US1167944A - Method of and means for melting metals. - Google Patents

Description

F. SHUMAN. METHOD OEAND MEANS FOR'MELTlNG METALS. APPLlcATloN FILED JULY 2o, 1909.

M6194@ Patented Jan.11,1916.

3 SHEETS-.SHEET 1.

Mmmm!! F. SHUMAN.

METHOD 0F AND MEANS FOR MELTlNG METALS.

APPLICATION FILED JULY 20, 1909.

Patented Jan. 11, 1916.

3 SHEETS-SHEET 2.

F. SHUMAN.

METHOD 0F AND MEANS FOR MELTING METALS APPLLCATION FILED JULY 20, 1909.

Patented Jan. 11, 1916.

3 SHEETS-SHEET 3.

WITNESSES FRANK SHUMAN, 0F PHILADELPHIA, PENNSYLVANIA.

l:METHOD OF AND MEA-NS FOR MELTING METALS.

Specification of Letters Patent.

Patentedv Jan. 11, 1916.

y Application led July 20, 1909. Serial No. 508,649.

To all whom it may concern Be it known that I, FRANK SHUMAN, a citizen of the United States, and a resident of the city and county of Philadelphia, State of Pennsylvania, have invented an Improvement in Methods of and Means for Melting Metals, of which the following is a specifica-- tion. l

My invention has reference to method of and means for fusing metals of low fusing points, and consists of certain'improvements fully set forth in the following specification and shown in the accompanying drawings which form a part thereof. v

My invention is adapted to all those industries in which it is necessary, for casting purposes, to .melt metals. or to keep the metal in the melted state forfpurposes such as in the manufacture of tin plates, in which the plates are dipped in the molten tin, and such as in galvanizing processes, in which iron is coated with Zinc by dipping in molten zinc.

My invention has utility in connection with all metals of low melting points such as tin, zinc, lead and various alloys of any of the above or other similar character. v

My invention also has for its object the recovering of metals of low melting characteristics from dross or refuse.

It is customary at the present time in con-l nection with the above stated uses of metals of low melting points and others of similar character, to employ coal or gas re under or against the vessels which contain the metal to be melted or to be kept melted. In the case of the use of coal as a fuel, it is very difficult to maintain the temperature at or near to the desired point; there are generally objectionable vapors given off; and, unless special precautions are taken, the air is in contact with the metals to be melted and dross and oXids form in objectionable quantities. These objections are particularly apparent when such metals are being recovered from dross or refuse, in which there are generally associated acid chlorid of ammonia or other fluxes. The objections above enumerated are also more or less present in cases where the heat is produced by a gas fire. although in this case it is more easy to maintain a substantially constant temperature.

By my improved method, hereinafter described, the above objections are eliminated, because oxidation of' the metal to be melted is prevented, and acids or iuxes are driven off at once when this is desired to be done. My improvements also enable the acids, fluxes, etc., to be recovered by being separated and conveyed away in suspension to a suitable condenser, the suspension medium being also the melting medium.

By the use of my improved method there 1s great saving owing to the fact that eXtra oxids are prevented from forming, and this 1s especially advantageous where it is desired to melt for casting purposes or for the recovering of metals Vfrom dross or refuse.

In carrying vmy invention into commercial of dross or refuse andvemploy said vapor,

gasor fluid as a vehicle for transferring the heat fr om the place of ygeneration to the metal or dross in the melting or vaporizing vessel or pot and at such place transfer a portion only of its heat to the metal or dross to melt the metal or vaporize the fluxes of the dross, and without the application of combustion directly applied thereto as heretofore practised.

My invention consists in causing the metal to be melted to be subjected to superheated steam, gas or fiuid medium under high temperature; further in circulating superheated steam, gas or fiuid medium repeatedly through or adjacent to the metal to be melted and when desired, supplying such additional steam, gas or fluid medium as may be required to compensate for that which may be lost or consumed; further in the above methods when employed for refining dross, the salts of the metal and fluxes are removed from the melting vessel by suspension and condensation at a point exterior to the said melting vessel. i

My improved method embodies the above specified features and also those which are more fully set out hereinafter and more particularly defined in the claims.

