Active carbon filtering
1. TYPE OF TECHNOLOGY
Active carbon adsorption.
2. RETAINABLE IMPURITIES
Volatile Organic Compounds (VOCs), both soluble and insoluble. Adsorption capacity increases with the size of the molecules to be retained.
3. RETENTION EFFICIENCY
Retention efficiency is 99%, decreasing with saturation of the active carbon.
4. EQUIPMENT AND PROCESS DESCRIPTION
The process entails condensation of the airborne solvent on a solid surface (through the action of Van der Waals forces). The most commonly used solid surface is the exceptionally porous material known as active carbon, whose efficacy in this matter is directly proportional to the degree of its porosity (1 g of active carbon can hold a total surface area of about 1,200 m2).
The solvent entrained by the air to be filtered condenses through capillary action and is retained in the active carbon. Besides the consideration of contact surface, the efficiency of this adsorption phenomenon is determined by several other factors: VOC concentration, humidity, temperature, speed of air flowing against the active carbon, contact duration and size of the active carbon particles.
Normally, the VOCs in question should not exceed 40 °C.
For example, against an air flow of 30,000 m3/h, a quantity of approx. 12 m3 of active carbon (7,500 kg) affords a contact duration of 1.5 seconds, and a contact air speed of 0.3 m/s.
5. APPLICABLE FIELDS
Active carbon filtering equipment can be used in any industrial process generating airborne VOCs and odours in sufficiently small concentrations: dyeing lines, the chemical industry, the food industry, etc.