US2253510A

US2253510A - Catalytic apparatus

Info

Publication number: US2253510A
Application number: US232134A
Authority: US
Inventors: George S Dunham
Original assignee: Houdry Process Corp
Current assignee: Houdry Process Corp
Priority date: 1938-09-28
Filing date: 1938-09-28
Publication date: 1941-08-26
Anticipated expiration: 1958-08-26

Description

A\18 26, 1941- G. s. DUNHAM 2,253,510

CATALYTI C APPARATUS Filed Sept. 28. '1938 2 Sheets-Sheet l AAAAAAAA AAAAAA Aug. 26, 1941. G. s. DUNHAM CATALYTIC APPARATUS Filed Sept. 28, 1938 2 Sheets-Sheet 2 nj f66 fSO Flc.. 7.

INVENTOR QewyeJZaW/n.

./Qta MMM ATTORNEY Patented Aug. 26, 1941 cA'rALmo APPARATUS George S. Dunham, Ardmore, Pa., asslgnor, by

mesne assignments, to Houdry Process Corporation, Wilmington, Del., a corporation of Del- Application September 28, 1938, Serial No. 232,134

3 Claims.

This invention relates to the art of treating materials, such as uids, for the purpose of effecting changes of a chemical or other nature and it is particularly concerned with the method and apparatus for controlling endothermic and/or exothermic reactions in which a contact mass, inert, reactive or of a catalytic nature, is employed for entering into, promoting or otherwise assisting a reaction.

Objects of the invention include: the provision of a simple and eiiicient method'and apparatus for carrying out numerous and different types of chemical reactions; to effect simultaneous control of a plurality of reactions of the same or different types and/or intensities; to construct an apparatus capable of conducting large scale operations and comprising parts designed to be easily assembled and disassembled; to construct an apparatus having a plurality of units which may be operated independently or together and which are readily removable for repair or replacement without affecting the operation of the remaining units; to provide apparatus having extensive heat exchange surface relative to the volume of contact masses; and to econornically and eiiiciently regulate the temperature of reactions with a minimum of heat exchange iluid. These and other objects and advantages of the invention will be apparent as the detailed descrlptionproceeds.

The invention involves the utilization of a body of heat exchange liquid which is passed or moved exteriorly of a plurality of reaction converters, all of which may be simultaneously engaged in carrying out reactions of the same type, temperature and/or intensity, or simultaneously engaged in reactions of different types and/or intensities at similar or different temperatures, for the purpose of regulating the temperature of the reaction or reactions being carried out. According to certain of its aspects, the invention embraces directing the movement of the heat exchange liquid in a path or paths which are predetermined according to the temperature, and/or nature of the reactions so as to simultaneously and effectively control the temperature of a number of converting units. To this end, the liquid may be moved over a single path to successively traverse the converting units, all of which may be engaged at substantially the same temperature in the same reaction or a group of the converters may be utilized for one reaction while others are simultaneously undergoing reactions of the same or different type and/or intensity at temperatures which are not -too widespread `liquid may move over separate converters 0r groups of converters at separately and individually controlled rates to compensate for differences in the nature and/or intensity of the reactions. The invention also includes a design of converting units which are particularly well adapted for positioning in groups and for providing an arrangement of converting units which minimizes or may even eliminate stagnant zones Within the moving body of heat exchange liquid while providing for extensive heat exchange surface.

The invention is readily applicable to commercial plants where numerous reactions found in both the organic and inorganic branches of chemical industry are independently carried out. Such reactions include the synthesis, decomposition, and other treatment of hydrocarbons and their derivatives, the purification of gases, promoted combustion of carbon monoxide, hydrocarbons and other burnable components of uid mixtures, production of ammonia, synthesis of sulphuric anhydride, the contact vaporization of liquids, etc. Typical applications of the invention may be found in the rening, decomposition, polymerization, molecular rearrangement and other treatment of hydrocarbon starting materials, such as bitumens contained in or derived from petroleum, coal, shale, schist and the like, or obtained by synthesis from non-hydrocarbon reactants. Several of such reactions may be the heat extracted and liberated by the different reactions will minimize or` eliminate the necessity of adjusting .the temperature of the liquid, while other forms of the invention may be more suitable for combinations of different endothermic or different exothermic reactions, in which case the heat exchange liquid will be supplied at a temperature above that of any of the endothermic reactions or below that of any of the exothermic reactions, and the temperature of the liquid adjusted in either direction to any desired extent after the liquid has traversed the converters. Combinations of different reactions m-ay also be controlled by supplying the liquid at a predetermined or selected temperature and the reactions controlled by varying the rate of flow of .the liquid over the converters according to the particular type or intensity of the reactions.

