US2404328A - Fuel fired vacuum furnace - Google Patents

Description

July 16,194& u. J. TURlN ET AL FUEL FIRED VACUUM FURNACE Filed Nov. 30, 1944 Peter' Patented July 16, 1946 FUEL FIRED VACUUM FURNACE John J. Turin, West Newton, Mass., and Arthur W. Peters, Toledo, Ohio, assignors, by mesne assignments, to surface Combustion Corporation, Toledo, Ohio, a c'orporation' of Ohio Application November 30, 1944, Serial'No.-.565,936

8 Claims. 1

The present invention relates to the manufacture of metallic magnesium by the thermal reduction of magnesium oxide and more particularly to an improved vacuum furnace for use in connection with such manufacture.

In the ther-mal reduction of magnesiumoxide with a reducing agent like ferrosilicon, it is customary to form the reacting ingredients into relatively small briquettes and then to heat these briquettes to reducing temperature in a vacuum.

Heretofora'in the case of fuel fired furnace s, it has been customary to effect the reduction of the' magnesium oxide on externally-heated, vacuum-tight retort. However, the upper temperature limit of the retort has been only about 2100- 2150 F. due to the retort beingmade of` a hea resisting alloy (a chrome nickel iron alloy) which at said temperature' is 'semi-plastic and readily deformable. At a temperature of 2100-2150 F. there is required some hours to effeot satisfactory reduction of the magnesum oxide whereas'at a temperature of only a few hundred. de'grees higher, reducton can be efiected more' completely and in substantially less time.

'The present invention has for its object to provide a fue] fired furnace which shall make it possible to heat the 'said briquettes of magnesium oxide containing material to reducing 'temperature without the use of an 'externally fired vacuum-tight retort and Withal to permit such heating to be effected more speedily and efiiciently than has heretofore been possible with fuel fired apparatus. Other related object will more fully appear hereinafter.

v For a consideration of what' we believe to be novel and our invention, attention is directedto the following specification and the claims appended thereto.

In the drawing: r

Fig. 1 is a vertical sectional view with parts in elevation of a furnace embodying the present invention. r u 4 Fig. 2 is a horizontal sectonal view on line '2-2 of Fig. 1. i

The improved furnace comprise's a Vacuumtight exterior metal shell or. casing 2 comprised of lower and upper portions ?a and 2b respectively, the shell having an interier lining 'I of heat insulating material. The top of the oasing hasa central opening encompassed by` a collar Zc, this opening being normally closed vacuumtight by a cap type closure Sadapted to seat on said collar. r

An internally cooled cylinder 6 depends from the closure 3 the pipe which delivers cooling me- V dium. to the-cylinder being indioated at6a. .'I'he purpose of thiscylinder 6 is to serve-as a con-` denser for magnesium vapor comingf.rom the reducing zone of the furnace presently .described.

A ball of the condensed magnesiumisindicated in broken lines at M. v i

To facilitate handling of theload constituted by the. closure 3 and. the-parts .Suspended .therefrom the closure is hung on anarm 36-01 athorizontally disposed beam affixed to..anv elevator post' 31 mounted in a.support 38- securedLtothe exterior 'shell of the furnacel An hydraulic cylinder for raising and lowering the-post 31 isdiagrammatically indioated. .atr39. A spare closure 3a withcondenser cylinder 6' attached is hung` the retort 20 through the top aperture ,l i, it being understood that the briquettes will first have been dumped into the drum 9 before the closure 3 is in`p1acef Before being dumped into the drum 9 the briquettes will have been `preleated to a temperature of 'about'1200-1300 F. for the purpose of drying and degasifying the same. To permit the briquettes to be temporarily held in the drum s 9 until the retort 20 has been made fully ready to receive them, there is provided above the aper r tur'll a stopper l 2 adaptedyto be operated by a rod' l3 extending upwardly therefrom to an op; erating lever'M. 'A hood`l6 above the stopper prevents jamming'of the stopper by the briquettes thereabove. The hood'is held in fixed position by'radial 'struts 16'. In thedrawing; the stopper is shown in down or' closed position. i The lever |4 is connected to' avacuum-tight Operating 'device I5 outside of the'furnace shell.

