US2130886A - Method of and apparatus for vaporization - Google Patents

Description

- P 1938. F. R. KEMMER METHOD OF AND APPARATUS FOR VAPORIZATION Filed Jan. 8, 1934 INVENTOR.

ATTORNEY.

Patented Sept. 20, 1938 PATENT OFFICE DIETHOD OF AND APPARATUS FOR VAPORIZATION Frank R. Kemmer, Larchmont, N. Y., auignor to Magnesium Products, Inc., Pltiaburgh, Pa., a corporation of Delaware Application January 8, 1934, Serial No. 705,829

. l'lClaims.

leased in contact with or in the presence of carbon" monoxide of carbon dioxide gas as for example in the cases of zinc, phosphorus and magnesium.

The presence of the carbon monoxide gas in admixture with the metallic vapors adds some diiilculty to or imposes certain limitations upon the direct condensation of the metallic vapor into the form of massive, compact or coherent metal.

In the case of zinc for example, when operating on the usual very small batches by the retort process, the condensation of zinc although accomplished to yield zinc directly in a liquid and coherent form, is nevertheless attended with fairly substantial losses of zinc. These difilculties increase when one attemptsto pass into extremely large units to take advantage oi lower investment and smelting costs as for example in the electrothermic smelting of very fine zinc flotation concentrates and in that case it has been found advisable to condense all the vapor initially to the solid phase in finely divided form and then recover the zinc in a coherent form by retreatment of the zinc powder.

In the reduction of magnesium oxide bearing ores using a carbonaceous reducing agent, the conditions are somewhat more complicated than in the reduction of zinc ores in that the resulting carbon monoxide reacts with the magnesium vapor below 2000 C. to form the oxide of magnesium. In order to preserve the magnesium in the metallic state it is necessary to chill the gaseous mixture with extreme rapidity through the range of temperature within which the reversion to oxide may take place and this, of course, resuits in the production of the metal in a finely divided solid state which requires further treatment to obtain the metal in coherent form.

My invention is directed to the treatment of metals, metallic powders, residues and the like but more particularly to the treatment of such metallic powders in a continuous manner and under close temperature control to permit the distillation of metal from such powder and its submanufacture on a large scale.

The present invention is directed to the use of 10 an apparatus in combination which will continuously feed metallic powder into a suitable distilling furnace, there to be subjected to radiant heat from a suitable source to volatilize the metal, remove the residue from the furnace in a con- 16 tinuous manner if desired and to continuously expose fresh powder to the distillation treatment.

The accompanying drawing is a vertical crosssectional view, some parts being shown in elevation, of an apparatus adapted for the practice of 20 my invention.

There is provided a holder i having an inlet opening 2, closed by a double valve 3 and having a pipe 4 controlled by valve 5 leading to a vacuum pump 8. Another pipe 1 controlled by valve 8 25 allows the entrance of an indiflerent gas from pipe 9 into the holder I. In the bottom of the holder is an outlet l0 controlled by a double valve ll allowing material from the holder to pass into the vertical pipe l2 which communicates with the 30 horizontal pipe i3 having a screw conveyor l4 therein driven through a shaft iii. The pipe i3 is attached at Hi to a pot or enlarged portion ll within a chamber l8. The chamber is formed by a metal or other shell. i 9 which is lined with heat 35 insulating material 20 and within the same a sec-- ond lining 2| of heat refractory material. In the upper part of chamber I8 is an outlet 22 for gases and vapors.

A resistor 23 is placed above the pot l1 and in 4 close proximity to the surface 24 of the material 25 which is to be treated.

In the operation of the apparatus the material is caused to flow from holder i through pipes l2 and I3 and into pot or vessel II. This exposes a thin film 24 to the heat generated by the resistor 23 causing vaporization of the metal or other material therein, and the film 24 moves slowly to the edge of the pot where the waste material spills over as shown at 26. This exposes a fresh film 24 continuously to the action of the heat radiating down from the resistor. The vapors pass upwardly from the pot l'l between the various elements of the resistor and into the space 28 above the same. In this passage the vapors become horizontal pipe 3| which connects at 32 with a vertical pot or holder 33 contained in chamber 34 formed by shell 35 surrounding the same. A pipe 36 controlled by valve 31 serves as a means for introducing at 38 an indifferent gas. A glass window 89 is secured to the side of chamber 35 to allow observation of the conditions therein.

In the bottom of the chamber is a screw conveyor M which forces the material 40 in the bottomwthereof to pct 42 and the waste material 13 is slowly removed from the chamber.

