Amino-acid salts for CO2 capture from flue gases (original) (raw)
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New Process Concepts for CO2 Capture based on Precipitating Amino Acids
Energy Procedia, 2013
This work summarises the results of the design of novel separation processes for CO 2 removal from flue gas based on precipitating amino acid solvents. The processes here described (DECAB, DECAB Plus and pH-swing) use a combination of enhanced CO 2 absorption ( ) and / or enhanced CO 2 desorption (based on pH-shift), which contribute substantially to the reduction of regeneration energy. An evaluation of these processes has been developed based on literature data, thermodynamic principles and experimental data. As solvent example, the potassium salt of taurine was selected. The results show that these processes are environmentally friendly (no emissions to the air, lower ecotoxicity) and have lower energy consumption than conventional MEA. The DECAB Plus process has been identified as the option with lower energy consumption (66% of conventional MEA-ie ca 2.4 GJ/t CO 2 ). This study has established the potential of precipitating amino acids as an energy effective alternative to alkanol amines. The future work will focus on determining the cost of CO 2 avoidance and investigating other solvents that will further lead to benefits over conventional processes.
Amino acid salts for CO2 capture at flue gas temperatures
2014
The amino acid salt potassium taurate has potential for use as a high-temperature absorbent for postcombustion CO 2 capture, because of its low volatility and high absorption rate. In this study, the densities and viscosities of 2-6 M taurate solution were determined over the temperature range of 293-353 K. We found that the CO 2 solubility of taurate solutions, measured using a stirred-cell reactor, is comparable to that of alkanolamines at high temperatures. The absorption rate of CO 2 into CO 2 -free and CO 2 -loaded taurate solutions was determined using a wetted-wall column. The K G of 4 M taurate at 353 K is similar in magnitude to the K G of 7 m monoethanolamine (MEA) at 313 K. We also found that the K G of taurate decreased with increased CO2 loading, although the K G values of taurate solutions are still comparable to CO 2 -loaded 7 m MEA solution. The reaction rate constant of taurate carbamate formation in this work agrees well with published values.
Analysis of Process Configurations for CO 2 Capture by Precipitating Amino Acid Solvents
Industrial & Engineering Chemistry Research, 2014
Precipitating amino acid solvents are an alternative to conventional amine scrubbing for CO 2 capture from flue gas. Process operation with these solvents leads to the formation of precipitates during absorption that need to be re-dissolved prior to desorption of CO 2 . The process configuration is crucial for the successful application of these solvents. Different process configurations have been analyzed in this work, including a full analysis of the baseline operating conditions (based on potassium taurate), the addition of lean vapor compression, multiple absorber feeds, and the use of different amino acids as alternative solvents to the baseline based on potassium taurate. The analysis is carried out with an equilibrium model of the process that approximates the thermodynamics of the solvents considered. The results show that the precipitating amino acid solvents can reduce the reboiler duty needed to regenerate the solvent with respect to a conventional MEA process. However, this reduction is accompanied by an expenditure in lower grade energy needed to dissolve the precipitates. To successfully implement these processes into power plants, an internal recycle of the rich stream is necessary. This configuration, known as DECAB Plus, can lower the overall energy use of the capture process, which includes the energy needed to regenerate the solvent, the energy needed to dissolve the precipitates, and the energy needed to compress the CO 2 to 110 bar. With respect to the energy efficiency, the DECAB Plus with lean vapor compression configuration is the best configuration based on potassium taurate, which reduces the reboiler duty for regeneration by 45% with respect to conventional MEA. Retrofitting this process into a coal fired power plant will result in overall energy savings of 15% with respect to the conventional MEA process, including compression of the CO 2 stream to 110 bar. Potassium alanate was found to reduce the energy use with respect to potassium taurate under similar process configurations. Therefore, the investigation of potassium alanate in a DECAB Plus configuration is highly recommended, since it can reduce the energy requirements of the best process configuration based on potassium taurate.
