The Recovery And The Use Of Arsenic In Heavy Non-ferrous Metallurgy

Arsenic is a kind of terribly harmful element in non-ferrous smelting .Because of its existing, the conditions of work become worse and the operations turn complicated. It is pernicious to erode the equipments, damage people's health and pollute the environment. So it is a great task for the metallurgical department to decrease the emission of Arsenic and research the way of its harnessing. The paper introduces systematically the recovery and the use of Arsenic in heavy non-ferrous metallurgy both theoretically and practically.The origin, existing and distribution of Arsenic in nature and the physico-chemical properties of Arsenic and its compounds are theoretically discussed in detail in the part of literature summary. The practice of producing Arsenic using the ways of pyrogenic and wet process and the method of producing metallic Arsenic and high purity Arsenic at home and abroad have been studied. The distribution and removal of Arsenic in heavy non-ferrous smelting such as copper, tin, lead and zinc are summarized. The main point of removal Cu is in the field of electrolyte purification. But the researches on the pyrogenic process to remove Cu are few. Because the content of Arsenic is about 0.5-5.5% in tin concentrate, roasting to remove As before smelting is the usual way. The researches in the field of lead and zinc smelting put the emphasis on the high-lead Arsenic converter dust, lead slime and secondary zinc oxide.It has been many years for ShaoGuan smeltery to produce lead and zinc in closed-top blast furnace. Shaft-furnace slag treated by the fuming furnace can receive secondary zinc oxide with high content of zinc ,which enriches over half Arsenic of flowsheet. So separating Arsenic from secondary zinc oxide has been researched.The experiments included both small and extended test. Because the Arsenic in secondary zinc oxide exists mainly in the form of arsenous oxide, which is volatile, the roasting method of adding reductant carbon to secondary zinc oxide is used to remove Arsenic. The researches include the influence of temperature, atmosphere, roasting time ,additive agent and the composition of raw material on the removal Arsenic.Small-scale experiment shows: When the roasting temperature is 900-1000,coke addition is 4-6%.staying time is 30-40 minutes and gas flow rate is over 0.0461m/s,the volatilization rate of Arsenic will be more than 90%.Extended test shows: If the staying time is 30-40 minutes in rotary kiln, gas flow rate is above 0.0461m/s,coke addition is 5-6% and roasting temperature is 850-900, the volatilization rate of Arsenic can ammount to over 90%.Under the above mentioned conditions, the volatilization rate of Zn is below 4%.The volatilization rate of Pb and Ge can be controlled to less than 10%.Thus it can be seen, the experimental results reach predicated object. It is completely feasible to remove Arsenic using the methods of smelting secondary zinc oxide in rotary kiln.