JPS62159705A - Intermediate pressure turbine warming apparatus of reheating condensing turbine - Google Patents

Abstract

PURPOSE:To aim at shortening of warming time for an intermediate pressure turbine, by mounting a freely adjustable valve for controlling the flow of the steam passing an intermediate pressure turbine for warming, downstream from the exhaust side of the intermediate pressure turbine. CONSTITUTION:A reheating condensing turbine consists of a high pressure turbine 3 driven by a steam generated by the steam generator 2 of a boiler 1, an intermediate pressure turbine 6 in which a steam reheated by a reheater 5 after finishing the work is introduced, and a double flow type flow pressure turbine 9 in which the exhaust of the intermediate pressure turbine 6 is introduced through cross over tube 25. And a generator 10 is driven by the power generated by turbines 3, 6 and 9. In such a turbine, a valve 11 with freely adjustable opening is mounted to the cross over tube 25. And at the turbine starting, both high pressure and intermediate pressure steam control valves 4, 7 are slightly opened, while a bypass valve 11 is set at smaller opening than that of the intermediate pressure steam control valve 7, so that warming by steam is available.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to turbine metal warming when starting a reheat condensing turbine from a cold state. In particular, the present invention relates to a warming device for an intermediate pressure turbine of a reheat steam turbine having a turbine bypass system.

[Prior art and its problems]

First, to start a steam turbine from a cold state, steam from the boiler is fed into the steam turbine at a low speed below the rated rotational speed of the turbine axle, and the temperature of the turbine axle and casing is gradually raised. After warming up while alleviating thermal stress and thermal expansion differences due to temperature differences between various parts, the engine speed is increased to the rated rotation speed. The prior art will be described below with reference to the drawings. FIG. 3 is a system diagram of a conventional reheat condensing turbine. In FIG. After flowing through the control valve 4 and working in the high-pressure turbine 3, it becomes medium-pressure and low-temperature steam and flows into the reheater 5 of the boiler 1 through the low-temperature reheat pipe 21 equipped with a check valve 22. do. The high-pressure turbine back air, which has been heated again to a high temperature in the reheater 5, passes through the high-temperature reheat pipe 23, flows into the intermediate-pressure turbine 6 through the intermediate-pressure steam control valve 7, and enters the intermediate-pressure turbine. It works at a low-pressure low-temperature steam. Back air from the intermediate pressure turbine 6 is guided to a double flow type low pressure turbine 8 through a crossover pipe 25. The exhaust port of the low-pressure turbine 8 is connected to a condenser 9, and the steam flowing through the low-pressure turbine 8 expands to the vacuum of the condenser 9, performs work, and becomes condensed water. The condensate is then sent back to the boiler by a pump (not shown). Note that the generator 10 connected to the shaft of the reheat condensation turbine generates electric power as the turbine performs work as described above. A bypass line 27 that branches off from the main steam line 20 and bypasses the high-pressure turbine 3 and is provided with a bypass valve 26 is connected to the low-temperature reheat line 21 . Further, a low-pressure turbine bypass line 29 that branches off from the reheating steam line 23 and bypasses the intermediate-pressure turbine 6 and the low-pressure