JP2002147701A - Exhaust heat recovery steam generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust heat recovery steam generating device which enables control of generated steam amount and steam temperature at the side of an exhaust heat recovery boiler without relying on the loaded condition of an exhaust gas generation source. SOLUTION: Exhaust gas bypaths 7, 10, 13 are provided to the region adjacent to a heat exchanger set-up region in an exhaust gas channel, for at least one of superheater 5, an evaporator 8, a reheater (not shown) and an economizer 11, and further, exhaust gas flow rate distributors 6, 9, 12 are disposed at the upstream side of the heat exchanger set-up region and the adjacent region. For instance, when the required temperature of the steam at the exit of the superheater is lowered, the distributor 6 at the upstream of the superheater is controlled to increase the flow rate of the combustion exhaust gas that passes through the bypath 7, so that the flow rate of the exhaust gas that passes through the superheater 5 is reduced. As a result, the heat exchange rate at the superheater 5 is lowered, making it possible to lower the steam temperature at the exit of the superheater.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust heat recovery steam generator, and more particularly to an exhaust heat recovery steam generator (exhaust heat recovery boiler) capable of controlling the amount of generated steam and the steam temperature.

[0002]

2. Description of the Related Art As an example of an exhaust heat recovery boiler, FIG. 3 shows a system of a conventional single-pressure type exhaust heat recovery boiler. The combustion exhaust gas 2 discharged from the exhaust gas generation source 1 passes through the inlet duct 3 and flows into the exhaust heat recovery boiler 4. Each bank of the superheater 5 ', the evaporator 8', and the economizer 11 '(or a reheater (not shown) may be arranged) is installed in the exhaust heat recovery boiler 4. The boiler feedwater 15 is superheated to superheated steam by the heat exchange between the boiler feedwater and the flue gas 2 which are supplied to the economizer 11 'and sequentially pass through the respective banks. Further, the exhaust gas which has flowed into the exhaust heat recovery boiler 4 and has been subjected to heat exchange to lower the temperature is discharged from the chimney 14.

[0003] The boiler feed water 15 is supplied from a feed pump 16 to a economizer 11 'and heated, then temporarily stored in a steam separator drum 17, and then supplied to an evaporator 8' and heated to form a brackish water mixture again. The steam is returned to the steam separator 17, and the separated steam is supplied to a superheater 5 'to become a superheated steam 18', which is sent to a steam engine or the like. At this time, the temperature of the superheated steam 18 'is adjusted by the cooler 22.
Done in

FIG. 4 shows a temperature distribution diagram on the exhaust gas side and the steam-water supply side of the boiler 4 shown in FIG. The combustion exhaust gas 2 discharged from the exhaust gas generation source 1 flows into the superheater 5 'after passing through the inlet duct 3. The flue gas 2 flowing into the superheater 5 'exchanges heat with steam in the superheater 5' to lower the temperature, and becomes a flue gas 23 'at the upstream of the evaporator 8'.
Next, the exhaust gas 23 'flows into the evaporator 8' and exchanges heat with the steam in the evaporator 8 ', whereby the temperature is reduced and becomes exhaust gas 24' in the upstream part of the economizer. Next, the exhaust gas 24 ′ flows into the economizer 11 ′ and exchanges heat with the feedwater 15, so that the temperature of the exhaust gas is reduced to become a combustion exhaust gas 25 ′ and discharged from the chimney 14.

As shown in FIG. 4, the temperature of the combustion exhaust gas 2 discharged from the exhaust gas generation source 1 decreases every time it passes through the superheater 5 ', the evaporator 8', and the economizer 11 '. The temperature decreases continuously through each bank.

On the other hand, the feed water 15 pressurized by the boiler feed pump 16 is heated by the economizer 11 ′ and rises in temperature, and then sent into the brackish water separating drum 17 to be kept at a constant temperature in a brackish water mixed state. The feedwater sent from the steam separator 17 to the evaporator 8 'is superheated by the superheater 5' and the superheated steam 1 at the superheater outlet is discharged.
8 'is obtained. The superheater outlet steam 18 ′ is supplied to the desuperheater 22.
After the spray water is injected to lower the steam temperature to the required temperature, the steam is sent to the demand equipment.

