Lean CO2 Loading Research Articles

Experimental Study of Regeneration Performance of Aqueous N,N-Diethylethanolamine Solution in a Column Packed with Dixon Ring Random Packing

Carbon dioxide (CO2) stripping from CO2-loaded aqueous N,N-diethylethanolamine solution (DEEA) was comprehensively investigated in a laboratory scale regeneration column packed with Dixon ring random packing. The regeneration heat duty (Qreb) of DEEA was evaluated as a function of various operating parameters, including rich CO2 loading, lean CO2 loading, solution flow rate, feed temperature, and DEEA concentration, as well as synergistic parameters (e.g., Δα × L and C × L). The experimental results showed that the Qreb was sensitive to these operating parameters. For example, the Qreb decreased significantly as the lean CO2 loading, rich CO2 loading, and DEEA concentration increased, indicating that the Qreb can be reduced by adjusting these operating parameters. In addition, CO2-loaded aqueous DEEA solution was observed to have a lower Qreb (of 2.17 GJ/t CO2) as compared to those of aqueous MEA and DETA solutions. Based on heat duty alone, DEEA can be considered to be an attractive solvent for amine-based postcombustion CO2 capture.

Mass transfer performance of CO2 absorption into aqueous DEEA in packed columns

A bench-scale absorption column packed with high efficiency Sulzer DX-type packing was used to determine the volumetric overall mass transfer coefficient (KGav) for CO2 absorption into an aqueous solution of DEEA. The effects of the main operating parameters, such as liquid feed temperature, DEEA concentration, lean CO2 loading, liquid flow rate, CO2 partial pressure, and inert gas flow rate were examined. The results showed that DEEA concentration, CO2 lean loading, and liquid flow rate had a significant effect on KGav while inert gas flow rate had little effect. In addition, CO2-loaded aqueous DEEA solution was observed to have a higher KGav as compared to that of aqueous MDEA solutions. Also, the performance of CO2 absorption with DEEA in structured packing in terms of KGav and cyclic capacity (Δα) were compared with the performance in a random packing column. The structured packing column performed better than the random packing column. Finally, two experimental KGav correlation models for CO2-DEEA system were proposed and found to be in satisfactory agreement with experimental results with AAD of 8 and 3%, respectively.

Mass-Transfer Characteristics of the CO2Absorption Process in a Rotating Packed Bed

This article presents systematic investigations on the mass-transfer characteristics, including the overall gas-phase volumetric mass-transfer coefficient (KGa) and the height of mass-transfer unit (HTU), of the CO2 absorption process into a mixture of diethylenetriamine (DETA) and piperazine (PZ) solution in a rotating packed bed (RPB). The effects of operating conditions, including PZ concentration, rotation speed, liquid volumetric flow rate, gas volumetric flow rate, gas treatment capacity of packing, inlet CO2 mole fraction, temperature, CO2 loading of lean solution, and distributor specification on KGa and HTU in the RPB, were systematically studied. Also, a comparison of CO2 absorption performance between the packed column with Dixon rings packing and the RPB is presented. Results indicate that both KGa and HTU were significantly affected by rotation speed, liquid volumetric flow rate, gas volumetric flow rate, temperature, and lean CO2 loading while the PZ concentration, inlet CO2 mole fraction, a...

Dynamic simulation and analysis of a pilot-scale CO2 post-combustion capture unit using piperazine and MEA

Post-combustion capture is a promising technology for developing CO2 neutral power plants. However, to make it economically and technically feasible, capture plants must follow the fast and large load changes of the power plants without decreasing the overall performance of the plant. Dynamic modeling and simulation is therefore needed to evaluate the performance of this plant under critical operation.In this work, we evaluate the transient response of an absorber and a desorber for step changes of key process parameters, e.g. flue gas flow and composition, lean and rich CO2 loading, etc. We show the results for the baseline 30 wt% MEA and the low energy piperazine (PZ) solutions. This analysis reveals that the absorber reaches steady-state faster using MEA compared to PZ. This is related to the shift of the mass transfer zone due to changes in temperature. The transient operation in the regeneration unit is somewhat similar while using both solvents: an initial fast decrease of the lean loading is followed by a slow transient period as the system approaches steady-state conditions. We show the presence of inverse response in the stripper column when the rich loading decreases or the feed’s temperature reduces using PZ solvent. Thus, we demonstrate that the dynamics of the MEA system cannot be extrapolated to other solvents.

