JPH0330764B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention prevents steaming of the economizers of each of a plurality of boilers located in a waste gas flow path and receiving water from a single water supply source, and prevents water level interference between drums. This invention relates to a waste heat recovery boiler that prevents.

A waste heat boiler is placed in the exhaust gas stream to recover heat from various types of exhaust gas, including exhaust gas generated by gas turbine power generation.
In this case, in order to improve waste heat recovery efficiency, a plurality of boilers, such as a mixed pressure boiler that includes a high pressure boiler and a low pressure boiler, may be installed. FIG. 1 shows an example of a conventional mixed pressure boiler. In the figure, the water in the deaerator 1 is stored in the main water supply pipe 1 by a low-pressure water supply pump 2.
5, the temperature is raised in a low-pressure economizer 3, and then supplied to a low-pressure drum 4.

The canned water in the low-pressure drum 4 circulates through the downcomer pipe 5 and the evaporator 6, and the generated steam is sent from the drum 4 as low-pressure steam _S1 to predetermined equipment such as a low-pressure turbine. On the other hand, a portion of the canned water that has descended through the downcomer pipe 5 reaches the high-pressure drum 9 via the high-pressure water supply pipe 16, the high-pressure water supply pump 7, and the high-pressure economizer 8. The canned water in the high-pressure drum 9 is also circulated through the downcomer pipe 10 and the evaporator 11 in the same way as the canned water in the low-pressure drum 4, and the generated steam is circulated through the high-pressure drum 9,
It passes through the superheater 12 and is supplied to equipment such as a high-pressure turbine as high-pressure steam _S2 .

In this type of boiler, the flow rate of the water supplied to the low-pressure economizer 3 and high-pressure economizer 8 is adjusted by the amount of water that passes through the main water supply pipe 15, so the valve 15a is throttled. When the water supply flow rate is reduced in response to the drop in boiler load, steaming occurs in each of the low-pressure and high-pressure economizers 3 and 8. In other words, since the amount of exhaust gas, which is a heating medium, passing through each boiler is always approximately constant, when the amount of feed water passing through decreases, the amount of heat absorbed per unit volume of feed water increases, causing steaming. In order to prevent steaming during such a load drop, it is necessary to maintain the pressure inside the economizer at a level higher than the saturation pressure with respect to the water supply temperature within the economizer. However, since the flow rate control valve 15a shown in FIG. 1 is placed on the inlet side of the low-pressure economizer 3, it is impossible to adjust the pressure of the low-pressure economizer 3.
Steaming cannot be prevented. Similarly, since the flow control valve 16a for the high-pressure economizer 8 is also arranged on the inlet side of the economizer, it is impossible to prevent steaming inside the high-pressure economizer 8.

In addition, the high pressure drum 9 and the low pressure drum 4 are connected to the downcomer pipe 5,
Since the high-pressure water supply line 16 and the high-pressure energy saver 16 are connected to each other, if the level of the high-pressure drum 9 fluctuates, the amount of canned water taken out of the low-pressure drum 4 will change, resulting in a level fluctuation of the low-pressure drum 4. .
In other words, mutual interference occurs between both drums, making it extremely difficult to maintain the level of both drums at a constant level. Therefore, the low pressure drum 4 is bypassed and the pipe line 1
7 may be provided, but in this case, if steaming occurs in the low pressure economizer, the gas-liquid mixture will flow directly into the high pressure water supply pump 7, causing the problem of cavitation of the pump 7.

Such a phenomenon occurs not only in a combination of a high pressure boiler and a low pressure boiler, but also in boilers having the same pressure.

An object of the present invention is to eliminate the problems of the prior art described above, and to constantly prevent steaming of each economizer in a set of multiple boilers located in a waste gas flow path, regardless of the boiler load. Another object of the present invention is to provide a waste heat recovery boiler in which mutual interference between boiler drums does not occur.

