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L aboratory of P hysical and A nalytical C hemistry

General Meeting Leuven, 23/11/2005. L aboratory of P hysical and A nalytical C hemistry. Frank De Smedt Hans Vankerckhoven Prof. C. Vinckier. KULeuven Department of Chemistry Laboratory for Physical and Analytical Chemistry (LPAC) Celestijnenlaan 200 F 3001 Leuven Belgium

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L aboratory of P hysical and A nalytical C hemistry

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  1. General Meeting Leuven, 23/11/2005 Laboratory of Physical and Analytical Chemistry Frank De Smedt Hans Vankerckhoven Prof. C. Vinckier KULeuven Department of Chemistry Laboratory for Physical and Analytical Chemistry (LPAC) Celestijnenlaan 200 F 3001 Leuven Belgium Tel: 0032 16 32 7376 Fax: 0032 16 32 7992 www.chem.kuleuven.be/research/LPAC/index.htm

  2. WP 1.4. : O3 generation testbed Laboratory of Physical and Analytical Chemistry Box nr 2 O3 generator box nr 1 Storage tank FRONT VIEW External control of O3 boxes by means of CL software MAXO Water pump (stainless steel) Water jet (Venturi-system)

  3. O3 generation testbed: 2 modules • MODULE 1: • Two ozone generation boxes, designed by Copperline and constructed by CL and Seaking • Air inlet and introduction into the Venturi injector • MODULE 2: • Venturi injector (mixing of gas and water) • Water pump (external water loop) • Storage tank (designed and constructed by Copperline and Seaking) •  see 2nd Technical meeting (Offenburg) + Report W.P. 1.3 Laboratory of Physical and Analytical Chemistry

  4. WP 1.4. : O3 generation testbed • OUTLINE •  HISTORY • AIR TIGHTNESS •  OZONE GAS CONCENTRATION [O3]gas •  Pure O2 •  N2/O2 (air) Laboratory of Physical and Analytical Chemistry Note: target = air as feed gas [O3]gas≥ 10 g/m3 (0.5 % v/v)

  5. W.P. 1.4: O3 generation testbed Laboratory of Physical and Analytical Chemistry HISTORY

  6. W.P. 1.4: O3 generation testbed CONSTRUCTION: Copperline (ETR) and Seaking INSTALLATION: beginning of july 2005 at LPAC (see Minutes of the installation)  LEAKS ! (new type of cover needed)  suggestion for a smaller air corridor (because of extreme low [O3]gas) ADAPTATIONS:new cover was constructed and installed at 2nd Technical meeting (CL-Seaking)  further adaptations to the cover by LPAC (reinforcement + screws) Laboratory of Physical and Analytical Chemistry

  7. W.P. 1.4: O3 generation testbed Laboratory of Physical and Analytical Chemistry Smaller air corridor (from 2.2 to 0.4 liter) Additional reinforcement

  8. W.P. 1.4: O3 generation testbed Laboratory of Physical and Analytical Chemistry AIR TIGHTNESS

  9. W.P. 1.4: O3 generation testbed CHECKING THE AIR TIGHTNESS by → air suction (Venturi system) → pressure (Mass Flow Controller) Laboratory of Physical and Analytical Chemistry

  10. W.P. 1.4: O3 generation testbed RESULTS AND DISCUSSION Laboratory of Physical and Analytical Chemistry Air suction Air pressure

  11. W.P. 1.4: O3 generation testbed Laboratory of Physical and Analytical Chemistry OZONE PRODUCTION

  12. W.P. 1.4: O3 generation testbed Laboratory of Physical and Analytical Chemistry PATT-devices: 6 per Box (2 per Module) Box 1: Module 1 to 3 Box 2: Module 4 to 6

  13. W.P. 1.4: O3 generation testbed PROTOTYPE 2 PROTOTYPE 1 Laboratory of Physical and Analytical Chemistry

  14. W.P. 1.4: O3 generation testbed Pure O2 as feed gas Laboratory of Physical and Analytical Chemistry Measurement of: [O3]gas , current I (mA) Variables: QO2 (FC: 0 – 60 dm3/hr) n° of Modules Power setting (% P)

