Live steam injection into Stripper outlet stream

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    imran-idris
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      At our site HPD (high pressure decomposer) operating at 240 Psig (16.55 Barg) is getting limited due to inefficiencies in Carbamate condenser (it exchanges heat of carbamate formation in TOYO’s ACES loop with Stripper outlet liquid stream). Liquid coming out of Stripper goes to Carbamate Condenser (CC) and then enters HPD top. As the temperature at outlet of Carbamate Condenser dropped from 315 °F (157 °C) to 292 °F (144.4 °C), the HPD outlet dropped from 320 °F (160 °C) to 306 °F (152 °C). Consequently LP loop as well vacuum section have become overloaded with Ammonia resulting in increased Ammonia losses at Urea plant making it inefficient, especially during summer season when cooling water temperatures are running higher.
      One possible solution (in our case HPD, LPD reboilers are fully loaded and temperature control valves are fully open) to this problem is injection of live steam at Carbamate condenser outlet to decompose Carbmate into CO2 and Ammonia before it enters HPD. although this would increase water in Urea leaving HPD, but would unload downstream section. The steam I am planning to use is at 424 °F (218 °C) and at pressure 300 psig (20.7 Barg), which once mix with the solution at carbmate condenser outlet, the temperature would drop to a new equilibrium between steam temperature and solution temperature. My concerns are these
      1. How much increase in Biuret formation is expected as a consequence of exposure of CC outlet solution to 424 °F steam?
      2. How much Urea would get hydrolyzed?
      3. How much steam would be required to increase CC outlet temperature to 315 F from 292 F. Currently HPD reboiler consumes 15.5 KPPH steam to increase temperature from 292 °F to 306 °F?
      4. How much additional water would go into HPD off gases?
      5. How much dilution would occure in HPD liquid outlet stream?

      Total flow of stripper outlet stream is around 205 T/h (Urea 40%, NH3 16%, CO2 15.5%, H2O 28%, Biuret 0.3%)

      Your valuable insight is appreciated in advance

      Regards,
      Imran

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