The'lower end of' the drum 9 rests'on the top wall IO of the retort'25` and its upper end is" slidably 'centere'd in the collar 2c. The underside of theclosure 3 is protected 'against overheating by a circular body 3' of heat insulating material carried thereby and adapted to project a short distance into the drum 9. body :permit's free movement of the rod l3. Ex tending-laterally from the collar 20 is a condut 5 which serves to connect the interior ofthe; fur

A `vertical groove in said u nace to a source of vacuum such as a vacuum pump. i i i The bottom of the furnace shell or casing 2 has a central opening encompassed by a collar 2d,

this opening being normally closed vacuum-fight by a closure 4 adapted to seat on the collar. A cylinder 4' of heat insulating material'on the closure closes the bottom of the retort. To permit'a 'waste receiving car to be d'sposed beneath the furnace, the latter is mounted on stand-" ards 35. i v 3 To facilitate handling of the load constituted by the closure 4, the closure is mounted on an arm 3| of a horizontally disposed ,beam affixed'to an elevator post 32 mounted in a support 33 af fixed to the furnace casing An hydraulic cylinder for raising and lowering the post is diagrammatically indicated at 34. A spare closure 4a is' bottom walls the retort is preferably comprised of a circumferential series of intercomn unicatipg i relatively narrow upright Channels !8, four such channel being shown. it being understood that briquette's dum ed into the retort will fill these channels. thereby substantially reducing thehorizontal distance that heat must travel radially inward to reach the center of the charge.

The retort 20 is surrounded by a refractorv structure 8 comprising an outer'circula'rwall j|9 spaced from' the retort to form a firing or combustion space about the retort. This structure 8 is preferably made of silicon carbide. and is 'so massive that after it has been heated. to a temperature of about 2700 F. it will contain enough heat not only to heat the charge of briquettesin the retort to reducing temperature but also to sustainthe endothermic reaction fort a period long enough to efie'ct substantially complete reduction of the magnesium oxide.

A burner 22 is positioned in the furnace wall to fire 'tangentially into ,said firing space 40 whereby to heat said structure `8 to the'saidelevated temperature, it being understood that this firingiis done only when -atmospheric pressure prevails within the furnace casing 2 and that the burner will be shut off vacuum-tight when 'a vacuum prevails in said furnace. `ln l 'iggz, the fuel supply pipe for the burner is indicated' at 23, the same being provided with a vacuum-tight shut-off valve 24. The burners may be lighted by inserting a torchthrough a lighting' passage 25 which is normally closed vacuum-fight by'a clc sure 25'. Thewaste heating gases fiow'from the combustion space 40 through a lateral port 28 to a waste gas fiue 27 which is normally'closed vacuum-tight by a closure 29. As shown inFig. 1, the firing space 40 is preferably divided into a vertical series of communi cating compartments by hori'zontally disposed reractory spacers -21, each having an aperture 2l' so arranged with respect to the aperture in the next adjacent'spacer that the fiaming fuel from the burner 22 must necessarily flow in 'a circuitous path in flowing upwardly to the waste gas fiue 21. Although only one burner has been shown, it' will be readily understood that there maybe a'vertical r ow of such burners. As shown r' in Fig. 1, the'inner face of the'wall 9 between adapted for its intended purpose.

e cumferential series of relatively'narrow upright- 4 the spacers 2| is preferably serrated to more readily absorb heat from the flaming fuel.

The mode of operation of the improved fumace may be briefiy summarized as follows: The refractory structure 8 is' heated to a temperature, of about 2700 F. before a vacuum prevails in the firing space 40' or, in other words, before a Vacuum prevails within furnace shell or ca'sing 2. Breparatory to producing a vacuum within the furnace the bumer 22 must, of course, be shut off vvacuum-tight. Also a charge of preheated briquettes Will have been dumped into the drum or barrel 9 in the upper part 'of the furnace preparatory to being dumped into the retort 20 as soonas the bottom closure 4 is in place and ?the furnace is otherwise ready to be evacuated. As soon as the briquettes have been dumped into the furnace the furnace is made yacuum-tight and the vacuum pump started. Heating up of the removal'of the top closure 3 to permit removal of i the condensed magnesium from the condenser 6; The furnace is then again made ready `for another charge by reheating the structure 8 a's will now be readily understood. In the meantime, the

'bottom closure 4 is removed to permitthe 'spent charge of briquettes in the retort to drop out of the furnace into a waste receiving car beneath the furnace. p

From the foregoing it will be seen that' the present invention provides a relatively simplegand practical fuel fired vacuum furnace which is well The present application is a continuation 'in part of our application Serial No. %55,260 filed August 18', 1942. i

What is claimed as new is: 1. In appa'ratus for the thermal treatment in a vacuum of a magnesium oxide containing material capable of evolving magnesium vapor, 'the e ccmbination which comprises a relatively tall heat conducting refractory structure defining a container for a charge of said material, the said structure being chambered to provide a combustion space, burner means for delivering fuel to said combustion space for heating said structure to an elevated temperature substantialiy higher than 2100 F. before producing a vacuum' in said reentrant channels for the reception of thesaid material.

