Brian Vaillancourt Mettler-Toledo Ingold Bedford MA 2010

1. MBAA-Rocky Mountain District Technical Summit25 June 2010Measuring Dissolved Oxygen with Optical Technology Brian Vaillancourt Mettler-Toledo Ingold Bedford MA 2010

2. Agenda • Introduction • Current Technology • Challenges with DO measurements • Oxygen Measurement in Breweries • New Optical Technology • Theory of Operation • Benefits • Summary

3. Introduction Technology Advancements

4. Optical DO measurement offers a solutions for these challenges with amperometric technology Current DO Measurement Today • Dissolved oxygen measurement in Breweries is predominantly amperometric • Proven technology • Technology offered by a multiple manufacturers • Extensive portfolio for a wide application coverage • Wide temperature range • CIP & Sterilizable • Accurate at low oxygen levels • There are challenges with amperometric technology: • Process conditions can damage the membrane • Speed of response from saturation values is slow • Flow dependences • The high Impedance measurement makes it susceptible to moisture problems But

5. Reduction of oxygen level in beer is directly linked to product quality and shelf life  cost savings Why Measure Oxygen – Key to Quality • Oxygen is considered one of the top beer spoilers • Oxygen in beer reduces the shelf life • The lower the DO when the product is packaged, the longer it will remain “Fresh, Crisp & Clean tasting” • DO in the beer before filling, contributes to nearly 1/3 of the total packaged oxygen “TPO” • Key requirements for successful oxygen control: • Avoid any ingress of oxygen at all process stages • Increasing demand for lower oxygen value in water and CO2 Requirements to oxygen measurement equipment: • Ability to measure in beer • Low limit of detection • Stable measurement signal • No flow dependence • Fast response • Low maintenance

6. Oxygen Measurements in the Brewery Brew house wort cooler water preparation mash tun lauter tun wort copper whirlpool O2 Fermentation/Storage DO DO DO DO DO storage tank fermentation tank yeast propagation Filtration/Filling bright beer tank CIP stations DO DO DO filling lines separator DO DO Kieselguhr filter PVPP filter DO waste water treatment water deaeration

7. Challenges for new Technology •  • Maintenance • planning • Diagnostics •  • Reliable Measurement • Robustness • Ease of use •  • The measurement works • Accuracy • Reliability

8. Optical DO systems allow you to concentrate on your process Keep your focus

9. Opto-Layer LED Sensor tip O2 O2 O2 Emitted fluorescence light Detector Fluorescence quenching is the basic principle of the optical oxygen measurement What is Fluorescence Quenching? • Fluorescence is a phenomenon where a material absorbs light (energy) of a specific wavelength (color) and after a short time emits light with a different wavelength (color) • Fluorescence quenching describes a reduction of the fluorescence intensity and a time shift caused by another substance (quencher, e.g. oxygen). • The quenching depends on the amount of oxygen present in the process solution. The oxygen is quantified by measuring the time shift.

10. Partial Pressure and Dissolved Oxygen • Henry’s Law states “ The partial pressure of a gas in a liquid is equal to the partial pressure of the gas in the vapor above the liquid.” Partial Pressure O2 in Air Transmitter 100% Equilibrium The sensors deliver information which is proportional to the oxygen partial pressure in the liquid. This information is translated by the transmitter into % saturation, mg/l or ppm Partial Pressure O2 in Liquid

11. System Pressure = 760 mm Hg System Pressure = 1580 mm Hg Partial Pressure PAir = 760 mm Hg PAir = 1580 mm Hg • The Dissolved Oxygen concentration in solution changes with change in partial pressure. • The user must compensate for changes in pressure to ensure an accurate measurement

12. PAir = 760 mm Hg PAir = 760 mm Hg 10M System Pressure = 760 mm Hg System Pressure = 1580 mm Hg Tank Pressure • Tank hydrostatic pressure has virtually no influence on DO measurement up to 100 meters depth. (<1.0%)

13. Partial Pressure • Partial Pressure is the pressure that a single gas exerts in a mixture of gases • Oxygen is 160 mm or 212.2 mBar at saturation • Humid Air displaces the Partial Pressure of Oxygen • Example At 20oC • 0% Humidity the Partial Pressure of Oxygen is 212.2 mbar • 23.3 mbar Humidity the Partial Pressure of Oxygen is 207.4 mbar • 4.8 mbar or 2.26% Difference between the Partial Pressure of Oxygen in Dry Air vs Humid Air

