DE1598351A1 - Determination of the oxygen demand of flammable substances in aqueous dispersions - Google Patents

Description

Determination of the oxygen demand of flammable substances in aqueous dispersions

The invention relates to a novel analytical apparatus for determining the oxygen demand of aqueous ^! Dispersions of flammable substances.

Drum contamination control is a long-standing problem and is becoming increasingly important as the population and industry grow in relation to detergents. On the threshold of the overall problem of contamination control is the measurement of contamination itself. One of the parameters useful for this purpose is that Oxygen demand of impurities.

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Nowadays this parameter is usually set by means of a

chemically promoted wet oxidation process measured. A description of this technique is given in Standard Methods for the Examination of Rater and t / Aste Water, "11th Edition (1960) pp. 399-402. Although good results are obtained from the professional practice of this procedure can do the same thing is cumbersome and time consuming. His Usefulness is also limited by the presence of certain combustibles in some sewage streams, the not easily susceptible to damp oxidation by chemical agents are to be subjected. In addition, the presence of chlorides in some waste waters collides with use the wet oxidation process.

"Combustible material" as used herein refers to any composition of matter that either is solid, liquid or gaseous, which chemically poor with gaseous oxygen under the influence of V / reacted. The term "aqueous dispersion" includes solutions and suspensions of combustible material.

The invention provides a method for the rapid determination of the; Oxygen demand of dilute aqueous Dispersions of flammable contaminants, as in

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water. The invention also provides an apparatus for Execution of the procedure mentioned.

The post-binding procedure includes the steps the course of a supplied gas stream, which consists of a inert gas which is at least about 10 and up to about 10,000, but preferably no more than about .1,000 parts per million, by volume of oxygen in an enclosed heated combustion zone, at a constant Contains extent. In the conaensation zone, the gas stream supplied is passed through a combustion-assisting E porous catalyst bed passed through. The combustion zone is at a combustion-supporting temperature heated. From the heated combustion zone, the gas flow is conveyed to a detector for small amounts of τοπ free oxygen flows through the catalyst bed and from there into the quantitative broken oxygen detector a small amount of a dilute aqueous dispersion of a combustible material in the gas stream in the combustion zone upstream of the catalyst bed injected * Bas the gaseous product resulting in a sieve then from the combustion zone through the rolling

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Pressure of the supplied gas flow swept into the oxygen detector.

The temperature of the combustion zone is maintained in the range of 600 to 1200 ° C. Although some oxidation catalysts permit the use of lower temperatures in the range of 600 to 800 C ^p, the preconceived Eesultate be achieved if * platinum used as a catalyst, and the heated combustion zone at a temperature in the range of 800 to 1000 C. Higher temperatures can be used if desired, but there is no apparent benefit in doing so.

The oxygen "which is from the original _t in the feed gas stream available as a result of oxidation of the combustible material which iet injected as an aqueous dispersion, pulled out, is set to a characteristic of the signal in relation generated by the oxygen detector. Since the feed gas stream contains only a small amount of oxygen, very small amounts of combustibles in the aqueous dispersion produce a large percentage deviation in the oxygen content of the gas flowing out of the combustion zone. In this way the procedure is - '_ ■' -.

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of the invention against small changes in the oxygen demand highly sensitive to dilute aqueous dispersions of flammable substances.

The most convenient characteristic of the signal from the point of view the easy measurement is its amplitude or deviation from the signal, which is the oxygen content of the Combustion zone outflow under steady state conditions or in other words the oxygen content of the corresponds to the supplied gas flow. This deviation can can be displayed graphically. It can also be the area under a curve, drawn through a drawing or the continuous Course of the signal is formed, as the signal characteristic can be used with the oxygen content should be related. Ί

If so reproducible states are used, such;

that an analysis ^ comparable to a second analyst I. the measured signal characteristic of the oxygen detector is slightly calibrated against the results obtained, the aqueous dispersions of flammable substances of known Use oxygen demand to meet the oxygen demand of aqueous dispersions of combustible substances to determine unknown oxygen demand.

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Either the signal amplitude or the area under the curve can be determined by suitable electronic devices can be measured using a conventional graphic Are coupled to the recorder. For example, a ■ '.... graphic integrator a means to create a 'recorded Measurement. The calibration of the measured value can be carried out visually or by a suitable electrical Circuit can be carried out as known or familiar to those skilled in the art.

