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Producing microchannels using graduated diffusion bonding of a stack of precision machined foils or sheets (laminates) to make a micro-channel reactor

A novel multi-step process for the diffusion bonding of laminates

National Energy Technology Laboratory

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Technology Marketing Summary
This patented invention is a method for producing microchannels using graduated diffusion bonding of a stack of precision machined foils or sheets (laminates) to make a micro-channel reactor. The method is a novel multi-step process for the diffusion bonding of laminates, which is independent of the channel width-to-fin lamina thickness (fin aspect ratio) and allows for laminae to uniformly and effectively bond. Unlike conventional hot-pressing methods, the NETL invention increases functional reaction surface area for higher conversion efficiency and reactor performance, and avoids micro-channel distortion that degrades fluid flow characteristics. This invention will have utility in micro-reactor design for heat exchangers, recuperators, heat-pumps, chemical separators, chemical reactors, fuel processing, and combustors.
Description
Microchannel technology is an emerging field of advanced chemical processing with applications in many industrial processes including chemical synthesis and biomass and synthesis gas fuel conversion. Microchannel reactors are composed of multiple stacked laminae containing multiple parallel arrays of microchannels with diameters in the range of 100–500 μm. When incorporated into microreactor designs, heat and mass transfer limitations are minimized allowing for process intensification. Compared to conventional reactors, the design allows for efficient and precise temperature control resulting in higher reaction rates, feedstock throughput, and conversion efficiency.
Conventional vacuum hot-pressing methods for bonding laminae to form multichannel reactors are limited by the channel fin aspect ratio at a given uniaxial pressure. Exceeding the fin aspect ratio results in distortion of the fins and produces a structure with poor flow properties. The current invention relates to a novel multi-step process for the graduated diffusion bonding of laminates, which is independent of the fin aspect ratio and allows for laminae to uniformly and effectively bond. The first process step
uses low uniaxial pressure and temperature to form weak diffusion bonding of laminates at interfacial contact areas. The second process step occurs under high isostatic gas pressure and temperature, producing a uniform pressure gradient across all laminate surfaces, which acts to further increase interfacial diffusion bonding. This invention allows for the fabrication of
seamless monolith structures containing nondistorted multiple parallel arrays of microchannels resulting in improved fluid flow characteristics.  Additionally, pores and unintentional voids present in the laminates are greatly diminished. Use of this method will increase functional reaction surface within stacked laminates allowing for higher conversion efficiency
Benefits

• Fluid flow characteristics are not degraded as a result of microchannel distortion.

• Laminates may be diffusion bonded regardless of fin aspect ratio.
• Increased functional reaction surface area allows for higher conversion efficiency.
• Fabrication process diminishes pores and unintentional voids present in the laminates.
• No need for sacrificial cores, internal gaskets, templates, brazing alloys, or binders.
Applications and Industries

This invention will have utility in micro-reactor design for heat exchangers, recuperators, heat-pumps, chemical separators, chemical reactors, fuel processing, and combustors.

Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Date
Patent 7,900,811
Patent
7,900,811
Method for producing components with internal architectures, such as micro-channel reactors, via diffusion bonding sheets
This invention relates to a method for producing components with internal architectures, and more particularly, this invention relates to a method for producing structures with microchannels via the use of diffusion bonding of stacked laminates. Specifically, the method involves weakly bonding a stack of laminates forming internal voids and channels with a first generally low uniaxial pressure and first temperature such that bonding at least between the asperites of opposing laminates occurs and pores are isolated in interfacial contact areas, followed by a second generally higher isostatic pressure and second temperature for final bonding. The method thereby allows fabrication of micro-channel devices such as heat exchangers, recuperators, heat-pumps, chemical separators, chemical reactors, fuel processing units, and combustors without limitation on the fin aspect ratio.
National Energy Technology Laboratory 03/08/2011
Issued
Technology Status
Development StageAvailabilityPublishedLast Updated
PrototypeAvailable03/12/201302/23/2016

Contact NETL About This Technology

To: Jessica Sosenko<Jessica.Sosenko@netl.doe.gov> <techtransfer@netl.doe.gov>