DE1803211A1 - Method and device for controlling metallurgical processes in an oxygen-containing atmosphere - Google Patents

Description

General Electric Company, 1 River Road, Schenectady, NY _} USA

"Method and device for controlling metallurgical processes in an oxygen-containing atmosphere"

The invention relates to a method and a device for controlling metallurgical and chemical processes which are carried out in oxygen-containing atmospheres. {

In particular, the invention relates to a method and an apparatus for controlling the processing or der.Reaktion of the products in oxygen-containing atmospheres, in which
First of all, it is determined to what extent the product is chemically attacked by oxygen in various process steps, such as reduction, oxidation, etc., and the result of this determination is used to adjust the gas atmosphere in such a way that the reaction conditions
ouvimalized.

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BATH ORIGINAL

When carrying out reactions on an industrial scale the reaction products depend to a large extent on the oxygen content influenced the atmosphere used (which is to be referred to as the gas phase in the following). Whether the oxygen from the gas phase reacts with the product or not, depends on the oxygen partial pressure, the temperature and type of product being made. If you know these factors, you can do them ^ Reactivity of oxygen from the gas phase (the so-called Regulate oxygen potential) so that the most favorable Influence on the product comes about.

Up to now it has been customary to measure one or more components in the gas phase, which is used in the process in question, and to draw conclusions from this measurement about the oxygen potential in the gas phase. These indirect measurements were then used to regulate the oxygen potential of the gas atmosphere. Examples of such indirect measurements are dew point determinations or CO and / or C0 _o measurements in the atmosphere of a furnace during the treatment of metals. However, such indirect measurements are imprecise by their nature, so that it is extremely difficult to set the oxygen potential in such gas atmospheres exactly to the optimum value. It would therefore be much more beneficial if one were to determine the oxygen potential of the gas atmospheres used directly in reactions on an industrial scale, • because then the reaction or the process could be controlled much better.

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The invention thus includes a method and a device for controlling or regulating metallurgical and chemical Processes that take place in a reaction vessel with an oxygen-containing atmosphere. A supply of process gas is required for this provided, which is supplied to the reaction vessel via a control device with which the gas throughput can be adjusted will. There are also sensors for direct measurement of the oxygen potential the gas atmosphere in the reaction vessel see that emit signals that are a measure of the oxygen potential are. These output signals from the sensors are then fed back via control devices and used to control the operation of the Control reaction vessel in such a way that the metallurgical process is optimized. In preferred embodiments the invention, the oxygen potential of the gas atmosphere is measured with the aid of a gas analyzer which is able to To determine equilibrium oxygen partial pressure of the gas atmosphere in the reaction vessel directly, so that one has an indication of the Oxygen potential of the gas atmosphere is maintained.

In other exemplary embodiments, the product can be a metal which is to be either reduced or oxidized and at which the equilibrium partial pressure at which the reduction or the oxidation begins is given by the following expression:

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If the process is an oxidation process, the process gas throughput is regulated so that pO <CP °° i ₍ j _a ob ^ ^{stt If, on the} other hand, the process is a reduction process, the process gas throughput is regulated so that pO.> P °° _Ma ob ^w ^ - ^{rd #}

In the following, the invention is to be described in detail on the basis of exemplary embodiments in conjunction with the drawings

will.

Figure 1 shows schematically oxygen in the gas phase and oxygen in the metal phase as well as the way in which the oxygen in the gas phase and in the metal phase interact.

Figure 2 is a block diagram of a control arrangement for control the protective gas atmosphere in an annealing furnace for tempering metals.

Figure 3 shows the profile of the H-O / Hp ratio in one. ]continually operated annealing furnace, which was obtained by direct measurement of the oxygen partial pressure in the gas atmosphere.

Figure ¹ I is a block diagram of a process control according to the invention for a reduction process.

FIG. 5 is a block diagram of an arrangement according to the invention for regulating a sintering atmosphere.

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Figure 6 is a block diagram of an arrangement for controlling a carburizing atmosphere.

Figures 7 and 8 are graphs showing the output of a gas generator for a carburizing gas depending on the carbon depletion characteristics and function of the air / fuel ratio, for ine e "i arrangement according to Figure 6 were calculated.

It has already been mentioned above that oxygen in a large number of large-scale reactions to one or the other V / he plays a role. If you therefore consider the partial pressure of oxygen continuously measures in the gases involved in such processes are involved, you can gain valuable information for the control of such processes. In the figure 1 is schematic the animal effect between oxygen in the gas phase and a metal that is being processed is shown. Of the Oxygen in the gas phase and the oxygen in the product are in a certain equilibrium with each other, which is given by the following relationships:

° 2 (g) -K ₁ = Ρ ₍

^Ρ 02 ^{/ Κ} 1

aM + bO HaOb
<^ MaOb

^Λ 2

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The individual symbols have the following meanings:

O ₂ s oxygen in the gas phase

0 = oxygen in the metal phase

P _Q2 = oxygen partial pressure in the gas phase

οί _n = oxygen activity in the metal phase

> ~ = Activity coefficient of oxygen in the

Metal phase

C _Q = oxygen concentration in the metal phase

K. = equilibrium constant for the first reaction

Kp = equilibrium constant for the second react

Of ,. = Activity of the metal in the metal phase

ö / ... _Λ . = Activity of the oxide in the oxide phase

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MO, = stoichiometric formula of the oxide away

a, b, c = stoichiometric reactive coefficients

From the relationships given above, it can be seen that the partial pressure of oxygen in the gas phase is directly related to the oxygen content of a product that contains oxygen in a Atmosphere is processed. If metals are involved in the systems, the partial pressure of oxygen also affects the speed with which metal oxides are formed, and the oxygen partial pressure also plays a role in the question of which one Metal oxides are formed. So if you have the partial pressure of oxygen measures in the gas phase and knows the temperature of the product and its chemical affinity for oxygen one determine to what extent the oxygen is in the gas phase

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interacts with the product, and that interaction can then be regulated or controlled.

