Study On The Characteristics Of Inorganic Salts Catalyzed Hydrothermal Carbonization Of Sludge

Due to the development of urbanization and industrialization,the production of sludge continues to increase,which poses a serious challenge to the ecological environment.Sludge contains various components that can be recycled and utilized through effective means.At present,sludge disposal methods can be divided into physical disposal,biological disposal and thermochemistry disposal according to the principle.Among them,the thermochemistry disposal technology represented by hydrothermal carbonization has unique advantages in realizing sludge stabilization,innocuity,reduction and recycling.However,the colloidal structure of sludge is difficult to be destroyed during hydrothermal carbonization,which resulting in low carbonization degree and high nitrogen content of sludge hydrochars.Therefore,this article focuses on the problems in sludge hydrothermal carbonization and conducts research on inorganic salt catalysis,deep eutectic solvents"dissolution"and oxidation to destroy the colloidal structure of sludge and strengthen sludge hydrothermal carbonization.The main work and conclusions of this article are as follows:（1）Based on the catalytic hydrolysis of polysaccharides by Cl^-,experiments were conducted to enhance the hydrothermal carbonization of sludge by coupling ultrasonic pretreatment with Na Cl.The results showed that ultrasonic pretreatment can effectively destroy the colloidal structure of sludge and release organic matter therein.The free radicals generated during ultrasonic pretreatment can increase the yield of hydrochars.Both ultrasonic pretreatment and Cl^-can promote the hydrothermal carbonization reaction of sludge.Cl^-can promote the hydrolysis of polysaccharides and reduce the content of polysaccharides in the system,which can inhibit the Maillard reaction and reduce the nitrogen content in hydrochars.The maximum denitrification rate can reach 36.31%.（2）Based on the strong solubility of deep eutectic solvents to Biopolymer,combined with the enhancement of Cl^-on the hydrothermal carbonization of sludge,experiments were carried out to promote the hydrothermal carbonization of sludge with chlorine containing deep eutectic solvents.The deep eutectic solvents involved include Zn Cl₂/urea,Ch Cl/urea and Ch Cl/oxalic acid.The research shows that deep eutectic solvents can"dissolve"the organic matter in the colloidal structure of sludge,thus achieving the goal of destroying the colloidal structure,Beneficial for releasing organic matter in the colloidal structure of sludge.Deep eutectic solvents can also promote polysaccharide hydrolysis,inhibit Maillard reaction,and enhance sludge hydrochars denitrification.When Choline chloride/oxalic acid is used as an auxiliary catalyst,the highest denitrification rate can reach 69.49%;In addition,adding deep eutectic solvents can also promote dehydration,decarboxylation,and other reactions during the hydrothermal carbonization process of sludge,improving the degree of carbonization of hydrochars.（3）Based on the oxidability of Fe（NO₃）₃,experiments were conducted to enhance the hydrothermal carbonization of sludge using Fe（NO₃）₃.The results showed that Fe（NO₃）₃can destroy the colloidal structure of sludge and promote the hydrolysis of organic matter.Fe（NO₃）₃also can improve dehydration,decarboxylation and other reactions during hydrothermal carbonization.Fe（NO₃）₃promotes protein deamination,thereby inhibits Maillard reaction and reduces the nitrogen content of hydrochars during the hydrothermal carbonization of sludge.The highest denitrification rate is 64.77%.This study focuses on the influence of the colloidal structure of sludge during hydrothermal carbonization.It effectively improves the carbonization degree of hydrochars and reduces the nitrogen content in sludge hydrochars,achieving the goal of clean combustion through auxiliary catalysis.This study provides new ideas for the hydrothermal carbonization treatment of similar organic waste.