US2996437A - Process and device for coking of fuels - Google Patents

Description

Aug. 15, 1961 R. K. MEWES ETAL PROCESS AND DEVICE FOR COKING OF FUELS 2 Sheets-Sheet 1 Filed Jan. 50. 1957 Aug. 15, 1961 R. K. MEWES ET AL 2,996,437

PROCESS AND DEVICE FOR COKING 0F FUELS Filed Jan. 30. 1957 2 Sheets-Sheet 2 United States Patent O 2,996,437 PROCESS AND DEVICE FOR COKING OF FUELS Rudolf K. Mewes and Max H. Goebel, Bochum, Germany, assignors to Dr. C. Otto & Comp. G.m.b.H., Bochum, Germany Filed Jan. 30,1957, Ser. No. 637,233 2 Claims. (Cl. 202-19) Natural fuels, more particularly coal and lignite, are not suited for many purposes without further preparations, since upon heating they give 01f volatile components in considerable amounts and the fuels break down prematurely, in other words, they do not have sufli'cient stability. Considerable groups of coals, particularly of small grain size, when heated in closed chambers with exclusion of air, are liable to shrink and form solid coke after having given oif their volatile components; the coke consists mainly of carbon and exhibits considerable stability when burned.

There is a demand to convert fuels, which do not possess the inherent capability of sintering, into briquettes which are of such stability during binning.

One means to process non-sintering fuels to make coke therefrom consists of adding binders thereto and shaping them into briquettes which are then subjected to coking.

The present invention relates to a coking process for such briquettes which are made, as a rule, from non-sintering fuels with the addition of binders. Coking takes place in a shaft furnace, either continuously or semi-continuously.

By semi-continuous operation we understand an operation in which feeding of the fuel briquettes is not done continuously, but at short intervals of about A of an hour to 1 hour, and the briquettes are removed from the furnace at the same rate.

One of the main difficulties in such a coking process in which briquettes are made by addition of binders to the fuel, consists in that the binder softens during the gradual heating of the briquettes which causes the latter to stick together in the furnace. This can then lead to a cluster formation of the briquettes in the coked goods or in any case to the formation of pieces which do not have the desired size for later use, for instance in a boiler for heating purposes or in a metallurgical furnace.

Many attempts have been made to avoid this conglomeration of briquettes. For instance, it has been tried to prevent sintering together of the pieces by controlling the rate of heating. With direct heating of a furnace, use was made of heating units having a width not much larger than that of the elliptic or cubic briquettes to be formed. However, none of the attempts hitherto made led to any commercial success.

It is the object of this present invention to solve this problem by devising a process and a furnace for carrying out the same in the following manner:

The heating of the fuel briquettes for the purpose of coking is carried out in a shaft furnace by means of rinsing gases, i.e. hot gases carrying off vaporizable constituents of the fuel, which are at least partly carried in a current parallel to the goods. More particularly, gas of such high temperature is made to impinge onto the surface of the pile which fills the shaft of the furnace, with such high temperature and in such an amount that hardening of the briquettes occurs to an extent that a resistant carbonized skin is formed on the surface of the briquettes. In order to secure such hardening in the binders contained on the surface or, as the case may be, hard- Pzftented Aug. 15, 1961 enable components in the fuel itself, the temperature impinging upon the surface of the pile of fuel should at least be 1,000 C. and should carry a heat load of at least 150,000 kilogram-calories per hour and per square meter.

Such a load of heat is unusual and has not been used in any of the known coking procedures. It should be noted that the hourly heat transfer fiom coke oven wall to charged coal in cokery furnaces made of ceramic material lies at 4,000 to 8,000 kcaL/h/squ. m. In iron retorts this heat addition has been increased to 10,000- 15,000 kcal.; in processes being based on rinsing gases alone the heat load used at the conventional gas velocities did not exceed 50,000, to 80,000 kcal./h./squ. m. In the process according to the present invention vthe heat load may be increased to 4000,000 kcal./h./squ. m.

Due to the fact that the surfaces of the briquettes are hardened by instantaneous heating and are converted to coke, to a large extent, they are very resistant during the further travel through the furnace to the jarring which takes place during the sliding down of the fuel. At the same time the surface layers have become porous and permit the passage of such gases which are set free during the heat penetration to the interior of the briquettes. Therefore, the briquettes will no longer sinter together. They will also approximately retain the shape in which they have been fed into the furnace, except for a certain shrinkage depending on the kind of fuel and binder.

