Aspen plus, using solvent of 30 wt% MEA; it has already validated results with a number of experimental data [12– 14]. However, the RPB model is not available in the commercial software; Kang [15] has developed this model based on a twofilm theory for mass transfer, which was successfully validated and showed good agreement with the results obtained from laboratoryscale experiments. In this study, pilot-scale results are reported using the PB and RPB absorber operating with a PB stripper results using 30 wt% MEA as the solvent. In addition, the results obtained from the experiments conducted using 30 wt% MEA are compared to those obtained from simulation using the rate-based model developed by Aspen Plus and Advanced Customer Modeler (ACM). 2. Experiment 2.1. Pilot plant setup The combustion product of a blast furnace gas was used as the inlet flue gas stream: 68 vol% of N2 , 30 vol% of CO2 , 1.5 vol% of O2 , water, SOx , and NOx . The pilot plant is designed to have a nominal capacity 0.1 ton/day of the flue gas. Fig. 1 shows the process flow diagram of the facility used in this study. The gas reacts with the recycled lean solvent in the absorber, and leaves the top of the absorber. Rich solution stream
containing the absorbed CO2 leaves the bottom of the absorber, and heat exchange with the hot lean solvent before entering the stripper. The desorbed CO2 leaving in the top of stripper, while the lean solvent stream is recycled back to the absorber after cooling. The PB column had a diameter of 0.1 m and a height of 2 m, which was packed with 16 mm SUS pall ring. The volume of the PB absorber was 15,707 cm3 . The RPB absorber had an inner diameter of 0.12 m, an outer diameter 0.36 m, and a height of 0.06 m, which was packed with a wire mesh packing; the packing volume was 5428 cm3 , approximately 1/3 of the PB column.
2.2. Operating procedure The operating procedures for the absorption of CO2 over PB are detailed below, and the flowsheet showed in Fig. 1 (green and blue solid lines represent the gas in and out and liquid in and out, respectively) (1) Open the valve 101 (V101) for the input of exhaust gas in the experiments. (2) Open cool water to the absorber (A101) and stripper (A102). (3) Open the valves 106, 108, 109, and 110 (V106, V108, V109, and V110) for recycling the exhaust gas to A101 and A102. (4) Open the exit valve (KSV-102) of cooling water of the columns for releasing the cooling wastewater. (5) Open the instrumentation glass panel, unscrew the emergency bottom, and start the power switch.
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N. Chamchan et al. / Journal of the Taiwan Institute of Chemical Engineers 000 (2016) 1–7 Table 1 Experimental data for PB and RPB absorber at CSC pilot plant with 30 wt% MEA. PB Liquid flow rate (kg/h) Energy consumption (GJ/ton CO2 ) Gas inlet flowrate (mol/h) Gas outlet flowrate (mol/h) CO2 gas inlet flowrate (mol/h) CO2 gas outlet flowrate (mol/h)
3
Table 2 Mass balance data for PB and RPB absorber at CSC pilot plant with 30 wt% MEA absorbent. PB
110 8.21 244.32 174.44 80.14 10.26
120 8.08 264.63 188.78 86.32 10.48
130 7.48 287.23 202.39 94.53 9.69
110 8.70 0.164 241.11 176.07 77.28 12.24
120 8.04 0.150 263.61 170.63 85.41 12.43
130 7.99 0.125 285.37 204.99 93.31 12.93
Liquid flow rate (kg/h) Actual MEA concentration (wt%) Rich loading (molCO2 /molMEA ) Lean loading (molCO2 /molMEA ) Liquid obtained (molCO2 /h) Gas loss (molCO2 /h) Mass balance error (%)
RPB
110 20.77 0.57 0.36 78.57 69.88 −12.43
120 20.06 0.57 0.36 84.35 75.84 −11.22
130 21.23 0.57 0.37 87.67 84.84 −3.34
110 20.27 0.55 0.37 65.72 65.04 −1.05
120 20.27 0.55 0.35 76.46 72.98 −4.77
130 20.00 0.54 0.36 76.64 72.21 −6.13
RPB Liquid flow rate (kg/h) Energy consumption (GJ/ton CO2 ) Rotation energy (GJ/ton CO2 ) Gas inlet flowrate (mol/h) Gas outlet flowrate (mol/h) CO2 gas inlet flowrate (mol/h) CO2 gas outlet flowrate (mol/h)