The reproducibility of this type of operation requires mainly the pausing of parameters such as sample size, combustion temperature, gas flow rate, Oxygen content of the supplied gas stream, catalyst type and device construction, which are either essentially are identical or functionally equivalent, over which this condition is met is easily repeated by repeating Änays £ "of a given dispersion of combustible material under a given range or range of Determine operating conditions. If for any analysis. the measured signal characteristic achieves an essentially constant value, the method can be considered reproducible be removed. In any case, the device should be used with a standard

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dispersion of combustible material with a known oxygen requirement can be selected or calibrated.

As used herein, the useful term * refers to that described as "total oxygen demand" is, on the amount of oxygen that must be delivered to the dispersion in order to keep the combustibles in it to convert their corresponding oxidation products. Any dissolved or otherwise unreacted oxygen is gasified when the sample is injected into the combustion zone and this oxygen goes from the one measured or apparent chemical oxygen demand of the combustible materials. That way is the measurement of the invention to meet the total oxygen demand to determine the dispersion.

Consideration of the device that is used to run is appropriate to the above method, will provide a further enhancement of the invention.

In other exemplary drawings show: Fig. 1 is a schematic representation of the essential Basic components of an analyzer according to the invention,

Figure 2 is a more detailed illustration of an automated embodiment of the invention for use

in the case of aqueous dispersions of flammable materials. 009821/0821

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ίο fig * 1 include the elementary components of the; Apparatus includes a delivery device 2 for the diluted oxygen supply flow, which device in this particular illustration consists of an arrangement of a delivery tank 3 for dissolved gas and an oxygen delivery tank 4, which together feed a supply gas line 6.

Nitrogen and oxygen are fed into the water flow line 6 through pressure and flow control valves 7

"I.

and 8 eye-measured. Tie line 6 leads the mixed gas stream into an enclosed combustion zone, which is determined by the light of the combustion pipe 15 in the heating zone 13 of an ileictroofens 9. A gas-permeable catalyst bed 16 of an oxidation-promoting catalyst is located in the heated combustion chamber. The temperature of the heating zone 13 is controlled by a variable force control 10 through the electrical input lines 11 and 12 which are connected to the terminals of a resistance heating coil 14.

Ilie injection of the aqueous dispersion that is to be analyzed, is performed by a suitable injection device, such as that as syringe 17 is shown. IJer course for the sample injection

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is such that the sample in the heating zone 1 $ at the Stored upstream of the catalyst bed 16 will be.

The gaseous outlet from the heating zone 13 flows through the gas line 19 into an unuoterbrooiien, quantitative oxygen detector 21 and emptied through outlet 20 to the atmosphere. The oxygen detector generates an electrical signal, which is transmitted by a electrical connection 23 is passed to a reading device, which in this example is a graphic recorder 26. . The signal, which can be measured as voltage or current, is proportional to and therefore related to the oxygen content of the gaseous effluent. If desired, the recorded signal can calibrated for direct reading of the signal as the oxygen content of the outflowing gas stream or be calibrated.

The total oxygen demand TOD is determined according to the following formula:

TOD -Q ₁ U ^ t ₁ ) - J ² Q (dt),

.V

where Q i is a function of t, telcbes is time, and

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and Q _{1 is} the oxygen content of the feed gas stream or in other words the oxygen content of the outflowing gas under steady state conditions, tj and t ₂ are in this regard the times of sample injection and the return of the oxygen content of the outflowing gas to that of the supplied gas stream. A graphical representation of the value of the above equation solved for | _r 05 is shown in Fig • 1 by the crosshatched area 31 between the base line 29 which represents the oxygen content deö supplied gas stream, and the. Curve 27 plotted by the graphic recorder 26 between t 1 and t ”.

