Several production methods of zinc oxide

Thread Content

This post was last edited by 955559 on 2018-11-17 21:22. Several methods for producing zinc oxide: 1. Direct method: Using zinc ore as raw material, it is subjected to high-temperature oxidation roasting, and coal is used in a chemical reaction to reduce it to zinc vapor; zinc vapor then reacts with hot air to produce zinc oxide. Currently, zinc ore and zinc ash are the main raw materials used. There are generally the following types of furnace structures: (1) Flat kiln. The high-temperature oxidation roasting process takes place in a cubic furnace made of refractory material, with slag flowing out from the bottom of the furnace. Raw materials include zinc ore and zinc ash, requiring a zinc content of over 30%. The production capacity is around 2 to 3 tons per day for a furnace with a surface area of about 6 square meters; the zinc content ranges from 85% to 99%. The equipment investment is approximately 400,000 yuan. Advantages include good color of the zinc oxide produced when burned with bituminous coal, low levels of sulfur and chlorine compounds, abundant raw materials, and broad market prospects for the product. (2) Rotary kiln. The high-temperature roasting process occurs in a circular iron tube tilted at about 20 degrees and measuring around 40 meters in length. Materials are fed from the top while slag is discharged from the bottom; steam is collected and oxidized to form zinc oxide. Raw materials can be various industrial zinc-containing waste materials, as long as their zinc content is above 16%. The production capacity is around 10 tons per day for a kiln with a length of about 1 meter; the zinc content ranges from 55% to 92%. The equipment investment is around 600,000 yuan. Advantages include lower requirements for raw materials, high recovery rates, and high production volumes. However, the color of the zinc oxide produced can be yellow or gray, and it contains higher levels of sulfur and chlorine compounds. It is generally used as raw material in other industries. (3) Smelting furnace. The specific production process is not well known. Raw materials include industrial zinc-containing waste materials with a zinc content of at least 14%. The production capacity is around 20 tons per day, with a zinc content ranging from 45% to 80%. The equipment investment is 1 million yuan. Advantages include high recovery rates and high production volumes. The color of the zinc oxide produced is slightly yellow or gray. If the production process is well controlled, the levels of sulfur and chlorine compounds remain low. 2. Indirect method: Zinc ingots are melted in an evaporation crucible; after heating, they vaporize and undergo oxidation upon contact with air. After cooling, the product is captured using a bag filter. The production capacity is around 5 tons per day, with a zinc content of 99.7%. However, nowadays, zinc slag is sometimes used to produce zinc ingots instead, resulting in zinc oxide with a content of around 99.5%. The equipment investment is 400,000 yuan. Advantages include high product purity, high production volumes, and easy process control. The zinc oxide produced is white with a slight yellow tint and has good reactivity. However, since the raw material is zinc ingot, its price fluctuates significantly based on the price of zinc ingots. 3. Chemical method: Sub-zinc oxide, ammonia water, and ammonium bicarbonate are mixed in a ratio of 1 (effective zinc):8:1–1.5 (by weight) and placed in an leaching tank. The mixture is heated to 50°C–80°C to initiate the reaction. After adjusting the pH value, impurities are removed. After 5–8 hours of evaporation, a solid-liquid mixture of basic zinc carbonate is obtained. The ammonia gas generated during this process is absorbed and recycled back to the leaching tank in step (1). The resulting zinc carbonate is then dried and roasted to produce zinc oxide with a content of around 99.8%. Raw materials include sub-zinc oxide produced by rotary kilns or smelting furnaces, or other zinc oxides with lower content. The production capacity is around 4 tons per day. The equipment investment is 1 million yuan. Advantages include high product purity and low levels of impurities such as lead, cadmium, and mercury. Since sub-zinc oxide contains a certain amount of lead, the waste lead sludge generated during production can help offset some of the production costs. It’s important to ensure a stable supply of raw materials and to develop markets for the product. Due to the recycling of ammonia gas during production, this method is also known as the ammonia-based process for producing zinc oxide