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Monitoring of a Steam Cracking Process using On-line Mass Spectrometry. Dr Kim Cooke Sira Ltd 29th April 2003. Overview. Introduction Problem Quadrupole Mass Spectroscopy Field Trials Results Conclusions. VAM 1.6. Validation of Novel Spectrometric Techniques for Process Monitoring
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Monitoring of a Steam Cracking Process using On-line Mass Spectrometry Dr Kim Cooke Sira Ltd 29th April 2003
Overview • Introduction • Problem • Quadrupole Mass Spectroscopy • Field Trials • Results • Conclusions
VAM 1.6 • Validation of Novel Spectrometric Techniques for Process Monitoring • 2 year project • DTI - National Measurement System • NPL • Sira Ltd • Protea • LGC-North West • CPACT
Ethylene Plant • UK World Scale Steam Cracker • Want to know composition of gas in transfer lines to maximise yields • Use GC to validate model based control • Current update time - 72 minutes • Reduced Update Time = Increased Profit!
Quadrupole Mass Spectrometry (QMS) • Take whole sample at 50ml/min • Look for parent ions e.g. C2H4 m/z = 28 • Calibrated and Quantitative measurements
Work carried out • 2 Field Trials carried out at Ethylene Plant • 21st November - 7th December 2001 • 19th August - 23rd August 2002 • Laboratory work • Running of Standards • Running of binary mixtures • Investigating stability
1st Field Trial Set Up Transfer Line Inlet GC Sample Flow QMS Vent QMS Bypass Gas Flow
Transfer Lines • Ethylene Plant measure: • CH4, C2H2, C2H4, C2H6, C3H8, C3H6, C4s as a bulk • First Field Trial identified: • ethene, ethane, methane, propene, propane, acetylene, methyl acetylene, iso-butane, n-butane, 1,3-butadiene, cis-2-butene, trans-2-butene. • benzene, toluene, H2S and HF
2nd Field Trial Set up Transfer Line Inlet Vent GC Sample Flow Vent Flowmeter QMS MFC NPX Std
Standards/Checks Used • NPX standard (BOC gases) • 1% Xenon, 86%Neon, 13% Propane • Ethylene Plant Standard • Ethylene, Ethane, Methane, Butane, Butene, 1,3 Butadiene, Methyl Acetylene, Acetylene, Propane, Propylene with Hydrogen balance. • Background air
2nd Field Trial • 2,263 cycles of data taken over 4 days • SEM 1855 - 1780, reset to N2 every morning • Background air and NPX standard samples every morning and evening • Plant standard run once a day • Sampled 12 transfer lines = 4 furnaces • Sampled 1 line every 6 minutes
Conclusions • QMS promising technique Reduced analysis time • Results affected by sampling technique • Good qualitative information • Quantitative information difficult Overlapping peaks • Chemometrics?