Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
  • G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
  • G01K11/3206—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres at discrete locations in the fibre, e.g. using Bragg scattering

Definitions

• the present invention relates to a method for measuring temperature or temperature profile in equipment and production facilities of the chemical and pharmaceutical industry - in the present context, further referred to as reactors - using fiber Bragg gratings as sensors, and the corresponding apparatus and devices Production plants themselves.
• PT100 or thermocouples are used for temperature measurement in chemical-pharmaceutical plants (see, for example, P. Profos and T. Pfeifer, Handbuch der vonn Messtechnik, Oldenbourg, 2002, H.-R. Tränkler, E. Obermeier (ed.), Sensortechnik - Handbook for Practice and Science, Springer Verlag, 1998, p 923 ff).
• Their industry-standard dimensions are the geometries of reactors of small dimensions, such as e.g. Capillary reactors or microreactors are not ideally adapted.
• capillary reactors are tube reactors with channel diameters of up to 10 mm.
• a microreactor is usually understood.
• the object was to provide an axial temperature profile in a reactor with small channel dimensions, e.g. a capillary or microreactor to measure in real-time during the ongoing reaction.
• a reactor with small channel dimensions, e.g. a capillary or microreactor to measure in real-time during the ongoing reaction.
• the problem here is the tight geometry, the accessibility of the reaction channel, the necessary explosion protection due to the substances involved if necessary and the corrosion resistance of the sensors used.
• FBG fiber Bragg gratings
• the particular advantage of these FBGs as probes is that a large number of measuring points (> 30) can be accommodated on a glass fiber, so that a temperature profile can be recorded over the entire reactor length even with a single fiber.
• a large number of measuring points > 30
• spatially almost arbitrarily distributed temperature measurements in procedural devices are possible with minimal infrastructure outlay for sensor supply and inquiry.
• the required minimum distance of the measuring points along the glass fiber is approximately 5 mm and has almost no limitation with respect to the maximum distance. In this way, temperature profiles can be recorded both in very short and in very long reactors.
• the necessary infrastructure for measuring a temperature profile can accordingly be kept small, since only one connection is necessary for measuring many measuring points.
• this measurement method can therefore be used both for classical apparatuses in chemical engineering, such as reactors, distillation columns, heat exchangers, mixers, separators, etc., with equipment dimensions in the meter range, where a measuring method with minimal space requirements is advantageous.
• reactors with small channel dimensions such as capillary reactors or microreactors of the inventive method, since the small diameter of the probe used (diameter 100 to 300 microns) allows easy access to channel cross sections, for example in the range 200 to 1000 microns.
• fiber-Bragg gratings are understood to mean optically active structures in the core of glass fibers, which are characterized by an essentially periodic modulation of the refractive index ("grating") along the fiber.
• This modulation of the refractive index results in partial backscattering of the incident light at each modulation step, and if the Bragg condition of the modulation steps is suitably chosen, then in the backscattered light constructive interference can be achieved for a narrow range of wavelengths [www. inventivefiber.com.sg/FBG.html, KO Hill et al., Appl. Phys.
• FBG's are between 1 mm and 25 mm long (see, for example, F. Ouelette, Spie's OEmagazine, p38, (2001), http://oemagazine.com/fromTheMagazine/jan01/Tutorial.pdf).
• FBG FBG
• the fibers are doped with germanium. This is the case with most commercially available fibers, with higher germanium concentration increasing photosensitivity.
• the FBG structure is written into the fiber core by means of a UV laser (wavelength about 240 nm) after the protective plastic coating has been removed or before it is applied.
• the structure of the FBG is defined either via a phase mask in the beam path of the laser or via the interference pattern, which results from the superimposition of two partial beams of the laser at the location of the fiber. To enhance the photosensitivity, it is customary to enrich the fiber with hydrogen before exposure under high pressure.
• FBG Frequency Standards for Diode Lasers [R. Kashyap, "Fiber Bragg Grating", Academic Press, 458 (1999), F. Ouelette, Spie's OEmagazine, p38, (2001)].
• Glass fibers suitable for this use are in principle all glass fibers based on silicon dioxide, in particular the glass fibers known and used in telecommunications based on silicon dioxide.
• a glass fiber provided with a plurality of FBGs is placed along the flow path of a reaction channel (exposed or along mechanical guides and holders) and led outwards via a feedthrough.
