US1251309A - Baking-furnace. - Google Patents

Description

R. K. WEHNER.

BAKING FURNACE.

APPLICATION man AUG.26.19.16.

Patented Dec. 25, 1917..

2 SHEETS-SHEET l.

Flr.

vR. K. WEHNER.

BAKING FUHNACE. AvvLlcArloN FILED AuG.2'6,419|e.

Patented Dec. 2.5, mi?.

2 SHEETSwSHEET 2- ffy UNITED STATES PATENT oEEIoE.

ROBERT K. WERNER, OF NEWARK, NEW JERSEY, ASSIGNOR T0 ISBELL-PORTER COM- PANY, OF NEWARK, NEW JERSEY, A CORPORATION OF NEW lYORK.

BAKING-FURNACE.

Specication of Letters Patent.

Patented Dec. 25, 1917.

Application led August 26, 1916. Serial No. 117,109.

To all whom z't may concern:

Be it known that I, ROBERT K. WEHNER, a citizen of the United States, residing at Newark, in the county of Essex 'and State of New Jersey, have invented certain ,new and useful Improvements in Baking-Furnaces, of which-the following is a Aspecification.

This ,invention relates to vgas fired baking furnaces of the ring type which are used for baking carbon electrodes employed 1n electric furnaces during the manufacture of aluminum. These electrodes are made of pulverized carbon mixed with a certain percentage of pitch and oil, and the purpose of these furnaces is to very gradually ralse the temperature of these green electrodes to about 11000 C., so as to slowly Adrive off all volatile matter and then to cool olf the electrodes ina like gradual manner.

The principal objects of the inventlon are to provide a furnace of the above type which is highly efiicient from a. fuel stand point, simple to control and which is easy to charge and dischar e.

Other'. objects and the novel features of the invention will be apparent from the following description taken in connection with the drawings.

My invention consists of steps in carrylng out the method of operating the furnace, structural characteristics and relative arrangement of the elements composing the furnace, which will be -hereinafter more fully described and particularly pointed out in the appended claims.

In the accompanying two sheets of d rawings similar reference characters indicate the same parts in the several figures, in which y l Figure 1, is a plan view of'a furnace embodylng the invention;

Fig. 2, is a vertical sectional view of the furnace taken on the line II-II of Fig. 1; Fig. 3, is a vertical sectional view taken on the line III- III vof Fig. 1; and

Fig. 4,' is 'a perspective view of an electrode such as is baked in this furnace.

The furnace illustrated consists of a battery of twelve ovens A1 to A1 inclusive, which are arranged in two parallel groups of six each to form a ring type furnace 1n which the firin can b e carried on continuously. It will e obvlous that any desired 'bustion or heatin number of furnaces may be employed under the principle to be described. The ovens are rectangular in outline and open at the top so they can be readily charged and discharged.

In between and adjacent tothese ovens are located a series of vertical up take comiues B in the hollow walls B1, B2 14, inclusive. Gas burners C, are located at the lower ends ofv the up iues B and discharge into the latter. In theysame walls with the combustion fiues B, are located one or more down take flues D through which the products of combustion may pass. In the present arrangement there is one down flue D for each of the three pairs of up fiues B. A series of horizontal flues E extends under the floor of each oven and leads from the lower ends of the down iues D by branches E to the lower ends of the up take heating flucs of the next oven in the series. f

A producer gas supply main F is located on each outer side of the battery of ovensv and eachmain has a series of outlet openings G, one of said openings G bein located opposite the end of each set o combustion iiues B. In between the two rows or groups of ovensis located a waste gas or products of combustion main H, also a secondary air main J, each of which likewise have openings H and J', respectively, opposite each set of combustion lues. An exhaust fan (not shown) is connected to the waste gas main H and a pressure fan (not shown) is connected to the secondary air main J.

Each wall has a gas fuel supply or burner flue L and these lues have inlets L opposite the outlets G in the mains F and extend beneath and discharge into the burners C. A movable connection piece K having an adjustable valve K adapted to connect any one. of the outlets G with the inlet L and f neet together the upper ends of the various sets of combustion flues B and down iiues D. Openings in these mains not in use are blanked off by suitable forms of covers C, (see Fig. 3).

