- Sewage Sludge is treated through anaerobic digestion to produce Methane, CH4
- During the process Hydrogen Sulphide, H2S, is also produced as a by-product
- Digester gas is saturated and the H2S turns into Sulphuric Acid, H2SO4
- Since the sourced ‘material’ can vary greatly, so can the levels of H2S and the resulting concentrations of H2SO4
H2SO4 corrodes most materials, especially yellow metals, low and high grades of steel, including stainless and only special acid resistant elastomers can cope long term
This problem of ‘saturated’ Biogas, unrecognised by general valve suppliers to the Water Industry, has led to low cost products with inappropriately selected materials being frequently used, resulting in a range of failures and costly repairs and extensive downtime.
What we were asked to do
Assist in writing new Biogas Handling TW Asset Standard, WWT 10.1, that would cover in part the requirements of:
- WIMES 9.01 –CHP Installations
- IGEM (Institution of Gas Engineers & Managers) Technical Gas Standards
Assist in writing new Guidance Notes for ‘Valves used for biogas applications’ in:
- WIMES 8.09 i2 –Valves
Produce ranges of Ball and Butterfly Valves for Isolation to solve the problems being faced:
- Valves seizing open/closed
- Liners swelling, decaying, becoming embrittled and disintegrate
- Valves leaking across the seat
- Valves leaking through the stem into the atmosphere
- Metallic & non-metallic, wetted and non-wetted materials corroding, internally & externally
To specify and supply:
- A range of CF8M Stainless Steel, Threaded & Flanged Ball Valves with NACE MR0175 Standard compliant materials, capable of meeting the UK Biogas, IGEM & WIMES standards, with appropriate leak-tight sealing and proven long term performance.
- NACE International (‘National Association of Corrosion Engineers’) give guidance on the corrosion resistant metals and elastomers for the prevention of Sulphide Stress Cracking caused by the presence of Hydrogen Sulphide in a ‘Sour Gas environment’.
- MR0175 was developed for the most aggressive corrosion areas within the Oil Industry, the Well-Head and Extraction applications, where the highest concentrations of H2S are found.
- A range of CF8M Stainless Steel, Flanged & Lugged Butterfly Valves with a Viton-Bio Acid Resistant Liner, suitable for Gas Service, capable of meeting the UK Biogas, IGEM & WIMES standards, with appropriate leak-tight sealing and proven long term performance.
- Base model is a Gas Service valve certified to EN 13774 –‘Gas Fittings: Shut-off valve for local distribution’ and EN161 –‘Gas Fittings: Pneumatically operated automatic shut-off valve’ with leak-tight ‘Dry-Shaft Liner Technology’, preventing stem leakage.
- Supplied with a Liner material of ‘FPM-006, Fluorelastomer(Viton-BIO)’, suitable for a media of Sulphuric Acid, Sour Gas, Natural Gas and other oils, hydrocarbons, chemicals & solvents.