US2030628A - Flash roasting - Google Patents

Description

Feb. l1, 1936.

INVENTOR Horace Freemaw 31m/w( A'rroRNEYs Feb. 11, 1936. H, FREEMAN A 2,030,628

FLASH ROASTING Filed Jan. s,I 1935 2 sheets-Sheet 2 INVENTOR` Horace Freeman 792,1( MV1/Uf@ AfrroRNEYs the furnace of Fig. 1;

Patented Feb. 11, 1936 n UNITED STATES FLASH ROASTING Horace Freeman, Montreal, Quebec, Canada, assignor to Nichols Engineering & Research Corporation of Canada, Limited, Montreal, Quebec, Canada, a corporation of Canada Application January 8, 1935, Serial No. 817

6 Claims.

'I'his invention relates to roasting furnaces and more particularly to furnaces for flash roasting relatively finely divided ore while in suspension within the roasting chamber of the furnace. Features of this invention have been found to be particularly adaptable to the roasting of sulphide ores such as pyrite and pyrrhotite for the production of sulphur dioxide gas and iron oxide products. However, the invention is adaptable to the roasting of various other `types of ores.

This invention is directed to improvements upon and modifications of the roasting apparatus and methods referred to in my United States Patent No. 1,812,397 and in my copending applications Ser. No. 433,471, filed March 5, 1930, Ser. N0. 601,138, filed March 25, 1932 and Ser. No. 633,439, led September 161932, reference to which is hereby made for a more complete description of such portions of the furnace and auxiliary apparatus and methods as may 'not be fully explained or repeated hereinafter.

The invention is especially directed to features of construction and methods for introducing the finely divided ore into the flash roasting chambers of furnaces of the types described in the above mentioned patent and applications, in such manner that the ore will be properly distributed and maintained in suspension to enable the methods referred to in 4said patent and applications to be carried out with a high degree of eiiiciency` and economy.

The invention consists of such novel featurea' arrangements, combinations of parts and methods. as maybe shown and described in connection oi?v a furnace construction embodying the invention;

Fig. 2 is a vertical sectional view of a nozzle assembly for introducing the ore into the top of Fig. 3 is a top or plan view of the assembly of Fig. 2;

Fig. 4 is a detailed view partly in section o1' the inner member or turbine of the assembly of Fig. 2; and

(Cl. 26S-20) Fig. 5 illustrates in perspective the said turbine member.

The furnace as shown in Fig. 1 may comprisel a relatively tall and substantially cylindrical roasting chamber having side walls as at I0 of a suitable refractory material, a somewhat arched roof I I of similar material and a converging relatively cone shaped lower portion I2 terminating at the bottom with a cinder outlet as at I3.

The relatively finely divided ore to be roasted may be introduced with a stream of air or other oxidizing fluid, through thenozzle assembly as at I4, preferably located substantially at the middle of the top or roof of the furnace. With the .nozzle assembly constructed in the manner hereinafter described, the ore particles are carried into the roasting chamber at a relatively low velocity and are distributed in the-chamber with considerable turbulence while being met by an additional supply of uprising air or other oxidizing fluid introduced through the cinder outlet I3, The gaseous products of combustion are preferably Withdrawn` from the furnace through one, two or more gas outlets as at I5, located in the Walls of theupper portion' of the chamber. The gaseous products of combustion are preferably withdrawn by a suitable suction fan capable of drawing into the roasting chamber through the cinder outlet I3, a sufficient supply of uprising air to maintain the falling particles in suspension for a short period and to provide an oxidizing medium suiilcient when taken with that introduced through the nozzle, to cause the ore to be roasted to the desired degree.