Due to recent developments in the field of electrochemical cells for measuring thermodynamic quantities, it is possible to measure the equilibrium oxygen partial pressure for controlling or regulating large-scale processes at extremely high temperatures (in the region of 1000 ^° C.). For example, an oxygen sensor has recently become commercially available which is suitable for the purposes in question here. This oxygen sensor is an oxygen concentration cell, which consists of a stabilized zirconium oxide electrolyte, which is provided with electrodes on two sides. These two sides can be exposed to different oxygen pressures. This electrolyte is designed as a tube closed on one side, so that it is particularly expedient to expose the inner electrode to a gas with a known oxygen partial pressure, such as air. If the two electrodes are used in two gases with different oxygen partial pressures, an electrical voltage is created between the two electrodes. The two gases are separated from one another by a calcium-stabilized zirconium oxide electrolyte, in which the conduction takes place via oxygen ions. The relationship between the electromotive force of the cell and the oxygen partial pressures in the two gases is described by Nernst's equation.

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When operating the oxygen sensors, the temperature of the sensor brought to a certain value, and also the oxygen partial pressure in one gas is known. So if you measure the emf between the two gases in the cell, the oxygen partial pressure of the one atmosphere being monitored can be calculated using the Nernst equation,

£ den. This measured oxygen partial pressure (Pq ₂₎ ^{stent d} ^ "rectly to the oxygen concentration in the gas as well as by its chemical composition. There are oxygen sensors', which may be used with a very small amount of filtering in industrial gases. Such sensors include their own filters, dryers and their own pumps for gas processing. in addition, such sensors have a needle valve and a gas meter on, regulate the gas flow rate and to measure. the temperature of these sensors is held at 85O ⁰ C plus or minus 5 ° C. for this, a solid state design proportional controller

* used. The output voltage of these sensors is passed through a complete amplifier circuit, so that this output voltage can be read off directly as oxygen partial pressure on a measuring instrument. The output voltage can also be fed to a recorder or a computer. The pO value is related to the measured equilibrium oxygen partial pressure P _o? linked by the following expression:

BATH ORI0INÄL

Such oxygen sensors are able to continuously measure the To measure the oxygen potential of gases that are used in large-scale industrial processes. They also have the following favorable properties;

(a) The output signal increases logarithmically with linearly decreasing oxygen partial pressure.

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(b) They have extremely low voltage "

Fluctuations on.

(c) Your continuous response speed is high (within 5 see.)

(d) 'Aggressive and particle-laden gas streams can be passed through the sensors without impairing their sensitivity.

If one wants to measure the composition of a gas used in an industrial process in order to control the process due to these 'έ measurement, the fundamental question of how many independent measurements is at a predetermined temperature and required at a given Gosamtdruck: 3ind in order to obtain reliable information with which further control can be carried out. The t'hcu-ci.rof. '■ · it ■ r- :: a number of independent Hosöungcn orforcicri Lc: i is, as (iac Cuv. ■ components or elements. For the control of many products it is not necessary, however, the entire r.usnmen -

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to determine the amount of gas that is being measured. Dig crucial Question regarding the. Measure the composition, one Gas or in conjunction with a special. Gas consists in what parameter of the gas is important and how it can be used. The answers to this question can be found in all, common to divide into two groups: 1) There is abundance in which

"The composition of the gas itself is important to the change in concentration of a specific component to measure the gas .. 2) There are also cases where the gas composition is used less accessible properties of Ga'- _(1. Ses to measure. This is usually done by calculating or by inserting it into a formula. In both cases it is not always necessary to carry out the minimum number of independent measurements in order to get to know the complete composition of the gas.

If the oxygen content of a process gas is more than about 0.1m, the other components of the gas act as diluents. In the case of an oxygen concentration in this range, paramagnetic before SciuerstoiT sensors and combustion meters have so far been used for process control. Lirnt left: door: ^r . The newly available oxygen sensors have been used in processes of the type of interest here, in which their ionic characteristic line and their insensitivity to particles in the gas phase make them very useful instruments. It should be mentioned that such newly available .. oxygen sensors together with other instruments

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have opened loan> in the production of steel after Oxygen blowing method to calculate how the oxygen from the lance is used in this oxidation process.

These newly available oxygen sensors are also used for determination the stoichiometric combustion point is very suitable. If the air-to-fuel ratio is above the stoichio- f If the metric combustion point is changed beyond, there is a drastic change in the equilibrium oxygen partial pressure in the products of combustion, and this leads to a sudden change in the output signal of the transmitter. The stoichiometric Burn point is a very good example of how a certain property is made up of several components Gas mixture can be determined by the oxygen sensors without the need for additional information.

