US3907648A

US3907648A - Method of manufacturing formed coke for blast furnaces without causing the fusion of the coke

Info

Publication number: US3907648A
Application number: US335868A
Authority: US
Inventors: Naomichi Nire; Takeo Sakai
Original assignee: Sumitomo Metal Industries Ltd
Current assignee: Nippon Steel Corp
Priority date: 1972-02-29
Filing date: 1973-02-26
Publication date: 1975-09-23
Anticipated expiration: 1992-09-23
Also published as: GB1392133A; ZA731141B; FR2174076A1; JPS4889901A; ES412045A1; BR7301520D0; JPS5214241B2; FR2174076B1; IT987887B

Abstract

A method of manufacturing formed coke for blast furnaces enabling efficient and economical operation of the blast furnace, wherein the phenomenon of fusion of the formed coke is suppressed or substantially eliminated by appropriately adjusting the total dilatation of the coal material prior to briquetting and the Trommel strength of the coal briquette.

Description

United States Patent Nire et al.

1 Sept. 23, 1975 METHOD OF MANUFACTURING FORMED COKE FOR BLAST FURNACES WITHOUT CAUSING THE FUSION OF THE COKE Inventors: Naomichi Nire, Takatsuki; Takeo Sakai, Nagareyama, both of Japan Assignees: Sumitomo Metal Industries Ltd.; Keihan Rentan Kogyo Co., Ltd., both of Japan Filed: Feb. 26, 1973 Appl. No.: 335,868

Foreign Application Priority Data Feb. 29, 1972 Japan 47-21240 US. Cl 201/6; 44/10 R; 201/21; 201/23 Int. CL". C10B 45/02; ClOL 5/00; ClOB 53/00 Field of Search 201/6, 5, 23, 22, 24, 21, 20119; 75/42; 44/10 R. 23.1 R; 202/123, 130

[56] References Cited UNITED STATES PATENTS 1.664.632 4/1928 Koppers 202/130 2,200,371 5/1940 Koppcrs 202/123 3.546.076 12/1970 Muller ct a]. 201/6 3.619.376 11/1971 Patel ct al 201/6 Primary Examiner-Jack Sofer Assistant ExaminerD. Sanders Attorney, Agent. or Firm-Watson, Cole, Grindle &

Watson ABSTRACT 3 Claims, 7 Drawing Figures 70741 OIL/1724770 0F MXTUEF M47544 Pfi/OK 70 59/01/57 TIA/6 US Patent Sept. 23,1975 Sheet 2 of2 3,907,648

F I 63A FIG.4B

FIG.4A

METHOD OF MANUFACTURING FORMED COKE FOR BLAST FURNACES WITHOUT CAUSING THE FUSION OF THE COKE This invention relates to improvements in the well known method of manufacturing formed coke. Ac-

cording to the method. formed coke is manufactured by carbonizing coal briquettes or cakes formed by pressure molding the blend coal which is composed of poor coking coal and non-coking coal as main materials and a small quantity of inert carbon material and coking coal as auxiliary materials and containing a proper amount of bituminous binder obtained from coal or petroleum.

This invention provides an improved method of manufacturing formed coke for blast furnaces without caus ing the fusion of the coke being carbonized. which is characterized in that the total dilatation of the blend material for the formed coke is made less than 27 percent. that the Trommel strength of the formed coke is made to be no less than 92 percent, and that the carbonization is done by using a coke oven where the carbonized formed coke can be discharged by its own weight.

Metallurgical coke. particularly blast furnace coke. is usually obtained by carbonizing a blended coal containing various hard coking coals in a conventional coke oven at a high temperature.

With the recent development of the steel inductry. the material coal of good quality is getting increasingly difficult to obtain inexpensively and in large quantity. This trend will be further serious in the future.