1 CO 2 capture from flue gas using amino acid salt solutions
2006
An initial kinetic study was performed on the reaction of CO2 with various potassium amino acid salt solutions at 298 K. Kinetics were measured at 0.5 kmol/m, reason for which only apparent kinetic constants are presented. The results were compared with the work of Kumar et al. [1] and Penny and Ritter [2].
Carbon Dioxide CO2 Capture Using Amino Acid Salt Solution
Journal of Physics: Conference Series
The concern of climate change and global warming has consecutively risen to progress research fields pledging to find the possible solutions. The use of fossil fuels for energy leads to an increase in CO 2 emission causing environmental problems like global warming and climate change. For industrial applications, aqueous solutions of amines are extensively used as chemical absorbent or solvent. However, amine reaction with CO 2 results in stable carbamate formation, which in turn leads to high energy usage for regeneration and promote additional corrosion problems. To overcome these restrictions, this study proposes a methodology to analyze the performance of new solvent namely amino acid salt solution. Evaluation of solvent performance in terms of CO 2 loading and designing of acid gas removal system, requires pressure solubility data and design properties like density, pH value and refractive index.
International Journal of Greenhouse Gas Control, 2015
Increasing concentration of CO 2 in the atmosphere contributing potential negative impact to the environment has been the subject of worldwide attention over the past few decades. CO 2 , one of the main greenhouse gases (GHG) is getting emitted to the environment from different industries such as fossil fuelled power plants, cement industry, refinery and synthetic ammonia production units etc. Gas scrubbing using aqueous alkanolamine solutions is the most promising retrofit option for post combustion carbon dioxide capture in recent days. The present study investigates an effective means of eliminating CO 2 from flue gas using two primary amines, namely conventional monoethanolamine (MEA) and a sterically hindered amine, 2-amino-2-methyl-1-propanol (AMP). The CO 2 absorption characteristics were experimentally examined in a packed column under various process conditions viz. CO 2 partial pressure, gas and liquid flow rates, solvent concentrations and operating temperature and pressure. While the regeneration of solvent was studied at the temperature range from 368 to 382 K. The present work reports mainly a comparative study of absorption and regeneration behaviour of the two alkanolamines which necessarily include the specific rate of absorption, percentage of CO 2 absorbed, CO 2 loading during absorption and residual CO 2 after solvent regeneration and regeneration efficiency. The specific rate of absorption of AMP and MEA are observed to be (2.11-4.03) × 10 −5 kmol/m 2 s and (5.36-9.55) × 10 −5 kmol/m 2 s, respectively. The maximum percentage of CO 2 absorbed using MEA is 99.13% and AMP is 98.88%. In case of solvent loading capacity (moles of CO 2 per mole of amine) AMP is much better than MEA; the value is 0.777 moles for AMP as compared to MEA value 0.478 moles. The regeneration efficiency of AMP ranging from 96.39 to 97.26% is superior over MEA which is in the range of (79.91-81.55) %. The entire experimental absorption rate data are plotted with the response surface methodology (RSM) fitted data which shows a good agreement with the experimental value for both the amine solvents.
