JPS6141362B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power generation facility consisting of a waste heat recovery boiler installed to recover thermal energy of medium and high temperature exhaust gas using water as a medium, and a steam turbine generator facility.

Conventionally, in this type of waste heat recovery power generation equipment, waste heat recovery boilers with different steam pressures are combined to generate steam with a variety of different pressures in order to recover the heat held in the exhaust gas to the lowest possible temperature. A method has been adopted in which steam is introduced into a mixed-pressure steam turbine.

As an example of this system, a known device having two different pressures, high and low, is shown in FIG.

In the figure, 1 is the low pressure boiler economizer, 2 is the low pressure boiler evaporator, 3 is the low pressure boiler brackish water drum, 4 is the high pressure boiler economizer, 5 is the high pressure boiler evaporator, 6 is the high pressure boiler brackish water drum, and 7 is the mixed pressure steam turbine, 8
is a generator, 9 is a condenser, and 10 is a water pump. Note that if a natural circulation boiler is used, a water drum is required, and if a forced circulation boiler is used, a circulation pump is required.
It is omitted in the figure.

Further, if necessary, the saturated steam leaving the brackish water drums 3 and 6 may be superheated by providing a superheater in the exhaust gas passage and then guided to the turbine, but this is also omitted from the drawing.

FIG. 2 illustrates the state of the exhaust gas temperature and water side temperature of this known device. In the figure, T indicates the temperature, and a, b, c, d, and e indicate the state of the exhaust gas at the point where the symbol is shown in Figure 1,
Similarly, f, g, and h indicate the temperature state of water or steam.

Further, Δ indicates a pinch point. The apparatus shown in FIG. 1 will be explained with reference to FIG. 2. In the low-pressure boiler section, the exhaust gas is cooled from Td to Te in the economizer 1 section, and the water side is heated from Tf to Tg. Evaporator 2
In the section, water evaporates at a constant temperature Tg and changes to saturated steam using the heat generated when the exhaust gas is cooled from Tc to Td.

Similarly in the high-pressure boiler section, in the economizer 4 section, the exhaust gas is cooled from Tb to Tc, while the water is heated from Tf to Th, and in the evaporator 5 section, the exhaust gas is cooled from Ta to Tb. During the process, water evaporates at a constant temperature Th and becomes saturated steam.
Thus steam with saturation pressure corresponding to Th and Tg
Steam having a saturated pressure corresponding to 1 is led to the turbine 7 to generate electricity, and water condensed in the condenser 9 is led again to the waste heat boiler by the feed water pump 10 to repeat the circulation.

However, in this known device, the water supply pump 10
The temperature of the feed water supplied to the economizer 4 of the high pressure boiler from Tf is the temperature of the feed water entering the economizer 1 of the low pressure boiler.
This method has the disadvantage that it is not a method for recovering heat from exhaust gas to a sufficiently low temperature.

The present invention was devised to eliminate this drawback, and FIG. 3 shows an embodiment of the present invention corresponding to FIG. 1, and an embodiment of the present invention corresponding to FIG. 2 on the exhaust gas and water side. Figure 4 shows the temperature conditions. To explain the features of the present invention with reference to FIG. 3, the entire amount of feed water pressurized by the feed water pump 10 enters the low pressure boiler economizer 1, and the saturated water in the low pressure brackish water drum 3 is removed by the feed water booster pump 11. Its feature is that it is then guided to the high pressure boiler economizer 4. To make this point even clearer, Figure 3 is explained in conjunction with Figure 4. The point is that the exhaust gas is cooled from Td to Te' in the economizer 1 section, while the water side is heated from Tf to Tg. It is the same as Figure 2, but if you look at the flow rate on the water side, in Figure 2 it is only the amount of steam generated by the high pressure boiler, whereas in Figure 4 it is the total amount of steam generated by the high pressure and low pressure boilers. As a result, the temperature rise on the water side is more gradual than in Figure 2.
Te′ becomes a value lower than the value of Te in FIG. In the evaporator 2, water is evaporated at a constant temperature Tg and converted into saturated steam using the heat generated when the exhaust gas temperature is cooled from Te' to Td. In economizer 4, in the process of cooling the exhaust gas from Tb to Tc′, the water becomes Ti (this is
(equal to Tg) to Th, but in Figure 2 it was heated to Th from Tf.
Comparing the two, the amount of heat required to heat water in the economizer 4 in Figure 4 is smaller than in Figure 2, so the value of Tc' is higher than the value of Tc in Figure 2. value. The process in the evaporator 5 is the same between FIG. 4 and FIG. 2.

