DE1912061A1 - Process control using a digital computer - Google Patents

Description

Description of the patent application of

SHELL INTERNATIONAL RESEARCH MAATSCHAPPIJ N.-V., 30 Carel van Blyandtlaan, The Hague / NETHERLANDS

concerning;

"Process control by means of a digital computer"

The invention relates to a method for regulating a process by means of a digital computer which directly regulates several process variables, which for this purpose receives the measured actual values of the process variables, the required setting or adjustment of an actuator and emits corresponding output signals for controlling the actuators in question, with in the memory of the computer a program for a control scheme is entered, by means of which a desired normal course of the process is achieved.

The above control method can be implemented without using conventional ■ Control devices or controllers are carried out as the computer both makes the comparison between the measured actual value

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. and a setpoint value of a process variable or a controlled variable, from "the comparison and possibly also derives / generates a control signal from further data in accordance with a specific formula. The computer also ensures that the actual values are called up in a desired order and that the generated control signals reach the intended locations. The direct digital control of a process variable According to the usual view, it also includes the cases in which the setpoint for a conventional analog controller working in a closed control loop by means of a. ^ i Digitally calculated and automatically fed to the controller will. Such cases occur, for example, when regulating a gas or liquid flow in a line in which the conventional regulators mainly regulate the random fluctuations in the current, but in which the setpoint is used on the basis of other information, e.g. on the basis of the quality of a product flow measured in a certain value scale, is calculated.

A digital computer can be used for direct control of one process or for direct control of several processes at the same time. In detail, this depends on the number of process variables to be controlled and on the capacity W of the computer.

In the event of a malfunction of an essential or functionally important However, in all parts of the process line, a new situation suddenly arises that requires immediate action makes in order to be able to continue the process in the best possible way until e.g. the part in question is repaired or is replaced and then normal operations can be resumed. The invention has the task the continuation of the process in the above situations

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can be achieved in a convenient way by direct control using a digital computer.

Based on a method of the type mentioned at the outset, this object is achieved in that according to the invention At least one emergency control scheme, which is based on the in the event of a malfunction of a certain important part the conditions occurring in the process line is switched off, is kept available in the form of a program, that is stored in the memory of the computer and, in the event of a malfunction, for direct process control by means of the computer is used.,

The programs for the operation of the computer can be structured so that in addition to the control scheme for the normal Implementation of the process also has one or more emergency control schemes running continuously. As long as not an important part of the Process line or the process equipment fails, 'leave the control scheme for the normal course of the process and not the emergency control scheme or * the emergency control schemes for control effects to lead. However, the output signals calculated by means of the emergency control scheme or the emergency control schemes are available always available and can be used if the measured actual values of the process variables are necessary do. With this method, part of the computing time is constantly used for the execution of the emergency control schemes.

If this should mean an impairment, a method can be used with advantage in which the computer in accordance with the signals derived from the faulty parts and fed to the computer automatically to the program or at least one of the programs for emergency control schemes is switched.

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With direct control using a digital computer, "the change to a different control scheme can take place without that wires or lines switched by human intervention or have to be turned over. The change in the control scheme means a change in the computer program, due to whose different signals are fed to the valves or other actuators. The change is very quick feasible.

The computer receives the actual values of the process variables and compares them this with the setpoints to determine if there is an abnormal situation. The assessment criteria for abnormal

fc male situations can be a simple comparison or several Actual and setpoint values and / or certain identifiers originating from the process line and also supplied to the computer include. The task assigned to the programs used can be referred to as "abnormal interpretation" will. Determine the criterion according to which the computer decides whether a component of the process line is normal or works incorrectly is a matter of programming. A special criterion may be required for each part of the route ' be. What is important is the decision about whether the process is by means of the normal control scheme can be continued satisfactorily if the deviation of a part from the normal Working method is determined. Usually this won't

ψ be possible if an essential part, such as a pump or a heater, fails completely. In this case, the program switches to the most suitable emergency control scheme. The rules for selecting an emergency control scheme are completely laid down in the computer program. In this way, in the event of an unsatisfactory operation of an important component, a programmed changeover to a suitable emergency control scheme is possible.

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It is preferable to switch to an emergency control scheme that a preliminary continuation of the process under normal conditions, but provides with reduced product yield. In this context it is important that after elimination the difficulty can be returned to the control scheme for normal process control without the actuators change their respective settings abruptly. In addition, although with a reduced yield, a ' Product created. If this is not feasible, it is preferred an emergency control scheme was selected that would allow the normal process conditions to be temporarily maintained with no product yield provides. In this E'all, too, after the disruption has been eliminated, it is possible without abrupt changes to the normal Control scheme. To return. If the process needs to be interrupted, an emergency control scheme is chosen, the one as possible provides for slow and gradual termination of the process. If the malfunction can be eliminated quickly, this is from Advantage because the process may not have come to a complete standstill. Depending on the type Many other emergency control schemes are conceivable for the disturbance or the combination of disturbances. It is e.g. also the choice of one Emergency control schemes are possible in which normal process conditions are maintained, but in which there is a product yield with abnormal properties. Under all circumstances, the emergency control scheme must continue the process effect in compliance with the safety conditions. The emergency control scheme preferably sees a gradual transition from normal to preliminary process conditions.

The method according to the invention can be applied to the most varied Processes are applied. In the following the invention for a rectification process and for a catalytic Reforming process, both processes with many degrees of freedom, further elaborated. . '.