In the cases just described, it is extremely advantageous to use the newly available oxygen sensors. In cases where the equilibrium oxygen partial pressure is determined by the reaction of the other gaseous components, i.e. where the concentration of free oxygen is below 10 atmospheres, nowadays only the newly available oxygen sensors come into question. Previously, other components of the gas phase were measured (such as CO, CO-, H ₀ O and H ₀ ) and these measurements are still made today for control purposes. These measured or assumed concentrations of the individual elements in the gas phase wer xen ^ u ** different

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Way combined to show how the gas phase das.endpro-. J the product of the process (e.g. an oxidation *, reduction or carburization process). The condition, what is done with this type of control is that the gas is in equilibrium or only slightly deviates from equilibrium, so that the thermodynamic references can be applied. For dew point determinations as well as for paramagnetic measurements or infrared examinations however, the gas sample does not reach a state of equilibrium at a precisely known temperature, as is the case with the newly available Oxygen sensors is the case. The application of this well-known Sensors is therefore based on requirements that are based on the newly available Oxygen sensors do not apply. In many cases the measurement results obtained with such instruments are used, by applying appropriate reaction equations indirectly increases the oxygen partial pressure of the gas determine. In such cases, one of the newly available can and should be used Oxygen sensors are used because with it one can determine the equilibrium oxygen partial pressure under known temperatures and can measure printing directly. Also is the equilibrium oxygen partial pressure a thermodynamically meaningful quantity. ·. -

Control theory.

One reason why the logarithmic characteristic of the newly available

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Oxygen sensors make these sensors particularly well suited is that the output of these sensors agrees with the general reaction equation with which the oxidation of a metal is described by oxygen:

(§-) H + (I /?) O ₂ > φ M _a 0 _b (7)

This equation applies when both the metal II and. also its oxide M 0, are solid or liquid.

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The Gibbs free energy of formation of the oxide according to equation (7) amounts to Δ G ° _{HQ per mole} free educational energy is. There are extensive calculations of values for ^G ^ ° Ma0b ^before V ^J are tabuliiert also depending on the temperature. These tables have also appeared in the so-called Ellingham diagrams in the form of graphical representations. The generalized ' pO value, which corresponds to the partial pressure of oxygen given by equation (7), is described by the following relationship:

PO ° fvT _n = - ^AG ° MaOb / b (8)

^u a ^u b 4,575 T

In this expression, AG ° _{M q is used} in cal / mole.

away

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Oxide MO, is reduced when pO is greater than pO ° _{M n} . from M _a u _b

The metal M, on the other hand, is oxidized when pO is smaller

as pO ° _{M n} .
a ^u b

Execution of the control . .
Control of a protective gas atmosphere.

Annealing metal parts in a protective gas atmosphere to temper these parts is a good example of how the oxygen partial pressure of a gas is determined by indirect measurements before the new oxygen sensors are available became. So far it has not been possible to get one. Oxygen-

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Partial pressure down to 10 atmospheres (which is equivalent to a dew point of about -60 ° C) to measure, which is necessary for some applications, such as bright annealing of strip material made of stainless steel. With the new oxygen sensors, such possible applications are readily available. Whether a metal is oxidized during annealing is a direct puncture of the equilibrium oxygen partial pressure in the protective gas atmosphere. The equilibrium oxygen partial pressure at which a metal begins to oxidize due to the thermodynamic laws is given in values of pO by the equation (δ). The protective gas throughput through the annealing furnace should be regulated so that the relationship pO is less than pO °. _Q , is maintained for temperatures at which the rate of oxidation is not restricted due to the reaction kinetics.

909826/0860

FIG. 2 shows a block diagram of an arrangement for controlling or regulating an atmosphere, with which the operation of an annealing furnace 11 can be controlled. The annealing furnace 11 is heated by any fuel system which is controlled by a controller 12 and temperature sensors 13. The controller 12 can be a digital process computer. The computer has analog-to-digital and digital-to-analog converters, *

with which once analog input signals, for example from the temperature sensors 13 »are converted into digital signals that the computer can process, and on the other hand the convert digital control signals generated by the computer into analog signals that are sent to the control devices for the fuel system are fed. In this way, the temperature is controlled at various points in the annealing furnace. Such temperature control devices, which work with process computers are known and therefore do not need to be described in detail. . - '

According to the invention, the annealing furnace 11 is now supplied with a process gas, the furnace from a gas generator 14 on different Places is fed. This gas generator 1 * 1 leads to the Annealing furnace at several points to protective gas of a known composition, its oxygen partial pressure at the outlet of the gas generator uiid at various points in the annealing furnace by measuring devices 15 using the newly available oxygen sensors. The output of these oxygen sensors is fed to the process computer 12, and äep process

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From this, the computer calculates the quantities required to achieve the desired values at the various measuring points To maintain oxygen partial pressure in the protective gas atmosphere. There is also a gas flow meter for this purpose and control loops are provided, which are shown at 16, and with which the throughput is measured and adjusted with the. P the protective gas is fed to the various points of the furnace.

