Apparatus For Gas-liquid Contact

Abstract

Apparatus for gas-liquid contact having a contact body mounted in a housing, said contact body being formed from a plurality of corrugated sheets of a fibrous web material impregnated with a polyepoxy-cross-linked plasticized rubber composition.

Parent Case Text

This is a continuation of application S.N. 330,101, filed Feb. 6, 1973 and now abandoned, which is a continuation-in-part of application S.N. 186,768, filed Oct. 5, 1971 and now U.S. Pat. No. 3,798,057 granted Mar. 19, 1974.

Description

The present invention relates to cooling towers for gas-liquid contact. More in particular, the present invention relates to cooling towers having a contact body mounted in a housing, said contact body being formed from a plurality of sheets of an impregnated fibrous web defining a plurality of channels or ducts in said contact body through which gas and liquid are passed.

A better understanding of the present invention and of its many advantages will be had by referring to the accompanying drawings, in which:

FIG. 1 is a vertical longitudinal section through one embodiment of a cooling tower according to the present invention;

FIG. 2 is a vertical longitudinal section of a further embodiment of a cooling tower according to the invention; and

FIG. 3 is a perspective view, partially in section, of a contact body adaptable to use in the cooling towers of the invention.

FIG. 1 shows one embodiment of a cooling tower comprising casing 10 in which is mounted contact body 11. The base of casing 10 is formed into sump 12 having float 19 and drainage line 20. A liquid, such as water, is introduced through liquid supply line 17 and passes over contact body 10 after discharge from perforations 18 in supply line 17. A gas, such as air, is introduced in cross-current or counter-current to the liquid flow through openings 13 in portions of casing 10 beneath the contact body. Air may be pulled in an upward direction by fan 15, driven by motor 16, both mounted in gas outlet 14 above contact body 11 in casing 10 or the fan may be eliminated in a natural draft system. When the water or other liquid in sump 12 reaches a pre-determined minimum level, float 19 activates valve and/or pump means (not shown) to introduce additional liquid into the circulating liquid system. Within the contact body, the gas and liquid introduced thereinto are in a heat-exchange relationship.

FIG. 2 shows a further embodiment of a cooling tower having casing 21 in which one or more contact bodies 22 are mounted. The base of the casing is formed into sump 23 having float 24 and drainage line 25. In this embodiment, a gas such as air enters channels or ducts within the contact bodies at uncovered portions thereof 26 and may be drawn upwardly, within the apparatus to outlet 29 equipped with fan 30 and motor 31 therefor. A liquid, such as water, is introduced into the cooling tower through liquid supply line 27 and escapes from the line through perforations 28. Conveniently, the liquid escaping perforations 28 is passed through pad 32 which more evenly distributes the liquid to the channels or ducts within contact bodies 22.

FIG. 3 shows a contact body suitable for use in the cooling towers of FIGS. 1 and 2. The body comprises a plurality of corrugated sheets 33, 34, 35, 36 with the corrugations in adjacent sheets, such as 33 and 34, being disposed at an angle to each other and the corrugations in alternate sheets, such as 33 and 35, or 34 and 36, being disposed in parallel, whereby a plurality of criss-crossing is formed within said contact body. When the contact body is mounted in a cooling tower, the corrugations are generally at an angle relative to the horizontal so as to permit the gravity flow of liquid therethrough. The angle at which adjacent corrugated sheets are disposed is not critical, and it is evident from FIGS. 1 and 2 that the angular disposition of the alternate sheets, as suggested by the crossing solid and dashed lines in contact bodies 11 and 22 in these Figures, may vary from apparatus to apparatus depending on a particular construction or particular function to be performed thereby.

The corrugations in the corrugated sheets of contact bodies like that shown in FIG. 3 are conveniently from 5 to 40 or 60 millimeters in height from trough to peak, and are usually from 10 to 30 millimeters. The corrugated sheets may be adhered one to another at points of contact within the contact body or may be held in fixed position by suitable spacing and retaining means at their edges.

Heretofore, contact bodies like that shown in FIG. 3 have been comprised of corrugated plastic sheets or, more conventionally, of sheets of a fibrous woven or non-woven web. (Webs of mineral fibers such as of glass or asbestos are preferred as being non-inflammable.) Such fibrous webs are impregnated with a resin, conventionally a phenolic resin or melamine-formaldehyde resin, to impart greater rigidity and wet strength thereto.

