Synthesis Gas Production From Chemical Looping Gasification Of Lignite By Using Manganese Ore As Oxygen Carrier

The most abundant coal reserves are in China all over the world,among them,the reserves of low rank coal account for more than 70%.With the increasing consumption of high quality coal such as anthracite and coking coal,the efficient and clean utilization of low-rank coal resources is increasingly important.As a new type of coal gasification technology,chemical looping gasification technology?CLG?has been successfully applied to coal,biomass and other solid fuels owe to its several significant advantages.It is an effective way to moderate the problem on energy demand by using chemical chain gasification technology to realize efficient and clean utilization of low rank coal.This article employed the manganese ore as selected oxygen carrier,which has the advantages for high reactivity,low cost,and can be directly used in chemical looping gasification without complex pretreatments,and Zhao Tong?ZT?lignite was used as a typical low rank coal.Experimental researches on lignite with manganese ore and modified manganese ore chemical looping gasification were carried out in the benchscale fixed bed reactor and a TGA reactor.In order to provide basic experiment data support for application of manganese ore in coal chemical looping gasification system,as well as the utilization for low rank coal resource utilization within chemical looping technology,the main research content includes the following parts:?1?the reduction characteristics of manganese ore as oxygen carrier were investigated in H₂-TPR and TGA apparatus,the XRD characterization results showed that the main active group included in manganese ore was Mn₂O₃,and the oxygen uncoupling process only occurred under inert atmosphere.Under H2 reduction atmosphere,there are two majority reduction peaks at 354.82? and 473.05?.Analyzed by TGA results,the weight loss and loss rate had been elevated obviously in the presence of manganese ore when it compared to lignite pyrolysis process.?2?lignite was selected as a typical low rank coal,and natural manganese ore was used as oxygen carrier.The experiments on syngas produced from lignite with manganese ore within chemical looping gasification were carried out in a bench-scale fixed bed reactor.The effects of the main operating conditions on the concentration distribution of gas products,lower heating value,carbon conversion and gas production were investigated,and the optimal reaction conditions were obtained.When the reaction temperature was 900?,the mass ratio was 1:4,and the steam flow rate was 0.0375g/min,the lower heating value was 9.69MJ/Nm3,the carbon conversion and the syngas yield are 74.01% and 1.05Nm3/kg,respectively.?3?The cyclic reactivity and stability of the oxygen carrier were tested via 10 cyclic experiments,and it was analyzed from the microstructure perspective by means of SEM,EDS,BET and other methods.The results showed that the reactivity of oxygen carrier slightly declined after several cycles,but it remained stable overall.After 10 cycles,the structure kept porous,although the phenomena of slight agglomeration and sintering occurred,and the blockage of coal ash to the pore was the main reason for the reactivity decline for oxygen carrier.In general,manganese ore is a suitable oxygen carrier in lignite chemical looping gasification process.?4?A CaO modified manganese ore was prepared by impregnation method as oxygen carrier,and the effect of the adding amount on the reaction performance was investigated in a fixed bed reactor,it indicated that Ca10 Mn was the selected oxygen carrier.As a result,it can enhance carbon conversion and syngas yield,reaching 78.16% and 1.11Nm³/kg,respectively.Analyzed by the result of XRD patterns,a new crystalline phase of Ca₂Mn₂O₅ generated at high temperature,which played catalytic effects on CLG process.Moreover,during the reduction process of Ca10 Mn,a decomposition reaction occurred and generated CaO;And the Addition of CaO might promoted deep reduction process of Mn₂O₃???Mn3O4???MnO.