US2574489A - Process of converting hydrocarbon material - Google Patents

Description

Nov. 13, 1951 I R. c. LASSIAT ET AL 2,574,489

PROCESS OF CONVERTING HYDROCARBON MATERIAL 7 Filed Dec. 19, 1947 2 SHEETS-SHEET 1 Zfinventors Rag mom! (lilac/via? q? euben 7. eliwVdg'e (Ittorneg Nov. 13, 195] 2 SHEETS-SHEET 2 Filed Dec.-

- Zhmentors Raymond Glaze/via? 4' Reuben Zfivage Gttomeg able.

Patented Nov. 13, 1951 PROCESS OF CONVERTING HYDROCARBON MATERIAL Raymond C. Lassiat, Swarthmore, and Reuben T. Savage, Ridley Park, Pa., assignors to Houdry Process Corporation, Wilmington, Del., a corporation of Delaware Application December 19, 1947, Serial No. 792,726

4 Claims. (01. 196-52) In the art of converting hydrocarbons, it is desirable for liquid phase hydrocarbon material to be applied directly to hot contact material as it gravitates downwardly through a reaction housing. This is true particularly when the charging stock contains heavy fractions because the latter, in the presence of the gravitating contact material, are either vaporized and converted, or converted directly to lower boiling products.

In prior practice involving utilization of a bed of gravitating contact material, the hydrocarbon charge material existed solely in the vapor phase upon entrance thereof to the reaction zone. In order to obtain vapors from a heavy liquid-containing charge, it was difiicult, if not impossible, to effect complete or substantially complete vaporization of the charge in simple heating equipment without at the same time producing low anti-knock rating gasoline often in substantial quantity. This, as will be understood, is undesir- Accordingly, in many catalytic cracking operations, it has been preferred in preparation of cracking stock to eliminate from crude petroleum or other source of hydrocarbons their content of heavy difilcultly vaporizable components, if any, resulting in loss of charge stock in the cracking process.

On the other hand, application of a charge containing such heavy components directly to hot catalytic material gravitating through a conversion zone permits utilization of the entire charge, including its heaviest portions, for obtaining products having desired characteristics. If the contact mass is essentially inert catalytically, vaporization and other desired changes of heavy charge components are effected at conditions susceptible of easy control to limit or eliminate undesired reaction processes. In either event, particularly when the hot contact mass and liquid-containing charge are contacted adjacent the upper end of the reaction zone, the vaporization and other changes are initiated under practically ideal conditions of heat transfer between the charge and the contact mass thereby minimizing or even eliminating undesired conversions resulting inevitably from time-temperature treatments of such hydrocarbon charges.

In the process herein disclosed, contact material having conversion temperature is fed into engagement with the upper surface of a bed of contact material which gravitates through a conversion housing and, as this operation proceeds, a divergingstream of hydrocarbon material com prising atomized liquid hydrocarbon material is directed downwardly from an atomizing zone into engagement with the contact material defining said upper bed surface. In accordance with the invention and for the reasons hereinafter described, the hydrocarbon material forming said diverging stream is distributed substantially uniformly throughout the area of a plane extending horizontally therethrough closely adjacent the upper bed surface.

More particularly, mixed vapor and liquid phase hydrocarbon material is supplied to the aforesaid atomizing zone and the resulting atomized mixture is applied to the contact material which gravitates through the conversion housing substantially exclusively at the aforesaid upper surface of the bed of gravitating contact material.

In the process of the invention, it is desirable for the upper surface of the bed of gravitating contact material to be maintained approximately level and, to this end, contact material having conversion temperature may be fed into engagement with the upper bed surface both at the periphery of the conversion housing and throughout a central area thereof. Preferably, however and as stated above, the atomized hydrocarbon mixture is applied to the contact material substantially exclusively at the upper bed surface.

Ordinarily, the aforesaid atomizing zone is positioned in a chamber of the conversion housing extending upwardly from the upper surface of the bed of gravitating contact material. In this chamber, sufficient vapor or gas pressure should be maintained to produce concurrent flow, as the operation proceeds, of the hydrocarbon materialwith respect to the gravitating contact material.

Various other objects and advantages of the invention will become apparent from the following detailed description.

The invention resides in the process of con-' verting hydrocarbon material, the process steps, the atomizer arrangement and features of the character hereinafter described and claimed.

