DE3501002A1 - MONITORING DEVICE - Google Patents

Description

, COAL INDUSTRY (PATENTS) LIMITED, Hobart House, Grosvenor Place, jLondon SW1X 7AE, UK

monitoring device

The invention relates to improvements in monitoring devices, in particular it concerns improvements in the passive monitoring of organic vapors present in an atmosphere.

It is known to take atmospheric samples in the workplace in order to Detect contamination. The two basic systems are the active and the passive system; the active system draws air into an apparatus using a pump and checks it then either continuously, for example by means of infrared ^

Analysis, or the impurity is absorbed on a material t / adsorbed which advertising treated by a known period of time * the can, in order to release the impurities for the purpose of analysis. A passive system works without the use of a pump and generally works by merging the atmosphere and

the accumulation of the contamination on a suitable material. Commercial devices are on the market for both systems, but in the opinion of the applicant these are not capable of producing atmospheres with very small amounts of organic vapors in the order of magnitude of ppm χ 10. For example be

the Niosh carbon absorption tubes with Si pi η personal sample pump in in the USA, Great Britain and in other countries on a large scale as an exact method for the detection of benzene or benzene, toluene, among others or toluene and dimethyl benzene or xylene (BTX) are used in the workplace. However, it is not recommended to use the Niosh system at concentrations to be used below 0.1 ppm. When the carbon tubes are replaced by vapor adsorption tubes, which are a polymer Use adsorbent, namely Tenax GC, so will the lower one

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_(The limit value of the detection has been improved to about 3 10 ppm, but the requirement of constant monitoring of each sample point excludes the simultaneous monitoring of a large area, such as the environment in a coking plant.

Passive monitors or dosimeters depend on the diffusion or spread individual organic vapors and the physical construction of the monitor. There are several passive ones Monitors on the market at relatively low cost have the possibility of application in large numbers without the requirement of labor intensive open surveillance. The majority of these monitors use a carbon impregnated element or carbon granules and are unable to get very low values for various reasons including the often high level of pollution of the adsorbent accurately measure air pollution. There are also commercial passive monitors that use a polymeric adsorbent, and though this brings an improved performance compared to the coal types

_3 gen, these still do not show an accuracy in the ppm χ range on.

The present invention provides a novel passive monitor, who is able to measure concentrations of organic vapors in the atmosphere in the range of ppm χ 10 "with accuracy, and the monitor comprises an adsorbent load and an adsorbent holder with a first sample chamber and a second desorption chamber, which are connected to one another and arranged so that the adsorbent charge can be positioned in the first chamber, in which it is exposed to the atmosphere and adsorbs organic contaminants and without at the end of the predetermined sample time Handling is transferred to the second chamber where the adsorbent can be treated to remove the organic contaminants to desorb so that they can be removed from the holder for analysis, the first chamber having a larger cross-sectional area as the second chamber.

The preferred adsorbent is a polymeric adsorbent, but can

be any adsorbent which is able to »add organic vapors at the required concentrations in the air adsorb and desorb substantially all of the adsorbed vapors without treatment with a liquid solvent would be required.

The desorption is preferably carried out by means of heating, and using a stream of pure gas to remove the desorbed material from the holder for analysis. The method of analysis is not critical provided it provides sufficient accuracy at the concentrations in question, and it is conveniently a chromatographic one Procedure.

The adsorbent holder expediently comprises two cylinders, with one has a relatively large diameter-to-length ratio and forms the first chamber and the other a relatively small one Has diameter-to-length ratio and the second chamber forms. Preferably, a simple inversion or rotation causes the adsorbent under the influence of gravity from a Chamber flows into the other, and a simple coaxial connection of the cylinders makes for straightforward and effective construction. The adsorbent holder must allow access to the atmosphere to be measured and still prevent the loss of adsorbent; in the same way, the adsorbent must not be lost when the desorption takes place. Appropriately this is Adsorbent held in place by means of a fine grid, which does not hinder the diffusion of the atmosphere to the adsorbent.

The adsorbent holder is preferably provided with a connecting device provided, via which a gas supply line can be connected, as well as with a connection device via which the the desorbed contaminant carrying gas can flow to an analyzer.

In the following the invention with reference to the drawing explained below. In dor drawing jreiqon:

₆ 3S01002

Figure 1 shows a monitor according to the invention in a cross-sectional view, “Who is currently taking atmospheric samples, and

FIG. 2 shows the monitor according to FIG. 1 in a cross-sectional view, with contaminants are being desorbed.