In short, this invention provides a waste heat recovery boiler device in which a high-pressure boiler and a low-pressure boiler are installed in a waste gas flow path, and the water supply to the low-pressure boiler is performed using a low-pressure water supply pump, a low-pressure economizer, a first flow rate control valve, and a low-pressure boiler drum. A high-pressure water supply pipe having a high-pressure water supply pump that branches from a low-pressure economizer outlet pipe that connects the low-pressure economizer and the first flow rate control valve to supply water to the high-pressure boiler device through a connecting pipe. This is a waste heat recovery boiler device characterized by:

Additionally, a flow rate regulating valve is provided in the pipeline connecting the high-pressure economizer outlet and the high-pressure drum to prevent steaming in the high-pressure economizer when the load is reduced.

Separately, the pipe that branches from the outlet pipe of the low-pressure economizer and further branches from the pipe that supplies water to the high-pressure economizer and circulates the water to the inlet of the low-pressure water pump, so the heat of the water that has been heated by the low-pressure economizer is A pipe line is provided to prevent energy loss and increase the flow rate of water supplied to the low-pressure energy saver, and a pipe line is provided on the inlet side of the low-pressure water supply pump to circulate and supply the water.

An embodiment of the present invention will be described below with reference to the drawings, with reference to a set of a high pressure boiler and a low pressure boiler located in a waste gas flow path.

In FIG. 2, reference numeral 18 denotes a feed water recirculation line, which connects the low-pressure economizer 3 and the low-pressure drum 4 to a line 19 (hereinafter referred to as "low-pressure economizer outlet line") and the deaerator 1. Connecting. Reference numeral 20 denotes a flow rate control valve provided on the downstream side of the feedwater recirculation line branch of the low-pressure economizer outlet line 19. Reference numeral 21 denotes a flow rate control valve for adjusting the amount of circulation, and the high-pressure water supply pipe 16 is connected to the water supply recirculation line 18 on the upstream side of this flow rate control valve 21.

On the other hand, on the high-pressure boiler side as well, a high-pressure economizer outlet pipe line 23 is arranged between the high-pressure economizer 8 and the high-pressure drum, and a flow rate regulating valve 22 is provided for this pipe line 23.

In the boiler described above, the water stored in the deaerator 1 flows into the low-pressure economizer 3 via the low-pressure water supply pump 2 and the main water supply pipe 15. By adjusting the amount, a predetermined amount is supplied to the boiler drum 4 via the low pressure economizer outlet line 19. In addition to adjusting the amount of water supplied to the drum 4, this flow rate control valve 20 also adjusts the pressure fluctuations in the economizer due to water being sucked into the high-pressure water supply pipe 16, as will be described later. Prevent steaming inside the economizer. That is, steaming is prevented by adjusting the pressure within the low-pressure economizer and the amount of feed water passing through the economizer.

The feed water that has reached the low-pressure drum 4 circulates through the downcomer pipe 5 and the evaporator 6, and the generated steam passes through the low-pressure drum 4 and is supplied to the low-pressure turbine as low-pressure steam _S1 .

On the other hand, the water supply that has reached the high-pressure water supply pipe 16 is pressurized by the high-pressure water supply pump 7 and then reaches the high-pressure economizer 8 . The amount of water supplied to the high-pressure drum 9 is adjusted using a flow rate adjustment valve 22 provided on the high-pressure economizer outlet pipe 23.
Steaming inside the high-pressure economizer can be prevented because this is done by adjusting the In other words, when the valve 22 is throttled down, the amount of water that passes through the high-pressure economizer 8 decreases, and the temperature of the water supply increases, but since the valve 22 is located at the outlet of the economizer, the pressure inside the economizer also increases. , the pressure will be maintained above the saturation pressure for the feed water temperature in the economizer. In other words, if the discharge pressure of the high-pressure water supply pump 7 is properly adjusted, the valve 22
This allows the water supply flow rate to be adjusted and the pressure within the high-pressure economizer to be maintained above the saturation pressure at all times.

