US3475278A - Method for producing coke briquettes - Google Patents

Description

Oct. 28, 1969 w. PETERS ET AL 3,475,278

METHOD FOR PRODUCING COKE BRIQUTTES Filed June 29, 1965 H07. l 56K/NG COKE COAL DEV/CE 50K/NG DEV/CE HEAT EXCHANGE@ An? 4 /co'oL/No DEV/c5 United States Patent O 3,475,278 METHOD FOR PRODUCING COKE BRIQUETTES Werner Peters, Wattenscheid, and Joachim Lehmann,

Essen-Haarzopf, Germany, assignors to Bergwerksverband G.m.b.H., Stuttgart, Germany Filed June 29, 1965, Ser. No. 467,997 Claims priority, applisati7o7nsermany, July 3, 1964,

Inf. cl. ciol 5/28 U.S. Cl. 201--6 5 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a method for producing coke briquettes, and more particularly, to a method for the' continuous production of coke briquettes which can be carried out without the addition of a special binder material.

Generally, coke briquettes are produced by briquetting coal with pitch at between about 50 and 80 C. and by coking the thus formed briquettes in coke ovens of special construction.

However, this method, although very simple, is used only on a limited scale due to the costs involved in briquetting the coal with the help of a binder material such as pitch. Coke briquettes produced in this manner cannot compete economically with regular lump coke.

It is therefore an object of the present invention to provide a method of forming coke briquettes which can be carried out in a particularly simple and economical manner and which can be easily adapted for continuous operation.

It is another object of the present invention to provide a method for producing coke briquettes which can be carried out without requiring the incorporation of a special binder material.

It is yet another object of the present invention to provide a method of producing coke briquettes requiring as starting materials only coke and a baking coal.

Other objects and advantages of the present invention will become apparent from a further reading of the description and of the appended claims.

With the above and other objects in view, the present invention contemplates a method of producing coke briquettes, comprising the steps of mixing coke particles and particles of a baking coal so as to form thereof an intimate mixture at a first elevated temperature being within the range of plasticization of the baking coal, briquetting the mixture while the same is at the lirst elevated temperature, embedding the thus formed briquettes in a pulverulent mass being at a second elevated temperature of between about 900 and 1200 C. and consisting o-f a material which is stable at temperatures of up to at least 1200 C. and which is inert with respect to the briquettes at the second temperature, the amount of the pulverulent mass being so chosen relative to the amount of the briquettes embedded therein that the embedded briquettes will be heated to a third elevated temperature of between about 800 and l100 C., keeping the briquettes embedded in the pulverulent mass for a period Patented Oct. 28, 1969 ice of time suflicient to heat the briquettes to the third elevated temperature and to cause coking of the same, thereafter separating the thus heated and coked briquettes from the pulverulent mass, and cooling the thus separated briquettes.

According to a preferred manner of carrying out the method of producing coke briquettes in accordance with the present invention, the same comprises the steps of continuously mixing betwe'en 5 and l part by weight of hot coke particles including up to 15% volatile constituents and having a particle size below 3 mm. and between l and 3 parts by weight of particles of a baking coal having a swelling index of between 2 and 9` and a particle size of up to about 1 mm. so as to form thereof an intimate mixture, the temperature of the hot coke being such that the thus formed intimate mixture will be at a first elevated temperature being within the range of plasticization of the baking coal, continuously briquetting the mixture without the admixture of a binding agent While the mixture is at the rst elevated temperature, coninuously embedding the thus formed briquettes in a pulverulent mass of sand being at a second elevated temperature of between about 900 and 1200 C., the amount of the pulverulent mass being equal to between 5 and 20 times the weight of the' briquettes and so chosen relative to the amount of the briquettes embedded therein that the embedded briquettes will be heated within a time period of up to about 30 minutes to a third elevated temperature of between about 800 and ll00 C., keeping the briquettes embedded in the pulverulent mass for a period of time sullicient to heat the briquettes to the third elevated temperature and to cause coking of the same, thereafter continuously separating the thus heated and coked briquettes from the pulverulent mass, and contacting the thus separated briquettes in countercurrent With a circulating cooling gas so as to cool the briquettes.

