JPS58178200A - Scavenging steam controlling device of heat exchanger - Google Patents

Abstract

PURPOSE:To reduce unstable phenomena in heat pipes and consequently prevent the thermal stress and deformation accompanying said phenomena by a method wherein a flow rate of scavenging steam, which is the heating steam of the heat exchanger to supply reheated high pressure turbine exhaust steam to a low pressure turbin, is optimum-controlled. CONSTITUTION:The flow rate of scavenging steam is controlled by a scavenging steam exhaust valve 11 in proportion to the opening of a drainage exhaust valve 10 by means of a controlling unit 50 (not shown in fig.). In the controlling unit 50, the flow rate of drainage GD 23 is calculated by an arithmetic unit 22 in proportion to the opening of the drainage exhaust valve 10. Next, the flow rate signal of the flow rate GD 23 is transmitted together with the flow rate signal of the flow rate of heating steam GS 25 to an adder 24 in order to calculate the flow rate of scavenging steam GV 26. Further, a scavenging steam ratio GV/GD is calculated by a divider 27. The set value set at a scavenging steam ratio setter 28 and the scavenging steam ratio GV/GD are compared with each other at an adder 29 and a valve opening signal AV 31 is calculated by an arithmetic unit 31 based upon a deviation signal alpha of said set value and ratio GV/GD and given as an operating signal to the scavenging steam exhaust valve 11 in order to control the flow rate of scavenging steam.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat exchanger, and particularly to a heat exchanger for reheating high-pressure turbine exhaust gas and supplying steam to each low-pressure turbine in a power plant or the like.

Conventional heat exchange 6 that heats steam guided to a low-pressure turbine via a high-pressure turbine is a heat exchange method in which the heated steam is passed through a heat transfer tube and the latent heat is imparted to the heated steam flowing outside the heat transfer tube. It is a system. The heated steam passing through the heat transfer tube flows down while condensing within the tube due to heat exchange with the steam to be heated, and flows in a cylindrical flow form as it moves toward the tube outlet. Furthermore, if the heated steam flowing into the heat exchanger tube is completely condensed within the heat exchanger tube before the outlet end of the heat exchanger tube, there is a possibility that a reservoir 9 of supercooled condensate may be formed within the heat exchanger tube. Disadvantages associated with this phenomenon of supercooling of the condensate are the occurrence of local thermal stress and heat exchange in the heat exchanger tube, or the instability of the two-phase flow of steam and condensate flowing inside the heat exchanger tube. There is a possibility that the reliability of the heat exchanger tubes may be seriously impaired.

One possible way to alleviate this problem is to derive the amount of scavenging steam from the heated steam to discharge the condensate generated in the heat exchange (transfer), but if the amount of scavenging steam derived is small This causes instability in the heat transfer tubes as mentioned above, and conversely, when the amount of scavenging steam is large, the generation of steam from the power generation plant is used as heating steam, so the power generation plant This had the disadvantage of causing a decrease in thermal efficiency.

The purpose of the present invention is to prevent the instability phenomenon in the heat transfer tubes from being reduced by optimally controlling the amount of scavenging steam produced by the heated steam of the heat exchanger that heats the steam supplied to the low-pressure turbine. The objective is to provide a control device for nine heat exchangers for OT function.

Next, one embodiment of the present invention will be described. FIG. 1 shows a typical example of a steam turbine plant using a heat exchanger to heat the steam supplied to a low pressure turbine. That is,
The exhaust gas of the high-pressure turbine 15 is guided into the body of the heat exchanger 1 through the heated steam pipe 18, where it is reheated by the heated steam flowing through the heat transfer f40, and after death is passed through the Jl reheat steam pipe. 19, through the second reheat steam pipe 20, and the first
It is designed to be guided to a low pressure turbine 16 and a second low pressure turbine 17. Also, for heat exchanger 1, /J
The hot steam enters the first header 2 through the heating steam pipe 4, flows through the heat transfer tube 41, and exchanges heat with the heated steam.
2nd header 3t - through, drain and steam and VC+ 11
11 and then discharged. The drain is passed through the drain discharge pipe 59 and into the drain tank 8K1w. A water level gauge 9 is installed in the drain tank 8 to detect the water level of the drain. This water riti9! water level 1gg
x2 enters the water level mJmdxaK, and in order to keep the water level constant, a valve opening signal 14 is sent from the cough water level regulator 13 to the drain discharge valve 1o, and the drain discharge Ji is kept constant and the water level is adjusted to a constant level. are doing.