My invention also consistsof certain improvements in apparatus Vfor the carrying on of the above defined process, and more particularly embodying a preferably closed vessel in which the metal to be melted may be sealed, a source of steam or gas, means for superheating the steam or gas, and pipes for conveying the steamv or gas to the recepunderstood by reference to the drawings,

- in which Figure 1 is a diagrammatic elevation illustrating a complete apparatus for the use of steam or Vapor as a melting medium and embodying my improvements; Fig. 2 is an elevation of a modification of the same when gases are to be employed as the melting medium; Fig. 3 is an elevation of a further modification of Fig. 1 in which a liquid may be employed and the superheater omitted; Fig. 4 is a diagrammatic plan view showing my invention applied to a plurality of melting pots; Fig. 5 is a cross section showing the preferred manner of insulating the pipes; and Fig. 6 is a sectional elevation of a modified form of condenser.

Referring first, to the structure shown in Fig. 1,.A is a steam boiler of any suitable construction or type. Steam is conveyed from the said steam boiler through a pipe T and thence through the coils of a superheater B where it is superheatedA to a suflicient number of degrees above the melting point of the metal to be acted upon to insure the ready melting of the said metal.

This superheatingmay be such as to raise A the steam to anywhere between 20 and 500 degrees above the melting point of the metal, to suit the desire of the operator. l do not restrict myself to the use of any particular temperature above that of the melting point of the metal to be melted. The superheated steam thus provided is delivered by a pipe S to the melting vessel C. This melting vessel or pot C would ordinarily be made of wrought iron, cast iron or steel. lt may be provided at the top with a covered port O which may be used for charging the vessel or pot with metal to be melted. The

- bottom of the melting pot may be provided with a drawing off plug N through which the molten metal may be runoff. The melting pot C may also be provided, if desired, with a surrounding jacket F. The superheated steam pipe S may be connected by a valved connection P with a coil D within the melting pot. It may also be provided with a valved blow-in pipe E for delivering live superheated steam directly into the interior of the melting pot and adjacent t-o the bottom thereof so'as to be under the' metal. A valved pipe connection Gr may also be same steam is used over` and over again, but 1s superheated before being caused to act upon the metal or the melting pot. The superheated steam will give up its highest degrees of heat to the metal-in the melting pot and the said steam will' be circulated by the pump at a lower temperature than that which it contained when passing through the pipe S to the melting pot.

Should it be desired to melt the metal by meansof the closed coil D, then the valve connections G and E are closed and the metal will be melted by contact with the.

closed coil. Should it be desired to melt the metal by the superheated steam jacket F alone, then the valve connection G is opened and the valve connections P and E are closed. It is levident that both the closed coil D and the steam jacket F may be employed at the same time. Tn conjunction with either the closed coil D and the jacket F, or with combinations of either of these, or separately from them, the live steam from the blow-in pipe E may be used to melt the metal. 1n these cases the valves in the pipes K, l and H would be properly adjusted.v lVhen melting metals the condenser shown at V in Fig. 1 would not be used, and hence the valve in pipe U would be closed.

After the circulating system has been fully charged with superheated steam` the same may be circulated over and over again by simply closing the valve t in the steam supply pipe T leading from the boiler A. Any

loss of superheated steam through leakage or otherwise may be made up by supplying additional steam from the boiler A. As the pressure inthe entire system is practically equal, the only work required of the pump L is to keep the superheated steam circulating, and very little power is therefore required to drive the pump.

My improved system of melting is economical in respect to the amount of coal necessary for any given weight of metal to be melted because the heat is-generated in the boiler and a superheater which utilizes the coal consumption to a `lfar better advantage than occurs with the ordinary melting pot. Outside of the slight loss by'radiation, only so much heat need be generated as is required to actually melt the metal.

