A forced circulation boiler was first introduced by La-Mont in the year 1925 which is used in Europe and America. This is a modern high pressure boiler (water tube type steam boilers) working on forced circulation system.
Working principle of La Mont Boiler
The image shows the flow circuit of La Mont Boiler.
I will explain working of each and every part in La Mont boiler one by one.
Steam separator drum
The la Mont boiler consists of a steam separator drum which is placed wholly outside the boiler setting . The drum receives a mixture of steam and water from the evaporator tubes and feed water from the economizer. The steam is separated from water in the drum.
The water from the drum is then drawn to the circulating (centrifugal) pump through the down-comer. The pump circulates water (“forced circulation”) equal to 8 to 10 times the weight of steam evaporated. This prevents the tubes from being overheated.
The circulating pump delivers the feed water to the distributing header with orifices at a pressure above the drum pressure.
The header distributes water through orifices into the evaporator tubes acting in parallel. Orifice in the header controls the flow of water to the evaporator tubes. Here part of the water is evaporated and a mixture of steam and water from these tubes enters the drum.
The steam produced in the boiler is nearly saturated. This steam as such should not be used in the steam turbine. The presence of moisture in it will cause corrosion of turbine blades, etc. to raise the temperature of steam and thereby to increase the turbine efficiency, superheater is used.
The principle of convection superheater is similar to steam generating tubes of the boiler. The hot flue gases at high temperature sweep over convection superheated tubes and raise the temperature of steam. Convection superheater thus receives heat from the flue gases flowing from the...
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