2; In apparatus f or the thermal treatment of material under vacuum, the combination which 'compries a'refractory structure defining a non- Vacuum tight container wherein a charge of said material will be placed for heating to treating temperature, a vacuum-tight casing wherein said structure is housed and wherein a vacuum must prevail in order that a, vacuum may prevail in said container, said refractory structure being so massive that when it has been heated to an elevated temperature substantially higher than the said treating temperature there will be present in said structure all of the heat required to maintain said charge at the said treating temperature, the said structure being chambered to provide a combustion space about-the 'said container, and burner means for delivering fuei to said combustion space forheating said structure'- to said elevated temperature before producing a vacuum in said casing.

3. In apparatus for the thermal treatment of material under vacuum, the combination which comprises a reiativelytall refractory structure defining an open top container wherein a charge of said material will be placed for heating to' treating temperature, a vacuum-tight casing wherein said structure is housed and wherein a vacuum must prevail in order that avacuum may prevail in said container, said refractory structure being so massive that when it has been heated to an elevated temperature substantially higher than the said treatirg temperature there' will be present in said structure all of the heat required to maintain said charge at the said treating temperature, the said structure being chambered to provide a combustion space about the said container, and burner means for delivering fuel to said combustion space for heating said structure to said elevated temperature before producing a vacuum in said casing.

4. In apparatus for the thermal treatment of material under vacuum, the combination which comprises a relatively tall refractory structure defining an open top container wherein a charge of said material will be placed for heating to treating temperature, a vacuum-tight -casing wherein said structure is housed and wherein a vacuum must prevail in order that a vacuum may prevail in said container, said refractory structure being so massive that when it has been heated to an elevated temperature substantially high er than the said treating temperature there will be-present in said' structure all of the heat required to maintain said charge at the said treating temperature, the said structure being chambered to provide a combustion space about said container, burner means for deiivering fuel to said combustion space for heating said structure' i vacuum of material capable of evolving magnesium vapor, the combination which comprises a r perature there will be present in said structure ail of the heat required to maintain said charge e at the said 'treating temperature, the said structure being chambered to provide a combustion space about said container, burner means for delivering fuel to said combustion spacefor heating said structure to said elevated temperature before producing a vacuum in said casing, and means {6. In apparatus for the thermal treatment'in a refractory structure defining a non-vacuum tight container for a charge of said material, the said structure being chambered to provide a combustion space about said container wherein fuel may be burned for heating said structure to an elevated temperature of about 2700 F. before producing a vacuum in said container, burner means fordeliverng said fuel to said combustion space, a vacuum casing wherein said structure is housed and wherein a vacuum must prevail in order that a vacuum may prevail in said container, said refractory structure being so massive that when it has been heated to said elevated temperature there will be present in said structure all of the to said elevated temperature before producing a ing a relatively tall non-vacuum tight container :r

wherein a charge of said material will be placed for heating to treating temperature, a vacuumtight casing wherein said structure is housed and wherein a vacuum must prevail in order that a vacuum may prevail in said container, said refractory structure being' so massive that when it has been heated to an elevated temperature substantially higher than the 'said treating tem heat required to maintain the said charge at ma nesium-evolving temperature, and means in said apparatus for condensing the magnesium vapor evolving from said charge. v

7. In apparatus for the thermal treatment in a vacuum of a magnesium oxide containing material capable of i evolving magnesium vapor, the combination which comprises a relatively tall heat conducting refractory structure defining a container for a charge of said material, the said structure being chambered to provide a combustion space about said container wherein fuel may be burned for heating said structure to an elevated temperature substantially higher than 2100 F. before producing a vacuum in said chamber, burner means for delivering said fuel to said combustion space, a vacuum casing wherein said structure is housed and wherein a vacuum must prevail in order that a vacuum may prevail in said container during the thermal treatment of said material, said structure being so massive that when it has been heated to said elevated temperature there will be present in said structure all of the heat required to react the charge of said material in saidcontainer.

8. In apparatus for heat treating material in a vacuum, the combination which comprises a refractory structure defining a container for said material, the said structure being chambered to provide a combustion space about said container wherein fuel may be burned for heating

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