The operation of the boiler is similar to an electric transformer. Two pressures are used to effect an interchange of energy. In the primary circuit, the steam at 100 bar is produced from distilled water. This steam is passed through a submerged heating coil which is located in an evaporator drum as shown in the figure. The high pressure steam in this coil possesses sufficient thermal potential and steam at 60 bar with a heat transfer rate of 2.5 kW/m2-°C is generated in the evaporator drum. Natural circulation is used in the primary circuit and this is sufficient to affect the desired rate of heat transfer and to overcome the thermo-siphon head of about 2 m to 10 m.
- Schmidth-Hartmann boiler consists of air preheater to heat the surrounding air which is required for combustion chamber. It also consist steam drum, super heater, and feed pump.
- Feed water preheater, primary separator is also used in this boiler. In Schmidth-Hartmann boiler there are two circuits one uses distilled water and other uses impure water.
- The Schmidth-Hartmann boiler is different from other boiler because in this boiler distilled water is used for generation of the high pressure steam which is recalculated without any wastage in the circuit.
- This high pressure steam is utilized for generation of low pressure steam from impure water.
- Distilled water from water drum enters into the primary evaporating tubes by natural circulation.
- Steam at 95-100 bar pressure is generated in the evaporating tubes with the help of hot flue gases circulated over the tubes from combustion chamber.
- This steam enters via primary separator into the tubes submerged in impure water of the evaporator or steam drum.
- The exchange of heat between high pressure steam and impure water allows the water to be converted into steam at a pressure of 55-60 bar which is further passed into super heater for superheating purposes.
- The superheated stem is finally supplied to the steam turbine.
- The condensate of high pressure steam collected from the drum passes through the feed water preheater where it heat the low pressure feed water up to its saturation temperature.
- The low pressure (L.P.) feed water is pumped into preheater with the help of feed pump.
- It can use impure water for generation of steam.
- As it can use impure water there is no requirement of water softening plant ultimately reduces cost.
- Any deposits in the evaporator drum due to impure water can easily brushed off by removing the submerged tube from the drum or by blowing off the water.