WO2010020320A1 - Oscillating flow fluid bed - Google Patents
Oscillating flow fluid bed Download PDFInfo
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- WO2010020320A1 WO2010020320A1 PCT/EP2009/005303 EP2009005303W WO2010020320A1 WO 2010020320 A1 WO2010020320 A1 WO 2010020320A1 EP 2009005303 W EP2009005303 W EP 2009005303W WO 2010020320 A1 WO2010020320 A1 WO 2010020320A1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
- B01J8/1818—Feeding of the fluidising gas
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
- B01J8/24—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique
- B01J8/40—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique with fluidised bed subjected to vibrations or pulsations
-
- 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
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/65—Raman scattering
Definitions
- the invention relates to a fluid bed with an oscillating gas flow for fluidizing particles.
- a fluid bed having a gas flow in a first downwards direction with back-flow pulses in a second upwards direction to facilitate fluidization and tumbling motion of the particles.
- One example of use is for micro reactors for measuring Laser Raman Spectra where the fluidized bed moves the particles continuously or in pulses to avoid heat damage caused by the laser.
- oscillating fluid bed according to the invention can however also be used for other applications involving fluid beds in general, such as fluid beds for production of catalysts, combustion, drying or coating.
- Raman spectroscopy is a spectroscopic technique used to study vibrational, rotational and other low-frequency modes in a system. It relies on scattering of monochromatic light, usually from a laser in the visible, near infrared or near ultraviolet range. The laser light interacts with phonons or other excitations in the system, resulting in the energy of the laser photons being shifted up or down. The shift energy gives information about the phonon modes in the system.
- Raman spectroscopy is commonly used in chemistry, since vibrational information is very specific for the chemical bonds in molecules and solids. It provides a fingerprint by which the molecule or solid can be identified.
- the Raman effect occurs when light impinges upon a molecule and interacts with the electron cloud of the bonds of that molecule.
- the incident photon excites one of the electrons into a virtual state.
- the molecule will be excited from the ground state to a virtual energy state, and relax into a vibrational excited state, which generates Stokes Raman scattering. If the molecule was already in an elevated vibrational energy state, the Raman scattering is then called anti-Stokes Raman scattering .
- a molecular polarizability change, or amount of deformation of the electron cloud, with respect to the vibrational coordinate is required for the molecule to exhibit the Raman effect.
- the amount of the polarizability change will determine the Raman scattering intensity, whereas the Raman shift is equal to the vibrational level that is involved.
- a sample is illuminated with a laser beam.
- Light from the illuminated spot is collected with a lens and sent through a monochromator . Wavelengths close to the laser line are filtered out, while the rest of the collected light is dispersed onto a detector.
- Spontaneous Raman scattering is typically very weak, and as a result the main difficulty of Raman spectroscopy is to achieve a high signal-to-noise ratio.
- Lasers are needed for a good signal-to- noise ratio and formula have shown higher laser power to give higher signal-to-noise ratio. But for materials that absorb laser radiation, heating may lead to thermal degra- dation and decomposing of the sample upon absorbing radiant energy. Since Raman spectroscopy is a scattering technique, the specimens do not need to be fixed or sectioned. This fact has been utilized to counter the thermal degradation effects on the samples from the laser.
- the disclosed technique reduces heat degradation but entails potential problems focusing the laser because of the vertical height of the fluidized particle bed induced by the upwards direction of the fluidizing gas flow, and because of the shakers induced mechanical vibrations, which may interfere with a clear microscope view.
- WO2005049663 discloses another example of utilizing fluidized bed technology in Raman spectroscopy. Polymer properties is determined, e.g. in a fluidized bed reactor, by ac- quiring Raman spectrum of sample comprising polyolefin, and calculating new principal component score from portion of Raman spectrum and principal component loadings. Fluidized beds in general comprising pulsed gas flows are known in other applications from WO2008061015, US6986625,
- a fluid bed which has a chamber or reactor with surrounding walls and a support to support particles to be fluidized against the gravitational force.
- the support is gas permeable to allow a fluidizing gas flow to pass through it.
- the permeability may be achieved by using a distributor plate with apertures or a porous disc.
