EP0255915A2 - Flame photometer with constant stream regulation - Google Patents

Flame photometer with constant stream regulation Download PDF

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Publication number
EP0255915A2
EP0255915A2 EP87110967A EP87110967A EP0255915A2 EP 0255915 A2 EP0255915 A2 EP 0255915A2 EP 87110967 A EP87110967 A EP 87110967A EP 87110967 A EP87110967 A EP 87110967A EP 0255915 A2 EP0255915 A2 EP 0255915A2
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EP
European Patent Office
Prior art keywords
pressure
control
throttle
differential pressure
flame photometer
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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.)
Granted
Application number
EP87110967A
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German (de)
French (fr)
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EP0255915B1 (en
EP0255915A3 (en
Inventor
Joachim Dr. Rer. Nat. Dipl.-Phys. Slupek
Thomas Dipl.-Ing. Müller
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Eppendorf SE
Original Assignee
Eppendorf Netheler Hinz GmbH
Eppendorf Geraetebau Netheler and Hinz GmbH
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Priority to AT87110967T priority Critical patent/ATE62746T1/en
Publication of EP0255915A2 publication Critical patent/EP0255915A2/en
Publication of EP0255915A3 publication Critical patent/EP0255915A3/en
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Publication of EP0255915B1 publication Critical patent/EP0255915B1/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
    • F23N5/08—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using light-sensitive elements
    • F23N5/082—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using light-sensitive elements using electronic means

Definitions

  • the invention relates to a flame photometer of the type mentioned in the preamble of claim 1.
  • Flame photometers with constant flow control of at least one of the fuel gas components enable the setting of a flame that burns with constant brightness over time, which permits a constant measurement evaluation of the spectral lines generated by test substances introduced into the flame. This enables accurate and reproducible measurements. It should be noted that both long-term constancy and short-term constancy must be given in order to enable evaluable measured values.
  • reducing valves that control a valve with a differential pressure controlled membrane.
  • the membrane is acted upon by the atmosphere on the one hand, which mostly corresponds essentially to the pressure behind the throttle, and on the other hand by the pressure in the buffer tank via the outlet line of the valve.
  • the membrane regulates the actual valve of the reducing valve to a middle position with a constant flow, which results in a uniform gas flow. Disturbing flutter of such a reducing valve should be avoided if possible.
  • the object of the present invention is therefore to provide a flame photometer of the type mentioned at the outset, which can be designed much more cost-effectively, precisely and reliably with regard to constant flow control.
  • a control valve is provided as the control valve, which does not work continuously like the reducing valves previously used, but digitally with only two switch positions OPEN and CLOSE.
  • Such a switching valve can therefore be controlled digitally in the technology customary today and, in a simple adaptation, allows the use of digital control and regulating devices which can be connected to computer controls in a simple manner.
  • the switching valve according to the invention is distinguished by considerable cost advantages and, owing to its simple design, by significantly reduced susceptibility to faults. Due to the buffer tank downstream of the switching valve, the pressure and flow fluctuations resulting from the discontinuous operation of the switching valve are evened out. With different control technology of the switching valve, which will be dealt with in the following (e.g.
  • the invention is therefore based on the knowledge that a switching valve for flame photometers previously not considered usable for the present purposes can be used, namely in a functional unit with a buffer tank, whereby a constant, constant gas supply is made possible by the interaction of the switching valve and the buffer tank.
  • the features of claim 2 are advantageously provided.
  • a certain pressure hysteresis is permitted here so that the differential pressure oscillates between two specified values when the switching valve is working.
  • the pressure hysteresis can be chosen to be very small.
  • the circuit complexity can be kept very low in such an operating mode.
  • the switching frequency of the switching valve in this operating mode depends on the volume of the buffer tank. If the volume is very large, the valve switches very slowly.
  • the switching valve and control can be designed accordingly simply and inexpensively.
  • the gas flow control shown in the figure is provided in a flame photometer, the other parts of which are omitted for the sake of simplicity.
  • gas is supplied to the burner via a gas line 1 in the direction of the arrow 2 fed.
  • the gas conducted via the gas line 1 can be a combustible gas mixture or one of the gas components required for combustion (fuel gas, oxidant).
  • the gas flowing through is to be kept constant in the flow with the control shown, so that the burner 2 operates at a constant time.
  • a switching valve 3 is interposed in the gas line 1 and, as indicated by corresponding switching symbols, has the two switching positions OPEN and CLOSE. It is operated electrically and is controlled cyclically via a control line 4.
  • a buffer tank 5 is connected downstream of the switching valve 3 in the gas line 1.
  • the gas pressure in the container 5 is fed via a line 6 to a pressure / voltage converter 7 which is connected via a line 8 to an input of a control device 9.
  • This compares the pressure value in the container 5 with a predetermined target value and regulates the duty cycle OPEN / CLOSE of the switching valve 3 accordingly via the control line 4 such that the pressure in the container 5 is kept essentially constant.
  • a throttle 10 is connected downstream of the container 5, through which the gas flows to the burner 2 via the gas line 1.
  • the flow resistance of the burner 2 indicated in the figure with the corresponding symbol is with flame photometers usually very small and even.
  • the gas line 1 therefore, there is generally a constant pressure essentially corresponding to the atmospheric pressure at the point between the throttle 10 and the burner 2.
  • the pressure difference between the inlet and outlet at the throttle 10 is thus kept constant by the pressure control in the container 5. Therefore, the flow through the throttle 10 and thus the total gas flow in the desired sense is constant.
  • a throttle 10 is to be used which has a resistance to the flow resistance of the burner 2 (inclusive of the gas line system between the throttle 10 and the burner 2) has considerably greater flow resistance.
  • the total pressure drop between the container 5 and the outlet 11 of the burner into the atmosphere is then determined by the flow resistance of the throttle 10, against which the flow resistance of the burner 2 can be neglected. Changes in the resistance at the burner 2 then result in only negligibly small changes in flow.
  • the control device 9 detects only the pressure in the container 5, that is to say the admission pressure of the throttle 10, via the pressure / voltage converter 7.
  • the atmospheric pressure is taken into account as the pressure behind the throttle 10.
  • the pressure / voltage converter 7 can in Usually be designed so that it compares the pressure on the line 6 with the atmospheric pressure and converts the differential pressure and passes it on to the controller 9.
  • a second pressure / voltage converter 12 is connected via a line 13, which is connected via a line 14 in parallel to the line 8 of the converter 7 to the control device 9, which in this case works as a differential circuit and the cycle ratio of the switching valve 3 readjusted such that the pressure difference between the gas pressures in lines 6 and 13, that is to say at the inlet and outlet of the throttle 10, remains constant.
  • the pressure / voltage converter 7 which is always present anyway, is a differential pressure sensor, one pressure input of which is connected to the container 5 and the other of which is connected to the atmosphere, this converter 7 can also be used in a simplified embodiment to determine the differential pressure across the throttle 10 will. For this purpose, one of its pressure inputs is connected to line 6 and its other pressure input is connected to line 13. The difference found pressure is converted into voltage and supplied to the control device 9 as an input variable. In this way, the second converter 12 can be saved when determining the differential pressure.
  • the switching valve 3 can be a pressure reducer, for. B. in the form of a further throttle, upstream to reduce the high feed pressure, for example a gas bottle, to a pressure level that can be processed by the switching valve 3.
  • the control device 9 is preferably designed as an electronic control device which compares the control variable arriving via line 8 or the difference between the control variables arriving via line 8 and 14 with an electrically predetermined setpoint value and, in the event of deviations, readjusts the cycle ratio of the switching valve accordingly via control line 4 .
  • an adjusting device for example in the form of a setting potentiometer 15, can preferably be provided, with which the electrical setpoint specification can be adjusted. In this way, the pressure in the container 5 or the differential pressure at the throttle 10 and thus the desired value of the gas flow to be kept constant can be set to the desired value, for example in order to obtain the desired flame size in the burner 2.
  • the adjustment device mentioned for the control device 9 can, for example, also be designed as a preselection control, with which certain preset flows can be selected, for example, by pressing a key. It can also be a control done from a computer, e.g. B. according to a certain program. In this way it is possible to select certain flows depending on the requirements, for example depending on the measurement method currently used in the flame photometer, for example if different flame intensities are required for different photometric methods.
  • the control device 9 can control the switching valve 3 as a function of the differential pressure at the throttle 10 in different operating modes.
  • a construction that is very simple to implement in terms of circuitry, which has proven itself in tests, consists in switching on the switching valve 3 when the pressure falls below a first, and switching on when a predetermined higher pressure is exceeded. This results in a pressure fluctuating in the container 5 between the two predetermined pressure values, although this hysteresis can be kept very small. If the volume of the container is large enough, the switching valve 3 works very slowly. The control and the switching valve can therefore be constructed very simply.
  • the switching valve can be controlled at a constant switching frequency with different pulse widths, that is to say, for example, with different lengths of the open time.
  • the repetition frequency can also be changed if the open time is constant.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Feeding And Controlling Fuel (AREA)
  • Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

