Abstract
A method for the determination of the plastic properties of coal using a constant torque Gieseler Plastometer is very useful to evaluate the metallurgical coals. But the most weak point of this method has been considered as the insufficient reproducipility between different laboratories.
Therefore, we studied on the standarization of the Gieseler Plastometer and the behavior of coals in the plastic stage using standard substance and retort made of acrylonitoril resin or quartz-glass.
Informations obtained are as follows
1. It is possible to improve the reproducibility using some standard substance, for example, Polybutene NO.2 or No.3 which is considerable as newtonian fluid, for calibrating each apparatus.
2. Using the standard substance of polybutene, it is recognized that the relations between fluidity (F), torque (Tq) and viscosity (η) are described by the following equation:
F=K0η (Tq-Tqs) α
where α=1, F <5000 ddpm
α>1, F>10000 ddpm
K0 is coefficient determined shape of the rabble arms and retorts. Tqε is the loss of the torque caused of the mechanical friction.
Therefore, for the purpose of calibration of the apparatus, it may be necessary to prescribe the values of K0 and Tqε.
3. Weissenberg effect is observed in the plastic stage of high fluidity coals (ex. domestic coals), that is, hollow space is found inside of the retort.
From these observation, it may be concluded that the reinvestigation of the method is necessary for the high fluidity coals.
