US2065218A - Manufacture of metallic fume - Google Patents

Description

Dec. 22, 1936. c GARESCHE- 2,065,218

MANUFACTURE OF METALLIC FUME Filed May 13, 1931 3 Sheets-Sheet l awzw Dec. 22, 1936.

c. F. GARESCHE 2,065,218 MANUFACTURE OF METALLIC FUME Filed May 13, 1931 3 Sheets-Sheet 2 w 4 1 V\ENTOR.

BY/ Y Z a A RNEYS.

Dec. 22; 1936. Y c; GARESCHE 2,065,218

MANUFACTURE OF METALLIC FUME Filed May 13, 1931 3 Sheets-Sheet 3 1 VENTOR. 0M2 W7 4/1" ATTORN s.

Patented Dec. 22, 1936 2,065,218 .MANUFACTUBE OF METALLIC Claude F. Garesch, South Orange, N. 3., as-

signor to National Lead Company, New York, N. Y., a corporation of New Jersey Application May 13, 1931, Serial No. 537,059

20 Claims.

The object is the improvement of apparatus and method for making. high grade metallic fume, particularly litharge and the invention consists generally in the manner of subjecting the lead or metal to the oxidizing reaction, and cooling and collecting the productsand in certain combinations of structure specially suited to such operations, separately and in combination, all as below explainedand as illustrated, but by way of example only, in the accompanying drawings.

In the latter, Fig. 1 represents in longitudinal vertical section a form of apparatus incorporating certain of the structural improvements and also adapted for performing the new method; Fig. 2 a. continuation of Fig. 1 partly diagrammatic; Fig. 3, a front view of the rotary combustion chamber and its metal supply appara tus, partly in section; Fig. 4, a plan of Fig. 3, and

Fig. a detail of the lead pressure control.

According to the method of this invention, in its preferred form, the metal or lead in finelydivided form is projected or sprayed into a combustion chamber and volatilized and oxidized' therein, in suspension in direct contact with fiame and excess oxygen, the resulting oxide fume being carried off by suction through a cooling system into a bag house or dust filter. The combustion chamber is rotated coincidently with the spraying for the purpose of elevating those particles of lead or oxide which fall out of the spray, not sumciently oxidized, and dropping these particles a second time and repeatedly through the flame, which procedure results in a high production of exceedingly fine-grained product. The tailings tumble out of the end of the rotary chamber and the fume or suspension products are drawn out through the cooling system wherein their temperature is reduced at such rate and under such control, as later pointed out, as to avoid over-oxidation on the one hand and, on the other hand and more particularly, so as to avoid excessive absorption of CO2 by the oxide as well as any condensation of the water vapor in the gases. The method of effecting this control and also the apparatus used therefor, are also a part of the invention though capable of independent use as will presently appear.

The combustion chamber I is cylindrical, preferably but not necessarily tapered at one end, about twenty-three feet long and eight feet outside diameter with a refractory lining which extends into the tapered part. It is mounted to revolve in any suitable way onan axis which is preferably horizontal so as to produce a prolonged secondary treatment of the fallen material. Its outlet end has a snug rotary fit in the wall of a stationary breeching 2, the upper part of which is connected with the cooling and collecting sys- ,tem and the lower partserves as a collecting bin 5 for discharged tailings and having conveying, mechanism 3 for removing them. An appropriate speed of rotation for the chamber is about one revolution in five minutes.

A fixed plate or wall 4 closes the reduced end of the chamber and forms the support for the burner. andspray mechanism for the lead or material to be treated. Oil or gas, and preferably the latter, is used as fuel and is introduced through a. circular opening 4" in plate 4 by a gas nozzle 5, of preferably annular shape as shown, supported concentrically in the plate opening 4- which is an air-admitting opening and projecting its flame approximately axially into the rotary chamber; it is supplied with gas from a gas pipe 6 under appropriate pressure to produce a long flame.