To cope with this trend. the use of poor coking coal and non-coking coal, which occur in nature and are inexpensively available almost in any region of the world.

as the main material in the manufacture of metallurgical coke have been investigated all over the world. Among various investigated method. the most effective and promising one is the formed coke method where mixture coal composed of poor coking coal and noncoking coal and containing a suitable quantity of binder such as pitch are molded with high pressure into briquettes 0r cakes having a constant form and then these coal briquettes are carbonized at a high temperature to obtain the formed coke. According to this method, particles of the coal having poor coking properties can be firmly bound together with the aid of binder and briquetting pressure, so that cokes having high strength can be obtained. Some excellent inventions relating to this method such as disclosed in Japanese Patent Publication No. 6678/1955, Japanese Patent Publication No. 8424/1965 and Japanese Patent Publication No. 5583/1971 are known. However, these inventions are not put to practice in industry from the grounds as will be given hereinafter.

According to the invention of the Japanese Patent Publication 6678/1955, formed coke is produced by adjusting the material proportionssuch that the caking component contained in the total material beforebriquetting is within a range between 60 and 66 percent. According to this methodfho'wever, good formed coke having a constant shape for blast furnaces cannot be obtainedwith material solely consisting of imported coal or containing 70 percentor more of imported coal since the fusion of the individual coal briquettes or cakes at the time of carbonization is severe. According to the invention ofthe Japanese Patent Publication No.

8424/1965. a step of charring treatment is involved. and it tends to increase the cost. Also. since lowtcmperature tar having small caking capacity is used as binder at the time of briquetting the char the strength of the formed coke is low. The method disclosed in the Japanese Patent Publication No. 5583/1971 requires 25 to 50 percent of coking coal to be incorporated into the coal material. so that. the material cost is high compared to the other methods. Also. it involves complicated steps of briquctting the material coal at a comparatively high temperature of 350 to 450C and carbonizing the briquettc by using sand at a high temperature of 900 to l.2()()C as the heat medium. Therefore. this method of production of formed coke on the industrial scale is impractical.

The present invention has been intended in view of the actual facts that coking coal of good quality is insufficient and that earlier inventions relating to the method of manufacturing formed coke using poor or non-coking coal as main material have not been put to practice in industry due to economical reasons. According to the invention there is provided a method of manufacturing high quality formed coke for blast furnaces economically and on the industrial scale by using poor coking coal and non-coking coal abundantly occurring in nature as main material. The inventors of the present invention noted that except for the economical aspect the prior-art for formed coke manufacturing techniques have not been put to practice inindustry due to the following grounds;

1. 1f use is made of the conventional coke oven for producing formed coke. unlike the usual coke oven operation the formedcoke after the carbonization cannot be discharged out of the oven by the pusher since the individual masses arenot integrally fused.

2. Coke ovens other than the afore-mentioned conventional one. for example the continuous coke oven which is thoroughly suitable for the carbonization of formed coke. have been developed merely on the experimental scale or on a small pilot plan scale and are not industrially practicable.

3. According to theearlier researches and inventions conditions for blending material coals for producing high quality formed coke for blast furnaces and physi-- cal conditions of the formed coke are not fully satisfactory.

As the best prior-art coke oven for producing formed coke for blast furnaces. they studied such ovens as ver tical coke oven and inclined coke oven, which do not require any pusher. and from which the carbonized product can be discharged by its own weight. and they have found that with these ovens it is possible to take the first step forward toward the industrialization. The vertical coke oven has a coke discharging door at the bottom of a coking chamber. After the earbonization, the coke is discharged by its own weight when the discharging door is opened. The inclined eoke oven has an inclined coking chamber inclined at an angle greater than the angle of repose ofthe carbonized product, and the carbonized product can be discharged out of the oven by its own weight when a discharging door pro vided in a lower portion of the coking chamber is opened. While coke ovens of these types are well known to be used for producing coke from ordinal coking coal as the main material. their use for carbonization of formed coke for blast furnaces as according to this invention is unprecedented.