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A rectification process with reflux and re-evaporation is provided in one with a condenser and a collector for the top product as well as with a reboiler Column carried out and is used to generate one or more products, the top product and the bottom or bubble product, · to which certain quality requirements are made. To do this, different states have to be regulated or within certain limits remain, e.g. the liquid level in the collector for the top product and in the bubble of the column or-also the quality of the .products or the product and the pressure in the column. A number of correction variables are available for this purpose, such as 3. the return, the overhead product removal, the bladder product removal, the coolant supply to the condenser, the heat supply to the re-evaporator and the raw mixture supply or the task. Regarding the regulation Many schemes are known of the normal course of a rectification process. It is also known the direct scheme to be used by means of a digital computer. Usually is the control scheme for a rectification process is highly complex and there are many important or functionally essential Components, e.g. pumps, the functioning of which can become faulty. Because of the complexity results in a rectification process the change to an emergency control scheme, the program of which is already in the memory of the computer, has particular advantages. The transfer takes place without delay and does not require any human intervention. . ■

A method for regulating a in a column with return, and re-evaporation performed rectification process is therefore characterized according to a further feature of the invention characterized that in the event of a malfunction or a complete If one or more essential components of the process line fail, a program for an emergency control scheme is used, which provides for the following control processes:

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1) Lowering the pressure in the column when the Pressure above a maximum value, increasing the pressure when it falls below a minimum value, but otherwise no influencing of the pressure;

2) Lowering the liquid level in the collector for the Top product when the liquid level rises above a maximum value and the liquid level rises when falling below a minimum value;

35) Lowering the liquid level in the column bubble when the liquid level rises above a maximum value and when it falls, raising the liquid level below a minimum value.

By choosing the sizes listed above from the possible controllable sizes are achieved that ensure safety and a quick return to normal process flow Elimination of the fault as long as possible.

In the event that the condenser does not cool sufficiently, a program for an emergency control scheme is used, which provides:

a), reducing the heat input to the reboiler during

Increase in pressure in the column above a maximum value;

b) Reduction of the overhead product removal and the return flow when the liquid level in the collector drops for the top product below a minimum value;

c) Increase the ßlasenprodukt removal when the increase in Liquid level in the column bubble above a maximum value.

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The above problem may be caused by the malfunction of a pump in a cooling water pipe or a fan for cooling air be caused. The switch to an emergency control scheme can then be carried out as a function of a signal, which is generated by a flow meter or flow meter in the corresponding coolant flow. A malfunction of the Condenser leads to a reduction or interruption of the condensation of the vapor leaving the column. The under a) listed measure reduces the formation of steam, the measure listed under b) prevents the complete Emptying the collector while the reduced re-evaporation makes measure c) necessary. The process is on _ as long as possible, among other things, because of the pressure in the column ^ to a maximum value compatible with the security requirements can increase. As long as the reverse flow is maintained the head and bladder products can be readily usable.

In case of insufficient re-evaporation of the re-evaporator a program for an emergency control scheme is used which provides:

d) reducing the supply of coolant to the condenser when the pressure in the column falls below a minimum value; ._

e) Reduction of the overhead product removal and.the return when the liquid level in the collector for the top product falls below a minimum value j

f) Increase bubble product withdrawal on rise the liquid level in the column bubble above a maximum value.

The above difficulty can be caused by a pump malfunctioning in

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a hot oil line or the interruption of the steam supply. The switch to an emergency control scheme can be performed in response to a signal received from a flow meter in the corresponding stream is produced. A malfunction of the re-evaporator leads to a reduced formation of steam. The measure listed under d) reduces the condensation of the steam, which under e) The specified measure prevents the collector from being completely emptied, while the reduced re-evaporation reduces the Measure f) required. The process continues for as long as possible, among other things because the pressure in the column is at a minimum value can sink. For columns with normal operating pressure

ρ ο

is above 1 kP / cm, the minimum pressure is around 1 kp / cm. In this case, too, head and bladder products can certainly do be useful as long as the rewind is sustained.

In the event of a fault or failure of the return pump. a program for an emergency control scheme is used which provides:

g) Increase the overhead product withdrawal on the rise 'the liquid level in the collector for the top product above a maximum value;

h) Decrease the coolant supply to the condenser during Increase in the liquid level in the collector for the top product above a maximum value;

i) -Reducing the heat supply to the reboiler during Increase in pressure in the column above a maximum value; ''

j) Reducing the removal of bladder product when the Liquid level in the column bubble below a minimum value.

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The changeover to the emergency control scheme can be carried out as a function of a signal that is generated by a flow meter in the return line. The malfunction of the return pump leads to filling of the collector, which is prevented by measure g). Measure h) leads to reduced liquid formation at the top of the column, which in turn requires measure i), since otherwise the pressure would rise too sharply. Measure j) is often necessary because the return flow has become smaller or has been completely interrupted. Because of the interrupted or reduced return flow, the top product no longer has the desired quality. However, the process continues as long as possible, ψ among other things because the pressure in the column can rise to a maximum value. The maximum value listed under h) is preferably selected to be greater than the maximum value listed under g). As a result, when the liquid level in the collector for the top product rises, the top product removal first increases. If this measure is sufficient, neither the coolant supply to the condenser nor the heat supply to the re-evaporator need to be reduced. Accordingly, the column continues to work harder. If, however, measure g) is unable to compensate for the supply of liquid, the liquid level in the collector continues to rise until the maximum value mentioned under h) is reached.

