Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Including solid – extended surface – fluid contact reaction...
Reexamination Certificate
1998-01-02
2001-08-21
Tran, Hien (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Including solid, extended surface, fluid contact reaction...
C202S158000, C261S112200, C422S222000
Reexamination Certificate
active
06277340
ABSTRACT:
The present invention relates to structured packing employed for fluid contacting systems such as a distillate tower or single or multiphase mixers and may be made catalytic for catalytic distillation.
Commercially, distillation is normally practiced as a multistage, counter current gas and liquid operation in a tower containing a packing device to facilitate the gas-liquid contacting that is necessary for both mass and heat transfer. Since multiple equilibrium stages exist in a tower, the compositions of the vapor and the liquid change throughout the tower length. The desired products can be removed as either liquid or vapor at an optimum location in the tower.
The more efficient the mass transfer device, the shorter the tower to achieve the same number of equilibrium stages. The mass transfer devices typically are separated trays which allow vapor to pass upwards through a small height of liquid or continuous packings which contain surfaces for gas-liquid contacting. The ability to approach vapor-liquid equilibrium is either designated by a fractional “tray efficiency” or a “Height Equivalent to a Theoretical Plate” (HETP) for a continuous packing. The lower the HETP, the more efficient the packing. The advantage of structured packings are high efficiency coupled with low vapor pressure drop. Low pressure drops are desired because of the increased cost to force gases upwardly in the tower to overcome high pressure differentials, if present.
Examples of catalytic distribution structures are disclosed in U.S. Pat. No. 4,731,229 to Sperandio, U.S. Pat. No. 5,523,062 to Hearn, U.S. Pat. No. 5,189,001 to Johnson, and U.S. Pat. No. 5,431,890 to Crossland et al. For example, the ′229 patent discloses reactor packing elements comprising alternating fluted and unfluted parts with troughs that are inclined relative to the vertical. Apertures are provided in the parts to provide reagent communication flowing through the packing. The troughs are inclined relative to the vertical to ensure optimum fluid contact and to provide liquid holdup, vertical troughs permitting undesirable minimum liquid holdup, i.e., excessive liquid flow.
Catalytic distillation combines the separation (distillation) unit operation with chemical reaction by placing a catalyst inside a distillation column. Since most reaction rates are composition dependent, it is possible to locate the catalyst in an optimal position. Also, in an equilibrium limited chemical reaction, it is possible to remove the product (by distillation) and drive the reaction forward. Most importantly, the use of catalytic distillation allows the use of fewer pieces of equipment. Thus, a prior two vessel reactor and distillation tower arrangement may now be combined into a single structure. U.S. Pat. No. 5,321,163 discloses a catalytic distillation system.
Improved prior art packing structures have been developed comprising composite substrate structures, sometimes referred to as micromesh, which are porous products comprised of fibrous network of material. U.S. Pat. Nos. 5,304,330; 5,080,962; 5,102,745 and 5,096,663, incorporated by reference herein, disclose the production of porous composite substrates comprising fibrous networks of material. A substrate mixture is comprised of typically metallic fibers for forming the porous composite and a structure forming agent which functions as a binder, which are dispersed in an appropriate liquid. After preforming, the liquid is removed and the composite heated to effect sintering of the fibers at junction points to produce a porous substrate composite comprised of a three-dimensional network of fibers. The structure forming agent is removed during or after sintering.
However, the porous material substrate in a packing structure of the type described above does not normally provide for fluid communication through the pores for the gases and liquids in the distillation process to provide for the needed desired contact mixing and desired low pressure drop. This is attributed to possibly capillary action due to the substrate material relatively small pore size. Such material may be for example 100 micron thick sheets (generally about 0.5-0.075 mm thick in one or more layers according to the desired strength) having the stiffness of conventional cardboard material, and sometimes referred to as a “paper,” although comprising metal fibers and stronger than paper of cellulose fibers. Such material has a high surface to void volume, comprising approximately 90-95% voids.
The present inventors recognize a need to provide a high efficiency structured packing that results in an improved distillation performance. Advantageously, the present inventors recognize such packing material may be coated with a distillation catalyst for reaction processing of the fluids in a distillation tower.
A structured packing element for a fluid processing and mixing tower defining a vertical axis according to the present invention comprises a sheet material element having a plurality of channels extending in an axial direction parallel to the vertical axis and a plurality of vortex generators in each of the channels forming substantially a tortuous fluid path in each of the channels in the axial direction.
In one aspect, the element has a plurality of apertures therethrough for permitting fluid in each channel to flow transversely the axial direction to and from adjacent channels.
In a further aspect, the sheet material is porous and comprises sintered metallic fibers.
The vortex generators may be triangular, or may have a trapezoidal body segment with a tip segment or may be rectangular wherein the channels are generally square when viewed in a direction along the axial direction.
The channels each may have opposing axially extending lateral side walls extending from an intermediate connecting wall, adjacent channels having a common lateral side wall with the connecting walls of adjacent channels lying in spaced planes to form a quasi-corrugation in a direction transverse the channels, the vortex generators extending from a common lateral wall into next adjacent channels.
A packing structure according to a further aspect of the present invention for a fluid processing and mixing tower defining a vertical axis comprises a plurality of sheet material elements, each element having a plurality of channels for extending in an axial direction parallel to the vertical axis, the elements being secured in abutting side by side relation to form an array of annularly enclosed interior channels and a plurality of axially spaced vortex generators in each of the channels forming solely a tortuous fluid path in each the channels in the axial direction.
In one aspect, the vortex generators each have a portion thereof in overlying relation in the axial direction for substantially blocking linear fluid flow in the axial direction.
In a further aspect, the channels have planar sides normal to an intermediate wall, the vortex generators being integral one piece with the sheet material and forming the apertures.
The vortex generators provide turbulence to maximize two phase fluid contact or maximize mixing of single phase fluids. The vortex generators also provide the desired liquid holdup in vertically oriented channels and provide liquid and gas communication to various portions of a channel and adjacent channels via apertures in the channel wealls to maximize inter fluid contact.
In a further aspect, a packing structure for a fluid processing and mixing tower defining a vertical axis comprises a plurality of porous sheet material elements, each element having a plurality of channels extending in an axial direction parallel to the vertical axis, the material normally precluding fluid communication between adjacent channels regardless the presence of pores in the material, the elements being secured in abutting side by side relation to form an array of annularly enclosed interior channels, the elements having openings therethrough for providing transverse fluid communication among the channels and a plurality of axially spaced vortex generato
Griffin Timothy Albert
Lloyd Jonathan
Paikert Bettina
ABB Lummus Global Inc.
Carella Byrne Bain Gilfillan Cecchi
Olstein Elliot
Squire William
Tran Hien
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