As described above, the supplied water that reaches the high-pressure drum 9 while preventing steaming circulates through the downcomer pipe 10 and the evaporator 11, and the generated steam passes through the high-pressure drum 9 and superheater 12 and is sent to the high-pressure turbine as high-pressure steam _S2. Supplied.

FIG. 3 is a diagram showing the relationship between the boiler economizer outlet pressure in the above embodiment and the conventional economizer outlet pressure.

In the figure, _P1 indicates the minimum pressure to prevent steaming in the economizer corresponding to each boiler load in the high-pressure boiler, and if the pressure is lower than this, steaming will occur in the high-pressure economizer. P ₂ likewise indicates the minimum pressure for steaming prevention in low-pressure boilers.

First, in a high-pressure boiler, the water supply control valve has conventionally been placed on the inlet side of the economizer, so when the valve is throttled in response to a drop in the boiler load, the pressure inside the economizer decreases, making steaming more likely to occur. P ₃ shows the relationship between the boiler load and the pressure inside the economizer using the conventional method, and as is clear from this figure, the load is approximately 75%.
Steaming will occur if the temperature is below. Similarly, in a low pressure boiler, the load is approximately 70% as shown in diagram _P4.
steaming occurs.

Next, P ₅ indicates the discharge pressure of the high-pressure water feed pump of the boiler according to the present invention, and as the boiler load decreases, the flow rate control valve on the high-pressure economizer outlet side is throttled, so the discharge pressure increases. _P5 shows the high-pressure economizer outlet pressure corresponding to each boiler load, and as shown in the diagram, the diagram is similar to diagram _P6 , and the pressure at each boiler load is reduced by the system loss. In any case, the high pressure economizer outlet pressure P ₆ is as shown in the above diagram.
It can be seen that steaming in the high-pressure economizer does not occur because it is always higher than P ₁ over the entire boiler load range.

Next, P ₇ shows the low-pressure feedwater pump discharge pressure, P ₈ shows the low-pressure economizer outlet pressure, and in this case too, the diagram P ₈ shows the steaming pressure in order to maintain a higher pressure than P ₂ over the entire boiler load range. No worries. Note that in a low-pressure boiler, the rate of increase in the outlet pressure of the economizer when the boiler load decreases is smaller than in the case of a high-pressure boiler; This is to bypass the water or flow into the high-pressure water supply pipe 16. Therefore, a sufficient amount of feed water is always ensured through the low-pressure economizer 3 regardless of the boiler load, and the feed water temperature is kept relatively low, so in reality, P ₂ is lower at each boiler load than in the case shown in the figure. and at each boiler load
The differential pressure between P ₈ and P ₂ will be greater than in the illustrated case.

In the first invention, the pressure in the low pressure economizer can be increased by the resistance of the first flow rate control valve,
Combined with an increase in the discharge pressure of the pump based on the performance of the low-pressure water supply pump at low loads, the effect of preventing steaming can be achieved. At the same time, the high-pressure water supply pump receives water at the increased pressure, so the power of the high-pressure water pump can be reduced.

In the second invention, since the second flow control valve is provided between the high-pressure economizer and the drum of the high-pressure boiler, the pressure inside the high-pressure economizer can be increased during low load, and the high-pressure economizer can increase the pressure in the high-pressure economizer. The effect of preventing steaming in the container can be mentioned.

In the third invention, a synergistic effect of the first invention and the second invention can be obtained. In the fourth invention, a pipe line is further branched from the pipe line to the high-pressure water supply pump that branches from the outlet pipe of the low-temperature economizer, and a part of the water supply is recirculated to the inlet side of the low-pressure water pump. It is possible to recover the retained heat of the water that has been heated by the economizer, improve thermal efficiency, and increase the amount of water that passes through the low-temperature economizer, further increasing the effect of preventing steaming. Can be done. Further, the recirculation pipe line is provided with a third flow rate regulating valve, and steaming of both the low pressure and high pressure economizers can be more effectively prevented by regulating the amount of water supplied.

