The detector dew point


(57) Abstract:

The invention relates to measuring technique and is intended to determine the dew point of the gaseous mixture, mainly of hydrocarbons. It can be used in technological devices petrochemical production, gas transport, as well as in the development of gas-condensate and gas fields. Essence: in the device source and the radiation detector optically connected with the cooled surface of the mirror through the optical fiber, and a radiation source optically connected with the core of the fiber and the radiation detector with the sheath of the fiber, the diameter of the shell does not exceed the diameter of the mirror. 1 table, 1 Il.

The invention relates to the physical dimensions and may find application in the oil and gas industry, meteorology and other fields of science and technology, where necessary moisture measurement gas.

Establishing the parameters under which condensation occurs formation of hydrocarbon gas mixtures, which can significantly improve the efficiency of operation of gas-condensate fields, to reduce the loss of condensate, a valuable hydrocarbon cheese is the most sensitive and low-inertia are optical detectors dew condensation hygrometers. They are based on the principle of measurement of luminous flux reflected from the surface condensation or passed through it, and check the dew point at the moment of changing intensity of the light flux. A number of optical detectors dew [1, 2, 3] contains placed in a controlled gas-cooled flat mirror, a light source, a cooling device, a sensor and a temperature Converter.

Detectors dew flat mirror have insufficient sensitivity in the determination of the dew point. This is because the process at which condensation is the formation of primary droplets on a separate randomly distributed centers of condensation, which are separate microscopic depressions or grooves on the condensation surface [4] Therefore, the condensation may begin on any part of the cooled mirror, for example in the wrong place, where the reflection of the light flux. Consequently, a further cooling of the surface of the mirror to achieve the attenuation of the intensity reflected from the mirror radiation. Due to the fact that the steam condenses on the surface, cooled with a certain pace, i.e. in the absence of thermodynamicist the cooling surface is a flat mirror with the aim of consistent detection of dew significantly reduces the accuracy in determining humidity: 10% for each degree of hypothermia [6] the Disadvantage of the traditional optical detectors flat condensation surface is also a narrow range of humidity control, namely, the lower limit of the chapel measurement of dew point, especially at low temperatures, due to the fact that under these conditions, changes dramatically the density of the crystals on the condensation surface: the condensate is rare, but large "Islands" that may not be in the field of view of the detector. The practical lower limit of conventional optical detectors at low temperatures is limited by the moisture content of 25-35% [7]

Higher sensitivity have hygrometers, optical detectors dew which contain reflective condensing surface in the form of a surface of the second order, providing invariance detection of dew from all over the surface to be cooled. Known, for example, hygrometers [8, 9, 10] in which the reflective surface is made in the form of powellites rotation, in one of the foci of which is the source and the second radiation detector. However, the detectors dew these hygrometers have the disadvantages inherent in this type of constructions, namely:

the complexity of manufacturing the reflective surface;

the complexity of maintaining the same temperature on the surface condensation due to its relatively large size;

stringent requirements on the alignment of the source and the photodetector;

greater intensity reflected from the entire condensing surface signal does not allow to detect the first drops of condensate, as their appearance is slightly weakens the reflected signal. Therefore, to noticeable changes of the output signal requires a large amount of condensate, i.e. a further reduction in temperature.

All of these listed features detectors dew elliptic mirror cause loss of precision measuring dew point. In addition, for each specific disadvantages.

The closest technical solution to offer a greater number of common features is the detector hygrometer dew point containing a cooled surface in the form of a concave spherical mirror, a light source placed on the side of the optical axis of the mirror, two photodetectors, one of which is installed in the focal plane of the mirror, two temperature-sensitive elements, one of which is placed in the zone of the cooler [11]

When known the benefits of this hygrometer he has insufficient tondemo surface radiation, excluding the tracking of the first drops of condensate due to excessive brightness of the optical spot.

The objective of the invention is to improve the accuracy of determining the temperature at which condensation by reducing the degree of supercooling controlled mixture of gases.

The technical result, which sent the invention consists in the exclusion of focusing reflected from the cooled spherical mirrors radiation on the entrance window of the photodetector, thereby enabling to detect the first drops of condensate and to improve the accuracy in determining the temperature at which condensation of a mixture of gases.

The task and the technical result is achieved by the fact that the detector dew point containing a cooled metal surface in the form of a concave spherical mirror, measuring the temperature of this surface, microglial, the source and the radiation detector, optically coupled with the surface of the mirror, and the radiation source is selected in the focus of the mirror, unlike the prototype source and the radiation detector optically connected with the mirror surface by using the optical fiber, and a radiation source optically connected with the core of the fiber and the receiver the way, the invention meets the criterion of "novelty".

Patent research showed that in all known devices to control all of the cooled mirror surface is focusing reflected from the surface to be cooled radiation on the entrance window of the photodetector (ed. St. USSR N 315999, 1969; 397830, 1973; 359994, 1976; 642665, 1979; 661485, 1979; 819648, 1981 , 885589, 1981; 979978, 1982; 1073668, 1984; 1569565, 1990; U.S. Patent N 4435091, 1984; application UK: N 1297296, 1978; 2043242, 1980). Focusing reflected from the cooled mirror radiation degrades the sensitivity of the detector due to excessive brightness of the optical spot on the entrance window of the photodetector, eliminating the tracking of the first drops of condensate, slightly weakening the intensity of the reflected signal.

The use of the invention allows to achieve a result that meets the need.

Thus, the invention meets the criterion of "inventive step".

The drawing shows the design of the device.

