JPH01318802A - Steam temperature control system for re-heating type combined plant - Google Patents

Abstract

PURPOSE:To reduce heat stress generated in a reheating type steam turbine and permit the safe operation of a reheating type combined plant by controlling a temperature difference between a main steam, generated by a reheating type waste heat retrieving boiler, and re-heated steam, within a limit value. CONSTITUTION:A main steam pipeline 21 and a reheated steam pipeline 22 are provided with temperature detectors 51, 52 for measuring the temperatures of main steam and reheated steam while a temperature difference between a main temperature and a reheated steam temperature, which are measured by the temperature detectors 51, 52, is operated in a control unit 53 to compare the temperature difference with a preset temperature difference limit value. When an actual temperature difference exceeds the limit value, a control apparatus 54 is operated so that the actual temperature difference is reduced to a value within the limit value. The temperature difference between the main steam and the reheated steam in a reheating type combined plant is controlled so as to be within the limit value in such a manner that the generation of a heat stress in a steam turbine 80 due to the temperature difference of the steam may be avoided whereby the safe operation of the plant may be contrived.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a reheat type waste heat recovery boiler used in a combined power generation plant that combines a reheat type waste heat recovery boiler, a gas turbine bean, and a reheat type steam turbine. This invention relates to a steam temperature control system for a recovery boiler.

[Prior art] Conventionally, N.M.E., 7l-GT-79 No. 1
Pages 6 to 17 (ASME, 7l-GT-79, PP1
．． As described in 6-17), a method for controlling the temperature of the steam generated from a non-reheat type heat recovery boiler to a constant value has been announced, but in a reheat type heat recovery boiler, There is no mention of a steam temperature control method.

On the other hand, regarding the steam temperature control of reheat boilers normally used in thermal power plants, various methods for accurately controlling the steam temperature itself have been published, as described in Japanese Patent Laid-Open No. 59-212606. Much effort has been focused on how to accurately control main steam temperature and reheat steam temperature.

[Problems to be Solved by the Invention] As described above, the prior art relates to steam temperature control of non-reheat type waste heat recovery boilers and steam temperature control of reheat boilers for ordinary thermal power plants.

These cannot be directly applied to exhaust heat recovery type and reheat type boilers.

Unlike boilers for regular thermal power plants, reheat type heat recovery boilers are simple heat exchangers that utilize waste heat from gas turbines, and the characteristics of the generated steam can also be passive depending on the condition of the exhaust gas from the gas turbine. Changes to

Here, the exhaust gas temperature of the gas turbine varies greatly depending on the ambient atmospheric temperature and the load on the gas turbine, so the temperature of the main steam and reheat steam generated from the reheat type waste heat recovery boiler also changes in the exhaust gas temperature. will change accordingly. Therefore, even if there is no temperature difference between main steam and reheat steam at the design point of the waste heat recovery boiler, if the atmospheric temperature or gas turbine load differs from the design point, the main steam and reheat steam will differ. There is a problem in that a temperature difference occurs and thermal stress is generated in a reheat steam turbine driven by the steam.

Furthermore, the temperature difference between main steam and reheat steam does not only occur during steady-state operation, but especially during startup and load changes, as the heat exchange characteristics of the reheat type waste heat recovery boiler become dynamic. In this case, an even larger temperature difference occurs. on the other hand,
One of the major characteristics of a combined cycle plant is its excellent operability, so frequent startups and stops and load changes are expected, and the above-mentioned temperature difference between main steam and reheat steam is expected.

Furthermore, the thermal stress caused by this has become a major obstacle to the operability.

The purpose of the present invention is to control the temperature difference between main steam and reheat steam generated in a reheat type waste heat recovery boiler to within a limit value, thereby reducing thermal stress generated in a reheat type steam turbine. The aim is to ensure safe operation of reheat type combined plants.

[Means for solving the problem] The above purpose is to provide a gas turbine, a reheat type waste heat recovery boiler that generates main steam and reheat steam using exhaust gas from the gas turbine, and a reheat type waste heat recovery boiler that generates main steam and reheat steam from the In a reheat type combined plant consisting of a reheat type main steam and a reheat type steam turbine driven by reheated steam,
A means for detecting main steam temperature and reheat steam temperature generated from a reheat type waste 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 control device that operates at least one or both of the main steam temperature control equipment and the reheat steam temperature control equipment so that the temperature difference between the main steam and the reheated steam is zero or within a predetermined limit based on the following. It is characterized by This is achieved by the steam temperature control system of the reheat combined plant.

Each device for main steam temperature control and reheat steam temperature control may be as described in claims 2 to 6, respectively.