It is well known that the boiler can be either a natural circulation boiler or a forced circulation boiler, and that the saturated steam exiting the brackish water drums 3 to 6 may be superheated by providing a superheater in the exhaust gas passage if necessary. This is the same as explained for the device.

It will be explained with reference to FIG. 5 that the above invention enables the temperature of the exhaust gas to be further lowered to a lower temperature than the known device. FIG. 5 is a superimposed drawing of FIGS. 2 and 4, and all symbols are the same as in FIGS. 2 and 4.

In FIG. 5, the solid line shows the state line on the water side as shown in FIG. 2, and the broken line shows that in FIG. 4. As is clear from the figure, the exhaust gas temperatures Tb and Td at the pinch point have the same value in both the systems shown in FIGS. 1 and 3.

In the energy saver 4, in the method shown in Fig. 3 which shows the present invention, the water supply side is already Ti (this is equal to Tg).
Since the temperature has increased to , the exhaust gas temperature decreases from Tb to Tc', but naturally Tc' is a larger value than Tc.

In economizer 1, when comparing the flow rate on the water side between the method shown in Figure 1 and the method shown in Figure 3, as mentioned above, the method shown in Figure 3 has a larger amount of water, so the exhaust gas temperature is lower than Td.
Although it can be lowered to Te', Te' becomes a smaller value than Te as is clear from Fig. 5. That is, Te−
This means that the amount of heat recovery can be increased by Te′.

Furthermore, as is clear from Fig. 5, this increase in the amount of recovered heat appears as an increase in the amount of evaporation in the evaporator 2, and the method shown in Fig. 3 increases this amount of evaporation more than the method shown in Fig. 1. This means that the output of the steam turbine can be increased by an amount commensurate with the above.

As described above, according to the apparatus of the present invention, high-temperature exhaust gas is used as a heat source and passed through a plurality of waste heat boilers to sequentially obtain high-pressure to low-pressure steam and guide it to a multistage steam turbine. The water in the drum is sent to the evaporator of the boiler, and is also supplied to the water economizer of the higher pressure boiler, thereby preheating the water supply of the high pressure boiler. The drawback of not being able to recover sufficient amount of heat can be resolved,
This provides an effective means for increasing overall thermal efficiency.

Therefore, when this device recovers waste heat and uses it for the purpose of power generation, it is extremely effective when used in combination with steam turbine generator equipment, and the heat held in the exhaust gas can be recovered to the lowest possible temperature. It is something.

In addition, although the above explanation was about the case where two types of pressures are generated by the waste heat boiler, it goes without saying that the present invention exhibits the same effect even when more types of pressures are generated.

[Brief explanation of the drawing]

Fig. 1 and Fig. 2 are system diagrams and heat diagrams for explaining the conventional device, Fig. 3 and Fig. 4 are system diagrams and heat diagrams corresponding to Figs. 1 and 2 for explaining the embodiment of the present invention. The diagram, FIG. 5, is a heat diagram obtained by overlapping FIGS. 2 and 4. 1...Low pressure boiler economizer, 2...Low pressure boiler evaporator, 3...Low pressure boiler brackish water drum, 4...High pressure boiler economizer, 5...High pressure boiler evaporator, 6...
High-pressure boiler brackish water drum, 7... Multi-stage mixed pressure steam turbine, 8... Generator, 9... Condenser, 10... Water supply pump, 11... Water supply booster pump,
Ta, Tb, Tc,...Th...Temperature.

Claims (1)

[Scope of Claims] 1. Steam obtained by passing the water supply through the economizer, a brackish water drum, and an evaporator is sent to the turbine via the brackish water drum, while exhaust gas as a heat source is passed from the evaporator to the economizer. A multi-stage mixed-pressure turbine is constructed by arranging a plurality of waste heat boilers installed in the boiler for heat exchange, and is driven by feeding high-pressure steam from each brackish water drum, and the brackish water drum of each boiler. A waste heat boiler device for a multi-stage mixed pressure turbine, comprising a system for feeding water to an evaporator of the boiler and a system for supplying water to an economizer of a higher pressure boiler. 2. The apparatus according to claim 1, wherein the pipe line for feeding the brackish water to the turbine via the brackish water drum is passed through an exhaust gas passage to be heated.