Gas Breakthrough from Urea Stripper to MPD

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  • #117093
    Aftab Adeel
    Participant
      • Participant

      This scenario is very possible but in my experience, in very low capacity plant where I have seen it happen, an emergency situation where LV at bottom of stripper was completely opened leaving no level inside the stripper, pressures and overall load on condensers were definitely increased, however BPCS was enough to keep the situation under control and pressure did not increase beyond 19 kg/cm2 in MPD. But that is only at one instant, and situation can vary on design of equipment, we have a new stripper installed which was not part of the original design.

      #116647
      mohammadianm
      Participant
        • Expert

        You are right, MP as well as LP loop shall be protected against high pressure scenario and release of huge amount of NH3, CO2 to the stack/ambient.
        It is now normal pratice in new plant’s design.

        #112222
        Mark Brouwer
        Keymaster
          • Expert

          Not in all CO2 stripping plants there is an interlock on low level in the CO2 stripper.
          And choking is not a real issue when there is low level in a Stamicarbon plant.
          Operators watch the pressure in the recirculation to detect passing through of CO2, the margin between operating pressure (4-4.5 bar) and set pressure (6 bar) is relatively large to avoid real issues.

          #112218
          pbaboo
          Participant
            • Expert

            In CO2 stripping process CO2 feed in stripper bottom and level of the stripper serves as a seal. At stripper low level the CO2 will diverted to downstream of stripper section resulting lines and condenser will badly choked so the level low interlocks is there in case of CO2 stripping. In Ammonia stripping the CO2 Feed in reactor, so this type of event cannot happen at low level, however pressure will increase at low level due to gas (Ammonia/CO2/H2O vapour) passing in MP section but line cannot be choked due to mixture of Gases not maximum CO2 as CO2 stripping process. The De-choking of CO2 is very tough job.

            Regards

            #112206
            majid-khan
            Participant
              • Participant

              I am waiting for a response.

              #112079
              majid-khan
              Participant
                • Participant

                Hope everyone is well. During a risk assessment we identified a credible scenario of gas breakthrough from Synthesis loop to MP loop.
                This is possible if the level control loop of the stripper fails.

                Considering the design pressure of MP Loop (27 kg/cm2) and operating pressure of HP Loop (147 kg/cm2), this can potentially rupture the MPD and can have very high consequences.
                There are PSVs available on MPD for this gas breakthrough scenario. However we think that there should be another IPL and we are interested in installation of an SIF i.e low level cut out on stripper (this will need installation of additional LT which itself is adding risk of leakage from SBT)

                What is your experience in this regard? Thanks a lot

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