In principle, all coal can be made into activated carbon. However, the quality of activated carbon produced by different coals varies greatly. In order to better adapt to the market and make rational use of resources, the raw materials for making activated carbon from coal in China are mainly weak caking bituminous coal from Datong, Shanxi and Taixi anthracite from Ningxia.
In addition, Xinjiang bituminous coal is also suitable for making activated carbon. In recent years, under the influence of coal seam development and economic development in Xinjiang, more and more manufacturers use Xinjiang bituminous coal to produce activated carbon. In addition, some enterprises in Shenmu, Shaanxi Province also use local bituminous coal to produce activated carbon, but the adsorption value of activated products is generally low, and the iodine adsorption value is mainly 400-700mg/g (national standard 87).
2 Carbonization activation section
"Activated carbon is a kind of carbonaceous adsorbent after carbonization and activation of carbonaceous materials." According to the definition of this sentence, there are two necessary steps in the production of activated carbon, namely carbonization and activation.
Carbonization is one of the main heat treatment processes in the manufacturing process of activated carbon. The commonly used equipment mainly includes fluidized bed furnace, rotary furnace and vertical carbonization furnace.
The carbonization temperature of coal-based activated carbon is usually 350-600℃. In the process of carbonization, due to the pyrolysis of raw materials, most non-carbon elements-hydrogen and oxygen are first eliminated in the form of gas, which excludes volatiles and moisture in raw materials, and the released carbon atoms combine into orderly crystalline products, commonly known as basic graphite microcrystals, which make carbon particles form initial pores and have the original structure of activated carbon. After raw materials are carbonized, we call them carbonized materials. Carbonized materials already have a certain adsorption capacity, but the adsorption capacity is extremely low. The iodine adsorption value of ordinary carbonized materials is only about 200 mg/g.
Activation methods are divided into physical activation method (also called gas activation method) and chemical activation method according to different activators.
The commonly used activation method of coal-based activated carbon is physical activation method, in which water vapor, flue gas (mixed gas of water vapor, CO2 and N2, etc.). ), CO2 or air is used as the activating gas, which is activated by contacting with carbonized materials at a high temperature of 800- 1000℃ (the most commonly used flue gas in actual production).
The activation process achieves the purpose of pore-forming through three stages: opening the original blocked pores, expanding the original pores and forming new pores. Activation is mainly through activation furnace equipment to carry out activation reaction to make holes. At present, the mainstream is SLEP furnace, Squet furnace (STK), rake furnace and rotary furnace. At present, SLEP furnace is the most widely used type of gas activation furnace in China.
3 finished product part
The finished product section is mainly made into products with different particle sizes according to the application needs. For granular carbon, there are three main processes: crushing, screening and packaging.
Crushing equipment usually adopts double-roller crusher, and the granularity of products is controlled by adjusting the gap between the two rollers to improve the yield of qualified granularity screening.
Screening equipment usually uses vibrating screen to screen the crushed materials into three types: larger particle size, qualified particle size and smaller particle size. In the actual production process, multi-layer screens are often added to the vibrating screen to screen out products with several particle sizes, and finally the products with qualified particle sizes are packaged and sold. In industrial applications, 500kg/ bag and 25kg/ bag are usually used for packaging. In addition, in the production process, special-purpose products also use stone removal machines and iron removal machines to reduce the ash content of the products.
For powdered activated carbon, it is mainly through grinding and packaging. At present, grinding in most factories is basically produced by Raymond mill equipment. By adjusting the analyzer of the mill, the finished carbon powder with particle size of 200 mesh and 325 mesh can be produced.
4 deep engineering part
For some special-purpose products, the finished carbon will be further treated by acid washing, alkali washing and water washing.
Among them, the purpose of pickling is mainly to reduce the ash content of activated carbon and avoid secondary pollution caused by activated carbon in use, so as to be better applied to food or other industries. In some application fields, activated carbon will need to be impregnated with chemicals to achieve better adsorption.