US3700564A - Continuous process of producing shaped metallurgical coke - Google Patents

Continuous process of producing shaped metallurgical coke Download PDF

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Publication number
US3700564A
US3700564A US855431A US3700564DA US3700564A US 3700564 A US3700564 A US 3700564A US 855431 A US855431 A US 855431A US 3700564D A US3700564D A US 3700564DA US 3700564 A US3700564 A US 3700564A
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Prior art keywords
shaped
coke
temperature
stage
briquettes
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Expired - Lifetime
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US855431A
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English (en)
Inventor
Willibald John
Paul Schmalfeld
Paul Lange
Roland Rammler
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GEA Group AG
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Metallgesellschaft AG
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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
    • C10B53/00—Destructive distillation, specially adapted for particular solid raw materials or solid raw materials in special form
    • C10B53/08—Destructive distillation, specially adapted for particular solid raw materials or solid raw materials in special form in the form of briquettes, lumps and the like

Definitions

  • ABSTRACT OF THE DISCLOSURE Improved process of producing shaped coke articles made by pelletizing coal with or without admixture therewith of coke and/or minerals such as ore, which process carbonizes the shaped article in a iirst stage for about 2 to 5 minutes with a concurrent solid, particulate heat carrier at about 500 to 600 C.; a second stage for about 30 to 90 minutes with a counter-current or transverse current solid, particulate heat carrier having an initial temperature of about 400 to 500 C. increasing to a final temperature of 500 to 600 1C.; and then in a third stage with a countercurrent or transverse current solid, particulate heat carrier having an initial temperature of about 550 to 650 C. increasing to a final temperature of 850 to 1000 C.
  • Shaped metallurgical coke of uniform particle size is increasingly preferred by the iron and steel industry because the use of preshaped or pelleted ore and of uniform pieces of sinter for charging blast furnaces is increasing and the efficiency of the blast furnaces is increased by the use of coke having a uniform particle size.
  • the shaped charge stock, whether ore or coke must have a high wear resistance, resistance to deformation, and crushing strength.
  • a shaped coke which has the same weight per piece as the preshaped ore. lExperience has shown that the most desirable weight of the shaped coke is about 30-50 grams per piece.
  • the shaped particles or pieces should have high crushing and abrasive strengths and should have no protruding edges. They should have such a shape as to promote the formation of relatively large voids in the blast furnace charge. A shape which is particularly desirable from this aspect resembles a pillow or loaf of bread and has slightly rounded edges.
  • briquettes or pellets made from coal or a coalcoke mixture are mixed with hot, dine-grained heat carriers, such as sand or other fine-grained materials. This mixing results in heating of the briquettes or pellets.
  • shaped pieces of coal or coke are embedded in sand and are carbonized by the action of hot gases to form a smokeless fuel.
  • the shaped pieces to be carbonized are made from comminuted coal or from lowtemeprature coke or mixtures thereof.
  • the coal and coke may consist of mixtures of components differing in origin. Fine-grained ore or mineral additives may be added to the carbonaceous material which is to be briquetted.
  • a known process for the high-temperature carbonization of fuel briquettes with the aid of solid heat carriers utilizes a shaft furnace, in which highly heated sand and the shaped carbonaceous articles are jointly moved in ⁇ downwardly directed, concurrent streams. As the briquettes enter the furnace, they are immediately subjected to the highest treating temperatures. The rate of temperature rise at the surface of the briquettes is initially very high and decreases as the temperature equalization between the sand and the shaped carbonaceous articles and between the surface and core of the shaped articles proceed. This treatment is satisfactory only with a few fuels, particularly with low-gas fuels, and the shaped coke made therefrom has in most cases only a moderate wear resistance.
  • U.S. Pat. 3,018,226 describes a process in which briquettes made from a mixture of caking bituminous coal and non-caking coal or coke and of pitch as a binder are carbonized by irst subjecting them to a heat shock so that the surfaces of the briquettes substantially immediately assume a temperature of between about 480 and 680 C., and the heating of the briquettes is continued so that the surface of the briquettes remains in that temperature range until the temperature has been equalized throughout the interior of the briquettes.
  • the briquettes are subsequently heated to temperatures in excess of 760 C. until the content of volatile constituents in the shaped coke article has been reduced to below 2%.
  • the briquettes may be heated with hot, inert gases or with fine-grained heat carriers and are preferably heated in the rst stage in a fluid-ized bed.
