US2944957A

US2944957A - Electrolytic drying apparatus

Info

Publication number: US2944957A
Application number: US688035A
Authority: US
Inventors: Frederick A Keidel
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1957-10-03
Filing date: 1957-10-03
Publication date: 1960-07-12
Anticipated expiration: 1977-07-12

Description

July 12, 1960 F. A. KElDEL ELECTROLYTIC DRYING APPARATUS Filed Oct. 3, 1957 75 6 7 RL %22 223 OE v H r z a TD m \A ma 0 j V n w W A A K. C- \N 3 C N I M f 4 m 3 \N 2 m. g R 4 3 F O x 7 2 Y B 7 5 5 3 l 2 2 O 2 w 5 n L O V m D E I. P M 2 L r 2,944,957 ELECTROLYTIC nn'rnsro APPARATUS Filed Oct. '3, 1957, Set. No. 688,035

4 Claims. (Cl. 204-275) This invention relates to an electrolytic drying apparatus for the drying of fluids, and particularly to an electrolytic drying apparatus for the drying of fluids which is coulometric in principle and which is adapted to regeneration of the water absorbing medium over an indefinite time. This application is a continuation-mpart of application S.N. 505,598, now issued as Patent 2,816,067 assigned to common assignee.

Numerous processes have been devised for the removal of water'fromfluids by absorptive and adsorptive processes; however, there are disadvantages arising from variations in the water-removal propensities of the moisture-removing medium in the course of use, difficulties in regeneration and relatively low efliciencies, particularly where the amount of water present in the fluid is small and measured in parts per million. A primary object 'of this invention is to provide an electrolytic apparatus for the drying of fluids whichis coulometric in principle and, therefore, consumes electrical energy indirect proportion to the amount of water which is removed. Another object of this invention is to pro- 2,944,957 Patented July 12, 1960 in which the deliquescent hygroscopic medium is cyclically exposed to the fluid to be dried and thereafter moved into and out of contact with electrode structures in order to effect regeneration in a separate chamber apart from the chamber in which the drying is effected are taught in divisional application Ser. No. 822,342, filed June 23, 1959.

Referring to Figs. 1 and 2, a preferred embodiment of this invention utilizes a metal conduit section 10 which is provided with flange ends 11 and 12 to which are secured

companion flanges

13 and 14, respectively, by bolts 15.

Flanges

13 and 14 are tapped for connection with the process fluid supply and delivery lines, the inlet connection for the apparatus depicted being shown at 19 in flange l3 and the outlet connection being indicated at 20 in flange 14. Flange 14 is further provided with an integral electrical conduit 21 for the reception of 1 insulated eleystrical lead 22 which supplies current to the vide an apparatus for the drying of fluids wherein the water-removing characteristics of the absorbent are'maintained at a high and substantially c'onstant level. An-

other object of this invention is to provide an apparatus for the drying of fluids which can be utilized for the drying of fluids in continuous flow. The manner in which these and other objects of this invention are obtained will become apparent from the following detailed description and the illustrative drawings, which:

Fig. l is a partially schematic view of a"prefe rre d embodiment of the apparatus of this invention shown in longitudinal section, N

Fig. 2 is a partially schematic sectional view ofseveral electrode elements and their relationship with respect to one another for the apparatus of Fig. 1',

Fig. 3 is a plot of percent efficiency versus applied voltage for the drying method of this invention, p h

Fig. 4 is a cross sectional view taken transverse the direction of fluid flow of a second embodiment of the apparatus of this invention.

Generally, this invention comprises electrolytic apparatus comprising in combination atleast one pair of electrically isolated electrodes disposed in close proximity to one another, a deliquescent hygroscopic substance which is electrically conductive only when wet anode elements as hereinafter described.

