Experimental And Mechanism Study On Simultaneously No And CO₂ Removal Using Modified Peanut Shells Char And CaO

Reduction of NO_x and CO₂ emissions is global issues.Coal char was used in Calcium-looping coupled CARBONO_x technology（Ca-L/CARBONO_x）to achieve simultaneously reduction in carbonation reactor of Ca-L process.However,the poor reactivity of coal char,the comsumption of reactants due to high concentration of residual oxygen（2～6%）in flue gas,and the generation of CO limit the development of this technology.In this study,a new scheme of using modified peanut shell biochar to replace conventional coal char was proposed.Peanut shell biochar was modified by acid pickling,N-doping or acid pickling combined N-doping to improve its reaction selectivity to NO and oxidation resistance.Physical and chemical adsorption apparatus（BET）,Fourier transform infrared spectroscopy（FT-IR）,X-ray fluorescence spectroscopy（XRF）and fixed bed reactor are used,which are developed in turn:（1）Effects of pickling and N-doping treatment on pore structure,surface functional groups distribution and NO removal characteristics of peanut shell biochar and its mechanism;（2）Study on the characteristics and reaction mechanism of simultaneously removal of NO/CO₂ by four kinds of modified peanut shell biochars blended with Ca O.The experimental results of NO removal performance of peanut shell biochar by pickling and N-doping treatment showed that parts of the ash in acid-washed peanut shell biochar（BC-A）was removed,leading to the collapse of large pore tunnels,thus greatly increasing the specific surface area.N-doping introduced nitrogen-containing functional groups into the surface of peanut shell biochar,however,the ash in peanut shell biochar inhibited the introduction of nitrogen-containing functional groups,which hindered the development of pore structure in the N-doping process.The number of micropores in N-doping peanut shell biochar（BC-N）decreased compared with that of original peanut shell biochar（BC）.However,the N-doping effect is effectively enhanced after the ash in peanut shell biochar is removed by acid pickling.Under the dual effect of good pore characteristics and N-doping operation,the reactivity and selectivity of acid pickling nitriding peanut shell biochar（BC-A-N）are greatly improved.The experimental results of NO/CO₂ removal by peanut shell biochar blended with Ca O showed that Ca O can provide active sites for CO and NO,and catalyzes the reduction of NO by CO.The appropriate reaction temperature of peanut shell biochar and Ca O for NO/CO₂ removal is 650 ^oC.The higher the O₂ concentration in the simulated flue gas,the more unfavorable it is for the removal of NO/CO₂ and the increase of CO emissions.The increase of char/Ca O mass ratio can effectively improve NO removal ratio,but also increase CO emissions.N-doping peanut shell biochar can reduce the amount of CO generated during the NO/CO₂removal process,but BC-A/Ca O and BC-A-N/Ca O have the best cooperative NO/CO₂removal performance.The NO removal performance of BC/Ca O decreased significantly with the increase of calcium looping times,but the NO removal performance of BC-A-N/Ca O remained basically unchanged without the influence of calcium looping times...