For an understanding of the invention and for an illustration of one form of apparatus with which the invention may be practiced, reference is to be had to the accompanying drawings, in which:

Fig. 1 is a vertical sectional view, partly in elevation, showing a conversionhousingand associated mechanism as constructed in accordance with one form of the invention;

Fig. 2 is an enlarged elevational View, partly in section, showing one form of atomizer which may be used in accordance with the invention;

Fig. 3 is an horizontal sectional view, partly in plan, taken on the line 3-3 of Fig. 2 looking in the direction of the arrows;

Fig. 4 is an horizontal sectional view taken on the line 4-4 of Fig. 1 looking in the direction of the arrows; and

Fig. 5 is a vertical sectional view, partly in elevation, showing a detailed feati e of the disclosed atomizer.

In pending application Serial No. 756,031, filed June 20, 1947, now Patent No. 2,533,561, there is disclosure of apparatus utilizable for establishing and maintaining, in a reaction or conversion housing, a gravitating stream of contact material which falls as a shower of such material prior to engagement thereof with the upper surface of a solid bed of contact material which gravitates through the lower portion of said housing. For purposes of explanation but without limitation thereof, the present invention is described in connection with apparatus of the character referred to above.

Thus, referring particularly to Fig. 1, there is shown a vertical housing I which, in horizontal cross section, may be circular or of any other suitable configuration. The housing 1 defines a reaction zone wherein hydrocarbon material is cracked or otherwise converted in the presence of contact material C which moves downwardly therethrough under the influence of gravity, the contact material C being introduced into said housing I in suitable manner, as by an inlet pipe 2 extending through the top housing wall at the center thereof. As shown, a shallow receptaclelike member 3 may be suitably supported in the upper portion of the housing I, said member 3 having a central discharge pipe l opening therethrough and depending therefrom. Slidably associated with the discharge pipe 4 is a horizontal valve member 5 having an operating handle extending through and terminating exteriorly of the housing I. The valve member 5 comprises a passage 5a, the diameter of which is suitably less than said internal diameter of the pipe 4.

Below the member 3, a horizontal frame 6 may be secured to interior surfaces of the housing I, the frame 6 carrying a tubular member l within which is disposed a conical member 8 which is suitably secured to said conical member 6, as by a horizontal frame 9. member 8 has diameter somewhat less than the interior diameter of the tubular member F and, by reason of the fact that these two members are symmetrically related to each other, there is an annular slot or passage If! therebetween at the lower ends thereof. As shown, the longitudinal axis of the conical member 8, the tubular member I and the pipe 4 are in coincidence and the axis coincides, preferably, with the longitudinal axis of the housing I.

In operation, regenerated or other heated contact material C having suitable conversion temperature passes continuously from the pipe 2 and, to suitable extent, fills the receptacle 3 which defines an upper zone of the housing I. When the valve member 5 is positioned as illustrated, namely, with its passage 5a alined with the pipe 4, a desired control is effected on the amount of contact material which gravitates downwardly through the discharge pipe 4 from the receptacle 3. The valve member 5, then, restricts the downward flow of contact material under the influence of gravity through that part of said pipe l above the plane of said valve member 5. After leaving the valve member 5, the contact material, in the The base of the conical manner described in the aforesaid application Serial No. 756,031, falls freely from the annular passage ID as a tubular diverging shower S of contact material until it comes to rest upon and at least partly defines the upper surface of a bed B of gravitating contact material which constitutes the reaction zone proper, the bottom surface of this bed of contact material engaging a tube sheet II horizontally disposed in the housing I and suitably secured to the interior surface thereof.

If desired, a plurality of pipes I2 may be spaced uniformly around the interior surface of the housing I. The upper ends of these pipes I2 communicate with the chamber defined by the member 3, which may support said pipes, and the lower ends thereof terminate at the upper surface of the aforesaid bed of contact material. The pipes I2 are adapted to be traversed by a portion, preferably a minor portion, as 20% more or less of the total amount of contact material which gravitates through the housing I. The pipes I2, when utilized, contribute as regards maintenance of the surface of the bed B at a level approximately that of the lower ends of said pipes.

