As part of the overall Uniflare gas train package, the desulphurisation system at the site features Allison Engineering’s AWITE Biogas analyser which is supplied with its own air compressor and uses a combination of PID and Fuzzy Logic control to automate the injection of small quantities of air (0.5 to 1%) into the gas stream within the digester. The oxygen converts the hydrogen sulphide (H2S) to elemental sulphur and water, a process which is automatic and does not require any operator input and so eliminates additional operational and maintenance costs.

The H2S concentration in the biogas produced from Anaerobic Digestion (AD) can be up to 2000 to 3000ppm and when the biogas is burnt in the CHP plant to produce electricity the H2S breaks down to produce a weak sulphuric acid that can cause corrosion within the engine which can lead to increased maintenance costs. For this reason many engine manufacturers stipulate a maximum H2S concentration in their warranty statements.

James Hladkij, AD technician, said: “Maintaining H2S concentration levels to less than 300ppm is essential. The Uniflare system has enabled us to achieve levels of less than 100ppm and at minimal operational cost”.