Jigging Cycle Research Articles

The effect of operating conditions on density stratification in a batch jig I: The influence on the equilibrium stratification profile

The study reported in this paper is the first in a series of two that investigated the influence of operating conditions on stratification in a batch jig. This paper focuses on an equilibrium study; the next on a kinetic study. Based on testwork and a detailed consideration of which operating conditions were relevant to the study, four factors were identified as being the primary operating variables influencing stratification in the test jig. These were the pulsion time, the pulsion hold-time; the amplitude of the jig cycle; and the depth of the particle bed in the jig. All other factors were found to be either dependent variables, or to exert no significant influence on stratification at equilibrium. Based on 32 equilibrium tests, it was found that the equilibrium stratification profile was essentially independent of operating conditions within a broad range of values. This finding has both theoretical and practical implications. The most significant of these is that the influence which operating variables have on jig performance appears to derive primarily from their influence on stratification kinetics and not from their influence on stratification at equilibrium.

The effect of operating conditions on density stratification in a batch jig II: The influence on stratification kinetics

This paper presents the second of a two part study on density stratification in a laboratory batch jig. The first study, reported elsewhere, investigated the effect of operating conditions on the stratification profile achieved at equilibrium. The study reported in this paper investigated their effect on the kinetics of density stratification under 18 different sets of conditions—5 for binary systems with different particle densities; and 13 for a ternary system with different configurations of the jig cycle. Although the study was academic in nature (it involved simple systems of 8 mm glass beads) it has provided insights into stratification dynamics that have significant practical implications. It has shown that reasonable rates of stratification can be expected in systems with density differences as low as about 150 kg/m3 provided sufficient jigging time is allowed. In addition, the study found that the quality of a density separation achievable in a jig is determined primarily by the properties of the feed to the jig and its mechanical configuration and not so much by how the operating variables of the jig are manipulated or ‘fine-tuned’. The extent to which what is achievable is actually achieved is dependent on stratification kinetics which are determined by both particle properties and the operating conditions in a jig.

Influence of Water Pulsation with Different Frequency and Amplitude on Orbit of a Particle Placed on a Fixed Screen

Gravity separation techniques such as jigging are based on the difference in the settling velocities of particles in water, which depends on the specific gravity, size, and shape of the particles. When a particle falls in stationary water, it is known that its settling velocity in the acceleration period before it reaches its terminal velocity depends on its specific gravity. Therefore, if one jigging cycle were completed before the particle reaches its terminal velocity, separation based on the difference in particle specific gravity would be promoted as the jigging frequency increases. However, there are few reports discussing whether the acceleration period in stationary water could be applied to an unsteady jigging movement. In this study, we used particles of around 1 mm, which are small particles for a jig, and investigated the relation between jigging frequency and particle movement. We have concluded from the results that although the reason is incorrect, the above classical hypothesis reflects the actual phenomenon, since the effect calculated in this study almost agrees with estimations obtained using the hypothesis developed by Gaudin.

Mathematic simulation of +13 mm particles motion in jig

To meet the needs of the jigging process control, attempt to combine the studying on jigging mechanism with the operating and detecting parameters so as to use them in practical producing control. On the basis of studying the motion characteristic of water in jig, the motion of particles with different size and density was researched. A laboratorial model jig and a high-speed dynamic analysis meter were used and 60 group conditions were designed in experiment. The motion rule and curves were gained through analyzing the huge amount of data and pictures with the high-speed dynamic analysis meter. The conclusion is that the characteristic of the position curve of the particles is similar with the typical damped vibration. Then the motion differential equation of the particles was educed imitating the damped vibration and the solution equations were gained. In the equations the motion parameters of the particles in jig, such as velocity, acceleration, force etc. are in a direct proportion to the air pressure, and have a definite non-linear relationship with the jigging cycle, thickness, mobility of the jig bed, mass and size of the particles and so on. The equations might be used directly in control process of jig.