Besides the advantages of continuous feed of metal bearing charge and continuous discharge of residue which result in large scale operations and low costs I find several other distinct and important advantages. For example, in my apparatus, the charge of raw material is fed in a direct line of approach to the resistor radiating heat against the upper surface of the charge and thereby acquires a substantial amount of preheat l in its travel toward the source of heat. Furthermore, by properly proportioning the energy in the source of heat (preferably a graphite resistor) to the rate of feed of charge I am enabled to carry out the distillation of metal from thin surface layers only, with the very important advantage that the metallic vapor being generated only at the thin surface layer passes or practically free'from finely divided solid particles which are carried along mechanically with the metallic vapor when such vapors are produced or liberated within the charge of material of such very fine subdivision in which such metallic condensates are usually produced. This, it will be readily noted, is a very distinct advantage because mechanically entrained solids which would otherwise be carried along with the metallic vapor in its condition of release and sudden expansion within the charge would be carried along and would collect with the rnetal on condensation. This would be a. serious drawback as in such an operation it is of the utmost importance that the system be closed and tightly sealed during the entire operation. Such mechanically suspended material would also settle out in the connections between the distilling and condensing apparatus and interfere with the free passage of metallic vapor therethrough and in a very short time prevent the passage of vapor entirely.

. Another advantage of my apparatus is that it permits the use of a large surface of material in juxtaposition to a large area of heating ele- 'ment and allows of distillation at a rapid rate with a minimum temperature gradient between the heating element and the charge. The use of widely distributed heat of low temperature gradient minimizes heat losses from the furnace and yields the vapor of the desired metal which is practically free from contamination by vapors of metals of higher boiling point than that of the metal desired.

Another important advantage of my apparatus is that the resulting metallic vapors are required to pass through and/or around the heating elements and are thereby superheated prior to entering the condenser. This superheat is very desirable in that it prevents condensation in the distillation furnace and in the connections leading to the condensing system and delivers the vapor to the condensing systems with such a de-. gree of superheat that condensation to the liquid state may be accomplished without extraneous heat if so desired. This is of particular importance in those cases where the distillation is carried out under pressures and temperatures considerably below the boiling temperature at atmospheric pressure and more especially where inert or protective gases are used in the disti1- lation.

This insures a sufliciently high temperature so that liquid metal may result from the condensing operation.

By vaporizing the metal at a low temperature there is avoided the vaporization of certain low boiling impurities and the thin surface layers which are exposed to theheat tend to minimize sudden or large degree of expansion of the metal to the vapor phase.

This avoids carrying along vapors of other materials and also dust or finely divided material in mechanical suspension. Because of the thin film there is no release of vapors from the body of the mass being treated thus preventing displacement of the material and rendering theextraction of metal therefrom more complete.

Although I have described my invention as setting forth a specific embodiment thereof it is, of course, obvious that various changes therein may be made within the scope of the invention. This apparatus may be used not only for distillation but also for causing chemical reaction to take place with the production of volatile material where the reacting ingredients are in the solid phase. The invention may be used for the purlfication of substances other than metals by volatilization with or without the use of a vacuum and at high or low temperatures. Various changes may be made inthe operation and in the construction of the device. For example, the resistor 23 need not be horizontal, but may be placed at an angle substantially parallel to the angle or repose of the film 2%. A plurality of resistors may, of course be used.

The feeding and the discharge device may be replaced by other devices capable of accomplishing the same results. The indifferent gas may be introduced at points other than those described and it isobvious that but a very small amount thereof is necessary and that it may be sufficient to utilize only such gas as is entrained in the incoming charge. Such entrained gas is introduced into the charge in holder 5 during the pretreatment with the indifierent gas to replace other gases which are capable of forming compounds with magnesium and which are removed from the charge by the vacuum pump. By the term indifferent as used in the claims I intend to include not only inert, but also reducing gases i with suitable material to maintain the distilling chamber against the entrance of air through the outlet end even when under a high vacuum.

This is especially advisable when distilling a in the charge very gradually expands and thus same. This allows the discharge of the residue at a small angle of repose. If desired this agitation may be done mechanically, as by moving the pot at intervals to agitate the charge.

In addition to the atmosphere of indifferent gas in the distillation furnace or in place thereof I may cause a stream of such gas to flow through the furnace to aidv in sweeping out the vapors and to render the process more effective. The vapors may be superheated by providing heating elements in the form of or including tubes, through or over which the vapors may be passed. When the apparatus is at or near atmospheric pressure, the chamber 34 and pot 33 may be omitted. These and other variations and changes may be made in my invention within the spirit thereof and the invention is not to be limited except by the claims appended hereto.

What I claim is:

l. A method of distillation of metal powders to recover purified metal therefrom which comprises removing deleterious gases from said powder, moving said powder into a zone of temperature above the vaporization point of said metal, radiating heat onto said powder to vaporize said metal and recovering the vapors.

2. A method of distillation of metal powders to recover purified metal therefrom which comprises moving said powder into a zone of temperature above the vaporization point of said metal, substantially continuously advancing said metal powder and causing during said advance relative movement of the particles of said powder so as to expose fresh surfaces to the action of heat, radiating heat onto said powder to vaporize said metal, maintaining a pressure below atmospheric in the system, and recovering the vapors.