This contribution is concerned with the experimental and simulative examination of a hybrid process consisting of a membrane stage for gas separation and a chemical absorption unit for the removal of CO 2 from gas streams. The feed stream to the separation process is the product of the oxidative coupling of methane (OCM) and contains 26 vol% CO 2 in addition to methane, ethylene, and ethane. For the investigation of the process a mini-plant was built at TU Berlin, operating at feed flow rates of up to 25 Nm 3 /h and pressures up to 32 bar. The mini-plant closely mimics industrial operating scenarios. The potential for the reduction of energy, equipment, and installation cost by using membranes is assessed and evaluated experimentally in comparison with state of the art separation techniques. The benchmark in CO 2 gas purification for high purity and high selectivity consists of a chemical absorption process using an amine-based absorbent. The mini-plant shows an energetic optimum at 5 MJ/kg CO2 for the absorption using 30 wt% monoethanolamine (MEA) to achieve a CO 2 removal from the feed gas of 90%. In addition, 37 wt% Nmethyldiethanolamine (MDEA) with 3 wt% piperazine as an activator are examined. The ternary amine is an example for a high performance absorbent showing energetic advantages in the regeneration step. Experimental studies in the mini-plant resulted in a specific energy demand of 3.47 MJ/kg CO2 . Installing a HZG 1 gas permeation module upstream to the absorption unit leads to a reduction of the specific energy demand per kilogram of captured CO 2 of 40%. The module is equipped with MATRIMID ® membranes and is found to reduce the CO 2 content of the feed gas to 17 vol%. Hence, equipment cost reductions in the absorption process by requiring fewer theoretical plates in both columns, and in general smaller utility equipment, i.e. heat exchangers and pumps, can also be achieved. Furthermore, a 1 HZG: Helmholtz-Zentrum Geesthacht Centre for Materials and Coastal Research, formerly known as GKSS, http://www.hzg.de/index.html.en decrease of the flow rate of the absorbent by 20% is attained. The described hybrid process configurations shows a stable separation performance during 500 operating hours with more than 50 start-ups and shutdowns at the investigated feed pressures of 5, 10, and 32 bar respectively. In order to address the somewhat lower product recovery of the hybrid process, two stage membrane arrangements will be assessed. These arrangements allow for the combination of different CO 2 -selective membrane materials in order to minimize the additional gas compression costs of such an installation. Two sequentially connected membranes, in comparison to a single stage, provide more options for optimization. Based on the simulation for the mini-plant level, ethylene recovery could be increased while allowing for the same CO 2 removal rate as in a one-stage system.
Post combustion CO2 capture with an amino acid salt
Energy Procedia, 2011
Amino acid salts are of great interest as potential solvents for CO 2 capture because they are considered to be environmentally friendly. In the present paper, results of experimental work with a pilot plant with 3.5M potassium sarcosine are presented. Both absorption kinetics and energy consumption are studied. The results show clearly that the amino acid salt system has a high absorption rate and high energy requirement compared to 30 wt-% MEA. The solvent system has been modeled in an in-house tool and simulation results are compared with the some performance results obtained experimentally. The soft-model approach developed for the potassium sarcosine solvent systems represents the absorber fairly well, while it seems to be too simplified to represent the stripper conditions. The present study is part of an ongoing EU project, Cesar.
Membrane-based carbon capture from flue gas: a review
Journal of Cleaner Production, 2015
There has been an increasing interest in the application of membranes to flue gas separation, primarily driven by the need of carbon capture for significantly reducing greenhouse gas emissions. Historically, there has not been general consensus about the advantage of membranes against other methods such as liquid solvents for carbon capture. However, recent research indicates that advances in materials and process designs could significantly improve the separation performance of membrane capture systems, which make membrane technology competitive with other technologies for carbon capture. This paper mainly reviews membrane separation for the application to post-combustion CO 2 capture with a focus on the developments and breakthroughs in membrane material design, process engineering, and engineering economics.
Comparative study of chemical absorbents in postcombustion CO2 capture
Energy, 2010
In order to reduce CO 2 emissions from a power plant, CO 2 can be captured either from the syngas that is to be burned or from the flue gases exiting the energy conversion process. Postcombustion capture has the advantage that it can be applied to retrofit existing power plants. In this paper the authors compare two primary amines (MEA and DGA) to ammonia with respect to their capability to capture CO 2 from a flue gas stream. The ammonia process captures CO 2 by formation of stable salts, which are separated from the solvent stream by filtration or sedimentation. These salts can be used commercially as fertilizers. Energy requirements are greatly reduced, since no heat is required for solvent regeneration, and no compression of the separated CO 2 is necessary. Energy, however, is required for the reduction of ammonia emissions. In order to obtain the solid ammonia salts, their solubility has to be reduced by modification of the solvent and by lowering absorption temperature. With and without separation of the salt products, ammonia proved to be an alternative solvent with high CO 2 removal efficiency. Simulation of all processes was carried out with Aspen Plus Ò and compared to experimental results for CO 2 scrubbing with ammonia.