1. Direct method: using zinc concentrate as raw material, high-temperature oxidation roasting and then adding coal to reduce to zinc vapor, zinc vapor and hot air oxidation to obtain zinc oxide. Now the main raw materials used are zinc ore, zinc ash, etc. There are generally the following furnace structures:
(A) flat kiln. The high-temperature oxidation roasting process is in a refractory-transformed cubic kiln. The slag is missing from below the kiln. Raw materials: Zinc ore, zinc ash, require zinc content of more than 30%. Production: about 2 to 3 tons per day of the furnace around 6 square meters. The content is between 85% and 99%. Equipment investment is about 400,000. Advantages: Because it is fired with anthracite, zinc oxide is good in color, sulfur, and chloride content is low. Abundant raw materials, products sell well.
(b) Rotary kiln. The high-temperature roasting process is performed in a circular iron cylinder with a length of about 40 meters and a tilt of about 20 degrees. The material is fed from above and the residue is discharged from the bottom. Vapors are collected and oxidized into zinc oxide. Raw materials: All kinds of industrial zinc-containing waste slag, generally more than 16% of the zinc content can be used, the output round iron drum is about 1 ton per day about 10 tons of cargo, the content is between 55%-92%, equipment investment is about 600,000 . Advantages: raw material requirements are not high, the recovery rate is high. High Yield. Some yellow zinc oxide, some gray. Sulfur chloride content is high. Generally used as a raw material for other industries.
(C) the smoke furnace. The specific production process is unknown. Raw materials: industrial zinc-containing waste residue, generally containing more than 14% of zinc, 20 tons of output per day, content of 45-80%. Equipment investment 1 million. Advantages: high recovery, high yield. Zinc oxide color yellowish or gray. If the production control is good, then the sulfur radical is not high.
2. Indirect method: The zinc ingot is melted into an evaporation crucible, heated and then gasified. The air is oxidized and collected by a cooling bag to obtain a finished product. The output is about 5 tons per day. Content of 99.7%, but now also use zinc dregs themselves into zinc blocks instead of zinc ingots, the production of zinc oxide content of about 99.5. Equipment investment 400,000. Advantages: high product content, high yield, easy to control process. Zinc oxide is slightly yellowish white. Good activity. However, because the raw material is zinc ingots, the price changes greatly with the price of zinc ingots.
3. Chemical method: zinc oxide, ammonia, and ammonium bicarbonate are placed in a leach tank at a ratio of 1 (effective zinc) of 8:1 to 1.5 (weight ratio) and heated to 50°C to 80°C for reaction. Adjust the pH value to remove impurities. Evaporate for 5 to 8 hours to obtain basic zinc carbonate precipitated liquid-solid mixture. The decomposed ammonia gas is absorbed and then recycled to the leaching tank of step (1) through the ammonia circulation system. The obtained zinc carbonate is dried by evaporation. , Roasted to obtain about 99.8% of zinc oxide. Raw materials: Zinc oxide or other low zinc oxide produced by rotary kiln or fuming furnace. Production: 4 tons per day. Equipment investment 1 million. Advantages: product purity, lead, cadmium, kun and other impurities. Since zinc oxide contains a certain amount of lead, the waste lead mud in the production process can also offset part of the production cost. Stable raw materials and market development should be mastered. Due to the recycling of ammonia in the production process, it is also called ammonia production of zinc oxide process.