FR2543687A1 - Method and device for continuously determining the content in one of its constituents of a possible heterogeneous mixture - Google Patents

Abstract

The invention relates to a method for continuously determining the content x in one of the constituents C1 of a mixture of at least two constituents C1, C2, which have different dielectric constants epsilon 1, epsilon 2. According to the invention, the dielectric constant epsilon 1,2 of the mixture C1 + C2, the density d1,2 of this mixture and the temperature of the latter are continuously measured. The content x is obtained by solving the following system of equations with three unknowns x, epsilon 2 and d2:

Description

Proucédé and device for the determination, continuously, of the content of one of its constituents, of an optionally heterogeneous mixture.

 The present invention relates to a method and a device for the continuous determination of the content of an optionally heterogeneous mixture, in one of its constituents. It applies in particular, but not exclusively, to the measurement of the water content of a mixture of water and at least one hydrocarbon, for example crude oil.

In general, it is known that the presence of water in a crude oil, usually in the form of an emulsion with a content ranging from 0 to 10% by volume, has many disadvantages, the most important of which consist in than
- the presence of water in the rough is a significant financial loss for the buyer, who pays the water at the price of crude
- This presence of water greatly increases the risk of explosion and fire (water stroke), during the distillation of the crude.

The invention therefore has two essential objectives, namely, on the one hand,
* develop a continuous analyzer to account for water in crude oil, mainly
- loading tankers
- unloading tankers
- and, in general, in any pipeline, and on the other hand,
* develop a device capable of detecting a "blow of water" at the entrance of a distillation unit.

 In order to achieve these results, numerous methods and devices have already been proposed, none of which, at present, have hitherto made it possible to obtain complete satisfaction.

 As an indication, one of these processes is to continuously distill, at a constant rate, a crude sample to be analyzed at a temperature such that all the water in the sample is in the vapor phase.

This vapor phase is then driven by a dry gas at a constant rate. The mixture is then applied to a hygrometer, which determines the water content.

This method has the following drawbacks
1) it requires sampling
2) it is complicated (control of the charge flow, the fractionation temperature, the gas flow rate, etc.);
3) it requires slaving the flow rate distilled to the flow in the pipe to obtain a representative measurement, which greatly complicates the device
4) it requires either a compressed air network or nitrogen bottles, which is an additional constraint.

 In another method, an attempt has been made to determine the water content of the crude oil by measuring the attenuation of a UHF wave emitted in the crude oil, it being understood that the attenuation in the water is much greater. only in the gross.

 However, it has been found that this method does not make it possible to achieve accuracies greater than 15%.

Moreover, this process requires the implementation
- a device for taking the sample from the pipeline
- a device for the conditioning of the sample
a differential measurement system, since the initial attenuation is a function of the nature of the crude; and so,
a crude drying system, for producing a dry crude passing through the reference cell of the differential analyzer.

 In addition, attempts have been made to determine the water content of the crude oil by various methods of drying the crude oil, in particular by centrifugation, filtration and electrostatic decantation, but none of these tests has yielded satisfactory results.

 It is very important for the determination of this water content by neutron activation, which consists of passing a stream of felts through the crude to activate the oxygen atoms of the water therein, then to measure the radiation of a sample thus irradiated.

 Indeed, despite many advantages, this method has the disadvantage of being expensive and deterrent due to radio activity. In addition, no satisfactory solution has been found to solve calibration problems.

 The object of the invention is to develop a method and a device which do not have the drawbacks of those previously described, and which makes it possible to dye in particular a relative accuracy of the order of 10%.

It was developed as a result of studies and tests that first allowed us to show a simple relationship between, on the one hand, the water content X and, on the other hand, the constant dielectric # of dry crude oil and the dielectric constant #h of the raw mixture + water
The measuring cell used during the tests consisted of a Lampard capacitor, that is to say a cylindrical capacitor whose armatures are deposited on a cylinder made of an electrically insulating material, mounted in series on a circulation pipe of gross of which it forms a section.

