Urea & Prill Production Sule Alabi Jonathan Arana Elizabeth Moscoso Oleg Yazvin Mentor: Dan Rusinak – Middough

 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

 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.

 Urea first detected in urine in 1773 by Rouelle.  First synthesized from Ammonia and Cyanic Acid by Woehler in 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.

ΔH = -159 kJ/mole ΔH = kJ/mole (1) (2) (Ammonium Carbamate) k = [AC]/ ( [NH 3 ] 2 [CO 2 ] ) (Urea) k = ( [Urea][H 2 O] ) / [AC]

 A counter current CO 2 Stripper will be used to drive the first reaction backward, decomposing the AC by decreasing the partial pressure of NH 3. 2 NH 3 + CO 2  AC  In the decomposition unit, by reducing the pressure, the second reaction will favor Urea over AC AC  Urea+water

ReactorStripperDecomposition Evaporator Recover System CO 2 NH 3 Urea Water Q QQ

Urea Plant TPD NH 3 (from NH 3 Plant) TPD CO 2 (from NH 3 Plant) Nominal 2% Purge Gas – TPD (to NH 4 NO 3 Plant) Prill Evaporator and Tower TPD Prilled Urea TPD Urea (to UAN Plant) TPD Water 750 TPD Urea Melt to Prill

 Once-Through Pass  Partial Recycle CO 2 Stripping  Total Recycle CO 2 Stripping

 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 NH 3 is converted and about 75% of CO 2 is converted.  Not an efficient method unless the unconverted materials are being utilized in other processes.

 This method was developed to recover and recycle some of the unreacted NH 3 and CO 2 from the decomposing unit back to the process.  About 70% of NH 3 and 87% of CO 2 are converted to urea.  Better use of the unconverted than once through.

Partial Recycle Plant PFD

 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 NH 3 to urea.  Our choice.

Total Recycle Layout

 Thermodynamic Limit on conversion per pass through reactor  Intermediate Product, Ammonium Carbamate, is extremely corrosive. Will need presence of O 2 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.

 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

 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. Prilling

 Kirk Othmer Encyclopedia  The Fertilizer Encyclopedia, 1976, Wiley Press  The Fertilizer Manual, 1979  UNEP, Fertilizer Manufacturing Processes  The Ullman Encyclopedia of Industrial Chemicals References

 Questions?