Study On Characteristic And Synergistic Effects Of Pressurized Pyrolysis Of Coal And Biomass

Considering the current energy situation in China,rich in coal and biomass and lack of gas and oil,and the urgent need for environmental protection,the coal and biomass co-pyrolysis/combustion technology can give the advantages of these two resources.Also,this technology enables clean and efficient utilization of coal,the transition of low-grade biomass fuels to high-grade fuels and to improve the quality of pyrolysis liquids and gas products.Pressurized co-pyrolysis could strengthen the interaction between coal and biomass,so this paper carried out research on pressurized pyrolysis of coal and biomass.In this paper,the thermogravimetric characteristics and reaction kinetics of coal,pine sawdust and their blends under pressure of 0.1-2.0 MPa were firstly studied by using pressurized thermogravimetric analyzer?PTGA?.It is found that the increase of pyrolysis pressure depresses the release of volatiles and increases apparent activation energy of the main pyrolysis stage by 56%-85%.The process of co-pyrolysis is not the accumulation of individual pyrolysis,but is affected by inhibition or acceleration effect of synergistic reaction.Compared to the calculated results,the experimental weight loss of co-pyrolysis increases 8%-23%in pressurized condition while decreases 6.7%in atmospheric condition.The apparent activation energy of co-pyrolysis in both atmospheric and pressurized condition is lower than that of individual pyrolysis during the main pyrolysis stages.In order to further investigate the yield and quality of the products,pressurized pyrolysis of coal,pine sawdust and their blends were performed in a fixed bed reactor.The gas,liquid and solid products of the pyrolysis were analyzed through scanning electron microscopy?SEM?,X-ray diffraction?XRD?and gas chromatography-mass spectrometry?GC/MS?.Results indicated that the yield of the gas and liquid products of pine sawdust pyrolysis are higher than those of Bernstein bituminous coal.As the pyrolysis pressure increases,the yield of gas and liquid products of pyrolysis of coal and pine sawdust decreases while the yield of char increases.What's more,the percentages of CH₄,C₂-C₃ and CO₂ in gaseous products increase while the ratios of CO and H₂ decrease as the pyrolysis pressure increases.The proportion of light tar in liquid products decreased first and then increased as the pyrolysis pressure increases.The co-pyrolysis of coal and pine sawdust shows no obvious synergistic effect in the yield of gas-solid liquid products but increases the proportions of CO₂,CO and H₂ in the gas product,and promoted more light tar in the pyrolysis process.To study the effects of pine sawdust char on the co-pyrolysis,the fast pyrolysis gas chromatography-mass spectrometry?PY-GC/MS?was used for the pyrolysis for the coal,pine sawdust,their blends,and blends of coal and pine sawdust char.Analysis on the light tar indicates that the co-pyrolysis of coal and pine sawdust does not increase the content of aromatic components in light tar,but improve the distribution of aromatics.The content of BTX in aromatic hydrocarbons is 62.4%,which is higher than 51.2%of coal pyrolysis alone.In addition,the pyrolysis for blends of coal and pine sawdust char indicates that the pine sawdust char improves the coal pyrolysis.The BTX content in the aromatic hydrocarbons is higher than 55%,which is also higher than that of coal alone.However,the effect of pine sawdust char on co-pyrolysis is limited,which does not increase with the proportion of char blending.