* ■ In the event of a fault or failure of the pump in the line for top product removal, a program for an emergency control scheme is used which provides:

k) Increasing the return flow when the liquid rises speed level in the collector for the top product over a maximum value;

1) Decrease the coolant supply to the condenser during

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Increase in the liquid level in the collector for the top product above a maximum value;

m) Reduce the heat supply to the re-evaporator during Increase in pressure in the column above a maximum value;

n) Increasing the bubble product withdrawal when the liquid level in the column bubble rises above a maximum value.

Switching to the emergency control scheme can be dependent on be carried out by a signal passed by a flow meter is generated in the overhead product stream. The malfunction the pump mentioned leads to the filling of the collector for the top product, which is prevented by measures k) and 1) will. Measure 1) leads to reduced fluid formation on the head, which in turn 'measures m) required, otherwise the pressure would rise to an unacceptably high value. In this case is also measure n) is necessary because less liquid is evaporated again. In this case, too, the process continues for that time continue as possible. The maximum value listed under 1) is expediently greater than that listed under k) Maximum value selected. The reasons for this are the same as those given in relation to the maximum values of measures g) and h).

The pumps for the return flow and for the overhead product removal are often combined into a single pump, which is in the, line from the collector to the branch point for the two streams is arranged. In the event of a malfunction or failure of this pump, a program is set up for an emergency control scheme uses, which provides:

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ο) Reduce the coolant supply to the condenser during Rise in the liquid level in the collector for the head product, above a maximum value; :

p) reducing the heat input to the reboiler when the pressure in the column rises above a maximum value; '"

q) Increase bubble product withdrawal on rise the liquid level in the column bubble above a maximum value. -

The transition to the emergency control scheme can be dependent on can be carried out by a signal generated by an ammeter near the pump. The measure o) prevents overfilling of the collector by reducing the formation of liquid in the condenser. The measure p) is required here to reduce the formation of steam, while the measure q) is required to prevent excessive Prevent filling of the bladder. The column continues to work for a long time, partly because the pressure is at a maximum value can increase.

If there is a malfunction in the line for the removal of bladder product arranged pump occurs, a program for an emergency control scheme is used, which provides:

r) reducing the raw mixture flow to the column during Rise in the liquid level in the column bubble above a maximum value;

s) Reduction of the overhead product removal and the return when the liquid level in the collector for the top product falls below a minimum value.

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The changeover to the emergency control scheme can be carried out as a function of a signal that is generated by a flow meter in the bubble product flow. A malfunction of the named pump leads to excessive filling of the bladder, which is prevented by measure r). Since the raw mixture flow or the task is reduced, finally no more top product will be withdrawn

ver

can. However / the column waits for a long time in a state of equilibrium. '

In the event of a relatively large reduction or interruption in the feed of the crude mixture to the column, a program for a Emergency control scheme is used, which ensures a corresponding reduction in the heat supply to the reboiler. In this In this case, the changeover to the emergency control scheme can be carried out as a function of a signal that is sent by a Flow meter is generated in the feed stream. The said Measure leads to the fact that the heat supply is adapted to the requirements. Alternatively, the emergency control scheme used ensure that the return and steam flow in the Column are kept constant at the last normal values or approximately at these values while the removal lines blocked for the head and bladder products. In this case the column works in equilibrium Further.

The measures listed under c), f), n) and q), which to prevent the bladder from filling excessively may not be sufficient. In this case it will preferably also the raw mixture feed to the column when the liquid level rises in the column bubble decreased a maximum value. The last-mentioned maximum value is preferably greater than that under c), f), n) and q) selected maximum value. When the liquid

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level in the bladder rises, the first thing to do is to remove the bladder product raised. If this measure is sufficient, the raw mixture supply need not be reduced. In this case the column continues to work harder. However, when the increased bladder product withdrawal the fluid supply cannot compensate, the 'fluid level in the bladder continues to rise until' the maximum value is reached which the raw mix feed responds. If, as is often the case in practice, the column has several columns connected in series can cause difficulties for example occur when the raw mixture feed or the feed stream is an outlet stream of the preceding column. It is then undesirable that the necessary reduction in the task current affects the free column, which is why part of the outflow in question temporarily into a storage tank is derived.

The measures listed under b), e) and s) lead to that the overhead product removal and the return flow are reduced at the same time. Preferably the ratio of the two Currents or the reflux ratio kept constant ·. This ensures a constant quality of the top product.

Additional emergency control schemes can be introduced, e.g. 3. by one on the reflux ratio and on the heat supply Quality control acting on the re-evaporator, so that the quality of the removed products even when used is better maintained by emergency control schemes.

In the above it was often mentioned that the changeover to a no't control scheme as a function of one by means of a flow meter generated signal can be performed. In practice, the transfer often occurs because of others Identifying marks to give a greater certainty about the species

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to have the malfunction. In the. The computer's memory can hold a more detailed program for performing a Diagnosis must be entered when a deviation occurs. There can be 3. the speeds of pumps, print heads or Temperatures must be recorded. The programs for the above emergency control schemes can be stored individually in the memory of the computer. On the other hand, it is also possible to use only one program for an emergency control scheme, all of the above Provides for measures. If a malfunction occurs, the entire program is then carried out, but of course not all of the programmed measures lead to control effects. If, for example, the coolant supply to the condenser is interrupted is, measure h) will not be carried out. In this case, however, the measures a), b) and c) generate automatically the desired effects.

