Energy Conversion System

Energy Conversion System1Topics to be covered:BoilerSteam CondenserDirect Energy Conversions:- Tidal, Geothermal energy etc.Jet Propulsive devicesRocket Propulsion2Unit I- Boilers Outcomes- You will be able to

Understand Boiler and its type.Explain classification of boiler.Analyze performance of chimney .

3The Theory of Producing SteamWater boils at 100C under atmospheric pressure. By higher pressure, water boils at higher temperature - e.g. at pressure of 10 bar boiling temperature is 184C. During the boiling process, pressure and temperature are constant, and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase. When all the water is vaporized , the steam is called dry saturated. In this condition the steam contains a large amount of latent heat. Further heating of dry saturated steam will lead to increase in temperature of the steam.Superheated steam4Steam GeneratorBoiler-: Boiler is an apparatus to produce steam.

Thermal energy released by combustion of fuel is used to make steam at the desired temperature and pressure.

The steam produced is used for:(i) Producing mechanical work by expanding it in steam engine or steam turbine.(ii) Heating the residential and industrial buildings(iii) Performing certain processes in the sugar mills, chemical and textile industries55Steam Generation TheoryWithin the boiler, fuel and air are force into the furnace. There, it burns to produce heat. From there, the heat (flue gases) travel throughout the boiler. The water absorbs the heat, and eventually absorb enough to change into a steam.To the left is the basic theoretical design of a modern boiler. Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water.

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7Boiler properties:

(i) Safety. The boiler should be safe under operating conditions.(ii) Accessibility. The various parts of the boiler should be accessible for repair and maintenance.(iii) Capacity. Should be capable of supplying steam according to the requirements.(iv) Efficiency. Should be able to absorb a maximum amount of heat produced due to burning of fuel in the furnace.(v) It should be simple in construction .(vi) Its initial cost and maintenance cost should be low.(vii) The boiler should have no joints exposed to flames.(viii) Should be capable of quick starting and loading.

8CLASSIFICATION OF BOILERS1. Water tube and Fire tube-Fire tube Boilers Water-tube Boilers The hot gases passes through the The water passes through the tubes tubes that are surrounded by water. and the hot gases produced by combustion of fuel, flow outside.

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Water tube- BABCOCK WILCOX BOILER112. According to the position of principle axis.(i) Vertical (ii) Horizontal (iii) Inclined3. According to position of furnace.(i) Internally fired: the grate combustion chamber are enclosed within the boiler shell(ii) Externally fired: furnace and grate are separated from the boiler shell.

4. According to the circulating water.(i) Natural circulation: Circulation set up by convection current or by gravity (ii) Forced circulation: Circulation set up for high pressure steam through pumps.

125. According to steam pressure.(i)Higher pressure: Boilers producing steam 80 bar and above are called High pressure boilers.eg- Babcock and Wilcox Boiler.(ii) Low pressure Boilers: Boilers producing steam Lower than 80 bar are called Low pressure boilers.eg-Cochran Boiler.6. According to application.(i) Stationary : Boilers which are used with stationary plants.(ii) Mobile: Boilers which are fitted on mobile carriages are called Mobile Boilers. (Marine, Locomotive)

13Comparison between water tube & fire tube Fire Tube Boilers Water Tube Boilers Hot gases inside the tube Water inside the tube Generally internally fired Externally fired Pressure limit 16 bar 100 bar Not suitable for large power Suitable for large power plant. Plant. Lesser risk on explosion More risk on explosion Occupies more floor area Occupies less floor area Difficult construction Simple construction Treatment of water not Treatment of water necessary necessary

14BOILER MOUNTINGS AND ACCESSORIES

BOILER MOUNTINGS :The necessary devices installed or mounted for the safety of boiler and its control are called boiler mountings.

15Boiler Accessories:

The devices which are installed in the boiler for their efficient operation and smooth working are called Boiler Accessories.

16Boiler Mountings for safety:

water level indicatorsTwo safety valves.Combined high steam and low water safety valve.Fusible plug.

Boiler Mountings for control:Pressure gaugeJunction or stop valveFeed check valveBlow-off cockMan hole and mud hole

17Boiler Accessories for efficient operation:

Water heating devices.Water feeding devices.Super heaterEconomizerAir preheater

18WATER LEVEL INDICATOR

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SC & WC- controlling the passage of water and steam.When these cocks are opened the water stands in the glass tube ate the same level as in boiler.C drain cock to blow out water.

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WATER LEVEL INDICATOR PRESSURE GAUGE (Bourdons)Essential feature is gauge is elliptical spring tube .Siphon tube is filled with condensed water.The steam pressure force the water into elliptical tube.Outward movement is magnified by link and transmitted to T.

