Bubble mineralization process

The phenomenon in which particles adhere to the bubbles is called mineralization of the bubbles, and the bubbles adhering to the particles are mineralized bubbles. The composition of the actual flotation process: four stages: contact, adhesion, lifting and foaming. In these four stages, the first two are the mineralization process of the bubbles. The way is collision mineralization and mineralization. Both may be combined at the same time to form a combined bubble mineralization.
The bubble mineralization process is very complicated. According to the physical and chemical principles, thermodynamic methods and kinetic methods can be used for research. Thermodynamics is a macroscopic method that can be used to determine the possibility of bubble mineralization. The kinetic study may explain the essence of the mechanism process of the bubble mineralization process, the influencing factors, the realization conditions and the speed of the process.

I. Thermodynamic analysis of bubble mineralization process
Principle: The second law of thermodynamics.
1. The free energy of the collision mineralization system changes:
Assume that the area of ​​the grain and bubble adhesion is 1 unit (1 cm ² ).
Free energy of the system before attachment: .
Free energy of the system after attachment: .
Free energy changes: .
Conclusion: By analysis, hydrophobic minerals can adhere to bubbles, and hydrophilic minerals cannot.
discuss:
(1) The lower the δAW value, the smaller the ΔE, the lower the possibility of adhesion and the actual error.
(2) Collision methods and flow patterns also have an effect.
(3) Uncertainty of the contact angle.
(4) The influence of the hydration of the ore particles and bubbles.
2. Thermodynamic analysis of precipitation mineralization
It is assumed that the bubbles deposited on the mineral surface are much smaller than the mineral surface. Moreover, the mineral surface is flat and the free energy of the precipitation mineralization system changes.



Note: S1=2πr(r+rcosθ) and S2=πr2sin2θ.
Discussion: (1) Let K = 2+ cos θ + sin 2θ cos θ, K, θ relationship: θ increases, K decreases.
(2) δAW is unchanged, ΔE, K relationship: K decreases, and ΔE increases.
(3) θ is invariant, δAW, ΔE relationship: δAW decreases, and ΔE increases.
Conclusion: With the increase of the wetting contact angle, the smaller the value, the smaller the free energy of the system, and the easier the microbubble is precipitated. That is to say, it is theoretically found that the microbubbles can be precipitated on the surface of the hydrophobic mineral. There is no principle for the precipitation of mineralization to work outside and improve selectivity.
Second, the dynamic analysis of bubble mineralization process
1. The close proximity and collision of the ore particles and bubbles:
Cause: The agitation of the flotation machine, the bubbles in the slurry rise to the floating and the ore grain down to the honorary title to use the surface force field between the interfaces.
Factors affecting the probability of collision: the amount of suspended minerals, the number of bubbles and surface area agitation strength, mineralization pathways and methods.
2. Hydration layer thinning and cracking:
There are hydration layers on the surface of the mineral and on the surface of the bubble. The thinning and rupture (or partial rupture) of the hydration layer consumes a mile of energy, causing the entire free energy to change.
(1) Changes in the free energy of the system when the surface of the strongly hydrated mineral excludes the hydrated film.
(2) The change of free energy when the surface of the moderately hydrated mineral excludes the hydrated film.
(3) Changes in the free energy of the system when weakly hydrated minerals exclude the hydration layer.
3. Bubble mineralization pathway:
Pathway: collision mineralization, precipitation mineralization.
Mineralization form: single bubble mineralization, group bubble mineralization, air floc.
4. Induction time:
From the moment of instant to the moment of attachment, the hydration layer is thinned, cracked, the expansion of the three-phase wetting periphery, and the time during which the particles adhere stably to the bubble.
Contact time: In the adhesion of particles and bubbles, the collision of particles and bubbles begins until the particles fall off the bubbles.
Adhesion conditions: induction time < contact time.
Influencing factors: (1) flotation reagents;
(2) particle size;
(3) the size of the bubble;
(4) Physical properties of the particles.
5. The mineral particles adhere to the surface of the bubble:
(1) Influencing factors:
Mineral particle size and fixation probability:

(2) The strength of the exfoliation of the ore and the strength of the surface hydrophobicity and the rate of solidification:
It is assumed that the adhesion of the ore particles to the bubbles in the still water is in equilibrium, and the mineral surface is smooth and uniform, and is much larger than the area of ​​adhesion.

A, adhesion F attached
F attached = πaδAWsin θ
B, shedding force: bubble lift or gravity of the ore particles F1
F1=VgΔ
Gas to liquid pressure difference (or additional shedding force) F2
Residual capillary pressure .
Hydrostatic pressure difference
.
C, equilibrium equation and adhesion conditions:
F attached = F1 + F2

Solid conditions:

From this static equilibrium single mineralization, the derived approximation can only be used to roughly analyze a major force affecting the adhesion strength of the ore-bubble polymer in order to find the main factors affecting the adhesion strength.
Under actual flotation conditions, inertial centrifugal force will be generated, which is the main force.
6. The kinetic process of precipitation mineralization:
A brief introduction to the kinetics of bubble precipitation on the surface of hydrophobic minerals.
A. Movement of gas molecules: At the moment of decompression, the gas molecules move to a region that is easy to be polymerized, and the inter-molecular force of the water is interrupted.
B. Generate a "bubble crystal nucleus".
The gas molecules polymerize in the van der Waals force to form a bubble crystal nucleus with a radius of R (ie, the minimum radius of the bubble that can stably exist in the liquid phase).
Bubble residual capillary pressure

Let P1 be the liquid surface pressure when the gas is saturated in the solution, and P2 be the liquid surface pressure when the gas is saturated in the solution after the pressure reduction.


C, the newborn bubble grows up.
Third, flotation speed
Flotation rate (Rate): unit time floating mineral slurry to be floated skimmer or recovery amount.
Flotation Rate Equation: An expression of the amount of foam product as a function of time.
Significance: evaluation of flotation process; analysis of influencing factors; improvement of flotation process; improvement of flotation machine design; optimization and automation of flotation process control.
Average speed of flotation
Features: simple
Actual: During the flotation process, the flotation speed of the minerals to be floated at different time periods is different, and begins to float faster, and then gradually slows down.
Experiment: Flotation speed experiment.
Flotation velocity equation
Belora Ladov equation
Principle: Statistical laws are applied to study flotation speed.
False: Flotation time
At the beginning of flotation, the number of ore particles in the slurry contains the number of ore particles that are intended to float, and the number of ore particles that are intended to float in the time is in the amount of the minerals that remain in the slurry. The number of bubbles, the probability that the particles are fixed in the bubble
There is a bubble in the time dt, and there is a mineral grain into the foam product, and the ore particle is proportional to the number of collisions of the bubble.
The graphic drawn in this way should be a straight line.
Description: a, pure mineral, narrow grain size, the same floatability. The liquid-gas interface is large. Its slope is positive.
b. The test result is a shape curve: when sorting, it is fast and slow.
c. The test result is a shape curve: when sorting, it is slow and fast.
The number of stages in the flotation speed equation.
The bubble mineralization process belongs to the interaction between the ore particles and the bubbles, and is similar to the interaction between the particles in the chemical reaction. The chemical reaction velocity equation discussed in the chemical mechanics can be simulated to derive the flotation velocity equation.
It varies with the concentration of the reactants. The concentration gradually decreases and the speed is slow.
In the flotation, the change of the flotation product over time is used to indicate the reaction rate.
Remaining in the pulp to be floating along but not rising to the purpose of mineral occupied by metal percentage.
Discussion: (1) Connotation.
(2) Flotation speed and series

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