Method and device for determining temperature of condensation point of gas

FIELD: measuring technique.

SUBSTANCE: method comprises step cooling of solid body, maintaining a constant temperature at each step for a time period, and step cooling down to a temperature of onset condensation. The condensation temperature is determined from the formula proposed.

EFFECT: enhanced accuracy of measurements.

2 cl, 3 dwg

 

The invention relates to the field of automatic control of technological parameters and indicators of the physical properties of natural gas and can be used in gas and other industries where there is a natural or other gas, and there is a need to control its quality, characterized by the dew-point temperature. Most commonly it can be used in the extraction, transport, storage and distribution of natural gas.

There is a method of determining the dew point temperature of the gas (Vyakhirev R.I., Gritsenko, A. I., Ter-Sarkisov P.M. Development and exploitation of gas fields. - M.: OOO "Nedra-business Center", 2002. 668-670 S. Moskalev, I.N., Bityukov B.C., Filonenko A.S., Gavrilin A.K., Fedosov V.M., Efremenko N.A. Bloomeria natural gas: State and problems. - M: IDC Gazprom, 1999, 15 C. (About. inform. Ser. Preparation and processing of gas and gas condensate) by measuring the temperature of condensation of moisture during cooling of the polished metal mirror. The known method is carried out using a device called a condensation hygrometer. The dew point temperature is fixed condensation hygrometer in the beginning of the condensation.

The disadvantage of this method is the low accuracy.

Indeed, in (Moskalev, I.N., Bityukov VS, Filonenko A.S., Gavri the John A.K., Fedosov V.M., Efremenko N.A. Bloomeria natural gas: State and problems. - M: IDC Gazprom, 1999. 16 C. (About. inform. Ser. Preparation and processing of gas and gas condensate) States "any hygrometer notes of the condensed phase, when it is already formed, i.e. at a temperature lower than the true temperature of the dew point by the value dTtr. The value dTtrdepends on the sensitivity of the hygrometer and in any case fundamentally different from zero".

The closest in technical essence and the achieved result is a method of determining the dew point temperature, implemented widely used in the gas industry condensation hygrometer KONG-prima-2 (Converter dew point "CONG-prima-2". user. CROW 2.844.001 D. NPF "Vympel", Russia, Saratov).

The known method consists in the following. Controlled gas is passed over the surface of the uniformly cooled mirror, this role is performed by bending the optical fiber, and when it falls condensate, measure the condensing temperature Tkthen the mirror is heated and when the condensate evaporates, determine the evaporation temperature Tu. Moments of condensation and evaporation is determined by changing the photo of the signal which in turn is determined by the intensity of the light beam from the Agen from the mirror. The dew point temperature is determined from the formula Ttr=(Tk+Tu)/2. The process of cooling and heating of the mirror, and determining the dew point temperature is carried out cyclically. In (Moskalev, I.N., Bityukov VS, Filonenko A.S., Gavrilin A.K., Fedosov V.M., Efremenko N.A. Bloomeria natural gas: State and problems. - M: IDC Gazprom, 1999, 16 C. (About. inform. Ser. Preparation and processing of gas and gas condensate) indicated "sometimes employ the technique of identifying the two temperature - dew point (Tkand the beginning of the evaporation (Tu), and the dew-point temperature is set to the average of these temperatures Ttr=(Tk+Tu)/2. (B principle it should be the same temperature, but in practice they differ 3-7°and more). This technique can correct the error, but only if seen us the values of Tkand Tuequally distant from the true dew point Ttrthat nobody should". In (Berliner M.A. Electrical measurements, automatic control and regulation of humidity. - M. - L., publishing house "Energy", 1965, 252 S.) this is repeated: "the fixation point, condensation of moisture on the surface of a solid body somewhat arbitrary. It is known that temperature detectable residue on the mirror and the temperature at which this plaque disappears vary greatly. Onordinary hygrometers as the dew point is taken arithmetical average of these temperatures, that creates the possibility for subjective error." Another factor affecting the accuracy of measurement of Ttr. described in (Berliner M.A. Electrical measurements, automatic control and regulation of humidity. - M. - L.: publishing house "Energy", 1965, 251 S.) "as the process of condensation does not occur on the surface of the water or ice, and on the surface of a metal mirror, the measurement result depends on the nature and condition of the surface and (Berliner M.A. Electrical measurements, automatic control and regulation of humidity. - M. - L.: publishing house "Energy", 1965, 252 C.) the temperature of the mirror is determined in a dynamic state, and thermal inertia of the mirror and thermometer may introduce additional error, the value of which depends on the cooling rate.