 It is clear that in this system, the dielectric is essentially constituted by the crude passing through the cylinder.

 The tests focused on different types of crude oils to which increased amounts of water were added.

The measurements were made at room temperature on mixtures circulating in the measuring capacity and not on mixtures at rest, the water content varying from 0 to 5% by volume.

les résultats sont donnés dans le tableau 1 ci-après où x est la teneur en eau en cm3/1.Calling

the results are given in Table 1 below where x is the water content in cm3 / 1.

TABLE 1

<tb> Oil <SEP> crude <SEP> Mass <SEP> Right <SEP> of <SEP> least <SEP> squares
<tb> volumic <SEP> (from <SEP> O <SEP> to <SEP> 5% <SEP> in <SEP> volume <SEP> of water)
<tb><SEP> to <SEP> 15%
<tb> Saharan <SEP> 0.804 <SEP> Y <SEP> = <SEP> 2.85 <SEP> 10-3 <SEP> x <SEP> - <SEP> 3.15 <SEP> 10-4
<tb> Kirkok <SEP> 0.844 <SEP> Y <SEP> = <SEP> 2.91 <SEP> 10-3 <SEP> x <SEP> -1.68 <SEP> 10-3
<tb> Zubair <SEP> 0.855 <SEP> Y <SEP> = <SEP> 3,12 <SEP> 10-3 <SEP> x <SEP> + <SEP> 1.00 <SEP> 10-5
<tb> Aramco <SEQ> 0.861 <SEP> Y <SEP> = <SEQ> 2.95 <SEP> 10-3 <SEP> x <SEP> - <SEP> 1.04 <SEP> 10-3
<tb> Aramco * <SEP> 0.861 <SEP> Y <SEP> = <SEP> 2.86 <SEP> 10-3 <SEP> x <SEP> - <SEP> 1.60 <SEP> 10-3
<tb> Gash <SEP> Saran <SEP> 0.871 <SEP> Y <SEP> = <SEP> 3.13 <SEP> 10-3 <SEP> x <SEP> - <SEP> 0.46 <SEP> 10 -3
<tb> Kursaniyah <SEP> 0.872 <SEP> Y <SEP> = <SEQ> 2.86 <SEP> 10-3 <SEP> x <SEP> - <SEP> 2.25 <SEP> 10-3
<tb> Forcados <SEP> 0.877 <SEP> Y <SEP> = <SEP> 3.22 <SEP> 10-3 <SEP> x <SEP> - <SEP> 1.90 <SEP> 10-2
<tb> Safaniyah <SEP> 0.885 <SEP> Y <SEP> = <SEP> 2.35 <SEP> 10-3 <SEP> x <SEP> - <SEP> 5.46 <SEP> 10-3
<tb> * Doping with fresh water. All other tests: doping
salt water at 30 g / 1.

 The examination of the preceding table shows that the results are rather homogeneous, except for those relating to Safaniyah crude oil.

 The analysis of the results can therefore be summarized by the following table.

TABLE 2

= (2,99 # 0,36) 10-3 x ou encore

= (2,99 + 0,36) 10-3 x
On constate donc que la variation de la constante diélectrique d'un brut sec, dopé à l'eau juequ'à 5 % en volume, est linéaire.<tb><SEP> With <SEP> Safaniyah <SEP> Without <SEP> Safaniyah
<tb> Number <SEP> of tests <SEP> 9 <SEP> 8
<tb>##<SEP> average <SEP> 2.92 <SEP>. <SEP> 10-3 <SEP> 2.99 <SEP>. <SEP> 10-3
<tb>#s
<tb> Difference <SEP> type <SEP> 0.25 <SEP> 0.15
<Tb>
So, if we exclude Safaniyah, we end up with the relation:

= (2.99 # 0.36) 10-3 x or even

= (2.99 + 0.36) 10-3 x
It can thus be seen that the variation of the dielectric constant from a dry crude, doped with water to 5% by volume, is linear.

