DE4111513A1 - Fluid contamination measurement - uses reaction chamber with carrier gas, to carry foreign matter to gas sensor - Google Patents

Abstract

To measure foreign matter in fluid, especially water, the fluid is brought into contact with a carrier gas in a reaction chamber (23) to bring the foreign matter at least partially into a gas phase. The presence of foreign matter in the gas mixt. is measured by a gas sensor (30) in the reaction chamber (23). The carrier gas is pref. introduced in the base area of the upright reaction chamber (23) where the water flows through. Sintered material (24) with fine pores, is at the base of the reaction chamber (23), and there is an outlet (25) for the water at the lower section of the chamber (23) connected to an outlet channel (26, 27) which follows an upward curve with its highest point below the level of the cover of the chamber (23). A cap (28) at the cover of the chamber (23) has a measurement channel (29) leading to a gas sensor (30), with heating for the measurement channel tube. The gas sensor (30) is within a heated housing. The reaction chamber (23) is held at a constant temp. within a temp. controlled housing (31). USE/ADVANTAGE - The system is used to monitor the presence of hydrocarbons and halogenated carbons in water to prevent environmental damage, and is also used to monitor communal and industrial waste water. The technique can detect very small concentrations of hazardous matter simply.

Description

The invention relates to a device for measuring Foreign substances in a liquid, especially water.

Due to the increasing pollution of rivers and Water through foreign substances, especially hydro substances and halogenated hydrocarbons, is one Measurement of environmentally harmful substances is urgently required. This also applies to the monitoring of municipal and indu urban wastewater.

The soiling to be recorded is usually organic pollution, namely mainly around hydrocarbons dissolved in water, ha logenated hydrocarbons and toxic decay products based on the soiling mentioned.

Problems arise with such surveillance Fact that even very little organic pollution tongues in the ppb and ppm range are reliably detected which must make high demands on the measuring technology poses.

Continuous measurement is an advantage here, so that there is constant surveillance and one on the one hand also very short-term contamination reliably be recorded and on the other hand very quickly Occurrence of contamination can be responded to.

Measuring methods are already known in which the Measurement by absorption and desorption of the samples with Using special filter media and subsequent photo metric or potentiometric evaluation leads. However, this disadvantageously requires ma  natural interventions and can only be done discontinuously carry out. Alternatively, Gaschro are sometimes also matographs used, the high sensitivity and Possess selectivity. However, the gas also allowed chromatography no continuous liquid transfer watch. In addition, the service expenditure is also here very high, especially due to the use an auxiliary gas (hydrogen).

A device for continuous measurement organi shear solvent in a liquid is from the DE 31 26 648 C2 known. There is a semiconductor gas sensor immersed directly in the liquid, but the through a liquid impermeable medium from the Liquid is separated. The liquid impermeable medium allows diffusion of the dissolved free Gases from the liquid to the semiconductor gas sensor, see above that its output signal is representative of the portion organic solvent in the liquid. These However, the device requires direct immersion of the gas sensor into the liquid with appropriate Sealing problems. In addition, with fluctuating rivers liquid mirrors require a position control of the sensor to ensure that this is always in the liquid is immersed but not completely in this is submerged. Also the requirements obviously the liquid impermeable, the gas permitting medium are proportionate high.

Furthermore, it is known from DE 32 21 063 C3, a Liquid by adding reagents for generation a chemical color reaction using a photo monitor metric measuring device. The reaction vessel is out there as a vertical cylinder forms the liquid to be monitored in the underside introduced. White into the reaction vessel  then supply lines through which the various Reagents can be initiated controlled. The be Known equipment requires somewhat higher constructive Effort and exact dosage. In addition, the liquid current flow interrupted during a respective measurement so that no completely continuous flows liquid monitoring is possible.

The invention has for its object a Vorrich device for measuring foreign substances in a liquid, especially water, to create a capture also very low concentrations of foreign matter at ver relatively simple structure allows.

