RU2091770C1 - Method of automatically controlling dust content in exhausted gases - Google Patents

Abstract

FIELD: environmental monitoring. SUBSTANCE: intensities of passed infrared radiation J_n and J_ny within 7.6-8.4 mcm range as well as intensity of forward-scattered infrared radiation and intensities of infrared radiation J_ny and J_py within 3.0-3.4 mcm range are recorded. Total dust and carbon dust contents are judged about, respectively, from proportions of values J_pJ_y and J_pyJ_ny. EFFECT: improved accuracy. 6 dwg

Description

 The invention relates to mining automation, and more particularly to automatic control of dust content, and can be used to control the furnaces of power plants, boiler houses and other thermal installations in which coal or fuel oil is burned, as well as to control ventilation and dust collection at various enterprises.

A known method of automatically controlling the dust content in the atmosphere, including transillumination of the controlled volume of the atmosphere by electromagnetic radiation, recording the intensities of the incident and transmitted radiation, which determine the dust content [1]
The disadvantage of this method is the influence of fluctuations in the content of CH ₄ , CO, CO ₂ , SO ₂ and NO ₂ , as well as the influence of redistributions of the content of coal, limestone and sandstone dust.

A known method for automatically controlling the dust content in the exhaust gas, including transillumination of the controlled volume of the exhaust gas with polyenergetic infrared radiation and recording the intensities of transmitted infrared radiation I _p and I _y in two wavelength ranges of 7.6-8.4 microns and 6.0-6, 8 μm, in which to determine the dust concentration as the intensity of the transmitted radiation, the sum of the intensities of the transmitted radiation in these two spectral ranges is used, while the widths of the spectral ranges of echivaniya and corresponding transmission intensity radiation is selected from the condition that the intensities of the transmitted radiation in those spectral ranges [2]
The disadvantages of this method are the narrow functionality due to the inability to control coal dust and low accuracy associated with the influence of changes in the intensity of the infrared radiation flux, pollution of the windows of the radiation source and the photodetector, and changes in the temperature of the exhaust gases.

 The aim of the invention is to expand the functionality due to additional control of the content of coal dust and at the same time increase accuracy by eliminating the effects of changes in the intensity of the infrared radiation stream from the source, pollution of the source and photodetector windows and changes in the temperature of the exhaust gases, as well as an increase in sensitivity to controlled dust contents.

This goal is achieved by the fact that in the known method for automatically controlling the dust content in the exhaust gases, including transillumination of the controlled volume of the exhaust gas with polyenergetic infrared radiation and recording the intensities of transmitted infrared radiation I _p and I _y in two wavelength ranges, one of which is 7.6 -8.4 microns, additionally record the intensities of forward-scattered infrared radiation in two wavelength ranges, one of which is 7.6-8.4 microns, and The axes of the transmitted and forward-scattered infrared radiation I _y and I _py are recorded in the wavelength range of 3.0-3.4 μm, the values of the two intensity ratios I _p / I _p and I _py / I _{y are} determined, and the contents of total and coal dust judged by the values of the relations, respectively, I _pn / I _p and I _py / I _y .

The main inventive act in creating a new method is to overcome a technical contradiction. The essence of the contradiction is as follows. In order to eliminate the influence of one perturbing factor in conventional engineering design, a correction signal about this perturbing factor is introduced. But at the same time, the measurement becomes more complicated and the reliability of sudden failures decreases. To eliminate the influence of three disturbing factors, it is necessary to introduce three correction signals, which will lead to a 4-fold complication of the method: one measurement of the main signal and three measurements of three correction signals. If you need to measure one more parameter, then you need to get another measured signal and three more correction signals to eliminate the influence of three disturbing factors. As a result, the measurement is already 8 times more complicated. In the new method, this technical contradiction is overcome: by measuring two relations, the effects of changes in the radiation intensity from the source, the effects of pollution of the windows of the radiation source and the photodetector, as well as the effects of changes in the temperature of the smoke are eliminated, and an additional measurement of the content of coal dust in the smoke is provided. In addition, the new method increases the sensitivity to the total dust content and to the content of coal dust in the smoke. To overcome the contradiction, all the distinguishing features of the method are essential: 1) additionally register the intensity of forward-scattered infrared radiation in the same wavelength range of 7.6-8.4 μm, 2) additionally record the intensity of forward-scattered infrared radiation in the wavelength range of 3.0- 3.4 microns, 3) the intensity of the infrared radiation transmitted through the smoke layer I _{y is} recorded in the wavelength range of 3.0-3.4 microns, 4) the intensity ratio I _pn / I _{p is} determined; 5) determine the value of the ratio of intensities I _ru / I _y , 6) on the content of total dust in smoke is judged by the value of the ratio of intensities I _rp / I _p , 7) on the value of the content of coal dust in smoke is judged by the values of two ratios of intensities I _rp / I _n and I _ru / I _at . If we exclude or replace with an equivalent one of these seven distinctive features, then the technical contradiction will not be overcome, that is, the goal will not be achieved. The need and sufficiency of all seven distinctive features to achieve the goal clearly follows from the description of the method below. None of these seven distinctive features are even known individually, individually. Moreover, the application of any of these signs to achieve the goal is unknown. Therefore, according to the authors, the combination of seven distinctive features meets the criteria of "novelty" and "inventive step".