- fluid beds In state of the art fluid beds normally the fluidizing gas flow has a substantially upwards direction, coming from under the permeable support, flowing through it and pushing the particles laying on the support in an upwards direction. Due to gravity, the particles will tend to fall back on to the support and the countering forces of the fluidiz- ing gas flow pushing in an upwards direction and the gravity forcing the particles downwards leads to an induced turbulence in the particles which makes them tumble, move or "boil". In some applications movement of the particles can be further enhanced by applying mechanical movement to the fluid bed reactor or to the support plate.
- the present invention reaches fluidization of the supported particles without mechanical movement by an oscillating gas flow and with an upward directioned gas flow necessary to move the particles, which is considerable smaller than in state of the art fluidbeds.
- the oscillating gas flow means that the supported particles in some periods will be ex- posed to a gas flow in an upward direction which is large enough to lift or move them.
- the oscillating gas flow has a net upward gas flow direction.
- the oscillations means that the upward flow in some periods are higher than in others, in which it has a force large enough to move or even lift the supported particles. In some periods the flow has an upward direction and is large, in others the flow is smaller an may even have a downward direction, where it either does not lift or move the particles as much or even lets the particles be fixed to the support.
- the magnitude and direction of the flow in the discrete waves of the oscillating flow are parameters than can be varied according to the application, as is the frequency of the oscillations. To achieve the oscillating flow a range of solutions can be applied: The flow stream can run through a rotating or opening and closing valve.
- a swinging wall or membrane can be applied to the flow system to induce pressure waves.
- the flow itself can be provided by a membrane pump which has the inherent oscillating flow properties.
- this embodiment excels in that the oscillations enables fluidization of particles with a much smaller net upward gas flow than would be necessary to lift or move the particles with a gas flow which is not oscillating.
- the fluidizing gas flow has a net zero direction, meaning that the oscilla- tions are shifting between a gas flow in an upward direction and a gas flow in a downward direction.
- the magnitude and periods of time with up- and downwards flow may vary with the oscillation frequency and amplitude, or the upwards flow periods may not even be of the same length as the downwards flow periods, as either of them can be in the form of a pulse. In this case the flow is most of the time either downwards or upwards interrupted by shorter back- pulses.
- the fluidizing gas flow has a net downwards direction.
- This embodiment is particular in that it allows for lifting or movement of the particles even though the net downwards direction forces the particles against the support in the same direction as the gravitational force. Because of the oscillations, there are periods with back-flow where the gas flow stream for a short moment is directed upwards, thereby moving or lifting the particles for a short moment depending on the frequency of the oscillation and the time and force of the back-flow. In some applications, the gas flow would move downwards most of the time interrupted by short periods of back-flow pulses where the particles would be moved or lifted. This embodiment is advantageous when doing spectroscopy analysis in reactors having a downward flow through a gas permeable support.
- a very simple way of achieving the fluidizing bed with oscillating gas flow according to the invention is then to provide the downward gas flow by a membrane pump, which applies the back-flow pulses caused by its inherent flow characteristics.
- this embodiment of the invention provides good control of the fluidized bed, since the net downward flow ensures a very small height of the fluidized bed.
- the net gas flow necessary to fluidize, lift or move particles in the fluid bed is significantly small according to the present invention, as there only intermittent is an upward gas flow present which is large enough to fluidize, lift or move the particles.
- the present invention is superior to the state of the art technology.
- the height of the fluidized particles bed is controlled which is advantageous for instance when focusing of measuring equipment is needed. •
- the oscillating fluidization is achieved simple and cheap. It can easily be a applied to existing fluid bed systems for instance by using membrane pumps.
- Motion of the particles can be induced discontinuously in pulses at a desired frequency.
- Method of fluidizing particles in a fluidized bed reactor comprising the steps of • supporting the particles on a first side of a gas permeable support comprised in the reactor
- a fluidized bed reactor for fluidizing particles com- prising a gas permeable support having a first and a second side, the particles are supported on the first side of said support, having a gas flow through said support, wherein the gas flow is oscillating and only intermittent has an upward directioned gas flow large enough to fluidize said particles.
- a fluidized bed reactor according to any of the features 5 - 7, wherein the oscillating gas flow creates pulses of back-flow in an opposite direction from the second side towards the first side of said support.
