US3010911A

US3010911A - Method of and apparatus for heat processing particulate solids

Info

Publication number: US3010911A
Application number: US757987A
Authority: US
Inventors: David W Robinson
Original assignee: Zonolite Co
Current assignee: Zonolite Co
Priority date: 1958-08-29
Filing date: 1958-08-29
Publication date: 1961-11-28
Anticipated expiration: 1978-11-28

Description

Nov. 28, 1961 D. w. ROBINSON METHOD oP AND APPARATUS FoP HEAT PROCESSING PARTICULATE SOLIDS 2 Sheets-Sheet l Filed Aug. 29, 1958 NOV 28, 1961 W ROBINSON 3,010,911

D. METHOD OF AND APPARATUS FOR HEAT PROCESSING PARTICULATE SOLIDS Filed Aug. 29, 1958 2 Sheets-Sheet 2 States The present invention relates to an improved method of and apparatus for heat processing particulate solids, and especially for expanding thermally expandible minerals, such as vermiculite and perlite.

Vermiculite, one material to which the present invention has particular application, is a micaceous mineral containing water of crystallization between its many layers. It has long been known that particles of this mineral, when adequately heated to cause the water 4to turn to steam, will expand orbe exfoliated, and that the resulting product is useful for a very broad range of purposes. In view of the usefulness of the exfoliated product, much effort has been expended in providing7 furnaces for exfoliating or expanding the raw mineral. Through the course of years, a generally approved type of furnace has evolved comprising a vertical column, burner means in the column, usually adjacent its top, and means adjacent the burner for introducing the mineral into the column, the mineral being exposed to the burner flame and in the preferred form of furnace gravitating through the column with the products of combustion, during which time its expansion is completed, and being collected in a bagging hopper or the like provided at the bottom of the column. Many other types of furnaces have also been proposed, including a general inversion of that described and generally horizontal installations. In all types, however, it is an object, at least in the modern art, to subject the mineral to an exceedingly sharp rise in temperature since the degree of expansion, which occurs only in the dimension normal to the face of the flakes or layers, is substantially directly proportional to the rapidity of ltemperature change of the particle. The faster the change, the greater the degree of expansion; and the greater the degree of expansion, absent over-heating, the lower the bulk density and the better the quality of the product.

In the expanding or heat treating furnace, care must be exercised to avoid over-heating of the mineral particles, and yet the particles must be uniformly heated if a consistent product is to be produced. Relative to overheating, vermiculite may fuse at about 1900-2400 degrees F. and become a substantially useless product. Also, over-heating results in clinkering oragglomeration of the mineral in the furnace, which is highly objectionable as it reduces furnace eiciency, creates a progressively worsening condition, results in non-uniform heat treatment of the entering particles, and causes frequent shutdown of the process. This has been a source of great trouble in prior proposals in the art. Also, prior art furnaces have suffered the disadvantages of relatively short life due to burning out of the refractory lining of the expansion chamber.

The object of the present invention is to provide an improved method of and improved apparatus for heat processing particulate solids, and especially for expanding vermiculite, perlite and mixtures of vermiculite and perlite, which overcome the above stated disadvantages, cause uniform heating of the particles, eliminate overheating, clinkering and agglomeration, produce a better quality product of lower bulk density and uniform characteristics, and increase' the service life of the furnace.

In particular, it is an object of the invention to provide an improved method of heat processing particulate solids characterized lby the step of substantially enclosing the source of heat in an encircling shroud or curtain of the particles being processed.

Another object of the invention is the provision of an improved method of heat processing particulate solids comprising the steps of introducing the solid particles'in the form of a tubular curtain between the flame of a heat producing burner and the wall of the furnace in which the burner is disposed, and causing the particles to move in the form of said tubular curtain through the furnace in the same direction as the combustion gases of said burner.