Since the exhaust heat recovery boiler system shown in FIGS. 3 and 4 is not provided with a reheating unit, the amount and temperature of the superheated steam 18 ′ depend on the operating state of the exhaust gas generating source 1. The amount and temperature of steam generated on the heat recovery boiler 4 side could not be adjusted.

[0008]

In the conventional exhaust heat recovery boiler system without reheating equipment shown in FIG. 3, an exhaust gas generation source 1 such as a gas turbine and an exhaust heat recovery boiler 4 having a constant heat transfer area are connected to an exhaust gas duct. Directly connected through. Therefore, the waste heat recovery boiler 4 in which the heat transfer area of the boiler is constant
The amount and temperature of steam generated in the boiler depends on the amount of exhaust gas passing through the boiler, that is, the load state of the exhaust gas generation source 1, and the amount of generated steam, that is, the amount of heat absorbed in the heat transfer tubes of each bank is determined on the side of the exhaust heat recovery boiler 4. Was impossible to control.

An object of the present invention is to provide an exhaust heat recovery steam generator capable of controlling the amount of generated steam and the generated steam temperature on the exhaust heat recovery boiler side without depending on the load state of the exhaust gas generation source. It is.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a superheater, an evaporator, a reheater and a economizer, which are heat exchangers for generating steam disposed inside a casing by introducing a high-temperature gas. In the exhaust heat recovery steam generator provided with at least a superheater, an evaporator and a economizer, at least one of the superheater, the evaporator, the reheater and the economizer has a heat exchanger installation area. The problem is solved by an exhaust heat recovery steam generator provided with an exhaust gas bypass passage in an adjacent region, and an exhaust gas flow distribution device provided upstream of the heat exchanger installation region and the exhaust gas bypass passage in the adjacent region.

[0011]

According to the present invention, for example, when the required steam temperature at the superheater outlet decreases, the exhaust gas flow distribution device upstream of the superheater is adjusted to increase the amount of combustion exhaust gas passing through the superheater bypass. Reduce the flow rate of exhaust gas passing through the superheater. Along with this, the amount of heat exchange at the superheater decreases, and the steam temperature at the superheater outlet can be reduced.

When the required steam amount or the required reheat steam amount is reduced, the exhaust gas flow distribution device upstream of the evaporator or the reheater is adjusted to adjust the flue gas passing through the evaporator or the reheater bypass passage. The volume is increased to reduce the exhaust gas flow through the evaporator or reheater. Accordingly, the amount of heat exchange in the evaporator or the reheater decreases, and the amount of generated steam can be reduced.

[0013] Similarly, when the temperature of the feed water at the outlet of the economizer approaches the saturation temperature of the boiler drum and steaming occurs inside the economizer, the exhaust gas flow distribution device upstream of the economizer is adjusted to control the economizer bypass. By increasing the amount of flue gas passing through the road, the flow rate of flue gas passing through the economizer is reduced. Along with this, the amount of heat exchange in the economizer is reduced, and the outlet water temperature at the economizer can be reduced.

[0014]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a single-pressure type exhaust heat recovery boiler 4 according to an embodiment of the present invention. The single-pressure type exhaust heat recovery boiler 4 shown in FIG. 1 is connected to an inlet duct 3 through which the combustion exhaust gas 2 discharged from the exhaust gas generation source 1 passes, and a chimney 14 is disposed downstream of the exhaust heat recovery boiler 4. I have.

The exhaust heat recovery boiler 4 is provided with a heat exchanger (a reheater is sometimes provided) composed of a superheater 5, an evaporator 8, and a economizer 11 from the upstream side of the exhaust gas flow.
A feature of the present embodiment is that an exhaust gas bypass is provided at a position adjacent to each heat exchanger, and an exhaust gas flow distribution device is provided at the exhaust gas bypass and at the inlet of each heat exchanger. . That is, the exhaust heat recovery boiler 4 in FIG. 1 includes a superheater exhaust gas flow distribution device 6, a superheater bypass passage 7, a superheater 5, an evaporator exhaust gas flow distribution device 9, an evaporator bypass passage 10, an evaporator 8, an economizer exhaust gas. Flow distribution device 1
2. It has a economizer bypass 13 and an economizer 11.