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

[Example 1] An example of the present invention will be described below with reference to FIG.

A reheat-type waste heat recovery boiler 10 that recovers waste heat from a gas turbine is equipped with a superheater 11 that superheats main steam and a reheater 12 that heats reheated steam. The superheater 11 may be divided into two parts, and in this case, the two divided superheater 11 are connected by a connecting pipe 24 as shown in the figure. The superheater 11 is connected by a main steam pipe 21 to a high-pressure turbine 81 that constitutes a part of a reheat steam turbine 80, and exhaust gas from the high-pressure turbine is passed through a low-temperature reheat steam pipe 23 to the exhaust heat recovery boiler. The steam heated by the reheater 12 is guided to the reheater 12 provided in the reheater 10 and is passed through the high temperature reheat steam pipe 22 to the reheat turbine 82 that forms part of the reheat type steam turbine 80. be introduced.

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

In this way, since it is possible to keep the temperature difference between the main steam and the reheated steam within the limit value in the reheating combined plant, 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 steam temperature control method.

The main steam temperature detector 51 and the reheat steam temperature detector 5
The difference between the main steam temperature and the reheat steam temperature measured in step 2 is calculated, and if the main steam temperature is higher, the temperature difference is compared with the temperature difference limit value, and the actual temperature difference exceeds the limit value. In some cases, the main steam temperature control equipment is operated via a controller. Conversely, if the reheat steam temperature is higher than the main steam temperature,
Since the sign of the temperature difference is negative, a sign inverter is used to change the sign of the temperature difference to a positive value, and then a comparison is made with the temperature difference limit value. If the actual temperature difference exceeds the limit value, the controller is activated. to operate equipment for controlling reheat steam temperature.

With the above steam temperature control method, as shown in Figure 3, the main steam temperature and the reheat steam temperature (Figure 3 (a)), which would cause a temperature difference during partial load of the gas turbine if the above temperature control is not implemented, are It becomes possible to control the higher steam temperature to be equal to the lower steam temperature (Figure 3 (b))
.

Here, FIG. 3(b) shows a case where "0" is set as the limit value of the steam temperature difference, but of course it is also possible to set a numerical value within a certain range as this limit value.
In this case, the main steam temperature and the reheat steam temperature will be operated with a temperature difference within the limited range.

FIG. 4 shows an embodiment according to the present invention. In this example,
As a device for controlling the main steam temperature, a desuperheater 31 is installed in the middle of the pipe 24 connecting the two divided superheaters 11, and as a device for controlling the reheat steam temperature, a desuperheater 31 is installed between the high pressure turbine and the reheater. A desuperheater 24 is installed in the middle of the low-temperature reheat steam piping 23 that connects to
Spray water is introduced via pipe 33.36 equipped with 2.35. The spray water may be a part of the water supply branched from the outlet side of a water supply pump installed in the combined plant, or a part of the water supply branched from the outlet side of the energy saver installed in the exhaust heat recovery boiler. is possible.

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 the main steam piping 21 that connects the superheater 11 provided in the exhaust heat recovery boiler 10 and the high-pressure steam turbine. A desuperheater 34 is installed as a device for controlling the reheat steam temperature in the middle of the reheat steam piping 22 that connects the steam turbines. Further, the attemperators 31 and 34 are connected through pipes 26 and 28 each equipped with an MA regulating valve 25 and 27.

Saturated steam is supplied as temperature-reducing spray steam from the steam generation drum 13 of the exhaust heat recovery boiler or from the middle of a pipe connecting the drum and the superheater 11. Here, the temperature difference between 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 is calculated by the control device 53, If the temperature difference exceeds a preset temperature difference limit value, a regulating valve 25 or 27 will be in operation.

According to this example, it is possible to keep the temperature difference between main steam and reheat steam within the limit value in a reheat type combined plant, and since steam is used for temperature reduction, when water is used, Compared to the above, there is no risk 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 combustion burner 43 for the purpose of 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 an auxiliary combustion burner 43 is installed upstream of the exhaust gas flow of the reheater 12. An auxiliary combustion burner 45 is installed in the reheater for the purpose of increasing the temperature of the exhaust gas flowing into the reheater. Further, fuel is supplied to the auxiliary combustion burners 43, 45 through fuel pipes 47, 48 each equipped with a valve 44, 46 for adjusting the amount of auxiliary combustion fuel.

Here, the auxiliary combustion fuel amount adjustment valves 44 and 46 operate so that the difference between the main steam temperature and the reheated steam temperature is within a limit value, and adjust the temperature of the exhaust gas flowing into the superheater 11 or the reheater 12. to control the main steam temperature or reheat steam temperature.