• the reflection spectrum of the prepared glass fiber is measured by means of a light source, a cross-coupler or circulator and a spectrometer.
• the spectrum is cyclically evaluated by means of a suitable device, preferably a computer or a digital signal processor.
• the focal points of the reflection profiles of the individual FBGs are linked to the local temperature via a calibration curve.
• the reflection profiles of the FBG are determined by their geometry so that overlaps in the expected temperature range are excluded. In this way, all introduced FBGs can be evaluated simultaneously by measuring the reflection spectrum of the prepared fiber.
• the calibration of the individual FBGs is recorded by immersing the entire fiber in an isothermal bath at various temperatures that cover the intended measuring range as completely as possible.
• the development of the entire temperature range is carried out by calculating a regression line or by fitting a second-order polynomial to the measured values of a respective fiber Bragg grating.
• the on-site calibration is also performed by comparing the respective local temperature at the location of the fiber Bragg grating, measured with a reference thermometer and the measured position of the center of gravity of the reflection of the fiber Bragg grating to be calibrated possible.
• the reactor is ideally operated at different temperatures in such a way that temperature fluctuations are minimized in each case.
• a reference thermometer e.g. a provided with fiber Bragg gratings and pre-calibrated glass fiber into consideration.
• the cladding of the glass fiber is removed, so that it is not dissolved by the reactants and can get into the product. This is possible because the used material of the measuring probe (quartz glass) is characterized by very good chemical resistance and allows the use for the vast majority of chemical reactions.
• the glass fiber is conducted in a protective tube which is materially closed to the reaction, in order to exclude the chemical influence of the reactants on the glass fiber.
• this protective tube can be filled with a suitable medium.
• This protective tube for this purpose consists of a suitably selected, i. sufficiently against the surrounding medium, e.g. the reactants, inert material.
• both ends of the glass fiber are led out of the reactor, so that the position of the reflection profiles of the FBG can also be determined by evaluating the transmitted portion.
• the glass fiber is integrated into a static mixer, which is located in the reactor.
• the glass fiber is introduced into the flow channel of a micromixer.
• the glass fiber is introduced or integrated into any microreactor, for example its flow channel or a mixer unit.
• the glass fiber can be introduced into a microreactor in such a way that it itself serves as a static mixer in the flow channel or in a reaction chamber.
• a plurality of glass fibers are fed into the reactor in order to open up further measuring points.
• the inventive method is basically suitable for all reactions or Heinrichs ⁇ methods in which a temperature measurement is useful, especially for reactions in the liquid phase, gas phase reactions and multiphase reaction systems.
• Temperature measurements are from -6O 0 C up to 115O 0 C, up possible, preferably suitable are the inventive FBG's for measurements up to 900 0 C, more preferably up to 250 0 C, most preferably up to 200 and especially to 150 0 C.
• Also subject of this application are apparatus and production facilities of the chemical-pharmaceutical industry which are equipped with the inventive FBG-equipped glass fibers as temperature sensors. These are preferably reactors, distillation columns, heat exchangers, mixers, separators, etc., more preferably reactors with small channel dimensions, e.g. Capillary reactors or microreactors.
• apparatuses of the food processing industry e.g., dryers, ovens, especially microwave ovens or induction ovens
• FBG-tipped glass fibers of the invention as temperature sensors.
• a fiber with eight measuring points (distances as shown in Scheme 3) was introduced.
• the introduction was carried out via a T-piece from the reactor outlet (Scheme 1), the fiber being sealed by using a seal customary in liquid chromatography for HPLC capillaries at the T-piece.
• an organometallic cryogenic reaction was carried out in the solvent tetrahydrofuran at a coolant temperature of -50 ° C.
• two components were intensively mixed at the inlet of the capillary, so that as a result of the strongly exothermic reaction, a temperature profile was formed in the reactor.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)
• Measuring Temperature Or Quantity Of Heat (AREA)

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• 2004
  • 2004-06-29 DE DE200410031324 patent/DE102004031324A1/de not_active Withdrawn
• 2005
  • 2005-06-16 JP JP2007518488A patent/JP2008504535A/ja active Pending
  • 2005-06-16 EP EP05750976A patent/EP1763659A1/de not_active Withdrawn
  • 2005-06-16 CN CNA2005800218208A patent/CN1981183A/zh active Pending
  • 2005-06-16 WO PCT/EP2005/006463 patent/WO2006000334A1/de not_active Application Discontinuation

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