By appearance zinc oxide is a white powder consisting of 0.15 to 10-μm or larger hexagonal particles. The finest particles are shaped as grains, and the larger ones as needles or starlets made of needles. The particles’ size and shape depend on the process conditions.
Chemically, the process for obtaining zinc oxide from metallic zinc is a reaction of zinc vapor oxidation:
Zn + 1/2 O2 = ZnO + 85,4 kcal
Technologically, the production of zinc oxide is a sequential process of zinc melting, distillation and its vapor oxidation in specially designed muffle furnaces* at 1,150 to 1,350°С.
- Metallic zinc ingots are loaded into the muffles using special fixtures.
- Zinc melts and evaporates.
- After leaving the muffle, zinc vapors are oxidized by ambient oxygen in the furnace oxygen chamber to form zinc oxide.
- The particles of zinc oxide pass through an air duct and cool down. The quenched zinc oxide suspension enters a bag filter system with automatic shaking** and afterwards is transferred into collecting hoppers.
- From the collecting hoppers the finished product is transferred to filling and packaging.
The Manufacturing Complex Bellit Ltd. has implemented a system for automatic process control by rarefaction and temperature in the oxygen chamber, combustion chamber, gas treatment system,
Due to a system for selective streamflow separation, it became possible to extend the finished product grade range.
Laboratory control is carried out on a shift basis to check the product quality for compliance with the following regulatory documents: GOST 202-84, GOST 10262-73, TU 20.30.21-001-12763691-2018.
A team of engineers and process engineers constantly work to improve the production process, to enhance its cost-effectiveness and environmental security. Manufacturing is carried out in accordance with operating procedures.
* The muffle is a hollow cylinder made of carbon-containing fireproof material, with a length of about 2 m, outside diameter of 0.25 m and wall thickness of 50 mm.
** The bag filter system consists of a large number of cylindrical fabric filters. The filters are connected with hoppers, to which zinc oxide is discharged when the filters are shaken. As air passes through the filter fabric, zinc oxide particles contained in the air are trapped, and the air passes through the fabric into the filter metal casing and is then discharged into the atmosphere. The discharged air contains not more than 10 mg/m3 solid particles.