US1742441A - Metallurgical furnace - Google Patents

Description

Jan. 7, 1930. F, A. J. FITZGERALD ET AL 1,742,441

METALLURGI CAL FURNACE Filed July 24, 1928 firron IVE) mated Jan. 1, 1930 UNITED STATES PATENT OFFICE FRANCIS A. J. FITZGERALD, OI NIAGARA FALLS, NEW YORK, AND JAMES KELLEKEB, OF CHIPIPEWA, ONTARIO, CANADA, ASSIGNORS 'IO TITANIA CORPORATION, OF L08 AN GELES, CALIFORNIA,

A CORPORATION 01' CALIFORNIA mz'mmoaercan summon Application filed July 24, 1928. Serial No. 834,981.

7 It is well known to those skilled in the art that certain combinations of titanium oxide and carbon when subjected to heat in an atmosphere of nitrogen gas reacts toform carbon monoxide and titanium nitride, as clearly set forth'in the United States Patents Nos. 1,391,147 and 1,391,148, issued September 20, 1921 to Bichowsky, et al.

The materials to be treated by our 1nven-. tion consist of titanium ore mixed with carbon and a suitable catalyst, such as sodium carbonate, as set forth in the Bichowsky patents. This material is ground to an extremely fine powder and mixed with some organic bond, such as glucose or molasses, after which it is briquetted so as to form a suitable charge for a furnace. One of the common'methods of reducing such a charge is to place 1t In a shaft furnace, using coke as fuel, as for example the reduction of iron ores in a blast furnace. However, in the process for WhlCh our invention is desi ned, a fuel-fired furnace can not be usedfor eating the briquettes to the desired temperature, because the reaction will not take lace except in an oxygen; free atmosphere. l3ecause of this reason it is essential that electric furnaces be emplo ed,

but an electric furnace with the usual s aft is not only difficult to control, but has a great many other objections, because of scaffolding, explosions, and the like.

The principal object of our 1nvent1on has been to provide a furnace 1n which the process described in the Bichowsky et alpatent referred to may be practiced in a continuous manner for the production of tltamum-nltrogen compounds.

Another object has been to provide a furnace in which the temperature of the reacting mass may be accurately controlled.

A further object has been to provide a furnace having heating means Wfllldt shall uniformly heat the charge contained 1n the fur-.

nace.

Moreover, our furnace is provided w th means for protecting the ,fimshed material from oxidation and for removing it from the furnace without nitrogen gas. 7 p v Furthermore, our furnace provides means permitting the escape of the roof 20, is a gate for preheating the nitrogen gas, and the untreated charge, and for recovering the combustible gases generated by the reaction.

The furnace hereinafter described attains the objects above recited and overcomes the disadvantages hereinbefore pointed out, and ishshplwn in the accompanying drawings, of w 10 Fig. 1 is a transverse, sectional elevation of our u made of steel and having its joints welded so 66 as to prevent the leakage of gas. The shell comprises a front wall 6, a rear wall 7, and end walls 8 and 9. A bottom 10 extends inwardly from the front wall 6 and a bottom 11 extends inwardly from the rear wall 7. The 70 front wall 6 is provided with a lining 14, and the rear wall The end walls 8 and 9 also have linings 16 and 17, respectively. These linings are made of refractory bricks of a type suitable temperatures of between 1400 and 1500 C. The roof of the furnace comprises preferably a plate 20 which is made of .graphite and may be supported by the linings 14, 16 and 17. This plate is preferably so removable. The top of the furnace and the roof 20 is covered with a layer 21 of suitable fire brick, carborundum fire sand, or the like.

Formed lengthwise in the top of the furnace, near the rear wall 7 thereof tudinal charging hopper 22. A plate 23 serves to cover the hopper during the operation of the device. The lining 15 is wider near its bottom than it is near its top and an inclined surface portions of the lining, whereby a chute 18 is formed between the hopper 22 and the chamber 24 for conducting the briquettes into'the furnace chamber 24. Arranged immediately above this chute,

25 which may also be of graphite and which orovides a fixed opening 26 at the end of the chute 18. k Arranged at the bottom of the chamber 24 and connecting the bottoms 10 and 11 is an inmace, and is taken on line'11 of to 7 is provided with a lining 15. 4 r

to stand ranged thatit is is a longijoins the upper and lower and preferably under the clined grate 30, comprising a stationary member 31 which may be welded to the bottoms 8 and 9 of the furnace shell. A movable member 32 is slidably carried by the stationary member 31 and is held in place preferably by means of the overhanging lips 33 of the stationarymember. A shaker rod 34 is attached to the movable member and passes through the end furnace lining 17 and end wall 9 of the shell. A stufling box 35 is carried by the shell at the point Where the shaker rod passes therethrough so as to make a gas-tight joint. A shaker arm 36 is carried by the wall and provides means whereby the grate may be shaken. The grate members 31 and 32 are preferably made of plates which are provided with apertures 40 and 41, respectively. These apertures are brought into registration by the movement of the movable grate member 32. Vertically extending rods 42 are carried by the movable member, and are moved through the charge in the furnace when the movable member is operated, whereby caking or crusting of the charge is prevented. The grate 30 is arranged at an angle which corresponds substantially to the angle of repose of thematerials being treated, so that an even thickness of briquettes is maintained on the grate when the furnace is being operated, as indicated by the dotted line 43 in Fig. 1. Obviously any suitable type of grate, other than that shown and above described may be employed in our device.

