A design methodology was developed for prilling towers based on simultaneous heat, mass, and momentum balances. Basic principles of the prilling process and related sub-models were considered for production of relatively mono size prills. The method was employed in the design of a prilling tower for production of ammonium nitrate prills from a highly concentrated solution. A special shower head spray, operating under laminar conditions in a Rayleigh jet break-up regime, was designed to enhance production of mono-size prills. Air was used at ambient conditions. The droplets leaving the shower head fall through the air stream in a counter-current fashion. Heat transfer from particles to air includes cooling in the fully liquid state, solidiﬁcation, and cooling in the fully solid state. The Computational Fluid Dynamics (CFD) simulation revealed the formation of aquiescent zone around the nozzle discharge region, which had a signiﬁcant effect on decreasing the secondary disintegration of the droplets, and hence narrowed down the size distribution towards the desired value.The size of the produced prills was larger than the predicted value due to the formation of ammonia bubbles inside the prills.