DE1598361B2 - 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 the French patent 1 378 323 a method for determining the inorganic Described carbon content of aqueous dispersions, in which the difference between the total carbon content and the organic carbon content of a particular system is determined. It is z. B. acidified the system to be analyzed and blow through with an inert gas. Any carbonate that may be present is formed by the acidification is converted into carbon dioxide, and the blowing removes the carbon dioxide from the system. That the blown system is then analyzed for its total carbon content. This procedure is subject to a failure in that some volatile organic carbon present in the system is removed when blowing. The organic carbon removed by the blowout therefore becomes registered as inorganic carbon.

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.

No element protection is claimed for the features specified above, rather only claims all of the above features a) to c).

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 inorganic carbon under reduced pressure.

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 another advantageous design at relatively low temperatures with formation of 2 ° of the invention characterized in that decompose as of carbon dioxide. In any event, the carrier gas is air, which is maintained with a constant Strops heating zone at a temperature below the flow rate of 1 to 4 bed volumes per ^ * at which significant combustion or minute is applied.
; Decomposition with regard to the organic constituents The carrier gas flow is practically caused by carbon of the analysis sample. 25 dioxide free. The best results are obtained when ■ According to a further advantageous embodiment, the carrier gas flow does not contain more than 50 parts per million, according to the invention, which is reactive to carbonate based on weight, of carbon dioxide. : Capable body made of a coated with phosphoric acid- Otherwise it can consist of any material, consisting of individual particles, which normally form at room temperature:. 30 gaseous, inert to carbon dioxide and pre-; Usually it is not reactive with carbonate. The preferred gases of operable particulate solids are nitrogen, argon, helium and purified; formed with an acidic coating, this solid- air. If desired, may even pure ^oxygen: materials must be chemically inert to acids. can be used provided that the heating zone; The acids or acidic substances that are used at temperatures in the lower range of the

When the coating is used, the given temperature range is maintained.

; strong, non-oxidizing acids. A special and preferred analyzer is made to achieve this

For best results, they consist of practically no- from an infrared analyzer of the non-dispersible

volatile protic acids. The preferred species that rely on a carbon dioxide analyzer

! Acids belong to the various oxyacids put by 4 °.

; Phosphorus, such as orthophosphoric acid, hexametaphos- The voltage signaling of this carbon dioxide

phosphoric acid or pyrophosphoric acid. The analyzer is also supported by suitable amplifiers and graphical

Sulfuric acid can be used, which is sufficiently diluted to transfer readings into the recorder

Jib was made so as not to be oxidative. Concentrations of organic inorganic carbon in the

"" Acids that can be converted to the sample being analyzed at sufficiently low temperatures or

Can be used to avoid decomposition, this can be read off directly. The conversion will

include terephthalic acid and benzenesulfonic acid. achieved by comparing the signal reading against

The acids can be applied to quartz splinters, quartz wool, via standard calibration curves, which are

^: acid-resistant, particulate, thermally hardened analysis of known samples under comparable operating

Plastics, silica and acid-inert metal cutting conditions are produced,

zel are applied to the particulate ma- In a preferred embodiment, in which

material for which the analytical values are obtained as a curve, which is reactive towards carbon,

To produce bodies with an acidic surface. 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 results in the direct readings of the summit ordi-

occupies. 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 embodiment whereby the measurement of the total carbon dioxide is taken, the body reactive to carbonate is promoted. per the entire cross-section of the line within the carbonate-reactive body 65 of the heating zone, and the liquid to be analyzed, but can also only occupy part of the cross-section of the keitsprobe will quickly enter the heating zone in a prak- heating zone. If it occupies the entire cross-section to the direction of the carrier gas flow through the cut, this body must be injected or injected with sufficient conduction in the 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 by hitting the reactive Body rapidly dissolves into its constituent parts. By decomposing everything bicarbonate or carbonate contained within the liquid is released as carbon dioxide in caused the carrier current.

As the gas stream continues to pass through the heating zone, the volatilized vapor 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. 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 shown there is a regulated carrier gas supply device 2 shown, which consists of an air pump 10 and an air cleaning device 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 control 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 furnace is regulated by means of a variable force control 26. The temperature readings inside the heating device 4 are obtained by means of a pyrometer 27.

The gaseous products from the heating zone 21 of the heating line 6 are passed through cooling devices 5, which in the illustrated preferred embodiment consists of 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-glass stopper 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 condensate trap 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. The carbon dioxide determination device shown in FIG. 1 consists of an electrically connected arrangement of a non-dispersing, carbon dioxide sensitive infrared analyzer 35 which supplies a variable voltage signal which is multiplied by means of a multiplier 38 for low voltage. The amplified electrical signal is then fed to a continuous graphic recorder 39 which plots a curve 41 on a continuous strip of paper f

42 represents. The amplitude or area under- ^ half of the 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 Amplifier gain control 43 and the registration voltage range control 44.

In FIG. 2 are the heating line 6 and the carbonate-reactive body 20 in detail shown. The heating line 6 consists of two separate parts, consisting of an inlet 64 and one cylindrical quartz tube 61 are made. Attached within inlet 64 is an injection tube 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 aligned coaxially with the pipe 61. The inlet 64 is connected to the cylindrical tube 61 by a ground glass joint 64. Within of the cylinder tube 61 is the carbonate-reactive body 20 with an acidic surface, that of one coated with phosphoric acid

7 8

Pack of quartz chips or chips 67 are practically non-adsorbent for carbon dioxide,

that with quartz wool 68 is on, the back is removed. Within the heating zone itself, 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, was used as flow is not necessary as long as the gas flow rate meter 14. Furthermore, a check valve was provided to regulate the flow rate to a constant speed. The heating cable 6 was equipped with an elekden can. Advantageously, however, the electrical muffle furnace 24, which has a voltage of measurement 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 a ground glass cover

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 kernel disturbances in all quantita- as injector 3 used. 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 used to withdraw the accumulated water from time to time by means of a stopcock 31 set up. The connecting gas lines 16 consisted of a 0.68 cm rubber tube.

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 led 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 span registration area controller 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 / l)

disturbance

175 ° C

200 ⁰ 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 liquid to be analyzed interferes with the achievement of the can give an exact value of organic carbon, d. that is, this results in a higher value than the actual carbonate carbon value. Nevertheless, the procedure is also used by the higher ones Temperatures at which disturbances occur are valuable due to the fact that disturbing 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 procedure described above are summarized in the following table:

Tabel the end
Na ₂ CO ₃ Π 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 A. 50 50 ²⁵ A 50 no B. 100 100 C. 0

^x ) Obtained by total carbon analysis after removal of carbon dioxide by acidification and purging.

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.