If desired, the control of the gas composition of the gas generator 1'J, which is carried out by the process computer, can be supplemented to form a full control loop if the composition of the protective gas atmosphere is particularly important. The feedback and negative feedback paths required for this have been shown in the figure by the dashed lines 17. In most applications, air is a main component of the protective gas that is emitted by the gas generator 14. In the arrangement shown, the amount of air which is fed to the gas generator Ik can be controlled via the return path 17, so that the composition of the protective gas emitted changes. This type of control or regulation together with the control of the protective gas throughput for the various! Setting the annealing furnace via the oxygen sensors 15 and the control circuits or Steuererkre.ise 16 makes it possible to regulate or control the composition of the protective gas very precisely based on the conditions at different points in the annealing furnace. The gas throughput of the furnace is set so that the Condition pO less than

* iird. "■ '■'" ■ "-

In the figure 3 is now the actual profile of the ratio IIpO / Hp applied, using a control arrangement according to FIG 2 was obtained in a continuous annealing furnace. To obtain the data shown in Figure 3, the partial pressure of oxygen was used monitored at various points in the furnace with oxygen sensors to identify those conditions (Ingress of outside air, excessive oxygen partial pressure in the cooling zone, etc.), under which the strip material oxidizes. The I Hess results obtained with the oxygen sensors can then be dasu via the computer and the associated control and regulation circuits use to regulate or control the operation of the annealing furnace so that the bright annealing proceeds optimally.

D irect reduction

Oxygen is removed from an oxide in a direct reduction process, and this oxygen then becomes part of the reducing gas. Such a reduction process is used for the production ' different metals are used. The ability of the reducing gas to remove oxygen from an oxide is a direct function the equilibrium oxygen partial pressure in the gas. The amount of oxygen per unit volume of reducing agent used Gas is withdrawn, determines the rate of reduction and thus the efficiency of the process. The efficiency of this Process is defined by the following expression:

P ° in - P ° out

pO -pO ⁰ -.

MaOb
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· ■}

In this expression, pO means. the oxygen partial pressure of the circulated gas on entry into the gas generator, with which the reducing gas produced or respectively for the reduction process is processed, and pO. the partial pressure of oxygen in the reducing gas as it leaves the gas generator. You can do this Data together with the throughput rates and the air / fuel ^ Use the substance ratio in the gas generator to determine the pO value and the flow rate of the reducing gas through the reduction vessel to regulate, to monitor the efficiency of the process and the speed of reduction, and ir.an can also be assisted on this data set the amount of gas that is fed back to the gas generator and that is newly generated in the gas generator.

Figure ^ is a block diagram of a Regelanor tion according to the invention for regulating or controlling a direct reduction process, which is intended for use with a reduction tank ™ 21. The reduction tank 21 is a counter-flow tank to which the oxides to be reduced are fed at one end in the direction of arrow 22. The reduced oxides then leave the reduction tank at the other end in the direction of arrow 21. The reducing gas is supplied by the gas generator 2 ¹ I and the production tank is supplied to the end at which the reduced oxide leaves the tank. The used reducing gas is taken off at the other end of the container. Part of the used reducing gas is fed back to the gas generator 2'I through the line 25 for processing, and another part is blown off via the line 26. So you can see that then

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reducing gas moves the reduction vessel in the opposite direction how the oxide to be reduced flows through. If desired, one can Part of the used reducing gas that goes to the gas generator 24 is supplied via line 25, flow through a gas cleaner, which is arranged in the line 25.

The gas generator 2 ^l \ can be a conventional gas generator in the; is used to generate the reducing gas for the editing vessel air. The air supply for the gas generator 2k is monitored and controlled in order to maintain the correct air / fuel ratio within the gas generator. The monitoring and control arrangements required for this have been designated by 28. This monitoring S7 and control arrangements 28 are in turn controlled by a process computer 12. The process computer 12 is a conventional digital process computer with analog to digital and digital to analog converters, to which data on the protein temperature within the reduction tank 21 are fed from the temperature sensor 13 so that the process temperature can be kept constant.

In addition to the components already described, the control arrangement according to FIG. K also has sensors for the oxygen partial pressure and control devices for the throughput of the reducing gas, which are designated 29 together. With the components summarized in block 29, the oxygen partial pressure at the outlet of the gas generator 2 * 1 (pO ,.) and the oxygen partial pressure in the used reducing gas are measured and adjusted, the fit-in gas generator draws in again via the line 25.

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will lead. This is the size ρθ ^ _η · In block 29, the newly available oxygen sensors can be used, and flow meters and control valves can also be provided with which the throughput of fresh reducing gas sum reduction tank and the proportion of the used reducing gas can be set , which is fed to the gas generator via the line 25 as well. Arrangements can also be provided for monitoring the production speed and the quality of the reduced metals which are produced in the container 21 by reduction. These arrangements have been combined in block 30.

During operation, the oxide to be reduced becomes the. Reduction tank 21 fed in the direction of arrow 22, and the reduced metal leaves the furnace at the other end in the direction of arrow 23. While the oxide migrates through the reduction tank, it is reduced by the gas y supplied by the gas generator 2k and the Flow through the reduction tank in a direction which is opposite to the direction in which the oxide migrates through the furnace. The reduction of the oxide takes place directly in the reduction tank, and thus the efficiency of the entire system is defined by the equation on page 17. The reduction process can be optimized by ^{properly regulating or controlling the quantities p0} in ^{and p0} out of ^{the gas at the} inlet ^and outlet of the gas generator 24. .

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Rege development e ne of sintering atmosphere.

If one wants to produce a sintered body from a certain oxide of a metal, of which there are several oxides, it is necessary to precisely adjust the equilibrium partial pressure of the oxygen in the sintering atmosphere. So For example, assume that a sintered body of a metal oxide of Λ together iTicnsetzunc MO is to be prepared, but not for interconnection

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setting M 0 / i ₊₂ \ · The relationship between these two metal oxides can be described by the following equation:

H 0, + c0 _o = M 0 ,, -.
from 2 a (b + 2c)

The equilibrium partial pressure of oxygen in the sintered atmosphere soot (in expressions of pO) can be maintained, that it satisfies the following relation:

Vo> M0. _{h +?} .

from a (b + 2c)

To find the correct partial pressure (pO value) according to this relationship to obtain, the throughput and the pO value of the sintering gas in the sintering furnace must be measured and adjusted.