- Fig. 1 is a view of a cut through a oscillating fluid bed with net downward directioned gas flow and pulses of fluid- izing back-flow according to an embodiment of the invention.
- Fig. 2 shows counts of Raman spectra in the following situations:
- Solid particles inside a cylindrical tube/reactor is fluid- ized by attaching a membrane pump to the exit of the tube/reactor:
- Solid particles of a size from 75 to 300 ⁇ m are filled in a cylindrical oscillating flow fluidized bed reactor (101 - figure 1) with open ends and sustained on a gas permeable support (102) such as a filter or a grid) .
- a membrane (diaphragm) pump (not shown) is connected to the bottom part of the reactor to create a net downwards gas flow (105) from the first side of the support towards the second side of the support (it is to be understood that net downwards means that the amount of downward flow is bigger than the amount of upward flow) .
- the inherent characteristics of the diaphragm pump provoke pressure and flow oscillations, meaning that the suction of the pump is not continuous homogeneous over time, but can be regarded as pulsed.
- a back- flow pulse is shown at position (106) .
- This pulsed suction creates a defined turbulence inside the tube/reactor and makes the particles (104) inside moving and circulating in vertical direction, which is sometimes called a fluidiza- tion of the solid particles.
- a gas flow (107) can be sent through the tube from top to bottom and thereby contact the solid particles.
- By adjusting the pump power to the gas flow it is possible to control the speed of the moving and circulating solid parti- cles.
- spectroscopic techniques in this case Raman spectroscopy
- Raman spectroscopy Raman spectroscopy
- heat is normally transferred to the solid particles which in turn might induce structural changes and sample damage.
- the heat transfer is significantly reduced when particles are moving since the contact time with the light source is reduced.
- the inherent limitations for spectroscopic techniques in general, where highly intense light sources are required are therefore annulled.
- Solid MoS 2 particles of a size from 150 to 300 ⁇ m are suspended in the tube/reactor while synthetic air (21% 02 + 79% N2) is flowing through the tube.
- the 632 nm light of a HeNe laser is directed onto the particles, and Raman spec- tra are taken under static, fixed bed and fluidized bed conditions, at different laser intensities and acquisition times (exposure times) .
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- Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
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- Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
Abstract
An oscillating gas flow fluidized bed reactor has a gas permeable support to support particles. An oscillating gas flow moves or lifts the particles even when having a net zero or downward directed fluidizing gas flow. The back- flow can be in the form of pulses created by a membrane pump.
Description
Title : Oscillating Flow Fluid Bed
The invention relates to a fluid bed with an oscillating gas flow for fluidizing particles. In particular it relates to a fluid bed having a gas flow in a first downwards direction with back-flow pulses in a second upwards direction to facilitate fluidization and tumbling motion of the particles. One example of use is for micro reactors for measuring Laser Raman Spectra where the fluidized bed moves the particles continuously or in pulses to avoid heat damage caused by the laser.
In the following the invention will be explained in rela- tion to Raman spectroscopy. The oscillating fluid bed according to the invention can however also be used for other applications involving fluid beds in general, such as fluid beds for production of catalysts, combustion, drying or coating.
Raman spectroscopy is a spectroscopic technique used to study vibrational, rotational and other low-frequency modes in a system. It relies on scattering of monochromatic light, usually from a laser in the visible, near infrared or near ultraviolet range. The laser light interacts with phonons or other excitations in the system, resulting in the energy of the laser photons being shifted up or down. The shift energy gives information about the phonon modes in the system. Raman spectroscopy is commonly used in chemistry, since vibrational information is very specific for the chemical
bonds in molecules and solids. It provides a fingerprint by which the molecule or solid can be identified.
The Raman effect occurs when light impinges upon a molecule and interacts with the electron cloud of the bonds of that molecule. The incident photon excites one of the electrons into a virtual state. For the spontaneous Raman effect, the molecule will be excited from the ground state to a virtual energy state, and relax into a vibrational excited state, which generates Stokes Raman scattering. If the molecule was already in an elevated vibrational energy state, the Raman scattering is then called anti-Stokes Raman scattering .
A molecular polarizability change, or amount of deformation of the electron cloud, with respect to the vibrational coordinate is required for the molecule to exhibit the Raman effect. The amount of the polarizability change will determine the Raman scattering intensity, whereas the Raman shift is equal to the vibrational level that is involved.
