Jorge Cuellar

The magnetically stabilized fluidized bed bioreactor: A tool for improved mass transfer in immobilized enzyme systems?

Abstract Studies were carried out using novel magnetic carrier particles in a magnetically stabilized fluidized bed (MSFB) to determine the degree of liquid phase mass transfer enhancement achievable over a range of magnetic field strengths. The carrier particles, beads of κ-carrageenan incorporating magnetite, ranging in size from 0.25 to 1 mm are used for enzyme immobilization. Results using a 113 mm diameter column showed that a more than five-fold increase in liquid velocity could be achieved when a current of 40 A was applied to a single magnetic coil. The “escape” velocity of the particles from the bed was found to be proportional to the magnetic field intensity squared. The effect was further increased (almost doubled) by inserting a steel rod into the centre of the bed.

Stainless steel microbeads coated with sulfonated polystyrene-co-divinylbenzene

A new kind of gel-type magnetic cation-exchange resin based on stainless steel microspheres coated with sulfonated polystyrene-co-divinylbenzene has been synthesized in a two-step process. First, magnetic polymeric beads were prepared by radical suspension polymerization, after which these particles were functionalized by a post-polymerization sulfonation process. The effects of slight modifications in the synthesis process (metal surface modification, initial contact between metal and catalyst, and the use of double polymerization) on the thickness of the polymeric layer were evaluated. Both the precursor magnetic polymeric beads and the final cation exchange resins were studied by scanning electron microscopy and X-ray energy dispersive (EDX) analysis. Finally, the cation exchange capacity of the resins was determined.

Fluid-solid mass transfer in magnetic filtration

Abstract A theoretical model for the process of magnetic filtration of paramagnetic particles suspended in water and a method for determining the kinetic parameters of the model is proposed. To validate the theory, 10 experimental runs were conducted on a cylindrical filter of 300 mm diameter, containing a concentric iron rod of 250 mm diameter and a bed of spherical iron beads of 8 mm diameter. The suspension was made from iron oxide powder particles in a size range between 2 and 30 μm. The current intensity circulating in the coil which surrounded the filter ranged from 240 to 350 A. and the suspension superficial velocity varied between 1 and 2.2 m/min. The model supposes that the filtration rate is proportional to both the particle concentration in the suspension and the fraction of the iron spheres that are not covered by the deposited paramagnetic particles. The results show that the model can adequately describe the physical phenomena occurring in the filter.

Simple design of a crossflow moving bed heat exchanger-filter (MHEF)

Abstract In industrial applications hot combustion gases are often used in direct-contact gas-solid heat exchangers, such as fluidized bed, fixed bed and moving bed exchangers(1). Granular beds are also often used for filtering dust particles carried by fluids(2). However, hot gas filters and gas-solid heat exchangers have been studied and designed separately and little consideration has been given to devices where heat exchange and filtration take place simultaneously. This paper describes the design of a crossflow moving bed heat exchanger-filter (MHEF)(3), a device which uses a moving granular bed for simultaneous dust filtering and heat recovery from hot gases. Charts are presented for determining the dust concentration leaving the device, contact area needed for a required dust concentration or temperature in the effluent gas, and other parameters of practical interest.

Determination of the magnetic susceptibility of solids used in the design of a magnetic valve for solids

Abstract A new method of determining the magnetic susceptibility of solids of a small size for a collar-type design of a magnetic valve for solids is presented. and of some composites (steel-alumina, iron-alumina and magnetite-alumina) were obtained at several magnetic field intensities and at temperatures rang