JPS6214041B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a waste heat recovery steam generation device, and more particularly to a device for preventing steam generation in an economizer for a steam generation device that effectively recovers waste heat from a gas turbine.

In order to recover exhaust heat from the high-temperature gas that imparts kinetic energy to the gas turbine, a waste heat recovery steam generator is placed downstream of the gas turbine. The general characteristics of the exhaust gas flow rate, exhaust gas temperature, and evaporation flow rate in this case are explained using Figure 1. When the gas turbine load is 3/4 or less of the rated load A, the gas flow rate GF ₁ and the economizer inlet gas temperature GT ₁ is almost constant, whereas the generated steam flow rate S ₁ is proportional to the gas turbine load.

In this case, it is theoretically desirable to set the temperature of the outlet water supplied to the drum so that it is close to the drum saturation temperature in order to improve the thermal efficiency of the device. Figure 2 shows this setting value, and the waste gas passing through the evaporator D and the economizer E of the waste heat boiler exchanges heat with the evaporator D and the economizer E, so that the temperature is increased as shown in GT _2. decreases. On the other hand, if the water supply temperature WT ₁ of the economizer E at rated load is set close to the saturation temperature ST at the outlet of the economizer, the water supply temperature WT ₂ at low load will reach the saturation temperature ST inside the economizer, resulting in energy savings. A portion of it evaporates inside the vessel, adversely affecting equipment operation, heat recovery, etc.
This is because, as shown in Figure 1, the exhaust gas flow rate and temperature are almost constant at the inlet of the economizer up to 3/4 of the turbine load, regardless of the turbine load.
This is due to the fact that the amount of water flowing through the economizer is small compared to the amount of heat recovered in the economizer. Conventionally, two methods have been used to prevent the generation of steam in the economizer. One method is to set the heat transfer area of the economizer small in advance, and the other is to keep the amount of water supplied to the economizer constant over the entire load range. In the former case, as shown in Figure 3, in order to avoid the steam generation phenomenon in the economizer in the entire load range, the outlet water supply temperature of the rated water supply temperature WT ₃ is set lower than the saturation temperature ST, and the The outlet water supply temperature of WT ₄ is set to be equal to or lower than the saturation temperature ST. Therefore, there is a drawback that the amount of heat absorbed by the economizer at rated load is low, and the amount of evaporation is reduced. Figure 5 shows a device implementing the latter method. In this figure, in order to keep the water supply flow rate of the economizer E constant over the entire load, the excess water from the water that exits the economizer E is is returned to the water supply pipe 1 via the return water supply pipe 7 and the return water supply pressure reducing valve 16. In this case, as shown in Figure 4, the amount of water supplied to the economizer is constant, so the water supply temperature at the rated time WT ₅
Since the outlet temperature of WT 6 has reached nearly the saturation temperature ST, the former drawback is resolved, but on the other hand, the economizer outlet temperature of the feed water temperature WT ₆ at low load decreases. However, since high-temperature return water is mixed into the water saver inlet water supply, the temperature of the feed water at the economizer inlet becomes higher, and the overall heat exchange efficiency between the water supply and waste gas decreases during low loads. The disadvantage is that the gas temperature GT ₃ at low load is higher than the gas temperature GT ₂ at rated conditions.

An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art, and to provide a device that prevents evaporation of feed water within the energy saver over the entire load range and obtains an efficient amount of evaporation. .

In short, the present invention provides a power economizer outlet water supply temperature control system that detects the temperature of the water supply at the outlet of the economizer and adjusts the flow rate of water to the economizer based on the detected temperature, and an amount of water stored in the drum of a steam generator. This system is equipped with a can water supply flow rate control system that maintains a constant flow rate.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 6, the water in the water supply pipe 1 is pressurized by the water supply pump 2, passes through the flow rate regulating valve 3, is heated in the economizer E, and then reaches the outlet pipe 5. A temperature detector 6 for detecting the temperature of the outlet water supply is installed on the outlet pipe 5, and the flow rate adjustment valve 3 is operated based on the detection result to adjust the flow rate of the water supply.
This keeps the outlet temperature of the feed water constant, and the temperature detector 6 and flow rate adjustment valve 3 constitute a feed water temperature control system. In other words, the water supply temperature at the outlet of the economizer is determined by this control system, as shown in Figure 7, at low load.
WT ₇ 's economizer outlet temperature is the temperature at rated load WT ₈
The temperature is adjusted to be almost the same as the exit temperature of the economizer. As mentioned above, the amount of water supplied from the economizer E is determined according to the water outlet temperature, so
The amount of water supplied to the drum 8 does not necessarily match. For this reason, unnecessary water supply is carried out by the drum water level detection device 9.
The drum water level control valve 10 connected thereto discharges the water through a water supply and discharge pipe 20 as a heat source for other devices. That is, the drum water level control valve 10 is operated based on the signal from the water level detection device 9, and the drum 8
The water level inside the tank is controlled so that it remains constant.

FIG. 8 shows a second embodiment. In this embodiment, the feed water temperature control system is the same as in the previous embodiment, but all of the feed water leaving the economizer E is introduced into the drum 8 from the outlet pipe 5. This drum 8 is provided with a can water discharge pipe 20a, and this pipe water discharge pipe is provided with a drum water level control valve 10a that communicates with the drum water level detection device 9, and constitutes a can water supply flow rate control system. There is. With this control system, the drum 8
Unnecessary portions of the water introduced into the system are discharged outside the system and used as various heat sources. In this case, the can water discharged from the drum 8 has reached a saturation temperature and is therefore used as a heat source with a high calorific value for other devices.

