Alfons Vogelpohl

Landfill leachate treatment by a photoassisted fenton reaction

A combination of the classical Fenton reaction (Fe(II)+H2O2) with UV light, the photoassisted Fenton reaction, has been investigated for the treatment of landfill leachate. The investigation has been carried out with an experimental set-up to establish the optimal treatment conditions. The degradation rate of organic pollutants is strongly promoted by the photoassisted Fenton reaction. The degradation rate depends on the amount of H2O2 and Fe(II) added, pH value, and radiation intensity. At a specific energy input of 80 kW m−3 the oxidation rate was increased to six times the rate without radiation (0 kW m−3). At the higher radiation intensity of 160 kW m−3 the degradation rate was about two times faster than at that of 80 kW m−3. Due to the regeneration of the consumed Fe(II) ions through the irradiation, the amount of ferrous salt to be added can be remarkably reduced. The optimum conditions were obtained with 1.0 × 10−3 mol 1−1 Fe(II) added, a pH value of 3, and a molar ratio of COD: H2O2 = 1:1. At a COD volume loading of less than 0.6 kg m−3 h−1, a COD degradation of more than 70% could be obtained with an energy input of 80 kW m−3.

Degradation of Organic Pollutants by the Photo‐Fenton‐Process

The Photo-Fenton-Process utilizing the combinations Fe(II)/H 2 O 2 /UVA and Fe(III) oxalate/H 2 O 2 /UVA was employed with success to degrade biorefractory organic pollutants in landfill leachate. The rate of degradation of the organic pollutants depends on the concentrations of hydrogen peroxide and the iron catalyst, the pH value and the concentration of dissolved oxygen. A comparison of the Photo-Fenton-Process with the H 2 O 2 /Fe(II) process and the H 2 O 2 /UVC process shows that the Photo-Fenton-Process gives a higher COD degradation and a reduced energy consumption of at least 30% compared to the H 2 O 2 /UVC process. By using photogenerated Fe(II) the amount of the iron catalyst required and the volume of sludge produced are strongly reduced.

Activated carbon column performance studies of biologically treated landfill leachate

In adsorption studies with a biologically pretreated landfill leachate using two activated carbon columns, the concentration of the non-biodegradable organic and chlorinated organic compounds, as well as the colour, could be reduced to an acceptable level. The results show a complex interaction of adsorption and desorption between the lower and higher molecular weight components of the leachate.

A simplified hydrodynamic model for a pulsed sieve-plate extraction column

Abstract A simplified stage-wise hydrodynamic model for simulation of a pulsed sieve-plate extraction column has been presented. The model is based on a drop population balance which takes into account drop breakage and coalescence in each stage. Each stage is represented by the actual column compartment between two sieve plates. Although experimental break-up parameters have been used in the model, the coalescence coefficients have been taken as the fitting parameters and the values which gave the best fit with the experimental data have been used. The predicted values have been compared with data from two different diameter pilot plant columns and the agreement is found to be quite satisfactory for the system butylacetate-water. The model can be used for coalescence parameter estimation of different drop sizes, which will be taken up as part of the extension of the present work.

A comparative study of wastewater treatment by chemical wet oxidation

Abstract A leachate from a municipal landfill and an industrial wastewater from an emulsion-breaking unit have been treated by chemical wet oxidation using ozone and hydrogen peroxide as oxidants. The best results were obtained with UV radiation resulting in the formation of OH· radicals. If ozone is used, mass transfer will be the limiting step in the degradation reactions. The specific consumption of hydrogen peroxide is drastically reduced if pure oxygen or air is dispersed into the wastewater. Under optimum conditions, the COD of the leachate and of the industrial wastewater could be reduced by 90% in c. 3 and 5 h, respectively.

Fluid dynamics in an impinging-stream reactor

Abstract Experimental results relating to the hydrodynamic behaviour of an impinging-stream reactor are presented and discussed. The parameters varied were the gas flow rate and the liquid flow rate while the quantities measured were the gas holdup, the mean bubble diameter and the absolute bubble velocity in the main reactor tube. From these quantities, the internal gas recirculation rate and the gas flow ratio have been determined. The internal gas recirculation rate is important in evaluating the mass-transfer performance of the impinging-stream reactor.

Mass transfer in high viscosity media

Abstract Even though high viscosity media are processed in a number of industries such as the chemical, pharmaceutical, petrochemical, and food industries, info Highly viscous media are processed in a number of industries but their mass transfer characteristics are hardly known. This study was started to partia 1. 1. bubble formation zone, 2. 2. bubble rising zone, 3. 3. droplet formation zone. The results show that the mass flows in these zones differ considerably, with the mass transfer in the droplet zone playing the dominant role. According to our results, an increasing viscosity leads to a large reduction in mass transfer which levels out for viscosities larger than 60 mPa s. Th The evaluation of high speed photographs shows no effect of liquid viscosity on either the average bubble or droplet size. Since the bubble formation f For viscosities less than 60 mPa s this effect can be partially compensated for by installing an additional layer of packing above the two-phase fluid.