The method according to the invention can also be used with advantage in a catalytic reforming process for light hydrocarbons, for example in a platforming process. Such a process is used to produce fuel components with a high octane number. In this process, a feed taken from a rectification column is fed to a feed preheater and then passed in vapor form together with a hydrogen-containing gas under pressure one after the other through, for example, three reaction vessels, a first reheater in front of the second reaction vessel and a second reheater in front of the third reaction vessel bring the gas mixture to the required temperature in each case. After cooling, the gas mixture is separated in a separator into a liquid product stream and a gas stream with a high hydrogen content. A partial flow of the gas represents the above-mentioned hydrogen-containing gas, which is recombined with the task in circulation via a compressor. The liquid flow from the separator is in one.

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, Stabilizer of dissolved gas and certain light coals = - hydrogen free, and as the desired fuel component taken. . '·

The regulation of the temperature of the reaction vessels, the gas pressure and the composition of the gas is of the utmost importance for the normal course of the platforming process. In addition, the separator and the stabilizer should meet the usual requirements for the pressure and the liquid level in the bladder and in the collector. The use of a digital computer for these purposes is known. _:

A method of controlling a catalytic reforming process for hydrocarbons is characterized according to a further feature of the invention that according to the invention in the event of a malfunction of one or more essential. Parts of the process line on a program for a control scheme is transferred which is already in the memory of the computer. The emergency control scheme is one in which:

1) the temperature of the reaction vessels does not exceed one Maximum value 'can increase;

2) the feed stream is controlled so that none Can form liquid in the reaction vessels;

j5) the reaction vessels without a simultaneous gas flow no Feed stream is supplied;

k) the pressure in the separator cannot rise above a maximum value;

5) the liquid level in the separator cannot rise above a maximum value and cannot fall below a minimum value;

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6) the pressure in the stabilizer cannot rise above a maximum value j

7) the liquid level in the collector for the top product of the stabilizer cannot rise above a maximum value and cannot fall below a minimum value.

The emergency control scheme has the task of protecting the expensive catalytic converter against destruction or deterioration, which through overheating, contact with liquid task and through Lack of hydrogen can be caused. Security measures are also applied. In addition, after Possibility of trying the various assemblies of the process line for as long as possible in operation or in equilibrium, so that after the malfunction has been eliminated can be returned to normal process conditions quickly and without hard transitions. ^ '

In the event of an interruption or a relatively large reduction in the feed to the reaction vessels, a program is started used for an emergency control scheme, which

aa) ensures that the feed preheater and the reheater are switched off.

Switching to the emergency control scheme can be dependent on be performed by a signal received from a flow meter is generated in the feed stream. Under normal operating conditions, the progression process is an endothermic one Process. A reduction or absence of the feed stream would lead to an increase in the temperature in the reaction vessels, which would damage the catalyst Could have a consequence.

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In the event of a malfunction of the gas compressor, a program for an emergency control scheme is used that ensures the following:

bb) Interrupting the feed stream to the. Reaction vessels; "·

cc) Switching off the feed preheater and the reheater.

The switch to the emergency control scheme can be dependent on be performed by a signal originating from a flow meter or pressure gauge in the gas stream. One Incorrect operation of the gas compressor lowers the hydrogen concentration of the reacting mixture and the pressure in the reaction vessels. This affects the life of the catalytic converter. The measures mentioned eliminate this Disadvantage,. .

In the event of a malfunction of the pump for the removal of foot or bladder product from the separator, a program is set up used for an emergency control scheme that ensures the following:

dd) reducing the feed flow to the reaction vessels when the liquid level rises in the Separator over a maximum value.

Switching to the emergency control scheme can be dependent on be carried out by a signal, .that from a flow meter originates in the bubble outlet or a liquid level meter in the separator. If as a result of measure dd) the If the feed flow falls below a minimum value, the emergency control scheme is set also sure that

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ee) the feed stream to the reaction vessels is interrupted and the feed preheater and reheater be switched off.

This prevents damage to the catalytic converter.

In the event of a malfunction of the feed preheater, a program for an emergency control scheme is used, which has the following ensures:

ff) Reduce the feed flow to the reaction vessels when the temperature of the outlet stream of the preheater falls below a minimum value.

A temperature sensor in the outlet stream of the feed preheater can provide the display or the identification symbol for the changeover to the emergency control scheme. If the temperature is in If the feed preheater falls, there is a risk that liquid will form in the first reaction vessel. This affects the catalyst to the strongest. ”Reducing the feed stream eliminates this risk.

In the event of a malfunction of the first reheater a program for an emergency control scheme is used that ensures the following:

gg) Increase the heat supply to the feed preheater at

Drop in temperature of the outlet stream of the first • reheater below a minimum value.

In the event of malfunction of the stabilizer capacitor wiTd, a program used for an emergency control scheme that ensures the following:

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hh) letting off steam from the stabilizer when the pressure in the stabilizer increases via a Maximum value;

ii) Decreasing overhead removal from the stabilizer when the liquid level in the collector for the top product falls below a minimum · value; ...

jj) reducing the return flow of the stabilizer during ' Drop in the liquid level in the collector for the top product of the stabilizer below a minimum value.

