USE OF A GAS DEVICE AND METHOD FOR MEASURING DICYAN IN THE PRESENCE OF HYDROGEN CYAN

Description

[0001] The present invention relates to the use of a gas measuring device for measuring dicyan in the presence of hydrogen cyanide and a method for measuring dicyan in the presence of hydrogen cyanide. STATE OF THE ART

[0002] Fumigation, or disinfection by fumigation, is a common method in agriculture for killing germs and bacteria on products that are later used and sold in the food industry.

[0003] In the past, fumigation was frequently performed with methyl bromide. Due to its strong carcinogenic effects, the use of methyl bromide for fumigation is already prohibited in some countries. Dicyan has proven to be an effective alternative.

[0004] Since dicyan often occurs together with hydrogen cyanide (HCN) during fumigation, there is a need to measure dicyan in the presence of hydrogen cyanide.

[0005] Semiconductor sensors are generally used to measure dicyan, but these have limited sensitivity and stability and are therefore not suitable or only conditionally suitable for detecting an exceedance of a workplace exposure limit of 5 ppm.

[0006] Dicyan can also be measured using a mass spectrometer. Such a method is disclosed in US 6001383 A. However, since mass spectrometers are cumbersome and complicated to use, they are also unsuitable or only conditionally suitable for detecting an exceedance of an occupational exposure limit of 5 ppm.

[0007] JP 2008 076 235 A describes a method for measuring dicyan in which hydrogen sulfides are vaporized from a sample in order to finally measure the sample using a hydrogen cyanide gas sensor.

[0008] US 2018328873 A1 discloses a sensor for detecting nitrogen trifluoride, which is catalytically split into nitrogen oxides. REVELATION OF THE INVENTION

[0009] Based on the prior art described above, the invention aims to provide a method for measuring dicyan that at least partially avoids these disadvantages. Therefore, it is an object of the present invention to provide a reliable and simple method for detecting when a permissible occupational exposure limit for dicyan is exceeded.

[0010] The foregoing problem is solved by the subject matter of the respective independent claims. Further features and details of the invention will become apparent from the dependent claims, the description, and the drawings. Features and details described in connection with the gas measuring device naturally also apply in connection with the method according to the invention, and vice versa, so that the disclosure of the individual aspects of the invention always makes, or can make, reciprocal references.

[0011] As a first step towards solving the problem, the use of a gas analyzer for measuring dicyan in the presence of hydrogen cyanide is presented. The gas analyzer comprises a measuring chamber, a heating element, and an electrochemical sensor. The measuring chamber contains a sample of dicyan. The heating element is configured to thermally decompose the dicyan in the sample into its fission products. The sensor is configured to detect the fission products of dicyan obtained through thermal decomposition.

[0012] The gas measuring device used according to the invention is configured to reliably and selectively determine the concentration of dicyan in the sample, even in the presence of hydrogen cyanide, with high sensitivity, in particular a sensitivity that allows dicyan to be reliably detected from a concentration of 1 ppm.

[0013] To measure the concentration of dicyan in the sample, the gas measuring device includes a main electrochemical sensor, which is used in combination with a heating element, such as a heating wire or a heating plate.

[0014] Since an electrochemical sensor cannot directly detect or measure dicyan, the invention provides that the respective dicyan molecules present in the sample are thermally split by means of the heating element. In particular, the heating element carries out a pyrolysis of the dicyan molecules. The thermal splitting produces decomposition products, such as nitrogen oxides or hydrogen cyanide, which can be detected by the main electrochemical sensor provided according to the invention.

[0015] It can be provided that the temperature set by the heating element for the thermal splitting of the respective dicyano molecules is selected depending on the reaction conditions present in the chamber of the gas measuring device. In particular, the temperature can be set depending on the catalysts present in the chamber. Alternatively or additionally, it is conceivable that the temperature is set depending on other reaction conditions, such as the relative humidity present in the chamber.

[0016] The heating element provided according to the invention can be freely arranged in the chamber of the presented gas measuring device. This means that the heating element and the sensor can be arranged separately from each other. Alternatively, a combined or integrated arrangement of the heating element and sensor in a single or combined component is also possible. Furthermore, the heating element can be configured to at least partially decompose dicyanin contained in the sample into nitrogen oxides, and the sensor can be configured to detect nitrogen oxides.

[0017] Since nitrogen oxides, such as nitric oxide or nitrogen dioxide, can be detected easily and accurately using an electrochemical sensor, setting the heating element to a temperature range for splitting dicyan into nitrogen oxides, i.e., nitric oxide and / or nitrogen dioxide, is particularly advantageous for operating the gas measuring device.