After the boiler has been utilized for supiso niemeer,

plying the necessary amount of steam into the circulating system, no further demand is made upon the boiler except to supply such additional amount of steam as may be necessary to compensate for the loss due to leakage, and consequently, a very small boiler would be required for a very large number ofl melting pots. By reason of theV fact that the steam is recirculated, the greatest economy results, becausey the steam is never wasted and as it is not condensed the latent heat of the steam always remains in it and the only loss to the heating medium is the amount of heat units'whi'ch are absorbed in the metal which is ymelted and such as might be lost by radiation. In no other system of melting could such an economy result. The loss by radiation may be reduced to a minimum by the proper insulation, not only of the melting pot but also of the piping and the circulating pump itself, as will be readily understood by an engineer familiar with thermo-dynamics.' To insure the most perfect insulation, the melting pot and pipes may be provided with vacuum jackets in which vacuum is maintained, said means being the most thorough method of insulation known. As the mechanical construction, however,will by conduction permit some small amounts of heat to find its way to the outer surface even with such method of insulation, material loss of heat units may in this case be obviated by proper non-conducting insulation of a fibrous nature surrounding the parts so to be insulated.

R represents the vacuum insulating jacket about the melting pot; R3, Fig. 5, represents the vacuum insulating jacket around the pipes; R2 Vrepresents a vacuum pump to maintain the vacuum in the jackets, and R the pipes leading from the jackets R and R3 to the vacuum pump R2.

C represents the fibrous non-conducting insulation above referred to about the melting pot, and C2 a similar insulation about the pipes. l

In the system above outlined, the heat which is utilized in producing thel melting and maintenance of the metal in the melted Astate is secured by the use of the superheater B and the amount of this superheating of the steam may be regulated to a nicety, thereby enabling the melting to be conducted under the most uniform conditions which is possible.

The pressure which is maintained in the system may be any pressure from one to five hundred pounds or more, and while the temperature is higher for the higher pressures, it is not desirable to utilize'the steam at high pressure without superheating it. The advantage of the invention lies rather in utllizingthe steam as a vehicle for conveym-g the heat from the superheating furnace to the metal to be melted, the said steam giving .11p only a portion of its heat and this being independent of the latent heat liberated by condensation since condensation is to be avoided.