14. Amperometric Sensor Cross Section of the Electrode Tip Electrolyte Layer Teflon S.S. Mesh Silicone (not to scale) Teflon

15. 3 2 1 Theory of Operation of Amperometric Sensors O2 diffuses through the gas- permeable membrane (the higher the partial pressure in the liquid, the more O2 diffuses) O2 is dissolved in the electrolyte O2 is reduced at the cathode The oxidation-reduction reaction generates a current The current is measured by the transmitter and converted 1 2 3

17. Due to the nonlinearity of the sensor signal, accurate calibration is essential for high accuracy Oxygen – Fluorescence Relation • The decay time and therewith the delay time (phase-shift) of the fluorescence light is directly related to the concentration of oxygen (quencher). But the shape of the function is not linear like amperometric and follows the so call Stern-Volmer equation. Optical Delay time O2 (Air concentration)

18. Sensor Current (nA) Delay time O2 (Air concentration) O2 (Air concentration) Optical vs. Amperometric Technology Optical Amperometric • Calculated non linear signal • Sensor-specific calibration • Calibration necessary because ageing of the sensor influences the whole calibration curve • Two-point calibration (Air & Zero) • Linearity between nA and Oxygen value • Direct information from the raw signal • Offset or slope correction possible because ageing prevailing influencesthe slope

19. Optical vs. Amperometric Technology

20. Optical sensors offer higher operational availability and improves handling safety Key Enhancements / Improvements: SOP Today's standard Optical Systems • Detach cap sleeve • Detach membrane body • Dispose electrolyte • Clean or replace membrane body • Clean electrode • Fill in electrolyte • Bubble free installation of membrane body • Clean outside • Install cap sleeve • Polarize sensor (6h) • Calibration • Detach cap sleeve • Detach OptoCap • Install new OptoCap • Install cap sleeve • Calibration Total: more than 6 hours Total: few minutes

21. Time consuming sensor verification is replaced by enhanced self testing of the whole measuring system Key Enhancements / Improvements Today's standard Optical Systems • Performance Check • Time consuming controlling and documentation • Response time • Air and zero current • Slope • Drift • Automated Self Test • Communication • Electronic component • Optical component • OptoCap quality Sensor status directly available without additional testing Total: about 30 minutes

22. The response time in liquid phase of the optical is 50% faster than amperometric systems leading to higher efficiency Sensor Performance: Response Time 20 Optical Amperometric 15 DeaeratedWater O2 / ppb 10 Beer 5 60 Seconds 0

23. The response time after a CIP cycle using non-degassed water is significantly shorter for optical sensors Sensor Performance: Response Time 2000 Optical 400 Water Beer Amperometric O2 / ppb 200 30 Minutes < 1 Minute 50 0

24. The optical sensor shows no significant stop-flow effect leading to reduced alarm frequency Sensor Performance: During No Flow 10 Optical Amperometric Flow Stop 8 6 O2 / ppb 4 2 0 6 1 2 3 4 5 Time / h

25. Sensor Performance: During No Flow • Process conditions that affect the operation of amperometric sensors are not affected with the optical sensor • Optical sensors will show actual DO in process which is difficult to accept • Which results in blaming the instrumentation and not dealing with actual oxygen ingress Flow Stopped Optical Sensor

26. Sensor Performance: Extensively Tested • Multiple optical system manufacturers were tested • Test included amperometric technology • The test period lasted 14 months

27. Sensor Performance: Other Benefits • Not susceptible to Hydraulic Shocks (measurement Stable) • No Damage from Hydraulic Spikes (Press-Vac) • Does not see CO2 bubbles as O2 • Only responds to the presents of O2 • Process Orientation of sensor is not important • Does not contain an electrolyte • Opto Cap life expectancy is 12+ Months • Easily replaced onsite and recalibrated • Does not require frequent “calibration”, but only “validation” • Verification has been necessary to become comfortable with this new technology

28. Sensor Performance: Not without issues • Optical spot can not be pulsed during CIP process or at high temperatures • Results in a shift in the calibration values • Most manufacturers deal with this issue by turning off the LED by a temperature shut-off or remote signal to the transmitter • More frequent pulse rate will deplete (bleach out) the optical spot at a faster rate • The pulse rate can be programmed • Multiple/Frequent (weekly) process calibrations will eventually require a two-point calibration be done • Drift rate is less than 1 ppb per month

29. Summary Optical oxygen measurement systems • Provide • Signal stability • Faster Response time • Extensively less maintenance then amperometric systems • Ease of maintenance • Process improvement • Improved product quality

30. From Brew House to Filler Lines Questions