US1941462A - Method of producing coked fuel agglomerates - Google Patents

Description

Jan. 2, 1934. E- H BUNCE 1,941,462

METHOD oF PRODUCLNG COKED FUEL AGGLOMERATES Filed Sept. 27. 1929 INVENTR Patented Jan. 2, 1934 PATENT OFFICE METHOD F PRODUCING COKED FUEL AGGLOMERATES Earl H. Bunce, Palmerton, Pa., assignor to The New Jersey Zinc Company, New York, N. Y., a corporation of New Jersey Application september 2'1, 1929 serial Ne. 395,586

2 Claims.

such briquettes retain their form until used, they frequently prematurely disintegrate during com-- bustion. More recently, it has been proposed to mix with the finely divided carbonaceous material 20 a suitable proportion' of a good coking coal and to coke this mixture into briquettes which will satisfactorily withstand ordinary conditions of aging,' weathering and handling. My present invention contemplates an improved method of making such coked fuel briquettes or agglomerates in consequence of which a relatively small amount4 of coking coal suffices to economically Y produce strong agglomerates that will not prematurely disintegrate during combustion. The invention is particularly applicable to finely divided carbonaceous materials possessing no coking quality, such, for example, as anthracite dust coal or culm, coke breeze, etc. Before such non-coking carbonaceous materials can be formed into coked agglomerates, a suitable proportion of an appropriate 'coking agent, such as bituminous coal, must be mixed therewith, as more particularly described hereinafter. The invention may also be practiced with advantage in produc- 40 ing coked agglomerates from nely divided carbonaceous materials possessing coking qualities amenable to the improved method of coking herein described.

The method of coking contemplated by the invention may be characterized as "rapid coking, since the aim is to form a shell of coke on the briquette or agglomerate as promptly as possible. This prompt formation of a shell of coke on the agglomerate is effected by initially subjecting the agglomerate to a high temperature rapid coking treatment so that a substantial layer of coke forms at the surface of the agglomerate in a relatively short time interval and while the main inner mass of the agglomerate remains substantiauy unaltered. 'me heet treatment at the high the .agglomerateu In practice, heat at or above the temperaturelevel required for coking is ap- 65. plied to the body of agglomerates to be coked 'so as to heat the surface layer of each agglomerate to the coking temperature as promptly as possible. Thus, the l'starting of the coking operation is at or above. the nishing temperature of coking, in contradistinction to those coking practices in which the material to be coked is gradually raised to the requisite coking temperature. Furthermore, in the practice of the invention, heat at this high temperature level, which is initially applied to the agglomerates, must be available in 'sufficient quantity to rapidly form the contemplated shell of coke on the agglomerate and to continue and complete the coking of the entire agglomerate.

The coking operation is preferably conducted by direct contact of a gaseous heating medium with the agglomerates. This is desirable since it insures the contemplated rapid as well as uniform heating of the surface of the agglomerates to the requisite coking temperature, and at the same time permits economic and efficient transfer of fheat from the heating medium to the agglomcrates. The charge of agglomerates should be exposed to the heating medium in the form of a relatively shallow or thin body through which a large volume of the heating gas passes at high velocity.

Any appropriate source of heating gas (inert to the charge under the conditions of coking) may be used in coking the agglomerates by direct heating. The heating gas must be substantially devoid of oxidizing influences. During the early or formative stage of coking, oxygen or oxidizing influences deleteriously affect the coking constituent or. fraction of the agglomerate, and it is particularly important that this stage of the coking operation be conducted in the absence of such oxidizing influences. 'Oxidizing influences should also be avoided during the later stages of the coking operation, since they tend to consume the coke.

The heating gas may be producer gas, illuminating gas, oil gas, natural gas, coke-oven gas, Water gas, and similar fuel gases, extraneously heated where necessary. The combustion gases resulting from burning such fuel gas, oil or coal (or similar solid carbonaceous fuel) may be used as the heating gas. Such combustion gases may be the exhaust gases from a contiguous thermic operation. When using such combustion gases, it may be desirable or even necessary to add a small quantity of unburned fuel gas to the combustion gases in order to react with or neutralize any oxidizing gases, such as excess oxygen, there-- in. Other inert gases, such as nitrogen, superheated steam, and the like, may also be used as the direct heating gas.

The heating gas may as a result of its method of production or previous use be of appropriate temperature for the coking operation. Where the gas is too hot for the contemplated coking operation, it should be appropriately cooled, as for example, by steam, water, or the like. If the heating gas is not of a sulciently elevated temperature for the coking operation, it must be appropriately heated. This may be advantageously accomplished by recuperation, or by regeneration, or by adding thereto an appropriate volume of a hotter gas, or by combusting some of the gas itself or a combustible constituent added thereto for the purpose.

