RU172097U1 - PHOTOMETRIC DEVICE FOR RECOGNITION OF MULTICOMPONENT IMPURITIES OF OIL PRODUCTS IN WATER - Google Patents

Abstract

The device relates to the field of photometry and relates to a photometric recognition device for multicomponent impurities of oil products in water. The device consists of a broadband source of ultraviolet radiation, a flow cell, a photodetector and a photodetector control and photo signal analysis device. The photodetector is made in the form of a diamond photodetector with a form of the photosensitivity hardware function depending on the bias voltage in the range 190–240 nm. The photodetector control and photo signal analysis device receives signals from the photodetector and, based on them, calculates the concentration of oil products in water according to an algorithm built on the basis of solving a system of linear equations based on the Bouguer-Lambert-Baire law of light absorption and the assumption that there is no interaction of oil products with water and a friend with a friend. The technical result consists in simplifying the design of the device. 3 ill.

Description

The utility model relates to the field of spectrophotometric equipment of the far ultraviolet sun-blind spectral range for the detection of hydrocarbon compounds and oil products in water. In this spectral range, lines of allowed intense electric dipole transitions of hydrocarbon molecules lie. This makes it possible to create and use spectrophotometric equipment for automatic high-precision detection of small concentrations of multicomponent oil products in water, vapors and gases of hydrocarbons in the air.

From the prior art, recognition devices for constituents of a multicomponent medium based on fluorescence [1] and spectrophotometric [2-4] analysis are known.

A multicomponent recognition device based on the analysis of fluorescence spectra and Raman scattering [1] has extremely high accuracy, does not require preliminary measurement of a large number of model media with known component concentrations, and microscopic amounts of substance are required for analysis. The disadvantages of such devices are their extremely high cost (laser (e) highly stable source (s) of radiation, monochromator, microscope) and high complexity in setting.

Spectrophotometric devices for determining the composition of multicomponent liquid and gas mixtures [2-4] are based on the analysis of probe radiation transmitted through the medium under study on the basis of the Bouguer-Lambert-Baire law and are analogues of our utility model. These devices use the principle according to which a large array of model media with known concentrations of individual components of the medium is measured first. Then, the absorption coefficient of the investigated multicomponent medium is measured in several characteristic spectral lines. Then, a mathematical model is constructed to solve a system of linear equations of dimension S × N, where S> N (N is the number of medium components that need to be recognized, S is the number of characteristic spectral lines in the absorption spectrum of the medium under study). The system of equations is solved using various mathematical methods (the regularization method [2], with the addition of correction factors [3], the least squares method [4]).

A spectrophotometer-gas analyzer [2] determines the concentration of water vapor in natural gas and other gases. For analysis, the absorption of the probe radiation of the near-IR range 1800–1940 nm, in which there are about 100 characteristic spectral absorption lines of water vapor, is used. The gas analyzer device includes a two-pass flow cell, scanning a single-beam monochromator and a rotating diffraction grating. The sounding radiation of the continuous spectrum is introduced into the cell through the collimating lens. After reflection from a spherical mirror and two passes through a cuvette with gas, this radiation is introduced through a collimating lens into a fiber light guide and transmitted to a monochromator consisting of two spherical mirrors and a rotating diffraction grating. After reflection from the second mirror, the radiation is recorded by a photo receiver. The principle of operation of the gas analyzer is based on scanning probe radiation with a spectral resolution of 1 nm and measuring the absorption coefficients of this radiation on many spectral absorption lines of water vapor. The advantages of this device is the high accuracy of recognition of water vapor and its concentration. Design shortcomings - a complex and whimsical mechanism in the field due to the presence of a rotating diffraction grating, three spherical mirrors, three collimator lenses.

. Затем через определенные промежутки времени в информативной области спектра регистрируются спектры поглощения исследуемой многокомпонентной жидкости. Далее составляется система линейных уравнений размерности п×m (причем n≤m), где n - число компонент жидкости, m - порядковый номер конкретной длины волны, на которой определяются коэффициенты экстинкции всей жидкости и отдельных ее компонент. Для каждой длины волны в спектре поглощения всей жидкости составляется одно уравнение вида:As a prototype in the implementation of the technical solution for the recognition of oil product components in water, we took the method [4] based on the Bouguer-Lambert-Baer absorption law. In this method, it is assumed that the components of the liquid interact weakly with each other, therefore, the extinction coefficient of a multicomponent liquid is equal to the algebraic sum of the extinction coefficients of the individual liquid components. To implement this method in the ultraviolet range, the absorption spectra of model liquids with known component concentrations are pre-recorded. This determines the boundaries of the informative spectral region, within which a change in the absorption spectra of model liquids is observed. Then, in this spectral range, the absorption spectra of the individual components of the medium are recorded, and the components of the medium for which the absorption is in the informative spectral region are distinguished. Then, in the same spectral region for the expected range of concentrations of these components, the spectra of extinction coefficient are recorded

