Off-Design Study of District Heating Power Plants on Base of Combined CycleProcesses with Peat as Fuel

摘要

District heating power (DHP) plants on base of combined cycle processes provideboth high energy efficiency and high ratio between electricity and district heat production. Since there are big indigenous deposits of peat in Finland, its use as fuel is of special interest. In this work the off-design of these DHP plants is studied. The changes regarding to the design point are the water content of wet peat, which is fed to the process, and the outside temperature. Before these examinations the DHP plants are designed. From the numerous alternatives one representative of each of the two fundamental possibilities 'Combustion' and 'Gasification' is chosen: (1) Pressurized Fluidized Bed Combustion (PFBC) plant and (2) Integrated Gasification Combined Cycle (IGCC) plant (with total gasification). In design the emphasis is on the examination of using an integrated steam or flue gas dryer in the DHP plants. For both design and off-design the parameters of interest are the peat input, the district heat and electricity production (gas turbine and steam turbine cycle) as well as the efficiencies and the power factor. The studies are carried out by the help of the PROcess SIMulationprogram PROSIM.