Method of Improving Steam Turbine Efficiency

Today more than 1,300 steam-turbine power plants in the country at least 30 years old, electric utilities and independent power producers today must optimize these plants to improve efficiencies to reduce operating and maintenance (O&M) costs, and to remain competitive.

The aim of every steam turbine design is an optimum efficiency operation characterizing an optimal energy conversion. Overall efficiency of a steam turbine power plant, however, strongly depends on the turbine's performance. Thus any improvement, however slight, can increase power availability, decrease equipment and component costs, and generate sizeable operating savings. In today's highly competitive and deregulated market, optimizing steam turbine operation is no longer a goal but, rather, a necessity for power producers to remain competitive.

Since a steam turbine's efficiency ultimately depends on its condition, relative to its design, as a turbine's condition deteriorates with use its efficiency degenerates proportionately. A thorough evaluation of a steam turbine's design and operating condition can help increase a plant's efficiency by identifying improvements in one or more of three areas:-

Method of Improving Steam Turbine Efficiency :
The following methods are used to improve the efficiency of steam turbine :

  1.  Reheating of steam ; 
  2.  Regenerative feed heating ;and 
  3.  Binary vapour plants . 

Reheating of steam :-
In "reheating of steam", the steam is removed from the turbine when it becomes wet.It is then reheated at a constant pressure by the flue gases, until it is again in the superheated state.It is then returned to the next stage in the turbine.
The reheating of steam in a turbine has the following advantages :
1. It increases the work done through the turbine.
2. It increases the efficiency of the turbine.
3. It reduces the wear on the blades, because of low moisture contents in low pressure stages of the turbine.

 Regenerative feed heating :-
In"regenetative feed heating", the heat is transfered from the steam in the turbine to the liquid(condensate)flowing around the turbine, such that the temperature of steam and liquid being same at any section in the turbine.

The process of draining steam from the turbine, at certain points during its expansion and using this steam for heating the feed water(in feed water heaters)and then supplying it to the boiler is known as "bleeding", and the corresponding steam is said to be bled.The effect of bleeding are :
1. It increases the thermodynamic efficiency of the turbine.
2. The boiler is supplied with a hot water.
3. A small amount of work is lost by the turbine, which decreases the power developed.

 Binary vapour plants :-
In"a binary vapour plant", mercury and steam is used.

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