The method of determining the dew point temperature

 

(57) Abstract:

The invention relates to the measurement of humidity of the gas, including natural, according to the method of determining the dew point temperature (TTR). In the method of determination of TTP-based temperature recording at the beginning of the dew on a cooled mirror is determined by the film thickness d of condensate falling on the mirror for one and the same time in three or more temperature points (T1T2T3), separated from TTR is definitely lower than a few degrees. Practically it is more convenient to use the change any other parameter, proportional to the film thickness of precipitated condensate (for example, changes in the intensity of light reflected from the mirror I~d after the appearance of the condensate on the mirror). Processing the obtained curve, determine the temperature at which the film thickness of precipitated condensate is equal to zero; this temperature is taken for TTP. Because the process of determining the TTP uses quantitative data, also obtained in the region where the effect of condensation significant (Tp>T1>T2>T3), and, in addition, involved three or more points, the value of π is measured with much greater accuracy than the Oia. 2 Il.

The invention relates to the field of measuring technique, namely the measurement of humidity of gases. It can also be used to determine the vapor pressure of other volatile component, such as vapors of higher hydrocarbons in natural gas.

One of the most common ways of measuring the humidity of gases is condensation. The analyzed gas is passed over the metal mirror, which is gradually cooled. At the same time are maintained by the state of the surface of the mirror and measured its temperature T. At a certain temperature T=Ttothe surface of the mirror begins to sweat it condensed droplets of water - falls the dew. Temperaturetocalled the dew-point temperature (TpTTP), is associated with a moisture content of gas and is a measure humidity [1].

Devices based on the described principle, called condensation hygrometers. Monitoring of the surface is conducted either by eye, or in more sophisticated devices - optical means with photocell as a receiver. When this occurs, the amount of light reflected from the mirror, and TTR is measured initially decrease because of race, the fact that dew is observed when the temperature is always slightly below Tp(Tp<T), which leads to measurement errors of a few degrees. Sometimes, in order to correct this error, it is suggested to observe the beginning of the evaporation film evaporation temperature Tandand Tpdefined as the average of two temperatures: Tp=1/2(Tp+Tto) [2]. However, this ratio gives higher accuracy only if the observed Ttoand Tanddeviating from the true Tpon the same number of degrees that usually fails. Thus, measurement of the Tpand in this case there is an error, the value of which is not defined and often reaches several degrees. This is a disadvantage of this method.

Solved technical problem is to provide a method of determining TTR with higher accuracy.

Based on the method of determining the dew point, namely, that the gas is passed over a cooled surface of a metal mirror, and register the value of the dew point temperature Tp(0)TTR at the beginning of the time of condensation.

New in the claimed method is that you;T1>T2>T3after which clean the surface of the mirror, set the temperature T1, stand it within a certain time tandand measure the thickness of the rolled film of condensate d1or change another informative parameter, proportional to the thickness of this film A1~d1and are thus the point M1defined by coordinates (T1d1) or (T1AND1), then similarly for the other selected values of temperature T2T3stand the mirror during the same time tandmeasure thickness respectively drawn films (d2and d3or change the settings for A2, A3and find the point M2and M3defined by coordinates (T2d2) and (T3d3) or (T2, A2) and (T3, A3), and then using the interpolation polynomial through points M1, M2and M3spend the curve of dependence of the film thickness d or the change of informative parameter And the temperature of the condensation surface T, i.e., build the function d(T) or A(T), extrapolate it to the intersection with the abscissa, and the value of the dew point temperature Tpn who will Do the explanation of the parameter A.

In most designs the condensation hygrometers fact condensation is fixed by defining a beginning of a change of some quantity that is physically associated with the appearance of the film of condensate on the mirror. In the most common hygrometers with optical registration system that can be change in the intensity arriving at the photodetector light I from the last scattering microcapsule forming a film of condensate; in the microwave hygrometers this may be a change in the amplitude of the signal U, or phase shift of the probing film of a monochromatic wave f, or changing the quality factor of the vibrating system Q, and so on, Thus, instead of the film thickness d can be registered changes of any informative parameter And provided that the change reflects the growth of the film falling on the mirror of the condensate, i.e. a~d.

A new set of essential features in the claimed method allows you to define TTF natural gas with higher accuracy, because, first, it is calculated as a certain limiting temperature at which d=0 or A=0, and is not determined by measurement at the beginning of the physical appearance of the film of condensate, which is in principle incorrect, and, secondly, when postinformation parameter A(T), uses not one, but three or more experimentally recorded points.

