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EP0599900A1 - Procede et dispositif utilisant un modele pour le reglage d'une colonne de rectification - Google Patents

Procede et dispositif utilisant un modele pour le reglage d'une colonne de rectification

Info

Publication number
EP0599900A1
EP0599900A1 EP92917011A EP92917011A EP0599900A1 EP 0599900 A1 EP0599900 A1 EP 0599900A1 EP 92917011 A EP92917011 A EP 92917011A EP 92917011 A EP92917011 A EP 92917011A EP 0599900 A1 EP0599900 A1 EP 0599900A1
Authority
EP
European Patent Office
Prior art keywords
variables
control
stream
model
manipulated variables
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP92917011A
Other languages
German (de)
English (en)
Inventor
Thomas LÜDER
Günter WOZNY
Lutz Jeromin
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Henkel AG and Co KGaA
Original Assignee
Henkel AG and Co KGaA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Henkel AG and Co KGaA filed Critical Henkel AG and Co KGaA
Publication of EP0599900A1 publication Critical patent/EP0599900A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/42—Regulation; Control
    • B01D3/4211—Regulation; Control of columns
    • B01D3/4227—Head- and bottom stream
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B13/00—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion
    • G05B13/02—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric
    • G05B13/04—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric involving the use of models or simulators