A flame photometer with constant flow regulation of at least one of the fuel gas components has a buffer container preceded by an on-off valve upstream of a throttle. In conjunction with the volume of the buffer container, the digitally operated on-off valve makes possible both a long-term and a short-term constant supply to the burner.

Description

Die Erfindung betrifft ein Flammenphotometer der im Oberbegriff des Anspruches 1 genannten Art.The invention relates to a flame photometer of the type mentioned in the preamble of claim 1.

Flammenphotometer mit Konstantflußregelung wenig­stens einer der Brenngaskomponenten ermöglichen die Einstellung einer mit zeitlich konstanter Hellig­keit brennenden Flamme, die eine zeitlich konstante Meßauswertung der von in die Flamme eingebrachten Testsubstanzen erzeugten Spektrallinien gestattet. Auf diese Weise werden genaue und reproduzierbare Messungen ermöglicht. Dabei ist zu beachten, daß sowohl Langzeitkonstanz als auch Kurzzeitkonstanz gegeben sein muß, um auswertbare Meßwerte zu er­möglichen.Flame photometers with constant flow control of at least one of the fuel gas components enable the setting of a flame that burns with constant brightness over time, which permits a constant measurement evaluation of the spectral lines generated by test substances introduced into the flame. This enables accurate and reproducible measurements. It should be noted that both long-term constancy and short-term constancy must be given in order to enable evaluable measured values.

