Study On Biomass Catalytic Pyrolysis And The Tar Catalytic Cracking And Reforming Over Steel Slag Based Catalysts

Biomass energy is a renewable energy with great potential,and pyrolysis gasification technology is an important way to transform its energy.Tar is an inevitable product in the process of biomass pyrolysis gasification.How to achieve efficient and low-cost catalytic conversion of tar directly affects system safety and energy conversion efficiency.Steel slag is a by-product of the iron and steel industry.It has a large output and is rich in metal elements such as iron,calcium and magnesium.It has important potential for preparing biomass pyrolysis and its tar cracking conversion catalyst.Based on this,a new type of catalyst was prepared from steel slag as the matrix.The effect of steel slag on the pyrolysis conversion characteristics of biomass was studied.The effect of steel slag on the pyrolysis and reforming reaction of biomass pyrolysis tar was systematically studied.On this basis,The steel slag catalyst was modified by nickel loading,and good tar conversion efficiency was obtained,which provided a new research idea for the preparation of low cost biomass tar catalyst.This article will conduct research from the following aspects:?1?The influence of calcined steel slag on the pyrolysis characteristics of pine chips was analyzed by thermogravimetry.The results show that the calcined steel slag has a stable structure,and its addition increases the maximum thermal weight loss rate of the sample and the corresponding temperature.The thermal activation energy of pine chips under steel slag blending conditions was calculated by distributed activation energy model?DAEM?and Flynn-Wall-Ozawa?FWO?method.The activation energy of pure pine samples was in the range of 0.2-0.8.Near 135 kJ/mol,the activation energy of pine pyrolysis was reduced to some extent after the addition of steel slag.The catalytic effect of steel slag on biomass pyrolysis was confirmed from the perspective of activation energy.?2?The catalytic reforming of pine tar was carried out by high temperature calcined steel slag.The results showed that after calcination at 800°C,relatively stable Fe₂O₃ and MgFe₂O₄ crystal forms were formed on the surface of steel slag,and the tar oil showed stable catalytic activity.The reforming temperature is 800°C.Under the catalysis of three cycles of steel slag,the tar conversion rate can reach 90.8%,and the non-condensable gas yield can reach 370.6 mL/g.The water vapor further enhances the tar and gas steam reforming reaction,and the gas yield is further improved up to 493.5mL/g,wherein the water gas shift reaction?WGSR?leads to an increase in the yield of H₂ and CO₂.During the reaction,the iron oxide on the surface of the steel slag is reduced to a low-valent iron oxide by the reducing gas?H₂ and CO?originally generated by biomass pyrolysis,and the long-term stability of the catalytic activity is maintained.?3?The nickel-loaded steel slag catalyst was prepared by the traditional impregnation method,and its catalytic and reforming properties for biomass pyrolysis tar were studied.The results show that the surface of the steel slag after calcination at900°C forms a stable form of Fe₂O₃ and MgFe₂O₄,and NiO particles with uniform distribution can be formed after loading nickel.The nickel-bearing steel slag has a high activity for catalytic reforming.The reforming temperature is 800°C.The nickel-based steel slag catalyst can achieve a conversion rate of 97.5%and a non-condensable gas yield of 463.0 mL/g.The steam reforming significantly enhanced the tar and gas steam reforming reaction,and the gas yield was further improved to 540.5 mL/g.The water gas shift reaction?WGSR?resulted in a significant increase in the H₂ and CO₂ yields.During the reaction,the surface iron and nickel oxide of the catalyst are reduced by reducing gases?H₂ and CO?to form a low-valent iron oxide and nickel elemental structure,and form a relatively stable surface porous structure,which is beneficial to the long-term maintenance of its catalytic activity.