How to determine N/C ratio ?

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  • #99682
    Mark Brouwer
    Keymaster
      • Expert

      density is the best indication for N/C ratio

      #99681
      pbaboo
      Participant
        • Expert

        Dear Channing;
        Mr. Majid is given useful information, regarding N/C ratio. In Urea plant the pressure & temperature is important tool for maintaining N/C ratio. If the plant once stabilized then there no problem at all the panel operator maintain the parameters.you can tally with design parameters. The Number of plant s there are no N/C ratio and analysis carried out once in week, but the plant are running normal.In future you can install N/C ratio meter in Reactor outlet.

        N/C ratio meter
        As NH3/CO2 mole ratio is most critical parameter of the plant, N/C ratio meter supplied by M/S. Stamicarbon, Netherlands is installed for continuous analysis of the sample of autoclave liquid outlet. As urea reaction is at equilibrium at autoclave outlet it is necessary that the reactants be present at a certain ratio at reactor outlet in order to achieve optimum yield of urea. The urea solution sample from the autoclave outlet enter the sampling consists of two hand operated, normally open, valves and one pneumatically actuated valve which is normally closed. The urea sample enters the cooler at a pressure of about 149 kg/cm2g and a temperature of 180 deg C. The urea solution is cooled down to a cooler outlet temperature of 50 deg C. Solution pressure is reduced to about 20 kg/cm2g by means of capillary pressure reducer. Fine pressure control downstream from the density cell is done by means of a back pressure regulator. The density cell measures the urea sample at approximately 20 kg/cm2g and 50 deg C. These are the conditions under which the N/C ratio will be linear with the density. When the pressure is too high or the cooling unit fails, high-pressure condensate from a separate pump enters the special three way valve automatically. The setting of the condensate pressure switch is such that the three way valve opens when condensate pressure at the inlet is higher than the actual process pressure of the urea. A predetermined amount of condensate flows through the sampling system thus cleaning the whole N/C metering system of liquid urea.
        regards,
        Prem Baboo


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        #99680
        Mark Brouwer
        Keymaster
          • Expert

          Dear Channing;
          When you have no analyzer or no proper Lab. results then below can be one way which you can use it to know more about the N/C for the carbamate systems (I am not fully sure if this is what you are looking for):

          In attached table you will see the N/C ratios and crystallization temperatures based on the material balance of a typical Stamicarbon plant.

          To find out the actual N/C ratios one way is to take carbamate sample in a pot and measure the crystallization temperature using a thermometer then compare the measured results with the crystallization temperatures in that table (a table like attached table for your plant material balance) then adjust the plant conditions (operating and crystallization points) to reach close to the figures in that table.

          #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?

            #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.

              #99677
              pbaboo
              Participant
                • Expert
                #93336
                nick102286
                Participant
                  • Participant

                  Hi everyone, I was hoping to get some advice as to what parameters, ex. pressures, temperatures, densities, etc., that one would look for to 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. As detailed as possible of an answer is fine with me. PM me info or PM me for my email if needed. ANY and ALL info pertaining to urea production/control/info is most appreciated. Ask or contact me if more info/drawings/sketches are needed.

                  Stamicarbon, CO2 stripping, 1700 tons per day synthesis, 1200 tons per day prilling, balance of 80% solutions, upgraded desorption section to include preflash heater, first desorber, hydrolizer, second desorber, reflux condenser, atmospheric absorber.

                  Thanks to all in advance!

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