JP2595046B2 - Steam temperature control system for reheat type combined plant - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a reheat-type waste heat recovery used in a combined power generation plant combining a reheat-type waste heat recovery boiler, a gas turbine, and a reheat-type steam turbine. The present invention relates to a boiler steam temperature control system.

[Prior Art] Conventionally, as described in ASME, 71-GT-79, pages 16 to 17 (ASME, 71-GT-79, PP16-17), non-reheating Although a method of controlling the temperature of steam generated from a waste heat recovery boiler of a mold to a constant value has been disclosed, there is no mention of a method of controlling a steam temperature in a reheat type waste heat recovery boiler.

On the other hand, regarding the steam temperature control of a reheat boiler usually used in a thermal power plant, various methods for accurately controlling the steam temperature itself have been disclosed as described in JP-A-59-212606. Much effort has been put into how to precisely control the main steam temperature and the reheat steam temperature.

[Problems to be Solved by the Invention] As described above, the related art relates to steam temperature control of a non-reheat type exhaust heat recovery boiler and steam temperature control of a reheat boiler for a normal thermal power plant. It cannot be directly applied to a heat recovery type and reheat type boiler.

A reheat type waste heat recovery boiler is a simple heat exchanger that uses waste heat from a gas turbine, unlike a boiler for a thermal power plant, and depends on the state of exhaust gas from the gas turbine.
The characteristics of the generated steam also change passively.

Since the exhaust gas temperature of the gas turbine greatly changes depending on the ambient air temperature and the load on the gas turbine, the temperature of the main steam and the reheat steam generated by the reheat type exhaust heat recovery boiler also changes with the change of the steam exhaust gas temperature. Will change. For this reason, even when there is no temperature difference between the main steam and the reheat steam at the design point of the exhaust heat recovery boiler, the main steam and the reheat steam are separated at the atmospheric temperature or the gas turbine load different from the design point. There is a problem that a temperature difference is generated and thermal stress is generated in a reheated steam turbine driven by the steam.

Furthermore, the temperature difference between the main steam and the reheated steam is not only at the time of steady state operation, but especially at the time of start-up and load change, etc., because the heat exchange characteristic of the reheated waste heat recovery boiler becomes dynamic, In this case, a larger temperature difference occurs. On the other hand, in the combined cycle plant, one of its major features is excellent operability, so frequent start-stop, load change operation is expected, and the temperature difference between the main steam and the reheated steam, and by extension, The thermal stress has been a major obstacle to the operability.

An object of the present invention is to control a temperature difference between main steam and reheat steam generated in a reheat type exhaust heat recovery boiler within a limit, thereby reducing thermal stress generated in a reheat type steam turbine. Thus, the safety operation of the reheat type combined plant is to be achieved.

[Means for Solving the Problems] The above object is achieved by a gas turbine, a reheat-type exhaust heat recovery boiler that generates main steam and reheat steam from exhaust gas from the gas turbine, and a reheat-type exhaust heat recovery boiler. Means for detecting the main steam temperature and the reheat steam temperature generated by the reheat type exhaust heat recovery boiler in a reheat type combined plant comprising a main steam and a reheat type steam turbine driven by the reheat steam. A temperature difference between the main steam and the reheat steam based on at least one of or both of the main steam temperature control device and the reheat steam temperature control device and the detection output of the detection unit so as to be zero or within a predetermined limit value. And a control device for operating at least one or both of the main steam temperature control device and the reheat steam temperature control device. Achieved by an air temperature control system.

Each device for controlling the main steam temperature and the device for controlling the reheated steam temperature may be those described in claims 2 to 6, respectively.

[Operation] With the above configuration, the temperature difference between the main steam and the reheated steam in the reheated combined plant can be set to zero or within a limit value so as to be suitable for safe operation of the reheated steam turbine.

[Embodiment] Hereinafter, an embodiment of the present invention will be generally described with reference to FIG.

A reheat-type exhaust heat recovery boiler 10 that recovers exhaust heat from a gas turbine includes a superheater 11 that heats main steam and a reheater 12 that heats reheat steam. The superheater 11 may be divided into two parts. In this case, the superheater 11 is divided into two parts.
Are connected by a communication pipe 24 as shown. The superheater 11 is connected by a main steam pipe 21 to a high-pressure turbine 81 constituting a part of a reheat-type steam turbine 80, and the exhaust from the high-pressure turbine is passed through a low-temperature reheat steam pipe 23, and the exhaust heat recovery boiler The steam is led to a reheater 12 provided in 10, where the heated steam is passed through a high-temperature reheat steam pipe 22,
Reheat turbine 82 forming a part of reheat type steam turbine 80
Will be introduced.

