Effect Of Hydrothermal Carbonization On The Structure And Pyrolysis And Gasification Reaction Characteristics Of Municipal Solid Waste

Gasification of municipal solid waste is an effective mean to realize its resource utilization.However,the characteristics of low energy density and high water content of municipal solid waste lead to high energy consumption in its utilization process.The complexity of its components also leads to large differences in the parameters and products of the gasification process,and complex process control and product separation.Therefore,it is urgent to seek a technology to treat municipal solid waste with low energy consumption and homogeneity.Hydrothermal carbonization technology is a process of high grade thermal upgrading of raw materials with water as the medium,which can improve both the energy density of raw materials and the homogenization degree of raw materials.It is also considered as a promising pretreatment method of biological wastes with high water content.The gasification technology combined with hydrothermal carbonization technology can realize the resource utilization of domestic waste.In this paper,for the purpose of efficient resource utilization of municipal solid waste,hydrothermal carbonization and hydrothermal carbon gasification of typical components of municipal solid waste(disposable bamboo chopsticks,waste paper and peanut shell)were studied,and the influence of hydrothermal carbonization on the structure and gasification process of municipal solid waste was investigated.The main research contents and conclusions are as follows:(1)Organic element analyzer,infrared spectrometer,scanning electron microscope,physical adsorption instrument,Raman analyzer and other characterization methods are used to study the effect of hydrothermal carbonization treatment on the structural properties of typical household waste hydrothermal carbon.The results show that increasing hydrothermal temperature or hydrothermal time can improve the carbonization degree of domestic waste,and increase the calorific value of hydrothermal carbon of domestic waste to 15.48～23.30 MJ/kg,improving its energy quality significantly.Hydrothermal carbonization can effectively improve the specific surface area of household waste.After hydrothermal carbonization,the specific surface area of disposable bamboo chopsticks and peanut shells increases from 0.25 m2/g and 0.61 m2/g to 5.79 m2/g and 30.01 m2/g,respectively.The specific surface area of waste paper also increased slightly.At the same time,after hydrothermal carbonization treatment,the aromatization degree of hydrothermal charcoal of disposable bamboo chopsticks and waste paper is improved,but the aromatization degree of hydrothermal charcoal of peanut shell was decreased.(2)Pyrolysis tar components and gasification reactivity of hydrothermal carbon prepared from typical components of household waste are studied via the pyrolysis gas chromatography-mass spectrometry and thermogravimetric in-situ analysis system.The results show that decarboxylation,dehydration and hydrolysis of lignocellulose during hydrothermal carbon pyrolysis can reduce the relative contents of keones and furans in the tar components,and simplify the structure of phenolic compounds in the tar components during the hydrothermal carbon pyrolysis of disposable bamboo chopsticks.After hydrothermal carbonization,hydrothermal pyrolysis of peanut shell can produce a large number of phenols and carbohydrates.The gasification reactivity of three typical components of domestic wastes decreases to varying degrees,which is mainly related to the aromatization degree,pore structure,alkali metal and alkaline earth metal content of hydrothermal char semi-coke.The factors affecting the reactivity of hydrothermal carbon gasification of domestic waste from high to low are as follows:alkali metal and alkaline earth metal elements>aromatization degree>pore structure.(3)The interaction mechanism between different components of MSW during hydrothermal carbonization and gasification was studied through hydrothermal carbonization and gasification of typical components of MSW.The results show that peanut shell and waste paper have an antagonistic action in the process of hydrothermal carbonization,which would reduce the yield of hydrothermal carbon.When the proportion of waste paper is 25%,there is a synergistic effect between disposable bamboo chopsticks and waste paper in the process of hydrothermal carbonization,which can produce a higher yield of hydrothermal carbon than the theoretical value,but a higher proportion of waste paper will lead to the synergistic effect into antagonism.The alkali metal and alkaline earth metal elements retained in waste paper hydrothermal carbon can effectively reduce the production of phenolic macromolecular compounds in the tar components of blending hydrothermal carbon,and significantly improve the gasification reactivity of disposable bamboo chopsticks hydrothermal carbon and peanut shell hydrothermal carbon.At the same time,there is obvious synergistic effect on the gasification reactivity of blending hydrothermal carbon.These alkali metals and alkaline earth metals are the key factors causing synergies among different waste components.