turbine 8 and is equipped with a bypass valve 28 is connected to the condenser 9 . Therefore, the steam from the steam generator 2 of the boiler 1 bypasses the high pressure turbine 3 and goes to the reheater 5, while the reheated steam from the reheater 5 bypasses the intermediate and low pressure turbines 6.8 and condenses. By adjusting the opening degree of the bypass valve installed in each pipe, the amount of steam sent to the high-pressure turbine, intermediate pressure, and low-pressure turbine can be controlled. I can do it. To start the reheat condensing turbine configured in this way from a cold state, the condenser 9 is evacuated by an ejector (not shown), and then the steam from the boiler 1 is sent to the reheat condensing turbine. Warming is performed while rotating the turbine in a low speed region below the rotation speed, and after warming is completed, the rotation speed is increased to the rated rotation speed. At this time, warming is performed by slightly opening the high-pressure steam control valve 4 and the intermediate-pressure 1-air control valve 7 to allow steam from the steam generator 2 passing through the main steam pipe 20 to the high-pressure turbine 3 and to the intermediate-pressure turbine. The reheating steam of the high pressure turbine back air that has passed through the reheater 5 is passed through the reheating steam pipes 23 and 24. In this case, if bypass pipes 27 and 29 are provided, the bypass valve 26 of the high pressure turbine is installed before ventilating the turbine.
By adjusting the opening of the low-pressure turbine bypass valve 28, the pressure in the reheat line, that is, the pressure in the pipeline consisting of the low-temperature reheat steam pipeline 21, the reheat steam pipeline 23, etc., is maintained at a predetermined pressure, for example, about 10 atg. can do. Therefore, when warming at a low speed, the internal pressure of the high-pressure turbine 3 is affected by the predetermined pressure of the reheat line, and the metal surface inside the high-pressure turbine reaches the saturation temperature of the predetermined pressure in a short time due to condensation heat transfer, e.g. If it is lQatg, it will be up to about 185°C. Therefore, heat soaking to a predetermined state can be completed in a short period of time. However, since the intermediate-pressure turbine is connected to the condenser 9 via the crossover pipe 25 and the low-pressure turbine 8, when the intermediate-pressure steam regulator 7 is slightly open, the intermediate-pressure steam regulator 7 After that, the pressure inside the turbine is mostly negative pressure (
(vacuum caused by the condenser). Therefore, the temperature can only be raised to less than the vacuum saturation temperature, that is, 100° C. (latg saturation temperature), by short-term heat transfer due to a-condensation of steam that has flown in for warming. Therefore, in an intermediate pressure turbine, after the metal surface dries out at a temperature below 100° C., the metal surface is warmed up to a predetermined temperature by convection heat transfer, and thus heat soaking is required at a speed below the rated rotation speed. However, even in the convective heat transfer range during heat soak after dryout, the internal pressure of the intermediate pressure turbine is low, so the thermal conductivity of the steam is low, making it difficult for the intermediate pressure turbine to warm smoothly. For this reason, it is necessary to perform warming by increasing the heat soak time, which lengthens the start-up time of the entire plant.Additionally, during the start-up time, the steam flowing through the bypass pipe becomes redundant, resulting in a large energy loss.

