Fluid processing device and method

• US 20040013585A1
• Filed: 06/06/2002
• Published: 01/22/2004
• Est. Priority Date: 06/06/2001
• Status: Active Grant

• Current Assignee: Battelle Memorial Institute
• Original Assignee: Battelle Memorial Institute
• Inventors: Whyatt, Greg A., Davis, James M.
• Granted Patent: US 6,994,829 B2
• Time in Patent Office: Days
• US Class Current: 422/189
• CPC Class Codes: B01B 1/005 Evaporation for physical or chemical purposes; Evaporation apparatus therefor, e.g. evaporation of liquids for gas phase reactions
• CPC Class Codes: B01J 19/0093 Microreactors, e.g. miniaturised or microfabricated reactors laboratory containers with capillary fluid transport in microfabricated channels or chambers B01L3/5027
• CPC Class Codes: B01J 2219/00162 controlling the pressure
• CPC Class Codes: B01J 2219/00783 Laminate assemblies, i.e. the reactor comprising a stack of plates
• CPC Class Codes: B01J 2219/00835 Comprising catalytically active material
• CPC Class Codes: B01J 2219/00873 Heat exchange
• CPC Class Codes: B01J 35/56 Foraminous structures having flow-through passages or channels, e.g. grids or three-dimensional monoliths
• CPC Class Codes: C01B 2203/0205 containing a reforming step
• CPC Class Codes: C01B 2203/0283 containing a CO-shift step, i.e. a water gas shift step
• CPC Class Codes: C01B 2203/044 Selective oxidation of carbon monoxide
• CPC Class Codes: C01B 2203/0445 Selective methanation
• CPC Class Codes: C01B 2203/047 the impurity being carbon monoxide
• CPC Class Codes: C01B 2203/0844 the non-combustive exothermic reaction being another reforming reaction as defined in groups C01B2203/02 - C01B2203/0294
• CPC Class Codes: C01B 2203/0883 by indirect heat exchange
• CPC Class Codes: C01B 3/16 using catalysts
• CPC Class Codes: C01B 3/384 the catalyst being continuously externally heated
• CPC Class Codes: C01B 3/583 the reaction being the selective oxidation of carbon monoxide
• CPC Class Codes: C01B 3/586 the reaction being a methanation reaction
• CPC Class Codes: C01C 1/0417 characterised by the synthesis reactor, e.g. arrangement of catalyst beds and heat exchangers in the reactor arrangement of several reactors C01C1/0405; fixed-bed reactors in general B01J8/02
• CPC Class Codes: C01C 1/0452 Heat exchangers
• CPC Class Codes: F28D 2021/0064 : Vaporizers, e.g. evaporators
• CPC Class Codes: F28D 9/0043 : the plates having openings therein for circulation of at least one heat-exchange medium from one conduit to another
• CPC Class Codes: F28D 9/0093 : Multi-circuit heat-exchangers, e.g. integrating different heat exchange sections in the same unit or heat-exchangers for more than two fluids
• CPC Class Codes: F28F 2210/02 : with particular branching, e.g. fractal conduit arrangements
• CPC Class Codes: F28F 2260/02 : having microchannels
• CPC Class Codes: F28F 2275/061 : by diffusion bonding
• CPC Class Codes: Y02P 20/52 : using catalysts, e.g. selective catalysts

Abstract

A fluid processing unit having first and second interleaved flow paths in a cross flow configuration is disclosed. The first flow paths are substantially longer than the second flow paths such that the pressure drop in the second flow paths can be maintained at a relatively low level and temperature variations across the second flow paths are reduced. One or more of the flow paths can be microchannels. When used as a vaporizer and/or superheater, the longer first flow paths include an upstream liquid flow portion and a downstream vapor flow portion of enlarged cross sectional area. A substantial pressure drop is maintained through the upstream liquid flow portion for which one or more tortuous flow channels can be utilized. The unit is a thin panel, having a width substantially less its length or height, and is manufactured together with other thin units in a bonded stack of thin metal sheets. The individual units are then separated from the stack after bonding.

Claims

1. A heat exchanger comprising:

a plurality of first microchannels and a plurality of second microchannels for conveying first and second fluids respectively;

wherein the first microchannels are in thermal contact with the second microchannels over a microchannel flow length of at least a first value;

wherein the second microchannels are in thermal contact with the first microchannels over a microchannel flow length not greater than a second value;

wherein the first value is at least about 4 times the second value.

2. The heat exchanger of claim 1 wherein a plurality of the second microchannels are interleaved between the first microchannels.