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SAFETY VALVESDead Weight safety valve

A is vertical cast iron pipe.V is gun metal valve and VS is gun metal valve seat.D is cast iron pipe for discharge steam.The steam pressure acts in the upward and balanced by the force of dead weights W.

Merits :-Simplicity of design.Gives satisfactory performance.

DEMERITS:- Unsuitable for mobile boilers. Not suitable for high pressure boilers.

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LEVER SAFETY VALVEWhen steam pressure becomes greater than normal working pressure the valve is lifted.It is fitted on boiler shell.Valve is made of gun metal.One end of lever is hinged and other end suspended a weight W.

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SAFETY VALVES

when pressure of steam rises above a certain level main valve V1 raises and it discharge excess steam.when the level of water falls below a certain level valve V2 raises and it discharge steam .HIGH STEAM AND LOW WATER SAFETY VALVE

FUSIBLE PLUGProtects boiler against damage due to due to overheating for low water level.When water level decreases, fusible plug gets uncovered by water and exposed to steam.upon melting of lining the fusible metal falls down and water falls from this opening onto furnace and thus quenches fire.

As water level goes down the heat available from furnace could not be completely utilized for steam formation and so the overheating may cause melting of fusible metal. Fusible metal is a low melting point metal. Thus upon melting of lining the copper plug (fusible metal) falls down and water falls from this opening onto furnace and thus quenches fire.26BLOW-OFF COCKIt is used for periodical cleaning by discharging the water and sediments from bottom of boiler

Blow off cock is fitted to the bottom of boiler shell.

Plug has rectangular opening which when comes in line with inlet and outlet passage then blow off cock is open and when opening is not in line then cock is closed.

Blow off cock has a plug of conical type put into the mating casing. Plug position is altered for opening and closing the flow27MANHOLEThis is provided at suitable position on the boiler shell so that the man can enter into boiler shell for inspection, maintenance and repairs. This hole is usually made in elliptical shape of the size convenient for a man to enter through this hole. The opening is closed by steam tight cover.JUNCTION VALVE:

The valve placed directly on a boiler in order to regulate the steam supply from boiler to steam pipe is called the Junction Valve.

STOP VALVE:

The valve used to regulate the steam supply from the steam pipe to the prime mover (steam engine or steam turbine) is called Stop Valve.FEED CHECK VALVEIt is a non return valve.

at the end of delivery pipe from feed water pump and is placed on boiler shell slightly below normal water level

During normal operation the check valve lifted due to the pressure of water from the feed pump and water fed into the boiler.

during the non working of feed pump the pressure in boiler shell is more and so the checkvalve gets closed.

It has a check valve whose opening and closing are regulated by the position of spindle30ANTIPRIMING PIPEIt is attached below the stop valve to avoid the water particles being carried away along with steam. It has closed pipe with closed ends of 1m and 2m length. The top side of the pipe has perforations. When the steam passes through it, due to inertia effect, the moisture of steam falls into the pipe and the steam with reduced moisture passes into the stop valve.BOILER ACESSORIESThe devices used to improve the performance and operation of the boilers are called boiler accessories. Feed pumpPump which is used to deliver feed water to the boiler.Reciprocating feed pumps are continuously run by steam from the same boiler.Other feed pumps are run either by small steam turbine or electric motor.

33Economiser34Heating feed water before enters in boiler.Recovers some heat from waste hot gases going to the chimneyIncreases Boiler efficiency.

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EconomiserSuper heater36A super heater is a device used to convert saturated steam or wet steam into dry steam by increasing its temperature.

It consists a set of small diameter U-Tubes in which heat flows and take the heat from flue gases.

Maximum steam temp in superheater reaches is about 540 c.Steam generated in the boiler passes the valve C and enters the U-tube through intake header.steam made dry and superheated in this tube and then taken for use through valve B via uptake header.Dampers control the quantity of flue gases. If superheated steam is not needed thn valve B and C will be close and steam has taken through valve A.

36Types of super heaterConvective super heater- the heat of the flue gases is transferred to the surface of superheater by convection. These are located at the path of hot flue gases

Radiant super heater- the heat of the flue gases is transferred to the surface of superheater by radiation. These are located at one or more wall of the furnace. Used in high pressure boiler.

Combination type of super heater- Combination of above two.

37Air preheater38

Increase the temperature of air before it enters the furnace.Recovers some heat from waste hot gases going to the chimney.Adv-Reheating of air increases furnace temperature it results rapid combustion of fuel with less soot, smoke and ash.It placed between economizer and chimney.38INJECTOR39Use to feed water into the boiler.

It consists set of nozzle.

Kinetic energy of steam is used to increase the pressure and velocity of the feed water.

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ReferenceMahesh M. Rathore, Thermal Engineering.Onkar Singh, Applied Thermodynamics.R.K.Rajput, Thermal Engineering.

4243Thank You