7 The electrode elements of the apparatus are indicated schematically in Figs. 1 and 2, the anodes being represented at 25 enclosed within annular electrical insulators 37 and the cathodes at 26, these being arranged in alternation as indicated and separated from one another by insulating discs 27. As shown most clearly in Fig. 2,

the anodes 25 and cathodes 26 are both provided with a. multiplicity of through going passages 30 which serve as passages for the flow of fluid to be dried axially of the conduit while opposing little resistance to such flow. If desired, the anodes and cathodes may, in fact, be made from screen material, platinum screen being suitable for the anodes and stainless steel screen for the cathodes. The insulating disc 27 may be fluid-pervious glass cloth or the like which is also sufficiently open to oppose a minimum of resistance to fluid flow therethrough. cathodes 26 and discs 27 are provided with central openings'3l for reception of the electrical conductors 33 which serve as the continuation of lead 22 between successive anode elements 25, and the cathodes and discs may be provided with radial slits, not shown,

"for convenience of assembly of the multiplicity of electrodes into the arrangement shown in Figs. 1 and 2. Conductors 33 are provided with annular insulators 34 barring short 'circuiting contact vwth adjacent cathode elements.

As indicated in Fig. 2, successive anodes may be joined in electrical circuit by conductors 33 which are soldered or otherwise joined to opposite-faces of anodes 25, the topmost anode of the assembly being in electrical connection with lead 22 running to the electrical power source 36. Cathode elements 26 fit tightly in abutting relationship with the inside of conduit llland are in electrically conductive relationship with the conduit, which is grounded at 35 to establ sh return connection with the grounded negative of the power source 36.

Switch 33 is interposed in the power circuit for control purposes. The power source should, of course, be of direct current type delivering a voltage sufiicient to effect electrolysis of any water absorbedlin the deliquescent hygroscopic substance coating the electrodes, a 45 volt radio B'battery being a' suitable source for very small drying installations. It will be noted that anodes 25 are of somewhat smaller diarneter than cathodes 26 and are insulated from contact with the inside of conduit 10 by the annular insulators 37.

From the foregoing, it will be understood that the anodes 25 are electrically insulated from the cathodes 26 by. discs 27. In the course of assembly, adjacent faces of the electrodes, passages 30 and discs 27 are well coated with a deliquescent hygroscopic substance which is electrically conductive only when wet and which is capable of absorbing Water from the fluid to be dried. This moving water quantitatively from the fluid. Phosphoric.

acid has proved to be completely satisfactory for the drying of fluid streams comprising one or more of the ingredients of. air, ethylene and halogen-substituted hydrocarbons such as the Freons and ethyl chloride, and is applied by merely brushing it on over the paired electrodes and also over discs 27 therebetween. 'Since the more concentrated solutions of phosphoric acid are relatively viscous, and are thus somewhat more diflicult to apply than dilute solutions "of the order of acid content, it is preferred to apply the acid in dilute mixture and then operate the apparatus without putting a fluid stream through it for a suflicient time to dry the acid thoroughly and thus bring it up to a hygroscopic level capable of absorption of water from a fluid stream toube dried, this condition being signalled by failure of the acid to further conduct the electric current. When the, acid is thus dehydrated by electrolysis prior to use in the drier, it displays strongly hygroscopic properties and, since during operation water absorbed in his completely removed by electrolysis without any vitiation of the acid, it remains hygroscopic indefinitely.

Other examples of suitable deliquescent hygroscopic substances which can be utilized according'to this invention are potassium hydroxide, sodium-hydroxide and potassium carbonate. Theuse of either sodium hydroxide of-potassium hydroxide singly. or in mixturcis'con- In operation, it will be' understood that the apparatus.

is first placed in readiness for absorption removal of waterfrom the fluid stream by drying throughelectro'lysis ofany water in the deliquescent hygroscopic substance by connection with the power source 36 for a suitable period, which may require 30 hours or more, the achievement of drying being indicated by a rapid increase in electrical resistance accompanied by a'drop in current flow. At this time wet fluid may be introduced through vinlet connection 19 and removed from the apparatus after transit through the passages of the electrode assembly through outlet 20. 'AsVthe fluid traverses the electrode assembly, it is brought-into intimate contact with the deliquescent hygroscopic substance spanning the electrodes and any water therein is removed by absorption and electrolyzed very quickly to hydrogen and oxygen which bubbles from the electrodes into the fluid stream and is carried from the apparatus by the stream.

