Thermal Regeneration of activated carbon
2020-09-04 09:50Introduction：Thermal Regeneration of activated carbon The heating regeneration process of lean carbon consists of four steps: drying, removal of carbonized material, and cooling. Its basic principle is shown in Fig. 4.2-3. After heating and regeneratio
Thermal Regeneration of activated carbon
The heating regeneration process of lean carbon consists of four steps: drying, removal of carbonized material, and cooling. Its basic principle is shown in Fig. 4.2-3. After heating and regeneration, the adsorption capacity and adsorption rate of carbon can be fully recovered, and the adsorption activity can reach or approach the level of new carbon. Therefore, heating regeneration is the main and necessary means of carbon regeneration.
1. drying
The carbon water content given to the regeneration equipment is generally 40%~50% . The main purpose of the drying process is to vaporize the moisture in the carbon micropores. The temperature is from 100 ℃ to 150 ℃. At this temperature, a small fraction of the substance is decomposed by heat or removed by distillation of water vapor.
2. carbonization
After drying and dehydration, the activated carbon continues to be heated to about 700 ℃. In the process of heating, the components with lower boiling point are volatilized and desorbed successively, and the residues are carbonized. This part of carbonization may cause micropore blockage and deformation of activated carbon, thus reducing the effective area of carbon.
3. ash removal
Carbonized organic matter must be vaporized and removed from micropores by gases such as water vapor, carbon dioxide and oxygen. The most important thing in this process is to vaporize only the organic carbonates attached to the activated carbon and to ensure that the matrix of the activated carbon itself is not damaged. The regeneration temperature and atmosphere should be strictly controlled. Among the gases used for carbon regeneration, oxygen has the greatest damage to carbon matrix, so the content of oxygen must be strictly controlled, and generally it should not exceed 2%. In production practice, steam is generally used as vaporization gas, which is because water vapor is relatively easy to obtain. In the drying stage of carbon, the activated carbon is dried, and water vapor is produced as vaporization gas at the same time. For other gases, additional input is required. In addition, water vapor can protect carbon from loss.
The chemical reaction of heating regeneration basically belongs to water gas reaction. When vaporizing with water, oxygen will inevitably infiltrate into the regenerative kiln and take part in the reaction. The reaction formula is:
2C+O2+H2O→CO↑+CO2↑+H2↑
C+H2O→H2↑+ CO↑-130.377J(Anaerobic time）
If carbon dioxide is used as a vaporized gas, the reaction formula is:
C+CO2→2CO↑-170.78J
4. cooling
The regenerated carbon discharged from the regeneration equipment can be quenched by water or cooled naturally in the air. The mechanical strength of carbon can be increased by water quenching, but the activity is slightly decreased. The mechanical strength of regenerated carbon cooled in air is lower, the loss of carbon is larger, but the activity is slightly higher than that of water quenching. This is due to the high temperature of regenerated carbon discharged from horizontal regenerative kiln, which is generally about 750 ~ 800 ℃, which is slightly red-hot, and combustion reaction occurs when oxygen enters the air, thus changing the pore structure of carbon and resulting in the above results.
