US2853285A - Method and apparatus for producing unicellular spherulized clay particles - Google Patents

Description

Sept. 23, 1958 J. M. NEFF ET AL 2,853,285

METHOD AND APPARATUS FOR PRODUCING UNICELLULAR SPHERULIZED CLAY PARTICLES Filed Oct. 18, 1952 2 Sheets-Sheet 1 I .1 q... (3 F 4 1 M a 14 I K E I 1/ k X \A- 43 ETYZEYTIET" xiv/7w JV. ZVEFF I EEOME .2. 1y i A 00/14 IN United States Patent METHOD AND ArPAnArUs FOR PRODUC- ING UNICELILULAR SPHERULIZED CLAY PARTICLES John M. Nefi and Jerome D. McLaughlin, Chicago, 111.,

assignors, by mesne assignments, to Kanium Corporation, Chicago, H1.

Application October 18, 1952, Serial No. 315,474

5 Claims. (Cl. 263-21) This invention relates to a method of and apparatus for spherulizing clay particles, and more particularly, to a method of and apparatus for expanding discrete particles of argillaceous material under controlled temperature and time conditions to produce hollow spheroids of suitable size and uniformity for use as light weight aggregate.

In accordance with the present invention, a method and apparatus is provided wherein argillaceous material, while suspended in a gaseous medium in finely divided discrete particle form, is subjected to a sufiiciently high temperature for a controlled period of time to effect complete fusion of the particles While so suspended, and the particles are then cooled to form hardened unicellular spheroidal particles that remain discrete and unagglomerated. The degree of expansion is indicated by the lower bulk density of the spherulized product. This may be as low as 15 lbs. per cu. ft. and will ordinarily be less than 50 lbs. per cu. ft. I

In order to insure spheroidal particles having a thin outer shell with only a single cavity, or cell, defined thereby, the clay particles must be rapidly heated and substantially completely melted and the expanded spheres must be resolidified before the confined but expanded gases can escape. This requires that the expanded spheres be removed from the highly heated zone at the instant of maximum expansion. If the expanded spheres are permitted to remain at above fusing temperatures too long, they will rupture and collapse, While if substantially complete fusion does not take place, the particles are only more or less rounded and not completely spherulized, and are multi-cellular, rather than unicellular.

It is therefore an important object of this invention to provide an apparatus for spherulizing argillaceous material to produce expanded, spheroidal particles, each having a thin, glass-like spherical Wall with a single cavity or cell sealed by such wall.

It is a further important object of this invention to provide a furnace or apparatus of the type described comprising a conduit defining a central inlet orifice, means defining a plurality of annular inlet orifices concentric with said central orifice, a first refractory-lined burner tunnel in communication with said orifices and extending expandingly therefrom in the form of a frusto-conical chamber having an 1630 cone angle and an axial height of ll.5 times its base diameter, a second refractory-lined burner tunnel communicatingly connected at the base of the first and extending expandingly therefrom in the form of a frusto-conical chamber having a 3450 cone angle and an axial height of 0.75l.5 times its base diameter, a refractory-lined cylindrical burner body communicatingly connected at the base of the second burner tunnel and extending therefrom 6-10 times the axial height of the second burner tunnel, and a discharge hopper mounted at the extending end of said burner body.

It is another object of this invention to provide a burner inlet comprising a plurality of pairs of concentric inlet pipes bundled together, a first inlet header communicating with the inner pipe of each pair for feeding fluid therethrough into a burner, a second inlet header tangentially aligned with said pipes and communicating with the annular space between the inner and outer pipes of each pair for feeding fluid through said spaces into the burner, a sleeve-like conduit enclosing the bundle pipes, and a third inlet header tangentially aligned with said sleeve and communicating with the space between said sleeve and the outer pipe of each pair for feeding fluid through said space into the burner.

Other and further important objects of this invention will become apparent from the following description and the appended claims.

