JP4083915B2 - Steam dryness measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for measuring a dryness indicating a moisture content in steam, that is, a ratio of a mass of dry saturated steam to a total mass per unit volume of a steam flow. In various boilers, equipment using steam power, drying equipment, etc., it is necessary to measure the dryness of steam for heat management. This is because the enthalpy of the steam varies depending on the moisture content.
[0002]
[Prior art]
As a conventional vapor dryness measuring apparatus, there is a squeeze dryness meter that measures the dryness of steam by using the isoenthalpy change of steam. This is because the steam on the primary side is introduced into the secondary flash chamber via the orifice, and is adiabatically expanded (isenthalpy change) in the flash chamber to discharge as superheated steam. Measure the dryness using the Mollier chart or the saturated steam table and superheated steam table by providing a heat insulating material to prevent heat dissipation and detecting the pressure of the primary steam and the pressure and temperature of the secondary steam. Is.
[0003]
[Problems to be solved by the invention]
The conventional squeeze-dryness meter has a problem that the error due to heat radiation is large because the heat retention efficiency of the heat retaining material is poor. Further, as disclosed in Japanese Patent Publication No. 6-58310, there is a problem that the dryness measuring device becomes large in size and expensive in the case where the warming chamber provided outside the flash chamber is evacuated by the extraction means. Therefore, the technical problem of the present invention is to provide a vapor dryness measuring apparatus that can efficiently keep the flash chamber warm with a simple structure.
[0004]
[Means for Solving the Problems]
The technical means of the present invention taken in order to solve the above technical problem is that the primary side steam is introduced into the secondary side flash chamber via the orifice, and is adiabatically expanded in the flash chamber and then passed through the control valve. A storage room configured to constitute a discharge steam flow path and provided with detection means for detecting the pressure of the primary steam and the pressure and temperature of the secondary steam, respectively, and communicating with the outside of the flash chamber from the flash chamber The secondary side steam is discharged from the flash chamber through the thermal insulation, and the opening degree of the control valve is determined based on the pressure and temperature of the secondary side steam detected by the detection means. its secondary steam is provided a control arithmetic unit for calculating the dryness of the primary steam based on the detected value detected by the respective detection means in condition that the superheated steam controls so that the superheated steam There bets as dry steam measuring device according to claim.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The dryness measuring apparatus of the present invention is provided with a heat retaining room communicating from the flash chamber outside the flash chamber, and discharges secondary side steam from the flash chamber through the heat retaining chamber. The flash chamber is kept warm by the secondary side steam. Therefore, the flash chamber can be efficiently kept warm with a simple structure.
[0006]
【Example】
An embodiment showing a specific example of the above technical means will be described (see FIG. 1). An orifice 3, a measurement container 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. The measurement container 4 has an inner container 6 communicating from the orifice 3 and an outer container 8 communicating through a plurality of openings 7 opened in the inner container 6. The inside of the inner container 6 forms a flash chamber 9. The storage chamber 10 is formed between the inner container 6 and the outer container. A pressure sensor 11 and a temperature sensor 12 are provided on the primary side of the orifice 3 in the steam flow path 2 to detect the pressure and temperature of the primary side steam, and a pressure sensor 13 is provided in the flash chamber 9 on the secondary side of the orifice 3. A temperature sensor 14 is provided to detect the pressure and temperature of the secondary steam. A microcomputer is provided as the control calculation unit 15 for controlling the opening degree of the control valve 5 and calculating the dryness.
[0007]
The pressure P1 of the primary steam detected by the pressure sensor 11, the temperature T1 of the primary steam detected by the temperature sensor 12, the pressure P2 of the secondary steam detected by the pressure sensor 13, and the pressure sensor 14 The detected temperature T2 of the secondary steam is supplied to the control calculation unit 15. Further, the control calculation unit 15 stores the relationship between the pressure and temperature of the saturated steam table, the enthalpy of pressure and saturated water, the relationship between the pressure and saturated steam, and the relationship between the pressure and temperature of the superheated steam table and the enthalpy of superheated steam. It is memorized in the state or regression equation.
[0008]
Next, the measurement of the vapor dryness by this apparatus will be described. The control calculation unit 15 supplies a drive signal to the control valve 5, opens the control valve 5, and controls the opening degree so that the pressure of the secondary side steam becomes a predetermined pressure.
[0009]
The control calculation unit 15 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 temperature in the saturated steam table, and this saturation temperature T ( If the temperature T2 of the secondary steam is compared with the temperature T2 of the secondary steam and the temperature T2 of the secondary steam is higher than the saturation temperature T (P2), the process proceeds to calculation of the dryness. If the temperature T2 of the secondary side steam is not higher than the saturation temperature T (P2), the opening degree of the control valve 5 is increased so that the pressure of the secondary side steam becomes lower, and the secondary side steam is controlled. If the temperature T2 of this becomes higher than the saturation temperature T (P2), the process proceeds to calculation of dryness.
[0010]
When the temperature T2 of the secondary side steam becomes higher than the saturation temperature T (P2), the control calculation unit 15 changes the pressure of the primary side steam from the pressure P1 of the primary side steam based on the relationship between the pressure and temperature in the saturated steam table. Calculate the corresponding saturation temperature T (P1) and compare this 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 degree is calculated and output as T1-T (P1).
[0011]
If the temperature T1 of the primary side steam is not higher than the saturation temperature T (P1), the primary side is determined based on the relationship between the primary steam pressure P1 and the saturated steam table pressure and saturated water enthalpy and the relationship between the pressure and saturated steam enthalpy. Calculate the saturated water enthalpy I1 'and saturated steam enthalpy I1'', and calculate the pressure from the secondary steam pressure P2 and temperature T2 based on the relationship between the superheated steam pressure and temperature and the superheated steam enthalpy. The enthalpy T2 of the secondary superheated steam is calculated, and the dryness X is calculated as (I2-I1 ′) / (I1 ″ -I1 ′) and output.
[0012]
【The invention's effect】
As described above, the present invention produces an excellent effect that the flash chamber can be efficiently warmed with a simple structure by warming the flash chamber with the secondary side steam of the warming chamber.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a vapor dryness measuring apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steam piping 2 Steam flow path 3 Orifice 4 Measuring container 5 Control valve 7 Opening 9 Flash chamber 10 Thermal storage 11, 13 Pressure sensor 12, 14 Temperature sensor 15 Control calculating part

Claims (1)

A primary steam is introduced into a secondary flash chamber through an orifice, and a steam flow path is formed which is adiabatically expanded in the flash chamber and discharged through a control valve . The primary steam pressure and the secondary side are configured. Provided with detection means for detecting the pressure and temperature of the steam, respectively, a warming room communicating from the flash room is provided outside the flash room, and the secondary side steam is discharged from the flash room through the warming room , Based on the pressure and temperature of the secondary side steam detected by the detection means, the opening degree of the control valve is controlled so that the secondary side steam becomes superheated steam, and the secondary side steam becomes superheated steam. A steam dryness measuring apparatus, comprising: a control calculation unit that calculates a dryness of the primary side steam based on a detection value detected by each of the detecting means in a state .

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