It has been found that the impregnated sheet materials used to form bodies in cooling towers in the prior art, while often satisfactory at pH values surrounding the neutral point (pH 7), degrade rapidly when in contact with water at higher or lower pH values. Melamine-formaldehyde resins, for instance, hydrolyze fairly rapidly at alkaline pHs. This is particularly undesirable because the acid chromates heretofore widely used as additives in water-cooled refrigeration and air conditioning systems are more and more being replaced by alkaline additives. In general, the contact bodies in prior art cooling towers are most useful at pHs between 6 and 9 and at temperatures below 110.degree.F. At pH values above or below these values and at temperatures above 110.degree.F., there is a strong tendency for the impregnating resin therein to be attached and removed from the sheets, resulting in weakening of the sheets and eventual destruction and collapse of the contact bodies.

Further, where the liquids employed in the gas-liquid interchange contain corrosive contaminants, for example organic solvents, a rapid attack of the resins employed in the prior art contact bodies, and subsequent rapid destruction of these bodies, has been experienced.

The cooling towers of the present invention employ contact bodies comprising a plurality of facially opposed corrugated sheets, as shown in FIG. 3, wherein the sheets are impregnated and coated with a mixture principally comprising a chlorinated hydrocarbon resin, a chlorinated additive thereto which functions as a plasticizer and/or film-forming agent, and a polyepoxy compound believed to function as a cross-linking agent. Optionally, the coating mixtures may contain pigments, particularly carbon black, and mineral fillers such as clays or powdered silica.

The webs forming the contact bodies employed in the cooling towers of the invention suitably may vary in thickness from 0.1 to 2 mm, generally from 0.1 to 1 mm. Such webs are conveniently impregnated by immersion thereof in an impregnating solution containing the aforementioned impregnating mixture in an organic solvent such as toluene for a time sufficient to saturate the web. Excess impregnating solution is removed, and the damp sheet is then formed (for example by vacuum forming) into corrugated sheets. Any remaining solvent is removed from the sheets by evaporation, generally at a temperature above room temperature and preferably at a temperature above about 100.degree.C. In commercial production, brief heating at 250.degree. - 300.degree.C. (30 - 60 seconds) is employed. The sheets are then formed into contact bodies as described above, either with the use of adhesive at points of contact between adjacent corrugated sheets or by spacing and supporting means at their edges.

The compositions used to impregnate the fibrous webs which form the sheets of the contact bodies of the cooling towers of the present invention principally comprise a chlorinated polymeric hydrocarbon, specifically a chlorinated polypropylene (hereinafter "chlorinated C.sub.3 polymeric hydrocarbon") or chlorinated rubber. The chlorinated rubbers are preferred, and may be either natural rubbers or synthetic rubbers. Both the natural and synthetic rubbers principally comprise isoprene (C.sub.5) units, and will be referred to hereinafter as "chlorinated C.sub.5 polymeric hydrocarbons."

The rubbers contained varying amounts of chlorine. Suitable commercially available materials (e.g. "Parlon") contain about 65 percent by weight of chlorine, for example, which insures good fire resistance. The rubbers are available in a variety of grades and molecular weights, for example between about 30,000 and 120,000 (weight average molecular weight).

Alternatively, chlorinated polypropylene resins, also commercially available (e.g., "Parlon") with about the same degree of chlorination (about 65 percent ), can be obtained in the same variety of grades as the chlorinated rubbers.

A plasticizer and/or film-forming agent is employed with these chlorinated C.sub.3 and C.sub.5 polymeric hydrocarbons. Particularly suitable agents include the chlorinated terphenyls and chlorinated paraffins, i.e., chlorinated higher aliphatic hydrocarbons having 20 - 30 carbon atoms.

These chlorinated terphenyls and paraffin hydrocarbons are available commercially (e.g., "Aroclor," "Chlorowax," "Chlorafin") containing different amounts of chlorine. Materials containing between about 40 percent and about 70 percent by weight of chlorine are particularly useful.

The plasticizing and/or film-forming ingredients described above are combined with the chlorinated polymeric hydrocarbon in amounts from about 5 to 100 percent by weight of the polymeric hydrocarbon, preferably in amounts from 5 to 50 or 5 to 25 percent by weight.

The polyepoxy compound which imparts particular rigidity and resistance to softening by heat to the compositions of the invention is believed, because of its polyfunctionality, to behave as a cross-linking agent in the compositions. The polyepoxy compounds are glycidyl ethers of polyphenols, specifically diglycidyl or polyglycidyl eithers of bisphenols such as bisphenol A and bisphenol F.

In general, the amount by weight of such a polyepoxy compound in the compositions of the invention may be between about 0.5 and 10 percent, by weight of the chlorinated polymeric hydrocarbon forming the principal ingredient.