Derartige Flammenphotometer der eingangs genannten Art sind seit längerem bekannt, beispielsweise aus der Literaturstelle
R. Herrmann - C.Th.J. Alkemade: Flammenphotometrie.Such flame photometers of the type mentioned have been known for a long time, for example from the reference
R. Herrmann - C.Th.J. Alkemade: flame photometry.

Hieraus ist es bekannt, als Steuerventil der ein­gangs genannten Art, Reduzierventile zu verwenden, die mit einer differenzdruckgesteuerten Membran ein Ventil steuern. Die Membran wird einerseits von der Atmosphäre beaufschlagt, die zumeist im wesentli­chen dem Druck hinter der Drossel entspricht und andererseits über die Ausgangsleitung des Ventiles vom Druck im Pufferbehälter. Bei gleichmäßig arbei­tendem Brenner, also im wesentlichen gleichmäßigem Gasfluß, regelt die Membran das eigentliche Ventil des Reduzierventiles auf eine mittlere Stellung mit konstantem Fluß ein, woraus sich ein gleichmäßiger Gasfluß ergibt. Störendes Flattern eines solchen Reduzierventiles soll nach Möglichkeit vermieden werden.From this it is known to use as a control valve of the type mentioned, reducing valves that control a valve with a differential pressure controlled membrane. The membrane is acted upon by the atmosphere on the one hand, which mostly corresponds essentially to the pressure behind the throttle, and on the other hand by the pressure in the buffer tank via the outlet line of the valve. When the burner is working uniformly, that is to say essentially a uniform gas flow, the membrane regulates the actual valve of the reducing valve to a middle position with a constant flow, which results in a uniform gas flow. Disturbing flutter of such a reducing valve should be avoided if possible.

Auch in jüngerer Zeit werden für die eingangs ge­nannten Zwecke noch derartige Reduzierventile ver­wendet, wie die DE-OS 34 07 552 zeigt. Das membran­gesteuerte Reduzierventil ist bei dieser Konstruk­tion dahingehend verbessert, daß es mit einer mo­torisch arbeitenden Einstelleinrichtung ausgerüstet ist.Even recently, such reducing valves have been used for the purposes mentioned at the outset, as DE-OS 34 07 552 shows. The diaphragm-controlled reducing valve is improved in this construction in that it is equipped with a motor-operated adjustment device.

Die bekannten Reduzierventile arbeiten in der Regel befriedigend, lassen sich aber nicht mit heutzutage erforderlicher sehr hoher Präzision regeln und wei­sen den Nachteil einer komplizierten Konstruktion mit entsprechender Anfälligkeit und hohen Kosten sowie den Nachteil aufwendiger Ansteuertechnik auf.The known reducing valves generally work satisfactorily, but cannot be regulated with the very high precision required today and have the disadvantage of a complicated construction with corresponding vulnerability and high costs as well as the disadvantage of complex control technology.

Die Aufgabe der vorliegenden Erfindung besteht da­her darin, ein Flammenphotometer der eingangs ge­nannten Art zu schaffen, daß hinsichtlich der Kon­stantflußregelung wesentlich kostengünstiger, prä­ziser und zuverlässiger ausbildbar ist.The object of the present invention is therefore to provide a flame photometer of the type mentioned at the outset, which can be designed much more cost-effectively, precisely and reliably with regard to constant flow control.

Diese Aufgabe wird erfindungsgemäß mit den Merk­malen des Kennzeichnungsteiles des Anspruches 1 ge­löst.This object is achieved with the features of the characterizing part of claim 1.

Erfindungsgemäß wird als Steuerventil ein Schalt­ventil vorgesehen, daß nicht wie die bisher ver­wendeten Reduzierventile kontinuierlich arbeitet, sondern digital mit nur zwei Schaltstellungen AUF und ZU. Ein solches Schaltventil kann also in heute üblicher Technik digital angesteuert werden und er­laubt in einfacher Anpassung die Verwendung digita­ler Steuer- und Regeleinrichtungen, die in einfa­cher Weise an Computersteuerungen angeschlossen werden können. Das erfindungsgemäße Schaltventil zeichnet sich durch erhebliche Kostenvorteile aus sowie aufgrund seiner einfachen Bauform durch we­sentlich verringerte Störanfälligkeit. Durch den dem Schaltventil nachgeschalteten Pufferbehälter werden die aus der diskontinuierlichen Arbeitsweise des Schaltventiles sich ergebenden Druck- bzw. Flußschwankungen vergleichmäßigt. In unterschied­licher Ansteuerungstechnik des Schaltventiles, worauf im folgenden noch eingegangen wird (z. B. Zweipunktregelung, Pulsbreitenregelung oder Puls­frequenzregelung) kann in engen Toleranzgrenzen ein hochkonstanter Differenzdruck an der Drossel und somit ein hochkonstanter Fluß erzielt werden. Der Erfindung liegt also die Erkenntnis zugrunde, daß ein bisher für die vorliegenden Zwecke nicht für verwendbar gehaltenes Schaltventil für Flammenfoto­meter einsetzbar ist, und zwar in Funktionseinheit mit einem Pufferbehälter, wobei durch Zusammenwir­ken von Schaltventil und Pufferbehälter eine gleichmäßige konstante Gasversorgung ermöglicht wird.According to the invention, a control valve is provided as the control valve, which does not work continuously like the reducing valves previously used, but digitally with only two switch positions OPEN and CLOSE. Such a switching valve can therefore be controlled digitally in the technology customary today and, in a simple adaptation, allows the use of digital control and regulating devices which can be connected to computer controls in a simple manner. The switching valve according to the invention is distinguished by considerable cost advantages and, owing to its simple design, by significantly reduced susceptibility to faults. Due to the buffer tank downstream of the switching valve, the pressure and flow fluctuations resulting from the discontinuous operation of the switching valve are evened out. With different control technology of the switching valve, which will be dealt with in the following (e.g. two-point control, pulse width control or pulse frequency control), a highly constant differential pressure at the throttle and thus a highly constant flow can be achieved within narrow tolerance limits. The The invention is therefore based on the knowledge that a switching valve for flame photometers previously not considered usable for the present purposes can be used, namely in a functional unit with a buffer tank, whereby a constant, constant gas supply is made possible by the interaction of the switching valve and the buffer tank.

