The Effect of Kaolin Concentration on Flock Growth Kinetics in an Agitated Tank

This paper reports on an investigation of the effect of initial solid particle concentrationon flock growth and flock shape characterized by the fractal dimension Df2. The experiments werecarried out in a baffled tank agitated by a Rushton turbine at mixing intensity 64W/m3 and constantdimensionless flocculant dosage DF/ck0 = 4.545 mg/g. The model wastewater (a suspension of tapwater and kaolin) was flocculated with Sokoflok 56A organic flocculant (solution 0.1% wt.). The size and shape of the flocks were investigated by image analysis. The flock growth kinetics was fitted according to a semi-empirical generalized correlation proposed by the authors. The dependences Af = 100.35ck01.532,  df,eq,max = 1.0474ck0-0.311 and (NtF)max = 1622ck0-0.393 were found. The fractal dimension Df2 was found to be independent of flocculation time and initial kaolin concentration, and its value Df2 = 1.470 ± 0.023 was determined as an average for the given conditions

The Effect of Kaolin Concentration on Flock Growth Kinetics in an Agitated Tank

This paper reports on an investigation of the effect of initial solid particle concentrationon flock growth and flock shape characterized by the fractal dimension Df2. The experiments werecarried out in a baffled tank agitated by a Rushton turbine at mixing intensity 64W/m3 and constantdimensionless flocculant dosage DF/ck0 = 4.545 mg/g. The model wastewater (a suspension of tapwater and kaolin) was flocculated with Sokoflok 56A organic flocculant (solution 0.1% wt.). The size and shape of the flocks were investigated by image analysis. The flock growth kinetics was fitted according to a semi-empirical generalized correlation proposed by the authors. The dependences Af = 100.35ck01.532,  df,eq,max = 1.0474ck0-0.311 and (NtF)max = 1622ck0-0.393 were found. The fractal dimension Df2 was found to be independent of flocculation time and initial kaolin concentration, and its value Df2 = 1.470 ± 0.023 was determined as an average for the given conditions

LOCAL VELOCITY PROFILES MEASURED BY PIV IN AN VESSEL AGITATED BY RUSHTON TURBINE

The hydrodynamics and flow field were measured in an agitated vessel using 2-D Time Resolved Particle Image Velocimetry (2-D TR PIV). The experiments were carried out in a fully baffled cylindrical flat bottom vessel 300 mm in inner diameter. The tank was agitated by a Rushton turbine 100 mm in diameter. The velocity fields were measured for three impeller rotation speeds 300 rpm, 450 rpm and 600 rpm and the corresponding Reynolds numbers in the range 50 000 < Re < 100 000, which means that the fully-developed turbulent flow was reached. In accordance with the theory of mixing, the dimensionless mean and fluctuation velocities in the measured directions were found to be constant and independent of the impeller rotational speed. The velocity profiles were averaged, and were expressed by Chebyshev polynomials of the 1st order. Although the experimentally investigated area was relatively far from the impeller, and it was located in upward flow to the impeller, no state of local isotropy was found. The ratio of the axial rms fluctuation velocity to the radial component was found to be in the range from 0.523 to 0.768. The axial turbulence intensity was found to be in the range from 0.293 to 0.667, which corresponds to a high turbulence intensity

LOCAL VELOCITY PROFILES MEASURED BY PIV IN AN VESSEL AGITATED BY RUSHTON TURBINE

The hydrodynamics and flow field were measured in an agitated vessel using 2-D Time Resolved Particle Image Velocimetry (2-D TR PIV). The experiments were carried out in a fully baffled cylindrical flat bottom vessel 300 mm in inner diameter. The tank was agitated by a Rushton turbine 100 mm in diameter. The velocity fields were measured for three impeller rotation speeds 300 rpm, 450 rpm and 600 rpm and the corresponding Reynolds numbers in the range 50 000 &lt; Re &lt; 100 000, which means that the fully-developed turbulent flow was reached. In accordance with the theory of mixing, the dimensionless mean and fluctuation velocities in the measured directions were found to be constant and independent of the impeller rotational speed. The velocity profiles were averaged, and were expressed by Chebyshev polynomials of the 1st order. Although the experimentally investigated area was relatively far from the impeller, and it was located in upward flow to the impeller, no state of local isotropy was found. The ratio of the axial rms fluctuation velocity to the radial component was found to be in the range from 0.523 to 0.768. The axial turbulence intensity was found to be in the range from 0.293 to 0.667, which corresponds to a high turbulence intensity

Dispersion Kinetics Modelling

Stirred tanks for dispersion, the pre-dispersion of two immiscible liquids or particulate solidliquid suspension are extensively used in the chemical, food, pharmaceutical and metallurgical industries, for purposes such as suspension/emulsion polymerisation, heterogeneous/phase-transfer catalytic chemical reactions, paint production and hydrometallurgical solvent extraction. The aim of this paper is to propose the simple dispersion model enabling the prediction of particle size changes over time and taking into account the type of breakup mechanisms, the non-homogeneity of local turbulent energy dissipation rate in an agitated vessel and the effect of the number of times the liquid passes through the impeller and the impeller zone. The model was successfully tested on data published by Ditl et al. (1981)