In the recent Japanese coal material situation. more than about 70 percent ofeoking coal for manufacturing blast furnace coke is imported. with less than 30 percent ofdomestic cokingbeing used. The proportions of the imported coking coal is thought to be increased in the future. In the manufacture of formed coke for blast furnaces using imported cokingcoal as the main material. therefore. with theknown technique. for instance the method of mixing: materials according to Japanese Patent Publication No. 6678/1955. the fusion of the individual coal briquettes at the time of carbonization is severe, reducing the merits of the formed coke. It has been proved that it is necessary for the prevension of fusion of the formed coke to adjust'theproportion of coal materials such that the total dilatation of the coal material after kneeding with addition of the binder such as pitch tar will not exceed 27 percent.

An object of the invention. accordingly. is to obviate drawbacks inherent in the prior-art techniques by the provision of a method of inexpensively manufacturing formed coke for blast furnaces by using a coking oven where the carbonized formed. coke can be discharged by its own weight and withoutcausing the fusion of the formed coke.

ln the drawing.

FIG. 1 is a graph showing the relation between fusion ration of the formed coke and total dilatation of the coal material according to the invention;

FIG. 2 is a graph showing the relation between fusion ratio of the formed coke and Trommel strength of the coal briquette;

FIG. 3A is a front view of a device for measuring the Trommel strength of the coal briquette used for the invention;

FIG. 3B is a side view of-the device of FIG. 3A1

, FlG..4A is a front view of a vertical coke oven;

FIG. 4B is a side view of the ovenof FlG. 4A; and

FIG. 5 is a side view of an inclined coke oven. FIGS. 4 and 5 schematically show special eokc ovens used for this invention.

Referring to FIG. 4, numeral 3 designates coking chamber, numeral 4 heating flue, numeral 5 charging hole. numeral 6 dishcarging door, and numeral 7 ascension pipe of coke oven gas. Referring to FIG. 5, which shows an inclined coke oven, numeral 8 designates coking chamber, numeral 9 charging hole, numeral 10 discharging door. The angle is greater than the angle of repose of the formed coke.

Referring now to HO. 1, the total dilatation is a value determined by one of coal dilatation testing methods as specified in the German standard DIN-51739. If the material contains more than a certain quantity of strongly dilatable component. the coal briquette undergoes extraordinary dilatation during the carbonizing step. causing fusion of adjacent formed coke to one another, so that fused coke would result. To produce formed coke of a constant form with good yield. therefore. it is necessary to hold the dilatation ofthe mixture material below a predetermined level.

Further. in order to produce formed coke with high strength. for instance with MS drum strength l5 mm index more than 92 percent. while preventing the fusion of coal briquettes being carbonized in the coke oven. it is necessary that the Trommel strength of the coal briquette before"earbonization 'is more than 92 percent in additionto the afore-mentioned total dilatation requirement. The 'lrommel'strengt'h is a value determined by a method similar to the method for measuring Trommel strength of steam locomotive engine fuel oval briquettes (JRS 61000-3593-09AR3 adopted by the Japanese National Railways. It is derived by loading 5 kg of a formed 'coke sample in a cylindrical iron container 2 having a length of 50 cm and a diameter of 50 cm andprovided with three stiring plates each having a length'of 50 cm. a width of 8 cm and a thickness of 0.32 cm. as shown in FIG. 3, rotating the container together with the sample at a speed of 25 rotations per minute for 2 minutes. then sifting the total sample with a square 15.9-mm-mesh sieve. dividing the weight of part'of the sample on the sieve by the total sample weight. and multiplying the result by 100.

It will be seen that the Trommel strength represents the strength of bond between individual material coal particles constituting the coal briquctte. If it is low. the bond ofcoal material particles is weak. so that coal briquette of low strength would be formed. The trommel strength of the coal briquctte is proportional to the HS drum strength l5-mm index of the formed coke. This relation will be apparentfrom FIG. 2.

If the Trommel strength of the coal briquette exceeds 92 percent. the fusion of the formed coke is extremely reduced. as will be seen from Tables 2 and 3.

As has been made apparent from the foregoing. the technical importance ofthe present invention resides in the following points:

l. A coke oven where the formed coke can be discharged by its own weight is used.

