process analytical techniques

Process Analytical Techniques Doosan Babcock

Contents

Background – CCPilot100+

Process Analytics

• On and Offline Gas Analysis

• Gas Flow Measurement

• On and Offline Liquid

• Liquid Flow Measurement

Measurement Accuracy

Conclusions and Recommendations

Process Analytical Techniques, Octavius CCS Conference 17-19 November 2015

Doosan Babcock

Introduction to CCPilot100+

• PCC demonstration plant using Doosan

Babcock technology

• 100 t/day slip stream from a 500MWe unit on

SSE’s Ferrybridge Power Station, making it

the largest PCC demonstration in the UK

• Two year test programme, fast-tracked build,

operating March 2012

• Funded by all the project partners

• Lessons learned to be incorporated into

future designs


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CCPilot100+ Test Programme Key Parameters

The test campaigns comprise a combination of parametric testing and

exposure testing to:

• Assess the durability of the solvent

• Permit process optimisation

• Provide data on plant design and scale-up


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Key Parameters

• CO2 capture rate and product compositions

• Steam consumption at reboiler.

• Amine and degradation product atmospheric emissions

• Absorber column efficiency

• Power and water consumption under differing operating regimes.

• Optimisation of thermal integration.

• Solvent testing and formulation for efficiency and durability

• Performance of construction materials including polymers

• Comparison of performance with other pilot plant for scale-up

CCPilot100+ Process Analytics

Process Conditions and Gas Analysis

Gas and solvent flow rates, temperatures and pressures On-Line Gas Analysis • FT-IR – Extractive multi-point heated

sampling system • Ammonia Tuneable Diode Laser – Cross-

duct, non-extractive • ppm Oxygen Micro-Fuel Cell – Extractive,

cold sampling system

Manual Gas Analysis • FGD Polisher Performance • PCC Based Emissions • Solvent Carryover • Degradation Products

Liquid Analysis

On-line liquid analysis • Solvent Concentration • CO2 Loading Off-line liquid analysis - On site laboratory Solvent • Amine Concentration • Conductivity • Density • pH • Heat Stable Salts (HSS) Concentration • Bound Amine Water (Ion Chromatography) • Cooling Water • Waste Water

Process Analytical Techniques Octavius CCS Conference 17-19 November 2015

Doosan Babcock

CCPilot100+ Gas and Liquid Sampling Locations


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Post Combustion Capture Process Analytics – Overview

• Well-established application of amine-based solvent scrubbing in the natural gas processing

and refinery industry

• Energy penalty associated with this technology is significant and successful performance of

this product is highly dependent on optimisation of process operating conditions.

• Process control systems capable of continuous optimisation of the capture process

• Major environmental challenges in the integration of chemical plant with utility scale fossil fuel

plant, particularly coal based,

• The introduction of novel airborne emissions, many of which will in turn require the

development of accompanying measurement techniques.


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Online Process Control – CO2, SO2, H2O, NH3, aerosols

Control of PCC flue gas process conditions and emissions require specific additional and more

onerous requirements to those currently provided by Continuous Emissions Monitoring Systems

(CEMS)

PCC-specific issues include:

• CO2 Capture performance - Low concentration CO2 • Solvent Protection - Low concentration SO2 • Water Balance - Solvent management i.e. amine solvent component concentration, water

droplets

• Solvent Degradation - NH3 as indicator of solvent degradation • Solvent Carryover – Aerosols causing Increased solvent and degradation product flue gas

emissions through entrainment


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Analyser Performance and Calibration : Demonstrating management, performance, and

maintenance of analytical equipment

Online Gas Analysis – Trace Components: Solvent, solvent

degradation products, SO3, NO2

• Trace levels of volatile and entrained solvent amine and amine degradation products.

Concentrations range from parts per million (ppmv) to parts per billion (ppbv)

• The novel nature, composition and low concentrations the PCC outlet solvent and degradation

product emissions generally preclude use of CEMS

• Sulfur trioxide contributes to solvent degradation, in aerosol form may also act as seed nuclei

for entrainment of solvent and solvent degradation products

• Nitrogen dioxide contributes to the production of nitrosamines

• Detailed descriptions of the various analytical techniques discussed below can be obtained

elsewhere

• Publicly available information on equipment performance is extremely limited


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Online Gas Analysis – Fourier Transform Infra-red

• Considerable work carried out on this type of instrument

• Showing promise on the Esbjerg PCC pilot plant and subsequent pilot plants

• Accepted as PCC state-of-the-art by English environmental authorities for the CCPilot100+ plant

