An Zhao

Post-combustion CO2 capture from the flue gas is one of the key technology options to reduce greenhouse gases, because this can be potentially retrofitted to the existing fleet of coal-fired power stations. Adsorption processes using solid sorbents capable of capturing CO2 from flue gas streams have shown many potential advantages, compared to other conventional CO2 capture using aqueous amine solvents. In view of this, in the past few years, several research groups have been involved in the development of new solid sorbents for CO2 capture from flue gas with superior performance and desired economics. A variety of promising sorbents such as activated carbonaceous materials, microporous/mesoporous silica or zeolites, carbonates, and polymeric resins loaded with or without nitrogen functionality for the removal of CO2 from the flue gas streams have been reviewed. Different methods of impregnating functional groups, including grafting techniques and modifying the support materials, have been discussed to enhance the performance of the sorbents. The performance characteristics of the solid sorbents are assessed in terms of various desired attributes, such as their equilibrium adsorption capacity, selectivity, regeneration, multicycle durability, and adsorption/desorption kinetics. The potential of metal-organic frameworks (MOFs) is also recognized to determine whether these novel materials provide better CO2 adsorption capacity under low CO2 partial pressure. A comprehensive critical review and analysis of the literature on this subject has been carried out to update the recent progress in this arena. A comparison of different solid sorbents at different stages is made. It also includes a brief review on techno-economic analysis and design aspects of sorbent bed contactor configuration. Finally, a few recommendations have been proposed for further research efforts to progress post-combustion carbon capture.

In this work, an experimental and theoretical investigation was conducted on the adsorptive removal of CO2 onto tetraethylenepentamine (TEPA) functionalized mesoporous SBA-15. The functionalization of SBA-15 silica with TEPA was achieved using a conventional wet impregnation technique. The structural properties of the mesoporous silica sorbents were characterized by nitrogen adsorption/desorption, SAXS, SEM, TEM, and FTIR techniques. The adsorption of CO2 on the amine-impregnated sorbent was measured by thermogravimetric method over a CO2 partial pressure range of 10–100 kPa and a temperature range of 30–100 °C under atmospheric pressure. The effects on CO2 adsorption capacity of temperature, partial pressure of CO2, amine loading, and moisture were evaluated. All the impregnated SBA-15 sorbents showed reversible CO2 adsorption behaviors with fast adsorption kinetics. The CO2 adsorption capacity measured at different temperatures suggests that the optimal adsorption temperature is 75 °C. The CO2 uptake of the amine-impregnated sorbent increased significantly in the presence of moisture. SBA-15 containing 60 wt % TEPA showed the highest CO2 adsorption capacity of 5.22 mmol/g in pure and humid CO2 at 75 °C. Temperature swing adsorption/desorption cycles were also explored using simulated flue gas in both dry and humid conditions, and it was found that CO2 uptake after ten cycles was within 90% of CO2 uptake of the first cycle. Different adsorption kinetic models have also been investigated to analyze the experimental data of CO2 uptake. The model was validated with the experimental results of isothermal adsorption measurements of CO2 on SBA-15/TEPA. It has been found that Fractional Order kinetic model (Chem. Eng. J.2011, 173, 72) is very good over the entire adsorption region of the study with a maximum average absolute deviation between experimental CO2 uptake and that calculated from the model of about 2.42%.

Parallel pump systems are widely used in industries. However, pumps are often operating under off-design conditions due to many reasons, which reduces the efficiency and reliability of the pumps. This paper aims at reducing the power consumption of parallel pump systems and improving the reliability of pumps by improving the operation points of pumps. To achieve this goal, a combination of selecting the proper number of pumps to put into operation and their speed is needed. Also, a control valve is adopted to further improve the operation points. The optimization model is built for a parallel pump system. Particle swarm optimization algorithm is used to solve the problem. Experimental verification shows that the proposed method improves the reliability and can also reduce power consumption for some cases compared to conventional PID speed regulation method. But for cases with large flow, extra power might be needed because the control valve introduces extra flow resistance in order to improve the operation point. The proposed method can be easily extended to applications based on their requirements on reliability.