The aforesaid tube sheet II supports a plurality of suitably spaced depending pipes I3 which open therethrough. The contact material passes through these pipes I3 and thereafter, in known manner, may be discharged from the housing 1 for passage through a conduit I4 which should contain a valve I5 utilizable for controlling the flow of contact material therethrough so that the contact material forming the bed B is restricted or impeded as it moves downwardly through the housing I in solid bed fashion under the influence of gravity.

Adjacent the lower end of the housing I, any suitable arrangement may be provided for disengaging cracked or converted vapors from the contact material C. To this end, as diagrammatically indicated, the aforesaid tube sheet II may support a plurality of tubes I8 which upstand therefrom and open therethrough, the tubes I5 supporting a plurality of suitably arranged channel members Il, or equivalent, which are disposed in inverted relation so that, in known manner, they may be utilized for disengagement of vapors from the contact material, the vapors thereafter entering the tubes It by way of passages 3a formed, respectfully, therein. A pipe I5 opens through the wall of the housing I below the tube sheet I I and communicates with the space above the adjacent conical piles of contact material. This pipe l8 may have as sociated therewith a control valve I9 and is adapted to receive and conduct the converted vapors to any suitable destination.

As shown in Fig. 1, any suitable atomizer such, for example, as the disclosed atomizer A is disposed in a chamber D bounded, at its lower end, by the zone defined by the upper surface of the bed B and, at its upper end, by the aforesaid zone defined by the receptacle 3. The atomizer A is located a suitable distance below the aforesaid conical member 8. It is disposed in 00-- incidence with the longitudinal axis of the freely falling shower of contact material with its longitudinal axis in coincidence with that of the housing 9 and it may be supported in any suitable manner, for example, by a pipe 2t extending from the exterior of the housing I to the interior thereof.

The atomizer A should be one which produces 5. spray or liquid particles having suitable dimensions from liquid hydrocarbon material admitted thereto. To this end, as shown particularly in Figs. 2, 3 and 5, the atomizer A may comprise a casing formed from upper and lower members 2| and 22 which are threaded or otherwise suitably secured to each other in casing-forming relation, the lower end of the aforesaid pipe 20 being suitably secured, as by a threaded joint, to the upper casing member 2| so as to communicate with the casing chamber. 'The casing member 22 comprises an outer horizontal portion 22a having circular configuration. Inwardly there of, said casing member 22 comprises an upwardly inclined portion 22b which, likewise, has circular configuration. Depending, in right-angle relation, from said casing member portion 22b is a tubular portion 220 which, at its lower end, is closed by a transverse wall portion 22d.

In accordance with the invention, each of the inclined and tubular portions 221) and 220 of the casing member 22 comprises a plurality of passages or ports 22c which are spaced apart preferably in uniform relation around the respective casing portions 22b and 220 circumferentially as regards the longitudinal axis of the atomizer. As shown particularly in Fig. 5, the respective passages 22a in the inclined portion 221) are alined with the passages 22c in the tubular portion 22c in right-angle relation.

When hydrocarbon material is to be cracked in the housing I, the contact material C hereinbefore referred to should be catalytic in character and the temperature thereof, upon admission to the housing I, should range between 800 F. and 1000 F. or higher for example, about 900 F. Any suitable kind of catalytic contact material may thus be utilized such, for example, as activated 'clay pellets, or synthetic silica-alumina pellets or beads, etc. having suitable major dimensions such as between 1% and of an inch. Other suitable catalysts for cracking include synthetic plural oxide composites, silicious or non-silicious in character and containing, for

example, zirconia, alumina or beryllia. In lieu of a cracking operation, other types of conversion operations such, for example, as one wherein hydrocarbon material of the character referred to below is desulphurized under known conditions with catalytic contact material of the general character referred to above, or equivalent. Or, reforming or dehydrogenation of naphthas or other normally liquid hydrocarbons may be effected in the presence of the above or other desired types of catalyst, certain of which are well known in the art.

During operation with suitable cracking contact material, vapors such, for example, as vaporized gas oil, naphtha or lighter hydrocarbons having suitable elevated temperature, as in a range from 850 F. to 950 F., may be admitted continuously to the chamber D by way of a conduit 23 opening thereinto adjacent the top of the housing I. Simultaneously, hydrocarbon material such, for example, as a suitable residual stock, topped or reduced crude which may be in mixed vapor and liquid'phase condition or substantially totally in the liquid phase and having temperature elevated into a suitable range as, for example, from 400 F. to 800 F. is charged continuously through the pipe 20 under superatmospheric pressure ranging, for example, from lbs. to 200 lbs. per square inch gauge.