In Fig. 1 presents a device that implements the inventive method. The device has cooled metal mirror 1, the light source 2, the receiver of the light flux 3 and the temperature sensor 4. This work almost all the condensation hygrometers with optical registration system: TTR, Kharkov-1M, Dewscope, Kong-prima 2 and others [1], [3].

In Fig.2 in the coordinates of the I-T presents a graph of the thickness of the informative parameter And, in this case the intensity of the light flux (AI), reflected from the mirror and registered by the photodetector 3 depending on the temperature of the condensation surface T, K.

The method is implemented as follows.

Set the amount of the light flux reflected from the mirrors in the receiver 3, I0; set the gas flow over the mirror 1. Slowly begin to understand the temperature of the mirror 1, while observing the amount of light entering the receiver 3 and the temperature of the mirror surface, recorded by thermometer. When condensation due to light scattering microcaps condensate intensity of light in preeschool temperature Tp0. The intensity I is parameter information.

Next, clean the mirror is mechanically or by using heat and produce three or more measurements of the magnitude of the attenuation of the intensity I in three or more temperature points T1, T2and T3... located a few degrees below Tp(0)for example:

1st measurement - at T1=Tp(0)-2oC;

the 2nd measurement - at T2=Tp(0)-4oC;

3rd measurement in the point T3=Tp(0)-6oC.

For measurements, the magnitude of I the following conditions are met.

Before each measurement, the condensing surface is cleaned. One of the cleaning methods can be heated mirrors and aging it at a temperature of 6080oC for 510 minutes with simultaneous purge gas above it.

After heating set temperature of the mirror is equal to one of the values of T1T2and T3... and maintain it at this temperature is always one and the same time tand=Const.

The value of tandlies usually in the range of 510 minutes.

On detected values of I that are related to the temperatures T1, T2and T3, i.e., p is one of the dependence of I on temperature: I=I(T).

Identify points M1, M2and M3with coordinates (I1; T1), (I2; T2) and (I3; T3), through which a smooth curve is performed using the interpolation polynomial before intersecting with the x-axis. The value of Tpthere will be a point lying on the curve I(T) with y I=0. Schematically this procedure is shown in Fig. 2. On the x-axis is the temperature of the condensing surface ToC, and the y - axis the change information of the parameter I, is proportional to the film thickness of the condensate.

The method was implemented in the laboratory, as well as when measuring dew point higher hydrocarbons and hydrocarbon dew point water natural gas in underground gas storage in the village. steppe (Saratov region). Was used condensation microwave hygrometer in which the status information of the condensing surface is read using radio waves of millimeter range [4]; information parameter is the amplitude of the signal from the UHF detector U. Control devices were regular condensation hygrometer "Kharkiv 1" and the latest fiber optic hygrometer company "Vimpel" "Cong-prima 2".

Using specified the drying gas, including in the case when the control devices gave a wide range of measured values TTP.

Sources of information

1. Khalifa A. L., Turevskiy E. N., Roly-poly centuries, Sugars Century, that is, the machine P. I. Instruments for determining the moisture content of natural gas, Moscow, IDC Gazprom, 1995, 45 S.

2. GOST 20060-83. Gases flammable, natural. Methods of determining the content of water vapor and dew point of the moisture. M.: Publishing house of standards, 1984, 16 S.

3. Moskalev, I. N., Bityukov B. C., Filonenko A. S., Gavrilin A. K., Fedosov C. M., I. Efremenko A. Bloomeria natural gas: state and problems. M: IDC Gazprom, 1999, 36 S.

4. Moskalev, I. N., Korotkin I. P., Moskalev M. I., Vyshyvany, I., Johren L. P. , Nuts, Y. I., Filippov A., Microwave equipment for the gas industry. Gas industry, 1997, 56, 58 S.

The method of determining the dew point in a gas, which gas is passed over a cooled metal mirror and record its temperature at the start of the condensation on the mirror surface, characterized in that pre-determine the dew-point temperature Tp(0)in the beginning, the moment of condensation, then choose at least three values of the temperature T1, stand it within a certain time tuand measure the thickness of the rolled film of condensate d1or the change of a parameter proportional to the thickness of this film AND1and find the point M1with coordinates (T1d1) or (T1AND1), then similarly for the other selected values of the temperature T2T3measure the corresponding thickness of the films (d2and d3or change the settings AND2AND3and find the point M2, M3with coordinates (T2d2), (T3d3) or (T2AND2), (T3AND3), and then using the interpolation polynomial through points M1, M2, M3spend the curve of dependence of the film thickness d or the change of informative parameter And the temperature of the condensation surface T, which determines the function d(T) or A(T), extrapolate it to the intersection with the abscissa, and the value of the dew point temperature Tpdetermine how the temperature value at which the function d(T) or A(T) vanishes.

 

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