Switching to the emergency control scheme can be dependent on be carried out by a signal that comes from a flow messef in the coolant flow. When this current is interrupted the pressure in the stabilizer rises and the liquid level in the collector for that which comes from the stabilizer increases, de head product falls. The measures mentioned keep this Effects within acceptable limits. By blowing off the gas, a quick adjustment to the preliminary situation is achieved achieved without having to change the re-evaporation. Hence the stabilizer continues to work pretty well. ... "'

In the event of a malfunction of the re-ventilator of the Stabilizer, a program for an emergency control scheme is used, which provides the following:. · .., '-

kk) Reduce the coolant supply to the condenser of the Stabilizer when the pressure in the stabilizer falls below a minimum value;

11) Decrease overhead removal from the stabilizer

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when the liquid level in the collector for the top product of the stabilizer falls below one Minimum value; .

mm) .Reduce the return flow of the stabilizer during Drop in the liquid level in the collector for the top product of the stabilizer below a minimum value.

Switching to the emergency control scheme can be dependent on be carried out by a signal that from a flow meter in the heating medium supply line to the re-evaporator or from a flow meter together with a temperature sensor originates in this line. The measures mentioned cause the stabilizer for the greatest possible duration is still in operation.

The minimum values listed under jj) and mm) are preferably smaller than the minimum values listed under ii) and or 11) chosen. The drop in the liquid level in the collector caused by the malfunction then leads first to a reduction in the overhead product removal and then, if necessary, to a reduction in the return flow. The stabilizer then remains in equilibrium for a longer period of time and its outlet, from which the bladder or foot product represents the most important part for the present purpose, maintains good quality over a long period of time.

In the event of a malfunction of the stabilizer return pump the emergency control scheme ensures the following:

nn) Reduction of the coolant supply to the condenser when the liquid level rises in the receiver for the top product of the stabilizer via a Maximum value;

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oo) Discharge of steam from the stabilizer on ascent of the pressure in the stabilizer above a maximum value.

The changeover to the emergency control scheme can be carried out as a function of a signal that comes from a through ■ flow meter in the return stream originates. Both measures. Aim on continuation of the process in the stabilizer until it reaches the assemblies determined by the assemblies in question Boundaries. After that, the stabilizer continues to work, but the bubble product no longer fulfills the requirements due to a lack of return flow Quality requirements.

t - An emergency control scheme for a specific part of the platforming process is supplemented by an emergency control scheme for a normal flow of other sections, if not also difficulties arise there.

For the repeatedly mentioned switch to emergency control schemes Depending on signals coming from flow meters, the same supplementary remarks apply as mentioned above above in connection with the description of the emergency control schemes for the rectification process.

The programs called for Notregelschemata for a Platformierungsprozeß can be used individually in the computer memory pre handen be f. Alternatively, there can be a single program for an emergency control scheme which provides for all of the measures mentioned. If difficulties arise, the entire emergency control scheme is carried out, although of course not all of the programmed measures lead to control effects. For example, if the return pump fails, measure jj) is not carried out; however, in this case, measures hh) and ii) ensure the necessary control effects.

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The invention and further advantageous details of the invention are explained in more detail by way of schematic drawings of examples. Show it:

Fig. 1 is a schematic representation. Using of symbols for conventional control devices to explain the means tasks performed by a computer when executing a program for a Emergency control scheme for a rectification process,

FIG. 2 shows a schematic representation that relates in a corresponding manner to the emergency control of a platforming process by means of a computer.

It is emphasized that none of the conventional control devices indicated by the rectangular symbols in the figures are actually present, but that the computer generates control effects which correspond to those of the conventional devices.

In FIG. 1, which relates to the manure control for a rectification process, a rectification column is denoted by 1. A raw mixture or the task is fed in via a line 2, if necessary also via a pump 3. From the At the top of the column, vapor passes through a line 4 to a condenser 5. The liquid obtained flows into a Collector 6. Part of the liquid is pumped into a return line 8 by means of a pump 7. The rest is done by means of a Pump 9 is fed into an overhead product removal line 10. At the Bladder 11 of column T will contain part of the Indian bladder

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Nen liquid is drawn off and returned to the column 1 by means of a pump 12 through a reboiler IJ. The rest of the E'lüssigkeit is by means of a pump 14 in a Bubble product removal line 15 passed. The condenser A coolant flows through a line 16 and a heating medium flows through the re-evaporator 13 via a line -17 " Pressure gauge or pressure transducer 18 ^ for the pressure in the Column 1 forwards signals to regulators 19 and 20. If the Pressure drops below a minimum value, the controller 19 inputs Signal to a selector 21 explained in more detail below, whereupon a valve 22 in line 16 for the coolant gradually closes. If the pressure rises above a maximum value, the controller 20 sends a signal to a selector 23 and to a ratio relay 24, thereby changing the ratio between the output of that relay and the output of a flow meter? or current sensor 42 in of line 2 '. As a result, a valve 25 closes in the, Line 17 for the heating medium gradually. A current sensor 26 measures the current, i.e. the amount of liquid per unit of time, in the return line 8 and sends a signal to a controller from which the valve 28 adjusts. A current sensor 29 measures the current in the sampling line 10 and gives a signal to a controller 30, which controls the setting of a valve 31 determined. The liquid level in the collector 6 is by means of a transducer 32 measured, its "output signal to controller 33 and 34 reached. When the liquid level in the collector 6 falls below a minimum value, the controller 33 gives a signal to an element 35 and to the setpoint input of the controller 30 from. The element 35 is used to set the ratio between the Sollvier th of the controller 27 ″ and 30 and thus the. Ratio between the flows in lines 8 and 10. The signal causes valves 3I and 28 in such a way gradually conclude that the currents through lines 8 and 10 remain proportional to each other.- When the liquid level in the collector 6 rises above a maximum value, the valves 31