3. A method of distillationof metal powders to recover purified metal therefrom which comprises moving a column of said powder upwardly into a zone of temperature above the vaporization point of said metal, radiating heat downwardly onto said powder to vaporize said metal, causing the residual unvaporized material to spill over said column and recovering the vapors.

4. A method of distillation of metal powders to recover purified metal therefrom which comprises continuously moving a column of said powder upwardly into a zone of temperature above the vaporization point of said metal, radiating heat downwardly onto said powder to vaporize said metal, causing the residual unvaporized material to spill over said column and recovering the vapors.

5. A method of distillation of zinc powder to recover zinc therefrom which comprises moving zinc powder into a zone of temperature above the vaporization point of zinc, radiating heat onto the zinc powder to vaporize-zinc, substantially continuously advancing said zinc powder and causing during said advance relative movement of the particles of said powder so as to expose fresh surfaces to the action of heat, maintaining a pressure below atmospheric in the system and condensing the vapors.

6. A method of distillation of zinc powder to recover zinc therefrom which comprises providing an indifferent atmosphere, moving zinc powder into a zone of temperature above the vaporization point of zinc, substantially continuously advancing said zinc powder and causing during said advance relative movement of the particles of said powder so as to expose fresh surfaces to the action of heat, radiating heat onto the zinc powder to vaporize zinc and condensing the vapors. I

7. A method of distillation of magnesium powder to recover magnesium therefrom which comprises moving magnesium powder into a zone of temperature above the vaporization point of magnesium, radiating heat onto the magnesium powder to vaporize magnesium, substantially continuously advancing said magnesium powder and causing during said advance relative movement of the particles of said powder so as to expose fresh surfaces to the action of heat, maintaining a pressure below atmospheric in the system and condensing the vapors.

8. A method of distillation which comprises introducing powdered material to be distilled into a zone of temperature above the vaporization point of said material, radiating heat onto the same to vaporize said material, causing the vapors to pass through the zone of heat to superheat said vapors, substantially all of said vapors passing through said zone of temperature and being substantially uniformly heated and condensing the same.

9. A method of distillation of metal powders to recover purified metal therefrom which comprises introducing said powder into a zone of temperature above the vaporization point of said metal, radiating heat onto said powder to vaporize said metal, causing the vapors to pass through the zone of heat to superheat said vapors, substantially all of said vapors passing through said zone of temperature and being substantially uniformly heated, and condensing the same.

10. A method of distillation of metal powders to recover purified metal therefrom which comprises providing a body of said powder, distilling metal from the surface layers of said body, moving fresh powder upwardly into position in place of said surface layers without disengagement of vapors within said body and recovering the vapors.

11. A method of distillation of metal powders to recover purified metal therefrom which comprises providing a body of said powder, preheating the same, distilling metal from the surface layers of said body without disengagement of vapors within said body, moving fresh powder upwardly in place of said surface layers and recovering the vapors.

12. An apparatus for distillation which comprises a conduit for powdered material to be distilled, an open topped vessel, said conduit being connected to and adapted to feed powdered material into said vessel, means for forcing said material over the edge of said vessel, a source of radiant energy above said vessel, an enclosure surrounding said vessel and said source of energy to prevent access of air and an exit conduit for vapors.

13. An apparatus for distillation which comprises a conduit for powdered material to be distilled, an open topped vessel, said conduit being connected to and adapted to feed powdered ma terial into said vessel, means for forcing said material over the edge of said vessel, 8, source of radiant energy above said vessel, an enclosure surrounding said vessel and said source of energy connected to and adapted to feed powdered material into said vessel, means for forcing said material over the edge of said vessel, :3, source of radiant energy above said vessel, an enclosure surrounding said vessel and said source of energy to prevent access of air, an exit conduit for vapors, and means for maintaining a pressure below atmospheric in said apparatus.

15. A method of distillation of zinc powder to recover zinc therefrom which comprises providing an indifferent atmosphere, moving zinc powder into a zone of temperature above the vaporization point of zinc, substantially continuously advancing. said zinc powder and causing during said advance relative movement of the particles of said powder so as to expose fresh surfaces to the action of heat, radiating heat onto the zinc powder to vaporize zinc, maintaining a pressure 2,1so,eac

below atmospheric in the system and condensing the vapors.

16. A method of distillation of magnesium powder to recover magnesium therefrom which comprises providing an indifferent atmosphere, moving magnesium powder into a zone of temperature above the vaporization point of magnesium, radiating" heat onto the magnesium powder to vaporize magnesium, substantially continuously advancing said magnesium powder and causing during said advance relative movement of the particles of said powder so as to expose fresh surfaces to the action of heat, maintaining a pressure below atmospheric in the system and condensing the vapors.

17. A method of distilling magnesium powder which comprises introducing said powder into a zone of temperature above the vaporization point of magnesium, radiating heat onto said powder to vaporize said magnesium, causing the vapors to pass through the zone of heat to superheat the vapors substantially uniformly, and condensing the same.

FRANK R. KEMMER.

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