This object is indicated with in claim 1 characteristics resolved.

Advantageous embodiments of the invention are in the Subclaims specified.

In the invention, the liquid is thus with a Carrier gas brought into contact so that in the rivers foreign matter at least partially into the Gas phase are transferred and deal with the carrier gas Mix. That from the carrier gas and the foreign gas compound gas mixture is by means of an alley sors measured. The gas sensor must therefore not in di be brought into direct contact with the liquid, so that no elaborate liquid shielding of the Sen sors is required. This simplifies the structure. The Liquid can flow with the carrier gas Liquid, be brought into contact so that a continuous liquid monitoring is available. Of course, it is also possible to measure solution to be carried out discontinuously if, for example only random samples are desired or the  Liquid flow is only discontinuous, such as with some waste water.

In an advantageous embodiment, the carrier gas in the Bottom area of the reaction chamber initiated so that the glass bubbles forming in the liquid rise above, which on the one hand creates a good mix effect and on the other hand that in the river liquid, especially gaseous foreign substances can diffuse effectively into the carrier gas bubbles nen.

It is advantageously located in the bottom area Reaction chamber with fine-pored frit. The frit does close contact of the carrier gas bubbles with the samples liquid, so that an effective transition of the dissolved Most foreign substances in the carrier gas and thus a white test degassing of the liquid is achieved. Also the contact time between carrier gas and fluid extended by the frit overall, so that the quantitative effect of violating the ge dissolved foreign substances in the gas phase.

It is beneficial to have the liquid drain in the bottom Arrange area of the reaction chamber so that safe it is made that only that liquid is pulled, which has passed through the reaction chamber and thus at least some of the foreign matter to be measured has given wisely.

To always have a certain liquid level in the Re The action line is to ensure the action chamber preferably with an upward manifold Mistake. The reaction chamber can therefore not be without desirably idle. It also works in the manifold each existing liquid as a gas seal, so that the foreign substances that have entered the gas phase are not  can escape through the drain, leading to measurement errors would lead.

By defining the manifold in such a way that its ma ximal height extension below the roof area of the Reaction chamber, it is automatically achieved that when the drain is open, there is automatically a flow liquid level in the reaction chamber, the is determined by the height of the manifold. In order to remains on the top of the liquid level Gas chamber in the reaction chamber, so that out Carrier mixture and foreign gas resulting gas mix in the simplest design directly in the roof range of the reaction chamber can be measured. It is but also possible, the gas sensor is not in the reaction mer roof area directly, but from this to let out a measuring line leading to the gas sensor leads. The spatial decoupling achieved in this way is between the reaction chamber and the gas sensor constructive design freedom increased. You can also the environmental conditions of the gas sensor with regard to Temperature, humidity and the like then targeted, regardless of those of the reaction chamber will.

The measuring line is preferably with a pipe heater provided so that the temperature of the sample gas to defi nated values is adjustable and / or condensation of the measuring gas on the measuring line wall prevents who that can.

In a preferred embodiment, the gas sensor is also in a heated sensor housing, so that its temperature can be adjusted to the desired values. This can cause temperature-related changes in the measurement signals, at the same foreign substance concentration, out  be switched. In addition, in the area of Gas sensor no signs of condensation.

To the vapor pressure in the reaction chamber essentially Chen constant, the reaction is preferred chamber kept at constant temperature. Hereby will ensure that the rate of transition of the Essentially exclude foreign substances in the gas phase Lich from the respective foreign substance concentration is true, so that clear, meaningful measurement get results.

The temperature of the reaction chamber can be in one ensure in a simple way that they are in one temperature-controlled housing is arranged. By the Other environmental influences can also be that could falsify the measurements.

An overflow vessel is preferably present, which from the liquid is flowing through. In the overflow vessel there is always an essentially constant Liquid supply volume from which the liquid can be removed and led to the reaction chamber. To automatically empty the overflow vessel to be able to, is preferably in the overflow vessel Float switch arranged which when the Liquid level below a lower limit Alarm signal there.

