Roasting section

Sulfuration roasting is a roasting method that turns certain metal sulfides and other compounds in the furnace into water-soluble sulfates under strict control of the furnace atmosphere and furnace temperature, which belongs to the pretreatment operation of hydrometallurgy.

The control conditions for the metal sulfide sulfation roasting mainly include temperature and air supply. In the industry, fluidized roasting furnaces (see fluidized roasting) are mostly used for sulfate roasting.

At the same temperature, the differentiation pressure of various sulfates is different, that is, their stability is different. The higher the temperature, the more unstable the sulfate is, and it is easy to differentiate into oxides. Using the difference in the stability of each sulfate, by controlling the appropriate roasting temperature, the so-called selective sulfation roasting that converts the metal to be extracted into soluble sulfate and makes other metals into insoluble oxides can be completed. The calcination temperature when iron is changed to oxide and copper and zinc are sulfated is considered to be a good sulfated calcination temperature. This temperature is 950K ± 50K. Roasting in this temperature range can produce copper, zinc and other leached and iron-insoluble roasted products.

The study indicates that when the air supply volume can make the SO3 in the gas phase have the largest value, it is the appropriate air supply volume for sulfation roasting. When selecting a good air supply volume, the condition of the sulfuric acid plant and the economic effect of heat energy use should be considered.

Sulfate roasting is used in the treatment of copper concentrate, copper-cobalt concentrate, cobalt-sulfur concentrate and low-grade polymetallic materials.

Sulfation roasting-leaching-electrolytic stacking is one of the primary processes of wet copper smelting. Sulfation roasting of copper sulfide concentrate is to convert copper in copper concentrate from sulfide to soluble sulfate, and iron sulfide to insoluble oxide. In the leaching operation, copper can be separated from iron and gangue ; In the roasting process, part of the sulfur in the concentrate is oxidized to form SO2 gas into the furnace gas for acid production.

Sulfate roasting was a common treatment method for cobalt-bearing sulfur concentrates at that time. Its intent was to desulfurize cobalt-bearing sulfur concentrates, control the appropriate temperature and air supply, and produce cobalt and nickel together with the production of sulfur dioxide-containing acid flue gas. , Copper and other non-ferrous metal sulfides are converted into soluble sulfate or basic sulfate, and iron is oxidized into insoluble Fe2O3. The calcined sand is further processed by hydrometallurgy to separate the non-ferrous metals from iron.

effect

Metal sulfates are easily differentiated into metal oxides and sulfur trioxide at high temperatures, but different metal sulfates have different differentiation temperatures. For example, iron sulfates differentiate at about 550 ℃, while copper, cobalt, and nickel sulfates Only differentiate above 700 ℃. Generally using this difference, copper, cobalt and nickel can be extracted from pyrite containing copper, cobalt and nickel, respectively.