If required, in order to maintain a pressure drop through the atomizer having proper magnitude for obtainingsatisfactory atomization of the liquid hydrocarbon material, the hydrocarbon charge traversing the pipe 20 may be supplemented to suitable extent by steam at proper pressure which may be admitted to said pipe 20- in any desired manner, not shown.

Accordingly, hydrocarbon material, at least partially inthe liquid phase, traverses the pipe 20, thereafter passes through the atomizer casing and, at relatively high velocity, is ejected from the passages 22c. As regards each set of these alined passages, streams of such" hydrocarbon material engage each other in angular relation to produce a resultant atomized mixture which passes downwardly along an axis as indicated at P, Figs. 1 and 2. As the atomized mixture is thus ejected downwardly, each stream thereof diverges as regards its axis P and, soon after leaving the atomizer passages 22c, all of these streams merge to form a combined stream comprising atomized liquid material having generally conical exterior configuration, Figs. 1 and 4.

When the conditions are proper, as determined principally by the diameters of the passages 22c forming one circular row thereof compared with the diameters of the passages 22c forming the other circular row thereof and the height of the atomizer A above the upper surface of the bed B of contact material, an atomized mixture having conical configuration as aforesaid may be obtained having diameter only slightly less than the internal diameter of the housing I. It is a feature of the invention, as indicated in Fig. 4, that, at the level of the upper surface of the bed B (and at other horizontal levels spaced to small extent above said upper bed surface)", the atomized mixture including the atomized liquid material is distributed substantially in a uniform manner throughout the area of each of said levels. This is attained (when the atomizer is properly positioned above the upper bed surface) principally by reason of the described sloping relation of the casing portions 22?) and 220 and, in addition, by the amount of liquid material traversing the passages 22:: of the respective rows thereof. It results, therefore, that respective unit surface areas of the contact material forming the upper bed surface receive substantially equal amounts of the atomized mixture. This is highly desirable because insuring substantially equal participation of all of the contact material in the cracking operation.

Should there be any substantial migration of atomized liquid material, in an operation of the character described, to the interior surface of the housing I, there will be resultant production or deposition, on this surface, of carbonaceous material which, in the course of time, breaks off into chunks of such material that move into and through the bed of contact material with resultant partial or complete plugging of the interior pipe outlets at the bottom of the housing as herein described.

Thus, in accordance with the invention, the

described substantially uniform distribution of the atomized mixture at various levels above the upper bed surface is effective as regards reduction of the amount of atomized liquid material which migrates in an undesired manner.

Moreover, the atomizer should be of such character, for example, as herein disclosed that it positively directs the atomized mixture substantially entirely toward the upper bed surface and, again, the atomizer should be of such character that, predominantly, it produces spray or small droplets, rather than fog or mist, from the liquid hydrocarbon material. Still further, in a detailed aspect of the invention and in order to minimize undesired migration of atomized liquid material, it is desirable for the material which isadmitted to the atomizer to be predominantly liquid phase material.

With an atomizer casing having interior configuration as indicated in Fig. 2, it may be desirable for a filler ring 24 to be associated with the interior surface of said casing as shown in Fig. 4. When a filler ring having the proper thickness is selected, the allocation of hydrocarbon material to the upper and lower rows or" passages 22c is controlled in an improved manner with resultant production or" a conical stream comprising atomized liquid material having the characteristics hereinbeiore described.

In an operation of the character described, it is desirable for the upper surface of the bed 8 of contact material to be approximately level at all times and it is for this reason that the disclosed arrangement comprising the pipe 4 and conical member 3 is provided. As regards the described shower S of contact material falling from the annular passage l8, it necessarily results that there is some application of the atomized mixture to the freely falling contact material. said application Serial No. 756,031, the density or compactness of the pieces of contact material forming the aforesaid shower of contact material is insufficient to prevent passage of the atomized mixture therethrough to substantial extent. The barrier effect, then, of this shower of contact material is minor and it does not prevent the atomized mixture from being distributed substantially uniformly, in the manner herein described, at and immediately above the top surface of the bed B. The application of the atomized mixture, then, to the contact material forming the shower S is incidental to the disclosed process since, as stated, this shower of contact material is utilized principally for bedleveling purposes. In lieu thereof, it shall be understood that the bed may be leveled otherwise as may be desirable and it shall also be understood that the invention, in a broader aspect, is not to be limited to any bed-leveling arrangement whatsoever.

