Coal Blending Theory-Retrospect and Prospect

Abstract

SynopsisThis paper summarizes a series of experimental studies conducted by the author et al., on coal blending theory which is a basic condition for the production of coke. A brief history is given of the condition of coking coal supply and past studies undertaken in Japan ranging from the establishment of basic concepts of coal blending in the period immediately after World War II to recent trends in the search for blending standards aiming at the improvement of hot properties of coke. The essential point in coal blending is to obtain uniform, strong-textured coke as a composite material by an optimum combination of various grades of coal having different heating properties, i.e., thermal transformation temperatures. With the above-mentioned in mind, the paper describes the classification of single coal on the basis of the blending theory, the estimation of coke strength, and the theory for size control of coal charge. Finally, the relation among coal blending, coke texture, reactivity with C02, and strength after the reaction with C02 is described, indicating the importance of future efforts for the improvement of hot properties of coke by the addition of caking additive.

A Novel Measurement Method for Coal Thermoplasticity: Permeation Distance

“…[1][2][3] In particular, Gieseler plastometer method and dilatometer test standardized by JIS M8801 have long been used for measuring the caking properties and finally controlling coke strength. [4][5][6] For example, Miyazu et al shows that Gieseler maximum fluidity (MF) of coal blend should be more than 200 ddpm to make high strength coke.…”

“…[1][2][3] In particular, Gieseler plastometer method and dilatometer test standardized by JIS M8801 have long been used for measuring the caking properties and finally controlling coke strength. [4][5][6] For example, Miyazu et al shows that Gieseler maximum fluidity (MF) of coal blend should be more than 200 ddpm to make high strength coke. 4) However, the effect of excessive MF on coke strength has not been clarified because high fluidity coal is thought to act as a binder in a coal blend to produce high strength coke while high fluidity coal produces highly-porous structure which leads fragile coke in case that the coal alone is carbonized.…”

“…[4][5][6] For example, Miyazu et al shows that Gieseler maximum fluidity (MF) of coal blend should be more than 200 ddpm to make high strength coke. 4) However, the effect of excessive MF on coke strength has not been clarified because high fluidity coal is thought to act as a binder in a coal blend to produce high strength coke while high fluidity coal produces highly-porous structure which leads fragile coke in case that the coal alone is carbonized. Nomura et al shows that high strength coke needs a certain level of product of bulk density and "specific dilatation volume" which is defined as the volume of expanded coal per unit mass and measured by dilatometer test.…”

Effective Utilization Technique for Coal Having High Maximum Fluidity and Long Maximum Permeation Distance by Weathering Processing

“…Because higher MF means basically greater caking property. 4) In addition, it was reported that shorter maximum permeation distance in same MF levels becomes higher coke strength. 2) Therefore, maintaining MF and reduction of maximum permeation distance of coal should be the most ideal upgrading by weathering processing.…”

“…Maximum fluidity (MF), which is measured by Gieseler plastometer method (conventional method, JIS M 8801 3) ) has been widely used as a caking index in cokemaking industry. 4) However, it has been pointed out that the conventional method has some problems in the measurement 5) and MF rarely has unclear relationship with coke strength. 6) In our previous study, 2) a new measurement method named as "permeation distance method" was developed in order to overcome the problems of conventional method and supplement the conventional evaluation of coal thermoplasticity.…”