FR2578068A1 - METHOD AND DEVICE FOR CONTROLLING A PROCESS OF HETEROGENEOUS TRANSFORMATION WITH KINETIC DIFFUSION ARRANGING IN A TURBULENT LIQUID CURRENT - Google Patents

Abstract

The invention relates to a method and a device for controlling a process of heterogeneous transformation taking place under kinetic conditions of diffusion in a turbulent flow of liquid. IN THE DEVICE, A SENSOR UNIT 1 OPERATING ON AN ACOUSTIC PRINCIPLE, AN AMPLIFIER 2, A SIGNAL PROCESSING UNIT 3 AND A COMPUTING UNIT 4 IS PROVIDED FOR IN A SERIES CHAIN, THE SIGNAL PROCESSING UNIT 3 BEING PROVIDED WITH AN ELECTRICAL CIRCUIT DIVIDING THE OUTPUT SIGNAL OF AMPLIFIER 2 INTO SPECTRAL AREAS AND DETERMINING THE USEFUL OR AVERAGE VALUES ASSOCIATED WITH THE SPECTRAL AREAS AS WELL AS THE RATIO OF SUCH VALUES. APPLICATION TO METALLURGICAL PLANTS.

Description

- 1 -

  The present invention relates to a method &

  a control device for a process of transformation

  heterogeneous composition taking place with kinetic diffusion

  in a stream of turbulent liquid.

  In the technical field, there are often processes where heterogeneous

  unwinds in a stream of liquid. As a transformation

  heterogeneous, we consider those corresponding to

  processes of chemical or physical transformation

  chemical, which occur on surfaces determined by

  for example on boundary surfaces

  (as in systems with a

  dispersion and another solid liquid phase

  or gaseous dispersion), on surfaces of

  catalytic properties, on electrodes immersed in a liquid and on the walls of a container

containing a liquid.

  Thus, the invention relates to the control of

  Heterogeneous transformation processes which satisfy the following conditions: the liquid is in turbulent flow and the heterogeneous transformation takes place under kinetic diffusion conditions. This latter expression means that the rate of conversion is determined by the rate of material transport from the interior of the liquid to the surface defining the

  transformation zone, or conversely of this

face inward of the liquid.

  When controlling transformation process

  heterogeneity taking place in a liquid, it is well

  to use direct methods, which consist in

  kill a sample and a physical analysis

  chemical or chemical sample. These processes can

  It is important to ensure the accuracy, necessary in practice, of measurement results, but it is practically impossible to use them for real-time monitoring of the process carried out; in the case of processes

  rapid industrial activities taking place under

  they are unable to serve as a basis for solving regulatory problems. In many cases, the actual sampling is:

  problematic, and in particular in industrial processes

  where the corresponding operation should be

  broken. A particular problem arises with regard to

  does not control the percentage of components that intervene

  in small quantities. Under such conditions, the taking of samples is in a known manner

  an element of control, but we must analyze the results

  obtained for several samples by a method

  statistics - only an increase in the number of

  samples can guarantee measurement results

  correct because, in a sample, the percentage to be de-

  finish can deviate strongly from the average value

real.

  Another group of known solutions correspond to

  processes where we examine a parameter that

  indirectly puts forward an analysis of the progression,

  that is, the speed of the transformation, in which case usually a parameter is selected which varies in a determined manner with the concentration. In this regard, one can cite pressure, temperature, color or sound, etc. The information can thus be obtained in a relatively fast manner but however, it is either imprecise or incomplete and for this reason it is impossible to use it as a correct basis in a regulation process. In the case of manufacturing

  from steel to the converter in the presence of oxygen,

  - 3 - a control procedure (Baptizmanski, V.I.etal, IWUZ,

  Tschornaja Metallurgija, 1982, 2, Pages 34-38),

  which is involved for the control an acoustic control

  tick. According to the proposed method, the acoustic phenomenon taking place during the oxygen insufflation is detected.

  in the steel bath, and in particular the characteristic level

  only sound pressure. It has been found that

  a sudden increase in the level of acoustic pressure

  in the case where the layer of slag placed on the surface

  face of the steel bath is so dense that we have to stop

  sufflation of an additional quantity of oxygen. Although it is then possible to prevent the generation of disruptive secondary processes, it is practically impossible to obtain the information guaranteeing the repeatability of the process, which would make it possible to determine the percentage

  carbon in the bath, especially with an acceptable error.

table.

