Author: Marco Scala Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The mixing of two or more fluids is a rather common operation in all industrial processes. The main target of the mixing is to increase the interface area between phases in order to improve mass and heat transfer and facilitate then chemical reaction. Among the multiphase mixing stands out the gas liquid dispersion. The aim of the present work is to examine a specific type of mixers, namely the static mixer. Static mixers are located into a housing or pipeline to ensure a high blending of fluids. They are usually made by a series of inserts, in turn designed by holes, helical elements and oblique blades. These elements cause local accelerations and stretching of the fluid currents to reach a high mixing efficiency. The wide applications of static mixers in numerous industrial processes require better knowledge of the hydrodynamics in these devices. The gas-liquid flow pattern through a Sulzer static mixer SMXTM mounted in a vertical cylindrical tube was investigated in this study. The main goal was to assess the performance of the Sulzer static mixer SMXTM for gas-liquid applications in industrial processes. Experimental data were collected from two main optical techniques, Backlight Shadowgraph Technique (BST) and Particle Image Velocimetry (PIV). 3D-printed static mixers were manufactured using transparent plastic in order to provide optical access. Three different liquids were used as the continuous phase, namely water, water with SDS and normal-heptane. The liquid phase was kept stagnant during the experiments. Five different lengths of mixers (with 1, 2, 5, 10 and 15 elements respectively) and several gaseous nitrogen flow rates from 1 to 10 l/h were analysed. The behaviour of the simple tube without mixing device, acting like a bubble column, was investigated as a reference, for comparison purposes with the SMXTM. Bubble diameter distributions at the inlet and outlet of the SMX mixers were evaluated. The velocity fields inside the mixers were quantified. The gas hold-up was also measured. The oxygen transfer performance in the SMX static mixer in air/water mixture was assessed by measuring the overall oxygen transferred. The mass transfer coefficient to the interfacial area kLa was determined and proved to be larger in the mixer. Volume-of-fluid numerical simulations of the mixer were performed with OpenFOAM. These 3D simulations were mainly focused on the behaviour of the SMX in an organic system at low gas flow rate (1 l/h). The numerical simulations were satisfactorily validated by experimental results. The comparison and the combination of the numerical and experimental results bring new insight into the flow pattern in a SMXTM static mixer.
Author: Henning Bockhorn Publisher: Springer Science & Business Media ISBN: 3642045499 Category : Science Languages : en Pages : 345
Book Description
The homogenization of single phase gases or liquids with chemical reactive components by mixing belongs to one of the oldest basic operations applied in chemical engineering. The mixing process is used as an essential step in nearly all processes of the chemical industry as well as the pharmaceutical and food ind- tries. Recent experimentally and theoretically based results from research work lead to a fairly good prediction of the velocity fields in differend kinds of mixers, where as predictions of simultaneously proceeding homogeneous chemical re- tions, are still not reliable in a similar way. Therefore the design of equipment for mixing processes is still derived from measurements of the so called “mixing time” which is related to the applied methods of measurement and the special - sign of the test equipment itself. The cooperation of 17 research groups was stimulated by improved modern methods for experimental research and visualization, for simulations and nume- cal calculations of mixing and chemical reactions in micro and macro scale of time and local coordinates. The research work was financed for a six years period within the recently finished Priority Program of the German Research Foundation (DFG) named “Analysis, modeling and numerical prediction of flow-mixig with and without chemical reactions (SPP 1141)”. The objective of the investigations was to improve the prediction of efficiencies and selectivities of chemical re- tions on macroscopic scale.
Author: M.F. Edwards Publisher: Elsevier ISBN: 1483136248 Category : Science Languages : en Pages : 213
Book Description
Fluid Mixing II documents the proceedings of a symposium organized by the Yorkshire Branch and the Fluid Mixing Processes Subject Group of the Institution of Chemical Engineers and held at Bradford University, on 3-5 April 1984. The conference covers all aspects of mixing including the assessment of mixture quality, experimental and theoretical studies of mixing, chemical reaction and mass transfer, heat transfer, novel experimental techniques, scale-up and optimization. This volume contains 12 papers that deal with topics such as drawdown of floating solids into mechanically agitated vessels; effects of water/cement ratio, intensity of mixing, age and cement particle size and shape upon rheological properties of cement grouts with and without admixture; and mixing of non-absorbent solids with liquids. Other studies cover the flooding transition of a Rushton turbine operating in a gas-liquid system; power consumption in a three phase (liquid-solid-gas) mixing process in a stirred vessel; and an experimental technique for studying the rate of inter-zone mixing.
