DE1598361C3 - Method for determining the inorganic carbon content of a liquid - Google Patents

Description

The invention relates to a method for determining the inorganic content of a liquid Carbon.

In French patent 1,378,323, there is no for the features indicated above Element protection is claimed, rather only the entirety of the features specified above is used a) to c) claimed.

The method according to the invention is practical all kinds of organic and aqueous liquids can be used, but will be most favorable used in aqueous dispersions of carbonaceous substances. In the context of the present Invention, the measured inorganic carbon content consists only of that in the liquid as Bicarbonate or carbonate or dissolved carbon dioxide.

At the temperature of the heating zone, the volatile components of the liquid are largely without Oxidation evaporates. All dissolved carbon dioxide is released into the carrier gas stream. In addition, non-liquid inorganic carbonates are deposited on the opposite side due to the evaporation Carbonate reactive body deposited. at

3 4

The elevated temperature of the heating zone allows this to be permeable to the flow of the carrier gas carbonates easily in contact with the acidic or from time to time volatilized liquid per surface of the carbonate-reactive body without causing excessive return carbon dioxide. The gases formed are to allow pressure. The heating zone reacting to carbonate due to the continuous flow of the body capable of movement is made up of substances that do not absorb the carrier gas in an analyzer for quantitative carbon dioxide.
Determination of the carbon dioxide content of a gas flushed A further advantageous embodiment of the invention stream. Preferably, the analyzer is characterized in that the carbon consists of such a device which gives an electrical dioxide content by comparing the respective received signal, for example an electrical voltage indicated measured values with the implementation of the display, the strength of which is proportional to the Concentration on aqueous systems with known transmission of carbon dioxide in the gases is. hold on to inorganic carbon under

Values obtained according to an advantageous embodiment of the comparable operating conditions

according to the method, the temperature is determined in.

the heating zone is kept between 100 and 250 ° C. A further advantageous embodiment of the invention, the heating zone is preferably kept at a temperature of 150 to 200 ° C as a liquid. At higher temperatures, an aqueous dispersion with up to 500 parts per million doors shows a tendency to interferences due to parts of inorganic carbon being used, from oxygen-containing organic substances, which is finally a further advantageous embodiment at relatively low temperatures with the formation of the Invention characterized in that decompose as of carbon dioxide. In any case, the carrier gas is air, which is maintained with a constant flow heating zone at a temperature below the flow rate of 1 to 4 bed volumes each at which significant combustion or minute is fed.
Decomposition with regard to the organic constituents The carrier gas flow is practically caused by carbon of the analysis sample. 25 dioxide free. Best results are obtained when

According to a further advantageous embodiment, the carrier gas flow does not exceed 50 parts per million,

of the invention is the reactive to carbonate based on weight, contains of carbon dioxide,

capable body from a coated with phosphoric acid- Otherwise it can be made of any material

The same solid, which is present in individual particles, is normally at room temperature

forms. 30 gaseous, inert to carbon dioxide and

Usually it is not reactive with carbonate. The preferred gases are

capable bodies of particulate solids are made up of nitrogen, argon, helium and purified

formed with an acidic coating, this solid- air. If desired, even pure oxygen can be used

substances must be chemically inert to acids. can be used provided that the heating zone

The acids or acidic substances that are used for forming at temperatures in the lower range of the coating include the given temperature range,
strong, non-oxidizing acids. To achieve a special and preferred analyzer, the best results consist of practically non-infrared analyzer of the non-dispersible protic acids. The preferred types of acid put on a carbon dioxide analyzer include the 40 different oxyacids.