  The object of the invention is therefore to create

  a method and a device for obtaining, without

  sample removal, concentration data cor-

  by indirect control in the case of a heterogeneous treatment process taking place under conditions

  kinetics of diffusion in a stream of turbulent liquid

  slow. The invention is based on the knowledge that the sound produced in a liquid by vibrations of bubbles

  (vapor, gas or cavitation bubbles)

  days in a turbulent liquid stream may be

  characterized by a variable spectral composition which relates to a well-defined value in relation to the magnitude of the diffusion coefficient in turbulence - the latter being characteristic of the transformation; when the value of the turbulence diffusion coefficient Dturb during the transformation occurring in a turbulent liquid flow increases, it can be concluded that there is a characteristic change in the continuous spectrum of the sound produced in a liquid. The essence of the change is that in a frequency band

  effectively covered, the relationship between a quantity

  energy tum below a frequency level and a

  quantum of energy above a frequency range as

  company increases. This principle can also be expressed

  in the following way: when increasing the

  their diffusion coefficients in turbulence, the

  amplitudes of the higher frequency components

  compared to those of the value components

  lower. This means that we can associate with the

  to be temporally variable a temporal function -

  who will be designated by R (t) - who stays in a relationship

  monotonic growth with the coeffi-

  diffusion in turbulence. The application of this principle is facilitated by the fact that the actual characteristic concentrations involved in processes

  heterogeneous transformation taking place in

  kinetics of diffusion in a turbulent liquid flow can be determined in a manner

  known, on the basis of the known real values of the coef-

  ficient diffusion in turbulence. In this respect, one must know the initial concentration, the relationship between

  the size of the area constituting the area of trans-

  time and / or concentration, where the latter is not constant, and in addition

  in the case of a transformation which may be

  rised by an equilibrium condition, the data deter-

  undermining the equilibrium concentration, and finally the magnitude of the constant intervening in the equation

the speed of transformation.

  The object of the invention is to provide a technical solution using the principles defined above, the control of the heterogeneous transformation process taking place under kinetic conditions of diffusion a turbulent liquid stream that can be realized on the basis of the analysis of the acoustic effect accompanying the liquid flow. In other words, the problem is to create a process and a device that allows

  to provide real-time control of various

  cessations of the aforementioned type when knowledge of initial values of the concentration and data concerning the active parameters involved in the transformation

  (for example the introduction of active substances).

  To solve the problem, a method and a corresponding device have been developed. The method is characterized by capturing an acoustic phenomenon or

  vibration generated by the oscillations of the existing bubbles

  both in the turbulent flow liquid, in that the sensed signal is subjected if necessary to noise filtering, in that subsequently the sensed signal is converted into an electrical signal reproducing its spectral composition and which is used as a signal of measure, characteristic

  the relative momentary value of the diffusion coefficient

  turbulence of the liquid for indirect control in

real time of transformation.

  Capture can be achieved both by means of

  of a microphone that also by means of a

  sure of the waves propagated by the medium. The capture of vibrations by

  the device for measuring the waves propagated by the medium is more

  tageux when the frequency of the frequencies of the sound produced by the liquidene

  concordepas with the band of audible sounds, and it is necessary

  when the liquid is placed under vacuum because in this

  the gaseous atmosphere ensuring the transmission of the ef-

acoustic fetus does not exist.

  The ratio between the noise level and that of the signal, which determines the capture efficiency, can be artificially improved by bubble generation. For example, a capillary action material or a solid material in powder form which is vaporized at the temperature of the liquid, or

well a gas insufflated.

  The signal reproducing the spectral composition can be produced from the signal picked up by many

  ways. One of the possibilities that have been found

  particularly advantageous is to select a frequency

  reference frequency in the spectral range covering the sensed signal, in which case the spectrum is divided into two ranges. We determine for one of the beaches and for the beach

  catchment, or for both beaches,

  their corresponding effectives or the mo-

  yen and divide them with each other. Usually

  the spectral range corresponding to the frequencies

  than the reference frequency and the

  corresponding value is compared with the associated value

  at the total spectral range. Experience shows that an increase in the ratio means an increase in

  diffusion coefficient in turbulence Dturb.

  According to another advantageous mode of implementation of the method according to the invention, the captured signal is subjected before the establishment of the effective value or the average value to a spectral transformation. The spectral transformation may include noise suppression by filtering and it consists in eliminating

  spectrum noise in one or more selected ranges

  from said spectrum. The spectral transformation can be carried out in a known manner by means of a series of narrowband filters, a spectrum analyzer, a computer associated with an analog / digital converter, and the like. The essence of the device also developed to solve the problem is that in a series chain there is provided a sensing unit operating on an acoustic principle, an amplifier, a signal processing unit and a signal processor. calculator, the unit

  signal processing circuit being provided with an electrical circuit

  which distributes the output signal of the ampli-

  in spectral ranges and determining the actual values or average values associated with them

as well as their reports.