. Then, at certain time intervals, the absorption spectra of the investigated multicomponent liquid are recorded in the informative region of the spectrum. Next, a system of linear equations of dimension n × m (with n≤m) is compiled, where n is the number of fluid components, m is the serial number of a specific wavelength at which the extinction coefficients of the entire fluid and its individual components are determined. For each wavelength in the absorption spectrum of the entire liquid, one equation of the form is made:

.

.

When compiling this equation, a fluid layer of unit thickness is assumed. For each absorption spectrum of a multicomponent liquid, by solving the system of linear equations constructed from equations of type (1), these unknown component concentrations are determined by the least squares method with respect to unknown C _i .

The technical result of our utility model is a significant simplification of the design of the device, based on the photometric principle of recognition of oil impurities in water, without loss of sensitivity and accuracy of detection of these impurities in comparison with analogues. The technical result is achieved by the fact that the device does not include optical mirrors and a diffraction grating or prism, but contains only a non-monochromatic ultraviolet radiation source, an optical collimator for generating a parallel beam of probe radiation through a liquid, an optical flow cell, a photodetector and a photodetector control and signal analysis unit. To maintain high accuracy in detecting oil impurities in water, it is proposed to use ultraviolet radiation in the spectral range of 190–240 nm. In this range, the absorption of light on π-π * and π-σ * allowed electronic transitions of hydrocarbon molecules is extremely intense. The absorption coefficient at wavelengths of about 200 nm for widespread petroleum products, such as benzene and isooctane, is (6 ÷ 10) ⋅10 ⁴ cm ^-1 (Fig. 1). Such absorption properties of hydrocarbon molecules allow real-time detection of their trace concentrations (up to 1 mg / liter of water, 10 ^-4 %) in water.

FIG. 1. The absorption spectrum of motor oil as an example of a mixture of heavy oil in the far UV range.

The essence of the utility model for the photometric method for recognizing petroleum substances in multicomponent media in the sun-blind spectral region is illustrated by a functional diagram (Fig. 2). The proposed model contains an ultraviolet continuous non-monochromatic source of probing radiation (Fig. 2, p. 1), a flow cell (Fig. 2, p. 2) with a collimator (Fig. 2, p. 5) for introducing a probe UV radiation, one diamond photodiode (Fig. 2, p. 3) for detecting probing UV radiation in the range 190–240 nm and a photodiode control unit and analysis of photo signals (Fig. 2, p. 4). The collimator (Fig. 2, p. 5) forms a region of uniform illumination of the flowing fluid with parallel rays of the probe radiation. A diamond-based photodetector (Fig. 2, p. 3) has a hardware function of spectral photosensitivity in the range 190–240 nm, which can strongly change its shape depending on the magnitude of the bias voltage applied to its electrodes (Fig. 3). The photodiode control unit (Fig. 2, p. 4) in the automatic mode generates a bias voltage of a different amplitude with a given step, supplied to the electrodes of the photodetector at regular intervals. Also, this control unit (Fig. 2, p. 4) monitors the electrical signals from the photodiode at specific bias voltages and calculates the concentrations of the components of the analyzed liquid medium.

FIG. 2. Schematic diagram of a photometric device for recognizing petroleum substances in multicomponent media in the ultraviolet sun-blind spectral region (1 — probe UV radiation source, 2 — flow cell, 3 — diamond-based photodetector, 4 — photodetector control unit and calculation of concentrations of the components of the liquid medium , 5 - collimator-objective; bold arrows indicate the movement of a liquid medium, dashed arrows indicate control of the photodetector using Block 4).