Tests on an experimental unit made up of an assembly of 19 electrode discs 2" in diameter separated one from another by 18 glass fiber discs showed. a removal efficiency in excess of 90% in the separation of water from air where the air flow rate was V2 c.f.m. and the input water concentration was 100 p.p.m. The anodes of the experimental unit were fabricated from 40 mesh platinum wire screen while the cathodes'were 100 mesh stainless steel screen. The voltage of the power source Was 25 v. and operation was conducted at atmospheric pressure and a temperature of about 30 C.', the pressure drop in transit through the unit being about 2 lbs/sq. in. per

cu. ft. per minute. The efliciency in terms of applied voltage was determined for the apparatus and the relase is maintained substantially constant and at a high level, the operating 'cost-is very low, especially when low concentrations of Water are to be removed, the apparatus A. tionship obtained is depicted in Fig. 3. In general, it can be. said that the removal of each part per million of water from one million cu. ft. of an air stream by the process of this invention requires 0.2 kw. hr. based on a supply voltage of 4 v. In the example hereinabove described the fluid dwell time was only of the order of about 0.2 second. I If this dwell time is doubled, as by doubling the length of the drying unit, the drying efficiency' is increased -to about 9.9%, and further lengthening of the drying path is accompanied by a corresponding increase in the drying efliciency.

It will be understood that the drying method of this invention is coulometric in principle and that water removed in the course ofoperation can be calculated in accordance With; Faradays "law, A determination of water removed from the fluid dn'ed can be obtained by determining the current drawn from the power source over a finite period of operation; however, in the interests of simplicity and economy it is preferred to determine water by electrolysis in accordance with the teachings of my copending application ,S.N. 505,599, filed May 3, 1955, now issued as Patent 2,830,945.

A second embodiment of the apparatus of this invention is shown in Fig; 4, wherein the electrodes comprise lcngths of screen disposed axially within the metal conduit 10, the cathode in this case being screen 40 in electrically conductive contact With the inside periphery of metal conduit 10, whilethe anode is screen '41 out of contact at. all points with conduit 10. The screens are separated throughout their widths and lengths by porous insulator 42, which may conveniently be a glass fabric. The anode-insulator-cathode assembly is soaked thoroughly with the deliquescent hygroscopic electrolyte substance and wound spirally in tight, compact convolutions to present a maximum surface area to contact with the fluid stream to. be dried. Any clearance between the outside ofthe electrode assembly and the inside of con- .duit '19 is preferably packed with an impervious material, not showm-to prevent bypasschanneling of the process stream. The electrical circuit for the embodiment of Fig. 4 is the same as that for the apparatus of Figs. 1 and 2, connection tothe anode being made by an insulated lead '22, while conduit 10- is grounded as indicated at 35.

The embodiments hereinabove described in detail discharge the products of electrolysis into the fluid stream which is dried and, in many cases, this is unobjectionable and overweighed by the simplicity of construction of the drying apparatus. In situations where such presence is not desired, either from the standpoint of product adulteration or vfire or explosion hazards incident to later possible recombination of the hydrogen with oxygen, it is preferred to' employ the apparatus operating on the cyclical principle. described in my divisional application hereinbefore referred, to.

From theforegoing itwill be understood that this .invention comprises drying apparatus which is adapted .to the drying ofboth liquids and gases and which possesses very great'advantages over drying apparatus now known to, the art, in thatthe efficiency of the drying agent per is readily controllable-and the drying action is selective .to Water in all systems wherein there are no other ma- ,terials present havingan-overvoltage lower than water. --It will be'understood that this invention can be modified in numerous respects without departure from the essential spirit, wherefor it is intended to be limited only within the. scope of the following claims.