Finally, the compositions present in the contact bodies used in the cooling towers of the present invention may optionally contain pigments and/or fillers. In particular, the compositions may contain up to about 2 percent, by weight of the chlorinated polymeric hydrocarbon, of a pigment such as finely divided carbon black which serves not only to color the composition but also affords some degree of ultraviolet protection to the resinous impregnant when the contact bodies are in cooling towers exposed outdoors.

Other fillers and extenders which may optionally be present in amounts up to 50 percent by weight of the chlorinated hydrocarbon resin components include minerals such as finely divided clays, amorphous silica, or aluminum oxide powders. The materials are used in finely divided form, generally with an average particle size of less than 2 microns in diameter, preferably less than 1 micron.

After impregnation of a fibrous web by the method described earlier herein, or by alternative methods, the dried web generally comprises from 10 - 30 percent of impregnant therein, by weight of the treated product. This amount of impregnant can be applied from solutions having a solids content of from 20 - 35 percent by weight, for example.

Cooling towers according to the present invention employing contact bodies formed from sheets of fibrous webs impregnated with a composition as described above have shown unusually long lifetimes for the contact bodies therein under circumstances in which conventional contact bodies disintegrate rapidly and would require replacement. The cooling towers of the invention are thus more trouble-free, require less maintenance, and can be employed for gas-liquid contact with liquids, such as those at high or low pH values or containing corrosive contaminants, under conditions in which cooling towers employing contact bodies of the type conventional in the prior art would be unusable or would require expensive maintenance for frequent replacement of the contact bodies.

Further, the towers of the present invention can be used to cool liquids from temperatures as high as 180.degree.F. without the same loss of contact body structural strength observed in towers employing contact bodies treated with prior art impregnants.

Finally, contact bodies comprising a web of mineral fibers treated with the impregnants described herein are substantially non-combustible and will not support flames.

Claims

What is claimed is:

1. Apparatus for gas-liquid contact having means for mounting a contact body therein and a contact body comprising a plurality of facially opposed corrugated sheets with the corrugations in adjacent sheets being disposed at an angle to each other and the corrugations in alternate sheets being disposed parallel to form a plurality of criss-crossing channels for gas and liquid, said corrugated sheets being a fibrous web impregnated with from 10 to 30 percent, by weight of the impregnated web, of a mixture comprising a chlorinated polymeric C.sub.3 or C.sub.5 hydrocarbon, about 5 to about 100 percent, by weight of said polymer, of a chlorinated terphenyl or chlorinated paraffin; and about 0.5 to about 10 percent, by weight of said polymer, of a polyglycidyl ether of a polyphenol.

2. Apparatus as in claim 1 wherein said contact body comprises sheets impregnated with a mixture which additionally comprises up to 2 percent of carbon black and up to 50 percent of mineral fillers, by weight of said polymer.

3. Apparatus for gas-liquid contact having means for mounting a contact body therein and a contact body comprising a plurality of facially opposed corrugated sheets with the corrugations in adjacent sheets being disposed at an angle to each other and the corrugations in alternate sheets being disposed in parallel to form a plurality of criss-crossing channels for gas and liquid, said corrugated sheets being a non-flammable web of mineral fibers impregnated with from 10 to 30 percent, by weight of the impregnated web, of a mixture comprising: (1) a chlorinated rubber or chlorinated polypropylene comprising about 65 percent by weight of chlorine; (2) about 5 to about 100 percent, by weight of said chlorinated rubber or chlorinated polypropylene, or a chlorinated terphenyl or chlorinated paraffin comprising about 40 to 70 percent by weight of chlorine; (3) about 0.5 to about 10 percent, by weight of said chlorinated rubber or chlorinated polypropylene, of a polyglycidyl ether of a bisphenol.

4. Apparatus as in claim 3 wherein said contact body comprises sheets impregnated with a mixture which additionally comprises from 0 - 2 percent, by weight of said chlorinated rubber or chlorinated polypropylene, of finely divided carbon black.

5. Apparatus for gas-liquid contact having means for mounting a contact body therein; said contact body comprising a plurality of facially opposed operatively interconnected sheets of an impregnated fibrous web defining a plurality of channels in said contact body through which gas and liquid are passed; said sheets being impregnated with from 10 to 30 percent by weight of the impregnated web, of a mixture comprising a chlorinated polymeric C.sub.3 or C.sub.5 hydrocarbon, about 5 to 100 percent, by weight of said polymer, of a chlorinated terphenyl or chlorinated paraffin; and about 0.5 to 10 percent, by weight of said polymer, of a polyglycidyl ether of polyphenol.

6. Apparatus as in claim 5 wherein said plurality of facially opposed operatively interconnected sheets includes corrugated sheets operatively connected to adjacent sheets in said contact body thereby to form said channels and to allow liquid to flow through said contact body.