Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
  • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
  • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
  • G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
  • G01N21/03—Cuvette constructions
  • G01N21/05—Flow-through cuvettes
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
  • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/30—Controlling by gas-analysis apparatus
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
  • G01N21/03—Cuvette constructions
  • G01N2021/0346—Capillary cells; Microcells

Definitions

• the invention relates to an optical measuring cell for gas absorption method and a gas monitor.
• a known solution is to flush the cuvette with a gas from a reservoir, for example a compressed gas cylinder, which does not contain the gas component to be measured and also does not absorb in the wavelength range used.
• a gas from a reservoir for example a compressed gas cylinder
• nitrogen can be used here if ambient air is used as the measuring gas.
• conventional measuring cells generally have large volumes depending on the application, such as typically> 100 cm 3 to several liters, a multiple of the measuring cell volume of purge gas is required for each purge, which leads to a considerable gas consumption in continuously running or a large number of measuring operations.
• the invention is based on the object of generating a stable zero of an optical gas sensor system, for example fixed wavelengths and non-scanning system, to describe a measurement path which is independent of changes / contamination of the optical measurement setup, or of the measurement cuvette, and which is as small as possible Sample gas volume is excellent.
• At least one hollow fiber with typical diameters in the sub-millimeter range is used to measure the gas-dependent absorption.
• both the gas to be measured and the light used for the absorption measurement are guided into the open-end core of the hollow fiber.
• the coupling of the light takes place in the longitudinal direction of the hollow fiber: by the flat reflection angle occurring such good reflection properties are generated that the light can be performed even with heavily curved hollow fiber, in particular glass fiber, several meters without significant losses.
• hollow fibers With hollow fibers one achieves the particular advantage of a large absorption distance and thus a sensitive gas detection with a small measuring cell volume.
• One meter of a hollow fiber with 0.5 mm diameter, for example, has a volume of about 0.2 cm.
• purge gas are so few cm required.
• a 3-liter bottle of purge gas with a pressure of 200 bar is sufficient for a recurring measurement every 10 minutes and a gas consumption of approx. 1 cm of gas per flush for more than ten years to supply the measuring instrument with purge gas. This can be a self-sufficient
• Measurement setup can be realized, the without tracking of auxiliary media, e.g. for rinsing, during its lifespan.
• the structure then consists of the optical measuring cell 14 and the purge gas generator Bl, which in turn essentially consists of a gas pump 10 and a gas filter 11.
• the invention is based essentially on the combination of the use of a hollow fiber as optical measuring cell with her typical volume. This is dependent on the fiber length and is in the range of usually less than or equal learning 3 per meter fiber length, which reduced demands on the over many rinsing cycles summed refill amount of the required purge gas are provided.
• the requirements for the purge gas supply can be met with small-volume gas cylinders or purge gas generators, as described above.
• the figure shows a measuring cell with gas delivery A, which has an optical measuring cell 14 with a hollow fiber 1.
• the figure presents in detail an embodiment of the invention.
• the arrangement consists of the optical measuring cell 14, the sample gas delivery and the Spülgasusually, and a purge gas supply.
• the optical measuring cell comprises the hollow fiber 1 as an absorption measuring cell with the light source 2, the photo-detector 3 and the control and evaluation circuit 4th
• the sample gas delivery comprises the sample gas intake tube 5, depending on an optional small-pore particle filter 6 and after the hollow fiber 1, a valve 7 in front of the sample gas pump 9, and a Gas outlet.
• a valve 8 closes off the measuring cell with gas delivery A in the direction of the purge gas supply B.
• the purge gas supply may consist of a purge gas pressure bottle B2.
• a purge gas supply means of a purge gas generator Bl which generates a purge gas which contains no gas to be detected in a measurement.
• the purge gas generator Bl includes the gas pump 10 and the actual gas generator.
• the purge gas generator consists of a purge gas reservoir, for example a DruckgasfIaschel2 with the throttle 13 for adjusting the gas flow.
• Sample gas delivery pump 9 is switched off.
• the purge gas flows through the hollow fiber 1 and rinses the measurement gas residues back into the measurement gas atmosphere 15.
• an optical absorption measurement is performed, initially the zero measurement. Which is carried out on a gas volume filled with purge gas in the hollow fiber.