  The device according to the invention is advantageously provided, in the signal processing unit,

  of an electrical circuit converting the output signal

  of the amplifier in different spectral ranges.

  In the signal processing unit of the

  In accordance with the invention, it is advantageous to

  for the execution of the determination functions, input filters, such as narrow-band filters, high-pass and low-pass filters, where appropriate one or more multiplication units, an adder

  as well as a component for determining the value of

  the average value, these components being placed in series in two lines, in which case the signals

  the output of a line are applied to a unit of

  vision which determines as a measurement signal the momentary values of the time function R (t). Multiplication units can perform the transformation

spectral.

  It is advantageous to provide the unit of cal-

  of inputs for the transmission of fixed values,

  Calibration data and real-time data.

  By means of the method and the device according to the invention, it is possible to carry out in real time the control of the heterogeneous transformation under conditions

  kinetics of diffusion in liquids in tur-

  bulent, which are not accessible for a

  rect. For this reason, they are particularly

  the problem of regulation in the production of steel, for the analysis followed by the content of

  sulfur of the iron and for the control of

  and the actions to be taken to maintain the

  sulfur content in a predetermined range.

  Other features and advantages of the invention

  will be highlighted in the rest of the description,

  given by way of non-limiting example, with reference to the accompanying drawings in which: Figure 1 shows a possible form of the signal processed by the method according to the invention; Figure 2 is a block diagram of the device according to the invention; 20. Figure 3 shows an advantageous arrangement of the electrical circuit involved in the signal processing unit of the device according to the invention; and Figure 4 shows another advantageous arrangement of the electrical circuit involved in the unit

  signal processing apparatus according to the invention.

  tion. It is particularly advantageous to apply

  the process according to the invention for the production of steel.

  In this respect, one of the problems encountered consists in determining the optimum moment of casting and thus in

  following a process where a pulverulent alloy material

  is introduced and dissolved in the steel bath

  kept in turbulent flow by induction stirring. The casting of steel into the molds can start at a

  determined degree, for example of 99%, of dissolution.

  Dissolution is a process that involves

  come kinetic conditions of diffusion. The pro-

  noise duct accompanying the flow of liquid is matched by an apparatus of

  which is fixed on the surface of the plate

  covering the container containing the steel bath and

  which captures acoustic vibrations up to 16 kHz.

  First of all, the noise caused by the

  frequency of the sector in the spectrum obtained by the

  sure, which means that part of the spectrum up to a frequency of 100 Hz is removed from this spectrum and

  therefore the influence of the trans-

  current trainer of the induction brewing unit

  tion. We thus obtain a function y = y (x) at a moment of the measurement, as shown for example by the

  Figure 1 where y denotes the amplitude and x the frequency.

  In Figure 1, f = 100 Hz defines the free frequency

  lower spectrum analysis spectrum, F = 16 kHz de-

  finishes its upper limit frequency and H = 5 kHz

  sets the reference frequency. This last

  ends in the spectrum two partial areas T1 and T2 corresponding to useful values that vary over time. The essence of the process is that the functions y = y (x, ti) corresponding to the instants

  are analyzed and, depending on the variations

  tions, the evolution of the process is determined. During

  the analysis, one can take for example

  the following values: the useful value Il corresponding to the partial area T1 between Hz and 5 kHz and the value I2 corresponding to the spectral range analyzed completely between 100 Hz and

- 10 -

  16 kHz. As a measurement signal, the report is used

  Il / I2, whose variable values over time determine

  min out the time function R (t). Based on the transition function, previously determined by measurements, of the turbulence diffusion coefficient Dturb and on the time function R (t), the momentary values of the turbulence diffusion coefficient Dturb can be determined. The momentary values obtained, the moment of introduction of the alloying material and the quantity of material introduced constitute the

  basic data, from which it can be determined

  values of characteristic concentrations of

the evolution of the dissolution.

  Another possibility is to determine the momentary values of the time function R (t) based on a ratio I3 / I2, where I2 denotes the value

  above-mentioned useful or average value and where the useful or

  their average I3 was determined by means of a function

  y (x, ti) .z (x), z (x) denoting a corresponding spectrum shaping function. With regard to z (x), one can select among other things a function

  increasing monotonousness of variable x, for example

  a thousand times the whole part of the ratio x / 1000.

  This operation is actually a transformation of the spectrum. Using this function, the influence of the amplitudes of the vibrations can be eliminated by filtering.

  below 1000 Hz and the influence can be increased

  higher frequencies. When carrying out the process according to the invention, the intensity

  the acoustic phenomenon can be advantageously

  in the case where the turbulent flow of the liquid

  is subjected to an action where bubbles are generated.