Typically, a sample is illuminated with a laser beam. Light from the illuminated spot is collected with a lens and sent through a monochromator . Wavelengths close to the laser line are filtered out, while the rest of the collected light is dispersed onto a detector. Spontaneous Raman scattering is typically very weak, and as a result the main difficulty of Raman spectroscopy is to achieve a high signal-to-noise ratio. Lasers are needed for a good signal-to- noise ratio and formula have shown higher laser power to give higher signal-to-noise ratio. But for materials that absorb laser radiation, heating may lead to thermal degra-
dation and decomposing of the sample upon absorbing radiant energy. Since Raman spectroscopy is a scattering technique, the specimens do not need to be fixed or sectioned. This fact has been utilized to counter the thermal degradation effects on the samples from the laser.
In "In Situ Ultraviolet Raman Spectroscopy of the Reduction of Chromia on Alumina Catalysts" by Vivian S. Sullivan, S. David Jackson, and Peter C. Stair (J. Phys . Dhem. B 2005, 109, 352-356 and earlier paper from 2000) a technique involving a fluidized bed sample cell combining gas flow and mechanical shaking to produce a fluidized bed of sample particles is disclosed. This minimizes the exposure to the laser for each individual location on the surface and re- duces the contribution of sample damage to the measured spectrum. The particles in the sample exposed to the laser beam is constantly moving in a fluid bed by means of an electromagnetic shaker attached to the base of the cell comprising the sample to facilitate tumbling of catalyst particles. The disclosed technique reduces heat degradation but entails potential problems focusing the laser because of the vertical height of the fluidized particle bed induced by the upwards direction of the fluidizing gas flow, and because of the shakers induced mechanical vibrations, which may interfere with a clear microscope view.
WO2005049663 discloses another example of utilizing fluidized bed technology in Raman spectroscopy. Polymer properties is determined, e.g. in a fluidized bed reactor, by ac- quiring Raman spectrum of sample comprising polyolefin, and calculating new principal component score from portion of Raman spectrum and principal component loadings.
Fluidized beds in general comprising pulsed gas flows are known in other applications from WO2008061015, US6986625,
WO03091644 and EP0979140.
It is an object of the invention to provide a fluidized bed which is simple and of low cost as compared to typical industrial fluidized bed technology.
It is a further object of the invention to provide a fluidized bed which fluidize and move particles supported on the bed yet maintains control of the height and motion of the bed.
It is yet a further object of the invention to provide a fluid bed which provides fluidization of particles supported on the bed even though the net gas flow has a downwards direction (downwards meaning from a first upper side of the support which supports the particles of the bed against gravity through the gas permeable support and substantially vertically downwards) .
It is a further object of the invention to provide a fluid bed which provides fluidization and movement of particles supported on the bed without the use of mechanical movement of the bed and potential inherent interference with analyse equipment .
It is a further object of the invention to provide a fluid bed which cools particles supported on the bed which are
under thermal influence by a laser beam or other energy emitting sources.
These and other objects are achieved by the invention as described below.
A fluid bed is provided which has a chamber or reactor with surrounding walls and a support to support particles to be fluidized against the gravitational force. The support is gas permeable to allow a fluidizing gas flow to pass through it. The permeability may be achieved by using a distributor plate with apertures or a porous disc.
In state of the art fluid beds normally the fluidizing gas flow has a substantially upwards direction, coming from under the permeable support, flowing through it and pushing the particles laying on the support in an upwards direction. Due to gravity, the particles will tend to fall back on to the support and the countering forces of the fluidiz- ing gas flow pushing in an upwards direction and the gravity forcing the particles downwards leads to an induced turbulence in the particles which makes them tumble, move or "boil". In some applications movement of the particles can be further enhanced by applying mechanical movement to the fluid bed reactor or to the support plate.
The present invention reaches fluidization of the supported particles without mechanical movement by an oscillating gas flow and with an upward directioned gas flow necessary to move the particles, which is considerable smaller than in state of the art fluidbeds. The oscillating gas flow means that the supported particles in some periods will be ex-
posed to a gas flow in an upward direction which is large enough to lift or move them.
