Optimization Of The Brine Refining Process In Chlor-alkali Industry

Chlor-alkali industry is one of the basic chemical industry,its large variety and high economic extension value products including caustic soda,chlorine,hydrogen and the derivative products of chemical industry are widely used in various fields of national economy and people's lives,such as industry,agriculture,national defense,architecture,and the lifeline of national economy sectors containing electronics,automobile.Thus,chlor-alkali industry has a pivotal position in the economic development,national economy and national defense construction.Chlor-alkali production were experienced causticizing,mercury,diaphragm method,ion membrane method and so on.No matter which method,the quality of saturated salt water used in electrolytic process is particularly important.The quality of the refined brine directly affects the safety and efficiency of electrolytic device,and have a crucial impact on downstream unit product quality.In order to protect the equipment,it is necessary to ensure the quality of refining brine.The basic principle of brine refining is adding refining agent such as sodium carbonate,sodium hydroxide and barium chloride solution and reacting with impurities in brine to remove the generating insoluble solids precipitation by clarifying,two-stage filter and metal ions adsorption to obtain the qualified refined brine meeting the requirements and ensure the stablity of the device.Based on the production principle,chloralkali plants have conducted many modifications for the brine refining process including reducing waste water,reforming refining process and other aspects,to stabilize the operation of the device.1.Optimization of crude salt qualityThe quality of the refining process of brine salt raw materials directly affect the quality of refined brine,in the production process of brine refining in the past,to control the quality of raw salt into the factory has been a focus of the work,salt quality indicators must be qualified to normal use,in which the ratio of calcium and magnesium in crude salt as the key control index.All the time,into the plant salt calcium magnesium ratio control in more than 1.5,in examining the impurities in the influence of calcium and magnesium ratio on refining brine,in combination with the practical operation of unit,determine the scope of the ratio of calcium and magnesium for our best 1.5-3,provide the basis for stable brine refining plant operation.2.The "water balance" work of deviceBased on the actual production situation of chlor-alkali industry,the industrial waste water and waste water quality was investigated to carry out a series of optimization and technology improvement,and finally part of drainage was used for production process and excessive waste water could be stored temporarily,etc.The water balance was achieved after continuous innovation and the "water surplus" problem was solved so that "zero emissions" of waste water from the caustic soda procedure was realized.3.Reform of removing SO42-processFor removing SO42-,high toxic barium chloride was no longer used,and replaced by nanofiltration membrane filtration process,which solved the problem of high operation cost using barium chloride,instability of salt water clarifying tank operation,high salt mud filter process load and so on.The reform greatly reduced the waste and stabled plant operation,meanwhile,economic and environmental benefit is obvious.4.Extended operating cycle of chelating resin towersThe introduction of new technology and adding poly acid salt in the salt water made it release substance after graphite electrode.The procedure extend the operation time of chelating resin towers for secondary brine refining,which made it from the original design of the 48 hours to 240 hours.The reform reduced the quantity hydrochloric acid,caustic soda and water used for regeneration of chelating resin towers,reduced the waste emissions,depressed the production cost and optimized the water balance.