Effect Of Compound Potassium Salt On Sawdust Pyrolysis And Its Catalytic Performance

As a kind of renewable energy,biomass can solve problems such as energy shortage and environmental pollution through thermochemical conversion.However,due to the problems of low efficiency and poor product quality in conventional thermal conversion technology,the addition of catalysts in the biomass pyrolysis process to carry out catalytic pyrolysis and catalytic gasification has become a key issue in thermal conversion technology.This paper studied the effect of compound potassium salt on the pyrolysis of wood chips and its catalytic performance,and compared it with different kinds of single potassium salt.Factsage software was used to conduct thermodynamic simulation and quantum chemical simulation of the catalytic pyrolysis process,and analyze the effect of catalyst on the pyrolysis of wood chips.The thermogravimetric experiment of catalytic pyrolysis was carried out,and the kinetic analysis was carried out.Through pyrolysis experiments and gasification experiments,the effects of catalyst addition,pyrolysis temperature and catalyst types on the pyrolysis process and gasification process products of wood chips were investigated,and the composition changes and distribution of pyrolysis products under different conditions were analyzed,and the most Excellent pyrolysis conditions.The results of thermodynamic simulation and quantum chemistry simulation show that potassium ions can promote the process of biomass pyrolysis.Thermodynamic simulation shows that when wood chips are pyrolyzed at 700℃,the H₂production reaches the highest.Quantum chemical simulations show that the addition of potassium salt catalyst can reduce the barrier of the dehydrogenation reaction,thereby promoting the production of these small molecules.Biomass catalytic pyrolysis thermogravimetric experiment results show that the pyrolysis process is divided into four stages:drying stage,initial pyrolysis,pyrolysis main weight loss zone and carbonization stage.After the potassium salt catalyst is added,the pyrolysis of the wood chips is promoted,the pyrolysis temperature is reduced,and the pyrolysis process of the wood chips is changed,so that the pyrolysis weight loss rate curve is changed.The composite potassium salt catalyst with the ratio of potassium hydroxide and potassium carbonate of 5:5 has the most obvious effect.Through kinetic analysis,it can be known that in the low temperature and high temperature range,the wood chip reaction mechanism follows the two-dimensional diffusion model and the random nucleation and subsequent generation model respectively.After adding the catalyst,the wood chips follow the three-dimensional diffusion model and the chemical reaction model respectively.When the conversion rate exceeds 20%,the activation energy during the pyrolysis process of wood chips is significantly reduced due to the effect of the compound potassium salt.Biomass pyrolysis experiments show that the composite potassium salt catalyst with the ratio of potassium hydroxide and potassium carbonate of 6:4 has the best catalytic effect.The content of H₂and CO₂in the product is increased,and the content of CH₄and CO is reduced,which improves the quality of pyrolysis oil and reduces the oxygen content in the oil.Comprehensive considerations consider that when the compound potassium salt（KOH:K₂CO₃）is added at 5:5,a pyrolysis temperature of800°C is the optimal gas production process.