Chapter: Mechanical Engineering : Internal Combustion Engines

Steam Boilers

Steam Boilers 1 Fire Tube & Water Tube Boilers 2 Internally Fired Boiler 3 Externally Fired Boiler 4 Cochran Boiler 5 Lamont Boiler



Steam Boilers

1 Fire Tube & Water Tube Boilers

2 Internally Fired Boiler

3 Externally Fired Boiler

4 Cochran Boiler

5 Lamont Boiler



STEAM BOILERS

Generates steam by transferring heat by burning of fuel to water.

 

         Energy released by burning fuel (solid, liquid or gaseous) is transferred to the water in the boiler.

 

Classification of boilers:


The steam boilers are classified as

 

According to flow of water and hot gases.

 

1.     Fire Tube Boilers

2.     Water Tube Boilers

According to the method of firing.

 

1.       Internally fired boilers

2.     Externally fired boilers

 

According to the Pressure developed

 

1.     Low pressure boilers

2.     High pressure boilers

 

In fire tube boilers,

 

           The hot gases pass through the tubes surrounded by water.

 

         The water is get heated up and converted into steam

 

         The exhaust gases are sent to atmosphere through chimney.

 

E.g    Locomotive boiler, Lancashire boiler.

 

 

1 FIRE TUBE & WATER TUBE BOILERS

 

According to flow of water and hot gases:

In water tube boilers,

 

           Water is circulated through number of tubes and the hot flue gases flow over these tubes.

 

A number of tubes are connected with boiler drum through headers.

 

 

           The hot gases flow over these tubes many times before escaping through the stack.

 

           The water is converted into steam and steam occupies steam space.

 

E.g. Babcock & Wilcox, stirling, BHEL boiler, Velox, Lamont, Lo-effler boilers. According to the method of firing:

 

In internally fired boilers, the furnace grate is provided inside the boiler shell.(E.g Lancashire, Locomotive boilers) In externally fired boilers,

•    The furnace grate is provided outside or built under the boiler shell.

 

2 INTERNALLY FIRED BOILER:



3 EXTERNALLY FIRED BOILER:

 

 

 

According to the Pressure Dev eloped:

 

In Low Pressure Boilers,Steam is produced at a pressure lower than 80 bar. (E. g.

Cochran, Lancashire, Locomotiv e)

 

In High Pressure Boilers,Steam is produced at a pressure more than 80 bar. (E. g.

Lamont, Velox, Benson, Lo-effl er boiler)

 

4 COCHRAN BOILER:


 

·        Coal is fed into the gr ate through the fire hole and burnt.

 

           Ash formed during t he burning is collected in the ash pit provided just below the grate.

 

           Ash is then removed manually.

 

         The hot gases from the grate pass through the combustion chamber to the horizontal fire tubes and transfer the heat by convection.

 

         The flue gases comi ng out of fire tubes pass through the smoke bo x and escape to the atmosphere through the chimney.

           Smoke box is provided with a door for cleaning the fire tubes and sm oke box.

 

         The working pressure and steam capacity of cochran boiler are 6.5 bar and 3500 kg /hr respectively.

 

5 LAMONT BOILER:


 

             It is a water tube, forced circulation and externally fired high pressure boiler.

•    The capacity of the p lant is 50 tonnes/hr

 

           Pressure of the steam generated is 170 bar.

 

           Temperature of the steam produced is 500o C

 

Working:

 

           Feed water is pumped to the boiler by the feed pump through the eco nomiser.

 

           Economiser preheats the feed water by using hot gases leaving the b oiler.

 

         The circulating pump circulates the water from the drum under high pressure to prevent the tubes from being ove rheated

         Water is evaporated into steam when passing through these tubes.

 

           The water and steam from the tube enters the boiler drum where the steam is separator.

 

         This steam is passed through a convection superheater and the steam is superheated by the flue gases.

 

           This super heated steam is supplied to the prime mover through steam outlet.

 

         The water level in the drum is kept constant by pumping the feed water into the boiler drum.

 

         The air is preheated by the flue gases before entering the combustion chamber to aid the combustion of the fuel.

           This type of boiler has a working pressure of 170 bar.

 

           They can produce the steam at the rate of 45000 kg per hour.


 

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail
Mechanical Engineering : Internal Combustion Engines : Steam Boilers |


Privacy Policy, Terms and Conditions, DMCA Policy and Compliant

Copyright © 2018-2023 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.