US2640016A - Manufacture of coke - Google Patents

Description

Patented May 26, 1953 MANUFACTURE OF COKE Samuel W. Martin, Chicago, 111.,

Great Lakes Carbon Corporation,

assignor to New York,

N. Y., a corporation of Delaware No Drawing. Application August 31, 1950, Serial No. 182,634

4 Claims.

This invention relates to novel compositions suitable for coke manufacture and to processes for coking such compositions. More particularly, this invention relates to compositions comprising caking coals and petroleum coke having properties which peculiarly render such coke of high utility when blended with caking coals in coke manufacture.

In accordance with well accepted and standardized practices, blast furnace and metallurgical grade cokes are prepared by the carbonization of various caking coals. Coking is effected by heating a caking coal or mixtures of various types of caking coal in a slot or beehive oven at temperatures up to 1204 C. during a 18 to 30 hour cycle. From an economy standpoint it is desirable to select and utilize the so-called high volatile caking coals. However, it is known to those skilled in the art that very few so-called high volatile caking coals are available which can produce satisfactory blast furnace or foundry grade coke without the blending of such coals with so-called low volatile coals of the Pocohontastype. Cokes prepared from the high volatile coals do not have su icient hardness and strength and have a tendency to degrade and produce fines in handling. The so-called low volatile caking coals are blended with the high volatile coals to increase the surface hardness of the coke and thereby increase resistance of the coke to abrasion. As previously mentioned, the addition of low volatile caking coals to carbonaceous compositions intended for coke manufacture may be quite costly, this often being due to the geographical location of such coal deposits with respect to the coke manufacturer. In addition, the low volatile caking coals continue in high demand and in rather short supply, this being partially due to the rigid specifications which have been placed on such a material.

As a substitute for the low volatile caking type coals, the use of low temperature char has been suggested and has met with some success. However, this' type of additive varies in its properties and specifications, nor has a constant supply of this material been assured coke manufacturers. The use of petroleum coke has also been suggested as a component for coke manufacture. Petroleum cokes having a volatile content of 8 to 13% have been admixed with high volatile caking coals followed by subjecting this mixture to carbonization. These attempts have been commercially unsuccessful, the probable reasons for which will be subsequently pointed out herein.

,It is an object of this invention to provide a novel composition well adapted to the manufacture of hard, dense, strong metallurgical coke.

It is a further object of the invention to provide a coke suitable for metallurgical, foundry and blast furnace practice and a process for its manufacture.

It is a further object of this invention to provide a raw material of uniform composition suitable for the manufacture of metallurgical and blast furnace coke.

It is still a further object of the invention to provide a process for the manufacture of a hard, dense coke having uniform physical properties.

It is still a further object of the invention to provide a process for the manufacture of blast furnace and foundry coke which obviates the use of and necessity for low volatile caking coals.

It is an additional object of the invention to provide a blast furnace or foundry coke having a reduced. ash content.

The above objects, as well as others which will become apparent upon an understanding of the invention as hereinafter described, are realized by preparing a composition comprising a mixture of caking coal and petroleum coke. The petroleum coke component has a volatile content of about 14-35% by weight and is further characterized by its ability to form a hard, dense agglomerate on being heated at a temperature of about 950 C. to substantially remove the volatile matter of the coke.

The petroleum coke or petroleum carbon which I employ in admixture with caking coals is produced by the non-catalytic pyrolysis of petroleum hydrocarbons, the latter including topped crude oils, thermally cracked petroleum residuums and/or recycle stocks from the thermal or catalytic cracking of petroleum fractions. The non-catalytic cracking of petroleum hydrocarbons involves the heating of particular petroleum fractions or components to a temperature of between about 412 to 490 C. The petroleum cokes thus produced which I have found to be useful in the present invention have a volatile content of about 14 to about 35% by weight, this volatile content being determined in accordance with the A. S. T. M. Procedure No. D271-48 as modified for peat and lignite, and being exclusive of water. In accordance with this procedure, a relatively small sample of petroleum coke is heated at 950 C. for a period of time between about 5 to 10 minutes. The difference in weight of the sample prior to and after heating constitutes the vola tile content of the coke. I have found that there are distinct and highly important differences between petroleum cokes having the same volatile content, and I have further found that only those petroleum cokes having a volatile content within the aforementioned range and which, in addition, form a hard, dense coke agglomerate while being heated in accordance with the previously mentioned ,A. 1S. T. M. procedure, or at a temperature of 950 C., are suitable for my purposes. As will be subsequently illustrated herein neither petroleum cokes having a volatile content less than about 14% nor cokes havinga volatile content between 14 and 35% which Will not agglomerate or form a hard, .dense ibutton" are suitable for the purposesiof this invention.

