Underflow Discharge Control via Fluidisation Zone
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Solution Overview
Problem
The control of underflow stream discharge from separators, particularly mineral particle separators, is challenging due to rapid discharge rates caused by hydrostatic pressure and bridging of coarse particles, leading to cycling and inaccurate targeting of suspension density set points.
Innovation Solution
An apparatus and method involving a pressurized fluid source connected to the discharge outlet to create a fluidization zone, with a control valve and a second conduit for removing material, allowing for controlled flow and preventing bridging by using a counter-flow of pressurized fluid and a peristaltic pump to manage the underflow stream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a valve is used to control underflow discharge, then discharge rate can be regulated, but rapid discharge occurs due to hydrostatic head and non-linear valve opening variations
Solution Approach 1:
A fluidisation medium is introduced as an intermediary substance between the slurry and the valve. This medium fluidises the slurry in the valve region, preventing coarse particle bridging and enabling smooth, controlled discharge. The fluidisation medium acts as a mediator that allows the valve to operate linearly and predictably without the harmful bridging effect.
Solution Approach 2:
The physical state of the slurry is changed from a packed, bridge-forming state to a fluidised state by introducing the fluidisation medium. This parameter change in the slurry's flow characteristics eliminates the non-linear valve behavior and rapid discharge cycles, providing stable and reliable discharge control.
2Productivity
If valve opening is increased to prevent particle bridging, then discharge rate increases, but suspension density falls below set point
Solution Approach 1:
The fluidisation medium serves as an intermediary that enables the valve to remain partially open without causing bridging. This allows continuous, controlled discharge that maintains suspension density at the desired set point, achieving both adequate discharge rate and precise density control.
Solution Approach 2:
The system uses feedback from suspension density measurements to adjust valve position. With the fluidisation medium preventing bridging, the valve can make fine adjustments based on feedback signals, maintaining suspension density at the set point while achieving the required discharge rate.
3Reliability
If valve is kept open to allow free passage of coarse particles, then blockage is prevented, but excessive and rapid discharge occurs
Solution Approach 1:
The fluidisation medium is introduced as an intermediary substance that allows the valve to maintain a partially open position without blocking. The fluidised slurry flows smoothly through the valve opening, preventing bridging while enabling precise control of the discharge rate, thus achieving both reliability and control accuracy.
4Volume of stationary object
If small vessel cross-section is used, then separator size is reduced, but valve must be large relative to vessel to allow particle passage
Solution Approach 1:
The fluidisation medium acts as an intermediary that enables the use of smaller valves in smaller vessels. By fluidising the slurry, the system ensures free particle passage through proportionally smaller valve openings, maintaining functionality while allowing compact separator design with appropriate valve-to-vessel size ratios.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution stabilizes the underflow discharge, allowing precise control of suspension density and preventing over-discharge, reducing cycling and bridging issues, enabling more efficient separation and minimizing the risk of blockages.
Implementation Method 1
directed to impede the flow of the underflow stream in the first conduit, thereby creating a fluidisation zone
Implementation Method 2
A first conduit is provided which is fluidly connected to the discharge outlet such that a flow of pressurised fluid from a source of pressurised fluid forms a counter-flow to the flow of underflow stream through the first conduit
Data Source
AI summary
An apparatus and method for removing an underflow stream is provided suitable for removing an underflow stream from a separator, such as a mineral particle separator. In one aspect, the separator can include a discharge outlet for discharging the underflow stream, and the apparatus can include a source of pressurised fluid, a first conduit for fluidly connecting the pressurised fluid source to the discharge outlet such that the pressurized fluid is directed to impede the flow of the underflow stream in the first conduit, thereby creating a fluidisation zone, and a second conduit fluidly connected to the first conduit so that material from the fluidisation zone flows into the second conduit for removal from the apparatus.