The immediate advantages'of this process are that the particles, which in the curtain formed thereby constitute a relatively thin layer, are (l) uniformly heated, (2) shield the wall surfaces of the furnace against overheating, and (3) move freely through the furnace without contacting hot surfaces on which they could form clinkers. These immediate advantages in turn result in (4) production of a uniform product, (5) increased service life of the furnace, (6) elimination of clinkering, (7) maintenance of high furnace eiciency over prolonged periods of use, (8) capability of use of an exceedingly high temperature source of heat, the temperature of which is substantially in excess of the fusion temperature of the particles, thereby to subject the particles to a sharp temperature rise of great magnitude and enhance the heat exchange process, (9) elimination of products of fusion, (l0) increased production rates, and (1l) substantially increased overall production of a high quality uniform product.

Moreover, it is an object of this invention, attributable at least in part to the above stated advantages, of providing an improved method of and improved apparatus for popping perlite by the principle of vertical dropthrough heat processing.

A further object of the invention is the provision of improved apparatus for heat processing particulate solids comprising means for producing a source of heat in one end of a furnace, dispersion means for introducing solid particles in the form of a tubular curtain around the source of heat, and a nozzle encompassing the source of heat for confining the curtain of particles to the vicinity of said source during their passage thereby.

A still further object of the invention is the provision, in a furnace for heat processing particulate solids, of the improvement comprising a burner having a flame nozzlel discharging into the furnace adjacent one end thereof, an ore confining nozzle disposed adjacent the outlet of said flame nozzle, and a dispersion member disposedl between said nozzles and having ports therein vopeningl adjacent the wallof said confining nozzle for introducing a tubular curtain of particles along said wall and for causing said tubular curtain of particles to move through the furnace along the furnace walls, said ore confining nozzle confining the tubular curtain of particles to the immediate vicinity of the flame and the Walls of the furnace maintaining the said curtain in the immediate vicinity of the hot products of combustion of the burner, said ,curtain of particles shielding said ore confining nozzle and the walls of the furnace from the ame andthe products of combustion,

Yet another object of the invention is to provide an improvedfurnace for heat processing particulate solids which, in its preferred embodiment, comprises an elongate vertical furnace chamber having an outlet at the lower end thereof, a burner adjacent the upper'end of the chamber having a flame outlet of a size smaller than the chamber directed downward toward the chamber, an ore conv ning nozzle of a size larger than the burner outlet disposed adjacent said outlet, a dispersion member disposed between the burner outlet and said nozzle and having spaced ports therein opening downwardly into the space between the projection of the burner outlet and the internal wall of the nozzle, a hopper for solid particles disposed above the chamber and said member, and a plurality of conduits extending downwardly from said hopper to said ports for supplying particles to be processed to said ports, the dispersion member causing particles gravitating therethrough, and induced by the burner to flow therethrough, to be discharged downwardly as a tubular curtain into the space between saidv nozzle and the iiame issuing from the burner outlet, this tubular curtain of particles in turn gravitating downwardly through the furnace chamber in substantially encompassing relation to the flame and the products of combustion issuing from the bu-rner outlet.

Other objects and advantages of the invention will be- Vcome apparent in the following detailed description.

Now, in order to acquaint those skilled in the art with the manner of practicing my improved method and of making and using my improved apparatus, I shall describe, in connection with the accompanying drawings, a preferred embodiment of my apparatus and a preferred manner of making and using the same.

In the drawings:

FIGURE l is a front view, partly in section and partly in elevation, of a heat processing furnace embodying the apparatus of my invention and capable of usein practica ing Vthe method of my invention;

FIGURE 2 is a side elevation of the furnace;

FIGURE 3 is an enlarged vertical section of the improved apparatus I have embodied in the furnace; and

FIGURE 4 is a cross-section of said apparatus taken substantially on line 4-4 of FIGURE 31.

