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

WP 1.4. : O 3 generation testbed L aboratory of P hysical and A nalytical C hemistry O 3 generator box nr 1 Storage tank Water jet (Venturi-system) FRONT VIEW External control of O 3 boxes by means of CL software MAXO Box nr 2 Water pump (stainless steel)

O 3 generation testbed: 2 modules L aboratory of P hysical and A nalytical C hemistry 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 2 nd Technical meeting (Offenburg) + Report W.P. 1.3

WP 1.4. : O 3 generation testbed L aboratory of P hysical and A nalytical C hemistry OUTLINE  HISTORY  AIR TIGHTNESS  OZONE GAS CONCENTRATION [O 3 ] gas  Pure O 2  N 2 /O 2 (air) Note: target = air as feed gas [O 3 ] gas ≥ 10 g/m 3 (0.5 % v/v)

W.P. 1.4: O 3 generation testbed L aboratory of P hysical and A nalytical C hemistry HISTORY

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 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 [O 3 ] gas ) ADAPTATIONS:new cover was constructed and installed at 2 nd Technical meeting (CL-Seaking)  further adaptations to the cover by LPAC (reinforcement + screws)

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed Smaller air corridor (from 2.2 to 0.4 liter) Additional reinforcement

L aboratory of P hysical and A nalytical C hemistry AIR TIGHTNESS W.P. 1.4: O 3 generation testbed

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed CHECKING THE AIR TIGHTNESS by → air suction (Venturi system) → pressure (Mass Flow Controller)

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed RESULTS AND DISCUSSION Air suction Air pressure

L aboratory of P hysical and A nalytical C hemistry OZONE PRODUCTION W.P. 1.4: O 3 generation testbed

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed PATT-devices: 6 per Box (2 per Module) Box 1: Module 1 to 3 Box 2: Module 4 to 6

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed PROTOTYPE 1 PROTOTYPE 2

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed Pure O 2 as feed gas Measurement of:[O 3 ] gas, current I (mA) Variables:Q O2 (FC: 0 – 60 dm 3 /hr) n° of Modules Power setting (% P)

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed Pure O 2 Gas inlet Gas outlet : PATT-module Air corridor O--O O--O : O 2 molecule : discharge

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed Pure O 2, Box 2, 1 Module activated Measurement of:[O 3 ] gas, current I (mA) Variables:Power setting (% P) [O 3 ] gas (g/Nm3) as a function of the % P of Module 4 (O 3 Box 2) at Q O2 = 60 l/hr. Gas temperature T gas = (30 ± 1)°C.  Linear between 15 and 75 % P, small decrease at % P > 75

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed Pure O 2, Box 2, 1 Module activated I (mA) as a function of the % P of Module 4 (O 3 Box 2) at Q O2 = 60 l/hr. Gas temperature T gas = (30 ± 1)°C.  Same trend as with [O 3 ] gas [O 3 ] gas as a function of I (mA) of Module 4 (O 3 Box 2) at Q O2 = 60 l/hr. Gas temperature T gas = (30 ± 1)°C.  Linear relationship between [O 3 ] gas and I

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed Pure O 2, Box 2, 1 Module activated Time dependence of O 3 buildup  First buildup is always slower Temperature-effect ?

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed Pure O 2, Box 2, 1 Module activated Reproducibility (from day-to-day)  Very reproducible ozone production

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed Pure O 2, Box 2, 3 Modules activated Variables: n° of Modules, position, Power setting (% P)  Cumulative O 3 production (n = 3)  Position in air corridor of no importance

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed Pure O 2, Box 2, 3 Modules activated Variables: Q O2  Exponential dependence of the O 3 concentration on Q O2  Reproducibility !