The shape of the spectral dependence of photosensitivity determines the hardware function of the photodetector. Therefore, probing UV radiation passing through the medium under study will give a different photocurrent for different hardware functions of the photodetector. When changing the magnitude of the bias voltage supplied to the electrodes of the photodetector, the shape (hardware function) of the spectral sensitivity of the photodetector changes (Fig. 3). The convenience and simplicity of controlling the spectral distribution of the sensitivity of diamond photodetectors by changing the bias voltage makes it possible to create a method for recognizing the composition of multicomponent liquids.

FIG. 3. Changing the shape of the spectral dependences of the photosensitivity of the diamond detector in the far UV range when bias voltage U _is applied to it, changing in the range 10–80 Volts with a step of 10 Volts.

The Bouguer-Lambert-Baer law is applicable only in the case of highly dilute solutions of liquids that interact weakly with each other (for example, water mixed with liquid petroleum products). Drops of oil products dispersed in water interact weakly with water, and the amount of oil products in water is so small that, when they are subsequently introduced into the water, drops of these liquids practically do not collide with each other and do not dissolve in each other.

Let us consider in general terms the problem of recognizing non-interacting fluid components. Let one test liquid be added to the water. Then, according to the Bouguer-Lambert-Baer law, for a unit liquid thickness, the probe radiation transmitted through this liquid is determined by:

,

,

where I (λ) and I ₀ (λ) are the spectral dependences of the intensity of transmitted and incident radiation;

ε (λ) is the spectral dependence of the extinction coefficient of the test substance;

C is the concentration of the test substance in the liquid.

If such a liquid is illuminated by a light source with a unit brightness (I ₀ = 1) in the entire studied spectral range, then the intensity of the radiation transmitted through this liquid will have the intensity:

.

.

The photocurrent arising in the photodetector circuit when illuminated by radiation of intensity I (λ) is equal to:

,

,

where S (λ) is the spectral sensitivity (hardware function) of the photodetector.

If water contains liquids of n types that do not interact with each other, then the photocurrent will be equal to:

,

,

where ε _i (λ) is the spectral dependence of the extinction coefficient of a single i component of the liquid;

C _i is the concentration i of the liquid component.

Then the dependence of the photocurrent on the intensity of the probe radiation (1) at the jth bias voltage, therefore, with the jth form of the photodetector hardware function, will look like this:

,

,

where S _j (λ) is the spectral sensitivity of the photodetector at the jth bias voltage; ε _{i, j} (λ) is the extinction coefficient of the ith component with the jth hardware function of the photodetector, determined according to Figure 2.

We transform equation (6) to a more convenient form:

.

.

Now we see that for n≥j, the following system of equations arises:

.

.

The values of ε _ji (λ) are known in advance and determined from preliminary experiments for each proposed substance (oil product), S _j (λ) are known dependences for our photodetector. By measuring the values of the photocurrent J _j at j different values of the bias voltage, then, by solving the system of linear equations (6), we can determine the concentration C _{1 ... n of} different components of the liquid.

Literature:

1. Gavrilov D.A. Device for contactless identification of substances and / or determination of concentrations of substances that make up a multicomponent mixture // Patent for invention, RU 115486 IPC G01N 21/65, G01J 3/44, the beginning of the patent on October 13, 2011.

2. Yu.A. Poplavsky, V.I. Serdyukov, L.N. Tit, A.P. Shcherbakov. Spectrophotometric Gas Analyzer-Hygrometer "Winter" // Scientific Instrumentation, 2009, volume 19, No. 3, p. 72-78.

3. Kataev M.Yu., Mitsel A.A. Identification of the composition of the gas mixture by absorption spectra // Avtometriya (1985), 4, P. 15-20.

4. Vasilevsky A.M., Kornilov N.V., Gurevich K.Ya., Sokolov A.A. A method for analyzing a liquid biological medium in the process of monitoring // Patent for the invention, RU 2212029, IPC G01N 21/00, the beginning of the patent 03.12.2001.

Claims (1)

A photometric recognition device for multicomponent impurities of oil products in water, characterized in that it consists of a broadband source of ultraviolet radiation, a flow cell, and a photodetector control and photo signal analysis device, characterized in that it is equipped with a diamond photodetector with a shape of the photosensitivity hardware function depending on the bias voltage in the range 190 ÷ 240 nm, from the signals of which the photodetector control and photo signal analysis device calculates centration oil in water according to the algorithm constructed based on solving a system of linear equations, constructed based on the law of light absorption Bouguer-Lambert-Beer and assuming no interaction with the water and oil from each other.

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