Method of quality control of natural gas by "dew point temperature for higher hydrocarbons" factor

FIELD: measurement engineering.

SUBSTANCE: controlled gas is subject to cool down due to passing it through layer of liquid, temperature of which liquid is kept equal to preset value of "dew point temperature for higher hydrocarbons". Correspondence of gas quality according to "of "dew point temperature for higher hydrocarbons" is determined by absence or presence of higher hydrocarbon film on surface of liquid. For the case, the liquid is chosen with density being higher than density of liquid state of hydrocarbons and in which liquid the liquid higher hydrocarbons do not solve. Water, diethylene glycol and methanol should solve in the liquid, which matter normally are present in controlled gas. Calcium chloride water solution of required concentration can be used as the liquid.

EFFECT: improved truth of quality control.

1 dwg, 1 tbl

 

The invention relates to the field of research or analysis of materials by determining their chemical or physical properties and can be used in the gas industry. Most commonly it can be used for quality control of gas during transportation and processing.

One of the main indicators of the quality of marketable natural gas is the dew point temperature of gas at higher hydrocarbons" (WU), i.e. the hydrocarbons from pentane (C5H10) and above (C5+in). The value of this indicator regulated Industry standard (OST 51.40-93. Gases flammable natural, supplied and transported along pipelines), according to which "the dew-point temperature of the gas in WU" cold zone of the Russian Federation shall be: in the summer of not higher than -5°and in the winter - not higher than -10°C.

The well-known "Method of controlling the quality of marketable natural gas in terms of "the dew-point temperature of the gas in WU"" (Moskalev, I.N., Bityukov, VA, Filonenko A.S., Gavrilin A.K., Fedosov V.M., Efremenko N.A. Bloomeria natural gas: State and problems. - M: IDC Gazprom, 1999, 36 S. (Survey information. Ser. Preparation and processing of gas and gas condensate). Il. Table 4). The quality control of gas on this indicator in practice carried out by determining the "dew point temperature of the gas is in WU" and then comparing the obtained values with the requirements of the OST. The definition of "dew point temperature of the gas in WU" exercise known condensation method according to GOST 20061-84. This GOST standardizes the condensation method of determining the "dew point of hydrocarbons" for natural gas not containing drip sediment hydrocarbons and glycols. In practice, the process is almost always present in the gas stream. The essence of the method (Vyakhirev R.I., Gritsenko, A. I., Ter-Sarkisov P.M. Development and exploitation of gas fields. - M.: OOO "Nedra-business CENTER", 2002, 666-667 C.) is in the visual or automatic measurement of the temperature at which condensation of hydrocarbons on the surface of the cooled metal mirror in continuous flow over him pre-dried sample gas and a fixed pressure. An important feature of the methodology of measurement is relatively slow cooling of the measuring mirror so that the speed of lowering the temperature of its surface does not exceed 1°C/min, and in the vicinity of the proposed dew point not more than 0.5°C/min (Makagon .F. Gas hydrates, preventing their formation and use. - M.: Nedra, 1985, 232).

This method of quality control of natural gas in terms of temperature dew point WU" (Moskalev, I.N., Bityukov, VA, Filonenko A.S., Gavrilin A.K., Fedosov V.M., Efremenko N.A. Bloomeria PR is native gas: State and problems. - M: IDC Gazprom, 1999, 36 S. (Survey information. Ser. Preparation and processing of gas and gas condensate). Il. Table 4) is the closest to the technical essence and the achieved result.

The known method consists in the following.