Referring now to the drawings, I have illustrated therein a heat processing or expanding furnace of a generally conventional construction which I have modifiedV in accordance with and for purposes of practicing the present invention. The furnace per se includes a verticallyextending frame I formed of standard structural steel forms and defining a tall, narrow, generally upright box. Mounted within the upper portion yof this box is means defining a furnace chamber 12, which means as illustrated includes a tubular refractory lining 14, suitably built up fromrchimney brick, a steel sheath 16 and a loose ll 1S of exfoliated vermiculite between the lining 14 and sheath 16. At its lower end, the chamber 12 is provided with an outlet 20 discharging into a bagging Ahopper 22 or the like, which is approximately twice as Wide as Athe means defining the furnace chamber andincludes adelivery spout 24. Connected tothe spout 24 is a conduit 26 establishing communication between the delivery spout and hopper and a cyclone type dust separator 28 which is mounted in an upright position on the frame 10. Ad-

jacent the means defining the chamber 12, the furnace f includes anexhaust flue 3i) which'overlies the open portion of the hopper 22. Within the hopper, immediately below the furnace chamber and the exhaust ue, the furnace also preferably includes a standard form of recuperator 32.

In use of this generally known type of expanding furnace, a burner is'pr'ovided adjacent the upper end of the tubular furnace chamber 12 and vermicuiite or alike mineral is introduced in particle form into the flame issu ing from the burner. The products of combustion of the burner ow downwardly through the chamber 12 and the vermiculite particles gravitate downwardly therewith, whereby the vermiculite is heated and exfoliated in the expansion chamber 12 during its descent therethrough. The exfoliated product then gravitates into the hopper 22 l, i and is discharged through the spout 24 into bags or railroad cars, the separator 2S removing tine sized particles which' are'carried into the exhaust cyclone. The prod-Y ucts of combustion from the burner also discharge downwardly into Vthe hopper, .andfrom thence ii-ow upwardly through theriiue 30, the hotrgases thus making two passesV Y over the tubes of the recuperator for known purposes,

'desired objectives, especially several problems have been encountered. First, it is difiicult uniformly to heat the particles of vermiculite being processed, so that the exfoliated product does not have the uniformity sought after. Second, the rate of heat exchange, or the rapidity of temperature increase in each particle, is not as great as desired, so that density is higher and quality lower than that known to be obtainable. Third, the flame and the products of combustion of the burner heat not only the vermiculite but the walls of the furnace liner. Radiation of heat from the walls has been thought to increase particle heating, but heating of the large wall surfaces to accomplish this result is quite ineliicient. Also this creates an exceedingly hot surface which is contacted by the vermiculite and to which the particles fuse, thus resulting in the accumulation of elinkers which impair furnace efficiency. Moreover, such heating of the walls causes physical breeakdown of the refractory brick, whereby the chamber must periodically be re-built. For these several reasons, production, both as to quality and rate, has fallen considerably short of in the light of the critical specifications required to be met by exfoliated vermiculite intended for the specialized uses which are rapidly being discovered.

The objects of the present invention are to overcome the stated disadvantages of known furnaces and to provide for a high rate of production of la lightweight, high grade exfoliated product of exceptional uniformity. According to the method of the invention, these objectives are attained by introducing into the furnace the solid particles to be processed in the form of a thin shroud encircling the flame aud the products of combustion of the burner and insulating the walls of the furnace from the flame and the hot gases. The apparatus that I prefer for practice lof my method is best illustrated in FIGURES 3 and 4;

As shown, the preferred apparatus includes a high out put burner v4i) mounted in a vertical position above the chamber and having its outlet or flame nozzle 42 aligned axially with and directed downwardly toward the chamber. The burner is of a known pressure type adapted to burn either gas or oil, or 'both gas and oil, and one burner I have found particularly Vsuitable is the Model 4017 burner produced by Thermal Research and Engineering Co., which burner has an output .of from about 400,000 to about 2,000,000 B.t.u. per hour. The burner includes a anged housing 44 by means of which I mount the same on a portion 46 of the frame 10 which is spaced upwardly from and overlies the chamber 12. To the upper side .of the frame portion 46, the burner 40 includes an air inlet 48, a gas inlet 50, and oil inlet S2 and an oil outlet 54 for supply of fuel and combustionair to the burner, the air inlet 48 suitably being connected to the outlet of the recuperator 32 for the purpose previously mentioned. rl'he nozzle 42 of the burner 40 is formed of refractory material and constitutes the combustion charnber of theV burner, from which is discharged, in a vertically downward direction,V ashort, generally cylindrical flame as is indicated in dotted lines.

