Activated carbon adsorption recovery technology - Adsorption capacity and adsorbed substances

Through the company's systematic training and self-study, I have gained a relatively in-depth understanding of the adsorption and recovery technology for organic waste gas. Here, I would like to share a few of the points that I consider to be particularly important.

First, the adsorption capacity of activated carbon

The adsorption capacity of activated carbon mainly involves two parts: dynamic adsorption capacity and static adsorption capacity. Dynamic adsorption capacity refers to the amount of adsorbate that is adsorbed when the adsorbent reaches the adsorption breakthrough point, while static adsorption capacity refers to the amount of adsorbate that is adsorbed when the adsorbent is fully saturated. Generally, static adsorption capacity is greater than dynamic adsorption capacity. Before reaching the dynamic adsorption capacity, the adsorption efficiency of the adsorbent can remain in a relatively stable and efficient state, while after exceeding the dynamic adsorption capacity and before reaching the static adsorption capacity, the adsorption efficiency of the adsorbent is unstable and shows a rapid decline trend.

According to the extensive experiments of the Huashi Jie research team, generally, the dynamic adsorption capacity of activated carbon is about 8% is relatively appropriate. It can also be simply converted to 1 ton of activated carbon can adsorb 80 kilograms of organic waste gas. Beyond this proportion has no practical calculation value because at this time, the adsorption efficiency of the adsorbent is rapidly decreasing. In terms of environmental protection standards, it cannot meet the standard for emission.

Second, the substances suitable for adsorption recovery

From the perspective of the characteristics of the substances that activated carbon can adsorb, activated carbon can adsorb a very wide range of substances, and the substances suitable for the adsorption recovery process of activated carbon and suitable for steam desorption regeneration, in general, need to consider the following aspects:

① Consider the temperature of steam desorption, which should not exceed 120℃. Generally, 100℃ of water vapor is used for desorption. Therefore, organic waste gas with a boiling point below 100℃ is more suitable for activated carbon adsorption recovery.

② Consider the need for water vapor desorption. Therefore, the subsequent condensation process will produce water. Therefore, it is necessary to consider whether the organic waste gas contains components that can be miscible or compatible with water. If a single component is soluble in water, generally, it is not suitable for steam desorption; while if some components are soluble in water and some are not, then based on this characteristic, they can be separated.

③ Consider the inlet temperature of the organic waste gas. Generally, it should be below 40℃. According to actual engineering cases, if the inlet temperature of the organic waste gas is higher than 40℃, the molecular activity of the organic waste gas becomes higher, making it less likely to be captured by the pore size of the activated carbon, and the adsorption efficiency of the activated carbon decreases. While below 40℃, the adsorption efficiency of the activated carbon is the highest. Therefore, in general conditions, if the inlet temperature of the organic waste gas is higher than 40℃, it needs to undergo pre-treatment for cooling. Generally, a surface cooler is used.