Developing the technology for the effective final concentration of gold-containing gravity concentrates

Jigging technology in a closed cycle is tested and optimized at one department of industrial gold mining for the final concentration of gravity concentrates with the use of PGShOK-50-2 sprinkling installation. The equation of regression—which adequately describes the dependence of the Goden selectivity index on the travel and vibration frequency of the cones, the specific consumption of the undersize water, and the height of the artificial bed during the operation of the jigging machine in such a mode—is obtained. It is established that, as the Au content in the starting product increases, which is promoted by the closed jigging cycle, its extraction into the concentrate (ɛ) also increases. As the operation of the concentration table is optimized, the influence of the frequency and travel length of the saddle, as well as of the angle of its transverse inclination, is investigated. The tailings of all apparatuses, which are used for the final concentration of gravity concentrates, are repurified by column flotation prior to output into the pile. The kinetics for gold grains of different fineness is investigated. As a result of optimizing the operation of a MOD-0.2 jigging machine and the SKO-0.5 concentration table, the extraction of metal from the crude concentrate into a product corresponding to requirements of refining (>92% of gold bullion) increased by 1.4–1.7% and was ≥98%. An increase in the productivity of the jigging machine, due to the use of jigging technology in a closed cycle and the stable operation of the concentration table, provided an increase in the productivity of the final concentration department of the gold-concentration installation on the whole.

Method to evaluate liberation characteristics of feed in a jigging plant

The roles of pulsating mechanisms such as the amplitude and frequency of the jig cycle are well established in jigging. Also well established are the roles of the size ratio and the volume fraction of the feed. In iron ore beneficiation plants, these process parameters are optimized to achieve the highest efficiency. However the role of one of the more important feed characteristics, the liberation characteristic of the feed, has not been studied in detail Evaluation of the liberation characteristics is difficult because the required washability test is not viable for iron ore feed. In this paper, a new method is proposed in which the liberation characteristics are measured through a separation efficiency value. In the new evaluation method, jigging parameters such as amplitude and frequency of the jig cycle are optimized from the fundamental understanding of the process dynamics and feed characteristics such as size distribution. Then, feeds with different liberation characteristics are tested to evaluate the liberation characteristics of feed in jigging.

An integral assessment of the role of critical process parameters on jigging

In jigging, amplitude and frequency of pulsation, and feed characteristics are the most important process parameters. Effects of these parameters on particle segregation during jigging are studied and explained through experimental as well as numerical means by drawing parallel to liquid/solid fluidization process. This is permissible because jigging could also be viewed as a repetitive process of fluidization and defluidization. Unlike a normal fluidization process, in jigging, particle segregation takes place under rapid rate of change of water velocity. The rate of change of water velocity is decided by the maximum water velocity of the jig cycle, which in turn is controlled primarily by the amplitude. Experimental evidence of the role of maximum water velocity on jigging is given. Next, the feed to the jig that varies in both size and density is conceived as a mixture of many density variant binary systems. This way, the effect of feed characteristic is conveniently analyzed through several indicators of the binary feed namely size ratio, volume fraction, and particle size. Finally, the effect of frequency is studied by considering the particles in the jig bed analogous to tuned mass dampers. This concept is used to explain the preferential segregation of particles at certain jig frequency.

Role of water velocity for efficient jigging of iron ore

Upgrading of iron ore by jigging has been an emerging trend. Typically −10.0 + 0.15 mm material is considered for jigging where the problem of separation of finer particles is inherent. A detailed investigation is carried out to understand the behavior of various size fractions of the feed material during jigging in order to improve the separation efficiency. It has been realized that the separation of particles is mostly influenced during the period when particles are fluidized. Fluidization of particles in jigs depends on the rate of change of water velocity that in turn is controlled by the maximum water velocity attained during the pulsion stroke of the jig cycle. Experimental results at different maximum water velocities show three important relations between the feed characteristic and the maximum water velocity. Firstly, coarser feed needs higher maximum water velocity for better jigging efficiency, secondly, maximum water velocity for a feed must be matched to the largest size of the particles present in the feed, and finally, even at optimal maximum water velocity different size fractions of a feed respond differently and as a result ideal separation is never achieved. These observations reinforce the need for sizing the feed and then optimizing the maximum water velocity for each feed. This study also brings into focus the concept of size ratio which is used to predict the segregation potential of binary particulate systems.