The cylindrical flame and the hot products of combustion of the burner discharge into an ore conlining Y Mounted betweenY andY concentrically with the

nozzles

42 and 56 is a dispersion ring or annulus 60, which is also preferably formed of refractory material and cemented or otherwise sealed to the

nozzles

42 and 56. At its lower end, the ring 60 is provided with a flat annular surface to engage hush against the upper surface of the nozzle 56, and its upper surface is suitably of frusto-conical shape c-onformably to receive the conical nose of the ame nozzle 42. In its upper surface, the ring 60 is provided at equal circumferential spacings with a plurality of inclined, generally radially extending ports 62 which open downwardly into the annular space between the flame and the wall of the nozzle 55, or more properly, into the annular space between the axial projection of the burner outlet and the wall of the ore confining nozzle. In the drawings, I have shown six such ports, as being preferred, but it is apparent that more or less ports could be provided as desired, since the number of ports or vanes is not critical. Communicating axially with each of the ports is a feed pipe or conduit 64, the six pipes extending upwardly to and being supported by the portion 46 of the frame 10 on which the burner is mounted and defining a circle circumscribing the burner. At the upper end thereof, each pipe terminates in a coupler or fitting 66 facilitating attachment thereto of secondary feed pipes or conduits.

Mounted on the frame portion d6 in upwardly extending relation thereto is a standard 68 which supports a feed hopper 70 in a position above the burner and the dispersion ring. This hopper is adapted for receptionof solid particles to be heat processed and includes a lower plate having therein tubular discharge stubs 72 of a number corresponding to the number of primary feed pipes 64. Between each stub 72 and the corresponding fitting 56 is extended a secondary feed pipe 74 which is detachably secured at its ends in sealed relation to the respective fitting 66 and stub 72. In addition, the hopper 70 preferably includes valve means (not shown) for controlling the rate of discharge of particles therefrom.

In use of the apparatus, the burner 40 is iirst set into operation to cause a short, generally cylindrical iiame to be directed downwardly into the ore confining nozzle 56 and the hot products of combustion of the burner to be discharged downwardly through the chamber 12 and upwardly through the flue 30, the hot gases during such passage transferring heat through the recuperator 32 to the combustion air for the burner. The valve means in the feed hopper 70 is then opened, whereupon solid particles are fed downwardly from the hopper through the pipes 74- and 64 to the ports 62 in the dispersion ring 60, a constant feed of particles to the ring 60 being assured by virtue both of the force of gravity and the inductive force created by the flame discharging into a relatively large area and causing a venturi effect at the ports 62. Due to this action, the ring 60 causes the solid particles to be dispersed in an annular curtain and to be discharged in that form downwardly into the annular space between the flame and the internal wall of the nozzle 56. Thus, the discharged particles are subjected to uniform contact with the iiame as the relatively thin curtain of particles descends through the particle confining nozzle. Also, the incoming particles and the air induced to flow downwardly therewith serve to keep the dispersion ring relatively cool and to insulate the nozzle S6 from the flame and the hot products of combustion. Consequently, the surfaces of the ring and nozzle are not heated to such extent as would result in fusion or clinkering of the solid particles contacting the same. Also, the incoming particles are immediateiy contacted with an exceedingly hot liame, preferably several hundred degrees hotter than the fusion temperature of the particles, whereby the particles are subjected to an instantaneous temperature rise of great wardly into and through the chamber 12 with the hot products of combustion from the burner, the particles mixing -with and absorbing heat from the hot gases and being further heat treated during their passage through the chamber 12. Due to the fact that the particles surround the ame and move continuously with hot gases, heat transfer is primarily between the ame and gases and the particles, whereby the particles are subjected to optimum and uniform heat treatment, the heat produced by the burner is most eifectively and efiiciently utilized, and excessive heating of the walls of the nozzle 56 and chamber 12 is avoided. By virtue of the latter function, hot surfaces on which the particles could fuse and form clinkers are eliminated and physical breakdown of the refractory materials of the chamber is mitigated, thereby to insure efficient operation of the furnace over exceptionally long periods of continuous use without necessity for cleaning lor repair. Also, due to the sharp initial rise in particle temperature upon contact with the ame, and the primary heat exchange relationship between the particles and the flame and hot products of combustion, the particles very rapidly complete their heating cycle so that the rate of :dow of particles through the furnace may be substantially increased over that conventionally accepted. Moreover, the coaction of the particles and the products of combustion facilitate complete liexibility of control, in that either fuel input or ore input, or both fuel input and ore input, may be adjusted in order to provide the proper heat treatment cycle.

