The Production Of Ammonium Nitrate

Moreover, the emission of SO2, NH3 and NO in the atmosphere and particular matter of the secondary compound can form also ammonium nitrate. At room temperature and standard pressure, the ammonium nitrate looks like white crystalline solid. The three figures below show the structure formula, and ball-stick model of the crystal structure of ammonium nitrate. Ammonium-nitrate-xtal-3D-balls-A.png

Marketing the ammonium nitrate as fertilizer became famous worldwide since 1920’s. Than the market started to become low in 2001 and 2002 due to the security concern that followed in September 2001 attacks on the World Trade Center which made it very difficult to produce, transport and handle ammonium nitrate. After that, because of the changes that accrued in agricultural subsidy policies, urea has become the most important compound. This is because urea has miner safety issues, higher nitrogen fertilizer content, and it is less expensive to manufacture. In 2004, the consumption of ammonium nitrate started to improve.

The ammonium nitrate is concentrated so the amount of ammonium nitrate present is more than in a given quantity of solvent such as water, NH3 and HNO3. This process is done in an evaporator. The feed enter the evaporator tank which is supported with the re-boiler heat exchanger. The heat exchanger re-boiled the ammonium nitrate solution until the solvents such as H2O, NH3 and HNO3 evaporated leaving a more concentrated solution called melt ammonium nitrate. Usually the amount of melt ammonium nitrate melt resulting from the evaporator is 95% to 99.8%. In addition, the evaporated solvent will be recycled back to the CSTR.

Additives such as magnesium oxide or magnesium nitrate which they are not widely used are sometimes added to the melt ammonium nitrate for many reasons. One of the reasons is to increase the crystalline transition temperature of the final ammonium nitrate solid product. Moreover, they are used to reduce the caking by removing the water or any other liquids, and to reduce the freezing point of molten ammonium nitrate to allow solidification to happen at a low temperature. The additive and the molten ammonium nitrate are mixed in a static mixer.

The most common process to produce solid ammonium nitrate with the spherical shape is prilling process. A prill tower is used to produce the prills of solid ammonium nitrate. On the top of the prill tower, the concentrated melt of ammonium nitrate melt is sprayed, and on the bottom of the prill tower, an air is rising by a blower. The falling droplets of ammonium nitrate is cooled and solidified into a spherical prills when they are encounter to a rising air.

Sometime the end products have low density prills due to the concentration of the molten ammonium nitrate. The low density prills have more porous than high density prills. Therefore, the prills will absorb moisture content more easily, and may cause lamps and product deterioration. Drying process by vaporization is required to remove water or any other liquid from the solid ammonium nitrate prills. In a static bed tower, the solid prills are placed there and from the bottom of the tower, a hot air is passed through the solid prills.

The desired end product is spherical ammonium nitrate solid. However, the solid product may produce in variety of sizes. A screen process is needed to check consistently the sizes of the solid product to have only the required size. The off size prills are recycled back to the evaporation process. The right size prills send to a cooling process, where it cools down the end product for further operations.

Coating process is needed to protect the product from agglomeration during storage and shipment. However, sometimes it is not needed. This is because the additives that were added before was melted before solidification. Therefore, there is no need to coat the products with clays or diatomaceous earth for product protection.

Finally, the end products of ammonium nitrate solid prills are manufactured. Therefore, there are ready for storage or shipment by bulk or bags.

2. Production of granulated solid ammonium nitrate

Processing granules solid ammonium nitrate is the same as the first production of prills of solid ammonium nitrate. However, this time instead of using prill tower, it uses rotary drum. This occurred by spraying concentrated ammonium nitrate in a rotating cylindrical drum onto small and fine particles of ammonium nitrate. As particular rotate in the rotary drum, layers of NH4NO3 are added to particles which form granules. The NH4NO3 solid will than goes to the scanner. The ammonium nitrate granules are cooled down to avoid lamps. The under-size granules are crushed and recycled back to the rotary drum as particles. On the other hand, the oversize granules are dissolved and recycled back to the solution process.

3. Ammonium nitrate solution process:

Ammonia gas NH3 and nitric acid solution HNO3 is added to a neutralization reactor. This process is an exothermic neutralization reaction which produced ammonium nitrate solution with steam. Therefore, the reactor that used is jacket continues stirred tank reactor the resulting steam which is vapor water, ammonia, and nitric acid is send to the ammonium nitrate scrubber to remove it from the neutralization reactor. The steam can be purified or can be condensed than purified. In addition, the steam can be used in the evaporator to concentrate ammonium nitrate solution or a pre heater. . The resulting solution is send to random tank after the solution is cooled. Finally the product is shipped to other plants for further processing. The picture below shows the production of ammonium nitrate solution.

Process selection:

The most significant aim in producing ammonium nitrate is to enhance the properties of agriculture around the world as a fertilizer. It improves the growth of the plants, gives nutrition, and makes it healthy and free from diseases. It is cheap and available in agriculture stores. It can also be used in explosive, but it is very dangerous and risky. It affects the public safety in the country. Therefore, production of spherical solid ammonium nitrate process is the best selection than the others for many factors.

Around 60% in the US and in other European countries companies produced solid ammonium nitrate NH4NO3 as a fertilizer. Moreover, granulation technique is old technique and it requires more complicated plants and a variety of equipments such as rotating drums, fluidized beds and more. Currently, there are no plants in Europe using this technique any more. Nowadays, most fertilizers companies use prill technique for the production of solid ammonium nitrate.

Conclusion

In brief, the production of ammonium nitrate was done by adding ammonia gas and nitric acid solution. The production of ammonium nitrate passed through three main unit operations, which they are neutralization, evaporation and solidification. The choice of the final product was influenced by the commercial matter. Chemical and physical properties ammonium nitrate shows how it can be used in industrial market. It can be used mostly in agriculture and as explosive agent. The aim of the process was to produce a spherical solid ammonium nitrate as a fertilizer to help improve the agriculture market. The prill tower was used instead of rotary drum to get the required end product. Some diagrams such as block flow diagram, process flow diagram and Aspen Hysys diagram was drown to shows the flow of the ammonium nitrate production.