It will be readily understood that the metals to be melted may be reduced'to the iuid state either by live superheated steam through the pipe E, by dry superheated steam through the coils D, or by use of the steam jacket F and it will further be understood that any combination of these three applications ofthe heat may be simultaneously employed in the treatment of any one batch of metal in the melting p ot. Under some conditions it will be advantageous to start the melting by blowing live superheated steam through the pipe'E as this will at once displace all the air in the melting pot and thereby avoid undesirable oxidizing ofthe metal to be melted. After the preliminary melting and removal of theair, the continuous maintaining of the metal in the molten state may be accomplished by use of the steam jacket F, or the steamcoil D or both, merely keeping enough livesuperf heated steam within the pot itself to prevent instead of the melting pot C being a closed vessel it will be open at the top in the usual n way and which might be broadly considered as existing if the top of the vessel C was open. However, in these cases it would be more preferable to use the steam jackets so as to leave the melting pot clear on the inside.v As my invention ,is not restricted in any sense to the form or construction of the melting pot, it will be readily understood -that the construction of the pot would be adapted for the particular commercial use of the invention desired. It is also understood that, whereas I have been describing my invention with reference to a single melting pot, a number of such meltingpots may be supplied with heating medium from a common source, as is indicated in the diagram Fig. 4. My invention is therefore applicable to one or more melting pots in connection with the common source of heat and with a common circulating apparatus or Puma Instead of employing superheated steam or vapors otherthanwater and having a suiiciently high temperature, for the heat conveying mediums in the melting operations, superheated gases may be employed instead, and these superheated gases are and nitrogen. Atmospheric air may be employed also, if desired, but in this case the original amount of oxygen contained in the air will slightly act upon the iron of the system. When this consumption of the oxygen has taken place, the circulation will be essentially with nitrogen, which is left. The oxidation of the iron will not be sufficient to prevent the use of air, if its use is desired. Liquefied carbonio acid, as a primary source ofan inert gas, may be excellently adapted to the use of my invention, and such use is indicated in Fig. 2, in which the general construction of the apparatus is as illustrated in Fig. l, but in place of the steam boiler A, I provide one or more liquefied carbonio acid cylinders A which are detachably connected by valve connections With the supply pipe T which connects with the junction box S. A battery of these corbonic acid cylinders A sufficient to more than fill the system should be employed. After the system has been filled the valve t in the pipe T ,is closed, as may be the valves on the cylinders. The carbonio acid gas in the system is then superheated by the superheater B, and circulated by the pipe L as in the case of Fig. 1 when employing steam. As the pressurel of the gas in these cylinders A is very high, it is unnecessary to use a pump Iin filling the system to the desired pressure and this may be accomplished by `closing the valve in the pipe M close to the junction box S and opening the vent m to allow the air in the system to be driven out when admitting the carbonio acid gas. lVhen the system is filled then thel vent fm` is closed and the large valve in the pipe Mais opened. In filling the system it would be necessary to o-pen all of the .valves on the valved pipe connections G,

E, P, H, 1 and K; but in case it was not desired to use free carbonio acid in the melting pot C, then the valved connections E and H would be closed. After they system has been filled with gas, the super-heater B is put into operation andthe gases in the pipes heated up to the desired temperature. 1t may then be used in exactly the same manner as the superheated steam, and Will contain and convey approximately as much heat per pound as gas. The pump L circulates the gas through the system just as in the case of superheated system and the whole action yfor the purposes enumerated will be the same. As these gases are entirely inert, they will prevent the oxidation of the metal being melted.

1n case it is desired to use atmospheric air, the system will be the same as indicated in Fig. 2 with the cylinders A removed.

,. In this case the valvem in the pipe may be temporarily Closed and the pump L will-be employed to suck air in through the valve t in the pipe T. and compress it in the pipe M until the proper pressure is provided, after which the valve t in the pipe T may be. closed and the valve m in the pipe opened. The pressure will then equalize throughout the system to that normally required and memsemay then be circulated as above described.

At long intervals it may be necessary to introduce a little more air to compensate lfor leaks, and this may be done, by working the force pump L T he total amount of air in the system would not be great and the oxygen of the same will be quickly absorbed by the melting metal when said airv is fed through'the pipe E in the pot, and also by the material of the pipes, leaving lfor normal use almost pure nitrogen.

Instead of employing steam from a`boiler A, as understood from the description of Fig. 1 and subsequently superheating it by means of the superheater B therein, 1- may employ a heat transferring medium in the form of vapor or steam' from higher boillng compounds than water, such for example as paraffin Which boils at about 650 degrees Fh. 1n view of the fact that this and similar materials boil at a sufficiently high degree'for melting purposes under my improvement, it -is not necessary to superheat such vapor, as in the case of steam from water. Apparatus for circulating boiling paraffin or similar compounds, is indicated in Fig. 3, in which the superheater is omitted and the pump L circulates the heating medium directly through the boiler A in place of circulating it through a superheater. Other hydro-carbon or inert stealns may also be generated and used under my invention in place of parafiin or water steam, if so desired. 1n those cases Wherethe melting temperature required is higher than the boiling point ofthe said heating compounds, they may be superheated as in the Case of Fig. 1, if so desired. In the usey of paraffin or molten hydro-carbons, it is possible to use this very hot melted material in the jacket F or in the coil D of the melting pot because, if not heated to above 600 degrees Fh., it may be retained as a fluid (liquid) and would be circulated by the pump L as a Huid. Care would be required to prevent this iuid paraflin becoming solid Within the piping, and consequently, when the system would be shut down, all of the piping would have to be drained before the paraiiin became cool enough to solidify. r1`he advantage of this liquid heat conveyer for metals of low melting points is, that a given volume of liquid will carry more heat than the same volume of gas or superheated steam, and