By way of more specific example, I 'will now describe the manner of use of my apparatus and the practice of my method for expanding vermiculite ore, and especially for production of No. 4 exfoliated vermiculite. The ore on which the invention is practiced is entirely conventional in all respects, the same being mined, milled t0 controlled size and deposited in the hopper 70 in conventional manners and to conventional specifications. The ore used is a natural equilibrium ore having a moisture content from about 5% to about 12%. The ore is to -be expanded to afford a given set of characteristics which characteristics are achieved by exfoliating the particles of ore at such temperature as to produce a predetermined percent shrinkage in the exfoliated product, all in accordance with the disclosure of the co-pending application of George E. Ziegler, Serial No. 632,275, filed January 3, 1957, now U.S. Patent No. 2,945,820, which application is assigned to the assignee of this application. Control of the process is effected by thermally responsive control means including a thermo-couple disposed in and measuring the temperature of the stream of particles dis? charging from the chamber 12, which control means is adapted to vary the rate of feed of fuel and/or raw ore to the furnace to maintain a pre-set particle discharge temperature, periodic checks being made on the percent magnitude, which as previously stated is highly advany tageous.

After initial contact with-the ame, the annular curtain of solid particles gravitates and is induced to iiow downshrinkage of the product to determine the accuracy of the thermal control and accommodate any necessary adjustment thereof. In the particular example under discussion, the percent shrinkage of the product is to be less than 20% and a suitable initial control temperature for the No. 4 grade is 1650 degrees F. v

The furnace chamber is suitably 12 inches in diameter and about l0 feet long. The flame nozzleof the burner may then be about 5 inches in diameter, in which lcase the inner diameter of the ore confining nozzle 56 is about 6.9 inches, thereby to afford a cross-sectional nozzle area approximately 90% greater than the cross-sectional area of the flame outlet. 1

The burner 40 is operated to produce a flame temperature of over 2500 degrees F., preferably about 3000 to 3500 degrees F., or about 1100 degrees above the fusion temperature of vermiculite, and to have an output 'of about 1,500,000 B.t.u. per hour. The flame projects about 8 inches beyond thenose of the outlet 42 and has a diameter about or more of the diameter of the outlet. Y

Vof the. exfoliating or expanding process.

For expansion of vermiculite ore, and with the burner operating as described, the ore is introduced into the furnace in the same manner as above defined. Production of the described grade of'exfoliated vermiculite having less than 20% shrinkage is, effected according to the present invention at a feed rate of approximately 3A ton of ore per hour and results in a yield of 43 to 44 fourcubic foot bags per hour of the ultimate product. The yield obtainable is over 25% 'better than that previously obtained and density is reduced'to between 6.8 and 7.3 pounds per cubic foot, a signiiicant reduction clearly illustrating the faster rate of expansion and the improved quality of the product. Despite the fact that arne temperature is about i100 or more degrees hotter than the fusion temperature of the vermiculite, there is no clinkering in the furnace and no evidence of fusion in the exfoliated product.