Controlled gas is passed over a cooled polished mirror line along which there is a temperature gradient, and plot this line where it begins to fall the condensate WU, measure the temperature of which is taken for the temperature of the dew point WU". Compare this temperature with the specified value (for example, with the value specified in the OST 51.40-93) and make a conclusion about the quality of marketable gas required "the dew-point temperature of the gas in WU". The device, which implements the described method, called optical condensation hygrometers (Moskalev, I.N., Bityukov, VA, Filonenko A.S., Gavrilin A.K., Fedosov V.M., Efremenko N.A. Bloomeria natural gas: State and problems. - M: IDC Gazprom, 1999, 36 S. (Survey information. Ser. Preparation and processing of gas and gas condensate). Il. Table 4). However, in view of the proximity of the optical properties of water and WU (Moskalev, I.N., Bityukov, VA, Filonenko A.S., Gavrilin A.K., Fedosov V.M., Efremenko N.A. Bloomeria natural gas: State and problems. - M: IDC Gazprom, 1999, 36 S. (Overview, Ser. Prepare the spacecraft and processing of gas and gas condensate). Il. Table 4. 18 C.), "the problem of establishing the nature of the precipitated condensate and obtain reliable information about the "dew point" of any substance (moisture or WU) we have identified. A careful analysis of the problem of alagomeji in the gas industry, the authors of the above review concluded that "... even in the absence of gas vapors diethylene glycol (deg) and methanol optical condensing hygrometer hardly distinguishes between the "dew point" on the water and WU (and often does not distinguish). Hydrocarbons and moisture (water) on the condensation surfaces are distinguished (Vyakhirev R.I., Gritsenko, A. I., Ter-Sarkisov P.M. Development and exploitation of gas fields. - M.: OOO "Nedra-business CENTER", 2002. 670 C.) color: the film hydrocarbons is on the border of rosy hue; the moisture has grayish-matte finish (as steamy mirror). Correctly (accurately) to determine the boundary is not always possible. Subjectivity leads to large errors in the determination of the "dew point temperature of the gas by WU and, consequently, unreliable control of marketable gas in the line "temperature dew point WU" the requirements of the standard (Vyakhirev R.I., Gritsenko, A. I., Ter-Sarkisov P.M. Development and exploitation of gas fields. - M.: OOO "Nedra-business CENTER", 2002, 671 S.) States, "it is Important to note that the definition is the temperature of the dew point moisture and hydrocarbons existing condensing appliances including "Kharkiv-1M", gas separation plants NCV of gas condensate fields is almost impossible. This is due to the presence of gas separation of large quantities of condensate, along with methanol and water, so on the mirror surface of the indicator to form a continuous film of liquid, and to determine separately the "dew point" vodomotornomu solution (BMP) and hydrocarbons cannot".

This is a disadvantage of the known method of controlling the quality of marketable natural gas in terms of "the dew-point temperature of the gas in WU".

The problem to which the invention is directed, is to create this solution, which was provided to increase the reliability of the quality control of marketable natural gas in terms of "the dew-point temperature of the gas at higher hydrocarbons".

The technical result of the invention is to increase the reliability of quality control marketable natural gas index ″dew-point temperature of the gas at higher hydrocarbons″.

The method of controlling the quality of natural gas in terms of "the dew-point temperature of the gas at higher hydrocarbons" (WU) by lowering the gas temperature, is that controlled the gas is cooled by passing it (sparging) through words is fluid (for example, an aqueous solution of calcium chloride)whose density exceeds the density of the liquid phase WU and which does not dissolve the liquid WOO, but dissolved water, diethylene glycol (deg) and methanol, the temperature of the liquid support equal to the desired value of the dew point temperature of the gas at WU, and gas quality in terms of "temperature dew point WU determined by the presence or absence of stains (film) WU on the surface of the liquid.

To achieve the mentioned technical result of the controlled gas is cooled by passing it (sparging) through. a layer of liquid, the temperature of which support equal to the value of the dew point temperature of the gas in WU", and match the quality of gas in terms of temperature dew point WU" is defined by the presence or absence of a film on the surface of the liquid, thus choose a liquid whose density exceeds the density of the liquid phase WU and it does not dissolve the liquid WOO, but soluble: water, deg and methanol present, usually in a controlled Gaza. Such fluid may be, for example, an aqueous solution of calcium chloride of the desired concentration. The concentration of an aqueous solution of calcium chloride picked so that the expected temperature dew point gas WOO" was greater than the freezing temperature of the solution.