The boiler feed water 15 is supplied from the feed water pump 16 to the economizer 11 and heated, then temporarily stored in the steam separator drum 17, and then supplied to the evaporator 8 and heated to form a brackish water mixture again to form brackish water. The steam is returned to the separation drum 17, and the separated steam is supplied to the superheater 5, and the superheated steam 18 is obtained. The obtained superheated steam 18 is sent to a steam engine or the like. At this time, the temperature of the superheated steam is adjusted by the desuperheater 22.

FIG. 2 shows a temperature distribution diagram on the exhaust gas side and the steam-water supply side of the boiler 4 shown in FIG. After the combustion exhaust gas 2 discharged from the exhaust gas generation source 1 passes through the inlet duct 3, in the superheater exhaust gas flow distribution device 6, part of the exhaust gas is distributed to the superheater bypass 7, and the remaining exhaust gas is superheated. It flows into the vessel 5. The combustion exhaust gas 2 flowing into the superheater 5 exchanges heat with steam in the superheater 5 to lower the temperature,
It mixes with the exhaust gas that has passed through the superheater bypass passage 7, and its temperature becomes a combustion exhaust gas 23 in the upstream part of the evaporator 8. Next, in the evaporator exhaust gas flow distribution device 9, a part of the exhaust gas is distributed to the evaporator exhaust gas bypass passage 10, and at the same time, the remaining exhaust gas flows into the evaporator 8 and exchanges heat with the vapor in the evaporator 8. As a result, the temperature decreases, and the gas is mixed with the exhaust gas that has passed through the evaporator bypass 10 in the upstream part of the economizer 11, and the temperature becomes the combustion exhaust gas 24.

Next, in the economizer waste gas flow distribution device 12, a part of the exhaust gas is distributed to the economizer bypass passage 13, and the remaining exhaust gas flows into the economizer 11 and exchanges heat with the water supply side. Is performed, the exhaust gas temperature is reduced, and the exhaust gas is mixed with the exhaust gas that has passed through the economizer bypass passage 13 to become the combustion exhaust gas 25 whose temperature has been reduced, and is discharged from the chimney 14.

In a conventional exhaust heat recovery boiler system not provided with a bypass, a combustion exhaust gas 2 discharged from an exhaust gas generation source 1 as shown in FIG.
Although the temperature decreases each time the gas passes through the economizer 11 ', the temperature of the exhaust gas naturally decreases continuously after passing through the banks 5', 8 ', and 11'. In the heat recovery boiler system, as shown in FIG. 2, the flue gas 2 discharged from the flue gas generation source 1 passes through the banks 5, 8, 11 and the flue gas 23, 24, 25 is adjacent to the banks 5, 8, 11 respectively. Since the exhaust gas can be mixed with the exhaust gas whose temperature has not relatively decreased through the bypass passages 7, 10, 13 provided, the degree of the temperature decrease is small.

On the other hand, the feedwater 15 pressurized by the boiler feedwater pump 16 is heated by the economizer 11 and rises in temperature.
It is sent into the brackish water separation drum 17 and becomes constant temperature in the brackish water mixed state. The feedwater sent from the steam separation drum 17 to the evaporator 8 is superheated by the superheater 5 to obtain superheated steam 18 at the outlet of the superheater. The superheater outlet steam 18 is supplied to the demand equipment after the spray water is injected by the desuperheater 22 to lower the steam temperature to the required temperature.