  • U.S. Pat. 3,018,227 describes a process of producing shaped coke articles in which briquettes made from a mixture of l0-35% by weight of a moderately caking bituminous coal, -45% by weight of coke produced in a fluidized bed, and 6-20% by weight of pitch, are rapidly heated to a temperature which is higher than the plastic range of the briquetting mixture but lower than 677 C. and are carbonized until the temperature has been equalized throughout each briquette, whereafter the briquettes are subjected to dry distillation at a higher temperature.
  • one aspect of this invention resides in the improved process of carbonizing pellets of the type referred to above by subjecting such to an initial sudden temperature rise for such a time that only the outermost layer of each pellet (briquette), which layer has a thickness of only a few millimeters, is rapidly heated above the plastic range of the coal mixture followed by subsequent resolidification.
  • the carbonization of the inside of each briquette must be carried out much 4slower and should suitably begin at a temperature which is lower than that which was used for the sudden heating of the surface layer.
  • the completion of carbonization of each briquette is carried out at a low rate of temperature rise and the end temperature at which the temperatures of the skin and core of each shaped article are equalized is below 600 C.
  • the briquettes which have thus been carbonized are subsequently subjected to dry distillation at temperatures up to 1000 C.
  • the highly different temperatures necessary in each of the several stages of the treatment according to this invention are achieved through the use of fine-grained solid, particulate heat carriers.
  • the process according to the invention is characterized by treating shaped carbonaceous articles in a first stage for two to ⁇ five minutes with a solid, particulate heat carrier which is heated to SOO-600 C. and moves concurrently with the shaped articles; treating the shaped articles in a second stage for 30-90 minutes with a solid, particulate heat carrier which moves countercurrent or transverse current with respect to the shaped articles and has an initial temperature of 40C-500 C., increasing to SOO-600 C., and finally treating the shaped articles in a third stage with a solid, particulate heat carrier which moves in a countercurrent or transverse current to the shaped articles and which has an initial temperature of S50-650 C., increasing to S50-1000 C.
  • the shaped articles consisting of briquettes or pellets are supercially carbonized in the rst stage lby being suddenly heated with heat carriers at a temperature of about 50G-600 C. s0 that the surfaces of the shaped articles are suddenly heated above the plastic range of the briquette mixture and then suddenly resolidiiied.
  • the resolidilication should be restricted to a depth of 1 to 3 millimeters.
  • the temperature of the heat carriers is reduced to about 450 C.
  • the temperature of the heat carriers is then slowly increased at a rate of 0.5-2 C. per minute until a temperature between 500 and 600 C.
  • the shaped articles When the shaped articles have been resolidiiied, they are subjected to dry distillation in the third stage while being heated to a temperature of 800-1000 C. at a rate of 3-10 C. per minute. It is desirable to heat the shaped articles at a lower rate first and at a higher rate thereafter. During this treatment, the shaped articles move preferably countercurrent or transverse current with respect to fine-grained solid heat carriers, which are at a temperatue of about S50-650 C. at the beginning and at a temperature of about 850-1000 C. at the end of their action on the shaped articles.
  • the ratio of the weight of the heat carriers to that of the shaped articles is about 2:1 to 4:1 in the first stage and should be sufficient to ensure that the soft, plastic briquettes are completely embedded in the solid, particulate heat transfer medium.
  • the ratio of the weight of the heat carrier to that of the shaped articles is in the range of about 3:1 to 6:1 so that a slow continuous temperature rise is carried out in this stage. A temporary plastic state of the shaped articles is accomplished in this range.
  • a ratio of the weight of the heat carrier to that of the shaped articles of about 1:1 to 2:1 is sufiicient.
  • the times and temperatures for and at which the treatment is carried out may be selected to influence the pore size and porosity of the carbonized product so as to obtain desired values of these parameters.
  • a treatment for a longer time generally reduces the pore size and porosity whereas the use of a temperature at the upper limit so that the time of the treatment is reduced will result in larger pores and a higher porosity.
  • the duration of the treatment and the upper temperature limit will be selected in each case dependant on the caking and expansion properties and the softening behavior of the coal-pitch mixture which is employed. These are determined experimentally for the individual coals and briquette mixtures used. It will be obvious that the carbonization of shaped articles having a higher weight per article will take more time than the carbonization of shaped articles having a lower weight per article.
  • the formation of proper pores is of great importance for the quality of a metallurgical coke.
