Explosivity off-gas MP inerts washing tower

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  • #117091
    Aftab Adeel
    Participant
      • Participant

      All of these calculations of UEL and LEL are based on dry analysis of MP vent (not involving moisture) and of course the most simple solution suggested to reduce the explosion probability in MP vent is to add steam in it.
      My concern is that, if steam has no role in the calculations of explosivity ranges in MP vent, then how does steam reduces the chances of explosion? If it dilutes the flammable gases, why is it not incorporated in the calculations?

      However, I have seen another practice where I work to reduce explosion risk in MP vent (SAIPEM) and that is to take washing tower out of service, flow of cold condensate to washing tower is isolated and ammonia solution pump at bottom is stopped, and that is to increase ammonia flow into the vent and hence reducing the hydrogen percentage in the process, now after reading this forum, I find many loopholes in this practice, what do you think will be issues by taking washing tower out of service?

      #117057
      sandeep-kochar
      Participant
        • Participant

        Thank you sir..
        can you upload full document of it.

        When i am calculating, i am getting LEL and UEL of MP vent mixture is 11.2% and 127.2% respectively.
        How UEL is >100% possible?

        LEL-and-UEL-calculation

        #117050
        Mark Brouwer
        Keymaster
          • Expert
          #117048
          pbaboo
          Participant
            • Expert

            Please find herewith. calculation Copy

            #117047
            sandeep-kochar
            Participant
              • Participant

              In SAIPEM plant, we are getting MP vent gases analysis as under :
              NH3-2%,
              h2- 36%
              O2-9%
              N2-39%
              CH4-4%
              CO-10%

              At present, we are venting its to blow down stack after mixing with steam.

              how to calculate its Upper Explosives’ Limit (UEL and Lower Explosive Limit (LEL)?

              #100895
              sbindiaster-1943
              Participant
                • Participant

                Dear Dinakar,
                Can U pl. get info about the GC used in the Lab, namely Make, Model, GC Columns, Detectors and any other info?
                Thanks and Regards,
                S.Balasubramanian

                #100894
                sbindiaster-1943
                Participant
                  • Participant

                  Dear Er.Prem Baboo,
                  Thank U for the info on NOx Analyzer.
                  BTW, in the Lab, the off-gas analysis is done using GC.
                  Can U pl. get info about the GC, Make, Model, GC Columns, Detectors?
                  Thanks and Regards,
                  S.Balasubramanian

                  #100888
                  dinakar
                  Participant
                    • Participant

                    Here in NFCL kakinada we have CS line .and we have two provisions ..when ever there is NG added at the upstream of MP condenser we will send the off gases to boilers and whe. In the weekly off gas analysis we are getting 1-2% of ammonia in the off gas. When ever there is no NG we will isolate to boilers n line up to blow down .

                    #100863
                    pbaboo
                    Participant
                      • Expert

                      Dear Mr.S.Balasubramanian,
                      1. No inerts gas analyser in the gas outlet line is installed. only flowmeter is installed in NG line.
                      The on line NOx monitoring system has been installed in HRU Exhaust, when ammonia increases NOx also increases. This is main indicator. The analyser of applied techno System and Model
                      ATS208A.Numbers of analyser are available in market e.g. Forbes Marshal for flue gases.Bridge on line analysers. Etc.

                      Regards,

                      Prem Baboo


                      Attachments:

                      #100861
                      sbindiaster-1943
                      Participant
                        • Participant

                        Thank U Er.Prem Baboo.
                        Good to know that it has been published.

                        I would like to know about the following regarding the monitoring of the Inert gas streams of the Inlet and Outlet of the MP Absorber.:
                        1) Any Online Gas Analyzer is installed in the Plant and if so, what Make, Model, Carrier Gas, Columns & Detectors are used in that GC, with some operational conditions details,
                        2) In the Lab, what Make, Model, Carrier Gas, Columns & Detectors are used in that GC, with some operational conditions details,
                        Can U pl.enlighten me on these.

