Passivation of Urea Reactor

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  • #101155
    amir-tafazol
    Participant
      • Participant

      Dear All
      We are using Stamicarbon old method for passivation by CO2 + Air. It is almost like what mentioned in previous post by POLICE but we keep passivation condition for 4 hrs. In new plants Stamicarbon suggested to use steam heating without adding air instead of CO2 passivation and it does not need to keep condition for at least 4 hrs. !!! In another plant of us, Toyo suggested to use steam + air for passivation and it is stated to keep condition for 4hrs. I am wondering if someone could help in this issue. What is the difference of these methods? which are the best? Can we use steam heating (with or without adding air) instead of CO2 passivation in stamicarbon process?

      Best Regards,
      Amir H. Tafazol
      Urea Process Engineer

      #101152
      mocznik-police
      Participant
        • Expert

        Dear Hussain,

        In Police we do passivation in specific conditions (STAC falling film HPCC plant):
        Necessary conditions during passivation:

        • Pressure in synthesis: ~ 8.0 MPa
        • O2 content in CO2: – above 1% (control on a regular basis)
        • Steam pressure in MP steam tank (steam for HP stripper): – 2.1 MPa
        • Steam pressure at steam tanks (connected with falling film HPCC): – 0.5 – 0.55 MPa
        • Cooling water temperature falling film HPCC: – 110 – 115 ° C
        • Minimal CO2 flow for synthesis: 60% yield
        • The pressure on the compressor CO2 min. 10.0 MPa, temperature 100 ° C (flow of CO2 for synthesis choked by valve)

        The time to reach the required conditions is about 3 hours *.
        The minimum passivation time under given conditions is at least 6 hours *.

        * for approximately 3 hours, the passivation conditions should be adjusted, followed by min. 6 hours to maintain the above conditions by passivating the synthesis apparatus.

        I hope it will help. Others – please share your experience.

        #93776
        Ahmad Hussain Iqtidar
        Participant
          • Participant

          Hi there everybody!
          Can someone please share with me the details of passivation of Urea Reactor?
          1. What is detailed passivation chemistry? Optimum temp and pressure?
          2. What possible parameters affect passivation rate during normal and startup conditions?
          3. Before startup passivation of HP Loop or ACES Loop is carried out, in which steam is given along with air? Does this steam affect passivation reaction?
          4. If temperature is the sole purpose of providing steam, why cant we pre heat the Air and then enter it in reactor?

          Thanks in advance 😛

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