Flotation Contactor with Throttling Duct for Bubble Size Control
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Solution Overview
Problem
Current flotation technologies face inefficiencies in separating fine and coarse particles due to limitations in bubble size control, shear intensity, and turbulence, leading to reduced recovery rates, especially for particles outside the intermediate size range.
Innovation Solution
An apparatus and method that generate fine bubbles and increase shear intensity by using a contactor with a throttling duct and flow manipulator to create a high-energy dissipation rate environment, ensuring intimate contact between bubbles and particles, and a draft tube to assist coarse particles in rising to the froth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional aeration devices are used to distribute bubbles uniformly across the column cross-section, then bubble distribution is improved, but bubble size becomes too large (1-5 mm) for effective fine particle capture
Solution Approach 1:
The aeration system is segmented into multiple independent porous sparger elements distributed across the column cross-section. Each sparger generates bubbles locally, allowing precise control of bubble size while maintaining uniform distribution through the segmented arrangement rather than a single large aeration device
Solution Approach 2:
Porous sparger materials are used to generate fine bubbles through the porous structure. The porous nature of the sparger elements creates numerous small bubble nucleation sites, producing bubble sizes suitable for fine particle capture while maintaining uniform distribution across the column
2Loss of time
If tall column cells (height-to-diameter ratio 2:1 to 10:1) are used to provide sufficient contact time, then particle-bubble contact time is improved, but device complexity and space requirements increase
Solution Approach 1:
Particle-bubble contact occurs preliminarily in a dedicated contactor device before the particles enter the main separation column. This preliminary contact action allows most particle capture to occur in a compact volume, reducing the required height of the separation column while maintaining adequate contact time
Solution Approach 2:
A separate contactor device acts as an intermediary between the aeration system and the separation column. This intermediary component provides a dedicated zone for intensive particle-bubble contact, decoupling the contact time requirement from the overall column height and allowing the column to be more compact
3Productivity
If high gas fractions are used to improve fine particle flotation, then fine particle recovery is improved, but coarse particle separation efficiency deteriorates due to excessive turbulence
Solution Approach 1:
The flotation system is segmented into two distinct operational zones: a high gas fraction contactor zone for fine particle capture and a low gas fraction separation zone for coarse particle handling. This segmentation allows each zone to be optimized for its specific particle size range without the adverse effects of the other zone's operating conditions
Solution Approach 2:
Different local conditions are provided in different zones of the system. The contactor zone has high gas fraction and intense turbulence optimized for fine particles, while the separation column has low gas fraction and calm conditions optimized for coarse particles. Each zone has locally optimized quality parameters matched to its function
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 approach significantly improves the recovery of fine and coarse particles by reducing bubble size, increasing shear intensity, and controlling the gas-liquid mixture, resulting in enhanced flotation efficiency and reduced operational costs.
Implementation Method 1
a contactor arranged to receive under pressure a supply of feed slurry incorporating particles suspended in a liquid and a supply of gas, the contactor being arranged to mix the slurry with the air forming a gas-liquid bubbly two-phase mixture
Implementation Method 2
an outlet from the contactor configured to provide a restriction to the flow of mixture therethrough and maintain the mixture within the contactor under pressure
Implementation Method 3
a flow manipulator downstream from the outlet configured to induce a high energy dissipation rate within the mixture passing therethrough
Implementation Method 4
increase shear intensity by using a contactor with a throttling duct and flow manipulator to create a high-energy dissipation rate environment
Implementation Method 5
a separation cell arranged to receive mixture from the flow manipulator and allow bubbles with attached particles to rise to the surface of liquid within the cell
Implementation Method 6
chemical reagents or collectors which have the effect of making the particles which it is desired to remove, water repellent or hydrophobic
Implementation Method 7
The hydrophobic particles attach to the air bubbles and rise to the surface of the cell, from which they can be removed by flowing over a lip under the action of gravity
Data Source
AI summary
A flotation separation apparatus for separating particles in suspensions, feeds slurry containing the particles through an inlet into a contactor where gas is fed through an inlet to mix with the slurry, for example in a downwardly plunging jet, to form a gas-liquid bubbly two-phase mixture under pressure from an outlet restriction in a throttling duct. The mixture is passed through a flow manipulator configured to induce a high energy dissipation rate, for example by way of a Shockwave formed in a diverging section of the throttling duct reducing the size of the bubbles and brining those bubbles into intimate contact with particles in the mixture which is released into a separation cell where a flow manipulating draft tube is provided to reduce turbulence in the mixture. Alternative apparatus and methods for inducing the high energy dissipation rate and for reducing turbulence in the mixture are also described and claimed.