What is Lancashire Boiler?
The Lancashire boiler is similar to the Cornish but has two large flues containing the fires instead of one.
Lancashire Boiler is a horizontal type and stationary fire tube boiler. Before we go further, let’s know the person who invented this boiler. Lancashire Boiler was invented in the year 1844, by William Fairbairn. But his patent was for the method of firing the furnaces alternately.
Generally, flue gases pass through the fire tube. It is present inside the boiler shell or body and for this reason, it is a fire tube boiler. Lancashire Boiler is an internally fired boiler because the furnace uses to present inside the boiler. This boiler generates low-pressure steam and it is a natural circulation boiler.
Basic Principle of Lancashire Boiler
This boiler consists of a horizontal cylindrical shell filled with water. It uses to surround by two large fire tubes. Heat exchanging is the basic working principle of this boiler. It is having a shell and tube-type heat exchanging system.
Generally, the flue gases pass through the fire tubes and water flows through the shell. In this way, the heat is a transfer from flue gases to the water. It is a low-pressure, internally fired, natural water circulation boiler. That’s means this boiler uses the natural current to flow the water inside the boiler during its operation.
Construction of Lancashire Boiler
As we discussed, this boiler is similar to a shell and tube-type heat exchanger. It consists of a large drum of diameter up to 4-6 meters and length up to 9-10 meters. This drum consists of two fire tubes of a diameter up to 40% of the diameter of the shell. The water drum is placed over the bricks works.
Three spaces create between the drum and the bricks, one is at the bottom and two are insides. Flue gases pass through the fire tubes and side and bottom space. The water level inside the drum is always above the side channels of flue gases, so more heat transfer to the water.
The drum is half-filled with water and the upper half-space for steam. The Furnace is located at one end of the fire tubes inside the boiler. The low brick is situated at the grates (space where fuel burns) which does not allow unburned fuel and ash to flow in fire tubes.
The boiler also consists of other necessary mountings and accessories like an economizer, super-heater, safety valve, pressure gauge, water gauge, etc. to perform better.
Working of Lancashire Boiler
Lancashire boiler is a shell and tube type, heat exchanger. The fuel is burned at the grate. The water is pumped into the shell through the economizer which increases the temperature of the water. Now the shell is filled with water. The fire tube is fully immersed in the water. The fuel is charged at the grate produces exhaust gases.
These flue gases first pass through the fire tubes from one end to another. These fire tubes transfer 80% to 90% of the heat to the water. The backward flue gases pass from the bottom passage where it transfers 8-10% heat to water.
The remaining flue gases pass from the side passage where it transfers 6-8% of the heat to the water. The brick is the lower conductor of heat, so works as a heat insulator. The steam produces in the drum shell is taken out from the upper side where it flows through the superheater if required. So the steam generated is taken out for process work.
Advantages of Lancashire Boiler
- Cleaning and inspection can be done easily.
- It is more reliable and can generate a large amount of steam.
- It required less maintenance.
- This boiler is a natural circulation boiler so lower electricity consumption than others.
- It can easily operate.
- It can easily meet with the load requirement.
- Lancashire boiler has a high thermal efficiency of about 80-90%.
Disadvantages of Lancashire Boiler
- This boiler required more floor space.
- This boiler has leakage problem.
- It requires more time to generate steam.
- It cannot generate high pressure steam if required.
- Grates are situated at the inlet of fire tube, which has small diameter. So the grate area is limited in this boiler.
Application of Lancashire Boiler
- Lancashire boilers are employed to operate steam turbines, locomotives, marines etc.
- The Lancashire boiler used in several industries like paper industry, textile industry, sugar industry, tire industry etc.