Grate-firing is one of the main technologies currently used for biomass combustion for heat and power production. However, grate-firing is yet to be further developed, towards a better technology for biomass combustion, particularly towards higher efficiency, lower emissions, and better reliability and availability. To better understand grate-firing of biomass and to establish a reliable but relatively simple Computational Fluid Dynamics (CFD) modeling methodology for industrial applications, biomass combustion in a number of different grate boilers has been measured and modeled. As one of the case studies, modeling effort on an 88 MW grate-fired boiler burning wheat straw is presented in this paper. Different modeling issues and their expected impacts on CFD analysis of the kind of grate boilers are discussed. The modeling results are compared with in-flame measurements in the 88 MW boiler, which shows an acceptable agreement. The discrepancies are analyzed from different aspects. The lessons learned and experience gained from this and other case studies are summarized and discussed in detail, which can facilitate the modeling validation effort as well as improve grate-firing technology. Some of the addressed measures will be tested in a modern 500 kW grate boiler rig.