Thus, the known method cannot provide high accuracy of determining the dew point temperature of the gas. This is his fault.

A device for implementing the known method (Converter dew point "CONG-prima-2". The user manual. CROW 2.844.001 D. NPF "Vympel". Russia, Saratov) consists of: sensing element (detector dew), made in the form of bending of the optical fiber, device, cooling and heating of the sensing element, a temperature sensor, mounted on the sensitive element, the device is and information display (liquid crystal display), computing device (controller)to the input of which is connected to the temperature sensor and to the output of the cooling unit and a heat sensitive element, and the display device information.

The known device operates as follows. Controlled gas washes the sensing element is cooled by the cooling unit and heating. Temperature dynamics of the mirror for one cycle determine the dew point temperature of the gas in a known manner (CONG-prima-2) is shown in figure 1, where the abscissa axis represents time and the ordinate is temperature sensitive element (mirror) and photocurrent (in units of analog-to-digital Converter of the computing device). The numerical values of the parameters given in Fig 1, do not claim high accuracy, they are only for the best explanation of the operation of the known device. More precise dynamics of operation of the device shown in (Converter dew point "CONG-prima-2". The user manual. CROW 2.844.001 D 22. NPF "Vympel". Russia, Saratov). Figure 1 shows the four phases of the operation.

A - phase heating and stabilization of the sensing element.

In - phase cooling and condensing temperature.

S - phase heating and search evaporation temperature.

D - phase heat sensitive element.

In-phase "And" ASU is coming heating and temperature stabilization mirror device level, sufficient to evaporate moisture. At the end of the stabilization period is check the status of the mirror (pollution) and calculated line registration 1-2 temperatures of condensation and evaporation, as a percentage of the current value of the level of photosignal.

In the cooling phase "In" the device operates at maximum cooling. If condensation forms on the sensitive element (mirror) value of photosignal decreases sharply - section E.

Crossing the line temperature line registration temperatures condensation confirms the presence of water on the mirror.

At the point C1 is fixed condensing temperature (figure 1 Tk=-16°C.). After fixing the condensing temperature of the computing device includes heated mirrors (section 0). By evaporation of the condensate value of photosignal increases rapidly and at the intersection with the center line of Desk temperatures of condensation and evaporation at the point C2 fixation evaporation temperature Tu(figure 1 Tu=-3°C). Then, the computing device calculates the dew point temperature of the formula

Ttr=(Tk+Tu)/2.

(In our case Ttr=(-16+-3)/2=-9,5°)

The computing device displays this value in the device information display (liquid crystal display). Next, the operation of the device is TBA enters its second measuring cycle, i.e. there is heating and temperature stabilization mirrors etc.

The disadvantage of this method, implemented using known devices is the low accuracy of determination of the dew point temperature of the gas.

The task to be solved by the invention is to create this solution, which was provided to improve the accuracy of determining the dew point temperature of the gas.

To achieve the mentioned technical result in a known method of determining the dew point temperature of the gas, comprising passing the gas being monitored over a cooled solid surface, cooling the latter carry out step (the value of dT at each step), (not monotonically from the maximum speed, as in the known method, the temperature of the cooled surface at each step (each step) measure and maintain a constant for a time sufficient to condense such a large number of moisture, which can recognize (to feel) detector dew, manual lowering of the temperature is carried out until until cooled to a solid surface will not appear condensation (dew, liquid phase), at the time of condensation (on the i-th step) measure the temperature T(i) chilled surface, and the temperature point the dew of gas is determined from the formula

where T(i) is the temperature of the cooled solid surface on the i-th step (step) measurement and stabilization;

T(i-1) is the temperature of the cooled solid surface

the previous step (step) measurement and stabilization.

