Method for manufacturing coke, coke, and method for evaluating homogeneity of coal blend

A method for evaluating homogeneity of a coal blend and manufacturing coke comprising:

• blending two or more coal brands to prepare the coal blend;
• stirring and mixing the coal blend to disintegrate at least a part of pseudo-particles that have been formed by agglomeration of coal particles in the coal blend, wherein a mixing apparatus is used in the stirring and mixing step, the mixing apparatus having a capability of controlling a degree of mixing of the coal blend to be 0.85 or more at 60 seconds after start of a mixing operation, the degree of mixing being calculated by the following equation (1):
• degree of mixing=(σC0−σC)/(σC0−σCf) (1)
• where the degree of mixing is a value calculated from the standard deviations of characteristic values which are respectively determined as follows:
• σC0 denotes the standard deviation of characteristic values when mixing is not performed at all,
• σCf=0, and
• σC denotes the standard deviation of characteristic values of samples taken from the mixed coal blend;
• taking samples from any positions of the coal blend before and after the stirring and mixing step;
• determining a characteristic value of each of the samples;
• calculating the degree of mixing from the standard deviations of characteristic values which are respectively determined for the samples having a value of (σC0−σCf)/Cave of 0.40 or more, where Cave is a weighted average characteristic value of the coal blend;
• evaluating the homogeneity of the coal blend on the basis of the degree of mixing which is calculated by the above equation (1);
• and
• charging the stirred and mixed coal blend into a coke oven to carbonize the stirred and mixed coal blend to form the coke.