Simultaneous NO/CO₂ Removal By CaO Deposited With Carbon/biomass Char In Calcium Looping Process

Calcium looping is a post-combustion CO2 capture technology for coal-fired power plants.It has been widely studied by scholars,owing to the following advantages:low operational cost,cheap sorbents and high technical readiness.Besides CO2 and SO2,NOx is another pollutant from coal-fired power plants,but there are few research for the simultaneous removal of CO2 and NOx during the calcium looping process.A novel strategy for simultaneous removal of CO2 and NOx during the calcium looping process by CaO deposited with carbon and biomass char was proposed.The CaO deposited with carbon and biomass char was prepared by pyrolyzing the biomass in presence of CaO.In this paper the mixture of CaO deposited with carbon and biomass char was prepared by pyrolyzing the biomass in presence of CaO.The simultaneous NO/CO2 removal performance of CaO deposited with carbon/biomass char was investigated in a bubbling fluidized bed reactor.The effects of carbon deposited on CaO,pyrolysis temperature,pyrolysis time,mass ratio of pine to CaO,O2 concentration and cycle number on simultaneous NO/CO2 removal performance of CaO deposited with carbon and pine char were studied.The microdistribution of carbon deposited on CaO was analyzed by TEM.The micromorphology and elements distribution of CaO with carbon/pine char were analyzed by SEM-EDX,and the pore size distribution of it was analyzed by N2 adsorption.The samples pyrolyzed under different temperature were analyzed by FT-IR.The reaction mechanism of simultaneous NO/CO2 removal by CaO deposited with carbon/biomass char was revealed.The simultaneous NO/CO2 performance of samples prepared by alga and terrestrial biomass were compared.The effect of biomass component content on simultaneous NO/CO2 performance was studied by using the biomass model compounds.The scientific basis of selecting biomass for simultaneous NO/CO2 removal realized by CaO deposited with carbon/biomass char was provided.TEM analysis showed that the surface and pore of CaO were covered by deposited carbon after the pine was pyrolyzed in presence of CaO and the thickness of deposited carbon is around 10nm.The NO removal performance of CaO deposited with carbon/pine char is much better than CaO/pine char.The NO was completely removed by CaO deposited with carbon/pine char.That proves the carbon deposited on CaO plays a very important role on promoting NO reduction.This is because the CaO grain is covered by deposited carbon,which improves the contact between active site of deposited carbon and CaO.The deposited carbon has little effect on CO2 capture during chemical reaction-controlled stage of CO2 capture.The NO can be completely removed by the CaO deposited with carbon/pine char prepared under different pyrolysis temperature(500～800℃)and the NO remove performance improves with increasing pyrolysis temperature.The CaO deposited with carbon/pine char possesses best simultaneous NO/CO2 removal performance when the pyrolysis time is 10 min.The NO remove performance increasing with increasing mass ratio of pine to CaO and the CaO deposited with carbon/pine char possesses best simultaneous NO/CO2 removal performance when mass ratio of pine to CaO is 20:100.The simultaneous NO/CO2 removal performance decreases with the increasing cycle number.The biomass specie has influence on simultaneous NO/CO2 removal performance.The algae is unsuited for simultaneous NO/CO2 removal in calcium looping process.The CaO deposited with carbon/biomass char prepared by pine,rice husk and bagasse by preferably simultaneous NO/CO2 removal performance and the NO remove performance followed the order bagasse>pine>rice husk.The NO remove performance increases with increasing the amount of carbon deposited on CaO.The samples prepared by the bagasse,which contains more hemicellulose and less lignin,possesses better simultaneous NO/CO2 removal performance.