Successful Completion of Agritech NH3/Urea Revamp Project

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  • #95765
      • Participant

      In addition to that;
      As we are using existing reactor Volume for increased inlet streams flow rates so residence time of material in reactor is decreased that will have a negative impact on urea conversion rate.
      Therefore stami proposed to add an additional plate for increased flow rates that will increase residence time of material in the reactor, furthermore stami also proposed to reduce the Numbers of holes in the remaining trays according to the provided scheme.
      Addition of tray and reducing the numbers of holes will also eliminate the chances of back mixing and channeling.

      For further details please go through the links to the following technical papers (also availablie in the Library):

      The calculation equation for retention time is

      t = VR / (VG + VL)
      In which
      VR Stands for reactor volume M3
      VG stands for Volume of gas phase M3/HR
      VL Stands for volume of liquid phase M3/HR

      Best Regards

        • Participant

        first of all, ALL of You congratulation for this achievement.
        InshALLAH we shall face no major problem at all.
        we successfully have prilling at 95% load.
        there is also changing In N/C,H/C,
        Steam requirement,steam production,reactor timing,Loop pressure,
        solution behavioral, So a number matter could able to discuss.
        here we increase the capacity to change the equipment as Mr AKBAR said above.
        May ALLAH keep it.
        we shall discuss time to time comeing emergencies or any problem.

          • Participant

          Generally, it’s not the height that dictates velocities.
          Height means ‘recovery’ and the cross sectional area or diameter means velocities.
          However, it is usually preferred to maintain a higher L/D ratio so as to prevent axial back-mixing and approach the reactor more to plug flow. Velocity can be adjusted by modifying the trays to have better gas-liquid contact.Not only the velocity but also the bubble diameter can be varied and thus the effectiveness of a tray/stage.
          [References :
          Dente, M., Rovaglio, M., Bozzano, G., & Sogaro, A., Gas–liquid reactor in the synthesis of urea, Chemical Engineering Science, 47(1992), No.9-11, pp 2475-2480
          Morikawa,H, Sakata, E. Kojima, Y, Nishikawa, G., Mega-capacity Urea Plants– TEC’s Approach, 2002]

            • Participant

            If the no. of trays wouldn’t have been increased then at higher flowrates the velocity of the reaction mixture would have been increased causing ineffective mixing of the reaction mixture and also more channeling.

            Trays are also used to suppress backmixing with in the reactor. At higher flowrates with previous reactor configuration having lesser trays, there would have been more violent backmixing.

              • Participant

              Reactor trays have been increased as volumetric flows increase, you need a larger volume.
              Volume of reactor/Molar Flow Rate = Conversion/(Rate of reaction)
              (Octave Levenspiel, Chemical Reaction Engineering, 3rd Ed, Chapter 5)

              Modification of trays are related to Fluid Dynamics: better ‘mass transfer’ something on a smaller/molecular level.



              Mark Brouwer
                • Expert

                Dear please tell me why you have increased the reactor trays and type of trays.

                  • Participant

                  Dear All,

                  By the grace of Almighty Allah Agritech Formerly Pak-American Fertilizers (PAFL) has fruitfully completed its Revamp Mission without any major even minor accident for capacity enhancement up to 125% of Ammonia/ Urea Plant.
                  Our Urea Plant Was designed on the Basis of TOYO ACES Technology now it is rehabilitated to Stami Carbon CO2 Stripping Process with the numerous Alteration, addition and Replacement of equipment and technology. Some of alterations are described as follows.
                  Addition of Trays in Reactors
                  Replacement of LPD with higher capacity
                  Addition of Extra Concentrator
                  Replacement of CO2 Compressor Machine with higher rate and Lower Discharge pressure as previous one
                  Replacement of Whole Vacuum system
                  Addition of Hydrogen Convertor
                  And many other changes carried out that will be completely described in revamp report.

                  At our Ammonia Plant also many changes carried out such as
                  Replacement of Air Compressor with Tybine A-101-J/JT
                  Rplacment of Syn Gas Compressor with Turbine A-103-J/JT
                  Replacement of Reformer Tube with Catalyst
                  Replacement of Secondary Reformer Catalyst
                  Replacement of Waste heat Boiler A-101-C and addition of one more steam drum A-101-FA.
                  Swap of CO2 Removal Section from Benfield Low energy system to a-MDEA Solution System.
                  And many other changes carried out that will be completely described in revamp report.

                  Congratulation to all Project Team, PAFL Management and PAFL Team for accomplishing an extraordinary Revamp project

                  This all made possible by the help of Allah.

                  Best Regards
                  Akbar Ali
                  Process Engineer Ammonia Revamp Project

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