US3926576A

US3926576A - Process for producing hot briquettes

Info

Publication number: US3926576A
Application number: US358199A
Authority: US
Inventors: Paul Schmalfeld; Dieter Sauter; Werner Peters; Erwin Ahland; Burkhard Bock; Joachim Lehmann
Original assignee: Bergwerksverband GmbH
Current assignee: Bergwerksverband GmbH
Priority date: 1972-05-12
Filing date: 1973-05-07
Publication date: 1975-12-16
Anticipated expiration: 1992-12-16
Also published as: IT987173B; GB1426793A; CA994101A; JPS4948701A; JPS5720358B2; GB1426794A

Abstract

Briquettes having improved crushing strength are made from hot coke containing mixtures at temperatures between 350* and 550*C. by admixing tar pitch with the hot coke and then pressure forming the briquettes on a double-roll press for example. A mixture of caking coal and tar pitch can also be mixed with the hot coke to form the hot briquettes.

Description

United States Patent Schmalfeld et al.

PROCESS FOR PRODUCING HOT BRIQUETTES Inventors: Paul Schmalfeld, Bad Homburg;

Dieter Sauter, Frankfurt am Main; Werner Peters, Wattenscheid; Erwin Ahland, Essen; Burkhard Bock, Duisburg; Joachim Lehmann, Essen-Haarzopf, all of Germany Assignees: Bergwerksverband GmbH,

Essen-Kray; Metallgesellschaft Aktiengesellschaft, Frankfurt am Main, both of Germany Filed: May 7, 1973 Appl. No.: 358,199

Foreign Application Priority Data May 12, 1972 Germany 2223078 Mar. 8, 1973 Germany 2311348 US. Cl 44/10 H; 44/10 C; 44/23 Int. Cl. C10L 5/00; ClOL 5/16; C10L 5/40 Field of Search ..44/13, 11, 1011,23, 10C

[56] References Cited UNITED STATES PATENTS 1,334,180 3/1920 Smith 44/23 1,912,002 5/1933 Loebell 44/23 3,073,751 1/1963 Gorin et al 44/23 X 3,655,350 4/1972 Utley 1 44/23 X 3,655,518 4/1972 Schmalfeld et a1. 208/1 1 X 3,663,186 5/1972 Dzhaparidze et al. 1 44/10 H 3,674,449 7/1972 Schmalfield et a1. 44/13 X Primary ExaminerCarl F. Dees Attorney, Agent, or Firm-Burgess, Dinklage & Sprung 5 7] ABSTRACT Briquettes having improved crushing strength are made from hot coke containing mixtures at temperatures between 350 and 550C. by admixing tar pitch with the hot coke and then pressure forming the briquettes on a double-roll press for example. A mixture of caking coal and tar pitch can also be mixed with the hot coke to form the hot briquettes.

29 Claims, 1 Drawing Figure US. Patent Dec. 16, 1975 PROCESS FOR PRODUCING HOT BRIQUETTES BACKGROUND This invention relates to a process of producing hot briquettes from a mixture at temperatures between 350 and 550C. which contains hot coke and is preferably briquetted on a double-roll press. It is known to make briquettes from binary mixtures consisting of coke and caking coal. The process embodiments which will be described more fully hereinafter show how tar pitch may be co-used in the production of hot briquettes. Tar pitch as such often has only a low market value.

A hot briquetting of caking coal in the plastic range between 350-550C. is suitably effected by mixing hot coke, which has been produced at temperatures of about 600900C., preferably between 700 and 850C., with the caking coal which has been predried and/or preheated. The mixture is preferably briquetted on a double-roll press. Processes and apparatus such as are described more fully in German Pat. No. 1,252,623 and US. Pat. No. 3,308,219, issued July 4, 1972, are suitably used for this purpose.

Depending on the caking property of the caking coal and the desired crushing strength and wear resistance of the hot briquettes, the mixture should contain 50-80 parts by weight of hot coke and of 50-20parts by weight of caking coal. The use of caking coal in an amount of 40% and more by weight, however, requires a higher technical expenditure. Besides, caking coals often have insufficient binding properties, which is specifically defined by the dilatation and plastic range in the dilatometer, or by the minimum torque in the Plastograph, by the rotations in the Gieseler Plastome ter, or by the swelling index or the caking value accord-"a ing to Roga and Damm, respectively.

