In one embodiment, the disclosure is directed to an apparatus including a microwave source that emits microwave energy in a frequency range of about 300 Mhz to about 300 Ghz. A microwave cavity in the apparatus includes a stationary input section, a stationary output section, and a rotating processing section between the input section and the output section. A waveguide receives microwave energy from the microwave source and transmits the microwave energy into at least one of the input section and the output section.
In another embodiment, the disclosure is directed to a method including continuously introducing a sample material into a processing section of a microwave cavity; wherein the processing section includes a secondary coupler; introducing microwave energy into the cavity, wherein the secondary coupler absorbs the microwave energy and heats the sample material to a target temperature; rotating the processing section; and continuously removing the processed sample material from the processing section.
In yet another embodiment, an apparatus includes a microwave source, wherein the source emits microwave energy in a frequency range of about 300 Mhz to about 300 Ghz; a microwave cavity including a stationary input section, a stationary output section, and a rotating processing section between the input section and the output section; a waveguide to transmit the microwave energy from the source and introduce the microwave energy into at least one of the input section and the output section, wherein the stationary input section, the stationary output section and the rotating process section include a mating flange assembly, wherein the mating flange assembly includes at least one of an electrically conductive layer and an microwave absorbing layer.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
Like reference numerals in the figures designate like elements.
In one embodiment, the present disclosure is directed to a microwave (MW) rotary kiln apparatus with a microwave cavity including a stationary input section, a stationary output section, and a rotating processing section between the input and the output section. After a sample is introduced into the sample input section, microwave energy is introduced into at least one of the stationary input section and the stationary output section to process a sample in the rotating processing section. In one embodiment, the rotating processing section includes a secondary coupling source, and this “hybrid” system can make possible continuous processing of a sample of a non-microwave absorbing or slightly-microwave absorbing material. The apparatus may include a single rotating processing section or multiple rotating processing sections in series with one another.
Referring to
The rotating processing section 18 may be rotated by any suitable means, which may include a power source 70 such as electric motor or an internal combustion engine, and a drive system 72 to connect the power source 70 to the rotating processing section 18, which may include an arrangement of gears, sprockets, V-belts, chains or the like.
The stationary input section 14 and the stationary output section 16 are attached to the rotating processing section 18 by a pair of supports 60, 64. The support 60 includes a first support member 61 attached to the stationary input section 14. The first support member 61 is attached to a second support member 62 by an appropriate fastener, in this embodiment an arrangement of bolts 63. The second support member 62 includes a bearing 81, which may be, for example, a ball-bearing ring, which accepts an appropriately sized groove or track in a first end of the rotating processing section 18 to allow free rotation of the rotating processing section 18. The first support member 61 may optionally include a bearing if desired (not shown in
The distance between the first and the second support members 61, 62 is optionally selected to prevent leakage of microwave energy from the space 85 between the first and the second support members 61, 62. However space 85, which is the distance between stationary input section 14 and rotating cavity 18, should be less than one quarter of the wavelength of the energy emitted by the microwave source 20. Optionally, the distance between the support members 61, 62 may be less than one quarter of the wavelength of the energy emitted by the microwave source 20.
Similarly, the support 64 includes a third support member 65 attached to the stationary output section 16, and a fourth support member 66 attached to the third support member 65 by an appropriate fastener, in this embodiment an arrangement of bolts 67. The fourth support member 66 includes a bearing 83, which may be, for example, a ball-bearing ring, which accepts an appropriately sized groove or track in a second end of the rotating processing section 18 to allow free rotation of the rotating processing section 18. The third support member 65 may optionally include a bearing if desired (not shown in
In the embodiment shown in
Either or both of the supports 60, 64 may optionally be at least partially encircled by a metallic screen (not shown in
For example, the metallic screen should have apertures similar to the screen on the face of a kitchen microwave unit, which is designed to prevent microwave energy with a frequency of 2.45 Ghz from escaping from the unit. For microwave energy launched within the cavity 12 of frequencies other than 2.45 Ghz, a corresponding screen with openings of less than one quarter of the wavelength of the launched frequency must be used.