                        Regards,
                        S.Balasubramanian
                        ————

                        #100860
                        pbaboo
                        Participant
                          • Expert

                          Dear Mr. S.Balasubramanian
                          The inerts gas washing column
                          The major modification done in National Fertilizers Ltd.Vijaipur,
                          1. The off gas lined to HRU as a fuel.
                          2. The ammonical water solution lined to L.P. section before L.P Condenser(E-8)
                          Advantages
                          1. The ammonia in inetrs washing column reduced to 0.3-0.6 % and also NOx came down in HRU exhaust.
                          2. The reflux reduced in MP.absorber(C-1)
                          3. The carbonate solution tank level control because the cold Condensate to L.P washing column flow now zero. The pressure control by M.P ammonical solution.
                          4. Now greenhouse gases control which was vented to atmosphere through B/D.
                          5. Now no problem by thundering in vent gases through B/D vent stack.

                          https://www.ureaknowhow.com/ukh2/board/viewtopic.php?f=7&t=1639#p8188

                          Regards,
                          Prem baboo

                          #100859
                          sbindiaster-1943
                          Participant
                            • Participant

                            In fact, this is a request for typical composition of Inert Gas and PFID
                            a) What is the typical Analytical Values for
                            1) Inerts typical composition in the inlet to Wash Tower to remove Ammonia
                            2) Inerts typical composition in the outlet to Wash Tower
                            3) Inerts typical composition after the addition of NG

                            b) Would appreciate Sharing the PFID of the MP Inerts Wash Tower

                            Regards,
                            S.Balasubramabian

                            #100181
                            pbaboo
                            Participant
                              • Expert

                              Dear Sara,
                              There are following manner to avoid explosive mixture
                              1. To remove Hydrogen in CO2 Compressor.
                              2. To add NG in MP condenser (in case of recovery of inerts gas as fuel.)
                              3. To add steam in MP vents d/s if inerts gas not recovered(vent to B/D)
                              Danger of Choking Burner in case of recovering inerts as a fuel,
                              The NG is having some amount of CO2 (2-5% depends upon source), so the Carbonate/Carbamate formation takes place and resulted choking of burner to avoid this phenomenon Some separate burner to be used for inerts fuel don’t mixed with NG.
                              If you remove Hydrogen in CO2 compressor then No question from recovering fuel because fuel(Hydrogen) already remove from Compressor.

                              How to reduce Ammonia in Inerts ?,

                              To increase the Cold Condensate(water) in inerts washing column(0.8-1.0 m3/hr)
                              And also read following useful links

                              https://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=7&t=1252&p=6417&hilit=explosive#p6415

                              https://www.ureaknowhow.com/ukh2/board/download/file.php?id=685

                              2016 10 Kletz Preparation in maintenance -6- Modification Part c

                              https://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=11&t=1442&p=7311&hilit=explosive#p7310

                              https://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=7&t=413&p=7434&hilit=explosive#p2357

                              https://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=7&t=413&hilit=explosive#p2036

                              https://www.ureaknowhow.com/ukh2/board/download/file.php?id=685

                              Regards,
                              Prem Baboo

                              #100179
                              Kashif Naseem
                              Participant
                                • Expert

                                I think best solution is to remove the H2 in feed entering to the reactor by H2 converter having catalyst .usually the catalyst life is 10-20 years .

                                Secondly NG option can be opted and need to analyse the vent periodically to analyse the explosive mixture zone. This seems to be risky and unreliable due to human involvement and error possibility.

                                #100176
                                sara471
                                Participant
                                  • Participant

                                  Dear Mr. S.K.Gupta,

                                  We are conducting a study to optimize Ammonia and fuel gas emission from our urea plant. We are planning to route MP Vent Gasses either to primary reformer as fuel in ammonia plant or blending with Purge Gas to be used a fuel for auxiliary boilers for steam production.

                                  We have a percentage of 6 to 14% Ammonia in MP Vent. The variation depends on several factors/limitations during normal operation. I am interested to know the possibility of Carbamate formation at burner tip if Ammonia is not removed/separated from these gases, considering we have up to 10% CO2 in Fuel Gas. Can you please provide the system (PFD and P&ID) details that you have installed at your site?

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