Here, the main steam pipe 21 and the reheat steam pipe 22 are provided with temperature detectors 51 and 52 for measuring main steam and reheat steam temperatures, respectively, and the main steam measured by the temperature detectors is used. The temperature difference between the temperature and the reheat steam temperature is calculated by the controller 53, and the temperature difference is compared with a preset temperature difference limit value. If the actual temperature difference exceeds the limit value, the actual temperature difference exceeds the limit value. The control device 54 as described in each embodiment described later is operated so that the temperature difference falls within the limit value.

Thus, since it is possible to keep the temperature difference between the main steam and the reheat steam in the reheat type combined plant within the limit value, it is possible to avoid the occurrence of thermal stress due to the steam temperature difference in the steam turbine 80, Safe operation of the plant can be achieved.

FIG. 2 shows an example of the above-mentioned steam temperature control method. The difference between the main steam temperature and the reheat steam temperature measured by the main steam temperature detector 51 and the reheat steam temperature detector 52 is calculated, and when the main steam temperature is higher, the temperature difference and the temperature difference are calculated. The limit values are compared, and if the actual temperature difference exceeds the limit value, the main steam temperature control device is operated via the controller. Conversely, if the reheat steam temperature is higher than the main steam temperature, the sign of the temperature difference becomes negative, so that the sign of the temperature difference is made positive by a sign inverter, and When the actual temperature difference exceeds the limit value, the controller for controlling the reheated steam temperature is operated via the controller.

According to the above steam temperature control method, as shown in FIG.
When the above temperature control is not performed, a main steam temperature and a reheat steam temperature (third temperature) at which a temperature difference occurs when the gas turbine is partially loaded.
It is possible to control any higher steam temperature in FIG. 3A to be equal to the lower steam temperature (FIG. 3B).

Here, FIG. 3 (b) shows a case where "0" is set as the limit value of the steam temperature difference. Of course, a numerical value having a certain range can be set as the limit value.
In this case, the operation is performed at a temperature difference between the main steam temperature and the reheat steam temperature that falls within the limited range.

FIG. 4 shows an embodiment according to the present invention. In the present embodiment, as a device for controlling the main steam temperature, a desuperheater 31 is installed in the middle of a pipe 24 that connects the superheater 11 divided into two,
As a device for controlling the reheat steam temperature, a desuperheater 24 is installed in the middle of a low-temperature reheat steam pipe 23 that communicates from the high-pressure turbine to the reheater 12, and regulating valves 32 and 35 are provided for the respective deheaters. The spray water is introduced through the pipes 33 and 36 provided with. The spray water may use a part of the feedwater branched from the outlet side of a feedwater pump installed in the combined plant or a part of the feedwater branched from the outlet side of the economizer provided in the exhaust heat recovery boiler. Conceivable.

FIG. 5 shows another embodiment according to the present invention. A desuperheater 31 is installed as a main steam temperature control device in the middle of a main steam pipe 21 connecting a superheater 11 provided in an exhaust heat recovery boiler 10 and a high-pressure steam turbine. A desuperheater 34 is installed in the reheat steam pipe 22 that communicates with the steam turbine as a reheat steam temperature control device. Also the cooler 3
Saturated steam is reduced from the steam generating drum 13 of the exhaust heat recovery boiler or the pipe connecting the drum and the superheater 11 through pipes 26 and 28 equipped with regulating valves 25 and 27, respectively. It is supplied as spray vapor for use. Here, the main steam temperature and the reheat steam temperature measured by the temperature detectors 51 and 52 provided on the main steam pipe 21 and the reheat steam pipe 22, the temperature difference between the two is calculated by the controller 53,
If the temperature difference exceeds a preset temperature difference limit value, the regulating valve 25 or the adjusting valve 25 for adjusting the amount of spray steam to the desuperheater having a higher steam temperature so that the temperature difference is within the limit value.
27 will work.

According to the present embodiment, it is possible to make the temperature difference between the main steam and the reheat steam in the reheat type combined plant within the limit value, and to use steam to reduce the temperature, so that water is used. In comparison with this, there is no danger of water droplets flowing into the steam turbine 80, and safe operation of the plant can be achieved.

FIG. 6 shows another embodiment according to the present invention. An auxiliary burner 43 for increasing the temperature of the exhaust gas flowing into the superheater is installed upstream of the exhaust gas flow of the superheater 11 provided in the exhaust heat recovery boiler 10, and upstream of the exhaust gas flow of the reheater 12. Is provided with an auxiliary burner 45 for raising the temperature of the exhaust gas flowing into the reheater. The auxiliary burners 43 and 45 have valves 44 and 46 for adjusting the amount of fuel for auxiliary combustion, respectively.
The fuel is supplied by the fuel pipes 47 and 48 having.