Definitions

  • the invention relates to a model-based method for controlling a multicomponent rectification column with two product streams, the model containing the link between the control variables and the manipulated variables.
  • Rectification columns are usually controlled with temperatures as auxiliary control variables for the product concentrations of interest.
  • temperatures are no thermodynamically clear correlations between the column temperatures and the product concentrations.
  • the temperature control therefore depends heavily on the working conditions of the column. Higher product purities and a reduction in energy consumption would indeed be achievable if the product concentrations themselves are used as control variables. However, these can only be determined at larger time intervals and with a corresponding delay, z. B. gas chromatography, so that continuous control is not possible.
  • the regulation also has to meet additional requirements. Its effect must be understandable for the plant operator. Economical maintenance of the control system requires simple implementation in the process control system. When commissioning, the control parameters should be adjustable in a manageable manner on-line. It is of particular importance that the control concept is independent of the working point in order to enable a wide range of uses. Since the measured values of the product concentrations are only available in larger time intervals, such as half an hour, and with the corresponding delay, the desired control system must allow such long combined scanning and dead times of the measured values.
  • the invention has for its object to provide a control method of the type mentioned, which on the one hand the above met the requirements for regulating the concentrations of both product streams of a multi-component system and, on the other hand, works as a system of two linear single-variable controllers, the manipulated variables of which are each assigned to a single controlled variable.
  • one control variable is the concentration of a first component in the first product stream and the other control variable is the concentration of a second component or the same component in the second product stream, that either distillate stream and steam stream or Distillate flow and heating steam flow or return flow and bottom product flow are selected by determining the current concentrations, transforming them into quantities which, according to a linearized simulation model, depend in each case on only one of the two selected control variables, and from the deviations of the current transformed control variables from theirs
  • the new manipulated variables are determined using the model.
  • the combinations of the manipulated variables are selected such that a manipulated variable is either directly associated with a shift in the concentration profile along the column height or a change in shape of the profile with the position unchanged substantially.
  • a manipulated variable is either directly associated with a shift in the concentration profile along the column height or a change in shape of the profile with the position unchanged substantially.
  • both effects, the change in shape and the displacement of the profile are always superimposed.
  • This property of the manipulated variable combination also proves to be an advantage, inter alia, when the plant operator influences the product concentrations by hand, since the control is thus considerably clearer.
  • the time behavior of the control structure is taken into account by discontinuing the current concentrations according to a time Converting the delay into the transformed manipulated variables, the linearized simulation model containing a first larger time constant describing the time behavior of the external streams of the column and a second smaller time constant describing the time behavior of the internal streams.
  • the aforementioned time delay results from the delay with which the current concentration values are available for the control.
  • the decoupling of the manipulated and controlled variables is also possible here, because the stationary, diagonal elements of the transmission matrix of the decoupled process that vanish in a stationary manner can be neglected when taking the time dependency into account.
  • control controller contains the inverse of the matrix describing the relationship between the transformed control variables and the manipulated variables. This enables a uniform and manageable procedure when designing the regulation for a multitude of application purposes.
  • the internal model control controller contains a first-order low-pass filter.
  • Each of the two individual control loops thus only has one free parameter, the size of which can be set without influencing the other loop.
  • the control according to the invention is preferably implemented by determining the new manipulated variables from the current concentrations by means of a computer or a circuit.
  • the invention also relates to a control device for performing ren of said method according to the invention.
  • the control device contains a measuring unit, e.g. B. a gas chromatograph with electronic evaluation unit for the current concentrations (XD ⁇ X B) ⁇ a computer or a circuit for processing the signals representing the concentrations and actuators for the manipulated variables, with the computer or the circuit from those supplied by the measuring unit Signals the new manipulated variables can be calculated and these can be converted into corresponding control signals for the actuators.
  • a measuring unit e.g. B. a gas chromatograph with electronic evaluation unit for the current concentrations (XD ⁇ X B) ⁇
  • a computer or a circuit for processing the signals representing the concentrations and actuators for the manipulated variables with the computer or the circuit from those supplied by the measuring unit Signals the new manipulated variables can be calculated and these can be converted into corresponding control signals for the actuators.
  • Figure 1 is a schematic representation of a
  • FIGS. 6 and 7 the course of the control and manipulated variables after a sudden increase in feed concentration, with different cycle times
  • FIG. 8 a schematic representation of a control concept that can be implemented in practice according to a
  • FIG. 9 shows the course of the control and manipulated variables of a column when the concentration setpoints change.
  • a multicomponent mixture is broken down into a distillate stream and a bottom product stream.
  • the components of the feed mixture come from a homologous series and the feed composition and the product specifications vary, so that there are a large number of different operating points of the system.
  • One of the possible operating points, which is assumed below, is listed in Table 1.
  • the task of the column is to obtain components 1 to 3 at the top of the column and to enrich components 4 and 5 at the bottom.
  • the permissible impurities in the distillate stream through component 4 and in the bottom product stream through component 3 are each 1%.
  • the concentration profiles shown in the lower part of FIG. 2 show a fundamentally different behavior. If the energy input 1 (manipulated variable G or V) is changed while the mass balance remains unchanged, the shape of the profile changes when the position is essentially unchanged. An increase in energy consumption results in higher product purity both at the top and at the bottom of the column. In addition, the profiles indicate that the effect of changing these manipulated variables is less than that of the distillate flow. The directionality is also less. These statements are also qualitatively independent of the working point.
  • a transformation of the standard This creates a stationary, completely decoupled relationship between the manipulated variables D and G and new output variables ff'und.und.
