US723631A - Method of heating material. - Google Patents

Description

No. 728,681. v 'PATENTED MAR. 24, 1903.

E. G. AGHESON. v METHOD OF HEATING MATERIAL.

APPLICATION FILED SEPT. 26, 1902.

no MODEL.

yzawwk UNITED STATES PATENT OFFICE.

EDWARD GOODRICH Q E O LO S MFORD TOWNSHIP, CANADA, ASSIGNOR TO THE ACHESO'N COMPANY, or NIAGARA FALLS, NE\V YORK, A CORPORATION OF NEW JERSEY- METHOD OF HEATING MATERIAL.

SPECIFICATION forming .part of Letters Patent No. 728,63L: and March 24, 1903.

Application filed September 26, 1902.

surrounds the core, 0 the relatively thin envelop of the white stuff, and d the residual or undecom posed charge. If the temperature I of the mass in immediateprox-imity to'the To all whom it may concern:

Be it known that I, EDWARD GOODRIC ACH'ESON, a citizen of the UnitedStates, residing in Stamford township, in the county of Welland, Province of" Ontario, Canada, have invented certain new. and useful Improvements in Methods of Heating Material,

of which the following is a specification.

This invention relates to a method of conducting such operations as are dependent upon definite temperature conditions. In the specific example hereinafter given the use Of electricity as a heating agent is described in connection with a chemical reaction taking place between relatively narrow temperature limits. My invention, however, is not restricted to electric-furnace operations, nor to operationstaking place at high temperatures, but is applicable in general to such processes as require for their most eflicient conduct definite temperature conditions throughout the mass under treatment.

I will describe my method as applied to the production of white stuif, referring to the accompanying drawings, wherein- Figure l is a diagrammatic view showing the relations of the several materials remaining in the furnace at the close of the ordinary carborundum operation. Figs. 2,3, and i are diagrams showing temperature conditions according to my method.

It is well known that in the production of carboru ndum or crystallized carbid of silicon a certain amount of an amorphous-compound technically known as white stufi is formed and that this amorphous compound, being produced at lower temperatures than the carbornndum, appears as a layer or envelop surrounding the latter. An analysis of this white stuff gives the following composition: carbon 37.3 per cent., silicon 59.1 per cent, leaving 3.6 per cent. compound of iron, aluminium, calcium, and oxygen in undetermined amonnts, the metals entered through impurities contained in the carbon and silicon of the charge. y

In Fig. 1, :1 indicates the carbon core, which. forms the heating resistance of the ordinary carborundum-furnace. bis the body of carborund um which at the close of the operation core be assumed as 6,000 Fahrenheit and that of the exterior portions as 1,000 Fahrenheit, it will be seen that the temperature limits within which the white stuff is formed thickness, and from this fact it may be concluded that the diiference between the temperature required for the production of the white stuff and the temperatures'at which such white stuff passes into the crystalline carborundum does not exceed a few hundred degrees. ,It follows, therefore, that in a furnace designed for the production of this niaterial with the maximum efiiciency the heat must be so distributed throughout the charge that the temperature will at no point attain that of its conversion into carborundum and at no point fall below that necessary for its production. 1

The white stuff, like carborundum, results from the reaction between carbon and silica, the silica being conveniently supplied in the form of sand. This mixed charge comprising the sand and carbon is practically infusible and possesses-a low degree of heat conductivity. The products of the operation-white stuff and the residual carbon of the core-are likewise solid bodies at the temperature of the reaction, and the white stuff possesses a heat conductivity not differing to any substantial extent from that of the original charge. 1

Referring now'to Figs. 2 and 3 of the drawings, it will be understood that if the heat be regions a a. within the mass the temperature gradient will fall in every direction around supplied to such a charge at a plural ty of the regions of application of the he'at. The

the gradient, as diagramrnaticradiating-surfaces. The gradientwill therefore fall at a definite rate to a region or regions of minimum temperature, between the.

regiojns of maximum temperature represefpted by the points-of application of the heat and. will fall; as indicated, at'a considerably higher rate toward the external orn'adiating surfaces of the mass. 7

