Study On Preparation And Desulfurization Performance Of Biomass Activated Carbon Based On Microwave Pyrolysis And Activation

With the continuous development of economy,the energy crisis and environmental pollution are becoming more and more prominent,which seriously restricts the sustainable development of society.The air pollution caused by SO2 emitted in the process of coal utilization has a serious impact on the environment and human life.Activated carbon flue gas desulfurization has the ability of cooperative treatment of a variety of pollutants,but also can achieve the recovery of sulfur resources,in line with the development trend of flue gas treatment resources,comprehensive.At present,coal and biomass are the main raw materials for the preparation of activated carbon.Coal resources are non-renewable,while biomass resources are abundant,cheap,renewable and low pollution.Biomass activated carbon with developed pore structure and specific surface area can be prepared by carbonization,activation and load modification,which is of great significance for improving desulfurization performance of activated carbon and economic value of biomass.Microwave heating has the characteristics of immediacy,integrity,selectivity and high efficiency.Applying it to biomass to prepare activated carbon can reduce the pretreatment requirement of raw materials and greatly reduce the pretreatment cost.And it can not only greatly improve the heating rate,but also reduce energy consumption.Moreover,the pore structure of activated carbon prepared is richer than that of conventional heating.With the continuous development of microwave technology,the preparation of activated carbon by microwave heating biomass has become a very important way of utilizing biological resources,which has attracted extensive attention from researchers at home and abroad.In this paper,soybean stalks rich in nitrogen-containing functional groups are used as raw materials,CO2 is used as activator,and Ferric nitrate nine-hydrate is used as catalyst precursor.Combined with the special advantages of microwave heating,microwave heating technology is applied to biomass pyrolysis-activation-loading.Further,a biomass-based desulfurization carbon material is prepared.The research focuses on the progress of pyrolysis of bean straw,the activation and catalyst add of solid products.To explore the variation law of product distribution;find out the best preparation conditions of activated carbon with high adsorption capacity and high thermal conductivity.Revealing SO2 adsorption characteristics and pore structure changes,and characterized the desulfurizers prepared under different conditions by XRD,ICP,SEM,thermal conductivity and regenerative desulfurization performance.Firstly,the pyrolysis experiment was carried out with soybean straw as raw material.The effects of microwave power,pyrolysis time and additives on the pyrolysis process of soybean straw were investigated.The distribution characteristics of pyrolysis three-phase products,the pore structure of pyrolytic carbon and the change of desulfurization capacity;finally,through comparative analysis,the optimal pyrolysis process was found to be microwave power of 900W and pyrolysis time of 10 min.The yield of the pyrolytic carbon obtained under the optimum conditions was 36.3wt.%,the specific surface area was 285.33 m2/g,and the sulfur volume was 59.1 mg/g.The types of nitrogen-containing functional groups before pyrolysis are mainly amides and amino groups.After pyrolysis,they are mainly amides and secondary amines,and the characteristic peaks of nitrogen-containing functional groups after pyrolysis are obviously weakened.Secondly,the pyrolysis carbon obtained by microwave power 900W and pyrolysis time of 10min was used as raw material,and activation experiment was carried out with CO2 as activator.The optimal activation level was obtained by orthogonal design and range analysis,and then by single factor experiment.The effects of microwave power,CO2 flow rate and activation time on product yield,pore structure and desulfurization performance were investigated.The optimal activation conditions were microwave power 900W,CO2 flow rate 0.1L/min and activation time 20min.The yield of activated carbon prepared under this next condition was 76.3wt.%,and the adsorption capacity of SO2 was 112.56 mg/g.The adsorption performance was superior to other conditions.The order of the three factors affecting the performance of activated carbon(from large to small)is microwave power,CO2 flow,and activation time.The prepared activated carbon has a relatively developed pore structure,and many small pores exist on the surface of the activated carbon and the macroporous wall,which is a key reason for the increase of sulfur capacity.Finally,the activated carbon prepared under the condition of microwave power 900W,CO2 flow rate 0.1L/min and activation time 20min was used as the carrier,and the load modification experiment was carried out by microwave heating.The optimal load level was obtained by orthogonal test design and range analysis.The effects of microwave power,loading and calcination time on the pore structure and desulfurization performance of the product were investigated by single factor experiment.The loading process conditions are 10%catalyst loading,microwave power 500W,and roasting time 10 min.The order of influence of the three factors on the performance of the desulfurizer(from large to small)is the catalyst loading,microwave power and baking time.The desulfurizing agent prepared under the optimal loading conditions had a specific surface area of 355.60 m2/g and a sulfur capacity of 146.3 mg/g.The surface active component of the desulfurizer is evenly distributed in small particles,and is arranged with relatively uniform fine pores,a certain number of large pores and mesopores,and the structure has more layering and more complicated honeycomb shape.XRD spectrum analysis,the main active components of the desulfurizer are Fe3O4,Fe2O3 and some Fe elements,of which Fe3O4 content is the most.The thermal conductivity of the desulfurizer increased with the increase of the active component,from 0.17 W/(m·K)to 0.28 W/(m·K),and the growth rate was 64.7%.After the desulfurizer is regenerated five times,it can maintain high SO2 adsorption capacity and can be recycled.