Auslegung von pulsierten Siebboden- und Sprühkolonnen für die Extraktion auf der Basis von Einzeltropfenuntersuchungen

Die Auslegung von pulsierten Siebboden-Extraktionskolonnen allein aufgrund von Literaturdaten ist bis heute nicht moglich. Es sind zusatzliche kostenintensive Pilotversuche mit dem Originalgemisch erforderlich. Ursache hierfur ist u.a. der noch weitgehend ungeklarte komplexe Stoffaustauschmechanismus zwischen zwei flussigen Phasen, der z.B. von oberflachenaktiven Substanzen und dem Marangoni-Effekt beeinflusst wird. Um den experimentellen Aufwand bei der Ermittlung der fur die Auslegung einer technischen Kolonne benotigten Ausgangsdaten zu minimieren, wurden am Institut fur Thermische Verfahrenstechnik Standardapparaturen entwickelt, an denen die erforderlichen fluiddynamischen Daten und Stoffubergangsparameter durch Messungen an Einzeltropfen unter Einsatz des jeweiligen technischen Gemisches ermittelt werden konnen. Aufbauend auf diesen Stoffaus tauschdaten und bereits fruher bestimmten fluiddynamischen Parametern werden die Tropfengrosen-, Holdup- und Konzentrationsprofile fur die Systeme Toluol-Aceton-Wasser und n-Butylacetat-Aceton-Wasser entlang einer PSE-Kolonne berechnet und mit Literaturdaten sowie eigenen, in einer halbindustriellen PSE-Kolonne gemessenen Werten verglichen. The Design of Pulsed Sieve-Plate Extraction Columns for Extraction on the Basis of Single Drop Experiments The design of pulsed sieve-plate extraction columns (PSE) on the basis of published data is not currently possible as it relais on additional and cost intensive laboratory experiments. This is due to the lack of knowledge about the complex mass transfer between two liquid phases which is strongly influenced by factors such as surface active impurities and the Marangoni-effect. In order to reduce the experimental effort in the determination of the required design input data, several standard experimental test units have been developed at the Institut fur Thermische Verfahrenstechnik that allow the determination of the needed fluiddynamic and mass transfer data. The test units are based on single drop experiments, and they use the technical mixture to be separated in practice. Finally, the meas ured mass transfer and fluiddynamic data are used to calculate the drop-size-, holdup- and concentration-profiles for the systems toluene-ace tone-water and n-butylacetate-ace tone-water in a PSE-column and a spray-column. The results are compared with experimental data reported in the literature and our own data obtained with a semi-industrial PSE-column.

Absorption of oxygen by aqueous glycerol solutions and squalane

Highly viscous media are used in a number of process industries, such as the chemical, petrochemical, pharmaceutical, and food industries. Design of mass transfer equipment for such media is very difficult because of the rather limited experimental data. Therefore, the absorption of oxygen from air into glycerol—water solutions has been studied under different operating conditions and sieve tray geometries (namely, hole diameter and hole spacing). Furthermore, the results of supplementary absorption experiments of oxygen into squalane (C30H62) show that the results with the system oxygen—glycerol—water are transferable to other systems. Chemical, pharmaceutical, and petrochemical as well as food industries have to deal increasingly with processes where mass transfer in highly viscous media is involved. Design of mass transfer equipment for such media is very difficult because of the rather limited experimental data. Therefore, a study was started to partially fill this gap; in particular, it deals with evaporation of pure cyclohexanol into air [2] as well as absorption of oxygen from air into glycerol—water solutions on a sieve tray [3-6]. In this paper the influence of the sieve tray geometry on mass transfer was studied. The following observations were made concerning the effect of hole diameter and hole spacing. 1. (1) In the bubble and spray regime (υG < 1 m s−1) for low viscosities there is no effect of the hole diameter on the efficiency. 2. (2) At higher viscosities and low gas velocities an increasing hole diameter results in a reduction of mass transfer. 3. (3) In the drop regime (υG > 1 m s−1), i.e. for high gas velocities, an improvement in the efficiency is noticed for sieve trays with larger holes. 4. (4) In the bubble and spray regimes there is no effect of the hole spacing on mass transfer for low and high viscosities. 5. (5) In the drop regime a better efficiency is obtained with higher hole spacing. The experimental results are explained well with the recently developed model based on high-speed photographs, which divides the two-phase fluid on a sieve tray into three distinct zones, as shown in Fig. 2. The droplet formation zone which represents break-up of the bubbles at the fluid surface into liquid laminae and droplets, as well as the mass transfer between the droplets formed and the surrounding gas, plays a dominant role with respect to the total mass transferred. Supplementary absorption experiments of oxygen into squalane have been carried out to indicate the transferability of the results to hydrocarbon systems. A comparison of these results with those of the absorption of oxygen into glycerol—water mixtures shows excellent agreement of the basic trends.

Mathematical Solution of the Two‐Dimensional Dispersion Model

The one-dimensional dispersion model under the assumption that the fluid is completely mixed in the radial direction is generally used to describe turbulent mixing in apparatus with axial flow. With increasing apparatus diameter, however, this assumption becomes less correct and it becomes necessary to take radial mixing into account. In this example a mathematical solution of the two-dimensional model is developd and applied to describe the turbulent mixing in a sieve-tray extraction column.