KR830001118B1 - Automatic drainage method - Google Patents

Abstract

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Description

Automatic drainage method

1 is a schematic diagram of a system showing steam conduits, analog sensing devices, electronic processors and valve actuations.

2 is a graph showing the correlation of steam temperature to steam pressure and the saturation temperature curve and variable settings for open drainage closure.

The present invention relates generally to automation systems for process plant and power plant management, and more particularly to an automatic drainage method for managing steam flow conduits.

In power plants or their management, the transfer of two-phase fluid from one place to another is very important for the discharge of any condensate that may occur along the fluid flow path. In particular, in the power unit, in order to discharge the condensate in the fluid transfer header in the upper shaft position of the turbo machine to the drainage, the water droplets are not entrained in the vapor and transported to the turbo machine. This is important from a point of view. Furthermore, it is desirable to quickly remove condensate from the turbo machine casing to eliminate the possibility of non-uniform thermal gradients (temperature differences due to heat) in the turbo machine body due to deformation of the turbo machine casing.

One prior art system for executing automatic discharge control is described and illustrated in US Pat. No. 3,694,103 to Cohen et al. In such a system, the load state of the turbine is adjusted by a pressure switch, such as actuating a drain valve so that the turbine load drops to a predetermined level by about 20% of the rated load. Thus, the drain valves will open at a predetermined set point. The system can make a significant change in the turbo machine pressure to control the drain valve position, while the steam temperature change at high pressure is not controlled while condensation can occur.

Another prior art system for detecting the generation of droplets in steam conduits is disclosed in US Pat. No. 4,063,228 to Egenburger and Miller. The system detects the rate of change of temperature in the steam conduit to detect the presence of water droplets. The difference from this invention is that it is used to determine the temporary set point health for the generation of water droplets which allows the conduit pressure to be compared with the actual operating state.

According to the present invention, hardware has been developed for an automatic drainage system that accurately reacts to all combinations of steam temperatures and pressures occurring in a steam conduit. It is designed and developed to complement the problem. The present invention provides a method of operating an automatic drainage device by drainage using a set point for opening and closing a variable valve in accordance with a substantial sensing condition in the vapor bed.

The present invention is dependent on the interrelationship between steam pressure and steam temperature which defines the saturation curve. The method essentially includes sensing the steam pressure in the steam conduit and converting the steam pressure to saturation temperature. In practice, the drain valve will close if the detected steam temperature exceeds the saturated steam temperature based on a predetermined value. In addition, when the actually sensed steam temperature appears as a saturation curve according to a predetermined reference value of steam pressure, the drain valve is opened. In this connection, a function generator for converting a temperature curve into a device is used in carrying out the present invention. The comparator then compares the actual steam temperature with the saturated steam temperature to control the position of the drain valve.

The present invention will be described below based on the accompanying drawings.

The present invention provides a method for operating a combined cycle power unit, wherein a heat recovery steam generator (HRSG) supplies steam to one or more steam turbines. Combined cycle power units are well known as power units and consist of at least one gas turbine, one steam turbine and a heat recovery steam generator. The heat recovery steam generator is thermodynamically coupled with the gas turbine and steam turbine, and the exhaust gas from the gas turbine passes through the heat exchange with the feed water to convert the feed water into steam. It may be one or more heat recovery steam generators and one or more steam turbines.

Moreover, it is obvious that the particular embodiments shown are reflected in the original design objectives of the present invention and at the same time the present invention can be applied to a process fluid conduit incorporating a two-phase fluid. Furthermore, in power plants using steam as the power fluid, the invention is also applicable to turbine casing drainage and other points sensitive to fluid condensation.

In FIG. 1, the fluid header 11 is connected to at least one heat recovery steam generator (not shown) with at least one steam turbine (not shown). Collection pots (13), (15) and (17) are fixed to the lower position of the fluid header. An electronic drainage apparatus for carrying out the present invention drains water from this collection port.

Sensors are used to obtain temperature and pressure data from the header and drainage ports. For example, the pressure transducer 25 measures the fluid pressure of the header 11 and generates an output current I proportional to the vapor pressure. The output current I is converted into the voltage V of the current to the transformer 27. The output of transformer 27 is applied to a function generator 29 which provides an electrical output equal to the saturation temperature at the measured pressure. As mentioned above, this saturation temperature is varied by the pressure that determines the variable set point for the automatic drainage device.

Each of the drain collection ports 13, 15 and 17 is individually equipped with thermocouples 33, 35 and 37 which measure the fluid temperature of each conduit connected to the steam header. Each output of the thermocouple is an electrical voltage proportional to the measured temperature. Each output of the thermocouple is selectively applied to voltage amplifiers 41, 42, and 43. Its output is applied to signal comparators 45, 47, and 49. The voltage amplifier to which the voltage signal for each thermocouple is applied separately is also the output of the function generator 29, the second input to each of the signal comparators 45, 47 and 49. Each signal comparator output is applied to each of the contact output isolators 55, 57, and 59 connected to the electric drain valves 61, 63, and 65. The second output from each output signal is a specific electrical signal indicative of system coupling by a coupling alarm F connected to each electrical contact device.

2 shows the correlation between steam temperature and steam pressure. Solid line A is the saturation temperature which changes with temperature and pressure. Function generator 29 is a programmable device of Model 2AP + SGC manufactured by The Foxboro Company (Foxboro, Massachusetts) that can electronically reproduce data on line A and apply it to a comparator. .

Dashed line B is a dotted line showing a curve for closing the electronic drainage. This line is set by line A but has a constant temperature difference of 100 ° F (37.7 ° C) higher than line A. This is any set point based on what is known and experienced about the system state and its requirements. Line C is a drain open line that occurs above about 50 ° F (88 ° C) of the saturation temperature line. The comparators 45, 47 and 49 are previously controlled to adjust this value to control each drain valve according to FIG.

The method of the present invention is carried out according to the following steps. Detects the fluid pressure in the fluid conduit, converts the fluid pressure into a voltage representing the saturation temperature, detects the fluid temperature at the drainage position, and compares the detected fluid temperature with the saturation temperature at each drainage position. And positioning each of the drain valves at one of the valve opening positions or the valve closing positions by the output of the comparing step.

The present invention also provides a step of closing the drain valve at any time when the actual temperature exceeds the saturation temperature as the temperature difference increases by 100 ° C, and opening the drain valve at any time when the actual temperature is 50 ° C or less of the saturation temperature as the temperature difference decreases. Is done.

Claims (1)

A method of controlling the opening and closing of a drain valve in a fluid conduit, wherein the fluid pressure is sensed in the fluid conduit, the fluid pressure is converted to a saturation temperature, the actual fluid temperature is detected, and then the saturation temperature and the actual Comparing the fluid temperature of the, and the step of positioning each of the drain valve to one of the valve opening position and the valve closing position by the output of the comparing step.

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