The conveyance of the liquid from the overflow vessel to the Re Action chamber is preferably a hose Line with pump, so that the Fördervo lumen can be regulated.

The accuracy and reproducibility of the measurement results nisse can be further increased by the fact that Liquid and the carrier gas in predetermined against  side flow rate ratio to the reaction chamber ge leads. The flow rates can be in each case can be set to constant values. But even then if variable flow rates, for example due to un different fluid seizures, who discontinued , it is nevertheless ensured that the mixing ratio nis always constant, so that the transfer rate the foreign matter in the carrier gas remains constant. The The measurement result will depend on the respective delivery rate essentially independent.

In a preferred embodiment, air is used as the carrier gas used, which is sucked in through a filter. In order to is not special for the device according to the invention l Carrier gas supply required, which is the simplicity and robustness of the structure promotes. In addition, he is device according to the invention universally everywhere there settable where liquid to monitor for foreign matter is.

To measure even relatively warm liquids an additional cooling device can be provided be about which the liquid is before it is introduced into the reaction chamber is cooled. So that the Set liquid to defined temperature values, so that reproducible measurement results are achieved.

The invention allows a very simple and yet effective measurement of foreign substances such as organi soiling, which is predominantly hydrocarbons dissolved in water, halogenated Koh Hydrogen or toxic decay products on the The basis of such contamination. Here, the Measuring components dissolved in water, such as per or Trichlorethylene, methylene chloride and others, as well non-halogenated hydrocarbons, in the gas phase transferred. In this case, as the carrier gas is dissolved  air is used. The invention also allows Detection of extremely low concentrations in ppb and ppm range. The operation of the invention Device can be classified as a phase exchange process be decorated.

The trace measurement of those transferred to the gas phase Foreign substances are advantageously carried out physically base, with the help of the gas sensor.

The invention is particularly useful in practice well suited and allowed in the context of environmental protection a continuous measurement of certain group and Sum parameters of foreign substances, especially organic solvents, in water. For example for drinking water treatment from bank filtrates short or long-term disturbances in the raw water, e.g. B. at or ganic pollution of the river water, in time recognized and appropriate steps taken. Even in the case of work accidents, e.g. B. tank leakage, Overflow of tank trucks and infiltration of pollutants a possible spreading in the soil can Groundwater can be noticed in time. this applies for both outpatient and inpatient facilities, e.g. B. groundwater investigations below industrial Plants in which organic solvents are processed be, or also when monitoring the groundwater below an airport site.

The device according to the invention can be "around the clock" operated and offers high availability at ge low maintenance. By specifying the specific components with sum and group parameters the foreign substances, especially organic ones Measure solvent very easily and yet precisely.

The invention is described below with reference to an embodiment Example with reference to the drawings nä described here. Show it:

Fig. 1 is a schematic representation of an embodiment of the device according to the Invention and

Fig. 2 shows a calibration curve.

In the exemplary embodiment shown in FIG. 1, the liquid to be measured, in particular water with foreign substances in the form of organic solvents or other components, is introduced into an overflow vessel 12 via an inlet line 10 with a shut-off or throttle valve 11 . The overflow vessel 12 is provided with an overflow 13 in its upper region, so that a liquid level in the overflow vessel 12 , which extends to the overflow 13 , is automatically established if there is sufficient fluid supply.

A level detector in the form of a float switch 14 is present in the overflow vessel 12 . If the liquid supply in the overflow container 12 is too low, the float switch closes and emits a signal, so that a fault message is generated if there is a lack of liquid.

Preferably, the liquid is continuously fed to the overflow container 12 so that continuous monitoring is achieved. However, it is also possible to only introduce liquid in batches into the overflow container, for example to carry out sample measurements.

