Direct rectification method of molten liquid crude cadmium

Abstract

The invention discloses a direct rectification method of molten liquid crude cadmium. A cadmium cake is placed in a crude cadmium smelting furnace to be smelted, the smelting temperature ranges from 500 DEG C to 700 DEG C, the adding proportion of sodium hydroxide is (15-16):100, the adding proportion of a reducing agent is (1-2):100, and impurities Zn, Pb, Cu and NaOH react to generate sodium salt which is generally called alkali slag; the density of the alkali slag is smaller than that of cadmium, so that the alkali slag is layered and floats on cadmium liquid; meanwhile, a small amount of CdO wrapped by the alkali slag is reduced into metal cadmium by a reducing agent, the alkali slag is cleared up regularly to remove impurities, and a crude cadmium solution containing larger than 98% of Cd and smaller than 0.05% of Zn is obtained; the crude cadmium solution passes through the bottom of a crude cadmium smelting furnace, flows out of a discharging opening controlled by a valve special for groove-free metal melt and flows into a middle maintaining furnace; the crude cadmium solution in the middle maintaining furnace is sucked into a vacuum rectifying furnace through a siphon tube of the vacuum rectifying furnace for high-temperature rectifying at the temperature of 400 DEG C to 500 DEG C; due to the fact that the volatilization temperature of cadmium is far lower than that of impurity elements, cadmium vapor is formed by liquid cadmium, and is condensed into liquid cadmium or a fine cadmium ingot in a condenser.

Description

technical field [0001] The invention relates to a method for direct rectification of molten liquid crude cadmium liquid. It belongs to the field of non-ferrous metal metallurgy technology. Background technique [0002] In the smelting of zinc, the cadmium in the zinc sulfide concentrate volatilizes into the smoke during the roasting process of the fluidized bed furnace. After the smoke is leached, the cadmium enters the leaching solution, and the leaching solution is purified by zinc powder to obtain copper cadmium slag, which is then leached and zinc powder Substitution results in sponge cadmium and copper slag, and the sponge cadmium is extruded into a dense cadmium cake through a cake press. Cadmium cake generally contains 70-85% cadmium and 3-5% zinc. [0003] In the existing technology of using cadmium cakes to produce refined cadmium ingots, the cadmium cakes are melted at 500-700°C, and sodium hydroxide and reducing agents are added to remove impurities and reduced,...

AI Technical Summary

Problems solved by technology

Since the crude cadmium solution cannot be directly rectified in the roughing furnace, it is necessary to cool the crude cadmium solution at about 600°C and cast the ingot, and then send it to the rectification furnace to heat up to 400-500°C for high-temperature rectification. A large amount of sensible heat cannot be used, resulting in high energy consumption

[0004] During the research and practice of this method, the inventors of the present invention have found that the above-mentioned process has solved the problem of recovering cadmium from sponge cadmium produced in the process of zinc hydrometallurgy, but the high-temperature molten crude cadmium liquid needs to be cooled during the recovery process. After the ingot is cast, it is sent to the rectification furnace for rectification, and the enthalpy of the high-temperature molten crude cadmium liquid cannot be utilized, which increases the energy consumption of sponge cadmium recovery, and ultimately increases its production cost

Images