Alternatively, changes in the oxygen content of the gaseous effluent from the combustion zone due to oxygen used to oxidize combustible material present in the injected aqueous dispersion _{f are} reflected in the amplitude or displacement of curve 27 from recorder baseline 29. Indeed, the shift of the recorded curve 27 from the baseline 29 directly pro- portional ι oxygen rings "used in the combustion of the sample with the total oxygen demand of the wässerii

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gene dispersion. ; -

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Währena «in graphic recorder 26 the set reading means 30 can be any conventional technique and a corresponding mechanism including such suitable electronic Signalaeßeinrichtung like them Are familiar to those skilled in the art for reading * the signals generated by the oxygen detector throw"

In practice, these are the basic oxygen demand values

usually by calibrating or calibrating the graphical deviations for unknown dispersions of combustibles Substances obtained against a calibrated curve, which touches on data, which for samples τοπ dispersions of combustible Substances are preserved that have known oxygen requirements. For calibration or machining technology, order Efficient work, as previously mentioned, care must be taken to ensure functionally equivalent operating conditions.

The means for supplying the evaporative oxygen feed stream can be any of several aögiichea take forms other than those specially illustrated. For example, the oxygen and the inert premixed · «in and the mixture can be sent to the

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combustion zone are supplied from a storage cylinder. This type is shown in FIG. In a different mode of operation a stream of inert gas is constantly and uniformly diluted with oxygen, which, as required, is produced by controlled electrolysis from water or by a controlled, oxygen-releasing chemical Reaction. The gas carrier can be any of the essentially inert gases, e.g. helium and argon. However, will nitrogen is used as the preferred gas carrier for convenience and economy.

The degree of flow of the gas flow can vary within wide limits. In practice, the gas flow rate should be set so as to generate easily measurable and recordable signal deviations. Good results are achieved by gas flow grade of 50 to 250 used cubic centimeters per minute, hs is noted that the knowledge of the actual flow level is not necessary for the invention as long as the flow degrees werdeniann controlled to a constant and predetermined heights.

The temperature required to effect combustion can be obtained by any conventional furnace but preferably an electric furnace is used. Such a furnace allows more precise temperature

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control and even heat distribution through the combustion zone hindurob. The temperature in such a Oven can be controlled, for example, by means of a voltage control on the power source for the oven.

The combustion zone is defined by a tubular quartz pipe, e.g. a Vycor-Eobr made of fused silicon and quartz. However, any inert material that maintains its shape and is essentially inert to oxygen and steam at elevated combustion promoting temperatures than Material for the construction for the combustion pipe is sufficient. In most operations, the combustion zone should not exceed a cross-sectional area of about 12 square centimeters and a total volume of about 200 cubic centimeters. The best dimensions in this regard will vary with changes in sample size, grass fluxes, catalyst bed size and combustion temperature.

As noted earlier, the method uses the Invention of a gas-permeable combustion-assisting device Catalyst bed in the combustion zone. The catalyst bed is some distance downstream in the heating zone;

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located from the inlet for the dilute oxygen feedstream / to define a sample expansion zone in the combustion zone upstream of the catalyst bed. This distance, or this distance is such that upon evaporation of the injected aqueous sample, a flashback, ie flow of vapors i> ^e is held gene the direction of flow of the diluted oxygen feed stream effective in the heated combustion zone. Harmful flashback can be detected by the formation of condensate in the lines which are used to trap the dilute oxygen feed stream and deliver it to the combustion zone. The optimum volume of the sample expansion zone in any given part of the apparatus will be determined, at least in part, by the sample size, permeability of the catalyst bed, and the temperature of the heated combustion zone. For example, the heated robe expansion zone should be at least about 5 cubic centimeters for an aqueous sample size of about 1 microliter to 10 microliter. Larger samples will correspondingly require 'larger' sample expansion zones.

Suitable catalyst materials for the gas permeable combustion supporting catalyst bed include

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solid platinum metal, palladium, bhodium, osmium and Ruthenium metals. Usually these metals are obtained in the form of wire or gaee, but special forms these are also useful. Other catalysts are the special oxides of certain metals, such like Hickel and Cobalt. At sufficiently high temperatures, silicon-containing substances are used for the purposes of the invention catalytic.

If desired, the catalytic material can be carried on a support such as asbestos or resin fiber "earth. In general, any combustion supporter can be used Catalyst can be used. "Combustion ^ - · supporting" means herein that the catalyst is oxygen holds in such a form that when touched ν, same with a reducing material the oxygen is available for the reaction.

The catalyst bed is essentially a loosely packed bed of one or more suitable catalyst materials or if the catalyst is in the form of When wire or gauze is present, the bed is essentially a lightly compressed mass of such iimaterials. In any case, it is sufficiently permeable

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for gas flow, so that excessive back pressure is avoided during injection and evaporation of the sample to be analyzed. The length of the catalyst bed can be varied considerably, but is desirable the bed at least about 5 inches long to ensure reproducible combustion.

