Team Echo Urea & Prill Production Sule Alabi Jonathan Arana Elizabeth Moscoso Oleg Yazvin Mentor: Dan Rusinak – Middough
Ammonia Based Fertilizer • Shale gas will be converted into a nitrogen based fertilizer to enhance the production of crops. • Plant Location: Williston Basin, NW corner of ND • Area is under the Bakken Shale Gas Formation and this will be our source for shale gas. • Area is in the north central grain basket. There will be many crops needing to be fertilized with Urea. Energy will not be consumed in the transportation of the fertilizer. • Its a natural product from a natural resource
Why Urea? • Urea has a high nitrogen content (47%) • Mainly used as a fertilizer and commercially used as a cattle feed supplement • Provides a source of nitrogen for plants. • Liquid Urea is used as a fast-acting fertilizer. • Prilled Urea is used as a controlled release fertilizer. • Also makes Urea Ammonium Nitrate (UAN 32) • Urea has the lowest transportation cost per unit of Nitrogen nutrient. • According to the International Fertilizer Association (IFA) there is an expected 17% increase in demand over 2009 to 2014.
History • Urea first detected in urine in 1773 by Rouelle. • First synthesized from Ammonia and Cyanic Acid by Woehler in 1828. This was the first synthesis of an organic compound from an inorganic compound ever. An important milestone for organic chemistry because it was the first time a molecule found in a living organism was synthesized in a lab. • At room temperature it is colorless, odorless, and tasteless. Non-toxic.
Urea Synthesis follow two basic steps ΔH = -159 kJ/mole (1) (Ammonium Carbamate) k = [AC]/ ( [NH3]2 [CO2] ) (2) ΔH = +31.4 kJ/mole (Ammonium Carbamate) (Urea) k = ( [Urea][H2O] ) / [AC]
Le Chatlier • A counter current CO2 Stripper will be used to drive the first reaction backward, decomposing the AC by decreasing the partial pressure of NH3. 2 NH3 + CO2 AC • In the decomposition unit, by reducing the pressure, the second reaction will favor Urea over AC AC Urea+water
BFD Q Q CO2 Q Reactor Stripper Decomposition Evaporator Water Recover System Urea NH3
Design Basis 522.76 TPD NH3 (from NH3 Plant) Urea Plant Nominal 2% Purge Gas – 31.37 TPD (to NH4NO3 Plant) 1045.55 TPD CO2 (from NH3 Plant) 750 TPD Urea Melt to Prill Prill Evaporator and Tower 786.94 TPD Urea (to UAN Plant) 112.5 TPD Water 637.5 TPD Prilled Urea
Competing Processes • Once-Through Pass • Partial Recycle CO2 Stripping • Total Recycle CO2 Stripping
Once-Through Pass • This is where the off gases were used as the feedstocks. • The cheapest method and simplest method both in capital and operating cost. • Only about 35% of NH3 is converted and about 75% of CO2 is converted. • Not an efficient method unless the unconverted materials are being utilized in other processes.
Partial Recycle • This method was developed to recover and recycle some of the unreacted NH3 and CO2 from the decomposing unit back to the process. • About 70% of NH3 and 87% of CO2 are converted to urea. • Better use of the unconverted than once through.
Total Recycle • This method is necessary to minimize emissions into air, land and water with due respect being given to the efficient use of energy and material resources. • This method is done by cooling all the unreacted and unconverted gases and sending them back to the reactor to form ammonia carbamate. • Most expensive but 99% conversion of NH3 to urea. • Our choice.
Urea Plant Challenges • Thermodynamic Limit on conversion per pass through reactor • Intermediate Product, Ammonium Carbamate, is extremely corrosive. Will need presence of O2 to promote passivity. • Occurrence of side reaction – Biuret formation at high temperatures. Biuret is toxic to plant-life. • Prill Dust must be managed with a “wet” tower.
Prilling • Prill – spherical pellets made by cooling falling liquid • Liquid Urea is pumped to the top of a tower where there is a spinning drum • Urea gets passed through holes in the drum • Urea falls while inert gas is being blown upward
Prilling • Urea gets cooled into hard spherical pellets • Pellets sorted by size • The addition of formaldehyde to pellets controls the rate at which Nitrogen is released, and makes them temporarily water insoluble; thus less susceptible to light showers or heavy dew.
References • Kirk Othmer Encyclopedia • The Fertilizer Encyclopedia , 1976, Wiley Press • The Fertilizer Manual, 1979 • UNEP, Fertilizer Manufacturing Processes • The Ullman Encyclopedia of Industrial Chemicals
Thank You! • Questions?