Classifications

• • 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
  • C10B57/00—Other carbonising or coking processes; Features of destructive distillation processes in general
  • C10B57/04—Other carbonising or coking processes; Features of destructive distillation processes in general using charges of special composition
• • 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
  • C10B57/00—Other carbonising or coking processes; Features of destructive distillation processes in general
  • C10B57/08—Non-mechanical pretreatment of the charge, e.g. desulfurization

Definitions

• the present invention relates to coke used in blast furnace ironmaking and a method for producing the same and, in particular, relates to coke blended with ashless coal obtained by extraction treatment of coal with a solvent.
• Coke used in blast furnace ironmaking is required to have various properties, e.g., a certain level of mechanical strength such that coke is not easily crushed in the blast furnace, reactivity, an apparent density, and the size and distribution of lumps necessary to ensure gas permeability in the blast furnace.
• a certain level of mechanical strength such that coke is not easily crushed in the blast furnace
• reactivity such as an apparent density
• As the raw material for coke satisfying such requirements usually, hard coking coal, which is referred to as "coking coal”, is used, which has high quality with a caking property, fluidity, or degree of coalification in a certain range, and which is expensive coal compared with coal generally used as fuel for boilers.
• Such hard coking coal softens and melts at about 400°C to form a viscous liquid, fuse together, and swells by including gas.
• Low-rank coal such as non-coking or slightly coking coal
• ASP asphalt pitch
• HPC ashless coal
• Patent Literature 1 discloses a technique for coking in which ashless coal is added to coal including low-rank coal and describes that when ashless coal is added in an amount of 5% to 10%, high-strength coke can be obtained.
• Ashless coal has a higher fluidity than coking coal (unmodified coal). Therefore, coke has a very strong structure when a large amount of ashless coal is added, even if a large amount of low-rank coal is blended.
• coke used in a blast furnace is also required to be formed of large and uniform particles. When a large amount of ashless coal is added, small particles tend to be mixed in the resulting coke. For this reason, there is room for further improvement in Patent Literature 1.
• the present invention has been achieved in view of the problems described above. It is an object of the present invention to provide coke with uniform quality, composed of large particles and having sufficient strength, in which the blending amount of hard coking coal is reduced, and a method for producing the same.
• the present inventors have found that the particle size of coke is decreased by volume break. As a result of verification of the mechanism of occurrence of volume break, it has been conceived that addition of a large amount of ashless coal causes volume break. Accordingly, the present inventors have decided to optimize the amount of ashless coal added so that overall fluidity can be secured by coal.
• coke according to the present invention is obtained by carbonizing a coal mixture including coal and 2% to 8% of ashless coal composed of a solvent-soluble component of coal, characterized in that the coal mixture has a maximum fluidity MF value (log (ddpm)) of 1.8 to 3.0.
• a method for producing coke according to the present invention includes a mixing step in which 2% to 8% of ashless coal is mixed with coal to obtain a coal mixture having a maximum fluidity MF value (log (ddpm)) of 1.8 to 3.0, and a carbonization step in which the coal mixture is carbonized.
• coking coal is selected on the basis of the average maximum fluidity value that can be calculated in advance and is blended and mixed with ashless coal in the mixing step, and the coal mixture is carbonized in the carbonization step.
• coke according to the present invention sufficient strength and particle size can be achieved while reducing raw material costs. Furthermore, in the method for producing coke according to the present invention, ashless coal can be produced, for example, from low-rank coal, and thus, raw material costs can be reduced. Furthermore, it is possible to produce coke with sufficient strength and particle size uniformly, regardless of the position inside the coke oven, by a simple production method.
• the coke according to the present invention is fed into a blast furnace for producing pig iron, and is obtained by carbonizing a coal mixture including coal and ashless coal under the general conditions as described later.
• Coal and ashless coal which are raw materials for coke, will be described below.
• one type or two or more types of coal having a quality which makes it possible to set the average maximum fluidity MF value of the mixture of coal and ashless coal to be within a specific range are used.
• low-rank coal classified as weakly coking coal or non-coking or slightly coking coal, which is difficult to use alone as a raw material for coke is used
• hard coking coal or semi-hard coking coal which is commonly used as a raw material for coke is combined for use.
• the low-rank coal refers to coal having a maximum fluidity MF value (log (ddpm)) of 2.0 or less and an average maximum reflectance Ro value of 1.1 or less.
• the maximum fluidity MF value represents thermal fluidity
• the average maximum reflectance Ro value represents the degree of coalification.
• weakly coking coal and non-coking or slightly coking coal can be blended at a blending ratio (including ashless coal) of about 50% at maximum, on the dry coal basis.
• dried coal may be produced by air drying or the like, coal in the state of containing moisture may be mixed with ashless coal and subjected to carbonization.