It is clear that to calculate the water content from the above formula, it is necessary to
- to measure #h;
- to know, or to determine E # @
However, each dry crude has a different dielectric constant. The various attempts to dry wet crudes that have been undertaken (centrifugation, filtration, electrostatic settling) have all failed.

 We then sought to correlate the dielectric constant of the crude with a characteristic quantity of this crude, which is not affected by the presence of water.

For theoretical reasons, a correlation with the square of the refractive index has been determined
# = f (n2)
and measured the refractive index of a number of crudes. The correlation established was the following # = 1.6744 n2 - 1.4243 with a correlation coefficient r = 0.92.

 However, this method requires the continuous measurement of the refractive index, a measurement that poses many difficulties at the level of the sampling loop.

 However, it has been found that there is a correlation between the dielectric constant and the density d. To study it in more detail, the density was expressed at the temperature G at which the dielectric constant had been measured. This study made it possible to obtain the relations and correlation coefficients r following t = 2.9.0 d15 - 0.18 with r = 0.94, when the temperature is equal to 15 C, and # = = 2.90 do - 0.16 with r = 0.95, for a temperature 4.

 These correlations are slightly better than the correlation 6 - f (2). However, they are clearly insufficient to lead to an acceptable accuracy on the knowledge of the water content.

 It was then attempted to exploit the Wagner formula based on the fact that when two liquids of different dielectric constant are mixed, the dielectric constant of the mixture varies according to their respective proportions.

qui peut s'écrire, dans le cas d'un mélange brut + eau

étant la constante diélectrique de l'eau.In particular, if a small volume x of a body of high dielectric constant 81 is mixed with a low dielectric constant body ##, the dielectric constant # of the mixture is governed by the relation

which can be written in the case of a raw + water mixture

being the dielectric constant of water.

e
However, using this formula directly leads to a much worse correlation than those previously obtained.

= constante relation dans laquelle :
M est la masse moléculaire du gaz
d est la densité du gaz, et,
P est la polarisation.The Applicant has therefore been led to look for another correlation. To this end, it is part of the existing relationship for perfect gases

= constant relation in which:
M is the molecular mass of the gas
d is the density of the gas, and,
P is the polarization.

Knowing that the dielectric constant of the air is equal to 1, we can write

ds étant la masse volumique du brut sec.By analogy the Applicant has therefore tried this formula on crude oils, this formula becoming, in the case in point:

ds being the density of the dry crude.

The manipulations involved sixteen pure dry crudes, ten dry crudes mixtures of which
- seven binary mixes
- two ternary mixtures
- a quaternary mixture.

ou encore

avec g (87,69 - 0,366 t)
Les résultats obtenus ont été les suivants TABLEAU 3

But, in this case, the parameter C @ no longer makes sense since the raw materials studied were dry. It was replaced by the expression of Ee as a function of the temperature.
e @e = @@, @@ - @, @@@ @ so that the formula tested is written