Vorteilhaft sind dabei die Merkmale des Anspruches 2 vorgesehen. Hierbei wird eine gewisse Druckhyste­rese zugelassen, damit beim Arbeiten des Schaltven­tiles der Differenzdruck zwischen zwei vorgegebenen Werten pendelt. Die Druckhysterese kann jedoch sehr klein gewählt werden. Der Schaltungsaufwand kann bei einer solchen Betriebsart sehr klein gehalten werden. Die Schaltfrequenz des Schaltventiles ist bei dieser Betriebsart vom Volumen des Pufferbehäl­ters abhängig. Bei sehr großem Volumen schaltet das Ventil sehr langsam. Schaltventil und Regelung kön­nen entsprechend einfach und kostengünstig ausgelegt werden.The features of claim 2 are advantageously provided. A certain pressure hysteresis is permitted here so that the differential pressure oscillates between two specified values when the switching valve is working. However, the pressure hysteresis can be chosen to be very small. The circuit complexity can be kept very low in such an operating mode. The switching frequency of the switching valve in this operating mode depends on the volume of the buffer tank. If the volume is very large, the valve switches very slowly. The switching valve and control can be designed accordingly simply and inexpensively.

Weiterhin vorteilhaft sind die Merkmale des Anspru­ches 3 vorgesehen. Bei diesen Betriebsarten des Schaltventiles, die an sich aus der Regelungstech­nik bekannt sind, kann eine hochgenaue Differenz­druckregelung erreicht werden, wobei wiederum der Regelungsaufwand kleingehalten und ein mechanisch sehr einfaches Schaltventil verwendet werden kann.The features of claim 3 are also advantageously provided. In these operating modes of the switching valve, which are known per se from control engineering, a highly precise differential pressure control can be achieved, the control effort again being kept small and a mechanically very simple switching valve can be used.

Weiterhin vorteilhaft sind die Merkmale des Anspru­ches 4 vorgesehen. Hierdurch wird der Regelungs- und Installationsaufwand verringert. Wenn der Strömungswiderstand der der Drossel nachgeschal­ teten Gasstrecke, die im wesentlichen nur aus dem Brenner besteht, ausreichend konstant ist, was in der Regel der Fall ist, so ergibt sich auch mit einer solchen einfachen Konstruktion eine ausrei­chend genaue Regelung.The features of claim 4 are also advantageously provided. This reduces the control and installation effort. If the flow resistance is followed by that of the throttle teten gas line, which consists essentially only of the burner, is sufficiently constant, which is usually the case, so results in a sufficiently precise control even with such a simple construction.

Dabei sind vorteilhaft die Merkmale des Anspruches 5 vorgesehen. Auf diese Weise wird erreicht, daß Änderungen des Strömungswiderstandes der der Dros­sel nachgeschalteten Gasstrecke gegenüber dem sehr großen Strömungswiderstand der Drossel vernachläs­sigt werden können, also Flußschwankungen ergeben, die unterhalb der Toleranzgrenze bleiben und den Betrieb des Brenners nicht stören. Dies ist insbe­sondere von Vorteil, wenn Brenner mit schwankendem Strömungswiderstand verwendet werden oder Brenner unterschiedlichen Strömungswiderstandes ausgewech­selt werden sollen.The features of claim 5 are advantageously provided. In this way it is achieved that changes in the flow resistance of the gas path downstream of the throttle compared to the very large flow resistance of the throttle can be neglected, that is to say flow fluctuations which remain below the tolerance limit and do not disturb the operation of the burner. This is particularly advantageous when burners with fluctuating flow resistance are used or when burners with different flow resistance are to be replaced.

Schließlich sind vorteilhaft die Merkmale des An­spruches 6 vorgesehen. Auf diese Weise kann sehr einfach durch Verstellung an der Regeleinrichtung der gewünschte Sollfluß eingestellt werden.Finally, the features of claim 6 are advantageously provided. In this way, the desired flow can be set very easily by adjusting the control device.

In der Zeichnung ist die Erfindung beispielsweise und schematisch dargestellt.In the drawing, the invention is shown for example and schematically.

Die in der Figur dargestellte Gasflußregelung ist in einem Flammenphotometer vorgesehen, dessen son­stige Teile der Einfachheit halber weggelassen sind.The gas flow control shown in the figure is provided in a flame photometer, the other parts of which are omitted for the sake of simplicity.

