Study On Preparation Of Corn Stalk Hydrochar And Its Co-combustion Characteristics With Municipal Sludge

At present,the shortage of primary energy makes it important to develop renewable energy.The output of municipal sludge in China is high,and incineration can effectively treat municipal sludge.However,the calorific value of municipal sludge is low,and auxiliary fuel needs to be added in the combustion process.Biomass is an ideal auxiliary fuel as a renewable energy source,but biomass raw materials without pretreatment are low-grade energy,and the co-combustion effect with municipal sludge is not good.In order to solve the above problems,this paper uses corn stalk as biomass material and adopts hydrothermal method to carbonize corn stalk.The physical and chemical characteristics of hydrochar,the mixed combustion characteristics of hydrochar and municipal sludge,and the pollutant emission characteristics during the mixed combustion process are deeply studied,as follows:Corn stalk hydrochar was prepared by hydrothermal method at different temperatures(200?,230?,260?).The physical and chemical properties and combustion characteristics of hydrochar were studied.The results show that with the increase of temperature,the mass yield of hydrochar decreases gradually,and the energy production rate reaches the highest level of 63.68%when the hydrothermal temperature is 230?.With the increase of temperature,the fixed carbon content and calorific value increase gradually,while the volatile matter content and oxygen content decrease gradually.After hydrothermal treatment,the samples mainly undergo dehydration,decarboxylation,condensation and aromatization reactions.The higher the hydrothermal temperature,the more intense the reaction and the stronger the aromatic characteristics of hydrochar.With the increase of hydrothermal temperature,the combustion curve of hydrochar shifts to the high temperature region,the ignition temperature increases continuously,and the burnout temperature decreases continuously.When the hydrothermal temperature is 230?,the comprehensive combustion characteristic index is the largest.After hydrothermal treatment,the physical and chemical properties and combustion characteristics of corn stalk have been improved to varying degrees,which is suitable for use as fuel.Thermogravimetric analysis was used to study the combustion characteristics and reaction kinetics of municipal sludge,corn stalk hydrochar and the blends,and Flynn-Wall-Ozawa(FWO)method was used to calculate the activation energy in the combustion process.The results show that increasing the heating rate will cause the thermogravimetric curve to shift to the high temperature region and cause thermal hysteresis.Increasing the proportion of corn stalk hydrochar in the blend will lead to an increase in weight loss rate,a decrease in ignition performance and a continuous increase in combustion performance.There is synergistic interaction between municipal sludge and corn stalk hydrochar in the co-combustion process,and the effect is most significant when the mixing ratio of corn stalk hydrochar is 50%and 70%.The FWO method is suitable for solving the kinetic parameters of the combustion process of municipal sludge,corn stalk hydrochar and the blend.When the blending ratio of corn stalk hydrochar in the blend is 50%and 70%,the average activation energy of the mixed combustion decreases significantly.Through the tube furnace combustion system,the effects of blending ratio and combustion temperature on the emissions of CO,NO,and SO2 during the combustion of municipal sludge mixed with corn stalk hydrochar were studied.The results show that with the increase of the mixing ratio of corn stalk hydrochar in the blend,the emissions of CO and NO gradually increase during combustion,and the emissions of SO2 generally show a downward trend.When the combustion temperature is 800?,the CO emission of the blend is the lowest.With the increase of combustion temperature,the NO emission of the blend gradually decreases and the SO2 emission gradually increases.This paper provide a reference for co-combustion and the emissions of CO,NO and SO2 during the combustion process of municipal sludge and corn stalk hydrochar.