Sight hole openings P closed by iron covers P', see Fig. 3, are provided overreaeh combustion flue B, to permit inspection of the heat. Movable 'dampers Q, controlled from the outside of the furnace by any suitable means, are installed to separate, if desired, the combustion flues B, into a plurality, preferably three, separate systems, thereby permitting closer adjustment of heats at the various parts of the ovens. 'Within the outer Walls at each end of the furnace are, due to the present form and grouping of the invention, three distinct fiues F', F 2, F3, which connect the down iiues D of one group of ovens with the combustion flues B of the other group of ovens, so that the two adjacent groups of six ovens each are capable of being operated as a single unit. Blocksy P, see Fig. 3, Which may be either solid or perforated as shown, are inserted in openings R, at the top of the down flues D, at any point of the series to throttle the gas and regulate the heat of any section of the furnace, or for other purposes to be hereinafter explained. Said blocks P are inserted and placed -in proper position by lifting the covers C. X and X2 see Figs. 2 and 3 are spaces filled with yielding material to permit the expansion of the ovens in eitherl direction due to the high heat developed in the furnaces and prevent the electrodes being subjected to any undue strain. Z is an opening for cleaning out and inspecting the burner flues L or burners C.

It will be readily understood that the vbaking furnace construction herein disclosed can be built above or below the ground, Without in any Way affecting the essential features and mode'of operation of the invention, and I contemplate building them in either of these two arrangements, depending upon the nature of the plant and Work to be accomplished.

While the principal objects and use of my invention are to bake carbon electrodes of a strong, efficient and uniform construction, I Wish it to be expressly understood that said invention is not solely limited to such application, as there are other arts to Which the same may be applied in which like processes are carried out and other materials vtreated involving similar heating and cooling operations.

The method of operatingthe furnace is as follows: Six (orany number) of ovens are pose that oven A1, is under fire, ovens A2 to AG are heating up, oven A7 is off or disconnected for unloading and refilling, and ovens A, to A12 are cooling down. In such case, air connection N Would be connected With the adjacent opening J, in the cross iue O over the lues in the Wall B. The openings R in the upper ends of the down-take flues D in the Wall B8 are then closed by means of imperforate fire clay plugs P (see Fig. 3). The dampers Q in the flues O in both of the Walls B8 .and B9 are removed and all openings on the top of furnace are closed. Air supplied through the air main J under pressure would then pass through the down-take flues D in the Wall B9, under the oven A8 through the horizontal flues E to the heating flues B in the Wall B10, through the down-take fines of this Wall and on to the heating flues of the next Wall, and so on through the Walls of all the ovens being cooled to supply air to the burners of the oven A1 being fired. The air thus serves to gradually cool the ovens preceding `the one fired and which have already been fired and at the same time the air is preheated for supplying oxygen for combustion purposes. The above-mentioned imperforate clay plugs or covers P introduced in the openings R at top of flues D and between the flues B in the Wall B8 prevent this air from going in the reverse direction from that intended.

The producer gas connection piece is con- -nected to the inlet of the burner Hue L in the Wall B1 and a suitable amount of producer gas is allowed to burn at the burners C in this Wall. The preheated air for combustion meets the fuel gas at the burners after passing through to fiuesB, D, E, etc., of the preceding ovens of the series as already described. The products of combustion then travel through the flues B, D, E, etc., of the succeeding ovens until they reach the Wall B8. At this point the Waste gas connection piece M is connected to the Waste gas main H and the products of combustion issuing at the top of openings of the flues B in Wall B8 are exhausted through after having given up practically all their heat to gradually raise the temperature of the ovens filled for firing. As described before, these products as Well as the secondary air may be kept in three separate streams by means of dampers Q, and it will be seen that it is only necessary to remove these dampers from the exit flue O in the Wall Bs as well as from the air inlet fiue O in the wall B, when it is desired to cut out one of the ovens for discharging or charging the saine.

Fig. 4 illustrates one of the electrodes X, usually three by fifteen inches,vbaked in the furnace here set forth, but it will be obvious that the use of the furnace, as above indicated, is not limited to such electrodes. Fig.

lio

2 shows an oven filled with electrodes. The green electrodes are packed in the various ovens surrounded by carbon dust or other filling material Y, and a foot or more of this filling material is placed over the top of the electrode to prevent radiation as Well as oxidation of the electrodes by contact with the atmosphere. The tops of allthe ovens, inlets L and other openings not in use are covered with metal covers, as heretofore explained.

When the electrodes in oven A1 have reached the desired temperature, the lire isadvanced by moving the producer gas connection piece K to 'the inlet L of the next wall B2, alsomoving the waste gas and air connection pieces M and N to the proper openings J, in Walls B9 and B10', respectively, making the proper changes in the dampers Q and the stopper plugs in openings R. By the time this change is ready to be made, oven A, should have been filled with green electrodes, andoven A, would be cool enough to be emptied and refilled.