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and 28 gradually opened via regulators 30 and 27. If the liquid level rises above a higher maximum value, the controller 3 ^ emits a signal to the selector 21. The selector gives priority to the stronger signal either from controller 19 or from controller 34, which leads to valve 22 gradually closing. A sensor 36 measures the liquid level in the bladder 11. The output signal of this transducer passes to controller 37 and 38. When the liquid level falls below a minimum value, the controller 38 closes a valve 39 in line de ^r I5 gradually. When the level rises above a maximum value, the controller 38 opens the valve 39 gradually. When the liquid level in the bladder 11 has a higher maxi. Malwert increases, the controller 37 outputs a signal to a valve in the line 2 ', whereupon this valve is gradually closed. The controller 37 can also open a valve 41 in the line 2 "and thereby divert part of the raw mixture supplied via the line 2 to another point. The transducer 42 measures the current in the line 2" and sends its signal to the ratio relay 24, which has the result that the ratio between the currents in lines 2 and 17 is kept approximately at a constant value. The selector 23 can be connected to a measuring device for quality, by means of which the ratio between the currents in the lines 2 and I7 can be influenced. In the same way, the element 35 can be connected to a measuring device for quality in order to be able to influence the ratio between the currents in the lines 8 and 10.

In Fig. 2, which relates to the emergency regulation of a platforming process refers, 5I denotes a line via which a task a feed preheater 53 by means of a feed pump 52 is supplied. The pre-warmed task passes; successively through a first reaction vessel 5 ^ ·,

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a first intermediate heater 55, a second reaction vessel 56, a second intermediate heater 57 and through a third reaction vessel 58. The product leaving the reaction vessel 58 passes through two heat exchangers 59 and 60 to a separator 61 which separates gas and liquid. The gas is partly diverted via a line 62 to a point outside of the platforming process and partly fed back into the process in circulation via a compressor 63. The liquid from the separator 61 lands via a heat exchanger 64 into a rectification column 65 *, the so-called stabilizer. The vapors emerging at the top of the stabilizer are fed to a jfc memory 67 via a condenser 66. Uncondensed vapors leave this store via a line 6S _3, while the liquid formed in the condenser is partly returned to the top of the stabilizer and partly discharged via a line 70 by means of a pump 69. A product stream, the platform product, leaves the bubble 7I of the stabilizer through a line 73 via heat exchangers 64 and 72 .

A transducer 76 measures the feed flow in line 5I. The output signal of the transducer 76 reaches two controllers 77 Ψ and 78. With the setpoint setting unchanged, the controller keeps the feed flow constant by adjusting a valve 79 in the line 5I. Two relays 80 and 81, which are explained in more detail below, are connected to the setpoint input of controller 77; If the feed flow falls below a minimum value, the controller 78 switches off the heat supply to the reaction vessels by closing the valves 82, 83 and 84, which are arranged in the fuel oil lines to the feed preheater 53, the first reheater 55 and the second reheater 57, respectively . Also will

909840/1091 - 27 -

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the valve 79 closed, so that not the slightest amount of cold feed material in any way to the catalyst can get.

A sensor 85 measures the gas flow from the compressor 63 By closing the valve 79 in the line 5I switches a regulator 86 from the feed flow when the measured gas flow falls below a minimum value. In addition, it will the valves 82, 83 and 84 in that described above Way closed. This protects the catalytic converter and prevents loss.

A sensor 87 measures the liquid level in the separator 61. The measured value is fed to a level controller 88, whose Output signal reaches a relay 81. As long as the liquid level is below the acceptable maximum value, the output signal of the controller 88 is a maximum. The relay receives two signals, namely the output signal just mentioned and a setpoint signal and outputs the lower of these two signals via a relay 80 as a setpoint signal to one Control 77 further. When the liquid: ^ csspiegel in the separator rises above a maximum value, the output signal of the controller 88 becomes smaller. As soon as the signal falls below the value of the Setpoint signal of the relay 81 has dropped out, the setpoint value of the controller 77 is also reduced and, accordingly, the feed supply or the feed stream is reduced.

A sensor 89 measures the temperature in the feed stream to the first reaction vessel 54 ". If the measured temperature is below a If the minimum value falls, the output signal of a controller 90 increases. .In the relay 80 this output is ssignal · 1 a other signal arriving there subtracted. When the temperature measured by the transducer 89 is sufficiently high is, the target value of the controller 77 is determined by the output signal

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BAO ORtG $ | fe «ü c

- 28 of the controller 90 not influenced.

A sensor 9I measures the temperature of the feed stream to the second reaction vessel 56 · V / If this temperature falls below a minimum value, e.g. due to malfunctions in the first reheater 55, the output signal of a controller 92 increases and, as a result, the valve 82 gradually opened. This leads to increased heat generation in the preheater 53 * ^so that the failure of the first intermediate heater 55 can be compensated for.

k A transducer 92 measures the pressure in the stabilizer 65. V / enn If this pressure rises above a maximum value, a controller 94 generates a signal which opens a valve 97. this leads to to a blow-off of steam from the memory 67 · V / enn der. If the pressure drops below a minimum value, a controller generates 95 " a 'signal' which valve 96 gradually closes. this leads to a reduction in the supply of coolant to the condenser 66.

