Experimental Study On The Characteristics And Mechanism Of Synergy Effect During Microwave Co-pyrolysis Of Lignite And Biomass

Lignite is the lowest degree of mineralization of mineral coal,which abundant and widely distributed in China.The unique molecular structure of lignite provides favorable conditions for the preparation of coal-based fine chemicals,while biomass provide a cheap source of hydrogen for lignite pyrolysis and increase the yield of lignite pyrolysis products.The microwave heating method with the advantages of fast heating and uniform heating can provide a good pyrolysis atmosphere for the co-pyrolysis process of lignite and biomass.Therefore,the development of lignite and biomass microwave co-pyrolysis technology has far-reaching economic significantly.This paper focused on microwave pyrolysis of lignite(Hailar lignite)and biomass(Palm kernel shell)and their co-pyrolysis by using modified quartz reactors,and the formation mechanism of synergy effect during microwave co-pyrolysis of lignite and biomass is analyzed.During the experiments,the pyrolysis products are characterized and analyzed by gas chromatography-mass spectrometry(GC-MS),gas chromatography(GC),Fourier transform infrared spectroscopy(FT-IR)and elemental analysis(EA).The results of individual microwave pyrolysis of lignite and biomass showed that the yield of tar and gas of lignite and biomass both increased monotonically with increasing of the pyrolysis temperature,the yield of char decreased with increasing the pyrolysis temperature.Lignite tar contains more single-ring aromatic compounds and aliphatic hydrocarbons,while higher content of single-ring aromatic compounds in biomass tar.The major gases released from lignite and biomass is H2 and CO.With increasing pyrolysis temperature,the functional groups(e.g.-OH,-C=O?-COOH)in char decomposed substantially.The results of microwave co-pyrolysis of lignite and biomass showed that the synergy effect promoted the yields of tar and gas during co-pyrolysis experiments.Gas chromatography-mass spectrometry(GC-MS)analysis of tar showed that the formation of aliphatic hydrocarbons was promoted during co-pyrolysis of lignite and PKS biomass.The synergy effect also promoted the formation of H2 and CO during co-pyrolysis.A two-stage pyrolysis reactor was used in order to investigate the mechanism of synergy during co-pyrolysis by isolating the secondary pyrolysis reactions.The two-stage pyrolysis results showed that secondary pyrolysis reactions were mainly responsible for synergy effect,resulting in higher gas and lower tar yields as a result of secondary tar cracking.HL and PKS chars promoted the formation of aliphatic hydrocarbons,CO,and CO as a result of decarbonylation,decarboxylation,and demethylation reactions.