In this embodiment, the steam having a lower steam temperature is controlled to match the temperature of the other steam having a higher steam temperature.

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

FIG. 7 shows another embodiment according to the present invention. Inside the exhaust heat recovery boiler 10, a partition plate 14 is arranged parallel to the flow direction of the exhaust gas.
The superheater 11 is placed in one exhaust gas flow path, and the reheater 12 is placed in the other exhaust gas flow path.
are arranged, and dampers 41, 42 are provided to adjust the exhaust gas flow rate of each exhaust gas flow path.

Here, by adjusting the amount of exhaust gas passing through the exhaust gas flow path in which the superheater 11 and the reheater 12 are arranged, respectively, using the dampers 41 and 42, the difference between the main steam temperature and the reheated steam temperature can be reduced. It is possible to keep it within a preset limit value.

According to this embodiment, the temperature difference between main steam and reheat steam in a reheat type combined plant can be kept within the limit value without introducing spray water, spray steam, auxiliary combustion fuel, etc. from the outside. This makes it possible to control steam temperature effectively in terms of plant thermal efficiency.

Further, FIG. 8 shows still another embodiment. The difference from FIG. 7 is that one of the exhaust gas flow paths, which is divided into two by a partition plate 14 in the exhaust heat recovery boiler lO, has a secondary superheater 16, a primary reheater 17 in order from the flow direction of the exhaust gas. A secondary reheater 18 and a primary superheater 15 are placed in the other exhaust gas flow path. The main steam passes through the primary superheater 151, then the secondary superheater 16, and then the main steam pipe 21 to the high pressure turbine, and the reheated steam passes through the primary reheater 171 and then the secondary reheater 1.
8 and goes to the reheat turbine via the reheat steam pipe 22. Even in the case of this specially designed exhaust heat boiler, the gas dampers 41.4 installed in each of the exhaust gas flow paths are
Similar effects can be obtained by operating 2.

In each of the embodiments described so far, only the temperature difference between the main steam and the reheated steam is controlled, and the temperature of each of these steams itself is not controlled to a predetermined value.

In contrast, in the embodiment shown in FIG. 9, the temperatures of the main steam and reheated steam themselves are controlled to a predetermined value, and the temperatures of both are also 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 is zero or is within the limit value. The set temperature and the set temperature of reheated steam are set in advance according to the load of the gas turbine or the temperature of exhaust gas from the gas turbine, etc., and the main steam temperature and reheated steam temperature are adjusted in each of the above-mentioned steps so that the set steam temperature is achieved. Operate appropriate main steam temperature control equipment and reheat steam temperature control equipment as in the example.

Note that either the main steam temperature or the reheat steam temperature is controlled to a preset temperature according to the gas turbine load or exhaust gas temperature, etc., and the other steam temperature is set to the controlled steam temperature. so that the difference is within the limit value,
The objectives of the invention can also be achieved by operating appropriate steam temperature control equipment.

In this embodiment, the main steam and reheat steam temperatures generated in the reheat type waste heat recovery boiler are controlled to a preset temperature according to the gas turbine load or exhaust gas temperature, etc., and the difference in steam temperature between the two is also controlled. Since it can be kept within a certain limit value, safe operation of the plant can be achieved even during sudden load changes.

[Effects of the Invention] As described above, according to the present invention, the temperature difference between the main steam and the reheated steam generated from the reheat type waste heat recovery boiler that utilizes the exhaust heat from the gas turbine is In addition, thermal stress can be suppressed within a limit value that does not generate thermal stress in a reheat steam turbine driven by reheat steam, and this has the effect of ensuring safe operation of a reheat combined plant.

[Brief explanation of the drawing]

FIG. 1 is a diagram generally showing an embodiment according to the present invention, and FIG.
The figure shows an example of the control block of the steam temperature control method according to the present invention, FIG. 3(a) shows the main control block when the present invention is not applied, and FIG. FIGS. 4 to 9 are diagrams showing changes in steam and reheated steam temperatures, respectively, showing other embodiments according to the present invention. io... Reheat type waste heat recovery boiler 11... Superheater 12... Reheater 21.
・・Main steam piping 22 ・・High temperature reheat steam piping 3
1...Main steam desuperheater 34...Reheat steam desuperheater 41, 42...Exhaust gas damper 43.45...Support m
Burner 51...Main steam temperature detector 52...Reheat steam temperature detector 53...Control device 54...Steam temperature control equipment 80...Reheat type steam turbine control is also included. Gas turbine load (%) Fig. 4 31 Main lid machine 5 Trout 7 32 Spraying 1 Water adjustment valve 33 Spray water piping γ Reheating shallow warmer 35 Spray 1 water 1 rotation Regulating valve 36 Sub 1 Mizunishigomiya Figure 5 2, : 1 25 Nubrella) Air Ji P Vertical Valve 3 I Main Steam Serpent Rinja 34 Tanzetsu Extinguisher Figure 6 η Combustion Chamber 4 43, 45 Auxiliary Combustion No. V-su 44, +6
Fuel 1 training # Fig. 7 14 Partition plate 4/, 42 Gas Danzmer - Fig. 8 j5-6 superheating gain j6 2 heat dissipators I7 - second son heats I8: Next re-diversion diagram