On the drawings:

Figure 1 is an elevational view, with a lower part in vertical section, of apparatus embodying this invention;

Figure 2 is an enlarged vertical sectional view of an upper part or burner inlet of the apparatus;

Figure 3 is a sectional elevation of a preferred clay feeding apparatus of the invention;

Figure 4 is an enlarged vertical sectional view of a preferred burner inlet of the invention; and

Figure 5 is a bottom plan view taken along the line V-V of Figure 4.

In Figures 1 to 3 of the drawings, which are illustrative of the apparatus of this invention, the reference numeral 10 indicates the burner structure generally. Said burner structure 10 is of tubular construction, adapted to be installed with its axis vertical.

As previously pointed out, this invention is based upon the discovery of an apparatus capable of operating under conditions such that the clay particles are rapidly heated and substantially completely fused, yet cooled sufficiently rapidly from the fused state to confine the expanding gases and thereby provide a thin outer shell and a single cell, or cavity. This means that the expanded spheres must be removed from the fusing temperatures at the instant of maximum expansion and then cooled to efiect solidification before the spherulized particles come in contact with a supporting surface or with each other.

The selection of a particular starting clay and a particular set of operating conditions for the purpose of obtaining optimum results is, of course, essentially a matter of experiment in the light of the teachings of the copending application of Jerome D. McLaughlin, Serial No. 279,093, filed March 28, 1952, now abandoned.

It will be appreciated that the mechanics of the instant spherulization process involve closely timed fusion and generation of expanding gases. Although the clays contain several sources of expanding gases, recent tests indicate that one of the principal sources is ferric oxide, which releases oxygen according to the equation:

Referring now to Figure 2, Which shows the upper part 11 of the apparatus for use in the instant invention, it will be seen that the upper part 11 preferably comprises a plurality of concentric pipes or conduits. The clay c is fed into the furnace, via the clay pick-up unit 12 (Fig. 3) in an air stream ac flowing through the centerrnost pipe 13 of the concentric pipes forming the upper part 11 shown in Figure 2.

In using the clay pick-up unit 12, the clay is fed into the top hopper 14 and onto the bladed rotor 15 mounted for rotation in the housing 16 (merging with the open hopper bottom) so that the rotor blades 17 contact the housing Walls and form air-seals. Movement of the rotor 15 causes the clay to be carried around to the housing bottom aperture 18 and to be dropped therefrom into the pick-up zone 19, through which passes a stream of air a that picks up the clay particles and carries the same in suspension ac through the pipe 13, ultimately leading through the concentric pipes shown in Fig. 2. The coaction between the rotor blades 17 and the housing 16 prevents uncontrolled entrance of air into the system with the clay.

The air-borne clay is carried along in the stream ac through the pipe 13 which, as above mentioned, passes through the center of the concentric pipe arrangement of the upper part or head of the apparatus 10, as shown in Figure 2 and designated generally by the reference numeral 11.

The fuel gas g enters the head 11 through an aperture 20 near the top and flows therefrom into two annular chambers 21 and 22, as shown by the arrows in dotted lines. It will be seen that the head 11 consists of a generally cylindrical housing 11a having an integral interior partition will arrangement for defining and separating a plurality of annular chambers each of which is, in turn,

afforded communication with one of the annular chambers defined and separated by the concentric pipes, generally designated by the reference numeral 23. I For example, the upper annular gas chamber 21 is surroundedly adjacent the centermost pipe 13 and this chamber 21 communicates with the annular chamber 21a between the pipe 13 and the adjacent concentric pipe 24. The gas may thus flow into the chamber 21 and then downwardly through the chamber 21a.

Additional air a enters the head 11 through the aperture 25, opposite the gas aperture 20, and flows therefrom into the annular chamber 26. From the annular chamber .26 the air then flows downwardly, as shown by the arrows in solid light lines, through the annular chamber 2611 between the pipe 24 and the next outer concentric pipe 27. Also, gas flows from the lower annular chamber 22 downwardly through the annular chamber 22a between the pipe 27 and the outermost concentric pipe 28.

It will thus be seen that the upper part of the apparatus presents a plurality of concentric annular openings or orifices which communicate alternatively with a suitable air source and a suitable fuel or gas source, respectively, so that such orifices are adapted to deliver alternately air and gas in concentrically aligned blasts surrounding the center air blast which delivers the air-borne clay particles.

