Previous works have reported cyclone dimensions to have an influence on MEIV. The MEIV obtained by Wang et al.
In short, the data obtained in earlier investigations on the MEIV of the cyclone for oil shale ash are not sufficient for its optimization.
It can be observed from Figure 3a that MEIV increases with increasing KA when the cyclone diameter remains unchanged.
Equation (1)  and Equation (2) , were used to predict the MEIV of experimental oil shale ash cyclones.
It can be seen from Table 2 that the MEIV obtained from Equation (1) decreased with increasing KA, in contrast to the result obtained by Equation (2) and the experimental data.
The MEIV values of experimental oil shale ash cyclones predicted from Equation (3) are also given in Table 2.
Based on the experimental MEIV, the maximum efficiency cross-sectional mean axial gas velocity (MECMAGV) in the cyclone body can be obtained.
During experiments on cyclones in series, it is necessary to calculate the MEIV of each cyclone stage based on cyclone dimensions to ensure its operation close to MEIV.
It should be noted that the MEIV of the cyclone increases when the gas viscosity is increased or the gas density decreased due to the rise in temperature.
The results showed that the MEIV of the cyclone for oil shale ash was 15 m/s, and for FCC fine catalyst, 23 m/s.
The balance between these opposite effects results in the phenomenon of MEIV. Because of the significant difference in particle geometry and thus in drag coefficient between oil shale ash and FCC fine catalyst, the inlet velocity producing the balance between the above effects for oil shale ash is smaller than that for FCC fine catalyst, as observed in our experiment.