SUMMARY The mixing ratio of tar pitch to hot coke also depends on the nature of the coke and of the tar pitch and usually lies between 10:90 and 30:70 parts by weight. The conditions are such that a tar pitch having higher binding properties may be used in a smaller amount. Similarly, a denser, stronger and less porous coke having a lower dust content requires a smaller amount of tar pitch than a coke having a higher porosity, lower strength and high dust content.

The preferred tar pitch. is high-boiling heavy tar which is liberated during the production of the hot coke. This tar pitch is usually recovered by a fractionating condensation and is obtained as a liquid laden with fine dust. The tar pitch is desirably used without any subsequent treatment and is admixed in a liquid state with the hot coke. As the mixture of tar pitch and coke is heated to the briquetting temperature, part of the tar pitch is distilled off and appears in the fractionating condensing unit as high-boiling heavy tar. This heavy tar can also be used to advantage as a binder for the hot coke. Because the tar pitch which distills off can usually be recovered with a low dust content, the heavy tar which has been distilled off may be used, if desired, also for another useful purpose.

In many cases, the amount in which the heavy tar is produced will not be sufficient so that tar pitch from another source must be added. It has beenfound that the requirements as regards the quality of the binder material are low. As additional material, normal coke oven tar pitch or, if desired, undistilled or only predistilled raw tar from coke ovens, gas works ovens, gas producers or low-temperature carbonizing ovens may be used. Besides, bitumen derived from petroleum may be used without any special thermal pretreatment if it has been derived from a napthene-aromatic asphaltbase petroleum. If the bitumen is derived from paraffinbase petroleum, it will desirably be heat-treated at temperatures above 400C., better above 500C., under atmospheric or superatrnospheric pressure. Natural asphalt is also well suited as a binder material.

used as shaped coke bodies for metallurgical purposes. 3

This object is realized basically by mixing tar pitch with coke in the preparation of the mixture to be briquetted.

DESCRIPTION OF THE DRAWING produces hot coke and tar pitch and Section II is the briguetting zone.

DESCRIPTION In a broad embodiment tar pitch is mixed solely with hot coke. In a preferred embodiment, caking coal is admixed with the tar pitch before being mixed with hot coke as described herein.

First, the coke is heated to such a temperature e.g., in the range 600900C. that the mixture produced has just the temperature which is required to produce a hot bn'quette having optimum crushing strength and wear resistance. This temperature depends on the nature of the coke and of the tar pitch and usually lies between 350 and 550C, preferably between 400 and 500C. The mixture is briquetted in this range or at a temperature up to 100C. lower.

Any tar pitch from another source which must be added is suitably fed into the condenser for the heavy tar produced in the process itself and in said condenser is heated to the temperature of the heavy tar and at the same time is intimately admixed therewith.

The tar pitch may be mixed first with part of the hot coke in order to heat it to an intermediate temperature.

In that case, a pasty, sticky substance may be formed, which can neither flow nor trickle. For this reason, the tar pitch is desirably admixed immediately with the total amount of the hot coke.

When the hot coke is collected in separate coarse and fine (cyclone dust) fractions, it will be desirable to admix the tar pitch initially and mainly with the fine fraction of the hot coke and thereafter to add the coarse fraction. It has also been found that it is useful to mix the tar pitch initially with. a small amount of fine coal dust, which has not been highly heated before and which may consist of predried dust recovered for flotation, or of carbon black or the like, or with dustlike or fine-grained coke which is cold or has not been highly heated. The resulting mixture should be sufficiently liquid and flowable.

The tar pitch is suitably mixed with the hot coke in a double-vane mixer having two shafts which rotate in the same sense. Such mixer is desirably used also to mix caking coal and hot coke. Such mixer is described more 3 fully in the German Pat. No. 1,252,623 and US. Pat. No. 3,308,219.

It has been found that at suitable briquetting temperatures the tar pitch is decomposed to a large extent as it is mixed with the hot coke so that the resulting hot briquettes have only a low residual tar content of 02-06% by weight as determined by the Fischer lowtemperature carbonization analysis. It has also been found that the tar pitch will be more easily decomposed in a mixture with the hot coke than the bitumen or tar of the caking coal when the latter has been heated by the admixing of the hot coke.

