Assessing coke readiness

An article by Rubchevskii and his colleagues on the assessment of coke readiness in terms of its electrical resistivity is discussed [1]. It is shown that the assessment of coke readiness on the basis of the yield of volatiles is incorrect and that the article does not adequately analyze existing methods for the assessment of coke readiness, such as expert evaluation; the APIR-S system for measuring the surface temperature of the discharged coke cake; the difference in the yield of volatiles for coke breeze and coke (ΔVdaf); two-probe measurement of the resistivity; monthly temperature measurements in the heating channels and correction of the coking temperature; and temperature measurement over the length of the boundary walls. The assessment of coke readiness on the basis of ΔVdaf, by the method employed at OAO EVRAZ NTMK, is shown to be effective. The various systems for measurement of the coke resistivity that are promoted in the article are unsuitable for coke-plant laboratories. The UESMETR-31 system (for monolithic samples) is very massive (~20 kg). The UESP-2 system for measuring the resistivity of powder, which is again quite massive (~15 kg), is the best suited to the assessment of coke readiness. However, its use is hindered by the enormous cost (200000 hryvnia) and various other defects mentioned in the article [1]. The comparative analysis of its performance in the article seems promotional rather than rigorous. Measurement of the resistivity of carbon powder (particle size 0.315–0.400 mm) in accordance with State Standard GOST 4668–75 requires the UESP-1 system, which consists of a complex set of devices and instruments. The conclusion reached is that coke’s yield of volatiles, which is the traditional characteristic used to assess its readiness, is no longer applicable for current coke ovens, as shown conclusively in [8–10]. For example, with temperature variation in the axial plane of the coke cake in the range 940–1290°C (five cases), the coke’s yield of volatiles Vco daf is consistently low: 1.1, 1.0, 1.0, 1.0, 0.9 [10]. This is confirmed by data on the constant mass yield of volatiles with change in the coking period and the coke readiness [2, Table 4]. A comparison in [1] shows that measurement of the resistivity in accordance with State Standard GOST 4668–75 and its measurement by the authors’ method are equivalent means of assessing the coke readiness. © 2015, Allerton Press, Inc.