Purification And Application Of Sodium Chloride Which Byproduct In DBM

Currently, the methods that purified industrial by-product salt has been reported are roasting method and dissolution recrystallization. The paper studies the roasting and the caustic methods (l.e.,the salt under basic conditions and washed repeatedly by saturated brine) that purified the sodium chloride byproduct.The experiments of roasting mainly study on the impact of different factors effect on the purification of sodium chloride byproduct, such as the roasting time, roasting temperature, the material thickness heap roasting process, the initial concentration of oxygen and the initial content of impurities in the materials, etc. The optimum operating conditions of roasting is that under the calcinations temperature of550℃roasted for30minutes. The bleaching rate experiment of product by calcined shows that the solution heated by water bath at60℃for one hour, the stable decolorization rate of the solution was greater than98%.The experiments of caustic method mainly study on the impact of different factors effect on the purification of sodium chloride byproduct, such as the pH value of washing liquid, caustic alkali concentration and the number of washing. Experiments shows that the optimum operating conditions of caustic method is that using the sodium hydroxide solution for mass concentration of50%to adjust the pH of the washing solution about7.2, and repeated washing more than7times, after washing the white chloride particles can be obtained.The paper introduces a new caustic method that can be applied in industrial, and has conducted the pilot experiments. The pilot experiment mainly study on the factors that can effect the application in industrial, such as the overflow rate of supernatant at wash tank liquid, the pH value of the washing tank, washing time, and concentration of sodium hydroxide solution and so on. The pilot results showed that the caustic process method is feasible. The optimum operating parameters of this method is that used the sodium hydroxide solution for mass concentration of50%to adjust the pH of the washing solution neutral or alkaline a bit, while controlled the flow rate of the circulation pump at0.2m3/h, and washed the samples about30min. The yield of the purified sodium chloride can up to about69%. And it can achieve the national standard level of industrial salt (GB/T5462-2003).