Systematic study of aqueous monoethanolamine‐based CO2 capture process: model development and process improvement

AbstractIn this paper, we present improvements to postcombustion capture (PCC) processes based on aqueous monoethanolamine (MEA). First, a rigorous, rate‐based model of the carbon dioxide (CO2) capture process from flue gas by aqueous MEA was developed using Aspen Plus, and validated against results from the PCC pilot plant trials located at the coal‐fired Tarong power station in Queensland, Australia. The model satisfactorily predicted the comprehensive experimental results from CO2 absorption and CO2 stripping process. The model was then employed to guide the systematic study of the MEA‐based CO2 capture process for the reduction in regeneration energy penalty through parameter optimization and process modification. Important process parameters such as MEA concentration, lean CO2 loading, lean temperature, and stripper pressure were optimized. The process modifications were investigated, which included the absorber intercooling, rich‐split, and stripper interheating processes. The minimum regeneration energy obtained from the combined parameter optimization and process modification was 3.1 MJ/kg CO2. This study suggests that the combination of a validated rate‐based model and process simulation can be used as an effective tool to guide sophisticated process plant, equipment design and process improvement.

Experimental study on the solvent regeneration of a CO2‐loaded MEA solution using single and hybrid solid acid catalysts

The performance of a hybrid solid acid catalyst consisting of a physical mixture of γ‐Al2O3 and H‐ZSM‐5 in terms of the rate and heat duty for solvent regeneration (i.e., CO2 stripping) of a CO2‐rich MEA solution was compared with the individual performance of γ‐Al2O3, H‐ZSM‐5, and H‐Y solid acid catalysts using MEA (2–7 mol/L), with initial CO2 loading of 0.5 mol CO2/mol MEA at 378 K. It was observed that any catalyst significantly decreased the energy required for CO2 regeneration. The performance of the catalysts investigated ranked as follows: γ‐Al2O3/H‐ZSM‐5 = 2/1 > γ‐Al2O3 > H‐ZSM‐5 > H‐Y if the process is in the lean CO2 loading region whereas it was H‐ZSM‐5 > γ‐Al2O3/H‐ZSM‐5 = 2/1 > γ‐Al2O3 > H‐Y if the process is in the rich CO2 loading region. These results highlight the joint dependence on Brønsted/Lewis acidity and mesopore surface area of heat duty for solvent regeneration. © 2015 American Institute of Chemical Engineers AIChE J, 62: 753–765, 2016

Technical and Energy Performance of an Advanced, Aqueous Ammonia-Based CO2 Capture Technology for a 500 MW Coal-Fired Power Station.

Using a rate-based model, we assessed the technical feasibility and energy performance of an advanced aqueous-ammonia-based postcombustion capture process integrated with a coal-fired power station. The capture process consists of three identical process trains in parallel, each containing a CO2 capture unit, an NH3 recycling unit, a water separation unit, and a CO2 compressor. A sensitivity study of important parameters, such as NH3 concentration, lean CO2 loading, and stripper pressure, was performed to minimize the energy consumption involved in the CO2 capture process. Process modifications of the rich-split process and the interheating process were investigated to further reduce the solvent regeneration energy. The integrated capture system was then evaluated in terms of the mass balance and the energy consumption of each unit. The results show that our advanced ammonia process is technically feasible and energy-competitive, with a low net power-plant efficiency penalty of 7.7%.

Comparative studies of stripper overhead vapor integration-based configurations for post-combustion CO2 capture

In this study, five absorption/stripping process configurations, including a conventional process, split flow with overhead exchanger, simple vapor recompression, and two new configurations-split flow with vapor recompression (SFVR), and improved split flow with vapor recompression (ISFVR) using 30wt% aqueous monoethanolamine (MEA) for CO2 capture from a 300MW power plant were simulated and compared, usingthe ProMax3.2 program. In the SFVR and ISFVR, the heat from the stripper overhead vapor and CO2compression system were recovered to the stripping column in order to reduce the reboiler duty and overall energy consumption. Sensitivity analyses were carried out to evaluate the effects of key parameters (e.g. lean CO2 loading and feed fraction) with regards to energy consumption. The simulation results showed that the innovative configurations SFVR and ISFVR could fully utilize the latent heat of the stripper overhead vapor and decreased the total equivalent works by 17.21% and 17.52%, respectively, compared with those of the conventional configuration. The minimal total equivalent works were 0.808GJ/tCO2 and 0.805GJ/t CO2, respectively. The split stripping with overhead heat exchanger process is the third with a total equivalent work of 0.86GJ/tCO2, while the simple vapor recompression configuration provided no reduction when compared with the conventional process.

