Figure 4: Production of ammonium nitrate fertilizer

Nitric acid is combined with a conditioning solution and then neutralized carefully with ammonia in a two-stage boiling process. The 89 percent ammonium nitrate solution is then evaporated and jet-sprayed into a prilling tower. The solidified fertilizer nuggets are then filtered through screens to a cooler, after which they are ready for packing and storage.

Source:   The New Illustrated Science and Invention Encyclopedia. Westport, CT: H.S. Stuttman, 1989.