By implementing this invention, since the feed water flow rate control valve is placed on the outlet side of each economizer, it is possible to adjust the flow rate of the feed water and also adjust the pressure inside the economizer, resulting in savings over the entire boiler load range. The pressure inside the coal boiler can be maintained above the saturation pressure with respect to the water supply temperature of the economizer, and there is no risk of steaming.

Furthermore, since the drum water level of one boiler is not influenced by the drum water level of the other boiler, mutual interference between the drums does not occur as in the case of two boilers installed in a conventional waste gas flow path.

[Brief explanation of drawings]

Figure 1 is a system diagram of a conventional mixed pressure heat recovery boiler.
FIG. 2 is a system diagram of a waste heat recovery boiler according to an embodiment of the present invention, and FIG. 3 is a diagram showing the relationship between economizer outlet pressure and boiler load. 2...Low pressure water supply pump, 3...Low pressure energy saver, 4
...Low pressure drum, 7...High pressure water supply pump, 8...
High pressure economizer, 9... High pressure drum, 16... High pressure water supply pipe, 18... Water supply recirculation pipe, 19... Low pressure economizer outlet pipe, 20, 22... Flow rate adjustment valve, 2
3...High-pressure economizer outlet pipe.

Claims (1)

[Claims] 1. In a waste heat recovery boiler device in which a high-pressure boiler and a low-pressure boiler are provided in a waste gas flow path, water is supplied to the low-pressure boiler by a low-pressure water supply pump, a low-pressure energy saver, a first flow control valve, and a low-pressure boiler. Water is supplied to the high-pressure boiler device through a pipe line connecting the boiler drum, and water is supplied to the high-pressure boiler device by a high-pressure water supply pump that branches from the low-pressure economizer outlet pipe connecting the low-pressure economizer and the first flow rate control valve. A waste heat recovery boiler device characterized by being operated by a water supply pipe. 2 In a waste heat recovery boiler device that has a high pressure boiler and a low pressure boiler installed in the waste gas flow path, water is supplied to the low pressure boiler through a pipe connecting the low pressure water supply pump, low pressure economizer, first flow rate control valve, and low pressure boiler drum. Water is supplied to the high-pressure boiler device through a pipe line branching from the low-pressure economizer outlet pipe connecting the low-pressure economizer and the first flow rate control valve. A waste heat recovery boiler device characterized by supplying heat to a high pressure boiler drum via a control valve. 3 In a waste heat recovery boiler system that has a high pressure boiler and a low pressure boiler installed in the waste gas flow path, water is supplied to the low pressure boiler through a pipe connecting the low pressure water supply pump, low pressure economizer, first flow rate control valve, and low pressure boiler drum. Water is supplied to the high-pressure boiler device through a pipe line equipped with a high-pressure water supply pump that branches from the low-pressure economizer outlet pipe line that connects the low-pressure economizer and the first flow rate control valve. A waste heat recovery boiler device characterized in that the waste heat is supplied to a high pressure boiler drum via a energy saver and a second flow rate regulating valve. 4 In a waste heat recovery boiler system that has a high-pressure boiler and a low-pressure boiler installed in the waste gas flow path, water is supplied to the low-pressure boiler through a pipe connecting the low-pressure water supply pump, low-pressure economizer, first flow rate control valve, and low-pressure boiler drum. The water supply to the high pressure boiler device is carried out through a conduit equipped with a high pressure water supply pump that branches from the low pressure economizer outlet conduit connecting the low pressure economizer and the first flow rate control valve. A third flow rate regulating valve is provided in a pipe that branches from the charcoal machine outlet pipe, further branches from a pipe that connects to the high-pressure water supply pump, and circulates water supply to the inlet side of the low-pressure water supply pump. Waste heat recovery boiler equipment.