Steam turbines for electricity generation

HEAT EXCHANGER Heat is extracted to raise steam to drive conventional turbines for electricity generation. 

Turbines for electricity generation are limited in their efficiency, in part by moisture present in the steam but also by the partial condensation that occurs during the loss of energy when work is done by steam passing over the turbine blades. Thus, an increase in steam temperature over and above that required for saturation (through the use of a superheater) reduces the potential for condensation to occur and raises the efficiency of the combustion-to-electrical generation process, perhaps by 4 to 5%. 

At a power plant, superheated steam at about 560°C (833 K) is used to drive a turbine for electricity generation. The temperature of the heat sink is about 38°C (or 311 K). The efficiency is given by... 

Btu/lb (11.6-15.8 milfion joules/lb). It is the most abundant economically recoverable coal globally and the main fuel burned in steam turbine-powered electric generating plants. Some bituminous coals, known as metallurgical or coking coals, have properties that make them suitable for conversion to coke used in steelmaking. Subbituminous coal has a 46-60... 

For a good detailed discussion of steam generation through the use of pulverized coal, the reader is referred to [89] and [91]. The use of gas turbines, and more specifically the combined cycle operation, offers a potentially attractive alternative route to steam turbines for power generation. Such a combined cycle is shown in Fig. 8.25 where it is seen that the fuel is burned in a gas turbine which generates electric power moreover, the exhaust gases from... 

Since 1900, manufacturers have made many step changes in the basic design of steam turbines. New technology and materials have been developed to support the industry s elevation of steam conditions, optimization of thermal cycles and unit capacity. Steam turbines will continue to be the principal prime mover for electricity generation well into the twenty-first century. 

Thermal solar farm generated heat used for electricity generation by steam turbine. 

The biomass fuelled IGCC demonstration plant at Vamamo consists of a 18 MW pressurised circulating fluidised bed gasifier, a 4,2 MW gas turbine and a 1,8 MW steam turbine. The low heat value gas produced in the gasifier is cooled in a gas cooler and cleaned in a candle filter at a temperature of 350-400°C before it is combusted in the gas turbine. The flue gas from the gas turbine is used for the production of steam in the heat recovery steam generator. The steam is superheated, together with steam from the gas cooler, and supplied to the steam turbine. Besides electricity, 9 MW heat for district heating purposes is produced. 

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