Von einer ebenfalls nicht dargestellten Gasversor­gung, beispielsweise einer Gasflasche, wird über eine Gasleitung 1 in Pfeilrichtung Gas dem Brenner 2 zugeführt.From a gas supply, also not shown, for example a gas bottle, gas is supplied to the burner via a gas line 1 in the direction of the arrow 2 fed.

Bei dem über die Gasleitung 1 geführten Gas kann es sich um eine brennfähige Gasmischung oder um eine der zur Verbrennung benötigten Gaskomponenten (Brenngas, Oxydans) handeln. Das durchströmende Gas ist mit der dargestellten Regelung im Fluß konstant zu halten, damit der Brenner 2 zeitkonstant arbei­tet.The gas conducted via the gas line 1 can be a combustible gas mixture or one of the gas components required for combustion (fuel gas, oxidant). The gas flowing through is to be kept constant in the flow with the control shown, so that the burner 2 operates at a constant time.

In der Gasleitung 1 ist ein Schaltventil 3 zwi­schengeschaltet, das, wie mit entsprechenden Schaltsymbolen angedeutet, die beiden Schaltstel­lungen AUF und ZU aufweist. Es wird elektrisch be­trieben und über eine Steuerleitung 4 taktweise angesteuert.A switching valve 3 is interposed in the gas line 1 and, as indicated by corresponding switching symbols, has the two switching positions OPEN and CLOSE. It is operated electrically and is controlled cyclically via a control line 4.

Dem Schaltventil 3 ist in der Gasleitung 1 ein Puf­ferbehälter 5 nachgeschaltet. Über eine Leitung 6 wird der Gasdruck im Behälter 5 einem Druck-/Span­nungswandler 7 zugeführt, der über eine Leitung 8 an einen Eingang einer Steuereinrichtung 9 ange­schlossen ist. Diese vergleicht den Druckwert im Behälter 5 mit einem vorgegebenen Sollwert und re­gelt entsprechend über die Steuerleitung 4 das Taktverhältnis AUF/ZU des Schaltventiles 3 derart nach, daß der Druck im Behälter 5 im wesentlichen konstant gehalten wird.A buffer tank 5 is connected downstream of the switching valve 3 in the gas line 1. The gas pressure in the container 5 is fed via a line 6 to a pressure / voltage converter 7 which is connected via a line 8 to an input of a control device 9. This compares the pressure value in the container 5 with a predetermined target value and regulates the duty cycle OPEN / CLOSE of the switching valve 3 accordingly via the control line 4 such that the pressure in the container 5 is kept essentially constant.

Dem Behälter 5 ist eine Drossel 10 nachgeschaltet, durch die das Gas über die Gasleitung 1 dem Brenner 2 zufließt.A throttle 10 is connected downstream of the container 5, through which the gas flows to the burner 2 via the gas line 1.

Der in der Figur mit dem entsprechenden Symbol an­gedeutete Strömungswiderstand des Brenners 2 ist bei Flammenphotometern in der Regel sehr klein und gleichmäßig. In der Gasleitung 1 herrscht an der Stelle zwischen der Drossel 10 und dem Brenner 2 daher in der Regel konstanter, im wesentlichen dem Atmosphärendruck entsprechender Druck. Die Druck­differenz zwischen Eingang und Ausgang an der Dros­sel 10 wird somit durch die Druckregelung im Behäl­ter 5 konstant gehalten. Daher ist der Durchfluß durch die Drossel 10 und somit der Gesamtgasfluß im gewünschten Sinne konstant.The flow resistance of the burner 2 indicated in the figure with the corresponding symbol is with flame photometers usually very small and even. In the gas line 1, therefore, there is generally a constant pressure essentially corresponding to the atmospheric pressure at the point between the throttle 10 and the burner 2. The pressure difference between the inlet and outlet at the throttle 10 is thus kept constant by the pressure control in the container 5. Therefore, the flow through the throttle 10 and thus the total gas flow in the desired sense is constant.

Sind Schwankungen des Strömungswiderstandes im Brenner 2 zu befürchten oder soll von der Konstruk­tion her zugelassen werden, daß der Brenner 2 gegen einen anderen Brenner anderen Strömungswiderstandes gewechselt werden kann, so ist eine Drossel 10 zu verwenden, die einen gegenüber dem Strömungswider­stand des Brenners 2 (einschließlich des Gaslei­tungssystems zwischen der Drossel 10 und dem Bren­ner 2) erheblich größeren Strömungwiderstand auf­weist. Der gesamte Druckabfall zwischen dem Behäl­ter 5 und dem Ausgang 11 des Brenners in die At­mosphäre wird dann durch den Strömungswiderstand der Drossel 10 bestimmt, gegen den der Strömungs­widerstand des Brenners 2 vernachlässigt werden kann. Änderungen des Widerstandes am Brenner 2 er­geben dann nur vernachlässigbar kleine Durchfluß­änderungen.If fluctuations in the flow resistance in the burner 2 are to be feared or should the design permit that the burner 2 can be exchanged for another burner with a different flow resistance, then a throttle 10 is to be used which has a resistance to the flow resistance of the burner 2 (inclusive of the gas line system between the throttle 10 and the burner 2) has considerably greater flow resistance. The total pressure drop between the container 5 and the outlet 11 of the burner into the atmosphere is then determined by the flow resistance of the throttle 10, against which the flow resistance of the burner 2 can be neglected. Changes in the resistance at the burner 2 then result in only negligibly small changes in flow.

