Results from atomization experiments and mathematical modeling of heavy fuel oil combustion in industrial furnaces are presented. A phase Doppler particle analyzer (PDPA) was used to characterize a heavy fuel oil spray supplied by an atomizer designed for glass melting furnaces. A unique calculation method for oil spray was developed to apply the results from the PDPA measurement as boundary inlet conditions for the computational fluid dynamics (CFD) simulation. Additional studies of the atomizer provided detailed in-flame measurements in a semi-industrial-scale glass melting furnace. The modeling results were compared with the measured in-flame data. The objective of this study was to improve the numerical simulation capabilities by incorporating atomizer-specific spray characteristics into a CFD program and to predict the effects of spray characteristics on the heavy fuel oil combustion.