At present, the domestic wet zinc smelting mainly adopts the roasting-leaching-electrowinning production process, and the zinc content in the acid leaching residue is generally 8-15%, some up to 20%, and the sulfur mass fraction is 6-12%, of which sulfuric acid The root mass fraction is 15-30%, mainly in the form of 0^0 4 (in this ammoniatic environment, the leaching rate of sulfate leaching in multiple stages can reach 70%). The zinc in the acid leaching residue is mainly in the form of ZnFe 2 0 4 . In order to recover these zinc, the treatment methods are currently available in the fire method and the wet method. The fire method is the rotary kiln evaporation method (Wilz method) and the fumigating furnace evaporation method. . The wet method has hot acid leaching or high temperature pressure leaching. The fire treatment process is long, the equipment maintenance is large, the investment is high, the working environment is poor, and a large amount of coal or metallurgical coking coal is consumed, which has low efficiency and large environmental pollution. Therefore, it is usually leached by hot acid or high-pressure leaching. These methods still have the disadvantages of: 1 consumption of a large amount of acid, low leaching rate, due to the large amount of calcium sulfate, calcium sulphate and other ultrafine particles to isolate the zinc oxide particles, resulting in Electrolytic zinc enterprises are difficult to leach in acid environment, and the second weak acid leaching is not meaningful because the recovery rate is too low. 2 If leached with strong acid, although ZnFe 2 0 4 is destroyed, the leaching rate is improved, but the iron leaching rate is also high (up to 60%). The pressure of iron removal is large, and more reagents are consumed. 3 High temperature and high pressure equipment is corroded. Serious, complicated equipment investment; 4 high operating costs, poor economic returns. 5 The last slag discharged is acid leaching residue, which brings new pollution to the environment. It has to be cured and landfilled, which not only pollutes the environment, but also wastes resources.
This type locks onto the doorframe, creating a robust barrier against drafts This type locks onto the doorframe, creating a robust barrier against drafts
By providing a tight seal around the door, the seal helps to deter intruders and prevent unauthorized access By providing a tight seal around the door, the seal helps to deter intruders and prevent unauthorized access
