S
M
Last name: SÁNCHEZ QUINTANILLA
First name: Miguel Angel
Premio Extraordinario de Doctorado US
In flows of dry particulate systems, electric charge is generated on particle surfaces by their collision with walls and with other particles. Charge build-up on single particles can yield local charge values high enough to surpass the limiting electric field for corona discharge into the surrounding gas. Then, local charge is decreased to a...
We report a novel experimental study on the jamming transition of dry fine powders with controlled attractive energy and particle size. Like in attractive colloids dry fine particles experience diffusionlimited clustering in the fluidlike regime. At the jamming threshold fractal clusters crowd in a metastable state at volume fractions depending...
We present measurements on the settling velocity of gas-fluidized beds of fine cohesive powders. In the solidlike regime ~solid volume fraction f.fc) particles are static, sustained by enduring contacts. The settling is hindered by interparticle contacts and is a very slow process. In the fluidlike regime (f,fc) permanent contacts no longer...
We investigate the dynamics of fine cohesive powders inside rotating drums. We show that these powders may be fluidized due to entrapment of ambient gas, and we determine the onset of fluidization. Experimental measurements on the bed expansion as a function of the rotation velocity have been performed. Drums of different diameters and fine...
A statistical analysis of granular avalanches in a half-filled and slowly rotated drum is presented. For large-sized grains the classical coherent oscillation is reproduced, i.e. we observe a quasi-periodic succession of regularly sized avalanches. As particle size is decreased, we see a crossover to a new complex dynamics characterized by...
We present a fluidized bed apparatus that enables us to test the bulk mechanical properties such as the yield stresses and compressibility of fine cohesive powders. Every measurement is preceded by driving the powder into the bubbling regime in which the material loses memory of its previous history. Then the gas flow is set to a given value to...
We present measurements of the tensile strength as a function of the consolidation stress for a set of fine cohesive powders ~xerographic toners! of 12.7 mm particle size and with a range of concentration of submicron fumed silica as flow control additive. This additive is well known for its ability to control interparticle adhesion force....
We have investigated the effect of vibrations on the stability of gas-fluidized beds of fine powders (particle size ~10 mm). The powder is uniformly fluidized by an adjustable gas flow that enables us to control the average solid volume fraction f0. The fluidized bed is then subjected to a vertical oscillatory motion of controlled amplitude and...
Fluidized fractal clusters of fine particles display critical-like dynamics at the jamming transition, characterized by a power law relating consolidation stress with volume fraction increment. At a critical stress clusters are disrupted and there is a crossover to a logarithmic law resembling the phenomenology of soils. We measure _ _...
We have investigated the self-diffusion in a stable gas-fluidized bed of fine powder. Two regimes have been observed: for gas velocities yg above the minimum fluidization velocity ym and below a critical gas velocity yc smaller than the minimum bubbling velocity yb the powder does not mix. Experimental measurements show the existence of yield...
In this work, we present experimental measurements of the yield stress of gas-fluidized beds of magnetizable particles stabilized by an externally imposed magnetic field. Powder samples consist of spherical magnetite particles 35-65 μm in size. The magnetic field is applied in the bubbling regime and the gas velocity is decreased. At a critical...
The calcium looping (CaL) process, based on the calcination/carbonation of CaCO3 at high temperatures, has emerged in the last years as a potentially low cost technology for CO2 capture. In this work, we show that the application of high intensity sound waves to granular beds of limestone and dolomite in a CaL reactor enhances significantly...
Fluidized beds of granular materials can be stabilized by interparticle attractive forces which confer the expanded bed an elastic modulus that stabilizes it against flow perturbations. Stabilization in a structure of enduring contacts is seen to occur naturally due to the universal van der Waals forces for ∼50 μm particle size beds albeit in a...
Gas-fluidized powders of fine particles display a fluidlike regime in which the bed does not have a yield strength, it expands uniformly as the gas velocity is increased and macroscopic bubbles are absent. In this paper we test the extension of this fluidlike regime as a function of particle size and interparticle attractive force. Our results...
The use of fluidized beds to remove submicron particles from gases has been investigated since 1949. High efficiency removal was achieved in the 1970's by imposing an electric field on a fluidized bed of semi-insulating granules that were able to collect the charged pollutant entrained in the fluidizing gas. In spite of their extended use...
We investigate the settling of an initially fluidized bed of a fine cohesive powder. Experimental results on the sedimentation rate cannot be fitted by theoretical and empirical equations existing in the literature and derived for non-cohesive spheres. We extend these equations to account for the adhesion-induced aggregation of fine particles....
Large scale pilot plants are currently demonstrating the feasibility of the Calcium-looping (CaL) technology built on the multicyclic calcination/carbonation of natural limestone for post-combustion and pre-combustion CO2 capture. Yet, limestone derived CaO exhibits a drop of conversion when subjected to multiple carbonation/calcination cycles,...
We report results from a statistical analysis of avalanches of cohesive powders in a slowly rotated drum. Interparticle adhesion, which diminishes the effect of inertia and whose magnitude strongly fluctuates in a local scale, makes avalanches in slightly cohesive powders eligible for displaying self-organized criticality. However, the results...
The behavior of a fluidized bed of fine magnetite particles as affected by a cross-flow magnetic field is investigated. A distinct feature of this naturally cohesive powder, as compared to noncohesive magnetic grains usually employed in magnetofluidized beds, is that the fluidized bed displays a range of stable fluidization even in the absence...
The fluidization behavior of a bed of fine magnetizable particles excited by an externally applied magnetic field is found to depend on the aggregative nature of the particles before the field was applied. Usually nonaggregated particles organize in quasivertical local linear chains when the field is applied. In contrast, naturally aggregated...