US2630315A - Combination heat-treating furnace and gas generator - Google Patents

Description

March 1953 r. w. MUNFORD 2,630,315

COMBINATION HEAT'TREATING FURNACE AND GAS GENERATOR Filed May 11, 1946 1 I x z 1 z 1 1 1 l/ Zhwentor attorney Patented Mar. 3, 1953 COMBINATION HEAT-TREATIN G FURNACE AND GAS GENERATOR Theodore W. Munford, Ottawa Hills, Ohio, assignor to SurfaceCombustion Corporation, Toledo, Ohio, a corporation of Ohio Application May 11, 1946, Serial No. 669,002

5 Claims.

The present invention relates to furnaces for heat treating steel articles in a controlled atmosphere and more particularly in an atmosphere comprised of a product gas rich in carbon monoxide and hydrogen. Such a product gas is commonly produced by reactinga feed gas containing a hydrocarbon gas such as natural gas with just enough air to convert the carbon of the hydrocarbon to carbon monoxide, the reaction being conducted in the presence of a catalyst such as nickel and at a temperature which is desirably above 1750 F. and generally between 1800-1850" F. A typical product gas will contain about 20.7% carbon monoxide; about 38.7% hydrogen; about 0.8% methane; no or substantially no carbon dioxide and water vapor, and the remainder nitrogen. A product gas having the composition described has special utility as a carburizing atmosphere with or without an enriching gas such as natural gas. Carburizing may be conducted at temperatures substantially lower than 1750 F., although common practice calls for operation between 1700-1750 F. Perhaps because of their different heat requirements, carburizing furnaces and gas generators for produc ing the said product gas are ordinarily constructed and operated as separate units. The object of l the present invention is to provide the heat treating furnace with a built-in gas generator of such form and construction that its installation will add comparatively little to the costof the furnace and which shall otherwise be well adapted for its intended purpose.

For a consideration of what I believe to be novel and my invention, attention is directed to the following specification and the claims appended thereto.

In the drawing:

Fig. 1 is a vertical section through a heat treating furnace embodying the present invention.

Fig. 2 is a fragmentary side elevation and vertical section of parts embodied in Fig. 1.

Fig. 3 is a fragmentary section on a somewhat enlarged scale of parts embodied in Fig. 1.

The type of furnace-with which the present invention is primarily concerned will usually embody a vertical cylindrical chamber comprised of a circumferential side wall I0, a bottom wall H and an annular roof l2 whose central aperture is closed by a removable lid or cover [3. To reduce leakage of gas from the furnace the lid may be surrounded by sealing means comprised of a blade and trough l4, it being understood that the trough will contain any preferred sealing material not shown. The furnace as a whole is supported from below on a framework having supporting legs I5. The furnace will also usually embody a fan [6 for circulating the furnace atmosphere through and around a vertical cylindrical sleeve 3 I, it being understood that the articles to be heat treated will be arranged within the sleeve by suspension or otherwise in a manner to permit the circulated atmosphere to flow between the articles. The fan is mounted for rotation about a vertical axis and is shown as of the radial type. The fan is mounted on a vertical drive shaft I! which is driven by an electric motor 20 through a drive belt 2|. The drive shaft is supported for rotation in a structur 22 which in turn is centered in and supported by a cylindrical support 23 which depends from the underside of the bottom wall of the furnace. The structure 22 embodies means not shown for maintaining the fan shaft relatively cool.

The sleeve 3| extends upwardly from a funnel 24 supported from below on circumferentiall-y spaced standards 25, the function of the funnel being to direct the downcoming circulated atmosphere towards the center of the fan for optimum circulation as will be readily understood. The funnel has been shown as comprised of upper and lower sections 2'! and 30 and the sleeve as seated on the rim of-the upper section where it is held in place by vertical pins 32 which interengage with apertured lugs 33, the pins being carried by the pedestals 25 and the lugs being carried by said sleeve. The articles to be heat treated may be hung on a fixture of the type shown in patent to Munford 2,336,951 and when so supported it is desirable that the load of the articles and fixture be taken by means other than the sleeve. To that end there may be provided an annular load-supporting member 34 next above the sleeve, the said member being supported by hangers 35 hung on pins 36 which in turn are supported by lugs 3'! carried by the annular roof structure I 2 of the furnace.

The necessary heat-treating temperature is maintained within the furnace chamber by a plurality of heat-radiating elements 40 arranged in circumferentially spaced relation within said chamber along the side wall l0 thereof. Each of said elements will preferably be an internally fired combustion tube of hairpin type hung from the furnace roof I2 with the lower end of the tube spaced from the chamber side wall by an abutment 45 carried by the latter. Each tube has its own burner 4| firing into one end thereof and has its exhaust leg connected to a common exhaust manifold 42 by a gas connection 43, The

fuel is supplied to the several burners ll by a gas manifold 48 to which the fuel is supplied by a gas supply main controlled by a main gas valve not shown whereby to permit all of the tubes to be fired as a unit by control of the main gas valve as will be readily understood. Th furnace as above described does not per se constitute part of the present invention but is typical of the type of furnace with which the invention next to be described has special utility.

