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In this article we will discuss about the design of loeffler boiler with the help of a suitable diagram.
In a LaMont boiler the major difficulty experienced is the deposition of salt and sediment on the inner surfaces of the water tubes. The deposition reduces the heat transfer and ultimately the generating capacity. This further increases the danger of overheating the tubes due to salt deposition as it has high thermal resistance. This difficulty was solved in Loeffler boiler by preventing the flow of water into the boiler tubes.
This boiler also makes use of forced circulation. Its novel principle is the evaporating of the feed water by means of superheated steam from the superheater, the hot gases from the furnace being primarily used for superheating purposes.
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Fig. 12.23 shows a diagrammatic view of a Loeffler boiler. The high pressure feed pump draws water through the economiser (or feed water heater) and delivers it into the evaporating drum. The steam circulating pump draws saturated steam from the evaporating drum and passes it through radiant and convective superheaters where steam is heated to required temperature.
From the superheater about one-third of the superheated steam passes to the prime mover (turbine), the remaining two-thirds passing through the water in the evaporating drum in order to evaporate feed water. This boiler can carry higher salt concentrations than any other type and is more compact than indirectly heated boilers having natural circulation. These qualities fit it for land or sea transport power generation.
Loeffler boilers with generating capacity of 100 tonnes/h and operating at 140 bar are already commissioned.
