F E R T I L I Z E R I N D U S T R Y L E C T U R E 1


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F E R T I L I Z E R I N D U S T R Y L E C T U R E 1

  2. 2. INTRODUCTION <ul><li>Fertilizers are composed of nitrogen, phosphorus, and potassium compounds. They also contain trace elements that improve the growth of plants. </li></ul><ul><li>Plants use nitrogen in the synthesis of proteins, nucleic acids, and hormones. </li></ul><ul><li>Plants also need phosphorus, a component of nucleic acids, phospholipids, and several proteins. </li></ul><ul><li>Potassium is another major substance that plants get from the soil. It is used in protein synthesis and other key plant processes. </li></ul><ul><li>Early scientists such as Francis Bacon and Johann Glauber describe the beneficial effects of the addition of saltpeter to soil. </li></ul><ul><li>Glauber developed the first complete mineral fertilizer, which was a mixture of saltpeter, lime, phosphoric acid, nitrogen, and potash. </li></ul><ul><li>A patent issued to Sir John Lawes, first outlined a method for producing a form of phosphate that was an effective fertilizer. </li></ul>
  3. 3. The Manufacturing Process Nitrogen fertilizers <ul><li>Ammonia can be synthesized from in-expensive raw materials. </li></ul><ul><li>Natural gas and steam are pumped into a large vessel. </li></ul><ul><li>Next, air is pumped into the system, and oxygen is removed by the burning of natural gas and steam. </li></ul><ul><li>This leaves primarily nitrogen, hydrogen, and carbon dioxide. </li></ul><ul><li>The carbon dioxide is removed and ammonia is produced by introducing an electric current into the system. </li></ul><ul><li>Catalysts such as magnetite (Fe 3 O 4 ) have been used to improve the speed and efficiency of ammonia synthesis. </li></ul>
  4. 4. The NPK Manufacturing Process Nitrogen fertilizers (contd.) <ul><li>2) Nitric acid: </li></ul><ul><li>Produced by first mixing ammonia and air in a tank. </li></ul><ul><li>In the presence of a catalyst, a reaction occurs which converts the ammonia to nitric oxide. </li></ul><ul><li>The nitric oxide is further reacted in the presence of water to produce nitric acid. </li></ul><ul><li>3) Ammonium nitrate: </li></ul><ul><li>Nitric acid and ammonia are used to make ammonium nitrate. </li></ul><ul><li>It is a good fertilizer component because it has a high concentration of nitrogen. </li></ul><ul><li>The two materials are mixed together in a tank and a neutralization reaction occurs, producing ammonium nitrate. </li></ul><ul><li>This can be granulated and blended with the other fertilizer components. </li></ul>
  5. 5. The NPK Manufacturing Process Phosphatic fertilizer: <ul><li>To isolate phosphorus from phosphate rock, it is treated with sulfuric acid, producing phosphoric acid. </li></ul><ul><li>Some of this material is reacted further with sulfuric acid and nitric acid to produce a triple superphosphate, an excellent source of phosphorous in solid form. </li></ul><ul><li>2) Ammonium phosphate: </li></ul><ul><li>Some of the phosphoric acid is also reacted with ammonia in a separate tank. </li></ul><ul><li>This reaction results in ammonium phosphate, another good primary fertilizer. </li></ul>1) Superphosphate:
  6. 6. The NPK Manufacturing Process <ul><li>Granulating and Blending: </li></ul><ul><li>To produce fertilizer in the most usable form, each of the different compounds, ammonium nitrate, potassium chloride, ammonium phosphate, and triple superphosphate are granulated and blended together. </li></ul><ul><li>The solid materials are placed into a rotating drum which has an inclined axis. As the drum rotates, pieces of the solid fertilizer take on small spherical shapes. </li></ul><ul><li>They are passed through a screen that separates out adequately sized particles. </li></ul><ul><li>A coating of inert dust is then applied to the particles, keeping each one discrete and inhibiting moisture retention. </li></ul><ul><li>Finally, the particles are dried, completing the granulation process. </li></ul><ul><li>The blending is done in a large mixing drum that rotates a specific number of turns to produce the best mixture possible. </li></ul><ul><li>After mixing, the fertilizer is emptied onto a conveyor belt, which transports it to the bagging machine. </li></ul>Composite fertilizer manufacture:
  7. 7. The NPK Manufacturing Process <ul><li>Bagging: </li></ul><ul><li>Fertilizers are typically supplied to farmers in large bags. </li></ul><ul><li>To fill these bags the fertilizer is first delivered into a large hopper. </li></ul><ul><li>An appropriate amount is released from the hopper into a bag that is held open by a clamping device. </li></ul><ul><li>The bag is on a vibrating surface, which allows better packing. </li></ul><ul><li>When filling is complete, the bag is transported upright to a machine that seals it closed. </li></ul><ul><li>The bag is then conveyored to a palletizer, which stacks multiple bags, readying them for shipment to distributors and eventually to farmers. </li></ul>
  8. 8. AMMONIA <ul><li>Uses: </li></ul><ul><li>85% of ammonia production is used for nitrogen fertilizers </li></ul><ul><li>40% of ammonia produced is used in urea production </li></ul><ul><li>Other solid nitrogen fertilizers are ammonium nitrate, ammonium sulfate and ammonium phosphates. </li></ul><ul><li>Synthesis: </li></ul><ul><li>Difficult to synthesize using Nitrogen from air due to the high BDE, IE&EA of Nitrogen molecule is very high. </li></ul><ul><li>N 2 +3H 2 ↔ 2NH 3 ∆H = -91.444 kJ/mol </li></ul><ul><li>Temperature is crucial parameter </li></ul>
  9. 9. Ammonia (mol%) in equilibrium synthesis gas; H 2 /N 2 =3mol/mol
  10. 10. AMMONIA SYNTHESIS REACTORS <ul><li>Reactor design in ammonia synthesis is critical since temperature control is crucial. Methods applied to achieve this are: </li></ul><ul><li>Quench reactors- Cold feed gas is added at different heights in the reactor. </li></ul><ul><li>The heat produced is removed between the catalyst beds by heat exchangers. Hence, heat is removed at the highest possible temperature. </li></ul>
  11. 11. ICI quench reactor Temperature-Concentration profile
  12. 12. Kellogg a) Vertical (left fig.) b) Horizontal (right fig.) quench reactors
  13. 13. Haldor Topsoe radial flow reactors
  14. 14. Multi-bed converter with indirect cooling; (a) catalyst, (b) feed-effluent heat exchanger, (c) cold bypass, (f) product.
  15. 15. Integrated Ammonia Plant
  16. 16. Specific energy requirements of various ammonia processes *Lower heating value Process GJ (LHV)*/t ammonia Classical Haber-Bosch (coke) 80-90 Reformer pressure 5-10 bar (1953-1955) 47-53 Reformer pressure 30-35 bar (1965-1975) 33-42 Low-energy concepts (1975-1984) 27-33 State of the art (since 1991) 24-26