For additional microwave leakage protection, a water jacket made of a microwave transparent material (such as Teflon) (not shown in
At least one of the stationary input section 14 and the stationary output section 16 include a source of microwave energy 20, which can emit energy in a desired range for processing a selected sample material. The microwave source 20 emits microwave energy in a range from about 300 MHz to about 300 GHz, and some suitable frequencies for processing materials include, but are not limited to, 2.45 Ghz or 915 Mhz. Other frequencies can be used as well, but the larger the wavelength (or as frequency decreases) emitted by the source 20, the minimum size of the rotating processing section 18 must be increased to allow the selected frequency to propagate through the cavity 12.
In some embodiments, the microwave energy is introduced into the microwave cavity 12 by a suitable waveguide 24. Waveguide 24 may extend some distance into the stationary input section 14 and/or stationary output section 16 (as shown in
A sample 30 is introduced into the stationary input section 14 via a sample port or hopper 32, which is welded or affixed to the stationary input section 14. The sample port 32 can optionally be equipped with a vibratory feeder or other device to promote sample materials to flow into the rotating processing section 18. The stationary input section 14 may also optionally be lined with insulation to protect the input section 14 and waveguide 24 from heat generated within the microwave cavity 12. The dimensions of the sample port 32 are selected to be sufficiently large to allow smooth flow of the sample 30, but should be sufficiently small to prevent leakage of microwave energy from the sample input section 14. Typically, the sample port 32 is affixed to an opening in the stationary input section 14 that has a diameter less than about one quarter of the wavelength of the energy emitted by the microwave source 20. For example, a the sample port 32 may be made of a cylinder 33 affixed to an opening in the stationary input section 14 that is 1 inch in diameter and 5 inches in length for energy at 2.45 GHz frequency. A larger diameter opening would require the cylinder 33 to be longer.
The sample port 32 allows the sample 30 to smoothly flow into the rotating processing section 18, where the sample 30 is tumbled and continuously exposed to microwave energy from the microwave source 20. Exposure to the microwave energy heats the sample to a selected target temperature, and after the sample reaches the target temperature the sample flows out of the rotating processing section 18 and enters the stationary output section 16. The temperature of the sample 30 may optionally be monitored by at least one temperature measurement device such as, for example, a thermocouple or pyrometer 34. The thermocouple is protected from microwave energy by a conductive metal coating or sheath 35, which is electrically grounded to the microwave cavity 12. The thermocouple 34 may be used for monitoring temperatures within the system, and may also be used as a control feedback to the microwave source 20 to control power input to maintain temperatures within the rotating processing section 18. The thermocouple can merely extend perpendicularly into the body of the stationary input section 14 (
The sample may be removed from the apparatus 10 through an output port 40, or may optionally be introduced into another downstream processing section (not shown in
In an alternative embodiment shown in
The bearing rings 450, 452 can reside in grooves or troughs fashioned into a central support member like member 19 in
The rotating processing section 418 may be rotated by any suitable means, which may include a power source 470 such as an electric motor or an internal combustion engine, and a drive system 472 to connect the power source 470 to the rotating processing section 418, which may include an arrangement of gears, V-belts or the like.