In a specific embodiment of my invention, a major portion of a high volatile calcing coal is blended with a minor portion of petroleum coke, the latter having a volatile content of about 14 to about 35% by weight and being further characterized by its ability to form a hard, dense agslomerate on being heated at a temperature of about 950 C. to substantially remove the volatile matter, are intimately blended and crushed or ground 80 that a major portion and preferably 60% of the mixture, will pass through an %3" screen. This mixtur is then heated in a slot oven to a temperature of 982 1204" C. for a period of about :30 to 18 hours. The resulting coke i found to b equivalent to a coke prepared from a high volatile caking coal in admixture with a minor portion of a low volatile or Pocohontas tyne cal in coal- Slot ovens or by-product ovens are well-known in the art. These ovens are elongated, narrow, Vertical chambers which are heated from the sides. A deep vertical bed of the material to be coked is placed in the slot oven and is then coked by virtue of indirect heating through the walls.

In a further embodiment of my invention I prepare a composition comprising a major portion of high volatile caking coal together with minor DOltions of a low volatile caking or Pocollentas t pe eal and P r l u e h n t 9 'QUS Y described properties or characteristics. he r tios of pe roleum coke to low volat le caking opal may be adjusted to meet the specifications of the coke manufacturers, but in any event the total amount of low volatile caking coal plus the petroleum coke will generally and prefstably e less than the unt Of hi h voiati caking coal in the mixture.

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While I may employ a petroleum coke having a volatile content of about 14 to 35% by weight, which coke in addition will have the agglomerating properties described herein, I find it to be preferable to employ a coke having a volatile content of between about 16 and about 20% by weight. It will be apparent-to thoseskilled in the art that theseranges of olatile contentimay and often do include minor amounts of petroleum coke having a volatile content falling outside of this range. While the improvements described herein can be obtained by the utilization of such materials, I have found it to be distinctly preferable to select apetroleum coke wherein all of the coke has a volatile content between 14 and 35% ;by Weight and preferably between 16 to 20% by weight.

In order to more fully illustrate the nature and character of my invention, but with no intention of being limited thereby, the following specific examples areset .forth. .In all of these examples, the cokes were prepared by heating a mixture of the indicated components, :of which mixture would pass a screen, to :a

" temperature of 982 to 1080 c. for a period of time varying between 18 to 24 hours. The 'resulting cokes are evaluated by their shatter, tumbler hardness (%+l) and tumbler stability A values. The shatter and tumbler tests were conducted in accordance with A. S. "I. M. procedures Nos. D141-48 and D249-29 respectively. The volatile matter (water free) was determined in accordance with the previously mentioned A. S. T. M. procedure.

In the examples set forth in Table I, a rather weakly caking high volatile coal (38 to 40% V. M.) was employed as a major component. This was intimately mixed with a low volatile caking coal (16 to 20% V. M.) and two petroleum cokes, one having a volatile content of 12% and which was of the non-agglomerating type and one having a volatile content of 18% and which agglomerated when heated at 950 C. to form a hard, dense button which would support a weight of two to three pounds or more. Acceptable values for shatter and tumbler for a coke prepared from this type of high volatile coal are indicated in the appropriate columns in the Control examples.

Table I l Percent Percent Percent Percent Shatter, Tumbler, Tumbler, Example If. V. V. Vol. Pet. Percent-l- Percent+ Percent-=1- Coal Coal Coke Coke 2 1 A h 71 85 7U 8U 70 30 71 .nn In a further embodiment of my invention, a 65 It is apparent from the above results that a mixture of to 75% by weight of high volatile caking coal and 5 to 25% by weight of petroleum coke is prepared and comminuted such that a major portion and preferably at least 60% of the mixture will pass through an /8 screen. The petroleum coke should preferably have a volatile content of about 16 to about 20% by weight and it is further characterized by its ability to form a hard, dense agglomerate on being heated at a temperature of about 950 C. to substantially remove the volatile matter.

coke prepared from a mixture of high volatile coal and petroleum coke having a volatile content of 12% by weight falls considerably short of acceptance for blast furnace coke. On the other hand, the use of petroleum coke having a volatile content of 18% and which will agglomerate" on heating to 950 C. equals, and in some instances, surpasses the minimum desired specifications.

In the following examples it was desired to prepare a coke suitable for blast furnace operation which would match a coke prepared from a tice, i. e. by the blending of high volatile and low high volatile caking coal and a medium volatile volatile caking coals.

