US2553561A - Process of converting liquid phase hydrocarbon material - Google Patents

Description

J. E EVANS I May 22, 1951 PROCESS OF CONVERTING LIQUID PHASE HYDROCARBON MATERIAL 3 Sheets-Sheet 1 Filed June 20, 1947 INVENTOR. $112204 flEr zmw J. E. EVANS May '22, 1951 PROCESS OF CONVERTING LIQUID PHASE HYDROCARBON MATERIAL Filed June 20, 1947 3 Sheets-Sheet 2 ill! INVENTOR. cfimw' EEVdIZJ ATTORNEY.

y 1951 J. E. EVANS 2,553,561

PROCESS OF CONVERTING LIQUID PHASE HYDROCARBON MATERIAL Filed June 20, 1947 s SheetsSheet :s

INVENTOR. Jzzzew 1 Emzu ATTORN EY.

upon entrance thereof to the reaction zone.

Patented May 22, 1951 PROCESS OF CONVERTING LIQUID PHASE HY DROGARBON MATERIAL James E. Evans, Wallingford, Pa., assignor to Houdry Process Corporation, Wilmington, DeL, a corporation of Delaware Application June 20, 1947, Serial No. 756,031

1 Claim. 1 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 fraction because the latter, in the presence of the gravitating contact material, are either vaporized and cracked or cracked 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 In order to obtain vapors from a heavy liquid-containing charge, it was difficult, 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 undesirable; Accordingly, in many catalytic cracking operations, it has been preferred in preparation of cracking stock to eliminate from crude petroleum or other source of hydrocabons their content of heavy difficultly vaporizable components, if any, resultantin loss of charge stock in the cracking process.

On the other hand, application of a charge containing such heavy components directly to hot cracking catalyst gravitating through a conversion zone permits utilization of the entire charge, including its heaviest portions, for the production of gasoline having desired characteristics. If the contact mass is essentially inert catalytically, vaporization and other desired changes of heavy charge components are eifected 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 unde-..

sired conversions resulting inevitably from timetemperature treatments of such hydrocarbon I charges.

a chamber above a bed of gravitating contact .material, the atomized liquid material being directed downwardly into engagement with the contact material. defining the topsurface of said bed and, more particularly, the atomized liquid material follows generally a conical path as it approaches the top surface of the bed of contact material.

From another aspect of the invention, the atomized liquid material, which is directed downwardly as described above, is engaged with gravitating contact material which falls freely as .a shower of such material prior to engagement thereof with the top surface of the bed of gravitating contact material. More particularly, the density of the aforesaid shower of contact material is such that passage of some or a substantial amount of atomized liquid therethrough is not prevented and, accordingly, from this aspect of the invention, some of the downwardly directed atomized liquid material engages the shower of contact material and some of it engages the contact material defining the top surface of the bed of contact material.

It is desirable for sufiicient vapor or gas pressure to be maintained in the described chamber above the bed of gravitating contact'material to produce concurrent flow, as the operation proceeds, of the hydrocarbon material with respect to the gravitating contact material, this being desirable in order for the conversion operation to be effected in a satisfactory manner.

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

My invention resides in the process of converting liquid phase hydrocarbon material, the process steps and features hereinafter described and claimed.

The atomizer disclosed herein is described and claimed in an application filed of even date herewith Ser. No. 756,032, filed June 20, 1947.

For an understanding of my 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 conversion housing and associated mechanism as constructed in accordance with one form of the invention;

Figs. 2 and 3 are horizontal sectional views, partly in plan, taken on the respective lines 2-2 and 33 of Fig. 1;

Fig. 4, is a vertical sectional view, partly in elevation, showing one form of atomizer utilizable in accordance with the invention;

Fig. 4a is a diagrammatic view illustrating the operation of my novel atomizer;

Fig. 4b is a fragmentary, vertical sectional view, partly in elevation, illustrating a modification of the atomizer shown in Fig. 4; and v Fig. is a horizontal sectional view, partly in plan, taken on the line 55 of Fig. 4.

Referring particularly to Fig. 1, I have shown a vertical housing I which, 'in horizontal cross section, may be circular or of any other suitable configuration. The housing I defines a reaction To "and extending downwardly therefrom.

Slidably associated with the discharge pipe 3a is'a horizontal valvemernber 31) having an operating handle extending through and terminating exteriorly of the housing I. The valvem'ember '31) comprises twospaced'passages 3c and 3d, the

diameter'of the passage'iic being "the'same a'sthe internal diameter ofthe pipe 3a an'd'the diameter of the passage 301 being suitably less than'said internaldiamete'r of the'pipe 3a.