• the coal is preferably in a pulverized form, and specifically, 80% or more of particles of the coal have a diameter of 3 mm or less.
• the particle diameter refers to the maximum length of the particle.
• the expression "80% or more of particles have a diameter of 3 mm or less” means that "80% or more of the particles of coal pass through a sieve with an opening of 3 mm".
• the coal with a particle size of 3 mm or less means powder or particles which, when pulverized coal is screened with a sieve (metal wire sieve, standard number JIS Z 8801-1(2006)) with an opening of 3 mm or less, pass through the sieve.
• Such coal may be pulverized in advance or pulverized while being mixed with ashless coal, which will be described in detail when the production method is described.
• Ashless coal is a type of modified coal obtained by modifying coal for the effective utilization of resources, and has been developed for efficient use as fuel.
• Ashless coal is modified coal obtained by removing ash and insoluble coal components as much as possible from coal, and is produced by a method in which, by subjecting coal to extraction with a solvent having a high affinity for the coal, an extract from which insoluble components, such as ash, are separated is obtained, and the solvent is removed from the extract by distillation or evaporation.
• Such ashless coal can be produced by a known method (for example, refer to Japanese Patent No. 4045229 ). Consequently, ashless coal does not substantially contain ash, and contains large amounts of organic substances which are soluble in the solvent and which have softening and melting properties.
• ashless coal has a wide molecular weight distribution ranging from a component with a relatively low molecular weight having two or three fused aromatic rings to a component with a high molecular weight having about five or six fused aromatic rings. Furthermore, ashless coal is dewatered in a state of mixture (slurry) of coal and the solvent before extraction and separation. Therefore, the moisture content is decreased to about 0.2% to 3% by mass, and ashless coal has a sufficient calorific value. Accordingly, ashless coal has a high fluidity under heating, and generally melts at 200°C to 300°C (has softening and melting properties) regardless of the grade of coal used as a raw material.
• ashless coal is preferably in a pulverized form with a size as small as possible, and specifically, the diameter (maximum length) is preferably 1 mm or less.
• ashless coal since ashless coal has a high volatile content, excellent thermal fluidity, and a high caking property, it can compensate the caking property of low-rank coal, such as weakly coking coal or non-coking coal. Furthermore, since ashless coal starts to flow at a temperature lower than that of coking coal, by adding and dispersing ashless coal into coal, ashless coal bonds coal particles together uniformly in the coke oven, including at the central portion of the oven in which the temperature rise is slow, in the carbonization process. Furthermore, since ashless coal has a higher swelling property than coking coal, even in the lower part of the coke oven in which a large load is applied, particles of ashless coal swell and spaces between coal particles are filled.
• ashless coal generates swelling pressure, thus bonding other coal particles together.
• occurrence of defects such as poor adhesion between coal particles (macrocracks) and excessive swells (coarse pores), which may act as starting points for breakage of coke, can be reduced, and it is possible to suppress variations in quality in the width and height directions in the coke oven.
• the content (blending ratio) of ashless coal in the mixture of ashless coal and coal (coal mixture, coal charge) is less than 2%, it is not possible to sufficiently obtain a caking property required in the case where low-rank coal is blended or the advantageous effects described above. Therefore, the content of ashless coal is set at 2% or more, preferably, 3% or more.
• ashless coal is produced by modifying inexpensive low-rank coal in many cases. Therefore, it is believed that, in coke (carbon) formed using such coking coal having a low degree of coalification, crystal growth is small (the breadth or thickness of the carbon network structure is small) compared with carbon derived from hard coking coal or the like having a high degree of coalification. Furthermore, as the amount of ashless coal increases, the continuous phase of ashless coal in coke increases, and when the continuous phase becomes excessive, the continuous phase itself may act as a starting point for breakage. Furthermore, in addition to volume break, breakage of coke also includes surface breakage. In the drum strength (DI) mainly used as the index for strength of coke, volume break is unlikely to be indicated.
• DI drum strength
• the content of ashless coal is set at 8% or less, preferably 6% or less. In such a manner, in the coke according to the present invention, the content of ashless coal is reduced to a certain level or less, and strength is secured by the original caking property of coking coal (coal) to some extent.
• the maximum fluidity MF value of the mixture of coal and ashless coal is set at 1.8 or more, preferably 2.0 or more.
• the maximum fluidity MF value of the mixture of coal and ashless coal is set at 3.0 or less, preferably 2.6 or less.
• the maximum fluidity MF value of the mixture of coal and ashless coal is defined as the value measured on the mixture, and can be measured by the Gieseler plastometer method in accordance with JIS M8801. However, in the case where the maximum fluidity MF value for each of various types of coal and ashless coal is known, approximate calculation may be performed by multiplying the blending ratio (mass%/(100%)) and summing up.
