The increasing need to improve profitability is a top priority for every sawmill’s management team. For both owners and managers there is a constant pressure to reduce costs and fully utilise resources. To this end, the use of the mill’s co-products as a fuel for combined heat and power plants (CHP) is becoming more attractive and commonplace.
This ability to produce both heat and power from a mill’s own small-scale power plant, by burning biomass from the mill itself, has been made possible by recently introduced technologies and products from Wärtsilä Biopower Oy.
Using BioPower technology, sawmills can typically convert 15-25% of the energy content of their co-products to electricity, and 55-70% to usable heat, depending on the process requirements and connections.
For example, in 2003 Wärtsilä delivered a BioPower CHP plant to Finnforest Corporation’s Vilppula sawmill in central Finland. With an annual production of 600,000m3, Vilppula is one of the world’s largest sawmills. The new CHP plant has an electrical output of 2.9MW and a heat output of 13.5MW. The plant also features an integrated 9.0MWth heat boiler fired by biomass.
In operation since early 2004, the plant has produced over 70% of the electricity needed by the sawmill as well as all the heat needed for wood drying. In addition, the plant also produces most of the district heat required for the town of Vilppula with its 2,000 inhabitants and local industrial enterprises.
Wärtsilä has also delivered a BioPower 2 HW plant with an electrical output of 1.3MW and a heat output of 8.0MW to Finnforest’s 280,000 m3/year sawmill in Renko in southern Finland. This plant, too, was brought into commercial operation at the beginning of 2004.
Long-term energy solutions
The main fuel for the new plants is the bark produced on site. “This solves the problem of energy generation at both sawmills in terms of sustainable development,” said Markku Kauppinen, technical director of Finnforest Corporation.
“If the market price of electricity continues to rise as strongly as at present, our improved self-sufficiency will have even greater value, besides being an economically feasible option which brings long-term competitiveness,” he added.
A Wärtsilä BioPower plant is also in operation in the Republic of Ireland at Grainger Sawmills Ltd. This plant has an electrical output of 1.83MW with a heat output of 3.5MW and was integrated into the existing sawmill using 400m of new conveyor system to deliver fuel from various locations around the site together with heat and electrical connections to suit the existing arrangement. The site installation work started in October 2003 with thermal production in April 2004 and electrical production in June 2004.
Standard solutions
The basic feasibility of biomass projects can be improved if the scale is such that all the fuel is available locally, but this necessitates the use of relatively small-scale steam systems. While these systems suit the local fuel availability and possible restrictions on grid connection, the cost of small-scale steam plant can be challenging.
However, following on from many years’ experience in building a wide range of engine-based power stations and CHP plants, Wärtsilä feels it has a cost-effective solution for turnkey biomass plants. The Wärtsilä BioPower plants are highly modular and based on proven standard components with a conservative design approach. This enables fast delivery and installation with many projects operational within one year from order.