An arrangement according to the invention for controlling or setting a sintering atmosphere is now shown in FIG. with which the required tight tolerances can be maintained. This arrangement is used in conjunction with a sintering furnace is used, with which the following reaction can be carried out:

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When performing a sintering process, according to this relationship expires, the sintering furnace 31 with the help of a Temperatu measuring and control arrangement 13 is kept at the correct temperature which works together with a computer 12. In addition, process gas is fed to the sintering furnace 31 from a gas generator 32. fe The process gas from the gas generator 32 is partly via a Line 33 is circulated, and the circulated part of the gas is then inside the gas generator with fresh gas (for example air) mixed and fed back to the sintering furnace. To adjust the composition of the process gas that the furnace 31 from the gas.

. generator 32 is supplied, are a throughput measuring device. -... and control valves are provided, which are summarized in block 3 ^ and controlled by the computer 12 v / ground. With these components of the arrangement summarized in block 3'l, the air / fuel ratio for the gas generator 32 is set in such a way that the process gas is fed to the sintering furnace 31 in the optimum composition. A gas analyzer and further control valves, which are combined in block 35, are provided for this purpose. In block 35, the newly available oxygen sensors are used, with which the oxygen partial pressure is determined in that portion of the sintering gas which is via line 3; the gas generator 32 is supplied again, and also with these oxygen sensors, the oxygen partial pressure in the process gas is measured at the outlet of the gas generator , which is then the

' Sintering furnace is fed. The data on the partial oxygen

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pressure are then fed to the computer 12, which uses it to calculate the information with which the throughput of the circulated sintering gas and the throughput of the sintering gas that is emitted from the gas generator 32 to the sintering furnace are set. In this way, the sintering atmosphere within the furnace 31 can be optimized for the course of the reaction, which is described by the relationship on page 21. Ä

Regulation of a reaction atmosphere for carburizing .

When carburizing metal parts, the aim is to ensure that carbon in the surface of the metal parts is contained in a certain amount Concentration is stored ", and that the carbon concentration decreases towards the inside according to a certain profile. Um To create a gas atmosphere with which metal parts can be carburized, a gas with a very specific carbon potential has to be used be generated. For this purpose, hydrocarbons are burned and the combustion products are processed (dried and cleaned). The equilibrium partial pressure of oxygen is a puncture of the various process variables, i.e. a function of the stoichiometric composition of the burned hydrocarbon, the air / fuel ratio, the efficiency during drying and cleaning as well as the extent and the speed of the carburizing itself. if one measures the equilibrium partial pressure of oxygen after each individual step, one can determine the carbon potential in gas

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to adjust.

In the figure 6 is a block diagram of an arrangement for Control or regulation of the gas generation, the gas processing and the use of the gas in a carburizing furnace. The carburizing furnace 41 receives carburizing gas from a gas generator 42, which is fed to the furnace 41 through assemblies 43 and 44 is supplied for drying and cleaning the gas. As already mentioned, hydrocarbons are used as fuels in the gas generator 42 burned, and the combustion products are supplied to the carburizing furnace 41 through the gas dryer and the purification equipment. To increase the combustion of the hydrocarbons control, a flow rate measuring device and control valves are provided, which are combined in block 45. These components of the arrangement are controlled by a digital process computer. In addition, the gas dryer 43 is also controlled by the computer 12. A conventional moisture meter and a controller, which are combined in block 46, are provided for this purpose. aside from that the gas cleaning system 44 is also monitored by the computer 12 via a known controller 47. At the outlets of the gas generator 42, the dryer 43 and the cleaning system 44 is the oxygen partial pressure measured by the measuring units 48, 49 and 51. The measuring units 48, 49 and 51 are the newly available ones Provided oxygen sensors with which the equilibrium partial pressure of the oxygen in the gas is measured after each step,

ORIGINAL

from which we can determine the carbon potential of the carburizing gas which is supplied to the Karburierungsofen ^1H. In addition, an arrangement 52 for determining the gas composition and the temperature in the carburizing furnace ¹ M is provided, which feeds the data on these variables to the computer 12. At the same time, with the arrangement 52 via the computer 12, the temperature in the carburizing furnace ^ l is regulated in the usual way.

The arrangement according to FIG. 6 is used for the carburizing furnace 4l carburizing gas with a certain carbon potential to generate and control. For this purpose, the equilibrium partial pressure the oxygen measured at the outlet of each stage, which is required for the generation of the carburizing gas, and each stage is controlled to optimize the carbon potential of the carburizing gas. The occurring here

~ 12 ~ 20

Oxygen partial pressures can be anywhere from 10 to 10 atmospheres, and so are the newly available oxygen sensors particularly well suited for use in the arrangement according to FIG.