The limiting temperatures, superior and inferior, of the particular reaction under con sideration are not accurately known. It may be assumed, however, and probably with an approximation to correctness, that such liiniting temperatures are 4,000 and 3,500? Fah renheit, respectively. these figures the regions of m'axima have been shown in Fig. 3 asso placed in relation to each other that the temperature of the intermediate minimum shall not be less than the inferior limit of the reaction. Thereby it is assured that: the'produc tion of the compound in question will take place throughout the entire intermediate region, while at the same time it will be stable at and around'the regions'of application of the heat. 7

In the diagrammatic illustrations of Figs. 2 and 3 two regions of maximum temperature are indicated, In'a practical furnace the number of such regions of maximum temperature may be-indefinitely increased, care being taken, as above explained, that they be I so located relatively to one another that the erated for twelve consecutive hours.

intermediate minima shall afiord sulficient heat for the accomplishment of the reaction or operation desired. For instance, I have employed a furnace having an internal length of forty-eight inches, width of twentyfive inches, and depth of twenty-five inches. this was placed a charge of carbon and sand. Within the charge mixture were embodied 'four cores of granular carbon, each core being two and one-half inches in diameter by forty-:-

nches. I

It will be obvious that the heat may be applied at the regions of maximum temperature along lines or along surfaces, either of which may constitute the regions of maxim um temperature herein referred to.

From the foregoing explanation it will be;

seen that-it is not suflieient for the operation of mymethod that a series of heating-conductors be employed, nor does a series of'con- 1 doctors equally spaced and embedded in the charge constitu te of itself an apparatus capall lll ll l l l ll lll ll ll Hi In accordance with ble of carrying out my method. It is necessary that the resistance conductors or other devices for the application of heat'to the mass of material be definitely spaced with relation to each other at distances largely determined by theheat conductivity of the charge, the duration of the operation, and the superior an'dinfe'rior temperature limits' of the operation. Under such conditions only will the temperature variations within, the mass of material under treatment fall-within the temperature limits of'the operation;

By the term mass of material under treatment as herein employed is meant not nee-- essarily the entire body of the charge, but such portions thereof as fall within the proper temperature limits. This includes substantially the'Iwhole of the mass lying betweenthe regions of application of the heat and such portions external thereto as are heated to the-necessary extent. It will be under-. "stood, however, that the portions'near the radiating-surfaces, in other words, the outer layers ofthe charge, constitute an inert envelop for the mass under treatment. Their function is practicallythat-of an inert protection and heat-retaining covering.

By the expression temperature limits of the reaction is meant the superior and inferior temperature limits between which the reaction can proceed. The inferior limit is the minimum temperature at which the reaction can be carried on, and the superior limit is the maximum temperature at which the product is stable.

I claim- 1. The method of conducting. reactions which proceed under. definite temperatureconditions, which consists in maintaining within a. mass of material regions of definite maximum and of minimum temperature, bo h of which are comprised within the temperature limits of. the reaction, whereby the op.-

eration'is conducted throughout theentire mass of the material under treatment.

2-. The method 'of' conducting reactions which proceed under definite temperature conditions and the product of which remains unfused at the working temperature, which consists in maintaining within a mass of material regions of definite maximumiand of minimum temperature both of which are comprised within the temperature limitsof the reaction, whereby the operation is conducted throughout the entire mass of the material under treatment. I

3. The method of conducting reactions which proceed under definite conditions of temperature and heat conductivity,v which consists in maintaining within a massof material regions of definite maximum and of minimum temperature, both of which are comprisedwithin the temperature limits of the reaction, whereby the operation is conducted throughout the entire mass of the material under treatment.

4. The method ofpio'ducing white stufi lid which consists in maintaining within a mass another that the temperature variations withcontaining silica and carbon in suitable proin the material under treatment shall be in- [5 portions, regions of definite maximum and eluded withinthe temperature limits of the 'minimum temperature, both of which are reaction, whereby the operation is conducted 5 comprised within the temperature limits of throughout the entire mass of the material the reaction, whereby the operation is conun'dertreatment.

ducted throughout the entire mass of the'ma- In testimony whereof I have signed my 20 terial under treatment. name to this specification in the presence of 5. The method of producing white stuff two subscribing witnesses. m which consists in maintaining within a mass I EDWARD GOODRIOH- AOIIESON.

containing silica and carbon in suit-able pro- Witnesses: portions a plurality of regions, of maximum FRANK L. FREEMAN,

temperature, so located with relation to one ALFRED T. F. HANSMANN.

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