Based On The Law Of Mercury Migration And Change During The Combustion Process Of The Iron-based Oxygen Carrier Chemical Chain

Coal as a primary energy occupies a leading position in China's energy structure.In addition to common pollutants(Sulphur Oxides,Nitrogen Oxides and carbon dioxide),the emission of mercury and its compounds have caused more attention.Recently,Chemical looping combustion(CLC)technology has emerged as a promising option to facilitate carbon dioxide inherent separation atlow cost.However,the study on CLC is still in a fresh field.As a result,the research on the laws of the heavy metals during Chemical looping combustion has a far-reaching significance on mercury pollution control.The present thesis investigates the effects of working condition,such as reaction temperature,gasification agent,reaction time.These results are very helpful to both prediction of mercury transformation and control of mercury emissions from CLC.This paper involved in this thesis is as follows:1.Various models of chemical and thermal equilibrium were used to predict chemical species of mercury in the flue gas from fuel reactor and air reactor.The software is HSC chemistry 6.0,the temperature range is from 0? to 1200?,and the pressure is 1 atm.Calculation models are based on different flue gas from fuel reactor and air reactor,different temperature and gasification agent.Possible reactions in different models are predicted.The thermodynamic calculation results showed that the reaction temperature is the main factor affect the process of mercury during coal gasification.Hg0(g)should be the stable form in the highest temperature regions of reactors and gasification agents.And the moisture is a strong inhibitor for mercury oxidation.With the ratio of O2/N2 increased from 5%to 21%,the released temperature decreased from 450? to 230?.2.The effects of temperature on mercury speciation and transport during coal chemical looping combustion based on Fe2O3 oxygen carriers were carried out in a vertical tube furnace device.The effect of temperature,gasification agent and reaction time on the oxidation mechanism of elemental mercury in flue gas from fuel reactor and air reactor were also investigated.The results indicated that the elevated temperature could enhance the mercury release from coal.The release rate of mercury increased as the reaction time increasing.Mercury in coal was completed released and the discharge rate reached 90%in 180s at high temperature in FR.The major mercury species was Hg0 and the ratio Hg0/HgT was 88%.The rate of Hg0/HgT was decreased with increasing temperature.Different temperature had effects on the components of flue gas.The elevated temperature could cause an increase in the SO2,NO and CO.SO2 could inhibit the oxidation process of mercury by inhibiting the formation of Cl/Cl2.The NO could promote the oxidation of mercury,but CO had an opposite effect.With the ratio of H2O/CO2 increasing from 0:1 to 1:1,the Hg2+/HgT decreased.The increasing ratio of O2/N2 was advantageous to reduce Hg0(g).3.NOx could oxidize mercury in the fuel gas.Further studies would be needed to investigate the effect of temperature and gasification agent on mercury,NO emission was studied,which was influenced by temperature and agent.The results showed that NO due to the reaction between NH3 and oxygen carrier was supported only when the oxygen carrier was reduced from Fe2O3 to Fe3O4.The experimental results and simulation results match well:the increased temperature could efficiently enhance the fuel conversion and fuel-N released in fuel reactor.Thus,the NO emission increased.However,due to the reducing atmosphere in the fuel reactor,NO formation was restrained,and NO could be reduced to N2,the NO emission maintained at a low value.