| Zinc oxide ore is the product of long-term weathering of sulfide lead-zinc deposits, it also can be used as a raw material for zinc. China is one of the countries which zinc oxide ore resources are more abundant, development and application of such ores have great economic value. As contained in the special properties of mineral, its flotation recovery is still a problem so far; If use of fire treatment, need with a lot of flux into and consume large amounts of fuel in order to meet its residue type, so high energy consumption high cost and no environmental; The greatest difficulty of sulfuric acid leaching of hemimorphite and zinc silicate ore in atmospheric pressure is leaching process generates silica gel is very difficult to filter; Alkaline leaching and ammonia leaching are put new demands on zinc hydrometallurgy technology and equipment, so only to remain in the laboratory or semi-industrial stage.This paper studied a new process of with air as the pressurized gas, pressure leaching of high silica lead-zinc oxide ore in sulfuric acid medium, theoretical and experimental research about the key technologies of the new process. The main elements and conclusions were summarized as follows.1,The relationship equation between standard Gibbs free energy ΔGθ and temperature T about the main sulfuric acid dissolved reaction and the relationship equation of the equilibrium constant K and the temperature T have been calculated. The following conclusions was obtained as follows:When the reaction temperature is50℃or so, the chemical reaction of lead-zinc oxide ore containing material with sulfuric acid can basically automatic right to; For the desilication reaction of silicic acid, the reaction is difficult to place at normal temperature in atmospheric condition, but when the temperature was higher than120℃, the reaction can be carried out automatically to the right.2,The ET-pH diagram of the Zn-H2O system and the Zn-Si-H2O system at different temperatures were calculated and plotted. The following conclusions was obtained as follows:in order to leach zinc compounds, the need to control the relatively high concentration of sulfuric acid when the high temperature condition; in order to ensure control in SiO2phase stable region, the need to maintain a relatively high temperature (≥120℃).3,The main problem about atmospheric acid leaching of high silica lead-zinc oxide ore in sulfuric acid medium are as follows:leach pulp is not easy to filter; requires strict control of process conditions; zinc recovery rate is not high, less than92%; zinc and silicon,iron or other impurities can not be effectively separated, so need to add the follow-up of silicon and iron removal treatment processes; large consumption of acid. Atmospheric leaching fluid and leaching pulp were easily converted into silica gel which can not be separated.4,The pressure leaching process conditions on the main component of lead-zinc oxide leaching effects and pulp filtration performance was systematic studied. The optimum condition was obtained as follows:liquid-solid ratio is3:1～4:1, sulfuric acid concentration120～140g/L, with air as the pressurized gas and pressure0.4-0.6MPa, leaching temperature110～130℃, ore particle size-0.074mm>95%, leaching time60min and stirring speed400～500r/min.Under this process conditions, Zn leaching rate>97%, Si leaching rate<1%, Fe leaching rate<6%, the rate of lead into slag>97%, the fluid production rate>1030L·m-2·h-1, leaching solution containing Zn2+118～131g/L, Fe0.0087～0.026g/L, Si0.04-0.16g/L. Compared with the acid leaching at atmospheric, pressure acid leaching process has the following advantages:good pulp filtration, high recoveries rate of zinc, fast speed of response, the process is simple, effective removal of silicon and iron, low acid consumption, strong adaptability of raw materials, etc.5,From solution desilicating study showed that:in order to avoid the production of silicone and ensure a better filter performance, need to controlling higher reaction temperature to facilitate the removal of silicon or lower acid concentration and the end pH range of slurry is3～5.5which can use of pH,electrolytes and other influence to bring together precipitated silica. The good filtration leaching residue in the XRD map showing the intensity and clarity of crystalline diffraction lines are more significant; But the poor filter residue showed X-ray diffraction intensity is weak and vague. SEM analysis showed that:the poor filter residue containing dendritic silica gel and filled with other small particles among them, so there is no much more space conducive to the flow of liquid.6,The pressure acid leaching of synthetic silicate zinc was studied. The results showed that elevated temperatures can damage the stability of silica gel and thus conducive to the dehydration process of silicate; The rate of fluid production increased with the end pH increases; When the amount of water volume in leaching system is greater than a certain limit, the leaching rate of silica increased significantly and promote the formation of silica gel; The negatively charged silica and positively charged ferric hydroxide sol in the role of electrostatic forces will be completely coagulation when the right condition was control.7,The kinetics of pressure sulfuric acid leaching of high silica lead-zinc oxide ore was systematic studied. The apparent activation energy of the reaction is14.3kJ/moL and the apparent reaction order of sulfuric acid and pressure affect is1.139and0.277respectively; Acid leaching process is affected by the proliferation of control. The macro-kinetic equation of four process conditions common affect the leaching of zinc was created as follows:8,The technology of pressure sulfuric acid leaching of high silica zinc oxide ore has been tracking inspection. Technical process conditions have been optimized and continuous production was also examined. The results show that the process has the following advantages:high recovery of zinc,pulp had good filtration performance, short process,easy to implement and control of reaction conditions,the leaching solution containing silicon and iron impurity low without additional processing,low production cost.
|
PDF Full Text Request