On the Effect of the Rotating Chamber Reverse Speed on the Mixing of SiC Ceramic Particles in a Dry Granulation Process

In order to control the accumulation of SiC ceramic particles on the wall of the rotating chamber in the frame of a dry granulation process,the effect of the wall reverse speed on the mixing process is investigated.In particular,an Euler-Euler two-phase flow model is used to analyze the dynamics of both SiC particles and air.The numerical results show that by setting a certain reverse rotating speed of the rotating chamber,the accumulation of SiC particles on the wall can be improved,i.e.,their direction of motion in proximity to the wall can be changed and particles can be forced to re-join the granulation process.Experimental tests conducted to verify the reliability of the numerical findings,demonstrate that when the reverse rotating speed of the rotating chamber is 4 r/min,the sphericity of SiC particles in the rotating chamber is the highest and the fluidity is the best possible one.

Influence of Nozzle Orifice Shape on the Atomization Process of Si3N4 in a Dry Granulation Process

In order to reveal the intrinsic fluid-dynamic mechanisms of a pressure-swirl nozzle used for Si3N4 dry granulation,and effectively predict its external spray characteristics,the dynamics of air-atomized liquid two-phase flow is analyzed using a VOF(Volume of Fraction)method together with the modified realizable k-εturbulence model.The influence of nozzle orifice shape on velocity distribution,pressure distribution is studied.The results show that the pressure difference in a convergent conical nozzle is the largest with a hollow air core being formed in the nozzle.The corresponding velocity of atomized liquid at nozzle orifice is the largest.Using a self-designed atomization experiment platform,the velocity and pressure of atomized liquid and the spray cone angle are measured for three nozzles with different orifice shapes.The micro-morphology of Si3N4 particles is also determined.These data confirm the correctness of numerical simulation.Considering atomization performance of the nozzle,the contraction conical nozzle is more suitable for the atomization of Si3N4 in practical production based on the dry granulation approach.

Optimization of residence time distribution in RCDG and an assessment of its applicability in continuous manufacturing

Knowledge of residence time is a critical aspect in developing control and material diversion strategies for continuous manufacturing processes in pharmaceutical manufacturing.Dry granulation is a promising continuous granulation technique as it is fast and economical.In this study,a step-change method to determine residence time in roll compaction/dry granulation is introduced.The factors roll speed and rotational speed of the impeller in the powder inlet unit of the compactor were evaluated using a central composite circumscribed statistical design of experiments in order to optimize the residence time.The fill volume in the compactor was varied exemplarily.It was found that high roll speed,low rotational speed of the impeller and low fill volume in the compactor are beneficial to generate fast transition through the compactor.The impact of roll speed increase was estimated.It can be concluded that despite fast residence time in the process,high roll speed and its subsequent high material throughput can generate a large amount of material that has to be discarded if material diversion is required.

Determination of particle exchange rates at over-flow weirs in horizontal fluidised beds by particle tracking velocimetry

Residence time distributions （RTDs） in horizontal fluidised beds have a huge effect on solid product properties and are infuenced by the internal design of the apparatus, e.g. the separation into different compartments by weirs. Weirs can be passed in or against the overall solid transport direction, with the back-flow resulting in axial dispersion, which is a measure of the spread of the RTD. Therefore, the ratio of exchange rates at weirs under different fluidisation conditions provides information on axial dispersion. In this work, a methodology based on particle tracking velocimetry is presented to obtain information on the exchange rates of particles at weirs in horizontal fluidised beds. The internal recirculation is studied for over-flow weirs with respect to different fluidisation conditions, providing a first step towards determining the effects of weirs and fluidisation conditions on axial dispersion and RTDs in horizontal fluidised beds.