1. Direct method: using zinc concentrate as raw material, after high temperature oxidation roasting and then adding coal to reduce to zinc vapor, zinc vapor and hot air are oxidized to obtain zinc oxide. The main raw materials used now are zinc ore, zinc ash, etc. There are generally several types of kiln structures:
(a) Ping Kiln. The high temperature oxidation roasting process is carried out in a cubic furnace with refractory conversion, and the slag leaks from under the kiln. Raw materials: zinc ore, zinc ash, requires zinc content of more than 30%. Production: about 6 to 3 tons per day for the furnace body of about 6 square meters. The content is between 85% and 99%. Equipment investment is about 400,000. Advantages: Because it is fired with anthracite, the color of zinc oxide is good, and the content of sulphide and chloride is low. Abundant raw materials, products are widely sold.
(2) Turning the kiln. The high-temperature roasting process is carried out in a circular iron cylinder with a length of about 20 degrees and a length of about 40 meters. The material is fed from above, and the slag is discharged from the bottom. The vapor is collected and oxidized to form zinc oxide. Raw materials: various industrial zinc-containing waste slags, generally containing more than 16% of zinc, can be used. The output of round iron cylinders is about 10 tons per day for about one meter, the content is between 55% and 92%, and the equipment investment is about 600,000. . Advantages: raw material requirements are not high, and the recovery rate is high. High Yield. Some zinc oxide colors are yellow and some are gray. High thiogen chloride content. Generally used as raw materials for other industries.
(three) smoke furnace. The specific production process is unknown. Raw materials: industrial zinc-containing waste residue, generally containing more than 14% of zinc, output of 20 tons per day, content of 45-80%. Equipment investment of 1 million. Advantages: high recovery rate and high output. Zinc oxide color is yellowish or gray. If the production is well controlled, the sulphur chloride is not high.
2. Indirect method: the zinc ingot is melted into the evaporation crucible, and after heating, the gasification is oxidized by air and collected by cooling to obtain the finished product. The output is about 5 tons per day. The content is 99.7%, but now it is also used to make zinc blocks instead of zinc ingots, and the zinc oxide content is about 99.5. Equipment investment of 400,000. Advantages: high product content, high output, easy process control. 3. Zinc oxide is white and yellowish. Good activity. However, since the raw material is zinc ingot, the price fluctuates greatly with the price of zinc ingot.
3. Chemical method: zinc oxyhydroxide, ammonia water and ammonium hydrogencarbonate are placed in a leaching tank at a ratio of 1 (effective zinc): 8:1 to 1.5 (weight ratio), and heated to 50 ° C to 80 ° C for reaction. Remove the impurities after adjusting the pH. Evaporation for 5-8 hours, and the basic zinc carbonate precipitation liquid solid mixture is obtained, and the decomposed ammonia gas is absorbed and then recycled to the leaching tank of the process (1) through the ammonia circulation system, and the obtained zinc carbonate is dried. , calcined to obtain about 99.8% zinc oxide. Raw material: Zinc oxide or other low-content zinc oxide produced by rotary kiln or fuming furnace. Production: about 4 tons per day. Equipment investment of 1 million. Advantages: The product has good purity and contains less impurities such as lead, cadmium and kun. Since the secondary 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 process to produce zinc oxide.