To achieve the mentioned technical result in the known device for determining the dew point of the gas containing the sensitive element of the detector (dew), a temperature sensor, a cooling unit and a heat sensitive element, the display device information of liquid crystal display (LCD), computing device, to the input of which is connected to the temperature sensor, the first output connected to the display device information, and the second output is connected to the cooling unit and a heat sensing element, the sensing element consists of two (first and second) of the capillaries, installed in series on line the controlled gas, the first capillary is placed in the cooling chamber and it fixed the temperature sensor and to the line controlled gas between the first and second capillaries are connected to the pressure sensor, the output of which is connected to a computing device

The inventive method consists in the following.

Controlled gas is passed over a cooled solid surface is d (in the particular case above the mirror), when this cooling is carried out step (temperature is reduced stepwise by the value of dT at every step, and not a monotonically with the maximum speed, as in the known method, the temperature of the cooled surface at each step (each step) measure and maintain constant (stabilize) for some time Tst, manual lowering of the temperature is carried out until until cooled to a solid surface will not appear condensation (dew, liquid phase), at the time of condensation (on the i-th step) measure the temperature T(i) chilled surface, and the dew point temperature of the gas is determined from the formula

where T(i) is the temperature of the cooled solid surface on the i-th step (step) measurement and stabilization;

T(i-1) is the temperature of the cooled solid surface in the previous step (step) measurement and stabilization.

For comparison with the known method figure 2 shows the dynamics of the temperature of the mirror and photosignal when determining the dew point temperature of the gas during one cycle of the proposed method.

Temperature stabilization for time Tst, the value of which is determined experimentally, allows high reliability (probably) get a sufficient amount of condensate (Rus is) on the cooled surface of a solid at constant temperature, to identify the fact of condensation. This eliminates the possibility of significant hypothermia the surface to be cooled due to the location of the insensitivity of the detector dew. Hypothermia surface is possible only within the size of the steps (which can be arbitrarily small), because the definition of dew point lead in the mode of stabilization of the temperature, but not in a monotonic (dynamic) process cooling.

The magnitude of the step of lowering the temperature of accept on the basis of the required accuracy and permissible time determining the dew point temperature of gas (less than the height of the step, the more accurate the determination of the dew point temperature of the gas, but the more time its definition). The absolute error in the determination of the dew point temperature of the gas, due to the finiteness of the magnitude of the steps is not more than 0.5 dT, i.e. half the height of the stairs.

In many production facilities gas industry (for example, in the transport of gas) the time factor determining the dew point temperature does not play a decisive role (at least within one hour). It is more important to determine the dew point temperature with high accuracy. It is the dew point temperature of the gas is one of the main indicators of the quality of marketable gas, determining the effectiveness and be the danger of gas transportation. Therefore, improving the accuracy of determining the dew point of the gas - current production task. A device for implementing the proposed method is shown in figure 3, where:

1 - inlet pipe line gas being monitored;

2 - filter solids (sand, scale and other);

3 - cooling chamber;

4 - the first capillary;

5 - mikeperry plot line of the gas being monitored;

6 - second capillary;

7 - temperature sensor;

8 - pressure gauge;

9 computing device (controller);

10 - display device information;

11 - temperature controller;

12 - driver unit temperature;

13 - output section of the line gas being monitored;

14 - line gas power;

15 - vortex tube (tube Wound);

16 - sleeve vortex tube;

17 - swirl;

18 is a line of cold gas;

19 - line hot gas;

20 - line mixed gas;

21 - line recycling of the mixed gas;

22 - line recycling of hot gas;

23 - adjusting valve;

24 - actuating mechanism.

