The main equipment of steam turbine plant consists of a boiler unit and a steam turbine.
In the steam boiler biofuel is burnt to produce heat energy, as a result feed water is converted into high temperature and high pressure steam, which then comes to the steam turbine where it performs mechanical work by expanding to lower pressure and therefore rotating turbine blades to produce electric energy in the generator. Steam extracted from the turbine is directed for process needs as well as for hot water heating for technological purposes, district heating, hot water supply, ventilation, humidity control. Heat energy may be converted into cold energy in the form of chilled circulating water in absorption refrigerating machines. Since for cold generation in such case biomass energy is used by means of extracted steam transformation through absorption chillers, the chilled water is sometimes called “bio-cold”.
For the purpose of correct boilers selection we use different technological solutions in terms of fuel combustion technologies selected: grate firing, bubbling fluidized bed (BFB) and circulating fluidized bed (CFB). Burning technology selection is according to specific properties of biomass to be combusted. Important properties of the biofuel are the following: volatile content, humidity, calorific value, ash content, chlorine and sulphur content, ash melting point temperature. We analyze solid fuel in laboratories before recommendation provision on the combustion technology selected.
Technical and economically feasible capacity of steam turbine plants using biomass is within the range of 2-30 MW of electric power.
When there are requirements for a smaller capacity, the steam piston engine could be installed with being feasible from 300 kWel till 2 MWel.