• the valve 8 is closed, the valve 7 is opened, the purge gas pump 10 is turned off and the sample gas pump 9 is put into operation. Now, the measurement gas flows through the hollow fiber 1 and an optical transmission measurement is performed. The ratio of transmission once with sample gas and once with purge gas (zero measurement) results in the gas-dependent transmission, independent of the fundamental transmission of the absorption path, of the hollow fiber.
• the process is analogous when the purge gas is provided from a compressed gas cylinder 12.
• sample gas and purge gas flow through the hollow fiber in the opposite direction.
• purge gas generators Examples of purge gas generators:
• the gas filter consists of a heated palladium membrane that is comparable to a Pd diffusion cell.
• the required pressure difference is provided by a gas pump.
• the filter is supplied with the contaminated hydrogen. Since only protons can diffuse through Pd, pure hydrogen results on the secondary side, which can be used as purge gas.
• an oxygen-ion pump cell provides conductive, for example, from about 600 0 C hot zirconium oxide, as oxygen supplier. Between the primary side and the secondary side of the heated zirconia ceramic, a voltage is applied, which leads to an oxygen transport through the ceramic. On the secondary side is pure oxygen, which can be used as purge gas.
• An additional pump is omitted in this embodiment, because the pumping action is already included in the principle of the cell. According to this principle, the reference gas oxygen can also be produced by the electrochemical decomposition of further oxygen-containing gases, such as H2O, CO2, CO, NO, NO2.
• Hydrogen or oxygen can be prepared in the liquid phase by electrolysis of acidified water.
• the gas generated at the cathode or at the anode can be used separately for rinsing.
• the electrolysis is always set in motion only when there is a need for purge gas. What is needed is an electrolysis cell and possibly a gas pump. Such a unit can be operated over several years, if only the above small purge gas quantities are needed.
• the reaction is started by adding the Al to the sodium hydroxide solution.
• the supply of Al stops.
• the apparatus consists of a respective reservoir for the NaOH and the Al, for example in the form of chips, a metering device for the aluminum chips and a gas pump.
• the design can deliver purge gas over several years, depending on the chemical supplies and number of purge cycles.
• Air is passed over glowing copper, allowing the oxygen to be completely extracted. What remains is a mixture of nitrogen with 1% argon, which does not bother.
• a gas pump is needed in addition to the Cu and the heating for the Cu nor a gas pump is needed. The process is only started if the measuring cell is to be rinsed. Maintenance is essentially necessary only for the replacement of the copper. Depending on the number of purging cycles and the amount of gas required, the device can be used for several years without maintenance.
• Oxygen can be prepared in accurately calculable amounts by adding dropwise potassium permanganate solution to a solution of hydrogen peroxide acidified with sulfuric acid.
• two storage tanks for the chemicals are needed, which are metered into a reaction vessel, and a gas pump.
• the process can proceed as follows: If a purge is to be started, a volume of hydrogen peroxide corresponding to the desired amount of oxygen is initially introduced into the reaction vessel and the potassium permanganate is added dropwise.
• An alternative method of representing oxygen is the decomposition of potassium chlorate or potassium permanganate by heating. At the beginning of the rinsing process, the chemical is heated until a sufficient amount of gas is generated. Then you stop the process by cooling.
• the storage vessel possibly a reaction vessel, a metering device for the chemical and a gas pump is needed. Only the stock of chemicals has to be added, the quantity determines the time interval of the maintenance.
• Water vapor can be removed from the air stream when passing through desiccant (silica gel or CaCl2).
• CO 2 can be removed from the air by reaction with CaO. Only the chemical containers and a gas pump are required. The gas drying device can be regenerated by simple heating, the CaO is consumed and must be topped up. The maintenance interval depends on the size of the chemical supplies and the need for purge gas.

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• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)
• Optical Measuring Cells (AREA)

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Citations (4)

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• 2006
  • 2006-11-22 DE DE102006055157A patent/DE102006055157B3/de not_active Expired - Fee Related
• 2007
  • 2007-11-19 WO PCT/EP2007/062481 patent/WO2008061949A1/de not_active Ceased
  • 2007-11-19 EP EP07822692A patent/EP2092300A1/de not_active Ceased
  • 2007-11-19 EP EP10015286.7A patent/EP2392914B1/de not_active Not-in-force
  • 2007-11-19 US US12/516,008 patent/US8570520B2/en not_active Expired - Fee Related
  • 2007-11-19 JP JP2009537611A patent/JP5230640B2/ja not_active Expired - Fee Related

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