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed Pure O 2, Box 2, 3 Modules activated Variables: Q O2  Linear dependency of the O 3 concentration on I (but different from 1 Module at constant Q O2 )

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed Pure O 2, Box 2, 3 Modules activated Capacity of the ozone generator a.f.o. Q O2 (3 Modules at 75% P)  exponential increase of the O 3 capacity a.f.o. Q O2 Capacity = [O 3 ] gas x Q O2

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed Pure O 2, Box 1+2, 6 Modules activated Variables: n° of Modules and Q O2  Cumulative O 3 production apparently does not hold for more than 4 Modules (air tightness problem Box 1?) 66 g/m 3 O 3 ~ 3 % v/v O 3

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed SUMMARY (pure O 2 )  [O 3 ] gas is linearly dependent on the power setting ( % P)  higher % P (> 75) result is equal or slightly lower [O 3 ] gas  the same dependence on % P is observed for I and AD-I’s  [O 3 ] gas is linearly dependent on I: I ↑  [O 3 ] gas ↑  O 3 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)  [O 3 ] gas is depending on Q O2 : Q O2 ↓  [O 3 ] gas ↑ (n = 3 and n = 6), again this production is reproducible from day to day  Q O2 ↓  I ↓  [O 3 ] gas ↑

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed N 2 / O 2 as feed gas: “air” Composition of air :

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed N 2 / O 2 Gas inlet Gas outlet : PATT-module Air corridor N--N O--O N--N O--O N--N O--O N--N O--O : O 2 molecule N--N : N 2 molecule : discharge More details in the LPAC-report

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed N 2 / O 2 as feed gas Measurement of:[O 3 ] gas, current I (mA) Variables:Q O2 (FC: 0 – 60 dm 3 /hr) n° of Modules Power setting (% P) composition feed gas (N 2 / O 2 )

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed N 2 / O 2 as feed gas Variables: n° of Modules, composition feed gas (N 2 /O 2 ) [O 3 ] gas as a function of the composition of the feed gas (O 2 /N 2 ) at 75% P (Modules of Box 2 and Module 4). Total gas flow = 60 l/hr. Addition of N 2 :  Beneficial between 60/40 & 80/20.  Identical behavior for 1 or 3 Modules (Box 2).

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed N 2 / O 2 as feed gas Addition of N 2 :  Modules behave differently then in the absence of N 2.

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed N 2 / O 2 as feed gas (versus pure O 2 ): effect of the gas flow Effect of the gas flow Q :  [O 3 ] gas ↓ as Q ↑ (for both)  O 3 generator capacity ↓ as Q ↓ (more pronounced with pure O 2 )

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed N 2 / O 2 as feed gas: is the increased O 3 gas concentration in the presence of N 2 an artefact or real ??  [O 3 ] liq follows [O 3 ] gas (in accordance with Henry’s Law)  Increase ozone production is real ! = N 2 -effect  Effect on pH and conductivity when N 2 is present

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed N 2 / O 2 as feed gas: effect on pH  Sharp decrease of pH and sharp increase of the conductivity when N 2 is present !  + Ultraviolet absorption observed

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed N 2 / O 2 as feed gas: UV-absorption  Ultraviolet absorption observed at 208 nm, even after degassing  presence of HNO 3 O 3 -free MilliQ- water after ozonation with N 2 presence

L aboratory of P hysical and A nalytical C hemistry W.P. 1.4: O 3 generation testbed N 2 / O 2 as feed gas:  NO x 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 !! → Effect of the presence of N 2 during ozone production on pH, conductivity and the UV-absorbance at 208 nm → Indication that HNO 3 is introduced in the water (acidification)

W.P. 1.4 : O 3 generation testbed L aboratory of P hysical and A nalytical C hemistry General conclusions  Design needs to be improved ! [O 3 ] 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 O 2 : → [O 3 ] gas ~ current I (1 versus 3 Modules) → “cumulative” effect of multiple Modules → [O 3 ] gas ~ 1/ gas flow Q → capacity O 3 generator exponentially increases as Q increases → good reproducibility → position Modules in air corridor of no importance

W.P. 1.4 : O 3 generation testbed L aboratory of P hysical and A nalytical C hemistry General conclusions  Ozone gas concentration / production With N 2 / O 2 : → addition N 2 not detrimental (40 – 20 %) → [O 3 ] gas ~ current I (different behavior) → [O 3 ] gas ~ 1/ gas flow Q → capacity O 3 generator exponentially increases as Q increases (less than pure O 2 ) → good reproducibility → NO x are formed as by-product → HNO 3 is formed when water is present (= acidification + possible corrosion)

L aboratory of P hysical and A nalytical C hemistry future * 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:O 2 + H 2 O and air as feed gas W.P. 1.4 : O 3 generation testbed