Shell International Oil Products is looking to convince gas processors that a new bacteria-based sulfur removal process is as reliable as conventional methods.
The Shell-Paques Gas Desulfurization Process was conceived by small Dutch firm Paques Bio Systems BV, but the two companies have been working for the last 4 years to develop the technology.
Pierre van Grinsven, business group manager, gas treatment, at Shell, told OGJ the process uses naturally occurring thiobacillus bacteria to remove hydrogen sulfide from natural gas by converting it to sulfur.
A conventional hydrodesulfurization plant comprises an amine scrubbing unit, a Claus unit, and a Claus tail gas unit; the Shell-Paques process requires dilution in a caustic solution followed by treatment in a bioreactor.
Van Grinsven said Shell had proved the process to the pilot stage and is developing several types of bioreactors in readiness for proving it on a commercial scale.
Currently the process is capable of producing up to 15 tonnes/day of sulfur, depending on concentration levels, in gases containing up to 80% H2S or in solutions containing up to 10 ppm.
A pilot plant built in Germany was proved up to a level of 20 kg/d sulfur output, but scaling up is reckoned to be simple because the process itself is relatively simple.
Paques has built five plants based on this process; they are working at only atmospheric pressure. Van Grinsven said Shell has extended the technology to high-pressure operations and has a number of potential applications in mind.
Process license
Shell recently licensed the Shell-Paques process to New Paradigm Gas Processing Ltd., a subsidiary of Canadian Chemical Reclaiming Ltd. (CCR), Calgary, for applications in Canada.
CCR sees two main applications in Canada: the removal of H2S from flare gas and the removal of H2S from gas produced from wells that are currently stranded because of the high cost of H2S removal.
"Our first intention is to do something for Canada's sour gas flares," said Van Grinsven. "Up to 10 tonnes/ day of H2S can currently be flared in Canada, but this level will be reduced in the near future.
"Also, we are at an advanced stage of preparations for application of the process at a gas processing plant in Holland and at a refinery in Egypt. We hope to announce the first commercial project within 1 month."
Shell's work so far has convinced it that the process has an H2S removal efficiency from natural gas streams of more than 99.9%, which compares with the current state-of-the-art.
"This will be the first application of a biotech conversion technology," said Van Grinsven. "The problem at first will be to convince gas producers that they can rely on bugs."