In one embodiment of the invention, the oscillating gas flow has a net upward gas flow direction. The oscillations means that the upward flow in some periods are higher than in others, in which it has a force large enough to move or even lift the supported particles. In some periods the flow has an upward direction and is large, in others the flow is smaller an may even have a downward direction, where it either does not lift or move the particles as much or even lets the particles be fixed to the support. The magnitude and direction of the flow in the discrete waves of the oscillating flow are parameters than can be varied according to the application, as is the frequency of the oscillations. To achieve the oscillating flow a range of solutions can be applied: The flow stream can run through a rotating or opening and closing valve. A swinging wall or membrane can be applied to the flow system to induce pressure waves. Or especially in small scale systems, the flow itself can be provided by a membrane pump which has the inherent oscillating flow properties. In any case this embodiment excels in that the oscillations enables fluidization of particles with a much smaller net upward gas flow than would be necessary to lift or move the particles with a gas flow which is not oscillating.
In another embodiment of the invention, the fluidizing gas flow has a net zero direction, meaning that the oscilla- tions are shifting between a gas flow in an upward direction and a gas flow in a downward direction. Again the magnitude and periods of time with up- and downwards flow may
vary with the oscillation frequency and amplitude, or the upwards flow periods may not even be of the same length as the downwards flow periods, as either of them can be in the form of a pulse. In this case the flow is most of the time either downwards or upwards interrupted by shorter back- pulses. Special for this embodiment is, that a fan or a pump is not actually needed to induce the lift or movement of the particles, since a membrane or the like may apply the upward flow gas stream lifting or moving the particles using the same gas that flows back in the downward flow period. Hence, in this embodiment, lift or movement of the particles in the fluid bed can be achieved in a closed system without the need to replace the gas in the system, as it is moving back and forth from each side of the gas per- meable support to the other.
In a further embodiment of the invention, the fluidizing gas flow has a net downwards direction. This embodiment is particular in that it allows for lifting or movement of the particles even though the net downwards direction forces the particles against the support in the same direction as the gravitational force. Because of the oscillations, there are periods with back-flow where the gas flow stream for a short moment is directed upwards, thereby moving or lifting the particles for a short moment depending on the frequency of the oscillation and the time and force of the back-flow. In some applications, the gas flow would move downwards most of the time interrupted by short periods of back-flow pulses where the particles would be moved or lifted. This embodiment is advantageous when doing spectroscopy analysis in reactors having a downward flow through a gas permeable support. A very simple way of achieving the fluidizing bed
with oscillating gas flow according to the invention is then to provide the downward gas flow by a membrane pump, which applies the back-flow pulses caused by its inherent flow characteristics. As a consequence, this embodiment of the invention provides good control of the fluidized bed, since the net downward flow ensures a very small height of the fluidized bed.
Common for all embodiments is that as compared to state of the art fluidized bed systems, the net gas flow necessary to fluidize, lift or move particles in the fluid bed is significantly small according to the present invention, as there only intermittent is an upward gas flow present which is large enough to fluidize, lift or move the particles. Especially in applications where a large gas flow is not essential, but moving of the particles at some frequency is essential, the present invention is superior to the state of the art technology.
Accordingly, when compared to state of the art interconnects, the main advantages of the invention are:
• The height of the fluidized particles bed is controlled which is advantageous for instance when focusing of measuring equipment is needed. • The oscillating fluidization is achieved simple and cheap. It can easily be a applied to existing fluid bed systems for instance by using membrane pumps.
• Motion of the fluidized particles can be achieved with very little gas flow and even with zero net flow. • Motion of the fluidized particles can be achieved even under net downward directed gas flow conditions.
• Motion of the fluidized particles can be achieved without mechanical movement of the fluid bed, the support or the like.
Motion of the particles can be induced discontinuously in pulses at a desired frequency.
1. Method of fluidizing particles in a fluidized bed reactor comprising the steps of • supporting the particles on a first side of a gas permeable support comprised in the reactor
• providing an oscillating gas flow through said support with only intermittent upward directioned flow large enough to fluidize said particles.
2. Method according to feature 1, further comprising the step of
• providing an oscillating and net downward directed gas flow from the first side towards the second side of said support.
