Activated Carbon - Production

Production

Activated carbon is carbon produced from carbonaceous source materials such as nutshells, peat, wood, coir, lignite, coal, and petroleum pitch. It can be produced by one of the following processes:

1. Physical reactivation: The precursor is developed into activated carbons using gases. This is generally done by using one or a combination of the following processes:
   • Carbonization: Material with carbon content is pyrolyzed at temperatures in the range 600–900 °C, in absence of oxygen (usually in inert atmosphere with gases like argon or nitrogen)
   • Activation/Oxidation: Raw material or carbonized material is exposed to oxidizing atmospheres (carbon dioxide, oxygen, or steam) at temperatures above 250 °C, usually in the temperature range of 600–1200 °C.
2. Chemical activation: Prior to carbonization, the raw material is impregnated with certain chemicals. The chemical is typically an acid, strong base, or a salt (phosphoric acid, potassium hydroxide, sodium hydroxide, calcium chloride, and zinc chloride 25%). Then, the raw material is carbonized at lower temperatures (450–900 °C). It is believed that the carbonization / activation step proceeds simultaneously with the chemical activation. Chemical activation is preferred over physical activation owing to the lower temperatures and shorter time needed for activating material.

Activated carbon is made from coconut shell mainly. It consists of 2 types; fine powder and pills or flakes. The fine powder is good at diffusing in water, so it is used in solution or liquid related industries. For example, it is used to bleach and absorb odor in sugar industry, to produce cooking oil in food industry, and to purify water. The pill or flake type is used in gas-purifying industries / products; such as, air purifier, poisonous gas preventor, and cigarette butt, etc.

The growth of activated carbon market depends on the growth of industries that use it, which vary greatly from air purifier industry, drinking water and tap water industry, metal-plated industry, and food industry. In addition, activated carbon can be used in household. Its major household usage is found in products that absorb odors; such as a refrigerator's stuffy smell, wardrobe's and closet’s smells, etc. Hence, it can be seen that activated carbon market is broad and has a potential for consistent demand in the country. Besides, it can be exported to use in the industries that need high quality activated carbon; such as, in particular kinds of air purifiers. However, the import figures are still higher than the export.

Important production materials include coconut shells, palm shells, oil, husks, and sawdust, all of which have to be burnt into ashes for activated carbon making. Also, chemicals such as zinc chloride and phosphoric acid are used.