Research On The Valorization And Disposal Technology Of Industrial Waste Salt

Industrial waste salt is a typical hazardous waste.It has obvious characteristics such as wide sources,large volume,scattered industries,and difficult management,which is in urgent need of safe disposal.With the progress of the national "Zero Waste City" demonstration pilot and the imminent implementation of "Standard for pollution control on the hazardous waste landfill"(GB18598-2019),it is of great significance to strengthen the valorization and the disposal of the industrial waste salt.First of all,this study targeted eight industrial waste salts from chemical raw materials,medicine,pesticides,and dyes industries in a chemical park.Through detailed characterization,it was found that the industrial waste salt production coefficients of different industries vary widely.The industrial waste salt from chemical raw materials,pesticides and medicines industries is mainly composed of sodium chloride with direct valorization potential.While the industrial waste salt from other industries are suitable for combined disposal due to the small volume or the original product differences.Industrial waste salt is generally corrosive,and has the characteristics of organic and heavy metal pollution.During resource utilization or landfill disposal,pretreatment to remove relevant pollution properties is essential.Secondly,in terms of the industrial waste salts with different organic matter contents,simultaneous resource recovery was used to produce sodium sulfate and hydrochloric acid(evaluate the effect of resource utilization by dechlorination efficiency).The low-organic industrial waste salt could be completely dechlorinated under the optimal conditions including L/S ratio of 3.77,sulfuric acid concentration of 40.80%,and heating time of 40.29 min,respectively.It is feasible for the simultaneous production of hydrochloric acid and sodium sulfate.However,the high-organic waste salt needs pyrolysis to decompose organic matter and dechlorination sequentially for the simultaneous recovery hydrochloric acid and sodium sulfate.The optimal pyrolysis conditions for pyrolysis were 437? and 43.2 min.Then,considering the cost,the pyrolysis residueswas treated at a L/S ratio of 3,sulfuric acid concentration of 42.61% and heating time of 34.26 min to reach the highest efficiency.Finally,the long-term landfill disposal process of industrial waste salt was simulated and studied.The results show that the packaging of industrial waste salt will greatly affect the generation of leachate.The estimated complete dissolution time of industrial waste salt without inner film packaging is 1.6 years,while that with inner film packaging is negligible.Effective front-end packaging like closed packaging with inner film plastic bags can block the dissolution of most pollutants,thereby achieving the purpose of improving the leachate water quality and reducing the difficulty and disposal cost.The dissolution rate of soluble organic matter is significantly faster than other components.In the early and middle stages of industrial waste salt landfill,the leachate always contains high refractory organic matter.In the industrial waste salt landfill process,whether or not packaging directly affects the landfill site settlement.It will cause rapid settlement in the landfill without properly packaging.The research conclusions can provide important references for the industrial utilization and disposal of industrial waste salt.