ASTM D6646 Determination of the Accelerated Hydrogen Sulfide Breakthrough Capacity of Granular and Pelletized Activated Carbon

Get Certified ASTM D6646 Testing for Reliable Activated Carbon Performance

ASTM D6646 testing provides comparative information about the hydrogen sulfide breakthrough capacity of activated carbon under the laboratory conditions specified by the standard. Reliable testing provides assurance to manufacturers of product quality, a comparison of the adsorption performance, optimization of production processes, and compliance with customer requirements for odour control and gas purification.

• Determines the hydrogen sulfide adsorption capacity of activated carbon per unit volume at 99.5% removal efficiency under the specified laboratory conditions.
• Evaluates granular and pelletized activated carbon for hydrogen sulfide removal from a humidified air stream.
• Compares the hydrogen sulfide breakthrough performance of different granular and pelletized activated carbons.
• Supports the development and quality assurance of products. 
• Helps in the selection of activated carbon for the gas purification systems used in industry. 

What are the uses of the ASTM D6646 test standard?

The ASTM D6646 test standard helps evaluate the ability of activated carbon to remove hydrogen sulfide from gas streams. It also helps laboratories compare adsorption performance, determine breakthrough time, and assess the suitability of activated carbon for gas purification applications. 

• Determines the hydrogen sulfide adsorption capacity of activated carbon under the specified accelerated laboratory conditions.
• Compares the apparent effectiveness of adsorption of various grades of activated carbon 
• Helps with quality control in the manufacture of activated carbon. 
• Supports comparison of virgin and newly impregnated or in-service granular and pelletized activated carbons for hydrogen sulfide removal in odor-control applications.
• Helps to make the right choices for gas purifiers with activated carbon. 
• Supports the development and research of better adsorption materials. 

Which Materials Can Be Tested Under ASTM D6646?

ASTM D6646 applies to granular and pelletized activated carbon to be used for hydrogen sulfide removal. The method applies to granular and pelletized activated carbons that meet the particle-size and other requirements of ASTM D6646 regardless of the carbonaceous precursor used. It can also be used for virgin activated carbon, impregnated activated carbon, catalytic activated carbon, and specialty adsorbents used in the field of odor control, purification of biogas, natural gas processing, wastewater treatment, industrial air filtering, and emission control.

Why is hydrogen sulfide breakthrough testing important?

Hydrogen sulfide is extremely toxic and corrosive and causes objectionable odors in many industrial gas streams. ASTM D6646 is an accepted standard used to measure the length of time that activated carbon will effectively remove hydrogen sulfide before breakthrough. It helps engineers choose the right adsorbent, determine optimal replacement cycles, improve system reliability, and reduce maintenance costs.

What Properties Does ASTM D6646 Measure?

The test determines the hydrogen sulfide breakthrough performance and adsorption capacity of granular and pelletized activated carbon under specified accelerated laboratory conditions.

Common Challenges and Troubleshooting

Common problems include non-uniform bed packing, gas leaks, flow-rate variation, inaccurate hydrogen sulfide concentration, moisture variation, and instrument calibration errors. Good sample preparation, leak-free connections, calibrated gas analyzers, a controlled environment, and a uniform gas flow rate improve measurement repeatability and accuracy.

Analysis Results and Interpretation

• ASTM D6646 calculates hydrogen sulfide adsorption capacity per unit volume of activated carbon at 99.5% removal efficiency and expresses the result in grams of H₂S per cubic centimeter of carbon (g H₂S/cm³ carbon).
• A longer breakthrough time under otherwise equivalent laboratory conditions generally indicates greater relative hydrogen sulfide breakthrough performance.
• A higher adsorption capacity indicates better hydrogen sulfide removal performance and potentially longer service life.
• A lower adsorption capacity or shorter breakthrough time indicates lower relative hydrogen sulfide breakthrough performance under the specified laboratory conditions.
• Laboratories can use these results to compare activated carbon performance and evaluate its suitability for hydrogen sulfide removal applications.

Link to ASTM D6646

ASTM D6646 Testing Technique, Process, and Data Collection

A humidified air stream (1% H₂S, by volume) is passed through the activated-carbon bed until the outlet concentration reaches the specified 50 ppm (breakthrough point). The laboratory then measures the amount of hydrogen sulfide removed at 99.5% efficiency from a unit volume of carbon. Technicians condition the activated carbon sample and then pack it into a test column. The controlled hydrogen sulfide gas mixture flows continuously through the packed bed under certain operating conditions. Technicians continuously monitor the outlet gas concentration during the test until hydrogen sulfide breakthrough. Technicians record the breakthrough time, gas-flow conditions, sample information, and inlet hydrogen sulfide concentration, then use these measurements to determine the adsorption capacity of the activated carbon.