[home] [Personal Program] [Help]

---

Session: Operational experience I
Session starts: Monday 07 October, 10:00
Presentation starts: 10:40
Room: Ruys & Rijckenvorsel Zaal

---

Stefano Ganassin (Triogen B.V.)
Quirijn Eppinga (Triogen B.V.)
Jos van Buijtenen (Triogen B.V.)

Abstract:
Organic Rankine Cycle systems are generally meant to convert relative low temperature heat into electricity. However, ORC systems have also proven themselves to be more versatile in cases of small sizes up to 1 MWe, irrespective of temperature. In the case of biomass combustion, the heat source temperature is high enough to motivate a water/steam cycle, unless the amount of heat to convert is small. Here ORC systems come also into play. As most ORC working fluids have a limited chemical stability at high temperatures, intermediate fluid circuits are applied for heating the evaporator. This can be either a thermal oil loop, or a system based on pressurized water. Apart from the extra investment, complexity and need for emergency cooling, such systems tend to increase losses in terms of heat transfer and pumping power for circulation. Moreover, the available temperature is not used for optimal Carnot efficiency. Based on the application of a chemically stable hydrocarbon, a system was designed for the direct heating of the working fluid by flue gasses from the combustion of biomass. Flue gasses, as they leave the biomass combustor, are cooled down to 530 °C by mixing with ambient air or recirculated flue gas. This temperature level is sufficient for the ORC working fluid to reach its desired highest cycle temperature of 325 °C. Moreover, condensable salts condense to particles and are separated before they can hit the heating surface of the evaporator, thus avoiding the formation of eutectic layers on the heating surfaces. Two units have been build using the Triogen 165 kWe ORC system: one based on a moving grid combustor and one based on a fluidized bed combustor. Specifics of plant lay-out will be given, together with first operating experience. The combined systems of biomass combustion and ORC open the possibility to use biomass for small scale electricity production. Units, so far only designed for the supply of heat for drying or district heating, can be extended to cogeneration plants for very flexible power-to heat ratios.