In order to make sure that there will be a suflicient amount of heat for rapid heating of the surfaces of the briquettes, particularly in semi-continuous operation, when the cold fuel briquettes are fed to the shaft furnace, it is possible to arrange in the furnace directly below the feed-in inlet for the fuel, one or several vertical rightangled triangular inserts which must be capable to store heat to such an extent that they will be at all times maintained at temperatures between 900 C. and 1,300 0., in spite of the continual or intermittent cooling by the fuel. Such an insert can be so designed that below the same piles of fuel descending laterally therefrom will be formed. One or several burners for rinsing gas open into the space above the surface of the pile. The gases introduced through the burners do not only impinge on the surfaces below the insert, but heat also the vertical right-angled triangular insert itself with the recently charged fuel descending along the upper faces of the insert in a thin layer.

Even if no such vertical right-angled triangular inserts are provided, gas burners should be arranged from which gas impinges immediately upon the surface of the pile. Inlet openings for the fuel may be on opposite sides of the shaft, while one or several burners for the rinsing gas may be arranged centrally in the shaft. The inlet openings for the fuel may be arranged in more than two rows and between each of them burners for the rinsing gas may be arranged. The rinsing gases may be flue gas, to which steam or return gas has been added; in addition to combustible gases, a certain amount of oxygen, for instance air, may be admitted through the burners in order to obtain as intense a heating action as possible, provided that the oxygen addition does not lead to any marked combustion of the surface layers of the briquettes.

The invention will now be more fullydescribed with reference to the accompanying drawings, in which several embodiments of the furnace have been illustrated by way of exemplification and not of limitation; it should be understood that many changes in the details can be made without departing from the spirit of the invention.

In the drawings:

FIG. 1 is a longitudinal section through a furance according to the invention with built-in recuperators and a diagrammatic showing of the gas circulation;

FIG; 2 is a transverse section through two furnace shafts arranged in series;

FIG. 3 is a longitudinal section through a difierent embodimentof a furnace shaft, the bottom part being broken away; and

FIG. 4 isyet another embodiment in similar showing.

Referring now to FIGS. 1 and 2, a furnace shaft is designated by 10; it is of substantially square cross-section and is bounded by a recuperator 11 on two sides. At the top of the shaftan inlet opening 12 is provided, and 13 designates a vertical right-angled triangular heat-storage body extending from one wall of the shaft to the opposite wall. Burners 14 serve for admission and generation of rinsing gas; they are arranged in walls 18 of thefurnace. In the central portion of the shaft, discharge openings 15 are provided for the escaping gas. A chamber 16 topped by vertical right-angled triangular slats 31 serves for admission of cooling gas. At the bottom an opening 17 is provided for the discharge of the final product, coke.

The storage body 13 is in the shape of an overhead structure with lateral ledges 20 below which the descending fuel accumulates and forms a space 21 into which the burners 14 are opening. The storage body is maintained at a temperature of, for instance, 1300 C. The fuel sliding along the top of the storage body in a moderately high layer, is subjected to high heating accompanied by a marginal coking of the pieces of fuel. The rinsing gas passes from the space 21 down through the'fuel and serves for providing an additional amount of heat thereto, so that coking proceeds into the interior of the briquettes. During this procedure, the gases cool down to for instance 900 C. and are withdrawn through openings 15 into the outer chamber 22 of the recuperator; from there they escape through pipes 23 arranged at the top and pass into a scrubber 25 provided with a sprinkling device 24. A suction pump 26 serves for maintaining a vacuum within the shaft and urges cooled gas partly through pipeline 27 into the chimney (not shown), partly via line 28 into space 16. Valves 29 and 30' are arranged for controlling the amount of the returned gas. Gas ascending from space 16 through the vertical right-angled triangular slats 31 is heated while passing through the descending fuel, simultaneously cooling the latter, and likewise arrives at the discharge openings 15. Through the recuperator, a mixture of rinsing gas and cooling gas is 'thereforepassing upward. The recuperator is equipped with heating tubes 32 which are partly fed with heating gas, for instance generator gas, partly with air. Both gases arrive by means of pipelines 33 at the burners 14 where they are mixed.

In FIG. 3 another embodiment of the device according to the'invention is shown in its upper part, thelower part being broken away. The shaft is again designated by 10, the ,recuperators by 11, the feeding opening 12 admits fuel to the shaft over the vertical right-angled triangular insert body 13. The main diiference between this arrangement and the one shown in FIGS. 1 and 2 consists in the provision of additional burners 38 above the surface of the pile of fuel 39. Pipelines 40 and 41 lead from collecting chambers 42 for the heated rinsing gas to burners 14 below the storage body 13, and to burners 38. In this arrangement the fuel is therefore heated at once at 39, when it enters through feed openings 12, and again later when .it arrives at the surface 21 below storage body 13. The heat acting on the fuel is therefore intense.

In the embodiment shown in FIG. 4, the shaft is again designated by 10, the recupenator by 11. The main difference between this embodiment and the others discussed above, consists in the absence of a storage body 13. There are two feed openings 43 for the fuel which are arranged laterally in the shaft, the burners 44 are again centrally arranged. In this way it is accomplished that a large surface of the descending fuel is exposed to the action of the burners.