A transducer 98 measures the liquid level in the accumulator. A controller 100 attempts the measured level by means of a Vc- = "tiIs 102 in the removal line 70 for the top product of the stabilizer at a setpoint ". If the} liquid level falls below the setpoint of controller 100, so this can ultimately lead to a complete closing of the valve 102. If this measure is not sufficient, the liquid level continues to drop, whereupon the regulator

99 gradually a valve I03 in the return line closes ". If the liquid level is above the setpoint of the controller

100 increases, valve 102 may eventually be fully open. If this measure is not sufficient, the liquid level continues to rise, whereupon the regulator 10-1 gradually closes the valve 96 so that the coolant supply to the condenser 66 is reduced.

909840/109

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Claims (1)

Pat en tan claims / flJ Method for regulating a process by means of a digital computer that directly regulates several process variables, which receives the measured actual values of the process variables, calculates the required setting or adjustment of an actuator and emits corresponding output signals for controlling the actuators in question, with a Program for a control scheme is entered, by means of which a desired normal sequence of the process is achieved, characterized in that at least one ftotregelschema, which is based on the conditions occurring in the event of a malfunction of a certain important part of the process route, in the form of a program ver - · is kept available, which is kept in the memory of the computer and is used for direct process control by means of the computer in the event of a malfunction _e 2c method according to claim 1, characterized in that the computer in accordance with the derived signals at the disturbed parts automatically to the program, or _o one of the programs for control schemes is switched at least ,, 3. The method according to claim 1 or 2, characterized in that a program for a jtöotregelschema is used that 'a preliminary continuation. 909840/109 BATH of the process under normal conditions, but with reduced Provides product yield. ^. Method according to Claim 1 or 2, characterized that a program for a control scheme is used, which means that normal process conditions are temporarily maintained with no product yield provides. 5. Method according to claim 1 or 2, characterized in that. that a program for .a need ~ A rule scheme is used that allows the process to end as slowly and gradually as possible. 6. The method according to any one of claims 1 to 5 »characterized in that a program for a Emergency control scheme is used, which provides a gradual transition from normal to preliminary process conditions. 7. The method according to any one of claims 1 to 6 for controlling one in a column with reflux and re-evaporation carried out rectification process, characterized ',. ^ indicates that in the event of an operational malfunction one or more essential parts of the process line uses a program for a lot rule scheme which provides the following control processes; 1) Lowering the pressure in the column when the pressure rises above a maximum value, increasing the pressure when falling below a minimum value, but otherwise no influencing of the pressure; 909840/1091 BATH ORIGINAL 2) Lowering the liquid level in the collector for the Head product when the liquid level rises above a maximum value and when the liquid level rises Falling below a minimum value; 3) Lowering the liquid level in the column bubble when the liquid level rises above a maximum value and when it falls, raising the liquid level below a minimum value. 8. The method according to claim 7 »characterized in that in the event of a malfunction of the Capacitor uses a program for an emergency control scheme that provides: a) reducing the heat input to the reboiler when the pressure in the column rises above a maximum value; b) Reduction of the top product withdrawal and the return flow • current when the liquid level in the collector drops for the top product below a minimum value; c) Increase bubble product withdrawal on rise the liquid level in the column bubble above a maximum value. 9. The method according to claim 7, characterized in that in the event of a malfunction of the re-evaporator a program for a wot control scheme is used, which provides: d) reducing the supply of coolant to the condenser when the pressure in the column falls below a minimum value; - l ± _ 909840/1 09 1 ■ '■ _ <- ■ St. e) Reduction of the overhead product removal and the return flow when the liquid level in the collector for the top product falls below a minimum value; f) Increasing the removal of bubble product when the liquid level in the column bubble rises above a maximum value, 10 * A process according to claim 7, characterized GEK e η η - is characterized in that in the event of a malfunction of the return pump a program for a .Notregelschema used is providing: P g) Increase the overhead product removal when the Liquid level in the collector for the top product above a maximum value; h) Reduce the coolant supply to the condenser when the liquid level rises in the receiver for the. Top product over a maximum value; i) Reduce the heat supply to the reboiler during Increase in pressure in the column above a maximum value; ^ j) Reduce the removal of bladder product when the . Liquid level in the column bubble below one Minimum value. ..11 · Method according to claim 10, characterized · characterized in that the maximum " selected value greater than the iiaximal value listed under g) will. - 5 909840/109 1 12. The method according to claim 7, characterized in that in the event of a malfunction the head product withdrawal paper is a program for an emergency control scheme is used, which provides: k) Increasing the return when the fluid level rises in the collector for the top product above a maximum value; 1) Reduce the coolant supply to the condenser when the liquid level rises in the receiver for the Top product over a maximum value; m) Reduce the heat input to the reboiler during Increase in pressure in the column above a maximum value; n) Increase the bladder product withdrawal when the Liquid level in the column bubble above a maximum value » 13. Method according to claim 12, characterized in that the maximum value listed under 1) greater than the maximum value listed under k) is selected » Ik. Method according to Claim 7, characterized in that in the event of a malfunction of the pump common for the return and the top product take-off, a program for an emergency control scheme is used which provides: o) Reducing the coolant supply to the condenser when the liquid level rises in the collector for the Top product over a maximum value; - 6 909840/1091 ρ) reducing the heat input to the reboiler when the pressure in the column rises above a maximum value; ' q) Increasing the bubble product withdrawal when the liquid level in the column bubble rises above a Maximum value. · ·. 