Lecture 10_PPE_Unit 3: Steam and Gas Power Plants

Program: Diploma (Mechanical)
Class: TY (ME) Semester: V
Course: Power Plant Engineering
Code: 22566
LECTURE 10:
Unit: 3. Steam & Gas Power Plants

02
wwwwwwwwwwww....ssssaaaannnnddddiiiippppffffoooouuuunnnnddddaaaattttiiiioooonnnn....oooorrrrggggMechanical Engineering Department, Sandip Polytechnic, NashikMechanical Engineering Department, Sandip Polytechnic, NashikMechanical Engineering Department, Sandip Polytechnic, NashikMechanical Engineering Department, Sandip Polytechnic, Nashik
Name of theName of theName of theName of the Trainer : Prof. Rushikesh Deoram SonarTrainer : Prof. Rushikesh Deoram SonarTrainer : Prof. Rushikesh Deoram SonarTrainer : Prof. Rushikesh Deoram Sonar
Years ofYears ofYears ofYears of Experience : 10Experience : 10Experience : 10Experience : 10
DomainDomainDomainDomain Expertise : Mechanical EngineeringExpertise : Mechanical EngineeringExpertise : Mechanical EngineeringExpertise : Mechanical Engineering
Qualification: M.E. (Design Engineering)Qualification: M.E. (Design Engineering)Qualification: M.E. (Design Engineering)Qualification: M.E. (Design Engineering)
Contact Details:Contact Details:Contact Details:Contact Details:
+91 9890481959+91 9890481959+91 9890481959+91 9890481959
rushikesh.sonar@sandippolytechnic.orgrushikesh.sonar@sandippolytechnic.orgrushikesh.sonar@sandippolytechnic.orgrushikesh.sonar@sandippolytechnic.org

03Unit III: Steam & Gas Power Plants
TOPICS COVERED IN PREVIOUS LECTURE:
TOPICS TO BE COVERED IN THIS LECTURE:
3.2 Steam Power Plants3.2 Steam Power Plants3.2 Steam Power Plants3.2 Steam Power Plants
* Fuel Handling Systems* Fuel Handling Systems* Fuel Handling Systems* Fuel Handling Systems
TOPICS TO BE COVERED IN THIS LECTURE:
* Steam Power Plants* Steam Power Plants* Steam Power Plants* Steam Power Plants
3.2.9 Pulverized Fuel Handling Systems3.2.9 Pulverized Fuel Handling Systems3.2.9 Pulverized Fuel Handling Systems3.2.9 Pulverized Fuel Handling Systems
3.3 Electro3.3 Electro3.3 Electro3.3 Electro----static Precipitatorsstatic Precipitatorsstatic Precipitatorsstatic Precipitators
3.4 Control Systems in Steam Power Plants3.4 Control Systems in Steam Power Plants3.4 Control Systems in Steam Power Plants3.4 Control Systems in Steam Power Plants
3.5 Maintenance Procedure3.5 Maintenance Procedure3.5 Maintenance Procedure3.5 Maintenance Procedure

3.2.9: PULVERIZED FUEL HANDLING SYSTEMS: IN POWER PLANTS
Two methods are in general use to feed the pulverized fuel to the combustion chamber of the power plant.
First is ‘Unit System’ second is ‘Central or Bin System’.
In unit system, each burner of the plant is fired by one or more pulverizers connected to the burners, while in
the central system, the fuel is pulverized in the central plant and then disturbed to each furnace with the help
of high pressure air current.
Each type of fuel handling system consists of crushers, magnetic separators, driers, pulverizing mills, storage
bins, conveyors and feeders.
The coal received by the plant from the mine varies widely in size. It is necessary to make the coal of uniform
size before passing the pulverizer for efficient grinding.
The coal received from the mine is passed through a
preliminary crusher to reduce its size to allowable limit
(30mm). The crushed coal is further passed over magnetic
separator which removes pyrites and trapped iron.

3.2.9:
PULVERIZED FUEL
HANDLING
SYSTEMS: IN
POWER PLANTS

3.2.9: PULVERIZED FUEL HANDLING SYSTEMS: 1. UNIT SYSTEM
In this system, each burner or a group of
burners and pulverizer constitute a unit.
Crushed coal is fed to the pulverizer through
feeder at a variable rate governed by the
combustion requirements of furnace and
steam generating rates required in the
boiler.
Hot air or fire gases are passed through the
feeder to dry the coal before feeding to the
pulverizer. The pulverized coal is carried
from the mill with the help of primary air
fan. This further carries the coal through
short delivery pipe to the burner. The
secondary air is supplied to the burner
before entering the fuel into the combustion
chamber.

3.2.9: PULVERIZED FUEL HANDLING SYSTEMS: 1. UNIT SYSTEM - Advantages
(1) It is simple in layout and cheaper than central system.
(2) The coal transportation system is simple.
(3) It allows direct control of combustion from the pulverizer.
(4) The maintenance charges are less as spares required are less.
(5) In the replacement of stokers, the old conveyor system can be used.
(6) Coal which requires drying for satisfactory function of the central system is generally supplied without
drying in the unit system.
(7) It affords better control of fuel feed into the furnace.

