Ammonium nitrate production prilling

Figure 12.16. A prilling tower for ammonium nitrate, product size range 0.4-2.0 mm. The dryer is not needed if the moisture content of the melt is less than about 0.5%.

In pressure-neutralized processes, the neutralizer usually operates at 4-5 atm and 175°-180°C. Nitric acid is fed to the neutralizer at a usual concentration range of 50%-60%. In some cases it may be preheated with byproduct steam. Ammonia is fed to the neutralizer in gaseous form. If it is available in liquid form, it is vaporized in a heat exchanger by steam or air. If. air is used the cooled air may be used to cool the prilled or granulated ammonium nitrate product. The neutralizer may be operated at a low pH (3-4) to avoid ammonia loss, and more ammonia may be added later to adjust the pH to 7. The concentration of the solution from the neutralizer is usuaDy in the range of 80%-87% ammonium nitrate. It is evaporated further by using steam from the neutralizer to a concentration of 94%-98%. In many plants, a final evaporator-concentrator is used to increase the solution concentration to 99.5%-99.8%. 

Urea processes provide an aqueous solution containing 70—87% urea. This solution can be used directiy for nitrogen-fertilizer suspensions or solutions such as urea—ammonium nitrate solution, which has grown ia popularity recentiy (18). Urea solution can be concentrated by evaporation or crystallization for the preparation of granular compound fertilizers and other products. Concentrated urea is sohdified ia essentially pure form as prills, granules, flakes, or crystals. SoHd urea can be shipped, stored, distributed, and used mote economically than ia solution. Furthermore, ia the soHd form, urea is more stable and biuret formation less likely. 

Three steps are essential to ammonium nitrate manufacture neutralization of nitric acid with ammonia to produce a concentrated solution evaporation to give a melt and processing by prilling or granulation to give the commercial soHd product. 

Ammonium Nitrate Plants - In ammonium nitrate plants, wet scrubbers can be considered for prill towers and the granulation plant. Particulate emissions of 0.5 kg/t of product for the prill tower and 0.25 kg/t of product for granulation should be the target. Similar loads for ammonia are appropriate. Other effluents that originate in a nitrogenous fertilizer complex include boiler blowdown, water treatment plant backwash, and cooling tower blowdown from the ammonia and nitric acid plants. 

Prill. An absorbent spherical form of a product, particularly ammonium nitrate. 

CHEMICAL PRODUCTS Ammonium Nitrate special purified product for industrial chemical use, available in solution, prill, and grained form. Also high-density grained material for formulation of military explosive compositions Composition D-2 Wax a densensitizing compound containing wax, nitrocellulose, and a wetting agent used in military explosive formulations... 

Ammonium nitrate prills are often mixed with fuel oil (liquid hydrocarbons) to produce a commercial explosive mixture known as ANFO which is used in quarrying. ANFO can be prepared in a factory by mixing both ingredients in a rotating container and dispensing the product into polyethylene or cardboard tubes. The tubes are then sealed and transported to the place of use. ANFO can also be prepared at the site where the explosive composition is to be used. Fuel oil is poured into a polyethylene bag containing ammonium nitrate and left for some time to allow the oil to soak into the ammonium nitrate. The ANFO mixture is then poured from the polyethylene bag into the hole (i.e. shot-hole) where the explosive mixture is detonated. 

FLOW DIAGRAM FOR THE PRODUCTION OF AMMONIUM NITRATE BY THE PRILLING PROCESS (LION OIL CO)... 

If properly proportioned and preheated, the reaction can be run continuously to produce molten ammonium nitrate containing very little water (1 to 5%), which can be formed into small spheres (prills) by dropping the reaction product through a shot tower or into flakes by cooling it on belts or drums. By fluidized bed treatment, it is possible to obtain a dry granular material as product batch processes have also been used. 

The resulting AN solution may be handled in various ways103. It can be stored as a solution, used in down-stream plants or sold as a solution it can be formed into solid AN by prilling or granulation, or it can be mixed with a solid filler. The most common filler is calcium carbonate in the form of ground limestone, dolomite or by-product calcium carbonate. This product is known as Calcium Ammonium Nitrate (CAN) and can be prilled or granulated. Granular products that contain AN and either ammonium or calcium sulphate are also manufactured. 

Prilling (see also Table 7.1) Production of ammonium nitrate, urea... 

Ammonium nitrate is hygroscopic and readily soluble in water (the saturated solution contains about 65% NH4N03). Transitions from one crystal form to another take place at + 125.2 °C = 257.4°F, +84.2 °C = 183.6°F, +32.3 °C = 90.1 °F and -16.9 °C = +1.6°F. The product shows a great tendency to cake. The difficulties therefore involved are avoided by transformation into Prills. Ammonium nitrate is marketed as dense prills and as porous prills. Both can be introduced in industrial explosives after milling except ANFO blasting agents, which need unmilled porous prills. 

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