POWER PLANT AUTOMATION USING PLC

BY:

SACHIN GUPTA(07BEE062)

PRASHANT YADAV(07BEE058)

UNDER GUIDANCE OF:

PROF. M.T.SHAH

What is Power Plant

Generation of electric power Classification on the basis of the form of

energy converted into electrical energy 1 Steam Power Stations 2 Hydroelectric Power Stations 3 Diesel Power Stations 4 Nuclear Power Stations

What is Automation

Automation is a word used in modern industries to express enhancement of operational efficiency

It’s main function is to reduce human interaction without losing the efficiency of the process

Utility Of Automation

Optimizes the use of process control equipment

Decreases the response time for process

Provides information about process status

Manages process logic at the plant floor level

Increases overall productivity and plant efficiency

Advantages Of Automation System

Higher productivity Superior quality of end product Efficient usage of raw materials and

energy Improved safety in working condition.

Drawback Of Relay Based System

These systems are prone to errors due to the involvement of humans in the data collection and processing using complicated mathematical expressions

Slow and inefficient processing Hard Wired Logic Control Bulky and complex wiring, also involves

lot of rework to implement changes in control logic

Thermal power plant

A generating station which converts heat energy of coal combustion into electrical energy

It contribute maximum to the generation of Power for any country.

It constitute 75.43% of the total installed captive and non-captive power generation in India.

Boiler

It is a closed vessel in which steam is produced from water by combustion of fuel

The boiler is the most important part of any power plant because it has very critical parameters & these must be controlled for continuous operation

Its automation decides the efficiency of a power plant

Critical Control Parameters In Boiler

Level Control Temperature Control Flow Control Pressure Control Combustion Control

Benson Boiler

Most boilers has main difficulty of formation and attachment of bubbles on the inner surface of the heating tubes.

It reduces heat flow and steam generation as they offers high thermal resistance than water film.

But in Benson boiler, pressure is raise to critical pressure (225 atm) so that steam and water have same density . So, it eliminate danger of bubble formation

Main principle of Benson boiler is that it eliminates the latent heat of water by first compressing the feed to a pressure of 235 bar, it is then above the critical pressure and its latent heat is zero

It makes use of Forced Circulation It does not use any drum

Diagram Of a Benson Boiler

Specifications of a Benson Boiler

Maximum Temperature is 650 degree Celsius

Maximum Working Pressure is 500 atm Generating Capacity is 150 tonnes/hr

Advantages Of Benson Boiler

Require less floor area Total weight is 20% less than other boilers because it has no drum, it reduces cost Start very quickly because of welded

joints Furnace walls can be more efficiently

protected by using smaller diameter and closed pitched tubes

Operated most economically by varying the temperature and pressure at part loads and overloads

Explosion Hazards are not severe as it consists of only tubes of small diameter and very little storage capacity

Superheater in a Benson boiler is an integral part of forced circulation , so no special starting arrangement for superheater is required

What is PLC

Programmable logic controller (PLC) is a defined by a National Electrical Manufacturers Association (NEMA) as a ”digital electronic device that uses a programmable memory to store instructions and to implement specific functions such as logic, sequence ,timing , counting and arithmetic operations to control machines and processes ”

It is used to execute complicated control operations in a plant

Advantages Of PLC

Reduced Space Energy saving Modular Replacement Easy trouble shooting Error diagnostics programmer Economical Greater life and reliability

Block Diagram of PLC

How PLC Works

Level Control The water level in the steam drum has to

be maintained within the desired limits. The reduction of drum level below the

low level mark will cause tube failures and level above the high level mark will cause water carry over to the turbine.

For controlling purpose, direct level gauge is used. A low level trip to shut down the boiler in case the water level falls below the allowable limit and a very high level trip the alarm circuit.

Temperature Control

During start up of the boiler adequate steam flow is not established through the super heater.

High rate of heat input if provided to the boiler furnace, will result in high furnace outlet temperature of the flue gas causing over heating and tube failure.

To control the rate of heat input into the boiler and maintain the flue gas temperature leaving the furnace , thermocouple sensor is used

Flow Control

For the generation of steam to be continuous, the air flow, fuel flow, water flow etc. should be adjusted simultaneously.

The flowmeter is a pipeline transducer, which converts flow into a measurable signal.

Pipeline transducer is likely to relate flow to differential pressure. This pressure signal is received by another transducer i.e. DP (differential pressure) transmitter converting differential pressure into an electrical signal.

Conclusion

The most important aspect of any power plant is the boiler control. Several techniques can be implemented to control the boiler in power plant. The method that has to be used relies on varied objectives like superior quality, increased efficiency, high profit etc.

Emphasis has been given to the automation process that is now rapidly taking its place in all the power plants across the globe.

References

A TEXTBOOK OF POWER PLANT ENGINEERING BY R.K.RAJPUT

A TEXTBOOK OF PLC AND INDUSTRIAL AUTOMATION BY MITRA AND SENGUPTA

A HANDBOOK OF POWER PLANT ENGINEERING

Future Scope

In next session , we will discuss pressure control ,

combustion control Also, control these parameters by

ladder logic using PLC

THANK YOU

Pressure Control

Combustion Control

Thermocouple

Made by connecting two dissimilar metals to create a small voltage (5 to 6 mV @ 100°C) Voltage changes with change in temperature Types1 Type T: Copper-Constantan Red/Blue2 Type J: Iron-Constantan Red/White3 Type E: Chromel-Constantan Red/Purple4 Type K: Chromel-Alumel Red/Yellow

Thermocouple Temperature measured in °C

K 0°C to 1180°C E -200°C to 870°C J 0°C to 750°C T -200°C to 350°C K Type thermocouple is used primarily

because of it’s better linearity

Bourden Tube

It contains a curved tube that is open to external pressure input on one end and is coupled mechanically to an indicating needle on the other end

The external pressure is guided into the tube and causes it to flex, resulting in a change in curvature of the tube. These curvature changes are linked to the dial indicator & indicate the corresponding value

Ladder logic for a lamp which is on for 5 min and then off for 5 min and this process is repeated for 1 hour