  For this purpose, a solid material is introduced in the form of

- 11 -

  powder having a vaporization point equal to the temperature of the liquid, a surfactant material or

  well we inject a gas so that the materials

  introduced do not exert an adverse influence

  the process to be controlled. The device according to the invention (FIG. 2) provides real-time control of the process of

  heterogeneous transformation taking place in

  Kinetics of diffusion in a turbulent flow of a liquid and it is also used for the implementation of the method described above. The device contains in a series chain a sensing unit 1 operating on an acoustic principle to perform the

  acoustic phenomenon taking place in the listening

  turbulent liquid, an amplifier 2, a signal processing unit 3 receiving the amplified signal and a calculation unit 4 producing a signal

  output depending on the processed signal. The unit of cal-

  ass 4 advantageously comprises inputs 11, 12, 13

  permitting the introduction of fixed values

  processes, calibration values and data

born in real time.

  The signal processing unit 3 and the calculation unit 4 of the device according to the invention can

  may also be arranged under a machine for calcu-

  In this case, the output signal of the calculation unit 4 is applied to other control or regulation devices of the process, which makes it possible to act on the process to be controlled by

  example by addition of specified materials, by increasing

  mixing intensity, etc. The signal processing unit 3 comprises an electrical circuit which can convert at will the

- 12 -

  output signal from amplifier 2 and thus provide the various information regarding the process to

  control. In the following, some possibilities have been

  Advantageous arrangement of this circuit: the output signal of the amplifier 2 connected to the pickup unit 1 is transmitted to several narrow-band filters 6 (FIG. 3), via a

  high-pass filter 15 and a low-pass filter 14 (Figure 4).

  The output signals of the filters are applied directly

  (Figure 4) or through units

  multipliers 7 (Figure 3), to summators 8 and

  following components 9 for determining the useful value or the average value. The outputs of these latter components are connected to a division unit

  analogue or digital 10. The output signal of the

  signal processing unit is the signal of the unit

  division 10, which represents, in the form of a

  measurement scale, the momentary values of the function

of time R (t).

  With the aid of the narrow-band filter 6, it is

  possible, if necessary, also to ensure the elimination

  noise filtering, which corresponds to a

  spectrum transformation operation.

  The sensor unit 1 of the device according to

  the invention is generally arranged in the form of a

  crophoneoud'unappareildemesuredesondespropagéesparlemilieu,

  whose output signal is converted by the processing unit

  3, which allows the computing unit to produce the signal necessary for an indication or

* for an activation of the action units.

  The invention will be explained in more detail

  cut in the following with the help of an example of

more concrete work.

- 13 -

EXAMPLE

  The problem is to ensure the desulfurization

  64 tons of steel in a bath. For this purpose, we

  a pulverulent active substance in a stream of gas

  neutral carrier.by means of a lance plunged into the bath.

  The molten steel remains in turbulent flow and

  in it there are not only bubbles produced

  by cavitation but also the bubbles of the carrier gas

  tor. Heterogeneous transformation under conditions

  kinetics of diffusion produces a reaction which is

  rolls on the surface of the dispersed parts, the said

  parts being produced as a result of reactions

  between the introduced active ingredient and the molten steel. During the reaction on said surfaces, the

  sulfur leaves the steel of the bath and enters the

  in dispersion. The dispersed parts leave the steel bath in a determined time, their area extent being virtually independent of the absence

of sulfur (the sulfur content).

  For the production of the measurement signal,

  that is, a signal representing the momentary value of

  the time function R (t), a sen-

  orientation and whose amplified signal is trans-

  set to a high-pass filter 14 having a band limit of 7 kHz and another high-pass filter having a lower pass limit of 100 Hz. The latter filters out the low-frequency noise, the source of which is

  located in the current transformer operating near

  you. The noises present the maximum amplitude at the frequency

  50 Hz. The output signals of the filter are

  directly connected respectively to a component 9 for determining the useful value and components 9 are connected

- 14 -

  to an analog division unit 10. In this way,

  electrical signals are produced which are proportional to the

  energy levels of the spectral range designated by T2 on

  Figure 1 and the total spectral range, the pro-

  portion determines the measurement signal, i.e. the

time function R (t).

