Solid-Fluid Contacting Apparatus

This invention relates to a solid-fluid contacting apparatus and more especially to a solid-fluid contacting apparatus suitable for use in adsorption and desorption of fluid components by solid adsorbents and for flow type catalytic reactions and regeneration procedures.

There have thus far been proposed various diverse methods using a fixed bed, a fluidized bed or a moving bed for establishing contact between a solid and a fluid, in connection with adsorption, desorption, catalytic reaction and regeneration procedures, as well as corresponding apparatus for industrial application of these methods. Where two different operations such as adsorption and desorption or catalytic reaction and regeneration are required to be effected simultaneously or in parallel for continuous operation over a long time period, it has been the usual practice in the art to install a number of similar pieces of equipment in juxtaposition for alternate or sequential use or to use a separate apparatus for the process step of secondary nature or the step which takes a relatively short time (e.g., regeneration), and then returning the regenerated solid material to the main process. However, these methods invariably require apparatus of complicated construction as well as complicated operations, resulting in large increases in production and equipment costs.

On the other hand, more recently the quantities of fluids to be handled have increased considerably due to construction of large-scale chemical plants or large-sized printing and coating installations, necessitating provision of large solid-fluid contacting apparatus for use in adsorption or other chemical reaction processes. The conventional types of solid-fluid contacting apparatus have thus far been adapted to cope with the increases in the amount of fluid to be handled by increasing the diameters of the apparatus in order to increase the cross-sectional area for fluid flow or simply by increasing the number of pieces of apparatus. In any event, these countermeasures only contribute to an increase in required floor space or to an increase in the degree of complication of the equipment. The recent enforcement of severe regulations against air pollution, for example, also necessitates installation of large activated carbon adsorption apparatus in printing and coating shops to remove and collect by adsorption the organic solvents which are entrained in the exhaust gases. Manufacturers who have only limited space cannot comply with such requirements, since under the present circumstances this would unavoidably require a substantial enlargement in floor space.

The present invention has as its object the elimination of the above-mentioned drawbacks of conventional solid-fluid contacting apparatus.

Another object of the invention resides in the provision of an apparatus of compact and simple construction which requires only an amount of floor space similar to that usually occupied by a single unit but which has a cross-sectional area available for fluid-solid contact comparable in effect to a number of juxtaposed units.

It is also an object of the invention to provide a solid-fluid contacting apparatus which permits different operations, such as adsorption and regeneration or reaction and regenerative reactivation, to proceed simultaneously within a unitary column structure.

In accomplishing the foregoing objects, there has been provided in accordance with the present invention a solid-fluid contacting apparatus, comprising: (a) an outer generally tubular housing member, preferably cylindrical in shape; (b) an inner generally tubular housing member defining a fluid flow channel therein and being placed inside of the outer housing member and being generally coaxially aligned therewith preferably concentrically, to define a space therebetween, preferably an annular space; (c) at least one means extending radially between the inner and outer housing members for partitioning the space into a plurality of axially spaced contacting zones; (d) at least one means extending axially within the inner housing member for partitioning the fluid flow channel into a plurality of fluid flow sub-channels; (e) means in each of the contacting zones for receiving the solid; and (f) a fluid flow inlet communicating between each of the subchannels and one of the contacting zones, a fluid flow outlet communicating between each of the contacting zones and its respective subchannel, and means positioned in each subchannel between the inlet and outlet for preventing fluid flow through the subchannel.

Further objects, features and advantages of the invention will become apparent as the invention is described more particularly hereafter in connection with a preferred embodiment of the invention which is employed by way of example as an adsorption column using packed layers of activated carbon for the adsorption of organic solvent vapors in an exhaust gas, reference being had to the accompanying drawings.

In the drawings:

FIG. 1 is a plan view, partly in section, of the fluid-solid contacting apparatus of the present invention, taken on the line 1--1 of FIG. 2;

FIG. 2 is a fragmentary vertical sectional view of the apparatus of FIG. 1;

FIG. 3 is a horizontal sectional view, taken in the line 3--3 of FIG. 2; and

FIG. 4 is an enlarged fragmentary vertical sectional view of a modified form of one of the layers of solid material.

The embodiment of the invention illustrated in FIGS. 1-3 is provided with four packed layers of activated carbon, of which three layers are used at any one time for adsorption by contact with the gas to be purified while one layer is sequentially subjected to an operation for regeneration of the spent activated carbon. The adsorption column 6 consists of an outer cylinder 1 and an inner cylinder 2, defining therebetween an annular space having a number of packed layers 3 of a solid, in this case, activated carbon, supported by or between suitable shelf means. The layers of solid material 3 may be arranged and supported as follows: (a) the solid material may be put into a bag of fluid permeable material and the bag then placed onto a plate (perforated plate or grid); (b) the solid material may be placed directly on such plate; or (c) the solid material may be packed in a space between an upper and a lower plate. In FIG. 4 the solid material is placed inside of porous bag 17 and the layer of solid is further confined between perforated plates 18. The packed layers 3 are separated independently from the adjacent layers by means of solid partition plates 4. The partition plates 4 divide the annular space into a plurality of axially spaced contacting zones or chambers 16, each of which contains solid material for contacting with the fluid. The inner cylinder 2 is divided into four independent fluid passages 7 through 10 by means of inner partition plates 5, and each fluid passage communicates with a corresponding one of the contacting zones 16 and the packed layer 3 contained therein.