therefore, the circulation need not be so rapid. Furthermore, no pressure need be carried on the system atall, and the leakage will he less. This hot liquid, however, can only be used through the open pipe E in the melting pot when contact of the liquid with the metal to be melted is no objection, as for instance, when merely the melting of metals is required. 1n this case, it would How off through the pipe H. The metal to be melted Vmay be put into the vessel C, and

itthoroughly and owv out at the pipe H.

The metal will melt down quickly. There will be a layer of paraffin on top of the melted metal which will thoroughly protect it from oxidation. When it is desired to draw off the meltedv metal through the plug N, a little of the metal must be left in the vessel, so that no melted paraiin will be drawn off. `IIt is evident that.in this case, the pot may be an open pot, ordinary precaution, however, being had that the' top of the pot is. above the overflow pipe H, as will be readily understood by any one skilled in the art.

When it is desired to recover metal from zinc or tin dross, or other refuse, with practically no loss, it is necessary to add to the apparatus a condenser such as shown in Figs. l and 2 or of the kind shown in Fig;

. 6. Any other suitable character of condenser may be employed to suit the requirements of the work. v

When melting down dross by either of the'methods employing steam or gas, it is desirable that a certain amount of the live superheated steam or gas be used through the pipe E in the melting pot; and a greater amount of such steam or gas may be so used at the beginning ofthe melting operation than toward the endvof it. Assuming that superheated steam is being employed, 1t will act in two ways, namely, to melt the metal, and lat the same time to drive off chlorids of tin or zinc, and chlorids of ammonia or' other materials which may be contained in the flux or which have been produced therein. This live superheated steam, by immediatelydriving off the air, prevents further oxidation, and by quickly driving off the acids prevents the eating up of more metals during the melting process. The superheated steam carrying these various materials (which are valuable), passes through the vapor pipe U into the condenser V where cold water surrounding the condenser coil induces condensation of the superheated steam together with anything it may have carried over and which may be condensable, and said condensation fluid flows into the vessel W. By condensing all the vapors formed during the melting, no loss of valuable material is'possible. The loss of these materials, by the methods heretofore in use, amount in many cases to as much as from one to five per cent. of the total metal contents, and to a loss of all of the fluxes. In those cases of metallic salts, such forexample as chlorid of tin, .which maybe" distilled vat moderate temperatures, these salts may be separated'from the dross by actual distillation or vaporization within the closed vessel or pot by the vuse of my process and apparatus, by the use of superheated steam or other fluid'circulating medium if brought to a temperature higher than the boiling point of the said salts. It will also be understood that by such distillation the salts of the metals may be carried over into thecondenser or a receiverof suliiciently low temperature to condense the metallic vapors and thus collect them in vessel W unchanged in composition but separated from the dirt and refuse of the dross. If this method is resorted to asa means of collecting the metallic salts, itis evident that the condensation point will be suiiciently high in temperature not to condense the steam or other circulating Huid and thisma be recirculated by returning it to the pipe M by the pump L and pipe W. Should the fluxes be chlorid of ammonia, which is frequently the case, lthen the liquid in the vessel W received from the condenser, (in case tin dross was melted) would contain chlorid of tin, and chlorid of ammonia. The tin may be recovered from this solution by precipitating it with caustic alkalis, 'or other well known chemical methods may be used. If desired, the tin may be recovered electrolytically. Caustic ammonia would ordinarily be used for precipitating the tin from its chlorid, and in this case after the tin is precipitated, pure chlorid of ammonia would remain as the solution. This chlorid of ammonia would afterward be boiled down and thereby concentrated.

