Manufacturing Process of Steam Activated Carbon
Steam activation is a widely used process for producing activated carbon. This process involves two main stages: carbonization and activation.
1. Selection of Raw Material
Material: Typically, materials like wood, coal, coconut shells etc. are used.
Preparation: The raw material is cleaned to remove impurities and dried to reduce moisture content.
2. Carbonization
Temperature: The raw material is heated to a temperature range of 600°C to 900°C in an inert atmosphere (e.g., nitrogen or argon).
Atmosphere: An inert atmosphere is maintained to prevent combustion and to facilitate pyrolysis.
Duration: The carbonization process can last from several hours to a day, depending on the material and desired properties.
Function: This process decomposes the material, expels volatile components, and forms a char with a basic pore structure.
3. Activation
Temperature: The carbonized material (char) is heated to a higher temperature range of 800°C to 1100°C.
Steam: Steam is introduced into the activation chamber. The steam reacts with the carbon in the char, oxidizing it and further developing the pore structure.
Reaction: The main chemical reaction during steam activation is:
C+H2O→CO+H2C+H2O→CO+H2
Duration: This stage can also last from several hours to a day, depending on the desired properties.
Function: The steam activation process enlarges the pores created during carbonization and increases the surface area of the carbon.
4. Cooling
Method: After activation, the activated carbon is cooled in an inert atmosphere to prevent oxidation.
Purpose: Rapid cooling helps in preserving the developed pore structure.
5. Washing and Drying
Washing: The activated carbon is washed with water and sometimes with acid to remove any soluble ash or residual activating agents.
Drying: The washed activated carbon is dried to remove any remaining moisture.
Method: Air drying, oven drying, or other suitable drying methods can be used.
6. Milling and Sieving• Milling: The dried activated carbon is milled to the desired particle size.
Sieving: The milled carbon is sieved to ensure a uniform particle size distribution.
Mesh Size: Depending on the application, different mesh sizes are used to achieve the desired fineness.
Manufacturing Process of Chemically Activated Carbon
Chemically activated carbon is produced by impregnating a carbonaceous material with chemical activating agents and then carbonizing the mixture at relatively low temperatures. Here is a detailed step-by-step guide to the process:
1. Selection of Raw Material
Material: Typically wood, but other carbonaceous materials such as coconut shells can also be used.
Preparation: The raw material is cleaned and dried to remove impurities and moisture.
2. Impregnation with Chemical Activating Agents
Chemicals Used: Common chemicals include phosphoric acid (H₃PO₄) and zinc chloride (ZnCl₂). Eco-friendly alternatives such as potassium hydroxide (KOH) or citric acid can also be used.
Mixing: The carbonaceous material is thoroughly mixed with the chemical activating agent. The ratio of chemical to raw material varies depending on the desired properties of the activated carbon.
Phosphoric Acid: Typically used in a 1:1 weight ratio with the raw material.
Zinc Chloride: Usually used in a 0.4-2.5:1 weight ratio with the raw material.
3. Carbonization
Temperature: The mixture is heated to a temperature range of 400°C to 500°C.
Atmosphere: The process is carried out in an inert atmosphere to prevent combustion.
Duration: The carbonization process can take several hours, depending on the material and the desired characteristics of the activated carbon.
Function: During this process, the chemical activating agents help to decompose the cellulose structure, enhance the development of porosity, and reduce tar formation.
4. Cooling and Washing
Cooling: After carbonization, the material is allowed to cool in an inert atmosphere to prevent oxidation.
Washing: The carbonized material is washed thoroughly with water and mild acid solutions to remove any remaining chemicals.
Washing Agents: Water, dilute hydrochloric acid (HCl), or other suitable solutions.
Purpose: This step ensures the removal of residual chemicals, enhancing the purity of the activated carbon.
5. Drying
Process: The washed activated carbon is dried to remove any remaining moisture.
Method: This can be done using air drying, oven drying, or other suitable drying methods.
6. Milling and Sieving
Milling: The dried activated carbon is milled to the desired particle size.
Sieving: The milled carbon is sieved to ensure uniform particle size distribution.
Mesh Size: Depending on the application, different mesh sizes are used to achieve the desired fineness.