  • the control can then be designed as a simple feedback of an output variable to a manipulated variable.
  • time constants Two time constants are used to describe the dynamics of the process.
  • the larger time constant 1 ⁇ describes the relationship between the external streams of the column, here the distillate stream D and the control variable "T " .
  • the smaller time constant T2 gives the influence of the internal streams, here the steam stream G, on the control variable
  • the secondary diagonal elements of the transmission matrix C of the decoupled process which vanish exactly in the stationary linear case, can also be neglected here, as will be shown below, and the model parameters are again determined using the simulation, while determining the operating point
  • the stationary nonlinear simulation is used, the use of dynamic simulation is necessary to determine the two required time constants.
  • the step responses generated here are evaluated with the means of linear identification. This is the prerequisite for the design of two linear inputs size controller available.
  • the internal model control procedure When designing the two one-size controls, the internal model control procedure is used, which limits the number of free control parameters per control loop to one.
  • the IMC method is easy to use for the time-discrete control problem with dead time considered here and allows practically unavoidable fashion errors to be taken into account in the design.
  • 5 shows the structure of the resulting control loop for the present problem.
  • the column 1 with the physical disturbance variables 2 and output variables Xp and Xg is arranged in the center of the structure. Although these are not directly measurable, they actually represent them of interest within the control loop. Behind it is the dynamics of the gas-atographical concentration measurement 3, formally divided into a dead time element and a switch. The measurement results available discretely at the output are subjected to the output decoupling 4.
  • the arrangement of the process model parallel to the controlled system is typical for IMC.
  • 5 output variables are determined and compared with those of the process in time with the concentration measurement.
  • the concentration setpoints specified by the operator are also scanned in time with the concentration measurement and, like the product concentrations, must be subjected to decoupling 6.
  • the controller input variables are determined at the comparison point with the output variable difference and fed to the IMC controller 7.
  • the manipulated variables determined by the controller in a time-discrete manner are forwarded to the corresponding control valves or subordinate flow control circuits and kept constant for the duration of a sampling interval.
  • the controller is designed according to known specifications and is not shown in detail here.
  • Each of the two single-size controllers contains a free constant, the filter parameter. Its increase stabilizes the system, but with a deterioration in the transient response of the control loop. Similar to conventional single-loop control with an integral component, this structure of the IMC controller ensures that the closed control circuit is stationary and accurate in the presence of modeling errors, even in the presence of this. This property is of paramount importance for practical use.
  • Fig. 6 shows calculation results thus obtained for the above-mentioned multi-component rectification.
  • the column operated at the operating point has an abrupt fault.
  • the concentration of component 4 decreases accordingly.
  • the analysis cycle time is assumed to be 0.5 h in accordance with the real behavior of a process gas chromatograph. Therefore, the first manipulated variables D and, in this example, heating steam flow V can only be calculated after 1 h (lower diagram).
  • the immeasurable curves of the product concentrations are shown here directly in the product streams (upper part). The concentrations have already moved very far from their target values within this time. Nevertheless, there are no stability problems with the control. Rather, with the dead time compensating controller it is possible to achieve the product specifications after a limited number of manipulations despite the malfunction.
  • the quadratic deviation of the controlled variables has the length of the tact and dead time of the measurement. As a rule, it is predetermined by measurement technology and cannot be changed. Their influence is illustrated in the following Fig. 7. In the same form as in FIG. 6, the system behavior after the same fault has occurred is shown here. In this case, however, the cycle time of the measurement is only 10 minutes. Accordingly, the controller determined in the same way as in the first case already calculates the first manipulated variables after 20 minutes. The system returns to the target values of the product concentrations after about half a time compared to FIG. 6.
  • the somewhat oscillating course of the heating steam control variable indicates a growing deviation of the non-linear system from the simplified model process, which is the basis of the controller. Short-term effects are just as little taken into account in this as the coupling, which increases with increasing frequency. This is also not necessary for combined tactile and dead times of 10 minutes or longer, as they often occur in practice.
  • the IMC structure of the control loop proves to be particularly advantageous for the systematic design of the controller
  • the simpler single-loop structure has advantages for implementation in practice. It contains fewer elements and is therefore easier to implement in the control system or on the process computer. Detailed questions that are important for operation, such as the commissioning of the controller, can also be solved more easily in the single-loop structure.
  • the IMC control loop was therefore analytically converted into a single-loop control loop. The resulting configuration is shown schematically in FIG. 8. The summation of the product concentrations determined by the gas chromatograph to form the above-mentioned low and high boiler fraction can be seen.
  • the decoupling 4 of the transformed output variables CT 'and o is obtained after the decoupling 4, and these are fed into a time-discrete size controller 8, 9 for determining the manipulated variables distillate current and energy input.
  • a time-discrete size controller 8, 9 for determining the manipulated variables distillate current and energy input.
  • 9 shows the process behavior achieved in a production column over a period of 12 hours. It is also a multi-component separation. The cycle time of the concentration measurement is 30 minutes, as in the simulation. However, the column has different internals and a different evaporator than assumed in the simulation studies. The working points also differ significantly.
  • the proportion of distillate here is about 75%.
  • the controller is designed as described above.
  • the Mode11para eter were determined in advance with the help of the simulation and adopted unchanged during the trial on site.
  • the course of the set and actual values of the low boiler at the top and bottom of the column is shown in a time-dependent manner in the upper drawing. The order differs for the distillate stream from that for the simulation results.
  • the actual values of the concentrations are only accessible after the measurement dead time of 30 minutes has passed.
  • the course of the manipulated variables in the lower part of FIG. 9 is vibration-free and poses no practical problems such as. B. abrupt changes or manipulated variable restrictions.
  • only the valve of the heating circuit was available for changing the energy consumption, the valve position of which is the one control variable here.