In der beschriebenen Ausführungsform erfaßt die Re­geleinrichtung 9 über den Druck-/Spannungwandler 7 nur den Druck im Behälter 5, also den Vordruck der Drossel 10. Als Druck hinter der Drossel 10 wird bei dieser Ausführungsform der Atmosphärendruck be­rücksichtigt. Der Druck-/Spannungswandler 7 kann in üblicher Weise so ausgelegt sein, daß er den Druck auf der Leitung 6 mit dem Atmosphärendruck ver­gleicht und den Differenzdruck wandelt und an den Regler 9 weitergibt.In the described embodiment, the control device 9 detects only the pressure in the container 5, that is to say the admission pressure of the throttle 10, via the pressure / voltage converter 7. In this embodiment, the atmospheric pressure is taken into account as the pressure behind the throttle 10. The pressure / voltage converter 7 can in Usually be designed so that it compares the pressure on the line 6 with the atmospheric pressure and converts the differential pressure and passes it on to the controller 9.

Zur exakten Erfassung der Druckdifferenz an der Drossel 10 kann eine alternative Konstruktion wie folgt vorgesehen sein.An alternative construction can be provided as follows for exact detection of the pressure difference at the throttle 10.

Am Ausgang der Drossel 10 ist ein zweiter Druck-/­Spannungswandler 12 über eine Leitung 13 ange­schlossen, der über eine Leitung 14 parallel zur Leitung 8 des Wandlers 7 an die Steuereinrichtung 9 angeschlossen ist, die in diesem Falle als Diffe­renzschaltung arbeitet und das Taktverhältnis des Schaltventiles 3 derart nachregelt, daß die Druck­differenz zwischen den Gasdrucken in den Leitungen 6 und 13, also am Eingang und Ausgang der Drossel 10, konstant bleibt.At the output of the throttle 10, a second pressure / voltage converter 12 is connected via a line 13, which is connected via a line 14 in parallel to the line 8 of the converter 7 to the control device 9, which in this case works as a differential circuit and the cycle ratio of the switching valve 3 readjusted such that the pressure difference between the gas pressures in lines 6 and 13, that is to say at the inlet and outlet of the throttle 10, remains constant.

Bei dieser Differenzdruckregelung kann der Strö­mungswiderstand im Brenner 2 und dessen Leitungs­system beliebige Werte annehmen, ohne die Konstant­haltung des Gasflusses zu stören.With this differential pressure control, the flow resistance in the burner 2 and its line system can assume any values without disturbing the gas flow being kept constant.

Da in der Regel der ohnehin stets vorhandene Druck/­Spannungswandler 7 ein Differenzdruckaufnehmer ist, dessen einer Druckeingang an den Behälter 5 und dessen anderer Druckeingang an die Atmosphäre an­geschlossen ist, kann dieser Wandler 7 in verein­fachter Ausführungsform auch zur Bestimmung des Differenzdruckes über der Drossel 10 verwendet werden. Dazu wird sein einer Druckeingang an die Leitung 6 und sein anderer Druckeingang an die Lei­tung 13 angeschlossen. Der ermittelte Differenz­ druck wird in Spannung gewandelt und der Steuerein­richtung 9 als Eingangsgröße zugeführt. Auf diese Weise kann bei Ermittlung des Differenzdruckes der zweite Wandler 12 eingespart werden.Since the pressure / voltage converter 7, which is always present anyway, is a differential pressure sensor, one pressure input of which is connected to the container 5 and the other of which is connected to the atmosphere, this converter 7 can also be used in a simplified embodiment to determine the differential pressure across the throttle 10 will. For this purpose, one of its pressure inputs is connected to line 6 and its other pressure input is connected to line 13. The difference found pressure is converted into voltage and supplied to the control device 9 as an input variable. In this way, the second converter 12 can be saved when determining the differential pressure.

Dem Schaltventil 3 kann in üblicher Weise ein Druckminderer, z. B. in Form einer weiteren Dros­sel, vorgeschaltet sein, um den hohen Speisedruck, beispielsweise einer Gasflasche, auf ein vom Schaltventil 3 verarbeitbares Druckniveau zu redu­zieren.The switching valve 3 can be a pressure reducer, for. B. in the form of a further throttle, upstream to reduce the high feed pressure, for example a gas bottle, to a pressure level that can be processed by the switching valve 3.