The resulting hot briquettes are desirably aftertreated by being carefully cooled with circulating inert gases, as is described, e.g., in co-pending application Ser. No. 237,813. Before the hot briquettes are cooled, they are desirably heated to temperatures of 550650C., e.g., of 600C, so that all tar is removed from them, their content of volatile constituents is reduced and their crushing strength and wear resistance are increased. DOS No. 2,247,101 contains a more detailed description of a useful and simple method of effecting this heating simultaneously with the cooling of the hot briquettes.

The process may also be used for a hot briquetting of only slightly caking coal, which is heated to a plastic state in the temperature range of 380-540C., preferably of 420480C. and to which a certain amount of tar pitch or of bitumen derived from petroleum is admixed in order to improve the caking property. In this case the proportion which may be admixed is restricted and should amount to 2l0%, preferably 3-6%, so that the heated coal will not be excessively cooled by the additional liquid binder which is admixed and which has not been heated to such a high temperature.

This technology is usually employed to produce a hot briquette which burns with little smoke and is particularly intended for use as a domestic fuel from a tar-containing fine coal, which may form smoke and carbon black as it is burnt. In this case it is desired to heat the coal only to the temperature which is essentially required and to keep the contents of liquid constituents in the hot briquettes so high, if possible, that the loss of material is minimized and a high reactivity of the hot briquettes ispreserved. These hot briquettes are suitably subjected to a thermal after-treatment according to Ser. No. 237,813 and DOS No. 2,247,101.

It has already been attempted to add tar pitch to a mixture of coke and caking coal in order to improve the caking property and to increase the crushing strength and wear resistance. This has not given the desired result because the hot briquettes were aftercarbonized and had only a low strength. It has now surprisingly been found that the quality of the hot briquettes can be considerably increased if the tar pitch is not admixed to the mixture of hot coke and caking coal but is initially admixed to the caking coal alone. The caking coal must first be intensely mixed with the tar pitch so that the latter is uniformly distributed on the caking coal before the hot coke is admixed to the caking coal which is laden with tar pitch.

The tar pitch can be admixed in a finely ground, dry state to the caking coal. In that case the temperature of the caking coal must be lower than the softening point of the tar pitch. The tar pitch may be admixed also in a liquid state. In this case, the temperature of the caking coal must be above the softening point of the tar pitch. It will depend on the specific conditions in each case which of these measures is to be preferred. Tar pitch from the same plant will preferably be admixed in a liquid state. Tar pitch from a more remote distillation plant is often preferably transported in a solid state. Because the caking coal must also be dried and must often also be preheated before it is processed so that the coke component need not be carbonized at an excessively high temperature, the caking coal has in most cases a temperature above C. so that the tar pitch will probably be admixed in most cases in a liquid state.

Before the tar is added, the caking coal is desirably ground to fine particles, which are in any case smaller than 1 millimeter'and preferably below 0.5 millimeter. In that case the tar pitch can be distributed better and can have a more intense action.

The tar pitch may consist of a residue which has been obtained in the distillation of tar in the conventional by-product oven and has been distilled to have a predetermined softening point. Alternatively it will be sufficient to distill only the low-boiling oils, which are more valuable, from the raw tar, and to admix the remainder in a liquid state, regardless of the softening point, to the caking coal.

The tar pitch which has been formed during the hot briquetting itself can be admixed to good advantage with the caking coal. The hot coke is conventionally produced by subjecting coal to a low-temperature distillation in a direct conjunction with the hot briquetting. In' that case both coal gases and tar vapors are liberated and are then condensed. Preferred low-temperature carbonizing processesare the low-temperature carbonization of coal with the aid of circulated, heated, fine-grained coke, such as is described, e.g., in US. Pat. No. 3,655,518.

As the caking coal enriched with tar pitch is admixed to the hot coke, gases and tar vapors are also produced and may be treated separately or in a mixture with the gases and tar vapors produced by the low-temperature carbonization of the coal to produce the hot coke. The coal gases which are produced are first subjected to a dry dust collection in a cyclone and are then fed into a tar scrubber, in which the high-boiling tars are subjected to fractional condensation. The lower-boiling tar oils and the process water are collected in the subsequent scrubber-coolers. The high-boiling tar fraction is then admixed entirely or in'part with the caking coal in order to increase the caking property of the caking coal.

The addition of tar pitch to the caking coal results also in a slight increase of the tar content of the hot briquette product. To avoid this increase, the temperature of the resulting mixture is slightly increased, usually by about 5C. and up to about 10C.