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  • Engineering & Computer Science (AREA)
  • Evolutionary Computation (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Artificial Intelligence (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Chemical & Material Sciences (AREA)
  • Medical Informatics (AREA)
  • Software Systems (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Feedback Control In General (AREA)

Abstract

L'invention concerne un procédé utilisant un modèle pour le réglage d'une colonne de rectification à plusieurs composants, présentant deux courants de produits, ledit modèle comprend les éléments de liaison entre les grandeurs réglées et les grandeurs de réglage. Afin que le procédé de réglage fonctionne comme un système de deux mécanismes régulateurs linéaires à une grandeur, dont les grandeurs de réglage sont associées respectivement à une seule grandeur réglée, le procédé selon l'invention est caractérisé en ce que l'une des grandeurs réglées est la concentration d'un premier composant dans le premier courant de produits, et que l'autre grandeur réglée est la concentration d'un second composant ou de composants identiques dans le second courant de produits, on choisit comme grandeurs de réglage, soit un courant de distillat et un courant de vapeur, soit un courant de distillat et un courant de vapeur surchauffée, soit un courant de recyclage et un courant de produits de bas de colonne, on détermine les concentrations réelles, on transforme celles-ci en grandeurs qui, selon un modèle de simulation linéarisée, dépendent chacune de l'une des deux grandeurs de réglage choisies, et on détermine les nouvelles grandeurs de réglage à partir des écarts des grandeurs réglées transformées réelles par rapport à leurs valeurs de consigne avec le modèle.
EP92917011A 1991-08-21 1992-08-13 Procede et dispositif utilisant un modele pour le reglage d'une colonne de rectification Withdrawn EP0599900A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19914127536 DE4127536A1 (de) 1991-08-21 1991-08-21 Modellgestuetztes verfahren zum regeln einer rektifikationskolonne
DE4127536 1991-08-21
PCT/EP1992/001854 WO1993003811A1 (fr) 1991-08-21 1992-08-13 Procede et dispositif utilisant un modele pour le reglage d'une colonne de rectification

Publications (1)

Publication Number Publication Date
EP0599900A1 true EP0599900A1 (fr) 1994-06-08

Family

ID=6438689

Family Applications (1)

Application Number Title Priority Date Filing Date
EP92917011A Withdrawn EP0599900A1 (fr) 1991-08-21 1992-08-13 Procede et dispositif utilisant un modele pour le reglage d'une colonne de rectification

Country Status (3)

Country Link
EP (1) EP0599900A1 (fr)
DE (1) DE4127536A1 (fr)
WO (1) WO1993003811A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6291134B1 (en) 1997-01-17 2001-09-18 Kodak Polychrome Graphics Llc Lithographic plate precursor
CN106227041A (zh) * 2016-08-31 2016-12-14 西南交通大学 一种h∞控制器及动车组网整流器的控制方法

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1429857B1 (fr) * 2001-09-19 2010-12-08 Bayer Technology Services GmbH Procede de commande de processus de la separation de melanges a plusieurs composants
RU2239223C2 (ru) * 2002-12-03 2004-10-27 Федеральное государственное унитарное предприятие Специальное конструкторско-технологическое бюро "Технолог" Санкт-Петербургского государственного технологического института (технического университета) Министерства образования Российской Федерации Устройство автоматического управления реактором полунепрерывного действия
RU2294237C2 (ru) * 2005-04-26 2007-02-27 Федеральное государственное унитарное предприятие "Специальное конструкторско-технологическое бюро "Технолог" Устройство автоматического управления реактором полунепрерывного действия
AT515437A2 (de) 2014-02-20 2015-09-15 Omv Refining & Marketing Gmbh Verfahren und Vorrichtung zur Korrektur einer Messung
CN116672745B (zh) * 2023-05-25 2025-08-01 南通大学 精馏控制模型生成方法、精馏控制方法及精馏装置
CN116870515A (zh) * 2023-07-13 2023-10-13 海澜智云科技有限公司 乙二醇自回热精馏的控制方法、系统以及设备

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL6412525A (fr) * 1964-10-28 1966-04-29
US3477916A (en) * 1967-01-04 1969-11-11 Monsanto Co Method of controlling distillation operation with on-off control response
US4544452A (en) * 1983-08-31 1985-10-01 Phillips Petroleum Company Control of a fractional distillation process
DE3906002A1 (de) * 1989-02-25 1990-08-30 Henkel Kgaa Modellgestuetzte analyse- und regeleinrichtung fuer rektifikationskolonnen

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9303811A1 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6291134B1 (en) 1997-01-17 2001-09-18 Kodak Polychrome Graphics Llc Lithographic plate precursor
CN106227041A (zh) * 2016-08-31 2016-12-14 西南交通大学 一种h∞控制器及动车组网整流器的控制方法

Also Published As

Publication number Publication date
WO1993003811A1 (fr) 1993-03-04
DE4127536A1 (de) 1993-02-25

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