From the overflow tank 12 , the liquid to be measured is drawn off via a line 15 which interacts with a metering unit in the form of a pump 16 .

By pump 16 , the amount of liquid conveyed via line 15 can be determined and regulated. The pump 16 is preferably formed as a peristaltic pump, but can also take other forms.

The pump 16 and part of the line 15 are accommodated in a housing 17 , which also encloses delivery components for the carrier gas, namely a control valve 18 with flow indicator and a metering unit in the form of a pump 19 , preferably a diaphragm pump. Any suitable gas can be used as the carrier gas. Preferably, however, due to the universal availability and simplicity, air is used as the carrier gas, which is sucked in via a filter 20 , preferably an activated carbon filter, and passed via a line 21 to the pump 19 .

The amount of the liquid quantity defined by the pump 16 from the overflow container 12 is removed in a fixed ratio to the carrier gas metering, ie to the carrier gas or air quantity conveyed by the pump 19 and the control valve 18 . The ge by the pump 16 promoted liquid is introduced via line 15 into a reaction chamber 23rd The reaction chamber 23 is preferably formed as a container standing on the right, which can be cylindrical and have a constant diameter. The line 15 opens into the upper half of the reaction chamber 23 .

The carrier gas, preferably air, conveyed by the pump 19 via the control valve 18 is also fed into the reaction chamber 23 via a line 22 . The feed point of the carrier gas into the reaction chamber 23 lies far below the entry point of the line 15 , preferably directly in the vicinity of the reaction chamber 23 .

Fine-pored frit 24 is located in the bottom space of the reaction chamber 23 . The carrier gas and the liquid come into contact in the fine-pored frit, and the foreign substances dissolved in the liquid, such as organic solvents, pass into the gas phase and rise upwards together with the carrier gas bubbles in the reaction chamber 23 through the liquid. The carrier gas is supplied so that it acts directly in the frit area, for which purpose the feed point of the carrier gas is preferably directly in the area of the frit 24 . For this purpose, the line 22 can be led into the interior of the reaction chamber 23 almost to the bottom thereof.

The liquid flows out of the reaction chamber 23 via an outlet 25 . The exit point of the outlet 25 from the reaction chamber 23 is in the bottom area, so that only liquid that has passed through the frit and has been degassed is removed. The drain 25 is connected to a curved section 26 which initially runs upwards and merges into a drain line 27 via a U-shaped bend, via which the liquid is discharged. The apex of the curved section 26 , ie the elbow, is below the roof area of the reaction chamber 23 , but in the upper half thereof, preferably at the level of the junction of the line 15 in the reaction chamber. Consequently, a permanent liquid level is reached in the reaction chamber 23 , which extends to the upper point of the elbow 26 .

In order to enable the reaction chamber to be emptied if necessary, it can be provided on the underside with a closable outlet via which the liquid and / or the frit 24 can be removed from the reaction chamber 23 .

In the upper region of the reaction chamber 23 , which serves as a stripper vessel, a cap 28 is placed, which prevents the gas mixture composed of carrier gas and foreign gas from escaping into the environment. At the top of the cap 28 , a measuring line 29 opens, which is hen with a built-in pipe heating for regulating the measuring line 29 at a constant temperature. The measuring line 29 leads the gas mixture to be measured to a gas sensor 30 , which is preferably designed as a semi-conductor gas sensor. The gas sensor 30 measures the impurity gas contained in the measurement gas, preferably on a physical basis.

The reaction chamber 23 with cap 28 and measuring line 29 and the gas sensor 30 are housed in a housing 31 which is provided with an outlet from the gas sensor 30 for the outlet of the measured gas. In order to keep the vapor pressure of the liquid sample with the foreign substances, such as the organic solvents, constant, the housing with the reaction chamber 23 and the built-in tube heating for the measuring line 29 are kept at a constant temperature. The temperature control is effected by a controller 32 . The controller 32 can also regulate the temperature of the housing 17 so that the carrier gas and liquid are regulated to suitable values, preferably the temperature value of the housing 31 , as soon as they enter the housing 31 . The previously coarsely filtered liquid preferably has a temperature of 20 ° C. in the inlet area. In order to be able to use at higher liquid temperatures, a cooler can also be provided to hold the liquid, e.g. B. cools to 20 ° C. The cooler can be arranged in the area of the inlet 10 or between the overflow tank 12 and the pump 16 .