Although the invention is not to be understood or understood A theoretical explanation of the basis for the effect of the invention is established can be the following explanation the function of the catalyst with reference to the analysis of aqueous dispersions of combustible substances the 'Form the basis for your optimal exercise.

It is believed that when an aqueous dispersion of combustibles is injected into the heated combustion zone, water vapor will dilute and envelop most of the combustibles. Vaporizable materials, such as inorganic refractory components of the waste stream are, of course, largely in place of the Sample evaporation remain. Under these circumstances, gaseous oxygen in the combustion zone cannot make enough contact with combustible vapors to cause the effective oxidation thereof for the purposes of the invention

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to execute. This inference is clear by removing the Catalyst bed established from the combustion zone of an otherwise operable instrument. In one such cases will be too little oxidation in terms of the measured differential of oxygen content between that of the inlet feed gas stream and that of the gaseous effluent containing the products of oxidation. However, if the catalyst is in the If the combustion zone is present, combustible materials become gasified when the aqueous dispersion is injected more effectively, if not fully, oxidized by oxygen held in the catalyst bed.

Since under this hypothesis the required oxygen is supplied by that held in the catalyst bed, likely reflects the initial gaseous effluent from the combustion zone immediately after injection of the sample to be analyzed showed no noticeable decrease in the oxygen content. It doesn't happen until that continued flow of the feed gas stream which sweeps the gasified combustible materials and their oxidation products through the system, τοη oxygen

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is bare, as a result of the supplementation of oxygen, which is kept under steady state conditions by the catalyst bed, that a pronounced decrease occurs in the oxygen content in the gaseous effluent from the combustion zone. If one accepts this explanation, it can be seen that for the best results of the invention can be achieved with a catalyst characterized by "the ability to give off oxygen and then quickly recover oxygen."

Aqueous dispersions of combustible materials are easily passed into the combustion zone by any means injected by various means.

A suitable injection means is a syringe, such as it is shown in FIG. Another injection uses gas pressure as the source of injection force. A preferred method is to use a small liquid Dropping sample into a vertically oriented combustion zone as shown in FIG.

A number of devices for the quantitative determination of the oxygen content of gas flows are known. , Preferred for use in the present invention are detectors that have a high sensitivity to low concentrations of gaseous oxygen. ;

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A solober detector is the electrolytic oxygen detection cell τοη Hersch, as it is from the US patent Hr. 2 805 191 originates. The Hersoh cell is most useful in that it provides a quick response generated with high accuracy or reproducibility. In general, however, there are some oxygen detectors useful, the τοη about 10 to 10,000 parts per million Measure oxygen as a dilution phase in a gas flow.

So that the useful life of the Herschtype oxygen detector is extended and its effect is ererbeesert, it is desirable to scrub the effluent gas stream in order to free it from COp and other acidic gases. this is conveniently carried out by bubbling the effluent gas through an alkali metal hydroxy bath which is enclosed in a gas scrubber.

A further illustration of the invention relates to FIG. 2, oil an automated total oxygen demand apparatus for the analyst ¹ clay aqueous dispersions. In this embodiment a mixed gas supply of nitrogen and oxygen was supplied from a gas cylinder 40 which was equipped with a pressure regulating valve 42. The connection of the gas

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The cylinder with the combustion tube 55 was the gas line. In this line there was a rotameter 47 to measure the gas flow rate. The gas line 45 for the gas line 44 was tapped just in front of the rotameter 47. This diverted a small amount of the mixed gas to the sample injector 50, a Beckmann model LG-4 liquid injection valve was used as an actual injector. The degree of flow in line 44 was controlled by valve 48 and measured by bubble flow meter 49. The sample injector 50 was actuated by air pressure applied intermittently through lines 51 and 52. The sample injection device 50 was equipped with a continuous utrom the wäsLeri _fc en Lispereion to be analyzed through line 5 & gespt-eat. The unused part of the flow was discharged through line 59. The * -jy, -, enäung the air pressure v, ur:, e Ouich a time-controlled electromagnet ceti.tiges pneumati. practice; Valve 53 performed.