.-Any ofthe well known chemical methods may be employed to suit the recovery of the particular fluxes which may be used,` and I amtherefore only referring to the above as examples.

Instead of the coil condenser V shown in Fig. 1, a spray condenser such as shown in Fig. 6 may be used. In this case the vapor pipe U from the melting pot enters the side of the condenser vessel V, and a cold water spray is provided by a pipe V2 and a perforated pan Y. The falling spray quickly condenses the vapor to a liquid form and absorbs itl in the spray water, which can be drawn off through the-pipe Z into the tank W and treated as before described. lAny other well known form of condenser, such as Glover towers or other devices, may be used in lieu of the condensers above. described, 4if so desired",`

In the recovery of metals from tin or zinc dross, or other refuse by my improved ,method, there will be no additional oXids formed, but as there are always considerable percentages of such oXids already in the dross, these cannot be preventedby the use of my improvements. After the melted metal has been drawn off from the melting pot, the man-hole O may be opened and the oxids and dirtV removed from the melting vessel.` The oXids can be removed from this dirt by solution and recovered thereby, or

by Other well ,known chemical methods.`

superheated steam with a condenser as above i described for the recovery of the metals and fluxes from dross, it is also possible to use heated gases for the same purpose, as indicated in Fig. 2 in which a condenser V is provided. lln this latter case, however, the

condenser must be made sufficiently strong.

to stand the, pressures, and thereby enable the gases to be pumped back so as to avoid any loss of said gases; the said gases being non-condeusable, may pass from the condenser in a cool. but not liquefied condition, and maytherefore be led back to the pump L b v a pipe ll" from the top to the closed vessel lli, and again put into circulation in the s vstem by being forced into the pipe M.

It is' evident that the pressure under which the system is operated may be varied4 between wide. limits, and would be dependent very largely upon the materials employed and upon the temperature required, and 'l therefore do not limit or restrict myself to any particular temperatures or pressui-es. n y For convenience, I may designate the heat cmiveyillg medium, Whether 1t be steam, gas

or liquid, as a fluid, and in using this term,

whether in the specification or claims it is to be understood that 1t 1s used 1n a generlc sense, as including any of the mediums mentioned, o1' other equivalents.

` ln the operation of my improved process, it will be understood that the heat imparted to the circulating medium by the superheater or primary generator is in effectcarried by the circulating;r medium as a vehicle and delivered to the lnetal to be melted without reducing the heat of the circulating mey dium below a normal temperature sufficient to maintain it in its pro-per circulating condition. My improvement is, therefore, a method of transferring heat units from one place of generation and delivering them to one of more places of utilization, without in any way destroying the properties of the conveying medium. thereby distinguishing my process from all those methods in com mon practice of superheating air and gases which are ultimately consumed by combustion at the place of utilization. In my method there is no combustion of the heat conveying steam or gas and very little more heat is required to be generated than what is sudicient for the purposes of liquefactiony of the metal, and consequently, the highest efficiency is attainable as compared with the applied in practice` but ll wish it to be un derstood that these are given by way of illustration and not as restrictions with reference'to the. scope and utilization of my improvements, and I thereby do not restrict myself thereto.

In this application ll make no claim to the method and means which involve the vaporization of metallic dross by means of the heated steam or gas and subsequently collecting them by condensation or otherwise and involving' features of the general description referred to in this application as the same are reserved for a divisional application. i

ln this application, l make no claim broadly to the melting of metals and appar ratus therefor, in which the heatingr fluid is brought into direct contact with the metal, as this subject matter is reserved for a divisional application. v

Having now described my invention what t claim as new and desire to secure by Letters Patent, is:

l. rllhe herein described method of melting metals which consists in heating a fluid, conveying the fluid w'ith its contained heat to a distance to the place of heating, melting a metal or keeping it liquid by transferring a portion only of the heat units contained in the fluid to the metal, recirculating the said fluid, and super-heating the circulated fluid before being again utilized for melting the metal or retaining the metal in a fluid condition.

