US2869845A - Crucible furnace - Google Patents

Description

Jam 20, 1959 J. D. SELVAGGlo :a1-)AL 2,869,845

v CRUCIBLE FURNACE Filed Oct. 21, 1955 llt United States Patent l 2,869,845 CRUCEBLE FURNACE John D. Selvaggio, Pittsburgh, and Calvin C. Wareham, Penn Township, Allegheny County, Pa., assgnors to United States Steel Corporation, a corporation of New `lersey Application (lctoher 21, 1955, Serial No. 542,065 3 Claims. (Cl. 263-2) This invention relates to an improved Crucible-type laboratory furnace.

Our furnace is especially useful for. preparing samples of iron ore, limestone or the like for analysis of their alkali content. Before such an analysis can be made, the alkali must be converted to a soluble form. This conversion can be accomplished by fusing the sample withappropriate reagents, such as a mixture of calcium carbonate and ammonium chloride. These materials are fused in an elongated nickel or platinum crucible whose bottom is heated to a high temperature, but whose upper portion must be kept relatively cool to prevent loss of alkali by volatilization. lOur furnace is used for heating the crucibles in this procedure, although obviously it may be used elsewhere where similar problems are encountered.

An object of our invention is to provide an improved furnace for supporting and heating elongated crucibles of the aforementioned type and confining the heat to Where it is actually needed.

A further object is to provide a compact draft-free furnace which can heat a large number of crucibles at a time while maintaining the upper portions of the crucibles relatively cool.

In accomplishing these and other objects of the invention we have provided improveddetails of structure, a preferred form of which is shown in the accompanying drawing, in which:

Figure l is a front elevational view, partly broken away, of a furnace constructed in accordance with our invention; and

Figure 2 is a vertical section on line Il--ll -of Figure l.

Our furnace comprises a metal frame preferably of welded angle iron construction, and a back wall 12, end walls 13 and front wall 14 of rigid insulating material, such as that sold under the trademark Transito The fro-nt wall is removably supported on a bracket 15, but the other walls can be permanently aiiixed to the frame 10. The top of the vframe is open. i A manifold 16 is fixed within the frame adjacent the bottom and carries a plurality of Bunsen burners 17, to which it also supplies fuel. Adjacent the upper ends of said burners the frame carries a support 18 on which a plurality of heat shields 19 are mounted, one for each burner.` Each of said heat shields is a rectangular block of rigid insulating material which contains an opening to accommodate the burner. The frame also includes an upper pair of downwardly sloping brackets 2t) and a similar lower pair of such brackets 21.

Either pair of brackets 20 or 21 is adapted to support a removable crucible rack 22. This rack includes a rigid angle iron frame of rectangular outline and a plurality of rectangular crucible supporting blocks 23 removably resting in said frame. The blocks 23 correspond with the respective burners 17 and are of'rigid insulating material. Each has an opening in which the lower end of an elongated nickel or platinum crucible 24 can be tted. The upper ends of the crucibles project Well above the upper faces of the blocks. When the rack 22 is placed on either set of brackets 20 or 21, the crucibles lie directly over the corresponding burners.

-In operation, as applied to preparation of samples for alkali determination, mixtures of sample and reagent are placed in the crucibles 24, which are mounted in the rack 2,869,845 Patented Jan. 20, 1959 2 22. First this rack is placed on the upper set of brackets 20. The burners 17 are lighted and the removable front wall 14 installed. The burners are adjusted first to produce a low llame and later a full flame and held thus for l5 to 20 minutes. Next the burners are turned oi and the rack is lowered to the lower set of brackets 21.

After the front wall is replaced, the burners again arel adjusted to full ame and heldfthus for about o-ne hour. During each burner operation the heat shields 19 prevent loss of heat downwardly and protect the manifold 16 against excessive heat. The blocks 23 prevent loss of heat upwardly and maintain the upper portions of the crucibles relatively cool to prevent loss of alkali by volatilization.

While we have shown and described only a single embodiment of the invention, it is apparent that modifications may arise. Therefore, we do not wish to be limited to the disclosure set forth but only by the scope of the appended claims.

We claim:

1. A furnace comprising a frame, walls of insulating material supported on said frame, a plurality of Bunsen burners mounted in the lower portion of said frame, means for supplying fuel to said burners, vertically spaced sets of supporting brackets in said frame above said burners, and a crucible rack adapted to be removably supported on either of said sets of brackets, said rack including a rectangular frame and a plurality of blocks of rigid insulating material supported thereon and corresponding with said burners, each of said blocks having an opening adapted to receive the lower portionv of an elongated crucible for exposure to a different one of said burners, said blocks being adapted to maintain the upper portions of the crucibles relatively cool.

2. A furnace as defined in claim l including heat shields of rigid insulating material surrounding each of said burners to prevent downward loss of heat.

3. A laboratory furnace for fusing samples of iron ore, limestone or the like preparatory to determination of their alkali content comprising a frame, walls of insulating material supported on said frame, a plurality of Bunsen burners mounted in the lower portion of said frame, means for supplying fuel to said burners, upper and lower vertically spaced sets of supporting brackets in said frame above said burners, a crucible rack including a rectangular frame and a plurality of blocks of rigid insulating material supported thereon and corresponding with said burners, each of said blocks having an opening, elongated crucibles adapted to receive samples for fusion fitted into the respective openings with their lower ends projecting below said blocks for exposure to said burners and their upper ends being open and projecting above the blocks, said upper brackets being adapted to support said rack during initial heating of said crucibles and samples therein, said lower brackets being adapted to support said rack during final heating of the crucibles `and samples, said blocks insulating the upper portions of said crucibles from said burners and thus maintaining the upper portions relatively cool to prevent loss of sample through the open ends by volatilization, and heat insulating shields of rigid insulating material surrounding each Iof said burners to prevent downward loss of heat.

References Cited in the le of this patent UNlTED STATES PATENTS 648,655 Cushing May l, 1900 824,338 Carey June 26, 1906 2,345,247 Erickson Mar. 28, 1944' 2,500,943 Haines Mar. 2l, 1950 2,520,133 Donovan Aug. 29, 1950 Y FOREIGN PATENTS 237,397 Great Britain July 30, 1925 522,800 Great Britain June 27, 1940

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