The gas sensor 30 is arranged in an integrated housing, which serves as a small gas measuring space, and is thermostatted separately. The temperature of the gas sensor and the gas measuring chamber is preferably adjusted so that it is just above the gas temperature, for. B. 3 ° C above. This avoids condensation of the gas to be measured in the area of the gas sensor 30 .

The gas sensor 30 is connected via an electrical line 33 to an evaluation device 34 , which causes the electrical supply to the gas sensor 30 , if necessary, and evaluates the output signal generated by the latter, depending on the concentration. The evaluation device 34 is also connected via an electrical line 35 to the housing 17 and the components therein to be supplied with voltage to these components and / or information about the operating parameters such as the current delivery quantity, the temperature and the like for evaluation direction 34 .

The zero point and standard value are checked and corrected before the device is started up and also later at fixed time intervals. This can be done in the manner described in DE 22 60 088 C2. To set the zero point, the gas sensor 30 is flushed with zero air, while in the calibration, ie the standard value setting, a comparison solution is introduced via the line 15 into the reaction chamber 23 , while at the same time carrier gas is supplied.

The electronic evaluation device 34 can be provided with two limit contacts, the first of which responds when low concentrations are exceeded and triggers an alarm. The second, higher set limit contact triggers a system of sampling, with which the individual measuring components can be evaluated selectively and quantitatively immediately or later. The sensitivity of the measuring range is thus set with the help of these limit contacts so that no alarm is triggered at average values of the water balance of organic solvents. The alarm trigger therefore says that there is a malfunction above the normal water composition, such as when introducing organic toxins, such as. B. perchlorethylene, trichlorethylene, methylene chloride or decay products from the chemical industry may occur.

As long as the second limit contact is not reached, d. H. the concentration is below this value, the foreign substances, especially the organic ones Solvent, measured summarily and quantitatively. At increased measured value can be a selective measurement of a several individual components in a simple way Controlled using a gas chromatograph, for the duration of the excessive measured value.

With the help of another limit contact, the continuous liquid sample in a system of Sampling will be initiated to make them late subject it to a test again.

The combined and ver used in the invention simple measuring method brings considerable economic and service-friendly advantages, as the con timely alerting of the operating personnel as well as a precise definition the interference component or interference components is possible. The limitation of specific components by sum or Group parameters for continuous measurement means with the multitude of those occurring in water organic pollutants a useful solution and bie tet the advantage of a fast measurement value acquisition  is particularly important because accidents are often only briefly, but with relatively high concentrations, may occur. Such accidents are discontinuous Devices working with difficulty are difficult to grasp. Derar Interruptions mean especially when it comes to drinking water reprocessing poses a special risk, since the Mene raw water often from a mixture of bank filtrate and groundwater exists. Just like the river water over monitoring also requires wastewater measurement from the municipality oil and industrial wastewater treatment plants Monitoring. If the time and the concentration of pollution, as well as the differences differentiation of the individual pollutants is of interest, this information can be obtained from one of the inventors device triggered selective measurement be obtained to take appropriate countermeasures Eliminate the interference component as quickly as possible to be able to take. The device can also Groundwater monitoring, e.g. B. in work accidents and Leakage from fuel tanks or containers with organic solvents. Here you can the spread of the pollutant in the groundwater locally or limit. There is also a conti Nuclear monitoring of the groundwater under landfill possible to keep up to date on the condition of the seepage and To be groundwater oriented. Another one area is in the monitoring of wastewater Activated carbon filter systems, in which the water separator of the filter system draining condensate, the its limits are in the lower ppm range, before which Introduction into the clarifier on traces of solvent must be watched.