Below the member 3, a horizontal frame is suitably secured to interior surfaces of the housing I, this frame'co'in'prising a plurality of bars 4 secured to each other in right-angular relation, Fig. 3. A tubular member 5 is welded or otherwise suitably securedto the aforesaid bars 4.

Disposed interiorly of 'thetubular membrli isa conical member'fi which may be supported in the position shown'by'la plurality of bars 'lsecured thereto and to said'tubular'member'fi. Theba'se of th'e conical memberfi has diameter'some'w'hat less than the interior diameter of the tubular member 5 and,'by'reas on of the fact that these two members are symmetrically related tofeach other, there is an annular slot 'orpass'age Etherebetween at the lowerends'ther'eof. shown, the longitudinalaxis of the conical 'inem'ber 6, the tubular member '5 and the pipe 3a a'reincoincia dence, and this axiscoincides, preferably, with the longitudinal axis of the'housing'l,

In operation, regenerated or otherheated contact material C havingsuitableconversion'temperature passes continuously from the pi'p'eZaiid, to'suitable extent, fills the receptacle 3 which'defines an upper zone orlocation of the housing I. When the valve member 322 is'p ositione'd as illustrated, namely, with its passage'sd' alined'vvith the pipe 3a, a desired control iseffected on the amount of contact material which'gravitat'es downwardly through the discharge pipe 3a from the receptacle 3. The valve member 311, then, restricts or chokes the downward flow of contact material under the influence of gravity through that part of said pipe 3a'above the plane of said valve member 32). After leaving the valve 'member'iib, the contact material, in the'manner hereinafter described, falls or moves downwardly undenthe influence of gravity 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, thebotfto'm surface of this bed of contact-material engaging a tube sheet 9 horizontally disposed in the housing -bo'unded, at its lower end, by 'the' zone '"or location defined by th upper sfirfa'ce'of the bed B and, at its upper end, by the aforesaid zone or location defined by the receptacle 3.

If'desired,-a plurality of pipes I0 may be spaced "uniformly around the interior surface of the housing I. The upper ends of these pipes ID communicate with the chamber defined by the jmemtr 3, which may support said pipes, and

the lower ends thereof terminate at the upper "surface er the aforesaid bed of contact material. They are adapted to be traversed by a portion, preferably a minor portion, as 20% more or less of the total amount of contact material gravitating downwardly "through the housing I. The pipes I 0, when utilized, "contribute as regards mainte- "nance'of the'surfaceofthe bed B at'a-levelapproximately that'of the lower ends of said pipes.

Any suitable arrangement may be utilized for discharging the contact material C' from the housing I. To this end and as diagrammatically indicated, a plurality offspacedhorizontal tube sheets 'Il may be'secured to theinteriorfsurface ofthe lowerend'portionoff the housing I below the'aforesaid tube sheet 9, the extreme lower end portion of the housing I, preferably, being conical as illustrated. 'A plurality "of suitably spaced tubes or pipes I2 open through'and depend from each of the tubesheets Band II. I As known in the-art, the tubes I2 "on "successively lower tube "sheets progressively'decrease in numberandthe internal diameter thereof progressively increases whereby-the contact material passesthrough the lower conical end portion of the housing "I so as to reach and traverse "a 'm'aindischa'rge pipe or conduit 13 which should be inclined -as illustrated. In known manner, a suitably controlled valve I3a is'associated with the pipe I3 to restrict the fiow'of'contact material therethrough and-cause the'bed B to be a choked bed by reason of the fact that downward movement, under the infiuence'of' gravityof thecontact material'formin'g said bed'B is restricted or impeded.

Adjacent the lower end of'the housing I, any

suitable arrangement may be provided for disspace above theadj'acent conical piles of con-.

tact material. This pipe I6 may have associated therewitha 'contro l valve 'I6a and-is adapted to receive and conduct the converted'vapors to any suitable destination.

Referring; to Fig.4, the atomizer A hereinbeforerefer'redto"should be one which produces fog, mist, spray or "other liquid particles having suitable dimensionsfromthe'liquid hydrocarbon "material admitted thereto. As shown, the

atomizer A comprises a casingwhich maybe formed from separate members II, I8 and I9 secured together in end-to-endrelation by welded joints or otherwise as may be suitable. ,The member I! is generally tubular and defines a circular passage in horizontal section. At its vupper end, said member I! comprises a circular .flange Ila. The member I8 has general frusto- 'conical configuration, the interior surface there- 'of being convexly curved as indicated at I8a. .The member I9 comprises horizontal and vertical portions related to each other in right-angular relation, the lower vertical portion. being closed by a plate which is welded or otherwise suitably secured thereto.