  • the porosity is suitably between 40% and 50% and the pores should not be too ne. Fine pores tend to become clogged more easily by soot or the like so that they become ineffective. Large pores do not present a sufficiently large reaction area. Whereas the disadvantage of the large pores is compensated to some extent by a higher porosity, larger pores result in a lower bulk density and in most cases in a lower Wear resistance. For this reason it is important to form medium size pores in the shaped article as far as possible.
  • the porosity and pore size may also be influenced by the caking capacity of the coal mixture and by the proportion of admixed binder, such as tar pitch or petroleum bitumen.
  • the porosity is too large, it may be reduced by using a leaner coal mixture and/or by a pre-admixing of the binder.
  • the carbonization time may be reduced or a coal mixture having a higher caking capacity may be used and/or the proportion of admixed binder may be increased.
  • the caking capacity of the coal and the proportion of binder are suitably selected so that the shaped articles are subjected to temperatures in the range between about S50-600 C. for a time which is as short as possible, e.g., 30 minutes, so that the total time of the treatment is as short as possible and the carbonizing apparatus has a high throughput capacity.
  • shaped articles having a higher caking and expansion capacity than those used before can be carbonized and processed into a high-grade shaped coke.
  • the proportion of admixed non-caking coal or coke can be reduced, as is often desired.
  • the resulting shaped cake has internal stress cracks to a smaller extent and has a higher abrasion resistance. This is of great advantage particularly when the coke is to be used in a blast furnace.
  • coals having excessively high caking and expansion capacities are used in the process according to the invention it is desirable to use a leaner mixture because otherwise too long treatment times would be required particularly in the second stage. This would increase the capital and operating costs of the plant and reduce the overall economy thereof. For this reason, such coals should be made lean but they need not be so lean for being carbonized by the process according to the invention as in the processes known before.
  • a non-caking coal or a slightly caking coal or cokes of various kinds or origins may be admixed to form the material to be briquetted. In many cases, suitable coal is not available and it is often undesirable and less economical to produce in a separate -plant additionalcoke for use in making a lean mixture.
  • the fine-grained heat carrier consists preferably of sand having a particle size of 0.2-2 millimeters, preferably of 0.5-1.0 millimeter.
  • Other known particulate heating media which may be used include sillimanite, corundum, coke or the like.
  • the shaped articles may be advanced on a horizontal or inclined grate and the particulate heat carriers may ow downwardly through a layer of said shaped articles in a transverse current.
  • the temperatures and flow rates of the heat carriers may be selected so that the shaped articles can be subjected to carbonization and dry distillation in accordance with the invention in different portions of the overall length of the grate.
  • a bed which consists of sand, coke or the like and which is continuously or periodically iluidized may also be used in the first heating stage.
  • the treatment in all three heating stages according to the invention or in one or two of said stages may be alternatively carried out with the aid of hot inert gases in a shaft furnace.
  • This mode of operation requires a higher expenditure, cannot be supervised as easily and does not result in a shaped coke having as uniform good quality. For this reason, it is preferable to use fine-grained solid particulate heat carriers in the carbonizing treatment according to the invention.
  • a first rotary kiln 1 is used to treat briquettes in the first stage and a second rotary kiln 2 to treat the briquettes in the second and third stages.
  • Briquettes at a temperature of about C., are introduced at a rate of 1000 kilograms per hour into the first rotary kiln 1 through a conduit 3.
  • Sand at a temperature of 550 C. is introduced at the same time at a rate of 3000 kilograms per hour through a conduit 4 into the first rotary kiln 1.
  • the briquettes charged to the second rotary kiln 2 are heated while moving countercurrent to the sand and in the first half of the rotary kiln are treated with a mixture of the sand from conduits 6 and 8. This mixture has an initial temperature of 500 C.
  • the sand is cooled to 400 C. until it reaches that end of the rotary kiln where the briquettes are charged and leaves the second rotary kiln 2 also, through conduit 7.
  • the briquettes are slowly and continuously heated by the sand and in the middle of the rotary kiln have a temperature of 520 C. at their surface and of 480 C. in their interior. While the coal is thus treated in a plastic state, it is subjected to a slow dry distillation during 40 minutes without the occurrence of undesired ⁇ phenomena due to expansion or cracking.
  • Part of the sand which is discharged at 7 is heated to the temperature of 900 C. and is divided among conduits 3, 6 and 8, in which it is mixed with sand at a lower temperature.
  • the vapors and gases which are thus evolved are vented through a conduit 11.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
US855431A 1968-09-05 1969-09-04 Continuous process of producing shaped metallurgical coke Expired - Lifetime US3700564A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19681796129 DE1796129A1 (de) 1968-09-05 1968-09-05 Verfahren zur kontinuierlichen Erzeugung von metallurgischem Formkoks