From test observations and samplings, it `appears that the bulk of the expansion of the ore occurs in the upper 1A of the furnace as a consequence of the particles being bathed in the flame. Yet, the length of the furnace is necessary to complete expansion to the desired percent shrinkage. Elf-Orts to decrease furnace length 'by increasing the duration of flame bathing or" the particles, and in particular by use of a spiral flame, proved totally ineffective, and in fact disadvantageous as the spiral action caused the ore to be comminuted. In the furnace as shown and described herein, the ore is both expanded and heat treated, clinkering is eliminated and furnace life is extended indefinitely. Yield is increased substantially, the density of the product is reduced, its quality increased, and there is substantially perfect Vuniformity of product. The furnace results in comparable improvement in the production of all grades of exfoliated vermiculite, and affords the same advantages `with respect to lboth the furnace and the quality and uniformity of the resulting product.

Jn addition to the foregoing, the present invention contributes substantially to completely automatic operation In particular, in testsV previously conducted, the operator set the yfurnace into operation according to the following sequence of operations: The combustion air blower, .oil pump, exhaust fan and separator motors were started. The cornbustion air pressure was adjusted to 1/2 inch, oil pressure to Vl() psi., and the burner started. When the burner produced a flame, the air was manually increased gradually to about 6' inches. After about two minutes Warmupk time, the -oil and air pressure were increased to 120 p.s.i. and l inches, respectively. When the temperature in the expansion chamber came up to 1550 degrees F., the operator put the furnace on automatic control and manually/'adjusted the fuel and air-*pressure to 18() p.s.i. and 44 inches, respectively, keeping the air in excess of the fuel. VThis operation took about l5 seconds. The ternperature immediately stabilized at i650' degrees F. and no more attention was needed throughout the run. Comparative runs clearly reveal a greater yieldV from the furnace Von automatic operation than on `the most careful manual operation. Thus, the invention aordsV not only improvements in the heat processing of particulate solids, but also facilitates fully automatic processing.

For the production of exfoliated vermiculite Vas de-V scribed ihereinbfefore,l I prefer lto employ a vertically disposed furnace chamber having the burner and ore dispersion ring at the top thereof. However, it is Ventirely fea-sible that the furnace can be utilized in Ian inverted posit-ion, and other positions intermediate the two opposite vertical positions, for processing of a widevariety of solids.V In particular, I have in mind application of myfn'iethod and apparatus to the popping horizontally andl ular aggregate, treatment of ores containing gold and platinum, and treatment of fluid coke from petroleum products to 'further remove the hydrocarbons not removed in convention equipment.

When yapplied to some of these uses, and especially when the furnace is installed other 'than vertically, it may be necessary in order to maintain an annular curtain of particles in surrounding relation to the llame and products of combustion, to blast the raw particles into the furnace by suitable means, such as pneumatic pressure. In any event, the apparatus, in its preferred form, has the basic malte-up described herein and is capable of performing my improved method, which broady stated comprises the steps of shielding the jet of extremely hot gases completely with a ring or curtain of particles, and blasting both the jet and the ring of particles into a tube which allows the gases and the particles to ow in the same direction until sufficient heat treatment of the particles has taken place.

In View of the foregoing, it is apparent that the objects and advantages of this invention have been shown to be attained in a convenient, economical and practical manner. My improved method of heat processing assures uniform heat treatment of the particles in a short period of time, and results in protecting the furnace against excessive yabuse and preventing clinkering therein. The preferred embodiment of my appara-tus is particularly effective in performing my defined method and constitutes a highly economical structure necessitating of perlite alone or inmixture with vermiculite, processr of lime, reduction of removal of sulphur ing of limestone in the production fine iron oxide Vmixed with colte,

from sulphides, spherulizing clay particles into a granverey little change in existing furnaces for modification of such furnaces in accordance with this invention.

Moreover, the apparatus and method described herein accommodate for the first time effective hea-t processing or expandingof perlite and mixtures of vermiculite and perlite in a vertical dropathrough furnace, thereby to increase production rates and the quality of the expanded products.

