Study On Absorption And Purification Of Heavy Metals From The Smelter Flue Gas

In recent years, metallurgical processing of minerals has become an important part of our industry with the rapid development of industry. Meanwhile, environmental pollution situation is increasingly serious and environmental problems attracted widespread attention of people. Composition of the exhaust gas that is produced in smelting process changes with different mineral raw materials. Mainly including SO2, SO3, CO and water vapor, also contain Pb, Cd, As, Hg and other heavy metals. Heavy metals are easy to accumulate in the body and difficult to discharge, even can cause a variety of visceral diseases, so are harmful to human health. Thus, the control of smelter flue gas is urgent, and it is of great significance to study efficient and economical methods of controlling and recycling heavy metals in the flue gas.This paper describes a method of using tubular atmosphere furnace as reactor to simulate flue gas containing heavy metals. Drawing the optimum temperature simulation of four heavy metal fumes lead, cadmium, arsenic, mercury and were:900℃,1000℃,400℃,450℃. The concentrations of simulated heavy metals flue gas are consistent with practical situations. In this paper, the purification of four heavy metals fumes lead, cadmium, arsenic, mercury with ammonium sulfide and sodium sulfide as absorption liquid are investigated, the effects of absorption solution concentration, pH, temperature and SO2on removal efficiency of heavy metals are also studied.The results of ammonium sulfide absorption of heavy metals in flue gas show that, the optimum purification conditions of lead is0.2mol/L for the concentration of ammonium sulfide solution, pH value is10, the reaction temperature is50℃. The maximum removal efficiency of lead is above96%, and the concentration of lead in the flue gas reduces to0.65mg/m3through; the optimum conditions of cadmium is0.2mol/L for the concentration of ammonium sulfide solution, pH value is10, the reaction temperature is50℃. The maximum removal efficiency of cadmium is above93.9%, and the concentration of cadmium in the flue gas reduces to0.45mg/m3through purification; the optimum conditions of mercury is0.8mol/L for the concentration of ammonium sulfide solution, pH value is10, the reaction temperature is40℃. The maximum removal efficiency of mercury is above99.9%, and the concentration of mercury in the flue gas reduces to0.01mg/m3through purification; the optimum conditions of arsenic for the concentration of ammonium sulfide solution is0.2mol/L, pH value is10, the reaction temperature is40℃. The maximum removal efficiency of arsenic is above93.4%, and the concentration of arsenic in the flue gas reduces to0.47mg/m3through purification; the purification of heavy metals is inhibited with the addition of sulfur dioxide in the flue gas.The results of sodium sulfide absorption of heavy metals in flue gas show that, the optimum purification conditions of lead is0.4mol/L for the concentration of sodium sulfide solution, pH value is12, the reaction temperature is40℃. The maximum removal efficiency of lead is above94.2%, and the concentration of lead in the flue gas reduces to0.65mg/m3through; the optimum conditions of cadmium is0.4mol/L for the concentration of sodium sulfide solution, pH value is12, the reaction temperature is50℃. The maximum removal efficiency of cadmium is above94.6%, and the concentration of cadmium in the flue gas reduces to0.45mg/m3through purification; the optimum conditions of mercury is1.0mol/L for the concentration of sodium sulfide solution, pH value is10, the reaction temperature is40℃. The maximum removal efficiency of mercury is above99.9%, and the concentration of mercury in the flue gas reduces to0.01mg/m3through purification; the optimum conditions of arsenic for the concentration of sodium sulfide solution is0.4mol/L, pH value is10, the reaction temperature is40℃. The maximum removal efficiency of arsenic is above93.5%, and the concentration of arsenic in the flue gas reduces to0.47mg/m3through purification; the purification of heavy metals is also inhibited with the addition of sulfur dioxide in the flue gas. Compared with ammonium sulfide, the absorption purification of heavy metals with sodium sulfide is required higher concentration and large energy consumption.This paper had researched comparatively the removal efficiency of Hg0and Hg2+with sulfide. The results showed thatwhen we use sulfide to remove Hg0, the removal efficiency of Hg0is less than70%, and the Hg0concentration of the flue gas is higher than the emission standards. Further study on the absorption of Hg0with HgCl2 solution, and investigate the relevant factors. The results showed that HgCl2can effectively remove Hg0from flue gas. the removal efficiency of Hg0can reach above98%, and acidic conditions is more conducive to remove Hg0. In addition, the research also showed reducing gas in the flue gas will lower removal efficiency of Hg0.