PTQ Q4 2025 Issue

Technology in Action

Fresh momentum for Paqell’s Thiopaq O&G: the biological SRU

1 , 000 , 000

Amine +claus (+ SCOT )

100 , 000

As global energy demand continues to climb alongside population and economic growth, the challenge of securing clean, reliable energy becomes more pressing than ever. In view of this energy-constrained society, fossil fuels remain a vital part of the energy mix, as decarbonised fuel alternatives remain insufficient to fully replace them in the near future. Tapping into smaller gas fields or those with contaminated gas, which need conditioning, will be part of the solution. One of the most frequent contaminants is hydrogen sulphide. Due to the presence of H 2 S, most gas streams require treatment to prevent the emission of SO 2 . Worldwide, emission require- ments have become much stricter, which increases the need for proper desulphurisation and sulphur recovery processes. Bridging the gap in sulphur recovery H₂S removal is notoriously challenging for small- to medium- sized gas streams and for ‘lean’ acid gases in particular. Traditional methods either come with high operating costs or require significant capital investment. For small amounts of sulphur up to 500 kg S/day, solid or liquid scavengers are an economic solution. For gas streams with a sulphur load of 100 tons/day and higher, the tradi- tional Claus SRU would be the best option. For gas streams with a medium sulphur load, in particular between 1 and 20 ton S/day, scavengers are not suitable due to their high Opex, while a traditional SRU has a relatively high Capex. Sustainable solutions are required to fill the gap. This is where Paqell’s Thiopaq O&G (TOG) steps in, offer- ing a biological approach that is both cost-effective and environmentally sound. This integrated process combines gas sweetening and sulphur recovery in a single unit, with

10 , 000

1 , 000

THIOPAQ O&G

100

Non-regenerable solids and liquids

0.01

0.1

Feed gas ow (MMNm/day)

caustic regeneration handled biologically. It is flexible enough to treat both high- and low-pressure gases (up to 80 bar), and can be applied directly at the source or downstream as a Figure 1 The economical envelope based on sulphur load, where TOG economics are favourable compared to other technologies. At the lower end of the sulphur load spectrum (<50 kg S/day, indicated by the red line), non-regenerable scavengers are typically more cost-effective, while for high sulphur loads (>150 ton S/day) the amine-Claus-SCOT train is most feasible (dark blue line). The area between the green and turquoise lines marks the sulphur load that is represen- tative for biofuel production facilities and gas streams in flare gas recovery projects. At the higher end of the sulphur load, cost effectiveness depends on the feed gas composition. The lower the H₂S % in the feed gas, the more favourable a TOG is as a SRU. Since its debut in the biogas sector in 1993, Thiopaq has been deployed in more than 350 installations worldwide. Its adaptation for oil and gas, Thiopaq O&G, has seen more than 25 successful start-ups globally since its launch nearly a decade later. The process consistently achieves H₂S con - centrations below 4 ppm (at ≥4 bar), and below 25 ppm at lower pressures. Self-sustaining catalyst, no more laborious catalyst change-outs One of the standout features of TOG is its self-replicating biocatalyst. This means that after initial seeding, the catalyst does not need to be replaced ever again during the lifetime of the plant. The catalyst is a mixture of naturally occurring sulphide-oxidising bacteria that multiply by catalysing the oxidation of dissolved sulphide into elemental sulphur. The characteristics mentioned above result in a major Opex reduction, while Capex remains competitive. In addi- tion, desulphurisation processes often have impacts on the sulphur recovery unit (SRU) for amine acid gas. Proven technology, expanding reach

Figure 2 Paqell’s Thiopaq O&G process

105

PTQ Q4 2025