Study Of The Effect Of Coal Ash On The Reaction Characteristic And Morphology Structure Of Oxygen Carrier In Chemical Looping Gasfication With Coal Char

Chemical looping gasification is a clean-energy technology with high efficiency,which had a great significance on energy conservation and emission reduction in coal-fired process.The production and separation of coal ash were key problems,before the application of chemical looping technology with solid fuels.In this work,influence of different kinds of coal ash and its components on the str ucture and reaction characteristic of Fe4Al6 were studied.The main contents of the work were as follows:?1?Effect of Shenmu bituminous ash on the reaction characteristic and morphology structure of Fe4Al6 oxygen carrier in chemical looping gasification with coal char was studied in a fluidized bed reactor.0-15% Shenmu bituminous ash promoted the reactivity of Fe4Al6 oxygen carrier in different reaction stages under reduction reaction temperature of 900 °C.However 20% Shenmu bituminous ash reacted with Fe4Al6 oxygen carrier in chemical looping gasification to form substance as Fe2SiO4,Fe Al2O4,Ca Fe4Al2O10 and Ca Al8Fe4O19.It was confirmed that these matter with a low-melting point aggravated the sintering problem of Fe4Al6 oxygen carrier.Moreover,15% Shenmu bituminous ash reduced the optimum reaction temperature of Fe4Al6 oxygen carrier,but when the reaction temperature exceed 950 °C,the ash played a harmful effect on chemical looping gasification with coal char.?2?Based on the contrastive analysis with Shenmu bituminous ash,the influence of Eerduosi lignite ash and Jindong anthracite on Fe4Al6 oxygen carrier in CLG were obtained.20% Eerduosi lignite ash reacted with Fe4Al6 oxygen carrier in chemical looping gasification to form substance with spinel structure?K2Fe22O34 and K2Fe10O16?.It has been proved that substance with spinel structure had a positive influence on reaction of Fe4Al6 oxygen carrier in CLG with coal char.Sintering problem of Fe4Al6 oxygen carrier was not found in 20% Eerduosi lignite ash experimental group.Under the synergistic effect of Jindong anthracite and Fe4Al6 oxygen carrier,carbon conversion rate of coal char was greatly increased,but more syngas were consumed by the oxygen-carrying components in ash.Moreover,Sintering problem of Fe4Al6 oxygen carrier was also not found in 20% Jindong anthracite ash experimental group.?3?Elements of K,Ca and Si deprived from coal ash may played an important role in the sintering problem of Fe4Al6 oxygen carrier in CLG with coal char.SiO2 had the most fatal influence on agglomeration of Fe4Al6 oxygen carrier.SiO2 reacted with Fe4Al6 oxygen carrier in chemical looping gasification to form aluminosilicate as Fe2SiO4 and FeAl2SiO6.These mater hindered the diffusion of syngas in Fe4Al6 oxygen carrier,and it also consumed more activecomponent of Fe-based oxygen carrier to inhibit the reactivity of Fe4Al6 oxygen carrier.CaO of coal ash had a stronger effect on agglomeration of Fe4Al6 oxygen carrier in CLG with coal char.Ca O reacted with Fe4Al6 oxygen carrier in chemical looping gasification to form some matter as Ca Al8Fe4O19,Ca Al2Fe2O6 and CaAl2FeO5.The matter was easily penetrated into Fe4Al6 oxygen carrier to cover its surface and reduced the gas-solid reaction active site of Fe4Al6 oxygen carrier.K₂O had a positive effect on the pore structure formation of Fe4Al6 oxygen carrier in chemical looping gasification,which improved the reactivity of Fe4Al6 oxygen carrier.Potassium gaseous phase resulted from coal ash under high temperature condition of chemical looping could react with Fe4Al6 oxygen carrier to form potassium ferrite with K-Fe-O structure.This structure conduced to more lattice oxygen to release from Fe4Al6 oxygen carrier.In addition,potassium ferrite had a stable structure similar to ?-Al2O3 that promoted the stability of Fe4Al6 oxygen carrier.