The invention will now be described in more detail by the following example. However, it should be understood that this is given by way of illustration and not of limitation, and that many changes in details can be made without departing from the spirit of the invention.

Example The briquettes to be employed are made from coke fines or anthracite with a binder. The binder consists of coke tar pitch and constitutes 10 to 15 percent of the total. Bitumen can be used instead of the pitch. An other addition to the briquette is 10 to 20 percent coking coal. The briquettes are manufactured on a rolling press or any other suitable press in a known manner and are given the customary shapes, e.g., egg, nut, cube, oblong or the often-used pillow shape, which latter form is preferred. The weight of the individual briquette lies between 50 g. and 3 kg. and depends upon the size of the blast furnace or similar appliance in which the coke produced is to be used.

The briquettes are charged into the furnace through opening 12 and are heated by means of the burners installed in the upper part of the furnace shaft. The temperature is advanced to approximately 600 C. within 20 to 25 minutes. During this time, a carbonized skin forms on the surface of the briquette which is of suflicient strength to prevent breaking or pulverization of the briquette when new briquettes are added.

During heating of the briquettes, the rinsing gases cool down to approximately 800-900" C. They move downward together with the briquettes and are drawn oif through the outlets 15. Depending upon the size of the briquettes, a time of 4 to 12 hours is required for the travel of the briquettes from the charger to the height of the outlets 15. During that time, after-cooking occurs.

The rinsing gases are conducted to the heat exchangers 22 by way of the outlets 15 where they are cooled, and

1 subsequently are purified in the scrubber 25. Pump 26 generates the vacuum necessary for removal of the rinsing gases. Part of the cooled and purified gases is conducted into the lower part of the shaft furnace through line 28. It rises counter-currently to the downward moving briquettes, cools these to approximately 200 C. and is drawn off through the openings 15 together with the hot rinsing gases which come from the upper part of the furnace.

The cooled briquettes are removed at point 17 by means of a roller conveyor or other known means.

A suitable material .having high heat storage capacity, for use in the insert 13, consists of high-density fire clay which has aheat conductivity of a: 1.53 kcal./m./ C./h. (kilogram calories per meter, degree centigrade and hour) and which has a porosity of approximately 20 percent.

What we claim is: I

1. A process for coking briquettes made of solid fuel in a shaft furnace, which comprises feeding solid briquetted fuel in intervals of 15 to 60 minutes from the top 'into said shaft so as to form a pile with a sliding upper surface in said shaft; heating said pile by means of flames from a burner above said pile, said flames directly impinging on said pile and transferringa quantity of heat of at least 150,000 kcal. per hour and per square meterto the surface ofsaid pile; admitting rinsing gas into the interior of said pile, said rinsing gas having a temperature of at least 900 to 1,000", C., whereby a carbonized skinis formed on the surface of the briquettes strong enough to prevent breaking of said briquettes; and discharging the coked briquettes at the same rate as they arefedinto said shaft.

2. The process according to claim 1, which comprises admitting additional gas for heating the top of the pile of fuel formed in the shaft in addition to the heating gas admitted to the interior of the pile.

References Cited in the file of this patent UNITED STATES PATENTS 5 Rosenthol May 26, 1925 Hubmann Sept. 1, 1925 Hubmann Nov. 6, 1928 Records Feb. 2, 1932 Wright July 12, 1932 Ackermann July 18, 1933

Claims (1)

1. A PROCESS FOR COKING BRIQUETTES MADE OF SOLID FUEL IN A SHAFT FURNACE, WHICH COMPRISES FEEDING SOLID BRIQUETTED FUEL IN INTERVALS OF 15 TO 60 MINUTES FROM THE TOP INTO SAID SHAFT SO AS TO FORM A PILE WITH A SLIDING UPPER SURFACE IN SAID SHAFT, HEATING SAID PILE BY MEANS OF FLAMES FROM A BURNER ABOVE SAID PILE, SAID FLAMES DIRECTLY IMPINGING ON SAID PILE AND TRANSFERRING A QUANTITY OF HEAT OF AT LEAST 150,000 KCAL. PER HOUR AND PER SQUARE METER TO THE SURFACE OF SAID PILE, ADMITTING RINSING GAS INTO THE INTERIOR OF SAID PILE, SAID RINSING GAS HAVING A TEMPERATURE OF AT LEAST 900 TO 1,000*C., WHEREBY A CARBONIZED SKIN IS FORMED ON THE SURFACE OF THE BRIQUETTES STRONG ENOUGH TO PREVENT BREAKING OF SAID BRIQUETTES, AND DISCHARGING THE COKED BRIQUETTES AT THE SAME RATE AS THEY ARE FED INTO SAID SHAFT.

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