In the particular embodiment shown, the fluid passage 7 is in communication with the uppermost packed layer 3, the fluid passage 8 with the second packed layer 3, the fluid passage 9 with the third packed layer 3, and the fluid passage 10 with the lowermost packed layer 3. The respective fluid passages have openings 11 and 12 apertured through the wall of the inner cylinder, one each on the upper and lower sides of the corresponding packed layers to provide inlets and outlets for the gases which are to be fed from the respective fluid passages to the contacting zones 16 for contact with the packed layers of solid material. The gas inlet and outlet (11 or 12) of each contacting zone are insulated from each other by means of a partition wall 13 located in the passage between the inlet and outlet. This is illustrated more clearly in FIG. 3 which shows passages 7, 9 and 10 open and passage 8 closed of by plate 13. In other words, the exhaust gas or the desorption steam flowing through the fluid passages within the inner cylinder is caused to flow into the contacting zone in the annular space between the inner and outer cylinders through an opening 12 or 11, whichever is positioned on the upstream side, whereupon it is caused to pass upwardly or downwardly through the respective packed layers 3 to effect the adsorption or desorption before being able to leave the contacting zone via the outlet opening. The gases which have passed through the respective packed layers are then led back into the respective fluid passage in the inner cylinder through the openings 11 or 12 on the downstream side as a refined gas or as desorption vapors.

Thus, four independent packed layers 3 are provided in the unitary structure of the adsorption column 6. As will be understood from the foregoing description, the different operations of, on the one hand, adsorption treatment of an exhaust gas and, on the other hand, desorption by steam can be performed in parallel fashion by a single adsorption column 6 by means of the four independent packed layers 3. In such an instance, an exhaust gas containing organic solvent vapors may be fed to three of the four fluid passages in the inner cylinder, for example, firstly to 7, 9 and 10 from the lower ends thereof by means of a suitable valve arrangement to refine and purify the gas by adsorption treatment through the corresponding packed layers. The solvent containing exhaust gas is prevented from entering the remaining fluid passage 8, to which instead steam is fed from the upper end thereof in order to desorb the organic solvent vapors which have been adsorbed by the solid in a previous step and collect them by the use of any means provided at the downstream of the lower end of the fluid passage. This desorption by steam (in one stage) and adsorption of vapors (in the remaining three stages) is shifted sequentially from one fluid passage to another to selectively desorb the adsorbed vapors from each layer of solid in turn.

In this instance, it is advantageous to use a center axle 14 for operating rotary valves at the upper and lower ends of the adsorption column in synchronism with each other. The structure of a suitable rotary valve is illustrated in FIGS. 1 and 2. A valve assembly comprising a plate 21 is rigidly secured, at both the top and the bottom of the inner cylinder 2, to the center shaft 14 which is coupled via coupling element 22 to a conduit 23 through which a first fluid passes. The plate 21, in this embodiment, is provided with four openings angularly equally spaced with each other, of which three openings are in communication with a chamber defined by a housing 31 while remainder one opening is connected to the conduit 23, for example, by means of a flexible pipe 24. Each conduit is connected via suitable sealing member, such as a conical shaped joint 25, to a fluid outlet 26 or inlet 27. To one of the conduits 23 is fixed rigidly a girth gear 28 to which, by means of a pinion gear 29, is mechanically coupled a suitable power source, such as a step motor 30, by which the center shaft 14 can be rotated. In the position illustrated, channel 8 is in communication with the conduit 23 at top and bottom to permit steam to be introduced via inlet 27, transported downwardly through the apparatus (as shown by the dashed arrows) and withdrawn from the apparatus via outlet 26 at the bottom. The remaining three channels 7, 9 and 10 are utilizable for treating a second fluid being introduced via inlet 32 provided in the bottom housing 31, being transported upwardly through the apparatus (as illustrated by the solid arrows in channel 9 shown in FIG. 2) and being withdrawn via outlet 33 in the housing 31 at the top.

In this manner, with the adsorption column according to the invention, the number of adsorption layers can be increased or reduced as desired in response to the amount of the gas to be treated or to the time durations of the switching cycles of different operations, completely independently of the available installation floor space. In addition, it becomes possible to simplify the construction and switching mechanisms of the respective gas passages and to reduce the installation, operation and maintenance costs to a considerable degree.

The invention has been described in connection with one embodiment in the form of an adsorption column using activated carbon for removing and collecting organic solvent vapors from an exhaust gas. However, it will be understood that, in addition to the adsorption column with packed layers of an adsorbent, the apparatus according to the invention can find wide applications as means for establishing contact between a solid and a fluid, including liquid as well as gas, for example, in fixed and fluidized beds for solid catalytic reactions, heat accumulating type heat-exchangers and the like. Such applications and other obvious modifications will be encompassed within the present invention, which is defined by the claims appended hereto.