or

with g (87.69 - 0.366 t)
The results obtained were as follows TABLE 3

= 1,46853 ds + 2,32643 = K avec un coefficient de corrélation r = 0,998.MEASURE <SEP> CALCULE
<tb> GROSS
<tb> OR <SEP> MIXES <SEP> OF <SEP> BRUTS <SEP> t C <SEP> ds <SEP> to <SEP> t C <SEP>#s<SEP> to <SEP> t C <SEP > G
<tb> ARZEW <SEP> 21.5 <SEP> 0.793 <SEP> 2.145 <SEP> 1.1646
<tb> EKOFISK <SEP> 18.9 <SEP> 0.800 <SEP> 2.179 <SEP> 1.1540
<tb> WUSHI <SEP> 26.0 <SEP> 0.807 <SEP> 2.145 <SEP> 1.1646
<tb> MURBAN <SEP> 22.5 <SEP> 0.824 <SEP> 2.251 <SEP> 1.1160
<tb> BEKAPAI <SEP> 23.4 <SEP> 0.828 <SEP> 2,210 <SEP> 1,119
<tb> HANDIL <SEP> 30.3 <SEP> 0.847 <SEP> 2.276 <SEP> 1.0812
<tb> ARAMCO <SEP> 22.6 <SEP> 0.851 <SEP> 1.375 <SEP> 1.0756
<tb> ZUBAIR <SEP> 23.0 <SEP> 0.854 <SEQ> 2.394 <SEP> 1.0709
<tb> KUWAIT <SEP> 23.2 <SEP> 0.861 <SEP> 2.429 <SEP> 1.0680
<tb> IRAQ <SEP> - <SEP> KIRKUK <SEP> 23.3 <SEQ> 0.862 <SEQ> 2.355 <SEQ> 1.0627
<tb> DUBAI <SEP> 23.6 <SEQ> 0.862 <SEQ> 2.469 <SEP> 1.0578
<tb> ISTHMUS <SEP> CACTUS <SEP> 20.2 <SEP> 0.864 <SEP> 2.420 <SEP> 1.0587
<tb> KURSANIYAH <SEP> 23.3 <SEP> 0.865 <SEP> 2.418 <SEP> 1.0562
<tb> GASH <SEP> SARAN <SEP> 21.4 <SEP> 0.869 <SEP> 2.485 <SEP> 1.0496
<tb> FORCADOS <SEP> 22.9 <SEP> 0.874 <SEP> 2.359 <SEP> 1.0340
<tb> SAFANIYAH <SEP> 23.2 <SEP> 0.881 <SEP> 2.500 <SEP> 1.0340
<tb> KIRKUK <SEP> - <SEP> MURBAN <SEP> 21.0 <SEP> 0.834 <SEP> 2,295 <SEP> 1,1014
<tb> KIRKUK <SEP> - <SEP> ARAMCO <SEP> 21.3 <SEP> 0.848 <SEP> 2.373 <SEP> 1.0800
<tb> MURBAN <SEP> - <SEP> KURSANIYAH <SEP> 21.2 <SEP> 0.848 <SEP> 2.344 <SEP> 1.0816
<tb> MURBAN <SEP> - <SEP> SAFANIYAH <SEP> 21.0 <SEP> 0.854 <SEQ> 2.376 <SEP> 1.0725
<tb> DUBAI <SEP> - <SEP> ZUBAIR <SEP> 21.0 <SEP> 0.859 <SEP> 2.417 <SEP> 1.0646
<tb> KUWAIT <SEP> - <SEP> ZUBAIR <SEP> 20.6 <SEQ> 0.859 <SEQ> 2.444 <SEQ> 1.0649
<tb> KUWAIT <SEP> - <SEP> SAFANIYAH <SEP> 25.1 <SEK> 0.871 <SEQ> 2.451 <SEQ> 1.0469
<tb> KUWAIT <SEP> - <SEP> DUBAI <SEP> - <SEP> KURSANIYAH <SEP> 21.1 <SEQ> 0.867 <SEQ> 2.450 <SEQ> 1.0535
<tb> DIRKUK <SEP> - <SEP> ZUBAIR <SEP> - <SEP> SAFANIYAH <SEP> 19.3 <SEP> 0.861 <SEP> 2.420 <SEP> 1.0628
<tb> BEKAPAI <SEP> - <SEP> ARAMCO <SEP> - <SEP> GASH <SEP> SARAN <SEP> - <SEP> SAFANIYAH <SEP> 24.2 <SEK> 0.855 <SEP> 2,419 <SEQ> 1.0682
<Tb>
We then tried to correlate G with ds, which allowed to obtain the following relation

= 1.46853 ds + 2.32643 = K with a correlation coefficient r = 0.998.

This expression can be expressed as follows: # - = f (d-, t)
s
Thus, by measuring the temperature and subject to knowing when or how to eliminate this magnitude in a system of equations, one can determine
s
The invention proposes, in order to eliminate the magnitude d5, to use the equation of mass equality
1000 dh = (1000 - x) + x of,
dh being the density of the wet crude,
de = f (t C) water density.

