Study On Removal Of Mercury And SO₂ Simultaneously With Ammonium Sulfide

In recent years, finish machining industry has gradually be taken attention, with the adjustment of industrial-scale development and the industrial structure, but however, mineral mining, smelting, and processing is still an important part of our industry. Compared to the traditional industries and emerging industries has defects such as environmental pollution, waste of resources, which has an increasing social concern and attention. In the conventional smelting industry, great harm to human body health, heavy metals in smelting gas easily enriched in human and animal body, it is difficult to discharge, cause various diseases, causing cancer and birth defects. Among them, the composition of smelting lead and zinc and other mineral and waste gas mainly includes:-Sulfur dioxide (SO2), sulfur trioxide (SO3), carbon monoxide (CO), water vapor and heavy metals Pb, Cd, As, Hg and etc.. Among these major pollutants, SO2 emissions from large emission concentration of about 0.05% to 25%; And about 52% mercury in zinc smelting process is flowing into the exhaust gas metallurgy, the main morphology is Hg0, Hg2+ and Hgp. but Hg0 is the main source of mercury emissions from zinc smelting process. Thus to explore suitable combined control and Resource Technology for nonferrous metals industry furnace flue gas SO2 and mercury (Hg0 and Hg2+) has important theoretical and practical significance to solve the urgent problem of the removal of pollutants in smelting industry.In this research we try to use the flue pipe and tube mercury vapor atmosphere furnace heated to high temperatures for the reactor to simulate heavy metal compounds containing two valence mercury (Hg0, Hg2+) of simulation of elemental mercury (Hg0) and ionic forms of mercury (Hg2+). The optimum conditions were respectively:under room temperature, gas flow rate 10ml/min and heated at 400 ℃, gas flow rate of 200ml/min, and adjusting the concentration of each pollutant flue gases (SO2 and Hg0, Hg2+) concentration range is consistent with the actual production, and then experimental platform has been establisied; Our experiment choose ammonium sulfide solution as absorption liquid to test smelter gases absorb mercury gas purification two valence states of mixed analog smoke containing sulfur dioxide, focus on exploration and research (NH4)2S removal of non-ferrous smelting process SO2 and two forms of mercury cooperative control optimum conditions. We will test the conditions of pH, ammonium sulfide solution concentration, gas flow rate, the reaction temperature on absorption processes; We will determine the reaction mechanism of the process of the reaction product by using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) characterizations analysis.Experimental results show that:Considering the removal rate and economic costs, the optimum conditions of the removal of elemental mercury (Hg0) with ammonium sulfide in smelting flue gas containing sulfur dioxide optimum conditions are:concentration of ammonium sulfide solution is at 0.8mol/L, pH value is at 7-4, the reaction temperature is 30℃, the maximum removal rate was more than over 89.45%, but after treatment elemental mercury (Hg0) can not reach the national emission standards, and for further depth mercury removal process is needed, but at this time the sulfur dioxide removal efficiency is more than 99.99% and reached the Air Pollutant Emission Standard (GB16297-1996); The optimum conditions of removal of ionic forms of mercury (Hg2+) with ammonium sulfide of in smelting flue gas containing sulfur dioxide are:concentration of ammonium sulfide solution is at 0.8mol/L, pH value is at 10-8 or 6-4, the reaction temperature is at room temperature (20℃), the total removal efficiency can reach 99.99%, emission concentration after treatment can reach national standards.Experimental results also show that:participation of sulfur dioxide to absorb reaction of mercury ions (Hg2+) is to remove a disincentive; And for elemental mercury (Hg0), sulfur dioxide is generally involved in inhibition, but at a lower concentrations of carbon dioxide when reacted, the reaction product was analyzed by proof that sulfur dioxide reacted with a solution of ammonium sulfide and generated elemental sulfur (S), hydrogen sulfide gas can oxidized elemental mercury (Hg0) to ionic mercury (Hg2+). Therefore, experiments showed that the sulfur dioxide to elemental mercury (HgO) removal can promote a certain degree.After analysis of product simultaneous removal of mercury and sulfur dioxide with ammonia oxidation by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis, the main product is HgS, (NH4)2SO4, (NH4) 2S2O3 and elemental sulfur and etc, the possible reaction principle is established. Experiments show that the product of ammonium sulfide method are easy to separation, recycling and secondary use, and it has a high removal rate, saving economic cost.