Referring to the drawings, it can be seen that the monitor comprises a holder body 1 with a first sample chamber 2 and a second desorption chamber 3. In FIG. 1, the end of the second chamber is closed by means of a screwed-in closure piece 4, and a charge 5 of 0.2 g of 250 to 500 μm "Tenax GC", a polymeric adsorbent, is held by a fine metallic lattice disk 6 with 150 [im openings worn. Another such washer 7 is carried at the open end of the chamber 2 on a removable nut 8 to prevent any particulate matter from entering the interior; if desired, a permeable membrane made of PTFE can be used in addition to the disk 7 or in place of it.

In the operating state of desorption, as shown in FIG is, the holder body is turned upside down and the adsorbent charge flows down to fill the desorbing chamber 3. The locking piece 4 is removed and replaced by a nut 9 which has a gas connection 10 to enable the mixture from gas and contamination is fed to a (not shown) gas chromatograph. The mother 8 is through a mother 11 replaced with a gas inlet 12.

In use, the monitor, as shown in Figure 1, on a desired location. The atmosphere contacts the relatively large surface area of that exposed on disc 6 Adsorbent and contaminants consisting of organic vapors are adsorbed. At the end of the preselected exposure time, for example after 8 hours, a closed nut (not shown) is used to close the open end of the monitor and the monitor can then be transported and used for a

to be retained for later analysis. When analyzing the in Fi-'gur 2 used, and the narrow desorption chamber 3, which carries the adsorbent, is inserted into a heating block, dry oxygen is passed through and the desorbed Impurities are analyzed in a gas chromatograph.

Initial tests have shown that the uptake of organic vapors as contaminants is approximately 15 times greater than that with commercially available passive monitor systems (Perkin Elmer Vapor Adsorption Tubes, which are in the passive operating mode be used). In addition to very precise evidence of very highly diluted organic substances, the monitor according to the invention can be used to detect very much higher concentrations of impurities for example in the ppm range for shorter exposure times of the order of minutes.

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Claims (6)

PA \ EN \ ANWAUt = BRQSE; +; R4RTNER European Patent Attorneys - Mandatalres en Brevets Europeens - rjgelassorte VertWer CiSiTn European Patent Office D-eO23 Munich-Pullach, Wiener Straße 2; Telephone (0 89) 7 93 30 71: Telex 5 212147 bros d; Cables: "Patentibus" Munich D. MRL BROSE Dipl.Hng., Dipl.-Wirtsch.-Ing. MCHASi RESCH Dipl.-Phys. COAL INDUSTRY (PATENTS) LIMITED, Hobart House, Grosvenor Place, London SW1X 7AE, UK Dale ^ * Jal1Uar ae 're-au PATENT CLAIMS 1. Passive monitor that is capable of measuring accuracy detect concentrations of organic vapors in an atmosphere in the range of ppm χ 10, characterized in that that this monitor contains a charge (5) of adsorbent and an adsorbent holder with a first Sample chamber (2) having a second desorption chamber (3) is connected so that the adsorbent charge (5) can be positioned in the first chamber (2) in which it is exposed to the atmosphere is exposed and adsorbs any organic contaminants and that at the end of a predetermined sampling time it can be transferred to the second chamber (3) without handling, in the adsorbent can be treated to desorb organic contaminants so that they can be removed from the holder for analysis be removed, and that the first chamber has a larger cross-sectional area than the second chamber. 2. Monitor according to claim 1, characterized in that the adsorbent (5) is a polymeric adsorbent. Telephone agreements only become binding upon written confirmation. 3. Monitor according to claim 1 or 2, characterized in that the • the first chamber (2) and the second chamber (3) each have a cylinder is, the first chamber (2) having a relatively large diameter-to-length ratio and the second chamber (3) has a relatively small diameter-to-length ratio. 4. Monitor according to one of the preceding claims, characterized in that that turning over from one position to another position is sufficient to cause the adsorbent (5) flows under the action of gravity from one chamber (2) to the other chamber (3) * 5. Monitor according to one of the preceding claims, characterized in that that a connecting device (11, 12) is provided via which a gas supply line can be connected, as well as a connection device (9, 10) via which a gas carrying desorbed contamination can flow out of the holder for the purpose of analysis.
20th 6. Method for passive monitoring of contamination in the form organic vapors in an atmosphere, characterized by the use of an apparatus according to any one of the preceding claims. 25th 30th 35