The apparatus specilically illustrated and described herein constitutes the preferred physical embodiment of my invention. However, this apparatus is capable of vvideV variation, dependent in part on use. First, the furnace chamber need not be circular in cross-section but could be of substantially Iany geometric or non-geometricrform. The ame nozzle need not be circular, nor need it have a cross-sectional configuration complementary to that of the furnace chamber. In any of these cases, the shroud or cur-tain of particles to be processed is introduced in generally tubular form, whether tha-t be a circular tube, a square tube, or a tube of other configuration. Moreover, the burner need not be disposed concentric With or'in axial align-ment with the chamber. For many uses, especially where the furnace is not vertical, it may prove advantageous to mount the burner'eccen-trioally and/or to cant the same relative 4to the furnace axis. It is not essential, though highly preferable, to utilize a confining nozzle that is larger than the flame nozzle. For example, by appropriate dign of the burner, a dame could be produced i iaving a hot central core and a somewhat cooler periphery and the curtain of particles could be introduced directly into the peripheral portion of the flame around the hot core. In such case, the confining nozzle could be of the same size as the flame, and even so the curtain of particles would effectively enclose lthe flame and shield the nozzle. Likewise, the furnace chamber'need not be of asize larger thanthe confining nozzle.

-Accordingly, while I have shown and described what I regard to be the preferredrembodiment of the apparatus of my invention, and have described what IV regard to be xthe preferred manner of practicing my improved-method, it is apparent -tha-t various changes, rearrangements Vand modiiications may be made therein without departing l claim:

l. A method of expanding vermiculite, perli-te and mixtures of vermiculite and perlite comprising the steps of vertically dropping a curtain of ore around a -heat treating llame, and confining the curtain of ore to the vicinity of and in substantially encompassing relation tothe llame and its hot products of combustion during vertical descent of the curtain of ore.

2. A method of preventing clinkering in furnaces for heat processing thermally expandable minerals, characterized by the steps of creating -a downwardly moving curtain of particles to be processed along the furnace walls and in encompassing relation to the source heat of the furnace, and causing said particles to move at a rate maintaining an effective temperature gradient between the source of :heat and said walls.

3. Apparatus for heat processing particulate solids comprising a burner having a ilarne nozzle, a particle conining nozzle disposed `to the outlet side of said flame nozzle, land dispersion means between said nozzles for introducing a curtain of the particles to be processed along the walls of said conning nozzle in substantially encompassing relation to the outlet of said llame nozzle.

4. Apparatus for heat processing particulate solids comprising a burner having a llame nozzle, a particle coniining nozzle disposed to the outlet side of said llame nozzle, dispersion means be-tween said nozzles for introducing a curtain of the particles to be processed along the walls of said confining nozzle in substantially encompassing relation to `said name nozzle, a hopper for particles to be processed, yand conduit means extending from said hopper to said dispersion means.

5. Apparatus for heat processing particulate solids comprising a burner having a flame nozzle, a particle conlining nozzle of a size larger than said llame nozzle disposed to the outlet side of said amenozzle, and dispersion means between said nozzles for introducing a curtain of the particles to lbe processed into the space between the projection of the outlet of said liame nozzle and the Wall of said confining nozzle.

6. In a furnace for expanding vermiculite, perlite and mixtures of vermiculite and perlite, the improvement comprising a burner having a llame nozzle discharging into the furnace, Ian ore confining nozzle disposed adjacent the outlet of said llame nozzle, and dispersion means disposed between said nozzles and having ports therein opening adjacent the walls of said conlining nozzle for introducing a curtain of ore along walls.

7. ln a furnace for heat processing particulate solids, the improvement comprising a burner having a flame nozzle of a size smaller than the furnace discharging into one end of the furnace, a particle confining nozzle of a size larger than said flame nozzle disposed adjacent the outlet of said llame nozzle, and a dispersion member disposed between said nozzles and having ports therein opening adjacent the walls of said confining nozzle for introducing a tubular curtain of particles to be processed along said walls in substantially encompassing relation to the heat treating lflame issuing from said llame nozzle and for causing said tubular curtain of particles to move through the furnace along the walls thereof in substanl@ tially encompassing relation to the hot products of combustion of said burner.

