Liquid heaters and vaporizers – Steam treatment – Boilers with superheaters
Patent
1998-08-14
1999-09-14
Walberg, Teresa
Liquid heaters and vaporizers
Steam treatment
Boilers with superheaters
1224791, F22G 504
Patent
active
059505745
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a boiler, and more specifically a boiler having a reheater for an electric power industries, and having a medium or a large capacity, a maximum continuous evaporation rate of which boiler is at least 500 t/hr.
In a power generation plant, steam which has done a work in a high pressure turbine to be in relative lower pressure is extracted out therefrom, reheated and supplied to a medium pressure turbine and a low pressure turbine to do a work therein, thereby enhancing a thermal efficiency of the turbines as a whole. The above-mentioned boilers are used, for example, in such a power generation plant.
In such a boiler, superheaters for generating steam of relative high temperature and relative high pressure and reheaters for generating steam of relative high temperature and relative low pressure are disposed in an upstream side exhaust gas passage through which exhaust gas generated due to combustion of fuel in a furnace passes. Particularly in the boiler having a medium or a large capacity, a maximum continuous evaporation rate of which boiler is at least 500t/hr, and which boiler is used in a power generation plant, the reheaters are disposed, like the superheaters, in the upstream side exhaust gas passage of relative high temperature so as to obtain high temperature steam.
There is a boiler in which a down stream side exhaust gas passage is divided into two or more sub passages along a flow of the exhaust gas, at a down stream portion of each of which sub passages a damper is provided for adjusting a flow rate of the exhaust gas passing through the respective sub passages. JP-A-59-60103 and JP-A-58-217104 disclose structures in which reheaters are disposed in one or two sub passages and superheaters are disposed in the remaining sub passages, respectively. JP-A-62-33204 discloses a structure wherein a superheater and an economizer are disposed in one of the sub passages, and an evaporator and an economizer are disposed in the other one.
In the upstream side exhaust gas passage communicated with an outlet of the furnace, through which exhaust gas of relative high temperature passes, a suspension type high-temperature side superheater is disposed, and a suspension type high-temperature side reheater is also disposed downstream of the high-temperature side superheater. Heat transfer is carried out more effectively in the upstream side exhaust gas passage, as compared with in downstream side exhaust gas passage. This is because a temperature of the exhaust gas in the upstream side exhaust gas passage is higher than that in the downstream side exhaust gas passage and there is a heating due to radiation from a combustion flame in the furnace. Since the high-temperature side superheater is disposed in the upstream side exhaust gas passage where an effective heat transfer is carried out, it becomes possible to prevent an area of heat transfer part of the superheater from increasing, namely it is possible to reduce dimensions of the superheaters as a whole as well as to obtain a higher heat transfer efficiency. As a result, it is possible to prevent increase in dimensions and a weight of the boiler as a whole.
It is also possible to reduce the dimension of the reheater as a whole by means of locating the high-temperature side reheater in the upstream side exhaust gas passage, through which the exhaust gas of relative high temperature passes (or in which a heat transfer rate is high), so that the high-temperature side reheater follows the high-temperature side superheater, as like the high-temperature side superheater does. However, since the dimensions of the high-temperature side superheater and the high-temperature side reheater disposed in the upstream side exhaust gas passage are reduced, it is hard to obtain heat transfer areas required to the high-temperature side superheater and the high-temperature side reheater as a whole by means of only these reduced high-temperature side superheater and the high-temperature side reheater. Therefore it is needed to provi
REFERENCES:
patent: 2980082 (1961-04-01), Firl
patent: 4198930 (1980-04-01), Pratt et al.
patent: 4442800 (1984-04-01), Seifert et al.
Kawase Takayo
Koda Fumio
Matsuda Junichiro
Mimura Tetsuo
Morita Shigeki
Babcock-Hitachi Kabushiki Kaisha
Walberg Teresa
Wilson Gregory A.
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