Experimental Study And Mechanistic Analysis Of Microwave Pyrolysis Of Waste Biomass

In today’s fast growing world economy and rapidly increasing population,the shortage in energy and raw material supply has made more and more difficult for us to meet the growing demand for living.All fossil resources are non-renewable and accompanied by serious environmental impacts,and thus the development of renewable and sustainable energy resources has been identified as a critical strategy to address energy supply shortage,environmental pollution and climate change crisis.As the only renewable carbon resource in the world,biomass energy can help China meeting its goal of carbon peaking and carbon neutrality.The low utilization rate of waste biomass in China has resulted in massive accumulation,which has created environmental problems.Therefore,there is an urgent need to study the effective and clean utilization of waste biomass.In this paper,experimental research and mechanistic analysis of the conversion of waste biomass using microwave fast pyrolysis technology were conducted as follows:（1）The pyrolysis characteristics and kinetics of industrial waste furfural residue were studied using thermogravimetry and online detection methods,and the general performance of furfural residue pyrolysis,gas phase release behavior and kinetic behavior during pyrolysis,thermodynamic parameters and pyrolysis reaction mechanism were investigated.It is found that the pyrolysis of furfural residue mainly produces carboxylic acids,nitrogenous compounds,aldehydes,ketones,alcohols,phenols,carbohydrates and aromatics,and the pyrolysis process also releases a large amount of small molecule gases,including H₂,CH₄,C₂H₂,CO,C₂H₆,etc.These compounds have potential use as energy and chemical raw materials.In addition,the activation energy of furfural residue pyrolysis was calculated by four kinetic parameter extraction methods,and the mechanism of furfural residue pyrolysis was found to be consistent with the powder law model reaction mechanism.This study provides comprehensive data and valuable insights into the pyrolysis of furfural residue,which helps to understand the composition,pyrolysis characteristics,kinetic behavior,thermodynamic parameters and reaction mechanism of furfural residue,and provides basic parameters and research ideas for the pyrolytic conversion and utilization of waste biomass.（2）The pyrolysis characteristics and product quality of furfural residue were studied in a microwave fixed-bed reactor,and the effects of pyrolysis temperature and catalyst type on the pyrolysis conversion and products of biomass were comprehensively explored.The results showed that the bio-oil yield increased with increasing temperature and reached the maximum（～25wt%）at about 550℃.The gas yield increased significantly with increasing temperature,while the biochar yield decreased.Catalytic pyrolysis significantly promoted the pyrolytic conversion of furfural residue and increased the gas yield,and kaolinite and ZSM-5 made the pore structure of biochar more regular and stronger,and ZSM-5 improved the graphitization of biochar.In addition,catalytic pyrolysis significantly reduced the acidity of bio-oil,and catalytic pyrolysis（especially Mg O）greatly reduced the content of ketones and promoted the production of alkenes and benzene derivatives in bio-oil,which is beneficial for the stability and quality of bio-oil.Microwave pyrolysis conversion of waste biomass proved to be a feasible technology to optimize product distribution and potentially improve the quality of pyrolysis products.（3）The microwave pyrolysis,catalytic pyrolysis and carbon dioxide assisted pyrolysis techniques were combined with industrial waste furfural residue,cellulose and lignin with K₂SO₄ as the main catalyst to investigate the microwave pyrolysis mechanism of waste biomass and model compounds with a view to converting biomass components into higher quality products.The results showed that aldehydes,ketones,phenols and oxygenated heterocycles were the major organic components in cellulosic-derived bio-oil,while for lignin-derived bio-oil,aldehydes and phenols were observed to be the major components.Favorably,the interaction of cellulose and lignin inhibited the release of HCl to some extent.The results demonstrated that the high phenolic content in furfural residue derived bio-oil mainly originated from the decomposition of lignin catalyzed by K₂SO₄.In addition,CO₂-assisted pyrolysis promoted the decomposition of biomass and exerted a strong promotion effect on biomass conversion,significantly increased bio-oil yield,reduced bio-oil acidity,and promoted the production of alcohols,olefins and alkanes in bio-oil,which was beneficial to the subsequent storage and utilization of bio-oil.The CO₂ atmosphere also reduced the defective structure of biochar,enriched the porous structure and surface roughness of biochar,and effectively increased the calorific value of biochar.Finally,the main reaction pathways of microwave pyrolysis of waste biomass were explored by combining the offline detection results of microwave pyrolysis and the online detection information of pyrolysis.（4）The effects of pyrolysis temperature and mixing ratio on the performance and products of microwave co-pyrolysis were studied with industrial furfural residue and textile dyeing sludge as raw materials.The results showed that the addition of furfural residue could significantly improve the pyrolysis performance and effect for the textile dyeing sludge which is difficult to be treated to avoid its pollution.The product distribution showed that the increase of furfural residue ratio increased the yield of bio-oil and gas and significantly decreased the yield of biochar.For bio-oil,the addition of furfural residue neutralized the strong alkalinity and inhibited the formation of nitrogenous compounds,and the content of phenols,furans and alkenes increased with the increase of furfural residue ratio.For biochar,co-pyrolysis facilitated the enrichment of carbon and hydrogen,increased the calorific value of biochar,and contributed to the pore development of biochar with increased carbonization degree and aromaticity.Co-pyrolysis significantly inhibited the release of sulfur compounds and nitrogenates from volatiles,while reducing the hazard level of heavy metals in biochar.In addition,principal component analysis showed that furfural residue had a more significant effect on co-pyrolysis.Microwave co-pyrolysis improved the quality of gaseous products,bio-oil and biochar,and reduced the hazard levels for further utilization.