The temperature dependence of Tamerza the Oia aqueous solution of calcium chloride from its concentration are shown in table 1, based on the data (Makagon .F. Gas hydrates, preventing their formation and use. - M.: Nedra, 1985, 107 S.).

Table 1.

The dependence of the freezing temperature of the aqueous solution of calcium chloride from its mass concentration
Concentration %of 21.926,627,530,0
Freezing point, °-21,2-34,6-38,6-55,0

The table shows that for quality control of commercial gas in the line "the dew point temperature of the gas in WU" requirements OST 51.40-93 (for example, -10° (C) it is possible to use an aqueous solution of calcium chloride with a concentration of not less than 22%, the freezing temperature which does not exceed -21°C.

The proposed method of quality control of natural gas in terms of "the dew-point temperature of the gas in WU" is as follows.

Controlled gas is passed (bubbled) through the layer of liquid (e.g. aqueous solution of calcium chloride), the temperature of which support equal to the desired value (for example, OST 5140-93) "dew point gas WOO", and match the quality of gas in terms of temperature dew point WU determined by the presence or OTS is dtiu film WU on the surface of the liquid, when choosing a liquid whose density exceeds the density of the liquid phase WU and it does not dissolve the liquid WOO, but dissolved water, deg and methanol. The quality control of commercial gas provide the appearance or absence of the film WU on the surface of the cold liquid. If the "dew point" of the controlled gas WOO more than the temperature of the fluid, i.e. gas quality does not meet the specified requirements for this indicator, the vapor phase WU is condensed, the resulting liquid phase VU, as less dense floats, and on the surface of the cold fluid (for example, on the surface of an aqueous solution of calcium chloride) appears thin film of condensed WU, which determines (detects) visually on specific iridescent color (color of discolouration). Otherwise, i.e. when the liquid film WU does not appear on the surface of the cold liquid, and means "dew point" of the controlled gas VU is less than the temperature of the cold fluid, as gas commodity corresponds to the requirements specified in terms of "temperature dew point WU".

When implementing the proposed method of controlling the quality of marketable gas in terms of temperature dew point WU" excludes the impact of the presence in a controlled gas water vapor, deg and methanol on doscover is there quality control of gas on this indicator, because these components by condensation in a cold fluid dissolved in it and do not float. In the proposed method the role of the detector dew (role chilled mirror surface, as in the condensation hygrometer) performs the surface of the chilled liquid, which has the above properties, thus avoiding the influence of water vapor deg and methanol on the reliability of the quality control of gas in terms of temperature dew point WU". The method gives an answer to the question of whether or not the gas quality in terms of "temperature dew point WU" specified requirements or are not satisfied.

The proposed method is implemented using a device, scheme of which is shown in the drawing.

The device comprises an input section 1 line controlled gas bubbling tube 2; bubbler 3, provided with an observation window 4; a bubbler filled with liquid 5, which does not dissolve the liquid WOO, but dissolved water, deg and methanol; heat-exchange device 6, for example, a coil located in the fluid; a temperature sensor 7, the sensing element which is liquid; the output line 8 of the controlled gas, which is equipped with shut-off and control device 9, for example, valve; automatic temperature controller 10, to the first input of which is connected to the temperature sensor, the second in the ode connected unit 11 temperature, and by the way - the actuator 12, the regulator 13 which is installed on the bypass line 14 cold gas; a cooling device 15, made for example in the form of a vortex tube (tube Wound) 16 containing the sleeve-aperture 17 with a hole in the center; swirl 18; adjusting valve 19, line 20 power strip, line 21 cold gas and hot gas line 22. The cooling device similar to the device that is used in the well-known condensation hygrometer "Kharkiv-1M" (Vyakhirev R.I., Gritsenko, A. I., Ter-Sarkisov P.M. Development and exploitation of gas fields. - M.: OOO "Nedra-business CENTER", 2002).

The device operates as follows.