In order to illustrate the invention, concrete embodiments thereof are shown in the accompanying drawings in which:

Fig. 1 is a vertical sectional view through assembled apparatus;

Fig. 2 is a fragmentary plan view of the same apparatus showing portions of some of the lconverters in section;

Fig. 3 is an enlarged view in sectional elevation of one of the converter units;

Fig. 4 is an enlarged view in sectional elevation showing a detail of the invention;

Fig. 5 is a sectional view on the line 5--5 of Fig. 2 with a portion of one of the bailles broken away and the reaction fluid headers and connections removed for the purpose of clarity; and

Figs. 6 and 7 are diagrammatic views showing modified arrangements for circulating the heat exchange fluid.

Referring to the drawings wherein similar parts in the several views are indicated by like characters of reference, I0 indicates a tank containing heat exchange liquid up to the level shown by the broken line II and a plurality of converters I2 which, as shown, are preferably completely immersed in the liquid. The converters comprise upper and lower manifolds I3, I4, respectively, which are connected by means of spaced tubes I5. A plurality of the converters are disposed in aligned groups within the tank Ill so as to provide a passageway I6 between the inner ends of the converters and generally centrally of thev tank. Risers I 'I and I8 are formed integral or rigidly secured to the upper and lower manifolds respectively of each of the converters, forming therewith integral units, and the risers extend from the manifolds and have their free ends terminating in flanges I9 and 20 positioned above and outwardly of the converters. Fluid mains are provided' to pass fluid to and from the converters and are positioned to permit the ready removal of any converter from the tank without affecting the operation of the remaining converters or the functioning of the apparatus and, as shown in Fig. l, groups of inlet and outlet mains are provided for adapting the apparatus to carry out operations which involve different fluids but it will be appreciated that any number of mains can be used within the scope of the invention. One group of mains 2|, 22, and 23 are positioned above and generally centrally of the tank and are joined to vertically disposed

headers

24, 24 through

valved branches

25, 25; 26, 26; and 21, 21; and the

headers

24, 24 are provided with flanges 28 which are bolted or otherwise secured to the anges I9 of the 11p- 75 per manifold risers I1 of each converter, providing valve controlled uld communication between each of the fluid mains and each of the converters, and forming the converters into batteries. Two sets of

fluid mains

29, 30, and 3I are similarly connected in fluid communication with each of the converters through headers 32, which have valved

branches

33, 34, and 35 connecting the mains, and also flanges 36 which are'bolted or otherwise secured to the flanges 20 of the lower manifold risers I8. With the various parts of the apparatus positioned as indicated any converter can be taken out of operation by cutting oil the flow of fluid thereto by means of the various valved branches, and can be bodily removed from the tank by breaking the flanged couplings to the risers I1 and I8 and lifting the unit through power applied to the ring 3'I.

Referring particularly to Figs. 2, 3 and 4 wherein the details of construction of the converter units are clearly shown, the tubes I5 contain a contact mass M of any known type suitable for any desired reaction and are of elongate cross-section providing a minimum of distance from their walls to the center of the mass and an extensive heat exchange surface and the tubes terminate in circular ends 40 to permit their being rolled into suitable openings in the walls 4I and 42 of the upper and lower manifolds respectively. The other wall 43 of the lower manifold is provided with screw threaded apertures to receive removable plugs 44, each of which has a reduced end 45, Fig. 4, which is received in a cylindrical screen 46 to which it is suitably secured. The screens are inserted through the apertures in wall 43 and into the ends of the tubes for retaining the contact material in place and permitting discharge of the material through the apertures, when it becomes necessary, by removing the plug and screen assembly. The upper manifold is provided with a removable cover 41 (Fig. 3) giving access to the interior of the manifold for lling the tubes, and a flat screen 48 is disposed within this manifold adjacent the tube ends to retain the contact material in place when the reaction fluid is admitted through the lower manifold and passed upwardly through the tubes. As indicated in Fig. 2, the tubes I5 are spaced in overlapping relation and angularly disposed relative to the manifold walls providing narrow substantially unbroken paths between the walls of adjacent tubes, and the converters are placed in the -heat exchange fluid tank so that the tubes of adjacent converters extend oppositely providing tortuous paths of travel for the heat exchange fluid in passing over the tubes.

