Optimisation of Biomass-fired Cogeneration Plants Using ORC Technology

orc2019 Tracking Number 5

Biomass-fired cogeneration projects are usually initiated in locations where a heat market exists and therefore most of the biomass-fired ORC systems had been installed in district heating systems. The biomass-fired modules are added to existing fossil-fuel-fired heating plants within either backfitting or modernisation projects focused on using locally available feedstock and making profits out of electricity generation and emission reduction. The critical issue of such projects is optimal design of the biomass-fired block and its integration with the existing heat only plant. The energy, ecological and economic performance of the integrated technological system depends on a set of decision variables concerning plant’s components and structure, working fluid selection, construction and operational parameters. The optimisation task must be properly formulated under site-specific economic and ecological constraints including different strategies to sell electric energy generated in cogeneration. In this paper the municipal heating plant in Krosno (Poland) is taken into account as the reference case. In 2013 there was commissioned the biomass biomass-fired cogeneration system with the Turboden T14 CHP SPLIT unit of 1255 kW net electric power. Basing on the operational experiences from this unit an optimisation study is performed in order to examine the influence of current economic and legal conditions on the optimal design characteristics of the plant. New structure of the plant is determined and compared with the existing one. There are taken into account different structures of the ORC unit (simple, with regeneration, with split heat exchanger), different working fluids, exhaust gas latent heat recovery unit, heat storage vessel and network water cooler. Different electricity, biomass and coal prices are taken into account as well as the influence of the EUA (European Emission Allowance) price is examined. The results reveal importance of the optimisation of design parameters as well as the dependence of the plant’s size and structure on local economic conditions.