The construction and operation of the nozzle assembly I4 and its associated parts will now be described. As above stated, thisassembly is preferably located either at or adjacent the middle of the roof ofthe furnace in order that the falling shower of ore particles will be maintained in a more or less concentric relationship to the walls of the furnace, thus substantially avoiding con' tact of the falling particles with the furnace walls, since under some circumstances contact of the particles while being roasted, with the walls, may result in troublesome accumulations on the walls. The nozzle assembly may preferably be mounted in a cylindrical nozzle protecting member as at I6, supported by suitable framework as at I1 and extending down through the roof II of the furf nace and terminating substantially` flush with the inner surface of the roof. A cylindrical nozzle member I8 may be removably mounted within this protective member. If desired', the members I6 and I8 may be of such diameters as shown `from the outer surface of the portion 23.

and oxidizing medium to the furnace. The bottom edgesV or the outlet .portions of the member I8 may preferably be somewhat constricted as at 2| for aiding in the control of the falling stream of ore and oxidizing medium.

A turbine member 22 may be removably mounted .within and adjacent the'lower end of the nozzle member I 8. This turbine member which is illustrated in detail in Figs. 3,-5, may comprise a central portion as at 23, preferably substantially cylindrical, forming a central ver` tical opening for directing a part of the ore -stream downwardly substantially axially of the furnace. This portion may be surrounded by a plurality of outer openings formed by a plurality of blades or vanes as at 24, which may be conveniently cast integrally with the portion 23 and extend in a. generally radial direction outwardly 'This turbine member my be heldin place. within the.nozzle member I8 as by one or more lugs or threaded pins as at 25 extending through -the walls of the member I8 and engaging lugs as at 26 formed on the vanes 24. The various blades or vanes 24 are preferably made alike and the active surfaces thereof start at the top in a substantially vertical'position, these surfaces being gradually curved so that at the bottom edges of the blades, the surface extends to a substantially acute angle in respect to a vertical plane. Although `the curvature of these blades may be varied somewhat, depending upon the proportions 'of the furnace, the kind of oretreatedv andthe pressure of the ore and oxidizing medium as in.- troduced through the nozzle. in the preferred example illustrated, the horizontal elements of the active surfaces of these blades may comprise substantially straight and radial lines, so arranged that the surfaces progress from a vertical position at the top edge of theblades gradually to an acute angle to the vertical at the bottom edges of theblades. As indicated in Fig. 2, the outer ends of the blades do not need to extend to the walls of the nozzle throughout their height. 4.In operationthe oxidizing medium and finely divided ore, preferably of a substantially uniform mixture, may be blown through a suitable conduit connected to the top of the nozzle whereby the mixturepasses downwardly through the nozzle under a relatively low pressure, for example, positive static prssure of from l" to 4':

Y w. g. Under normal operating conditions with a furnace and with a nozzle of the proportions indicated in the drawings forthe roasting of pyr'ite, I have found that pressures of from '1/2" to 1" w. g. give most satisfactory results. However, if a portion of the outlet gases are recirculated back into the nozzle intake for the purpose of improving temperature control conditions within thefurnace, it may be desirable to increase the pressures somewhatascompared with those last above stated. The pressure should preferably be too highl lest the'ore particles be driven into the combustion chamber too rapidiy to permit time.

for complete combustion. Also,' if the pressure is too high, ore particles may impinge upon the f furnace walls, which may lead to the difficulty above mentioned, i. e., the formation of troublesome accumulations on the walls. 'I'he pressure should also be suillciently low so that gas is not driven'out through the cinder opening at the bottom of the furnace. 1

In passing through the nozzle member I 8, a substantial part of the incoming ore and oxidizing medium pass down through the central opening in the cylindrical portion 23. This stream of the material acts as an axis, giving direction to the ore and gases'. The remainder of the ore and oxidizing medium pass through the outerv openings between the blades 24, much of it impinging against the curved surfaces of the blades, so' that these outer streams are given a rotational movement providing `jets which intersect and cut into and through the central `jet. 'This results in a substantial turbulence of the ore and oxidizing medium. scattering the same as ar downwardly expanding cone, which however does not extend to its maximum dimensions until at its portions of maximum diameter, ds not extend into substantial contact with the furnace walls.