When the heating gas contains or is itself a fuel gas, it is frequently advantageous to combust the gas exiting from the charge undergoing coking, and to utilize the resulting heat of combustion for heating the gas-exiting side of the charge. This may be accomplished by adding oxygen to the gas exiting from the charge and supplying the resulting heat of combustion, preferably by radiation, to the gas-exiting side of the body of charge-undergoing coking. In this manner a certain compensationpis eected for the natural drop in temperature of the heating gas in passing through the body of charge undergoing coking. i

When, in practicing the present invention, the coking operation is carried out by direct contact of the agglomerates with a gaseous heating medium, the heating gas should be of such temperature that the surface of each agglomerate is rapidly heated to 800 C. or higher. I have obtained very satisfactory results with a heating gas entering the body of agglomerates undergoing coking at a temperature of 800 C. or higher and exiting from the body of agglomerates at a temperature of from 700 to 800 C., but not lower than 550 C. The drop in temperature of the heating gas in passing through the agglomerates may be minimized by the extraneous application of heat to the gas-exiting side of the body of agglomerates, as for example in the manner hereinbefore described. The coking of the agglomerates, under the preferred conditions herein described, will take from 10 to 90 minutes, depending upon the size of the individual agglomerates, the depth or width of the body of charge, and the temperature, volume and velocity ofthe heating gas.

While I prefer, in practicing the invention, to coke by direct contact with 'a gaseous heating medium, the requisite heat for coking may be supplied to the agglomerates in any other appropriate manner, provided, of course, that the supply of heat is adequate to effect the rapid surface coking of the agglomerates characteristic of this aspect of the invention.

Any suitable apparatus may be employed for exposing a shallow or thin body of agglomerates to the heating medium. Thus, the charge of agglomerates undergoing coking may be supported on a stationary or moving hearth or perforated grate, or may be supported within a vertically disposed or inclined chamber operated intermittently or continuously, but preferably arranged to permit progressive movement of the agglomerates therethrough by the action of gravity. In this connection, the invention contemplates coking the fuel agglomerates by appropriately supporting a relatively narrow vertical column of agglomerates and passing a hot gaseous heating medium transverselythrough the column of agglomerates. This aspect of the invention. preferably combined with the rapid coking practice hereinbefore described, may Very advantageously be carried out in the cross-current vertical coking apparatus illustrated in the accompanying drawing, in which Fig. 1 is a sectional elevation of the apparatus,

Fig. 2 is a cross section of the apparatus on the section line 2--2 of Fig. 1, and

Fig. 3 is a plan view of one of the slotted tiles in the wall construction of the coking chamber.

The furnace illustrated in the drawing comprises a brick-work structure 5, of oval horizontal section, having a gas inlet flue 6 and a gas outlet ue'?. The coking chamber 8 is built midway between the ends of the structure 5, thereby providing on one side a gas distributing chamber 9 communicating with the inlet 6 and on the other side a similar chamber 10 communicating with the outlet 7. Clean-out openings 20 are provided in the curved ends of thestructure 5. One side wall l2 of the coking chamber is substantially vertical, while the other side wall 13 is slightly inclined outwardly so that the cross sectional area of the chamber increases from the top to the bottom. Both side walls of the coking chamber are permeable to the passage therethrough of gas in considerable volume. This permeability is provided by uniformly distributed openings or slots in each side wall.

In the coking retort illustrated in the drawing, the vertical side walls 12 and 13 are similarly built up of tiles or plates 14 having uniformly distributed slots 15. These tiles or plates may be made up of refractory material, such as silicon `carbide alone or mixed with clay, or of temperature-resistant metal alloys, such as alloys of iron, chromium and nickel. .The tiles are held in position by spaced cross beams 16 having their ends-appropriately supported in the brick-work structure 5 of the furnace. The inner faces of the beams 16 have longitudinally grooved heads 17 in which the lugs 18 and 19 of the tiles are engaged. The shorter lug 18 rests on the bottom of the lower o f the engaging grooves, while the longer lug 19 extends only a short way into the upper engaging groove. By raising any tile, its lower lug 18 can be disengaged from its groove and the tile removed and a new tile -inserted in its place without disturbing any other tile in the wall.

The upper end ofthe coking chamber passing through the roof of the furnace structure 5 has a Water jacket 21. A charging extension or hopper 22 provided with a swinging gate 23 is mounted above the water jacket. A pipe 24 connects the extension 22 with the gas-exiting chamber 10.