The invention thus provides a device which low effort and high availability at low Work costs and the measured values documented can hold. Here, very small con  record concentrations in the lower ppm and ppb range, however, it also detects higher concentrations ren. At the same time with the invention, a club fold measuring method created with the phase out exchange works and be carried out continuously can, the in the liquid, especially what this, dissolved gaseous pollutants in the gas phase transferred and quantitative with the help of a gas sensor be evaluated.

The accuracy of the measurement that can be carried out with the invention is illustrated by the curve shown in FIG. 2, which illustrates the calibration curve of tri chloroethane. Obviously, even extremely low concentrations of trichloroethane below 1 ppm lead to a clear fluctuation on the measuring scale. The concentration is plotted on the abscissa, while the ordinate represents the scale parts, ie the respective measurement range. The invention is preferably designed for continuous long-term monitoring of liquids for Ver impurities, but of course discontinuous operation, depending on the area of application, is possible, as is monitoring the concentration of desired substances, provided that they are carried by carrier gas from the liquid the gas phase can be transferred.

Claims (17)

1. Device for measuring foreign substances in a liquid, in particular water, characterized by a reaction chamber ( 23 ) in which the liquid is brought into contact with a carrier gas, the foreign substances being at least partially converted into the gas phase, and by a gas sensor ( 30 ) for measuring the gas mixture formed in the reaction chamber and composed of the carrier gas and the foreign substances which have passed into the gas phase. 2. Device according to claim 1, characterized in that the carrier gas is introduced in the bottom region of the preferably upright, through which the liquid flows reaction chamber ( 23 ). 3. Apparatus according to claim 1 or 2, characterized in that fine-pored frit ( 24 ) is introduced in the bottom region of the reaction chamber ( 23 ). 4. Device according to one of the preceding Ansprü surface, characterized in that an outlet ( 25 ) for the liquid speed is arranged in the lower region of the reaction chamber ( 23 ). 5. The device according to claim 4, characterized in that a device connected to the drain ( 25 ), drainage line ( 26 , 27 ) has an upwardly extending curved section. 6. The device according to claim 5, characterized in that the highest point of the curved section is below the roof area of the reaction chamber ( 23 ). 7. Device according to one of the preceding Ansprü surface, characterized in that in the roof area of the re action chamber ( 23 ) a cap ( 28 ) with a gas sensor ( 30 ) leading measuring line ( 29 ) is attached. 8. The device according to claim 7, characterized by a tube heating for the measuring line ( 29 ). 9. Device according to one of the preceding Ansprü surface, characterized in that the gas sensor ( 30 ) is housed in a heated sensor housing. 10. Device according to one of the preceding claims, characterized in that the reaction chamber ( 23 ) is kept at a constant temperature. 11. Device according to one of the preceding claims, characterized in that the reaction chamber ( 23 ) is arranged in a temperature-controlled housing ( 31 ). 12. Device according to one of the preceding claims, characterized by an overflow vessel ( 12 ) through which the liquid flows. 13. The apparatus according to claim 12, characterized in that a float scarf ter ( 14 ) is arranged in the overflow vessel ( 12 ). 14. The apparatus according to claim 12 or 13, characterized in that the overflow vessel ( 12 ) and the re action chamber ( 23 ) via a hose ( 15 ) with a pump ( 16 ) are connected to each other. 15. Device according to one of the preceding An sayings, characterized in that the flow rates of liquid and carrier gas in predetermined Relationship. 16. Device according to one of the preceding claims, characterized in that the carrier gas is air, which is sucked in via a filter ( 20 ), preferably an active carbon filter. 17. Device according to one of the preceding claims, characterized by a cooling device for cooling the liquid before introduction into the reaction chamber ( 23 ).