(6) Open the KSV-101 valve and KSP-101 pump for increasing the pressure in A101 and switch to automatic control. (7) Regulate the CO2 analyzer. (8) Set the opening degree for changing the input rate to 11.2 m3 /h. (9) Set the KSV-101 and V106 to automatic control and set the recycle pressure to 1.14 kg/cm2 and 0.1 kg/cm2 . (10) Set a small output stream in KSV-102 for releasing some wastewater. (11) Ensure that valves 111, 112, and 113 (V111, V112, and V113) are closed and place the absorbent solvent into storage tank 1. (12) Open V113 after storage tank 1 through pump 103 (P103) for pumping MEA to storage tank 2, and after overbrimming the absorbent solvent, close V113. (13) Open V111, close V109, V110, and pump 102 (P102), as well as set the recycle rate. After filling the absorbent in A102, close V111, and open V109 and V110. (14) Through P102, the absorbent recycles to A101. (15) The exhaust gas (gas in) contacts with the absorbent, and the vent gas (gas out) emits at the top of A101. (16) When P101 is opened, the rich-CO2 solvent (liquid out) will pump back to A102, and the recycle is being built. (17) Wait for the absorbent to attain saturation: the CO2 concentration in the liquid in is same as the liquid out. Open the reboiler for heating the solvent. (18) Wait until the system is stabilized, then sample the lean solvent (liquid in) and rich solution (liquid out) and record the temperature, pressure, flow rate, and CO2 concentrations. (19) After step 18, set a new recycle rate and return to step 13. The procedures for the absorption of CO2 using the RPB are listed below, and only few the differences between with procedures for the absorption of CO2 over PB (dotted line represent flows when operated in RPB mode, solid line represents flow when operated in PB mode). (1) Open valve 102 (V102) for inputting gas into the RPB; (2) open the cool water to the RPB and stripper (A102); (3) open valves 105, 108, 109, and 110 (V105, V108, V109, and V110) for recycling exhaust gas to A101 and A102; (6) open the KSV-103 valve and KSP-101 pump for increasing the pressure in the RPB and switch to automatic control; (9) set the KSV-103 and V105 to automatic control; (10) set a small output stream in KSV-104 for the timely release of some wastewater; and (15) the exhaust gas (gas in) contacts with the absorbent, and the vent gas (gas out) is emitted at the top of the RPB. Table 1 list the results obtained from the experiments using 30 wt% MEA with PB and RPB. In each set of experiments, absorp-
Liquid flow rate (kg/h) Actual MEA concentration (wt%) Rich loading (molCO2 /molMEA ) Lean loading (molCO2 /molMEA ) Liquid obtained (molCO2 /h) Gas loss (molCO2 /h) Mass balance error (%)
tion was performed at three rates of recycling liquid: 110, 120, and 130 kg/h. 2.3. Mass balance Although a nominal solution concentration of 30 wt% MEA was used, this solution was used for a period of time in other experiments. Hence, these concentrations may change because of loss of vaporization or degradation. As a result, the concentrations of amine in the recycled lean solvent and rich solutions were titrated, as well as CO2 loading. Table 2 lists the results obtained from titration as well as mass balances calculated by these results. The concentration of MEA in the 30 wt% MEA solution is approximately 20 wt%. Given the rich and lean loading as well as the amine concentration, the increased CO2 in the liquid can be calculated as follows:
CO2 Captured in liquid (Rich loading − Lean loading )wt% of Amines = (Molecular weight of Amines) × Liquid flowrate × Liquid flowrate
(1)
CO2 Extracted in gas = CO2 Inlet flowrate − CO2 Outlet flowrate (2) Mass balance (MB) errors are defined as follows:
MB Error% = 1 −
CO2 Captured in liquid CO2 Extracted in gas
× 100%
(3)
The MB errors were found to range between 1% and 13%. The accuracy of mass balance can be rechecked in systems. 2.4. Experimental results Fig. 2a compares the %CO2 removal between PB and RPB obtained using MEA. In all cases, as compared to PRB, PB exhibits a slightly higher capture ratio as the flow rate of the liquid is between 110 and 130 kg/h. These results indicate that absorption performance is more or less the same in an RPB with one-third the packing volume of PB. For measuring the performance of mass transfer, the HTU of a PB can be expressed as the height of packed column divided by the log mean of inlet and outlet of CO2 concentration.
