Research On Resource Recycling Of Products By Neutralizing Waste Acid From Chemical Industry

The emissions of a large number of waste acid on the production process of chemical industry caused a great pollution on the environment,in order to control acid waste water, the method which adding lime (or carbide) into waste acid during the production process was used currently on chemical enterprises, and can be obtained products of neutralization reaction-chemical waste gypsum. Each year a large number of chemical waste gypsum produced in our country, but almost all have not been effectively used, not only caused great pressure on the environment, but also is a waste of resources. Based on this phenomenon, the problem about the resources utilization of chemical waste gypsum which be obtained from neutralization reaction was researched in this paper. And related conclusions are as follows:1. With different technology to deal with waste acid or different technology to calcine chemical waste gypsum, the performance of plastering gypsum prepared with the anhydrite raw materials will be different. The handling using Limestone relative to the carbide, the color of the raw gypsum is more white, but its viscosity is greater, the strength is slightly lower. By modern testing methods to analyze, the main phase of chemical waste gypsum is CaSO4·2H2O, and contains a certain amount of organic impurities. When this kind of chemical waste gypsum was pretreated by calcination, the calcination temperature is less than about 600℃, the organic impurities in raw materials volatile almost completely. The different gypsum phase were obtained at different calcination temperature, above 600℃, the raw material contains only anhydrite.2. By separate studying of various additives of plastering gypsum,we found that the water-reducing effect of different types or different content of superplasticizer is different, the greater the superplasticizer dosage, the greater the strength. The greater content of water retaining agent, the higher the water retention rate of plastering gypsum, but the strength will decline. When content of water retaining agent on surface layer and bottom plastering gypsum is respectively 0.16%,0.13%, not only their water retention rate satisfies the requirements and didn't crack, but also the strength can be up to standard. Activator is the most important factor which affect on the performance of plastering gypsum, the greater the dosage, the shorter the setting time. JF1 was used as the activator in this article, when content less than 0.4%, with the dosage increased, the intensity is rising, the content more than 0.4%, the intensity will decrease.3. The impact of the content of sand in the plastering gypsum mortar on setting time and strength are very great, The greater the amount of mixed sand, can greatly reduce the economic cost, but will also extend the setting time and lower the intensity. When cement-sand ratio is 1:3 in the experiment, its performance can well meet the requirements. Both river sand and slag sand can used as aggregate of plastering gypsum mortar, and the river sand is better than the slag sand under the same conditions. On this basis, by changing the dosage of setting accelerator to adjust the setting time, the greater dosage, the shorter the setting time, when the content is 5%, the performance index can meet the requirements.4. Through comprehensive analysis of the orthogonal experiment, we summarized the optimum formula of the plastering gypsum. The various performance of anhydrite plastering gypsum which were prepared as optimum formula can meet the standards of JC/T517-2004 "plastering gypsum",and didn't crack when plastered on the walls of many different materials.