Experimental Study On Preparation Of Multi-source Biomass-based Activated Carbon

With the development of social economy and the rapid growth of global energy demand,the role of biomass as renewable energy in the global energy system is becoming more and more important.China’s biomass resources are rich,and the potential for use is huge.Pyrolysis of biomass into pyrolysis charcoal and wood vinegar liquid,and pyrolysis charcoal through physical activation method to prepare activated carbon,can achieve a comprehensive utilization of agricultural and forestry waste.In this study,the characteristics and pyrolysis characteristics of multi-source biomass were explored.Judging from the results of component analysis,the hemicellulose content of fruit cores is the highest,and that of hardwoods and softwoods is the highest.The content of straws is relatively moderate,while the content of lignin in date trees very high.The difference between the industrial analysis and elemental analysis results of each biomass is relatively small.From the industrial analysis,more than 70%of its components are volatiles,and the fixed carbon content is less than 20%.From the elemental analysis,the biomass The main elements are C and O,both of which are above 35%.The relevant laws of biomass pyrolysis were explored,and the pyrolysis of biomass was roughly divided into five stages(take fruit as an example):drying section(25℃-120℃),preheating section(120℃-190℃),volatile analysis section(190℃-680℃),pyrolysis molding section(680℃-910℃),re-decomposition section(above 910℃).Different biomasses are sorted according to the temperature corresponding to their pyrolysis stage from high to low:core>hardwood>softwood>straw,core>fruit wood>special wood.The effect of pyrolysis conditions on pyrolysis products was explored using pine wood as the raw material.In biomass pyrolysis,pyrolysis temperature has the greatest influence on the yield of pyrolysis products,followed by the particle size of the raw materials.Compared with the effect of pyrolysis temperature on product yield,the effect of pyrolysis time and heating rate on product yield is minimal.For the activation of CO2 and water vapor,the major factors affecting the activation yield and iodine adsorption value are the activation temperature and activation time,followed by the activation gas concentration and flow rate,and the influence of the heating rate is relatively minimal.When CO2 and water vapor are co-activated,one of the activated gas concentrations is fixed.With the increase of the variable activated gas concentration,the activation yield is getting lower and lower,and the iodine adsorption value is getting higher and higher.In the multi-source biomass pyrolysis and activation experiments,the yield difference of multi-biomass pyrolysis products is obtained.The pyrolysis charcoal yield is roughly as follows:core>straw>hardwood>softwood,core>fruit wood>special wood.The yield of wood vinegar is roughly:hardwood>softwood>core>straw,fruit wood>special wood>core.The final yield of activated carbon is roughly:core>hardwood>softwood>straw,core>fruit wood>special wood.From the test results of iodine adsorption value,the samples other than straw activated carbon can reach at least the second-class level,and the core and fruit wood activated carbon even reach the first-class level.Most of the surface functional groups of each biomass activated carbon have certain similarities,and each has its own unique surface functional groups.All types of activated carbon have detected a rich pore structure.The structure of core activated carbon mainly comes from the seed pores on the seed coat and the structure of the catheter,and other types of activated carbon come from the thin-walled tube bundle structure of the catheter.In terms of its surface micro-area composition,the core micro-area of the core activated carbon is mainly K,and the wood and corn stalk activated carbon is mainly K and Ca.In addition to the elements K and Ca which are more abundant in cotton straw activated carbon,Na,Mg and Cl were also detected.The results of this study can be used to guide the production of wood vinegar,pyrolysis charcoal and activated carbon from multi-source biomass,and have guiding significance for the treatment and resource utilization of agricultural and forestry wastes.