3.2.9: PULVERIZED FUEL HANDLING SYSTEMS: 1. UNIT SYSTEM - Disadvantages
(1) The mill operates at variable load as per load on the power
(2) The total capacity of all mills must be higher than for the central system with the load factors common in
practice.
(3) The degree of flexibility is less than that of central system.
(4) In event of failure of the auxiliaries of one of the burner, the burner has to put off as there is no reserve
capacity.
capacity.
(5) The fault in preparation unit may put the entire steam generator out of use.
(6) Strict maintenance is desired as the operation of the plant directly depends upon the pulverizing mill.
(7) There is excessive wear and tear of the fan blades as it handles air and coal particles.

3.2.9: PULVERIZED FUEL HANDLING SYSTEMS: 2. CENTRAL SYSTEM
The crushed coal is fed to the drier from the
raw coal bunker by gravity. The drying of coal is
effected either by using hot gases, preheated air
or bled steam. The dried coal is fed to the
pulverizer with the help of feeder. The
pulverized coal is carried from the pulverizer
mill with the help of air and it is separated in the
cyclone separator.
cyclone separator.
The separated pulverized coal is transferred to
the central bunker (bin) with the help of
conveyor. The central system uses practically all
the equipments used in the unit system with
higher capacity of each part. Storage bins are
also used in addition to other equipments. This
bin may contain from 12 to 24 hours supply of
pulverized coal. The energy consumption of this
system lies between 15 to 25 KWHr per ton of
coal pulverized.

3.2.9: PULVERIZED FUEL HANDLING SYSTEMS: 2. CENTRAL SYSTEM - Advantages
(1) The central system is flexible and changes can be made to accommodate quick changes in demand.
(2) There is greater degree of flexibility as the quantity of fuel and air can be separately controlled.
(3) The pulverizer always runs at its rated load irrespective of the load on the plant, therefore its power
consumption per ton of coal crushed per hour is less.
(4) Burners can be operated independently of the operation of coal preparation.
(5) The pulverizer can be shut down when sufficient reserve capacity has been achieved. The same can be
used during peak load periods.
(6) The fan handles only air therefore there is no problem of excessive wear of fan blades.
(7) It offers good control over the fineness of coal.
(8) The boiler accessories are unobstructed.

3.2.9: PULVERIZED FUEL HANDLING SYSTEMS: 2. CENTRAL SYSTEM - Disadvantages
(1) The initial setup cost is high and occupies a large space.
(2) The power consumption of auxiliaries is high.
(3) The overall power consumption per ton to coal handled is higher than unit system.
(4) There is possibility of fire hazards due to the stored pulverized coal.
(4) There is possibility of fire hazards due to the stored pulverized coal.
(5) The coal transportation system becomes more complex.
(6) Dryers are essential.
(7) The operation and maintenance charges are higher than the unit system of same capacity.

3.3: ELECTROSTATIC PRECIPITATOR: Introduction
An electrostatic precipitator (ESP) is defined as a
filtration device that is used to remove fine particles
like smoke and fine dust from the flue gases.
Electrostatic Precipitator can also be defined as a
type of air cleaner or filter that utilizes electric
energy for removing the impurities, dust particles
energy for removing the impurities, dust particles
from the air.
It is the commonly used device for air pollution
control. They are used in industries like steel
plants, thermal energy plants.

3.3: ELECTROSTATIC PRECIPITATOR: Working Principle
It consists of two sets of
electrodes: positive and negative.
The negative electrodes are in the
form of a wire mesh and the
positive electrodes are in the form
of plates.
These electrodes are vertically
The gas borne particles such as ash are ionized by the high voltage discharge electrode by the corona effect.
These particles are ionized to negative charge and are attracted to positively charged collector plates
These electrodes are vertically
placed and are alternate to each
other and connected to a DC
Source.

Electrostatic smoke precipitators work by forcing dirty flue gas (the gas escaping from a smokestack) past
two electrodes (electrical terminals), which take the form of metal wires, bars, or plates inside a pipe or smokestack.
The first electrode is charged to a very high negative voltage. As the dirt particles move past it, they pick up a negative
charge.
Higher up the pipe (or further along, if it's a horizontal pipe), there's a second electrode consisting of metal plates
charged to a high positive voltage (50,000–00,000 volts is typical).

Since unlike charges attract, the negatively charged soot particles are attracted to the positively charged plates and stick
there.
From time to time, the collecting plates have to be shaken to empty away the soot; that can be done either manually (by
someone brushing them clean) or automatically (by some kind of automated shaking or brushing mechanism in a process
called rapping).

3.3: ELECTROSTATIC PRECIPITATOR: Advantages & Disadvantages
3.3 ELECTRO-STATIC PRECIPITATOR (Advantages)
The durability of the ESP is high.
It can be used for the collection of both dry and wet impurities.
It has low operating costs.
The collection efficiency of the device is high even for small particles.
It can handle large gas volumes and heavy dust loads at low pressures.
It can handle large gas volumes and heavy dust loads at low pressures.
3.3 ELECTRO-STATIC PRECIPITATOR (Disadvantages)
Can’t be used for gaseous emissions.
Space requirement is more.
Capital investment is high.
Not adaptable to change in operating conditions.

