The use of single and twin-screw extruders for solid-phase reactions is a promising method to intensify a process in a more sustainable manner.In this manuscript,we report a detailed analysis of the residence time dis...The use of single and twin-screw extruders for solid-phase reactions is a promising method to intensify a process in a more sustainable manner.In this manuscript,we report a detailed analysis of the residence time distribution(RTD)in vertical single-screw reactors.The results will help in the selection of the right screw design that would help achieve the desired residence time,which is necessary for a reaction to happen.Experiments were conducted in three vertical screw reactors(having fixed shaft diameter)with varying dimensions using granular free-flowing powders of sodium chloride and silica with a mean particle size of∼25μm.RTD behavior was modeled using the radial particle velocities in the screw reactor's centrifugal field.Further,a method is proposed for estimating the axial dispersion coefficient of dry powders in such sheared flows using true and bulk densities of the powder and the screw shear rate.This dispersion coefficient is used in the axially dispersed plug flow model to describe the RTD behavior of screw reactors with acceptable accuracy.The theoretically predicted and experimentally obtained dispersion coefficients are found to be similar thereby confirming the suitability of the model.展开更多
Here we report experiments on particle cluster settling at high Reynolds number in quiescent liquid contained in a vessel.The particles were observed to spread at the vessel bottom surface in a near-circular annular s...Here we report experiments on particle cluster settling at high Reynolds number in quiescent liquid contained in a vessel.The particles were observed to spread at the vessel bottom surface in a near-circular annular shape after settling irrespective of the shape of the vessel cross-section and particle shape,size,and types.Effect of different parameters such as mass,type and aspect ratio of the particles,height,and viscosity of liquid was investigated on spreading behaviour.Formation of the hemispherical bottom cap of the cluster that bounces upon hitting the vessel bottom surface was found to be responsible for the final circular annular shape of the settled structure.Particle leakage from the cluster was seen in the form of a tail.In the liquid having viscosity beyond 100 cP,cluster breakage was observed that resulted in hindered settling and asymmetric shapes of finally settled particles.The observations are useful to understand the overall area over which settling and spreading of such clusters can be observed.展开更多
基金funding from CSIR(MLP100926)and SERB(DST,Govt.of India)(CRG//2023/001897-G)for this work.
文摘The use of single and twin-screw extruders for solid-phase reactions is a promising method to intensify a process in a more sustainable manner.In this manuscript,we report a detailed analysis of the residence time distribution(RTD)in vertical single-screw reactors.The results will help in the selection of the right screw design that would help achieve the desired residence time,which is necessary for a reaction to happen.Experiments were conducted in three vertical screw reactors(having fixed shaft diameter)with varying dimensions using granular free-flowing powders of sodium chloride and silica with a mean particle size of∼25μm.RTD behavior was modeled using the radial particle velocities in the screw reactor's centrifugal field.Further,a method is proposed for estimating the axial dispersion coefficient of dry powders in such sheared flows using true and bulk densities of the powder and the screw shear rate.This dispersion coefficient is used in the axially dispersed plug flow model to describe the RTD behavior of screw reactors with acceptable accuracy.The theoretically predicted and experimentally obtained dispersion coefficients are found to be similar thereby confirming the suitability of the model.
基金The authors thank the Dept.of Science&Tech.(Gol)for the funding through Swarnajayanti Fellowship DST/SJF/ETA-03/2014-15Dr.Sayan Pal acknowledges the Council of Scientific and Industrial Research(CSIR)for doctoral fellowship。
文摘Here we report experiments on particle cluster settling at high Reynolds number in quiescent liquid contained in a vessel.The particles were observed to spread at the vessel bottom surface in a near-circular annular shape after settling irrespective of the shape of the vessel cross-section and particle shape,size,and types.Effect of different parameters such as mass,type and aspect ratio of the particles,height,and viscosity of liquid was investigated on spreading behaviour.Formation of the hemispherical bottom cap of the cluster that bounces upon hitting the vessel bottom surface was found to be responsible for the final circular annular shape of the settled structure.Particle leakage from the cluster was seen in the form of a tail.In the liquid having viscosity beyond 100 cP,cluster breakage was observed that resulted in hindered settling and asymmetric shapes of finally settled particles.The observations are useful to understand the overall area over which settling and spreading of such clusters can be observed.
