Answer to Question #293633 in Mechanical Engineering for king

Question

 Explain the constructional details and working of the following boilers in details. ➢ Cochran Boiler ➢ La-Mont Boiler ➢ Velox Boiler Also write their significance and applications in various industries

Answer 1

Cochran Boiler is a multi-tubular vertical fire tube boiler having a number of horizontal fire tubes. It is the modification of a simple vertical boiler where the heating surface has been increased by means of a number of fire tubes. The efficiency of this boiler is much better than the simple vertical boiler.

Parts of Cochran Boiler:

A Cochran Boiler is consisted of following parts:

1. Shell
2. Grate
3. Combustion Chamber
4. Fire tubes
5. Fire hole
6. Firebox (Furnace)
7. Chimney
8. Man Hole
9. Flue pipe
10. Fire Brick Lining
11. Feed Check Valve
12. Blow Off Valve
13. Ash Pit
14. Smoke Box Door
15. Anti Priming Pipe
16. Crown
17. Pressure Gauge
18. Safety Valve
19. Water Level Indicator
20. Water Level Gauge
21. Fusible Plug
22. Stop Valve

Working Principle of Cochran Boiler:

The Cochran boiler works as same as other fire tube boiler.

First, The coal is placed at the grate through the fire hole.

Then the air is entering into the combustion chamber through the atmosphere and fuel is sparked through fire hole.

Then flue gases start flowing into the hemispherical dome-shaped combustion chamber. This flue gases further moves into the fire pipes.

Heat is exchanged from flue gases to the water into the fire tubes.

The steam produce collected into the upper side of the shell and taken out by when the required pressure generated.

The flue gases now send to the chimney through a firebox where it leaves into the atmosphere.

Now, this process repeats and runs continuously. The steam generates used into the small industrial processed.

Applications of Cochran Boiler:

The application of Cochran boiler are:

• Variety of process applications industries.
• Chemical processing divisions.
• Pulp and Paper manufacturing plants.
• Refining units.

Besides, they are frequently employed in power generation plants where large quantities of steam (ranging up to 500 kg/s) having high pressures i.e. approximately 16 megapascals (160 bar) and high temperatures reaching up to 550 °C are generally required.

Lamont Boiler Definition:

LaMont boiler is a high pressure forced circulation water-tube boiler in which water is circulated through an external pump through long closely spaced tubes of small diameter.

The pump is employed in order to have adequate and positive circulation in steam and hot water boilers.

A Lamont Boiler consists of several parts like:

• Economizer
• Centrifugal Pump
• Evaporator Tube
• Grate 
• Furnace
• Superheater
• Water Steam Separator Drum
• Air Preheater

Working Principle of Lamont Boiler:

Lamont boiler works on the principle of forced circulation of water within the boiler with the help of the centrifugal pump.

It’s working totally depends upon the pump. The centrifugal pump circulates the mixture of steam and water through the small diameter tubes of the boiler.

A feed pump forces the water into the economizer where the temperature of water increases.

This water forced into the evaporator tube by using a centrifugal pump driven by the steam turbine. Water passes 10 – 15 times into the evaporator tube.

The mixture of saturated steam and water is formed inside the tube. This mixture sends to the steam separator drum which is outside the boiler. 

Steam from the separator sends to the superheater, where the saturated steam converts into superheated steam.

The water again sends to the economizer where it again passes by the evaporator tubes.

The air from the air preheater enters into the furnace where fuel burn.

The flue gases first heat the evaporator tube then passes by the superheater.

These gases form the superheater again use to preheat the air into air preheater before exhausting into the atmosphere.

This working pressure of this boiler is above 170 bar and have the steam generation capacity of about 50000 kg/hour at temperature 773 K.

Applications of Lamont Boiler:

Boilers are mostly used in power plants where steam turbines are used for the generation of electricity.

Velox Boiler:

Principle:

When the velocity of the gas is greater than the speed of sound, its heat transfer rate is also increases. So more heat is transfer from gas to water as compare when the heat transfer at the subsonic speed. This is the basic principle of of it. This boiler can increase the heat transfer rate or can say steam generation rate without increasing boiler size. This is why; Velox boiler is most successful boiler in the gas turbine industries.

Construction:

Velox boiler is a water tube forced circulation boiler. It has a gas turbine driven air compressor, which compresses the air. This compressed air enters into the vertical combustion chamber, as result, high rate of heat release from the fuel, which increases the flue gases velocity up to the sound velocity. This is a force circulation boiler, so pump is used to circulate water inside the boiler. This boiler also consist water and fire tube to maintain the flow of gas and water inside the boiler. This boiler also consists other necessary mounting and accessories like economizer, super heater, blow off valve, safety valve etc.

Working:

The Velox boiler works as a basic heat exchanger. The working of this boiler is as follow.

The air is compressed by air compressor driven by gas a turbine driven. This compressed air passes from the combustion chamber, where more heat release by the fuel which increase the velocity of the flue gases up to sound velocity. From the bottom of combustion chamber, this flue gases pass from the fire tubes. These fire tubes surrounded by the evaporator water tubes.

The water from the economizer passes from the evaporator tube force by a circulating pump. This water passes 15 – 20 time from the evaporator tube at very high speed. Due to this high speed circulation, heat is transfer from the gases to the water at very high rate. The mixture of water and steam is formed which further passes from the water and steam separator.

The steam from the steam separator passes to the super heater and further for process work. The remaining water in the steam separator again passes from the evaporator tube. The flue gases from the fire tubes send to the super heater tubes, where it increases the steam temperature. The gas from the super heater sends to the turbine where it rotates the gas turbine and then passes from the economizer.

Advantages:

1. This boiler has high heat transfer rate.

2. It has great flexibility.

3. it is compact in design.

4. It is easy to control. It is fully automatic.

5. It has great thermal efficiency of about 90 – 95%.

Today we have discussed about Velox boiler. If you have any query regarding this boiler, ask by commenting below. If you like this article, don’t forget to share it on social networks. Subscribe our website for more informative articles. Thanks for reading it.