Disposed interiorly of the member I1 is a passage-defining member 2|, the upper surface of which may be welded or otherwise suitably secured to a plate 22 which may be secured to,

the aforesaid flange IIa by bolts23. The upper interior surface of the member 2I, as indicated at 21a, may be defined by a curved surface having parabolic or other suitable configuration.

The lower interior surface of said member 2I, as

indicated at 2 lb, may have conical configuration.

Seated upon the plate 20' and welded or otherwise suitably secured thereto is a member 25 which may be tubular and which, at its upper end, is closed by a plate 25 secured in suitable manner to said member 24, as by a welded joint, or equivalent. The lower exterior surfaceof the member 24 flares outwardly tosome extent as indicated at Ma. As clearly appears, thelongitudinal axis of each of the members 2| and 24 should coincide with the longitudinal axis of the casing defined by the members I'I, I8 and I9 and, further, the surfaces 2| a, 2!?) of member 2I together with the surface 24a of member 24 should.

be symmetrical with respect to said longitudinal zontal portion are alined with the respective passages I921 in the vertical portion in straightline relation or in the sense that each set of alined passages has a common longitudinal axis.

Referring to Figs. 1 and 4, the aforesaid plate 22 is shown as comprising a central opening adapted to receive one end of a pipe 26 which extends horizontally through the wall structure of the housing I. The pipe 26 may support the atomizer A and, as hereinafter described, is traversed by hydrocarbon material. As indicated, the longitudinal axis of the atomizer A 6 pellets or beads'tc. having suitable major iimensions such as between t: 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 ofa 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 elfected in thepresence of the above or other desired types of catalyst, certain 'of which are well known in the art.

Hydrocarbon material having suitable temperature such, for example, as in a range from 800 F. to 900 F. and in any desired proportion of suitable vapor phase and suitable liquid phase material such as a charge having approximately to more or less in the vapor phase and .the remainder in the liquid phase is supplied continuously to the pipe 26 under superatmospheric pressure ranging, for-example, from 10 lbs. to 200 lbs. per square inch gauge or otherwise as may be required for causing the atomized hydrocarbon mixture to reach its intended destination While minimizing engagement thereof with the interior surface of the housing I, such engagement causing undesired formation of carbonaceous material on said housing surface. This hydrocarbon material passes downwardly through the casing defined by the memhers I], I8, I9 and then through the sets-of alined passages Isa. The aforesaid vapor phase material may be a suitable vaporized gas oil, naphtha or lighter hydrocarbon and the aforesaid liquid phase material may be a suitable residual stock, topped or reduced crude.

As regards each set of aligned passages I9a, streams of hydrocarbon material pass, respectively, in opposite directions along substantially a straight-line path as indicated at P, Fig. 4a,

which is related to a horizontal plane by an angle of approximately 45 or otherwise as may be suitable. These streams -engage each other in head-on relation in a zone as indicated at a, Fig. 4a, and, due to such engagement and also due to the presence of the barrier defined by the horizontal and vertical portions of the member I9, there is a resultant stream of atomized material which passes downwardly in an inclined direction along a path having an axis substantially as indicated at P1, Fig. 4a, which may be and preferably is related to the path P in approximately right-angle relation. The atomized material, after it leaves the zone a, exists preferably as a mist or fog and, as it moves from the atomizer A, there is substantial divergence thereof as regards the axis P1. With an arrangement of the character described, efflcient and satisfactory atomization of the liquid material results by reason of the fact that the aforesaid streams of material for each set of aligned passages I 9a engage each other in head-on relation as specified and, further, by reason of the sion to the housing I, should range between 800' Rand 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 deflecting effect exercised on the material by said horizontal and vertical portions of the member I9.

It will be understood that a corresponding stream of atomized material passes fromeach shown, although unnecessarily, "it follows that the respective streams of atomized liquid 'maaerial "pass-along paths radiating froin a {coin- -inon center which coincides with the longitudi -nal a xis of the atomizer -'A. Due to the con- -s 'ergence of each stream, ail of the streams quickly lose their density as such and mergeto form a combined stream wherein the atomized particles -are'distributed more or less uniformly, --this combined "stream, in diverging relation, bemgdirecteddownwardly along generally a'c'onieai 'path.