Figure 1 shows the attenuation spectra of the absorption of infrared radiation (hereinafter IR radiation) with moisture H ₂ O, CO, CH ₄ , N ₂ O, O ₃ , CO ₂ , HDO and the solar IR spectrum; figure 2 - dependence of the attenuation coefficients of infrared radiation of coal dust (curve 1), limestone dust (curve 2) and sandstone dust (curve 3) on wavelength λ; in Fig.3 the dependence of the intensity of the transmitted I _p and forward scattered I _p IR radiation through the smoke layer d on the total dust content C _p in the exhaust gases; 4 depending on the intensity ratio of h _p = I _p / I _p of C _n for _n 0≅C ≅170 g / m ^3; figure 5 - dependence of the ratio η _p = I _p / I _p from C _p at 170 g / m ³ ≅C _p ≅ 340 g / m ³ ; Fig.6 dependences of the relative sensitivities of the transmitted S _p and forward scattered S _{p of} IR radiation to the total dust content C _p of the content of C _{p itself} , as well as the dependence of the relative sensitivity of S _about C _p .

A method for automatically controlling the total dust content C _p and the content of coal dust C _y in smoke is implemented by the following sequence of operations.

 A controlled smoke layer of thickness d is exposed through polyenergetic infrared radiation.

The intensity of the IR radiation transmitted through the smoke layer with a thickness d of I _p is recorded in the wavelength range from 7.6 to 8.4 microns.

The intensity of forward-scattered smoke in a layer of smoke with a thickness d of IR radiation I _p is recorded in the same wavelength range from 7.6 to 8.4 microns.

The intensity of the infrared radiation I _y passed through the smoke layer with a thickness d is recorded in the wavelength range from 3.0 to 3.4 μm.

The intensity of forward-scattered IR radiation is recorded in a smoke layer of thickness d I _ru in the wavelength range from 3.0 to 3.4 μm.

The intensity ratio η _p = I _p / I _{p is} determined.

=I_pу/I_у.Determine the value of the ratio of intensities

= I _pu / I _y

The ratio η _p determines the total dust content C _p in the smoke.

The values of the ratios η _p and η _y determine the content of coal dust C _y in smoke.

 The invention is illustrated by the following circumstances.

The intensity of the infrared radiation passing through the smoke layer with a thickness d _p I _p exponentially decreases with increasing total dust content C _p in the smoke according to the formula:
I _p = I _op exp (-K _p dC _p ),
where I _{op the} intensity of the transmitted infrared radiation at C _p = 0; K _p the attenuation coefficient of infrared radiation by dust. If d is measured in meters (m), and the content of C _p is measured in g / m ³ , then to obtain the dimensionless product K _p C _p d, the coefficient K _p must be expressed in m ² / g.

коэффициент рассеивания ИК-излучения пылью, K_р коэффициент ослабления рассеянного вперед ИК-излучения пылью, Если C_п измеряется в г/м³, а d в м, то σ_п и K_р, как и K_п выражаются в м²/г.The intensity of the infrared radiation I _p scattered in the forward direction in the smoke layer of thickness d _p varies with C _p according to the formula:
I _p = I _op + σ _p dC _p exp (-K _p dC _p ), (2)
where I _{op the} intensity of forward scattered IR radiation at C _p = 0;

coefficient of scattering of IR radiation by dust, K _p the attenuation coefficient of forward scattered IR radiation by dust, If C _p is measured in g / m ³ and d in m, then σ _p and K _p , like K _p are expressed in m ² / g .

