IR Spectroscopy as Process Analytical Tool For post combustion - - PowerPoint PPT Presentation

For post combustion capture processes

• Dr. L. Geers

IR Spectroscopy as Process Analytical Tool

FTIR as PAT for PCC 2

Introduction

Post-combustion capture (PCC) The extraction of CO2 from (power plant) flue gases

• Total cost of post combustion capture is around 40 € / ton
• CO2 emission rights cost around 15 € / ton
• Hence, PCC costs need to go down process optimization

FTIR as PAT for PCC 3

Post-combustion CO2 capture process

Flue gas Purified flue gas SO2 scrubber CO2 absorber CO2 desorber Lean solvent Rich solvent Heat exchanger CO2

FTIR as PAT for PCC 4

Efficiency compromising factors

• Thermal degradation of amino acid due to heating/cooling

cycles

• Chemical degradation of amino acid due to formation heat

stable salts

• Contamination of solution with other species in flue gas
• Evaporation of water from amino acid solution
• Temperature fluctuations

In-line process monitoring enables process optimization and lowers operational costs

FTIR as PAT for PCC 5

Specifications of process monitoring tool

Determination of concentrations of amino acid, CO2, and heat stable salts

• in-line during processing,
• with time scale < 15 min,
• accurate within 10%,
• prepared for speciation (near future).

Weapon of choice: FTIR spectroscopy with ATR flow cell.

FTIR as PAT for PCC 6

PCC process monitoring

Flue gas Purified flue gas SO2 scrubber CO2 absorber CO2 desorber Lean solvent Rich solvent Heat exchanger

FTIR

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From IR spectra to concentrations?

[Amino acid] [CO3

2-]

[HCO3

• ]

[Carbamate] [Heat Stable Salts] [ ... ? ... ]

?

• Overlapping absorption peaks of different species
• Broad O-H band for water obscures peaks of other species
• Chemical reactions cause peak shifting or disappearance
• Temperature fluctuations affect spectra

Chemometrics are necessary: Partial Least Squares Regression

FTIR as PAT for PCC 8

PLS model construction

• Input data configurations
• Full spectrum
• Truncated spectrum without “OH band”
• Unimportant Variable Elimination pre-processing

Bad convergence of PLS model for all configurations, due to irrelevant correlations in spectra?

• Pre-processing methods
• Multiplicative Scatter Correction (usually for NIR)
• Standard Normal Variate (usually for NIR)
• Direct Orthogonal Signal Correction (or DOSC)

DOSC filtering (2 compts.), PLS model (4 compts.) R2=0.998

FTIR as PAT for PCC 9

Experiments

Calibration + validation

• 52 solutions with different concentrations of

amino acid, CO2, and SO2

• CO2 concentration measured with

phosphoric acid method

• SO2 could not be measured directly

assumed all SO2 absorbed by liquid

• IR Spectra collected with FTIR spectrometer

and ATR flow cell Testing in-line monitoring

• Event identification during processing
• Model robustness for unknown species

Pilot plant

FTIR as PAT for PCC 10

Calibration and validation matrices

(37) (15)

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Validation of amino acid concentration

Prediction accurate within 3%

Prepared amino acid concentration (M) Reconstructed amino acid concentration (M)

FTIR as PAT for PCC 12

Validation of CO2 concentration

Prediction accurate within 3%

Measured CO2 concentration (M) Reconstructed CO2 concentration (M)

FTIR as PAT for PCC 13

Validation of amino acid concentration

Prediction accurate within 1%

Prepared SO2 concentration (M) Reconstructed SO2 concentration (M)

FTIR as PAT for PCC 14

Process event identification

CO2 + SO2 SO2

Water replenishment

Reconstructed amino acid concentration (M)

4h 10’ 8h 20’ 12h 30’ 19h 4’ 23h 14’ 0h

Time

FTIR as PAT for PCC 15

Model robustness test – CO2 in rich stream

CO2 CO2 + SO2 CO2 + SO2 + NOx

FTIR as PAT for PCC 16

Model robustness test – SO2 in rich stream

CO2 CO2 + SO2 CO2 + SO2 + NOx

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Conclusions

• PLS model needs DOSC pre-processing
• FTIR with PLSR able to monitor amino acid, CO2, and SO2

concentrations within 3% in artificial flue gas

• Events in the pilot plant experiments can be identified using the

method

• Model robustness is compromised at high concentrations of

foreign species

• Calibration needs to be done with used process solvent

Next steps

• Assess robustness in pilot plant with real flue gas
• Incorporate temperature as a process variable
• Get more detailed analysis of samples
• Research stage speciation (i.e. discern CO3

2-, HCO3

• , amino

acid, carbamate, SO3

2-, HSS, ...)

FTIR as PAT for PCC 18

Contact information

• Dr. L. Geers – Senior research scientist process intensification

+31 (0)15 26 92 384, leon.geers@tno.nl

• Dr. A. van de Runstraat – System engineer CO2 capture

+31 (0)15 26 92 886, annemieke.vanderunstraat@tno.nl

• Dr. E. Goetheer – Technology manager CO2 capture

+31 (0)15 26 92 846, earl.goetheer@tno.nl