Lie injection of the i. robe ..ur £ e by a stainless steel irrigation needle 57 outside light through line 44 geech & ii'er.eri GaSv-jerk the trobe

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, in the combustion tube 55 through the injection T-piece 56 dropped.

In the combustion tube 55, welohes a Quarzrobr was, there was a catalyst bed of a Quarzwoll- ■ - cram 60 and this plug a bed of platinum ^one I gaz.ekugeln 61. The bed of Platingaaekugeln 61 sat n geg *

; a slight narrowing 63 in the wall of the combustion tube ^ * i 55.1 The bottom of the combustion pipe 55 was duroh united Ball verb charge 65 connected to an outflow gas line 70. The pipe carried the gas flowing out of the pipe, combustion zone 66 in, the electric furnace 67 to a j Gas scrubber 74, the carbon dioxide from the outflowing 'j Gas by weight 25% aqueous potassium hydroxide 75 S

distant. This washer gave moistened and carbonated f Dioxide-free gas to an electrolytic oxygen j detector 78 through gas line 76.

The oxygen detector 78 was close to the teaching

by Herscb in U.S. Patent No. 2,805,191.

In particular, a lead foil 81 was round in an inert one!

Plastic core 80 of 2.54 centimeters wrapped in a durometer. The film 81 was bedeokt by a spongy membrane 82 \ ^v in the form of a water-swellable Äthylzellulosefilmes.

The silver wire 84 was wrapped around the membrane

and the connection in an obr 85 ^ esetet, which about 1/4 was full with 25 tiger aqueous potassium hydroxide 75 by weight. Connecting wires 91 and 92 related to this the lead foil 81 and the silver wire 84 were attached, carried the signal output of the ropes · the wires 91 and 92 were electrically connected to an amplifying graphic recorder 100.

Using the foregoing apparatus, a feed gas stream such as nitrogen containing 200 parts per million by volume of oxygen was contemplated. The gas entered combustion tube 55 at a constant rate of about 120 cubic centimeters per minute. Some gas flowed through line 44 and thence through lens injector 50 at the rate of approximately one bubble per second. The oven temperature was brought to 900 ° C. laughing. the gas flow rates and temperatures had stabilized, a 19 microliter sample of the aqueous dispersion became. which should be analyzed is injected into the combustion zone. This was carried out with the illustrated electromagnetically controlled pneumatic liquid injection device b0. As the gas flow continued after the robe injection, the oxygen detector responded and the recorder showed a decrease in the oxygen content of the

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Exhaust gas combustion zone. Lies was recorded as a deviation 102 from baseline 101. The amplitude dieeer deviation was determined and using previously generated Mchungsdaten that were obtained under the same be triebsDedindungen, it was found from the amplitude that they represented the theoretical Totalsauers'toffbedarf of the analyzed sample of the aqueous flammable Mattriales.

. -In the above way, a number of aqueous dispersions of combustible materials are analyzed for their total oxygen requirement.

I’ll love these analyzes compared to theirs theoretical energy requirements are given below. The theoretical oxygen demand was calculated according to the equation:

^! »Wj ^{+ in +} f ⁺ § - §> ° 2> ^nCÜ 2 ⁺ » ^{ϊ0 +} ^ ² Ψ

Tabel \

Experiment solved burning- observed calculated Ko. Ur '. Materiel (2) mg / 1 Γ.υ.Ρ. (Ι) mg / 1 l.0..L ,, (1)

1 _n zi lyltic acid 9i - *, o 100.0

I Ii 'r.ol 9S, o 100, ö

1 rri :: thyltn-alycol 38.3 100.0

4 ^ ii-Jopylen-Glyooi 99.4 '100.0

i: Broi:; a-n, ri, diethyl-analin 97.6 100.0

id? r, i7 10j, c

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Book 13ο. Ivisperaiertü distillery observed Calculated available material (2) wji T.ü.Dd) mg / 1 TQDd)

7 KaMum sulfate

8 NaMum phosphate

9 "potassium chloride

10 Chloreise-noxyäul

11 chlorine iron

12 phosphoric acid

(1)! .Lilli ^ ranim p.ro liter of iotalsaueittof! 'Needs

(2) Tests V-12 actually did not contain any combustible material. The results line up. iirksamkeit of the process, v, ^r hen iiaterialien with no TOD vorhanöen