3. The heat exchanger of claim 2 further comprising a primary heat transfer surface in thermal contact with the first microchannels and at least one secondary heat transfer surface extending from the primary heat transfer surface a distance substantially greater than the smallest dimension of the first microchannel.

4. The heat exchanger of claim 3 wherein the secondary heat transfer surface extends from the primary heat transfer surface in a direction substantially parallel to the primary heat transfer surface.

5. The heat exchanger of claim 2 wherein the first value is at least about 8 times the second value.

6. The heat exchanger of claim 1 wherein the plurality of first microchannels are vaporization microchannels including a liquid flow path in fluid communication with a vapor flow path having a cross sectional area substantially greater than the cross sectional area of the liquid flow path.

7. The heat exchanger of claim 6 wherein the liquid flow path includes a tortuous flow path for establishing a pressure drop in the liquid flow path to control distribution of the first fluid in the plurality of first microchannels.

8. The heat exchanger of claim 1 formed as a stack of thin sheets integrally bonded, the stack including alternating recessed sheets having holes at opposing ends wherein the recesses in the sheets define at least a portion of the first and second microchannels.

51. The heat exchanger of claim 1 wherein the first microchannels are reaction microchannels including a reaction catalyst.

52. The heat exchanger of claim 51 wherein the reaction catalyst is a catalyst for a sabatier reaction, a preferential oxidation reaction, a steam reforming reaction, a partial oxidation reaction, a water gas shift reaction, a reverse water gas shift reaction, an ammonia synthesis reaction, a methanol synthesis reaction, an esterfication reaction, an olefin hydration reaction, a MTBE synthesis reaction, or a selective methanation reaction.

53. The heat exchanger of claim 51 wherein the second flow paths are reaction microchannels including a reaction catalyst.

54. The heat exchanger of claim 53 wherein the reaction catalyst in the second flow paths is a combustion catalyst.

9. The heat exchanger of 8 wherein the first plurality of microchannels define a flow path between the holes and the second plurality of microchannels define a flow path separate from the holes and in a direction generally orthogonal to a line connecting the holes.

10. A vaporizer comprising:

a plurality of generally parallel first vaporization flow paths for conveying a vaporizing fluid interleaved and in thermal contact with a plurality of second generally parallel flow paths for conveying a heat exchange fluid;

wherein each of the first vaporization flow paths include a liquid flow portion in fluid communication with a vapor flow portion having a cross sectional area substantially greater than the cross sectional area of the liquid flow portion; and

wherein the liquid flow portion of each of the first vaporization flow paths include at least one tortuous microchannel having at least three turns of at least about 60 degrees for establishing a substantial pressure drop through the respective liquid flow portions.

11. The vaporizer of claim 10 wherein the at least one tortuous microchannel includes at least five turns of at least about 90 degrees.

12. The vaporizer of claim 11 wherein the at least one tortuous microchannel includes at least ten turns of at least about 90 degrees.

13. The vaporizer of claim 10 wherein the second flow paths for a second heat exchange fluid are microchannels having a microchannel flow length substantially less than the flow length of the portion of the first vaporization flow path in thermal contact with the second flow paths.

14. The vaporizer of claim 10 wherein the liquid flow portion of each of the first vaporization flow paths include a plurality of tortuous microchannels in parallel flow and each having at least three turns of at least about 60 degrees.

15. The vaporizer of claim 14 wherein the plurality of tortuous microchannels are in fluid communication with a common tortuous microchannel.

16. The vaporizer of claim 14 wherein the plurality of tortuous microchannels are in communication with a corresponding plurality of vapor flow portions distinct from each other near their junctions with the tortuous microchannels.

17. The vaporizer of claim 16 wherein the corresponding plurality of vapor flow portions are microchannels in fluid communication with a common vapor outlet header.

18. The vaporizer of claim 17 wherein the vapor flow paths are in fluid communication with a common vapor outlet header.

19. The vaporizer of claim 10 wherein the second flow paths for conveying a heat exchange fluid are not in direct thermal contact with the tortuous microchannel of the liquid flow portions to substantially prevent vaporization of the vaporizing fluid when it is flowing through the tortuous microchannel.

20. The vaporizer of claim 10 wherein a vaporizing fluid is in the vaporization microchannels and the pressure drop through the liquid flow portions of the first flow paths is at least about equal to the pressure drop through the vapor flow portions of the first flow paths.

21. The vaporizer of claim 10 formed as a stack of thin sheets integrally bonded, the stack including alternating recessed sheets having holes at opposing ends wherein the recesses in the sheets define at least a portion of the first and second flow paths.

