Process Analytical Technologies - ETH Z · Analytical Strategy Measurement of the Oxygen...

||Analytical Strategy

Measurement of the Oxygen Concentration in a Chemical Process

25.10.2016 1

Process Analytical Technologies

Raphael Etter, Felix Fleckenstein


1 Introduction

2 Terminology

3 Requirements for Analytical Methods in Industrial Applications

4 General Methods

5 Discussion of our Example

6 Questions?

7 References & Image Sources

25.10.2016Raphael Etter, Felix Fleckenstein 2

Table of Contents


Why is knowledge of the reaction parameters crucial?

Yield

Quality & purity

Desired properties

Efficiency

Feed back vs feed forward

Toxic waste -> filters

Safety


1 Introduction


1 Introduction

2 Terminology


4 General Methods


6 Questions?



Table of Contents


Currently

Physical placement of the method

Inline – inside, in situ

Online – direct contact, bypass

Atline – close proximity, manual work required

Offline – further away (external lab), manual work required

Only describes where, not how


2 Terminology


Purpose-Based Nomenclature [Minnich et al.]

Description with terms

In situ

Real time

Automation


2 Terminology


1 Introduction

2 Terminology


4 General Methods


6 Questions?



Table of Contents


Conditions

High T, p

Large ΔT, Δp

Corrosive conditions

Electromagnetic interferences

Movement & vibrations

Possibly explosive environment




Ideal method

Correct measurements without interferences (dust, other gases)

Automatically correct for changing conditions

Automated, real time

No pretreatment required

Low maintenance, few consumed parts

High reliability & availability

Insensitive to shock & vibration

No N2(l) or He(l) cooling required

Inexpensive

Easy to use




1 Introduction

2 Terminology


4 General Methods


6 Questions?



Table of Contents


Winkler Titration (1888)

Measures dissolved O2 in H2O

Pretreatment

Analyte is consumed

Need for additional chemicals

Accurate

Offline

Not or hard to automate

Not real time

Time-consuming

Trained personnel needed

Not selective


4.1 General Methods

2Mn(OH)2 + O2 2MnO(OH)2

MnO(OH)2 + 2I- Mn2+ + I2I2 + 2S2O3

2- 2I- + S4O6

2-


MS

High sensitivity

O2 conc. hard to quantify

Complicated

Difficult to automate

Expensive

Hard to realize for ATEX zone 2

Ionization, electric field

High vacuum

Maintenance intensive

Prone to disruptions


4.2 General Methods


Chromatographic

GC often used in industry

Relatively inexpensive

Real time, automation?

Possible, but challenging

Hard to realize due to detection method and explosion safety

LC not applicable


4.3 General Methods


NMR

Cannot measure oxygen

Safety issues

Electric coils

Hard to quantify

Expensive

Complicated

Real time?

Needs strong magnets (He(l) cooling)


4.4 General Methods


Electrochemical

Safety issues

Inline/online problematic

Can be dealt with

Depends on atmosphere

Real time

Automatable

Consume analyte

Interferences from other gases

Possible if no high precision is required


4.5 General Methods


Paramagnetic Measurement

Works for O2

Inexpensive

Needs magnetic field

Real time

Automatable

Online

Easy to operate

Low maintenance


4.6 General Methods


Spectroscopic (UV/VIS, Fluorescence, IR, RAMAN)

Non-invasive

In situ

Real time

Automatable

Inexpensive

Frequently used in industry

Selective

Sensitive

Easy

Quantifiable

Remotely using optical fibers


4.7 General Methods


1 Introduction

2 Terminology


4 General Methods


6 Questions?



Table of Contents



5.1 Synthesis of Ethylene Oxide in Industry

Direct oxidation of ethylene with oxygen

2 H2C=CH2 + O2 2 C2H4O

Silver catalyst

Multi tubular reactor

Side reactions:

H2C=CH2 + 3 O2 2 CO2 + 2 H2O

2 C2H4O + 5 O2 4 CO2 + 4 H2O



5.1 Synthesis of Ethylene Oxide in Industry

Suppress side reactions

Prevent ethylene oxide from further oxidation

Avoid explosions

Conclusion:

Controlled temperature and pressure

Limitation of the oxygen concentration

Eliminate all possible ignition sources

Careful monitoring of the oxygen concentration



5.2 How to monitor oxygen

High reliability

Insensitive to vibrations and mechanical

instabilities

Compensates fluctuations in pressure

Fully automated

Continuous measurement

Short response time

Real-time coupling to control unit

Low cost

Initial cost

Cost of operation

Minimal maintenance required

long maintenance interval

No or just a few consumable parts

Long lifetime

Suitable for ATEX zone 2


Wet chemical methods

Not able to automate

Reference method

Chromatography

Optical Spectroscopy

UV/VIS

IR

Raman

Paramagnetic measurements

Methods of choice due to:

Technical simplicity

Low Maintenance

No need for cooling or high vacuum

Low cost


5.2 How to monitor oxygen


Tunable Diode Laser Absorption

Spectroscopy (TDLAS)

Interference-free measurement

Inline measurement in real-time

Continuous monitoring

Robust

Operates at room temperature

No consumable parts

Low cost

Well established


5.3 Our Method of choice


ATEX Zone 2

Abnormal conditions:

Randomly occurring explosive

atmosphere (≤ 10 h / year)

Minimal standard

Higher standards can always be

applied


5.4 ATEX



5.4 ATEX


CE 0035 II 2G Ex ia IIC T4


5.4 ATEX

Temperature class T4: up to 135°C

Ignition protection EX ia: highest intrinsic safety

Explosion group IIC: Suitable for applications above ground

(C: highest security standard)

Device class 2G: Suitable for ATEX zone 1 (explosive gaseous atmosphere)

Certification body CE 0035: TÜV Rheinland Zertifizierungsstelle für Druckgeräte, Köln

Device group II: Not suitable for mining


Recommendation: TDLAS

Operates inline

Low cost (initial and operational)

High degree of automation

High reliability

Selectivity

Resists mechanical instabilities

Ability to compensate pressure and temperature fluctuations

Certified for ATEX Zone 2 and higher


5.5 Summary



6 Questions?


Figure Sources: Slide 6: C. Minnich, S. Hardy, S. Kramer, Stopping the Babylonian Confusion: An Updated Nomenclature

for Process Analyzers in PAT Applications, Chem. Ing. Tech. 2016, 88 (6), 694–697

Slide 16: http://www.mbe-ag.info/files/biogas/D2d_Datasheet_Parox_1200_EN_03.2016%20w.Applic.pdf

(24.10.16)

Slide 23:

I. Linnerud, P. Kaspersen, T. Jæger, Gasmonitoring in the process industry using diode laser

spectroscopy, Appl. Phys. B 67, 297–305 (1998)

Slides 24, 25:

ATEX Richtlinien 95 und 137, ABB

http://www.smi-online.net/ABB/ABB%20ATEX%20Info.pdf (20.10.2016)


7 References

http://www.mbe-ag.info/files/biogas/D2d_Datasheet_Parox_1200_EN_03.2016 w.Applic.pdf

http://www.smi-online.net/ABB/ABB ATEX Info.pdf


C. Demuth, Chemische Sensoren in der Bioprozessanalytik, Chem. Unserer Zeit, 2014, 48, 60 – 67.

ATEX Richtlinien 95 und 137, ABB

http://www.smi-online.net/ABB/ABB%20ATEX%20Info.pdf (20.10.2016)

C. Minnich, S. Hardy, S. Kramer, Stopping the Babylonian Confusion: An Updated Nomenclature for

Process Analyzers in PAT Applications, Chem. Ing. Tech. 2016, 88 (6), 694–697.

I. Linnerud, P. Kaspersen, T. Jæger, Gasmonitoring in the process industry using diode laser spectroscopy,

Appl. Phys. B 67, 297–305 (1998).

R. W. Kessler, (Hrsg.), Prozessanalytik - Strategien und Fallbeispiele aus der industriellen Praxis, Wiley-

VCH (2006).

Xu-dong Wang, O. S. Wolfbeis, Optical methods for sensing and imaging oxygen: materials, spectroscopies

and applications, Chem. Soc. Rev., 2014, 43, 3666.

L. W. Winkler, Ber. Dtsch. Chem. Ges. B, 1888, 21, 2843–2854.


7 References

http://www.smi-online.net/ABB/ABB ATEX Info.pdf

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