2. In the well-known method of manufacturing formed coke using poor coking coal and non-coking eoalas main material. the total dilatation ofthe mixture material before briquetting is held below 27 percent. to thereby eliminate or avoid the fusion of the formed coke.

3, The requirement that the formed coke for blast furnaces should have a JlS drum strength lS-mm index more than 92 percent is met by having the Trommel strength of thecoal briquette to be more than 92 percent. Doing so is also effective in suppressing the phenomenon of fusion of the formed coke.

Some embodiments of the invention will now be given.

EMBODIMENT I Table 1 shows various kinds and qualities of coal used for research in the invention.

Coking coal and soft coking coal listed in Table l are used for producing blast furnace coke with a presently conventional coke oven.

The materials listed in Table l were used to prepare mixtures shown in Table 2.. The mixtures were then kneededjn; a kneeder with steam blown into the kneeder. Then, these mixturesare pressure molded into Masce. type. of 53 mm X 45 mm by using a briquette machine of double roll-.type with a roll diameter of 66 cm. The coal briquettes thus obtained were cooled down to a normal temperature and then sub- Table. l

Kind and Quality of Coal Used Drum Ash (Z Volatile CBl strength Kind of coal (Note I matter ("/1) (Note 2) IS-mm Informative (Note 1) index 7!) reference (note 3) Coking coal 9.4 26.8 (i 931 Non-coking l2.b 32.2 Not coking coal Poor coking 13.2 20.7 3 36.0 Finely crushed coal (A) to a grain size Poor coking 8.] l4.() l 0 less than 3 mm coal (B) Petroleum cokc 0.5 [0.9 Not coking 0 Soft coking 7.5 42.8 69.2

coal Hard pitch ).2 91.3 Coal tar 2 91.3

and coke) (Note l Determined by the method prescribed in HS M XXII-I963 (Method for proximate analysis of coal (Note 2) Determined by the method prescribed in S M H80l-l960 (Method for testing of coal) (Note 3) Determined by the method prescribed in S K ZIS l-l960 (Method for testing ot'cokc) Table 2 Proportions of Coal Materials (in "/1 by weight) Test number I 2 3 Coking coal l0 l5 l0 Non-coking coal l5 Poor coking coal (A) l5 10 Poor coking coal (B) 50 50 50 Petroleum coke l0 l0 10 Soft coking coal 5 Hard pitch 7 7 7 Coal tar 3 3 3 Total I ()0 I00 I00 Table 3 Quality of Coal Briquette and Formed Coke 'l'est number I 2 3 Material Ash ("/4) 7.4 7.5 7.8 before hriquetting Volatile matter (/(1 24.] 2 l .3 23.6 Total dilatation ('71) 39.0 28.7 27.5

# 'lrommel strength of 93.0 94.] 92.6 coal hriquette (/1) Formed Ash ('71) 9.4 9.3 9.8 Coke Volatile matter ('71) 1.0 0.9 0.9

Drum strength 92.55 92.40 93.75 l5-mm index ('2; AS'IM hardness factor (:10 60.5 new Fusion ratio ('5) 16.6 l().l 2.0

Mark indicates figures as an average for It) IHCLMJIH'IIIL'IHS.

As is shown in Table 3. the drum strength l5-mm index for the formed coke is above 92 percent in any of the tests. Thus. any sample can be used well for blast furnaces. In the test No. l the fusion factor of the formed coke is slightly high. The fusion factor here is calculated from an equation Fusion factor (in =A/B l0() where A is the total weight of formed coke. and B is weight of coke with a grain size exceeding mm. The normal briquette not fused has average dimensions 48 X 48 X 31 mm.

The drum strength lS-mm index of the formed coke underwent fusion is 91.9 percent in the average. which is slightly lower than the formed coke strength required, but even the fused coke may be used for smallscale blast furnaces. ln order to produce coke of a constant grain size with good yield, however. the fusion should be avoidedas much as possible by appropriately adjusting the proportions of the coal materials used coal briquette and the method of manufacturing coal briquette. Comparing the results in Table 3 and proportions of materials shown in Table 2. in the test No. l. 5 percent of soft coking coal with a total dilatation of 24.1 percent isj mixed. In the Test No. 2, the proportions of the coking coal and poor coking coal (A) are mixed 5 percent higher than those in the test No. 3. This difference in thematerial proportions is thought to have delicate effects upon the phenomenon of fusion of the formed coke.

