Preliminary Study On Preparation Of Biochar And Its Slow-release Fertilizer By Sulfitation Method Sugar Filter Mud

Filter mud is a large-scale of sugar production,due to its high water content,it is not convenient for transportation,storage and use,it becomes a burden on the environment.However,the filter mud is a good biomass resource with good prospects for comprehensive utilization.The comprehensive utilization of the development of filter mud is of great significance for extending the sugar industry chain and improving the economic benefits of sugar factories.Biochar based fertilizer is a new type of high-efficiency slow-release fertilizer,which can not only improve the soil environment,but also release fertilizer nutrients slowly,which has a more stable promoting effect on crop growth and yield.In this study,sugar filter mud was used as biomass carbon source to prepare biochar,then carbon-based slow release fertilizer was prepared to improve the utilization value of filter mud resources and promote the healthy and sustainable development of sugar industry.Firstly,the thermogravimetric analyzer is used to study the pyrolysis characteristics and pyrolysis kinetics of the filter mud,then,pyrolysis of biochar by slow pyrolysis,the properties,physicochemical properties,surface properties and adsorption characteristics of biochar under different temperature conditions were investigated.Finally,biochar was prepared under optimized conditions,the urea biochar-based fertilizer was prepared by granulation.The molding effect,the maximum compressive strength and the leaching effect of the fertilizer were measured to study the molding condition,mechanical properties and sustained release effect of the fertilizer.The specific research contents and results are as follows:1.Perform industrial analysis and elemental analysis on the filter mud,then heat it from room temperature to 800? at a heating rate of 5,10,15,20,25,30 ?/min under nitrogen atmosphere for thermogravimetric analysis(TGA).Pyrolysis test,combined with Kissinger,FWO and KAS three kinds of model-free conversion method to study the pyrolysis kinetics of the filter mud.The results showed that the contents of C,H,N,S and O were 24.96%,4.04%,1.98%,5.82%and 18.86%,the ash content was 44.34%,the volatile content was 52.88%,and the HHV was 11.39 MJ/kg.The pyrolysis of the sludge is mainly divided into three stages.The main weight loss process is between 150-510 ?,and the pyrolysis of the filter mud is more favorable at a lower heating rate.The average E? calculated based on FWO and KAS methods is 322.28 kJ/mol and 321.93 kJ/mol,the average ?H is 289.04 kJ/mol and 288.24 kJ/mol,the average AG is 207.87 kJ/mol and 208.01 kJ/mol,and the value AS is negative continues increase to a positive value,indicating that the filter mud is a very promising biomass material,and the entire pyrolysis process conforms to the second law of thermodynamics,which is a complex multi-step endothermic process.2.Biochar was prepared by pyrolysis at temperatures of 200,300,400,500,and 600 ?,and a series of indicators of biochar were measured.The results show that the pyrolysis temperature has a significant effect on the properties of biochar.As the pyrolysis temperature increases,the biochar yield and volatile matter decrease,the ash content increases,the pH value increases,the number of surface functional groups and acidic functional groups decreases,and the surface active groups such as C-O and C-O-C and-CH3 and-CH2 gradually disappear.The atomic ratio of H/C,O/C,and(N+O)/C is reduce,which indicates that the biochar has enhanced aromaticity and stability,and hydrophilicity and polarity are weakened.The adsorption capacity of iodine value continued to increase,and the adsorption value of iodine value of biochar prepared at 500 ? reached a maximum of 170.38 mg/g.3.The surface properties and adsorption characteristics of biochar were prepared by pyrolysis at temperatures of 200,300,400,500,and 600 ?.The experimental results show that the pyrolysis preparation temperature is beneficial to the development of biochar pore structure.The pyrolysis temperature has a significant effect on the average pore size,pore volume,pore size distribution and specific surface area of biochar.The pyrolysis temperature at 500 ?,The biochar specific surface area reaches a maximum of 83.71 m2/g.Under the same amount of biochar,the adsorption of urea on biochar at the five preparation temperatures situation,when the adsorption time was 40 min,the adsorption temperature was 45 ?,and the initial concentration of urea solution was 100 mg/mL it is good.The adsorption performance of biochar prepared at 500 ? is significantly better than that of biochar prepared at other temperatures.4.The carbon-based urea fertilizer was prepared by granulation method.The results showed that the 22-26%water addition was beneficial to the formation of biochar-based fertilizer and the maximum crashing strength.The biochar content is increased,and the rate of formation of the fertilizer and the strength of the crushing resistance are lower.The slow release effect of slow release fertilizer is obviously better than that of traditional fertilizer,and the release effect is better with the increase of biochar content and soluble starch content.From the aspects of molding rate,maximum crushing compression force,sustained release performance and economy,when the ratio of urea to biochar is 1:5,the soluble starch content is 10%,and the water addition amount is 24%,the carbon is selected.The sustained release effect of the base fertilizer is the best,and the release of the carbon-based fertilizer belongs to the first-order release model,and the release mechanism is diffusion.