22. A vaporizer comprising:

a stack of thin sheets integrally bonded, the stack including alternating recessed sheets having holes at opposing ends wherein the recesses in the sheets define at least a portion of first and second distinct flow paths;

wherein the first flow paths are operable to convey a vaporizing fluid between the holes and include a liquid flow portion in communication with a vapor flow portion having a cross sectional area substantially greater than the cross sectional area of the liquid flow portion, the liquid flow portion including at least one tortuous microchannel;

wherein the second flow paths are separate from the holes and in thermal contact with at least a portion of the vapor flow portion of the first flow paths.

23. The vaporizer of claim 22 wherein each of the liquid flow portions of the first flow paths include a plurality of tortuous microchannels in parallel flow.

24. The vaporizer of claim 22 wherein the length of each of the second flow paths is substantially less than the distance between the holes.

25. The vaporizer of claim 22 wherein the length of each of the second flow paths is less than about ⅛

of the distance between the holes.

26. A method comprising:

providing a single pass cross-flow heat exchanger comprising interleaved first and second flow paths wherein at least one of the first and second flow paths include at least one microchannel;

conveying a first fluid in the first flow paths;

conveying a combustion gas in the second flow path through an active hot gas flow region of the heat exchanger to transfer heat to the first flow path;

wherein the volumetric heat transfer intensity based on the volume of the active hot gas flow region is at least about 30 W/cm3 and the thermal efficiency, defined relative to an infinitely long countercurrent heat exchanger at the respective fluid inlet conditions, is at least about 70%; and

wherein the pressure drop of the combustion gas through the second flow path in inches of water is less than about 10 times the inverse of the pressure of the combustion gas in atmospheres at an inlet to the second flow paths.

27. The method of claim 26 wherein the volumetric heat transfer intensity is at least about 40 W/cm3.

28. The method of claim 27 wherein the pressure drop in inches of water is less than about 5 times the inverse of the pressure of the combustion gas in atmospheres at an inlet to the second flow paths.

29. The method of claim 26 wherein the pressure drop in inches of water is less than about 5 times the inverse of the pressure of the combustion gas in atmospheres at an inlet to the second flow paths.

30. The method of claim 26 wherein the Reynolds number of the flow of the hot gas in the heat exchanger is less than about 500.

31. The method of claim 30 wherein the first fluid includes a liquid and the first flow paths are vaporization flow paths including a liquid flow section in communication with a vapor flow section of substantially greater cross sectional area than the liquid flow section.

32. The method of claim 26 wherein the first and second flow paths each include at least one microchannel.

33. A method of vaporizing a liquid comprising:

flowing a first stream including liquid through a plurality of first vaporization microchannels each including a liquid flow portion in fluid communication with a vapor flow portion having a cross sectional area substantially greater than the cross sectional area of the liquid flow portion wherein the liquid flow portions each include at least one tortuous microchannel liquid flow path for establishing a pressure drop through the liquid flow portions;

heating the first stream with a second fluid flowing through second flow paths in thermal contact with the vapor flow portions of the first vaporization microchannels to vaporize at least a portion of the first stream in the vapor flow portions; and

while heating the first stream, maintaining the pressure drop through the liquid flow portion of each of the plurality of first vaporization microchannels at least about equal to the pressure drop through the vapor flow portion to control flow of the first stream through the plurality of first vaporization microchannels.

34. The method of claim 33 wherein the distance from the tortuous microchannel liquid flow paths to the closest second flow path is substantially greater than the distance from the vapor flow portions of the first vaporization microchannels to the closest second flow path to avoid direct thermal contact between the tortuous microchannel liquid flow paths and the second flow paths to substantially prevent vaporization of the first stream in the tortuous microchannel liquid flow path.

35. The method of claim 33 wherein the first stream includes water and heating the first stream includes vaporizing the water to steam.

36. The method of claim 35 wherein the first stream is substantially devoid of liquid water at an outlet of the first vaporization microchannels.

37. The method of claim 36 wherein heating the first stream includes superheating the steam a substantial amount.

38. A method of vaporizing a liquid comprising:

flowing a first stream including liquid through a plurality of first vaporization microchannels each including a liquid flow portion in fluid communication with a vapor flow portion having a cross sectional area substantially greater than the cross sectional area of the liquid flow portion;

heating the first stream with a second fluid flowing through second heat exchange microchannels in thermal contact with the first vaporization microchannels to vaporize at least a portion of the first stream;

wherein the Reynolds number of the flow of the second fluid in the second heat exchange microchannels is less than about 1000 and the pressure drop of the second fluid through the second heat exchange microchannels in inches of water is less than about 10 times the inverse of the pressure of the second fluid in atmospheres at an inlet to the second heat exchange microchannels.

