Carbon Dioxide Separation Process Research Articles

Evaluating the thermodynamic potential for carbon capture from internal combustion engines

This work explores the potential for use of carbon dioxide separation processes, colloquially known as carbon capture, to accelerate decarbonization of the transport sector. Thermal swing absorption processes using an aqueous, CO2-selective solvent, provide an efficient means of separating CO2 from other exhaust gas constituents. Amine-based solvents–well known from acid gas treating and other post-combustion carbon capture processes–are highly selective, have a fast rate of reaction with CO2, and can use waste heat to drive the separation process. This work demonstrates how amine-based processes can be deployed for carbon removal from a generic exhaust gas source produced by an internal combustion engine (ICE) using waste heat in the exhaust. It includes an estimation of the exhaust enthalpy-limited capture rate for various sources considering the capture system performance, the CO2 concentration, and the exhaust temperature.CO2 capture rates of around 25–80% are shown to be thermodynamically feasible for various ICE applications using waste exhaust heat for solvent regeneration. Rates of around 15–50% are attainable without providing additional energy, if exhaust heat is also used to power the capture system pump and compressor. Although a higher exhaust CO2 concentration reduces the specific energy requirements of the separation process, the total energy required for a given capture rate increases due to the greater amount of CO2 removed. Thus, maximum capture rates are highest for applications with high exhaust temperature and low CO2 concentration (such as diesel generators), and lowest for applications with very low exhaust temperature such as ships. This analysis also shows that the potential for CO2 avoidance using carbon capture systems far exceeds that of organic rankine cycle waste heat recovery systems. Overall, expanding the use of carbon capture to ICE applications can provide an efficient means of utilizing waste exhaust heat while providing significant reductions in the energy industry's scope 3 greenhouse gas emissions.

Thermodynamic analysis of a novel zero carbon emission coal-based polygeneration system incorporating methanol synthesis and Allam power cycle

To improve the coal utilization efficiency and cut down the carbon footprint, a novel zero carbon emission coal-based polygeneration system is proposed for methanol production and power generation, which innovatively integrates a direct-fired supercritical carbon dioxide cycle (Allam cycle) for carbon capture. The water–gas shift reaction and carbon dioxide separation process are removed in the methanol synthesis subsystem. The syngas generated by coal gasification is directly fed to the methanol reactor and the released syngas from the methanol synthesis unit is combusted with the pure oxygen to drive the Allam cycle for efficient power generation. Comparing with the individual methanol production system and coal-based Allam cycle, the carbon and hydrogen element footprints are changed, which can reduce the energy consumption for carbon capture, and the recovered heat from the hot raw syngas and methanol synthesis unit is utilized more efficiently by integration of the Allam cycle. The energy and exergy analyses of the proposed system have been performed using the developed models based on the mass and energy balance. Results show that the fuel saving ratio of the proposed system is 5.3% and the exergy destruction is reduced by 10.8%, comparing to the individual systems. In addition, the net power output of the proposed system is also 29.4% greater than that of the typical polygeneration system. The proposed concept might provide a new approach to efficient utilization of coal for methanol synthesis and power generation with nearly zero emission.

Thermodynamic performance of a new hybrid system based on concentrating solar system, molten carbonate fuel cell and organic Rankine cycle with CO2 capturing analysis

This paper presents the performance analysis of the process consisting of the molten carbonate fuel cell (MCFC), parabolic dish collector (PDC), linear Fresnel reflector (LFR), Organic Rankine Cycle (ORC) and the gas turbine, with the carbon dioxide separation process. In proposed novel process, the MCFC waste heat is used to generate additional electricity in the ORC. In addition, a gas turbine embedded in the process also generates electricity. This hybrid system also uses two concentrating solar collectors, i.e. LFR and PDC. The former raises the water temperature b7efore mixing with fuel and the latter raises the temperature of the mixture (water and fuel) before entering the reformer. Furthermore, in present study the performance of parabolic trough collector is investigated, assuming it provides the required duty of evaporator of ORC. Finally, the present study examines the process of carbon dioxide separation. The results revealed that, overall, electrical and exergy efficiency of the hybrid cycle is 58.02 %, 44.2 % and 74.9 %, respectively. Furthermore, the total exergy destruction rate and removal efficiency of the system are 13.67 MW and 78.9 %, respectively. In addition, about 35 collectors of LFR and 55 collectors of PDC are needed to supply the required duty of solar thermal collectors.

