UK: Temporary chillers are being used to provide essential cooling during the service and maintenance of energy-from-waste biodigester plants.

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.

During maintenance, the process must be reversed and a chiller is used to cool the contents of the biodigester in order to arrest biological activity.

Carrier Rental Systems has been in the position of being able to supply temporary equipment for both the heating and cooling processes. In addition to supplying packaged boiler plant for the start-up process, the Surrey-based company can also supply packaged Carrier AquaForce 30XA air-cooled screw chillers to stop the process.

In a recent example, Carrier Rental Systems supplied a 100kW Carrier 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.

Explaining the benefits of using hire equipment, Marc White, director of Carrier Rental Systems, said: “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.”