In order to ensure that the intensities I _p and I _{p are} independent of the influence of changes in moisture, CO, CO ₂ , other gases in the smoke, as well as changes in the contents of sandstone C _ps and limestone C _and dust (that is, to eliminate the effect of redistribution of the contents of coal C _у , sandstone C _ps and limestone C _and dust at C _p C _y + C _ps + C _and const), it is necessary to select the corresponding wavelength range of the detected infrared radiation.

From the graphs shown in figures 1 and 2, it is seen that in the wavelength range from 7.6 to 8.4 microns there are no strong absorption bands of infrared radiation by the main gas components of the smoke and in this wavelength range there are no strong absorption bands of infrared moisture . In addition, in this wavelength range, the attenuation coefficients of infrared radiation of sandstone K _ps and limestone K _and dust are close to each other K _ps ≃ K _and .. Therefore, in the wavelength range from 7.6 to 8.4 μm, the intensity of the transmitted I _p and the IR radiation scattered forward by I _p will depend only on the total dust content in the smoke C _p and will in no way depend on the redistribution of the contents of C _y , C _ps and C _and at C _p const.

From the graphs shown in figures 1 and 2, it can be seen that in the wavelength range of IR radiation from 3.0 to 3.4 μm, there are no strong absorption bands of IR radiation by moisture and the main flue gases, the content of which can vary greatly, carbon dioxide and carbon monoxide gases. Therefore, the attenuation coefficients of infrared radiation in the wavelength range from 3.0 microns to 3.4 K _to moisture, carbon monoxide and carbon K _g K _{to the} gases can be ignored, since they are not less than a hundred times smaller than the attenuation coefficients IR -radiation various components of dust: K _0, K 0 _g, K _to 0, K _n >> K _a, K _n >> K _r, K _{n to} >> K, K _y >> K _a, K _y >> K _g , K _y >> K _k , K _ps >> K _c , K _ps >> K _g , K _ps >> K _k , K _and >> K _c , K _and >> K _g and K _and >> K _to .

From the graphs shown in figures 1 and 2, it can be seen that in the wavelength range of infrared radiation from 3.0 to 3.4 μm, the attenuation coefficients of limestone and sandstone dust are equal to each other K _ps K _and . In addition, in this wavelength range, the attenuation coefficients of infrared radiation by coal dust are almost three times different from the attenuation coefficients of infrared radiation by natural dust components (limestone and sandstone).

Thus, the wavelength ranges of 7.6-8.4 microns and 3.0-3.4 microns for the task of separately controlling the total dust content in smoke C _p and controlling the content of coal dust in smoke C _y are optimal. In the first wavelength range, the dependence of intensities is provided only on C _p , and in the second only on C _y and C _pores C _ps + C _and .

From the dependences I _p f (C _p ) and I _p f ₁ (C _p ) shown in FIG. 3, it can be seen that with an increase in C _{p, the} first intensity I _p exponentially decreases. With increasing C _{p, the} intensity I _p grows in the measurement range of C _p from 0 to C _{p max} when (+ K _p C _{p max} d) 1, that is, when C _{p max} (-K _p d) ^-1 .

In this range of changes C _p from 0 to C _{p max} (K _p d) ^{-1 the} value of the ratio of intensities:
η _p = [I _op + σ _p dC _p exp (-K _p dC _p )] [I _op exp (-K _p dC _p )] ^-1 (3)
grows smoothly with increasing C _p , as shown in figures 4 and 5. It can be seen that the dependence η _p f ₂ (C _p ) is more abrupt than the dependence I _p f (C _p ) or I _p f ₁ (C _p ) To evaluate the gain in increasing the sensitivity of the ratio S ₀ to the total dust content C _p , as well as to the content of coal dust C _y , against the corresponding sensitivities of the transmitted I _p and forward scattered I _p IR radiation to C _p or to C _y when recording, respectively, I _p or I _p , let us estimate these sensitivities themselves.

и не зависит от изменений C_п или C_у.The relative sensitivity to C _p or to C of _the transmitted infrared radiation I _p by the absolute change in the total dust content C _p or the content of coal dust C _y from (1) is written in the form:

and does not depend on changes in C _p or C _y .