The resulting air-gas blast passes downwardly through the orifices, as described, and into the lower part or .furnace portion 29 of the apparatus 10. The upper part 11 is secured directly over and aligned with the top opening or furnace tunnel 30 of the furnace 24 which is defined by downwardly diverging frusto-conical refractorylined walls 31 mounted in a suitable cylindrical housing 32. Aligned with and immediately below the tunnel 30 is a second conduit 33 defined by downwardly diverging frusto-conical refractory-lined walls 34 mounted in a suitably shaped frusto-conical superstructure housing 35, the divergence of the walls 34 being slightly greater than the divergence of the walls 31.

The divergence of the furnace tunnel 30 and the superstructure conduit 33 accommodates the increase in volume of the air-gas stream resulting from the formation of the products of combustion. It has been found that the angles of such divergence are important to the best operation of the apparatus. For example, the angle of the sides of the tunnel walls 31 (measured from a vertical axis) should be about 8-l5 which is a cone angle of twice 8-15, or 16-30; and the angle of the sides of the superstructure walls 34 should be about 1725. Also, the length x of the tunnel 30 should be about 1-1.5 times the major or bottom diameter thereof; and the length s of the superstructure conduit 33 should be about 0.75-l.5 times the major diameter which, in turn, should be about 14-16 times the burner gas orifice area.

In general, it has been found that in the burner inlet just described the total (cross-sectional) area of the two burner gas orifices (21a and 22a) should be at least about 0.96 square inch and the total area of the air orifices (26a and the centermost pipe 13) should be at least about 0.92; and this ratio may be advantageously altered to as much as 1 to 10 (gas orifice area to air orifice area), with a ratio of about 1 to 6-10 preferred, in larger sizes of burners, as will be described hereinafter.

The aforementioned dimensions have been found to be of unique significance in an air-gas burner because such dimensions effect an unusually advantageous cooperation between the refractory action of the Walls, the burning temperatures, and the speed of flow of the gases and the clay particles carried thereby.

The superstructure housing 35 is suitably mounted on the main cylindrical furnace housing 36, as for example by bolts (not shown) sealingly securing together the flanges at 37. Within the housing 36 and suitably secured thereto, are generally cylindrical refractory-lined walls 38 extending substantially the full height of the housing 36. The top portion 38a of such refractory walls extends downwardly from the bottom mouth of the superstructure conduit 33, being aligned therewith and having substantially the same diameter. As can be seen, the top wall portion 38a contains a plurality of longitudinally extending grooves 39 so as to expose an inside refractory wall 40 having a surface area substantially greater than the surface area of truly cylindrical smooth walls of the same diameter. The grooved refractory walls thus define a high-radiation or radiator chamber 41 wherein a maximum radiating surface effects maximum heat radiation. It has been found that the length r of the radiator chamber 41 should be about twice the length s of the superstructure conduit 33.

Below the radiator chamber 41 is a zone 42 wherein the spherulized clay and the products of combustion are effectively cooled, so as to complete the spherulizing action and to cool the suspended spheres to minimize subsequent aggregation. Such a cooling zone 42 has the refractory wall lining 38 mounted therein to protect the housing 36 and the over-all length l of the zone 42 should be about 2-4 times the length r of the radiator zone 41.

The cooling zone 42 terminates with a restricted hopper-like open bottom member 43 suitably mounted on a supporting base 44, which also mounts the bottom of the housing 36 and refractory walls 38. Near the bottom of the cooling zone 42 there are provided air passages 45, separated by annular spacers 46, through which air may be passed to pre-heat the same (e. g., to about 450 F.) for subsequent introduction into the furnace head 11 and to assist in cooling the products of combustion Within the zone 42. Such a heat-exchange arrangement and the supporting structure for the furnace 29 will be readily understood by those skilled in the art and need not be further described.

The dimensions of the instant furnace 10 have been found to be critical in that they effectively control the flow rate of clay particles through the necessary hot zone and they additionally control the extent of heat radiation from the refractory-lined walls, so that by proper coordination between these two principal variables the desired time-temperature control may be obtained.