 This equation expresses the fact that the mass of the volume of mixture is equal to the sum of masses of the volumes of dry crude and water constituting it.

avec #e = 87,69 - 0,366 t
A = 1,46853
B = + 2,32643 et 1 000 d@ = (1 00O - x) ds + sa
De ces trois équations, on tire une équation du type :
x = f(#h, dh, t)
D'une façon plus précise, l'équation précédente se présente sous la forme #1x@ + #2x@ + #3x + #4 = 0 # équation dans laquelle #1, #2, #3, #4 ne dépendent que des trois paramètres #h, dh et t.In conclusion, for the calculation of the water content of a crude oil / water mixture, we thus have a system of three equations with three unknowns, namely:

with #e = 87.69 - 0.366 t
A = 1.46853
B = + 2,32643 and 1,000 d @ = (1,00O-x) ds + s
From these three equations, we draw an equation of the type:
x = f (#h, dh, t)
More precisely, the preceding equation is in the form # 1x @ + # 2x @ + # 3x + # 4 = 0 # equation in which # 1, # 2, # 3, # 4 depend only on three parameters #h, dh and t.

 As previously mentioned, the invention is not limited to the determination of the water content of a crude mixture + water.

 More generally, it relates to the continuous determination of an optionally heterogeneous mixture, in one of its constituents.

 It is particularly suitable in the case where, at a low content x, a body of strong dielectric constant # 1 is mixed with a body of low dielectric constant # 2.

Thus, according to the invention, the process for the continuous determination of one of the constituents C1 of a mixture of at least two constituents C1, C2 circulating in a pipe and having dielectric constants # 1, # 2 , different, temperature functions, includes the following operations
a) the continuous measurement of the temperature t of the mixture C1 + C2 circulating in the pipe
b) the continuous measurement of the dielectric constant # 1,2 of the mixture C1 + C2 ;;
c) the calculation of the content x of the mixture C1 + C2 by constituting C1, by means of a formula x = f (# 1,2, d1,2, t) obtained from a system of three equations to three unknowns, namely

1 000 d1,2 = = (1 000 - x) d2 + x d

1,000 d1,2 = = (1,000 - x) d2 + xd

 dl, d2, d1,2 being respectively the densities, functions of the temperature of the constituents C1, C2 and the mixture C1 + C2.

 Of course, the invention relates to the application of the method described above to the determination of the water content x of a mixture of at least one hydrocarbon and water by substituting the different parameters of the equations 1 ', 2' , 3 ', by those used in equations 1, 2, 3 previously mentioned.

 It should be noted that, in Formula 1 (Crude Oil Specific), the coefficient 2.99x10-3 used is an average coefficient.

 Thus, if we use, for each crude, its own coefficient K, it is clear that we substantially reduce the errors.

The invention thus proposes to use, for the determination of this own coefficient K, the technique of the metered addition which consists in deliberately injecting a determined quantity of water into the crude in measurement.
The operation is carried out in a circuit mounted as a bypass on the crude pipeline
It is recalled that the crude is characterized by the general equation t

formule dans laquelle #ho est la constante diélectrique du mélange brut + eau mesurée dans la dérivation avant l'ajout dosé et #h1 est la constante diélectrique du mélange après l'ajout dosé.On ajoute un pourcentage déterminé d'eau, par exemple 1% en velume (soit 10 cm3/litre) ; l'équation 6 devient alors :

d'où K =

At time t = o, the water content (unknown) is xo:

where #ho is the dielectric constant of the raw + water mixture measured in the bypass prior to the metered addition and # h1 is the dielectric constant of the mixture after the metered addition. A specific percentage of water is added, for example 1 % in velvet (ie 10 cm3 / liter); Equation 6 then becomes:

hence K =

Simultaneously, using Equation 4, with
K = 2.99.10-3, an approximate xo 'value of xo is determined.

 A # @ s value is determined using formula 6 using the numerical values x = x'o, K = 2,99,10-3, #h = #ho.

