Classifying – separating – and assorting solids – Stratifiers – With liquid treatment
Patent
1998-03-06
2000-06-06
Walsh, Donald P.
Classifying, separating, and assorting solids
Stratifiers
With liquid treatment
209489, 209491, 209496, B03B 552, B03B 1104, B03B 1100
Patent
active
060707380
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
(1) Field of Invention
THIS INVENTION relates to the dynamic monitoring and control of jigs.
(2) Prior Art
The University of Queensland has patented and developed a control system for jigs that is centred on the concept that the jig can be controlled in response to measurement of the time variation of a signal during a cycle for the jig pulsation. The idea of signal averaging over a number of jig cycles is also invoked to provide more accurate signals and the Patent refers particularly to the measurement of density in the jig bed as a function of time. The Abstract of Australian Patent No. 596858 (AU-B-76489187) states:
"The density of the material in the jig bed is measured in consecutive short segments over the jig cycle, the time period of each segment not being greater than one-tenth the cycle time of the jig, to determine the density signature or profile of the jig. By controlling the operating parameters (e.g. inlet and outlet valve opening and closing, underbed water flow rate, discharge gate position and jig working air (pressure) of the jig, the density signature or profile is maintained within a control envelope for efficient stratification of the mineral."
It is relevant to outline some basic aspects of the physics of operation of jigs, including centrifugally-aided jigs also known as Kelsey jigs. These concepts are also applicable within minor modification to moving screen jigs.
The separation in a jig occurs as a result of the passage of a pulsating flow of water through a bed of particles that are supported on a screen or punched plate. As the water flows through the screen and into the bed of particles (pulsion phase of flow--consider such a flow direction to be positive or `upward`), the fluid drag on the particles supports more and more of the weight of the bed of particles until at some critical velocity, the bed of particles lifts. Further increase in fluid velocity causes fluidisation and dilation (decrease in the volume fraction of solids) of the bed. As the pulsion phase of the flow finishes and the fluid velocity reverses and increases in velocity downwards, the dilation of the bed rapidly decreases and the bed is forced back against the bed plate. Further increase in the downward velocity causes a significant pressure drop to develop across the bed.
Superimposed on this pulsating flow is a relatively small constant upflow of water through the bed. The purpose of this flow is to supply a current of water above the bed plate that will assist in the transport of the particles in a direction perpendicular to the pulsing flow. In a continuous jig, the particles of coal or mineral are transported from the feed end of the jig to the discharge end and the bed becomes progressively more stratified or better separated or better sorted as the material moves from the feed end to the discharge end.
The extent of separation is gauged by the extent to which particles of different size and true particle density become sorted in the bed. For example, for a particle bed composed of only one size of particle, but having a range of particle densities, an arrangement of particles in the bed such that particle density decreases monotonically from the bed plate towards the top of the bed would be considered to be perfectly sorted or separated.
The manner in which particles of differing density move from one layer to another in the bed as separation progresses depends on the extent to which the particle bed dilates and the relative vertical motion of the particles in response to the fluid flow through the particle bed. When a broad distribution of particle sizes exists in the bed, particle motion can also occur in the bed by a trickling mechanism wherein small particles move through the interstices of the packed bed.
One must also distinguish between two general methods of jigging separation, namely `through the screen` separation or `over the screen separation`. In the first case, the bed becomes stratified or sorted with high density particles moving towards the bed plate and
REFERENCES:
patent: 4265744 (1981-05-01), Weiffen
patent: 4358827 (1982-11-01), Abbott
patent: 5028317 (1991-07-01), Lyman
patent: 5541831 (1996-07-01), Thomas
Jonkers Andrew
Lyman Geoffrey John
Martin Brett C.
The University of Queensland
Walsh Donald P.
LandOfFree
Dynamic monitoring and control of jigs does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dynamic monitoring and control of jigs, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dynamic monitoring and control of jigs will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2207071