Spirax Sarco and Dallol Energy solve wet biomass limit 09 May 2014

Spirax Sarco and Dallol Energy have delivered the boiler controls and steam system for a wet biomass system designed to deliver steam to a distillery and to heat 200 neighbouring Scottish homes via district heating.

The Wick, Caithness, plant is now owned and operated by Ignis Wick – a subsidiary of Ignis Biomass – which took it over from Highland Council in 2012 after the initial project experienced technical and commercial problems.

Victor Buchanan, director at Dallol Energy, explains that, with most of the old equipment stripped out of the energy centre building, his company delivered a 3.5MW boiler and plant steam distribution system designed to use locally sourced clean woodchips as the fuel.

"For this project we needed a reputable partner that could help us design, commission and install a whole new boiler house and steam distribution system," states Buchanan, director at Dallol Energy.

"We knew we could trust Spirax Sarco's knowledge and technology and they were happy to trust our biomass expertise," he adds.

The biomass boiler generates steam at 20 bar g, with the plant steam system reducing pressure to 10 bar g before sending some to the Pulteney Distillery, while the rest passes through a heat exchanger that generates hot water for the district heating scheme.

Key to the success of this project was the innovative use of a steam accumulator vessel, which acts as a buffer between the biomass boiler and the rest of the steam circuit.

This completely handles steam demand variations but also deals with the usual disadvantage of wet biomass boilers in steam raising duty – that of the long ramp up time from start-up to delivering process steam.

"This application can completely change the way that wet biomass steam systems are used in the future," insists Buchannan.

"Any distillery, food factory or commercial steam user that is run on fossil fuel can benefit from a massive reduction in energy costs, made even more attractive by the government in the shape of the RHI [Renewable Heat Incentive]," he continues.

"Supply chain sustainability is also a big plus and there is certainly a marketing advantage to run off local forestry rather than gas or oil from goodness knows where."

Buchannan also insists that the long-term cost of running the system on wet biomass fuel is significantly lower than dried biomass, since prior drying of the fuel is not required.

In addition, a wider range of fuel is available, including wood that can be sustainably sourced from local forestry suppliers, with prices that follow the local wood market instead of international energy markets.

Spirax Sarco provided the accumulator to Ignis specifications, along with all steam distribution equipment, including the heat exchanger skids and the boiler house controls on the project, as well as the boiler hot well and steam accumulator.

The boiler house has been equipped with supervisory control and monitoring systems and level controls, as well as automated heat recovery blowdown systems to minimise energy losses.

There are also two backup oil-fired boilers on standby, covering biomass boiler maintenance, etc.

Brian Tinham

Related Companies
Ignis Biomass Ltd
Spirax Sarco Ltd

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