Process Raman Analysis

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Process Raman Analysis

• Calibration transfer through standardisation
• D.Halley C.Chem MRSC
• Dr. R. Manoharan
• Dr. S. Ananth

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Outline

• Description of an on-line simultaneous four
  channel analyzer
• How analyser standardised response is achieved.
• Example showing benefits and on-line performance
  

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Simulplexed Four Channel Process Raman
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Cost Effective Four Channel Analyzer

• Takes advantage of 2D CCD
• Same spectrograph, CCD and electronics
• Additional laser and probes
• Four process streams are monitored simultaneously

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Calibration transfer through standardisation

• Analyser standardised response
• Internal referencing for multi-mode laser
• Photometric compensation (Y-axis)
• X-axis calibration
• Advantages
• Allows use of multi-mode diode laser
• Analyzer stability and long-term reliability
• Analytical accuracy and repeatability
• Calibration transfer (intra- and inter)

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Standardization Internal Referencing

• Low cost, long life, multi-mode laser (810 nm,
  500 mW)
• Compact, rugged and easy to replace.
• Mode hopping, if not compensated, makes
  measurement unreliable and inaccurate.

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Internal Referencing How ?
Dual beam concept using diamond as dynamic Raman
reference
Diamond
Detection
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Collection
Splitter
Multimode Diode laser, 810 nm
Sample Probe
Excitation
95
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Internal Referencing Performance
Compensation
SEC ()
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Photometric Compensation Why and How ?

• Y-axis correction
• Photometric response correction for optical
  components
• Varies after hardware maintenance and from
  analyzer to analyzer
• Photometric reference is used for standardization

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Calibration Transfer
Photometric Standardization
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Photometric Compensation Performance
No Compensation
Before filter change
After filter change (M-Distance, 400-1200)
With Compensation
Raman shift (cm-1)
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Photometric Correction Performance
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Application example

• Aromatics production plant
• product feed stream composition
• final product purity analysis
• For multipoint monitoring
• build master calibration model on one channel or
  use library cal. model for copy applications
• transfer to other channels or different analyser
• on-line tuning using process spectra.
• Major benefit in analyser commissioning time

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Online Measurement Modeling
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Aromatics plant - final product purity
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Aromatics plant - purification feedstock