2. rihe herein described method of melting metals which consists in heating a Huid` conveving' the fluid with its contained heat to a distance to the place of heating, melting a. metal or keeping it liquid by transferring a portion only of the heat units contained in the fluid to the metal, recirculating the said fluid, superheating the circulatedl Huid before being again utilized for melting the metal or retaining` the metal in a duid condition, and adding from time to time additional quantities of the duid to that in circulation to compensate for losses in leakage, etc., whereby the normal quantity of the duid maybe practically maintained.

3. The herein described method of melting metals which consists in supportingr the metal in a vessel, generating steam and superheating it to a higher temperature than llSU the melting point of the metal,A conveying the steam into close proximlty to the metal within the vessel, and transferring a portion of the heat of the steam in excess ofthe latent heat therein to reduce the metal to the lmelted state.

4. The herein described method of melting metals which consists in supporting the vmetal in a vessel, generating steam and superheating it to a higher temperature than the melting point of the metal, conveylng the steam into close proximity 'to' the metal within the vessel, transferring a portion of the heat of the steam in excess of the latent heat therein to reduce the metal to the melted state, and recirculating the steam within the vessel, transferring a portion vof the heat of the steam in excess of the latent heat therein to reduce the metal to the melted state, recirculating the steam afteracting upon the metal without condensing it, whereby said steam is successively superheated and utilized for imparting heat to' the metal for maintaining said metal in a fiuid condition. and from time to time adding sufficient additional steam to that in circulation for compensating for any loss of volume therein.

ing metals which consists in supporting the l metal in a vessel, generating steam and su- -perheating it to a higher temperature than the melting point of the metal, conveying the steam into close proximity tothe metal within the vessel, transferring a. portion of the heat of the steam in excess of the latent heat therein to reduce the metal to the melted state, and preventing the loss of the heat of the steam in its action. upon the metal in the vessel bv maintaining about the vessel a non-conducting insulation.

7. The herein described method of melting metals which consists in supporting the l prlsmg a space 1n whlch -a partlal vacuum exists. Y 4

8,. The herein described method of melting or maintaining metals in a molten condition, which consists inl maintaining the metal in a viuid condition by absorption of heat Irom a heating medium without changing the chemical compound of said medium, K

circulating the medium froml a relatively distant place to a point adjacent lto the metalto be melted and kept in fluid condi-- tion, raising the tem erature of the heating medium at the relatlvely distant place to a temperature higher than that required to melt themetal, and recirculating the heating lmedium repeatedly whereby it may act as a continuous preheated lconveyer for transferring the heat received at the relatively distant place and delivering it to the metal to retain it in the melted condition.

9. The herein described method of melting or maintaining metals in a molten condition, which consists in maintaining the metal in a fluid condition by absorption of heat from a heating medium without changing the chemical composition of' said medlum, circulating the medium from a relatively distantl place to a point adjacent to themetal to be melted and kept in fluid condltion, ralsing the temperature of the heating medium at the relatively distantplace to. a temperature higher than that required v`to ineltjthe-metal, recirculating the heating Vmedium repeatedly whereby it may act as a conveyer for transferring the additional heat received at-the relatively distant place and delivering it to the metal to retainitin the melted conditionfand preventing material vloss of heat by radiation by carrying on the process of circulation and melting within a non-conducting surrounding.

10. Theherein described Inethodof maintaining a plurality of batches of metal in the fluid condition from a common source of heat, which consists in heating a Huid vat one place to a temperature greater than the molten metals, circulating the said fluid to a plurality of different oints, simultaneously transferring heat rom said fluid to Vdifferent batches of metal respectively located at saidvplurality of different points without condensing the heating fluid and returning the heating fluid to the source of heat to be preheated and-recirculated.

