Method for Particle Size Control During the Drying and Granulation in Fluidized Bed

The fluidized bed process presented in this paper is suitable for recovery of solids from solutions in the form of granules. The solution is sprayed into the bed and as solvent evaporates, solid material is deposited on the surface of fluidizing particles. During this process, particle growth takes place by surface layering and/or agglomeration. A special grinder is used in the fluidized bed to control particle growth by causing selective disintegration of large particles. For steady state operation, the most important task is to determine the existing particle size distribution in the fluidized bed. A special method was developed to measure torque and stress fluctuations* in the bed of particles. Using a correlation between torque and stress fluctuations and particle size, this method and device can be used for direct control of the rotation speed of the grinder to produce granules of given size in the fluidized bed. Results of torque and stress measurements and their correlation to particle size are presented

Torque Measurements and DEM Simulations in a Couette-type Device with Application to Particle Size Measurements

A continuously operating modified Cuette-type shearing device has been developed for in-situ measurements to estimate the average particle size during size enlargement processes in fluidized bed granulator. It was proven by experiments that well-defined correlation exists between the mean torque and the average particle size being in the device. DEM simulations revealed interesting aspects of this method

Particle Size Control by Torque Measurements in Fluidized Beds during Drying and Granulation from Solutions

The fluidized bed process presented in this paper is suitable to recover solids from solution in form of granules. Solution is sprayed into the bed and, as the solvent evaporates, solid material is deposited on the surface of fluidizing particles. During this process, particle growth takes place by surface layering and/or agglomeration. A special grinder is used in the fluidized bed to control particle growth by causing selective disintegration of large particles. For steady state operation, the most important task is to determine the existing particle size distribution in the fluidized bed. A special method was developed to measure torque and stress fluctuations in the bed of particles. Using a correlation between torque and particle size, this method and device can be used for direct control of the rotation speed of the grinder to produce granules of given size in the fluidized bed. In this paper, the results of torque measurements and their correlation with particle size are presented

Computer Tomograph Measurements in Shear and Gravity Particle Flows

The paper reports the recent results obtained on the applicability of cross-sectional digital imaging method to study particle flow characteristics in 3D particle beds forced to move by gravity or shear. X-ray CT imaging technique is widely used in medical diagnostics and, during the last decades, its spatial and temporal resolution has been improved significantly. In this study, an attempt was made to use this technique for engineering purposes. Two experimental set-ups with different types of particle flows were investigated using Siemens Somatom Plus type CT equipment. A series of trials were carried out in a small model hopper with flat bottom and almost cylindrical side wall slightly deviating from verticality. Non steady-state flow was studied during the outflow of particulate material from this vessel, through a central hole at the bottom. Further investigation was fulfilled in a modified Cuette-type shearing device to study steady-state shear flow. This equipment consisted of an almost cylindrical vessel identical to that used for gravity flow measurements, and a smaller inner cylinder rotating within this vessel concentrically, around its vertical axis. The surface of the inner cylinder was notched vertically, i.e. perpendicularly to the direction of rotation to increase wall friction between the particles and the cylinder. Almost spherical sucrose granules, also used for gravity flow measurements, were filled into the gap between the rotating cylinder and the outer wall of the equipment. Movement of particles took place due to shear, generated within the particle bed. By using X-ray CT technique, cross-sectional digital images were obtained in every two seconds for both types of particle flows. For this, the cross-sectional variation of the local Hounsfield density values were measured in a matrix of 0.1x0.1x2.0 mm space elements. It was proved that the applied non-invasive crosssectional imaging technique was suitable to distinguish the stationary and moving particle regions, and by this, to estimate the location of the boundary zone between them

Identification of Thermal Degradation Process of Starch in Production of Environmentally Friendly Flocculants

Chemical modification of starch can be used to produce environmentally degradable flocculants. This is carried out at elevated temperature, which in turn causes thermal degradation, influencing the quality of the product. Starting from experimental results and the probabilistic nature of the process stochastic model was established to identify the rate and the mechanism of degradation under various conditions. It was concluded that applying moderate temperature around 143 Celsius ensures sufficient production rate without excessive thermal degradation

Particle Size Control by Torque and Stress Measurement in Fluidized Bed Drying and Granulation from Solutions

The fluidized bed process presented in this paper is suitable for recovery of solids from solutions in the form of granules. The solution is sprayed into the bed and as solvent evaporates, solid material is deposited on the surface of fluidizing particles. During this process, particle growth takes place by surface layering and/or agglomeration. A special grinder is used in the fluidized bed to control particle growth by causing selective disintegration of large particles. For steady state operation, the most important task is to determine the existing particle size distribution in the fluidized bed. A special method was developed to measure torque and stress fluctuations* in the bed of particles. Using a correlation between torque and stress fluctuations and particle size, this method and device can be used for direct control of the rotation speed of the grinder to produce granules of given size in the fluidized bed. Results of torque and stress measurements and their correlation to particle size are presented

Water delivery to the TRAPPIST-1 planets

Three of the seven rocky planets (e, f, and g) in TRAPPIST-1 system orbit in the habitable zone of the host star. Therefore, water can be in liquid state at their surface being essential for life. Recent studies suggest that these planets formed beyond the snow line in a water-rich region. The initial water reservoir can be lost during the planet formation due to the stellar activity of the infant low-mass star. However, a potential subsequent water delivery event, like the late heavy bombardment (LHB) in the Solar system, can replenish planetary water reservoirs. To study this water delivery process, we set up a simple model in which an additional 5 -50 M⊕ planet is embedded in a water-rich asteroid belt beyond the snow line of TRAPPIST-1. Asteroids perturbed out from the chaotic zone of the putative planet can enter into the inner system and accreted by the known planets. Our main finding is that the larger is the orbital distance of planet, the higher is the amount of water delivered to the planet by an LHB-like event