Fluidization

A three dimensional transient model is developed to simulate the local hydrodynamics of a gas–liquid–solid three-phase fluidised bed reactor using the computational fluid dynamics (CFD) method. The CFD simulation predictions are compared with the experimental data of Kiared et al. [1999. Mean and turbulent particle velocity in the fully developed region of a three-phase fluidized bed. Chemical Engineering & Technology 22, 683–689] for solid phase hydrodynamics in terms of mean and turbulent velocities and with the results of Yu and Kim [1988. Bubble characteristics in the racial direction of three-phase fludised beds. A.I.Ch.E. Journal 34, 2069–2072; 2001. Bubble-wake model for radial velocity profiles of liquid and solid phases in three-phase fluidised beds. Industrial and Engineering Chemistry Research 40, 4463–4469] for the gas and liquid phase hydrodynamics in terms of phase velocities and holdup. The flow field predicted by CFD simulation shows a good agreement with the experimental data. From the validated CFD model, the computation of the solid mass balance and various energy flows in fluidised bed reactors are carried out. The influence of different interphase drag models for gas–liquid interaction on gas holdup are studied in this work.

In this work, a complete dynamic model of a continuous industrial fluidized bed granulator for urea production is presented. Three growth and three cooling chambers in series are simulated. Mass, energy and momentum balances are solved for all the fluidized beds together with the population balance equation (PBE). Since each granulator chamber can be modelled as a continuous stirred tank (CST), the multichamber granulator is represented by a series of CSTs.Applying the developed model, the open-loop behaviour of the product granulometry is particularly investigated. With this aim, and to further develop efficient control strategies, different step disturbances are assayed. Based on the results of the performed sensitivity study, it can be concluded that the log-normal distribution function gives an appropriate description of the PSD in each chamber, the granulometry response times control the dynamics of the complete granulation circuit, the seeds' PSD is the variable that most affect the outlet particle size distribution, and that mild recycle ratio values are adequate to stabilize the granulator operation.A complete dynamic model of a continuous industrial fluidized bed granulator for urea production is presented. Mass, energy and momentum balances are solved for all the fluidized beds together with the population balance equation. Applying the developed model, the open-loop behaviour of the product granulometry is particularly investigated.

Softening at drinking water treatment plants is often realised by fluidised bed pellet reactors. Generally, sand is used as seeding material and pellets are produced as a by-product. To improve to sustainability, research has been carried out to replace the seeding material by re-using grained and sieved calcite pellets as seeding material. An explicit fluidisation model is developed to predict the fluid bed state in fluid bed pellet softening reactors with calcite as seeding material. The fluidisation theory is extended in a model whereby soft sensors are derived and experimentally tested for a wide range of seeding material and pellets. With the soft sensors porosity, particle size and pressure drop can explicitly be calculated. Pilot research has been carried out to calibrate and full-scale experiments to validate the fluidisation models. Four different fluidisation models were reviewed from which the original Richardson-Zaki fluid bed model has been selected as the best explicit...

This paper examines the fundamental characteristics of an inverse liquid -
solid inverse fluidized bed reactor. In this reactor , many experiments were performed using three sizes of polypropylene spherical solid, lighter than water with different diameters ..................

Soft-sediment deformational structures are important diagnostic features of paleoseismic studies. These seismites result from local vigorous fluidization and hydroplastic deformation formed during liquefaction as a direct consequence of permanent deformation of ground surface due to earthquakes of large magnitude.The region of eastern Ladakh, Spiti Basin and the upper Sutlej River basin record a concentration of earthquakes in a well defined NE-trending seismic zone sub-parallel to the strike of Leo-Pargil Horst and the Kaurik-Chango Fault Zone. Soft-sediment deformational studies of the fluvial and fluvio-lacustrine sequences near Sumdo village, along Sangla valley of Himachal Pradesh and near Saspol village of Ladakh indicate that the Kaurik-Chango Fault Zone is a seismogenic fault causing liquefaction and fluidization as the consequence of earthquake activity in the past. Thermal Luminescence (TL) date of the deformational structures near the Sumdo village constrains the paleoseismic activities of large magnitude between 90,000 years (third activity) to 26,000 years (last geological evidence) with a recurrence interval of approximately 10,000 years during the Quaternary period.