With the nozzle parts of the relative proportions substantially as shown in the drawings `and with the nozzle member I8 having an inside diameter of approximately l ft., I have found that a. furnace chamber having an inside diameter of about 11 ft. and with vertical dimensions in -the proportion shown in Fig. 1, gives excellent results. However, with such a nozzle, the furnace diameter may well be varied from, in the neighborhood of 10 ft. to vliift. depending upon the character of theore being treated, and various other conditions. l

The height of the turbine member 22 within the nozzle member I8 may be suitably adjusted by' trialuntil the best roasting conditions ,are

secured, and this member may then be ilxed in the desired position byproperly 'locatingthe threaded pins 25 in the nozzle walls. Inthe event it is desired to alter the roasting conditions or treat various different ores, the turbine medium from the cinderoutlet Il, with the gasesr of combustion going out the outlets at the top, is more fully set forth in the above mentioned copending applications. 1

I find that the outlet of the nozzleas'sembly should preferably just project through the 'roof of the furnace, whereas if it projects down into 'the furnace` to any y. great extent, interfering crusts may accumulate on its'outside walls, `ultimately obstructing the flow at the outlet of the nozzle and interfering with its proper vdetail with respect to' a preferred and satisfactory example, it will be understood by those skilled in the art after understanding the invention as above described,` that various changes and modiiications may be made without departing from the,spirit and scope of the invention, and it is intended therefore in thedappended claims to cover all such changes and modications. f

What is claimed as new and is desired to be secured by Letters Patent is:

1.l In a furnace for ash roasting finely divided ore particles in suspension, a roasting chamber, a nozzle at the midportion of the roof of said chamber for introducing the ore particles with a stream of gaseous medium, an opening being pro'- vided within said nozzle for discharging the central portion of said stream in a vertically downward direction, said opening being surrounded by an annular space providing additional 'ore discharge openings within said nozzle, and a plurality of curved vanes within said annular space for creating a turbulent condition in the ore and gaseous medium passing through said annular space.

2. In a furnace for ash roasting ilnely divided ore particles in suspension, a roasting chamber, a nozzle at the upper part of said chamber for introducing the ore particles with a stream of gaseous medium, ,means xed within said nozzle adjacent its outlet for controlling a spray of the o re particles from 4the nozzle, said means having a central portion with an opening for discharging a central jet of the particles substantially axially of .the spray, and a plurality of vanes extending fromsaid central portion for engaging ore particles forming the part of the spray surrounding Asaid central jet, said vanes having curved surfaces for creating a turbulent condition in said surrounding portions of the stream, and said turbulent condition extending into said central jet whereby the ore is distributed as a downwardly expanding conical spray.

3. In a'furnace for flash roasting finely di-V vided ore particles in suspension, a roasting chamber, a nozzle at the midportion of the roof of said chamber for introducing the ore particles with a stream of gaseous medium, means within said nozzle and adjacent its outlet for controlling the form lof the spray of ore emanating therefrom, said means having a central opening for discharging the middle portion of said spray in a vertically downward direction, and a plurality of vanes surrounding said central opening for engaging the ore forming outer parts of said spray and for imparting to said outer parts a turbulent fined within a downwardly expanding conical space.

5. In a furnace for flash roasting iinely divided ore particles in suspension, a roasting chamber,

a nozzle at the `midportion of the` roof ofsaid 'chamber for introducing the ore particles with a stream of gaseous medium, an opening being provided within said nozzle for discharging the central portion `oi said stream in a vertically downward direction, said opening being surrounded by an annular space providing additional ore discharge openings within said nozzle, a plurality of curved vanes within said annular space for creating a turbulent condition in the ore and gaseous medium passing through said annular space, means for introducing at the f.-

lower part of said chamber an uprising supply of gaseous medium, andoutlet means at the upper part of the chamber for the gases of combustion.

6. A process of roasting ores which comprises introducing the same in finely dividedL form into the top of a roasting chamber with a stream of air or other oxidizing medium under a relatively low pressure, controlling said ore particles as a falling spray consisting of a vertically downwardly directed central jet surrounded by a turbulent annular rotating downwardly expanding jet intersecting said central jet and distributing the ore as a falling spray substantially confined within a downwardly expanding conical space, introducing an uprising stream of gaseous medium in the chamber, and. withdrawing the 'gaseous products of combustion from the upper portion of the chamber.

HORACE FREEMAN.

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