HTUPB =
HPB yCO , inlet ln y 2 CO , outlet
(4)
2
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Fig. 2c shows the estimated energy consumption (GJ/ton CO2 ) of the captured CO2 . However, energy consumption using RPB is similar to, albeit slightly higher than, that of the PB; the values were higher in comparison to the standard values reported in literature because of undersized heat exchanger used, attributed to leakage during the experimental period. In the RPB operation, electrical power is required to rotate the RPB. The powers required for each experiments were logged and given in Table 2 and Fig. 2c. They were small compared to the energy consumption of the reboiler. 3. Modeling studies 3.1. Model development The implementation model in ACM is based on the RPB model introduced by Kang [15]. The following assumptions were utilized for model development with respect to the adopted absorber based on the assumptions made by Kvamsdal et al. [16]. For the chemical reaction which occurs only in the liquid phase, the equilibrium reaction parameters was taken from Austgen et al. [17]. On the other hand, the kinetic reaction used the Aspen plus databanks [18]. Moreover, Onda et al. [19] and Tung and Mah [20] were used as gas and liquid mass transfer correlation, respectively on model of RPB. However, in case of PB model, Billet and Schultes [21] mass-transfer correlation was applied in both ACM and Aspen Plus rate based simulation. As compared to the plant operation, the advanced mathematical model can describe the behavior of the RPB absorber. Dependent variables in this model can possibly vary with the radial position in the absorber. The explanation of this behavior involves a partial differential equation and an algebraic equation. However, the PB model was also developed on the basis of the same assumption, as well as the RPB model, albeit considering a different flow direction. 3.2. Model validation The in-house model for PB were validated using pilot plant data from literature using PB [22– 24]. Furthermore, the PB simulations were also compared with the Aspen plus platform for ensuring the reliability of the result. In case of Sulzer structured packing, such as Mellapak 250Y, CV and CL constants are not available for the Billet and Schultes masstransfer correlation; hence, this validation uses previously reported values [25] of 0.983 and 0.270 for CL and CV , respectively. On the other hand, no previous study has reported the use of not only Mellapak 250Y but also pall ring metal 16 mm [21]; hence, in general, a constant number of pall ring 25 mm is used instead, as 1.440 and 0.336 for CL and CV , respectively. Fig. 2. Comparison of the MEA absorbent in PB and RPB (a) %CO2 removal (b) HTU and (c) energy consumption.
For an RPB, HTU can be defined as the volume of the packing divided by the log mean of inlet and outlet of CO2 concentration multiply with the log mean of the inner and outer areas.
HTURPB =
VRPB
yCO
ln y
2 , inlet
CO2 , outlet
×
(5)
Aouter −Ainner ln
Areaouter Areainner
As can be observed in Fig. 2b, the HTU of the RPB is only 1/10 that of the PB for MEA. Hence, the performance of an RPB absorber is substantially better than that of a PB absorber.
3.2.1. Pilot plant in Newcastle, Australia [22] The pilot plant located at the CSIRO Centre to test the solvent and process improvements at a pilot-scale. This process was designed to operate with a CO2 capacity of 25 kg/h and maximum inlet gas flowrate of 72 nm3 /h. The absorber is packed bed column which has 8 packed section with the 16 mm metal pall ring with 0.308 m of height per section and 0.148 m of diameter. The column has a total height of 5.7 m. The stripper was designed with the same number of packing and size of column. The outlet gas from the stripper passes through a condenser to remove water and then releases to the atmosphere. 3.2.2. Pilot plant in Lyngby, Denmark [23] This process of CO2 capture is a standalone packed bed column located at Center for Energy Resources Engineering (CERE)
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Fig. 3. Agreement of %CO2 removal between simulation and experimental results (a) published PB pilot-plant (b) CSC pilot-plant.
which can be used for model development and test their ratedbased model. The absorber is designed with 10.5 m which can vary the height of the packing from 1.6 to 8.2 m. with a packing diameter of 0.084 m. The absorber was made from pyrex glass with the structured packing of Sulzer Mellapak 250Y which is separated into 10 sections. A steady state of this process is received when the process variables varied less than 4%. Therefore, this pilot-plant experiment has a good reliable mass balance with an important factor to validate the model with the experimental data.
Furthermore, the RPB model is validated by the data obtained from China Steel Corporation (CSC) pilot plant; however, only one pilot plant is operated using the RPB absorber; nevertheless, the same assumption can be made for the PB model compared to experiment and Aspen plus, demonstrating that this model predicts accurate results with this assumption, so this model can be used in RPB as well as in PB. Table 4 shows the characteristics of the RPB absorber.
3.2.3. Pilot plant in Kaiserslautern, Germany [24] This pilot plant located at the Laboratory of Engineering Thermodynamics (LTD) with the full cycle of CO2 capture process with the typical flowsheet. This experimental data was used to validate theirs in-house model for designing the suitable scale-up process. The absorber is designed with 5 packing sections, in each contain structured packing Sulzer Mellapak 250Y with 0.84 m of height per section. The diameter of the absorber is 0.125 m. Furthermore, the stripper with the same diameter as well as in absorber but with the total height of 2.52 m. For the summary process descriptions of each pilot plant are listed in Table 3. Therefore, the in-house PB model is compared with the commercial software, Aspen plus, to validate the assumption of the pilot-scale model.