Energy Minimization and Ammonia Abatement for CO2 Capture Using a Blend of Ammonia and 2-Amino-2-Methyl-1-Propanol Solution

An aqueous ammonia based CO2 capture offers several advantages over the conventional monoethanolamine (MEA) solvent, including a high CO2 loading capacity, low stripper heat duty, a lower degradation rate of solvent, low equipment corrosion, and the ability to capture multipollutants. However, in order to make an aqueous, ammonia-based CO2 capturing process economically feasible, attention must be paid to the following issues: ammonia slip due to the high evaporation rate of ammonia, energy input for CO2 regeneration, and CO2 removal efficiency improvements. In conventional, aqueous ammonia-based CO2 capture, the process either needs to operate at very low temperatures or must include wash-water columns to mitigate ammonia slips, which increase the capital and operational costs of the system. In this paper, a blended solution of 2-amino-2-methyl-1-propanol (AMP) and ammonia was used to analyze the CO2 capture efficiency, ammonia slip, and stripper heat duty. Our results show that, using the blended (30 wt.% AMP + 3 wt.% NH3) solution for CO2 capture, the ammonia slip was reduced by 64% at a lean CO2 loading of 0.07, CO2 capture efficiency was increased by 17.2%, and the heat duty requirement for CO2 regeneration was reduced by 80% at a stripper inlet temperature of 60°C. Moreover, the loss of AMP due to evaporation was 0.042 kg/day.

Comparative studies of heat duty and total equivalent work of a new heat pump distillation with split flow process, conventional split flow process, and conventional baseline process for CO2 capture using monoethanolamine

Two absorption/stripping process configurations, namely a new heat pump distillation with split flow process (HPDSFP) and split flow process with an overhead heat exchanger, were evaluated to minimize the energy consumption of CO2 capture from a 300MW power plant flue gas using 30wt% aqueous monoethanolamine (MEA). Their performances were compared with that of the baseline MEA process. All the processes were simulated using ProMax3.2 program. A rigorous model built on SWEET kinetics of ProMax was used to simulate the exothermic, reversible chemical reactions in MEA-CO2 system in the absorption/regeneration process. Sensitivity analyses were performed to evaluate the effects of key parameters (e.g. solvent circulation rate and lean CO2 loading) on energy requirement. Comparison of the HPDSFP, the split feed process with an overhead heat exchanger and the baseline process was conducted in terms of total equivalent work. In this work, the minimal total equivalent works of HPDSFP, the split flow process and baseline process were 0.37, 0.50 and 0.56GJ/tCO2, respectively. The simulation results showed that the new process configuration HPDSFP and split flow process with an overhead heat exchanger resulted in large improvements with reductions of total equivalent work by 10.7% and 33.9%, respectively.

Energy minimization in monoethanolamine-based CO2capture using capacitive deionization

Post-combustion CO2 capture using monoethanolamine (MEA) is a mature technology; however, the high energy input requirements for solvent regeneration are still a challenge for MEA-based CO2 capture. In this paper, a novel approach is presented in which a conventional CO2 absorption–desorption system is integrated with capacitive deionization (CDI) in such a way to minimize the heat duty requirement of the stripper. The CO2-rich solution drawn from the absorber column is first sent to CDI where ionic species are adsorbed at oppositely charged electrodes during the charging cycle, and an ion-free solution is sent back to the absorber. The adsorbed ions released during the regeneration cycle are sent to the stripper column. The concentrated solution from the CDI process that was sent to the stripper required low heat duty to regenerate the solvent because of the high CO2 loading of the solution. The feasibility of the suggested modelling technique is verified at various stripper inlet temperatures and lean CO2 loadings. The results indicate that 10–45% of the total energy supplied to the stripper can be conserved at a lean CO2 loading of 0.0000–0.0323 using the suggested process model. Moreover, the required size of the stripper column will be small due to the small volume of the concentrated ionic solutions from the CDI cell, eliminating the initial cost of the CO2 capture system. Copyright © 2014 John Wiley & Sons, Ltd.

Experimental and Process Modelling Study of Integration of a Micro-turbine with an Amine Plant

An integrated model of a micro-turbine coupled to a CO2 capture plant has been developed with Aspen Plus, and validated with e xperimental data obtained from a Turbec T100 microturbine at the PACT facilities in the UKCCS Research Centre, Beighton, UK. Monoethanolamine (MEA) was used as solvent and experimental measurements from the CO2 capture plant have been used to validate the steady-state model developed with Aspen Plus ® . The optimum liquid/gas ratio and the lean CO2 loading for 90% CO2 capture has been quantified for flue gases with CO2 concentrations ranging from 3 to 8 mol%.