Optimal Design of a Carbon Dioxide Separation Process with Market Uncertainty and Waste Reduction

The aim of this work is to optimize the conceptual design of an amine-based carbon dioxide (CO2) separation process for Enhanced Oil Recovery (EOR). A systematic approach is applied to predict the economic profitability of the system while reducing the environmental impacts. Firstly, we model the process with UniSim and determine the governing degrees of freedom (DoF) through a sensitivity analysis. Then, we proceed with the formulation of the economic problem, where the employment of econometric models allows us to predict the highest dynamic economic potential (DEP). In the second part, we apply the Waste Reduction (WAR) algorithm to quantify the environmental risks of the studied process. This method is based on the minimization of the potential environmental indicator (PEI) by using the generalization of the Waste Reduction algorithm. Results show that the CO2 separation plant is promising in terms of economic revenues. However, the PEI value indicates that the higher the profitability, the larger the environmental risk. The optimal value of the DEP corresponds to 0.0274 kmol/h and 60 °C, with a plant capacity according to the mole flow rate of the produced acid gas. In addition, the highest environmental risk is observed at the upper bounds of the DoF.

Influence of organic co-solvents upon carbon dioxide chemical absorption

Present research work analyzes carbon dioxide chemical absorption using different types of alkanolamines (primary, secondary and tertiary) with the presence of several organic co-solvents. These additional substances have been considered as interesting additives in previous works that can produce improvements upon the overall carbon dioxide separation process. On the basis of this hypothesis, this research analyses the influence of these solvents upon the absorption process using two parameters: absorption rate and carbon dioxide loading. Two different types of co-solvents have been tested analyzing the effect of their concentration in the liquid phase. Also the influence of these substances upon the reaction mechanism has been studied.

Optimization-based approach for design and integration of carbon dioxide separation processes using membrane technology

The purpose of this paper is to examine carbon dioxide (CO2) separation process using membrane technologies. In achieving this goal, we develop an optimization model to design and integrate the CO2 separation using multi-stage membrane technologies by maximizing the total profit calculated with the total capital and operating costs, and the expected revenue from the CH4 selling. Using the proposed model, we are able to determine the optimal design and operation strategies of the individual membrane and compressor to meet the design specification (i.e., purity and recovery rate) in the scenarios of different CO2 market prices.

Design of energy-saving carbon dioxide separation process using fluidized bed

Carbon dioxide capture and storage technology has attracted recent attention for the mitigation of CO2 emissions; however, to facilitate its commercial implementation, its capture cost should be further decreased. This research proposes an innovative energy-saving process using chemical absorption by a solid in a circulating fluidized bed. In this process, the reaction heat that accompanies absorption is successfully supplied through a heat pump to achieve thermal decomposition in a regenerator, thereby leading to recirculation of all process heat. Absorption and fluidization experiments were conducted to determine the separation performance. An energy balance of the proposed process was simulated using the experimental data with a commercial process simulator. The simulation results indicate that the proposed CO2 separation process has large energy-saving potential when compared with conventional approaches.

Characterization of carbon dioxide capture by glucosamine: Liquid phase speciation and degradation

Carbon dioxide capture by chemical absorption can be improved attending to the reaction mechanism due to the different stoichiometry shown by the most important reactions (mainly production of bicarbonate/carbonate ion, and carbamate) involved in the process. The weight of each reaction upon the carbon dioxide absorption determines the loading value and the rate of amine consumption which can influence upon reaction rate. On the other hand, the degradation rate of amines during the regeneration step can play a very important role in carbon dioxide separation process increasing the amount of amine make-up flow-rate.