• the average maximum reflectance Ro value of the mixture of coal and ashless coal is preferably 0.95 or more, more preferably 1.0 or more.
• the maximum reflectance Ro value increases as the amount of high-rank coal, such as hard coking coal, increases, and hard coking coal has a high swelling property.
• the average maximum reflectance Ro value of the mixture of coal and ashless coal is preferably 1.3 or less, more preferably 1.2 or less.
• the method for producing coke according to the present invention includes a mixing step in which ashless coal is mixed with coal, and a carbonization step in which the coal and the like are carbonized. The individual steps will be described below.
• coal and ashless coal are mixed to obtain a coal mixture.
• the blending ratio and the maximum fluidity MF value of the coal mixture are as described above.
• these coals are simultaneously pulverized. Since coal has lower pulverizability than ashless coal, as described above, when 80% or more of particles of coal are pulverized to a diameter of 3 mm or less, ashless coal is pulverized to particles with a diameter of 1 mm or less at the same time.
• coal and ashless coal are fed through a hopper into a known mixer, and stirring is performed while pulverizing by an ordinary method. Thereby, secondary particles of ashless coal are easily pulverized and coal is also pulverized. Note that the procedure and method of mixing are not particularly specified, and for example, ashless coal and coal which are pulverized in advance may be mixed.
• the conditions for carbonization are not particularly limited, and usual carbonization conditions in the coke production using a coke oven can be employed.
• the coal mixture is charged into a chamber oven, in which about 30 tons can be charged through a charging hole, and carbonization is performed.
• the bulk density is set at 730 kg/m 3 or more.
• insufficient strength due to the low fluidity can be compensated to some extent.
• the bulk density is preferably set at 750 kg/m 3 or more.
• the carbonization is performed under the conditions at a temperature of preferably 950°C or higher, more preferably 1,000°C or higher, and preferably 1,200°C or lower, more preferably 1,050°C or lower, for a time of preferably 8 hours or more, more preferably 10 hours or more, and preferably 24 hours or less, more preferably 20 hours or less.
• ashless coal was produced in a Hyper-coal continuous production facility (Bench Scale Unit) by the method described below.
• the ashless coal was pulverized such that 100% (all) of the ashless coal had a particle size (maximum length) of 3 mm or less.
• the ashless coal and various types of coal shown in Table 1 were each adjusted to a moisture content of 7.5% by mass, and mixed at the blending ratio shown in Table 2, on the dry coal basis.
• the maximum fluidity MF values (log (ddpm)) of coal and ashless coal shown in Table 1 were measured by the Gieseler plastometer method in accordance with JIS M8801.
• the average maximum reflectance Ro value was measured in accordance with JIS M8816.
• the maximum fluidity MF values and the average maximum reflectance Ro values were calculated from the blending ratios of various types of coal and ashless coal, which are shown in Table 2.
• 100% of coal was pulverized so as to have a particle size of 3 mm or less and the pulverized coal was mixed.
• the mixture (coal charge) was placed inside a retort made of steel, and by applying vibration to the retort, the bulk density was adjusted to the value shown in Table 2. Then, the retort was placed in an electric furnace of a both-side heating type, and the mixture was subjected to carbonization under a nitrogen stream, thereby forming a sample. The carbonization was performed under conditions in which the temperature was raised at 3°C/min, heating was performed at 1,000°C for 20 minutes, and then, the retort was taken out of the electric furnace and left to cool naturally. Furthermore, as an evaluation reference, a sample (No. 20) was produced using coal having a high maximum fluidity MF value in which non-coking coal was not blended and ashless coal was not added.
• the drum strength index DI 150 15 is shown in Table 2. Specifically, in accordance with JISK2151, the sample was rotated in a drum for 150 revolutions, then screened using a sieve with an opening of 15 mm, and the weight ratio of the remaining portion was calculated. The acceptability criterion for strength is set to DI 150 15 of 84.8% or more. Note that the coke strength was measured using samples whose particle size distribution had been measured by the method described later.
• Coke was dropped twice using shatter equipment, and was subjected to impacts of 30 revolutions using a drum tester.
• the particle size distribution was measured using sieves with square openings of 100, 75, 50, 38, 25, and 15 mm.
• the average particle size was calculated from the formula (1) below. Note that no samples remained over the sieve with a square opening of 100 mm.
• the calculated average particle size is shown in Table 2.
• the acceptability criterion is set at an average particle size of 45.0 mm or more.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Chemistry (AREA)
• Coke Industry (AREA)

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• 2012
  • 2012-07-06 JP JP2012152145A patent/JP2014015502A/ja active Pending
• 2013
  • 2013-06-28 WO PCT/JP2013/067936 patent/WO2014007184A1/ja active Application Filing
  • 2013-06-28 KR KR20147036467A patent/KR20150021543A/ko not_active Application Discontinuation
  • 2013-06-28 CN CN201380035619.XA patent/CN104428398A/zh active Pending
  • 2013-06-28 EP EP13813557.9A patent/EP2871226A4/de not_active Withdrawn
  • 2013-07-05 TW TW102124182A patent/TWI504738B/zh not_active IP Right Cessation

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