| With the acceleration of urbanization,the amount of municipal sludge in my country is increasing year by year.Due to the characteristics of the sludge itself,it is difficult to dehydrate,and it contains a large number of bacteria,pathogens and heavy metals.The existing treatment technology often has certain limitations.Therefore,it is of great significance to clean and efficiently treat the sludge to achieve reduction,harmlessness,and resource utilization.In addition,with the development of our society,the amount of coal mining is increasing year by year.Coal washing is a prerequisite for coal processing,transformation and pollution control;a large amount of coal slime will be produced during the coal washing process,due to its fine particle size,The characteristics of high water content and high ash content make it difficult to utilize resources.Hydrothermal carbonization is a technology that can convert organic solid wastes with high moisture content into hydrochar and is a green treatment technology.This paper proposes that coal slime blended with sewage sludge can improve the quality of hydrochar through hydrothermal carbonization,which is of great significance for the efficient and clean utilization of sewage sludge and coal slime.In this paper,Taiyuan municipal sewage sludge and Pingshuo coal slime are selected as the experimental raw materials.The hydrochar is prepared in a high-temperature and high-pressure reactor by using Taiyuan municipal sewage sludge,Pingshuo coal slime and the mixture of them under different conditions.Furthermore,using Scanning Electron Microscope(SEM),X-ray Diffractometer(XRD),etc.to analyze the hydrochar,and preliminarily discuss the characteristics of hydrochar.The main conclusions are:(1)In the process of sewage sludge hydrothermal carbonization,the hydrothermal temperature,time and acid addition have a greater impact on the distribution of hydrochar.The hydrochar yield decreases with the increase of temperature,time,and acid addition.Microspheres are formed in the hydrochar under the condition of pH=2 adjustment by sulfuric acid;most of the calorific value in the sewage sludge is retained in the hydrochar;the comprehensive combustion index of the hydrochar decreases with the increase of the hydrothermal temperature and the reaction time.The organic content in the liquid phase from sewage sludge hydrochar increases with the increase of the reaction temperature.(2)In addition,in the process of coal slime hydrothermal carbonization,the temperature,time and acid addition also have an effect on the distribution of hydrochar.The solid phase product yield decreases slightly with the increase of temperature,time,and acid addition.With the increase of temperature and residence time,the surface of coal slime hydrochar will appear structural densification;after coal slime is hydrothermally carbonized,its calorific,volatile and ash content are both higher,burning time is more shorten,comprehensive combustion index is higher,and the combustion process is more concentrated.(3)At last,in the process of co-hydrothermal carbonization,as the amount of coal slime increases,the co-hydrochar yield gradually approaches the yield of hydrochar from coal slime hydrothermal carbonization alone,and the actual co-hydrochar yield is higher than the theoretical value.When the ratio of the two is 1:1,the yield synergy coefficient of the two samples is the highest;the surface structure of the hydrochar prepared by mixing coal sewage sludge with sewage sludge is compact,and microspheres with rough surface are formed at the ratio of 1:1.With the increase of in the amount of coal slime added,the calorific value is higher.When the ratio of the sewage sludge and coal slime is 1:1,the synergy coefficient is the highest,and at this ratio,the degree of coalification and graphitization of the co-hydrochar increases.The combustion performance of co-hydrochar gradually increases with the increase of blending ratio of coal slime,and the combustion process becomes more concentrated. |