 A value K 'is then determined closer to the value. real K using formula 8 using numerical values fs ~ # 's and measured values #ho and #h.

 Then we iteratively restart the two previous steps of the calculation which give x "o, #" s and K ".

 The convergence takes place in three or other passages.

 Moreover, it turns out that the inaccuracy on the measurements of # @, d @ and t causes an error on the determination of x. Accordingly, the invention proposes to acquire n measurements of each of the parameters and donate the average.

Thus, the error will be divided into two parts. Practically one acquires one hundred points of each parameter before averaging, and the acquisition frequency is ten points per second and per parameter.

 In addition, the Applicant has been able to verify experimentally that the influence of the salt content of the crudes and the temperature in a temperature range of 5 to 650C was negligible.

 As previously mentioned, the invention also relates to an apparatus for implementing the method according to the invention.

This apparatus essentially comprises, in the simplest case (without reduction of error by the technique of the metered addition)
at least one main measurement cell making it possible to determine, continuously, the dielectric constant # h of the crude passing through the canslisation
a temperature sensor t intended to measure the temperature of said crude
a densimeter, for example a gamma-ray densimeter, which measures the density dh of the crude and
a calculation unit intended to perform the calculation of the water content of the crude by solving the system of three equations with three unknowns

= Ads + B et
1 000 dh = (1 000 - x) d5 + x de
Dans le cas où l'on désire accroître la précision en utilisant la technique de l'ajout dosé précédemment décrite, lXappareillage comprend en outre9 en dérivation sur la canalisation, un circuit comprenant en série deux cellules secondaires de mesure de la constante diélectrique semblables à la cellule principale, un débit-mètre permettant de mesu- rer le débit Fb dans la dérivation en amont de la première cellule secondaire, et un circuit d'injection d'eau à un dés bit Fe entre les deux cellules secondaires, à un débit réglable.

= Ads + B and
1000 dh = (1000 - x) d5 + x from
In the case where it is desired to increase the accuracy using the technique of the metered addition previously described, the apparatus further comprises9 in branch on the pipe, a circuit comprising in series two secondary cells for measuring the dielectric constant similar to the main cell, a flowmeter for measuring the flow rate Fb in the branch line upstream of the first secondary unit, and a water injection circuit with a bit-wise unit Fe between the two secondary cells, at an adjustable flow rate .

In this case, the aforesaid calculation unit is also designed to perform, using the measurement parameters, the iteration calculation of the specific K coefficient of the crude 9 in the manner previously indicated.
In the same way, in order to minimize the errors on the measurement of the parameters #h, dh, t, #ho, # h1 Fb, Fe, the calculation unit could be designed to calculate an average value of these parameters on nn number determined measuring points, for example on 50 or 100 points.

An embodiment of the invention will be described below, by way of non-limiting example, with reference to the accompanying drawings in which g
Figure 1 is a hydraulic diagram of an apparatus for determining the water content of a crude oil / water mixture;
FIG. 2 represents, in perspective, a measurement cell which is more particularly suitable for measuring the dielectric constant of a mixture, possibly heterogeneous, of at least two liquids;
FIG. 3 is a theoretical diagram of the measuring circuit of the aforementioned dielectric constant.

With reference to FIG. 1, the apparatus for determining the water content x of a crude oil + water mixture involves
On the one hand, mounted in line on the pipe 1 a temperature sensor 2, a measuring cell 3 of the dielectric constant Eh of the crude mixture + water, and
h a densimeter 4, for example with # rays, and
On the other hand, a bypass circuit 5 with respect to the cell 3, which comprises, from upstream to downstream, a flowmeter 6 measuring the flow in the bypass and two secondary cells 7, 8 for measuring the constant dielectric of the crude mixture + water passing in the bypass 5.

 This apparatus further comprises a pump 9 for injecting water between the two secondary cells 7, 8.