  15. W.P. 1.4: O3 generation testbed O--O O--O O--O O--O O--O O--O O--O O--O O--O Pure O2 : PATT-module Laboratory of Physical and Analytical Chemistry Air corridor Gas outlet Gas inlet O--O : O2 molecule : discharge

  16. W.P. 1.4: O3 generation testbed Pure O2 , Box 2, 1 Module activated Laboratory of Physical and Analytical Chemistry Measurement of: [O3]gas , current I (mA) Variables: Power setting (% P) [O3]gas (g/Nm3) as a function of the % P of Module 4 (O3 Box 2) at QO2 = 60 l/hr. Gas temperature Tgas = (30 ± 1)°C.  Linear between 15 and 75 % P, small decrease at % P > 75

  17. W.P. 1.4: O3 generation testbed Pure O2 , Box 2, 1 Module activated Laboratory of Physical and Analytical Chemistry I (mA) as a function of the % P of Module 4 (O3 Box 2) at QO2 = 60 l/hr. Gas temperature Tgas = (30 ± 1)°C.  Same trend as with [O3]gas [O3]gas as a function of I (mA) of Module 4 (O3 Box 2) at QO2 = 60 l/hr. Gas temperature Tgas = (30 ± 1)°C.  Linear relationship between [O3]gas and I

  18. W.P. 1.4: O3 generation testbed Pure O2 , Box 2, 1 Module activated Laboratory of Physical and Analytical Chemistry • Time dependence of • O3 buildup • First buildup is always slower Temperature-effect ?

  19. W.P. 1.4: O3 generation testbed Pure O2 , Box 2, 1 Module activated Laboratory of Physical and Analytical Chemistry Reproducibility (from day-to-day)  Very reproducible ozone production

  20. W.P. 1.4: O3 generation testbed Pure O2 , Box 2, 3 Modules activated Laboratory of Physical and Analytical Chemistry Variables: n° of Modules, position, Power setting (% P)  Cumulative O3 production (n = 3)  Position in air corridor of no importance

  21. W.P. 1.4: O3 generation testbed Pure O2 , Box 2, 3 Modules activated Laboratory of Physical and Analytical Chemistry Variables: QO2  Exponential dependence of the O3 concentration on QO2  Reproducibility !

  22. W.P. 1.4: O3 generation testbed Pure O2 , Box 2, 3 Modules activated Laboratory of Physical and Analytical Chemistry Variables: QO2  Linear dependency of the O3 concentration on I (but different from 1 Module at constant QO2)

  23. W.P. 1.4: O3 generation testbed Pure O2 , Box 2, 3 Modules activated Laboratory of Physical and Analytical Chemistry Capacity of the ozone generator a.f.o. QO2 (3 Modules at 75% P) Capacity = [O3]gas x QO2  exponential increase of the O3 capacity a.f.o. QO2

  24. W.P. 1.4: O3 generation testbed Pure O2 , Box 1+2, 6 Modules activated Laboratory of Physical and Analytical Chemistry Variables: n° of Modules and QO2 66 g/m3 O3 ~ 3 % v/v O3  Cumulative O3 production apparently does not hold for more than 4 Modules (air tightness problem Box 1?)

  25. W.P. 1.4: O3 generation testbed SUMMARY (pure O2) Laboratory of Physical and Analytical Chemistry  [O3]gas is linearly dependent on the power setting (15 - 75 % P)  higher % P (> 75) result is equal or slightly lower [O3]gas  the same dependence on % P is observed for I and AD-I’s  [O3]gas is linearly dependent on I: I ↑  [O3]gas ↑  O3 production is reproducible from day to day & from Module to Module  the ozone production is cumulative when multiple Modules are used for n = 3, but not for n = 6 (Modules in two separate Boxes)  [O3]gas is depending on QO2: QO2↓  [O3]gas↑ (n = 3 and n = 6), again this production is reproducible from day to day  QO2↓ I ↓ [O3]gas↑

  26. W.P. 1.4: O3 generation testbed N2 / O2 as feed gas: “air” Laboratory of Physical and Analytical Chemistry Composition of air :

  27. W.P. 1.4: O3 generation testbed O--O : O2 molecule N--N : N2 molecule : discharge N2 / O2 : PATT-module Laboratory of Physical and Analytical Chemistry Air corridor N--N O--O O--O O--O N--N N--N N--N N--N N--N Gas outlet Gas inlet More details in the LPAC-report