Phosphorus, such as orthophosphoric acid, hexametaphos- The voltage signaling of this carbon dioxide anaphoric acid or pyrophosphoric acid. Sulfuric acid, which is sufficiently diluted, converts the recorder into readings that have been converted into the in order not to be oxidizing. The organic, inorganic carbon concentrations in the acids, which can be transferred to the analyzed sample at sufficiently low temperatures or which can be used to avoid decomposition, can be read directly from this. The conversion will include terephthalic acid and benzenesulfonic acid. achieved by comparing the signal reading against the acids can be produced on quartz splinters, quartz wool, using standard calibration curves, which are produced by anic acid-resistant, particulate, thermally hardened analysis of known samples under comparable operating plastics, silica and acid-inert metal cutting conditions.
In a preferred embodiment, in the case of which the analytical values for the material which is reactive toward carbon are obtained as a curve, bodies with an acidic surface are applied in order to produce the particulate material. whose amplitude is a concentration of the carbon

Another advantageous embodiment of the invention oxide concentration in the gaseous product is manure is characterized by the fact that the carrier gas is the actual inorganic carbon content

flow with constant flow rate of the examined liquid in relation to the

is passed through the heating cable and the opposite maximum amplitude or the peak of the curve,

Gas-permeable bodies via carbonate with previous calibration of such readings

sig and the entire cross-section of the heating zone yield the direct readings of the summit. This ensures that the entire 60 naten the inorganic carbon concentration of the

Carbonate and bicarbonate with the compared to Carbo- examined liquid.

nat reactive body comes into contact, in the preferred practical version whereby the measurement of the total carbon dioxide decreases the body which is reactive towards carbonate will. per the entire cross-section of the line within

The carbonate-reactive body 65 of the heating zone, and the liquid to be analyzed?

however, only part of the cross-section of the test is quickly transferred to the heating zone in a practical

Occupy the heating zone. If it covers the entire transverse table to the direction of the carrier gas flow through the

cut, this body must have sufficient conduction injected or injected in a parallel direction.

dust so that it reacts to the carbonate Body hits. Alternatively, the carbonate-reactive body in the Heating zone attached, and a liquid sample that has been sprayed or dripped into any part of the conduit is allowed into the interior of the heating zone and to the carbonate reactive body. After injecting the liquid to be analyzed results When they hit the reactive body, they quickly evaporate into theirs Components. Through the decomposition of all bicarbonate or Carbonate is caused to be released as carbon dioxide into the carrier stream.

As the gas stream continues to pass through the heating zone, the exhausted steam becomes inclusive of the evolved carbon dioxide usually to a temperature at or below that the device then used to determine the carbon dioxide is cooled. Normally the gaseous reaction product is cooled to about normal room temperature. if If the gases cool down, condensates can form. This condensate is collected in a trap, from which the accumulated liquid can be withdrawn from time to time. Although a uniform Cooling of the gas product and thus a constant separation of the condensate from the cooled If gases are favorable for optimal operation, good results can also be achieved if only with a minimal cooling of the gas product is carried out, as is done, for. B. occurs if the gases in the Analyzer can be passed through an air-cooled tube. It is also possible to carry out the procedure in such a way that that no condensate forms when the analyzer is operated at an elevated temperature above the Dew point of the gas flow formed is operated.

Typical apparatus for performing the analytical procedure described above is explained in more detail with reference to the drawing. In

F i g. 1 is given a schematic representation of a complete device that is used to carry out the analysis of liquid systems for their inorganic carbon content according to the invention suitable is;

F i g. 2 shows the general design of an explanatory, carbon dioxide-releasing heating cable, which contains the essential, carbonate-reactive body with an acidic surface.

The in F i g. The device shown in FIG. 1 consists of the basic components of a carrier gas supply device 2, devices for the injection or injection of a liquid sample 3, heating devices 4, inside which a heating line 6 is attached, and a carbon dioxide determination device 7. Die Heating line 6 contains a carbonate-reactive body 20 with an acidic surface Release of carbon dioxide.

In particular, in the preferred embodiment illustrated, there is a regulated carrier gas supply device 2, which consists of an air pump 10 and an air cleaner 11 for removal consists of carbon dioxide. Through these device components is practically of carbon dioxide free air is pressed into the carrier gas flow device 8, which in the illustrated embodiment from a series arrangement of a pressure carrier 12, valve 13, flow meter 14 and Check valve 15 consists. These components of the device are operational in the specified Sequence connected with suitable connecting gas lines 16. Then to the check valve 15, the gas flow is guided into the inlet end of the heating line 6. This end of the line is set up so that they receive the sample injection device 3, for example the syringe 23 shown

ίο can.