39. The method of claim 38 further comprising providing a vaporizer formed as a stack of thin metal sheets bonded by integral metal-to-metal bonds, the stack including alternating recessed sheets having holes at opposing ends wherein the recesses in the sheets define at least a portion of the first and second microchannels.

40. A method comprising:

forming a plurality of individual fluid processing units together and then separating the units after some degree of assembly into individual units;

wherein forming the plurality of individual units together includes forming integral metal-to-metal bonds in a stack of thin metal sheets, the stack including alternating recessed sheets wherein the recesses in the sheets define at least a portion of flow paths for the individual fluid processing units, and

wherein the width of the individual units after the separation is substantially less than the height of the stack of thin metal sheets.

41. The method of claim 40 wherein forming integral metal-to-metal bonds includes diffusion bonding.

42. The method of claim 40 wherein forming integral metal-to-metal bonds includes exerting pressure on the stack of thin metal sheets.

43. The method of claim 40 wherein separating the units includes cutting the material between the units.

44. The method of claim 43 wherein the cutting is performed by wire EDM.

45. The method of claim 40 wherein the recesses in the sheets define at least portions of first and second generally orthogonal flow paths wherein the second flow path spans the width of the individual unit and the first flow paths generally spans the length of the unit, and wherein the length of the unit is at least about 4 times the width of the unit.

46. The method of claim 45 wherein the first and second flow paths are microchannels.

47. A method for vaporizing a liquid to produce superheated vapor:

flowing a first stream including liquid through a plurality of first vaporization microchannels disposed between a macrochannel inlet and a macrochannel outlet, each vaporization microchannel including a liquid flow portion in fluid communication with a vapor flow portion having a cross sectional area substantially greater than the cross sectional area of the liquid flow portion;

vaporizing and substantially superheating the first stream in the first vaporization microchannels by heating the first stream with a second fluid flowing through second heat exchange microchannels in thermal contact with the first vaporization microchannels along the microchannel flow length of the first vaporization microchannels.

48. The method of claim 47 wherein the microchannel flow length of the first vaporization microchannels is at least about 4 times greater than the microchannel flow length of the second heat exchange microchannels.

49. The method of claim 48 wherein first and second microchannels are formed in a panel having first and second faces each having a length and a height wherein the second heat exchange microchannels extend between the first and second faces and wherein the width of the panel between the first and second faces is substantially less than the length and the height of each of the faces.

50. The method of claim 47 wherein flowing the first stream includes flowing the first stream through a tortuous microchannel to maintain a substantial pressure drop in the liquid flow portion.

55. A method comprising:

providing a stack of thin sheets integrally bonded, the stack including a plurality of recessed sheets having holes at opposing ends wherein the recesses in the sheets define at least a portion of a plurality of generally parallel first vaporization flow paths operable to convey a vaporizing fluid between the holes and including a liquid flow portion in communication with a vapor flow portion having a cross sectional area substantially greater than the cross sectional area of the liquid flow portion, the liquid flow portions of each of the first vaporization flow paths including at least one tortuous microchannel for establishing a pressure drop through the liquid flow portion of the first vaporization flow paths;

flowing a first fluid containing liquid into each of the first vaporization flow paths while maintaining a sufficient pressure drop in the liquid flow portions to control distribution of the first fluid to each of the first vaporization flow paths;

while flowing the first fluid, heating the first fluid to vaporize at least a portion of the liquid while in the vapor flow portions.

56. The method of claim 55 wherein heating the first fluid includes heating the first fluid with a second fluid flowing through second flow paths interleaved between the first flow paths and formed from the recesses in the stacked sheets.

57. The method of claim 55 wherein heating the first fluid includes heating with an electric heater.

58. A fluid processing device comprising:

a plurality of first reaction flow paths having a smallest dimension less than about 1 cm and including a reaction catalyst; and

a plurality of second heat exchange microchannels interleaved and in thermal contact with ones of the first reaction flow paths;

wherein the first flow paths are in thermal contact with the second microchannels over a flow length of at least a first value;

wherein the second microchannels are in thermal contact with the first flow paths over a microchannel flow length not greater than a second value;

wherein the first value is at least about 8 times the second value.

59. A method for forming a heat exchanger system comprising:

forming a stacked array of thin sheets forming a portion of a fluid processing system, the stacked array defining a first and second face having a plurality of distinct gas microchannels therebetween; and

connecting the stacked array to a separately formed gas header for distribution of a gas to the plurality of distinct gas microchannels in the stacked array;

wherein each of the first and second faces has a length and a width substantially greater than the distance between the faces.

60. The method of claim 59 wherein the stacked array is bonded to form metal to metal bonds.

61. The method of claim 59 wherein the array is bonded in a diffusion bonding process and the separately formed gas header is not.