  28. W.P. 1.4: O3 generation testbed N2 / O2 as feed gas Laboratory of Physical and Analytical Chemistry Measurement of: [O3]gas , current I (mA) Variables: QO2 (FC: 0 – 60 dm3/hr) n° of Modules Power setting (% P) composition feed gas (N2 / O2)

  29. W.P. 1.4: O3 generation testbed N2 / O2 as feed gas Laboratory of Physical and Analytical Chemistry Variables: n° of Modules, composition feed gas (N2/O2) [O3]gas as a function of the composition of the feed gas (O2/N2) at 75% P (Modules 4+5+6 of Box 2 and Module 4). Total gas flow = 60 l/hr. Addition of N2 :  Beneficial between 60/40 & 80/20.  Identical behavior for 1 or 3 Modules (Box 2).

  30. W.P. 1.4: O3 generation testbed N2 / O2 as feed gas Laboratory of Physical and Analytical Chemistry Addition of N2 :  Modules behave differently then in the absence of N2.

  31. W.P. 1.4: O3 generation testbed N2 / O2 as feed gas (versus pure O2): effect of the gas flow Laboratory of Physical and Analytical Chemistry • Effect of the gas flow Q : •  [O3]gas↓ as Q ↑ (for both) • O3 generator capacity ↓ as Q ↓ (more pronounced with pure O2)

  32. W.P. 1.4: O3 generation testbed N2 / O2 as feed gas: is the increased O3 gas concentration in the presence of N2 an artefact or real ?? Laboratory of Physical and Analytical Chemistry •  [O3]liq follows [O3]gas (in accordance with Henry’s Law) • Increase ozone production is real ! = N2-effect • Effect on pH and conductivity when N2 is present

  33. W.P. 1.4: O3 generation testbed N2 / O2 as feed gas: effect on pH Laboratory of Physical and Analytical Chemistry • Sharp decrease of pH and sharp increase of the conductivity when N2 is present ! • + Ultraviolet absorption observed

  34. W.P. 1.4: O3 generation testbed N2 / O2 as feed gas: UV-absorption Laboratory of Physical and Analytical Chemistry O3-free MilliQ-water after ozonation with N2 presence • Ultraviolet absorption observed at 208 nm, even after degassing • presence of HNO3

  35. W.P. 1.4: O3 generation testbed N2 / O2 as feed gas: Laboratory of Physical and Analytical Chemistry • → Effect of the presence of N2 during ozone production on pH, conductivity and the UV-absorbance at 208 nm • → Indication that HNO3 is introduced in the water (acidification) • NOx is obviously being produced as a by-product •  In the presence of water (thus also in the feed gas): formation of acidic acid: corrosion problems possible !!

  36. W.P. 1.4 : O3 generation testbed General conclusions Laboratory of Physical and Analytical Chemistry • Design needs to be improved ! [O3]gas much higher with smaller air corridor Still some leaks in the Box cover Multiple Boxes ? (parallel or in series ?) • Ozone gas concentration/ production With pure O2: → [O3]gas ~ current I (1 versus 3 Modules) → “cumulative” effect of multiple Modules → [O3]gas ~ 1/ gas flow Q → capacity O3 generator exponentially increases as Q increases → good reproducibility → position Modules in air corridor of no importance

  37. W.P. 1.4 : O3 generation testbed General conclusions Laboratory of Physical and Analytical Chemistry • Ozone gas concentration/ production With N2 / O2: → addition N2 not detrimental (40 – 20 %) → [O3]gas ~ current I (different behavior) → [O3]gas ~ 1/ gas flow Q → capacity O3 generator exponentially increases as Q increases (less than pure O2) → good reproducibility → NOx are formed as by-product → HNO3 is formed when water is present (= acidification + possible corrosion)

  38. W.P. 1.4 : O3 generation testbed future Laboratory of Physical and Analytical Chemistry • * Gas flow path (smaller ?) • * (better) Air tightness & safety aspects • * Geometry of the ozone producing section • * Number of PATT-modules (more in 1 Box ?) • * Electronics of the PATT-modules (delay effects in the ozone production + faster programming of the modules) • * Introduction system (see report on Storage tank) • * Compactness of the Box (more compact) • more experiments: O2 + H2O and air as feed gas

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