It will be seen that the heat conservation of this type of ring furnace is very large. Practically all the heat extracted from the electrodes being cooled is recovered by the secondary air used for combustion, andthe heat in the products of combustion is practically all transferred to the electrodes in the long series of ovens being heated up.

In former types of furnaces where the system is operated under vacuum, cold air is drawn in through all leaks causing great loss in efficiency. In the present furnace the air is introduced under sufficient pressure so that the flues at the point of'combustion may be operated practically at atmospheric pressure. This will tend to keep the differential between the flues and the atmosphere at a minimum at all parts of the system and greatly increase the etliciency of the furnace.

The system of fiues arranged between and underneath the electrodes to be treated eX- poses a minimum amount of wasteful radiation surface and provides convenient means for inspecting all points under combustion. Refractory material of 96% silica is used in those. combustion walls which are subjected to the higher tem eratures. This material is much more re ractory and has greater conductivity than the clay material ordinarily used.

While the preferred form of construction has been shown and described in detail itl will be clear that numerous changes may be made without departing from the spirit of the invention.

Owing to there being no oven on the right of the wall B4, or on the left of wall B11, as illustrated in Fig. 1, the burners C are preferabl)7 not used in said walls B or Bn, however, should at any time il; be desired to increase the capacity of the plant, by adding to the ends of the 'furnace other ovens, this can be readily done without disturbing the operation of the installed ovens, by simply adding the necessary ovens, connecting gas and air flues, when the said burners C in the walls B, or B11 will be used.

It will also be readily seen that any one or more of the ovens can be cut out for repairs if so desired, without being required to entirely shut down the plant, and the ovens are inspected and repaired at the same time that they are cut out for emptying and refilling. The time usually employed for making any repairs thatthe ovens are apt to need, short of actually rebuilding, can be done in the length of time that an oven would normally be out for emptying and refilling. If longer time than this should be required for repairs, the burning of the gas or fire could be advanced in the series without advancing the waste gas connection piece M, and hence reducing the number of ovens in series. This change of arrangement ofthe waste gas connection piece M would naturally reduce slightly the efliciency of the furnace as regards to the fuel consumption for the time being. More than one oven can be cut out of the series by simply advancing the air connection piece N, by placing it two or more hollow walls ahead of the waste gas connection piece M, and hence the ovens sol between the waste gas connection piece M y and air connection piece N are not being heated or preheating the air, as will be readily seen by reference to Fig. 1.

The different dotted arrows in Fig. 1 and full arrows in Figs. 2 and 3, accordingto the key indicated above oven A, of Figa-3, show the directions of movement of the gas, air and waste gases in passing through a furnace constructed and arranged to operate twelve ovens.

What I claim is:

1. In a baking furnace, the combination of an oven having side Walls provided with up flues and downflues, fuel burners discharging into the up fiues, passages extending under the ioor of the oven for connecting the down iues of one wall with the up flues of the other Wall, and means for supplying fuel to the burners.

2. In a gas fired furnace for baking carbons and the like, the combination of a battery of ovens open at the top and having side walls between them provided with up fines and down flues therein, said down lues being arranged between the up flues, the flues in the walls of the ovens being in communication with each other in series and none of said iues being in communication with the interior of said ovens, gas burners discharging into the up flues, passages extending under the floors of the ovens for and means for supplying fuel gas to any of the side walls and the burners, means for supplying air to any of said side walls and lflues, and means for receiving and conducting away the products of combustion from any of the walls and fines.

3. In a furnace for baking carbons and the like, the combination of a battery of ovens provided with walls having iues therein, the flues in the walls of the ovens being in communication with each other in series and none of the flues in communication with the interior of said ovens, burners in said flues, a fuel supply pipe having a series of outlets individual to the flues, a device for connecting any of said outlets to its corresponding Hue, covers for the other outlets of said fuel supply pipe, means for supplying air to any of the walls and its iiues, and means for withdrawing the products of combustion from any of the walls and its iues. 4. In a gas fired furnace for baking carbon electrodes and the like, the combination of a battery of ovens having side walls between them provided with up fiues and down iiues, gas burners discharging into the up lues, anV air supply flue in each side wall leading to the upper ends of the up and down flues and connecting these iues together and also supplying air to the burners, a fuel supply iiue in `each side wall leading to the gas burners, and flues leading from the lower ends of the down flues under the ovens to the' lower ends of the up fines, wherebyV the products of combustion from the oven being fired may be conveyed to the succeeding ovens to be fired to gradually raise their temperature.