Author: Wai Man R. Lau Publisher: ISBN: Category : Fluidization Languages : en Pages :
Book Description
Abstract: Slurry bubble columns and gas-solid fluidized bed reactors are some of the most commonly used industrial processes. Considerable interests have been recognized in the field of physical, chemical, petrochemical, electrochemical, and biochemical operations (Fan, 1989). In these reactor systems, large axial dispersion of phases and high flow patterns can be achieved by the excellent macromixing characteristics. It also provides excellent heat and mass transfer without the aid of external mechanisms and relatively easy operation. Despite the advantages of operations, the transport behavior in these systems is very complex and a comprehensive knowledge of the hydrodynamics, heat and mass transfer and mixing are required for successful application of these systems. Some aspects of the fundamental characteristics of evaporative liquid jets in gas-liquid-solid flows are studied and some pertinent literature is reviewed. It is found that the injection of an evaporative liquid jet decreases the minimum fluidization velocity at a high pressure due to the additional gas flow generated from liquid evaporation. Fluidizing gas velocities have no significant effect on the jet penetration length in a dense phase fluidized bed while it reduces the radial dispersed distance of the evaporative liquid. The tomographic images of liquid nitrogen injection in a dense phase fluidized bed indicate a distribution of reduced bubble sizes compared to a dry bed. The hydrodynamics, gas-liquid mass transfer properties and liquid entrainment phenomena in a high pressure and high temperature bubble column is investigated. Effects of pressure on hydrodynamics and mass transfer properties are mainly through the change in gas and liquid physical properties, which in turn changes the bubble dynamics that govern the transport phenomena. Experimental results show that liquid velocities have a direct influence on kl while other factors have a dominant effect on the interfacial area over kl. Liquid entrainment in bubble columns is controlled by the droplet formation during bubble bursting at interface. Effect of pressure on liquid entrainment is to due to the higher drag force exerted on the liquid droplet with higher gas density and the formation of smaller droplet by the smaller bubbles at high pressure.
Author: P. J. Cullen Publisher: John Wiley & Sons ISBN: 9781444309881 Category : Technology & Engineering Languages : en Pages : 304
Book Description
The mixing of liquids, solids and gases is one of the most commonunit operations in the food industry. Mixing increases thehomogeneity of a system by reducing non-uniformity or gradients incomposition, properties or temperature. Secondary objectives ofmixing include control of rates of heat and mass transfer,reactions and structural changes. In food processing applications,additional mixing challenges include sanitary design, complexrheology, desire for continuous processing and the effects ofmixing on final product texture and sensory profiles. Mixing ensures delivery of a product with constant properties. Forexample, consumers expect all containers of soups, breakfastcereals, fruit mixes, etc to contain the same amount of eachingredient. If mixing fails to achieve the requiredproduct yield, quality, organoleptic or functional attributes,production costs may increase significantly. This volume brings together essential information on theprinciples and applications of mixing within food processing. Whilethere are a number of creditable references covering generalmixing, such publications tend to be aimed at the chemical industryand so topics specific to food applications are often neglected.Chapters address the underlying principles of mixing, equipmentdesign, novel monitoring techniques and the numerical techniquesavailable to advance the scientific understanding of food mixing.Food mixing applications are described in detail. The book will be useful for engineers and scientists who need tospecify and select mixing equipment for specific processingapplications and will assist with the identification and solving ofthe wide range of mixing problems that occur in the food,pharmaceutical and bioprocessing industries. It will also be ofinterest to those who teach, study and research food science andfood engineering.
Author: Marco Scala
Author: Henning Bockhorn
Author: M.F. Edwards
Author: Wai Man R. Lau
Author: Jaromír J. Ulbrecht
Author: Chunxiao Li
Author: P. J. Cullen
Author: Nicholas P. Cheremisinoff
Author: 
Author: A.K. Jagota