The apparatus so far described affords wide flexibility of operation adapting it to large scale chemical operations of a complex nature. The converters may be used in parallel by admitting fluid simultaneously from one of the mains to the upper or lower manifolds or by admitting fluid simultaneously to some upper and some lower manifolds which can be accomplished by reversing some of the converters and connecting the upper manifolds of some, and the lower manifolds of other converters to common fluid mains, or some may be operated in parallel for one step of a process while others are operated in parallel for another or other step or steps of a process. The converters may also be operated in sequence, such as for example, reactions which are stepwise wherein the starting material receives different stages of treatment, one stage of treatment being carried out in one or more converters\and the reaction products passed kto other converters directly from the first converters for another stage of thev reaction.

One practical use of the apparatus may be consldered'to be the conversion, transformation or other treatment of hydrocarbons. For such operations,-the reaction fluid may be admitted for the on-stream period to the upper or lower manifold of certain or all of the converters and the reaction products withdrawn from the other manifold of each converter. For example, assuming all the valves are closed, the hydrocarbon fluid can enter the tubes through main 2| and upper manifolds I3 by opening valved branches 25 and the products of reaction withdrawn from the tubes through manifolds i4 and mains 29 by opening valved branches 33. Whenever it becomes necessary, af-ter a period of use, to regenerate the mass in place to remove any deposits of a coky, tarry or other nature in order to restore the activity of the mass, the flow of the fluid is stopped by closing the

valved branches

25 and 33 and steam or other inert iluid admitted to the tubes through the main 22 and valved branches 26 to purge the mass of any combustible or explosive hydrocarbons and the resulting mixture removed through the valved branches 34 and mains 36 or the combustible hydrocarbons may be removed by applying a vacuum to one of the

mains

22 or 30. After the purging step, the flow of steam may be stopped or reduced by regulating the valves in branches 26 and the step of regeneration carried out by admitting a medium such as air or other oxygencontaining gas to the tubes through the main 23 and valved branches 21 and the fumes of regeneration removed by the valved branches 35 and mains 3|. When the regeneration is completed, which can be readily ascertained from experience or by an analysis of the fumes, the ow of the regenerating medium is interrupted by closing valves in branches 21 and the tubes may then be purged oi' regenerating medium by vacuum or byvadmitting steam or other inert gas, and the cycle of operation continued.

Several arrangements for supplying the heat exchange liquid to the converters for controlling the reaction are illustrated. As indicated in Figs. l, 2 and 5, one arrangement consists in disposing baiiles 50 within the passageway I6 between the'rows of converters to form a channel The baiiles terminate short of the tank walls and one end of each joins a tubular housing 52 as indicated at 53 (Fig. 2 and 5), while the other ends are free providing direct communication between the channel and tank. One or more slots 54 are provided in the top half of the housing and a portion is cut away in the bottom half on the line 55 permitting fluid to enter and leave the housing. The housing 52 provides a zone for a fluid circulating apparatus, which may take the form of a simple impeller 56, since the pressure drop of the liquid in travelling over the converters is very small due to the comparatively large passageways provided by the converters. The impeller 56 is rotatably driven through a shaft 51 and motor 58 to pump the liquid from the housing through the channel 5| and over the converter tubes. In order to prevent any short circuiting of the heat exchange fluid and to direct it over the converter tubes, deflectors 59 (Fig. 2) are provided on the side walls of the tank and also on the bafiles 50. Supports 60 (Figs. 1, 2 and 5) are positioned on the bottom of the tank for the converters and extend lengthwise thereof in order to prevent any short clrcuiting of the liquid beneath the converters. Heat exchangers such as coils 6| (Fig. v2) may be provided for controlling the temperature of the heat exchange liquid when it is necessary and may be positioned at any convenient place within the tank. With this arrangement, the converters may beoperated so that adjacent ones are undergoing reactions of different types and/or intensities such as an endothermic reac-tion lin some converters and exothermic reactions in other converters which alternate with those undergoing the endothermic reaction. The heat exchange liquid may be supplied to the` converters at a temperature approximately intermediate the temperatures of :the particular endothermic and exothermic reactions which are being carried out and the variation in the temperature of the liquid will be minimized and in some instances approach zero since the temperature increase of the liquid, due to the converters undergoing the exothermic reaction, will tend to be offset by the temperature absorbed by the converters undergoing the endothermic reaction. This arrangement will permit the liquid to be continuously circulated with little or no adjustment of the temperature of the liquid.