[0018] The gas detector may also include a processing unit configured to calculate the concentration of hydrogen cyanide in the sample based on sensor readings. Alternatively, the gas detector may include a processing unit and the sensor configured to detect hydrogen cyanide. The processing unit may be configured to calculate the concentration of hydrogen cyanide in the sample based on sensor readings taken during a first time interval before thermal decomposition by the heating element, and the concentration of dicyanide in the sample based on sensor readings taken during a second time interval after thermal decomposition by the heating element.

[0019] Using a processing unit, such as a computer or any other type of programmable circuit, the concentration of dicyan in a given sample can be determined from the measurements taken by the gas detector's sensor, using, for example, a predefined coefficient. To determine or update the coefficient, the sensor can be calibrated using a calibration sample.

[0020] The sensor can be sensitive to hydrogen cyanide. To avoid interaction between hydrogen cyanide already present in a sample and hydrogen cyanide generated by a thermal cracking process, the concentration of hydrogen cyanide already present in the sample is determined before the thermal cracking process. Accordingly, the difference between measurements taken before and after the thermal cracking process allows conclusions to be drawn about the concentration of dicyanide that was cracked into hydrogen cyanide, and thus about the initial concentration of hydrogen cyanide present in the sample.

[0021] The gas measuring device has a surface that acts as a catalyst in the thermal decomposition of dicyan.

[0022] By means of a catalyst or a catalytic surface, the temperature that the heating element provided according to the invention must supply for a thermal cracking process of dicyan molecules can be reduced. Furthermore, by a suitable selection of a material and a corresponding surface, in combination with a suitable selection of the temperature set by the heating element, the respective cracking products generated by the cracking process can be influenced, so that, for example, nitrogen oxides or hydrogen cyanides are formed by the cracking process.

[0023] The surface comprises at least one material selected from the following list consisting of: ruthenium and rhodium.

[0024] Depending on the choice of material(s) for the surface provided according to the invention, more or less thermal energy is required for thermal cracking. Accordingly, depending on the choice of material or material combination, a suitably appropriate heating element can be selected, preferably one with minimal energy consumption.

[0025] The material or material combination of the surface provided according to the invention can be provided directly or supported on aluminum oxide, zirconium oxide, silicon oxide, cerium oxide or ceramic.

[0026] It may also be provided that the sensor and the heating element are combined into an integrated component and that the heating element is configured to heat a surface of the component.

[0027] A compact and energy-efficient measuring unit can be provided by means of an integrated component, which could be, for example, a pellistor with a pellistor bead. The outer surface of the pellistor bead can consist of a catalytic material that reduces the amount of energy required for a thermal cracking process.

[0028] It may also be provided that the heating element or a combination of heating element and surface is configured to split dicyan contained in the sample into nitrogen oxide or hydrogen cyanide.

[0029] Through the combined action of a heating element and a catalytic surface, the fission product generated during a thermal cracking process can be precisely controlled. In particular, the catalytic surface area, or the energy input provided by the heating element, can be dimensioned such that nitrogen oxides or hydrogen cyanides are produced.

[0030] It may also be provided that the measuring chamber includes a filter unit that is permeable to dicyan and impermeable to hydrogen cyanide.

[0031] To minimize the influence of hydrogen cyanide on the detection of dicyan, the presented gas detector can include a filter that prevents hydrogen cyanide from entering the chamber of the gas detector. Alternatively, the filter unit can be a membrane, such as a PTFE membrane, which is permeable to hydrogen cyanide and dicyan and which is configured to minimize the influence of flow on detection by the sensor provided according to the invention.

[0032] It may also be provided that the gas measuring device includes a pump for introducing the sample into the measuring chamber.

[0033] The presented gas measuring device can be based on the principle of diffusion as a passive gas measuring device or include a pump by means of which a sample can be actively taken from an environment and introduced into the chamber of the gas measuring device.

[0034] It may also be provided that the gas measuring device includes a secondary sensor, with the sensor configured to detect nitrogen oxides and the secondary sensor configured to detect hydrogen cyanide.

[0035] Using two sensors, namely one sensor for detecting nitrogen oxides and a secondary sensor for detecting hydrogen cyanide, the concentrations of both gases, i.e., dicyan and hydrogen cyanide, can be determined.

[0036] In a second aspect, the presented invention relates to a method for measuring dicyan in the presence of hydrogen cyanide, wherein the method comprises a provision step for providing a possible embodiment of the presented gas measuring device, a feeding step for feeding the sample into the measuring chamber of the gas measuring device, a cracking step for thermally cracking dicyan contained in the sample by means of the heating element of the gas measuring device, and a detection step for detecting cracking products of the dicyan generated by the cracking step by means of the sensor of the gas measuring device.