Dispersion Kinetics Modelling

Stirred tanks for dispersion, the pre-dispersion of two immiscible liquids or particulate solidliquid suspension are extensively used in the chemical, food, pharmaceutical and metallurgical industries, for purposes such as suspension/emulsion polymerisation, heterogeneous/phase-transfer catalytic chemical reactions, paint production and hydrometallurgical solvent extraction. The aim of this paper is to propose the simple dispersion model enabling the prediction of particle size changes over time and taking into account the type of breakup mechanisms, the non-homogeneity of local turbulent energy dissipation rate in an agitated vessel and the effect of the number of times the liquid passes through the impeller and the impeller zone. The model was successfully tested on data published by Ditl et al. (1981)

Accounting for small transport companies and use its information outputs for control of the company

Cílem této diplomové práce bylo definovat vazby mezi účetnictvím, finanční analýzou a finančním řízením. První krok ke splnění tohoto cíle vyžadoval věnovat každé této oblasti samostatnou pozornost a to zejména ve vztahu ke vstupům a výstupům jednotlivých oblastí. Druhým a závěrečným krokem bylo hledání vazeb mezi jednotlivými oblastmi, které bylo provedeno na zpracování konkrétního příkladu. Postup zde byl takový, že na základě výstupů účetnictví jsem provedl finanční analýzu, jejíž výstupy sloužily jako podklad pro finanční řízení. Na základě provedeného příkladu se proto domnívám, že účetnictví, finanční analýza a finanční řízení představují uzavřený systém firemních financí.The objective of this diploma project was define the structure among the accounting, the financial analysis and the financial management. The first step for realize of this objective required to present independent attention to the each. The main attention was present to the entrances and the exits. The second step was define the structure. This was practise on the concrete example. The finish is following: the accounting, the financial analysis and the financial management are creating the closed system of the corporation finance.Katedra dopravního managementu, marketingu a logistikyDokončená práce s úspěšnou obhajobo

Hydrodynamics and Mass Transfer in a Concentric Internal Jet-Loop Airlift Bioreactor Equipped with a Deflector

The gas–liquid hydrodynamics and mass transfer were studied in a concentric tube internal jet-loop airlift reactor with a conical bottom. Comparing with a standard design, the gas separator was equipped with an adjustable deflector placed above the riser. The effect of riser superficial gas velocity uSGR on the total gas holdup εGT, homogenization time tH, and overall volumetric liquid-phase mass transfer coefficient kLa was investigated in a laboratory bioreactor, of 300 mm in inner diameter, in a two-phase air–water system and three-phase air–water–PVC–particle system with the volumetric solid fraction of 1% for various deflector clearances. The airlift was operated in the range of riser superficial gas velocity from 0.011 to 0.045 m/s. For the gas–liquid system, when reducing the deflector clearance, the total gas holdup decreased, the homogenization time increased twice compared to the highest deflector clearance tested, and the overall volumetric mass transfer coefficient slightly increased by 10–17%. The presence of a solid phase shortened the homogenization time, especially for lower uSGR and deflector clearance, and reduced the mass transfer coefficient by 15–35%. Compared to the gas–liquid system, the noticeable effect of deflector clearance was found for the kLa coefficient, which was found approx. 20–29% higher for the lowest tested deflector clearance

The Liquid–Liquid Dispersion Homogeneity in a Vessel Agitated by a High-Shear Sawtooth Impeller

The agitation of immiscible liquids or solid suspensions is a frequent operation in chemical and metallurgical industries. The product quality yield and economy of the processes are significantly affected by mixing conditions. Prediction of mean drop size distribution (DSD) during agitation is fundamental for processes in many branches of industry where the mass transfer is crucial. This contribution aims to analyze the homogeneity of a dispersed system in a vessel agitated by a high-shear sawtooth impeller. The homogeneity of liquid&ndash;liquid dispersion is determined by comparison of Sauter mean diameters and drop size distribution (DSD) from different measured regions and for various dispersion times. The experiments were carried out in a baffled vessel for various impeller speeds. The sizes of droplets were obtained by the in-situ measurement technique and by the image analysis (IA) method

Beer foam decay: effect of glass surface quality and CO2 content

The effect of beer glass surface quality and CO2 content in beer on foam decay was investigated using our experimental method. The effect of beer glass surface quality on foam decay was experimentally investigated for: i) cold & clean glass surface, ii) warm & clean glass surface, iii) cold & greasy glass surface, and iv) cold & dusty glass surface. The fastest foam decay was observed for greasy glass surface. It was found that increasing CO2 content in beer: i) the liquid content in the foam decreases, and ii) the foam breaks down faster. The foam decay and growth kinetics of foam-liquid interface were statistically treated using own models