A discharge hopper 44 is located beneath the furnace and connects the bottoms 10 and 11. It is provided atits lower end with some suitable means of permitting the finished product to be discharged therefrom without permitting gas to escape during such discharge. For convenience, I have shown a r0- tatable valve 45 for accomplishing this end. This valve is provided with an opening 46 running preferably its full length and with end walls 47. The valve is cylindrical in form and is mounted between suitable cylindricalsurfaces 48 formed at the mouth of the hopper 44. A discharge opening 49 is formed between the tops of the surfaces 48 and a discharge opening 50 is formed between the bottoms of such. surfaces. The proportion of the discharge openings 49 and 50, and the opening 46 of the'valve are such, in relation to the length of the cylindrical surfaces 48. that upon rotation the discharge opening 49 will be closed by the valve 45 before the opening 5 is opened by the registration therewith of tl e opening 46; of the valve. The end walls 4 of the valve are provided with shafts 51 which preferably pass through stufiing boxes 52 carried bv the end walls 53 of the hopper, whereby leakage of gas is prevented at these points. Any suitable means such as a crank .56 may be attached to one of the shafts 51 .for rotating the valve.

The furnace is preferably supported some distance above the floor upon suitable legs or braces 54 and 55.

Arranged in the chamber 24, above the charge contained therein, is an electric resistor .60 which extends across the furnace and is held by two electrodes 61 and 62. These electrodes pass through the lining 14 and wall 6 of the furnace and are connected in any well known way with a suitable source of electric current. An observation tube 64 is arranged in the top of the furnace and passes through the layer 21 of insulating material and roof 20, having its lower end extending into the chamber 24. This tube is made of any suitable material which will withstand high temperatures and the action of carbon monoxide, such, for instance, as Acheson graphite. This tube is for the purpose of observing the rate of reaction and the progress of the reaction in the briquettes.

The observing tube is preferably provided treatment by means of any suitable tempera-.

ture indicating device, such as an optical pyrometer, thermocouple, or total radiation pyrometer.

Since the Bichowsky processes are carried out in the presence of nitrogen I provide suitable means for supplying such gas to the interior of the furnace These means comprise tubes 70, 71 and 72. The tubes and 71 are preferably arranged in the chamber 24 and immediately over the grate 30, so that the gas will pass up through the charge of briquettes disposed upon the grate. The tube 7 2 is preferably arranged near the bottom of the discharge hopper 44. Each of these tubes may be formed with a slot 7 3 or' suitable apertures may be provided if desired. I The slots or apertures are arranged at the lowermost point of the tubes so that they will not become clogged by the charge. By placing the tube 72 near the bottom of the hopper, the ho per is thus filled with nitrogen ga's, there y preventing any reversible action that might occur when the titanium nitride is hot. The tubes may be formed of the ordinary iron or steel piping, and they maybe suitably connected together, as shownthe drawings, and to a main supply pipe When carrying out the Bichowsky process by means of our device, the briquettes to be treated are fed into the charging hopper 22 until it is full.

Because of the construction" and arrangement of the gate 25, the chamber 24 will also be filled to approximately the level shown by the dotted line 43. Nitrogen 'gas is now introduced into the furnace through the tubes 70, 71 and 72 until the air in the furnace is completely displaced by nitrogen. The charging hopper is now closed by means of the cover 23 and the observation tube 64 is also closed by means of the cap 65, whereby a sli ht internal pressure of the nitrogen gas is rought about and maintained within the furnace. The electric current is now switched on and, after a few minutes, the load in the furnace is brought up to its maximum so as to permit the most rapid heating of the furnace and briquettes. When the furnace temperature, as measured through the temperature tube 66 reaches approxi mately l000t0 1100 (3., the stream of nitro gen is increased, since a slight reaction takes place even at these temperatures. The rate' of reaction is determined by opening the top of the observation tube 64 and observing the color of the flame and the chemical composition of the gases. It has been found that the optimum operating temperatures lie between 1100 and 1550 (l, and when the furnace has attained the desired temperature for optimum rate of reaction, the required amount of nitrogen gas is permitted to enter through the tubes 70, 71 and 72. At this point the cover 23 of the charging hopper 22 is removed,

ermitting the gases to pass through the riquettes in this hopper. The gases passing out through the charging hopper and through the observation tube 64 consist primarily of carbon monoxide, and nitrogen and react with any metallic oxides in the hopper 44, because the briquettes at this point will have reached a sufficient temperature to bring about a reducing action in an atmosphere of carbon monoxide, and in this place in the furnace it has been found that all the iron oxides present in the titanium ore are reduced and that, also, a preliminary nitrification of the material takes place. he gases passing up through the hopper 22 maybe collected and used elsewhere, since they are combustible, or else they may be burned directly at the opening'of the hopper. In the passageof these gases up through the hopper, the charge of briquettes contained therein are preheated before they are charged into the chamber 24 of the furnace...

