Industrial Steam turbine Based power plants
1) These are
thermal power plants.
2) Fuel used
in these power stations is Coal, Oil or Natural gas. (Fossil fuels)
3) In many countries steam turbine power plants
produce bulk of the energy.
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4) In
these plants Boilers convert chemical energy of the fuel into heat energy and
iturbines use this energy in steam coming from Boiler to rotate the generator
and produce electricity.
5) In
refineries oil is abundantly available as bi product hence oil will be uded
as fuel, otherwise coal or natural gas are used based on cost and
availability.
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First step :Conversion of chemical energy to heat
In the Boiler furnace, Fuel and air mixture is burnt and
enormous heat energy is released.
Second Step :Conversion of heat into mechanical energy
In steam turbine the energy in the steam is employed to rotate the turbine.
Which in turn operates the generator to produce power.
Associated processes in Steam
Turbine based Power plants
Feedwater heating and deaeration
The feedwater used in the boiler is a means of transferring heat energy
from the burning fuel to the mechanical energy of the spinning steam turbine.
The total feedwater consists of recirculated condensate water and
purified makeup water. Because the metallic materials it contacts are
subject to corrosion at high temperatures and pressures, the makeup water is
highly purified before use. A system of ion exchange.
Deaeator primarily helps to remove dissolved oxygen from
feedwater in addition it also helps to condition the water by dosing various
chemicals.
In deaerator water is sprayed and maintained at high
temperature to help the oxygen to escape
from the system. Remaining oxygen is eliminated by dosing oxygen removing
chemical hydrazine, Ph controlling chemicals are also dosed in Deaerator..
Boiler operation
The boiler is a rectangular furnace of around 40 feet height and 20 feet
length and width.
Oil is fired from four burners located in front side. Air required for
effective combustion is fired through a fan.
Steam turbine generator
The turbine generator consists of 13 stages of blades. Steam starts to flow
from first stage at 103 Kg/Cm2. At fourth stage it reaches 42 Kg/Cm2. At the
final stage pressure is maintained at vacuum.
Steam
condenser
The condenser condenses the steam from the exhaust of the turbine into
liquid to allow it to be pumped. If the condenser can be made cooler, the
pressure of the exhaust steam is reduced and efficiency of the cycle increases.
The condenser is usually a shell and tube type heat exchanger.
Cooling water circulates through the tubes in the condenser's shell and the
low pressure exhaust steam is condensed by flowing over the tubes as shown in
the adjacent diagram.
The condenser, in effect, creates the low pressure required to drag steam
through and increase the efficiency of the turbines. The limiting factor is the
temperature of the cooling water and that, in turn, is limited by the
prevailing average climatic conditions at the power plant's location
From the bottom of the condenser, powerful condenstae pumps recycle the
condensed steam (water) back to the water/steam cycle through deaerator.
