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Power Generation Overview

Power generation using fossil fuel fired steam supply systems involves the conversion of the chemical energy in the fuels into electrical energy.  This energy conversion requires many complicated systems and components.  The steam generator gets relatively cheaper and smaller in size as the fuel consideration changes from solid coal to oil and to gas.  This is why the type of fuel, fuel transportation, fuel handling and storage at site, fuel processing requirements before combustion, and the final products of combustion are very important at the inception of a power generation project, especially with regard to siting and environmental effects.  The fuel systems, whether pulverized coal, oil, or gas, must be carefully designed and engineered to match the rate of steam generation and energy production.

 The steam circuit includes numerous systems associated with a typical power generating plant. The main cycle alone includes such systems as the main steam system, the hot reheat system, the cold reheat system, the condensate system, the feedwater system, the extraction steam system and the heater drain system.  Each of these systems, requires physical piping drawings and schematic piping and instrument diagrams of the equipment, piping, valves, and the controls and instrumentation included in the system as well as the system process flow.

The power plant heat rejection system consists of another important group of equipment  This system includes very large circulating water pipes and circulating water pumps and appurtenances which pass cold water through the condenser tubes to condense the cascading exhaust steam on the outside of the tubes from the low pressure turbine.  For once through systems, the circulating water system flows from a river through the condenser and then back into the river where the rejected heat is dissipated further downstream.  In closed loop systems, the circulating water flows from the basin of a hyperbolic natural draft cooling tower or mechanical draft cooling tower to the condenser tubes and then returns warm water to the tower where the heat is dissipated to the air in counterflow to the warm water cascading to the basin at the bottom of the tower.  Some plants have large lakes which are used for heat dissipation instead of towers. 

The demineralized water treatment system of the plant supplies treated water to the main cycle condensate to “makeup” for any losses due to leaks or blowdown. Similarly, a source of makeup water and a treating system are supplied for closed loop circulating water systems to make up for evaporative losses.

The plant service water system supplies large amounts of water at the station for cooling, washing and flushing. Service water is used for cooling various equipment heat exchangers such as turbine oil coolers, generator hydrogen coolers and hydraulic coupling coolers; for general station service such as hose and wash connections and for flushing.  Recirculated demineralized water is usually provided for cooling various fan and pump bearings, and for air compressor cylinders and coolers.

 In addition to the major systems, there are systems for venting equipment, drainage, heating, air conditioning, sealing, control and instrumentation, sampling, fuel handling, ash handling depending on the type of plant.