It has thus been found, according to the present invention, that coke briquettes may be produced continuously and without requiring a special binding agent, by briquetting finely pulverulent coke with baking coal admixed thereto, at a temperature which must be within the range of plasticization of the baking coal, and preferably at a temperature Within the lower half of the range of plasticization such as about 30 C. above the softening point of the baking coal. The thus formed briquettes, preferably while still hot, are then embedded in a nely pulverulent material which has been heated to between about 900 and 1200 C. so that the thus embedded briquettes will be heated by the pulverulent material. The amount of briquettes and pulverulent material is so adjusted relative to each other that the briquettes, preferably within 30 minutes or less, will be heated to a temperature of between about 800 and 110 C. or about less than the initial temperature of the heated pulverulent material. Thereby, the baking coal portion of the briquettes is subjected to coking and the briquettes are converted into coke briquettes. The thus formed coke briquettes are then separated from the heated pulverulent material and cooled.

Surprisingly, it has been found that by proceeding in this manner and notwithstanding the sudden exposure of the freshly formed briquettes to the relatively very high temperature of the pulverulent material, the coking of the briquettes takes place without difficulties, primarily without deformation of .the briquettes and without crack formation therein and, furthermore, that the thus formed coke briquettes are of considerable mechanical strength.

The method of the present invention has important advantages. Since the coking period is very short, up to 30 minutes, relatively small installations suice for the coking of large quantities of briquettes. It is a further important advantage of the present invention that it is possible to carry out the process in a continuous and thus substantially automatic manner. Furthermore, the process of the present invention makes it possible to recover and use in a simple manner the sensible heat of the various materials.

The briquettes are produced by compressing a mixture of coke and baking coal, without any additional binding agent, at a temperature which is to be within the range of plasticization of the baking coal, preferable within the lower half of the range of plasticization or about 30 C. above the softening point of the baking coal, which softening point is determined by means of a Brabender plastograph. The range of plasticization of making coals generally is between about 380 and 500 C.

Any kind of coke may be used as the starting material for the process of the present invention. Particularly good results are achieved by using low temperature cokes containing upto about volatile constituents. The particle size of the coke which is subjected to briquetting preferably should be below 3 mm. and most preferably between about 0.2 and 2.0 mm.

All types of baking coals which soften and swell upon heating under exclusion of air may be admixed to the coke for forming the mixture which is then to be briquetted.

Particularly good results are obtained with coals having a swelling index of between 2 and 9. The particle size of the baking coal preferably will be below 1 mm. and most preferably below about 0.2 mm.

It is advantageous to mix coke of such high temperature with cold or preheated coal that without additional heating of the thus formed mixture, the same will have the desired briquetting temperature.

Preferably, between 5 and 1 parts of coke will be mixed with between 1 and 3 parts of coal and most preferably between 3 and l parts of coke will be mixed with 1 part of coal (all parts by weight). The proportion of baking coal will depend primarily on the binding power of the same. A larger proportion of coal having a lower swelling index should be admixed than of coal having a higher swelling index.

The hot briquetting of the mixture is preferably carried out in heat-insulated pelletizing drums, or roll or stamping presses known for such purpose.

The further heating and coking of the briquettes preferably is carried out immediately after formation of the briquettes, by embedding the freshly formed briquettes in a hot finely pulverulent mass consisting, for instance, of quartz sand having a grain size of about 0.1-1.0 mm. The proportion of sand or other suitable heating material relative to the weight of the embedded briquettes is to be such that the equalization temperature between the heat carrier such as sand and the briquettes will be between about 800` and 1l00 C. This is achieved by preheating the sand or the like to between about 900 and 1200 C. and to embed the briquettes in about 5 to 20 times their weight of the thus heated sand or the like. Sand as the solid, pulverulent, heated material may be replaced by any other solid nely pulverulent material which can withstand temperatures of up to about 1200 C. without decomposition or melting and which up to such temperatures is inert with respect to the briquettes.

The coke briquettes formed according to the present invention possess a resistance against localized pressure which is similar to that of coke produced in chamber furnaces, for instance high quality foundry coke.

The gas which is freed upon coking of the freshly formed briquettes while the same are embedded in the hot sand or the like consists primarily of hydrogen and carbon monoxide, and may be used, for instance, for prereducing ore. The cooling of the coked briquettes may be carried out in a circulating gas stream free of oxygen so that the sensible heat withdrawn from the hot, coked briquettes will be recovered in the circulating gas stream and may be further utilized.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specic embodiments when read in connection with the accompanying drawings in which the figure is a diagrammatic view of an arrangement for carrying out the process of the present invention.