3. Method according to feature 2, further comprising the step of
• exposing the particles to pulses of fluidizing back- flow in an opposite direction from the second side towards the first side of said support as a result of the oscillations.
4. Method according to any of the features 1 - 3 further comprising the steps of
• exposing the measured particles to laser excitation
• measuring spectra of the particles fluidized by the oscillating gas flow.
5. A fluidized bed reactor for fluidizing particles com- prising a gas permeable support having a first and a second side, the particles are supported on the first side of said support, having a gas flow through said support, wherein the gas flow is oscillating and only intermittent has an upward directioned gas flow large enough to fluidize said particles.
6. A fluidized bed reactor according to feature 5, wherein the net gas flow direction is downwards from the first side towards the second side of said support.
7. A fluidized bed reactor according to feature 5, wherein the net gas flow is zero.
8. A fluidized bed reactor according to any of the features 5 - 7, wherein the oscillating gas flow creates pulses of back-flow in an opposite direction from the second side towards the first side of said support.
9. A fluidized bed reactor according to any of the features 5 - 8, wherein the oscillating gas flow is provided by a membrane pump.
10. Use of a fluidized bed reactor according to any of the features 5 - 9 or the process according to any of the fea- tures 1 - 4 to test catalyst particles by means of spectroscopy, such as laser exitated Raman spectroscopy.
The invention is further illustrated by the accompanying drawings and examples of embodiments of the invention.
Fig. 1 is a view of a cut through a oscillating fluid bed with net downward directioned gas flow and pulses of fluid- izing back-flow according to an embodiment of the invention.
Fig. 2 shows counts of Raman spectra in the following situations:
(a) fluid bed conditions with 6 minutes of full power laser exposure
(b) fixed bed conditions with 6 minutes of 1/8 power laser exposure (c) fixed bed conditions with 1 minute of full power laser exposure
(d) fixed bed conditions with 6 minutes of full power laser exposure.
Position number overview:
101. Oscilating flow fluid bed reactor
102. Gas permeable support
103. Transparent closure
104. Particles 105. Net downwards gas flow
106. Back-flow pulse
107. Gas flow in top of the reactor
EXAMPLES
Example 1 :
Solid particles inside a cylindrical tube/reactor is fluid- ized by attaching a membrane pump to the exit of the tube/reactor:
Solid particles of a size from 75 to 300 μm are filled in a cylindrical oscillating flow fluidized bed reactor (101 - figure 1) with open ends and sustained on a gas permeable support (102) such as a filter or a grid) . A membrane (diaphragm) pump (not shown) is connected to the bottom part of the reactor to create a net downwards gas flow (105) from the first side of the support towards the second side of the support (it is to be understood that net downwards means that the amount of downward flow is bigger than the amount of upward flow) . The inherent characteristics of the diaphragm pump provoke pressure and flow oscillations, meaning that the suction of the pump is not continuous homogeneous over time, but can be regarded as pulsed. A back- flow pulse is shown at position (106) . This pulsed suction creates a defined turbulence inside the tube/reactor and makes the particles (104) inside moving and circulating in vertical direction, which is sometimes called a fluidiza- tion of the solid particles.
A gas flow (107) can be sent through the tube from top to bottom and thereby contact the solid particles. By adjusting the pump power to the gas flow it is possible to control the speed of the moving and circulating solid parti- cles. The major advantages of such fluidized particles
(bed) inside a tube/reactor are known from the literature
(see also: O. Levenspiel, "Chemical Reaction Engineering", 3rd edition 1999, John Wiley & Sons, Chapters 19 - 20) . In this example it is possible to access optically the solid particles in the inner part of the tube from the top through a transparent closure (103) .
If a light source is directed onto the particles from the top into the reactor, different spectroscopic techniques (in this case Raman spectroscopy) can be performed on the fluidized particles. When using powerful and intense light sources (e.g. lasers), heat is normally transferred to the solid particles which in turn might induce structural changes and sample damage. The heat transfer however is significantly reduced when particles are moving since the contact time with the light source is reduced. The inherent limitations for spectroscopic techniques in general, where highly intense light sources are required are therefore annulled.