S. A furnace for heat processing particulate solids comprising an elongate furnace chamber having an outlet at one end thereof, a burner adjacent the other end of said chamber, said burner having a llame outlet of a size smaller than said chamber discharging into said chamber, a heat treating nozzle of a size larger than said burner outlet disposed adjacent said burner outlet, a dispersion member disposed between said burner outlet and said nozzle and having ports therein opening into the space between the axial projection of said burner outlet and the wall of said nozzle, and means for supplying particles to `be processed to said ports in said member, said dispersion member causing particles supplied thereto to be discharged as a generally tubular curtain into the space between said nozzle and a flame issuing from said burner outlet and causing the said tubular curtain of particles to move through said furnace chamber in the same direction as and in encircling relation to the llame and the products of combustion issuing from the burner outlet.

9. A furnace for heat processing particulate solids, especially vermiculite, perlite and mixtures thereof, comprising an elongate vertically disposed furnace chamber having an outlet at the lower end thereof, a burner adjacent the upper end of said chamber, said burner having a flame outlet of a size smaller than said chamber directed axially downward toward said chamber, a particle confining nozzle of a size larger than said burner outlet disposed coaxially within the upper end of said chamber, a dispersion ring disposed concentrically between said burner outlet and said nozzle and having spaced ports therein opening downwardly into the space between the axial projection of said burner outlet and the internal wall of said nozzle, a hopper for solid particles disposed above said chamber and said ring7 and a plurality of conduits extending downwardly from said hopper to said ports for supplying particles to be processed to said ports, said burner in operation discharging'a short llame and products of combustion downwardly into said nozzle and inducing ow of air and solid particles through said ports in said ring, said dispersion ring causing particles supplied thereto to be discharged downwardly as a generally tubular curtain into the space between said nozzle and the llame issuing from said burner outlet, the said curtain of particles gravitating downwardly as a tubular curtain through said furnace chamber to the chamber outlet in 4the same direction as and in encircling relation to the llame and the products of combustion issuing from the burner outlet, said curtain of particles thereby being disposed between the walls of said nozzle and the lfurnace chamber and the said llame and products of combustion to insulate said walls from the source ofl heat and mitigate the occurrence of hot surfaces on which` the particles could form clnkers.

References Cited in the file of this patent UNITED STATES PATENTS 1,854,387 Wickenden Apr. 19, 1932 2,421,902 Neuschotz .lune l0, 1947 2,621,034 Stecker Dec. 9, 1952

Claims

1. A METHOD OF EXPANDING VERMICULITE, PERLITE AND MIXTURES OF VERMICULITE AND PERLITE COMPRISING THE STEPS OF VERTICALLY DROPPING A CURTAIN OF ORE AROUND A HEAT TREATING FLAME, AND CONFINING THE CURTAIN F ORE TO THE VICINITY OF AND IN SUBSTANTIALLY ENCOMPASSING RELATION TO THE FLAME AND ITS HOT PRODUCTS OF COMBUSTION DURING VERTICAL DESCENT OF THE CURTAIN OF ORE.

3. APPARATUS FOR HEAT PROCESSING ARTICLATE SOLIDS COMPRISING A BURNER HAVING A FLAME NOZZLE, A PARTICLE CONFINING NOZZLE DISPOSED TO THE OUTLET SIDE OF SAID FLAME NOZZLE, AND DISPERSION MEANS BETWEEN SAID NOZZLES FOR INTRODUCING A CURTAIN OF THE PARTICLES TO BE PROCESSED ALONG THE WALLS OF SAID CONFINING NOZZLE IN SUBSTANTIALLY ENCOMPASSING RELATION TO THE OUTLET OF SAID FLAME NOZZLE.