Practical Applications of Raman Spectroscopy for Process AnalysisSpectroscopy for Process Analysis

Brian J. Marquardt & Bernd Wittgens**, Charles Branham and David J. Veltkamp

Center for Process Analytical ChemistryCenter for Process Analytical ChemistryUniversity of Washington

** Sintef, Trondheim, Norway

Absorption systemCO2 to sequestrationClean Flue gas

Sweet natural gas Leanamine

DesorptionAbsortioncolumn

pcolumn

Reboiler

Flue gasRaw natural gas Loaded

amine

R A l i f G /Li idRaman Analysis of Gas/Liquid Reactor at Elevated PressureReactor at Elevated Pressure

Evaluate Raman as an online tool for evaluatingEvaluate Raman as an online tool for evaluating gas scrubber absorbent performance Experiments were performed in a gas/liquid reactor at elevated pressuresreactor at elevated pressuresEfficient and reproducible sampling was needed to interrogate both the liquid and gas phases of h ithe reaction

Reaction of Methyl Ethanolamine y(MEA) and CO2

MEA + CO2 + H2O HCO3- + MEAH+ColdHot

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Why is this reaction important?Environmental implications of CO2 release from the burning of fossil fuelsNeed for efficient chemical processing to effectivelyNeed for efficient chemical processing to effectively reduce excess stack emissions into the environmentRemoval of C02 from natural gas

Raman could be a useful tool for monitoring the absorption of C02 and absorbent performance in real-time for process controlfor process controlCan Raman be an effective sensor for monitoring both gas emission (CO2, SO2, …) and absorbent quality/capacity simultaneously in a wet scrubber toquality/capacity simultaneously in a wet scrubber to improve efficiency and control?

Experimental 785 nm Raman System

Ballprobe connected inline with high pressure fittingLaser power = 160 mW at sample -50º C detector tempLaser power = 160 mW at sample, 50 C detector temp.Exposure time 6 sec, 5 accums./spectrum (30 sec/spectrum)

Charge reactor with 20 mL of absorbent and H2OMethyl ethanolamine (MEA)Methyl ethanolamine (MEA)Methyl diethanolamine (MDEA)

Bubble CO2 gas at pressure through absorbent while collecting Raman datacollecting Raman data

Pressure range 5 – 60 psi CO2

Monitor reaction with Raman to determine absorbent CO2 saturation point at a given partial pressure of CO2CO2 saturation point at a given partial pressure of CO2

Gas/Liquid Reactor Setup

Raman Sampling Probe

Reactant Stds: Raman Spectra

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Reactant Raman Spectra

• 70% Water - 30% MEA• 70% Water - 22% MEA – 8% MDEA

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Gas/Liquid Reactor Setup

CO2 and H2O Raman Spectrum

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MEA Water and COMEA, Water and CO2 - Challenge: Comparison of standards to reaction

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MEA Water and COMEA, Water and CO2 - Pressure step 10,32 and 58 psi

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CO2 and MEA at 30 psi

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CO2, MEA and MDEA at 30 psi

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Summary

Initial experiments indicate that Raman is an effective analysis tool for following these CO2absorption reactionsabsorption reactionsMore experiments need to be performed to evaluate and modify the reactor to ensure good gas mixing with the liquid absorbentwith the liquid absorbent

Problems with foaming and liquid evacuating the cellBy optimizing the reactor system it should improve the reproducibility of both the reaction and the p odu b y o bo a o a doptical sampling and lead to more consistent resultsA successful demonstration of Raman applied to a liquid/gas reactor to improve process control of a q /g p preaction at moderate pressure

Work in progress

Designed single test reactor (3rd generation)“Miniaturized” reactor for improved gas liquid contactOptimize gas/liquid separationOptimize gas/liquid separation

Design and application is under patentingTest of new absorber commence in autumn 2008

Conditions: < 1700 PsiConditions: < 1700 PsiTemperature: < 200 C

Improve instrumentation for process monitoringPressure temperature and flowPressure, temperature and flowABB FT-IRRaman