Analysis of a laboratory jigging system for improved performance

The movement of water through the jig bed is the key to better stratification of particles. In this study a systematic analysis of the movement of water in a conventional pressurized pulsion and gravity induced suction cycle is analyzed using an instrumented jig. Detailed analysis of a single jig cycle indicates that this approach to jigging confines its operation to a narrow range of frequencies with interdependencies of amplitude and frequency of the water waveform. To improve the jigging operation, identical water movement in both the pulsion and the suction phase of the jig cycle is required. It has been accomplished, first, with the controlled application of air pressure during both phases of the jigging cycle, and second, by the implementation of a timer control operation of the air valves. This paper gives a brief account of the changes that are made to the jigging system leading to decoupling of the strong correlation between amplitude and frequency of the water waveform, and increase in the operating range of the frequency of pulsation. In the modified jig set-up, the amplitude and frequency of pulsation are varied over a wide range to generate different patterns of waveforms. The most suitable waveform is used to study the jigging behavior of different particulate systems. The role of amplitude and frequency on the progress of the bed stratification during jigging is established.

Properties of a Jigging Bed Analyzed with a High Speed Analyzer (Part 2): A Series of Motion Equations of the Water in the Jig

In order to help explain stratification in a jig, it is useful to study the motion of the jigging pulse water. With the help of a laboratory model jig and a high-speed dynamic analysis meter, water flow in the model jig was observed and analyzed. Based on the experiments and vibration theory, a series of motion equations of water in the jig were developed. In the equations, the motion parameters of the water, such as velocity, acceleration, and force are directly proportional to the air pressure, and have a definite nonlinear relationship with the jigging cycle, thickness, and mobility of the jig bed.

A new energy dissipation theory of jig bed stratification. Part 1: energy dissipation analysis in a pilot scale baum jig

The dynamic energy dissipation within a jigging cycle has been mechanically analyzed using data developed in a highly instrumented and controlled pilot scale Baum jig. The analysis is based on the use of the energy and momentum equations for the fluid. It was found that energy balances on the water in the jig failed to close because of elastic deformation of the jig body, rather than inaccuracies in the measurement techniques or failure to account for heat transfer. This deformation problem appears to be common in either pilot jigs or commercial jigs. An empirical means of correcting the energy balance was devised and applied to the data with some success. Using this compensation method, the energy balance was improved. The likely energy balance indicates that (i) less than 7% of the energy of the incoming compressed air is expended in the jig system, (ii) less than 5% of the energy from the compressed air is actually dissipated in the jig bed, (iii) the kinetic energy input from the hutch water supply is effectively negligible, in comparison to the energy input from the compressed air, and (iv) about 2.5–3.7% of the energy from compressed air is dissipated around the bed plate.

The Mechanical Behaviour of Water and Gas Phases in a Pilot Scale Baum Jig

Abstract Seven signals were accurately measured and data logged in exhaustive experiments using a highly instrumented and controlled pilot scale Baum jig. These signals provide a basis for understanding the effect of the operating parameters on the air and water behaviour in the jigging process. The measurements include the air pressure, water pressures and displacement, the hutch water flowrate. A Fourier decomposition method was applied to remove signal noise and smooth the signals. Water velocities and accelerations are calculated from the smoothed displacement data. The frequency of pulsation, air pressure in the accumulator and inlet period of the air cycle play significant roles in determining the air and water behaviour in the jigging process. The bed thickness. expansion period of the air cycle, hutch water flowrate and the rate of opening of the inlet valve are less important. The characteristics of four typical air cycles, namely, the conventional Baum jig cycle. Mayer cycle. Jeffrey/Bird cycle and the cycle with a long inlet period were investigated. The substantial differences in water motion generated by the four cycles demonstrate the importance of selecting a suitable air cycle. The jig beds used in the study were composed of synthetic particles (3 to 35 mm) having densities in the range 1.3 to 2.0 tonnes/m3.