The Varec Biogas 235 Series Gas Purifier is designed as a cost effective method for hydrogen sulfide removal. The process removes hydrogen sulfide (H2S) from biogas.
Biogas is generated by the anaerobic digestion of organic solids that contain small amounts of H2S. It is produced in anaerobic digesters, lagoons, and municipal landfills.
Although the total percentage of H2S in biogas is relatively small, it is often sufficient enough to corrode metals and damage equipment. This can create maintenance and operational problems especially in plants where the biogas is recovered to fuel engine-generators or boilers. In addition to corrosion problems, H2S is a toxic air pollutant that can create a severe odor nuisance in minute concentrations. The treatment of biogas for removal of sulfur compounds has become increasingly important due to stringent regulations restricting sulfur emissions.
Biogas contains H2S in concentrations from 500 to 3000 ppm or more, depending on the influent wastewater composition. The odor of hydrogen sulfide becomes offensive at 3 to 5 ppm. An atmospheric concentration of 300 ppm can be lethal.
Even small amounts of hydrogen sulfide can cause piping corrosion, gas engine pitting, and piston ring clogging. Many engine manufacturers require the H2S content to be as low as 100 ppm.
When biogas is burned or flared, the H2S can generate sulfur dioxide (SO2) emissions. H2S removal is a must when your local Regulatory Commission limits SO2 emissions.
The 235 Series Purifier is designed to remove most of the H2S from the biogas stream. It is usually installed upstream of a gas engine generator or boiler.
The following parameters should be measured for proper sizing and operation of the purifier:
Inlet biogas flow rate, inlet and outlet biogas pressures, inlet and outlet H2S concentrations, condensation (drip water), pH of drip water, and estimated bed life.
Isolation valves (supplied by others) are recommended for field installation in the inlet and outlet piping of each compartment. Drip traps are recommended for installation in the drain connections of the purifier compartments to provide for safe condensate removal. It also provides the means to verify that the media is kept moist.