How to Make Coal-Based Activated Carbon

Activated carbon is one of many industrial adsorbents, which is a multi-functional adsorbent. Activated carbon can be made from a variety of carbonaceous feedstocks, including raw coal, wood, coconut shells, palm shells, petroleum coke, and more.

Coal, as the most abundant carbon-containing raw material in the world, is widely used in the production of coal-based activated carbon. Among them, coal activated carbon production lines are mostly distributed in countries and regions rich in coal resources. What is the production process of coal-based activated carbon? What equipment is needed for the production of coal-based activated carbon? A detailed answer will follow.

Selection of Coal-Based Activated Carbon Raw Materials

Anthracite
lignite
Lignite
peat
Peat
Coal-tar

Coal-based activated carbon, also known as coal activated carbon, is a general term for a large class of activated carbon products manufactured from various raw coals through different processes. Coal activated carbon can be divided into two types: formed carbon and raw coal directly crushed carbon according to different manufacturing processes.

Carbonization of Coal-Based Activated Carbon

Activated carbon is a carbonaceous adsorbent formed by the carbonization and activation of carbon-containing materials. Therefore, the production of coal-based activated carbon requires two necessary sections, namely carbonization, and activation.

Carbonization is one of the main heat treatment processes in the activated carbon manufacturing process, and the main production is carried out in the activated carbon carbonization plant. Commonly used equipment mainly includes activated carbon rotary kilns, fluidized furnaces, and vertical carbonization furnaces.

Coal-based activated carbon plant
Coal-based activated carbon plant

Coal activated carbon is usually carbonized at a temperature of 350-600 °C. In the carbonization process, most of the non-carbon elements – hydrogen and oxygen are firstly eliminated in the form of gas due to the high-temperature decomposition of the raw material, excluding the volatile matter and moisture in the raw material, and the released element carbon atoms are combined into a general called basic graphite microstructure. The orderly crystallization product of the crystal makes the carbon particles form preliminary pores and has the structure of the original form of activated carbon.

After the raw material is carbonized, we call it carbonized material. The carbonized material already has a certain adsorption capacity, but the adsorption capacity is extremely low. After testing, the iodine adsorption value of the general carbonized material is only about 200mg/g.

Activation of Coal-Based Activated Carbon

The activation method of coal-based activated carbon is divided into the physical activation method (also called the gas activation method) and the chemical activation method according to the different activators.

Coal-based activated carbon rotary kiln in carbon activation plant
Coal-based activated carbon rotary kiln in activation production line

Coal-based activated carbon is carried out in activated carbon activation production equipment. The commonly used activation method is the physical activation method, using water vapor, flue gas (mixed gas of water vapor, CO2, N2, etc.), CO2, or air, etc. as the activation gas, Contact with carbonized material at a high temperature of 800 ℃-1000 ℃ for activation.

The activation process achieves the purpose of pore formation through three stages opening the originally blocked pores, expanding the original pores, and forming new pores.

Finished Product Treatment of Coal-Based Activated Carbon

Granular activated carbon (GAC)

The finished product section is mainly made into products with different particle sizes according to application needs. For granular activated carbon, there are mainly three processes crushing, screening, and packaging.

The crushing equipment usually adopts a double-roller crusher. By adjusting the gap size between the double-rollers, the particle size of the product is controlled to improve the yield of qualified particle size screening.

The screening equipment usually uses a vibrating screen to screen the crushed materials into three types: larger particle size, qualified, and smaller particle size. In the actual production process, multi-layer screens are often added to the vibrating screen to screen out products within several particle size ranges, and the products with qualified particle sizes are packaged and sold after screening. In addition, in the production process, stone removal machines and iron removers are also used for special-purpose products to reduce the ash content of the products.

Granular activated carbon
powder activated carbon
Honeycomb activated carbon

Powder activated carbon

For powdered activated carbon, there are mainly two processes grinding and packaging. Grinding powder is basically produced by Raymond mill equipment in most factories. By adjusting the analyzer of the mill, finished powdered carbon with a particle size of 200 mesh and 325 mesh can be produced.

Deep Processing of Coal Activated Carbon

For some special-purpose products, the finished coal activated carbon will be further processed such as acid washing, alkali washing, and water washing.

The purpose of pickling is mainly to reduce the ash content of activated carbon and avoid secondary pollution caused by activated carbon during use so that it can be better used in food or other industries. There are also some application fields that require activated carbon to impregnate agents to achieve better adsorption.

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