The cylindrical members 490, 492 may optionally slide and advance/retract along the outer surfaces 493, 495 of the input sections 414, 416 to allow removal of the rotating processing section 418 and provide an adjustable choke to prevent leakage of microwave energy from the microwave cavity 412 (the cylindrical member 492 is shown in a retracted position in
The cylindrical members 490, 492 are made of a conductive material such as a metal and may slide over the rotating processing section 418 to prevent leakage of microwave energy from the microwave cavity 412. The cylinders 490, 492 could be optionally be electrically connected to the rotating processing section 418. An interior surface of the cylindrical members 490, 492 may optionally include at least one of metal brushes, metal pins, metal dimples and the like (not shown in
Referring to
The rotating processing section 18 further includes a secondary coupling layer 104 which is typically located within the insulating layer 102. The secondary coupling layer 104 is very microwave absorptive and may be a pure single-phase absorbing material, or a composite material made of several different materials that are microwave absorbing and non-microwave absorbing. Suitable microwave absorbing materials include, but are not limited to, electrically semiconducting materials (n-type or p-type semiconductors), ionically conducting materials (ion conductors), dipolar materials, magnetically permeable materials, or a material that changes phases or undergoes a reaction to alter its microwave absorptive properties. Suitable materials for the secondary coupling layer 104 include, but are not limited to, SiC, partially stabilized zirconia, magnetite, zeolites, and β-alumina.
The material in the secondary coupling layer 104 should be selected to facilitate heating a sample that is non-microwave absorbing or weakly microwave absorbing at ambient temperature, up to a temperature at which the sample becomes microwave absorbing or dielectrically lossy. This change in the microwave absorbing properties of the sample, as a function of increasing temperature provided by the secondary coupling layer 104, can make possible continuous microwave-assisted processing of a non-microwave absorbing sample within the rotating processing section 18.
In some embodiments, the secondary coupling layer 104 is attached to the insulating layer 102 by a high-temperature ceramic cement. The secondary coupling layer 104 can also be attached to the insulating layer 102 by forming the body 100 with periodic “teeth” or gears around the circumference of the end of the rotating processing section 18 that could be fit into mating ceramic gear set that is attached to the outer insulation via cementing or as a gear assembly mating with the outer insulation.
Additionally, a non-microwave thermal energy source can be used to supply additional heat within the rotating processing section 18 to create a “hybrid” system. This thermal source can be in the form of electrical resistance heating, gas-burner heating as well as other electromagnetic sources, such as infrared or IR heating. Using a non-microwave energy source can aid the secondary coupling layer 104 in heating the sample or even remove the need for the layer 104 altogether.
In some embodiments the secondary coupling layer 104 may be a substantially continuous tube-like or cylinder-like layer, while in other embodiments the layer 104 may be made of bricks, squares, plates, rods, discs or any other geometric shape affixed around the inner surface of the insulating layer 102 or imbedded within the insulating layer 102 in some manner. These bricks, squares, rods or any other geometric shape material are microwave absorbing materials maybe applied to the insulating layer 102 by, for example, tape casting, slip casting, sol-gel techniques, CVD, PVD, electrostatic coating, drop coating, brush coating, spray coating. In other embodiments, alternative application techniques may be used to attach the bricks, rods, and the like to the insulating layer 102, including, but not limited to, gluing or cementing individual articles or pieces as well as groups of articles or pieces of the microwave absorbing materials to the insulating layer 102. In other embodiments layer 104 can actually be applied to layer 102 as a coating or a paste of materials that are microwave absorbing.
In other embodiments, a protective layer of, for example, a ceramic material, may be applied to the secondary absorbing layer 104 to prevent direct contact with the sample being processed or to prevent potential reaction of the materials in the absorbing layer 104 with atmosphere within the rotating processing section 18 or within the entire apparatus 10 at elevated temperatures. This protective layer or coating may be applied at any thickness deemed appropriate to curtail or prevent any reactions caused by contact with the sample being processed or the gases from the atmosphere within the entire apparatus. This coating maybe oxide-based, non-oxide based or mixtures of oxides and non-oxide materials.
Referring to
The stationary input section 214A is a stationary portion of the apparatus 200 that separates the first rotating processing section 218 and the second rotating processing section 228, and is essentially a transition zone that can be used to for adding more temperature probes, an additional sample feeder, an additional microwave source, or to choke microwave energy from entering the cavities rotating processing sections 218 and/or 228. Additionally, the section 214A can contain ports for use of pyrometer or for the addition of another sample feeder or to add a process cover gas.
