Gas desulfurization

Biogas is increasingly important as a source of sustainable energy. However, biogas produced through anaerobic digestion often contains high levels of hydrogen sulfide (H₂S). H₂S removal is necessary to prevent health, safety & environmental risks, and corrosion of equipment such as gas engines, boilers and piping.

The THIOPAQ^® process was invented and developed by Paques, in cooperation with universities, to solve the problem of H₂S in gas. It has become the go-to technology for biological H₂S removal, with hundreds of references worldwide, across a wide range of industries.

Almost any gas containing H₂S can be purified by the THIOPAQ^®, including biogas, syngas, vent streams, and geothermal gas. The process can be combined with any anaerobic wastewater treatment or digestion system. (Bio)gas flows from 50 Nm³/hour to more than 50,000 Nm3/hour can be treated, equivalent to sulfur loads ranging from 10 kg/day to 50,000 kg/day.

The THIOPAQ^® obtains very high H₂S removal efficiencies, with outlet H₂S concentrations of less than 25 ppm. The system has a wide turn-down, and can easily handle large fluctuations in gas flow. The produced sulfur effluent stream is free of sulfide, so discharge is no problem. What’s more, the elemental sulfur produced by the THIOPAQ^® can be used as a high-quality organic fertilizer.

Whether at a biorefinery in Scandinavia, a dairy in China, a bioethanol plant in Brazil, or an oil&gas facility in the US, the system is trusted by clients world-wide. No matter if you are looking for a small unit or very large design – a THIOPAQ^® is available. Standardized systems enable short project lead-times, while Paques’ experienced engineering team can tailor the unit to meet your specific needs.

Gas desulfurization is a must when biogas is upgraded to natural gas quality and injected in the grid (Renewable natural gas, RNG), used as vehicle fuel, or liquified (bio-LNG). The THIOPAQ^® is a perfect fit for biogas upgrading, and has been successfully used for biogas upgrading projects worldwide. The system has negligible methane slip, does not dilute the biogas with air, and does not add any oxygen into the gas. It can be used irrespective of the upgrading method: be it via membranes, amines, or any other technology.

The THIOPAQ^® combines fast chemical absorption to remove H₂S from (bio)gas and a robust biological recovery of sulfur. It consists of an absorber column coupled to a biological reactor and sulfur recovery device.

In the absorber, H₂S-containing gas is brought in contact with washing water via countercurrent exchange, where H₂S readily dissolves into the slightly alkaline wash water.

In the bioreactor, naturally-occurring bacteria oxidize the sulfide to elemental sulfur particles, simultaneously regenerating the washing solution. This allows the alkaline washing solution to be continuously reused in the absorber column, leading to very low operational costs.

The sulfur produced in the system is separated in a solids separation step, and can be reused as a high-quality, organic fertilizer.