Claims (1)

[Claims] 1. A gas turbine, a reheat type waste heat recovery boiler that generates main steam and reheat steam using exhaust gas from the gas turbine, and main steam and reheat generated from the reheat type waste heat recovery boiler. In a reheat type combined plant consisting of a reheat type steam turbine driven by steam, a means for detecting the main steam temperature and reheat steam temperature generated from a reheat type waste heat recovery boiler, and a means for controlling the main steam temperature. at least one or both of the equipment and the reheated steam temperature control equipment, and a main steam temperature control device so that the temperature difference between the main steam and the reheated steam is zero or within a predetermined limit value based on the detection output of the detection means. A steam temperature control system for a reheat type combined plant, comprising a control device that operates at least one or both of a device and a reheat steam temperature control device. 2 The main steam temperature control equipment is installed on a part of the superheater installed in the reheat type waste heat recovery boiler, on the steam piping on the outlet side of the superheater, or inside the reheat type waste heat recovery boiler. It consists of a spray type attemperator installed on the piping connecting between the divided superheaters and a valve that adjusts the supply of spray fluid to the spray type attemperator, and is used to control the temperature of reheated steam. The equipment is a part of a reheater installed in a reheat type waste heat recovery boiler, or on the inlet side steam piping or outlet side steam piping of the reheater, or inside the reheat type waste heat recovery boiler. 2. The spray attemperator according to claim 1, comprising a spray attemperator provided on a pipe communicating between the installed and divided reheaters, and a valve for regulating the supply of spray fluid to the spray attemperator. Steam temperature control system for reheat type combined plant. 3. The steam temperature control system for a reheat type combined plant according to claim 2, wherein the spray fluid is detemperatured water. 4. The steam temperature control system for a reheat type combined plant according to claim 2, wherein the spray fluid is reduced temperature steam. 5 The main steam temperature control equipment consists of an auxiliary combustion burner installed upstream in the exhaust gas flow direction of the superheater included in the reheat type waste heat recovery boiler and a valve that adjusts the supply of fuel to the auxiliary combustion burner. The reheat steam temperature control device adjusts the auxiliary combustion burner installed upstream in the exhaust gas flow direction of the reheater included in the reheat type waste heat recovery boiler and the supply of fuel to the auxiliary combustion burner. The steam temperature control system for a reheat type combined plant according to claim 1, comprising a valve. 6 The inside of the reheat type waste heat recovery boiler has a flow path divided into two by a partition plate, etc. in the flow direction of exhaust gas, and a superheater is installed in one of the exhaust gas flow paths, and a superheater is installed in the other exhaust gas flow path. The reheat type combined according to claim 1, wherein a reheater is installed, and the main steam temperature control device and the reheat steam temperature control device include an exhaust gas damper that adjusts the flow rate of exhaust gas in each of the exhaust gas flow paths. Plant steam temperature control system. 7. The control device adjusts the load of the gas turbine or the temperature of the exhaust gas from the gas turbine in advance so that the temperature difference between the main steam and the reheated steam generated from the reheating type waste heat recovery boiler becomes zero or within a predetermined limit value. Operate the main steam temperature control equipment and reheat steam temperature control equipment so that the main steam temperature and reheat steam temperature match the main steam temperature and reheat steam temperature set according to the main steam temperature and reheat steam temperature, respectively. A steam temperature control system for a reheat type combined plant according to any one of claims 1 to 6. 8. The control device sets the temperature of either main steam or reheat steam generated from the reheat type waste heat recovery boiler to a set temperature that is preset according to the load of the gas turbine or the temperature of exhaust gas from the gas turbine. Operate the main steam temperature control equipment and reheat steam temperature control equipment so that the temperature of the other person matches the above temperature, and the difference between the temperature of the other person is zero or within a predetermined limit value. A steam temperature control system for a reheat type combined plant according to any one of claims 1 to 6.