In the example shown in
In addition to, or in the absence of, choking member 302, a screen or an arrangement of bars (not shown in
The screen may optionally be insulated from the hot sample and any secondary couplers in the rotating processing sections 218, 228. In another embodiment, the screen (or the choking member 302) can be attached to the rotating processing sections (permanently affixed or locked/screwed into the rotating cavity to allow removal for maintenance) such that the choke system can be a part of the rotating cavity.
Additionally the screen can serve as a support to keep insulation layer 102 and layer 104 (
In another aspect, the present disclosure is directed to a method for processing a sample. Referring again to
The sample is then removed from an output port 40 in a stationary output section 16 of the microwave cavity downstream of the rotating processing section 18.
In the presently described method, the speed of throughput is determined by the set angle of the apparatus and the speed of the rotating cavity, as typical in a conventional rotating kiln. Any or all of the apparatus set angle, the rotating speed of the rotating processing section 18, and the optional secondary coupler material in the rotating processing section 18 can be selected to provide continuous flow or substantially continuous processing of the sample. In this application the term continuous refers to a process in which the sample is supplied continuously (in an uninterrupted flow) to the sample port 30, and then continuously withdrawn from the output port 40.
Embodiments will now be described in the following non-limiting examples.
Referring to
Referring to
After the coated paste along the alumina tube 506 and within the microwave unit 500 was allowed to dry, the microwave unit 500 (1.2 kW total power) was set on “high,” which allowed the total output power to be applied, for a period of 9 minutes before a glowing was observed within the coated alumina tube 506. The unit 500 was shut down, the door was opened, and a thermocouple was placed through the circular opening of the alumina fiberboard in contact with the alumina tube 506, and a temperature of 746° C. was recorded.
An uncoated alumina tube with the same dimensions as the previously coated alumina tube in Example (1)A above was inserted through the chokes 504 as shown in
Using the same setup as described in
Using the same setup described in
Using the same setup described in
Referring to the schematic in
The two end sections 602, 604 were stationary and did not rotate in this example, and both serve as inlets for microwave power (or alternatively one section may input energy and the other may not). In
An arrangement of cylindrical “chokes” 612 having a 1.5 inch (3.8 cm) inner diameter and 5 inches (13 cm) in length were welded to the end sections 602, 604 for sample output/input, but were appropriately sized to prevent leakage of energy in the frequency range of 2.45 GHz. End chokes 612A were included to allow viewing of the operation of the unit 600.
In the area between each section 602, 604 and the center section 606 are mating flanges or collars 615 that form rotary choke assemblies 614. When the device 600 is in operating position the flanges 615 in the rotary choke assemblies 614 are nearly in contact. At the interface between mating sections 602, 604, 606, layers of electrically conductive and/or microwave absorptive materials were arranged from the inner diameter of the flanges 615 to the outer diameter thereof (see end view of a section 602, 604 or 606 in
In this example, the electrically conductive layer 616 was a beryllium copper foil, and the microwave absorptive material 618 was a barium ferrite rope. These layers allowed the rotary choke assemblies 614 to act as microwave chokes.
The flanges 615 were brought into contact by sliding the stationary ends 602, 604 forward until the flanges 615 on each section abutted the flanges 615 on the rotatable center section 606.
To add stability within the rotary choke assemblies 614 and further reduce microwave leakage, bearing rings (not shown in
The sample inlet funnel 608 fed into a process tube 620, which was made of alumina and silica fiberboard. The process tube 620 included three sub-sections 620A, 620B, 620C, each supported by insulating rings 621. Affixed around the inner diameter of the process tube 620 were SiC/Al2O3 (containing 7% SiC by weight) composite bricks 622 fabricated by hot-pressing techniques. The bricks 622 measured 2 inches (5 cm) by 4 inches (10 cm) by 0.3 inches (0.8 cm). The process tube 620 included 3 rows of bricks 622 down the length thereof, and each row contained 3 bricks 622 mounted roughly 120 degrees apart around the inner circumference of the process tube 620. The bricks 622 were held in place with alumina ceramic cement.
