SMALL SCALE BIOMASS FUELLED PLANTS FOR COMBINED HEAT AND POWER

asme-orc2015 Tracking Number 59

A high efficiency Organic Rankine Cycle (ORC) power unit of 165 kWe has been developed by Tri-O-Gen B.V. of The Netherlands. The ORC system is based on a thermally stable hydro-carbon as a working fluid, hence suitable for direct use of intermediate temperature heat sources. The unit is capable of transforming heat flows at temperatures between 350 and 600 ºC into electricity. Typical applications involve the exhaust gasses of gas- or diesel engines and small gas turbines. Further applications involve biomass combustion, incinerators, industrial residual heat and industrial flares. This paper describes the application of biomass fuelled cogeneration units, as in operation and on order now. Wood or biomass is gaining interest as energy source for small district heating networks, while it is already widely used when available as a by-product, e.g. in sawmills. During combustion, temperatures reached are way above the level needed for the heating purpose. Hence, there is a considerable amount of exergy available, which can be used to generate electricity. By applying an Organic Rankine Cycle (ORC) system, flue gasses from the wood combustor deliver their high temperature heat to be converted into electricity, leaving lower temperature heat to be supplied to the district heating grid, or to be used for local heating and drying. This can be done in various ratios between power and heat, thus following the varying heat demand while maintaining total system efficiency. Triogen developed an innovative system, where the ORC is connected directly to the flue gas flow, without the need of an intermediate system, including connections to the available heat sink. The system set-up, flue gas cleaning and eventual evaporator cleaning are described in this paper, together with operational experience gained so far in several units.