Design Of CO2 Capture Processes Research Articles

Optimum design of industrial post-combustion CO2 capture processes using phase-change solvents

Phase-change solvents (PCSs) is a class of chemicals that promises significant cost reductions in post-combustion CO2 capture. However, their use in the design of efficient absorption/desorption processes is challenged by their non-ideal behavior. A generic and flexible model is proposed for the design of phase-change CO2 capture process systems, that enables the effective identification of highly performing flowsheet configurations and recycle stream redistribution policies. The validation of the model using experimental data for the PCS mixture of MAPA/DEEA (3-(Methylamino)-Propylamine/2-(Diethylamino)-Ethanol) indicates only 4% and 0.5% differences in the reboiler duty and in the absorption and desorption temperatures. The novel PCS mixture of S1N/DMCA (N-Cyclohexyl-1,3-Propanediamine/N,N-Dimethylcyclohexylamine) and the PCS MCA (N-methylcyclohexylamine) are used in the optimum design of CO2 capture process units in two industrial cases; a quicklime production plant and a gas-fired power plant. The reboiler duty of S1N/DMCA reaches 2.1 GJ/ton CO2 and the solvent exhibits up to 47% lower operating costs than the conventional MEA (Monoethanolamine), with only 1.7% higher capital costs. The loading of S1N/DMCA reaches up to 1.35 mol CO2/mol of solvent at the exit stream of the phase-separator, whereas this solvent exhibits up to 181% higher CO2 release efficiency than MEA in the desorber. S1N/DMCA is an excellent option for plants with flue gas CO2 concentration as low as 3.5 mol%.

Renewable and Electroactive Biomass-Derived Tubes for CO2 Capture in Agroindustrial Processes

Tube-shaped renewable carbon materials were developed to work as separation agents for CO2 capture in agroindustrial and intensive farming facilities. The tubes have electrical properties and moderate CO2 adsorption capacities. These materials can be heated directly through the Joule effect by applying an electric potential between the ends and thus reaching temperatures higher than 473 K in a few seconds with an applied voltage of near 10 V. The tube’s temperature can be easily controlled by manipulating the applied voltage, which is of interest for the development and design of CO2 capture processes through electric swing adsorption. The tubular form of the material also provides the alternative to be filled up with adsorbents like zeolite and metal–organic frameworks to produce highly selective structured adsorbents based on renewable carbon materials with the advantage of providing direct Joule heating. These materials were studied as separation agents to be part of cycles like vacuum swing adsorption, electric swing adsorption, and both combined. The tubes were tested through consecutive and repeated adsorption and Joule heating desorption experiments. The dynamics of the tube’s temperature and the CO2 gas-phase composition showed consistency and repeatability. The results revealed the robustness and reliability of the biomass-derived tubes to work as separation agents for CO2 capture.

Thermodynamic modeling of CO2 absorption in aqueous potassium carbonate solution with electrolyte NRTL model

Aqueous potassium carbonate (K2CO3) solution is a favorable choice for CO2 removal due to low costs and lessened environmental impacts compared to amine solutions. To support process development of CO2 removal with aqueous solutions, we present a comprehensive thermodynamic model for the H2O + K2CO3 + CO2 ternary system using electrolyte Nonrandom Two-liquid (eNRTL) activity coefficient model. Experimental data of vapor-liquid equilibrium, heat capacity, excess enthalpy, mean ionic activity coefficient and osmotic coefficient are simultaneously used to determine the temperature dependent eNRTL binary interaction parameters for the ternary system and its binary subsystems. Covering a wide temperature range of 273.15–473.15 K, the K2CO3 concentration up to saturation, and the CO2 loading range of 0–3.6, the model satisfactorily represents all the thermodynamic properties for the system. The model should be a very useful tool in the research, development and design of CO2 capture processes involving concentrated K2CO3 solutions at elevated temperatures and pressures.

Process design and optimization of MEA-based CO2 capture processes for non-power industries

Aqueous MEA-based CO2 capture is one of main technologies for CO2 capture. However, there are various different sources of flue gases from different industries which have different flow conditions. In particular the CO2 content is very important and it will have a critical impact on the associated design of CO2 capture processes. In this study a superstructure optimization methodology is applied to ranges of different flue gases found in non-power industries such as cement, steel and refinery plants. Optimization of both operating conditions and structural modifications reveals the optimal configurations of equipment for the different industrial sources of CO2. A case study is given to address how energy consumption and process design of MEA-based CO2 capture systems is influenced by CO2 concentration in the feed gas. It is shown that flue gas splitting is the most significant and useful process modification for all the different flue gases tested in particular for low CO2 content flue gases. At higher CO2 contents the optimal designs are shown to require a combination of process modifications to give an even greater reduction of energy requirements.

Development of novel sub-ambient membrane systems for energy-efficient post-combustion CO2 capture

A substantial increase in CO2/N2 selectivity of the membrane under sub-ambient temperature conditions allows the design of CO2 capture processes in an energy-efficient and cost-effective manner. An innovative sub-ambient temperature membrane process is proposed in this study for the separation of CO2 from power plant flue gases, in which the high membrane selectivity is strategically utilized with the aid of a simple, external refrigeration cycle. In the new membrane process, a sweeping-integrated single membrane module integrated with a purification column is sufficient to achieve a high purity of 99.9% CO2 product with 90% CO2 recovery. Process optimization is utilized to determine cost-effective operating conditions and appropriate membrane configurations. The optimized sub-ambient temperature membrane process is shown to reduce the overall CO2 capture cost by 13% as well reducing the parasitic load by 16%, compared to a conventional multi-stage membrane process operated at ambient temperature conditions. The sensitivities of CO2 capture cost and energy with respect to key design variables such as pressure ratio, membrane performance (i.e. CO2 permeance and CO2/N2 selectivity) and CO2 recovery are investigated to provide conceptual insights and design guidelines for developing efficient membrane processes for the capture of CO2.