Should I choose activated carbon or other adsorption media for chemical filters?

Activated carbon is one of the most common media found in chemical filters, but it is not the only option and is not necessarily suitable for all gases.

The choice of activated carbon or other media depends on the target gas, its concentration, temperature and humidity conditions, and how strict the outlet requirements are. The material name is just the starting point. What really needs to be checked is the efficiency, capacity and penetration performance under the corresponding gas. Please refer to the specific gas classification Discussion on why chemical filters should be selected according to the target gas .

What can activated carbon do and where are the boundaries?

Activated carbon works by physical adsorption. There are a large number of micropores on its surface, and gas molecules are adsorbed to the pore surface as they pass through. This mechanism is effective for some organic compounds, such as some solvent volatiles and odor components.

But physical adsorption is selective. For low-concentration, weakly polar organic matter, activated carbon may perform better. For highly polar or low molecular weight gases, such as ammonia, formaldehyde, and some acidic gases, the adsorption capacity of ordinary activated carbon may be limited.

Humidity can also affect performance. In a high-humidity environment, water molecules may compete with the target gas for adsorption sites, reducing the effective capacity. If the airflow humidity is high, it is necessary to evaluate whether it is suitable to use activated carbon directly, or whether pretreatment is required.

So activated carbon is not a universal answer. Which scenario it is suitable for needs to be judged based on the target gas, concentration and environmental conditions.

What are the directions for other media?

When ordinary activated carbon is not suitable, other types of media can be considered.

Impregnated activated carbon. Through chemical impregnation treatment, activated carbon can react to specific gases or enhance adsorption. Different impregnation recipes correspond to different target gases, such as acidic gases, alkaline gases or specific organic compounds.

Special chemical adsorbent. This type of media is usually designed for a certain type of gas and captures target molecules through chemical reactions. Capacity and efficiency data need to correspond to specific gases and operating conditions.

Composite filter material. Combine media with different functions to handle mixed contamination. For example, one layer handles acidic gases and one layer handles organic matter. The combined solution needs to check the performance of each layer separately to avoid mutual interference.

Reactive media. Some media remove gases through neutralization, oxidation, or other reactions. The selection of such media should consider the reaction products, usage conditions and replacement methods. Specific products can be referred to the chemical filter product range . Description of

Unify the conditions when comparing

Comparison between different media requires conditional alignment.

The target gas must be consistent. The data of a medium on toluene cannot be used to judge the effect on ammonia. The reverse is also true. The report should specify the test gas, concentration, air volume and temperature and humidity conditions.

The test conditions should be close to actual working conditions. The sample data is obtained under specific conditions and cannot be applied directly without conditions. If the actual concentration, humidity or air volume is significantly different from the test conditions, re-evaluation is required.

Focus on capacity, not just initial efficiency. High initial efficiency does not mean long life. Capacity data can help determine how long it will last under target loads. For specific life assessment methods, please refer to Discussion of how long chemical filters last .

Resistance and system matching should also be compared. Different media may have different resistances. After adding a filter section, the fan operating point will change, and the system margin needs to be checked. For specific accounting methods, please refer to Discussion of how much the added resistance of the chemical filter will increase the fan's electricity usage .

Additional requirements for clean environments

Chemical filters used in clean rooms or equipment must not only meet gas processing capabilities, but also meet cleanliness requirements.

Release gas and powder. Some media may release trace amounts of organic matter or generate dust during operation. If the filter section is located upstream of the clean area, it is necessary to confirm whether the media meets clean compatibility. For specific verification methods, please refer to Discussion on how to verify the low outgassing requirements of ULPA .

Structurally sealed. The frame, sealing gasket and edge banding material of the chemical filter must also match the use environment. Bypass air leakage will allow untreated air to bypass the filter material and affect the outlet concentration.

Maintenance method. Replacement operations in clean environments may involve downtime, isolation and containment. Replacement of channels and operating spaces must be confirmed during the design stage. Device-side applications such as FFU with chemical filter or MAU box-type chemical filter , interface and maintenance methods need to be checked together.

Project judgment example

A certain project requires the treatment of ammonia-containing waste gas and a small amount of organic solvents.

The initial plan is to use ordinary activated carbon. After operation, it was found that the smell of organic solvents improved, but the ammonia concentration did not decrease significantly. Testing confirmed that ordinary activated carbon has limited adsorption capacity for ammonia and requires a medium for alkaline gases.

Adjustment plan: Add a chemical filtration section for ammonia after the original activated carbon section to form a composite configuration. After the resistance, interfaces and maintenance methods of the two-stage filters were rechecked, the system operation returned to normal.

This case shows that activated carbon and special media are not alternatives, and sometimes need to be used in combination. involving For the configuration of the chemical filter product series , it is recommended to provide the target gas list and working conditions to the supplier for verification.

Key points for selection and acceptance inspection

About Aili Industrial’s filter material selection support

The core of the selection of activated carbon and special media is to match the characteristics of the target gas and the filter material. The more complete this information is, the more targeted the selection will be.

Aili Industrial has independent manufacturing capabilities in filters, motors, fans, control systems and sheet metal processing, and can provide chemical filter product series and supporting air supply equipment. For projects that need to distinguish between activated carbon and special media, the target gas, concentration, temperature, humidity, and air volume can be combined to help check the filter material type and configuration method. When the filter is matched with MAU, FFU, EFU and other equipment, the resistance, interface and maintenance methods can be confirmed uniformly.

Related products:Chemical filter product series、MAU box chemical filter、FFU comes with chemical filter . Provide target gas list and system conditions when enquiring, which will help confirm the appropriate filter material solution. The specific selection is subject to the technical documents and test results confirmed by the project.