In FIG. 7, graphic representations are shown which are based on calculated values. It is the exit of the gas generator (together with dryer and cleaning system) compared to carbon depletion and carbon activity in the furnace. In Figure 7, the abscissa represents carbon depletion

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in the gas, while various other calculated properties of the carburizing gas are plotted on the ordinates. The curves of Figure 7 were obtained by simulation with a digital computer, and the calculated properties that were presented are the partial pressure of oxygen (pO and log Pq ₂ ) ^{on the} left edge and the carbon activity (AC) on the right edge. As can be seen from FIG. 7, data about the carbon depletion and the carbon activity in the carburizing gas and thus about the carbon potential in the carburizing atmosphere can be obtained directly from the measurement of the equilibrium partial pressure of the oxygen in the carburizing atmosphere.

Figure 8 is a similar graph showing other calculated properties of a carburizing atmosphere are applied. In particular, there is the direct relationship between the equilibrium partial pressure of oxygen and the Air / fuel ratio shown, which is used to control a Gas generator for the carburization system of Figure 6 can be used.

Four different embodiments of the invention are described been. There are, however, a far greater number of metallurgical and chemical processes that take place in an oxygen-containing process Atmosphere to which the method and arrangements according to the invention are applicable. The invention

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therefore contains a * method and devices for control or control of processes in an oxygen-containing gas atmosphere, after which the ability of oxygen in the gas phase is determined with the products that are subjected to the process are to react, for example by reduction, oxidation, carburization or other comparable phenomena, and after the result of this determination is used for the purpose of optimizing the process, the preparation, the gas atmosphere to control.

BATH

Claims (1)

