Mark C. Leaper

Aggregation and caking processes of granular materials: continuum model and numerical simulation with application to sugar

Aggregation and caking of particles are common severe problems in many operations and processing of granular materials, where granulated sugar is an important example. Prevention of aggregation and caking of granular materials requires a good understanding of moisture migration and caking mechanisms. In this paper, the modeling of solid bridge formation between particles is introduced, based on moisture migration of atmospheric moisture into containers packed with granular materials through vapor evaporation and condensation. A model for the caking process is then developed, based on the growth of liquid bridges (during condensation), and their hardening and subsequent creation of solid bridges (during evaporation). The predicted caking strengths agree well with some available experimental data on granulated sugar under storage conditions.

Ion Exchange Extraction of Heavy Metal Ions from Wastewater

Abstract In this study, ion‐exchange resins of the cation exchanger universal (KU)‐2 type with functional sulfate groups, a carboxyl‐containing cation exchanger of a carboxyl containing cationite (KB) type, and polyampholyte amphoteric carboxyl containing ion exchanger (ANKB)‐35 were studied for Ni2+ and Cu2+ ion extraction from water solutions. The high value of the ion‐exchange capacity of the ionate KU‐2 compared with the complex formation amphoteric ion‐exchange resin ANKB appeared to be more suitable for use in wastewater treatment. The wet KU‐2‐20 resin has larger static ion‐exchange capacity than other gel resins. This paper presents a technological circuit and installation for local treatment of rinsing water of nickel plating with subsequent metals utilization. It was found that the gradual accumulation of nickel occurs during multiple solution circulations with a low rate.

Investigating the dynamics of segregation of high-jetsam binary batch fluidised bed systems.

Abstract Batch fluidised bed systems of jetsam concentrations x =0.5 and 0.75 were fluidised over a range of velocities, causing segregation into a jetsam-rich defluidised layer and a flotsam-rich fluidised layer. The dynamics of segregation from an initial fully mixed condition were examined by measuring both the concentration within the fluidised layer and the position of the interface between the two layers over time. It was found that the dynamics of both these characteristics could be approximated by a first order equation approaching an equilibrium with a rate constant. Within the aspect ratio range 0.8–1.2, results showed that provided segregation occurred, the type of distributor plate and the aspect ratio of the bed did not affect the equilibrium concentration within the fluidised layer, although segregation with a perforated plate proceeded at a slower rate than with a porous plate. The relationship between the fluidising velocity and the rate constant was not clear. The interface dynamics were greatly affected by the presence of flotsam trapped within the defluidised layer at low fluidising velocities. Where this was not the case, both the equilibrium position of the interface and the rate constant ω h showed an inverse linear dependence on the excess gas velocity.

The relationship between particle properties and fluidizing velocity during fluidized bed heat transfer

Abstract This study optimized the value of the ratio of the fluidization velocity to the minimum fluidization velocity, u/u mf, required to obtain the maximum wall-to-bed heat transfer conditions in a bed of fluidized particles heated by an external steam jacket. This was done both in terms of particle size and density, and the positioning and size of the heat transfer area. It was found that the optimized value of u/u mf could be expressed in terms of the inverse of the product of particle density and diameter, giving a much better fit than that of Todes (1965). In addition, by varying the size and position of the heat source on bed of particles of constant composition, new correlations were created in terms of these parameters for u/u mf at optimum heat transfer.

A Comparison of Compacting and Caking Behavior of Carbonate-Based Washing Powders

Two types of sodium carbonate powder produced by spray drying (SD) and dry neutralization (DN) were studied for their compaction properties using a uniaxial compression tester. A comparison was also made with Persil washing powder. Dry neutralized sodium carbonate showed greater resistance to compression and also produced a weaker compact when compressed to 100 kPa. Spray-dried sodium carbonate had an absence of fine particles but compacted easily. Differential scanning calorimetry (DSC) showed that both types of powder were predominantly amorphous in nature. Moisture sorption measurements showed that both powders behaved in a similar way below 50% relative humidity (RH). However, dry neutralized sodium carbonate had a high moisture affinity above this RH. Particle structures were also examined using scanning electron microscopy, showing the heterogeneous interior of the spray-dried particles.