5. In a furnace for baking carbons and the like, the combination of a battery of ovens, each of said ovens havin a set of heatin lues in communication witheach other an none in communication with the interior of said ovens, means for supplying fuel to any set of the flues tc fire the ovens, means for causing the products of combustion t0 pass through the flues in the walls of ovens to be fired to gradually raise the temperature of these ovens to the firing temperature, andl means for controllingl the low of the products of combustion in distinct and independent currents throughout any of the flues so` as to permit closer regulation of the heat at any and various parts of the ovens..

6. In a furnace for baking carbons and the like, the combination of a batteryof ovens having heating flues in the walls thereof, means for supplying fuel to the flues to fire the ovens, means for causing the products of combustion to pass through Hues in the walls of 'the' ovens to be fired to gradf uall raise the temperature of these ovens to t e firing temperature, and one or more movable dampers working in the flues for separating the products of combustion into ranged in two parallel groups, each groupl of ovens having side walls between them provided with up flues and down fines, and

flues connecting the flues of the two groups,`

gas burners dlscharging into the up flues, air supply fines in the side walls leading to the upper ends of the up and down ues to connect these iues together and also for supplying air to the burners, an air supply main adapted to be connected with any one of the air flues, a fuel supply flue in each side wall leading to the gas burners therein, gas supply means adapted to be connected with any one of the fuel supply flues, flues leading from the lower ends of the down iues under the ovens to the lower ends of the up flues, a waste gas main adapted to be connected to any one of the air fines except the one to which the air supply main is connected, the arrangement being such Vthat the products of combustion from the oven being red may be conveyed under and around the succeeding ovens to be fired to gradually raise their temperature and finally discharge into said waste main, so that the air for combustion may be conveyed under and around the preceding ovens already fired to gradually cool them and preheat the air supplied to the burners for combustion.

8. In a gas fired ring type furnace for baking carbons and the like, the combination of a battery of ovens arranged in two parallel groups and having heating lues in the walls thereof,-gas burners discharging into said flues, gas supply mains extending along the outer sides of the grou s of ovens and having outlets therein, one or each of said ues, a device for connecting any one 0f said outlets to a liuc, an air main located between the groups of ovens and having outlets therein, means for connecting the outlets of said air main to the flues of the ovens, an exhaust main located between the groups of ovens and having inlets therein, means for connecting the inlets of the exhaust main to the lues of the ovens, and passages connecting the flues to permit air to flow to the a oven being fired and to permit the products of combustion to flow from the oven being fired to the flue connected with the inlet o said exhaust main. l

9. In a gas fired ring type furnace for baking carbons and the like, the combina-.

tion of a battery of ovens having heating or combustion lues in the walls thereof in communication with each other and none in communication with the interior of the ovens, gas burners discharging into said fines, means for supplying :fuel under pressure to any o f said burners, means for supplying preheated air under pressure to any of said Hues, and means for exhausting the products of combustion from any of said Hues, the arrangement being such that the differential between the Hue pressure and atmospheric pressureV at any point in the furnacev is maintained at a minimum, so that the leakage of cold air directly from the outside atmosphere into the heating Hue will be kept at a minimum, and maintain at the same time practically atmospheric pressure at the point 'of combustion or burning of the fuel.

10. The method of operating a ring type furnace having a series of ovens each of which is provided with combustion or heating Hues connected with each other and having no communication with the interior of the ovens, which comprises admitting fuel under pressure to the combustion Hue of the oven being Hred, admitting air under ressure to the series of connected Hues o the ovens that have been Hred and positively exhausting the products of combustion through the Hues around all of the ovens to be fired and at the same time by said exhausting, drawin to the combustion Hue of the oven being red, the air preheated in passin through the Hues surrounding'the ovens red, whereby the How of the fuel, air and products of combustion is uniform and under absolute control and the differential between the Hue pressure and atmospheric pressure at any point in the furnace i capable of being maintained at a minimum, so that the leakage of cold air directly from the outside atmosphere into the heating Hues will be kept at a minimum and maintain at the same time practically atmospheric pressure at the point of combustion or burning of the fuel. 4 f In testimony whereof I hereby aHix my signature.

ROBERT K. WEHNER.

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