The lead which is the material to be treated in the present case is taken from the kettle shown in Fig. 3 and piped therefrom in a molten state, through pipe, I and branch pipe 8 to the lead atomizing nozzle 9, which is located within andv concentric to the gas burner 5. By this nozzle the molten lead is atomized with air under pressure supplied by pipe I!) and pre-heated to say 900 F. in the air heater (diagrammatically indicated), the lead spray being axial and therefore combined or mixed with the flame. The particular design of the lead spray nozzle is of no consequence, so long as it produces extremely fine atomization, which is important; nozzles suitable for this purpose are known to the art; and in place of 'such atomizing apparatus, any suitable injector means for introducing fine lead powder previously manufactured could be substi- 40 tuted. From, the air used for atomizing and that drawn through the plate opening with the mixed blast of spray and flame, an excess of oxygen is drawn into and is present in the chamber.

Referring to Fig. 3, the lead supply system comprises a kettle ll set in a suitable furnace I2, which is desirably sunk below the floor level so that the kettle will not be too high to be conveniently charged with lead pigs. The pump l3 for transferring the molten lead from the kettle 5 to the spray nozzle is submerged in the molten lead well below the dross level and supported in this position on the lower end of a tubular support l4, which is attached by its upper end to the supporting bed plate l5 of the electric motor It by which the pump is driven, the bed plate l5 being carried on three rigid columns l'lsecured to the rim of the kettle as indicated in Fig. 4. The pump l3, which may be an ordinary centrifugal pump such as hertofore used for pumping molten lead, is driven by a shaft l8 which is housed within the tubular pump support M. In this position it is found that the shaft is likely to be interfered with by the dross and for this reason the support is provided with two opposing clearing slots l9, extending from below the lead level to a point somewhat above it, so that it may readily be cleared of obstruction. By locating the pump at,

one side of the kettle it is out of the way of the lead pigs filled into the opposite side, and further protection of the pump against injury from this source is provided by a guard 20, rigidly suspended and anchored in the kettle from a cross bar 2| spanning the kettle mouth. The pump support I4 is bolted to and held rigid by this same cross bar by U-bolt 22 (Fig. 4)

The lead delivery pipe I, as already stated,

leads to the nozzle pipe 8, but from this point it continues on as a return pipe 23 leading back to the kettle. The proportions of these pipes and of the lead nozzle are so related that a considerable excess of molten lead is constantly returned to the kettle through the pipe 23 and the circulation thus maintained suflices to keep the circulating pipe hot and the lead delivered at the nozzle always at the proper temperature required for fine atomizing, thus avoiding the inconvenience of having many gas-jets playing on the pipe, as now commonly employed in lead-spraying equipment. Adequate pressure for discharging the fluid lead from the spray nozzle is produced by restricting or choking the return passage 23, which is done in the case in hand by means of a tapered, slab-sided plug 24 movably mounted in the open end of the return pipe 23 below the liquid level, being held in adjusted position by a holder rod 25, which may be clamped on one of the motor-support columns 11 or elsewhere as convenient, so that the choke can be adjusted to give the pressure desired but never wholly stop the flow which would permit freezing of the lead in the otherwise unheated pipe.

With the kettle located close to the floor level as indicated, and the lead circulating pipes I and 23 extending upwardly therefrom to the spray nozzle and kept hot bythe circulation as described, such pipes may easily have a proper pitch so that on shut down of the pump the lead still molten will flow by gravity back to the pump leaving the pipes empty for resumption.