The caking coal is desirably mixed with the tar pitch in a double-vane mixer having two shafts which rotate in the same sense. The amount of caking coal is much smaller than the amount of the mixture of caking coal and hot coke. For this reason the mixing shafts of the mixing mechanism for admixing the tar pitch may be much smaller in diameter than those of the mixing mechanism for mixing the caking coal and the hot coke. For this reason the mixing mechanism for admixing the tar pitch should be separate of the mixing mechanism for admixing the hot coke. Two mixing mechanisms involve a double expenditure for bearings and drive means and involve a larger overall height. For this reason, the two mixing mechanisms are suitably mounted on the same shaft. In this case the mixing shafts of the mixing mechanism for the tar pitch should be smaller in diameter and the lead of the mixing vanes in this mechanism should be smaller than in the mixing mechanism for the hot coke and the mixing section for the tar pitch should merge directly into the mixing section for the hot coke.

The admixing of the high-boiling tar pitch which is formed in the process itself to the caking coal results not only in an improved caking property of the coal but enables also an economically desirable utilization of the tar pitch. Unless all tar pitch formed in the process is required to improve the caking coal, the tar pitch which is formed during the production of the hot, finegrained coke which is required is desirably admixed to the caking coal, the tar vapors and gases which are liberated in the mixer or intermediate storage container preceding the press are supplied to a separate apparatus for condensing the tar pitch, and the latter tar pitch is used entirely or in part for different purposes. This division will be desirable because, by experience, the tar pitch formed in the production of the fine-grained coke contains dust whereas the tar pitch formed by hot briquetting contains little dust and, because it has been formed at a low temperature, has usually a lower viscosity and lower binding properties.

The caking coal enriched with the tar pitch is usually mixed with the hot coke to produce a mixture at a temperature of 420550C., preferably 450500C. During this mixing operation, the tar pitch is distilled off and coked. The resulting tar vapors have such a boiling range that they are separated in the condensing apparatus of the hot briquetting equipment and increase the amount of tar pitch that is formed.

An example of the process of producing briquettes from coke, caking coal and tar pitch will be described more fully with reference to FIGURE 1. Section I is the equipment for producing the hot coke and consists in this case of a low-temperature carbonizing' unit in which fine-grained coke is circulated as a heat carrier, and of an associated condensing unit. Such equipment has been described, e.g., in US. Pat. No. 3,655,518.

Section II is hot briquetting equipment proper, and is also provided with a condensing unit.

Section I comprises a pneumatic elevator conduit 1, in which the circulating fine-grained coke is heated, a bin 2, in which the coke is separated from the entraining gases, a mixer 3 for mixing the fresh coal, supplied through a conduit 13, to the circulating coke, and an intermediate storage bin 4 before the elevator conduit 1. The gases and tar vapors which are liberated in the mixer 3 and intermediate storage bin 4 are withdrawn through a cyclone 5 into a first condensing stage 6, in which the high-boiling tar pitch is condensed and separated. Tar pitch is recirculated through this stage by a pump 7 to scrub the gases and tar vapors and to collect the fine dusts which are entrained. A cooling is effected in this stage by an evaporation of injected water or by an indirect cooling of the circulated tar pitch. The gases and tar vapors are usually aftertreated in two further condensing stages.

Section II comprises a mixing mechanism 10 by which the hot tar pitch which has been separated in condensing stage 6 and is supplied through conduit 11 by the pump 25 is admixed to the caking coal which is suitably predn'ed and, if desired, preheated and which is fed to the mixing mechanism 10 in conduit 12. The caking coal which has been enriched with tar pitch is then admixed to the mixing mechanism 14, in which the caking coal is mixed with hot coke, which is supplied in conduit 15. The hot coke is maintained at such a temperature that the mixture has the temperature which is most desirable for making briquettes of optimum quality. The mixture then flows through the stirred intermediate storage container 16 into the double-roll press 17, in which the hot briquettes are formed.

The gases and vapors which are liberated in the mixer 14 and in the container 16 are supplied into the condensing stage 18, if desired, through a cyclone 24. The high-boiling tar pitch is separated in the condensing stage 18. As with the condensing stage 6, the tar pitch separated in the condensing stage 18 is circulated through the latter by a pump 19. In stage 18 cooling is effected to adjust temperature such that the collected tar pitch can still at least be pumped. This tar pitch is fed by a pump 26 in conduit 20 to the mixer 10 in order to improve the caking property of the caking coal but may also be supplied entirely or in part to other uses through conduit 21.