What is claimed is: I

1. An apparatus for drying a flowing fluid comprising in combination a closedconduit, fluid inlet and outlet openings axially spaced one from another in said conduit, an electrode pair disposed axially in said conduit between said fluid inlet and outlet openings at least one of said pair of which is out of contact with said conduit consisting of two spirally arranged electrical conductors out of electrically conductive contact with each other, a deliquescent hygroscopic substance which is electrically conductive only when wet spanning said electrode pair over a length suificient to absorb a substantial amount of water from said fluid in the course of passage of said fluid through said conduit, and a direct current power source of voltage sufiicient to electrolyze absorbed water in said deliquescent hygroscopic substance connected across said electrodes.

2. An apparatus for drying at flowing fluid comprising in combination a closed conduit provided with fluid inlet and outlet ports axially spaced one from another, electrode pairs within said conduit consisting of alternately disposed perforate electrical conductors arranged substantially coaxial with said conduit between said fluid inlet and outlet ports and out of contact with each other, successive ones of which constitute anode elements and cathode elements, a deliquescent hygroscopic substance which is electrically conductive only when wet spanning said conductors over a length sufficient to absorb a substantial amount of water from said fluid in the course of passage of said fluid through the openings in said conductors, a direct current power source of voltage sufficient to electrolyze absorbed water in said deliquescent hygroscopic substance and electrical leads connecting said power source across said electrode pairs.

3. An apparatus for drying a flowing fluid according to claim 2 wherein successive ones of said electrical conductors are separated by fluid-pervious elements fabricated from material of electrically insulating nature.

4. An apparatus for drying a flowing fluid comprising in combination a closed conduit provided with fluid inlet and outlet ports axially spaced one from another, at least one electrode pair within said conduit consisting of alternately disposed perforate electrical conductors disposed out of contact with each other between said fluid inlet and outlet ports, successive ones of which constitute anode elements and cathode elements, a deliquescent hygroscopic substance which is electrically conductive only when wet spanning said conductors over a length sufficient to absorb a substantial amount of water from said fluid in the course of passage of said fluid in proximity to said conductors, a direct current power source of voltage suificient to electrolyze absorbed water in said deliquescent hygroscopic substance and electrical leads connecting said power source across said electrode pairs.

DAdrian June 13, 1933 Staverman Sept. 18, 1956 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 2 944 957 July 12 1960 Frederick Aa Keidel L It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters .Patent should read as corrected below.

Column Spline 38 for 'of" read m or a Signed and seaied this 3rd day of January 1961c (SEAL) Attest:

KARL H, AXLINE ROBERT c. WA-TsoN Attesting Oificer Commissioner of Patents

Claims

4. AN APPARATUS FOR DRYING A FLOWING FLUID COMPRISING IN COMBINATION A CLOSED CONDUIT PROVIDED WITH FLUID INLET AND OUTLET PORTS AXIALLY SPACED ONE FROM ANOTHER, AT LEAST ONE ELECTRODE PAIR WITHIN SAID CONDUIT CONSISTING OF ALTERNATELY DISPOSED PERFORATE ELECTRICAL CONDUCTORS DISPOSED OUT OF CONTACT WITH EACH OTHER BETWEEN SAID FLUID INLET AND OUTLET PORTS, SUCCESSIVE ONES OF WHICH CONSTITUTE ANODE ELEMENTS AND CATHODE ELEMENTS, A DILIQUENSCENT HYGROSCOPIC SUBSTANCE WHICH IS ELECTRICALLY CONDUCTIVE ONLY WHEN WET SPANNING SAID CONDUCTORS OVER A LENGTH SUFFICIENT TO ABSORB A SUBSTANTIAL AMOUNT OF WATER FROM SAID FLUID IN THE COURSE OF PASSAGE OF SAID FLUID IN PROXIMITY TO SAID CONDUCTORS, A DIRECT CURRENT POWER SOURCE OF VOLTAGE SUFFICIENT TO ELECTROLYZE ABSORBED WATER IN SAID DELIQUESCENT HYGROSCOPIC SUBSTANCE AND ELECTRICAL LEADS CONNECTING SAID POWER SOURCE ACROSS SAID ELECTRODE PAIRS.