The heating line 6 has a heating zone 21, which consists of the part of the line that is inside the heating device 4 is formed. In the illustration, the heating device 4 consists of an electric furnace

24. This oven is operated by means of a variable force return 26 regulated. The temperature readings within the heating device 4 are measured by means of a Pyrometer 27 received.

The gaseous products from the heating zone 21 of the

so heating line 6 are passed through cooling devices 5, soft in the illustrated preferred embodiment from a water-cooled cooler 28 exists in series with condensate removal devices 9 and optionally a gas filter 30 connected is. The shown condensate removal device 9 consists of a U-shaped condensate trap 29, which is provided with a ground plug 31 for the removal of liquid from time to time. Of the Cooler 28 cooled with water takes up the exhaust gases directly from the heating line 6 and guides them directly to the cond. 29.

The components through which the gas flow occurs are connected by pipe connections 16, so that there is a gas flow.

The in F i g. 1 shown carbon dioxide determination device consists of an electrically connected Arrangement of a non-dispersing, carbon dioxide sensitive infrared analyzer 35, which supplies a variable voltage signal, which is duplicated by means of a multiplier 38 for low voltage. The amplified electric Signal is then fed to a continuous graphic recorder 39 which is a Represents curve 41 on a continuous strip of paper 42. The amplitude or the area below of curve 41 is a function of the carbon dioxide concentration in the determination cell 36 of the Infrared analyzer 35. After passing through the determination cell 36, the gas product is sent to the Atmosphere discharged through a vent 37. Regulations in the determination device 7 are the Gain control 43 and the registration voltage range control 44.

In FIG. 2 are the heating cable 6 and the opposite Carbonate reactive bodies 20 are shown in detail. The heating cable 6 consists of two separate ones Parts consisting of an inlet 64 and a cylindrical quartz tube 61. Within the Attached to the inlet 64, there is an injection pipe 62, which is used to accommodate injection or injection devices, for example in the form of a syringe, is suitable. The injection pipe 62 is located aligned coaxially with tube 61. The inlet 64 is ground to the cylindrical tube 61 through a Glass connection 64 connected. The opposite is located within the cylinder tube 61 Carbonate reactive body 20 with acidic surface, which consists of a coated with phosphoric acid

7 8

Packs of quartz chips or chips 67 are practically non-adsorbing for carbon dioxide,

is, which is covered with quartz wool 68 on the back. Within the heating zone it is necessary that

are based. Each end of the composite heating the building materials against the carrier gas at the

Line 6 is to be connected to the following to release the carbon dioxide on the opposite

and previous device components applied via carbonate-reactive bodies

suitable. Inlet and outlet consist of small pipe- elevated temperatures are inert. To such

shaped connections 69 and 70. Materials include, for example, melted

Although certain preferred embodiments are silica and glazed ceramics,
The above-described device inventory In the specific embodiment of the advantages have been explained, numerous alternatives are available in the device according to FIG. 1 was given for the skilled person. For example, rubber pipes are used to form the connection between the carrier gas supply device 2 and only lines 16. A pressure regulator was necessary to provide a limited flow of gas 12 for the gas flow and needle valve 13 pre-regulated at a controlled flow rate. They see. A combination of a precision sapphire sphere knowledge of the actual flow velocity 15 within a flow measuring tube served as flow is not necessary as long as the gas flow rate meter 14. Furthermore, a non-return valve was present, which could be regulated to a constant velocity. The heating cable 6 was equipped with an elekden can. Advantageously, however, the Strö- Irish muffle furnace 24, which has a voltage of ming speed, can be set to a certain value of 120 volts and a maximum power consumption of. For this purpose, each grain can be operated 20 700 watts, heated. The force control bination of mechanical devices for supply 26 consisted of a transformer with variable voltage and regulation of a flowing gas stream.
Position of the one shown. The heating cable 6 was as in FIG. 2 shown on-

With regard to the heating device 4, any front can be built. The tube 61 was made of molten silicon

Direction, which is made for the formation of a regulated heating 25 cium dioxide. It had an inside

zens within a moderately increased temperature meter of 1.27 cm and a length of 40 cm. A

rich, for example from 100 to 250 ° C suitable gas inlet 64 was in the form of a T-glass tube.