The condensing stage 18 can be followed by two additional condensing stages 2.2 and 23 for separating the lower-boiling tar oils. These tar oils often differ in nature from the tar oils which are separated in the condensing stages 8 and 9 because they have been formed at different degasification temperatures and the coal from which the hot coke is produced often differs from the caking coal. When a different utilization is not desired, the condensing stages 22 and 23 may be eliminated and the gases and vapors may be conducted from the condensing stage 18 into the condensing

stages

8 and 9.

The tar vapors withdrawn from the mixer 14 and the container 16 in most cases contain only small amounts of dust so that the incorporation of the cyclone 24 is often not required.

In the following examples, which are intended to illustrate the invention without limiting same in any manner, the apparatus used was as is shown in the drawing and described herein.

EXAMPLE 1 When 10% by weight of tar pitch are admixed with 90% by weight caking coal in 1 0, and 30% by weight of the caking coal-pitch mixture are admixed with by weight of hot coke at 455C. in 14, the resulting briquettes had a crushing strength of I35 kilograms per square centimeter. If the proportion of tar pitch is increased from 10 to 20% by weight, the crushing strength is increased to 162 kilograms per square centimeter.

When 10% tar pitch is added to the caking coal in 10 so that 36% by weight of caking coal, 4% by weight of tar pitch and 60% by weight of coke were charged to the press 17, the crushing strengthwas increased to 183 kilograms per square centimeter.

CONTROLS 30% by weight of a medium-caking coal were admixed with 70% by weight hot coke at 455C. in 14. The resulting briquettes have a crushing strength of 101 kilograms per square centimeter.

When the amount of caking coal used is increased from 30 to 40% by weight, the resulting hot briquettes have a crushing strength of 147 kilograms per square centimeter.

1f the tar is added to the mixture of caking coal and hot coke in 14, the briquettes made from a mixture of 24% by weight of caking coal, 70% by weight of coke and 6% by weight of tar pitch had a crushing strength of only 131 kilograms per square centimeter.

It is apparent that an unexpected and useful increase in crushing strength will result if the tar pitch is admixed with the caking coal before it is mixed with the hot coke.

EXAMPLE 2 With anincrease in the amount of tar added to the caking coal, the residual tar content of the briquettes will also be increased if the mixing is effected at the same temperature. The following test run shows that the increase of the residual tar content in the briquettes can be opposed by an increase of the mixing temperature.

When 30% by weight of caking coal and 70% by weight of hot coke are mixed as in the Controls above to provide a mixture at 455C, the resulting briquettes had a crushing strength of 101 kilograms per square centimeter and contained 0.5% by weight of residual tar. When 20% tar pitch were added to the caking coal so that the mixutre consisted of 24% by weight of caking coal, 6% by weight of tar pitch, and 70% by weight of hot coke, and the mixture had the same temperature of 455C, the resulting briquettes had a crushing strength of 161 kilograms per square centimeter and a higher residual tar content of 0.8% by weight. When the temperature at which the hot coke was supplied was increased so that the same mixture had a temperature of 460 rather than 455C, the residual tar content was reduced back to 0.5% and the crushing strength was reduced to 155 kilograms per square centimeter.

By increasing of the temperature of the mixture in 14, the influence of the addition of tar pitch to the caking coal on the residual tar content of the briquettes was compensated whereas the crushing strength was only slightly decreased.

The residual tar content of the briquettes may also be decreased by subjecting the hot briquettes to a thermal aftertreatment such as is disclosed in the Opened German Applications Nos. 2,1 15,838 and 2,247,101, wherein the hot briquettes are left for a certain time at a temperature close to the briquetting temperature or are even somewhat heated. This results in a further strengthening of the structure and in a decrease of the residual tar content of the briquettes.

The following examples relate to the briquettes made from mixtures of coke and tar pitch without caking coal.

