Mono Muncher smells sweet at Holsworthy Biogas

A Mono TR Muncher installed at a Devon Biogas plant keeps the digestion process working efficiently, plus ensures that the plant complies with the regulations on animal by-product disposal

A Mono TR Muncher installed at Holsworthy Biogas Plant in Devon is not only keeping the plant digestion process working efficiently, but is ensuring that food waste is reduced to a particle size of 12mm to comply with the regulations governing animal by-product disposal.

Holsworthy is home to the UK's first Biogas Plant, taking in 75,000 tonnes of food waste and animal manure per year and using the gases produced by anaerobic digestion to generate electricity and piped hot water, which is utilised by the surrounding community.

The digestion process requires the waste to be in a mostly liquid form when it is pumped into the digestion tank, to achieve maximum efficiency in gas production.

Therefore, the waste is pumped to the TR Muncher which macerates and reduces it to a homogenous product, ideal for the digestion processes.

The Mono TR Muncher is a twin shaft, low speed, high torque grinder.

Biodegradable waste passes through a series of cutters, which revolve at differential speeds to pull apart, crop and shear any solids, such as bones, flesh, offal and vegetable waste.

Liquid passes through the cutter stacks, whilst the solids are trapped and macerated to a small, consistent particle size, to help comply with legislation and improve process efficiency.

The design of the Muncher incorporates an intelligent auto reverse sequence controller, which enables the Muncher to unblock itself and restart automatically when necessary, without the need for manual intervention.

The cutter stacks are inclined at 25 degrees from the vertical axis to allow any solids that are difficult to grind to drop clear of the cutters into the trash trap, on reversal of the cutter stacks.

The trash trap is fitted with a large diameter access port to enable easy removal of any rejected debris.

The design also saves on maintenance downtime and associated costs, as the cantilever drive shaft eliminates the need for bottom seals and bearings, significantly reducing wearing components and offering cost savings on replacement parts.

The complete drive, gearbox and cutter assembly can be easily and quickly removed from the unit casing without removing the main body from the pipework, saving time on routine maintenance procedures.

The regulations regarding the disposal of animal by-products state that particle size cannot exceed 12mm and the ability of the Muncher to achieve this was a key consideration in the specification of the equipment.

Mono was able to reassure the plant engineers that the TR Muncher would stand up to the challenge.

This particular Muncher is fitted with 8.0mm thick cutters, a primary consideration in controlling particle size.

The cutters also have seven teeth around the circumference to further control the particle 'length' between the tooth cropping action.

Lastly, in order to offer a consistent and effective 'cut' on fleshy and stringy material the two cutter shafts rotate at different speeds - tearing and ripping the fleshy material, combined with a scissor action across the opposing cutter faces.

Installed in 2005, the TR Muncher has operated faultlessly and the engineers at the Holsworthy Plant have been delighted with its performance.

Commenting on the Muncher, Operations Director Jake Prior said "We have been very pleased with the performance of the TR Muncher.

Its capabilities also reassure us that we are fully compliant with current regulations ".

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