PC-JUN22-PG48-49.1_Layout 1 13/06/2022 14:07 Page 49
ANAEROBIC DIGESTION
Infra-red cameras can identify methane
leakage on AD plants and prevent financial, environmental and safety impacts
the operation of AD plants. These are widely expected to include the need to demonstrate via an Environmental Management System (EMS) the effectiveness of covers, containment methods and abatement systems. As part of this, sites will need to have leak detection and repair plans in place. The EA is looking to introduce formal methods
to monitor and record methane leaks from AD plants and on-site containment systems. Therefore, such leaks will need to be prevented and continuously monitored and repaired when necessary. Some environmental permits already include a requirement for a regular Leak Detection and Repair (LDAR) programme and this is likely to become more widespread. Although there can be a number of causes of
biogas leakage, common areas are more prone to leakage than others. These frequently include: • Cable grommets (where a submersible
stirrer cable passes through the digester wall), in particular where they are not greased or maintained properly. • Valves and covers operating at the wrong
pressure, resulting in over- or under-pressure, which prevents seals and surfaces sealing properly.
• Burst plates on digester roofs and concrete
roof joints. • Gas membrane connections. • Flange and pipework connections. • Carbon filters. • Any areas where maintenance is carried
out. Most minor issues can be fixed relatively
easily by on-site personnel, while moderate issues may require spare parts or external specialists. In the worst cases it may be necessary to temporarily close plants until affected areas can be ventilated and issues repaired. Plant operators and managers should ensure
regular Leak Detection and Repair (LDAR) programmes (including leak detection surveys) are carried out. Such inspections should be carried out every twelve months unless a risk assessment suggests a different timetable. The FM BioEnergy leak detection service covers a full AD plant survey with a methane-sensitive monitor and laser, as well as infra-red devices, including: • Survey of all tanks, CHP, biogas upgrading
equipment, roof membranes, pipes and flanges.
• Analysis of emissions from CHP and
double membrane covers. • Report with images, videos and repair
priority table. As well as regular scheduled checks,
leak detection surveys should also be carried out when plants begin full-scale operation; after significant maintenance work has been carried out; if your feed-to- gas conversion is lower than expected (but the biology remains stable); and of course, if you can smell biogas. The cost of detecting a potential leak and making the necessary repairs is minimal, but the implications of leaving it to chance could be major.
FM BioEnergy
www.forfarmers.co.uk/fm-bioenergy
ESI Technology Limited
HYDROGEN COMPATIBLE PRESSURE MEASUREMENT SOLUTIONS
Compatible with Hydrogen based environments
Pass tested to ISO11114-4:2017
Superior Silicon on Sapphire sensing technology
Made from specialist titanium alloy and stainless steel material
www.esi-tec.com JUNE 2022 | PROCESS & CONTROL 49
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