EXAMPLE 3 A sub-bituminous gas coal which contained 35% volatile constituents, based on waterand ash-free coal, was subjected to a low-temperature carbonization at 680C. The hot coke at 660C. was mixed with the tar pitch formed by the low-temperature carbonization and the mixture containing 85% coke and tar pitch by weight was briquetted on the press at a temperature of 440C. The crushing strength of the cooled briquettes was at 135 kilograms per square centimeter. Low-temperature carbonization analysis of the briquettes showed thay they contained only traces of tar. The briquettes subjected to a temperature of 550C. for minutes so that the strength of the cooled briquettes was increased to 161 kilograms per square centimeter.

EXAMPLE 4 lf.20% by weight of tar pitch were added rather than 15% by weight as in Example 3 and the mixture was hot-briquetted in the same manner, the resulting briquettes had a strength of 142 kilograms per square centimeter. The strength was increased to 193 kilograms per square centimeter by the subsequent heating to 550C.

EXAMPLE 5 If tar pitch formed by the lowtemperature carbonization and having a softening point according to Kramer-Sarnow of 126C. was replaced by 20% by weight coal tar pitch produced in a conventional coke oven plant and having a softening point of C., the green briquettes had a strength of 155 kilograms per square centimeter and the briquettes aftertreated at 550C. had a strength of 195 kilograms per square centimeter. Thus, low-temperature tar pitch and coke oven tar pitch are virtually equivalent.

EXAMPLE 6 When the tar pitch was replaced by 20% by weight bitumen having a softening point of 98C. and derived from petroleum, the green briquettes had a strength of 139 kilograms per square centimeter and the hot briquettes aftertreated at 550C. had a strength of 239 kilograms per square centimeter. The bitumen derived from petroleum is virtually equivalent and after the thermal treatment was even superior. This desirable result was produced although the bitumen derived from petroleum developed only insufficient binding properties when it was used as a binder in the briquetting of coal at temperatures of 100C. and the resulting briquettes were coked.

EXAMPLE 7 Fine-grained anthracite was heated to 750C. and was mixed with coal tar pitch having a softening point of 80C. to provide a mixture which contained 80% by weight anthracite and 20% by weight coal tar pitch and had a temperature of 460C. This mixture was briquetted to form briquettes which contained 0.8% of residual tar and in the cold had a strength of kilograms per square centimeter so that they were entirely suitable as a low-smoke domestic fuel. An aftertreatment at 550C. for 20 minutes reduced the residual tar content to zero and increased the strength to 173 kilograms per square centimeter.

What is claimed is:

1. Process for producing hot briquettes which comprises:

a. forming a premixture of caking coal with tar pitch,

b. mixing the premixture of step (a) with hot coke forming a mixture having a temperature in the range of 420-550C and containing 2-10 weight percent tar pitch and 20-50 weight percent of caking coal, and

briquetting the mixture of step (b) in a double-roll press to form said hot briquettes.

2. Process of claim 1 wherein said coke is heated to a temperature in the range of 600-900C 3. Processof claim 1 wherein the caking coal is a medium-caking coal heated to a temperature of 400500C. to preserve a certain amount of caking therewith.

9 p 4. Process of claim 1 wherein the tar pitch is premixed in a ground, dry state and the temperature of the caking coal is below the softening point of the tar pitch.

5. Process of claim 1 wherein the tar pitch is premixed in a liquid state with the caking coal which is at a temperature above the softening point of the tar pitch.

6. Process of claim 1 wherein the caking coal is ground to a particle size below 1 millimeter.

7. Process of claim 1 wherein the tar pitch is from a source other than the hot coke or is bitumen derived from petroleum.

8. Process of claim 1 wherein fine coke dust, coal dust, carbon black or the like is first mixed with the tar pitch.

9. Process of claim 1 wherein the tar pitch is formed by distillation of raw tar recovered in a conventional by-product oven.

10. Process of claim 1 wherein the tar pitch is formed during the production of the hot coke.

11. Process of claim 1 wherein tar pitch is liberated when the caking coal premixture is mixed with the hot coke and is thereafter recovered and used in the process.

12. Process of claim 9 wherein said raw tar is first distilled to remove valuable, lower-boiling constituents.

13. Process of claim 1 wherein the tar pitch is a heavy tar obtained by a fractionating condensation of tar vapors formed during the production of the hot briquettes.

14. Process of claim 1 wherein the addition of tar pitch is compensated for by increasing the temperature of the premixture-hot coke mixture thereby preventing an increase in residual tar and/or volatile components in the hot briquettes.

15. Process of claim 1 wherein the briquettes formed are held for 20-60 minutes at a temperature which is as close as possible to the briquetting temperature and are subsequently cooled.