Pocohontas type coal. For illustrative purposes, The above examples have been recited by way two petroleum cokes were selected having volatile of illustration and not limitation. contents of 13 and 16% by weight, neither of 5 Having thus completely described the nature which would agglomerate when heated at 950 and character of the invention, I claim: 0. in accorda ce i p ced es p e s y 1. A process for manufacturing metallurgical scribed herein. The shatter and tumbler figures oke which comprises forming an intimate mixf r e n r e p s lndlcate acceptable ture consisting essentially of caking coal at least l s 1 s Dartlcular lnstallce- 0 a major portion of which is of the high volatile Table II Percent Percent Percent Percent Shatter Tumbler Tumbler gfi H. V. g x Pet. Vol. Pet. Percent- 1- Percent-l Percent-I Coal hontas Coke Coke 2 1" 34 Control 90 39 69 7 9o 10 1a 37 27 65 so 1s 4s 39 e1 so 20 1s 40 35 so The above results indicate that petroleum coke type, and five to twenty-five per cent of petrohaving a 13% volatile content is an inferior ad- 25 leum coke, the major portion of the particles of ditive to high volatile caking coals for the manusaid mixture passing a /8 inch screen, forming facture of blast furnace coke as is a 16% volatile a deep bed of the mixture in a narrow, vertical content petroleum coke which will not agglomcoking zone, coking the mixture by indirect heat crate upon heating to 950 C. It was subseat a temperature of about 982 to 1204 0., said quently indicated that the 16% V. M. coke conpetroleum coke consisting essentially of coke havtainedasubstantial amount of oilymaterial which ing a volatile content in the range of 14% to was removed during the volatile content A. S. T. about by weight as determined by A. S. T. M.

M. test and which could also be removed merely procedure No. D271-48 as modified for peat and by heating the petroleum coke to a temperature of lignite, and exclusive of volatile material evolved 400 to 500 C. 35 at temperatures of 400-500 C., and further char- In the example set forth in Table III, petroacterized by forming a dense, hard, agglomerated leum cokes having several volatile contents, and coke when heated according to said procedure.

all of which agglomerated on heating to 950 2. The process of claim 1 wherein the volatile C., were mixed with a high volatile caking coal content of said coke is about 16% to about 20% (38% V. M.) in the indicated amounts. The shat- 40 by weight.

ter and tumbler properties were deter- 3. The process of claim 1 further characterized mined, values of +50 and +60 respectively bein that the mixture contains 95% to 75% of high ing a minimum requirement for this particular volatile caking coal.

coke. 4. The process of claim 1 further characterized in that the coal is a mixture of a major Table III portion of high volatile caking coal and a minor portion of a low volatile caking coal, the quantity Percent shatter Tumbler, of high volatile caking coal being in excess of the Example fi t gfifii PBIZIQIHH ff total proportion of low volatile caking coal plus the petroleum coke. 17 1o 61 72 SAMUEL W. MAR'I'IN'. 17 20 e0 71 g; :3 3i 3; References Cited in the file of this patent 33 i8 Z2 Z3 UNITED STATES PATENTS 32 $3 Z}, Number Name Date 1,815,918 Knowles July 28, 1931 OTHER REFERENCES I have s Shown that y Selecting a D Chemistry and Industry, vol. 51, No. 22, May

leum coke having certain properties and blending 5o 27, 1932 pages 4 7.459, Petrolemn c k by such a coke with high volatile caking coals and/or M u t 1,

low volatile caking coals, I have been able to pro- Industrial and Engineering Chemistry, vol. 36, duce metallurgical grade and blast furnace coke No. 12, December 1944, pages 1140-1144, Petroof a quality comparable to or superior to cokes leum Coke" by Berry et a1. (Copies available in prepared in accordance with conventional prac- 65 Scientific Library.)

Claims (1)

1. A PROCESS FOR MANUFACTURING METALLURGICAL COKE WHICH COMPRISES FORMING AN INTIMATE MIXTURE CONSISTING ESSENTIALLY OF CAKING COAL AT LEAST A MAJOR PORTION OF WHICH IS OF THE HIGH VOLATILE TYPE, AND FIVE TO TWENTY-FIVE PER CENT OF PETROLEUM COKE, THE MAJOR PORTION OF THE PARTICLES OF SAID MIXTURE PASSING A 1/8 INCH SCREEN, FORMING A DEEP BED OF THE MIXTURE IN A NARROW, VERTICAL COKING ZONE, COKING THE MIXTURE BY INDIRECT HEAT AT A TEMPERATURE OF ABOUT 982* TO 1204* C., SAID PETROLEUM COKE CONSISTING ESSENTIALLY OF COKE HAVING A VOLATILE CONTENT IN THE RANGE OF 14% TO ABOUT 35% BY WEIGHT AS DETERMINED BY A.S.T.M. PROCEDURE NO. D271-48 AS MODIFIED FOR PEAT AND LIGNITE, AND EXCLUSIVE OF VOLATILE MATERIAL EVOLVED AT TEMPERATURES OF 400-500* C., AND FURTHER CHARACTERIZED BY FORMING A DENSE, HARD, AGGLOMERATED COKE WHEN HEATED ACCORDING TO SAID PROCEDURE.