Study On Heat Treatment Of Sodium Chloride Waste Salt By Product From Glyphosate Industry

Industrial wastewater was required to achieve nearly no discharging according to the the increasingly stringent environmental management across the country,thus multi-effect evaporation was applied in wastewater treatment,which produces a large amount of industrial waste salt.At present,most domestic industrial waste salt is classified as hazardous waste according to its large storage,complex composition and toxic organic component.There is a urgent need to deal with the hazardous waste-industrial waste salt,however,existing treatment methods needs to be further studied or verified.Heat treatment is one of the proper methods for organic matter treatment in waste salt.This paper focus on sodium chloride type waste salt,the pollutant produces by glyphosate synthesis industry,studied the characteristics of the organic matter in the high-temperature combustion and pyrolysis process,and investigated the total organic matter in the sodium chloride type waste salt,in order to provide supporting method for the design,operation and optimization of waste salt heat treatment system.Firstly,analyze the production process of sodium chloride waste salt in the glyphosate synthesis industryto analyse the possible toxic and harmful substances produced from the original material.The result of phase analysis and determination shows the main element compositionof sodium chloride type waste salt in the glyphosate synthesis industry was mainly sodium chloride and a small amount of sulfate,which have a good prospect of resource utilization.Secondly,a set of special equipment was designed to solve the problem of chloride ion interference in the determination of total organic carbon in sodium chloride type waste salt and to avoid damage to the instrument,which completely oxidize organic matter to CO₂ in a quartz glass tube reactor at high temperature.CO₂ was the fixed with lye absorption column.,after and constant volume,use TOC analyzer to measure the content of,so as to calculate The content of organic carbon in waste salt was measured through measuring the content of inorganic carbon in the elution solution of the column.Finally,the heat treatment of sodium chloride type waste saltproduced in glyphosate industry was studied by the combined analysis method of thermogravimetry and infrared.Results showed that the weight loss process of oxygen-enriched combustion and anoxic pyrolysis of the organic matter in the waste salt is similar,and the phenomenon of melting and volatilization of the waste salt occurs at same temperatures（air atmosphere 756 ^oC,pyrolysis atmosphere 713 ^oC）;kinetic analysis showed that the apparent activation energy of the reaction temperature range of the waste salt in the pyrolysis atmosphere is lower than that of the combustion atmosphere,indicating that the organic matter in the waste salt is more likely to react under the pyrolysis atmosphere.The precipitation of gaseous products during the heat treatment process mainly concentrated in 400 ^oC～650 ^oC,and,the gas evolution temperature range of the anoxic pyrolysis process is narrower compared with the oxygen-enriched combustion process.The gases produced during the oxy-fuel combustion process of waste salt organic matter was mainly CO₂ and H₂O.Besides CO₂ and H₂O,some SO₂was produced under the high temperature stage as well..The results of the heat treatment process of waste salt in a tube furnace shows that both oxygen-enriched combustion and anoxic pyrolysis can remove the organic matter in the waste salt efficiently under the heat treatment temperature of 500 ^oC～600 ^oC for more than 20minutes.In addition,the sulfate content in the waste salt after 600 ^oC pyrolysis treatment is greatly reduced,which meet the requirements for sulfate content of first-level standard of refined industrial salt,which shows that the organic matter and sulfate in waste salt can be removed at the same time under the pyrolysis conditions.