NO793435L

NO793435L - METHOD AND APPARATUS FOR PERFORMANCE OF LIQUID / GAS ANALYSIS

Info

Publication number: NO793435L
Application number: NO793435A
Authority: NO
Inventors: Knut Finborud
Original assignee: Norsk Hydro As
Priority date: 1979-10-26
Filing date: 1979-10-26
Publication date: 1981-04-28

Description

Knut FinborudKnut Finborud

Flåttenlia 25Flåttenlia 25

3900 Porsgrunn3900 Porsgrunn

Foreliggende oppfinnelse gjelder fremgangsmåte og apparat for utførelse av væske/gass-analyser. Utstyret gir en kontinuerlig måling og er derfor spesielt godt egnet til prosess-analyse, men vil også gi raske og sikre resultater ved laboratorieanalyser. The present invention relates to a method and apparatus for carrying out liquid/gas analyses. The equipment provides continuous measurement and is therefore particularly well suited for process analysis, but will also provide fast and reliable results for laboratory analyses.

Metoden kan brukes til å bestemme konsentrasjonen av en komponent i en væske når denne komponenten kan avdrives som gass, f.eks. ved tilsetning av en reagens, ved avspenning eller- oppvarming av væsken (desorpsjonsanalyse) . På den annen side kan metoden brukes til gassanalyse når gassen inneholder en komponent som lar seg absorbere i væske, dvs. gasser som f.eks. saltsyre (HC1) , kullsyre (CC>2) , ammoniakk (NH3), vinylklorid (VCM) osv. The method can be used to determine the concentration of a component in a liquid when this component can be carried off as a gas, e.g. by adding a reagent, by relaxing or heating the liquid (desorption analysis). On the other hand, the method can be used for gas analysis when the gas contains a component that can be absorbed in liquid, i.e. gases such as hydrochloric acid (HC1), carbonic acid (CC>2), ammonia (NH3), vinyl chloride (VCM), etc.

Det eksisterer i dag mange kjente systemer for væskeanalyser, hvor utgangspunktet er en flerkanals slangepumpe som doserer målevæske og reagenser som blandes i en blandespiral for å fremkalle fargereaksjoner eller andre kjemisk/fysikalske forandringer i væsken (auto-analysator). Den foreliggende oppfinnelse går ut på at i et slikt system drives måle-komponenten - eller en med denne gassen sammenhørende komponent - av som gass, og at mengden av denne gassen måles på en helt spesiell måte ved hjelp av en optoelektronisk lesegaffel. Herved oppnås raske og sikre målinger ved bruk av overraskende enkelt utstyr. There are many well-known systems for liquid analysis today, where the starting point is a multi-channel hose pump that doses measuring liquid and reagents that are mixed in a mixing spiral to induce color reactions or other chemical/physical changes in the liquid (auto-analyser). The present invention assumes that in such a system the measuring component - or a component associated with this gas - is driven off as gas, and that the amount of this gas is measured in a very special way by means of an optoelectronic reading fork. In this way, fast and safe measurements are achieved using surprisingly simple equipment.

Når det dreier seg om absorpsjonsanalyse, brukes slange-pumpen til å dosere målegass og flytende absorpsjonsmiddel inn i et glassrør, og restgassen som er igjen etter absorp-sjonen (inert) registreres som bobler av den optoelektro-niske lesegaffel. When it comes to absorption analysis, the hose pump is used to dose measuring gas and liquid absorbent into a glass tube, and the residual gas remaining after absorption (inert) is registered as bubbles by the optoelectronic reading fork.

Behovet for en desorpsjonsanalysator foreligger f.eks. i prosesser hvor kalsiumnitrat konverteres til ammoniumnitrat ved tilsetning av ammoniakk og kullsyre..-Kullsyre skal fore- -i ligge i et visst overskudd og kan i en filtrert prøve bestemmes ved at kullsyren drives av som gass ved å tilsette salpetersyre. The need for a desorption analyzer exists e.g. in processes where calcium nitrate is converted to ammonium nitrate by adding ammonia and carbonic acid..- Carbonic acid must be present in a certain excess and can be determined in a filtered sample by driving off the carbonic acid as a gas by adding nitric acid.