The sensor element (detector dew) devices are sequentially installed on the line controlled gas first 1 and second 2 capillaries with a pressure sensor 8 installed in michaellara section line 5 gas being monitored. A cooling unit and a heating g is for is a vortex tube 15 tube Wound) with the cooling chamber 3, adjusting valve 23 and actuating mechanism 24 mounted on the line 22 of utilization of hot gas. The first capillary tube 4 with a fixed temperature sensor 7 is placed in the cooling chamber 3, the entrance of which is connected to line 20 of the mixed gas (cold - line 18 and the hot - gas line 19), and the output line 21 of the utilization of the mixed gas. The sensors 7 and 8, respectively, the temperature and pressure are connected to a computing device 9, containing the temperature controller 11 and sets the temperature unit 12. The first computing device 9 is connected to the device 10 information display (e.g. liquid crystal display), and the second output to the actuator 24.

A device for determining the dew point temperature of the gas works in the following way. Controlled gas passes through the input section 1 line controlled gas through the filter 2, where it is cleaned from mechanical impurities and the liquid phase (if available) and then through the first 4 and second 6 capillaries is given on the output line 13 for disposal or into the atmosphere. The capillary 4 and 6 is made in the form of a helical pairs, forming a threaded connection of the spiral canal of the small orifice. When steady-state single-phase mode in michaellara section line 5 controlled gas is set to a gas pressure, which is passed in real-time is measured by the pressure sensor 8 and the computing device 9. First, the capillary 4 is placed in the cooling chamber 3, it is washed with cold gas and thus is cooled.

At step cooling of the first capillary comes step (step), when the temperature of the gas in the first capillary is smaller than the dew point temperature of the gas at operating pressure (pressure in the first capillary). In this case, due to maintenance (stabilization) of the temperature in the cooling chamber for a certain period of time in the first capillary condensed sufficient moisture, which partially or completely covers the channel of the capillary. This leads to the fact that the pressure measured by the pressure sensor 8 decreases. When it decreases to the pre-set value, the computing device 9, zapominalsia the temperature of the first capillary at each step of the measurement and stabilization in real time, calculates the dew point temperature of the formula

where T(i) is the temperature of the first capillary on the last i-th step (step) measurement and stabilization;

T(i-1) is the temperature of the first capillary in the previous step (step) measurement and stabilization.

After calculating the dew point temperature of the gas computing device 9 displays this value on the display device (display) 10 and then generates a task to a reg is eToro 11 temperature for heating the first capillary 4. The temperature of the gas in the cooling chamber increases. The liquid phase in the first capillary evaporates, which leads to the increase of pressure in michaellara section line 5 gas being monitored. When this pressure reaches a pre-specified value, the computing device 9 starts a new measuring cycle.

The device cooling and heating gas works in the following way. The gas from the gas line 14 power gas enters the vortex tube 15. Thanks to the swirler 17, the gas is introduced tangentially. Passing through the vortex tube 15, the gas is divided into 18 cold and hot 19 flows. Cold stream passes through the Central hole of the sleeve 16 and is discharged in the line 18, and the hot partly in line 20 of the mixed gas, and the remaining amount through the actuator 24 is diverted for recycling or in the atmosphere. In-line mixing of the cold stream and part of the hot flow mixed. Depending on the position of the adjustment valve 23 and the regulatory body of the actuator 14 varies the flow rate of hot stream flowing in line 20 dilution. Accordingly, changes the temperature of the gas in the cooling chamber 3 and the temperature of the capillary 4. The signal from the temperature sensor 7 is supplied to one of inputs of the controller 11 of the temperature. Actually is a software block computing device 9, implements, n is the sample, digital PID control law. To the second input of the regulator 11 temperature enters the setpoint temperature T0generated by the master unit 12 (a program of the computing device 9). Digital temperature controller 11 compares these signals and, depending on the sign and magnitude of the difference (error control) acts on the actuator 24 to maintain the temperature T0. When implementing digital PID control law calculation of regulatory impact (for example, the magnitude of the displacement of the regulatory body of the actuator 24) performed by the algorithm has the form (Isermann R. Digital control system. TRANS. from English. - M.: Mir, 1984. - 541 S.):

U(i)=U(i-1)+q0·eT(i)+q1·eT(i-1)+q2·eT(i-2),

where U(i) - regulating effect of the temperature controller on the i-th step;

U(i-1) - regulating effect of the temperature controller on the i-1 step;

eT(i)=T(i)-T0(i) - error temperature control of the first capillary on the i-th step;

T(i) - current value of the temperature at the i-th step;

T0(i) the set-point temperature on the i-th step;

q0, q1, q2 - settings digital controller.