Относительная чувствительность величины отношения ^ηп ^{или η}у к C_п или к C_у из (3) запишется в виде:

Графики зависимостей S_п, S_р и S_о от C_п или от C_у приведены на фиг.6. Видно, что отношения S_о в пределах концентраций 0<C_п<C_пmax или 0<C_у<C_уmax является наибольшей.The relative sensitivity to C _p or to C of _the intensity of forward-scattered IR radiation I _p by the absolute change in the contents of C _p or C _y from (2) is written in the form:

The relative sensitivity of the ratio ^η p ^{or η} y to C _p or to C _y from (3) can be written as:

The dependences of S _p , S _p and S _o on C _p or C _y are shown in Fig.6. It can be seen that the ratio S _о within the concentration range 0 <C _p <C _{p max} or 0 <C _y <C _{y max} is the largest.

An analysis of formulas (3) shows that the same relative changes in the intensities I _p and I _p (no matter how many times at the same time they do not change) do not lead to the slightest changes in η _p and η _y . Therefore, the magnitude of the ratios η _p and η will not change _in any way either from a change in the intensities from the radiation source, or from pollution of the source or photodetector windows, or from changes in the temperature of the exhaust gases, since any of these three reasons leads to identical relative changes in both intensities I _p and I _p .

что соответствует содержаниям C $\genfrac{}{}{0ex}{}{\text{′}}{\text{п}}$ = b_п(2a_п)^-1 или

. Рабочим участком является восходящая ветвь, соответствующая содержаниям

или

.The dependence η _p f ₂ (C _p ) or η _y f ₂ (C _y ) according to formula (3) is a transcendental equation from which C _p or C _{y is} not explicitly determined, which is inconvenient for measurements, since you have to resort to complex and cumbersome methods for numerically solving equations (3) with respect to C _p or C _y . As seen from the graphs in Figures 4 and 5, the relationship η _n f ₂ (C _n) or dependence η _{2 n,} f (C _y) of formula (3) can be approximated by the expression
η _p = -a _p C $\genfrac{}{}{0ex}{}{\text{2}}{\text{P}}$ + b _p C _p ,
η _y = -a _y C $\genfrac{}{}{0ex}{}{\text{2}}{\text{at}}$ + b _y C _y - a $\genfrac{}{}{0ex}{}{\text{′}}{\text{P}}$ C $\genfrac{}{}{0ex}{}{\text{2}}{\text{P}}$ + b $\genfrac{}{}{0ex}{}{\text{′}}{\text{P}}$ C _p . (7)
In the general case, dependences (7) are quadratic parabolas with an ascending branch, a gentle maximum, and a falling branch. The middle of the gently sloping maximum is achieved when the derivative of η _p or η _{y with} respect to C _p or with C _y

which corresponds to the contents of C $\genfrac{}{}{0ex}{}{\text{′}}{\text{P}}$ = b _p (2a _p ) ^-1 or

. The work site is an ascending branch corresponding to the contents

or

.

или 0 < C_у< 0,9C $\genfrac{}{}{0ex}{}{\text{′}}{\text{у}}$ . Поэтому аппроксимирующая кривая считается приемлемой по самым строгим критериям.The approximation errors at the work site do not exceed 0.2% of the measured contents of C _p or C _y in the entire range of their contents

or 0 <C _y <0.9C $\genfrac{}{}{0ex}{}{\text{′}}{\text{at}}$ . Therefore, the approximating curve is considered acceptable according to the most stringent criteria.

Меньшие из значений C_п1 и C_у1 находятся на рабочих участках парабол (7), а большие значения C_п2 или C_у2 находятся на падающих ветвях парабол. Так как

, то для обеспечения C_п<b_п(2а_п)^-1 или C_у<b_у(2а_у)^-1 в формулах (9) перед корнем нужно брать зак (+), а неизвестные общее содержание пыли и содержание угольной пыли в дыме определять по однозначным формулам