The portion of the process tube 620 in the section 602 was arranged over a stainless steel or quartz outlet funnel 610 which allows the sample to exit through the choke 612.
In the embodiment shown in
Temperature is measured by thermocouples 650 that extend into the processing tube 620 within the rotary section 606. Using a controller system, the feedback from the thermocouples 650 was used to control the internal temperature with the tube 620. In another embodiment, temperature can be monitored wirelessly by affixing a receiver to the stationary sections 602, 604. The receiver can receive signals from transmitters attached directly to the thermocouples 650.
12 kW of microwave power was launched through the system by attachment of twelve 1 kW magnetrons 640 (6 affixed on each of the stationary sections 602, 604) and the temperature in the process chamber 620 was adjusted to about 1000° C. as measured by the thermocouples 650. The rotating chamber 606 was set for 8 rpm (revolutions per minute) and the system was adjusted such that the process chamber 620 had a downward angle of about 4° to allow sample flow along the direction of the arrow A of
Kaolin powder was poured into the sample inlet pipe 608, and after about 20 minutes sample began to trickle out of the process chamber 620 in a steady stream and into the outlet port funnel 610. The temperature of the sample was measured as about 850-870° C., which was likely due to cooling as the samples exited the system.
Under the same conditions as set forth in Example (2)A above, anatase powder (TiO2) was loaded into and fed through the sample inlet funnel 608 and allowed to pass through the process tube 620 at 800° C., above the conversion temperature of anatase to rutile (about 570-610° C.). The resulting sample powder was collected in a stainless steel bin and characterized using x-ray diffraction to show the rutile phase of TiO2.
Various embodiments of the invention have been described. These and other embodiments are within the scope of the following claims.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/US2011/055462 | 10/7/2011 | WO | 4/4/2013 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2012/048284 | 4/12/2012 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
3749874 | Edgar | Jul 1973 | A |
3952421 | Wilson | Apr 1976 | A |
4037070 | Kirpichnikov | Jul 1977 | A |
4310739 | Hatem | Jan 1982 | A |
4406937 | Soulier | Sep 1983 | A |
4441003 | Eves, II | Apr 1984 | A |
4559429 | Holcombe | Dec 1985 | A |
4677278 | Knoll | Jun 1987 | A |
5227026 | Hogan | Jul 1993 | A |
5718356 | Nottingham | Feb 1998 | A |
5961870 | Hogan | Oct 1999 | A |
6020579 | Lewis | Feb 2000 | A |
6104015 | Jayan et al. | Aug 2000 | A |
6833537 | Risman | Dec 2004 | B2 |
20040104514 | Ishikawa | Jun 2004 | A1 |
20040182855 | Centanni | Sep 2004 | A1 |
20060054618 | Agrawal et al. | Mar 2006 | A1 |
20080099325 | Ludlow-Palafox et al. | May 2008 | A1 |
20080302787 | Erskine | Dec 2008 | A1 |
20100025394 | Jussel | Feb 2010 | A1 |
20100025395 | Laubersheimer | Feb 2010 | A1 |
20100032429 | Rundquist | Feb 2010 | A1 |
20100059509 | Imai et al. | Mar 2010 | A1 |
20120129358 | Ogawa | May 2012 | A1 |
Number | Date | Country |
---|---|---|
1898017 | Jan 2007 | CN |
201129918 | Oct 2008 | CN |
2530059 | Dec 2012 | EP |
2005331158 | Dec 2005 | JP |
2008264656 | Nov 2008 | JP |
2009-97773 | May 2009 | JP |
20010075210 | Sep 2001 | KR |
20090008960 | Sep 2009 | KR |
9902016 | Jan 1999 | WO |
02079113 | Oct 2002 | WO |
Entry |
---|
Response to Examiner's Report dated Mar. 24, 2015, from counterpart Australian Patent Application No. 2011311838, filed Jun. 19, 2015, 8 pp. |