Here, the auxiliary fuel amount regulating valves 44 and 46 operate so that the difference between the main steam temperature and the reheat steam temperature is within the limit value, and the superheater
The main steam temperature or the reheat steam temperature is controlled by adjusting the temperature of the exhaust gas flowing into the reheater 11 or 11.

In this embodiment, the control is performed so that the lower steam temperature is adjusted to the other higher steam temperature.

In this embodiment, the auxiliary burners 43 and 45 are installed upstream of the superheater 11 and the reheater 12, respectively, on the exhaust gas side, but at the time of designing the exhaust heat recovery boiler, the main steam temperature or the reheat steam temperature is reduced. If it is clear that any one of the steam temperatures always becomes lower than the other even when the atmospheric temperature and / or the gas turbine load changes, a superheater or a reheater for heating the steam having the lower steam temperature is used. The object of the present invention can be achieved by installing an auxiliary burner only on the exhaust gas upstream side.

FIG. 7 shows another embodiment according to the present invention. The inside of the exhaust heat recovery boiler 10 is divided into two parts by a partition plate 14 in parallel with the flow direction of the exhaust gas.
A reheater 12 is disposed in the other exhaust gas channel, and dampers 41 and 42 for adjusting the exhaust gas flow rate in the respective exhaust gas channels are provided.

The difference between the main steam temperature and the reheat steam temperature is adjusted by adjusting the amount of exhaust gas passing through the exhaust gas passage in which the superheater 11 and the reheater 12 are arranged by the dampers 41 and 42, respectively. It is possible to set it within the limit set in advance.

According to the present embodiment, the temperature difference between the main steam and the reheat steam in the reheat type combined plant can be kept within the limit value without introducing spray water, spray steam or fuel for auxiliary combustion from the outside. As a result, effective steam temperature control can be performed in terms of thermal efficiency of the plant.

FIG. 8 shows still another embodiment. 7 is different from FIG. 7 in that one of the two exhaust gas passages divided by a partition plate 14 in the exhaust heat recovery boiler 10 has a secondary superheater 16 and a primary reheater 17 in order from the exhaust gas flow direction. And a secondary reheater 18 and a primary superheater 15 are arranged in the other exhaust gas flow path. The main steam passes through the primary superheater 15, then through the secondary superheater 16, through the main steam pipe 21 to the high-pressure turbine, and the reheat steam passes through the primary reheater 17, then the secondary reheater 18. Through the reheat steam pipe 22 to the reheat turbine. In the case of the non-heat recovery boiler having this structure, the same effect can be obtained by operating the gas tampers 41 and 42 provided in the respective exhaust gas passages.

In each of the embodiments described so far, only the temperature difference between the main steam and the reheat steam is controlled, and the control for making the temperature of each of the steam itself predetermined is not performed. On the other hand, in the embodiment shown in FIG. 9, the temperatures of the main steam and the reheat steam themselves are controlled to a predetermined value, and both temperatures are controlled within a predetermined limit range. That is, in the embodiment shown in FIG. 9, the temperature difference between the main steam generated from the reheat-type waste heat recovery boiler and the reheat steam becomes zero or within the limit value. The set temperature of the reheat steam and the set temperature of the reheat steam are set in advance according to the load of the gas turbine or the temperature of the exhaust gas from the gas turbine, and the main steam temperature and the reheat steam temperature are set so as to be the set steam temperature. Operate the appropriate main steam temperature control equipment and reheat steam temperature control equipment as in the example.

In addition, one of the main steam temperature and the reheat steam temperature is controlled to be a temperature set in advance according to the gas turbine load or the exhaust gas temperature, and the other steam temperature is controlled by the controlled steam temperature. So that the difference between
The purpose of the present invention can be achieved by operating a suitable steam temperature control device.

In the present embodiment, the temperature of the main steam and the reheat steam generated in the reheat type exhaust heat recovery boiler is controlled to a temperature set in advance according to the gas turbine load or the exhaust gas temperature, and the difference between the two steam temperatures is also controlled. Since it can be within a certain limit value, safe operation of the plant can be achieved even when the load suddenly changes.

[Effects of the Invention] As described above, according to the present invention, the temperature difference between the main steam and the reheat steam generated from the reheat type exhaust heat recovery boiler using the exhaust heat from the gas turbine, the main steam, The reheat steam turbine driven by the reheat steam can be suppressed within a limit value that does not generate thermal stress, and there is an effect that the safe operation of the reheat combined plant can be ensured.

