RU2192001C1 - Method of determining weight portion of water in crude oil and residual distillation products by measuring dielectric permittivity at different frequencies - Google Patents

Abstract

FIELD: analytical methods in oil industry. SUBSTANCE: invention relates to analytical technology of rapid determination of water and oils (mixtures of oils) and residual distillation products and can be used in different areas for analysis of a large number of combustive-lubricating materials and a series of heavy organics. In particular, at temperature from 0 to 100 C and higher, from difference of dielectric permittivities measured at frequencies 1 kHz and 1 MHz, one finds, for a given oil, value of dielectric permittivity corresponding to anhydrous oil at 20 C and calculates weight portion of water from the following formula:

, where Δε_e = ε_t-ε₂₀°_C-m₁•(20-t) is increase in dielectric permittivity at low frequency and temperature t^°C caused level of water in oil; concentration coefficient at temperature t k_ε,t = k_ε,20+m₂•(20-t), where k_ε,20 is concentration coefficient at 20 C; ε_t,ε₂₀°_C are dielectric permittivities at low frequency for test oil at t^°C and for anhydrous oil at 20 C; and m₁,m₂ denote temperature coefficients. EFFECT: enabled rapid determination of water in oil during oil production, transportation, storage, and processing without performing chemical analyses. 2 ex

Description

 The invention relates to analytical technology for the rapid determination of water content in oils (oil mixtures) and residual distillation products. It can be used at various industrial and other facilities for the analysis of a wide range of fuels and lubricants (fuel oil, diesel engine oils) and a number of other heavy organic compounds.

 Currently, there are practically no accessible, operational analytical technologies (methods) for determining the water content in the process of moving large masses of oils. Even at refineries (oil refineries), the analysis of water in oils is accompanied by a long-term procedure: taking samples collected dropwise with the help of special dispensers 3 times a day, and the subsequent long-term procedure for conducting multivariate experiments. The most widely used Dean-Stark method. Thus, during the analysis, very large masses of the product are pumped without a proper assessment. This negatively affects the process of oil refining, leading to an increase in unjustified costs for the development of technology and additional environmental protection.

 The procedure for determining the water content in selected oil samples by the Dean-Stark method is as follows.

100 g of the test oil is heated in a mixture with 100 cm ^{3 of the} solvent in a Dean-Stark device [1]. The solvent, evaporating, carries away the moisture contained in the oil. Vapors of water and solvent condense in the refrigerator, and distilled water settles to the bottom of the receiver - a graduated trap. The percentage of water in the oil product is calculated from the amount of water in the trap.

 When determining water according to the Dean-Stark method, there are a number of negative features. First, the metal flask should be thoroughly dried and the solvent dehydrated. Secondly, the loading of the mixture and the reading of condensed water in the trap should be carried out at the same room temperature. If the contents of the trap are cloudy, it is recommended that it be kept in a heated water bath until light comes on, and then, after bringing to room temperature, take readings.

 The flask with the test mixture should be heated evenly to avoid possible foaming and discharge of the mixture.

The water content in percent X _{in is} calculated by the formula
X _in = V • 100 / G,
where V is the volume of water in the receiver-trap in ml;
G - weight of oil in grams.

 Rapid determination of the mass fraction of water in oils by the proposed method during their extraction, transportation, storage and processing not only reduces the analysis time of the selected samples, but also allows continuous monitoring without sampling at all stages.

 The usefulness and effectiveness of the invention is massive. First of all, the application of the invention significantly eliminates the subjective error in the analysis, even with sampling. Continuous, non-selective analysis of the flow in oil pipelines, in reservoirs at various levels by their height, carried out at all stages from production to oil refining, including at the terminals, and carried out in a unified way, gives a complete picture of the water content in oil in the process of promotion and storage of the product, and data on the results of the analysis can be transferred to almost any distance and displayed on the central display.

