Jump to main content.


Activated Carbon Adsorber

  General Description General Description
  Monitoring Information Monitoring Information
  Costs Costs
GENERAL DESCRIPTION

In adsorption, gaseous pollutants are removed from an air stream by transferring the pollutants to the solid surface of an adsorbent. Activated carbon is the most commonly used adsorbent, although zeolites, polymers, and other adsorbents may be used. There is a limit to the mass of pollutants that can be collected by an adsorbent. When this limit is reached, the adsorbent is no longer effective in removing pollutant. To recover the ability to capture gaseous pollutants, adsorbents typically are "regenerated;" i.e., the pollutant is desorbed (removed) from the adsorbent. This regeneration may occur off-site or on-site. (A special case of on-site regeneration occurs when the adsorbent is used to concentrate pollutants for on-site thermal or catalytic oxidation. These concentrators are discussed separately and can be accessed by clicking on the link provided below.)

The most common types of adsorber systems use fixed beds (as opposed to fluidized beds, or the moving beds that are common in concentrator systems). One type regenerates on site; the second type, called a carbon drum, uses off-site regeneration. Carbon drum systems are low-capital-cost systems, used only when air flow rates and mass flow rates of pollutants are low. Regeneration, either on-site or off-site, typically uses either elevated temperatures (i.e., thermal desorption, sometimes using steam) or below-atmospheric pressures (vacuum regeneration). In some cases the solvent recovered from desorption (e.g., toluene from publication rotogravure printing operations) is re-introduced into the process; in other cases, it is disposed.

Several types of capacity are important to adsorbers. Saturation capacity is the maximum capacity the adsorbent can hold. However, before saturation capacity is reached, the adsorbent reaches its breakthrough capacity, which is the amount of pollutant that can be adsorbed before a significant pollutant concentration exits, or breaks through, the bed. Heel capacity is the amount of pollutant that remains in the bed after it has been regenerated. Working capacity is the difference between breakthrough capacity and heel capacity, and represents the amount of material that can be adsorbed in each working cycle. A typical working capacity is 10-20 pounds of contaminant per 100 pounds of carbon.

Adsorption systems are usually limited to sources generating organic compounds having a molecular weight of more than 50 and less than approximately 200. Low molecular weight organics usually do not adsorb sufficiently. High molecular weight compounds adsorb so strongly that it is difficult to remove these materials from the adsorbent during the desorption cycle. These molecular weights are provided as a guideline, and the suitability of an adsorption system should be considered on a case-by-case basis.

  Schematic of Regenerative Carbon Adsorber

Adobe PDF File

(1 p, 21K)  
  Training Video

Video RM File

(10284K)  
  EPA Air Pollution Control Cost Manual, Section 3.1, Chapter 1 - Carbon Adsorbers

Adobe PDF File

(48 pp, 139K)  
  EPA Technical Bulletin - Choosing an Adsorption System for VOC: Carbon, Zeolite, or Polymers?

Adobe PDF File

(32 pp, 263K)  
  Training Tool

Executable EXE File

(5417K)  
Top of Page Section Divider
MONITORING INFORMATION

General Information
The primary indicators of the performance of carbon adsorbers are the adsorber outlet VOC concentration; regeneration parameters including regeneration cycle timing, total regeneration stream (steam or nitrogen) flow or the vacuum achieved during regeneration; and carbon bed activity sampling. Other indicators of adsorber performance include bed operating temperature, inlet gas temperature, gas flow rate, inlet VOC concentration, pressure differential, inlet gas moisture content, and leak check monitoring.

The Compliance Assurance Monitoring (CAM) Technical Guidance Document (TGD) provides a source of information on monitoring approaches for different types of control devices. Specific information provided in the CAM TGD related to carbon adsorption include example CAM submittals based on case studies of actual facilities. Click on the links below for Appendix A: Example CAM Submittals for Carbon Adsorbers.

  Schematic of Regenerative Carbon Adsorber - Primary Indicators of Performance

Adobe PDF File

(1 p, 26 K)  
  CAM Rule

 
  Appendix A: Example CAM Submittals for Carbon Adsorbers

Adobe PDF File

(25 pp, 387K)  
Industry Specific Information
To search for additional monitoring information specific to an industry, click on the monitoring information by industry type section link provided below.

  Monitoring Information by Industry Type Section

 
Top of Page Section Divider
COSTS

Costs of carbon adsorption are discussed in the EPA Air Pollution Control Cost Manual, Section 3.1, Chapter 1 - Carbon Adsorbers. Costs of monitoring systems, both Continuous Emission Monitors and parametric monitoring systems, are addressed in the EPA Air Pollution Control Cost Manual, Section 2, Chapter 4 - Monitors.

  EPA Air Pollution Control Cost Manual, Section 3.1, Chapter 1 - Carbon Adsorbers

Adobe PDF File

(48 pp, 139K)  
  EPA Control Cost Spreadsheet for Calculating Carbon Adsorber Capital and Annual Costs (Second Edition)

Excel Spreadsheet

(17K)  
  EPA Background Document for Control Cost Spreadsheets

Adobe PDF File

(16 pp, 54K)  
  EPA Air Pollution Control Cost Manual, Section 2, Chapter 4 - Monitors

Adobe PDF File

(42 pp, 542K)  
Be sure to check the EPA Clean Air Technology Center website periodically for updates at
www.epa.gov/ttn/catc/products.html.

 

| Office of Air Quality Planning & Standards | Technology Transfer Network |
| Clearinghouse for Inventories & Emissions Factors |

Local Navigation