Oppfinnelsen skal nedenfor beskrives mer detaljert under henvisning til de medfølgende tegninger, hvor Fig. 1 skjematisk viser en utførelsesform av måleutstyret når det brukes som desorpsjonsanalysator. Videre viser Fig. 3 en utf øjrelsesform av måleutstyret når dette benyttes f or ab-sorps jonsanalyse . The invention will be described below in more detail with reference to the accompanying drawings, where Fig. 1 schematically shows an embodiment of the measuring equipment when it is used as a desorption analyser. Furthermore, Fig. 3 shows an embodiment of the measuring equipment when it is used for absorption ion analysis.

Ved å bruke en flerkanals slangepumpe 2 kan man dosere målevæske 3 fra prosesstrømmen og reagens 4 fra en beholder 1 By using a multi-channel hose pump 2, measuring liquid 3 can be dosed from the process stream and reagent 4 from a container 1

(i eksemplet er reagensen salpetersyre). De to væskene(in the example the reagent is nitric acid). The two liquids

blandes sammen i en manifold 5. Gassutviklingen starter der hvor de to væskene møtes. Den påskyndes sterkt ved å kjøre faseblandingen gjennom et fiberfilter 6 (glassvattfilter f.eks.). Mikrobobler holdes tilbake i filteret og samles i bobler av målbar størrelse. Gassen samler seg i klart av-grensede bobler av den type som er så karakteristisk for autoanalysatorsysterner. Forholdet mellom den gjennomsnitt- are mixed together in a manifold 5. Gas development starts where the two liquids meet. It is greatly accelerated by running the phase mixture through a fiber filter 6 (glass wool filter, for example). Microbubbles are retained in the filter and collected in bubbles of measurable size. The gas collects in clearly defined bubbles of the type so characteristic of autoanalyzer systems. The ratio between the average

lige lengde av gass-segmentene og væske-segmentene er et mål for den gassmengde som drives av fra hver volumenhet væske, og dermed et mål for gassens konsentrasjon i væskeprøven. equal length of the gas segments and the liquid segments is a measure of the amount of gas that is driven off from each unit volume of liquid, and thus a measure of the concentration of the gas in the liquid sample.

Som absorpsjonsanalysator vil slangepumpens funksjon væreThe function of the hose pump will be as an absorption analyser

noe annerledes, som skjematisk vist i Fig. 2. Som eksempel har.utstyret vært brukt til å bestemme luft i saltsyregass. something different, as schematically shown in Fig. 2. As an example, the equipment has been used to determine air in hydrochloric acid gas.

Målegassen pumpes med en eller flere store pumpeslanger gjennom ledningen 3 frem til en manifold 5. Her blandes gasstrømmen med flytende absorpsjonsmiddel 4, som-pumpes inn med en mindre pumpeslange. I eksemplet er absorpsjonsmid-delet natronlut. Saltsyregassen absorberes i reagensvæsken i absorpsjonsstrekningen 6, mens inertgassen blir igjen som luftbobler avgrenset av væskesegmenter. Forholdet mellom den gjennomsnittlige lengde på gass-segmentene og væske-segmentene er et mål for konsentrasjonen av inertgass i målegassen. Absorpsjonsstrekningen 6 gis en lengde som bestemmes av absorpsjonshastigheten. I det aktuelle eksemplet kan den gjøres meget kort, noen få cm. The measuring gas is pumped with one or more large pump hoses through the line 3 to a manifold 5. Here the gas flow is mixed with liquid absorbent 4, which is pumped in with a smaller pump hose. In the example, the absorbent is caustic soda. The hydrochloric acid gas is absorbed in the reagent liquid in the absorption section 6, while the inert gas remains as air bubbles delimited by liquid segments. The ratio between the average length of the gas segments and the liquid segments is a measure of the concentration of inert gas in the measurement gas. The absorption stretch 6 is given a length which is determined by the absorption rate. In the relevant example, it can be made very short, a few cm.