As stated, hydrocarbon vapors, which in connection with a cracking operation preferably have temperature substantially higher than that of the liquid hydrocarbon material admitted to the atomizer A, may be passed into the housing I by way of the conduit 23. These vapors pass through the housing I concurrently as regards the contact material C and in the presence thereof are converted to cracked pro-ducts. In so doing, the heat content of-these vapors, by reason of the temperature relation referred to immediately above, assists as regards vaporization of the liquid hydrocarbon material entering said housing I through the atomizer A and said vapors provide a desired control on the relative quantities of contact material and hydrocarbon material traversing the housing I. Simultaneously, in the manner described above, an atomized mixture is engaged principally with the contact However, as described in the aforematerial forming the top surface of the bed B with resultant vaporization of the atomized liq uid material and formation of cracked products which pass through the housing I concurrently with respect to the contact material C. As regards the total charge entering the housing I, the ratio of vapors to -liquid material may be such as is suitable and desirable. Thus, for example, between 10% and 30% of the charge may be in the liquid phase and the remainder in the vapor phase. In this connection, it will be understood that the vapor phase material is proportioned in a desired manner between the conduits 20 and 23.

Accordingly, in view of the foregoing, it will be understood that hydrocarbon material admitted to the housing I by way of the pipes 20 and 23 is converted in the presence of the contact material C to produce cracked products. As the operation proceeds, hydrocarbon vapors, principally, fill the aforesaid chamber D under pressure determined by the pressure existing in the hereinbefore described outlet pipe l8. In known manner, a suitable sealing medium, such as a stream of flue gases, is admitted to the top of the housing I by way of a pipe la, Fig. 1, this sealing medium being maintained under pressure slightly greater than that of the said hydrocarbon vapors last named in order to prevent passage of these hydrocarbon vapors upwardly through the pipe 2. Due to this pressure relation which exists in the chamber D, hydrocarbon material admitted to said chamber by way of the pipes 20 and 23, as described above, is caused to pass downwardly concurrently as regards the gravitating contact material, this hydrocarbon material being cracked in the presence of said contact material and the resulting cracked vapors being disengaged therefrom at the channel members ll whereupon they are passed to any suitable destination by way of the hereinbefore described outlet pipe l8. In known manner and by suitable means, not shown, a suitable gaseous medium such as steam is admitted to the lower portion of the housing I, below the pipe [8 and under pressure above that existing at the level thereof, to prevent passage of the hydrocarbon vapors through the pipe I4.

As herein shown, the pipe 20 comprises a curved portion which is located vertically above the atomizer A. When mixed phase material traverses the pipe 20, heavy material, due to centrifugal action, is concentrated at one side of said curved pipe portion. Accordingly, a suitable orifice arrangement, not shown, should be disposed in the vertical portion of the pipe 20 above the atomizer in order to remix the liquid and vapor phase material.

The preceding description relates to catalytic conversion processes but the invention is not to be so limited. Thus, the contact material C may be substantially inert catalytically such, for example, as fused alumina (Alundum) fused silica and alumina, heat-resistant quartz or quartz pebbles, fused silica and alumina, fused silica, etc., this material having approximately spherical qr chunk-like configuration and the major dimensions ranging between A; to of an inch. for example. With contact material of this character, hydrocarbon vapors may be admitted to the housing I by way of the pipe 23 under the conditions hereinbefore described and the atomizer A may be supplied with at least partially liquid phase heavy hydrocarbon material such, for example, as entire crudes, reduced or topped crudes, crude bottoms, residual or heavy bottoms, distillation residuums, etc., all of which contain heavy, difiicultly vaporizable fractions or components such as tar, asphalt or the like in various proportions. Inert contact material of the character described should gravitate through the housing I while having temperature within a range between 899 F. and 1259 F. and the heavy hydrocarbon material should be supplied to the atomizer A while having temperature ranging up to 750 F. or higher. When the operation is of this character, the liquid portion of the heavy hydrocarbon material is vaporized and viscosity-bro-ken, in the example shown, in response to engagement thereof with the freely falling inert contact material and that forming the top surface of the bed B, the resulting vaporized products being withdrawn from the hous ing 5 by way of the conduit 13.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim as our invention:

1. In a process wherein hydrocarbon material undergoes conversion in the presence of a bed of particles of contact material ina confined zone, which bed gravitates downwardly through a conversion zone; the method of contacting hydrocarbon material at least partially in the liquid phase with said contact material which comprises feeding said hydrocarbon material to an atomizing zone located within said confined zone above said bed, spraying atomized liquid hydrocarbon material downwardly from said atomizing zone as a body of spray whose horizontal cross sectional area continuously expands and produces a substantially continuous area of horizontally uniformly distributed spray at the base of said body, maintaining the surface of said bed at a level where said surface is substantially coextensive with said area, and contacting substantially all of the surface of said bed with said spray of atomized liquid whereby uniform distribution of said atomized liquid on the particles of contact material is effected.

2. The method of claim 1 in which a portion of the contact material falls freely as a disperse shower through said body of spray and onto the surface of said bed.

3. In a process wherein hydrocarbon material undergoes conversion in the presence of a bed of particles of contact material in a confined zone, which bed gravitates downwardly through a conversion zone; the method of contacting hydrocarbon material at least partially in the liquid phase with said contact material which comprises feeding said hydrocarbon material to an atomizing zone located within said confined zone above said bed, spraying atomized liquid hydrocarbon material downwardly from said atomizing zone from a plurality of separated points along continuously expanding paths, said paths merging to produce a substantially continuous area of horizontally uniformly distributed spray, maintaining the surface of said bed at a level substantially coextensive with said area and contacting substantially all of the surface of said bed with said spray of atomized liquid whereby uniform distribution of said atomized liquid on the particles of contact material is effected.

4. In a process wherein hydrocarbon material undergoes conversion in the presence of a bed of particles of contact material in a confined zone, which bed has a circular upper surface and gravitates downwardly through a conversion zone; the method of contacting hydrocarbon material at least partially in the liquid phase with said contact material which comprises feeding said hydrocarbon material to an atomizing zone located within said confined zone centrally above said bed, flowing a plurality of small streams of said hydrocarbon material from a circular locus downwardly at a small acute angle to the vertical axis of said bed, flowing a second plurality of small streams of said hydrocarbon material radially outwardly and normally to the first plurality of streams in impinging relation thereto, and directing the resultant body of atomized liquid downwardly toward the surface of said bed.

RAYMOND C. LASSIAT. REUBEN T. SAVAGE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Commercial T. C. C. Operation on Partially vaporized Charge Stocks by H. D. Noll et al.,

Houdry Pioneer, October 1946, (Figure 1) page 1.

Claims (1)

1. IN A PROCESS WHEREIN HYDROCARBON MATERIAL UNDERGOES CONVERSION IN THE PRESENCE OF A BED OF PARTICLES OF CONTACT MATERIAL IN A CONFINED ZONE, WHICH BED GRAVITATES DOWNWARDLY THROUGH A CONVERSION ZONE; THE METHOD OF CONTACTING HYDROCARBON MATERIAL DOWNWARDLY FROM SAID LIQUID PHASE WITH SAID CONTACT MATERIAL WHICH COMPRISES FEEDING SAID HYDROCARBON MATERIAL TO AN ATOMIZING ZONE LOCATED WITHIN SAID CONFINED ZONE ABOVE SAID BED, SPRAYING ATOMIZED LIQUID HYDROCARBON MATERIAL DOWNWARDLY FROM SAID ATOMIZING ZONE AS A BODY OF SPRAY WHOSE HORIZONTAL CROSS SECTIONAL AREA CONTINUOUSLY EXPANDS AND PRODUCES A SUBSTANTIALLY CONTINUOUS AREA OF HORIZONTALLY UNIFORMLY DISTRIBUTED SPRAY AT THE BASE OF SAID BODY, MAINTAINING THE SURFACE OF SAID BED AT A LEVEL WHERE SAID SURFACE IS SUBSTANTIALLY COEXTENSIVE WITH SAID AREA, AND CONTACTING SUBSTANTIALLY ALL OF THE SURFACE OF SAID BED WITH SAID SPRAY OF ATOMIZED LIQUID WHEREBY UNIFORM DISTRIBUTION OF SAID ATOMIZED LIQUID ON THE PARTICLES OF CONTACT MATERIAL IS EFFECTED.

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