• Used on all three OCTAVIUS pilot plant tests

• Produces a full infrared spectrum of the sample gas, % to low ppmv levels as long as the flue gas

composition and approximate concentrations in the sample matrix are known

• Not strictly continuous, sampling time depends on the time required for the Fourier transformation

computer software to eliminate background and interferent spectra. In practice, FTIR instruments

can typically analyse 8 individual components from % to ppm levels in 30 seconds

• Review historical sample spectra for the presence of additional components


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Online Gas Analysis – Fourier Transform Infra-red

Equipment Limitations

• Spectral interference

• ‘Measuring’ trace components - limits of detection

• Loss of reactive trace components through absorption / condensation in sample conditioning

system. Comprehensive equipment specification is essential

• FTIR instruments cannot measure O2. This is typically measured separately, using a zirconia

sensor

Calibration

• Often limited to checking the performance of instrumentation optics through background zero

checks

• Standard calibration gases can be used to verify accuracy of library spectra

• With volatile or reactive trace components, benign surrogate gas compounds which provide

similar spectral responses in the appropriate spectral region is a well-established alternative

• Dynamic calibration using micro syringes to provide definitive library spectra


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CCPilot100+ Online Gas Composition Measurement – FTIR


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• Configured to measure:

Water Oxygen

Carbon Dioxide Carbon Monoxide

Sulphur Dioxide Oxides of Nitrogen

Hydrogen Chloride Ammonia

Amines (if present in library database)

• Computer controls sample switching unit, runs FTIR

measurements and synchronised results to Capture Plant DCS

• Used as main CEMS for environmental emissions

• High reliability achieved in both sample system and FTIR unit

FTIR (Gasmet DX 4000)

CCPilot100+ Online Gas Measurement – Sample Collection

• Gas samples continuously extracted

• Hot Filtration used to evaporate sample stream droplets

• Heated sample lines and equipment maintains all condensables above

dewpoint

• ‘Hot Switching Unit’ for sample stream selection

• Fast sampling loop to minimise ‘memory effects’

• Pumped into FTIR Unit for Analysis


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Online Gas Analysis - Mass Spectroscopy

• Capable of detecting a wide range of gases

• In principle, capable of measuring individual gas compositions in range in concentrations,

from % to ppmv.

• Industrial instruments incorporate an ion source which fragments the relevant flue gas

molecules in proportion and these fragments are identified from their mass to charge ratios

on instrument detectors

• Preliminary studies on a Proton Transfer Reaction, Time of Flight (PTR-TOF) and Ion

Molecule Reaction (IMR) mass spectrometer encouraging, the former able to identify a wide

number of possible trace solvent degradation products


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Online Gas Analysis - Mass Spectroscopy


• Degree of molecular fragmentation. PTR-TOF and IMR instruments used ‘soft ionisation’

to minimise such fragmentation

• Discriminating ppmv amines from the other typical flue gas components such as NO, CO2

and nitrogen.

• Molecular weight interference with other major species can also prevent detection e.g.

ppmv levels of NH3 and % water vapour levels

Calibration

• Used to confirm selectivity and molecule fragment proportioning

• For some volatile components, dynamic calibration of the appropriate species using micro

syringes


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Online Gas Analysis - Gas Chromatography

• Used in the petrochemical industry for volatile organic compounds and some inorganic gases

• Separates the flue gas sample into the individual components, measurement at a dedicated

detector

• Detectors use thermal conductivity, flame ionisation, flame photometry, photo-ionization or electron capture

• One equipment supplier recommends this type of instrument for absorber outlet offgas amine


• Non-continuous, batch sample passed through a component separation column before analysis.

• Column / detector type determines the selectivity and sensitivity

• Column contamination can cause significant issues

Calibration

• For reactive/volatile gases, surrogate gases with similar transport and detection characteristics


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Online Gas Analysis - Flame Ionisation Detection

• Used for measuring homologous hydrocarbon compounds

• Not direct measurement of amine concentration only the hydrocarbon

equivalent based on the calibration gas used, typically methane.

• Examined at the Esbjerg pilot plant and showed reasonably good

correlation with amine concentration

• Used in conjunction with gas chromatography


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It should be noted that many of the above observations have been based on Doosan

Babcock’s involvement in PCC pilot plant development activities, publicly available

information on equipment performance is extremely limited

Online Gas Flow Measurement

Accurate flue gas flow rate measurement is essential for optimal CO2 capture efficiency,

by maintaining the correct Absorber liquid/gas ratios . May also be used in calculation of

capture rate

• Accurate measurement of flue gas flow rate can be problematic in the large ducts with

particular regard to flue gas velocity maldistribution

• Pressure loss devices exhibit a square law reduction in differential pressure with

decreasing gas flow rate

• Unrecoverable pressure loss should be minimised

• Recent developments in thermal mass flowmeter technology have apparently

overcome the problems associated with droplets and condensation; these devices

also have a better turndown capability than the pressure drop devices


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Online Gas Flow Measurement – Duct Lengths


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EN ISO 5167-5:2003 Measurement of fluid flow by means of pressure differential devices

inserted in circular cross-section conduits running full – Part 4 Venturi Tubes

Offline Gas Analysis


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In commercial PCC plants, manual emissions measurement objectives are likely to match those

currently required on industrial power plant i.e.

