Mathematical Modeling of Particle Stratification in Jigs

Recognizing mathematical modeling as a powerful tool for systematic process analysis and control, this paper attempts to critically'review the theories and mathem-atical models which have been advanced to explain and simulate the behaviour ofjigg ing process. The existing literature on mathematical modeling and quantitative analysis of jigging has been divided into six subheads : (i) classical theory, (ii) potential theory, (iii) dispersion models, (iv) energy dissipation theory, (v) stochastic analysis and (vi) empirical models. A new modeling approach based on Newtonian mechanics is used to describe the stratification behavior of particles in jig. In this approach,the motion of solid material is treated using the discrete element method (DEM) while the corre-sponding motion of the liquid is determined by marker and cell (MAC) technique. For illustration purpose, a jig bed consisting of 100 particles of two different densities is simulated. Preliminary results show that the model predicts the stratification of particles reasonably well

Simulation of industrial gravity separation processes using a general purpose simulator

Gravity separation processes have been used in the mineral industry to separate particles under the action of hydr-odynamic and gravitational forces. Although these equip-ments are extensively used for tonnage processing in coal industry, their use has been now extended to waste trea-tment such as separation of valuable metallic matter from slag. However, these processes never run at their best due to lack of understanding of the process and the under-lying principles of separation. For efficient operation it is desirable that trial runs and pilot tests are conducted but these are often time consuming and expensive. Against this background, this paper attempts to show the capabi-lities of numerical simulation to gain a better under-standing of the process with a view to improve its performance.Data from different coal washeries are colle-cted to simulate the behaviour of the plants. Results of simulation utilizing jigging for coal washing is found to be in good agreement with the plant data. The same coal is also treated in other gravity separation processes in order to decide upon a particular washing circuit

Circuit simplification by adopting flotation columns.

Pilot scale studics on the beneficiation of low-grade fluorspar and copper-lead-zinc ore were investigated using flotation columns. Acidspar concentrates suitable for HF production can be produced by adopting two-stage column cleaning in place of multi-stage cleaning by conventional flotation cells. A three-column canfiguration in the place of four-stage cleaning in acidspar circuit and four in metspar circuit was suggested. Similarly, it was demonstrated that a single stage cleaning by flotation column was found to be sufficient in the plnce of two-stage cleaning by conventional flotation cells to obtain bulk concentrates of Cu-Pb-Zn

Bio-dissolution of metals from activated nodules of Indian Ocean

The biodissolution of valuable metals from ferro-manganese nodules of Indian Ocean in presence of Aspergillus niger is a slow process. In order to improve the kinetics of bioleaching, the sea nodules were activated in high energy attrition mill thereby changing the granulometry and surface charge characteristics of the particles. The zeta potential, particle size distribution and surface area of the activated material were recorded and bioleaching was carried out by A.niger in the pH range 4.0-5.5. The mechano-chemical activation of the mixed particles (≤ 75 µm) of nodules in 10 min reduced almost 86 % material to ≤ 10 µm size with a change in zeta potential from -18 to -34 mV. Bioleaching of metals from the activated nodules was compared with that of the dissolution pattern of metals in presence of A.niger without any pretreatment as well as those under the chemical leaching conditions. The results showed the bio-recovery of more than 95% copper, nickel and cobalt each in 15 days time when the nodules activated for 10 min was leached at 5 % (w/v) pulp density, 4.5 pH and 35 ºC temperature. Bio-leaching of these metals was observed to be similar from the nodules activated for 30 min. The non-activated nodules showed ≥ 89% metal recovery in 25 days under the above conditions. The mechano-chemical activation of sea nodules has thus been found to improve the kinetics of the process and has also resulted in to the availability of wider pH in the range of 4-5 for the processing

Psycho-Social Behavioural Problems In Urban Primary School Children

Research Problem: What is the magnitude and correlates of psychosocial behavioural problems in primary school children of an urban area. Objectives:     i)    To  know  the  prevalence of psychosocial behavioural problems in primary school children of Agra Corporation.  ii) To see the impact of various biosocial factors on the prevalence of above problems. Design: Cross sectional study by questionnaire method and observation. Setting: Primary schools run by Agra Corporation. Participants: All the children studying in 7 primary schools selected from 108 schools run by Agra Corporation. Sample Size: 520 primary school children. Study Variables: Age, sex, socio-economic class and family size. Statistical Analysis: By percentage, Z - test and Chi-square test. Result: A majority of the study children (63.7%) were having some psychosocial behavioural problem or the other, the most common problem being educational difficulties (59.8%), The average number of problems per child was 2.9. The prevalence was highest in children from middle-sized families of low socio­economic class and in age group above 13 years

Fast Algorithms For Josephson Junction Arrays : Bus--bars and Defects

We critically review the fast algorithms for the numerical study of two--dimensional Josephson junction arrays and develop the analogy of such systems with electrostatics. We extend these procedures to arrays with bus--bars and defects in the form of missing bonds. The role of boundaries and of the guage choice in determing the Green's function of the system is clarified. The extension of the Green's function approach to other situations is also discussed.Comment: Uuencoded 1 Revtex file (11 Pages), 3 Figures : Postscript Uuencode