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A steam generator is a form of low water-content boiler, similar to a flash steam boiler. The usual construction is as a spiral coil of water-tube , arranged as a single, or monotube , coil. Circulation is once-through and pumped under pressure, as a forced-circulation boiler . [ 1 ]
Although the definitions are somewhat flexible, it can be said that older steam generators were commonly termed boilers and worked at low to medium pressure (7–2,000 kPa or 1–290 psi) but, at pressures above this, it is more usual to speak of a steam generator. A boiler or steam generator is used wherever a source of steam is required.
The Hartford Electric Light Co. (U.S.A.) has a 10,000kW turbo-generator driven by mercury vapour, which reaches the turbine at 70 lb. per sq. in. (gauge), 880°F. The mercury vapour is condensed at 445°F and raises 129,000 lb. steam per hr. at 280 lb. per sq. in. pressure. The latter is superheated to 735°F and passed to the steam turbines.
Once this water is inside the boiler or steam generator, the process of adding the latent heat of vaporization begins. The boiler transfers energy to the water by the chemical reaction of burning some type of fuel. The water enters the boiler through a section in the convection pass called the economizer. From the economizer, it passes to the ...
The higher cost of turbines and the associated gears or generator/motor sets is offset by lower maintenance requirements and the smaller size of a turbine in comparison with a reciprocating engine of equal power, although the fuel costs are higher than those of a diesel engine because steam turbines have lower thermal efficiency. To reduce fuel ...
A typical single-shaft system has one gas turbine, one steam turbine, one generator and one heat recovery steam generator (HRSG). The gas turbine and steam turbine are both coupled in tandem to a single electrical generator on a single shaft. This arrangement is simpler to operate, smaller, with a lower startup cost.
The steam generating boiler has to produce steam at the high purity, pressure and temperature required for the steam turbine that drives the electrical generator. Geothermal plants do not need boilers because they use naturally occurring steam sources. Heat exchangers may be used where the geothermal steam is very corrosive or contains ...
These boilers however are great with steam production due to the large volume inside the boiler and the surface area of the steam output. In order for these boilers to operate properly, they require a long warm-up process, and are prone to thermal shock of the boiler. These boilers can be rated up to 500,000 lb/hr. [2] The wall membrane of the ...