JP2000346305A - Method and apparatus for measuring dryness of saturated steam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a heat retaining amount of saturated steam per unit heretofore ignored by measuring a temperature and a pressure of steam pressure reduced by pressure reducing a predetermined flow rate of the saturated steam, calculating a specific enthalpy of the saturated steam before pressure reducing from its superheat degree, and measuring dryness of the saturated steam. SOLUTION: The method for measuring dryness of a saturated steam comprises the steps of first measuring a flow rate of the saturated steam to be measured, branching part of the steam to separate a drain water, measuring an amount of the drain water, then reducing pressure to a pressure for generating a large hear drop while stabilizing the flow rate and the pressure of the steam to be measured at constant values, simultaneously measuring the temperature and the pressure of the pressure-reduced steam, calculating a specific enthalpy of the saturated steam to be measured from the measured temperature, and measuring dryness of the saturated steam before the pressure reduction corresponding to the obtained specific enthalpy value based on a temperature- specific enthalpy curve.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for measuring the dryness of saturated steam.

[0002]

2. Description of the Related Art Conventionally, steam, particularly saturated steam, has been used as an energy source for various devices and plants. As shown in the temperature-specific enthalpy diagram of FIG. 2, the inside of the temperature-specific enthalpy curve (Q) is a saturated vapor phase, and the region to the right of the clipping point (A) of the curve (Q) is overheated. The vapor phase, the left is the aqueous phase. The boundary line (Q1) between the superheated vapor phase and the vapor phase is a dry saturated steam having a dryness of 100%, and the saturated steam inside the dry steam has a dryness of 100%.
% Of moisture saturated steam. Saturated steam is
Since the temperature and pressure have constant properties, the saturated steam has constant pressure and temperature regardless of its dryness, but the pressure and temperature are constant as is clear from the temperature-specific enthalpy diagram. However, the specific enthalpy (thermal calorie) possessed varies depending on the degree of dryness. By the way, the management of saturated steam at the site of the conventional steam utilization equipment is generally performed for five items, namely, pressure, temperature, flow rate, specific enthalpy and flow velocity. Is used, the wet state of the saturated steam is not considered, and the difference between the calorific value of the dry saturated steam and the calorific value of the wet saturated steam is currently ignored.

[0003] However, the saturated steam used in the actual steam utilization equipment varies depending on the structure, system, load, etc. of the equipment, but is not less than a small amount of water and becomes wet saturated steam. The actual amount of heat held by the steam does not match that of the dry saturated steam. The dryness of steam is not only closely related to the performance of the heat exchanger, but also is useful for preventing the reduction of the capacity of steam ejectors, etc., and improving the dryness of steam is extremely important for energy saving measures. Element. However, a method of measuring the dryness of such saturated steam not only instantaneously but also as a value per unit has not been known.

[0004]

SUMMARY OF THE INVENTION The present invention measures the temperature and pressure of depressurized steam by depressurizing saturated steam at a constant flow rate, and calculates the specific enthalpy of the saturated steam before depressurization from the degree of superheat. It is an object of the present invention to measure the dryness of the saturated steam, thereby making it possible to measure the heat retention of the saturated steam per unit, which has been neglected in the past.

[0005]

In order to solve the above-mentioned problems, a first aspect of the present invention is to measure a flow rate of a saturated steam to be measured and to branch a part of the steam to drain water. After separating and measuring the amount of drain water, the pressure and pressure of the measurement steam are reduced to a pressure that generates a large heat drop while the flow rate and pressure of the measurement steam are kept constant, and the temperature and pressure of the reduced pressure steam are simultaneously measured. Calculating the specific enthalpy of the measurement-specific saturated vapor from the measured temperature, and measuring the dryness of the saturated vapor before decompression corresponding to the obtained specific enthalpy value based on the temperature-specific enthalpy curve. Features.

Further, the means adopted in the second invention is a steam flow means for measuring the flow rate of the saturated steam for measurement, a means for extracting a part of the saturated steam for measurement and separating and measuring the drain, A means for stabilizing the pressure and flow rate of the steam at a constant level, a means for reducing the saturated steam for measurement to a pressure at which a large heat drop is generated, an adiabatic expansion means for rapidly expanding the reduced pressure steam, and an adiabatic expansion means for the adiabatic expansion means Means for measuring the pressure and temperature of the measured steam, wherein the specific enthalpy of the measuring steam is calculated based on the measured temperature, and the dryness of the measuring steam is measured.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below. According to the present invention, in order to measure the dryness per unit, first, the flow rate of the saturated steam to be measured is measured, a part of the steam is branched to separate drain water, and the amount of drain water is measured. After that, the measurement steam is controlled to a constant steam flow rate, while reducing the pressure to a pressure that generates a large heat drop while stabilizing the pressure, simultaneously measuring the temperature and pressure of the reduced pressure steam, and measuring the measured steam. The specific enthalpy of the saturated steam before decompression is calculated from the degree of superheat of the temperature, and the dryness of the saturated steam before decompression corresponding to the obtained specific enthalpy value is measured based on the temperature-specific enthalpy curve. Features. The calculation of the specific enthalpy of the saturated steam before the decompression from the measured steam temperature after the decompression can be obtained by Equation 1. Therefore, by measuring the temperature after the decompression, the saturated steam before the decompression (the saturation to be measured) can be obtained. Vapor) specific enthalpy value.
When the obtained specific enthalpy value is applied to a temperature-specific enthalpy curve corresponding to the pressure before the pressure reduction, the dryness of the saturated steam before the pressure reduction becomes clear.

