Taking mass transfer limitation into account during ozonation of pollutants reacting fairly quickly

2004 ◽  
Vol 49 (4) ◽  
pp. 25-30 ◽  
Author(s):  
H. Benbelkacem ◽  
S. Mathé ◽  
H. Debellefontaine
Keyword(s):  
Mass Transfer ◽  
Batch Reactor ◽  
Kinetic Regime ◽  
Mass Balances ◽  
Fast Reaction ◽  
Mass Transfer Limitation ◽  
Intermediate Regime ◽  
Gas Concentration ◽  
By Products ◽  
Slow Kinetic

Various situations observed when oxidizing organic compounds via ozone in a semi-batch reactor are illustrated. The resistance to the transfer of ozone from gas to liquid is accounted for using the film model. The mass balances are numerically solved simultaneously within the reactor and within the film to produce time dependent profiles of concentrations, Hatta, enhancement and depletion factors. Firstly, theoretical profiles are exemplified for various kinetic regimes from slow to fast; reaction occurs either in the bulk, in the film or in both. This shows the drastic importance of the shapes of the gas concentration profiles - both at the exit of the reactor and in the liquid phase - in determining the regime. Then, a typical example dealing with fumaric acid ozonation is shown. Firstly, the acid itself oxidizes rapidly producing an intermediate regime: part of the reaction occurs within the film, part within the bulk and the rate constant can be determined. Then, the by-products oxidize more slowly producing a typical regime: reaction occurs within the bulk, the concentration of dissolved ozone is almost 0 and the mass transfer coefficient can be determined. Finally, when all organics have oxidized, the self-decomposition of ozone governs a slow kinetic regime: the concentration of dissolved ozone is close to equilibrium.

Conversion rate and mass transfer limitation in trickle bed reactors in the presence of a fast reaction

2004 ◽  
Vol 59 (22-23) ◽  
pp. 5411-5416 ◽  
Author(s):  
M. Banchero ◽  
L. Manna ◽  
S. Sicardi ◽  
J.G. Boelhouwer ◽  
M.I. Urseanu ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Conversion Rate ◽  
Fast Reaction ◽  
Mass Transfer Limitation ◽  
Trickle Bed Reactors ◽  
Trickle Bed

Field investigations on reactive settling in an intermittent aeration sequencing batch reactor activated sludge process

2000 ◽  
Vol 41 (1) ◽  
pp. 127-135 ◽  
Author(s):  
A.A. Kazmi ◽  
H. Furumai
Keyword(s):  
Mass Transfer ◽  
Activated Sludge ◽  
Batch Reactor ◽  
Phosphorus Release ◽  
Activated Sludge Process ◽  
Intermittent Aeration ◽  
Mass Transfer Limitation ◽  
Batch Tests ◽  
Field Investigations ◽  
Ph Decrease

The overall reactions during settling in an intermittent aeration SBR activated sludge process have been studied on a full scale. Several field investigations were conducted during settling in different seasons. Nitrate, MLSS, phosphate and TOC profiles were obtained at specified depths. Mass balances of nitrogen were made in order to evaluate the effect of different MLSS and seasonal conditions on nitrogen removal during settling. Total nitrogen reduction of more than 30% was achieved during settling by maintaining high MLSS in order of 3000 mg/L. Residual DO plays an important role in causing delay of denitrification for lower MLSS sludge concentration. Phosphorus release was observed in the bottom of the reactor and its occurrence was well coincident with the pH decrease. Denitrification rates and their temperature dependency were determined. Temperature coefficient θ was found to be 1.083 (valid in the range of 17–27°C). Mass transfer limitation during batch sludge settling was discussed. It was found out from batch tests with and without mixing, that denitrification rate was reduced by 40% under mass transfer limiting conditions.

