nick102286

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Viewing 15 posts - 1 through 15 (of 19 total)
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  • in reply to: high stripper exit temp and high backend pressure #101144
    nick102286
    Participant
      • Participant

      We have had this issue MANY times at our plant. The stripper is your problem but the cause can vary, from our experience it is either:

      1. Uneven liquid distribution due to tubes being plugged/fouled/erroded. We had this happen when oil got into our NH3 supply to our Urea plant.

      Symptoms- high stripper liquid outlet temp., high back end pressures and temps., NH3/CO2 ratio off.

      Solution- shutdown, inspect, clean equipment.

      2. Stripper flooding- this is the one we see most often when increasing synthesis rate, it is caused by sending too much liquid to the top section of the stripper.

      Symptoms- high stripper outlet temp., high back end pressures and temps., increase in reactor level valve opening, decrease in stripper steam demand.

      Solution- drastically cut synthesis production for several hours. Keep synthesis rate low for a few hours even after everything returns to normal, then increase rate.

      3. High stripper level in the bottom section- we did this several times because at first we had a low level and CO2 was slipping to back end and causing high pressures and low temps. So we raised level and everything got better. We knew the level indication was not accurate so we continued raising the level. At a certain point the liquid level will touch the shell side of the tube sheet.

      Symptoms- high stripper outlet temp., high back end temps. and pressures.

      Solution- SLOWLY begin to lower the level in the stripper over the course of 12 hours.

      4. Stripping effientcy- too low steam pressure to the stripper/too high water level in stripper shell/too high water level in saturator/inert build up on shell side. We have had all of these happen, operators forgot to open the inert outlet valve for the stripper shell side MANY times after a plant startup.

      Symptoms- same as previous.

      Solution- verify valves are open, verify equipment levels.

      in reply to: Urea graphics and operating platforms (DCS) #101092
      nick102286
      Participant
        • Participant

        Thank you so much for your detailed reply, it was very informative and helpful.

        in reply to: Urea graphics and operating platforms (DCS) #101090
        nick102286
        Participant
          • Participant

          Yokogawa is who we are currently interested in.
          1. Have you had any problems with it?
          2. Is there anything you would like added?
          3. How does it compare to what you previously had?
          4. What would you change about it?

          Any and all information would be most appreciated. Thank you all in advance.

          in reply to: High NH3 pump discharge PSI #100936
          nick102286
          Participant
            • Participant

            Thank you all for your replies.
            High PSI seen when increasing rate to 1700+ TPD.
            No recent maintenance on ejector.
            Have not checked strainer yet but I will.
            So adjusting NH3 ejector hand wheel will not help any?

            in reply to: High Opening of LP Inert Vent #100718
            nick102286
            Participant
              • Participant
              quote naseemce:

              is 1700 MT/day original design capacity or after increased load?

              LP section load is dependent on HP stripper LV opening .

              Share your HP stripper outlet composition temp and loop pressure.

              LPC solution outlet temperature and composition pressure.

              1200T/D design
              1700T/D after upgrades
              30-35% urea out of reactor
              60-65% urea out of stripper
              2100psi in synthesis section
              3.0 NH3/CO2 ratio in synthesis section
              2.0 NH3/CO2 ratio in L.P. section

              in reply to: High Opening of LP Inert Vent #100713
              nick102286
              Participant
                • Participant

                Stamicarbon CO2 Stripping Plant
                1700 tons/day Synthesis Production
                No Medium PSI section

                L.P. section pressure: 20-30psi
                Outlet temp. of L.P. Carbamate condenser: 155-160 degrees Fahrenheit
                Outlet temp. Of H.P. Stripper: 340-345 degrees Fahrenheit
                Biuret purge to L.P. condenser: 35 gallons per minute
                NH3 H2O to top of L.P. Scrubber: 10 gallons per minute
                Weak Carbamate solution from Desorption to L.P. condenser: 10-15 gallons per minute
                Outlet temp. Of Rectifying Column: 280-285 degrees Fahrenheit

                L.P. section pressure valve and bypass valve are always 100% open. Set point for L.P. section PSI is 20psi.

                in reply to: Stamicarbon CO2 stripper issues at high rates #100600
                nick102286
                Participant
                  • Participant

                  Stripper level remains constant

                  in reply to: Stamicarbon CO2 stripper issues at high rates #100597
                  nick102286
                  Participant
                    • Participant

                    I am going to review some more data and trends but it seems that the stripper level remains constant

                    in reply to: Stamicarbon CO2 stripper issues at high rates #100595
                    nick102286
                    Participant
                      • Participant

                      Dear Mark,
                      Stamicarbon plant. Synthesis section has reactor, Carbamate condensor, scrubber, NH3 ejector with hand wheel, CO2 stripper

                      in reply to: Stamicarbon CO2 stripper issues at high rates #100594
                      nick102286
                      Participant
                        • Participant

                        It is a butterfly valve

                        in reply to: Stamicarbon CO2 stripper issues at high rates #100579
                        nick102286
                        Participant
                          • Participant

                          Dear Mark,

                          Thank you for your reply. We’ve noticed that the flooding occurs at 1700tpd when synthesis psi is less than about 2060psi. When synthesis psi is around 2090psi we can get about 1730tpd without the stripper flooding. At about 1750tpd, even with synthesis psi at 2090psi the stripper will flood if the reactor level valve is opened past about 80%. We put the stripper in service in 2001, 2300 tubes, 25-22-2 material. Is there anything we can do as far as operating parameters to keep this flooding situation from occurring?

                          in reply to: How to determine N/C ratio ? #99679
                          nick102286
                          Participant
                            • Participant

                            I know that I won’t be able to tell exactly what the ratio is without lab analysis but what are some things I can look at that would tell me roughly where the ratio is at? NH3 side? CO2 side? Somewhere in the middle?

                            in reply to: How to determine N/C ratio ? #99678
                            nick102286
                            Participant
                              • Participant

                              determine N/C ratio in the plant, in all the sections of the plant, due to the fact that we do not have a gas chromographer or accurate lab analysis.

                              in reply to: HP AMMONIA PUMP GEAR BOX COOLING #96845
                              nick102286
                              Participant
                                • Participant

                                Have you tried using a heavier weight oil? The higher the oil weight, the longer it takes to thin out, the thinner the oil, the quicker it will heat up. With an air cooled system it sounds like ambient temperature will greatly effect the oil temperature. Have you considered an oil cooler, shell and tube type, with cooling water? How about the discharge pressure of the oil? It could be a clogged filter, which would increase the temperature and pressure.

                                in reply to: HP Scrubber problem: URGENT #96838
                                nick102286
                                Participant
                                  • Participant

                                  Dear Mr. Norozi,

                                  How often is the HP inert valve at the scrubber flushed and what percent open is it? What is happening to the rest of your synthesis section? How is your NH3 to CO2 ratio? Are the any other temperatures cooling besides the scrubber outlet? When I read cooling temperatures and increased synthesis pressure, my first thought was that you were too high on the NH3 side.

                                Viewing 15 posts - 1 through 15 (of 19 total)
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