Gas separation: processes – Selective diffusion of gases – Selective diffusion of gases through substantially solid...
Reexamination Certificate
2003-10-21
2004-12-28
Spitzer, Robert H. (Department: 1724)
Gas separation: processes
Selective diffusion of gases
Selective diffusion of gases through substantially solid...
C096S004000, C096S009000, C096S011000, C055S524000, C210S321840
Reexamination Certificate
active
06835232
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to apparatuses and methods for separation of a desired fluid from a fluid mixture. More particularly, the present invention is generally directed to a fluid separation module having several groups of multiple fluid separation assemblies separated by plate members that allow the fluid mixture to pass through the multiple fluid separation assemblies simultaneously.
2. Description of the Invention Background
Generally, when separating a gas from a mixture of gases by diffusion, the gas mixture is typically brought into contact with a nonporous membrane which is selectively permeable to the gas that is desired to be separated from the gas mixture. The desired gas diffuses through the permeable membrane and is separated from the other gas mixture. A pressure differential between opposite sides of the permeable membrane is usually created such that the diffusion process proceeds more effectively, wherein a higher partial pressure of the gas to be separated is maintained on the gas mixture side of the permeable membrane. It is also desirable for the gas mixture and the selectively permeable membrane to be maintained at elevated temperatures to facilitate the separation of the desired gas from the gas mixture. This type of process can be used to separate hydrogen from a gas mixture containing hydrogen. Thus, in this application, the permeable membrane is permeable to hydrogen and is commonly constructed from palladium or a palladium alloy. The exposure to high temperatures and mechanical stresses created by the pressure differential dictates that the permeable membrane be robust. The palladium and palladium alloy of the permeable membrane is the single most expensive component of the fluid separation device, so it is desirable to minimize the amount used in the construction of the fluid separation assemblies while still providing fluid separation assemblies that are strong enough to withstand the mechanical stresses and elevated temperatures of typical operating conditions.
One type of conventional apparatus used for the separation of hydrogen from a gas mixture employs several fluid separation assemblies in a fluid separation module, wherein the fluid separation assemblies are planar disks that are coaxially aligned and stacked in a vertical direction. This type of configuration of the fluid separation assemblies is commonly referred to as being a “series operation.” The module has a feed gas inlet, a permeate outlet and a discharge gas outlet. The path of the gas mixture containing hydrogen travels along the outer surface of each of the fluid separation assemblies one at a time, wherein some of the hydrogen of the gas mixture is free to enter the fluid separation assembly by the permeable membranes and is directed to the permeate outlet and the remaining gas mixture serpentines through the passageway contacting each of the remaining fluid separation assemblies one after the other. As the gas mixture travels through the passageway, it contacts the outer surfaces of several other fluid separation assemblies one at a time, wherein more of the hydrogen remaining in the gas mixture permeates the permeable membranes and follows the path resulting in this purified hydrogen passing to the permeate outlet. The remainder of the hydrogen depleted gas mixture exits through the discharge gas outlet located at the opposite end of the module after flowing over the entire stack of fluid separation membrane assemblies. The disadvantage of this type of conventional fluid separation assembly is that the fluid membrane assemblies located at the bottom of the module are not fully utilized. The hydrogen content of the feed gas mixture is depleted to the point where the driving force (i.e., the partial pressure of hydrogen) required to diffuse hydrogen through the permeable membranes of the fluid separation assemblies in the lower portion of the module is very low.
Another conventional fluid separation configuration recycles the hydrogen depleted feed gas mixture. Recycling of the hydrogen depleted feed gas mixture back into the feed stream allows this type of fluid separation configuration to operate like a fully mixed reactor by exposing all of the fluid separation assemblies to a hydrogen feed gas mixture of identical composition. The disadvantage of this type of fluid separation configuration is that it is expensive to recompress the hydrogen feed gas mixture which is necessary to overcome the pressure losses as the hydrogen feed gas mixture moves through the module.
Thus, the need exists for a method and apparatus for inexpensively and effectively separating a desired fluid from a fluid mixture that can reliably withstand high operating pressures and temperatures.
SUMMARY OF THE PRESENT INVENTION
The present invention provides a fluid separation module having groups of multiple fluid separation assemblies that operate in parallel, creating a large permeable membrane surface area for the fluid mixture to pass through. These groups of multiple fluid separation assemblies can then be assembled in a module in varying configurations or numbers depending on the specific application.
The present invention further provides a fluid separation assembly having a thin design that reduces the weight and volume of the fluid separation assembly. This thin design allows the subassemblies to be positioned in close proximity to each other in the module, which increases the packing density of the permeable membrane material (i.e., increases the permeable membrane surface area per unit of total volume of the fluid separation module).
The present invention provides the incorporation of turbulence inducing mechanisms in the feed channel to further increase the turbulence and mixing of the feed stream. These mechanisms may also be used as a support structure,for catalytic material. Having a specialized catalytic surface in close proximity to the permeable membrane surface aids the kinetics of secondary chemical reactions to completion as the hydrogen is removed from the feed stream through the permeable membrane.
The present invention provides several feed redistribution plates that direct the feed flow through each group of multiple fluid separation assemblies that operate in parallel thus, reducing the number of components of the fluid separation module.
The present invention provides a mechanical seal on each of the feed redistribution plates to ensure that feed gases pass across the fluid separation assemblies.
The present invention provides a fluid separation assembly having a fluid permeable membrane and a wire mesh membrane support adjacent the fluid permeable membrane, wherein the wire mesh membrane support has an intermetallic diffusion bonding barrier.
The present invention further provides a method for separating a desired fluid from a fluid mixture comprising providing a housing having a wall; providing a first plurality of fluid separation assemblies positioned adjacent one another; providing a second plurality of fluid separation assemblies positioned adjacent one another; positioning a plurality of plates adjacent and between the first and second plurality of fluid separation assemblies; forming a passageway defined by the plates and the housing wall; passing fluid through the passageway and through the first plurality of fluid separation assemblies and through the second plurality of fluid separation assemblies.
Other details, objects and advantages of the present invention will become more apparent with the following description of the present invention.
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Frost Chester B.
Krueger Brett R.
Kirkpatrick & Lockhart LLP
Spitzer Robert H.
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