Study On Chemical Looping Gasification Of Pine Sawdust Based On Hematite As Oxygen Carrier

In the tense energy situation,fossil energy represented by coal still occupies the status of China's main energy.In view of the non-renewability of fossil energy such as coal and the unreasonable utilization of coal resources in China,vigorously developing clean and renewable new energy has become the leading direction to alleviate the energy crisis and reduce environmental pollution in China,among which biomass energy has a broad prospect.In the utilization of biomass energy,biomass chemical looping gasification technology has shown a good development prospect.In this paper,the syngas was prepared from pine sawdust by chemical looping gasification in a small fluidized bed reactor with hematite as oxygen carrier.The effects of O/C ratio,steam flow rate,and reaction temperature on the quality of syngas were studied,and tar analysis and cycle experiments were performed.At the same time,the activity of oxygen carrier was improved by adding active metal by impregnation method,and its reaction performance was explored.Finally,the oxygen carriers were characterized by XRD,ESEM and BET.The main contents and conclusions of the study are as follows:?1?When the O/C ratio was 0.2,the steam flow rate was 0.15 mL/min and the reactor temperature was 850°C,the best gasification effect was achieved.The yields of CO,CH₄,and H₂ were 2.43 L,0.77 L,and 1.4 L,respectively.When hematite is used as oxygen carrier,some of the macromolecular organic compounds in biomass tar are cracked to generate micromolecular organic compounds or syngas,and the tar content is significantly reduced,which is conducive to the operation and safety of biomass chemical-looping gasification system.?2?The XRD results of hematite show that the reduction of hematite is inhibited under the presence of water vapor,and Fe₂O₃ can only be converted to Fe₃O₄.The results of ESEM and BET analysis showed that the surface sintering phenomenon of the oxygen carrier particles after repeated cycles was obvious,and the specific surface area declined from 2.63m²/g to 1.35 m²/g.?3?Under the optimal experimental conditions,CaO-hematite,MgO-hematite and CeO₂-hematite as oxygen carrier for pine sawdust chemical looping gasification cycle test,the quality of syngas production is higher than hematite as oxygen carrier.Among them,CeO₂-hematite is the best,and its efficiency of carbon conversion,gasification efficiency,gas yield and the lower calorific value of syngas are 91%,95.86%,1.20 Nm³/kg and 12.81MJ/Nm³,respectively.When three kinds of modified hematite are used as bed materials,the tar content of biomass was lower than that of hematite as oxygen carrier,and CeO₂-hematite has the strongest ability to enhance the decomposition of tar.?4?The XRD results of oxygen carrier particles shows that the main components of CaO-hematite are Fe₂O₃,CaO and Ca₂Fe₂O₅.The main components of MgO-hematite are Fe₂O₃ and MgFe₂O₄,and the main components of CeO₂-hematite are Fe₂O₃ and CeO₂.The main components of three kinds of modified oxygen carrier has not changed after five cycles.The results of ESEM and BET analysis show that:Compared to CaO-hematite,MgO-hematite and CeO₂-hematite have higher sintering resistance and thermal stability.