In addition, the steam discharged from the second header 3, that is, the scavenging steam, is VC configured such that the flow 1k thereof is regulated and discharged through the scavenging steam f6 through the steam exhaust valve 11. .

Here, the scavenging steam discharge valve 11 is replaced by the drain discharge valve 10 (
7) It is controlled by a control device 5° according to the opening degree.

Next, FIG. 2 shows a control block diagram of the control device 5, which controls the ratio of 4-gas steam to the condensing filter and the amount of scavenging steam in 1-heat generator 1.

First, in the control device 50, the lsl calculation device 2
2, the drain flow rate (GD) 23 is calculated based on the valve opening degree of the drain discharge valve lO, and then it is measured by the flow meter 7 installed in the heated steam pipe 4, and the heated steam t (Gs) 25 is calculated.
At the same time, the flow rate signal is transmitted to the first adder 24 to calculate the scavenging steam amount (Gy) 26. That is, 1 t of steam (
Gy) 5 Heating steam amount (Gs) - drain flow rate (Go).

Furthermore, the output steam ratio (Gma/GD) is calculated by the divider 27.
Calculate. Scavenging steam amount ratio setting device 28Fi, heat exchanger tube 4
The scavenging steam amount ratio when no instability phenomenon occurs in the 2nd) JD
11629, and based on the deviation signal α between the two, the second calculation station 30 calculates the second valve opening signal (A, ) 31, and this signal is used as the scavenging steam discharge valve 11Km operation signal. It is designed to control the amount of scavenging steam by giving

Note that the second arithmetic unit [at t30, the set value and the actual 4
Based on the difference signal α from the vapor density ratio (Gma/GD), the valve m degree is increased as α increases, based on the valve P l1eA t when α is zero, and conversely, α decreases. , 6, the valve opening degree is calculated and outputted so as to reduce the valve opening degree.

Next, FIG. 3 shows another embodiment of the present invention, in which the opening degree of the scavenging steam exhaust valve 11 is determined by the turbine output. ll
4Ii represents a block diagram when controlling the amount of scavenging steam.

As the turbine output decreases, the scavenging steam rate increases, but the rfl nail vapor deposition in the combined heating steam chamber increases, resulting in a decrease in the thermal efficiency of the plant. Therefore, the valve opening degree is adjusted so as to keep the turbine cutting edge and the four-gas steam filter ratio constant.

That is, the turbine output 21 is controlled by the control device 15o #! 3
A calculation device 32 is manually operated, and there outputs a tiger S3 valve opening signal 33 that matches the turbine output, and the scavenging steam exhaust valve 11 is adjusted using this signal to control the amount of scavenging steam.

As explained above, according to the present invention, by controlling the amount of scavenging steam, which is heat-exchanged steam, instability within the heat transfer tube can be reduced, and the thermal stress associated with it can be reduced. This has the effect of realizing a scavenging steam control device for a heat exchanger that can prevent thermal deformation.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a steam turbine plant equipped with a scavenging steam control device for a heat exchanger which is one embodiment of the present invention, and Fig. 2 is an example of the configuration of the scavenging steam control device shown in Fig. 1. -The detailed control block diagram, tIN3 diagram, shows the m'
;USS is a block diagram showing a control device.

Claims (1)

[Claims] 1.Heating steam passes through the U-shaped heat transfer tube, and its latent heat is
In a heat exchanger that supplies heated steam flowing outside the heat exchanger tube, scavenging steam piping that discharges scavenging steam, which is heated steam that has passed through the heat exchanger tube, from the header of the heat exchanger tube, and condensation generated within the heat exchanger tube. Scavenging steam to the drain pipe that discharges water.
A control device is provided, which includes a control valve and a drain valve, and further includes a control device that calculates the ratio of the amount of scavenging steam to the amount of condensation of the drain based on the opening degree of the drain valve, and adjusts the opening degree of the scavenging steam regulating valve. Scavenging steam control device for heat exchanger that uses % mold.