Fig. 6 is a diagrammatic view of another arrangement i'or circulating the heat exchange liquid and comprises a tank 65 which is partltioned to form two separate chambers each of which is adapted to contain a battery of converters. The chambers are interconnected at both ends through

fluid lines

66, 61 and 68 forming a circuit for the liquid in the tank and a pump 69 is provided in one of the lines of the circuit for forcing the fluid from one chamber into the other. Heat exchangers 10 vare provided in the circuit for adjusting the temperature of the heat exchange liquid, when it is necessary,

Aafter the liquid has traversed the converters or, if

it is unnecessary, the liquid can by-pass the heat exchangers 10 through the lines 1| and valves 12 after the valves 13 are closed. This arrangement is well adapted for carrying out an endothermic reaction in one compartment and an exothermic reaction in the other compartment and for controlling the reactions by supplying the liquid to the rst compartment at a temperature above that of the reaction and to the other compartment at a temperature below that of the reaction with suitable temperature adjustment, if any is required, before recirculation. However, it is also adapted to similar or other combinations of different endothermic or di'erent exothermic reactions. It is particularly feasible for reactions having a Wide temperature spread since reactions of approximately the same temperature may be effected in one compartment and reactions of a different temperature in the other compartment and adjusting the temperature of the liquid in either direction after its passage through each compartment in accordance with the type of reaction carried out in the compartment which the liquid has traversed.

In Fig. 7, still another arrangement for circulating the heat exchange fluid is shown which is adapted for carrying out a plurality of different reactions wherein provision is made for controlling the reactions by circulating the heat exchange liquid at approximately the same temperature but-at different rates over the converters in accordance with the temperature and/or intensities of the different reactions. The arrangement comprises a heat exchange liquid tank having partitions 16 extending inwardly of the tank and baffles 11 disposed transversely thereof, and adjacent the middle of the tank forming substantially separate liquid zones for each converter but allowing sufiicient communication for all the zones to attain the same liquid level. The liquid `circulating .system consists of a line 18 which is positioned outwardly of the tank and has branches 'I9 extending therefrom and joining the tank in communication with the liquid zones. Pumps 80 are disposed in the branches for circulating the liquid in each zone at any selected rate. A second line 8| joins the line 13 and is positioned between the baies 'I1 and has valved branches 82 extending therefrom and communieating with the inner ends of the liquid zones to control the flow of fluid from each zone in accordance with the rate selected. A heat exchanger 83 for adjusting the temperature of the liquid after its passage through the tank is provided and a Surge tank 84 may be placed in the circuit for storing the liquid before it is recirculated. With this arrangement, the heat exchange liquid can be supplied at approximately the same tempe'rature to all the different zones but at a greater rate over the converters absorbing or liberating the most heat, and with this arrangement, different reactions may be carried out in each zone and the liquid admitted to the zones at approximately the same temperature but the different temperatures of reaction will be controlled by varying the rate of flow of the liquid o ver the converters in accordance with the type and/or intensity of the reactions. For example, for reactions which are intense, such as strongly exothermic or strongly endothermic reactions, the liquid would be circulated at a rapid rate; while for the less intense reactions, the liquid would be supplied at reduced rates depending upon the intensity of the reactions.

The various arrangements for supplying the heat exchange liquid to the converters may be used for simultaneously controlling many combinations of different reactions. Some will be indicated by Way of further explaining the invention but are in no wise to be considered as limiting the invention. Exothermic and simultaneously conducted but lower temperature endothermic reactions may be effectively controlled by supplying the heat exchange liquid at a temperature or temperatures intermediate that of the two reactions with or without independent control of the rate of circulation of the liquid over individual converters or groups of converters. Examples of such a combination of reactions may be found in the decomposition of hydrocarbon starting materials to yield products of similar or different boiling range with the aid of contact material which may be periodically regenerated in place by combustion of burnable deposits formed thereon or therein. A typical illustration is the catalytic cracking of higher boiling hydrocarbons in the presence of adsorptive silicious contact masses within the temperature range of '775 F. to 925 F. involving periodic burning of coke and the like from the contact mass at higher temperatures, say, from 900 F. to 1050 F., but usually at least 950 F. to 1000 F. Through control of the rate at which the selected heat exchange liquid (for example, a' fuel mixture of sodium nitrate and sodium nitrite) is circulated over a given number or battery of converters, its net temperature change resulting from supplying and removing the respective heats of reaction cil may be restricted to Va very small amount even down to 5 F or 10 F.

