New generation biomass power plant

Paul Boughton

Control technology helps deliver green energy as innovative biomass power plant goes on stream in Italy.

With the design and build of power stations often delayed by planning objections or lengthy construction timescales, Siemens' PCS7 process control system has been utilised on a new generation biomass power plant which is attracting worldwide interest from parties seeking green energy solutions.

Staffordshire, UK-based, Biomass Power Ltd and solution partner, Capula Limited, have specified Siemens' PCS7 control technology to help support a market-leading turnkey design and build power plant solution and overcome the traditional challenges facing any power station development.

Set up in 2009, Biomass Power Ltd brought together the industry knowledge of a number of experts with in-depth experience of the biomass and general power sector.[Page Break]

Gap in the market

Under the leadership of managing director, Ben Talbott and engineering director, Martin Riley, the company spotted a gap in the biomass power plant market. Their solution was to seek to overcome the inherent issues normally associated with biomass power station development, such as planning restrictions, development timescales and fuel handling limitations.

Martin Riley, from Biomass Power, explains: "While biomass plants have been around since 2000, in the UK obstacles to obtaining planning permission for power plants that were often in excess of 30 metres high was becoming a real problem. Potential development was being delayed as planners and communities objected to large-scale building construction.

"Add to this the considerable timescales involved in the thermal design of the process technology and delivery of the building on-site and it was clear that an alternative approach was required.

"We thought there must be another way of dealing with the problem. The key to our market offering has been our ability to create the entire biomass gasification process in a horizontal and modular turnkey format, as opposed, for instance, to the traditional and large-scale vertical solution.

"We design and manufacture at our premises and then simply turn up on site to effectively bolt the design together, thereby saving significant amounts of time and expense.

"This approach allows us to confine the entire biomass power plant process technology solution within sub 10 metre high buildings and as a result counter-acts planning objections about scale, as well as drastically reducing the construction timeframes.

"Our plants, for example, do not look out of place within any normally recognised industrial site."[Page Break]

Smaller-sized power stations

Biomass Power concentrate upon smaller-sized power stations of up to 5MWe, viewing them as the way forward in terms of generating green power within locations that would not be able to accept larger-sized buildings towering over the surrounding area. In addition, the Biomass approach is also based strategically on local supply, such as seeking to create fuel for its power plants directly generated from waste materials available from local sources.

Alongside the modular plant design created by Biomass Power, sits the highly attractive flexibility with the process technology able to handle a wide envelope of waste streams for fuel. While the majority of biomass plants across Europe seek only the cleanest fuels from which to develop power, Biomass Power's solution enables it to easily handle an extensive list of waste streams including forestry, agricultural residues, straw and miscantus.

Martin Riley continues: "We don't look at clean biomass fuel, we look at waste - and especially local waste - as the key source of fuel from which to generate energy. Our technology allows us, unlike many others, to process a diverse range of waste matter. This offers real flexibility to the marketplace and is why we are receiving a lot of interest from across the world in our technology."[Page Break]

The Italian Job

One of the first Biomass Power plants about to be commissioned in the summer of 2012 is located in Bagnolo di Po, Rovigo in Italy.

The multi-million pound contract has seen the construction of a biomass power plant set in a highly rural agricultural region where there would have been strong opposition to any proposal to build a traditional and large-scale power plant.

In this case, the horizontally-based and less intrusive Biomass Power design concept was accepted by the local planners.

The plant has a capacity of 15-20MW thermal and is rated at 3.25-4.25MWe gross producing green electricity which is to be exported to the grid.

In the Bagnolo region, as well as using local farming residue as fuel, the subsequent electricity generated by the plant will provide power to the local general hospital and the renewable energy power plant is anticipated to help save nearly 12,000 tonnes of carbon annually.[Page Break]

Gasification process

The plant's technology is based upon a highly optimised process of gasification, followed by secondary combustion which has the capability of handling a wide range of fuels at levels of up to 30-40,000 tonnes per year.

A heavy duty moving floor feeds the fuel into a reciprocating step grate via a finitely controlled metering device. The grate gasifies the fuel to produce a volatile gas. This is then combusted at above 850°C to ensure complete combustion.

Once the gasification and then secondary combustion is complete, the hot gas is exchanged via a water tube boiler into 450°C steam at high pressure. This is then used to produce high efficiency electricity in a vacuum condensing turbine.

Finally, once the hot gases are released from the boiler at low temperature they go through a dust filtering treatment process which monitors flue gas emissions constantly to ensure compliance with existing emission standards.[Page Break]

Standardised approach

Martin Riley explains the benefits he derives from the selection of PCS7: "We began discussions with combustion experts Capula for the Bagnolo and future projects, as we wanted to move away from previous control systems which we felt were often dis-jointed, hard to upgrade and challenging to maintain over a period of time.

"Capula identified the standardised approach and operational efficiencies we could obtain via Siemens' PCS7 control system.

"We closely examined the benefits it would deliver and the combination of many valued enhanced control features such as fault-finding and real time data availability, together with Siemens' worldwide back-up and ongoing technical support, made it the ideal choice as the control system for our turnkey power plants going forward."

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