Для определения значений градуировочных коэффициентов a_п и b_п первого градуировочного уравнения и a_у и b_у, a $\genfrac{}{}{0ex}{}{\text{′}}{\text{п}}$ и b $\genfrac{}{}{0ex}{}{\text{′}}{\text{п}}$ второго градуировочного уравнения (7), можно пользоваться любым методом градуировки. Изменение метода градиуровки лишь изменит ее трудоемкость, но никак не повлияет на значение коэффициентов. Один из приемлемых методов градуировки описан в книге А.М. Онищенко. Оптимизация приборов для контроля состава веществ. М. Машиностроение, 1990, с. 18-29, с. 155-156, с. 251-256.From the approximating equations (7), we can obtain two values of C _p and C _y :

The smaller values of C _p1 and C _y1 are on the working sections of the parabolas (7), and the larger values of C _p2 or C _y2 are on the falling branches of the parabolas. Because

, then to ensure C _p <b _p (2a _p ) ^-1 or C _y <b _y (2a _y ) ^-1 in formulas (9), it is necessary to take zak (+) before the root, and unknown total dust and coal dust in smoke determine by unambiguous formulas

To determine the values of the calibration coefficients a _p and b _{p of the} first calibration equation and a _y and b _y , a $\genfrac{}{}{0ex}{}{\text{′}}{\text{P}}$ and b $\genfrac{}{}{0ex}{}{\text{′}}{\text{P}}$ the second calibration equation (7), you can use any calibration method. Changing the calibration method will only change its complexity, but will not affect the value of the coefficients. One of the acceptable calibration methods is described in the book of A.M. Onishchenko. Optimization of instruments for controlling the composition of substances. M. Engineering, 1990, p. 18-29, p. 155-156, p. 251-256.

Example. The intensity ratios of transmitted I _p and I _pu and forward scattered I _p and I _pu IR radiation in the wavelength ranges of 7.6-8.4 μm and 3.0-3.4 μm, respectively, with a smoke layer thickness of 1 m were determined the total dust content C _p and the content of coal dust C _y in the ranges of their measurements from 0 to 340 g / m ³ . In this 10 I _op, I _ou 10, d 1, m, _n and K 0.005 m ² / g, K _pu 0.0047 m ² / g, _Op I 0.1, I 0.1 _ou, K _P = 0.008 m ² / g, K _ru 0.0078 m ² / g, σ _p 0.2 m ² / g and σ _y 0.19 m ² / g. The relative sensitivity and all other parameters of this example are shown in Fig.3-6. The error in measuring the total dust content in smoke (standard deviation of the error) did not exceed 0.4% of the measured content. The error in measuring the content of coal dust in smoke (standard deviation of the error) did not exceed 0.47% of the measured content. Such a high accuracy of measurements of the total dust content and the content of coal dust does not provide any of the methods for measuring the dust content.

 To determine the technical and economic efficiency of the new method of automatic control of dust in smoke as a base object, we will take the prototype as the most perfect. The technical advantages of the new method compared to the prototype are as follows: 1) the functionality is expanded 2 times due to the additional measurement of coal dust content, 2) the effect of changes in intensity from the radiation source is reduced to zero (due to a change in the supply voltage of the source, due to changes in the resistance of the filament from wear and other causes), 3) the effect of pollution of the source and photodetector windows is reduced to zero, 4) the effect of changes in the temperature of the exhaust gases is reduced to zero (since bye temperature changes lead to similar changes in relative intensities of the transmitted and steam forward scattered infrared radiation for any wavelength), 5) increased sensitivity to the total dust content and coal dust.

 Five major technical advantages have led to a reduction in measurement errors of more than ten times. At the same time, the calibration and measurement process was simplified in comparison with the prototype. In addition, the cost of measuring one content is reduced by about 40% by combining two measurements in one device for implementing the method.

Claims (1)

A method for automatically controlling the dust content in the exhaust gases, including transillumination of the controlled volume of the exhaust gas with polyenergetic infrared radiation, and recording the transmitted infrared radiation intensities I _n and I _{n y} in two wavelength ranges, one of which is 7.6 8.4 microns, different in that it additionally register the intensity of forward scattered infrared radiation I _p and I _{p y} at two wavelengths, one of which is 7.6 8.4 microns, wherein the intensity I _{n y} and I _{p y} registers comfort in a wavelength range of 3.0 - 3.4 micrometers, determined values of two intensity ratios I _p / I _n and I _{p y} / I _{n y,} and on the total dust content and the content of the coal dust are judged respectively by the values of the relationship I _p / I _n and I _{p y} / I _{n y} .

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