[0037] The presented method is particularly suitable for operating the presented gas measuring device.

[0038] The procedure may include a further detection step for hydrogen cyanide. Hydrogen cyanide detection can be used in addition to the detection of fission products to determine the concentration of hydrogen cyanide in the sample, alongside information on the concentration of dicyan. Alternatively, hydrogen cyanide detection can be performed solely to detect fission products.

[0039] It may also be provided that the detection of hydrogen cyanide by means of the sensor is carried out in a first detection step before the thermal splitting and in a second detection step after the thermal splitting. PREFERRED EXAMPLES

[0040] Further measures improving the invention will result from the following description of some embodiments of the invention, which are illustrated in the figures.

[0041] They each show schematically: Figure 1 is a schematic representation of a possible embodiment of the gas measuring device according to the invention, Figure 2 is a schematic representation of a possible embodiment of the sensor provided according to the invention, Figure 3 is a schematic representation of a sequence of the method according to the invention.

[0042] In Fig. 1 A gas measuring device 100 is shown. The gas measuring device 100 comprises a measuring chamber 101, a heating element 103 and an electrochemical sensor 105.

[0043] To measure the concentration of dicyan in the presence of hydrogen cyanide, a sample located in the measuring chamber 101 is heated by means of the heating element 103 and, as a result, thermally decomposed. The decomposition products formed by the thermal decomposition are detected by the sensor 105. Based on the measured values ​​obtained by the sensor 105, the concentration of dicyan in the sample can be determined, for example, using an optional computing unit 107.

[0044] Alternatively, the measured values ​​obtained by sensor 105 can be used directly to display the concentration of dicyan in the sample. For this purpose, sensor 105 can be connected, for example, to an output unit 109, such as a display and / or a speaker.

[0045] It may be provided that the computing unit 107 is configured to issue a warning via the output unit 109 if a concentration of dicyan or hydrogen cyanide detected in a particular sample exceeds a predetermined threshold.

[0046] The Gas Detector 100 is a mobile or portable gas detector with a power source, so that the gas detector can be used "in the field".

[0047] In order to minimize the energy requirement for thermal cracking of dicyan molecules in the sample or to control or regulate a cracking process into selected cracking products, such as nitrogen oxides or hydrogen cyanide, the catalytic surface 111 is arranged in the chamber 101, in particular on the heating element 103.

[0048] In Fig. 2A sensor 200 is shown. The sensor 200 is an integrated component and comprises a measuring electrode 201, a heating element 203, and the catalytic surface 205 in the form of a pellistor bead, which surrounds the heating element 203 or is designed as an integral part of the heating element 203. Accordingly, heat energy generated by the heating element 203 is transferred to the catalytic surface 205.

[0049] As soon as a dicyan molecule comes into contact with the catalytic surface 205, the dicyan molecule is thermally split, for example into nitrogen dioxide and carbon dioxide, due to the heat energy introduced into the catalytic surface 205 and due to the catalytic properties of the catalytic surface 205.

[0050] The Sensor 200 is specifically configured for the detection of nitrogen dioxide and accordingly determines a measured value depending on the measured concentration of nitrogen dioxide. The determined measured value is proportional to the concentration of dicyan and allows an assessment of whether the dicyan concentration in an environment is above or below a predefined threshold.

[0051] In Fig. 3A method 300 is described. The method 300 comprises a provision step 301 for providing a possible embodiment of the presented gas measuring device, a feeding step 303 for feeding the sample into the measuring chamber of the gas measuring device, a cracking step for thermally cracking dicyan in the sample using the heating element of the gas measuring device, and a detection step 305 for detecting cracking products of the dicyan generated by the cracking step using the sensor of the gas measuring device. REFERENCE MARK LIST

[0052] 100 Gas detector 101 Measuring chamber 103 Heating element 105 Sensor 107 Computing unit 109 Output unit 111 Catalytic surface 200 Sensor 201 Measuring electrode 203 Heating element 205 Catalytic surface 300 Procedure 301 Preparation step 303 Feeding step 305 Detection step

Claims

1. Use of a gas measuring device (100) for measuring cyanogen in the presence of hydrogen cyanide, wherein the gas measuring device (100) comprises: - a measuring chamber (101), - a heating element (103, 203), - an electrochemical sensor (105, 200), wherein the measuring chamber (101) receives a sample containing cyanogen, wherein the heating element (103) thermally decomposes the cyanogen contained in the sample into decomposition products, wherein the sensor (105, 200) detects the decomposition products of the cyanogen that are obtained by the thermal decomposition, wherein the gas measuring device (100) has a surface (111, 205) that acts as a catalyst in a process of thermal decomposition of cyanogen and wherein the surface (111, 205) comprises at least one material from the following list of materials: ruthenium and rhodium.