P a t e η t a ns ρ r ü c h e: 1. Arrangement for controlling or regulating a process in which a product in a controllable reaction vessel in a oxygen-containing gas atmosphere is processed or implemented, characterized in that a Source for process gas is provided, which is fed to the reaction vessel via a control device, that in the reaction vessel a measuring device for directly measuring the oxygen potential the gas atmosphere is arranged, and that the output of this measuring device is fed back to the control device is, so that the process gas throughput to the reaction vessel can be regulated for the purpose of optimizing the process. 2. Arrangement according to claim 1, characterized in that the measuring device for direct measurement of the oxygen potential of the gas atmosphere in the reaction vessel is a gas analyzer with which the equilibrium partial pressure the gas atmosphere in the reaction vessel can be measured directly, thereby providing a measure of the oxygen potential in the gas atmosphere is recoverable. · BATH ORIGINAL ;! »Ll | jjll! P: ai! Ip!» ;. -29- 3 · Arrangement according to claim 2, characterized in that that the product subjected to the process is a metal, that the process is a reduction or an oxidation and that the equilibrium partial pressure of oxygen at which the reduction or oxidation of the metal begins, is given by the following expression: ^ o. . ** · ^ϋ MaOb / b J ^pu HaOb 'ΙΓ7575Τ' with Ag ° "Q, = Gibbs' free energy of formation of the MaOb in Kai / Mol MaOb = stoichiometric formula of the oxide b = stoichiometric coefficient of the oxide reaction T = temperature in ° Kelvin 4. Arrangement according to claim 3, characterized in that the process is an oxidation process for · | is a metal, and that the process gas throughput at temperatures at which the rate of formation of the oxide is not limited by the reaction kinetics is controlled so that the relationship pO is less than PO ° M _a whether ^er ^^ ^lt , where "pO" is a is the logarithmic expression of the partial pressure of oxygen derived from the measured partial pressure of oxygen P _n according to the following ^U 2 equation is calculated: pO = log ( / 2 909826/0860 5. Arrangement according to claim 3 »characterized in that the process is a reduction process for a metal, and that the process gas throughput at temperatures at which the rate of formation of the oxide is not limited by the reaction kinetics is controlled so that the relationship pO is greater is fulfilled as pO ° »w) _b , where" pO "is a logarithmic expression of the oxygen partial pressure, which is derived from the measured oxygen partial pressure P _n according to the following ^U 2 equation is calculated: pO = log ( ρ 1/2
° 2 6. Arrangement according to claim 2, characterized in that that the product subjected to the process is a metal, that the process is an annealing process in a controllable manner Annealing furnace and that the equilibrium partial pressure of the oxygen, at which the oxidation of the metal begins, is given by the following expression: A O qO _. ^ ^G MaOb / b MaOb 2,303RT
MaOb with 4g ° w _nh = Gibbs free energy of formation of the MaOb ir Kai / Mol MaOb = stoichiometric formula of the oxide b = stoichiometric coefficient of the oxide reaction T = annealing temperature in ° Kelvin R = gas constant (1.98718) 909826/0860 7. Arrangement according to claim 6, characterized in that the process gas throughput at temperatures at which the rate of formation of the oxide is not limited by the reaction kinetics is controlled so that the relationship pO is greater than Ρθ ° _{Η & ΟΙ)} ^e , where "pO "is a logarithmic expression of the oxygen partial pressure, which _{is calculated from the measured oxygen partial pressure P Q} according to the following f equation: pO = log (i) ρ 1/2 ° 2 8. Arrangement according to claim 7, 'characterized in that the equilibrium partial pressure of the oxygen is measured at different points of the annealing furnace, that further devices for measuring the temperature are provided at different points in the annealing furnace, and daPj the feedback circuits for returning the measurement results to the control device for the process gas have a computer in which the measured equilibrium partial pressure of the oxygen at the measured temperature is compared with a target value for pO ° ,, _Oh and by which the control device for the process gas is controlled so that at temperatures at which the rate of formation of the oxide is not restricted by the reaction kinetics, the relationship pO greater than P °° ^ _a ob is maintained. 9 0982 6/08 6 0 9. Arrangement according to claim 5 j thereby g e Jc g η η - ' draws that the reactionaries foot a vessel for direct Reduction is in which the amount of oxygen taken up per unit volume of the reducing gas is the rate of reduction and the efficiency in accordance with the following expression certainly: , P ° in - ^p0 out
^pO in - ^p ° ^W Ma0b v / obei pO. and pC), expressions for the equilibrium part-in out pressure of oxygen at the inlet and outlet of the process gas source are that the control devices for the process gas flow meter and control arrangements for Hessen and Control the amount of process gas which are supplied to the reduction vessel and removed from it, and that the feedback circuits for feeding back the measurement results to the control device have a calculator in which in accordance with the The above-mentioned relationship control signals are generated with which the oxygen potential and the flow rate of the process gas are controllable to the reduction vessel. 10. Arrangement according to claim 9j, characterized in, that the reduction vessel is a countercurrent vessel that the process gas is circulated in one direction through the vessel is the direction of transport of the metal oxides to be reduced the opposite is that the process gas BAD ORIOINAU source has a gas generator to which at least a portion of the process gas and fresh gas circulated through the reduction vessel are supplied and from which the reduction vessel is supplied with process gas, that also the oxygen partial pressure in the process gas delivered to the reduction vessel (PO ₀₁₁ +.) and from the gas analyzer is measured in that part of the circulated process gas (pO.), which is delivered from the reduction vessel to the inlet of the gas generator and that the flow rate measuring and control device controls the amount of fresh gas that is fed to the gas generator. 11. Arrangement according to claim 10, characterized in that that a device for measuring the operating temperature of the reduction vessel is provided, the Auagangssignal for regulating this temperature is fed to the computer as an input parameter, and that a device for Monitoring of the reduction rate is provided, the information about the amount of reduced metal is provided to the computer feeds, so that the efficiency and the course of the reduction process is also checked. 12. Arrangement according to claim 4, characterized in that that the reaction vessel is a sintering furnace in which the sintered body is made from a very specific oxide of a metal can be produced, of which several oxides are present, wherein the desired metal oxide MaOb and the interfering metal oxides are related by the reaction equation MaOb + c0 ₀ = Ma0 (b + 2c) that the control devices for the process pass flow meters and control arrangements with which the throughput of the process gas through the sintering furnace is measured and is controlled, and that the measurement results obtained are fed to a computer in the return branches, from which the process gas throughput and its pO value are set so that the relationship pO ° _MaOb greater than pO greater than P °° _Ma o (b + 2c ) is maintained. 13 · Arrangement according to claim 12, characterized in that g e k e η η -, draws that the sintering furnace is a furnace through which the process gas can be circulated, that the process gas wave is a Has gas generator to which at least part of the process gas and fresh gas circulated through the sintering furnace is fed and from which the sintering furnace is supplied with process gas, that also the oxygen partial pressure in the gas analyzer Process gas delivered to the sintering furnace and in that part of the circulated process gas that is measured by the gas generator is supplied again, and that the Durchsat2meß- and control arrangement adjusts the amount of fresh gas that is supplied to the gas generator is. 909826/0860 BAD OftKDNAL -35- I ¹ I. Arrangement according to claim k, characterized in that the reaction vessel is a carburizing furnace, that the process gas source is a gas generator in which hydrocarbons are combustible as fuel, and the combustion products of which are fed to the carburizing furnace, that the partial pressure of oxygen from the gas analyzer is in the The combustion products released by the gas generator to the carburizing furnace and the partial pressure of oxygen in the atmosphere are measured in the carburizing furnace itself and that the measurement results obtained are fed to a computer located in the return branch, from which the control device for the process gas is controlled in such a way that in the carburizing atmosphere of the furnace, the relation pO greater than P °° p ^ _a whether is ^continuously fulfilled. 15. Arrangement according to claim 14, characterized in that that the combustion products of the gas ™ generator passed through a dryer and a gas cleaning system before they are fed to the carburizing furnace, both of which are provided with regulators, that the oxygen partial pressure is measured in the combustion products at the outlet of the gas dryer and at the outlet of the gas cleaning system, and that the measurement results obtained are fed to the computer, in which control signals for the controller of the dryer are obtained therefrom and the gas cleaning system are derived. 90982 6/0860
