Mercury In Coal-fired Boilers Ammonia Desulfurization Sediment Enrichment Recovery Experimental Study

Mercury emissions form coal-fired power plants has been identified as hazardous pollutants to human health and the environments. Now, our country has taken control on the heavy metal pollution contained in the flue gas such as mercury, but the problem among the recent developed mercury control technology in the multi-pollutant control technologies is low attention on the secondary pollution caused by the status changed mercury. So this paper mainly discusses the research about recycling mecury technology, which has important theoretical value and practical significance for realizing complete removal of mercury and reducing secondary pollution.This paper had a research on the solution characteristic of HgNH₂Cl. The result showed the solution of HgNH₂Cl in HCl solution is the best with minimum requirement on HCl solution concentration, usage and reaction temperature, it can be dissolved completely in short time. The higher concentration, the more usage and the higher reaction temperature they are, the better solution of HgNH₂Cl it will be.The paper conducted another research on the acid solubility characteristic of sludge during ammonia desulphurization process by using HCl solution, selectively investigating the influence of acid concentration, acid solution usage, reaction temperature and reaction time on the sludge weight loss ration. The result showed there exists lots of acid soluble materials. The weight loss is mainly influenced by the HCl solution concentration and its usage. In the experiment, we can find the weight loss ration is rising with the higher concentration, more usage and longer reaction time. And during the reaction temperature rising, the ration first increases and then decreases, and after analysis, we found the reason is a new dissolvable material is produced in the higher temperature. The paper conducted an experiment on mercury leaching from HgNH₂Cl contained in the sludge. The result showed there is no resistances material in the sludge during the mercury leaching. When the sludge is 5g(included 0.05g HgNH₂Cl), HCl solution concentration is 1%, its usage is 50ml, reaction time is 60 min, and temperature is 50℃, the mercury of HgNH₂Cl in sludge leaching rate can reach 98%.At last, the paper initially researched on the experiment and mechanism by using scanning electron microscope and X-ray diffraction. The result indicated that lots of soluble material exist in the sludge, such as (NH₄)₃AlF₆,(NH₄)₂SO₄, most of them changed to new materials, such as (NH₄)₂AlF₆,NH4Cl. In the experiment adding HgNH₂Cl, there is no mercury compounds exist in the left solid after acid dissolution, but Hg(OH)NO₃ are detected in the solid by evaporation of filter liquor, then it proves that HgNH₂Cl is dissolved in the filter liquor.