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3838988A (en) * 1972-06-12 1974-10-01 Agency Ind Science Techn Method of manufacturing briquets and coke in the molded form with asphalt as the binder
US4169767A (en) * 1977-06-27 1979-10-02 Koa Oil Company, Limited Process for calcining coke
US4218288A (en) * 1979-02-12 1980-08-19 Continental Oil Company Apparatus and method for compacting, degassing and carbonizing carbonaceous agglomerates
US4233117A (en) * 1976-06-18 1980-11-11 Bergwerksverband Gmbh Manufacture of abrasion-resistant coke
US4269662A (en) * 1979-02-12 1981-05-26 Conoco, Inc. Apparatus for compacting, degassing and carbonizing carbonaceous agglomerates
US4764318A (en) * 1986-03-20 1988-08-16 Ruetgerswerke Aktiengesellschaft Process for the continuous coking of pitches and utilization of the coke obtained thereby

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3838988A (en) * 1972-06-12 1974-10-01 Agency Ind Science Techn Method of manufacturing briquets and coke in the molded form with asphalt as the binder
US4233117A (en) * 1976-06-18 1980-11-11 Bergwerksverband Gmbh Manufacture of abrasion-resistant coke
US4169767A (en) * 1977-06-27 1979-10-02 Koa Oil Company, Limited Process for calcining coke
US4218288A (en) * 1979-02-12 1980-08-19 Continental Oil Company Apparatus and method for compacting, degassing and carbonizing carbonaceous agglomerates
US4269662A (en) * 1979-02-12 1981-05-26 Conoco, Inc. Apparatus for compacting, degassing and carbonizing carbonaceous agglomerates
US4764318A (en) * 1986-03-20 1988-08-16 Ruetgerswerke Aktiengesellschaft Process for the continuous coking of pitches and utilization of the coke obtained thereby

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Publication number Publication date
GB1256576A (pt) 1971-12-08
DE1796129A1 (de) 1972-03-02

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