is to be used. In the same way, the the, where the crossbar of the T is ground glass

Sample injection devices 3 by a mechanical link 63 at one end for connection to the

Apparatus are formed which had fused silica tube 61 for feeding 30 and a

measured aliquots of a liquid and to the syringe needle about 5.2 cm long made of stainless steel

Injection of the same under force on the opposite steel at the opposite end of the cross bracket

Carbonate reactive body in the heating line 6 as a receiving device for the sample injector

suitable is. For example, the introduction of the device was attached in the form of a syringe. if

to be analyzed liquid sample in the heating line 35 the components of the heating line 6 assembled

The syringe needle was coaxial with the

acts that are directed towards the delivery of regulated quantities along the longitudinal axis of the pipe 61. The trunk of the

the spray mass are suitable. T-piece of glass resulted in an approach 69 for the connection

Cooling and removal of the obtained with a rubber pipe 16 of 0.48 cm Condensates from the carrier gas stream are desired - if necessary, the heating line 6 with the carrier gas supply device procedural steps to be applied, since account 2 was connected. A hypodermic syringe was made densat no disturbances in all quantita- used as injection device 3. Within the tive carbon dioxide determination method results. Ge tube 61 and against a narrowing notch 66 however, if desired, the cooling of the gas about 24 cm from the inlet end thereof may be a gas product from the heating cable to the usually 45 more permeable, more reactive towards carbonate desired extent can be achieved by attaching this body 20 of about 11 cm in length. This z. B. by the described, cooled with water consisted of quartz fragments 67 from 1.7 to 3.3 mm Cooler 28 are performed. On the other hand, air and quartz wool 68. The fabrics were in the heat-cooled Cooler, the connecting tube 6 in a simple manner by lightly tamping quartz wool extension pipe between the heating line 6 and the ana- 50 against the narrowing bracket 66 with a glass lysator Can also be effective on this stab and adding enough quartz fragments up Purpose to be used. brought into a pack of 11 cm in length. the

If not necessary, it will be.

it is preferred to use a gas filter 30, which together with 10 cm ^{3 of} an 85% phosphoric acid through

borrowed particles entrained with the gas product before the pipe was poured.

its introduction into the cell of determination of the Ana After assembling the individual parts, the lysators withhold. Infrared carbon dioxide detectors heating line 6 in the electric muffle furnace 24 so are preferred, but any analytical preparation can be used so that the tip of the syringe needle 62 is directed which was used to display the amount of in the rade outside the heating zone 21 of the oven 24, The carbon dioxide present in the gas product, however, in such a position that after the injection desired sensitivity and specificity is suitable, the total amount of the aqueous sample within be used. of the heating zone 21 on the carbonate-reactive

Since only low temperatures are used, active body 20 was deposited,

A wide variety of building materials can be used in the die formed when a test sample is injected

Gas flow train can be applied. In addition, 65 gas products were passed through a gas duct,

it is advantageous if at least in the guide the elements from a row arrangement of a water

for the gaseous product then to the heat-cooled cooler 28, a U-shaped water trap 29

line such building materials are used, which consisted and a gas filter 30, which a filter

element contained 10 to 13 microns. The water trap 29 was collected from time to time for withdrawal Water set up by means of a stopcock 31. The connecting gas lines 16 passed from a rubber tube of 0.68 cm.

The carbon dioxide determination device 7 used with the above device consisted of an infrared analyzer connected to a 13.3 cm determination cell 36 which was used to analyze Carbon dioxide was set, was equipped. The determination cell 36 was at a temperature of 45 ° C to prevent the formation of condensate, which affects the accuracy of the analysis result would disturb. The indication of the analyzer 35 was provided by electrical lines 53 and 54 fed to a low voltage amplifier 38. Subsequently, the reinforced indication of the analyzer to a graphic recorder 39 through electrical lines 51 and 52. The recorder 39 was set to operate by the voltage registration range control 44 Range set from 0 to 5 mV. The gain control 43 of the amplifier 38 was set to a specific Level adjusted so that the desired sensitivity of the recording device 39 revealed.