3.3: ELECTROSTATIC PRECIPITATOR: Applications
The most common application of Electrostatic precipitator is an industrial application for a smoke, which is
accumulation of hard elements floating in the atmosphere.
The dry electrostatic precipitators are used for collecting dry particles like cement, ash, etc.
The wet electrostatic precipitators are used for removing the wet particles like oil, tar, resin, acid, etc.
Electrostatic Precipitators are used in steam plants for removing the dust from flue gases.
Electrostatic Precipitators are used in machine shops and chemical plants for removing oil mists and acid mists.
Electrostatic Precipitators are used in machine shops and chemical plants for removing oil mists and acid mists.
These are used to clean the blast or metallurgical heating system gases.
ESPs are used to remove the bacteria and fungus in the medical field.
ESPs are used in air conditioning systems for sanitizing air.
ESPs are used to recover the materials in the flow of gas.

3.4: CONTROL SYSTEMS OF POWER PLANTS: TYPES
1. ANALOG
Analog control is the representation of numerical quantities by means of physical variables such as current, air
pressure, voltage, rotation, resistance, Electromagnetic Field (emf), etc.
Analog control over the last 30 years has consisted primarily of two types:
(A) Pneumatic: The use of air pressure ( or other gases occasionally) as the power source to represent numerical
values.
(B) Electronic: The use of current, voltage, resistance, emf etc. As the power source to represent numerical
values.
values.

2. Microprocessor-Based Control Stations
These are a digital standalone single controller type, or a split-architecture control system offering powerful,
configurable control capability on a modular basis.
These units can accept standard analog electronic inputs plus digital inputs and give analog outputs plus digital
outputs.
By connection to a data highway for communication, other operator interfaces are easily added.
By connection to a data highway for communication, other operator interfaces are easily added.

3. Computer-Based Control Stations
Direct Digital Control (DDC) Or Supervisory Control (SC).
DDC control can perform all of the control functions, operator displays and graphics, reports and calculations
for efficiency and controller tuning, or a computer can be used as a supervisory control for analog control
system, microprocessor based control units, or as a data logger with graphic displays.
Choice of analog versus microprocessor based control units or computer (DDC) (SC) should be based on relative
cost and future requirements.
cost and future requirements.

3.4: CONTROL SYSTEMS OF POWER PLANTS: DESIRABLE CHARACTERISTICS
1. Accuracy : effective controls generate accurate data and information.
2. Timeliness : There are many problems that require immediate attention.
3. Flexibility : The business and economic environment is highly dynamic in nature.
4. Acceptability : Controls should be such that all people who are affected by it are able to understand them
fully and accept them.
fully and accept them.
5. Integration : When the controls are consistent with corporate values and culture, they work in harmony with
organizational policies and hence are easier to enforce.
6. Economic feasibility : The cost of a control system must be balanced against its benefits.
7. Corrective action : An effective control system not only checks for and identifies deviation but also is
programmed to suggest solutions to correct such a deviation.

3.5: STEAM POWER PLANT CONTROLS: MAJOR CONTROLS
1. Combustion control
2. Feed water control
3. Steam turbine generator control
4. Safety devices and interlocks
5. Flow meters
6. Pressure gauges
7. Temperature sensors :-
7. Temperature sensors :-
a. Thermometers
b. Thermocouples
c. Resistance temperature detector
d. Transmitters

3.6: MAINTENANCE PROCEDURE OF MAJOR COMPONENTS OF STEAM POWER PLANT
There are generally 3 types of maintenance philosophies followed in most of the plants :
Preventive Maintenance
Condition based Maintenance
Breakdown Maintenance

In this lesson, We have learnedIn this lesson, We have learnedIn this lesson, We have learnedIn this lesson, We have learned
SUMMARY
3.2.9: PULVERIZED FUEL HANDLING SYSTEMS IN POWER PLANTS
3.3 : ELECTRP-STATIC PRECIPITATOR
3.4 : CONTROL SYSTEMS OF POWER PLANTS
3.5 : STEAM POWER PLANT CONTROLS
3.6 : MAINTENANCE PROCEDURE OF STEAM POWER PLANTS

Our Next Video Lecture Topic
3.7 : GAS TURBINE POWER PLANT
3.7.1 & 2: OPEN CYCLE AND CLOSED CYCLE POWER PLANTS
3.8: COMPONENTS OF GAS TURBINE POWER PLANTS
Till Then Stay Connected,
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3.8: COMPONENTS OF GAS TURBINE POWER PLANTS
3.9: METHODS TO IMPROVE THERMAL EFFICIENCY
3.10: MAINTENANCE OF MAJOR COMPONENTS OF GAS POWER PLANTS

Lecture 10_PPE_Unit 3: Steam and Gas Power Plants

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