US3421335A

US3421335A - Rectification column

Info

Publication number: US3421335A
Application number: US587450A
Authority: US
Inventors: Rudolf Becker
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 1965-10-22
Filing date: 1966-10-18
Publication date: 1969-01-14
Anticipated expiration: 1986-01-14
Also published as: GB1128229A; NL6614782A; DE1519599A1; JPS5342752B1; DE1519599B2; DE1519599C3

Description

Jan. 14, 1969 R. BECKER RECTIFICATION COLUMN Sheet Filed Oct. 18. 1966 RUDOLF BECKER lXVllYTU/Q RIUKS a Aitomey Sheet Jan. 14, 1969 R. BECKER RECTIFICATION COLUMN Filed Oct. 1a. 1966 RUDOLF BECKER ].\'\'E4\"TOR Afton: e y

United States Patent 51,951 U.S. 01. 62-42 Int. Cl. Fj 3/02 6 Claims ABSTRACT OF THE DISCLOSURE A rectification column having a greater horizontal dimension than its vertical dimension and provided with an array of thick and thin vertically spaced rectification plates with throughgoing openings allowing the passage of gas and liquid between the stages. The housing of the column has a pair of vertical Walls which are spanned by the thicker plates constituting reinforcing members welded to the walls along respective horizontal lines while the thin plates are disposed between the thick plates. Along its exterior, the walls are formed with outwardly convex metal strips joined to the structure at the seams at which the thicker plates are welded to the walls.

My present invention relates to a rectification column of the horizontal-plate type wherein the plates are vertically spaced and, more particularly, to an improved compact column for the refluxing and separation components of a fluid stream, preferably in cryogenic applications.

The conventional rectification column is circular in cross section with a vertical height usually considerably greater than the diameter. The diameter is frequently determined by the allowable transport clearance (e.g. the width of a freight car or diameter of a tunnel) and is, consequently, relatively small. The plates are substantially of the same diameter as the inside of the column, horizontally disposed and axially (i.e. vertically) aligned. Since the space between the plates preferably is, as determined empirically, an inverse function of the fourth power of the diameter, conventional columns of small diameter have correspondingly large plate spacings and consequently relatively great height.

This height has the disadvantage that operating costs are great due to the hydrostatic heads involved in the pumping of liquids; the small diameter results in high gas velocities and relatively deep depth of liquid retained on the plates, both factors contributing to a high pressure drop and loss of energy in fluid circulation.

Further columns of heights exceeding that permissible on conventional transport means necessitate fabrication in parts, increasing fabrication costs and field-erection expense.

It is an object of the present invention to obviate these ditficulties.

This is accomplished, according to the invention, by making the principal axis of the rectification column horizontal and by mounting the plates parallel to this axis, the plates conforming to the horizontal cross section of the interior of the column as .atorestated. By so doing, not only is it possible to locate the plates surprisingly close together, but-even more surprisinglythe length of the horizontal column is less than the height of the vertical column for the same capacity, as will be demonstrated hereinafter. Transport problems are now minimized and field erection greatly simplified.

Further the gas velocities and pressure drop over the column according to the present invention are advantageously reduced, resulting in lower operating costs.

The above objects, advantages and features of my present invention will become more readily apparent from the following detailed description, reference being made to the accompanying drawing in which:

FIG. 1 is a side view in perspective, partially cut away;

FIG. 2 is a detail of the head plate of FIG. 1 drawn to a larger scale; and

FIGS. 3 and 4 are side views, in perspective, similar to FIG. 1 but illustrating other embodiments of the invention.

In the drawing I show a housing 1 including generally flat vertical side walls 16, one of which is visible, generally flat vertical heads 10, an upper arched hood 17 and a lower arched hood 17', this housing being substantially a rectangular prism with a horizontal longitudinal axis. Tie rods 4, resisting internal thrusts, penetrate side walls 16 and are locked thereto by nuts or the like.