[0008]

(Equation 1) cp is, 0.5kcal / kg ℃ h ₂ is specific heat at constant pressure, the specific enthalpy value h ₁ of the measuring saturated steam, specific enthalpy value t ₁ of the saturated vapor after decompression, the temperature of the dry saturated steam after decompression t ₂ is later reduced pressure measured actual temperature.

For example, the case of measuring the dryness of saturated steam of 7 kg / cm ² will be described. First, the flow rate of steam measured by a steam flow meter is measured, a part is branched, and drain water is removed by a separator. Then, the amount of drain water contained is measured. Next, the saturated steam for measurement is kept at a constant vapor pressure while keeping the flow rate constant, and is reduced to 0 kg / cm ² (atmospheric pressure), which causes a large heat drop by the pressure control valve, and rapidly expanded in the expander. Let it. Then, the temperature and pressure in the expander are measured simultaneously.
7 kg of saturated steam, if it is 100% dry,
The specific enthalpy value is 660 kcal / kg. When the dry saturated steam is reduced to 0 kg, the specific enthalpy value is 64.
Since it is 0 kcl / kg, the steam should be in a superheated state and show a temperature of 143.39 ° C. according to the equation (1). However, when the measurement steam is wet saturated steam, the measured temperature in the expander is displayed as a lower temperature.
Therefore, by substituting the measured actual temperature into Equation 1 for calculation, a specific enthalpy value of saturated steam corresponding to the temperature can be obtained, and a temperature-specific enthalpy curve (Q) is obtained.
7kg corresponding to the specific enthalpy value obtained by using
The degree of dryness of saturated steam for measurement can be known. For example, if the measured temperature in the expander is 133 ° C., the specific enthalpy value of 0 kg of saturated steam is 640 kcal / k.
g, the specific enthalpy value of the saturated steam for measurement calculated from Equation 1 is 656.5 kcal / kg, and the dryness of the steam for measurement is about 99%. The dryness of the measurement steam obtained is for a constant flow rate of steam and is not an instantaneous value, so that the dryness per unit of saturated steam can be measured.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the present invention will be described with reference to FIG. In the figure, reference numeral (1) denotes a steam flow meter, which measures the flow rate of measurement steam introduced via an emergency shutoff valve (2). After the flow rate measurement, a part of the measurement steam is branched and sent to the drain separator (3), where the drain is separated and measured. Steam for measurement is steam flow control valve (4) and pressure reducing valve
(5) Steam flow control valve while stabilizing flow and pressure
In (6), the pressure is reduced to a low pressure capable of generating a large heat drop, and the volume is rapidly expanded in the adiabatic expander (7). And inflator
(7) Pressure and temperature in (8) and temperature indicator
Measure simultaneously in (9). (10) is the measured inflator (7)
It is a steam dryness indicator that displays the dryness of the measurement steam from the specific enthalpy value calculated based on the temperature in the inside.

[0011]

According to the present invention, the dryness of saturated steam actually used can be measured per unit,
The amount of heat of the saturated steam actually used can be known.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of a dryness measuring apparatus according to the present invention.

FIG. 2 is a temperature-specific enthalpy diagram of steam.

[Explanation of symbols]

 (1) Steam flow meter (2) Emergency shut-off valve (3) Drain separator (4) Steam flow regulating valve (5) Pressure reducing valve (6) Steam pressure regulating valve (7) Adiabatic expander (8) Pressure indicator ( 9) Temperature indicator (10) Dryness indicator

Claims (2)

[Claims] First, the flow rate of the saturated steam to be measured is measured,
And part of the steam is branched to separate the drain water, and after measuring the amount of the drain water, the pressure and pressure of the measuring steam are stably kept constant, and the pressure is reduced to a pressure that generates a large heat drop,
The temperature and pressure of the depressurized steam are simultaneously measured, and the specific enthalpy of the measurement-specific saturated steam is calculated from the measured temperature, and the dryness of the saturated steam before decompression corresponding to the obtained specific enthalpy value is calculated as the temperature − A method for measuring the dryness of saturated steam, wherein the measurement is performed based on a specific enthalpy curve. Means for measuring the flow rate of the saturated steam for measurement, means for extracting a part of the saturated steam for measurement and separating and measuring the drain, and stabilizing the pressure and flow rate of the saturated steam for measurement at a constant level. Means, means for reducing the pressure of the measurement saturated steam to a pressure that generates a large heat drop, adiabatic expansion means for rapidly expanding the reduced pressure steam, and measuring the pressure and temperature of the steam adiabatically expanded by the adiabatic expansion means. Means for calculating the specific enthalpy of the measurement steam based on the measured temperature and measuring the dryness of the measurement steam.