The contact material'C, exceptfor the deflect-- "action thereon of the conical member 6,

eyes or falls f'reely downward under the infiiience of gravity while travelling along the path from the valve member 31) to thet'op of the bed theyelocity df'the contact material constantly i dreas'ingwhile it travels along saidpath. The tubular-member 5is provided solely to prevent un'desi'red bouncing movement of the contact "-nia'terial toward the wall structure of the casing I "after engagement thereof with the conical men bei 6 and the horizontal dimension of the annular passage 8 definedin part by said tubular-member? is such that it does not restrict or "choke downward movement of the contact material. Therefore, at and below said annular passage 8, the contact material falls freely as a shower S of such material which, in horizontal section, may be approximately circular, the longamma axis thereof coinciding generally with 'thevertical axis of the housing i. By reason of the foregoing and further by reason of the "fact'that the'base diameter of the conical member G is'substantial, for example, approximately -or'nearly one-half the internal diameter of the housing I, it follows that the individual pieces of contact material C, while falling below said 'conicalmember 6, are spaced from'each other to substantial extent. Thus, the density or compactness of this falling shower of contact ma- 'terial is such that it does not prevent or bar passage therethrough of some or even a substantial portion of the atomized liquid material which is directed downwardly in an inclined'di- "rection by the atomizer A and engaged with an inner, circumferentially complete area thereof, said atomizer A, with this end in view, being supported by the pipe 25, or equivalent, interiorly of and generally concentrically with respect to said'shower of contact material The atomized liquid material which thus passes through the freely falling shower S of contact material continues on its downward course and, as shown in Fig. 1 is deposited on the contact material defining a portion of the upper'surface of the bed B which, as hereinbefore stated, forms the reaction zone proper. More particularly, the atomized liquid material is thus engaged with the bed B at least throughout the outer bed area.

When liquid hydrocarbon material is to be engaged with contact material for conversion purposes, it is highly desirable for such liquid material to be in atomized condition in'order'to obtain satisfactory distribution thereof on the contact material. Further, it is desirable for the operation to be conducted under conditions such that atomized liquid material directly 'engagesthe top surface of the bed B rather than the interior surface of the housing I because, 'by so doing, deposition of carbonaceous material on said. interior housing surface is prevented. With the arrangement'of my invention, 'a sub- 'stantial portion ofthe atomized liquid material agefe'iee i :wayofthepipe I3.

hel -{said spent contact material is regenerated perature thereby obtaining maximum benefit from the heat contact "of the contact mass and maximum duratidnbfthe period of engagement therewith du'ri'n'g g'ravit'ating -moveine'nt thereof.

ncccr-amg y, in view offthe ipregoing, itwill be understood that atomized'li quid 'hydrdcarbonmaterial is applied to the falling shower 'of contact material and also to the contaetmaterial forming {the top 'surface of the bediB. As the operation proceeds, hydrocarbon vapors, principally,

inined by the pressure existing in the hereinbethe aforesaid chamber-D under pressure deterfore'described outlet conduit I6. In known manner, a suitablesealing medium, such as a stream of flue gases, is admitted'to the top of the housing I by a pine 2a, Fig. 1, this sealingmedium being maintained under pressure slightly greater 'than'that of said hydrocarbon vapors in order to preyent 'passage ofthese' hydrocarbon vapors upwardly through the pipe 2. Due to this-pressure relation whioh eiiis'ts in'the chamber D, hydrocarbon material admitted thereto through the atomizer A is caused to pass downwardly concurrently regards the contact material forming Ithe bed B, "this hydrocarbon material being cracked in the presence of said contact material and thefresulting cracked vapors being disengaged therefrom at the channel members I5. Thereafter, in the form of the invention herein shown, these cracked vapors enter the tubes I4 byway of the respective'passages I ta, pass downwardlythrough said tubes and enter the space below thetube sheet/9, said cracked vapors passing toany suitable destination by way of the hereinbefo'r'e' described pipe I6.

As the operation proceeds, the spent contact fmat'erialC passes through the'groups of tubes I2 in successionand then leaves the housing I by Thereafter, insuitable manand then returned to the inlet pipe 2 for re-admission to'said'housing I.

The atomizer A herein described functions in a h'i'glfly satisfactory manner to produce desired atomized material when mixed phase hydrocarbon material is passed thereto by way of the pipe .28. During operation, the 'mixed phase material 'passesthrou'gh the pipe ZB'and then traverses the casing definedby the members I'i, I8 and I9. While passing through the member 2 l, the curved "surface? I'a thereof establishes a. desired turbulent chnditi'o'n of the m xed phase material so that it does not m'ov'eaxially of the aforesaid casing into direct engagement withthe plate 25. By so doing deposition of liquid hydrocarbon material in this area isminimize'cl.

