Steam control for advanced waste disposal

Spirax Sarco's steam control equipment lies at the heart of one of the UK's most advanced waste disposal facilities.

Spirax Sarco's steam control equipment lies at the heart of one of the UK's most advanced waste disposal facilities.

The Compact Power Avonmouth plant in Bristol uses a sophisticated system of pyrolysis, gasification and high temperature oxidation to dispose of up to 8000t of waste per year.

Offering lower costs than conventional disposal methods, the plant heats waste to 800C in the absence of oxygen releasing hydrocarbon gases.

In a separate operation the carbon residues are gasified using high temperature steam to produce hydrogen and carbon monoxide.

The combined gases are subsequently oxidised at 1250C, releasing energy and producing a low-NOx and zero-dioxin exhaust gas.

Heat released from the process is fed to a 25bar(g) steam boiler that powers a steam turbine to generate electricity, which is used on site.

The list of Spirax Sarco equipment in the plant spans the company's full product range.

Products installed include boiler level controls, automatic boiler blowdown systems, a blowdown vessel, deaerator heads, pressure reducing stations, isolating and safety valves, flowmeters and a condensate return system.

A custom-engineered turbine bypass station is also installed to bypass steam from the turbine when it is not in use.

The station takes in steam at 25bar(g) from the boiler and reduces it to 0 bar(g) via a desuperheater, from which it is passed to a condenser for recirculation back to the boilerhouse.

Controlling the high steam velocities and resulting superheat presented a technical challenge to Spirax Sarco engineers, but one which they have solved to produce a unit that runs extremely efficiently.

Avonmouth is the first commercial plant of its type and is used to process difficult substances such as clinical, pharmaceutical and other special wastes.

"The plant has more than met its objectives by demonstrating the technology's reliability, extremely low emissions and that, being modular, it can be scaled up easily", explains John Acton, Chief Executive of Compact Power.

"Larger plants could export electricity".

"Quite early on we decided to standardise on Spirax Sarco products because of their high quality, excellent availability of spares, good documentation and the company's engineering expertise.

We also sent some of our engineers to attend steam courses at the Spirax Sarco training centre in Cheltenham", says Acton.

According to Acton, Compact Power is now looking at building a second commercial plant, possibly in Dumfrieshire in Scotland, at a site for which the company has already gained planning permission.

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