Example 2:
Solid MoS2 particles of a size from 150 to 300 μm are suspended in the tube/reactor while synthetic air (21% 02 + 79% N2) is flowing through the tube. The 632 nm light of a HeNe laser is directed onto the particles, and Raman spec- tra are taken under static, fixed bed and fluidized bed conditions, at different laser intensities and acquisition times (exposure times) .
As can be seen in Figure 2, a good quality spectrum of M0S2 is obtained when measuring under fluidized conditions (a: 6 minutes full laser power, fluidized bed) . However, the MoS2 particles are thermally transformed into α-MoC»3 (see
the counts marked by "*") when spectra are taken at the same laser power for the same exposure time but under static/fixed bed conditions (d: 6 minutes full laser power, fixed bed) . Structural changes are observed even for much shorter exposure times (c: 1 minute full laser power, fixed bed) . In order not to damage the sample under static/fixed bed conditions, the laser power has to be reduced significantly resulting in a spectrum with one order of magnitude lower Raman signal intensity (b: 6 minutes 1/8 laser power, fixed bed) .
Claims
1. Method of fluidizing particles in a fluidized bed reactor comprising the steps of • supporting the particles on a first side of a gas permeable support comprised in the reactor
• providing an oscillating gas flow through said support with only intermittent upward directioned flow large enough to fluidize said particles.
2. Method according to claim 1, further comprising the step of
• providing an oscillating and net downward directed gas flow from the first side towards the second side of said support.
3. Method according to claim 2, further comprising the step of
• exposing the particles to pulses of fluidizing back- flow in an opposite direction from the second side towards the first side of said support as a result of the oscillations.
4. Method according to any of the claims 1 - 3 further com- prising the steps of
• exposing the measured particles to laser excitation
• measuring spectra of the particles fluidized by the oscillating gas flow.
5. A fluidized bed reactor for fluidizing particles comprising a gas permeable support having a first and a second side, the particles are supported on the first side of said support, having a gas flow through said support, wherein the gas flow is oscillating and only intermittent has an upward directioned gas flow large enough to fluidize said particles .
6. A fluidized bed reactor according to claim 5, wherein the net gas flow direction is downwards from the first side towards the second side of said support.
7. A fluidized bed reactor according to claim 5, wherein the net gas flow is zero.
8. A fluidized bed reactor according to any of the claims 5
- 7, wherein the oscillating gas flow creates pulses of back-flow in an opposite direction from the second side to- wards the first side of said support.
9. A fluidized bed reactor according to any of the claims 5
- 8, wherein the oscillating gas flow is provided by a membrane pump.
10. Use of a fluidized bed reactor according to any of the claims 5 - 9 or the process according to any of the claims 1 - 4 to test catalyst particles by means of spectroscopy, such as laser exitated Raman spectroscopy.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DKPA200801129 | 2008-08-20 | ||
| DKPA200801129 | 2008-08-20 |
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| Publication Number | Publication Date |
|---|---|
| WO2010020320A1 true WO2010020320A1 (en) | 2010-02-25 |
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| PCT/EP2009/005303 WO2010020320A1 (en) | 2008-08-20 | 2009-07-22 | Oscillating flow fluid bed |
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| WO (1) | WO2010020320A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20160258059A1 (en) * | 2013-07-15 | 2016-09-08 | Gwangju Institute Of Science And Technology | Fluidized bed atomic layer deposition device for manufacturing nanocoating particles |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3242974A (en) * | 1961-02-14 | 1966-03-29 | Lambert Freres & Cie | Method of heat exchange by means of a surface between fluids on the one hand and granular or powdered materials on the other hand |
| WO2005049663A2 (en) * | 2002-10-15 | 2005-06-02 | Exxonmobil Chemical Patents Inc. | On-line measurement and control of polymer properties by raman spectroscopy |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3242974A (en) * | 1961-02-14 | 1966-03-29 | Lambert Freres & Cie | Method of heat exchange by means of a surface between fluids on the one hand and granular or powdered materials on the other hand |
| WO2005049663A2 (en) * | 2002-10-15 | 2005-06-02 | Exxonmobil Chemical Patents Inc. | On-line measurement and control of polymer properties by raman spectroscopy |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20160258059A1 (en) * | 2013-07-15 | 2016-09-08 | Gwangju Institute Of Science And Technology | Fluidized bed atomic layer deposition device for manufacturing nanocoating particles |
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