Because the value of U(i) is calculated by the controller 11 of the temperature according to the law, having integral component of the regulatory impact on usage is sustained fashion mechanism 24 will occur as long while the current temperature value T(i) becomes equal to a given value of T0i.e. until the error regulation will not be equal to zero. The required quality temperature control is ensured by setting the corresponding values of the tuning parameters q0, q1, q2the controller 11. At small bars quantization settings q0, q1, q2can be calculated using the tuning parameters K, Tuand Tdanalog PID controller (Isermann R. Digital control system. TRANS. from English. - M.: Mir, 1984. - 541 C.) according to the formula

q0=K·(1+Tk/(2-Tu)+Td/Tk);

q1=-K·(1+2·Td/Tk-Tk/(2·Tu));

q2=K·Td/Tk;

where K - coefficient of analog PID-controller:

Tu- constant integration of analog PID;

Td- constant differentiation analog PID;

Tk- quantum quantization.

The set-point temperature T0(i) at the i-th step in the cooling mode is calculated from the formula

T0(i)=T0(i-1)-dT

where dT is the height of the step of lowering the temperature.

At the same time as the initial specified value take the temperature of the gas being monitored, suggesting that this temperature above the designated temperature is URS dew point (which in most cases is observed in the systems of gas transportation).

The height of the step of lowering the temperature of the dT take on the basis of the required accuracy and permissible time determining the dew point temperature of gas (less than the height of the step, the more accurate the determination of the dew point temperature of the gas, but the more time its definition). The absolute error in the determination of the dew point temperature of the gas is not more than 0,5dT, i.e. not more than half the height of the steps. Indeed, if the (i-1)-th step, i.e. at the temperature T(i-1), the condensate in the first capillary is not dropped, and the i-th step, i.e. at T(i) is disconnected, then the value of the dew point is between these temperatures. Because the computing device determines the dew point temperature of the formula

where T(i)=T(i-1)-dT

then the absolute error due to the finiteness of the height of a step of lowering the temperature could not be more half the height of this step. Modern measurement and temperature control allow to stabilize the temperature with high accuracy (for example, with an absolute error of 0.2°and below). This gives grounds to assert that the use of the proposed solution allows to increase the accuracy of determining the dew point temperature of the gas.

1. The method of determining the dew point temperature of the gas measured by the I temperature of condensation on the cooled surface of a solid body, characterized in that the cooling solid body exercise step, while the temperature at each step (each step) support ongoing for some time, manual lowering of the temperature is carried out until until cooled to a solid surface will not appear condensation (dew, liquid phase), at the time of condensation (on the i-th step) measure the temperature of the cooled surface and the dew point temperature of the gas is determined from the formula

where T(i) is the temperature of the cooled surface at the i-th step (step) measurement and stabilization;

T(i-1) is the temperature of the cooled surface in the previous step (step) measurement and stabilization.

2. Device for the automatic determination of the dew point temperature of the gas containing the sensitive element of the detector (dew), a temperature sensor, a cooling unit and a heat sensitive element, the display device information (for example, liquid crystal display), computing device, to the input of which is connected to the temperature sensor, the first output connected to the display device information, and the second output of the cooling unit and a heat sensitive element, wherein the sensing element detector (dew) the imp is replaced in the form of two (first and second) of the capillaries, installed in series on line the controlled gas, the first capillary is placed in the cooling chamber and the temperature sensor is fixed, and to the line controlled gas between the first and second capillaries are connected to the pressure sensor, the output of which is connected to a computing device.



 

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