Coal mixture, method for manufacturing coal mixture, and method for manufacturing coke

A coal mixture comprising:

• large-permeation-distance coal;
• and
• permeation-distance-decreasing coal,
• wherein:
• a mass fraction of the permeation-distance-decreasing coal in the coal mixture is in a range derived by multiplying a mass fraction of the large-permeation-distance coal by 0.25 or more and 3.0 or less,
• the permeation-distance-decreasing coal has a mean maximum vitrinite reflectance Ro of 1.25% or more and a total inert amount TI of 30 vol. % or less,
• the permeation-distance-decreasing coal makes a permeation distance of a 1:1 coal mixture of the permeation-distance-decreasing coal and the large-permeation-distance coal smaller than or equal to a value calculated by multiplying a weighted average value by a constant 0.67, the weighted average value being calculated from permeation distances of the large-permeation-distance coal and the permeation-distance-decreasing coal at a mass ratio of 1:1 thereof,
• the large-permeation-distance coal has a permeation distance (mm) that is determined by the following steps:
• placing a material having through-holes penetrating from an upper surface to a lower surface of the material on the top of a coal sample packed in a container;
• heating the coal sample to permeate into the through-holes;
• and
• determining a distance over which the coal permeates into the through-holes as the permeation distance (mm), and
• the permeation distance (mm) of the large-permeation-distance coal is more than a value of criteria permeation distance derived by using the following equation [II]:
• criteria permeation distance=a′×log MF+b [II],
• where MF is the Gieseler maximum fluidity (ddpm) of the coal,
• a′ is a constant defined as a coefficient of the common logarithm log MF of a Gieseler maximum fluidity MF multiplied by a value in the range of 0.7 or more and 1.0 or less, when a regression line that passes through the origin is drawn based on data sets of the determined value of permeation distance (mm) and log MF of at least one of coal brands having a log MF of less than 2.5, and
• b is a constant defined as a value equal to or more than the average value of the standard deviation of permeation distance and equal to or less than a value derived by multiplying the average value by 5, when determination is performed plural times for the same sample of one or more kinds of coal selected from among the coal brands which are used for deriving the regression line.

A coal mixture comprising:

• large-permeation-distance coal;
• and
• permeation-distance-decreasing coal,
• wherein:
• a mass fraction of the permeation-distance-decreasing coal in the coal mixture is in a range derived by multiplying a mass fraction of the large-permeation-distance coal by 0.25 or more and 3.0 or less,
• the permeation-distance-decreasing coal has a mean maximum vitrinite reflectance Ro of 1.25% or more and a total inert amount TI of 30 vol. % or less,
• the permeation-distance-decreasing coal makes a permeation distance of a 1:1 coal mixture of the permeation-distance-decreasing coal and the large-permeation-distance coal smaller than or equal to a value calculated by multiplying a weighted average value by a constant 0.67, the weighted average value being calculated from permeation distances of the large-permeation-distance coal and the permeation-distance-decreasing coal at a mass ratio of 1:1 thereof, and
• the large-permeation-distance coal has a permeation distance (mm) of 15 mm or more, the permeation distance being determined by the following steps (1) to (4):
• (1) preparing a coal sample by pulverizing coal so that particles having a particle diameter of 2 mm or less constitute 100 mass % of the coal sample and packing the pulverized coal into a container so that a bulk density is 0.8 g/cm3 and a layer thickness is 10 mm,
• (2) placing glass beads having a diameter of 2 mm on the top of the coal sample so that the thickness of a glass bead layer is more than or equal to a permeation distance;
• (3) heating the coal sample from room temperature to a temperature of 550° C. at a heating rate of 3° C./min in an inert gas atmosphere with a load of 50 kPa being applied to the top of the glass bead layer so that the coal sample melts and permeates into the glass bead layer, and
• (4) determining the permeation distance (mm) of the coal sample which has permeated into the glass bead layer.