In operation, the mixed blast of lead spray, flame and air extends axially into therotating chamber,-or with a slight upward direction, and the volatilization and oxidation occur while the lead is in suspension, the fume being drawn 011 through the breeching by suction applied to the bag house or conduit, as by a fan 26 (Fig. 21' or equivalent suction device. falling out of the blast, insufiici'ently oxidized, drop to the cylinder wall and particularly in the zone of the hottest flame, stick to the cylinder lining. Then as the chamber revolves these particles are continuously carried to a point directly above the hottest flame zone where the rising heat causes them to melt so as to drop through the flame, thu's subjecting them again and again to the high flame temperature and in this way increasing inmeasurable extent the yield from the apparatus. S uoh heavier particles as are not thus volatilized or reduced to a size that will Some heavy particles permit them to be carried ofi by the gas current eventually fall out of the discharge end of the rotating chamber, where they are removed as tailings, and are useful in various relations. The entire refuse from the operation is discharged automatically and continuously in this way, without requiring that the chamber be entered for cleaning at the risk of lead-poisoning from breathing the dust. Sanitation is further promoted by the suction withdrawal of the fume which prevents outward leakage of dust. Besides serving to lift and drop and re-suspend fallen particles in the flame the rotation of the chamber serves the further useful efiect of reducing and practically avoiding wear of the refractory lining. The most vulnerable spot on the lining tends to develop just above the flame, due to the heat of the latter and the reaction heat, but as the chamber is rotating a new and relatively cooler surface is continuously being brought to the top so that the heat is distributed and in consequence the tendency for oxide to dissolve the refractory bricks, wearing them away, is correspondingly reduced. The taper of the chamber conforms more or lessto the,expanding contour of the blast or spray and tends to reduce eddy currents, and more particularly, prevents occasional puffs of lead-laden gas out through the air entrance 4" into the room. The yield of volatilized product is customarily in the order of 50% of the lead fed, but is subject to variation by control of the fineness of the spray and may be made as high as where there is no desire to have a large yield of tailings.

From the breeching 2, the gaseous 'fume and suspended oxide pass through a'cooling conduit in the form of grouped goose-necks 21 'as customary and wherein the fume is condensed and cooled and some of it collects in the hoppers at the bases of the goose-necks. The particular design of this cooling apparatus may be as preferred or as customary and for that reason is shown only in conventional form.

According to this invention however, the cool.-

- ing conduit, that is to say, the group of goose- 29 at its ground level and with equivalent windows or louvers 30 near the roof above the goosenecks, so that by regulating the opening of these doors and windows the flow of air around and over the goose-necks can be controlled to augment or diminish the cooling efiect as desired. The

goose-necks are ordinarily some forty feet high giving a natural chimney-stack effect in the vertical spaces between and around them and regulation of the natural thermally induced air currents in this way is found sufficient without using forced air currents although the latter method also is practical. In this way it is possible when producing litharge to'control the rate and degree of cooling the lame, so that the unintentional production of red lead as by over-oxidation in the goose-necks next adjacent to the combustion chamber; and also the danger of charring the bags are readily avoided, At'the same time the temperature can be sustained above the point say about F. where C02 in the gases becomes absorbed by the product, converting it into carbonate and above the point where water vapor, present in the'gases'from the use of hydro-carbon fuels, will condense inside the goose-necks. The

pheric temperature.

safe temperature for the avoidance of condensation of course depends on the amount of moisture present, that is to say, the dew point of the gases which may vary, but is easily determinable. If condensation occurs, it will injure the product and may rust the goose-necks themselves besides also clogging the pores of the filter bags. It is thus possible, simply by regulation. of windows and doors, as indicated, to maintain a uniformly efficient and proper temperature gradient in the cooling gases and in consequence, to promote a desirable uniformity of the product, doing entirely away with the prevailing practice of controlling cooling by'cutting in and out certain of the goose-necks and the manipulation of large sized valves and dampers to that end. By the enclosure of the cooling system and regulation of the heat-transfer through the wall of the conduit, all of the goose-' necks are kept in operation all of the time, the length of the gas path being fixed for allconditions with corresponding saving of delay and labor and quite regardless of variation of the atmos- In order to maintain the bag house temperature low enough to avoid danger of charring bags, the general rule is that the temperature of the entering gases should not exceed 210 F., and in hot weather it isthe com- 'mon practice in existing systems to admit outside air into the conduit gases just ahead of the bag house or filter, thus diluting in order to cool them, but by the dilution a greater filtering capacity is needed for the bag house than would be required merely to filter the combustion products. By thepresent method of cooling therefore, a substantial saving of investment, in filtering equipment, is also accomplished.

