The process of energy conversion in PLTU takes place through 3 stages, namely:
First, the chemical energy in the fuel is converted into heat energy in the form of pressurized steam and high temperature.
Second, the heat energy (steam) is converted into mechanical energy in the form of rotation.
Third, the mechanical energy is converted into electrical energy.
The steam power plant uses a closed-air steam fluid working fluid. The closed cycle means using the same fluid repeatedly. The sequence of circulation is briefly as follows:
The first water is loaded into the boiler until it fully fills the entire surface of the heat transfer. In this water boiler is heated with hot gas burning fuel with air so it turns into steam.
Second, the steam produced by the boiler with a certain pressure and temperature is directed to rotate the turbine so as to produce a rotating mechanical power.
Thirdly, a direct coupled generator with a rotating turbine generates electrical energy as a result of the rotation of the magnetic field in the coil, so that when the turbine is rotated it generates electrical energy from the output terminal of the generator
Fourth, the exhaust steam out of the turbine enters the condenser to be cooled with cooling water to convert back into water called condensate water. The condensed condensate water of the steam is then used again as boiler feeding water.
Thus the cycle is continuous and repetitive.
The power plant cycle which is a closed cycle can be described with a T - s diagram (Temperature - Entropy). This cycle is the application of ideal rankine cycle. The sequence of steps is as follows:
a - b: Water is pumped from pressure P2 to P1. This step is an isentropic compression step, and this process occurs at the filler water pump.
b - c: The pressurized water is raised in temperature until it reaches its boiling point. Occurs in LP heater, HP heater and Economiser. .
c - d: Water transforms into a saturated vapor. This step is called vapourising (evaporation) with isotherar isotherm process, occurs in boiler that is in wall tube (riser) and steam drum.
d - e: Steam is heated further until the steam reaches its working temperature to superheated vapor. This step occurs in the boiler superheater with isobar process.
e - f: Steam performs work so that the pressure and temperature drop. This step is an isentropic expansion step, and occurs inside the turbine.
f - a: The heat dissipation of the latent steam so that it turns into condensate water. This step is isobar isothermis, and occurs inside the condenser.
Parts of PLTU
Main Section
The main parts contained in a PLTU are:
Boiler
The boiler serves to convert water (feed water) into superheated steam to be used to rotate the turbine.
Steam turbine
The steam turbine serves to convert the heat energy that the vapor contains into a rotating energy (mechanical energy). The turbine shaft is coupled with the generator shaft so that when the turbine spins the generator also spins.
Condenser
The condenser serves to condense the spent vapors from the turbine (steam that has been used to rotate the turbine).
Generator
The generator functions to convert the turbine energy from the turbine into electrical energy.
Supporting Tools
The supporting equipment contained in a steam power plant in general is:
Desalination Plant (Unit Desal)
This equipment serves to convert brine into fresh water by distillation method (combination of evaporation and condensation). This is because the nature of sea water is corrosive, so if the seawater is allowed directly into the main unit, it can cause damage to the PLTU equipment.
Reverse Osmosis (RO)
It has the same function as desalination plant but the method used is different. In this equipment used semi-permeable membrane that can filter salt-salt contained in sea water, so that fresh water can be produced as in desalination plant.
Pre Treatment on units using groundwater / river cooling
For steam power plants that use groundwater / river water, pre-treatment functions to remove sediment, dirt and minerals contained in the water.
Demineralizer Plant (Unit Demin)
Serves to eliminate the mineral content (ion) contained in fresh water. Water as the working fluid of the steam power plant must be free of minerals, because if water still contains minerals it means that its conductivity is still high so it can cause GGL induction when the water passes through pipeline in PLTU. This can cause corrosion of PLTU equipment.
Hydrogen Plant (Hydrogen Unit)
PLTU used hydrogen (H2) as coolant Generator.
Chlorination Plant (Chlorine Unit)
Serves to produce sodium hypoclorite compounds (NaOCl) used to intoxicate / weaken marine microorganisms in the water intake area. This is intended to avoid scaling of condenser pipes and desal units due to the proliferation of marine micro organisms.
Auxiliary Boiler (Boiler Aid)
Generally an oil-fueled boiler, which serves to produce steam (steam) used at the time of the main boiler start up and as auxiliary steam (auxiliary steam).
Coal Handling (Coal Service Unit)
Is a unit that serves the coal processing of ship loading and unloading (ship unloading) on the dock, the distribution to the stock area until the distribution to the bunker unit.
Ash Handling (Unit Services Abu)
It is a unit that serves both ash ash and fly ash from Electrostatic Precipitator hopper and SDCC (Submerged Drag Chain Conveyor) on the main unit to ash valley (ash valley)
Each major component and supporting equipment is equipped with systems and tools that support the work of the component. Disorders or malfunctions of one of the major component parts will be able to cause disruption to the entire PLTU system.
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Also read the following related article
PLTU Power Cycle
Boiler working principle
The working principle of condition
