Determining the electrical resistivity of coke powder

In order to improve means of determining the electrical resistivity of coke powder, existing methods are analyzed. Their basic deficiency is that it is difficult to identify and eliminate the influence of transient electrical resistance between the electrodes and the coke-powder sample, because it is impossible to ensure constant packing density of the powder column at constant pressure. Therefore, to eliminate fluctuations in the transient resistance, constant packing density of the sample is required. That may be ensured if the pressure varies over the sample. The influence of transient resistances on the measurement result may be eliminated by improving the pressing system and constructing a two-probe cell and also by replacing the potentiometer, milliammeter, voltmeter, rheostat, and battery with an up-to-date measuring module. Recommendations for improvement in the apparatus and method used in determining the resistivity of coke are developed, for use in a prototype system. In improving the resistivity determination, the constant parameters are the sample mass; the volume of the sample (and hence its density); and the current passing through the sample. The variable is the pressure applied to the coke sample. A method of determining the electrical resistivity of coke powder is developed, and three improved systems are created. Two undergo industrial tests at PAO Zaporozhkoks and ChAO Makeevkoks. The tests confirm the known dependence of the resistivity on the final coke temperature (in the range 900–1150°C) and the possibility of using the resistivity in judging the condition of the coke and correcting the coking temperature of the batch. Since the final coking temperature determines the size and strength of the coke particles, other conditions being equal, the condition of the coke (its readiness for use) may be assessed on the basis of a set of physicochemical characteristics.