Steam Plant & Boilers

Steam Plant & Boilers

Dr. Ahmed F. Elsafty

Mechanical and Marine Eng. Dept.

Arab Academy for Science, Technology and Maritime Transport.

References:

.1: بحرية – هندسة معلوماتمرسى. محمود م

2. Introduction to Marine Engineering.D. A. Taylor.

Thermodynamics:

The T-S Diagram:

T

S

K

kJ/kg K

Liquid

Wet MixtureSuper Heat

Carnot Cycle:

• Is the most efficient cycle for given temperatures of source and sink.

Rankine Cycle:

4-1 Boiler 2-3 Condenser

1-2 Turbine 3-4 Pump

Rankine Cycle with Superheat:

• 1st Tube bank: Dry Sat. Steam at 6• 2nd Tube bank: Superheated steam at 1[ smaller bore

tubes]

• Receiver:– Can receive stem from other boilers.

• Surge Tank or hot well:– Science the quantity of feed water varies with

the different demands on the boiler, it is necessary to provide a storage of condensate between the condenser and the boiler feed pump.

Rankine Cycle with Superheat:

Efficiency:

• Rankine Efficiency=

QWWb

pT

R

boiler in the suppliedHeat

outputNet work

We always neglect pump work<<<< WT

Boilers:

• Simplified boiler arrangement.

Boiler Types:

1. Water-tube:– High pressure– High temperature– High capacity steam applications.

e.g. – Steam for main propulsion turbine– Cargo pump turbines.

Water-tube boilers:

• Foster Wheeler D-Type Boiler

Due to its D shape.

Water-tube boilers:

Foster Wheeler Type ESD I boiler- [External Super-heater D]Foster Wheeler Type ESD I boiler- [External Super-heater D]

1st S/H

2nd S/H

Water-tube boilers:

Foster Wheeler Type ESD III mono-wall boiler

Water-tube boilers:

Foster Wheeler radiant-type boiler

Heat is transmitted by infra-red radiation.

[ESD VI]

Furnace wall construction:

Mono-wall or membrane wall.

Tangent wall

Boiler Types: [cont’d]

2. Fire-tube:– Small quantities– Low pressure steam.

e.g.– For Auxiliary purposes as on diesel engine

powered ships.

Fire-tube Boilers:

1. Package boiler

Package boiler

Fire-tube Boilers:

2. Cochran boiler

3 .Composite boilers:

• Permits steam generation either by oil firing when necessary or by using the engine exhaust gases when the ship is at sea.

Fire-tube Boilers:

Boiler Types: [cont’d]

3. Other Boiler arrangements:– Steam-to-steam generators.– Double evaporation boilers– Exhaust gas exchangers– Auxiliary steam plant system– Exhaust gas boilers

Other Boiler arrangements:

Horizontal Steam-to-steam generator:

Other Boiler arrangements:

Double evaporation boilers

Primary circuit is a conventional water-tube boiler, which provides steam to the heating coils of a

steam-to-steam generator, which is the secondary system.

The complete boiler is enclosed in a pressurized casing.

Other Boiler arrangements:

• Exhaust gas heat boiler

• Auxiliary steam plant system [in diesel powered tankers]

Boiler Mountings [fittings]:

• Safety valves.• Main steam stop valve.• Auxiliary steam stop valve.• Feed check or control valve.• Water level gauge.• Pressure gauge connection.• Air release cock.• Sampling connection• Blow down valve.• Scum valve.• Whistle stop valve.

• Automatic feed water regulator.

• Low level alarm.

• Super-heater circulating valves.

• Sootblowers.

Boiler Mountings [fittings]:Water-tube boilers

Water level gauges:

Tubular gauge glassPlate-type gauge glass

Water level gauges:

Water level gauges:

Remote water level indicator

Safety valves:

Ordinary spring-loaded safety valve

Safety valves:

Improved high-lift safety valve

Safety valves:

Soot blower

Combustion:• Air supply.

– Forced draught [fans]

• Fuel supply system.

Fuel burning:

Pressure jet burner

Fuel burning:

Rotating cup burner

Fuel burning:

Steam blast jet burner

Boiler operation:• Follow the instruction manual for your boiler.

But In general:• Preparation:

1. Check the uptake for exhaust gases. i.e. any damper should be operated.

2. All vents, alarms, water and pressure gauge connections should be opened.

3. The super-heater circulation valves or drains should be opened to ensure a flow of steam through the super-heater.

4. All drains and blow-down valves should be closed.

Boiler operation:• Preparation:

5. The boiler should be filled to slightly below the working level with hot de-aerated water.

6. The various header vents should be closed as water is seen to flow from them.

7. The economizer should be checked to ensure that it is full of water and all air vented off.

8. Forced draught fan should be operated.

9. Valves of the fuel oil system should be checked for correct positioning….etc.

10. Circulation and heating of fuel.

Raising steam:

• Start the draught fan for 5 min.

• Turn the burner on.

• Adjust the fuel pressure to ensure complete-steady combustion.

• Close the super-heater header vents once steam issues from them.

•