A discharging device consisting of an inclined 'chute 25 and a rotatably mounted cylinder 26 is operatively associated with the lower end of the coking chamber 8. The lower end of the chute is closed by a pivotally mounted gate 27 biased to its closed position by a counter-weight 28. A pipe 29 connects the lower end of the chute with the gas-exiting chamber 10.

When the furnace is in operation, the coking chamber 8 is filled with agglomerates undergoing coking. Periodically, an appropriate amount of coked agglomerates is Withdrawn from the chamber by opening the gate 27 and rotating the cylinder 26, and simultaneously a corresponding amount of fresh agglomerates is introduced into the hopper 22. The coking chamber is thereby maintained full and the green or fresh agglomerates are charged with a minimum drop or fall.

The hot heating gas for coking is introduced through the gas inlet 6 and is distributed from the chamber 9 through the openings 15 in the tiles 14 of the vertical wall 12 into the coking chamber 8. The gas flows transversely through the body of agglomerates in the coking chamber and out through the openings in the side wall 13 into the chamber 10 and to the gas outlet 7. The heating gas may be forced through the apparatus, but is preferably drawn through by suction fans communicating with the gas outlet 7. Pipes 24 and 29 produce a slight suction (as a result of the draft in the gas outlet 7) in the charging hopper 22 and the discharging chute 25 respectively, thereby ameliorating the deleterious effect of such air as unavoidably enters the hopper and the chute. The pipes 24 and 29 are omitted where the heating gas is forced through the apparatus (instead of drawn through by suction, as in my present preferred practice), since they would be inoperative in that case.

The invention is of particular advantage in producing coked agglomerates of anthracite dust coal, coke breeze, and other finely divided noncoking carbonaceous materials. In accordance with the invention, from l0 to 20% by weight of a bituminous coking coal is mixed with the noncoking carbonaceous material. The finely divided materials are preferably of a graded particle size such as results from hammer-mill crushing, although such graded particle size is not essential. The mixing is preferably effected in a Chilean mill or edge-runner, and the agglomerating is preferably effected by briquetting, although extrusion and other methods of agglomerating may be resorted to if desired. If necessary, a conditioning agent or a binder, such as sulfite liquor, tar, pitch, or the like may be added during the mixing in the edge-runner. The agglomerates when ready for coking will contain from 5 to 12% by weight of moisture, and it is characteristic of the invention that these relatively moist agglomerates may be immediately subjected to the highest temperature required for coking. It is advantageous to transfer the agglomerates direct from an agglomerating apparatus, for example a briquetting press, to the coking apparatus, whereby the moist agglomerates are immediately subjected to the heating medium at a temperature at or above the finishing temperaturev of coking. A

It is my preferred practice to use a free-flowing bituminous coal in the agglomerate mixture as the coking agent, since such a coal is particularly amenable to the high temperature rapid coking method of the invention. However, the coking agent may consist of a blend of bituminous coals including some free-flowing coal, or may be a bituminous coal possessing of itself such properties as adapt it for this method of coking. While it is my preferred practice to effect the contemplated coking action by bituminous coal, other equivalent carbonaceous coking agents may be substituted in whole or in part for the bituminous coal, such as tar, pitch, and the like.

'Ihe invention, while of particular advantage in forming coked agglomerates consisting in large part of non-coking carbonaceous materials, may be successfully applied to the coking of finelyv divided carbonaceous materials possessing such coking and other properties as adapt them for coking by the `method of the invention. Thus, the agglomerate mixture may consist in whole lor in large part of such carbonaceous materials, with or without the inclusion of non-coking carbonaceous material.

I claim:-

l. The method of producing coked fuel agglomerates which comprises agglomerating a mixture of finely divided carbonaceous material and an agent that forms a bond when coked, progressively advancing the agglomerates while in free contact with one another by gravity through an upright coking chamber, and yheating the ag- 110 glomeratesl to their coking temperature in the course of their travel through said chamber by passing a hot gas through and in direct contact with the agglomerates in a direction approximately transverse to the direction of travel of lthe agglomerates through the chamber, said hot gas entering the agglomerates at a temperature of at least 800 C. and leaving the agglomerates at a temperature not lower than 550 C.

2. The method of producing coked fuel agglomerates which comprises agglomerating a mixture of finely divided carbonaceous material and an agent that forms a bond when coked, progressively advancing the agglomerates in free contact with one another through a coking chamber, subjecting the agglomerates in the course of their travel through said chamber to a coking operation in which the agglomerates are initially heated by direct contact with a gaseous heating medium passed transversely therethrough and having a temperature of at least 800 C. upon entering the agglomerates and a temperature not lless than 550 C. upon leaving the agglomerates EARL H. BUNCE.

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