Notice of the Second Office Action, and translation thereof, from Counterpart Chinese Patent Application No. 201180058454.9, dated Jan. 16, 2015, 8 pp. |
Response to Examiner's Report dated Nov. 22, 2014, from Counterpart Australian Patent Application No. 2011311838, dated Feb. 22, 2015, 17 pp. |
Patent Examination Report No. 2, from Counterpart Australian Patent Application No. 2011311838, dated Mar. 24, 2015, 3 pp. |
Canadian Office Action from Canadian counterpart application No. 2,814,008, dated Feb. 26, 2014, 2 pp. |
Chinese Office Action from Chinese counterpart application No. 20118005845.9, dated Aug. 5, 2014, 13 pp. |
Australian Office Action from Australian counterpart application No. 2011311838, dated Nov. 22, 2014, 2 pp. |
Response to Chinese Office Action from corresponding Application Serial No. 20118005845.9 filed on Nov. 25, 2014 (9 pages). |
International Preliminary Report on Patentability from corresponding PCT Application Serial No. PCT/US2011/055462, 7 pages, dated Apr. 18, 2013. |
International Search Report from corresponding PCT Application Serial No. PCT/US2011/055462, 3 pages, dated Apr. 17, 2012. |
Third Office Action, and translation thereof, from counterpart Chinese Patent Application No. 201180058454.9, dated Apr. 27, 2015, 12 pp. |
Fifth Office Action, and translation thereof, from counterpart Chinese Patent Application No. 201180058454.9, dated Apr. 20, 2016, 21 pp. |
Decision on Rejection and Translation from counterpart Chinese Application No. 201180058454.9, dated Dec. 21, 2016, 2014, 8 pp. |
Response to Extended Search Report dated May 9, 2017, from counterpart European Application No. 11831718.9, filed Dec. 6, 2017, 7 pp. |
Extended Search Report from European Application No. 11831718.9, dated May 9, 2017, 9 pp. |
Response to Indian Office Action dated Sep. 5, 2018, from counterpart Indian application No. 865/MUMNP/2013, filed Sep. 24, 2018, 62 pp. |
Examination Report from counterpart European Application No. 11831718.9, dated Oct. 4, 2018, 5 pp. |
Response to Indian Office Action dated Sep. 5, 2018, from counterpart Canadian application No. 865/MUMNP/2013, filed Sep. 24, 2018, 62 pp. |
Examination Report, and translation thereof, from counterpart Indian Application No. 865/MUMNP/2013, dated May 9, 2018, 7 pp. |
Notice of the Fourth Office Action, and translation thereof, from counterpart Chinese Patent Application No. 201180058454.9, dated Sep. 2, 2015, 8 pp. |
First Office Action, and translation thereof, from counterpart Chinese Patent Application No. 201810699018.3, dated Apr. 1, 2020, 18 pp. |
Second Office Action, and translation there of, from counterpart Chinese Patent Application No. 201810699018.3, dated Sep. 23, 2020, 21 pp. |
Response to Examination Report dated Oct. 4, 2018, from counterpart European Patent Application No. 11831718.9, filed Feb. 1, 2019, 11 pp. |
Notice of Intent to Grant and Text Intended to Grant from counterpart European Patent Application No. 11831718.9, dated Apr. 23, 2020, 32 pp. |
Hearing Response, a communication issued by the Indian Patent Office, from counterpart Indian Application No. 865/MUMNP/2013, dated Nov. 20, 2020,12 pp. |
Refusal Order, a communication issued by the Indian Patent Office, from counterpart Indian Application No. 865/MUMNP/2013, dated Nov. 20, 2020, 12 pp. |
Third Office Action, and translation thereof, from counterpart Chinese Application No. 201810699018.3, dated May 10, 2021, 10 pp. |
Number | Date | Country | |
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20130200071 A1 | Aug 2013 | US |
Number | Date | Country | |
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61390828 | Oct 2010 | US |