FIG. 9 shows a third embodiment, in which the feed water temperature control system has been modified. Excess water supplied from the energy saver E flows into the return water supply pipe 7b. This return water supply pipe 7b is connected to a water supply storage tank 11 installed on the upstream side of the water supply pump 2 of the water supply pipe 1.

This embodiment is particularly effective when feed water cannot be supplied to other equipment, and furthermore, by causing heat exchange to take place between the heated return feed water and the low temperature feed water, the feed water to be introduced into the economizer is You can raise the temperature to some extent.

FIG. 10 shows a fourth embodiment. In this embodiment, the return feed water introduced into the feed water storage tank 11 is cooled in the container by heat exchange with the low temperature feed water.
It is depressurized and re-evaporated in the container. 13 is a pressure detection device that detects the pressure inside the container; 14 is a steam pipe 12
This is a pressure regulating valve that is installed in the pressure detection device 13 and communicates with the pressure detection device 13. As a result, the water supply storage tank 11
The return water that has flowed into the system is evaporated and sent to various devices via steam piping 12 for use.

FIG. 11 shows a fifth embodiment. All of the embodiments up to the above have used the flow rate regulating valve 3 as one of the components of the feed water temperature control system, but in this embodiment, a feed water pump rotation speed regulating device 15 is used. Specifically, the economizer outlet temperature detection device 6 and the water supply pump rotation speed adjustment device 15 are connected, and the amount of water supplied to the economizer E is controlled by adjusting the rotation speed of the water supply pump 2. This embodiment has the advantage that the driving energy of the water supply pump 2 can be saved, especially when the load is low.

According to the present invention, generation of steam in the economizer of the waste heat steam generation device of a gas turbine can be prevented, and the device will not be adversely affected.

In addition, efficient steam generation can be performed over the entire load range, and the thermal energy of Durbin waste gas can be used effectively.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between waste gas flow rate, economizer inlet gas temperature, evaporation flow rate, and gas turbine load. Figure 2 is a diagram showing the relationship between feed water temperature at rated time and feed water temperature at low load. , Fig. 3 is a diagram of the water supply temperature when the outlet temperature of the economizer is kept low at the rated time, Fig. 4 is a diagram showing the water supply temperature when the water supply flow rate to the economizer is kept constant, and Fig. 5 Fig. 6 is a system diagram showing the water supply route according to the conventional method for the energy saver, Fig. 6 is a system diagram of the steam generator showing the first embodiment of the present invention, and Fig. 7 shows changes in the temperature of the feed water according to the present invention. 8 is a system diagram of a steam generator showing a second embodiment, FIG. 9 is a system diagram of a steam generator showing a third embodiment, and FIG. 10 is a system diagram of a steam generator showing a fourth embodiment. System diagram of steam generator FIG. 11 is a system diagram of a steam generator showing a fifth embodiment. DESCRIPTION OF SYMBOLS 1... Water supply pipe, 2... Water supply pump, 3... Economizer water supply flow rate adjustment valve, 5... Energy saver outlet water supply pipe, 6... Water supply temperature detection device, 7, 7a... Return water supply pipe, 8... Drum, 9... Drum water level control device, 10...Drum water level control valve, 11...Water supply storage tank, 12...Steam piping, 13...Pressure detection device, 14...Pressure adjustment valve, 1
5... Water pump rotation speed adjustment device, E... Energy saver.

Claims (1)

[Scope of Claims] 1. A steam generator that generates steam using waste gas, and a water economizer that heats water supplied to the steam generator using the waste gas, in which the water supply to the energy saver is Economizer outlet feed water temperature control system that controls the temperature of the economizer outlet feed water to below the saturation temperature over the entire load range, and canned water supply flow rate control that maintains the water level in the steam generator drum at a constant level. A waste heat recovery steam generation device characterized by having a system. 2. The economizer outlet water supply temperature control system is characterized by a economizer outlet water supply temperature detection device installed in the economizer outlet water supply piping, and a economizer water supply flow rate adjustment valve that is activated by a signal from this temperature detection device. A waste heat recovery steam generation device according to claim 1. 3. The power supply water supply temperature control system at the outlet of the cost saver is comprised of a temperature detection device for the water supply temperature at the outlet of the cost savings device and a water supply pump rotation speed adjustment device that is activated by a signal from the temperature detection device. Waste heat recovery steam generator. 4. A patent claim characterized in that the canned water supply flow rate control system is a drum water level detection device installed in the drum of a steam generator and a drum water level control valve installed in a water supply and discharge pipe and activated by a signal from the detection device. The waste heat recovery steam generator according to item 1, item 2, or item 3. 5 The canned water supply flow rate control system is connected to a drum water level detection device,
Claim 1: A drum water level control valve installed in a can water discharge pipe and a drum water level control valve that is operated by a signal from the water level detection device.
The waste heat recovery steam generation device according to any one of Items 1 to 3. 6 The canned water supply flow rate control system is connected to a drum water level detection device,
A water supply storage tank provided upstream of a water supply pump in a water distribution pipe, and a drum water level control valve installed in a return water supply pipe connected to the water supply storage tank and operated by a signal from a drum water level detection device. The waste heat recovery steam generation device according to any one of items 1 to 3. 7. Claim 6, characterized in that the water supply storage tank of the canned water supply flow rate control system is provided with a pressure detector and steam piping, and the steam piping is provided with a pressure regulating valve that is activated by a signal from the pressure detector. The waste heat recovery steam generation device described in Section 1.