EMBODIMENT 2 Table 4 shows results of testing for confirming the re lation between the fusion factor of the formed coke mentioned in the previous embodiment l and the total dilatation of the all mixed materials prior to the briquetting and testing for seeking the relationship between Trommel strength of the coal briquette and quality of formed coke.

The method of producing coal briquette and formed coke is cntirely the same as in the embodiment l.

Table 4 Results of Testing of Manufacture of Formed (.oke Test Number 4 5 7 Proportions Coking coal 10 10 i (in 7! by weight) Non-coking coal 40 -.10-' 10 Poor coking coal (A) 15 '10 10 Poor coking eoal (B) 50 50 50 Petroleum coke 5 10 10 Soft coking coal 10 l Pitch 7 7 7 4 Coal tar 3 3 3 3 Total 100 100 100 100 Coal materi- Ash WI) 7.7 9.1 7.4 7.24 a1 before briquetting Volatile matter (7: 24.9 22.8 22.7 22.5 Total dilatation (/r) 51.8 24.9 27.5 17.4

Trommel strength 94.8 93.6 88. 89.1 coal briquette (71) Formed coke Ash (/(1 10.1 1 1.5 10.0 1 0.0 I

Volatile matter ("/r) 1.2 1.1 1.1 1.0 Drum strength 91.90 93.65 91.50 91.80 15-min index (71) ASTM hardness factor 595 63.7 58.9 59.9 33.7 0.7 19.9 21.0

# Fusion factor (/1 1 Mark indicates figures as an average for 10 measurements.

ln 'the test No. 4. the proportions are based on the method of adjusting the material proportionsas set forth in the Japanese Patent Publication No. 6678/1950, that is. the material are set such that the caking component contained in the total material prior tobriquetting is within a range between and 66 percent. In this case, the fusion of the formed coke reaches as high as about 34 percent. This means that with the material mainly consisting of imported coal due to the recent coal situation, the method of the Japanese Patent Publication does not permit the manufacture of formed coke of a constant form with'good yield.'

In the test No. 5 the total dilatation of'the mixture coal prior to briquetting is low, and the coal" briquette has enough Troi'nmel strength. Thus; in this example formed coke of high quality with very little fusion can be obtained. i

In the test No. 6 the same material proportions as 'in the test No. 3 are used. and the briqquettingis done I with low pressure. In thiscase. Drum strength l5'-r'n'm index the formed coke is low, and the fusion factor is high. f

1n the test No. 7, the coal briquette is produced under the same conditions as in the embodiment 1 except for a reduction by 3 percent of the pitch in the binder and an increase by 3 percent of the coking coa'l. In this case, since the binder content is reduced. the Trommel strength of the coal briquette is reduced. As a result, the fusion of the formed coke reached 21 percent.

The results of the afore-mentioned embodiments l and 2 are shown in FlGS. l and 2. It will be seen that by holding the total dilatation of the all material prior to the briquettingto be less than 27 percent and the Trommel'strength of the coal briquette to be higher than 92 percenL-it is-possible to" produce formed coke for blast furnaces having a constant form 'with very little fusion.

the end of carbonization can be discharged by its own weight by' opening the discharging door. Since no discharging operation by a' pusher as is involved in the conventional coke oven is required; the vertical coke oven is-best suited to-the carbonization offormed coke. While it is known to use the coke oven of this type for the production of the conventional coke with material mainly composed of the coking coal. the use of this oven for the charbonization of formed coke for blast furnaces as accordingfttfthis invention is unprecedented.

The inventors of this invention produced about 10.000-tons of formed coke for blast furnaces in about three months with the same material proportions and formedcoal manufacturing conditions as in the test No. 3 mentioned above in the embodiment 1. Table Sshows the quality of formed coke for blast furnaces obtained in this period and the quality of the ordinal coke for blast furnaces.