For å få et mål på forholdet mellom den gjennomsnittlige lengde av gass-segmentene og væske-segmentene, benyttes det en optoelektronisk lesegaffet 7, som plasseres slik at den "ser" på tvers gjennom glassrøret ved utløpet av blande-strekningen. Lesegaflenes gap er vanligvis 3 til 4 mm, og den utvendige diameter på glassrøret må passe til dette. Lesegaffelen er i dette tilfelle koblet slik at den gir et "on-off"-signal, alt ettersom det befinner seg væske eller gass foran lesegaffelens lysdiode. Væske i røret gir vanligvis høy belysning på grunn av lysbryting (linseeffekt). Ved å la utgangsstrømmen fra lesegaffelen styre et elektronisk eller elektromekanisk relé 9, vil dette registrere lengden av gass- og væske-segmentene. In order to obtain a measure of the ratio between the average length of the gas segments and the liquid segments, an optoelectronic reading gaff 7 is used, which is placed so that it "sees" across the glass tube at the outlet of the mixing section. The reading forks' gap is usually 3 to 4 mm, and the outside diameter of the glass tube must match this. In this case, the reading fork is connected so that it gives an "on-off" signal, depending on whether there is liquid or gas in front of the reading fork's LED. Liquid in the tube usually provides high illumination due to light refraction (lensing effect). By letting the output current from the reading fork control an electronic or electromechanical relay 9, this will register the length of the gas and liquid segments.

Releet som styres av lesegaffelen gir signaler som er godt egnet for digital behandling etter kjente metoder. Her skal det beskrives en enkel metode for å frembringe et analog-signal som er et mål for den analyserte gasskonsentrasjon. Det nevnte relé 9 kan styre en opp- og ut-ladning av en kondensator 13 over to like store motstander 11 og 12. Ved å gi motstand-kondensatorkoblingen en egnet tidskonstant (eksempelvis 10-30 sek.), vil spenningen over kondensatoren gi et entydig mål for den gassmengde som er utviklet ved desorpsjonsanalyse eller den gjenværende gassmengde (inert) ved absorpsjonsanalyse. Spenningen kan registreres med et instrument med høy inngangsimpedans 14 og 15. The relay which is controlled by the reading fork gives signals which are well suited for digital processing according to known methods. A simple method for generating an analogue signal which is a measure of the analyzed gas concentration will be described here. The aforementioned relay 9 can control an up and down charge of a capacitor 13 across two equally sized resistors 11 and 12. By giving the resistor-capacitor connection a suitable time constant (for example 10-30 sec.), the voltage across the capacitor will give a unambiguous measure of the amount of gas developed by desorption analysis or the remaining amount of gas (inert) by absorption analysis. The voltage can be recorded with a high input impedance instrument 14 and 15.

Instrumentet kan under visse forutsetninger betraktes som en absolutt måler, men det mest naturlige er å kalibrere instrumentet med kjente standarder. En bemerkelsesverdig fordel med metoden er den gode nullpunktstabilitet. Under certain conditions, the instrument can be considered an absolute meter, but the most natural thing is to calibrate the instrument with known standards. A notable advantage of the method is the good zero point stability.

Med den analoge motstand-kondensatorkobling som ovenfor beskrevet, blir målingen ulineær. Graden av ulinearitet kan påvirkes ved å forandre skriverens måleområde eller den påtrykte likespenning. With the analog resistor-capacitor connection as described above, the measurement becomes non-linear. The degree of non-linearity can be affected by changing the printer's measuring range or the applied DC voltage.

Målingen er avhengig av målemediets trykk og temperatur når det passerer lesegaffelen. Trykket stabiliseres naturlig til atmosfæretrykk ved å bruke fritt avløp umiddelbart etter lesegaffelen. Temperaturen kan eventuelt reguleres med termostatbad rundt blanderøret. The measurement depends on the pressure and temperature of the measuring medium when it passes the reading fork. The pressure is naturally stabilized to atmospheric pressure by using a free drain immediately after the reading fork. The temperature can optionally be regulated with a thermostatic bath around the mixing pipe.