In Figures 4 and 5, which show a superior burner inlet structure that is adapted for use with the instant furnace 10, primed reference numerals are used to designate parts or elements corresponding to those shown in Figure 1. For example, it will be seen that the burner inlet or head 11' consists of a generally cylindrical housing 11a having interior partition walls for defining and separating a plurality of chambers each of which is, in turn, afforded communication with one of the chambers defined and separated by a bundle of pairs of concentric pipes, generally designated by the reference numeral 23'. The air-borne clay is carried along in the stream ac through the pipe 13' which, as in the previous device, passes along the centerline of the head 11'.

Actually, the pipe or conduit 13 leads downwardly into a top cylindrical chamber 47, which is defined by an annular top wall 48, a partition wall 49 spaced therebelow and the cylindrical outside walls of the head 11 (which are Welded together at abutting surfaces as indicated in the drawing). in the floor or partition wall 49 of the chamber 47, there is a centrally located aperture 50 to which is connected 21 depending central pipe 51, which extends downwardly to define at its bottom 51a a central inlet orifice 51a for the furnace.

A second inlet chamber 52, positioned below the chamber 47, is defined by the partition wall 49, a second partition Wall 53 spaced therebelow, and the cylindrical walls of the head 11', which members are secured together by welds. The bottom partition wall 53 of the chamber 52 is centrally apertured, so as to provide an aperture aligned with the aperture 50 of the first partition wall 49. The aperture in the partition wall 53, indicated generally at 54, is slightly larger than the downwardly extending pipe 51, and there is secured at the mouth of the aperture 54 a larger pipe 55, concentrically positioned with respect to the pipe 51 so that the pipes 55 and 51 define therebetween an annular chamber 56 communicating with the inlet chamber 52.

A third inlet chamber 57, positioned below the second inlet chamber 52, is defined by the second partition wall 53, a bottom wall 58 for the head 11', and the cylindrical centered walls of the head 11', Which are secured together by welds as shown. Actually, the bottom wall 58 is a rather narrow annular member having a very large aperture 59 therein in which is seated a large sleevelike conduit 60, which is substantially concentric with the pipes 51 and 55.

It will thus be seen that the pipes 51, 55 and 6t define a plurality of annular inlet chambers or orifices for the furnace. As previously mentioned, the pipe 51 defines, at its bottom 51a, a central inlet orifice. The pipe 51 and the pipe 55 define therebetween a concentric annular chamber 56, which at its bottom 56a defines an annular inlet orifice for the furnace. The pipe 55 and the sleevelike member 69 also define therebetween a generally annular chamber 61, which aifords communication between the third inlet chamber 57 and the furnace It It will be noted, however, that the generally annular chamber 61 defined by the pipe 55 and the sleeve 60 has circumferentially spaced therein a plurality (namely, 6) pairs of concentric pipes 62 and 63, which are positioned sum'oundingly of the pair of concentric pipes 51 and 55, but which are otherwise of substantially the same size as the pair of concentric pipes 51 and 55. As will be seen, the inner pipe 62 of each pair of pipes, like the central inner pipe 51 is suitably mounted in an aperture in the partition wall 49 and secured thereto and extending downwardly therefrom substantially the same distance which the pipe 51 extends downwardly. The outer pipe 63 of each of the pairs of pipes, like the outer pipe 55 in the center of the head 11', are each suitably mounted in apertures in the partition wall 53 and secured thereto, so that each is concentrically aligned with its respective inner pipe 62 and each extends downwardly therewith, so that all of the pipes may terminate at substantially the same orifice level.