Mass transfer impacts in flocculent and granular biomass from SBR systems

2004 ◽  
Vol 50 (10) ◽  
pp. 203-212 ◽  
Author(s):  
D. Gapes ◽  
B.-M. Wilén ◽  
J. Keller
Keyword(s):  
Mass Transfer ◽  
Particle Size ◽  
Oxygen Uptake ◽  
Activated Sludge ◽  
Uptake Rate ◽  
Oxygen Uptake Rate ◽  
Batch Reactor ◽  
Average Particle Size ◽  
Gas Analysis ◽  
Average Particle

An experimental study was conducted to describe mass transfer impacts within nitrifying aggregates sourced from sequencing batch reactor (SBR) activated sludge systems. Flocculent and granular sludge with high nitrification activity was obtained in two laboratory SBR systems, supplied with a synthetic, ammonium-based feed. The flocculent biomass was fractionated using a sieving procedure, in order to obtain biomass fractions with different particle size distributions. The oxygen uptake rate (OUR) response to changes in dissolved oxygen concentration was measured under highly controlled conditions in a titrimetric and off-gas analysis (TOGA) sensor, and the results used to assess mass transfer effects. As the average particle size of the biomass increased, mass transfer limitations were found to increase significantly. Empirically fitted, apparent KS,O2 values were demonstrated to be highly dependent on particle size, and reflect the mass transfer limitations occurring in the aggregates within a given system. Such parameters thus have little to do with the actual biokinetic parameter from which they are derived. The results obtained from the TOGA sensor study were consistent with those obtained from a microelectrode study on the same nitrifying granules. Together, these studies add considerable weight to the conclusion that consideration of external and internal mass transfer limitations is vital to the accurate description of activated sludge treatment processes, particularly those with a high oxygen uptake rate.

scholarly journals Jet aeration as alternative to overcome mass transfer limitation of stirred bioreactors

2018 ◽  
Vol 18 (4) ◽  
pp. 244-253 ◽  
Author(s):  
Sebastian Weber ◽  
Sebastian Schaepe ◽  
Stephan Freyer ◽  
Michael-Helmut Kopf ◽  
Christian Dietzsch
Keyword(s):  
Mass Transfer ◽  
Mass Transfer Limitation ◽  
Stirred Bioreactors

Reactor scale-up in AOPs: from laboratory to commercial scale

2004 ◽  
Vol 49 (4) ◽  
pp. 13-18 ◽  
Author(s):  
C.S. Zalazar ◽  
M.D. Labas ◽  
C.A. Martín ◽  
R.J. Brandi ◽  
A.E. Cassano
Keyword(s):  
Formic Acid ◽  
Large Scale ◽  
Flow Reactor ◽  
Acid Output ◽  
Water Solution ◽  
Batch Reactor ◽  
Scale Up ◽  
Mass Balances ◽  
Tubular Flow Reactor ◽  
Tubular Flow

A procedure to scale-up photoreactors employed in AOPs using laboratory information has been developed. Operating with a model compound the proposed procedure was applied to the decomposition of formic acid in water solution using hydrogen peroxide and UV radiation. With laboratory experiments the parameters of the kinetic equation were obtained in a small batch reactor operated within a recycling apparatus. The whole system was modeled employing radiation and mass balances. These balances were used together with a non-linear parameter estimator to derive the model kinetic constants. Then, these results were used in the modeling of the large-scale reactor to predict exit conversions in an isothermal, continuous, tubular flow reactor that is 2 m long and has a volume of 12 l. Once more, radiation and mass balances were used to predict formic acid output concentrations. Experimental data in the large-scale apparatus are in good agreement with theoretical predictions.

Triphase Catalysis Using Silica Gel as Support

2013 ◽  
Vol 11 (1) ◽  
pp. 347-352
Author(s):  
T. Sankarshana ◽  
J. Soujanya ◽  
A. Anil Kumar
Keyword(s):  
Potassium Permanganate ◽  
Silica Gel ◽  
Reaction Rate ◽  
Phase Transfer ◽  
Supported Catalysts ◽  
Batch Reactor ◽  
Kinetic Regime ◽  
Rate Of Reaction ◽  
Potential Applications ◽  
Triphase Catalysis

Abstract The oxidation reaction of 2-ethyl-1-hexanol with potassium permanganate in the presence and absence of silica-gel-supported phase-transfer catalyst (PTC) in triphasic conditions was studied. In a batch reactor, the performance of the solid-supported catalysts was compared with unsupported catalyst and without the catalyst. The effect of speed of agitation, catalyst concentration, potassium permanganate concentration and temperature on reaction rate was studied. The reaction is found to be in the kinetic regime. The rate of reaction with the catalyst immobilised on the silica gel was less compared to the catalyst without immobilisation. Triphase catalysis with supported PTCs has potential applications in the continuous quest for greener industrial practices.

