SULFOTHANE™

Biogas is a valuable renewable energy source receiving ever more attention. Biogas can be generated by the anaerobic treatment of industrial wastewaters, by the digestion of manure and other bio-wastes, and is released as landfill gas from covered landfill sites.

Before the biogas can be utilized, it is essential to remove the sulphur compounds, which are mainly present in the biogas as sulphide (H2S). Sulphur can cause severe corrosion in boilers and engines utilizing biogas. Sulphur is an essential nutrient for living organisms, and is found for instance in proteins. During the production of biogas, the sulphur is converted biologically to H2S. Fortunately, biological processes can also be used to remove the H2S from the biogas.

 

FEATURES & BENEFITS

The SulfothaneTM Desulphurization Unit can be seen as a combination of an alkaline washing column combined with a biological production of elemental sulphur in combination with an alkalinity recovery step.

FEATURE OF THE SULFOTHANE™ PROCESS

It is important to note that in the SulfothaneTM process the elemental sulfur is produced in a bioreactor and not in the scrubber itself. Due to this feature, clogging problems that generally occur in conventional caustic or liquid iron based scrubbing systems, are prevented in our scrubber. Overall, the biological produced sulfur increases the operational reliability of the system and enhances the H2S absorption.

BENEFITS OF THE SULFOTHANE™ PROCESS

• Deep H₂S removal efficiency
• No addition of air (N2, CO2 and O2) to biogas stream, therefore very suitable for further biogas upgrading without changing clean biogas flow and composition
• Small footprint
• Most reliable and robust H2S removal process, applicable to high turn down ratios and S-load fluctuations.
• Very fast and stable start-up procedure with small biomass inoculum
• Significant chemical savings (caustic, active carbon, iron ore) leading to much lower operating cost.
• No risk of clogging in the scrubber column

PROCESS DESCRIPTION

The biogas is lead through a scrubber column where it is mixed and separated with wash water, removing H2S and some CO2 under alkaline conditions. No air (O2 and N2) will be added. Thus the composition of the biogas remains almost unchanged except for the removal of H2S.

In a second step the loaded wash water will enter a slightly aerated bioreactor where aerobic sulphur bacteria oxidize all H2S to produce elemental sulphur and recover alkalinity. The H2S free (unloaded) wash water will be returned and re-used in the scrubber. The separated sulphur sludge will be removed to further use or disposal.

SULFOTHANE™ GENERAL PRINCIPLE MAIN STREAMS

NUTRIENTS

The conversion of H2S into elemental sulphur is a biological process and requires a minimum amount of nutrients (trace elements) for good and healthy bacteria growth and operation of the plant. Therefore a dosing unit is foreseen to add a nutrient solution (Vithane-S) to the bioreactor.

Biothane's laboratory is provided with analysis equipment to determine all of the individual trace elements of a given wastewater sample. By this, adequate nutrient dosing advice can be given according to the outcomes of the analysis.

Vithane® is a special micro-nutrient solution nourishing the bacteria with the necessary vitamins' for optimal performance.

Next to bulk supply we deliver Vithane® on-site in differing package variants ranging from 20 liter cans to 900 liters IBC's.

Please call our biomass and nutrients service number in The Netherlands:

+31 15 2700 111 or send us an e-mail.