Gas analyser shock for top AD plant
21 Sep 2012
London - Managers at Fernbrook Bio’s Rothwell Lodge biogas plant near Kettering had a shock when a gas analyser installed as part of the construction of the plant came due for its annual service.
The price quoted would have covered the cost of buying a completely new system within three years, explains Carl Woolley, site manager at the plant, which won the best anaerobic digestion project at the 2012 UK AD & Biogas Awards.
“It just wasn’t practical,” said Wooley. “We looked at the market and different types of analyser and selected the Gas Data Click! System where we can just change small parts as required instead of larger more expensive ones.
“We are able to get the unit serviced locally, the parts are smaller and easier to change and I am able to manually select which sample point I want to test.”
Gas analysis is crucial to the Fernbrook operation, which accepts 30,000 tonnes of segregated food wastes from homes and businesses in the surrounding area.
“The digesters are just like giant stomachs,” said Wooley. “If you over feed them the gas quality drops and if you under feed them the gas quality goes up. This fluctuation can cause problems with the combined heat and power (CHP) engines.
“If our methane quality changes too much our CHPs can’t cope and then turn off, so we lose power generation - and money. Also, if our hydrogen sulphide (H2S) content is too high, it creates more wear on the engines and our service costs get higher.
Gas analysers show the methane content which is one of the first indicators on how well the digester is working. They also track H2S content, so that, if this gets too high, chemicals can be added to the digester to reduce the amount and save on damage to CHPs.
Fernbook now have two digesters on site and planning permission for a third, to enable it to increase the site capacity to 45,000 tonnes per year.
“This gives us a higher return on gate fees and more power production whilst also reducing waste going to landfill and helping the environment,” concluded Wooley.