  With a view to the preparation of the control,

  several times a follow-up of the desul-

  furation, and in particular with a view to determining the transition function between the time function R (t)

  and the turbulence diffusion coefficient using

  the device according to the invention. The sulfur content of the steel is determined by measurements based on flame photometry that are carried out on samples taken before and after the treatment (in the metallurgical plant before casting and in the steel bath before the spill). in molds). From the values obtained for the time function R (t) and

  also from the analysis data, we were able to

  calculate that the kinetic equation for the actual sulfur concentration S (t) in the case of values of R (t) between 0.05 and 0.80 could be written in the following concrete form: dS ( t) R (t)

- = - 0.89

  dt S (t) - E (t) In this equation, E (t) denotes the concentration of sulfur in the equilibrium condition and in this respect,

  for theoretical reasons, we can indicate the equa-

S0 E (t) = 1 + 0.0225 m (t)

- 15 -

  o NA means the sulfur content before the treatment (before casting in the metallurgical plant) and m (t)

  means the quantity of the active ingredient injected

  at the time of treatment and determined by electronic weighing. Real-time process control is

  performed in such a way that the measurement signals

  having the time function R (t) are applied to the device according to the invention and that the signals

  measuring device of the electronic weighing device

  plotted to a mini-calculator, which calculates on the basis of the concrete kinetic equation, after the introduction of the SO value and at short time intervals, the values of the actual sulfur concentration S (t), and which ensures the display of said values. Between the

  sampling necessary for the determination of

  sulfur content and the start of treatment.

  It is necessary to provide for a period of

  20 to 30 minutes during which the sulfur content can be determined. The actual process to be controlled has a duration of about 3 to 10 minutes, depending on the speed of obtaining the

sulfur desired.

  The control aims on the one hand to avoid rejects because of a too strong sulfur content,

  on the other hand to prevent a solution of the nitrogen from the environment in place of sulfur

  removed, and to avoid the use of excessive quantities

  tients of active ingredient. (Nitrogen can replace

  sulfur in steel in the case where the amount of sulfur

  fre in the steel bath is too weak).

  After the control checks, as indicated above, it was determined that the values

- 16 -

  concentrations indicated by the device matched,

  taking into account the range of tolerances, with

  their measured by photometric flame analysis. The concordance was confirmed in the case of 21 verified checks.

  The device according to the invention and the

  corresponding supply provide relatively

  for accurate real-time control of the process.

  mentioned above, in which case no sampling of

  tillon is necessary. A particular advantage is that, under specified conditions (when so-called Reynolds analogy is satisfied), the value of the turbulence diffusion coefficient can

  to be used as a basis for calculating the viscosity

  turbulence and conductivity coefficient

thermal turbulence.

  Although control measures and calculations are necessary to obtain the correct measurement results, and although the process also needs to be monitored during the checks, the proposed method and the corresponding device make it possible to obtain reliable results. correct data that is needed during real-time checks. In this way, a solution to an unresolved problem has been developed.

the current time.

- 17 -

Claims (7)

R E V E N D I C A T I ONS   1. A method for controlling a heterogeneous transformation process taking place under kinetic conditions of diffusion in a turbulent flow of   characterized in that an acoustic phenomenon is   or vibration caused by the vibrations of bubbles existing in the liquid flowing in turbulence, in that the captured signal is converted into an electrical signal reproducing the spectral composition of the phenomenon and which is used as a measurement signal characteristic of the momentary relative value of the turbulence diffusion coefficient for real-time indirect control of transformation.   2. The process according to claim 1, characterized   in that gas and / or vapor bubbles are pro-   picks artificially in the liquid.   3.- Method according to one of claims 1 or   2, characterized in that, during the conversion of the captured signal into an electrical signal reproducing its composition   spectrum, the selected signal is divided into two domains.   spectral states and the ratio of useful values   or corresponding average values.   4. Method according to one of claims 1 to 3,   characterized in that the sensed signal is spectrally transformed prior to conversion to a signal electric. -   5.- Device for controlling a process of   heterogeneous transformation taking place under conditions   kinetics of diffusion in a turbulent flow of liquid, especially for the implementation of the process   according to one of claims 1 to 4, characterized in that - 18 -   that is provided in a series chain a unit of   capture (1) operating on an acoustic principle, an   plifier (2), a signal processing unit (3)   and a computing unit (4), the processing unit of   (3) being provided with an electrical circuit dividing the output signal of the amplifier (2) into   spectral domains and determining the values used in   the average values or values associated with the domains   as well as the ratio of said values.   6. Device according to claim 5, characterized in that the signal processing unit (3) is provided with an electrical circuit transforming the output signal of the amplifier (2) into different spectral domains.   7.- Device according to one of claims 5   or 6, characterized in that the computing unit (4) is provided with inputs (11, 12, 13) transmitting values   data, real-time data and standard data. swimming.