To carry out the analytical procedure described, it is necessary to select a suitable sample size. This can be in the size of 1 microliter up to 100 ml. The smaller the sample, the longer the durability of the body reactive to carbonate. A preferred sample size is in the range of 5 to 40 microliters. When an analysis is started, the heating cable 4 is switched on and on Temperature in the range between 100 and 250 ° C, preferably from 150 to 200 ° C brought. Within of the preferred temperature range, the sample becomes rapidly without decomposition of the main ones organic substances volatilized. The carrier gas and the flow rate are also turned on adjusted to the desired constant amount, so that a size between 0.5 and 10, preferably 1 and 4 bed volumes of the carrier gas per minute. The bed volume is the denotes empty space in the heating zone of the heating pipe. Depending on the size of the bed volume the carrier gas flow rate during operation can be from 10 to 80 ecm per minute. It should be noted that for best results the gas flow rate is somewhat

ίο depend on the bed volume. For example result in the case of a small bed volume with high gas flow rates or large bed volumes too low gas flow velocities give rise to analytical error results. if also integration calculations to correlate the registered signal with the actual inorganic signal Carbon content of the analyzed sample can be made, consists of the most convenient and quickest Evaluation of the registered signal in the assessment of only the amplitude (peak height) of the registered Curve. To get a well-defined amplitude or sharp peaks, bed volumes are required and gas flow rate are adjusted so that curves with well-defined amplitudes are formed within a relatively short period of time, for example from 3 to 50 seconds. To this The purpose is through a few trials using varying gas flow rates with a given heating line 6 and a reactive body, the choice of one is easy allows effective gas flow rate. Among the liquids to which the inventive The method and apparatus applicable include both aqueous solutions and dispersions of substances that contain inorganic carbon. In addition, organic liquid solutions can be used and dispersions are analyzed for their inorganic carbon content. Though best Results are obtained if the sample does not contain more than 500 ppm inorganic carbon, it is possible to analyze liquids with much larger amounts of carbon in this form.

The results of these tests are summarized in Table I below.

Table I.

link

concentration
(g / I)

disturbance

175 ° C

200 ° C

225 ° C

250 ⁰ C

urea

Oxalic acid

Calcium acetate
Formic acid

Methanol

Butyric acid ..
o-phthalic acid
Benzoic acid.
dl-malic acid
Malonic acid ..
Citric acid
Chloroform ..
Acetic acid ...
Picric acid ...
Tartronic acid.
Cane sugar ..

0.5000
1.0506
1.4682
0.4306
0.2670
0.7342
1.3844
1.0177
1.1174
1.0406
1.6010
0.9949
0.5000
2.1214
1.0000
2.8525

no
no
no
no
no
no
no
no
no
no
no
no
no
no

Yes
no

slightly

Yes

no
no
no
no
no
no

slightly
slightly
slightly

no
no
no

Yes

Yes

Yes

Yes

no
no
no
no
no
no

Yes

Yes

Yes

no
no
no

Yes

Yes

Yes

Yes

no
no
no
no
no
no

Yes

Yes

Yes

no
no
no

Yes

Yes

Using the apparatus specifically described above, a number of experiments were carried out to demonstrate the importance of the analytical method and its valuable application. In one series of tests, the heating zone was maintained at temperatures of 175, 200, 225 and 250 ° C prior to successive determinations of a given composition. The bed volume of the heating cable was 50 cm ³ . Quartz fragments coated with phosphoric acid and quartz wool were used to produce a carbonate-reactive body of 10 cm length within the heating cable. Virtually carbon dioxide-free air was used as the carrier gas with a flow rate of about 70 cm ³ per minute. For the specified bed volume, only a very small change in the registration value was found at a flow rate of between 40 and 200 cm ³ per minute.

Various substances were examined for possible interferences in the analytical process. One Group of organic compounds was chosen from the point of view of their suitability for formation of carbon dioxide either by direct decomposition or by acid hydrolysis. A sufficient one Amount of each of these substances was dissolved in water so that if one ended completely If decomposition had occurred, 100 mg carbonate carbon per liter would have been obtained.

From the above values it follows that the presence of certain substances in the to be analyzed Liquid will interfere with the achievement of the exact level of organic carbon can, d. that is, the result is a higher value than the actual carbonate-carbon value. In spite of this, the process is also effective at the higher temperatures at which faults occur Valuable because of the fact that interfering substances are relatively rare.

