Auxiliary fuel injection into the air blast benefits blast furnace operation by reducing coke consumption and carbon dioxide emissions, stabilizes process, and increases productivity. Heavy oil is a side stream product of petrochemical industry and it is used to replace part of the coke. Atomization of the heavy oil and mixing it with the air blast is one of the main challenges that limit high injection rates. The aim of this work is to develop CFD model of the raceway-tuyere area of the blast furnace that provides knowledge about droplet sizes and mixing behavior of the heavy oil with air blast. Atomization of the heavy oil is modeled with Wave Breakup Model, where breakup time and droplet size constants have been adjusted and validated using experimental results from physical set-up. CFD models based on the physical set-up and the actual blast furnace were made. Wave Breakup Model coupled with the CFD has good agreement with the experimental study in physical set-up. Further, CFD model is applied to study the actual blast furnace with heavy oil injection. The droplet volume median diameters in a function of the dimensionless air blast velocity are consistent in both cases having valid dynamic similarity. Mixing between the air blast and the heavy oil is poor without nozzle and most of the liquid mass is concentrated in the center of the air blast. With increasing the air blast velocity mixing gets poorer. According to modeling work, improved mixing and atomization was achieved with alternative nozzle geometries used in the tip of the oil lance.