JP2000241329A - Device for measuring degree of steam dryness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a device for measuring the degree of steam dryness for automatically and rapidly measuring the degree of dryness. SOLUTION: A stem channel 2 is composed where a primary-side stem flowing through steam piping 1 is introduced to a flash chamber 4 at a secondary side through a control valve 3 as an orifice, is heat-insulated and inflated in the flash chamber 4 for unloading via a control valve 5. Sensors 6, 7, 8, and 9 are provided to detect the pressure and temperature of primary-side steam and those of secondary-side steam. A control operation part 10 is provided to control the opening of the control valve 5 so that the secondary-side steam becomes overheated based on the pressure and temperature of the secondary-side steam being detected by the sensors 8 and 9 and to calculate the degree of dryness of the primary-side steam based on the pressure of the primary-side steam and the pressure and temperature of the secondary-side steam being detected by the sensors 6, 8, and 9 while the secondary-side steam is overheated. Since the opening of the control valve 5 is automatically controlled and the degree of dryness of the primary-side steam is calculated so that the secondary- side steam is overheated, the degree of dryness can be automatically and rapidly measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the moisture content in steam, that is, the degree of dryness indicating the ratio of the mass of dry saturated steam to the total mass per unit volume of a steam flow. In various boilers, equipment using steam power, and drying equipment, it is necessary to measure the dryness of steam for heat management. This is because the enthalpy of the steam varies depending on the water content.

[0002]

2. Description of the Related Art A conventional steam dryness measuring apparatus is disclosed, for example, in Japanese Patent Publication No. 6-14004. This is to introduce a primary steam into a secondary flash chamber through an orifice, to form an adiabatic expansion in the flash chamber, and to constitute a steam flow path for discharging through a control valve. A sensor for detecting the pressure and temperature of the secondary steam is provided, and the secondary steam becomes saturated steam based on the pressure and temperature of the secondary steam detected by the sensor for the opening degree of the control valve. And the dryness of the primary steam is calculated based on the pressure of the primary steam and the pressure of the secondary steam detected by the sensor in a state where the secondary steam has become saturated steam. It is provided with a control operation unit.

[0003]

Since the conventional steam dryness measuring device controls the opening of the control valve so that the secondary steam becomes saturated steam, it takes a long time to measure the dryness. There was a problem. That is, the opening degree of the control valve must be gradually changed so that the temperature of the secondary steam becomes equal to the saturation temperature corresponding to the pressure of the secondary steam. This is because it is difficult to match the saturation temperature corresponding to the pressure of the secondary steam. Therefore,
A technical object of the present invention is to provide a steam dryness measuring device capable of automatically and quickly measuring dryness.

[0004]

Means for Solving the Problems The technical means of the present invention taken to solve the above technical problem is to introduce the primary steam into the secondary flash chamber through the orifice, Forming a steam flow path for adiabatic expansion and discharging through a control valve, providing sensors for detecting the pressure of the primary steam and the pressure and temperature of the secondary steam, respectively, and controlling the opening of the control valve to Based on the pressure and temperature of the secondary steam detected by the sensor, control is performed such that the secondary steam becomes superheated steam, and the secondary steam is detected by the sensors in a state where the secondary steam becomes superheated steam. The steam dryness measuring device is provided with a control operation unit for calculating the dryness of the primary steam based on the detected value.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The dryness measuring device of the present invention automatically calculates the dryness of primary steam by automatically controlling the opening of a control valve so that the secondary steam becomes superheated steam. That is, since the secondary steam is simply superheated steam, the opening of the control valve can be easily and quickly controlled, and the dryness can be automatically and quickly measured.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment showing a specific example of the above technical means will be described (see FIG. 1). A control valve 3 as an orifice, a flash chamber 4, and a control valve 5 are arranged in a steam flow path 2 branched from a steam pipe 1 through which steam to be measured flows. A pressure sensor 6 and a temperature sensor 7 are provided on the primary side of the control valve 3 in the steam flow path 2.
Is provided to detect the pressure and temperature of the primary steam, and a pressure sensor 8 and a temperature sensor 9 are provided in the flash chamber 4 on the secondary side of the control valve 3 to detect the pressure and temperature of the secondary steam. . A microcomputer is provided as the control operation unit 10 for controlling the opening of the control valves 3 and 5 and calculating the dryness.

