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Simdis Course . AC Analytical Controls January 2001. Simdis - Introduction. Distillation is the most widely used separation process in the petrol industry
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Simdis Course AC Analytical Controls January 2001
Simdis - Introduction • Distillation is the most widely used separation process in the petrol industry • Knowledge of the boiling range is essential for quality assurance regulatory compliance refinery process control physical property predictions
Simdis Vs. Physical Distillation • D86, D1160 generates an average boiling point of a mixture at a given point • D 2892, 15 theoretical plate, true boiling point • Time consuming, labor intensive, imprecise
Simdis Vs Physical Distallation • GC analysis simulates a “true boiling point” • Simdis provides TBP of the individual components in a mixture at a given point • Automated • Accurate results • Fast • Detection of contamination or entrainment
Simdis Theory • The technique of simulated distillation is based upon the assumption that individual components of a sample elute from a GC column in order of their boiling point.
Available Simdis Methods Final boiling point • ASTM 3710 260 °C • ASTM 2887 538 °C • 2887 extended 620 °C • Ht 750 750 °C
ASTM D 3710 • Gasoline, naphtha, kerosene • Final boiling point (FBP)<260°C • Packed or capillary column
ASTM D 2887 • Petroleum products • Final boiling point (FBP)<538°C • Packed or capillary column • Cryogenic option
ASTM D 2887 Extended • Petroleum products • Final boiling point (FBP)<620°C • Capillary column • Cryogenic option
Ht 750 • Crude's and crude fractions, petroleum products • Boiling range from 35°C-750°C • Capillary column • Cryogenic option
Requirements • non-polar stationery phase • linear temperature program • compensation of column bleeding
Hardware • Gas chromatograph • Programmable temperature vaporizer (PTV injector) • FID detector • Column
Typical Gas Chromatograph Fixed Mol-Sieve Traps Restrictors Injection Port Regulators Detector Electrometer Flow PC Controller Column Carrier Hydrogen Air Gas
Flame Ionization Detector Schematic FID Detector Assembly Air Inlet Capillary Column End-Position (1-2 mm from Top of Jet) Jet H2 Inlet + Make-Up Exit End of Column
CO H 0 2 2 + + CHO CHO CO H 0 + 2 2 CHO + The FID is a destructive, mass sensing detector. Cations generated in the flame are counted and produce the detector signal. Analytes that have the greatest number of low oxidation state carbons produce the largest signal. + CHO CHO CO 2 H 0 2 H 0 2 H H 2 2 CH 4 H H 2 2 CH 4 H H CH 2 2 4 H H CH 2 2 4 Column CH H H 4 2 2 Jet CH H H 4 2 2 Flame Ionization Detector
System Startup • Electrical connections • Gas connections – carrier, FID • GC and auto sampler configuration • Installation of liner & column • Installation of septum and syringe • Check flows
Simdis Theory • A n-paraffin standard is analyzed to determine retention times • The times relate to the n-paraffin boiling points • A boiling point calibration curve is created by the software
AC SIMDIS D 2887 Calibration AC SIMDIS Analyzers
Calibration Report AC SIMDIS Analyzers
Calibration Curve AC SIMDIS Analyzers
Boiling Point Curve AC SIMDIS Analyzers
Simdis Theory • Every analysis should be corrected for column bleeding • Analyze a blank in every sequence • The blank signal is automatically subtracted from every sample and reference signal
Simdis Theory • The net signal is used to determine boiling points • IBP at 0.5 % of the total area • FBP at 99.5 % of the total area • The total area lies between start and end elution point • The start and end time are determined by elution algorithms
Simdis Theory • A reference sample is analyzed to check system performance
AC SIMDIS D 2887 Reference AC SIMDIS Analyzers
AC SIMDIS D 2887 reference reports AC SIMDIS Analyzers
AC SIMDIS D 2887 Reference Reports AC SIMDIS Analyzers
Starting Analysis • Make & run a sequence • Calibration • Observe results • Reprocess if necessary
Chromatogram: Boiling point (°C) 100 0 200 300 400 500 600 700 800 70000 65000 60000 55000 50000 45000 40000 35000 Signal 30000 25000 20000 15000 10000 Start Time End Time 5000 FBP IBP 0 0 5 10 15 20 25 30 35 40 45 Retention time (min) Non Fitting Blank
Chromatogram: Boiling point (°C) 200 300 400 500 600 700 800 3000 2800 2600 2400 2200 2000 1800 1600 Signal 1400 1200 1000 800 600 400 Start Time End Time 200 FBP IBP 0 0 5 10 15 20 25 30 35 40 45 50 55 Retention time (min) End Time Found Incorrectly