I claim:

1. Apparatus of'the kind described comprising in combination, a combustion chamber rotating on a substantially horizontal axis, means for projecting flame and finely divided lead into such chamber, a stationary cooling and fume collecting conduit connected to said chamber and a suction device for maintaining negative pressure in said chamber and conduit.

2. Apparatus of the kind described comprising in combination a combustion chamber mounted to rotate on a substantially horizontal axis and connected at its outlet end with a stationary'cooling and fume'collecting conduit, pressure means at its opposite end for projecting a mixed blast of finely divided metal and flame with air into said chamber said air serving to oxidize the metal in suspension, means for rotating said chamber, whereby fallen particles are resuspended in the blast, and means for regulating the transfer of heat from the fume through the wall of said conduit.

3. Apparatus of the kind described comprising in combination a rotary combustion chamber, a stationary cooling and fume collecting conduit connected to one end of said chamber, a tailings conveyor associated with the same end, a stationary plate or wall closing the other end of the chamber and provided with an air-admitting aperture, a fluid fuel burner and an atomizing'nozzle for metal both discharging under pressure through said air-admitting aperture into the chamber and suction means for withdrawing fume and combustion products through said conduit.

4. Apparatus of thekind described comprising in combination, a substantially horizontal cylindrical chamber tapered at one end and provided with a refractory lining extending into said tapered end, means for projecting a blast of flame and fume producing material axially into the chamber through the tapered end thereof, adapted to cause vaporization in suspension in said chamber, a stationary fume cooling conduit connected to the other end of said chamber, and means for rotating said chamber.

5. Apparatus of the kind described comprising in combination, a substantially horizontal cylindrical chamber tapered at its receiving end and provided with a refractory lining extending into the tapered part, means for rotating the chamber, a fixed closure plate or-wall covering the tapered end, means for projecting a blast of finely divided or atomized molten metal and flame,- approximately axially into the rotating chamber through said closure plate and tapered end, a stationary offtake connected with the other end of the chamber, a cooling conduit connected to said oiftake and suction means connected to said conduit.

6. In apparatus of the kind described, the combination of a melting kettle for metal, a remote discharge ,outlet for the molten metal, a pump in the heat of the kettle, a delivery pipe from pump to outlet, a return pipe from the outlet to kettle, and a constriction in the return pipe for regulating pressure at the outlet. V

7. In apparatus of the kind described, a melting kettle for metal, a heat source therefor, an outlet for the molten metal remote from the kettle, a pump submerged below the surface. of the metal in the kettle, a delivery pipe from pump to outlet, a return pipe from-outlet to kettle and aconstriction for the return pipe below the surface of the metal in the kettle.

8. Apparatus of the kind described comprising in combination, a combustion chamber, means for projecting hydrocarbon flame and finely divided or atomized molten metal under pressure into such chamber, a fume cooling conduit connected to said chamber, a suction device for withdrawing fume through the conduit, and means for-regulating the contact of atmosphere with said cooling conduit.

9. Apparatus of the kind described comprising in combination a rotary combustion chamber connected at its delivery end with a stationary fume conduit, means for projecting a mixed blast of finely divided or atomized molten lead, flame and air, axially into the other end of said chamber, means for rotating the chamber, an enclosure for said conduit and means for regulating air flow through the enclosure and over said conduit.

10. The method of making fumed lead oxide which comprises passing lead oxide fume from a combustion chamber through a cooling conduit and controlling the contact of atmosphere with the exterior of said conduit so as to keep the temperature of the flowing gases therein above the point at which CO2 in such gases is absorbed by the lead oxide therein.