Amino Acids as Carbon Capture Solvents: Chemical Kinetics and Mechanism of the Glycine + CO2 Reaction

Amino acids are potential solvents for carbon dioxide separation processes, but the kinetics and mechanism of amino acid–CO2 reactions are not well-described. In this paper, we present a study of the reaction of glycine with CO2 in aqueous media using stopped-flow ultraviolet/visible spectrophotometry as well as gas/liquid absorption into a wetted-wall column. With the combination of these two techniques, we have observed the direct reaction of dissolved CO2 with glycine under dilute, idealized conditions, as well as the reactive absorption of gaseous CO2 into alkaline glycinate solvents under industrially relevant temperatures and concentrations. From stopped-flow experiments between 25 and 40 °C, we find that the glycine anion NH2CH2CO2– reacts with CO2(aq) with k (M–1 s–1) = 1.24 × 1012 exp[−5459/T (K)], with an activation energy of 45.4 ± 2.2 kJ mol–1. Rate constants derived from wetted-wall column measurements between 50 and 60 °C are in good agreement with an extrapolation of this Arrhenius expressi...

Preparation and Carbon Dioxide Separation Performance of a Hollow Fiber Supported Ionic Liquid Membrane

In this study, we prepared polyethersulfone hollow fibers using double colaminar flow in a coaxial microfluidic device. The structures of the hollow fibers were adjusted by changing the composition of the dope solution. The produced hollow fibers were used as a support for room temperature ionic liquids to study their potential for carbon dioxide/nitrogen separation. The stability of supported ionic liquid membranes with different structures was evaluated using two different ionic liquids. The effect of the permeate direction and the support structure on the pure gas permeability and ideal selectivity was also studied. The ideal selectivity, represented by the ratio between the permeabilities of carbon dioxide and nitrogen, was compared with data in the literature described by the Robeson upper bound correlation. High selectivity values obtained for carbon dioxide compared with those for nitrogen indicated that the produced supported ionic liquid membranes have good potential for carbon dioxide separation processes.

ChemInform Abstract: Development and Evaluation of Porous Materials for Carbon Dioxide Separation and Capture

AbstractReview: 92 refs.

Development and Evaluation of Porous Materials for Carbon Dioxide Separation and Capture

The development of new microporous materials for adsorption separation processes is a rapidly growing field because of potential applications such as carbon capture and sequestration (CCS) and purification of clean-burning natural gas. In particular, new metal-organic frameworks (MOFs) and other porous coordination polymers are being generated at a rapid and growing pace. Herein, we address the question of how this large number of materials can be quickly evaluated for their practical application in carbon dioxide separation processes. Five adsorbent evaluation criteria from the chemical engineering literature are described and used to assess over 40 MOFs for their potential in CO(2) separation processes for natural gas purification, landfill gas separation, and capture of CO(2) from power-plant flue gas. Comparisons with other materials such as zeolites are made, and the relationships between MOF properties and CO(2) separation potential are investigated from the large data set. In addition, strategies for tailoring and designing MOFs to enhance CO(2) adsorption are briefly reviewed.

Vapor-liquid equilibria of water+monoethanolamine system

The accurate design of carbon dioxide separation processes by the absorption method requires knowledge of the vapor-liquid equilibrium of aqueous alkanolamine systems. MEA (monoethanolamine) is widely used for the separation of carbon dioxide by the chemical absorption process. The equilibrium apparatus was tested by comparing the measured VLE data for the methanol+ethanol system with the literature data. The isobaric vapor liquid equilibrium data were measured for the water+MEA binary system by using a modified Stage-Muller equilibrium still with circulation in both phases. The vapor liquid equilibrium data of water+MEA were measured in the pressure range from 50.0 to 70.0 kPa and temperature range from 355.2 to 430.3 K. The measured data were correlated with the UNIQUAC and NRTL activity coefficient models.

Development of carbon dioxide separation process using continuous hollow-fiber membrane contactor and water-splitting electrodialysis

Studies on the development of carbon dioxide (CO2) separation process using continuous hollow-fiber membrane contactor (HFMC) and water-splitting electrodialysis (WSED) as an alternative method for the conventional processes are reported. Several experiments for CO2 recovery and absorbent regeneration using HFMC–WSED hybrid system were performed. In this study, four widely used absorbents (KOH, NaOH, K2CO3, and N-methyldiethanolamine) were examined and compared in terms of the process efficiency. The results showed that KOH was the best absorbent for this hybrid system due to its high ionic conductivity. In addition, several operational problems including the proton leakage and gas molecule diffusion through the membranes were considered. The results of continuous experiments showed that the continuous recovery of CO2-rich absorbents was reliably performed during the tests without any problem.