Die Steuereinrichtung 9 ist vorzugsweise als elek­tronische Steuereinrichtung ausgebildet, die die über die Leitung 8 ankommende Steuergröße bzw. die Differenz der über die Leitung 8 und 14 ankommenden Steuergrößen mit einem elektrisch vorgegebenen Sollwert vergleicht und bei Abweichungen über die Steuerleitung 4 das Taktverhältnis des Schaltven­tiles entsprechend nachregelt. Dabei kann vorzugs­weise eine Verstelleinrichtung, beispielsweise in Form eines Stellpotentiometers 15 vorgesehen sein, mit der die elektrische Sollwertvorgabe verstellt werden kann. Auf diese Weise kann der Druck im Be­hälter 5 bzw. der Differenzdruck an der Drossel 10 und damit der Sollwert des konstant zu haltenden Gasflusses auf den gewünschten Wert eingestellt werden, um beispielsweise im Brenner 2 die ge­wünschte Flammengröße zu erhalten.The control device 9 is preferably designed as an electronic control device which compares the control variable arriving via line 8 or the difference between the control variables arriving via line 8 and 14 with an electrically predetermined setpoint value and, in the event of deviations, readjusts the cycle ratio of the switching valve accordingly via control line 4 . In this case, an adjusting device, for example in the form of a setting potentiometer 15, can preferably be provided, with which the electrical setpoint specification can be adjusted. In this way, the pressure in the container 5 or the differential pressure at the throttle 10 and thus the desired value of the gas flow to be kept constant can be set to the desired value, for example in order to obtain the desired flame size in the burner 2.

Die erwähnte Verstelleinrichtung für die Steuer­einrichtung 9 kann beispielsweise auch als Vor­wahlsteuerung ausgebildet sein, mit der beispiels­weise über Tastendruck bestimmte voreingestellte Flüsse wählbar sind. Es kann auch eine Ansteuerung aus einem Computer erfolgen, z. B. nach einem be­stimmten Programm. Auf diese Weise ist es möglich, je nach Anforderung bestimmte Flüsse zu wählen, beispielsweise je nach dem im Flammenphotometer zur Zeit verwendeten Meßverfahren, wenn also beispiels­weise für unterschiedliche fotometrische Verfahren unterschiedliche Flammenintensitäten erforderlich sind.The adjustment device mentioned for the control device 9 can, for example, also be designed as a preselection control, with which certain preset flows can be selected, for example, by pressing a key. It can also be a control done from a computer, e.g. B. according to a certain program. In this way it is possible to select certain flows depending on the requirements, for example depending on the measurement method currently used in the flame photometer, for example if different flame intensities are required for different photometric methods.

Die Regeleinrichtung 9 kann das Schaltventil 3 in Abhängigkeit vom Differenzdruck an der Drossel 10 in unterschiedlichen Betriebsarten steuern.The control device 9 can control the switching valve 3 as a function of the differential pressure at the throttle 10 in different operating modes.

Eine schaltungstechnisch sehr einfach realisierbare Konstruktion, die sich in Versuchen bewährt hat, besteht darin, das Schaltventil 3 bei Unterschrei­ten eines ersten tieferliegenden Druckes auf­zuschalten und bei Überschreiten eines vorgegebenen höheren Druckes zuzuschalten. Hierbei ergibt sich also im Behälter 5 ein zwischen den beiden vorge­gebenen Druckwerten schwankender Druck, wobei diese Hysterese aber sehr klein gehalten werden kann. Wenn der Behälter in seinem Volumen entsprechend groß ist, arbeitet das Schaltventil 3 sehr langsam. Die Regelung und das Schaltventil können folglich sehr einfach konstruiert werden.A construction that is very simple to implement in terms of circuitry, which has proven itself in tests, consists in switching on the switching valve 3 when the pressure falls below a first, and switching on when a predetermined higher pressure is exceeded. This results in a pressure fluctuating in the container 5 between the two predetermined pressure values, although this hysteresis can be kept very small. If the volume of the container is large enough, the switching valve 3 works very slowly. The control and the switching valve can therefore be constructed very simply.

In anderen Betriebsarten kann beispielsweise das Schaltventil bei konstanter Schaltfrequenz mit unterschiedlichen Pulsbreiten angesteuert werden, also beispielsweise mit unterschiedlichen Längen der Auf-Zeit. Es kann auch bei konstanter Länge der Auf-Zeit die Folgefrequenz verändert werden.In other operating modes, for example, the switching valve can be controlled at a constant switching frequency with different pulse widths, that is to say, for example, with different lengths of the open time. The repetition frequency can also be changed if the open time is constant.

Claims (6)