Oppfinnelsens første utførelseseksempel er beskrevet for anvendelse i en prosess hvor den ene målbare komponent drives av som en gass ved tilsetning av en spesiell reagens. Oppfinnelsen er imidlertid ikke begrenset til bruk av spe-sielle reagenser. Således kan gasskomponenter også avdrives ved at væsken står under trykk og avspennes idet den passerer gjennom blanderøret. Et eksempel på en slik anvendelse er måling av C02i kullsyreholdige væsker. Videre kan måle-prinsippet benyttes for måling av luft, henholdsvis oksygen, i vann ved helt enkelt å varme opp vannet, f.eks. ved å føre en blandespiral gjennom et varmebad, slik at luften drives av som gass på grunn av oppvarmingen. Oppfinnelsen er således med enkle tilpasninger generelt egnet for å måle gass/væske-blandinger. The invention's first embodiment is described for use in a process where the one measurable component is driven off as a gas by the addition of a special reagent. However, the invention is not limited to the use of special reagents. Thus, gas components can also be driven off by the liquid being under pressure and relaxed as it passes through the mixing tube. An example of such an application is the measurement of C02 in carbonated liquids. Furthermore, the measuring principle can be used for measuring air, respectively oxygen, in water by simply heating the water, e.g. by passing a mixing spiral through a heating bath, so that the air is driven off as a gas due to the heating. The invention is thus, with simple adaptations, generally suitable for measuring gas/liquid mixtures.

Claims

1. Procedure for measuring the concentration of a component in liquid/gas mixtures where measuring medium and any reagents are pumped into a mixing zone to induce changes in the medium, characterized by the medium being pumped through a glass tube or the like. under conditions which cause the formation of liquid and gas segments, after which the quantity ratio between gas segments and liquid is continuously read.

2. Method according to claim 1 for measuring a component in a liquid that can be carried off as a gas, characterized in that the liquid is pumped into the glass tube or the like. under conditions that cause the gas to drift off in the form of gas bubbles, after which the quantity ratio between gas bubbles and liquid is read.

3. Method according to claim 1 for measuring the concentration of inert residual gases in a mixture with a gas component that can be absorbed in a liquid, k a, r a k-terized by constant amounts of analysis gas and absorption liquid being pumped continuously through a glass tube or the like. where absorption takes place, and that the non-absorbable part of the gas collects in bubbles, after which the quantity ratio between gas bubbles and liquid is read.

4. Method for measurement according to claim 1, 2 or 3, characterized in that the ratio between liquid and gas bubbles is read using an electronic reading fork which "sees" transversely through the mixing tube or its extension and with the reading fork set in a bistable state as that it can control an electromechanical or electronic relay and cause this to switch on or off, depending on whether there is liquid or gas in the reading fork's registration field.

5. Method according to claim 4, characterized in that the reading from the reading fork is used to influence a relay which, in an energized state, charges up a capacitor from a constant direct voltage source across a resistor, and in a non-energized state, discharges the capacitor across an equal resistance, whereby the capacitor -sator's charge becomes a measure of the relay's temporal percentage switch-on and thus a measure of the ratio between the gas and liquid volume in the pipe.

6. Apparatus for measuring the concentration of a component in liquid/gas mixtures according to the method in claims 1-5, comprising a pump device, preferably in the form of a multi-channel hose pump (2), a manifold (5) and a mixing tube ( 6) of glass etc., characterized in that at the outlet of the mixing tube (6) or at a subsequent glass tube, an electronic reading fork (7) is arranged which "sees" through the glass tube, and is set in a bistable state, as the reading fork with electronic connections is connected to a relay (9) which is designed to switch on and off, depending on whether there is liquid or gas in the reading fork's light beam.

7. Apparatus for measuring the concentration of a component in liquid/gas mixtures according to claim 5, characterized in that the pump has a channel for the supply of reagent to the manifold (5), by which expelled gas bubbles are formed which are read by the fork (7).

8. Apparatus for measuring the concentration of a component in a liquid/gas mixture> is, according to claim 5, characterized in that the pump is arranged for the supply of measuring gas and absorption reagent to the manifold (5), whereby inert gas bubbles are formed which are read by the fork (7) .

9. Apparatus according to claim 8, characterized in that the relay (9) in the energized state charges a capacitor (13) from a constant direct voltage source across a resistor (11) and that the relay in the non-energized state discharges the capacitor across another, equally large resistor (12), which capacitor is connected to a measuring instrument (15) with a high input impedance.