Rate based modeling of absorption and regeneration for CO2 capture by aqueous ammonia solution

A rate-based model, RateFrac, in Aspen Plus process simulator, is used to simulate the CO2 absorption and regeneration processes of a research scale pilot plant. The simulation results of the CO2 absorption and regeneration predicted by the rate-based model are in good agreement with the experimental data. The effects of lean solvent flow rate, NH3 concentration, CO2 loading, and temperature on the absorption process were analyzed. Optimization analysis for the CO2 regeneration process was carried out. The operation parameters include temperature of the rich solvent, temperature of the condenser, inner diameter and packed height of the stripper. Under the optimal operation conditions, the regeneration energy is 3.63MJ/kgCO2, which is much lower than that reported for the research scale pilot plant (4–4.2MJ/kgCO2).

Screening and Characterization of Advanced Amine Based Solvent Systems for CO2 Post-Combustion Capture

Carbon dioxide chemical absorption with amine based solvents is currently the state-of-the-art technology for post-combustion carbon capture. However, many technical challenges still remain that need to be addressed to make it cost-effective. Through bench-scale tests, this research work is focused on developing and characterizing advanced amine-based solvents. Screening of amine solvents is performed to identify suitability on the basis of solvent maximum concentration, rich CO2 loading, lean CO2 loading, cyclic CO2 loading and energy requirement. The five alkanolamine solvents which are experimented upon in this work are: monoethanolamine (MEA), diethanolamine (DEA), N-methyldiethanolamine (MDEA), Piperazine (PZ) and 2-Amino-2-methyl-1-propanol (AMP). These solvents are taken as reference solvents to allow comparison with literature data and to establish confidence in the experimental methods used for solvent evaluation. CO2 outlet concentration curves from the absorption experiments show that piperazine reaches equilibrium faster than any other solvent and the CO2 loading capacity from phosphoric acid titration method is highest in piperazine with a value of 0.92.

A new pilot absorber for CO2 capture from flue gases: Measuring and modelling capture with MEA solution

A pilot absorber column for CO2 recovery from flue gases was constructed and tested with aqueous 30wt% monoethanolamine (MEA), a primary amine, as capture solvent. The pilot plant data were compared with a mathematical rate based packed-column model. The simulation results compared well with the pilot plant data.The packed height of the column can be varied from 1.6 to 8.2m by means of five different liquid inlets. The column has an inner diameter of 100mm and is packed with structured Mellapak 250Y packing. Counter-current flow is used.The pilot plant performance was investigated by changing three parameters: the absorption height, liquid flow rate, and the loading of lean MEA. This was done using a synthetic flue gas consisting of 10% CO2 with a flow rate of approximately 33m3/h at ambient temperature and atmospheric pressure. 23 runs were performed.It was observed that while CO2 recovery increases with an increase in flow rate of absorbent and absorption height, it decreases as the lean CO2-loading of the absorbent increases. In addition it has been possible to obtain temperature bulges in the bottom part of the absorber by the applied operation conditions. Bulges are observed at liquid flows around 4.2L/min and below. The results showed that is was possible to achieve 80% recovery with 3.3m absorption height and a liquid flow of 2.1L/min. The simulations show good agreement with the experimental values, although slight deviations arise as the CO2-loading increases and the temperature bulge becomes more distinct.

96/02068 Feed selection and radiocaesium intake by reindeer, sheep and goats grazing alpine summer habitats in Southern Norway

Chemical absorption using aqueous amine is one of the most feasible options for post-combustion CO2 capture. One of the main challenges of this technology is its high energy requirements. Absorber intercooling was considered as a viable method to offer benefits in terms of solvent absorption capacity and mass transfer efficiency in CO2 absorption processes. However, the effectiveness of absorber intercooling on overall energy requirements depends on other factors such as lean loading and liquid to gas ratio. This study evaluates the benefits of using two different configurations of absorber intercooling, i.e. “in-and-out” and “recycled” intercooling when using 30 wt% aqueous monoethanolamine (MEA) to capture 90% CO2 from a natural gas fired turbine with 4 mol% CO2. The Lean CO2 loading was varied from 0.15 to 0.42 (mol CO2/mol MEA) to determine the lean loading at which the application of intercooling is most significant. Absorber intercooling provides the most benefit at lean loading from 0.30 to 0.34. The use of in-and-out and recycle intercooling at 0.34 lean loading, provided 15.6 and 15.8% reduction in the total equivalent work associated with 32.0% and 36.6% reduction in required packing area when using 1.2 times the minimum liquid flow rate. At lean loading greater than 0.34, the benefit of absorber intercooling is a trade-off between reduction of solvent flow rate and total energy requirement and the drawback of greater packing area in the absorber. The greatest saving in total equivalent work, 17%, was observed at the 0.36 lean loading associated with nearly 60% more packing area when using 1.2 times the minimum solvent flow rate. At very low lean loading and very high lean loading absorber intercooling does not offer significant benefit.