Controlled gas passes through the input section 1 line controlled gas bubbling tube 2 and further, barbotine through the fluid layer 5 filled in the bubbler 3, is discharged through the output line 8 and valve 9 in line recycling gas being monitored (not shown). The liquid 5 in the bubbler 3 cooled by the coil 6, in which line 21 is served cold gas from the cooling device 15. As the device cooling generator (cold) is used, for example, a vortex tube (tube Wound) 16. In principle, may be used any other cooling device (for example, propane or carbon dioxide refrigerator, semiconductor is whether thermopile thermopile and others). However, in terms of the gas industry should be the preferred tube Wound as to produce (generate) cold is used in this case the energy of compressed gas are always available in abundance on the control objects (pipelines, installation of complex gas treatment, gas metering stations, and other), and therefore there is no need for the construction and operation of a more complex and less reliable cooling devices. The flow of cold gas fed to the coil 6, is controlled by bypass part of the cold gas through the bypass line 14 by means of the actuator 12, acting on the regulatory authority 13. The temperature of the liquid 5 in the bubbler 3 is maintained constant by means of an automatic system of regulation established by the temperature sensor 7, an automatic regulator 10, the actuator 12 and the regulator 13. The set-point temperature of the liquid equal to the desired dew point temperature-controlled gas WOO, set using the knob 11. If the temperature of the liquid 5 in the bubbler 3 does not equal the specified value, the controller 10 generates a regulating effect on the actuating mechanism 12 until the temperature of the liquid in the bubbler 3 becomes equal to the specified value. During the formation of the regulatory impact on Ministers the national integrated law (PI-law) automatic stabilization of the temperature of the liquid is without a static error. As a result of controlled bubbling gas through a layer of chilled liquid temperature of the gas is reduced almost to the temperature of the liquid). If the "dew point temperature" of the gas being monitored by WUmore of the fluid temperature (TW), i.e.,, stands out from the gas liquid phase VU, which has a lower density than the density of the cold liquid, floats on the surface of this liquid. Desired flow controlled gas at an operating pressure determined experimentally set by means of the valve 9 and is maintained for some time, obviously sufficient to highlight (for detection), the amount of liquid WOO. After this time, the valve 9 is closed, than stop bubbling and provide an opportunity will be smooth (not disturbed) the surface of the liquid. The fact of the appearance of spots WU on the surface of the liquid, visually observed through the observation window 4, suggests that the quality of marketable gas in terms of "the dew-point temperature of the gas in WU" does not match the specified value. If within a deliberately long time of bubbling spots WU on the surface of the liquid does not appear, this means that the gas quality in terms of "the dew-point temperature of the gas in WU", meets the requirements is found.

The device 15 cooling gas works in the following way. Gas from a pipeline (not shown) on line 20 of the power strip through the swirler 18 tangentially enters the vortex tube 16 where it is divided into hot and cold streams. The cold gas passes through the Central hole of the sleeve aperture 17 and is discharged in the line 21, and the hot - via adjusting valve 19 in line 22 and line utilization (not shown). Adjusting valve 19 serves to adjust cost ratio of cold and hot gas streams and, accordingly, the temperature of the cold gas.

The proposed method eliminates the influence of those present in a measured gas, water, deg and methanol, the quality control of natural gas in terms of "the dew-point temperature of the gas at higher hydrocarbons".

The use of the proposed technical solution makes it possible to increase the reliability of the quality control of gas in terms of "the dew-point temperature of the gas at higher hydrocarbons".

The method of controlling the quality of natural gas in terms of "the dew-point temperature of the gas at higher hydrocarbons" (WU) by lowering the gas temperature, wherein the controlled gas is cooled by passing it (sparging) through the layer of liquid (e.g. aqueous solution of calcium chloride), the density of which is greater than p the h liquid phase WU and which does not dissolve the liquid WU, but dissolved water, diethylene glycol (deg) and methanol, the temperature of the liquid support equal to the desired value of the dew point temperature of the gas at WU, and gas quality in terms of "temperature dew point WU determined by the presence or absence of stains (film) WU on the surface of the liquid.



 

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