2. Use (100) according to claim 1, wherein the heating element (103, 203) decomposes cyanogen contained in the sample at least partially into nitrogen oxides, and the sensor (105, 200) detects the nitrogen oxides.

3. Use according to claim 1 or 2, wherein the gas measuring device (100) comprises a computing unit (107) configured to calculate a concentration of hydrogen cyanide contained in the sample on the basis of measured values determined by the sensor (105, 200), or the gas measuring device (100) comprises a computing unit (107) and the sensor (105, 200) is configured to detect hydrogen cyanide, wherein the computing unit (107) is configured to calculate a concentration of hydrogen cyanide contained in the sample on the basis of measured values determined by means of the sensor (105, 200) during a first time period before a process of thermal decomposition by the heating element (103 203) and to calculate a concentration of cyanogen contained in the sample on the basis of measured values determined by means of the sensor (105, 200) during a second time period after a process of thermal decomposition by the heating element (103, 203).

4. Use according to any of the preceding claims, wherein the sensor (105, 200) and the heating element (103, 203) are combined to form an integrated component and the heating element (103, 203) heats a surface of the component.

5. Use according to any of the preceding claims, wherein the heating element (103, 203) or a combination of the heating element (103, 203) and the surface (111, 205) decomposes cyanogen contained in the sample into nitrogen oxide or into hydrogen cyanide.

6. Use according to any of the preceding claims, wherein the measuring chamber (101) comprises a filter unit that is permeable to cyanogen and impermeable to hydrogen cyanide.

7. Use according to any of the preceding claims, wherein the gas measuring device (100) comprises a pump for introducing a sample into the measuring chamber (101).

8. Use according to any of the preceding claims, wherein the sensor (200) or the heating element (103, 203) comprises a pellistor bead.

9. Use according to any of the preceding claims, wherein the gas measuring device (100) comprises an auxiliary sensor, wherein the sensor (105, 200) detects nitrogen oxides and the auxiliary sensor detects hydrogen cyanide.

10. Method (300) for measuring cyanogen in the presence of hydrogen cyanide, wherein the method comprises: - providing (301) a gas measuring device (100), wherein the gas measuring device (100) has a measuring chamber (101), a heating element (103, 203), an electrochemical sensor (105, 200) and a surface (111, 205) that acts as a catalyst in a process of thermal decomposition of cyanogen and comprises at least one material from the following list of materials: ruthenium and rhodium, - feeding (303) a sample comprising cyanogen and hydrogen cyanide into the measuring chamber (101) of the gas measuring device (100), - thermally decomposing (303) cyanogen present in the sample by means of the heating element (103, 203) of the gas measuring device (100), - detecting (305), by means of the sensor (105, 200) of the gas measuring device (100), decomposition products of the cyanogen that are produced by the thermal decomposition.

11. Method (300) according to claim 10, wherein the method (300) furthermore comprises: - detecting hydrogen cyanide.

12. Method (300) according to claim 11, wherein the step of detecting hydrogen cyanide by means of the sensor (105, 200) is carried out in a first sensing step chronologically before the thermal decomposition (303) and in a second sensing step chronologically after the thermal decomposition (303).

13. Method according to any of claims 10 to 12, wherein the sensor (200) or the heating element (103, 203) comprises a pellistor bead.

14. Method according to any of claims 11 to 13, wherein the gas measuring device (100) comprises an auxiliary sensor, wherein the sensor (105, 200) detects nitrogen oxides and the auxiliary sensor detects hydrogen cyanide.

15. Method according to any of claims 11 to 14, wherein the gas measuring device (100) comprises a computing unit (107) that calculates a concentration of hydrogen cyanide contained in the sample on the basis of measured values determined by the sensor (105, 200), or the gas measuring device (100) comprises a computing unit (107) and the sensor (105, 200) detects hydrogen cyanide, wherein the computing unit (107) calculates a concentration of hydrogen cyanide contained in the sample on the basis of measured values determined by means of the sensor (105, 200) during a first time period before a process of thermal decomposition by the heating element (103 203) and calculates a concentration of cyanogen contained in the sample on the basis of measured values determined by means of the sensor (105, 200) during a second time period after a process of thermal decomposition by the heating element (103, 203).