[Purpose of the invention]

In view of the above-mentioned points, an object of the present invention is to provide an intermediate-pressure turbine warming device for a reheat-condensing turbine that can shorten the warming time of the intermediate-pressure turbine of the reheat-condensing turbine.

[Key points of the invention]

According to the present invention, the reheat condensing turbine is provided with a pipe line that bypasses both the high pressure turbine and the intermediate pressure turbine. This is achieved by adding a means to reduce the amount of back air by half compared to the amount of air supplied to the intermediate pressure turbine.

[Embodiments of the invention]

The present invention will be described in detail below based on the drawings. FIG. 1 is a system diagram of a reheat condensing turbine according to an embodiment of the present invention. In FIG. 1 and FIG. 2, which will be described later, the same parts as in the conventional example shown in FIG. 3 are given the same reference numerals. In Figure 1, boiler 1. Steam generator2. Reheater5. High pressure turbine 3. Medium pressure turbine 6, low pressure turbine 8. The functions of the condenser 99, generator 10, bypass valves 26, 28, etc. are the same as those of the prior art, so their explanation will be omitted. A valve 11 whose opening degree can be freely adjusted is provided in a crossover pipe 25 which is a conduit leading to the pipe 9. By the way, when starting the reheat condensing turbine from a cold state, the condenser is evacuated as described above, and the high-pressure steam control valve 4 and the intermediate-pressure steam control valve 7 are slightly opened at low speed to allow the steam to flow. At this time, the bypass valve 11 is further set to the opening degree of the intermediate pressure steam control valve 7 or less. As a result, the internal pressure of the high-pressure turbine is maintained at the reheat line pressure, that is, about 10 atg, by adjusting the opening of the high-pressure turbine bypass valve 26 and the intermediate-pressure and low-pressure turbine bypass valves 28, as described above. The internal pressure of the pressure turbine 7 can be adjusted from about 10 atg to a pressure between the vacuum of the condenser by adjusting the opening of the valve 11, so by adjusting the opening of the valve 11, the pressure can be adjusted to about 7 atg, which is appropriate for warming. be able to. Therefore, as explained in the prior art section, the metal surface of an intermediate pressure turbine can reach approximately 170°C in a short time due to condensation heat transfer.
(saturation temperature of 7atg), and conventional warming can be performed in a shorter time. FIG. 2 is a system diagram of a reheat condensing turbine equipped with a warming device for an intermediate pressure turbine according to a different embodiment of the present invention. In FIG. 2, the crossover pipe 25 is provided with a valve 12 that can be opened and closed, and is further provided with a pipe 30 that guides the back air of the intermediate pressure turbine to the condenser.
1 is provided. With this configuration, the warming that occurs when the reheat condensation turbine is started from a cold state is achieved by closing the valve 12 and adjusting the opening of the valve 11 as described above to increase the pressure inside the intermediate pressure turbine. The same effect can be obtained.

【Effect of the invention】

As is clear from the above description, according to the present invention, the flow rate of steam flowing through the intermediate pressure turbine can be freely adjusted for warming when the reheat condensation turbine is started from a cold state. By installing a valve after the exhaust side of the intermediate pressure turbine, the pressure of the steam flowing to warm the intermediate pressure turbine can be increased by adjusting the opening degree of this valve. Condensation transfer makes it possible to raise the temperature to a high pressure saturation temperature in a short time, and warming can be performed in a shorter time than conventionally. Furthermore, as a result of shortening the warming time, the amount of steam released into the bypass line during warming is also reduced, which has the effect of reducing energy loss during startup.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a reheat condensing turbine equipped with an intermediate pressure turbine warming device according to an embodiment of the present invention, and FIG. 2 is a system diagram of a reheat condensing turbine equipped with an intermediate pressure turbine warming device according to a different embodiment of the present invention. Turbine System Diagram FIG. 3 is a system diagram of a reheat condensation turbine.

Claims (1)

[Claims] 1) Steam from the boiler is passed through a high-pressure turbine, its back air is heated in a reheater and sent to an intermediate-pressure turbine, and the back air is supplied to a low-pressure turbine through a crossover pipe. , which is led to a condenser to become condensed water, and which is branched from the main steam line to the high-pressure turbine, bypasses the high-pressure turbine, and is connected to the back air line of the high-pressure turbine via a bypass valve. and a pipe line that connects the reheated steam from the reheater to the condenser via a bypass valve, bypassing an intermediate pressure turbine and a low pressure turbine. In a turbine, a reheating system is provided on the back air side of the intermediate pressure turbine, and is characterized by an additional means for reducing the amount of back air by half compared to the amount of air supplied to the intermediate pressure turbine, which is activated only when the turbine is started. Medium pressure turbine warming device for condensing turbine. 2) The means for reducing the back air amount of the intermediate pressure turbine by half as described in claim 1 means that a control valve is interposed in the middle of a crossover pipe that connects the intermediate pressure turbine and the low pressure turbine. An intermediate pressure turbine warming device for a reheat condensing turbine, characterized by: 2) The means for reducing the back air amount of the intermediate pressure turbine by half as described in claim 1 means that a pipe line connecting the intermediate pressure turbine and the condenser is provided with a control valve interposed therebetween, and the cross An intermediate pressure turbine warming device for a reheat condensing turbine, characterized in that a stop valve is interposed in the middle of an overpipe.