Views: 7 Author: China xicheng Publish Time: 2021-04-28 Origin: China xicheng
In the exhaust gas treatment process, a filter device should generally be installed before the activated carbon adsorption tower, which we usually call pretreatment, except for dust-free gas. The upstream filter mainly prevents dust from clogging the activated carbon material.
The main factors affecting the adsorption efficiency and service life of activated carbon are the type and concentration of polluting waste gas, the temperature, pressure, relative humidity, and residence time of the waste gas flow.
The adsorption capacity of activated carbon is mainly affected by its specific surface area, pore size, intermolecular force, chemical bond synthesis, and other factors. In practical applications, the key to designing an activated carbon adsorption device is the filtration area of the activated carbon, the filtration wind speed, and the efficiency of the activated carbon—layer thickness.
The filtration wind speed of the activated carbon adsorption device can be found in the "Technical Specifications for Industrial Organic Waste Gas Treatment Engineering by Adsorption Method" (HJ2026—2013). Fixed bed adsorption can be found. The gas flow rate of the particulate adsorbent should be less than 0.6m/s, and fibrous adsorption should be used. The flow rate of the agent gas should be less than 0.15m/s, and the gas flow rate of the honeycomb adsorbent should be less than 1.2m/s; the filter area can be calculated according to the processing air volume and the filter wind speed.
The thickness of the carbon layer of the activated carbon adsorption device needs to be combined with factors such as the concentration of waste gas, the removal efficiency, and the replacement time of activated carbon.
Generally, two methods are used to calculate the carbon layer thickness:
One is to determine the total loading of activated carbon according to the required replacement cycle of activated carbon, and then calculate the thickness of the carbon layer based on the filter area;
Second, considering the size of the adsorption box, the wind resistance of the carbon layer, and the filtering wind speed, a thickness value is directly selected based on experience.
The above design is based on the case where the adsorption rate of activated carbon is a constant value or infinitely large to be negligible. However, the actual adsorption rate cannot be effectively calculated at present. Different carbon, different filtration wind speeds, different wind pressure, etc., will affect the carbon layer's absorption rate.