16. Process of claim 1 wherein the hot briquettes formed, are first heated and then cooled in a separate treating shaft.

17. Process of claim 1 wherein the tar pitch and the caking coal are premixed in a double-vane mixing zone having two mixing shafts which rotate in the same direction.

18. Process of claim 1 wherein premixing of the tar pitch and caking coal and subsequent mixing of the 10 premixture with the hot coke are carried out in a common double-vane mixing zone having two mixing shafts rotating in the same direction, the tar pitch and caking coal being premixed in the first section of the mixing zone, and the hot coke being mixed with the premixture in the second section of the mixing zone.

19. Process of claim 18 wherein the caking coal is fed to the double-vane mixing zone at the leading end thereof, the tar pitch is fed to said zone closer thereafter and the hot coke is fed to said zone at a point about one-third of the effective mixing length of the zone from the leading end thereof.

20. Process for producing hot briquettes which comprises mixing fine-grained hot coke or anthracite having a temperature in the range of 600900C solely with lO-3O percent by weight tar pitch to produce a mixture having a temperature in the range of 400550C. and briquetting said mixture on a doubleroll press.

21. Process of claim 20 wherein said mixture is briquetted in said temperature range or at a temperature up to C. lower.

22. Process of claim 20 wherein the tar pitch is from a source other than the hot coke or is bitumen derived from petroleum.

23. Process of claim 20 wherein fine coke dust, coal dust, carbon black or the like is first mixed with the tar pitch.

24. Process of claim 20 wherein the tar pitch is formed by distillation of raw tar recovered in a conventional by-product oven.

25. Process of claim 20 wherein the tar pitch is formed during the production of the hot coke.

26. Process of claim 24 wherein said raw tar is first distilled to remove valuable, lower-boiling constituents.

27. Process of claim 20 wherein the tar pitch is a heavy tar obtained by a fractionating condensation of tar vapors formed during the production of the hot briquettes.

28. Process of claim 20 wherein the briquettes formed are held for 20-60 minutes at a temperature which is as close as possible to the briquetting temperature and are subsequently cooled.

29. Process of claim 20 wherein the hot briquettes formed, are first heated and then cooled in a separate treating shaft.

Claims

1. PROCESS FOR PRODUCING HOT BRIQUETTES WHICH COMPRISES: A. FORMING A PREMIXTURE OF CAKING COAL WITH TAR PITCH, B. MIXING THE PREMIXTURE OF STEP (A) WITH HOT COKE FORMING A MIXTURE HAVING A TEMPERATURE IN THE RANGE OF 420*-550*C. AND CONTAINING 2-10 WEIGHT PERCENT TAR PITCH AND 20-50 WEIGHT PERCENT OF CAKING COAL, AND BRIQUETTING THE MIXTURE OF STEP (B) IN A DOUBLE-ROLL PRESS TO FROM SAID HOT BRIQUETTES.

2. Process of claim 1 wherein said coke is heated to a temperature in the range of 600*-900*C.

3. Process of claim 1 wherein the caking coal is a medium-caking coal heated to a temperature of 400*-500*C. to preserve a certain amount of caking substance before the tar pitch is subsequently admixed therewith.

4. Process of claim 1 wherein the tar pitch is premixed in a ground, dry state and the temperature of the caking coal is below the softening point of the tar pitch.

18. Process of claim 1 wherein premixing of the tar pitch and caking coal and subsequent mixing of the premixture with the hot coke are carried out in a common double-vane mixing zone having two mixing shafts rotating in the same direction, the tar pitch and caking coal being premixed in the first section of the mixing zone, and the hot coke being mixed with the premixture in the second section of the mixing zone.

20. PROCESS FOR PRODUCING HOT BRIQUETTES WHICH COMPRISES MIXING FING-GRAINED HOT COKE OR ANTHRACITE HAVING A TEMPERATURE IN THE RANGE OF 600*C-900*C SOLELY WITH 10-30 PERCENT BY WEIGHT TAR PITCH TO PRODUCE A MIXTURE HAVING A TEMPERATURE IN THE RANGE OF 400*-550*C. AND BRIQUETTING SAID MIXTURE ON A DOUBLE-ROLL PRESS.

21. Process of claim 20 wherein said mixture is briquetted in said temperature range or at a temperature up to 100*C. lower.