1. Flammenphotometer mit Konstantflußregelung wenigstens einer der Brenngaskomponenten mittels eines Steuerventiles, das den Gaszufluß zu einem Pufferbehälter steuert, welchem über eine Drossel der Brenner nachgeschaltet ist, wobei das Steuer­ventil in Abhängigkeit vom Differenzdruck über der Drossel den Druck im Pufferbehälter derart regelt, daß der Differenzdruck konstant bleibt, dadurch gekennzeichnet, daß das Steuerventil als AUF/ZU-­Schaltventil (3) ausgebildet ist, das von einer in Abhängigkeit vom Differenzdruck regelnden Regelein­richtung (9) gesteuert wird.1. Flame photometer with constant flow control of at least one of the fuel gas components by means of a control valve which controls the gas flow to a buffer tank which is connected via a throttle to the burner, the control valve depending on the differential pressure across the throttle regulating the pressure in the buffer tank in such a way that the differential pressure remains constant, characterized in that the control valve is designed as an OPEN / CLOSE switching valve (3) which is controlled by a regulating device (9) which regulates as a function of the differential pressure. 2. Flammenphotometer nach Anspruch 1, dadurch gekennzeichnet, daß die Regeleinrichtung (9) das Schaltventil (3) bei Unterschreiten eines vorge­gebenen Differenzdruckes Auf-schaltet und bei über­schreiten eines vorgegebenen zweiten höheren Diffe­renzdruckes Zu-schaltet.2. Flame photometer according to claim 1, characterized in that the control device (9) switches the switching valve (3) on when the pressure drops below a predetermined differential pressure and switches on when a predetermined second higher differential pressure is exceeded. 3. Flammenphotometer nach Anspruch 1, dadurch gekennzeichnet, daß die Regeleinrichtung (9) das Schaltventil (3) in Abhängigkeit von einem vorge­wählten Differenzdruck in Pulsbreitenregelung bzw. Pulsfrequenzregelung steuert.3. Flame photometer according to claim 1, characterized in that the control device (9) controls the switching valve (3) in dependence on a preselected differential pressure in pulse width control or pulse frequency control. 4. Flammenphotometer nach einem der vorherge­henden Ansprüche, dadurch gekennzeichnet, daß die Regeleinrichtung (9) in Abhängigkeit vom Vordruck (6) der Drossel (10) regelt, wobei als Ausgangs­druck der Drossel (10) der Atmosphärendruck be­rücksichtigt wird.4. Flame photometer according to one of the preceding claims, characterized in that the control device (9) controls the throttle (10) as a function of the admission pressure (6), the atmospheric pressure being taken into account as the output pressure of the throttle (10). 5. Flammenphotometer nach Anspruch 4, dadurch gekennzeichnet, daß der Strömungswiderstand der Drossel (10) um so viel größer ist als der der nachgeschalteten Gasstrecke (2), daß bei Änderung des Restwiderstandes sich ergebende Gasflußfehler unterhalb einer vorgegebenen, zulässigen Fehler­grenze bleiben.5. Flame photometer according to claim 4, characterized in that the flow resistance of the throttle (10) is so much greater than that of the downstream gas path (2) that when changing the residual resistance resulting gas flow errors remain below a predetermined, permissible error limit. 6. Flammenphotometer nach einem der vorherge­henden Ansprüche, dadurch gekennzeichnet, daß die Regeleinrichtung (9) eine Verstellvorrichtung zur Einstellung des gewünschten Differenzdruckes auf­weist.6. Flame photometer according to one of the preceding claims, characterized in that the control device (9) has an adjusting device for setting the desired differential pressure.
EP87110967A 1986-08-06 1987-07-29 Flame photometer with constant stream regulation Expired - Lifetime EP0255915B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT87110967T ATE62746T1 (en) 1986-08-06 1987-07-29 FLAME PHOTOMETER WITH CONSTANT FLOW CONTROL.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3626644 1986-08-06
DE3626644 1986-08-06

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EP0255915A2 true EP0255915A2 (en) 1988-02-17
EP0255915A3 EP0255915A3 (en) 1988-10-05
EP0255915B1 EP0255915B1 (en) 1991-04-17

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EP87110967A Expired - Lifetime EP0255915B1 (en) 1986-08-06 1987-07-29 Flame photometer with constant stream regulation

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EP (1) EP0255915B1 (en)
AT (1) ATE62746T1 (en)
DE (1) DE3769395D1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4110343A1 (en) * 1990-03-30 1991-10-02 Hitachi Ltd PLASMA ANALYZER FOR TRACK ELEMENT ANALYSIS
EP0836054A1 (en) * 1996-10-11 1998-04-15 Gaggenau Hausgeräte GmbH Method and device for controlling the size of the flame of a gas cooking apparatus

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2200487A1 (en) * 1972-09-14 1974-04-19 Vaillant Joh Kg
DE3005784A1 (en) * 1979-03-05 1980-09-18 Perkin Elmer Corp MEASURING AND CONTROL SYSTEM FOR THE FLUID FLOW IN A BURNER FOR THE ATOMIC SPECTROSCOPY
EP0068589A1 (en) * 1981-06-23 1983-01-05 Conma N.V. Method and device for controlling the pressure of a fluid and/or the amount per unit of time of a flow
GB2155205A (en) * 1984-03-01 1985-09-18 Bodenseewerk Perkin Elmer Co Gas control device for a burner for an atomic absorption spectrometer

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2200487A1 (en) * 1972-09-14 1974-04-19 Vaillant Joh Kg
DE3005784A1 (en) * 1979-03-05 1980-09-18 Perkin Elmer Corp MEASURING AND CONTROL SYSTEM FOR THE FLUID FLOW IN A BURNER FOR THE ATOMIC SPECTROSCOPY
EP0068589A1 (en) * 1981-06-23 1983-01-05 Conma N.V. Method and device for controlling the pressure of a fluid and/or the amount per unit of time of a flow
GB2155205A (en) * 1984-03-01 1985-09-18 Bodenseewerk Perkin Elmer Co Gas control device for a burner for an atomic absorption spectrometer

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4110343A1 (en) * 1990-03-30 1991-10-02 Hitachi Ltd PLASMA ANALYZER FOR TRACK ELEMENT ANALYSIS
EP0836054A1 (en) * 1996-10-11 1998-04-15 Gaggenau Hausgeräte GmbH Method and device for controlling the size of the flame of a gas cooking apparatus

Also Published As

Publication number Publication date
EP0255915B1 (en) 1991-04-17
DE3769395D1 (en) 1991-05-23
EP0255915A3 (en) 1988-10-05
ATE62746T1 (en) 1991-05-15

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