Carrier Rental Systems is supplying high performance temporary cooling and heating equipment to support the UK’s rapidly expanding energy-from-waste biodigester facilities.

Biodigester plants harness natural biological processes using bacteria to breakdown organic matter to produce methane. The gas is then used as a fuel source to generate electricity. The benefit is that food and agricultural waste that would otherwise be sent to landfill can be used to produce clean energy.

When new plants are commissioned, an external energy source is required to warm the organic feed stock within the biodigester, to initiate biological activity. Once this process becomes established, it produces its own heat as a result of the biological activity and becomes self-perpetuating.

A temporary heating source, therefore, is required during the start-up phase to prime the system. Carrier Rental Systems is supplying packaged boiler plant, buffer tanks and associated pipework on a hire basis for this purpose to several new energy-from-waste plants around the country.

In one recent example, the company supplied a hire boiler package to a biodigester project at Forres, in the north of Scotland. A Carrier Rental Systems’ 250kW boiler was used over a six week period during its commissioning phase to gradually raise the temperature within the digester tanks to 45deg C, at which point the system produced enough power to initiate the onsite generator.

Biological activity in a digester may sometimes stall, due to a problem with the feedstock or other external condition that causes the system to cool. Carrier Rental Systems recently supplied a temporary boiler package to a major water treatment plant in Dartford to address such a problem, maintaining production until the issue could be remedied and a long-term solution found.

A HIAB crane and trailer was used to deliver a 2MW packaged boiler to site, supported by a 20,000ltr fuel tank. This was connected by flexible pipework to the main flow and return heating coil using the customer’s flange connections.

Once installed and commissioned, the boiler soon generated sufficient hot water to restart the biological process, and production of methane was quickly re-established. The timely intervention overcame the need to remove the inactive contents from the bio-digester and start the process from scratch, saving time, money and lost productivity.

Carrier Rental Systems is also providing packaged Carrier AquaForce 30XA air-cooled screw chiller on a hire basis for use in biodigester facilities undergoing maintenance. Here, in a reverse of the above process, a chiller is used to cool the contents of the biodigester in order to arrest biological activity.

In a recent example, Carrier Rental Systems supplied a high efficiency 100kW AquaForce chiller to an energy-from-waste plant in Reading, which was due for major maintenance work. The chiller was connected to the plant’s main process heat exchanger, enabling rapid cooling of the biodigester contents as they passed through. This quickly reduced the temperature within the reactor vessel, progressively arresting biological processes, enabling maintenance work to commence.

Marc White, director of Carrier Rental Systems, said: “The hire approach provides a highly cost-effective solution for such energy-from-waste plants based on a biodigester. In the case of heating during the initial phase, it overcomes the need to invest in permanent capital plant for customers, which would in any case no longer be needed after the first few weeks of commissioning.

“At a more advanced stage of the production cycle, hire chillers are an excellent option in order to stop the activity within the biodigester, as they allow essential maintenance and upgrade work to be carried out much more quickly and effectively, and at less cost.”

www.carrierrentalsystems.co.uk