Referring now to the drawing, coke which is still hot as it comes from the coking furnace or which has been preheated, is passed from container 1 through conduit 2 into mixing device 3, while simultaneously baking coal is admixed from container 4 through conduit 5. The hot mixture passes from mixing device 3 through conduit 6 into a briquetting device 7, such as a roll press or a heat insulated pelletizing drum, wherein the mixture is briquetted. The thus formed hot briquettes are passed through conduit 8 into coking device 9 into which simultaneously hot sand is introduced through conduit 10. The briquettes and the hot sand, with the briquettes embedded in the hot sand, pass jointly through coking device 9. In the vicinity of the lower end portion of the coking device, sand is withdrawn therefrom and recycled through conduit 10 by means of a suitable pneumatic conveying device 1. Conduit 10 includes a heating device (not illustrated) for reheatng the sand withdrawn from coking device 9 to-the temperature of between 900 and 1200 C., at which temperature the sand is to be re-introduced into the coking device 9.

The coked briquettes leave coking device 9 through conduit 12, while gases formed during the cooking of the briquettes in contact with the hot sand in coking device 9 leave the coking device through conduit 13.

The thus withdrawn coke briquettes are then cooled in shaft cooler 14 with circulating cooling gas which is blown by means of fan 15 through shaft cooler 14 in counter-current to the briquettes passing therethrough. The thus cooled briquettes are withdrawn from shaft cooler 14 through conduit 16.

The cooling gases which were heated 'by contact with the briquettes in shaft cooler 14, pass through a suitable heat exchange device 16 so as to be cooled and at the same time to permit utilization of the heat content of the spent cooling gases, prior to being reintroduced into shaft cooler 14.

The following examples are given as illustrative only, without, however, limiting the invention to the specific details of the examples.

EXAMPLE I A low-volatile bituminous coal containing on a waterfree basis 16% of volatile constituents is coked at a temperature of 610 C. in a tluidized bed using nitrogen as the uidizing gas. parts by weight of the thus produced coke, having a particle size of up to 2 mm. are mixed with 50 parts by weight of a fat coal containing on a water-free basis 29% of volatile constituents and having a particle size of up to 0.2 mm. The coke is mixed with the fat coal immediately after discharge of the coke from the fluidized-bed coking furnace, and thus at a temperature approaching 610 C., so that within ten seconds of mixing, a coke-coal mixture having a temperature of 405 C. is formed. The thus formed hot mixture is compressed into briquettes in a stamping press which operates in such a manner that the piston will exert for a period of one second a pressure of 350 kg./cm.Z on the respective portion of the coke-coal mixture. lImmediately after being expelled from the stamping or briquetting press, the thus formed briquettes are introduced into and embedded in sand which had been preheated to 1100 C., whereby about 20 parts by weight of preheated sand are used for embedding l part by weight of freshly formed briquettes. After about 10 minutes, the briquettes are again separated from the sand and it lwill be found that they have been completely coked in contact with the hot sand. The thus formed coke briquettes are then cooled in countercurrent in a circulating stream of cooling gas.

The localized pressure resistance of the thus obtained coke briquettes, determined with a steel ball of 8 mm. diameter amounts to 150 kp. The Km-value, as a measure of the reactivity of the thus produced coke briquettes, is found to be between 0.1 and 0.15 cm.3/g. sec. It is thus comparable with the reactivity of high quality metallurgical coke. The reactivity as described above, is determined in accordance with the method described by W. Peters and H. Echterhoif in the Journal Blast Furnace, Coke Oven and Raw Materials Proceedings, Philadelphia, vol. 20 (1961).

EXAMPLE II 450 parts by weight of hot coke as it comes from the coking furnace and having a particle size of up to 3 mm., produced by coking high-volatile coal having on a waterfree 4basis 35% volatile constituents, are continuously mixed `within the course of one hour with 150 parts by weight of a dry fat coal containing on a water-free basis 22% volatile constituents and having a particle size of up to 1 mm. Mixing is carried out in a mechanical mixing chamber. Thereby a hot mixture having a temperature of 410 C. is formed and the same is passed into a roll briquetting press wherein the mixture is converted into 600 parts by Weight of briquettes per hour, each briquette having a weight of about 60 grams. The freshly produced briquettes are continuously passed into a shaft coking device into which simultaneously an amount of corundum equal to about six times the amount of the concurrently introduced briquettes is introduced. The temperature of the thus introduced corundum is 1100 C. Thereby the briquettes are embedded in the hot sand, and within 16 minutes heated to an equalization temperature of 940 C. After remaining in the shaft for a total of 2O minutes the briquettes are practically completely degasied. The individual briquettes, after degasication, have weight of 50 grams and, consequently, per hour 500 parts by Iweight of coke briquettes are withdrawn from the lower end portion of the shaft reactor, separated from the hot corundum, and then cooled in a shaft cooler, with countercurrently passing cold circulating gas to a briquette temperature of about 200 C.