In the operation of the instant head 11, the primary air and suspended clay ac is introduced through the pipe 13 into the top chamber 47 and from there through the central pipe 51 and the surrounding peripherally arranged inner pipes 62, and out through the bottom orifices 51a and 62a. The fuel or gas is introduced through the gas inlet 6 which is tangentially aligned with the middle chamber 52 (which chamber is a generally cylindrical chamber having a bundle of pipes 51 and 62 centrally positioned therein) 50 as to afford a generally annular outer portion 52a for the chamber 52 wherein the tangentially directed gas or fuel enters at 64a so that it may develop a swirling motion. The swirling motion of the gas is particularly beneficial because it imparts to the gas a horizontal velocity component, as well as the downward vertical velocity component which is developed by the gas as it passes through the annular chamber 56 between the pair of concentric pipes 51 and 55 and the annular chambers 65 between each of the pairs of concentric pipes 62 and 63. In the instant device, such annular chambers 56 and 65 are the sole means for admitting the gas into the furnace 10. The secondary air a (Fig. 5) is introduced into the head 11' through the secondary air inlet 66 and into the bottom chamber 57. The chamber 57, like the chamber 52, is generally cylindrical in shape, but contains the bundle of concentric pairs of pipes, as hereinbefore described, so that the chamber 57 is. provided with a generally annular outer chamber portion wherein the secondary air introduced through the tangentially aligned air inlet 66 may develop a swirling motion, so that it also will have a horizontal velocity component as well as a vertical downward velocity component as it passes downwardly through the chamber 61, which is the space between the inside walls of the sleeve 60 and the outside walls of the outer pipes 55 and 63 of the pairs of concentric pipes.

It has been found that a uniquely advantageous feature of the instant head 11' is that the total air orifice area, which is about 14 square inches for the primary air through the pipe 51 and about 14- square inches for the secondary air at the bottom exit of the chamber 61, for a total of about 28 square inches is approximately 8 times the total gas orifice area (which is the total of the bottom cross-sectional areas of the annular chambers 56 and 65, or about 3 /2 inches).

It has been found that the instant head 11' effects unusually good fiame control, so as to obtain advantageous results in carrying out the instant process, by the use of an air-gas volume ratio of 8:1, and in using the instant head 11', the vertical downward velocity component of the primary air, the secondary air and the gas is substantially the same. This feature, coupled with the increased horizontal velocity component (efiected by the swirling action resulting from the use of tangentially aligned inlets) apparently produces a uniquely superior admixture of air and gas immediately after the air and gas are discharged from the inlet orifice into the burner, and, accordingly, an unusually well controlled combustion area is created so as to obtain optimum results in the production of spherulized clay particles employing the instant apparatus.

It will thus be seen that the instant invention also cornprises a process for generating a controlled high temperature combustion zone in a furnace, that comprises introducing air and fuel gas into a combustion zone in the form of parallelly aligned alternate streams of substantially the same linear velocity components in the direction of the combustion Zone. provides for imparting to each such streams a non-linear or normal-to-the-linear velocity component or, in other words, swirling such streams so that as each is released into the combustion zone at a common orifice plane the streams may be most advantageously mixed. It has been found that if the linear velocity component of one such stream (either the air or the gas) is substantially different from the other, then definitely inferior temperature control and flame formation are obtained. Also, if feed air or gas is not introduced substantially tangentially into the respective air or gas parallelly aligned streams, so as to impart the swirling or non-linear velocity component thereto, the resulting flame formation is noticeably poorer and the results in the spherulization process are correspondingly poorer. For example, the instant burner head 11' has been found to produce a much more luminous flame (having a greater heat transfer coefficient than a clear flame) than the flame produced by other burner head designs, using air and gas (mol) ratios of about 8:1.

By the use of an air: gas ratio of about 1 to 6-10, and preferably about 1:8, in a burner head such as the head In addition, the invention 11' of Figures 4 and 5, wherein the ratio of total air orifice area to total gas orifice area is substantially the same as the airzgas feed ratio (so that the linear velocities of both air and gas streams at the orifices are substantially equal), it has been found that a definitely superior luminous flame is obtained.