• Where CEMS equipment is not capable of measuring a recognised PCC airborne pollutant

concentration

• To field test or calibrate AMS (Automatic Measurement Systems (CEMS)) for conformance

assessment

Sampling and analysis techniques developed over recent years through national government

and EU-funded projects such as CESAR. More recently, Ramboll and Sintef having been

undertaking similar activities

Until international standard methods and suitable accreditation processes have been

developed, use only specialist emissions testing organisations with the appropriate sampling

and demonstrable experience.

EN 15259 EN 15259: 2007 – Air Quality – “Measurement of stationary source emissions –

Requirements for measurement sections and sites and for the measurement objective plan and

report”

Online Liquid Analysis – Overview

Online liquid analysis is largely associated with process optimisation including;

• Maintaining recirculating solvent composition targets for optimal capture and regeneration

efficiencies

• Maximising waterwash emissions removal efficiency.

Solvent CO2 capture performance can be affected by;

• Rapid changes in system water balance through changes to inlet and outlet flue gas

temperature

• Gradual reduction in amine activity through accumulation of thermal, oxidative and acid-

gas degradation products in the circulating solvent

• Where blends have significantly different volatilities, evaporative losses affect blend

proportions

• Reclamation losses


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Online Liquid Analysis – Overview

• The need for online solvent concentration monitoring will depend on the ability of the

process to maintain water balance and the durability of the solvent. Ideally, solvent

concentration would be monitored through routine offline analysis.

• Solvent – specific pilot plant trials offer a means of assessing solvent behaviour and

therefore such monitoring requirements.

• As publicly available information on equipment performance is extremely limited, many of

following observations have been based on Doosan Babcock’s involvement in PCC pilot

plant development activities

• An online autotitration measurement system was used on the CCPilot100+ trial. Although

no online systems were used in the OCTAVIUS pilot plant trials, an indirect chemometrics-

based system was assessed at both TNO Maasvlakte and EnBW Heilbronn


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Online Liquid Analysis - Autotitration

• Used in industrial amine sweetening plant for CO2 loading and solvent concentration analyses

• Automates established laboratory techniques.

• Solvent-specific method can require significant maintenance including provision of reagents and

disposal of waste

• For CCPilot100+ demonstration tests, method developed for the CCPilot100+ solvent and

benchmark MEA via both laboratory and pilot plant experiments

• Due to the sequential nature of the autotitration process, cycle time was significant, taking

approximately 13 minutes for both CO2 loading and solvent concentration

• Good measurement accuracy was achieved

.


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CCPilot100+ Online Liquid Measurement – Solvent Loading and

Concentration

• System can be configured to carry out a range of procedures

• CCPilot100+ has 3 analyser units, carrying out blended solvent concentration measurements as well as lean and/or rich CO2 loadings where appropriate

• Critical for maintenance of water balance in the process (especially during testing programme)

• Results considered sufficiently accurate for control decisions but speed not sufficient to deliver online process control

• Solvent concentration approx. 1% error*

• Solvent loading approx. 5% error*

*Compared to offline laboratory analysis


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CCPilot100+ Online Liquid Measurement – Accuracy and Reproducibility

Concentration Accuracy

Solvent

• Accuracy determined using direct measurement of a number

of samples using laboratory titrator

• Average difference 0.98% / Maximum 1.85%

CO2 Concentration

• ‘Standard’ sample of NaHCO3 tested for ‘Lean’

• 5M MEA ‘standard’ used for ‘Rich’

Reproducibility

Solvent

• Relative Error 0.6%

CO2 Concentration

• Lean – Relative Error 2.3% Rich – Relative Error 1.3%


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Potential to continuously analyse multiple components including amine intermediates such as

carbamates.

However, amine solvent analysis brings particular challenges, particularly in degraded solvent;

• The high concentrations of water and CO2 with major spectral footprints

• Solvent concentrations exceeding instrument calibration ranges

• Solvent molecule as carbamate

• Multiplicity of degradation products introducing potential spectral interference

TNO has undertaken considerable laboratory and pilot plant work to overcome these problems

through the development of multivariate chemometric techniques. Results with

monoethanolamine (MEA) have been encouraging


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Online Liquid Analysis - Fourier Transform Infrared Spectroscopy

Online Liquid Analysis - Raman Spectroscopy

• Similar to infrared, using component-specific wavelength and intensity to measure

concentration, it differs in that it relies on the molecule’s light scattering properties.