In further attempts, other acidic coatings were used in place of the phosphoric acid coatings used with favorable results. The other acids included 42% aqueous phosphoric acid and 50% aqueous sulfuric acid.

Further attempts using aqueous solutions of acetic acid and sodium carbonate as well

ίο Mixtures, hereby using the performed above procedure. Solutions were made containing 100 mg of total carbon contained per liter. The results of these experiments in the analytical test described above

»5 driving are summarized in the following table:

Tabel the end
Na ₂ COa II Found not-
volatile ¹ ) Theoretical 50 Carbon content , 51 20 attempt Carbon content 50 (mg / 1) 50.5 solution (mg / 1) 0 Carbonate 100 No. from HOAc 100 50 no ₃ < ^A 50 50 ²⁵ A 50 no B. 100 100 C. 0

') Obtained by total carbon analysis according to Removal of carbon dioxide by acidification and blowing out.

The analytical method according to the invention has been successful in analyzing a number of aqueous Waste liquids, brines from underground formations, and a wide variety of liquids Applied to petroleum products.

1 sheet of drawings

Claims (8)

Patent claims: 1. Method for determining the inorganic carbon content of a liquid characterized by the combination of the following features: a) a carrier gas stream practically free of carbon dioxide is passed through a heating zone, which contains a carbonate-reactive body with an acidic surface and at a temperature above 100 ° C and below that temperature is kept at the organic Decompose components of the liquid; b) a small amount of the liquid to be analyzed is put into the heating zone injected onto the carbonate reactive body; c) the carbon dioxide content of the gas mixture formed in the heating zone is determined in a downstream Analyzer determined. 2. The method according to claim 1, characterized in that the temperature in the heating zone is kept between 100 and 250 ° C. 3. The method according to claim 2, characterized in that the carbonate reactive Body made from a solid, coated with phosphoric acid, in individual particles is formed. 4. The method according to claim 1 or 2, characterized in that the temperature in the heating zone 150 to 200 ° C. 5. The method according to claim 1 or 2, characterized in that the carrier gas flow with a constant Flow rate is passed through the heating cable and the opposite carbonate reactive body is gas-permeable and occupies the entire cross-section of the heating zone. 6. The method according to claim 1, characterized in that the carbon dioxide content by a comparison of the measured values obtained in each case with those obtained when the method was carried out aqueous systems with known contents of inorganic carbon below comparable Operating conditions obtained values is determined. 7. The method according to claim 6, characterized in that the liquid is an aqueous one Dispersion containing up to 500 parts per million parts of inorganic carbon is used. 8. The method according to claim 6, characterized in that the carrier gas is air, which with is fed at a constant flow rate of 1 to 4 bed volumes per minute, is used. a method for determining the organic carbon content of aqueous dispersions is described. It is z. B. acidified the system to be analyzed and blown it with an inert gas. The acidification converts any carbonate that may be present into carbon dioxide, and the Bubbles removes the carbon dioxide from the system. The blown system is then on its Total carbon content analyzed. This method ίο is subject to an error in that part of in volatile organic carbon present in the system is removed when blowing. The through the Organic carbon removed by blowing is therefore withdrawn from its intended use. Although the method described above is useful to some extent, it follows that the error introduced in the determination due to the presence of volatile organic substances a need for an improved method of determining the inorganic carbon in liquids, like aqueous dispersions. The object of the invention is to provide an analytical method in which the content a liquid of inorganic carbon with an accuracy of plus or minus a few parts can be determined per million parts. This object is achieved by the invention. The invention therefore relates to a method to determine the inorganic carbon content of a liquid caused by the union the following features: a) A carrier gas stream practically free of carbon dioxide is passed through a heating zone, which contains a body which is reactive towards carbonate and has an acidic surface a temperature above 100 ° C and below that temperature is maintained at the organic components of the liquid decompose; b) a small certain amount of the liquid to be analyzed is in the heating zone on the opposite Injected carbonate reactive body; c) the carbon dioxide content of the gas mixture formed in the heating zone is determined in a downstream Analyzer determined.