Examining predictive correlations for equilibrium concentration profiles in jetsam-rich systems

Abstract A bi-component fluidized bed system of glass ballotini and beach sand ilmenite of d 50 values 124 and 179 μm and particle densities of 2500 and 4500 kg/m 3 , respectively, was examined, with the concentration of ilmenite above 50%. The results were compared with Rowe and Nienows empirical correlation for flotsam-rich systems to assess the potential difficulties in using existing correlations for the system examined. The empirical relationship between the mixing ratio and the normalized fluidizing velocity for this specific system was found to be a modified version of the existing correlation. It was also found that segregation also occurred within the jetsam component, with some fine jetsam particles behaving as flotsam whilst the jetsam at the bottom of the bed was coarser than the original sample.

Application of permanent dry high intensity magnetic separation for the processing of spent FCC catalyst.

This paper discusses the application of permanent dry high intensity magnetic separation to improve the efficiency of Fluidised Catalytic Cracking (FCC) systems used in oil refining, causing preferential removal of deactivated (spent) catalyst from the process. It was shown that this technique can provide efficient separation of spent catalyst from fresh, despite some loss of fine particles. The effects of particle segregation were also investigated, with both magnetic and nonmagnetic particles. Separation was found to be particularly good for material above 90gm, but efficiency decreased below this particle size. The paper concludes with recommendations for the implementation of the technology.

Measuring the flow properties of small powder samples using an avalanche tester

ABSTRACT The feasibility of using a small-scale avalanche tester to measure the flow properties of pharmaceutical lactose powders was examined. The modes of behavior observed in larger systems were displayed and showed a clear distinction between angular, free-flowing particles and more spherical particles of similar flow characteristics. Angular Lactohale LH100 particles showed slumping behavior at a rotational frequency of 0.33 Hz that disappeared at higher frequencies. Spherical lactose powder with a similar flow function to LH100 only showed rolling behavior under the same conditions, as did more cohesive powders LH200 and LH300. Further investigation of the LH100 data using fast Fourier analysis showed that the slumping frequency was one tenth of the rotational frequency.

Horizontal deflection of single particle in a paramagnetic fluid

This paper describes the horizontal deflection behaviour of a single particle in paramagnetic fluids under a high-gradient superconducting magnetic field. A glass box was designed to carry out experiments and test assumptions. It was found that the particles were deflected away from the magnet bore centre and particles with different density and/or susceptibility settled at a certain position on the container floor due to the combined forces of gravity and magneto-Archimedes as well as lateral buoyant (displacement) force. Matlab was chosen to simulate the movement of the particle in the magnetic fluid, the simulation results were in good accordance with experimental data. The results presented here, though, are still very much in their infancy, which could potentially form the basis of a new approach to separating materials based on a combination of density and susceptibility.Graphical abstract

A force balance model of a spouted bed for Darcy and non-Darcy flow in the annulus

Abstract —A mathematical model based on Mamuro and Hattoris force model including the drag force effect on the particles in the annulus of a spouted bed was constructed. The results from this model were compared with previous work, including Mamuro and Hattoris model for Darcys law and Epstein and Levines model and that proposed by Hattori et al. for non-Darcy flow in the annulus, none of which included the effect of drag force on particles. Results presented in the paper showed that when drag force was included in the force balance model, a lower value of Ua/Umf, the ratio of superficial fluid velocity in the annulus to minimum fluidization velocity, was obtained. Z/Hm, the ratio of axial distance from fluid inlet to the maximum spoutable bed depth, increased compared with models where the effect of drag was absent. Our results also showed an increase in radial cross flow from the spout to the annulus, especially in the lower part of the bed compared to those obtained by Mamuro and Hattori. The proposed model was found to be sensitive to Janssens factor, J , and also displayed a qualitative agreement with the Hattori et al. model which was proposed for non-Darcy conditions.