The pressure P1 of the primary steam detected by the pressure sensor 6 and the temperature T1 of the primary steam detected by the temperature sensor 7
And the pressure P2 of the secondary steam detected by the pressure sensor 8,
The temperature T2 of the secondary steam detected by the pressure sensor 9 is supplied to the control calculation unit 10. Further, the control calculation unit 10 stores the relationship between the pressure and temperature in the saturated steam table, the enthalpy of the pressure and the saturated water, the relationship between the pressure and the enthalpy of the saturated steam, and the relationship between the pressure and the temperature in the superheated steam table and the enthalpy of the superheated steam in the table. It is stored in a state or by a regression equation.

Next, measurement of steam dryness by this apparatus will be described. The control operation unit 10 first supplies a drive signal to the control valve 3 to open the control valve 3 and control the opening degree to be a predetermined orifice. Next, a drive signal is supplied to the control valve 5, and the control valve 5 is opened to control the opening degree such that the pressure of the secondary steam becomes a predetermined pressure.

The control calculation unit 10 calculates a saturation temperature T (P2) corresponding to the pressure of the secondary steam from the pressure P2 of the secondary steam based on the relationship between the pressure and the temperature in the saturated steam table. The temperature T (P2) is compared with the temperature T2 of the secondary steam. If the temperature T2 of the secondary steam is higher than the saturation temperature T (P2), the process proceeds to the calculation of the dryness. If the temperature T2 of the secondary steam is not higher than the saturation temperature T (P2), the opening degree of the control valve 5 is increased to control the pressure of the secondary steam to be lower, and the secondary steam is controlled. If the temperature T2 becomes higher than the saturation temperature T (P2), the process proceeds to the calculation of the dryness. Even if the control valve 5 is fully opened, if the temperature T2 of the secondary steam is not higher than the saturation temperature T (P2), the opening degree of the control valve 3 is reduced to reduce the pressure of the secondary steam to a lower pressure. So that the temperature T2 of the secondary steam becomes the saturation temperature T (P2)
If it is higher, the process proceeds to the calculation of the dryness.

[0010] When the temperature T2 of the secondary steam becomes higher than the saturation temperature T (P2), the control calculation unit 10 determines the pressure P1 of the primary steam.
Calculate the saturation temperature T (P1) corresponding to the pressure of the primary steam based on the relationship between the pressure and the temperature in the saturated steam table, and compare the saturation temperature T (P1) with the temperature T1 of the primary steam, If the temperature T1 of the primary steam is higher than the saturation temperature T (P1), the superheat
Calculate and output as 1-T (P1).

If the temperature T1 of the primary steam is not higher than the saturation temperature T (P1), the pressure P1 of the primary steam is used to calculate the enthalpy of the saturated steam table, the enthalpy of the saturated water, and the relationship between the pressure and the enthalpy of the saturated steam. Enthalpy of saturated water of primary steam
While calculating I1 'and enthalpy of saturated steam I1'',
From the pressure P2 and the temperature T2 of the secondary steam, the enthalpy T2 of the secondary superheated steam is calculated based on the relationship between the pressure and temperature in the superheated steam table and the enthalpy of the superheated steam, and the dryness X is calculated as (I2-I
1 ') / (I1''-I1') and output.

[0012]

As described above, according to the present invention, the degree of dryness of the primary steam is calculated by automatically controlling the opening of the control valve so that the secondary steam becomes superheated steam. Has an excellent effect that it can be measured automatically and quickly.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a steam dryness measuring apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steam piping 2 Steam flow path 3, 5 Control valve 4 Flash chamber 6, 8 Pressure sensor 7, 9 Temperature sensor 10 Control operation part

Claims (1)

[Claims] 1. A steam flow path for introducing primary steam into a secondary flash chamber via an orifice, adiabatically expanding the flash chamber, and discharging the steam through a control valve. And a sensor for detecting the pressure and temperature of the secondary steam, respectively, and the secondary steam is superheated steam based on the pressure and temperature of the secondary steam detected by the sensor to determine the opening of the control valve. And a control operation unit for calculating the dryness of the primary steam based on the detection values detected by the sensors in a state where the secondary steam is superheated steam. Degree measuring device.