11. In apparatus for melting metals, the combination of a melting potand external source of heat, a circulating system of piping for conveying a heating medium successively through thel source of heat and the melting pot, and means for recirculating the fluid in the system of circulatingpiping.

'12. In apparatus for melting metals, the combination of a sealed melting not and external source of heat, a circulating system of piping for conveying a heating medium successively through the source of heat and the melting pot, and means for recirculating the fluid iii the system of circulating piping. y

13. In apparatus for melting metals, the

combination of a melting pot and external sourceA of heatameans for delivering the heating medium to the melting pot whereby it may be brought into conductive relation with the metals to be melted, a returnsystem of piping for conveying a heating medium successively and repeatedly through the source of heat and the melting pot, and means for recirculating the fluid in the system of return system of piping'.

14. ln apparatus for melting metals, the combination of a melting pot and external source of heat, insulating means surrounding the melting pot to prevent loss of heat by radiation therefrom, a recirculating system of piping for conveying a heating medium successively through the source of heat and the melting pot, and means for recirculating the fluid in the system of circulating piping.

15`. In apparatus for melting metals, the

combination of a melting pot and external source of heat, insulating means surrounding the melting pot to prevent loss of heat by radiation therefrom consisting of a vacuum jacket, a i'ecirculating system of piping for conveying a heating medium successively through the source of heat and the melting pot, and means for recirculating` the fiuid in the system of circulating piping. 16. In apparatus for melting metals, the combination of a melting pot having ini ternal heating pipes for heating medium, an

external -source of heat, insulating means surrounding the melting pot and intei'nal heating pipes to prevent loss of heat by l radiation therefrom, a recirculating system of iiinv' for conveyinlr a heatin medium b n b successively through the source of heat and internal heating pipes of the ineltin pot, and means for recirculating the fluid v1n the system of circulating piping.

17. 1n apparatus for melting metals, the combination of a melting pot and' external source of heat, a return system of piping for conveying a heating medium successively and repeatedly through the source of heat and the melting pot, and means for recir- 1 culating the fluid in the system of circulating piping, and means for supplying additional quantities of the heating medium into the return system of system from time to time to compensate for loss.

18. 'llhe herein described method of imelt 'ing metals, which consists in passing a .heatmeme/i contact therewith to heat it and simultaneously also passing some of the heating fluid directly 1in contact with the metal to melt it, mixing both of said portions of theheating Huid after having melted the metal, and recirculating the heated fluid after it has acted upon the metal to melt it, whereby the metal is kept in a molten state.

20. '.llhe herein described method of melting metals, which consists in passing a heating fluid adjacent to the metal but out of Contact therewith to heat it and simultaneously also passing some of the heating fluid directly in contact with the metal to melt it, recirculating the heating fiuid after it has acted upon the metal to melt it whereby the metal is kept in a molten state, and superheating the heating fuid before it is caused to act upon the metal.

21. The herein described method of melting metals, which consists in passing superheated steam adjacent to the metal but out of Contact therewith t0 heat it and simul taneously also passing some of the superheated steam directly in contact with the metal to melt it.

22. The herein described method of melting metals, which` consists in passing superheated steam adjacent to the metal but out of contact therewith to heat it and simultaneously also passing some of the super heated steam directly in contact with the metal to melt it, recirculatng the superheated steam after it has acted upon the metal to melt it whereby the metal is kept in a molten state, and again superheating the to melt it whereby the meta-l is kept in a molten stateVand again super-heating the previously superheated and used steam before it is caused to again act upon the metal.

23. The method of meltingY metals which consists in passing superlieatcd steam heated to a temperature greater than the melting temperature of the metals through the metal to be melted to retain it in molten condition.

lln testimony of which invention, l hereunto set my hand.

A.. G. Monnaimi., S. A. BLEND.

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