[Brief description of the drawings]

FIG. 1 is a diagram generally showing an embodiment according to the present invention, and FIG.
FIG. 3 is a diagram showing an example of a control block of the steam temperature control method according to the present invention. FIG. 3 (a) shows a case where the present invention is not applied, and FIG. 3 (b) shows a main case where the present invention is applied. FIGS. 4 to 9 show changes in steam and reheat steam temperatures, respectively, showing another embodiment of the present invention. 10 ... reheat type waste heat recovery boiler, 11 ... superheater, 12 ... reheater, 21 ... main steam pipe, 22 ... high temperature reheat steam pipe, 31
…… Main steam cooler, 34 …… Reheat steam cooler, 41,42 ……
Exhaust gas damper, 43, 45… combustion burner, 51… Main steam temperature detector, 51… Reheat steam temperature detector, 53 …… Control device, 54 …… Steam temperature control equipment, 80 …… Reheat Type steam turbine

Claims (8)

(57) [Claims] 1. A reheat-type exhaust heat recovery boiler for generating main steam and reheat steam from exhaust gas from a gas turbine, a gas turbine, and a main steam and reheat steam generated from the reheat type exhaust heat recovery boiler. In a reheat type combined plant comprising a driven reheat type steam turbine,
Detecting means for detecting a main steam temperature and a reheat steam temperature generated from the reheat type exhaust heat recovery boiler; at least one or both of a main steam temperature control device and a reheat steam temperature control device; and a detection output of the detection means. And a controller for operating at least one or both of the main steam temperature control device and the reheat steam temperature control device such that the temperature difference between the main steam and the reheat steam is zero or within a predetermined limit value based on A steam temperature control system for a reheat type combined plant, characterized in that: 2. The apparatus for controlling main steam temperature includes a part of a superheater installed in a reheat type exhaust heat recovery boiler, a steam pipe on an outlet side of the superheater, or a reheat type exhaust heat recovery apparatus. The reheater comprises a spray desuperheater provided on a pipe communicating between divided superheaters installed in a boiler, and a valve for controlling supply of a spray fluid to the spray desuperheater. The steam temperature control device is a part of the reheater installed in the reheat type exhaust heat recovery boiler, on the inlet side steam pipe or the outlet side steam pipe of the reheater, or on the reheat type exhaust heat A spray desuperheater provided on a pipe installed in a recovery boiler and communicating between divided reheaters, and a valve for controlling supply of a spray fluid to the spray desuperheater. Item 2. A steam temperature control system for a reheat combined plant according to Item 1. 3. The steam temperature control system according to claim 2, wherein the spray fluid is desuperheated water. 4. The steam temperature control system for a reheat type combined plant according to claim 2, wherein said spraying fluid is reduced temperature steam. 5. An apparatus for controlling main steam temperature, comprising: an auxiliary burner installed upstream of a superheater provided in a reheat type exhaust heat recovery boiler in a flow direction of exhaust gas; and a supply of fuel to the auxiliary burner. The reheat steam temperature control device comprises an auxiliary burner installed upstream of the reheater in the exhaust gas flow direction of the reheater provided in the reheat type exhaust heat recovery boiler, and a fuel supply to the auxiliary burner. 2. A valve for regulating the supply.
The steam temperature control system of the reheat type combined plant described in the above. 6. A reheat-type exhaust heat recovery boiler has a flow path divided into two by a partition plate or the like in a flow direction of exhaust gas, and a superheater is installed in one of the exhaust gas flow paths, and the other exhaust gas is provided. The reheater is installed in the flow path, and the main steam temperature control device and the reheat steam temperature control device comprise an exhaust gas damper for adjusting an exhaust gas flow rate in each of the exhaust gas channels. Steam temperature control system for reheat combined plant. 7. The control apparatus according to claim 1, wherein the control unit is configured to control the load of the gas turbine or the gas turbine so that the temperature difference between the main steam generated from the reheat-type waste heat recovery boiler and the reheat steam is zero or within a predetermined limit value. Main steam temperature control equipment and reheat steam temperature control so that the main steam temperature and the reheat steam temperature match the main steam set temperature and the reheat steam set temperature set according to the exhaust gas temperature The steam temperature control system for a reheat type combined plant according to any one of claims 1 to 6, wherein the system operates equipment. 8. The controller according to claim 1, wherein the temperature of one of the main steam and the reheat steam generated from the reheat type exhaust heat recovery boiler is set in advance in accordance with the load of the gas turbine or the temperature of the exhaust gas from the gas turbine. Main steam temperature control equipment and reheat steam temperature control so that the temperature of the other person matches the set temperature and the difference between the temperature of the other person and the temperature of the other person is zero or within a predetermined limit value. The steam temperature control system for a reheat-type combined plant according to any one of claims 1 to 6, wherein the system operates a device for use.