The memberZZl. is provided in order to restrict fthefp'ath leadingl't'o the passages I911 in the vertic'alpoltion of the member I!) so that the width thereof 'is substantially the samea-s the width of the path leading to the'passages Iea in the hori- 'z'o'ntal portion of said member I9. The curved surface"I'8aof'themember I8 and the flared surface 24a of the tu'bula'r. member 24 serve as a refinement for the .purposelast noted. When the BIfOIlS/Eiid1)'alll'lsHal/19' Substantially the'sarn'e Width 9 as stated, each resultant stream of atomized material passes along a path substantially as indicated at P1, Fig. 4a, which, as stated, is related to the path P approximately in right-angle relation.

As indicated in Fig. 4b, the tubular member 24 may be so constructed that the width of the path leading to the passages [9a in the vertical portion of the member [9 is substantially less than the width of the path leading to the passages l9a in the horizontal portion of said member [9. If so, a greater amount of hydrocarbon material traverses the passages last named and, accordingly, each resultant stream of atomized material passes along a path, for example, as indicated at P2, Fig. 4a, which is more vertical than the path P1. It will be understood that a result the reverse of that described immediately above is obtained if the arrangement is such that the width of the path leading to the passages I9a in the horizontal portion of the member I9 is less than the width of the path leading to the passages I911 in the vertical portion of said member I 9.

By reference to Fig. 4a, it was hereinbefore stated that, as regards each pair of alined passages lSa, the impinging or engaging streams of hydrocarbon material move in opposite directions along the same straight-line path or substantially so. This is desirable because, with this condition of atomization, the resulting atomized material more closely approximates actual fog or Lmist than is the case when angularly related streams of ma terial engage each other in impinging relation. Hence, by my invention, the impinging streams may have desired high velocity in order to obtain adequate dispersion of the atomized mixture and effective absorption thereof by the contact mate rial. However, such high velocity of the impinging streams of material causes improved atomization as described above and does not effect proportionate increase in the resulting velocity of the fog or mist. Therefore, resulting from the described impingement and, in addition, the deflecting effect of the plate portions 19a, there is a reduced tendency of the latter to migrate to the interior wall surface of the housing I.

In view of the foregoing, it will be understood that an important feature of the invention relates to the application of atomized liquid hydrocarbon material to freely falling contact material and the contact material forming the top surface of the bed of such material. One form of an atomizer suitable for accomplishing this purpose has been illustrated and described but it shall be understood that this phase of the invention is not "to be limited to an atomizer of any particular form. Obviously, for this purpose, various equivalent atomizing arrangements may be utilized as desired.

The atomizer A herein disclosed is adapted particularly for the reception of mixed phase hydrocarbon material from the pipe 26. However, in accordance with the invention, the hydrocarbon material transversing the pipe 26 may be entirely in the liquid phase or substantially so. If so, it is desirable for the disclosed atomizer to have reduced dimensions and for the members 2| and 24 to be omitted therefrom.

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, etc., this material having approximately spherical or chunk-like 75 1946 (pages 1-8). v

' 10 configuration and the major dimensions ranging between A; to of an inch, for example. With contact material of this character, 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, diiiicultly vaporizable fractions or components such as tar, asphalt or the like in various proportions. If vapor phase material is supplied to the atomizer A, this material may be hydrocarbon vapors, steam or the like. Inert contact material of the character described should gravitate through the housing I while having temperature within a range between 800 F. and 1250 F. and the partly liquid 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-broken, 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 housing I by way of the conduit I6.

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 claim.

I claim as my invention:

In a process wherein hydrocarbon material undergoes conversion in the presence of a bed of particles of contact material, which bed gravitates downwardly through a conversion zone and is formed, at least in part, by particles of contact material falling freely downward onto the upper surface of said bed as a curtain of contact material laterally enclosing and bounding a zone above said bed: the method of dispersing liquid hydrocarbons on the particles of contact material in said curtain which comprises introducing hydrocarbon material at least partially in the liquid phase to the interior of the zone bounded by said curtain; flowing paired high velocity streams of said hydrocarbon material upwardly and downwardly, respectively, at a location substantially axial with respect to the zone bounded by said curtain; and engaging said upwardly and downwardly directed streams in head-on relationship so as to atomize liquid hydrocarbons in said streams by the force of collision of oppositely flowing streamsand so as to thereafter flow thus atomized liquid hydrocarbons from said location unobstructedly toward said curtain at resulting reduced velocity.

' JAMES E. EVANS.

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

UNITED STATES PATENTS Number Name Date 2,429,545 Bergstrom Oct. 21, 1947 2,458,162 Hagerbaumer Jan. 4, 1948 OTHER REFERENCES Simpson, Oil and Gas Journal, May 12, 1945 (pages 88-90).

Noll et a1., Houdry Pioneer, vol. 1, No. 2, Oct.

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