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Claims (10)

Claims 1. Procedure for measuring the oxygen demand of an aqueous dispersion of combustible material, accomplished by the following procedure &eobritt; (1) The continuous flow of an inert gas flow of inert gas, which contains at least 1Ö and up to 10,000 parts per millipn of volume of hydrogen at a constant level through an enclosed combustion zone at a combustion-supporting temperature in the range of 60Ö ^@ to! 200 ° C and in the combustion zone i the flow of the Bescbiokungsstromes through a combustion-unp supporting catalyst bed, (2) the flow of effluent gas from the combustion zone into a permanent quantitative detector for gaseous oxygen for production an electrical signal, which varies with the oxygen content of the outflowing gas and ' (3) While continuing the previous procedure, never inject a small amount of the aqueous Dispersion of combustible material into the combustion zone upstream of the catalyst bed, whereby an electrical signal in relation to the total oxygen demand of the aqueous dispersion is generated. 009821/0821. _ or BADORiQIhAL 2. The method according to claim 1, characterized by measuring the amplitude of the maximum deviation of the signal kit generated by the oxygen detector in step 3 with reference to that generated in step 2. 3. The method according to claim 1, characterized by calibration or calibration of the difference between the electrical signal generated in step 2 and the maximum deviation of that generated in step 3 to total oxygen demand to determine the aqueous dispersion. 4. The method according to any one of claims 1 - 3 _f, characterized in that the combustion- supporting temperature in the range τοη 800 ° to about 1000 ° C lie & t. 5. The method according to any one of claims 1-4, characterized in that the dilute aqueous .Dispersion contains less than 1 l · by weight of combustible material. 6. The method according to any one of claims 1-4, characterized in that that the degree of flow of the charge gas flow ranges from 50 and up to 250 cubic centimeters (stp) per kinute. 7. Apparatus for determining the oxygen requirement of a aqueous dispersion of combustible material, marked by a device (2) for feeding a 009821/0821 " ²⁷ " BATH ORIGINAL i) escbiokung ^r sg ^r asstromes of an inert uaset, which contains at least 10 upwards to 10,000 leile per iuillion by volume oxygen, a combustion line (1b) with an inlet and a üuslaß, which combustion line has an heating zone (13), in the Lieh a combustion-supporting, porous Katalysatorpett (16) uefindet, wherein the Vei-brennungslcitung a sample injection means (17) for achnelien injection of a small!.! close of the aqueous dispersion of combustible material in the üeizzone can absorb and one device (9) for heating the Burn hazard. to 'a Tfeniperatur im Beroioh from 600 to 1200 ° C in a ü'ärmeauiiti.ui / ühvtrhülle with the combustion line, also tint, ^ inrici iun _b (i.1) for the quantitative discovery of the amount of oxygen in one Ga ^ Lt rom, Aotoi the device for the supply of a feed gas stream, the combustion line and the device for the quantitative discovery of the oxygen with suitable 3 flow lines for the formation of a gas draft in the an _b 6 (_. fc. u ι. · ^: i. order are connected. 8. ii.ppera1 i: acL claim 7, characterized in that aas \ vtrtitniiungsunterstützende porous catalyst bed (16) - 28 - 009821/0828 BATH ORIGINAL fills the cross-section of the combustion pipe, however a sample expansion zone on the upstream side of the catalyst bed exposes an iTobentin injector (17) in operative communication with the combustion line for injecting a small predetermined one Lienge an aqueous dispersion of one analyzing combustible Iviateriales in the heating zone (15). the combustion pipe to the.-tromauf Windwärts side of the catalyst betted is present, as well as a permanent detector (21) is lower for the quantitative detection ^ oxygen quantities in a gas stream, wherein said i ^ imichtung for supplying a Leschickungsgasstromet, _b the 7erbrennungsleitun and the device for the quantitative Discovery of oxygen are connected with suitable fluid lines for the formation of a gas flue in the order given. 9. Apparatus according to claim Y and 8, characterized in that that the catalyst bed (16) consists of platinum and is at least 5 cm long. characterized, 10. Apparatus according to any one of claims 7-9, / that the same a graphic recorder (26) which is electrically connected to the line (21) for the detection of oxygen connected is. 009821 / 082g Blank page