Urea & Prill ProductionSule Alabi

Jonathan AranaElizabeth Moscoso

Oleg YazvinMentor: 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 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.

CO2 2NH 3 NH2COONH 4

NH2COONH 4 NH2CNOH2 H2O

ΔH = -159 kJ/mole

ΔH = +31.4 kJ/mole

(1)

(2)(Ammonium Carbamate)

(Ammonium Carbamate)

k = [AC]/ ( [NH3]2 [CO2] )

(Urea)

k = ( [Urea][H2O] ) / [AC]

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

Reactor Stripper Decomposition Evaporator

Recover System

CO2

NH3

Urea

Water

Q Q Q

Urea Plant

522.76 TPD NH3

(from NH3 Plant)1045.55 TPD CO2

(from NH3 Plant)

Nominal 2% Purge Gas – 31.37 TPD(to NH4NO3 Plant)

PrillEvaporator and

Tower

637.5 TPD Prilled Urea

786.94 TPD Urea(to UAN Plant)

112.5 TPD Water

750 TPD Urea Melt to Prill

Once-Through Pass Partial Recycle CO2 Stripping Total Recycle CO2 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 NH3 is converted and about 75% of CO2 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 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.

Partial Recycle Plant PFDPartial 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 NH3 to urea.

Our choice.

Total Recycle LayoutTotal Recycle Layout

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.

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.

PrillingPrilling

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

ReferencesReferences

Questions?