The detector dew point consists of a short metal housing 1 in which is placed the shell 2 and the core 3 fiber-optic light guide. The detector is equipped with a temperature measuring unit 4, which with the maturity of 5 to Windows 6 for controlled pumping of gases. At the bottom of this cavity is mounted a concave spherical mirror 7, the temperature of which is controlled by thermocouple 4, and microglial 8. Out of control (in the field of atmospheric pressure), the fiber is divided into the shell and the core, protected by a rubber coating 9 and 10. The radiation source 11 (for example, led AL-107 or semiconductor laser ILPN-109), the sensor 12 (e.g., PD-8K) placed in special holders 13 and 14 are installed on the front panel of the secondary device. When the radiation source is associated with the core fiber and a radiation receiver with a sheath of the fiber, the diameter of which does not exceed the diameter of the cooled mirror.

The detector dew point operates as follows.

The detector is installed in the housing of the measuring chamber by means of threaded connections and seals the controlled environment using a blade seal. The radiation source 11 generates an optical signal of the infrared range, which core 3 of the fibre falls on a concave mirror, is fixed by soldering on Mikrokreditna type TAMO-8. While the core 3 of the optical fiber placed in the focus of the mirror 7. The mirror 7 is formed by the ode. Because the diameter of the shell does not exceed the diameter of the cooled mirror, and thus, the beam reflected from mirror rays on the shell falls on the photodetector. For controlling the operation of the emitter in the secondary device, which has a radiation source, the support channel included in the scheme, comparing the sent and received signals. In the initial state in the absence of condensate on the mirror 7, these signals are balanced.

At lower temperature controlled environment due to the adiabatic expansion of the gas (as is the case in the test chambers pipelines) or due to the inclusion of microblades 8 the temperature of the mirror 7 is reduced. This is indicated by thermocouple 4, placed near the mirror. When the condensation on the cooled surface of the concave metal mirror 7, the intensity of the reflected laser radiation is sharply reduced due to double scattering: primary scattering on microcaps incident on mirrors radiation and secondary scattering passed through the condensate and reflected from mirrors radiation. In addition, the molecular absorption of radiation in the condensate layer is greater than in Gaza. The decrease in intensity of halogen with exceptiona the Ala offset in the comparison circuit, which is the dew point temperature. This signal can be monitored and the pressure at which detects the occurrence of condensation. As follows from the description of the operating principle of the proposed detector, an electronic circuit generally follows the scheme presented in the device selected for the prototype [11] the Device as a sensing element in the proposed detector is very easy to implement and reliable in operation. First of all greatly simplified aligning concave mirror relative to the radiation source: moving cylindrical cavity 5 with the mirror 7 to the screw thread of the housing 1, to achieve the maximum reflected signal and fix this situation. No offset relative to each other of the core and shell eliminates the need to align the positions of the source and the radiation detector, as is the case in the prototype. Hard, fixed layout elements of the optical system of the detector, its minor dimensions: h mm allow you to place it in high-pressure installations. The detector can be used in the pressure range of 0.1-20 MPa, in the temperature range 253-373 K. Expanding range of applications in Otley is s thus from exposure to low temperatures and high pressures. Unlike the prototype of the proposed detector excluded focusing reflected from the cooled mirror radiation, which does not allow to detect the first drops of condensate, as their appearance is slightly weakens the intensity of the reflected pre-focus signal.

The detector proposed design was tested in a high pressure autoclave when determining the parameters of the condensation of n-pentane. The table shows the results of measurements and comparison with literature data [12]

You can see that the comparison of test data with tabular [12] confirms the reliability and greater functionality of the proposed detector. The test device [11] is selected prototype, in similar conditions was not possible due to the fact that the detector prototype is designed for normal pressure.

When dimensioning the condensation of explosive gases, such as mixtures of hydrocarbons at high pressures, the temperature of the controlled environment reduced by adiabatic expansion of gases. Power microblades in this case should be disabled. Otherwise, the detector remains the same.

Sources Who USSR N 256500 G 01 N 21/50, 1970.

3. The UK Patent N 2043242 G 01 N 25/68, 1980.

4. Tanaka H. Theoretical study of drip condensation. - "Heat transfer". So 101, No. 1, 1979. 72-79 C.

5. Umur A. Griffith R. Mechanism drip condensation. -"Heat transfer". So 101, No. 1, 1979. 135-144 C.

6. Berliner M. A. Status and direction of development of means of measurement and automatic control of humidity abroad. M Tsniiteneftehim, 1967. 21-81 C.

7. Zaitsev C. A. and other air Humidity and its measurement. L. Gidrometeoizdat, 1974. 38 C.

8. USSR author's certificate N 115828 class. 42 e, 416, 19567

9. French Patent N 2196977 G 01 N 21/006, 1974.

10. USSR author's certificate N 359994 G 01 N 25/66, 1974.

11. USSR author's certificate N 1460685 G 01 N 25/66, 1989 (prototype).

12. Vargaftik, N. In. Handbook of thermophysical properties of gases and liquids. M State. publishing house of physical-matemat. the literature dealing with. 1962. 202 C.

The detector dew point containing a cooled metal surface in the form of a concave spherical mirror, measuring the temperature of this surface, microglial, the source and the radiation detector, optically coupled with the surface of the mirror, and the radiation source is selected, the focus of sea, moreover, the radiation source optically connected with the core of the fiber and the radiation receiver with a sheath of the fiber, the diameter of the shell does not exceed the diameter of the mirror.


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