A plurality of horizontal, rectangular plates, 8a and 8b, axially extending and conforming in outline to horizontal sections of housing 1 are vertically spaced. apart therein, each plate being provided with a multiplicity of openings 7, the openings of adjacent plates being staggered longitudinally and transversely in the respective horizontal planes. Certain plates 8a are load-bearing plates contributing to the structural rigidity of housing 1 and have a rigid fastening 12, usually a weld, joining them to the heads 10. To further reinforce, the generally flat vertical heads 10, a plurality of arched (inwardly concave) members 11 connect the fastening means 12 at heads 10 at the junctures with plates 8a as is particularly portrayed in FIG. 2. Openings 9 are provided in web plates 10' which span the junctures for pressure equalization between the rectification stages defined between the plates.

Between plates 8a are one or more intermediate plates 8b which are not structurally attached to the heads and have lesser thicknesses than plates 8a; the intermediate plates are suspended therefrom by hanger assemblies 19.

At least two connections for inlet and outlet, 2 and 3 respectively, are provided, together with at least one intermediate reflux connection 18 as is common in conventional rectification columns.

FIG. 3 shows another embodiment in which the housing comprises a cylindrical shell 15 with dished heads 13. Interior plates 8, which may be identical with one another, are shaped at the ends 8' to conform to the curvature of dished heads 13. The inlet and outlet and the slots communicating between stages are otherwise identical with those illustrated in FIG. 1, and

FIG. 4 shows still another embodiment in which the housing comprises a square shell 19, being otherwise identical with FIG. 1.

The compact shape of the rectifying column in the present invention, as has been heretofore described, permits the convenient pairing of this unit on a common mounting with an evaporator or plate heat-exchanger of similar profile to the rectification column. Such a com panion unit 14 is shown in FIG. 1 in dotted lines, and

can be connected to the rectification column in a conventional manner known to the art with a minimum of piping. The unit 14 may be of the type described in my Patent No. 3,256,704, granted June 21, 1966. Moreover, direct-heat exchange through the housing walls is possible.

The operation of the cryogenic rectification column (e.g. in a Linde-Frankl air-rectification process) is in accord with conventional practice, with variation as dictated by the requirements of the fluids to be fractionated. Basically, a vapor from an evaporator 14 is admitted in the lower section of the column through the inlet 3 and a liquid phase is introduced at a higher level between plates through the inlet 18, to flow countercurrent to the rising vapor phase, a vapor-enriching exchange taking place through liquid-vapor contact on the plates 8n and 8b and at the openings 7. The latter may be flanked by downwardly extending fianges 7' reaching close to the surface of the next lower plate and bent from the sheet metal contituting the respective plate. The vapor phase is removed, for instance, through connection 2 and the liquid phase is removed or returned to the evaporator through 3 which may serve commonly as a vapor inlet and liquid outlet.

An additional advantage of the horizontal and substantially rectangular plates is that the inactive surface in the interchange of gases and liquids is reduced from that of the vertical column plates which are generally circular. Circular plates are known to have between 20% to 35% of the plate surface lot through dead peripheral wall junction and non-mixing zones at the bubble caps. The present invention with the larger rectangular plates has approximately only 5% in active surface.

Total space is reduced since not only is the profile of the equipment lower, but the length of the horizontal column is less than the height of an equivalent vertical column, as is made evident by the following example in which it is shown that the length of equivalent columns may be reduced by one-half in the present invention.

It is seen from the foregoing that, in accord with the present invention, this operation is more advantageously carried out than with conventional vertical rectification columns. For an equal loading, the rectification column according to the present invention is much lower in height that is otherwise the case, and hence the hydrostatic head against which a liquid-phase feed pump must work is greatly reduced.