Fig. 3a shows the agreement of %CO2 removal between the experimental and simulation data obtained from the pilot plants with different process condition and characteristics of PB, flue gas, and solvent. It should be pointed out that the pilot results selected cover a large range of capture efficiencies achieved by different means. The pilot plant results of Newcastle achieved variations between 70 and 100% by varying the L/G ratio which the increasing of L/G ratio. Furthermore, the pilot plant in Lyngby adjusted the height of packing from 1.6 and 8.2 m. and L/G ratios but vary the operating conditions. The data selected are in the range of 90–100%, and had been validated by Llano-Restrepo et al.[11]. The pilot plant in Kaiserslautern, provided data in the lower range of 40–60% for model validation. The in-house ACM PB model simulation results
3.3. Model results
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N. Chamchan et al. / Journal of the Taiwan Institute of Chemical Engineers 000 (2016) 1–7 Table 3 Characteristics of the pilot-scale PB absorber and stripper. Parameters
unit
Sønderby et al. [23]
Notz et al. [24]
Saimpert et al. [22]
CSC (2015)
Absorber Diameter Packing height Packing type Pressure Gas inlet Gas in temp. molCO2 frac. in Liquid inlet Liquid in temp. MEA conc. Lean loading
m m – atm mol/min °C – kg/h °C wt% molCO2 /molMEA
0.1 4.9–8.2 Mellapak 250Y 1 24.5–26.7 24.8–28.2 0.094–0.104 260–564 20.0–27.9 30 0.112–0.300
0.125 4.2 Mellapak 250Y 1 2.56–2.74 47.1–48.7 0.054–0.132 125–275 46.3–48.5 30 0.260–0.353
0.148 2.46 Pall ring 16 1 13.8–25.4 35.4–40.4 0.087–0.089 120–222 39.3–41.5 32.4–36.2 0.182–0.210
0.1 2.0 Pall ring 16 1 4.07–4.41 24.8–26.6 0.326–0.329 110–130 35.1–35.6 30 0.357–0.365
Stripper Diameter Packing height Packing type
m m –
– – –
0.125 2.52 Mellapak 250Y
0.148 2.46 Pall ring 16
0.1 2.0 Pall ring 16
Table 4 Characteristics of the RPB absorber at CSC pilot plant. Parameters
Unit
Value
Inside diameter Outside diameter Packing height Motor speed Packing type Total surface area Porosity
m m m RPM – m2 /m3 –
0.12 0.36 0.06 1600 Stainless wire mesh 246.1 0.9832
agreed well with the experimental results. They are also similar to Aspen Plus Rate-based model predictions. With the model validated, the ACM-PB and ACM-RPB models were applied to experimental runs obtained from our pilot plant in CSC. There are in general good agreement as show in Fig. 3b. The ASPEN Plus Rate-based model also agrees well with the experiments. The stripper energy consumption was also compared in Fig. 4. They were obtained using the ASPEN Plus Rate-Based model for the stripper. The simulated rich solution streams were heat exchanged with the bottom stream coming out of the stripper, so that the stream reached temperature of the rich solution going into stripper, or heated by the exchange duty provided by experimenters. The reboiler duty was adjusted so that regenerated solvent recovered lean loading used in the absorption. The simulated results obtained for the Newcastle plant and the Kaiserslautern plant were higher than the experimental values. No data was provided by the Lygnby plant. For the CSC plant, model predictions agree well with experiments in Fig. 4b. It should be pointed out that in the CSC plant, the heat was provided by electricity and the amount of heat generated can be recorded with accuracy. In addition, the average absolute average deviation (%AAD) of CO2 removal efficiency as 5.72% for PB using Aspen plus, 5.84% for PB using ACM, and 4.18% for RPB using ACM. For energy consumption, predicts the simulation result of 11.19%AAD for PB using Aspen plus, 11.44%AAD for PB using ACM, and 2.19%AAD for RPB using ACM. The good agreement between the simulation of both commercial platform and the in-house model demonstrates reliable results. 4. Conclusions In this study, the performance of PB and RPB absorber were compared in absorption–regeneration process using MEA solvents.
Fig. 4. Agreement of energy consumption between simulation and experimental results (a) published PB pilot-plant (b) CSC pilot-plant.
Better separation efficiency is observed by using an RPB absorber, proven by the significant decrease in the HTU, and the use of only 35% of PB absorber volume, while the energy consumption is almost the same. The experimental results are also consistent with in-house ACM PB and RPB model predictions integrated into an ASPEN plus flowsheet.
Acknowledgment This work was supported by the Ministry of Science and Technology, Republic of China, under Grant 105-3113-E-0 07-0 01, China Steel Corporation under Grant RE-1046-3-9, and National Tsing Hua University under Grant 105N508CE1.
Please cite this article as: N. Chamchan et al., Comparison of rotating packed bed and packed bed absorber in pilot plant and model simulation for CO2 capture, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.08.046
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Please cite this article as: N. Chamchan et al., Comparison of rotating packed bed and packed bed absorber in pilot plant and model simulation for CO2 capture, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.08.046