 The advantage of the proposed method is that without the cost of reagents, without resorting to time-consuming, multivariate, and multivariate chemical analyzes, the mass fraction of water in oils is determined based on measuring the frequency characteristics of dielectric constants and establishing their relationship (correspondence) with the initial value for anhydrous (dry ) oil of a given field (oil mixture) with a certain fractional composition. As a result, an expression (formula) inherent in the nature of oils was experimentally found that allows using operational equipment to conduct operational analyzes.

 The essence of the present invention is as follows.

или, подставляя конкретные значения,

(1)
где Δε_t - приращение диэлектрической проницаемости на низкой частоте (1 кГц) при температуре t^oС, обусловленное количеством воды в нефти;
ε_t - диэлектрическая проницаемость измеряемой нефти на низкой частоте (1 кГц) при данной температуре t^oС;

- диэлектрическая проницаемость сухой нефти на низкой частоте (1 кГц) при 20^oС;
2,532; 0,055; 0,017 - эмпирические коэффициенты, присущие природе нефтей;
Δε = ε_1кГц-ε_1MГц - разность диэлектрических проницаемостей, определенных на низкой (1 кГц) и высокой (1 МГц) частоте при одной температуре t^oС;
m₁=0,00154 - температурный коэффициент диэлектрической проницаемости для нефтей, 1/1^oС;
k_ε,t=0,05+0,00011•(20-t) - концентрационный коэффициент, т.е. приращение диэлектрической проницаемости, приходящееся на единицу массовой доли воды при данной температуре, 1/%;
k_ε,20 = 0,05 - эмпирический концентрационный коэффициент при 20^oС, 1/%;
m₂= 0,00011 - температурный коэффициент концентрационного коэффициента, 1/%,^oС;
t - температура,^oС.At a given temperature in the range from 0 ^o С to 100 ^o С and higher, the dielectric constant of the corresponding anhydrous (dry) oil at a temperature of 20 ^o С is found for a given oil at a temperature of 1 kHz and 1 MHz, and the mass the proportion of water is calculated by the formula

or, substituting specific values,

(1)
where Δε _t is the increment of the dielectric constant at a low frequency (1 kHz) at a temperature t ^o C, due to the amount of water in the oil;
ε _t is the dielectric constant of the measured oil at a low frequency (1 kHz) at a given temperature t ^o С;

- dielectric constant of dry oil at a low frequency (1 kHz) at 20 ^o C;
2.532; 0.055; 0,017 - empirical coefficients inherent in the nature of oils;
Δε = ε 1 kHz-ε _{1 MHz} - the difference in permittivity determined at a low (1 kHz) and high (1 MHz) frequency at a single temperature t ^o С;
m ₁ = 0.00154 - temperature coefficient of dielectric constant for oils, 1/1 ^o C;
k _{ε, t} = 0.05 + 0.00011 • (20-t) is the concentration coefficient, i.e. increment of dielectric constant per unit mass fraction of water at a given temperature, 1 /%;
k _{ε, 20} = 0.05 - empirical concentration coefficient at 20 ^o С, 1 /%;
m ₂ = 0.00011 - temperature coefficient of the concentration coefficient, 1 /%, ^o С;
t is the temperature, ^o C.

 The invention is implemented as follows.

Determine the relative permittivity at low (1 kHz) and high (1 MHz) frequencies and their difference at a given temperature in the range from 0 ^o C and above. Further, according to the above formula, the percentage of the mass fraction of water in oils is determined.

 Examples of specific performance.

 Example 1

 1. The determination of dielectric constants is carried out using the E7-12 immitance meters at a high frequency (1 MHz) and E7-14 at a low frequency (1 kHz) complete with a DP sensor connected alternately to them [2].

First, connect the capacitive sensor to the E7-12 immitance meter, and then to the E7-14 immitance meter or vice versa and determine the values of its electric capacitance with air at a frequency of 1 MHz (C _{0.1 MHz} ) and at a frequency of 1 kHz (C _{0.1 kHz} ):
C _{0.1 MHz} = 9.00 pF;
C _{0.1 kHz} = 9.01 pF.