As described above in connection with Fig. 6, when two or more simultaneously conducted reactions are effected at substantially different temperature levels, the heat exchange liquid may advantageously traverse successive paths to contact in each chamber one or a group of converters engaged in one of the reactions. Chemical processes in which this flow of the liquid nds application include: relatively high temperature decomposition o-f hydrocarbon starting material such as catalytic cracking, reforming, dehydrogenation of gases and the like, usually conducted at temperatures of 800 F. or above, followed by relatively low temperature catalytic polymerization of ordinarily gaseous unsaturated hydrocarbons e'ected, for example, at' temperatures of 550 F. or below; two-stage production of hydrogen from natural or refinery gases, wherein the temperature of the first stage may be in the neighborhood of 1200 F. and that of the second stage of the order of 900 F. to 950 F.; the polymerization of ordinarily gaseous hydrocarbons in liquid phase effected with the aid of adsorptive contact mass at about 300 F. or below, followed periodically by regeneration of the contact mass at temperatures of 900 F. or above. When each of a pair of reactions is endothermic, as is the case in the above mentioned production of hydrogen, the temperature control liquid advantageously passes in heat exchange relation first with higher temperature and then with lower temperature reaction zones with intervening cooling, if necessary. The reverse of this flow may advantageously be employed when simultaneously controlling two or more exothermic reactions, as is the case with the above indicated polymerization process, while either direction of flow may be utilized for the control of both endothermic and exothermic reactions, as exemplied by simultaneously conducted decomposition and polymerization, as set forth above, the particular direction chosen for any given combination of such reactions depending upon the intensity and desired temperature level of each of the reactions. When temperature adjustment of the heat exchange liquid between successive temperature control stages is necessary or desirable, it is often practicable and advantageous to effect at least a portion of that adjustment by heat exchanging all or a portion of the liquid leaving one of its successive paths against at least a part of the liquid entering the same or another path, and such heat exchange is embraced within the scope of the invention.

For a plurality of reactions which may be simultaneously conducted at or near the same temperature level, the heat exchange liquid may traverse a single path or a number of paths in contacting each ofthe converting units, depending upon the nature of each reaction and the rate of heat absorption or evolution from each. When companion reactions are each relatively mild, the liquid in following a single path may successively contact a number of converting units, some of which are engaged in one reaction while in others, another change is taking place. Such may be the case, for example, in controlling the two or multiple stage transformation of higher boiling hydrocarbons into lower boiling products, with or without removal of the desired product between successive stages, in

which case the first stage may be conducted at a selected temperature within the range of 750 F. to 850 F. with each of the following stages being conducted at temperatures a few degrees higher than the preceding stage, as Within the range of 760 F. to 900 F. In such instances, the heat exchange liquid may be supplied at a temperature of F. to 100 F. or more higher than the highest desired converter temperature. Other processes in which this type of flow finds application is in the two-stage dehydration of alcohols, each stage being effected, for example, within the temperature range of 750 F. to 850 F. and in the polymerization of ordinarily gaseous hydrocarbons effected at temperatures up to about 500 F. followed by catalytic hydrogenation of the resulting polymers at temperatures which may be 50 F. higher or lower than that employed for polymerization.

As set forth in the detailed discussion of Fig. 7, the heat exchange liquid may flow at individually controlled rates over converting units engaged in reactions which evolve or absorb heat at different rates. Typical processes toward which this aspect of the invention finds particular application include: contact vaporization of heavy residual hydrocarbons effected, for example, within the temperature range of 750 F. to 900 F., with the aid of an inert or relatively inert contact mass or spreading material, followed by catalytic transformation of the resulting vapors into lower boiling hydrocarbons within the temperature range of 750 F. to 850 F. (in such a process, the heat exchange liquid would normally be supplied at higher rates over the contact vaporizing units); the plural or multistage conversion of sulphur dioxide into sulphuric anhydride, utilizing, for example, a vanadium catalyst within the temperature range of 750 F. to 800 F. (in this instance, the heat exchange liquid is advantageously passed at higher rates over converters utilized for the first stage or stages of the reaction); the use of a metallic contact mass to promote combustion of carbon monoxide and to assist in removing corrosive sulphurous impurities from a stream of flue gases or the like involving periodic reactivation of the sulphated metal, e. g., copper, by reduction, both of which steps may be effected at about the same temperatures within the range of 450 F. to 1200 F. or higher (control advantages are usually realized in this operation when the selected temperature control liquid is moved at higher rates over converters engaged in the combustion step) and certain hydrocarbon reactions involving, for example, alternate endothermic transformation of starting materials and exothermic regeneration of the contact mass effected at a temperature no more than one or two hundred degrees higher than the transformation (for this type of alternating reactions, the control liquid is passed, at a suitable temperature intermediate or approaching either reaction temperature, at accelerated rates over converters in which the regeneration is taking place).