Table 5 Quality of Formed Coke for Blast Furnaces and Conventional Furnace Coke I lote" 1 Figures forf'theconventional blast furnace coke indicate values'afterthe cutting and screening.

(Note 2) The water absorption factor is the totalmoisture content (in percent by weight) obtained after submerging coke with grain size of 30 to 40 mm in water for 24 hours. The quality of the formed coke for blast furnaces according to the invention is superior to the coke produced with the conventional coke oven in the drum strength and grain size. Particularly. according to the invention, the grain size of the formed coke for blast furnaces is substantially within a range between 50 and 25 mm. and the proportion of powdery coke (l mm) is less than compared with the conventional coke. Also. the water absorption factor of the formed coke is about one half that of the conventional coke. which is very useful in the reduction ofthe coke ratio in the blast furnace.

It is to be emphasized that the formed coke for blast furnaces according to the invention. when used in the blast furnace, is superior to the cokes obtained according to earlier inventions and obtained with the conventional coke oven in the following points:

a. it is economical since no expensive coking coal is used. b. Since its strength is high, the operation of the blast furnace can be stabilized and improved. c. Since the fusion is little. coke of uniform grain size can be obtained. d. Since the grain size is within a predetermined range, no coke cutter is required. e. Since the pulverization factor is low. the mass coke yield is high.

f. Since the grain size is uniform. the ventilation of the blast furnace can be improved.

g. Since the water absorption is low. the coke ratio of the blast furnace can be improved.

What is claimed is:

l. A method of manufacturing a blend ofcoal niaterir als for use in producing formed coke for blast furnaces from a blend of different materials without causing the fusion of the coke. the blend being composed of 7() to percent by weight of poor coking and non-coking coal as the main material. 20 to percent by weight of auxiliary material including inert carbon substance and coking coal and l() percent by weight of a binder so as to make the total of the blend material percent. including blending various proportions of the different materials until both the average value of the total dilatation of the blend prior to briquctting is held to less than 27 percent and the Trrommel strength of the coal briquettc is held to more than 92 percent.

2. A method of manufacturing formed coke for blast furnaces according to claim 1. wherein use is made of a coke oven permitting the discharging from the oven of the carbonized formed coke after carbonization of the coal briquette by the weight of the coke itself.

3. A method of manufacturing formed coke for blast furnaces according to claim I, wherein the blend is produced into a coal briquette by pressure molding

Claims

1. A METHOD OF MANUFACTURING A BLEND OF COAL MATERIALS FOR USE IN PRODUCING FORMED COKE FOR BLAST FURNACES FROM A BLEND OF DIFFERENT MATERIALS WITHOUT CAUSING THE FUSION OF THE COKE, THE BLEND BEING COMPOSED OF 70 TO 90 PERCENT BY WEIGHT OF POOR COKING AND NON-COKING COAL AS THE MAIN MATERIAL, 20 TO 0 PERCENT BY WEIGHT OF AUXILIARY MATERIAL INCLUDING INERT CARBON SUBSTANCE AND COKING COAL AND 10 PERCENT BY WEIGHT OF A BINDER SO AS TO MAKE THE TOTAL OF THE BLEND MATERIAL 100 PERCENT, INCLUDING BLENDING VARIOUS PROPORTIONS OF THE DIFFERENT MATERIALS UNTIL BOTH THE AVERAGE VALUE OF THE TOTAL DILATION OF THE BLEND PRIOR TO BRIQUETTING IS HELD TO LESS THAN 27 PERCENT AND THE TRROMMEL STRENGTH OF THE BRIQUETTE IS HELD TO MORE THAN 92 PERCENT.

2. A method of manufacturing formed coke for blast furnaces according to claim 1, wherein use is made of a coke oven permitting the discharging from the oven of the carbonized formed coke after carbonization of the coal briquette by the weight of the coke itself.

3. A method of manufacturing formed coke for blast furnaces according to claim 1, wherein the blend is produced into a coal briquette by pressure molding.