EXAMPLE Present practice dictates that the plate-surface area F varies inversely as the square root of the plate spacing H,

a relationship which may be expressed as:

K F t and, where Fv and Fh, are the plate areas of a vertical and horizontal column respectively and Hv and Hh. are the plate spacings of such columns, respectively, it can be seen that Thus with a horizontal column in accord with the present invention wherein the length is 5.5 m., width 3.6 m., and having 25 plates set 0.10 m. apart, it will be evident that there are 24 interplate spaces at 0.10 m., a total of 2.4 m., to which must be added top and bottom gas passage spaces under the hoods of 0.6 m. each, giving a total height of 3.6 m., thereby defining the dimensions of the rectifier. Best results are obtained with an interplate spacing, for all rectifiers, according to the invention having horizontal longitudinal axes of 80 to 200 mm. and preferably about 100 mm.

For purposes of comparison, a conventional vertical column 3.6 m. in diameter may be hypothesized. Such a column will have plate areas of 10.2 m. as compared to the plate area of 19.8 m? for the horizontal column. Now, employing the relationship (2) above:

whence 1112:04 m.

Now, 24 spaces at 0.4 m. requires 9.6 m. height, plus 1.2 111. each for the conventional vertical still head and foot, gives a total height of 12 m. for the vertical cylindrical rectification column of conventional design. Such columns commonly require an interplate spacing of at least 300 mm. and may have spacing ranging to 600 mm.

It is seen in the above example that not only is the height rediced 8.4 m. by use of the invented column, but the overall length, important in shipping, is reduced by 6.5 In.

My invention has been illustrated in a single example embodiment which is in no way restrictive. Those skilled in the art can make numerous revisions according to design preferences; such revisions are, of course, included within the spirit and scope of the appended claims.

I claim:

1. A rectification column comprising: an elongated housing having a horizontal longitudinal axis, an array of parallel horizontal first plates extending parallel to said axis, spaced apart within said housing and conforming in shape to the interior cross-section thereof, said first plates being provided with openings communicating between the interplate spaces of said array; inlet means for admitting a gas and a liquid into said housing for rectification therein; outlet means for removing gas and liquid from said housing; said housing including an arched upper hood spaced above said array and an arched lower hood spaced below said array to permit passage of a gas and a liquid therebet-ween, a pair of axially extending, parallel side walls, transverse tie rods connecting said side walls, and end walls transverse to said longitudinal axis, said first plates being rigidly fastened to said end walls; parallel horizontal intermediate plates axially extending and vertically spaced between said first plates, said intermediate plates being provided with openings for passage of said gas and liquid therebetween, said end walls being reinforced with arches transverse to saidt axis and bridging said first plates while being rigidly fastened in common with said first plates at said end plates, said end walls being provided with pressure-equalizing ports opening into chambers formed between said end walls and each of said arches.

2. A rectification column defined in claim 1 wherein said first plates and said intermediate plates are substantially rectangular.

3. A rectificzation column as defined in claim 1 wherein said plates are separated by a vertical distance of to 200 mm.

4. A rectification column as defined in claim 3 wherein said distance is about mm.

5. In a rectification column comprising a housing having at least one horizontal dimension greater than its vertical dimension, the improvement which comprises an array of vertically spaced generally horizontal and substantially rectangular rectification plates mounted in said housing and provided with openings constituting said plates as respective rectification stages, said rectification plates being composed of thicker and thinner plates with said thinner plates being disposed between the thicker plates, the thicker plates being secured to opposite walls of the housing along opposite edges of the thicker plates where by said thicker plates structurally reinforce said housing, said opposite walls of said housing being formed with outwardly convex elongated metallic strips bridging corresponding pairs of adjacent edges of the thick plates and welded together therealong.

5 6. The improvement defined in claim 5 wherein said walls are provided with flat vertical inner wall members, said strips being welded to said fiat 'Wall members contiguously along longitudinal edges of the strips.

References Cited Harris 261-113 XR Newhall 261113 XR Dennis 62-42 Becker 62-42 NOR-MAN YUDKOFF, Primary Examiner.

V. W. PRETKA, Assistant Examiner.

Bardo 202-158 XR 10 202158; 261113 US. Cl. X,'R.