Modified Equation for Gassy Decomposition. Sima Chervin Eastman Kodak Company H. K. Fauske FAI LLC

Transcription

1 Modified Equation for Gassy Decomposition Sima Chervin Eastman Kodak Company H. K. Fauske FAI LLC

2 Outline Problem Statement Use of Gassy Decomposition Equation Modified Gassy Decomposition Equation (Freeboard) Application of the Freeboard Equation Verification of the Freeboard Equation Conclusion

3 Problem Statement Vent sizing/vessel loading for synthetic chemical reactions that involve very energetic components (decomposition energy >1000 J/g, VSP dp/dt max ~10, ,000 psi/min)

4 Details Reactions: ~5 10% concentrations of energetic component Vessels: gal glass lined with 4 10" vent diameter

5 Process Example A B 100 water, C, 3 h C Chemical properties: C decomposes, VSP dp/dt = 30,000 psi/min, T o = 130 C, T p = 350 C, m = 36 g Vessel: 750 gal, DP = 150 psi, 10" vent, F = 0.7 Loading: C = 150 kg, water = 1500 kg

6 Process Example Runaway Scenario: vessel is set for distillation (instead of reflux), water is distilled off, 150 kg of C is not in contact with temperature probe. Therefore, heating is triggered, resulting in temperature reaching 130 C and decomposition of 150 kg of C Task: calculate the allowed loading of C

7 Equation for Gassy Decomposition (Fauske, 2000) A V 1 v dp/ 0.61 Cd m P dt MW R T P Cd M v dp m A / dt MW R T

8 Vessel Loading Using Gassy Decomposition Equation Amount of C (kg) (30,000 psi/min, T p = 350 C, 36 g, v = 2.3 L) P (psi) 10", F = 0.62, DP = 150 psi (2DP)

9 Vessel Loading Using Gassy Decomposition Equation Only 87 kg can be loaded at 2DP Vessel-free volume (~3330 L) was not taken into account in the equation An equation is needed that incorporates expansion of gases in vessel-free volume

10 Freeboard Equation (developed by H. Fauske for Eastman Kodak Company) A V 1 v dp/ dt 0.61 Cd m Pfb MW R T Pmax Pfb Pmax Patm P max maximum pressure in a closed test, psi

11 Freeboard Equation )) max ( / )/( / max ( Patm P m u A Cd dt dp v M m u A Cd dt dp v M P Pfb P m u A Cd dt dp v M / ) max ( ) max ( Patm P P P P Pfb

12 Vessel Loading Using Freeboard Equation Amount of C (kg) (30,000 psi/min, T p = 350 C, 36 g, v = 2.3 L, P max = 2200 psi at 10% load) P (psi) 10", F = 0.62, DP = 150 psi (2DP) P fb (psi) 10", F = 0.62, DP = 150 psi (2DP)

13 Vessel Loading Using Freeboard Equation (Other Examples) dp/dt, psi/min Gassy eq. Loading, kg Moles of gas P max, psi 10% load Total P Contain. Loading, kg Freeboard eq. Loading 30, , ,

14 Vessel Loading Using Freeboard Equation Use of Freeboard equation allows to significantly increase vessel loading in comparison with the amount calculated using Gassy Decomposition equation The impact is most significant for decompositions that release a limited amount of gas, but at a very fast rate

15 P max Determination Determined experimentally and adjusted for largescale mass/volume ratio Closed VSP test at 1 C/min heating rate (up to 800 psi) ScanARC at 5 C/min heating rate (up to 10,000 psi) Phi factor experimental Vessel Phi factor

16 Direct Scale-up VSP Test 750 gal with 8" vent vessel can be simulated by 120 ml can with 1/16" vent Test the same mass/volume ratio as in large scale (test phi factor vessel phi factor) If maximum pressure generated during test is lower than allowed (e.g., 2DP), loading is acceptable

17 Direct Scale-up VSP Test Advantages the sample is exposed to the same pressure profile during the test as in large scale only insignificant venting into the containment occurs during the fastest part of decomposition. Therefore, there is no cooling effect of the containment on decomposition gases during the peak event (dp/dt is measured inside the can) Issues if there are vessel loading changes, a new test is needed

18 Freeboard Equation Verification Using Direct Scale-up VSP Test Conduct a direct scale-up VSP test and a closed test to determine P max Calculate the pressure buildup in the VSP can under the specific test conditions (P fb ) using Freeboard equation Compare the calculated pressure (P fb ) and the experimental pressure (P exp ) from the direct scale-up test

19 Freeboard Equation Verification Chem. Mass, g P max, psi Vent, " P fb, psi P exp, psi P, psi dp/dt, psi/min Phi PMT / , / , / , / , TRI / , Nitro / , PMT / ,

20 Experimental Results PMT, 6 g Pressure, psi P1 60 P Time, min

21 Experimental Results PMT, 6 g Pressure Rate vs. Temperature P psi/ minute Temperature, C

22 Experimental Results PMT, 12 g P1 400 Pressure, psi P Time, min

23 Conclusions Calculated P fb ~ P exp Calculated P >> P exp Presented results demonstrate that the Freeboard equation can be used to accurately predict the maximum pressure generated in a vessel during a Gassy Decomposition reaction

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