BATH ORIGINAL; ' 16. The arrangement according to claim 15, characterized in that the control device for the process gas flow meter and control arrangement! for measuring and adjusting the air / fuel ratio of the gas generator, that devices for measuring and controlling the temperature are connected to the carburizing furnace, and that the measurement results given by the control device for the process gas and the devices for measuring and controlling the temperature in the carburizing furnace _s supplied to the computer, which in turn controls the control device for the process element and the devices for measuring and controlling the temperature in the carburizing furnace. 17. The arrangement according to claim 2, characterized in that the gas analyzer -a solid oxygen having ion electrolyte, which is arranged between two electrodes, and that a gas with a known oxygen partial pressure one side of the electrolyte and the gas to be measured is supplied to the other side of the electrolyte. 18. A method for controlling or regulating a reaction, in which a product in a controllable reaction vessel in a oxygen-containing gas atmosphere is processed or converted, characterized in that the supply of process gas to the reaction vessel is controlled, 909826/0860
BATH ORIGINAL that the oxygen potential in the gas inside the reaction vessel is measured directly and a signal is derived from it that is a measure of the oxygen potential, and that this signal is used to control the supply of process gas to the reaction vessel via a return branch. 19. The method according to claim 18, characterized characterized marked ä that the oxygen potential is measured in the gas within the reaction vessel with a gas analyzer with which the equilibrium partial pressure of oxygen is obtained which is a measure of the oxygen potential in the gas atmosphere is measured directly. 20. The method according to claim 19, characterized in that in the reaction that is controlled or controlled v / ird, a metal is either reduced or oxidized, and that the equilibrium partial pressure of oxygen, of which is reduced or oxidized to the metal, is given by the following expression: A r ° n ° - MaOb / b
^pu MaOb "" ~~ 4,575T withAG ° j. _Ob = Gibbs free energy of formation of the MaOb in Kai / Mol MaOb = stoichiometric formula of the oxide b = stoichiometric coefficient of the oxide reaction T = temperature in ° Kelvin 909826/0860 21. The method according to claim 20, characterized in that a metal is oxidized in the reaction to be regulated or controlled, and that the process gas throughput at temperatures at which the rate of formation of the oxide is not limited by the reaction kinetics is controlled so that the Relationship pO smaller than ^p0 ° Ma0b ^eri " ^üllt i ^st » where "pO" is a locarithmic expression of the oxygen partial pressure, which is _{calculated from the measured oxygen partial pressure P Q} according to the following equation: pO = log (■ ρ 1/2
° 2 22. The method according to claim 20, characterized in that a metal is reduced in the reaction to be regulated or controlled, and that the process gas throughput at temperatures at which the formation rate of the oxide is not limited by the reaction kinetics is controlled so that the Relationship pO greater than pO .. ₀ . is fulfilled, where "pO" is a logarithmic expression of the oxygen partial pressure, which is _{calculated from the measured oxygen partial pressure P Q} according to the following equation · v / ird: pO = log (-) 1/2 909826/0860 BATH ORIGINAL. 23. The method according to claim 19, characterized in that that in the reaction which is controlled or regulated, a metal is annealed in a controllable annealing furnace and that the equilibrium partial pressure of oxygen from which the metal begins to oxidize is given by the following expression: _nn o A ^b MaOb / b ^pu MaOb "" 2 with AG ° _m ob ^{= G} i ^bbs ' ^scne free energy of formation of the HaOb in Kai / Mol MaOb = stoichiometric formula of the oxide b = stoichiometric coefficient of the oxide reaction T = annealing temperature in ° Kelvin R = gas constant (1.98718) 2h. A method according to claim 23, characterized in that the process gas flow at temperatures at which the rate of formation of the oxide is not limited by the reaction kinetics is controlled so that the relationship pO is Grüsser as P °° M _a whether ^eri> lev el where " pO "is a logarithmic expression of the oxygen partial pressure, which is _{calculated from the measured oxygen partial pressure P n} according to the following equation: pO = log (ί) ρ 1/2 ° 2 909826/0860 -HO- S is 25 · The method of claim 24, characterized in that the equilibrium partial ^eme n of the oxygen at different locations in the heating furnace ^sen that further the temperature is measured in the annealing furnace at a number of locations, and in that these measured words with desired values for P ° ° M _a Ob ^{and Tem} P ^era tures at the measuring points are compared, whereby control signals are derived with which the temperature in the furnace and the process gas throughput are regulated so that at temperatures at which the rate of formation of the oxide is not yet limited by the reaction kinetics , the relationship pO greater than pO ° _{MaOb is} maintained. 26. The method according to claim 22, characterized in that that the reaction to be controlled or regulated is carried out in a vessel for direct reduction at which the rate of reduction and the efficiency of the per unit volume of the reducing gas absorbed Oxygen quantity is determined according to the following expression: P ° in - P ° out • ^pO in * P ° where pO _in and pO Qut are the _external pressures for the partial equilibrium pressure of the oxygen at the inlet and outlet of the process gas source are that the process gas throughput to and from 909826/0860
BAD ORIÖiNÄL Reduction vessel is measured ', and that in accordance with the above expression, the oxygen potential by changing the process gas throughput from the source to and from the reduction vessel in order to optimize the reduction is varied. 27. The method according to claim 21, characterized in that the reaction to be controlled or regulated is carried out in a sintering furnace in which sintered bodies are produced from a very specific oxide of a metal, of which several oxides are present, the desired metal oxide MaOb and the interfering metal oxides are related by the reaction equation MaOb + cOp = MaO (b + 2c) that the properties and the throughput of the process gas are measured at the inlet and outlet of the sintering furnace and that control signals for setting the throughput and the pO are based on these measurement results Value of the process gas can be obtained with which the relation pO ° _MaOb greater than pO greater than P °° _Mao (b + 2c) ^a ß ^ehalfce n. 28. The method according to claim 21, characterized in that that the controlled or regulated reaction is carried out in a carburizing furnace, the as a process gas, the combustion products of burned in a gas generator hydrocarbons are supplied, which before Entering the carburizing furnace to be processed after that 309826/0860 the oxygen partial pressure in the process gas at each processing stage is measured and also the oxygen partial pressure at the outlet of the gas generator and in the carburizing furnace that furthermore the air to fuel ratio for the gas generator and the temperature of the carburizing furnace are measured and is regulated, and that for the purpose of optimizing the carburization, the process gas generation and its preparation, the process gas throughput and the furnace temperature according to these oxygen partial pressure measurements can be set. 90982.6 / 0860 BATH ORIGINAL