As an example, using the burner head 11a, 9. run was made in accordance with the general procedure outlined in the application of Jerome D. McLaughlin, Serial No. 279,093, now abandoned. The clay shale used was the Maquoketa shale of particle size -35+l00 mesh; and fuel gas was used at a rate of 335 cubic feet per hour, with a total air feed of eight times that rate at room temperature, so as to obtain temperatures of about 2600 F. and a very luminous flame. At least 8 vol. percent of the resulting expanded spherulized clay product floated, which is considered a very good proportion.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

We claim as our invention:

1. In a furnace of the type described, a burner unit comprising a conduit defining a central inlet orifice, means defining a plurality of annular inlet orifices concentric With said central orifice, a plurality of circumferentially spaced orifice units in the outermost annular inlet orifice, each of said units defining a middle orifice and an annular orifice concentric thereto, first inlet header communicating with said central orifice and said middle orifices, a third inlet header communicating with the outermost annular inlet orifice, a second inlet header communicating with the annular orifices of said orifice units, a first refractory-lined burner tunnel in communication with said orifices and extending expandingly therefrom, a second refractory-lined burner tunnel in communication with the expanded end of the first and extending expandingly therefrom at a greater rate of expansion than the first, and a refractory-lined cylindrical burner body in communication with the expanded end of the second burner tunnel.

2. In a furnace of the type described, a burner unit comprising a conduit defining a central inlet orifice, means defining a plurality of annular inlet orifices concentric with said central orifice, a plurality of circumferentially spaced orifice units in the outermost annular inlet orifice, each of said units defining a middle orifice and an annular orifice concentric thereto, first inlet header communicating with said central orifice and said middle orifices, a third inlet header communicating with the outermost annular inlet orifice, a second inlet header communicating with the annular orifice of said orifice units, a first refractory-lined burner tunnel in communication with said orifices and extending expandingly therefrom in the form of a frusto-conical chamber having a 1630 cone angle and an axial height of 1-1.5 times its base diameter, a second refractory-lined burner tunnel communicatingly connected at the base of the first and extending expandingly therefrom in the form of a frustoconical chamber having a 3450 cone angle and an axial height of 0.751.5 body communicatingly connected at the base of the second burner tunnel and extending therefrom 6-10 times the axial height of the second burner tunnel, and a discharge hopper mounted at the extending end of said burner body.

3. In a furnace of the type described, a burner unit comprising a plurality of pairs of concentric inlet pipes bundled together, a first inlet header communicating with the inner pipe of each pair for feeding fluid therethrough, a second inlet header tangentially aligned with said pipes and communicating with the annular space between the inner and outer pipes of each pair for feeding fluid through said spaces into the burner, a sleeve-like conduit enclosing the bundled pipes, a third inlet header tangentially aligned with said sleeve and communicating with the space between said sleeve and the outer pipe of each pair for feeding fluid through said space into the burner, a first refractory-lined burner tunnel in communication With said sleeve and pipes for receiving fluid therefrom and extending expandingly therefrom in the form of a frusto-conical chamber having a 1630 cone angle and an axial height of 1-1.5 times its base diameter, a second refractory-lined burner tunnel communicatingly connected at the base of the first and extending expandingly therefrom in the form of a frusto-conical chamber having a 3450 cone angle and an axial height of 0.75-1.5 times its base diameter, a refractorylined cylindrical burner body communicatingly connected at the base of the second burner tunnel and extending therefrom 6-10 times the axial height of the second burner tunnel, and a discharge hopper'mounted at the extending end of said burner body.

4. In the method of spherulizing and expanding a clay shale by heating the same in the manner described, an improved method of generating a flame in a combustion zone for carrying out the heating of the shale particles, that comprises introducing fuel gas and air, bearing the shale particles, into the combustion zone through substantially uniplanar orifices in the form of a plurality of alternating parallelly aligned gas and air streams having the same linear velocity, and imparting a non-linear velocity component to such streams.

5. In the method of spherulizing and expanding a clay shale by heating the same in the manner described, an improved method of generating a flame in a combustion zone for carrying out the heating of the shale particles, that comprises introducing fuel gas and air, bearing the shale particles, into the combustion zone through substantially uniplanar orifices, in the form of a plurality of alternating parallelly aligned gas and air streams having the same linear velocity, and directing air and gas feed tangentially into the respective air and gas streams to impart thereto a non-linear velocity com ponent prior to passing through said orifices.

References Cited in the file of this patent UNITED STATES PATENTS

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