For the majority of the reactions and particularly those whose temperatures of reaction are above 600 F., the preferred heat exchange medium will be a low vapor pressure type of liquid, for example, fused salts or low melting point metals including eutectic and other alloys; however, for reactions having extremely low temperatures of reaction, water may be used, and for reactions having a higher temperature such as polymerization of gases in liquid phase and the refining of gasoline, a higher boiling type of liquid such as mercury or diphenyl may be used.

It will be appreciated that .the foregoing specific examples of process and apparatus are given merely for the purpose of pointing out the invention by means of operative embodiments thereof and that the invention is to be limited only within .the scope of the appended claims.

`What I claim is:

1. Apparatus for controlling chemical reactions comprising an open tank containing liquid, a plurality of converters seated within said tank so as to be removable readily therefrom, said converters being arranged in spaced parallel rows, each having upper and lower fluid manifolds and a reaction chamber therebetween, a plurality of fluid headers positioned outwardly of said tank, certain of the headers having connections with the upper manifolds and certain having connections with the lower manifolds so as to place the converters in a battery and to provide for the passage of fluid through the converters simultaneously, said connections being detachable and permitting the independent removal of any converter from the battery, means for selectively cutting off the ilow of fluid through any converter when it is desired to remove the same from the tank while permitting the passage of fluid through the remaining converters of the battery, a pair of partitions positioned between the converter rows providing an independent compartment for each converter row and a liquid channel therebetween said partitions being constructed so as to provide communication between said liquid channel and the converter compartments, and means in said liquid channel for circulating the liquid over the rows of converters.

2. Apparatus for controlling chemical reactions comprising an open tank containing liquid, a plurality of converters seated within said tank so as to be removable readily therefrom, said converters being arranged in spaced parallel rows each having upper and lower fluid manifolds and a reaction chamber therebetween, a plurality of fluid headers positioned outwardly of said tank,

certain of the headers having connections with the upper manifolds and certain having connections with the lower manifolds so as to place the converters in a battery and to provide for the passage of iiuid through the converters simultaneously, said connections being detachable and permitting the independent removal of any converter from the battery, means for selectively cutting oi the flow of iiuid through any converter when it is desired to remove the same from the tank while permitting the passage of fluid through the remaining converters of the battery, partitionsv disposed between the converter rows providing an independent compartment for each converter row and a liquid channel therebetween, said partitions being constructed so as to provide communication between said liquid channel and the converter compartments. a slotted housing within the tank in communication with the liquid channel and means in said housing for circulating the liquid through the channel and in heat exchange relation with the converters.

3. Apparatus for carrying out chemical reactions and controlling the temperature Vthereof which comprises a tank containing heat exchange liquid, a plurality of converters within said tank and means for circulating the liquid over the converters, said converters each having upper and lower manifolds and a plurality of spaced tubes therebetween containing contact material, said tubes being oblong in cross section and positioned with their vertical axes in parallel and their horizontal axes oi' greater length disposed at the same acute angle to the manifold walls,

said converters being arranged in a battery with the tubes of adjacent converters disposed so that the lines oi.' their horizontal axes of greatest length meet at an angle to provide a zig zag path of travel of the liquid in passing over successive converters.

GEORGE S. DUNHAM.

CERTIFICATE OF CORRECTION. patent No. 2,255,510. August 26, 19m.

GEORGE S. DUNHAM.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 11 first column, line I'(l, for the word "fuel" read --fused-; page 6, first column, line 6, claim 5, for "greter" read --greatest; and that the said Letters Patent should be read with this-correction therein that the same may conform to the record of the case 'in the Patent Office.

Signed and sealed this r[th day of October, A. D. 19ML Henry Van Arsdale, (Seal) cting Commissioner of Patents.