scholarly journals The Impact of Iron Oxide Concentration on the Performance of Molten Oxide Electrolytes for the Production of Liquid Iron Metal

2019 ◽  
Vol 51 (1) ◽  
pp. 365-376
Author(s):  
Jan Wiencke ◽  
Hervé Lavelaine ◽  
Pierre-Jean Panteix ◽  
Carine Petitjean ◽  
Christophe Rapin
Keyword(s):  
Mass Transfer ◽  
Iron Oxide ◽  
Liquid Iron ◽  
Mass Transfer Limitation ◽  
Oxide Concentration ◽  
Ohmic Drop ◽  
Geometrical Form ◽  
Flow Through ◽  
Molten Oxide ◽  
The Impact

AbstractThe effect of iron oxide concentration on the conductive behavior of a molten oxide electrolyte has been investigated at 1823 K using stepped linear scan voltammetry. To maximize the current flow through the electrolyte the ohmic drop in the cell was minimized by shortening the electrode distance. The acquired current was then interpreted by means of an ohmic drop correction, taking into account the conductivity of the alumina-silicate electrolyte and the geometrical form factor of the cell. Via this methodology, a mass transfer limitation in dependence of the iron oxide concentration was identified. This mass transfer limitation vanishes above 7 wt pct of iron oxide where charge transfer starts to be limited solely by electrochemical reaction kinetics. In the analyzed range of concentration, an impact of iron oxide on electronic conduction was not measurable. In addition to these findings, the faradaic yield of the anode half-reaction was determined by the life-measure of O2-production. Hereby, a domain of an anodic yield close to 100 pct for various iron oxide concentrations was identified. Based on these findings, suitable conditions for the electrochemical production of liquid iron were determined.

Volatile organic compound adsorption in a gas-solid fluidized bed

2004 ◽  
Vol 50 (4) ◽  
pp. 233-240 ◽  
Author(s):  
Y.L. Ng ◽  
R. Yan ◽  
L.T.S. Tsen ◽  
L.C. Yong ◽  
M. Liu ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Activated Carbon ◽  
Adsorption Capacity ◽  
Fluidized Bed ◽  
Residence Time ◽  
Fixed Bed ◽  
Gas Concentration ◽  
Adsorption Characteristics ◽  
Bubbling Bed ◽  
Intraparticle Mass Transfer

Fluidization finds many process applications in the areas of catalytic reactions, drying, coating, combustion, gasification and microbial culturing. This work aims to compare the dynamic adsorption characteristics and adsorption rates in a bubbling fluidized bed and a fixed bed at the same gas flow-rate, gas residence time and bed height. Adsorption with 520 ppm methanol and 489 ppm isobutane by the ZSM-5 zeolite of different particle size in the two beds enabled the differentiation of the adsorption characteristics and rates due to bed type, intraparticle mass transfer and adsorbate-adsorbent interaction. Adsorption of isobutane by the more commonly used activated carbon provided the comparison of adsorption between the two adsorbent types. With the same gas residence time of 0.79 seconds in both the bubbling bed and fixed bed of the same bed size of 40 mm diameter and 48 mm height, the experimental results showed a higher rate of adsorption in the bubbling bed as compared to the fixed bed. Intraparticle mass transfer and adsorbent-adsorbate interaction played significant roles in affecting the rate of adsorption, with intraparticle mass transfer being more dominant. The bubbling bed was observed to have a steeper decline in adsorption rate with respect to increasing outlet concentration compared to the fixed bed. The adsorption capacities of zeolite for the adsorbates studied were comparatively similar in both beds; fluidizing, and using smaller particles in the bubbling bed did not increase the adsorption capacity of the ZSM-5 zeolite. The adsorption capacity of activated carbon for isobutane was much higher than the ZSM-5 zeolite for isobutane, although at a lower adsorption rate. Fourier transform infra-red (FTIR) spectroscopy was used as an analytical tool for the quantification of gas concentration. Calibration was done using a series of standards prepared by in situ dilution with nitrogen gas, based on the ideal gas law and relating partial pressure to gas concentration. Concentrations up to 220 ppm for methanol and 75 ppm for isobutane were prepared using this method.

Sign in / Sign up

Export Citation Format

Share Document