| Academic concerns have been raised with respect to the impact of the increasing concentration of carbon dioxide in the atmosphere on the environment as global warming. This global recognition has attracted great attention in relation to the creation, development and improvement upon technologies and strategies for the reduction of CO? emissions. Carbon capture and storage (CCS) is one of the most effective CO2emission abatement strategies in the world. Among all the post combustion capture technologies, adsorption process relying on well-engineered solid adsorbents is suggested as a promising option due to simple equipment, low energy requirement, less corrosion problems, easiness to achieve automatic operation and operating flexibility. In this work, a novel adsorbent zeolite13XAPG was employed as the selective adsorbent for CO2/N2separation. The feasibility and efficiency of adsorption technology for post-combustion CO2capture from Hue gas using zeolite13XAPG were evaluated by fundamental experiments, simulation and pilot-scale experiments in an existed coal-fired power plant.Firstly, the adsorption equilibrium isotherms of CO2and N2on zeolite13XAPG were measured by a magnetic suspension balance. The adsorption heat was caculated from adsorption equilibrium data. Then Multi-site Langmuir model was employed to fit the experimental data with good agreement, and the fitted parameters were adopted in the prediction of binary competitive adsorption equilibrium, providing basic data for the design of adsorption process.Secondly, adsorption kinetics of CO2/N2on zeolite13XAPG was investigated by the experimental data of breakthrough and desorption curves. A mathematical model based on the bi-LDF approximation was derived from mass, energy and momentum balances. Diffusion coefficient and transfer parameters were calculated through the comparison of experimental and simulated results. Moreover, it was found from experiments that the adsorption capacity of H2O was much larger than CO2, and the adsorption of H2O had a significant impact on the CO2adsorption capacity on zeolite13XAPG. so a dehumidified unit was usually required before the adsorption unit in the capture process.thirdly, several adsorption processes by fixed bed packed with zeolite13XAPG were explored for CO2/N2separation by experiments and simulation, including vacuum pressure swing adsorption (VPSA) process (single bed. multibed and two-stage VPSA unit). temperature swing adsorption (TSA) process and hybrid vacuum pressure swing adsorption (VTSA) process. It was found that VTSA process was the most effective and promising process. However, the cycle time of VTSA process was too long due to the temperature swing process. Therefore, the VPSA process was adopted in the pilot-scale experiments for CO2capture from flue gas in an existing coal-fired power plant.At last, an experimental evaluation combined with simulation was performed for CO2capture from flue gas using a pilot-scale single and two-stage VPSA unit in Shanghai Shengneng XingHuo thermo-power plant. The desulfurized flue gas passed through the dehumidifying unit to remove moisture and then was supplied to the carbon capture plant. With a single3-bed8-step VPSA unit packed with261kg zeolite13XAPG, CO2can be concentrated to75.7%with a CO2recovery of90.3%from flue gas at feed flowrate of37.0Nm3/h, and the power consumption was measured onsite as2.08MJ/kgCO2. The purity was lower than the demand for storage (>95%), therefore a two-stage VPSA unit with the effluent from the second unit recycled to the inlet was designed and tested. The first unit was the same as the single VPSA unit before and the second VPSA unit packed with68.6kg pitch-based ACBs was operated as2-bed6-step cycle. With this process, a CO2purity of95.6%was obtained with recovery of90.2%at the feed flowrate of35.5Nm3/h, and the power consumption was2.44MJ/kgCO2(lower than absorption). With the development of the adsorbent and further optimization of the processes, the adsorption technology can be a promising CO2capture technology. |
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