In the above exhaust heat recovery boiler system, when the required amount and the temperature of the superheated steam generated from the exhaust heat recovery boiler 4 are different, the heat absorption amount is adjusted on the side of the exhaust heat recovery boiler 4 as follows. (1) When the required temperature of the superheater outlet steam 18 decreases, the superheater exhaust gas flow distribution device 6 is adjusted to increase the amount of combustion exhaust gas passing through the superheater bypass passage 7 and pass through the superheater 5. Reduce exhaust gas flow. Accordingly, the amount of heat exchange in the superheater 5 decreases, and the superheated steam 18 at the superheater outlet can be reduced to the required temperature. (2) When the required steam amount decreases, the exhaust gas flow distribution device 9 upstream of the evaporator 8 is adjusted to increase the amount of combustion exhaust gas passing through the evaporator bypass passage 10, and the exhaust gas passing through the evaporator 8 is increased. Reduce flow rate. Accordingly, the amount of heat exchange in the evaporator 8 decreases, and the amount of generated steam can be reduced. (3) Although not shown, when the reheater, the reheater bypass duct, and the exhaust gas flow distribution device are installed on the upstream side thereof, if the required temperature of the reheater outlet steam temperature decreases, The exhaust gas flow distribution device upstream of the reheater is adjusted to increase the amount of combustion exhaust gas passing through the reheater bypass duct and reduce the exhaust gas flow passing through the reheater. Along with this, the amount of heat exchange at the reheater decreases, and it becomes possible to lower the reheat steam temperature at the outlet of the reheater. (4) According to the operation state of the exhaust gas generation source 1, the economizer 11
When the outlet feed water temperature approaches the boiler drum saturation temperature and steaming occurs inside the economizer 11, the economizer 1
1 by adjusting the exhaust gas flow distribution device 12 to increase the amount of combustion exhaust gas passing through the economizer bypass 13.
1 to reduce the flow rate of exhaust gas. Accordingly, the amount of heat exchange in the economizer 11 is reduced, and the outlet feedwater temperature of the economizer 11 can be reduced.

In the above exhaust heat recovery boiler system, the exhaust gas bypass passages 7, 10, 13 and the exhaust gas flow distribution devices 6, 9, in parallel with the superheater 5, the evaporator 8, and the economizer 11, respectively.
Although an example in which the 12 is provided is shown, the present invention is not limited to this, and at least one heat exchanger (transfer) among the superheater 5, the evaporator 8, the reheater (not shown), and the economizer 11 is provided. A configuration in which the exhaust gas bypass passages 7, 10, 13 and the exhaust gas flow distribution devices 6, 9, 12 are provided in parallel with the heat pipe group) can be used.

The above-mentioned exhaust heat recovery steam generator is a vertical steam generator in which exhaust gas flows vertically, but the present invention can also be applied to a horizontal steam generator in which exhaust gas flows horizontally.

[0024]

According to the present invention, it is possible to cope with a change in the required temperature of the superheater outlet steam temperature or the reheater outlet steam temperature and the required steam amount, and to further prevent the occurrence of steaming inside the economizer. Can be.

[Brief description of the drawings]

FIG. 1 shows a case where an exhaust gas bypass passage and an exhaust gas flow distribution device are installed in front of them in a single-pressure exhaust heat recovery device according to an embodiment of the present invention in parallel with a superheater, an evaporator, and a economizer. FIG.

FIG. 2 shows a thermal equilibrium diagram of the single-pressure type exhaust heat recovery apparatus of FIG.

FIG. 3 shows an overall configuration diagram of a conventional single-pressure exhaust heat recovery device.

FIG. 4 is a thermal equilibrium diagram of the single-pressure exhaust heat recovery apparatus of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Exhaust gas generation source 2 Combustion exhaust gas 3 Inlet duct 4 Exhaust heat recovery boiler (single pressure type) 5 Superheater 6 Superheater exhaust gas flow distribution device 7 Superheater bypass passage 8 Evaporator 9 Evaporator exhaust gas flow distribution device 10 Evaporator bypass passage 11 Energy saving device 12 Energy saving device exhaust gas flow distribution device 13 Energy saving device bypass passage 14 Outlet duct / chimney 15 Boiler feedwater 16 Boiler feedwater pump 17 Drum 18 Superheated steam 22 Desuperheater 23 Combustion exhaust gas (front of evaporator) 24 Combustion exhaust gas (The upstream of the economizer) 25 Combustion exhaust gas (smoke outlet)

Claims (1)

[Claims] 1. A superheater, an evaporator, which is a steam generating heat exchanger disposed inside a casing by introducing a high-temperature gas.
An exhaust heat recovery steam generator provided with at least a superheater, an evaporator, and a economizer among the reheater and the economizer, wherein at least any one of the superheater, the evaporator, the reheater, and the economizer is used. An exhaust gas bypass passage is provided in an area adjacent to the heat exchanger installation area, and an exhaust gas flow distribution device is provided upstream of the exhaust gas bypass path in the heat exchanger installation area and the adjacent area. Steam generator.