11. The method of manufacturing metallic oxide which comprises projecting a blast of finely-divided metal. substantially horizontally into a combustion chamber in the presence of flame and excess oxygen thereby volatilizing and oxidizing the metal while in suspension, coincidently collecting on the floor of the chamber such unvolatilized particles as fall out of the blast, rotating said chamber so' as to elevate and drop such particles repeatedly through the flame, and continuously withdrawing, cooling and collecting the oxidation products from said chamber.

12. The method of oxidizing lead which comprises projecting a combined blast, of finelydivided lead, previously heated compressed air and flame into a combustion chamber thereby volatilizing and oxidizing a considerable portion of the lead while in suspension in the blast, collecting on the floor of such chamber such unvolatilized particles as fall from the blast, rotating said chamber to lift and drop said particles through the flame, continuously withdrawingv by suction, and cooling and collecting the oxidized fume product, and coincidently discharging the tailings.

13. In apparatus of the kind described, the combination of a heated melting kettle for molten metal, a spraying nozzle for metal above and remote from the kettle, a pump and pipes by which the pump circulates molten metal from kettle to nozzle, and nozzle to kettle, the return flow pipe being arranged to aiford a. gravity evacuation of moltenmetal from the nozzle on cessation of the pump, and said pump being disposed below the level of the molten metal in the kettle and subject to the heat of the kettle, whereby the lead therein is melted when the kettle lead is melted.

14. In apparatus of the kind described, the combination of a heated melting kettle for molten metal a spraying nozzle for metal above and remote from the kettle, a pump situated below the metal level and in the heat of the kettle, and pipe connection means, whereby the pump supplies the nozzle, including an orifice through which the nozzle is evacuated by gravity on the cessation of the pumping, said orifice being also subject to the heat of the kettle.

15. In apparatus of thekind described the combination of a melting kettle for metal, a remote spray nozzle for the molten metal, a pump in the heat of the kettle, adelivery pipe from pump to nozzle, a return pipe from nozzle to kettle and a constriction in the return pipe for regulating the 1 pressure at the nozzle, said restriction comprising a plug removably held in the open end of the return pipe.

16. Apparatus of the kind described comprising in combination, a combustion chamber rotating on a substantially horizontal axis, pressure means for introducing flame and subdivided metal into such chamber for reaction therein, a stationary cooling and fume-collecting conduit connected to said chamber, suction means connected to said conduit for promoting fiow through the same and means for removing tailings from the end of said chamber.

17. Apparatus of the kind described comprising a reaction chamber producing vapor at high temperature, a cooling conduit for said vapor, said 18. In apparatus of the kind described, the" combination of a heated melting kettle, a spraying nozzle above and remote from the kettle, a pump submerged in the melt in the kettle, a pipe connection whereby the pump supplies the nozzle, a return pipe from the nozzle having its outlet orifice in the kettle, both said pipes being pitched to drain into the kettle on pump shut-down, and

a restriction in the return pipe for regulating the pressure at the nozzle, said'restriction comprising a plug removably held in said outlet orifice.

19. Apparatus of the kind described comprising in combination a combustion chamber rotating on a substantially horizontal axis, pressure means for simultaneously introducing flame and subdivided material into one end of such chamber for reaction therein, a stationary breeching closing the opposite end, a cooling and collecting conduit connected to said breeching, a tailings conveyor associated with the lower part of said breeching and means for maintaining flow of the reaction products from the chamber through said conduit.

20. Apparatus of the kind described comprising in combination a combustion chamber rotating on a substantially horizontal axis, pressure means for simultaneously introducing flame and subdivided material into one end of such chamber for reaction therein, a stationary breeching closing the opposite end, a long cooling conduit connected to said breeching, a housing enclosing said conduit and provided with means for adjusting the flow of air over said conduit within the housing, a product collector at the end of the conduit, a tailings collector associated with said breeching and means for maintaining flow of the reaction products from the chamber through said conduit and collector.

CLAUDE F. GARESCHIZ.

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