15 ο The method according to claim 7, characterized in that in the event of a malfunction of the Bladder product removal pump a program for a lsi ο t rule scheme is used, which provides: r) Reduction of the raw mixture flow to the column on the rise the liquid level in the column bubble above a maximum value; , s) Reduction of head product removal and return when the liquid level in the collector for the top product falls below a minimum value 16. The method according to claim 7, characterized in that in the case of a relatively strong Verrxagerung or interruption of the supply of raw mixture to the column, a program is used for an emergency control scheme, which a provides a corresponding reduction in the heat supply to the reboiler. 17 »Method according to one of claims 8, 9, 12, 13 or 1 ^, characterized in that a program is used for an emergency control scheme which also includes reducing the crude mixture feed to the column as the Provides liquid level in the column bubble above a maximum value. '- 7 909840/10 9 1 -iris 18. The method according to AnsOruch 17, thereby g e k e η η ze i without t that the maximum value of the liquid level in the column bubble is selected to be greater than the maximum value which determines the increase in bubble product removal. 19 · Method according to one of claims 8, 9 or 15, characterized characterized in that the reflux ratio is kept constant » 20. The method according to claim 7, characterized in that in the event of a malfunction or several essential parts of the process line a toot control scheme is applied, which provides a combination of the measures listed in claims 8 with 18. 21. The method according to any one of claims 1 to 6 for regulating a catalytic reforming process for hydrocarbons, characterized in that in the event of a malfunction in one or more essential parts of the process line, a program for an iMot control scheme is used in which 1) - the temperature of the reaction vessels does not exceed one Maximum value can increase; 2) the feed stream is "controlled" in such a way that no liquid can form in the reaction vessels; 3) no feed stream is fed to the reaction vessels without a simultaneous gas stream; k) the pressure in the separator cannot rise above a maximum value; 5) the liquid level in the separator does not rise above a maximum value and not below a minimum value can fall off; 6) the pressure in the stabilizer cannot rise above a maximum value; 9-09640 / 1091 " ⁸ " hu 7) the liquid level in the collector for the top product of the stabilizer cannot rise above a maximum value and cannot fall below a minimum value. 22. The method according to claim 21 ,. characterized marked in ¹ characterized in that is used in the event of a break 'of the object of supply to the Reaktionsgefäß.en a program for a Notregelschema which provides for: aa) Switching off the feed preheater and the reheater. 23. The method according to claim 21, characterized in that g e k e η η indicates that in the event of a malfunction of the gas compressor, a program for an emergency control scheme is used, which provides: bb) interruption of the feed flow to the reaction vessels j ' cc) Switching off the feed preheater and the reheater. 2 * 4-, method according to claim 21, characterized indicates that in the event of a malfunction of the pump for the removal of the foot product from the separator a program for an emergency control scheme is used which provides: _dd) 'Reduction of the feed flow to the reaction vessels when the liquid level rises in the Separator over a maximum value. . '- 9840/3 25. The method according to claim 2 ^, characterized in that the program for an iMdtregelschema also provides:. ^v _ ee) interrupting the feed stream to the reaction vessels and switching off the feed preheater and the reheater when the feed rate falls below a minimum value. 26. The method according to claim 21, characterized in that in the event of a malfunction of the feed preheater a program for an emergency control scheme is used, which provides: ff) Reduction of the feed stream to the reaction vessels when the temperature of the outlet stream drops Preheater below a minimum value. 27. The method according to claim 21, characterized in that in the event of a malfunction of the first reheater a program is used for a control scheme that provides: gg) 'Increase the heat supply to the feed preheater when the temperature of the outlet stream of the first reheater falls below a minimum value. 28. The method according to claim 21, characterized in that in the event of a malfunction of the Condenser of the stabilizer a program for a wot, control scheme is used, which provides: hh) venting steam from the stabilizer when the pressure in the stabilizer rises above a maximum value; - IQ 0/1091 -KT- ii) Decreasing overhead removal from the stabilizer when the liquid level in the collector for the top product falls below a minimum value j jj) reducing the return flow of the stabilizer during Drop in the liquid level in the collector for the top product of the stabilizer below a minimum value. 29. The method according to claim 21, characterized in that in the event of a malfunction of the Recover the stabilizer one program for one Emergency control scheme is used, "which provides:, -. kk) Reduction of the coolant supply to the condenser of the ρ stabilizer when the pressure in the stabilizer drops below a minimum value; 11) Reduce overhead removal from the stabilizer when the liquid level in the receiver drops for the stabilizer overhead product below a minimum value; mm) Reduce the return flow of the stabilizer during Drop in the liquid level in the collector for the top product of the stabilizer below a minimum value. 30ο Method according to claim 28 or 29, characterized in that the reduction of the return flow determining minimum value less than., which the "Decreasing the top product withdrawal determining minimum value is chosen. 31. The method according to claim 21, characterized in that in the event of a malfunction Return pump of the stabilizer a program for a water control scheme is used, which provides: nn) Reduce the coolant supply to the condenser during Rise in the liquid level in the collector for the 909840/1091 - H - Stabilizer overhead product above a maximum value; oo) Letting off steam from the stabilizer when the pressure in the stabilizer rises above a maximum value. 32. The method according to claim 21, characterized in that in the event of a malfunction one or more essential parts of the process line, an emergency control scheme is used, which is a combination the measures listed in claims 22 with 31 provides. 6965 ·. 9098 40/1091