H2S Removal Technology

biological gas desulfurization

Thiopaq O&G

H2S removal from gas streams is notoriously difficult for small to medium sized sulfur sources and for ‘lean’ acid gases in particular. Most other solutions result in either high operational cost or in laborious operations. Or both…

With Thiopaq O&G, Paqell offers a way out. The Thiopaq O&G process integrates gas desulfurization with sulfur recovery in a single unit. This means natural gas can be treated directly from the source, or Thiopaq O&G can be used as sulfur recovery unit (SRU) treating amine acid gas. Thiopaq O&G can be applied to low and high pressure gases.

Benefits include:

  • High sulfur removal rates, >99.99%
  • Proven technology with over 20 units installed in oil and gas
  • Over 300 units installed in biogas applications
  • Robust and stable process: easily capable of handling large swings in operation
  • Fast and simple start-up after upset upstream of the Thiopaq O&G unit
  • Inherently safe operation: no free H2S downstream absorber
  • Ambient temperatures throughout the system
  • Bioreactor and sulfur recovery section operate at atmospheric pressure
  • Low total cost of ownership, low OpEx compared to chemicals- based technologies
  • Non hazardous waste streams
  • High up-time: >99% availability
Licensed Thiopaq O&G units worldwide
Thiopaq O&G units under construction
metric tons of sulfur removed per day (combined)
Active microorganisms

Thiopaq process animation


Thiopaq O&G technology can be used to remove hydrogen sulfide and recover sulfur from different types of gas steams:

  • Natural gas
  • Refinery gas
  • Fuel gas
  • Flare gas
  • Sour gas
  • Acid gas
  • Associated gas
  • Claus tail gas
  • Various types of process off gasses
  • Biofuels production off gas
  • Biogas

Process description

The THIOPAQ O&G process consists of three sections. The absorber section, the bioreactor section and the sulfur separation section.

In the absorber, the H2S is removed from the feed gas stream using a sodium hydroxide solution. This creates an aqueous sulfide solution in the bottom of the absorber.

The solution is pumped to the bioreactor. There the THIOPAQ O&G microorganisms convert the sulfide to elemental sulfur.

Elemental sulfur is recovered from the bioreactor solution in the sulfur separation section.



The first step of the desulphurization process is a gas-liquid contactor that absorbs the Hydrogen Sulphide as Sulphide.

But the key to the THIOPAQ O&G Process is the biological aspect, i.e. the conversion of sulphide to elemental sulphur through the activity of bacteria belonging to the group of naturally occurring sulphide oxidising organisms such as Thiobacilli. These are autotrophic organisms, which means that CO2 is required as their sole carbon source. The organisms are naturally occurring and are not genetically manipulated or modified.

Biological fertilizer

Bio sulfur

Another important feature of the THIOPAQ O&G Process is the fact that the produced sulphur, also known as biosulphur, has special properties. The biosulphur does not show the hydrophobic behaviour which is typical of the chemically produced sulphur from Claus and redox processes, for example. This has a very positive effect on the operation: the solution behaves like a relatively stable suspension without clogging or other nuisances.