The measuring cells 3, 7 and 8 of the dielectric constant of the raw + water mixture are based on the principle of the Lampard capacitor. It will be recalled that this capacitor consists of a tubular section 11 of electrically insulating material bearing on its outer surface axially extending reinforcements, namely:
at least two opposite main armatures 12, 13 connected to a circuit for measuring the dielectric constant, and a secondary electrode 94 having a guard electrode, intercalated between the two main armatures and connected to ground.

 This guard electrode 94 effectively forces the electromagnetic field to be established exclusively inside the trench 11.

 However, in order to make the result of the measurement independent of the heterogeneity of the raw mixture + water, a cell of similar structure is advantageously used, but whose reinforcements 12, 13, 14 are arranged obliquely with respect to the generatrices of the section 11 and wrap helically around it (Figure 2).

 Thanks to this arrangement, everything happens as if the electromagnetic field was turning. around the crude passing through the tubular section 11, so that the measurement of the dielectric constant is made independent of the position of the molecules or the water droplets inside the section.

This measuring cell further comprises a heat-insulating sleeve 15 held by a sheet-metal sheath 16, which serves as a shield and protects the assembly formed by the tubular sleeve 11, the armatures 12, 13 and the guard electrode 14. There is also shown, in broken lines, a connecting element 17 by flanges between the tubular section and the crude line.
The armatures 12, 13 of the measuring cell are connected to a measuring circuit 18 of the dielectric constant of the raw mixture + water passing inside the section.

 As shown in FIG. 3, this measuring circuit comprises a current-biased transformer differential measuring bridge 20 excited by a frequency generator 21 at 40 KHz. The output of this differential bridge 20 is connected to a synchronous detector 22 via a preamplifier 23 with a very low noise, then a broadband amplifier, with large gain and zero phase shift 24. The set of measurements and . constituted provides about 1 V per picofarad.

As previously mentioned, the main measurement cell 3 makes it possible to directly obtain the dielectric constant # h of the raw mixture + circulating water in the section. The secondary cell 7 makes it possible to obtain the dielectric constant du of the flow emanating from the channel which circulates in the bypass and the secondary cell 8 makes it possible to obtain the dielectric constant of said flow, to which a known quantity of the flow has been added; water
In this regard, we recall that the #ho parameters are involved in the determination of the hi
K specific to the crude.

 It should be noted that, for matters relating to the location of the quilting, the water content of the crude passing through the diversion may be different from the water content passing through the main pipe, without affecting in any way the validity of the water supply. calculation.

 In addition, it is possible to add to the apparatus described above a flow meter on the main pipe 1, which would calculate the amount of water contained in the crude.

 Of course, for the preparation of the various calculations previously mentioned, the apparatus according to the invention involves a possibly microprocessor computing member. In this latter case, the computation unit may also perform multiple operations such as, for example, the density of the crude, statistical analyzes, price calculations, the API degree of the crude.

Claims (12)

 1.- Method for the determination, continuously, of the content x in one of the constituents C1 of a mixture of at least two constituents C1, C2, flowing in a pipe (1) and having dielectric constants # 1 , F different, characterized in that it comprises the following operations:  the continuous measurement of the dielectric constant # 1,2 of the mixture C1 + C2 using a measurement cell t3) mounted in line on the pipe (1)  - the continuous measurement of the temperature t of the mixture C1 + C2 flowing in the pipe (i) 9  continuous measurement of the density d1,2 of said mixture, and  the calculation of the content x by constituting C1 by solving the system of three equations with three unknowns x, # 2, d2

 1000 d1,2 = (1000 = x) d2 + x d1 in which the second equation is determined experimentally and d1, d2, d1,2 are respectively the densities of the constituents C1, C2 and the mixture C1 + C2 .  2.- Method according to claim 1, characterized in that, in the case of the continuous determination of a mixture of at least one hydrocarbon and water flowing in a pipe (1), the parameters involved in the calculation the water content x of the mixture are then as follows:  # 1,2 = #h is the dielectric constant of the mixture measured in line on the pipe (1) # 2 = #s is the dielectric constant of the dry hydrocarbon;  # 1 = #e = 87.69 - 0.366 t is the dielectric constant of water at temperature t;  d1 = ds is the density of the dry hydrocarbon;  d1,2 = dh is the density of the mixture measured in line on the pipe  K1 = K is the eigenvalue of the dry hydrocarbon.  3. Method according to claim 2, characterized in that, in order to determine the constants A and B involved in the equation

