Gas solid riser reactors find application in fluid catalytic cracking, combustion etc. Scale up and design of such systems pose great challenge. Computational fluid dynamics (CFD) modeling offers the advantage in ease of evaluating various operating and design parameters with fewer requirements of extensive physical experiments. Eulerian - Eulerian approach is the most commonly used approach in modeling these flows. It requires appropriate specification of drag coefficient for interphase momentum coupling. Conventionally employed drag relations, based on packed bed or minimum fluidization conditions, needs correction functions to predict the observed increased slip velocity in riser flows. Newer energy minimization multiscale model predicts effective drag coefficient of riser flow based on multi scale approach. The present work explores the usefulness of extended EMMS model in developing drag coefficient correction factors for high solid flux riser flows. Evaluation was done by comparison with available literature data on pressure drop and/or solid holdup. The Eulerian – Eulerian two-fluid model was also used to study the salient features of the gas solid riser flows for a varied set of operating conditions. User defined subroutines has been employed to render the boundary periodic and mimic fully developed flow profiles. The effect of gas density, particle size and particle classification has been investigated and conclusions drawn accordingly.