A Technology Research Of Chlor-alkali Brine Refining Slurry Comprehensive Recovery

With the development of chlor-alkali industry, The salt slurry which produced inbrine refining process by chlor-alkali industry is causing environmental pollution andresource waste problem, and this situation is more and more prominent. In order toimprove the level of circular economy of chlor-alkali industry, the study was establishedaccording to the technology and the status quo of salt slurry in chlor-alkali of Gansurare-earth Company, and combined with the company of the waste residuecomprehensive recycling requirements. In the laboratory the study on the salt slurry acidleaching, leaching liquid purification, purify liquid fractional precipitation separation Caand Mg and surface modification and acid leaching residue desilication recyclingBaSO4were conducted. Preliminarily determined the process scheme and parameters ofusing salt slurry to prepare Mg(OH)2, MgO, CaCO3, BaSO4and other products.First, the leaching and purification experiment of salt slurry was conducted,through the experiment the main factors of the leaching and purification were analyzed,and the leaching process parameters as follows: the liquid-solid ratio was5:1, theacidity was2.00mol/L, the leaching temperature was60℃, Ca2+and Mg2+leaching ratewas98.23%. The optimum process parameters of hydrolyzed purification experimentwere as follows，the temperature was90℃, pH=6~7, the reaction time was3h and theremoval rate of Fe3+、 Al3+and other impurity ions were more than97%.Then calcium and magnesium purification were separated and its surfacemodification test was conducted. By investigating the main factors influencing theprecipitation separation and modification, reaching the optimum process parameters asfollows, For magnesium precipitation and modification process parameters:15%surfactantA（SDBS：PEG2000=2:1）dosage was10mL, ultrasonic (40KHz) dispersion timewas2min, NaOH dosage was1:1calculated by Mg2+:OH-, reaction temperature was30℃, precipitation time was2h, the recovery rate of Mg was66.46%, the purity ofMg(OH)2was96.49%, coated ratio was3.26%，the minimum particle size was0.2um.For calcium precipitation and modification process parameters: on condition ofultrasonic(40KHz) dispersion,3%polyacrylate sodium dosage was5mL, the velocity ofkiln gas access into solution was100L/h, reaction temperature was50℃, reaction pHwas11, reaction time was1h, Ca recovery rate was90.31%, the product CaCO3puritywas90.46%, coated ratio was1.60%, the minimum particle size of CaCO3was0.15umand coating modification effect was good.In the final experiment that the acid leaching residue was carried out a experimentof alkali leaching desilication to recycle BaSO4with SiO2concentration as the mainindex, investigated the reaction time, temperature, acidity, liquid-solid ratio impact ofdesilication, respectively. Reach the best desilication process parameters as follows，the NaOH concentration is50%, liquid solid ratio was2.5, dissolution temperature was120℃, agitation leaching time was5h, and the purity of the final product BaSO4was85.32%, BaSO4straight yield was87%.The comprehensive recycling and utilization of the salt slurry testing scheme,which can realize recycling BaSO4, the preparation of modified CaCO3, modifiedMg(OH)2and MgO from salt slurry.After purification, the Ca and Mg rich fluid usefractional step method to separate Ca and Mg, realized the separation of Ca and Mg, andat the same time, realized surface modification of Mg(OH)2and CaCO3。Simulationwith the gas of carbonate calcining kiln and acid leaching recovery of CO2of RareEarth Company, as precipitant of Ca ions, preliminary realized recycling of carbonresource. The results of the research have important theoretical guidance significanceand application value for improving the level of environmental protection and circulareconomy.