The localized pressure resistance of the thus obtained coke briquettes, when determined by applying pressure with a steel ball of 8 mm. diameter, is found to equal 152 kp. The Km-value or reactivity of the thus produced coke briquettes is found to equal 0.125 cm.3/g. sec.

EXAMPLE III Highly volatile coal containing on a water-free basis 35% of volatile constituents is subjected to coking, at a temperature of 600 C., in a flu-idized bed operated with air as the fluidizing gas. The thus-formed coke has a particle size of up to 1 mm. 450 parts by weight per hour of the thus produced coke are-mixed in a continuous manner with 150 parts by weight per hour of a cold, dry fat coal containing on a water-free basis 22% of volatile constituents having a particle size of up to 0.5 mm. The thus formed mixture of three parts of hot coke for each part of cold coal has a temperature of 425 C., and is continuously introduced into a heat insulated pelletizing drum wherein 600 parts by Weight of spherical agglomerates each having a diameter of about 25 mm. and a Weight of about 9 grams are formed.

The thus formed pellets are coked as described in Example 1. The localized pressure resistance of the thus obtained coke pellets or briquettes, when determined with a steel ball of 8 mm. diameter equals 200 kp. For the reactivity of the thus formed coke pellets or briquettes a Km-value of 0.2 cm.3/g. sec. is found.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A method of producing coke briquettes, comprising the steps of forming an intimate mixture between (a) from 5 to 1 parts by weight of coke particles including up to 15% of volatile constituents and having a particle size below 3 mm., and (b) between 1 and 3 parts of weight of baking coal having a swelling index of between 2 and 9 and a particle size of up to 1 mm., said baking coal having a predetermined plasticization temperature range between about 380 and 500 C.; maintaining said intimate mixture of coke particles and particles of baking coal at said predetermined plasticization temperature range of said baking coal until said baking coal is in plasticized state; briquetting said thus obtained intimate mixture of coke particles and plasticized particles of baking coal so as to form coherent briquettes from said intimate mixture of coke particles and plasticized particles of baking coal; embedding the thus formed coherent briquettes in a pulverulent mass being at a 'second elevated temperature of between -about 900 and 1200 C. and consisting of a material 4which is stable at temperatures of up to at least l200 C. and which is inert with respect to said briquettes at said second temperature, the amount of said pulverulent mass being so chosen relative to the amount 0f the briquettes embedded therein that said embedded briquettes will be heated t0 a third elevated temperature of between about 800 and 1100 C. wi-thin a time period of up to about 30 minutes; keeping said briquettes embedded in said pulverulent mass for a period of time suicient to heat said briquettes to said third elevated temperature and to cause coking of the same; thereafter separating the thus heated and coked briquettes from said pulverulent mass; and cooling the thus separated briquettes.

2. A method as defined in claim 1 wherein said forming of said intimate mixture, said briquetting, said embedding and said separating are carried out in a subs-tantially continuous manner.

3. A method as defined in claim 1, wherein Said briquetting is carried out in the absence of a binding agent.

4. A method as defined in claim 1, wherein said intimate mixture is formed in part of hot coke particles having a temperature sufficiently high so tthat the thus formed mixture will be -within said predetermined plasticization temperature range.

5. A method as defined in claim 1, wherein said cooling of said separated briquettes is carried by contacting said briquettes in countercurrent 'with a cooling gas.

References Cited UNITED STATES PATENTS 2,743,216 4/1956 Jahnig et al. 201--12 2,776,935 1/1957 Jahnig et al 201-12 XR 2,979,441 4/ 1961 Friedrich 201-22 3,018,226 1/1962 Batchelor et al. 201--12 XR 3,117,918 l/1964 Batchelor et al. 201--6 XR 3,316,155 4/ 1967 Holowaty et al. 201--6 NORMAN YUDKOFF, Primary Examiner D. EDWARDS, Assistant Examiner U.S. Cl. X.R. 201--12, 22

Images