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EP-4737535-A1 - COKE PRODUCTION METHOD

EP4737535A1EP 4737535 A1EP4737535 A1EP 4737535A1EP-4737535-A1

Abstract

Provided is a new index for biomass-derived raw material that can replace a portion of coal used in the production of coke for blast furnaces, and a means for producing high-strength coke even when biomass-derived raw material is blended with coal. In a mass distribution of surface tension measured for carbonized biomass to be blended into a coal blend for coke production, a proportion of the carbonized biomass having a value of surface tension equal to or greater than a lower limit value γ min is 60 mass% or more of the total, and volatile content of the carbonized biomass on a dry basis is 4.0 mass% or more.

Inventors

  • KAWAI, YUYA
  • DOHI, YUSUKE
  • TAKASHIMA, TAKANORI
  • IGAWA, DAISUKE

Assignees

  • JFE Steel Corporation

Dates

Publication Date
20260506
Application Date
20240425

Claims (8)

  1. A method of producing coke, the method comprising: dry-distilling a mixture obtained by blending a defined proportion of a coal blend for coke production with carbonized biomass produced by heat-treating biomass, wherein, in a mass distribution of surface tension measured for the carbonized biomass, a proportion of the total carbonized biomass having a value of the surface tension equal to or greater than a lower limit value γ min is 60 mass% or more, and volatile content of the carbonized biomass on a dry basis is 4.0 mass% or more.
  2. The method of producing coke according to claim 1, wherein the lower limit value γ min of the surface tension is greater than a mass average value γ ave in a mass distribution of surface tension measured for a sample obtained by heating the coal blend up to a softening and melting temperature.
  3. The method of producing coke according to claim 1, wherein the lower limit value γ min of the surface tension is greater than 35.0 ± 3.0 mN/m, which is a mass average value in a mass distribution of surface tension measured for a sample obtained by heating the coal blend to 450 °C.
  4. The method of producing coke according to claim 1, wherein the lower limit value γ min of the surface tension is equal to 38.2 mN/m.
  5. The method of producing coke according to any one of claims 1 to 4, wherein the defined proportion of the carbonized biomass in the mixture is 1.0 mass% or more and 8.0 mass% or less.
  6. The method of producing coke according to any one of claims 1 to 5, wherein the biomass that is a raw material of the carbonized biomass contains at least one of palm kernel shells or woody biomass.
  7. The method of producing coke according to any one of claims 1 to 6, wherein measurement of the mass distribution of the surface tension for the carbonized biomass is carried out by a film flotation method.
  8. The method of producing coke according to any one of claims 1 to 7, wherein a proportion of the carbonized biomass having a particle size of 3.0 mm or less is 70 mass% or more, and a proportion of the coal blend having a particle size of 3.0 mm or less is 70 mass% or more.

Description

TECHNICAL FIELD The present disclosure relates to a method of producing coke using biomass as a portion of raw material. BACKGROUND Coke is a mainly carbon agglomerate product obtained by dry-distilling coal. Blast furnace coke used in a blast furnace functions as a heat source and a reducing agent, and also as a support material that secures gas permeability and liquid permeability inside the blast furnace. Therefore, in order to secure stable operation of the blast furnace, the agglomerate coke is required to have sufficient mechanical strength. In the production of blast furnace coke, a coal blend in which multiple types of coal are blended in a defined proportion is used. The coal blend is dry-distilled at a temperature of 1000 °C or higher either as is or after being molded, to obtain agglomerated coke in which coal particles are bonded together. By using a type of coal called caking coal, which has a property of easily softening and melting, as a portion of the coal blend, it is possible to obtain coke that has high strength. Two types of measured values of coal have conventionally been used as indices for managing coke strength. One is an average maximum reflectance of vitrinite (hereinafter referred to as "Ro") as specified in Japanese Industrial Standard M 8816:1992 "Solid mineral fuels - Methods of microscopical measurement for the macerals and reflectance". The higher the Ro value of coal, the higher the degree of carbonization and the stronger the coke matrix tends to be. The other is maximum fluidity according to a Gieseler plastometer (hereinafter referred to as "MF"), as specified in Japanese Industrial Standard M 8801:2004 "Coal-testing methods". The higher the MF value of coal, the more the coal tends to soften, melt, and flow when heated. Patent Literature (PTL) 1, previously filed by the applicant, describes that when selecting a combination of coal types to constitute a coal blend, coal before blending is heated to 500 °C, cooled, and ground, and a measured value of surface tension of the powder is used as a new index. According to this, when coal powders having a small difference in weighted average values of surface tension are combined, the strength of the resulting coke is higher than when coal powders having a large difference in the weighted average values of surface tension are combined. In recent years, societal efforts to mitigate the impact of global warming by decreasing carbon dioxide emissions into the atmosphere, one of the greenhouse gases, have been accelerating. For this reason, studies are underway to replace a portion of the coal used to make coke with carbon-neutral raw material such as biomass. For example, in PTL 2, a method of producing coke is described in which woody biomass material that has been heat-treated at a temperature higher than 300 °C and 400 °C or less is mixed with coal and dry-distilled in a coke oven. Further, in PTL 3, a method of producing highly reactive blast furnace coke is described, in which biomass is heated to 1000 °C or higher to pyrolyze the biomass, and the resulting solid biomass char having a diameter of 1 mm or less is added to a coal blend. CITATION LIST Patent Literature PTL 1: WO 2013/145680 AlPTL 2: JP 2005-272569 APTL 3: JP 2014-077086 A Non-Patent Literature NPL 1: M.C. Williams and D.W. Fuerstenau, "A Simple Flotation Method for Rapidly Assessing the Hydrophobicity of Coal Particles", International Journal of Mineral Processing, Vol. 20, No. 1-2, Netherlands, June 1987, p.153-157. SUMMARY (Technical Problem) When attempting to replace a portion of the coal used to make coke with a biomass-derived raw material, even a small substitution ratio can significantly decrease the strength of the resulting coke. Conventionally, Ro and MF, which are effective indices for managing the strength of coke, are both indices for measurement of coal. Therefore, when attempting to measure Ro and MF for a sample consisting only of biomass-derived raw material, the properties of coal and biomass are significantly different, and therefore it is either impossible to carry out the measurements, or even if the measurements could be carried out, the measured values are not appropriate for use as indices for managing the strength of coke including biomass-derived raw material. Further, the surface tension previously proposed by the applicant as a new index is an index based on the weighted average value of the surface tensions measured individually for coals that soften and melt when heated to 500 °C. However, biomass does not soften or melt when heated. For this reason, surface tension alone cannot be used as an index for managing the strength of coke containing biomass-derived raw material. Therefore, a new index is needed to manage the strength of coke containing biomass-derived raw material. In view of the problems described above, it would be helpful to provide a new index for biomass-derived raw material that can replace a portion of the coal used