Modular biomass avoids trouble in the fields

London – The startup of a new biomass plant in Bagnolo di Po, Rovigo in Italy, scheduled soon, could mark a significant step forward for the bio-power industry, the plant’s UK developers believes.

The facility has a capacity of 15-20 MW thermal and is rated at 3.25-4.25 MWe 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.

But the most significant aspect of the project is the way it has avoided planning challenges in such a rural agricultural region, according to Biomass Power Ltd, which developed the technology for the multi-million pound project.

Staffordshire-based-Biomass Power was set up in 2009, under the leadership of managing director, Ben Talbott and engineering director, Martin Riley, who spotted a gap in the market – the need to overcome the planning restrictions, development timescales and fuel-handling limitations of biomass power plants.

“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 meters high was becoming a real problem,” explains Riley.

“Developments 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.”

To address these issues, Biomass Power developed an entire biomass gasification process in a horizontal and modular turnkey format – as opposed to the traditional and large-scale vertical solution.

The modular structure meant components could be manufactured at the company’s own premises and then assembled on site, thereby saving time and money.

This approach allows the company to confine the entire biomass power plant process technology solution within sub 10 meter high buildings, according to Riley.

“[This] counter-acts planning objections about scale, as well as drastically reducing the construction timeframes,” he commented. “Our plants, for example, do not look out of place within any normally recognised industrial site.”

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.

The 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. Biomass Power’s process technology is said to handle a wide range of waste streams including forestry, agricultural residues, straw and miscantus

“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,” said Riley. “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.”

The plant’s technology is based upon an 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.

With regard to selecting a control system for the process, Riley explains: “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.”

Enhanced control features such as fault-finding and real time data availability, together with worldwide back-up and ongoing technical support, made the Siemens system “the choice as the control system for our turnkey power plants going forward,” Riley concluded.