1. Branch: C.E Batch: 2014-15 Sem: 3 rd Karan Rana (130990105052) Meet Shah (130990105053) Avi Vegda (130990105062) Group Members

2. Content  Raw material  Physical property  Chemical reaction  Flow sheet  Major engineering problem  Uses

3. Raw material of Urea  Ammonia (NH 3 )  Carbon dioxide(CO 2 ) Physical property of ammonia  It is a colorless gas.  It can be easily liquefied at room temperature by applying a pressure of about 8-10 atmosphere (atm).

4. Physical property of carbon dioxide FormulaCO 2 Molecular weight (gm\gmol)44.01 Boiling point (k)194.5 Melting point (k)216.6 odorodorless viscosity0.07 cp at 194.5k Specific gravity1.555

5. Physical properties Structural formula= Molecular formula = CH 4 N 2 O or NH 2 -CO- NH 2 Molar massMolar mass (Mol Wt. ) 60.06 g mol −1 AppearanceWhite solid Density1.32 g/cm 3 Melting point133–135 °C SolubilitySolubility in waterwater107.9 g/100 ml (20 °C) 167 g/100ml (40 °C)

6. Urea Production Process from Ammonia and Carbon-dioxide  Urea is manufactured by reacting ammonia and carbon dioxide in autoclave to form ammonium carbamate.  The operating temperature is 135 0 C and 35 atm pressure.  Urea production consists of main two reactions. 1. Formation of ammonium carbamate. 2. Dehydration of ammonium carbamate to produce molten urea.

7. Chemical reaction 1) CO 2 + 2NH 3 NH 2 COONH 4 ∆H= -37.4 Kcal/gm mol 2) NH 2 COONH 4 NH 2 CONH 2 + H 2 O ∆H= + 6.3 Kcal/gm mol  Undesirable side reaction taking place is: 3) 2NH 2 CONH 2 NH 2 CONHCONH 2 + NH 3 (Biuret)

8. Flow sheet

9. Process description 1. Ammonia pumping : Liquid ammonia is pumped from the multistage pump which maintain the reaction pressure in the vertical stainless steel vessel. 2. Carbon dioxide compression : ammonia plant directly boost the carbon dioxide from the compression section as it readily form at the CO 2 section of ammonia production plant. 3. Urea synthesis tower: It is lined with film of oxides to protect form corrosion. Catalyst bed is placed in the inner side of the autoclave structure and 180- 200 atm pressure at temperature about 180-200 deg centigrade is maintained. Plug flow operation take places and molten urea is removed from the top of the tower.

10. Process description 4. Distillation tower and Flash drum: This high pressure slurry is flashed to 1 atm pressure and distilled to remove excess ammonia and decomposed ammonia carbamated salts are removed and recycled. 5. Vacuum Evaporator: The solution is fed to vacuum evaporator for concentrating the slurry. 6. Prilling Tower: It is dryer where the molten slurry is passed from top of the tower into a bucket which rotates and sprinkles the slurry and air is passed from the bottom. All the moisture is removed as the urea form into granules during it journey to the bottom of the tower. This granules are sent by conveyor to the bagging section.

11. MAJOR ENGINEERING PROBLEMS 1) Carbamate decomposition and recycle:  There are many processes that can be used for the manufacture of urea. Main difference in competing processes is in the recycle design.  Since, conversion is only 40-50 % per pass, the unreacted off gases must be recirculated or used economically elsewhere.  Recompression of off gases is virtually impossible because of corrosion and formation of solid carbamate in compressors.

12. MAJOR ENGINEERING PROBLEMS 2) Production of granular urea:  Biuret formation is another problem. Vacuum evaporation of urea from 80% to about 99%, spraying to air cool and solidification must be done just above the melting point of urea and with a minimum residence time in the range of several seconds. 3) Heat dissipation in the autoclave:  The exothermic heat of reaction can be removed by coils or wall cooling.

13. MAJOR ENGINEERING PROBLEMS 4) Corrosion:  This has been the major reason why the NH 3 - CO 2 process was slow to develop.  Minimum pressure and temperature conditions with excess NH 3 are desirable to reduce the severe corrosion rates.  Under these conditions, stainless steel can be used in the autoclave.

14. Uses  Agriculture  More than 90% of world production of urea is mostly use for as a nitrogen-release fertilizer. Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use. Therefore, it has the lowest transportation costs.  The most common impurity of synthetic urea is biuret which impairs plant growth.

15. Commercial uses  An ingredient in some skin cream, moisturizers, hair conditioners. Explosive  Urea can be used to make urea nitrate, a high explosive that is used industrially and as part of some improvised explosive devices.