PAQUES – THIOPAQ® Regenerative H2S Scrubber
Leading in biological wastewater and gas treatment
For over 30 years, Paques has helped industries to reduce water and carbon footprints and reclaim valuable resources. Paques’ anaerobic water purification systems produce energy (biogas) from wastewater, while purifying the water and facilitating water reuse. After the introduction of the first BIOPAQ® reactor in 1981 Paques developed a broad portfolio for integrated water and gas treatment in close cooperation with partners. All the solutions proved to be cost-effective and highly reliable. Leading companies from a variety of industries worldwide select Paques as their partner for meeting their purification and sustainability obligations.
In more than three decades, Paques became one of the leading players in water and gas treatment and currently Paques has offices and/or production facilities in the Netherlands, China, Brazil, the United States of America and India and a network of professional partners worldwide. Since 2021 Paques is fully owned by the SKion group.
The THIOPAQ® was developed by Paques, in cooperation with universities, research institutes and customers. It can be applied to a wide range of biogas streams containing H2S and can be combined with all biological anaerobic systems. The ‘caustic’ solution in the THIOPAQ® scrubber is continuously biologically regenerated. In the scrubber, the gas containing H2S is brought into contact with the washing water in counter currently. Absorption of H2S under slightly alkaline conditions (pH 8-9) enables a chemical reaction with hydroxide ions. The hydroxide used in the scrubber is regenerated in the bioreactor. The system obtains a very high H2S removal efficiency, exceeding 99.5% and usually achieving <25 ppm in the treated gas. Both the small bleed stream (consisting of sodium salts) and the produced sulfur are free of sulfide, so discharge is no problem. After treatment in the THIOPAQ® scrubber, the biogas can be used in a gas engine or boiler or can be transported in a local micro gas grid. Upgrading to biomethane, which can be brought into the gas distribution network for use as fuel for vehicles is another possibility. The elemental sulfur, produced by the THIOPAQ® can be used as a high-quality fertilizer.
Currently >40 THIOPAQ® scrubbers are in operation in the USA and Canada and another about 15 are in various stages of completion at RNG plants at dairy farms all over the US. At those dairy farms the THIOPAQ® scrubbers treat flows from a few hundred to >4,000 scfm with H2S concentrations that are generally in the range of 2,000 to 6,000 ppm.
Technology Strengths, Weaknesses and Critical Indicators
Anaerobic Digester Associated Technology:
NOTE: There are several technology types that are used as part of an integrated manure management system that includes an anaerobic digester and are not applicable to manure management in other cases. The impact of these technologies on the critical indicators are represented as those of an entire anaerobic digester system.
- Long usable life and can be run reliably
- Creates energy and generates environmental credits
- Requires proper preparation of the feedstock
- Requires other technologies for energy utilization
- Requires other technologies for digestate handling
- Proper feeding & system monitoring is required to avoid system downtime
- Proven technology for odor control, GHG reduction and pathogen reduction
H2S scrubbing represents one of the biggest technological challenges for anaerobic digester systems. This technology is required before most internal combustion engine generator sets as well as for systems that are upgrading biogas to Renewable Natural Gas (RNG) for injection into the national gas grid.
The THIOPAQ® system offers a unique opportunity to utilize a technology that can be used in both of these types of systems, because it does not directly inject air or oxygen into the biogas, yet offers effective H2S removal. Claiming a very high removal rate with low operating cost, paired with worldwide experience with H2S removal in a verity of industries including dairy this technology is worth considering for any digester project.
1. OPERATIONAL HISTORY