In the present invention the gas generator comprises a gas permeable column of catalytic material 53 in an upright reaction tube or tubular casing 46 which preferably extends into the furnace chamber through the bottom wall ll thereof to facilitate installation and removal of the tube for inspection and repairs. The means for holding the tube in place may comprise screw studs which depend from the furnace bottom to and through a radial flange on a reducer 41 of which the lower end of the tube is comprised. Coupled to the reducer is a gas inlet fitting 50 for the feed gas which is to be reacted to produce said product gas, it being understood that said feed gas is conducted to said gas inlet fitting from a source of supply not shown. The said catalytic material 53 will ordinarily be comprised of crushed refractory material like firebrick impregnated with any preferred catalyst of which nickel nitrate is an example. There is no advantage in extending the catalytic material into the lower or unheated portion of the tube and, therefore, the material 55 in that portion will usually consist of an aggregate of untreated firebrick. The

foot of the column of aggregate material in said tube 46 rests on a multi-apertured plate 54 at the upper end of the gas inlet fitting 50.

Because the catalyst-holding tube 48 is exposed to the prevailing temperature in the furnace chamber, it tends to assume such temperature but for reasons hereinbefore explained the practical minimum temperature for producing the aforesaid product gas will usually be substantially higher than the maximum temperature which will ordinarily be permitted to be maintained in the furnace chamber. The present invention provides the required additional heat in a relatively simple and practical way as will presently appear.

For descriptive purposes, one of the furnace heating elements 40 is specially identified in the drawing by reference character 51 and its burner and exhaust connection by reference characters 58 and 59, respectively. The said heating element 5! and the said catalyst holding tube 46 are in substantial vertical alinement and the tube is of such form and height as to encompass a sub stantial portion of said heating element 51 whereby to provide within the tube 46 a source of heat to heat the catalytic material and the feed gas flowing therethrough to the desired reaction temperature independently of the prevailing furnace chamber temperature. It will be understood that because the heating element 5'! has its own burn-,

er 58 it is a simple matter to adjust the rate of fuel supply to said element to insure that the proper reaction temperature will be maintained within the reaction tube 46. It will be readily appreciated that the partial envelopment of the heating element 5! by the reaction tube 46 does not seriously interfere, if at all, with the proper heating of the furnace chamber and that because said reaction tube is within the furnace chamber the heat loss from the tube is reduced to a minimum and the product gas enters said chamber from said tube in substantial equilibrium with the prevailing furnace temperature. It will be readily appreciated that the heat radiating elements need not necessarily be internally fired combustion tubes but may be electric heating elements.

From the foregoing description it will be seen that the present invention provides a relatively simple and practical catalytic gas generator for supplying to a furnace chamber a product gas of controlled composition.

What I claim as new is:

1. A controlled gas atmosphere heat treating furnace comprising a furnace chamber, a tubular member arranged in said chamber for heatin the same and having means associated therewith for heating such tubular member, a catalytic gas generator comprising a tubular member having a catalyst therein and means for supplyme said gas generator tubular member with gas for treatment under the influence of heat generated by said heating means and in the presence of said catalyst, and a communication between said catalytic gas generator tubular member and the interior of said furnace chamber through which gas treated in said catalytic gas generator tubular member is supplied to said furnace chamber, said tubular members being relatively disposed, one around the other.

2. In heat treating apparatus, in combination, a furnace having a chamber wherein articles may be heated in a controlled gas atmosphere, a catalytic gas generator arranger within said chamber and comprising a casing which is exteriorly exposed to the ambient temperature in the furnace chamber and which contains a catalyst, a heating element extending within said casing and into said catalyst for producing therein a temperature substantially higher than the temperature prevailing in the furnace chamber, means for supplying the casing with gas for treatment under the influence of heat generated in the casing by the heating element therein and in the presence of said catalyst, and a communication between said casing and the interior of the furnace chamber through which gas treated in said casing is supplied to said furnace chamber.

3. In heat treating apparatus according to claim 2, the said casing being defined by an upright tubular body which extends into the furnace chamber from below and which is removable therefrom by downward displacement and the said heating element being supported from above the top of said body for downward projection thereinto.

4. A controlled gas atmosphere heat treating furnace comprising a furnace chamber, means comprising a tube arranged in said chamber for heating the same, means for generating heat in said tube, a gas atmosphere generator inside of said furnace chamber and comprising a container having a gas permeable mass of catalyst therein, means for supplying said container with gas for treatment under the influence of heat generated in said tube and in the presence of said catalyst, said catalyst being arranged about said tube in direct heat exchange relation with the latter so that the operating temperature of said catalyst may be maintained independent of the operating temperature within said furnace chamber, and a communication between said container and the interior of said furnace chamher through which gas treated in said container is supplied to said furnace chamber.

5. A heat treating furnace comprising a work receiving chamber having heat generating means and work supporting means therein constructed and arranged relative to each other so that heat may efiiciently be transferred by convection from said heat generating means to Work arranged on said work supporting means, a gas atmosphere generator in said chamber in direct and intimate heat exchange relation with said heat generating means, said heat generating means and said generator being relatively disposed in direct contact and one around the other, said generator being provided with an outlet within said furnace chamber, said outlet being in open communication with the interior of said chamber for discharging a gas atmosphere from said generator into said chamber to come in contact with said heat generating means and Work supported by said work supporting means, and mechanical means for circulating the gas atmosphere in said chamber between said heat generating means and said work for transferring heat from said heat generating means to said work, said heat generating means comprising a REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,907,331 Millifi May 2, 1933 1,934,614 Peterson Nov. '7, 1933 2,188,275 Comstock Jan. 23, 1940 2,235,401 Gier, Jr. Mar. 18, 1941 2,254,047 Roth Aug. 26, 1941 2,274,209 Ness Feb. 24, 1942 2,278,891 Munford Apr. 7, 1942 2,381,306 Peck Aug. 7, 1945

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