When the briquettes on the top of the grate 30 have been treated for the required amount of time, the flame issued from the observation tube 64 will be seen to go down. The grate 30 is then shaken a definite amount, whichawill cause some .of the treated briquettes to fall through the-openings 40 and 41 in the/ grate members 31 and 32, respectively, and be deposited in the discharge hopper 44. After these treated briquettes are passed through the grate, a thin layer of green bri- Since the discharge hopper 44 is not pro- I vided with any refractory lining, it will be seen that theheat contained in the finished briquettes as they are passed through the grate 30 will be permitted to radiate. If the radiation is not rapid enough to cool off the finished briquettes in the allotted time, water may be used in the hopper for the purpose. By cooling the briquettes before they are discharged through the valve 25, oxidation of the product is prevented.

The temperature of the briquettes, by means of our device may be maintained within very close limits by adjusting the amount of electrical energy supplied to the resister 60, which is an essential requirement in the carrying out of the Bichowsky processes.

The amount of nitrogen gas fed to the furnace is depended upon the rate at which the briquettes are being treated, and the point at Which new briquettes are to be fed into the furnace, which is indicated by the flame condition at the opening of the observation tube 641 Since reaction does not take place until the nitrogen as reaches the top of the-charge, the gas will e preheated by the charge before it reaches the top thereof.

Obviously, some modifications of the details herein shown and described may be made without departing from the spirit of my invention or the scope ofthe appended claims, and I do not,'therefore, wish to be limited to the exact embodiment herein shown and described, the form shown being'merely a preferred embodiment thereof. 1

Having thus described our invention, what we claim is:

. 1. An electric furnace for the production of titanium-nitrogen compounds, comprising a ,Iefractory body forming a chamber, an in clined grate arranged at the bottom of the chamber for supporting the charge, and a radiant resistor. carried'by the body and arranged within the chamber some distance "above the charge.

charge, a charging hopper formed in the upper part of the body, and a chute connecting the charging hopper with the chamber.

3. An electric furnace for the production of titanium-nitrogen compounds, comprising a refractory body forming a chamber, an inclined grate arranged at the bottom of the chamber for supporting the charge, a radiant resistor carried by the body and arranged within the chamber some distance above the charge, and means for admitting nitrogen gas into the chamber.

'4. An electric furnace for the production of titanium-nitrogen compounds, comprising a refractory body forming a chamber, an inclined grate arranged at the bottom of the chamber, a radiant resistor carried by the body and arranged within the chamber some distance above the grate, a gas-tight discharge hopper arranged below the grate, and means for admitting nitrogen gas into the chamber and discharge hopper.

5. An electric furnace for the production of titanium-nitrogen compounds, comprising a refractory body forming a chamber, an inclined grate arranged at the bottom of the chamber, a radiant resistor carried by the body and arranged within the chamber-some distance above the grate, a charging hopper formed in the upper part of the body, a chute connecting the discharge hopper with the chamber, a gas-tight discharge hopper arranged below the grate and means for admitting nitro en gas into the discharge hopper. 6. An e ectric furnace for the production of titanium-nitrogen compounds, comprising a refractory body forming a chamber, an inclined grate arranged at the bottom of the chamber for supporting the charge, a radiant resistor carried by the body and arranged within the chamber some distance above the charge, a charging hopper formed in the upper part of the body, a chute connecting the charging hopper with the chamber, and a gate carried by the body for limiting the size of the chute.

7. An electric furnace for the production of titanium-nitrogen compounds, comprising a refractory body forming a chamber, an inclined grate arranged at the bottom of the chamber for supporting the charge, a radiant resistor carried by the body and arranged within the chamber some distance above the charge, a charging hopper formed in the upcharging hopper with the chamber, and means for admitting nitrogen gas into the chamber. c

8. An electric furnace for the production of titanium-nitrogen compounds, comprising a refractory body forming a" chamber, arTin- "clined grate arranged at the bottom of the chamber for supporting the charge, a radiant resistor carried by the body and arranged within the chamber some distance above the charge, and means for admitting nitrogen into the charge.

9. An electric furnace for the production of titanium-nitrogen compounds, comprising a refractory body forming a chamber, an inclined grate arranged at the bottom of the chamber for supporting the charge, a radiant re s1stor carried by the body andarranged within the chamber some distance above the charge, and means for admitting nitrogen gas lntot the charge and immediately above the gra e.

v 1Q. An electric furnace for the production of titanium-nitrogen compounds, comprising a refractory body forming a chamber, an inclined grate arranged at the bottom of the chamber for Sig) orting the charge, a radiant resistor carrie y the body and arranged within the chamber some distance above the charge, and means for directing a flow of nitrogen gas up through the charge.

'In' testimony whereof, we have hereunto signed our names.

FRANCIS A. J. FITZGERALD. JAMES KELLEHER.

per part of the body, a chute connecting the v

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