Steam power plant equipment list

In our previous blog, we have discussed the Equipment of the steam power plant that was the part on, and in our second part, we are going to discuss the other equipment of the steam power plants such as prime mover, spray pond, cooling tower, control room, switchyard.

prime mover

A Prime mover is a device that converts stored energy in steam into rotating mechanical energy.

Prime movers used in steam power plants are either reciprocating engines or steam turbines.

 The most common steam turbines used are impulse turbines and reaction turbines. And the other different types of turbines are condensing and non-condensing turbines, back pressure steam turbines, extraction steam turbines.

Steam turbine gives high speed (standard speed is 3000 rpm and 1500 rpm. The maximum sizes of these turbines are 1000 MW.

spray ponds and cooling tower

Before learning about the function of spray ponds and cooling towers, let’s look at their necessity in power plants.

In modern fossil-fuel steam power plants, about 10-15% of heat input is rejected in the atmosphere through the chimney, while 48-52% of the input heat is rejected to cooling tower and spray ponds through the condenser.

To cool this big amount of heat in cooling towers, a large amount of water is required. Artificial water sources or natural water sources like rivers, seas, lakes/canals, etc.

Water is pumped from the water source to an open channel and taken to the circulating pump through strainers. Where strainers are also known as mesh basket, which is used to remove large and small debris particles from a high quantity of steam.

After passing through strainers, this circulating water will pump through condenser tubes. During this process, the circulating water takes up the heat of exhaust steam, and it becomes hot.

The hot water from the condenser is discharged at a suitable location towards the down source.

The above explained is the cooling process of hot exhaust gases in the cooling towers or spray ponds.

In case if the natural or artificial source of water is not available as a source of cooling water from the condenser, which is generally warm water can be cooled and reused for the purpose.

In this case, water is first obtained from a tube well or some other source and stored in the tank. Then, it is pumped into the condenser from the tank, usually by a centrifugal pump.

The water there absorbs the latent heat from the exhaust steam and gets warm; the warm water is then cooled utilizing spray ponds or cooling towers. Small plants use spray ponds, and medium and large plants use cooling.

spray pond

The spray pond consists of a water tank. Hot water is distributed by pipes throughout and sprayed through nozzles at a suitable pressure.

The water is cooled by both convection and evaporation. The sprayed water comes in contact with the atmospheric air and is cooled. Mostly the water is cooled by evaporation as the heat for evaporation is withdrawn from the water itself with the result that it is cooled.

A small amount of cooling due to conduction and radiation also. Since the cooling is mainly affected by evaporation, it is necessary to expose as large a surface as possible.

In the design of spray ponds, the most important part is the nozzle, and it must produce spray, not a sheet of water. Therefore, the spacing between nozzles should be around 2.5 – 3 meters and about 1.2- 2.5 meters above the water’s surface.

cooling tower

A cooling tower is a wooden or metallic rectangular structure packed with baffling devices inside.

The hot water is led to the tower top, falls down through the tower, and is broken into small particles while passing over the baffling devices. Air enters the tower from the bottom and flows upward.

 The air vaporizes a small percentage of water, cooling the remaining water. Finally, the air gets heated and leaves the tower at the top. The cooled water falls down into a tank below the tower from where it is pumped to the condenser, and the cycle is repeated.

The splitting of water into small droplets, the draught provided by the tower, and the large evaporating surface help to cool water very quickly- practically during the time while it is descending.

Although eliminators are provided at the top of the tower to prevent the escape of water particles with air, there is a loss of water to the extent of around 5%. This loss has to be made up of water drawn from a well or other sources.

Air can be circulated in cooling towers the natural draught, mechanical draught, or mechanical natural draught.

In natural draught, air movement is induced by a large chimney and the difference of densities between the air inside and outside the chimney.

In mechanical draught, fans move air, either induced that pulls the air through the tower or the forced type that pushes the air through.

A combination of mechanical and natural draught incorporates both a chimney and fans. The natural draught towers are being gradually replaced by mechanical draught types because the latter requires less pumping head, less space, and less windage loss.

control room

The control room is the power plant where all the devices can be operated remotely.

This device includes a panel of alternator and feeder, synchronizing gear, protective gear, automatic voltage regulator, communication arrangement, etc.

A separate battery room and motor-generator set or rectifier are also installed for supplying to make and trip the circuit of switchgear.

switchyard

The switchyard of the power plant includes transformers, circuit breakers, and switches for connecting and disconnecting the transformer and circuit breaker, lightning arrester for the protection of the power station against lightning strokes.

In short, the switchyard contains all the electrical protecting equipment.