• In principle, Raman spectroscopy offers significant advantages over FTIR; minimal

sample conditioning, better resolution, multiplexing using fibre-optics, there is no

publically available information on the successful use of this technology for online amine

analysis in post combustion CO2 capture.

• As fluorescence can be a major spectral interferent in Raman spectroscopy, performance

with aged solvent may be problematic.


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Online Liquid Analysis - Chemometrics

• Combining relatively standard online liquid analytical instrumentation with multivariate

analysis modelling to provide solvent CO2 loading and concentration analysis

• Examines sensitivities of the various devices to changes in solvent composition using

calibration solutions

• Once the most suitable instrumentation has been selected, a more comprehensive laboratory

study is carried out using an extensive range of calibration standards containing all the

expected solvent composition permutations and contaminants.

• The performance of the chemometric model is then assessed through online testing and

analysis.

• However, development of the chemometric method requires significant preparatory work,

especially where novel solvents and blends are involved. This would include the preparation

of mixtures which sufficiently represent aged solvent


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Offline Liquid Analysis • Most widely used method In the amine sweetening industry

• In post combustion capture, may be additional requirements for hazardous emissions

• The range of MEA-based degradation products is reasonably well established. These typically

comprise:

• Oxidative and thermal degradation products Inorganic and organic ions

• Aldehydes, amides, alkylamines Nitrosamines and nitramines

• Variety of laboratory-based methods for the chemical analysis of % level amine concentration

and CO2 loading, a standard reference method for PCC has yet to be established

• As the remaining solvent degradation components tend to be at ppm and ppb level, both

sampling and analysis requires a similar level of expertise to that required for the trace flue gas

emissions analysis. The specialist laboratories such as SINTEF and TNO involved in earlier

European pilot plant projects have gained considerable practical experience. Where possible,

appropriately accredited laboratories should be used

• Sample management i.e. preparation, labelling and transport (including trans-boundary) require

careful organisation


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Online Liquid Flow Measurement

• In tandem with flue gas flow measurement, accurate solvent flow measurement is essential for

maintenance of optimal CO2 capture efficiency

• Pipe diameters are much smaller than those encountered in gas flow so undisturbed pipe length

criteria should be achievable

• Liquid flow measurement devices can generate pressure differentials orders of magnitude higher

than those available for flue gas, allowing a much wider range of suitable equipment

• Major problem with solvent flow rate determination is associated with liquid density. As lean and

rich solvent densities can differ significantly, correction of volumetric equipment to mass flow

problematic:

• It is unlikely that equipment liquid density libraries will include novel solvent.

• Although a direct measurement of mass flow would resolve this problem, the industry standard, the Coriolis meter is currently restricted to smaller pipe diameters

• One compromise is to use the Coriolis meter for purely fluid density measurement in

combination with a typical volumetric device to obtain liquid mass flow rate.


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Measurement Accuracy

• Commercial plant performance guarantees, defined or negotiated with the client, will be directly or

indirectly dependent on the quality of these measurements


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The above schematic shows a simplified version of the error hierarchy for the CO2 capture

process, based on the regeneration energy requirements (as steam consumption) and online

flue gas process conditions. Similar versions can also be produced for the other methods of

CO2 capture rate determination i.e. solvent recirculation rich and lean loadings or CO2 product

flow

Conclusions And Recommendations

• Application of Post-Combustion Carbon Capture technology to full scale will require process control systems

capable of delivering continuous optimisation of the capture process for cost-effective performance and

environmental emissions control

• Existing power plant flue gas CEMS equipment is capable of achieving the required analytical performance for

the major flue gas constituents. Although online environmental monitoring of ppm level solvent and trace

component emissions is more problematic, pilot plant testing has shown FTIR may be a cost-effective means

of monitoring many of the expected pollutants. However, further development and demonstration is required

for this and alternative systems

• Existing power plant flue gas manual emission measurement techniques can be for those species either

unsuitable or below detection levels for online analysis. Through pilot plant and laboratory studies, sampling

and analysis methods are well developed

• Online analysis of solvent concentration and CO2 loading requires significant development. With differing

solvents and variable contamination by pollutants and degradation products, analytical selectivity and

sensitivity are major challenges. Although the use of chemometrics appears promising, the extensive

preparatory work for specific solvents precludes the possibility of off-the-shelf procurement of equipment

• Offline liquid analysis has made significant progress, again through development via laboratory and pilot

plant studies


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process analytical techniques

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