 = Ads + B, a series of measurements are carried out on dry hydrocarbons, for example on different types of dry crude oils, in which the temperature t at which the hydrocarbon is located is determined for each of these hydrocarbons, the density ds and the dielectric constant #s of this hydrocarbon at said temperature, the value is calculated

 and correlates the value G previously calculated with the density d5, which makes it possible to obtain the constants A and B.  4. A process according to one of claims 2 and 3, characterized in that, in the case of determining the water content of crude oil mixture and the constant K is substantially equal to 2.991O 3 the constant A is substantially equal at 1.46853 and the constant B is substantially equal to 2.32643.  5.- Method according to one of claims 2, 3 and 4, characterized in that, in order to increase the accuracy of the constant K, one proceeds according to the technique of the metered addition, which consists in injecting voluntarily into a circuit (5), shunted on the pipeline (1) of crude oil, a determined quantity y of water in the measuring crude, to measure the dielectric constant Eh of the crude + water mixture  ho circulating in the bypass, before the metered addition, to measure the dielectric constant # h1 of the mixture circulating in the bypass, after the metered addition, and to perform the calculation of the value K by means of an iterative procedure.  determining an approximate value x 'o of the water content of the crude by the method according to claim 1, using K = 2.99.  6. Process according to claim 5, characterized in that the calculation of the value K comprises  when the addition is 1% by volume.

 - the determination of a value And closer to the real value of K by means of the formula  with K = 2.99.10-3

 the determination of an approximate value # 's using the formula  determining the actual value of K by iteratively repeating the two previous calculation steps until convergence is achieved.  6. Method according to one of claims 2 to 6, characterized in that, to increase the accuracy of the water content x of the crude, the parameters are measured #h, dh, t, #ho, # h1, Fb , Fe, in a plurality of points and the average value of each of these different parameters is used.  7. Apparatus for implementing the method according to one of the preceding claims, characterized in that it comprises  at least one main measuring cell (3) arranged in line on the crude pipe and which is intended to determine the dielectric constant # h of the crude passing through the pipe (1)  a temperature sensor (2) for measuring the temperature of said crude  a densimeter (4), for example with gamma rays, which measures the density dh of the crude, and  a calculating element intended to perform the calculation of the water content x of the crude by solving the system of three equations with three unknowns

 1000 dh = (1000 - x) ds + x of  and

 8. Apparatus according to claim 7, characterized in that it further comprises, in branching on the channel, a circuit (5) comprising in series two secondary cells (7, 8) for measuring the dielectric constant. similar to the main cell (3), a flow meter (6) for measuring the flow of the mixture passing through the bypass (5), and a water injection circuit 69) between the two secondary cells, at an adjustable flow rate , the aforesaid calculation unit being then designed to perform, using the measured parameters, the iteration calculation of the specific K coefficient of the raw  9. Apparatus according to one of claims 7 to 8, characterized in that the aforesaid cells (3, 7 and 8) for measuring dielectric constant consist of a tubular section (ii) of electrically insulating material, on its outer surface axially extending armatures, namely at least two opposite main armatures (12, 13) connected to a circuit for measuring the dielectric constant, and a secondary electrode (14) interposed between the two main armatures and connected to the mass.  10. Apparatus according to claim 9, characterized in that the armatures (12, 13, 14) are arranged obliquely with respect to the generatrices of the section and wind helically around it.  11. Apparatus according to one of claims 7, 8, 9 and 10, characterized in that further comprises, on the pipe, a flow meter, so as to allow the measurement of the amount of water contained in the crude .  12. Apparatus according to one of claims 7, 8, 9, 10, 11, characterized in that the aforesaid computing device comprises at least one microprocessor also allowing to carry out multiple complementary operations.