Potentialities of photocatalytic process in decomposition of pollutants from food technologies
Introduction Photocatalytic processes enable a transformation of light energy into electric or chemical one. An expansion of following branches which are connected with research and application of photocatalytic technologies can be expected: Electricity production using photovoltaic cells Controlled biomass production using a photosynthetic ability of green plants, algae, etc. Photocatalytic transformation of carbon dioxide into substances of high energy content Degradation of pollutants
A light illuminating a semiconductor particle causes an electron excitation from the energy lower valence band into the higher conduction band and creates electrically charged centres: photon + semiconductor = h+ + e- where e- is a mobile electron and h+ is the positive centre. The electron causes reduction and an oxidation occurs in the positive centre. Positives centres are strong oxidants. Radicals OH, the strongest known oxidizer, arise in presence of water. Organic compounds on the catalyst surface or near the catalyst are oxidized into carbon dioxide, water and inorganic salts.
Principles of photokatalytic process
Photocatalytic reaction is affected by: a) the energy of the illuminating light, b) the ability of the catalyst to absorb light quantum, which is given by the size of particles and their chemical and crystallographic structure in a nano-scale, - nanocrystalline TiO 2 c) the technical design
Advantages of practical applications of photocatalytic processes The photocatalysis is a modern technology, whose number of applications grows exponentially. It fulfils a conception of sustainable development and improvement of quality of life in a near future: High energy demands tends to use other alternative energy sources like the solar energy, whose application does not increase an amount of carbon dioxide in the atmosphere. Photocatalytic oxidation processes use natural resources without chemicals. Photocatalytic degradation of organic compounds used in air and water purification does not produce other wastes burdening the environment. Connection of photocatalysis with membrane technologies improves a potential of both technologies.
A potential of photocatalysis in an area of agricultural and food technologies: New ecological system for treatment of waste water, groundwater and production of drinking water. Improved sanitation and hygienics in industrial workplaces, households and application of surfaces with photocatalytic coating. Higher air quality, removing of microorganisms, toxic compounds, odours and ethylene in working and storage areas. Economical benefits in comparison with conventional techniques.
c/c o (mg/l) 1,00 Phenolic substances decomposition Fotokatalytický rozklad fenolu - vliv teploty 0,90 0,80 0,70 0,60 30 st. o C 40 st.c o C 50 st.c o C 0,50 0,40 0,30 0,20 0,10 0,00 0 5 10 15 20 25 30 35 40 čas (min) Time (min)
conductivity (ms) Decomposition of oxalic acid Legend: p1, p2 two trials made under the same conditions with catalyst, pra the same experiment with no catalyst used 10 9 8 7 6 5 p2 p1 pra 4 3 2 1 0 0 20 40 60 80 100 120 140 160 180 200 time (min)
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MODELOVÁNÍ A SIMULACE POTRAVINÁŘSKÝCH VÝROB Modelling and simulation of food processes and technology Příklad 1: Kontinuální chromatografická separace Příklad 2: Bezodpadová výroba cukru a ethanolu v cukrovaru Example 1: Continuous chromatography separation Example 2: Non-waste production of etanol and sugar
Continuous chromatography separation Diskontinuální a kontinuální chromatografická separace KCHS-SMB-8-N Continuous chromatographic separator kontinuální chromatografický separátor princip založen na chromatografickém systému se simulovaným tokem pevné fáze pevná fáze: Lewatit MDS 1368 Na kolona: vnitřní objem 1 l, délka 2000 mm maximální tlak 0.4 MPa celkový příkon: 2 kw
Diskontinuální a kontinuální chromatografická separace Modelování průběhu procesu y 1 2 3 4 5 6 7 8 dm=ρdv=ρadx dm r,in /dτ dm r,out /dτ 0 x x+dx 2 c r cr ( x) cr ( x) D v r 2 r (1 ) K r x x q r f ( c ) K r r c r c ( 0) c ( 0; x) r r x P1 Feed Eluent P3 1 2 3 4 5 6 7 8 P2 P5 Simulace procesu Extract Raffinate cr x 0 vr D r c r c in cr x xl 0 Q Ex Section I Q E 3 4 Section II 2 Liquid p. Q Re 5 Section IV 1 Solid p. 6 8 7 Q F Section III Q Ra
Diskontinuální a kontinuální chromatografická separace Řízení procesu distribuované řízení výpočet distribučních koeficientů z diskontinuálních měření odhad operačních parametrů na počátku procesu archivace měřených hodnot vyhodnocování běžících procesů fuzzy řízení Operátorský panel Základní schéma řízení SMB CHROMATOGRAPHY STATION Standard Industrial Signals PC WinCC PLC OPC SERVER RS 232 conductivity, refraction MATLAB DATABASE
Diskontinuální a kontinuální chromatografická separace Aplikace diskontinuální separace kontinuální separace Desorption curve for lactose hydrolyzate g/l 60 50 40 GOS Lac Glc Gal 30 20 10 0 0 10 20 30 40 50 60 t/min Frakcionace melasy: - izolace betainu - izolace sacharosy Frakcionace hydrolyzované syrovátky: - izolace galaktooligosacharidů
Modelling and Simulation Non-waste production of sugar and ethanol in sugar factory Biofuel production Implementation of novel processes Crystallization of stillage
Standard scheme
Technological scheme of TTD
TTD scheme cont.
Model of TTD scheme
Model of TTD scheme : 5st part
New scheme of ICT Prague
New scheme of ICT Prague cont.
Fig.: SUGAR BEET Extraction EXHAUSTED PULP Complete technological scheme that would connect sugar and ethanol production. ICT Prague Refinery Raw juice filtration (pulp separation) Microfiltration of raw juice PERMEATE RAW SUGAR MOLASSES WHITE SUGAR RAW JUICE Beet pulp RETENTATE Film evaporating (permeate thickening) Cooling crystallization (during the campaign) MOTHER LIQUOR Storage of mother liquor (during the campaign) Fermentation P a r t i a l s t i l l a g e r e c i r c u l a t i o n Molasses fermentation Dilution and fermentation of mother liquor (out of the campaign) CRUDE ETHANOL Refinery Distillation STILLAGE BIOETHANOL Crystallization Stillage thickening Drying DRIED BEET PULP NaSOKSO 24, 24 FEEDING PELLETS
Stillage Crystallization
Fig. : Results of mass balance Model 1: 100 % of raw juice is used for sugar production, i.e. 100 % of juice goes to purification Model 5: total processing of raw juice to ethanol, i.e. 0 % of juice goes to purification.
Model 1: CONCLUSION Model 5: If all raw juice is used for sugar production, we could obtain: 28 t/h of sugar, 19 t/h of ethanol, 40 t/h of feeding pellets 21 t/h of carbon dioxide Using all raw juice for fermentation yields: 0 t/h of sugar, 31 t/h of ethanol, 43 t/h of feeding pellets 36 t/h of carbon dioxide. The shown scheme provides large possibilities to suggest production according to calculations monitoring a financial profit from the product sales. A large amount of produced CO 2 is also valuable byproduct for beverage industry. Salt content in dried beet pulp can be reduced by crystallization. Also this potentiality will be evaluated.
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Bezodpadová výroba cukru a ethanolu v cukrovaru Kombinovaná technologie VŠCHT: Membránová filtrace, fermentace a přímá krystalizace surové šťávy