2. Fill (immersed) sensor and oil at the same temperature, in the present example equal to 10 ^o C, alternatively its electrical capacitance measured at a frequency of 1 MHz _{(1 MHz)} and at a frequency of 1 kHz (C _{1 kHz):}
C _{1 MHz} = 22.00 pF;
With _{1 kHz} = 23.42 pF.

3. Determine the relative dielectric constants at the given temperature at a frequency of 1 MHz (ε _1MGts) and at a frequency of 1 kHz (ε _{1 kHz):}
ε = C _{1MGts 1MHz} / _0,1MGts C = 22.00 / 9.00 = 2.444;
ε _{1 kHz} = C _{1 kHz} / C _{0.1 kHz} = 23.42 / 9.01 = 2.599.

4. Determine the difference in permittivity at a given temperature:
Δε = ε _{1 kHz} -ε _{1 MHz} = 2.599-2.444 = 0.155.

Пример 2.5. By the formula (1) determine the mass fraction of water in a given oil as a percentage:

Example 2

An additional 3.21% water was added to the crude oil analyzed in Example 1, the oil temperature being 20 ^° C. in this case. Having performed the same operations as described in Example 1, using the values of the previously measured electric capacitances of an empty sensor at frequencies 1 MHz and 1 kHz (C _{0.1 MHz} = 9.00 pF; C _{0.1 kHz} = 9.01 pF) the dielectric constants of this oil are calculated from the measured values of the capacitance of the sensor filled with oil at frequencies of 1 MHz and 1 kHz at a temperature of 20 ^o C (respectively, C _{1 MHz} = 23.49 pF; C _{1 kHz} = 24.77 pF) and they are found to be value:
ε = C _{1MGts 1MHz} / _0,1MGts C = 23.49 / 9.00 = 2.610;
ε _{1 kHz} = C _{1 kHz} / C _{0.1 kHz} = 24.71 / 9.01 = 2.742;
Δε _t = 2.742-2.610 = 0.132.

Литература
1. Химия нефти. Руководство к лабораторным занятиям. - Л.: "Химия", Лен. отделение. 1990.By the formula (1), the mass fraction of water in percent of this watered oil is calculated:

Literature
1. Chemistry of oil. Guide to laboratory exercises. - L .: "Chemistry", Len. branch. 1990.

 2. Copyright certificate 578603. Three-electrode sensor. 1977. Bulletin 40.

Claims (1)

The method for determining the mass fraction of water in oils and products of residual distillation, characterized in that at a given temperature in the range of 0-100 ^o C and above the difference in dielectric permittivities determined at electromagnetic frequencies of 1 kHz and 1 MHz, for this oil, the dielectric the permeability of the corresponding anhydrous (dry) oil at 20 ^o C, and the mass fraction of water is calculated by the formula

or, substituting specific empirically derived values

where Δε _t is the increment of the dielectric constant at a low frequency (1 kHz) at a temperature t ^o C, due to the amount of water in the oil;
ε _t is the dielectric constant of the measured oil at a low frequency (1 kHz) at a given temperature t ^o С;
ε ₂₀ ° _C = 2.532 + 0.55 • Δε-0.017 • (Δε) ² - dielectric constant of dry oil at a low frequency (1 kHz) at 20 ^o C;
2.532; 0.055; 0,017 - empirical coefficients inherent in the nature of oils;
Δε = ε 1 kHz-ε _{1 MHz} - the difference in permittivity determined at a low (1 kHz) and high (1 MHz) frequency at a single temperature t ^o С;
m ₁ = 0.00154 - temperature coefficient of dielectric constant for oils, 1/1 ^o C;
k _{ε, t} = 0.05 + 0.00011 • (20-1) - concentration coefficient, i.e. increment of dielectric constant per unit mass fraction of water at a given temperature, 1 /%;
k _{ε, 20} = 0.05 - empirical concentration coefficient at 20 ^o С, 1 /%;
m ₂ = 0.00011 - temperature coefficient of the concentration coefficient, 1 /%, ^o С;
t is the temperature, ^o C.