Study On Catalytic Pyrolysis And Resource Utilization Of Distillers' Grains

China is a major brewing country,producing over a hundred million distiller's grains(DG)every year.If the DG cannot be disposed of in a timely and reasonable manner,it may cause serious environmental pollution and a waste of resources.How to recycle these biomass wastes and turn them into treasures is a major challenge for the ecologically sustainable development of the liquor-making industry.The current value-added utilization ways of DG have certain limitations,and the pyrolysis method has attracted extensive attention from researchers because of its advantages such as high energy utilization,fast reaction rate,large product application potential,low secondary pollution,good economy,and favorable large-scale industrial applications.The gas-phase product of pyrolysis is a clean and efficient gas fuel,but its application is limited due to lower yield and gas quality.Catalytic pyrolysis is considered to be an effective measure to increase the yield of syngas while improving the quality of fuel gas.This study explored a new process route for the utilization of DG waste from the perspective of catalytic pyrolysis of biomass and analyzed the law of catalytic pyrolysis of DG and its product characteristics.It is found that the five catalysts(nickel-based catalysts,potassium-based catalysts,iron-based catalysts,molecular sieves,dolomite)added in the experiment can promote the secondary cracking of tar.Among them,the nickel-based catalyst is the most active,and the mass yields of the three forms(gas,liquid,solid)obtained by catalytic pyrolysis are 42.85,25.01,32.14 wt.%,the volume yield of gas reach 413.10 m L/g from 308.52 m L/g,the hydrogen yield double by 2.72 times to4.69 mmol/g,and the volume concentration ratio of H₂ and CO are the highest(25.44%and 30.48%,respectively).Besides,all five catalysts can improve the quality of tar to a certain extent,and the molecular sieve catalyst has the most obvious improvement effect on the tar composition.Meanwhile,the changes in the three-phase product yield and gas-phase composition of the catalytic pyrolysis of DG under different reaction conditions were also investigated,and the operating conditions corresponding to the maximum gas production rate and optimal gas production quality were found:the final reaction temperature is 900?;the nickel loading is 8 wt.%;the addition ratio of catalyst dosage is 50%(separable,recycled and reused);the solid residence time is 20 minutes.Under this condition,the mass yields of the three forms(gas,liquid,solid)obtained by catalytic pyrolysis are 69.67,1.56,28.78wt.%,the volume yield of gas reach 600.06 m L/g,and the volume concentration ratios of H₂ and CO are 35.10%and 35.39%,respectively.Finally,in order to develop the application field of catalytic pyrolysis products of distiller's grains,the application potential of pyrolysis gas as fuel,the adsorption performance of distiller's grains-based biochar(DGBC),and the ecological risk of nickel leaching in the adsorption process of DGBC are discussed.The results show that the gas-phase products under the optimal catalytic pyrolysis conditions can meet the energy requirements of the coupled drying pyrolysis process of DG,and the energy utilization rate of the system is 62.06%;As the pyrolysis temperature rises,the degree of carbonization and aromaticity of distillers grain-based biochar(DGBC),the specific surface area,and micropore volume increase,while its hydrophilicity,polarity,and surface functional groups decrease;DGBCs prepared at different temperatures all have a certain adsorption effect on heavy metals and atrazine(AT).DGBC prepared at 900?has the highest adsorption capacity for Pb²⁺and AT,which are 89.92 mg/g and 13.35 mg/g,respectively;In addition,the leaching concentration of nickel in biochar at different pyrolysis temperatures,solid-liquid ratio,and environmental p H values is far lower than the national limit,which indicates that nickel is successfully immobilized in DGBC and the ecological risk is low.