Studies On The Co-pyrolysis Characteristics Of Shenmu Coal Blends With Corn Stalks

Coal,one of the most important fossil fuels,will still play a major role in China's energy consumption in the coming decades.However,the use of coal causes serious environmental problems.The biomass energy is renewable energy,which can provide about 14%of the world's energy consumption.However,the supply of biomass raw materials has limited its large-scale industrial applications.Co-utilization of coal and biomass can make up the deficiency between them,and is a potential and promising technology.As the initial stage in the process of co-thermochemical conversion,co-pyrolysis plays a crucial role in the subsequent process.During the process of co-pyrolysis,the interaction between coal and biomass has an impact on the process of co-pyrolysis and the characteristics of co-pyrolysis char.Therefore,this paper conducts an in-depth study on the co-pyrolysis process and the characteristics of co-pyrolysis char,and reveals the synergistic mechanism in the co-pyrolysis process.It provides theoretical basis and basic data for the engineering application of coal and biomass co-utilization technology.The component segregation during coal grinding process affects the chemical structure,pyrolysis reactivity and pyrolysis gas-phase products of coal with different particle sizes.In order to determine the appropriate sampling criteria,a series of infrared structural parameters and devolatilization composite index were constructed to semi-quantitatively characterize the chemical structure and pyrolysis reactivity of six different sizes of Shenmu coal.Finally,the effect of component segregation on pyrolysis gas-phase products was studied by thermogravimetric-Fourier transform infrared combined analyzer(TG-FTIR),and the accuracy of infrared structure parameters was verified.The results show that the hydrogen content and some typical functional group structures are obviously affected by component segregation.With the particle size of Shenmu coal decreasing,the ash content gradually increases,the pyrolysis reactivity becomes worse,and the release of CH₄,aliphatic hydrocarbons,and light aromatic hydrocarbons gradually decreases.Through the analysis of pyrolysis gas phase products,it can be determined that the infrared structural parameters established in this paper are accurate and reasonable.In addition,according to the experimental results,a comprehensive infrared structural parameter S is constructed,and it is determined that under the experimental conditions in this paper it is positively correlated with the devolatilization composite index D.Finally,the sampling standard of this paper is obtained,and it provides the theoretical basis for the following research methods.During the process of co-pyrolysis,the presence of coal and biomass may affect the pyrolysis process of each other.In addition,the interaction between char and volatiles also promotes synergistic.In this paper,the chemical structure differences,co-pyrolysis characteristics and kinetic analysis of coal and biomass were studied.In order to study the co-pyrolysis process more comprehensively,the co-pyrolysis characteristic parameters were used to study the interaction between coal and biomass and their influence on the whole co-pyrolysis process.The results show that coal is rich in aromatic C=C structure,while biomass is rich in OH and C–O structure.During the co-pyrolysis process,experimental R_B is higher than the calculated value,while experimental R_coal is lower than the calculated value,and experimental T_coal moves towards low temperature.At the initial stage of pyrolysis reaction,the growth trend of the blend activation energy curve is consistent with that of biomass.With the pyrolysis temperature increasing,the blend activation energy is influenced by both coal and biomass.The conversion of char has an important effect on the overall thermochemical conversion efficiency,and the interaction between volatiles and char during the co-pyrolysis process seriously affects the characteristics of the co-pyrolysis char.The effects of co-pyrolysis of Shenmu coal and corn stalks on the physicochemical properties,alkali and alkaline earth metals(AAEM)content and reactivity of co-pyrolysis char were studied in this paper.The results show that the co-pyrolysis process of coal and corn stalks has little or no effect on char yield,but can promote the formation of plastic mass.Coal can inhibit the release of K and Mg in corn stalks,but the blending of coal and corn stalks can promote the release of Ca.With the pyrolysis temperature increasing,the aromatic C–H functional groups in char samples first increase and then decrease,and the carbon structure changes from small aromatic ring structures to large aromatic ring structures with 6 or more benzene rings.The interaction between coal and corn stalks during co-pyrolysis is more important than that between coal char and corn stalks char during co-gasification.The reactivity of co-pyrolysis char is the best when the mass ratio of corn stalks is more than 70%and the co-pyrolysis temperature is about 600?During the process of co-pyrolysis,AAEM can influence the synergistic effect of coal and biomass.Both AAEM in coal and AAEM in biomass have influences on the co-pyrolysis process.In order to explore the influence of AAEM on the co-pyrolysis process,this paper studied the physicochemical properties and reactivity of co-pyrolysis char of four blends:RC&RCS,HC&RCS,RC&HCS and HC&HCS.The results show that the co-pyrolysis char yield obtained from the four blends presents a trend of RC&RCS>HC&RCS>RC&HCS>HC&HCS.The effect of co-pyrolysis on char yield is very slight and can be ignored.During the process of co-pyrolysis,the presence of corn stalks is beneficial to the generation of spherical particles from coal char,and the promotion effect of HCS is greater than that of RCS.The interaction between the blends promotes the reactivity of co-pyrolysis char,which is more obvious in the co-pyrolysis char with the participation of corn stalks.In summary,based on the co-pyrolysis process of coal and biomass,this paper studied the characteristics of co-pyrolysis,the physicochemical structure and reactivity of co-pyrolysis char,as well as the effect of ion-exchangeable AAEM on them,and discussed the mechanism of synergistic effect during the co-pyrolysis process.The results provide theoretical guidance and basic data for the co-pyrolysis process of coal and biomass,and play a positive role in promoting its efficient and clean utilization...