Explosivity off-gas MP inerts washing tower

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Viewing 14 posts - 16 through 29 (of 29 total)
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  • #98902
    pbaboo
    Participant
      • Expert
      quote imran.idris:

      I am totally in agreement with Mr. S K Gupta and in my opinion adding natural gas in MP absorber at plants where MP vent gas is either flared or used in furnace is the best option.
      Mr. S K Gupta! can you please share a PFD / P&ID for referenced modification at some Indian plant?
      regards,
      Imran

      Dear Imran
      The Inerts gas having about 40% fuel like H2 & CH4, we are using in CPP for HRU burners.We have four stream of Urea plants having Inerts flow 700- 1000 Nm3/hr flow per stream.This scheme saving a big amount of Energy.It is also dangerous if you are venting through vent stack in rainy season(thundering).
      Please find attached herewith flow diagram as we are injected NG before MP condenser so that CO2 in NG can be removed in MP absorber, to disturbed explosive limit d/s of control valve.

      Regards,
      Prem Baboo

      #96244
      imran-idris
      Participant
        • Participant

        Usually at all plant Sp and TOYO plants fresh Ammonia coming from Ammonia plant contains 2~3 NMC (methane+Nitrogen)/ MeT of Ammonia and it has never been hilighted as a problem. I doubt that adding NG in MP abosrber would pose an issue in booster pump. In fact the amount of NG needed is also not very high.

        #96243
        jain-rakeshj
        Participant
          • Participant

          When we adding NG in MP off gas, it may be possible that NG may dissolve in ammonia and it may create problem in ammonia booster pump. Can you share some high light on this aspect?

          #96238
          smartajay
          Participant
            • Participant

            Dear all,

            I just wanted to throw some light on the topic as such. Electrostatic charge accumulation is the basic thing behind the ignition of the explosive gases & accumulation of static charge are a function of the flow rate,gas velocity, pipe diameter, and pipe length.. In operative plant pipe length, pipe diameter and velocity are fixed, as such, so to avoid this accumulation we r installing aluminium strips across the flanges. And also the material for our pipe is CS. Steam may prove to be a helpfull source in avoiding the gas mixture to move to its explosivity range.

            #96232
            Ban
            Participant
              • Expert

              Regarding this topic, i would like to know what kind of material did you use for the MP venting line, CS or SS, because i concern about corrossion. And in worst case if explosion occurs, how can we isolate the MP ammonia source spread to the environment.

              #96223
              waheed-bhatti
              Participant
                • Expert

                Explosive mixture details.
                In SP plants explosive mixture become in MP inert washer. Using steam is an option but it condenses in the line and resulting in explosive mixture again. U can shift your explosive mixture range.

                #96221
                vsridhar
                Participant
                  • Participant

                  This scheme of adding NG and using the resultant gas in Aux boiler is successful at NFCL,Kakinada also.
                  V Sridhar,
                  SIUCI,
                  Oman

                  #96219
                  imran-idris
                  Participant
                    • Participant

                    I am totally in agreement with Mr. S K Gupta and in my opinion adding natural gas in MP absorber at plants where MP vent gas is either flared or used in furnace is the best option.
                    Mr. S K Gupta! can you please share a PFD / P&ID for referenced modification at some Indian plant?
                    regards,
                    Imran

                    #96025
                    s-k-gupta
                    Participant
                      • Participant

                      Dear Dellil

                      Yes, there is a risk of explosion in MP Inert washing tower if composition of mixture is in explosive range. Unfortunately in Urea plant one can keep mixture out of explosion zone only by varying Ammonia. Certainly it is at the cost of valuable ammonia. We may reduce ammonia from the gas mixture without bringing it in explosive zone by reducing Hydrogen. Hydrogen comes along with CO2. In one Urea plant in India, Hydrogen removal system was installed but due to operational problem and running cost the scheme was dropped.

                      We can recover Ammonia in Inert washing tower and immediately mix steam to push the mixture out of explosive zone. Adding natural gas (down stream of control valve) is a practice followed where the gases are to be burnt in flare stack. In a few plants in India natural gas is added in up stream of MP Condenser, it passes through the MP absorber, MP Ammonia condenser and finally MP Inert Washing Tower. Here Ammonia % in out going gases is reduced up to 1%. Final gases down stream of control valve is sent to Ammonia plant Reformer where it is used as a fuel. Natural gas is added in upstream of MP Condenser just to remove all CO2 along with the gas. There is no need of putting steam in Inert washing tower. This is a proven scheme.

                      Scheme suggested by Snam in your plant is already working in OMIFCO, Oman .

                      Regards,

                      S.K.Gupta
                      IFFCO , INDIA

                      #96006
                      tkbatra
                      Participant
                        • Participant

                        We are using enriched Oxygen ( Pure O2 and dilutent N2) for passivation of Urea synthesis loop. O2/N2 are injected at suction of CO2 compressor in a way that O2/
                        inerts ratio at CO2 comp discharge are < 4%. This avoids the explosive mix in inert washing column.

                        Now, we want to replace N2/O2 mixture with air. But, this shall make the O2/inerts ratio on the higher side.

                        What are the other options to avoid the explosive mixture in the MP inert washing Column once we start injecting air .

                        TKBatra

                        #95985
                        Mark Brouwer
                        Keymaster
                          • Expert

                          I think one uses dry basis composition to check the explosivity as steam / moisture easily can condense and to assume a worst case situation it is better to work with dry compositions.

                          #95983
                          jain-rakeshj
                          Participant
                            • Participant

                            Normally the gas explosive of the inert washing tower is done on the dry basis. When we add steam then the composition will be on the wet basis.
                            Which method is correct to check the explosiveness of the mixture ?

                            #95969
                            Mark Brouwer
                            Keymaster
                              • Expert

                              One has to plot the gas composition in the explosion diagram to check if the mixture is explosive yes or no. Ammonia has its own exploive area (although smaller than hydrogen) and adding methane will increase the explosive area. Adding steam will shift the composition towards the inert side, but to be checked how much steam is needed to get the mixture out of the explosive area.

                              Best way to avoid explosion risks is by removing the hydrogen from the feeds.
                              So install a hydrogen converter in the CO2 feed and use ammonia which is first flashed to atmospheric pressure.

                              #92513
                              dellilmed
                              Participant
                                • Participant

                                Dear sir,

                                It’s proven the existence of the explosion hazard in the line of the off-gases of the MP inerts washing tower which is connected to the blow-down exactly the continuous flare.

                                There are some point of view I want to share:
                                1- As we know that we never operate that line under 5% of Ammonia, which can lead to the hazard of explosion, so the best way to be safe is an amount of Ammonia to be lost to get up of 5%, the worst thing is the loss of Ammonia.
                                2- Other plants suggest the use of steam, and work under 5% (Is it safe???).
                                3- Our plant suggest the use of Natural gas (Also is it safe???).

                                My opinion is that safety is first, so which is the best way from upward list? and is there any other way to eliminate that loss and work is total safely?

                              Viewing 14 posts - 16 through 29 (of 29 total)
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