چكيده به لاتين
Environmental concerns such as global warming and climate change have inspired researchers to develop more effective and improved processes for carbon dioxide (CO2) capture as the most important greenhouse gases (GHG).The main source of CO2 production and emission is the burning of fossil fuels in power plants and petroleum industries. Among the post combustion CO2 capture technologies, the absorption using amine solutions is applied in several industries. However, it has several issues including solvent losses, corrosion, hazardous byproducts, and high-energy requirement for regeneration. Therefore, the adsorption process using solid sorbents in fluidized bed is an encouraging alternative in CO2 capture from flue gas. In this project, the experimental evaluation and numerical simulation of CO2 capture from simulated flue gas using dry regenerable alkali metal carbonate based adsorbent K2CO3/Al2O3 in the fluidized bed were accomplished. Therefore, the solid sorbent particles of K2CO3/Al2O3 were prepared with the conventional impregnation technique and the sorbent was also characterized by XRD, BET, and SEM techniques. First, carbonation reaction was studied using a fixed bed reactor using response surface methodology (RSM). Then, based on the fixed bed results, the experiment of CO2 capture in a micro fluidized bed was investigated by RSM coupled with Box-Behnken design (BBD). In addition, the kinetic study was performed. Regarding to the analysis of variance (ANOVA) results, the temperature, the gas flow rate, the vapor pretreatment amount, and the mole ratio of H2O/CO2 are the most important factors affecting the adsorption capacity and the reaction rate constant, respectively. In addition, the semiempirical polynomials were developed to find the optimum condition corresponding to the highest adsorption capacity and reaction rate. Consequently, the optimum independent variables were 60 °C, 562 CCM, 22.2 mg of H2O, and 1 condition for the temperature, gas flow rate, vapor pretreatment amount, and mole ratio of H2O/CO2, respectively. The best response values of 67.39 and 86.97 mg of CO2/g of sorbent and 0.3402 and 0.1872 (min−1) were predicted for the adsorption capacity and reaction rate constant for fluidized and fixed bed, respectively, at the optimum conditions which were verified experimentally. Also, a CFD model for simulating CO2 capture in a circulating fluidized bed (CFB) was developed. Based on the simulation results, the optimum riser and downer velocity and temperature were 5.46 m/s, 0.2 m/s, 333.4 °K, and 564.4 °K, respectively. Also, in this optimum condition continuous CO2 removal from the CFB were predicted as 95.277%. In addition, the mean Sherwood and turbulence diffiusion coefficient in CFB were calculated as 0.000122 and 0.341 m2/s2, respectively. Finaly an equation for the removal percent of CO2 in CFB based on the non-dimentional numbers is presented with coefficient of determination (R2) 0.982. The optimized operating conditions were presented by means of RSM and validated. The results of this study could be applied for design and scale-up of CO2 capture from flue gas using solid sorbent in fluidized bed reactors.
