WO2023071904A1

WO2023071904A1 - Test system and method for dynamic interaction force between flotation particles and bubbles

Info

Publication number: WO2023071904A1
Application number: PCT/CN2022/126400
Authority: WO
Inventors: 邢耀文; 桂夏辉; 孙丽娟; 曹亦俊; 刘秦杉; 何琳; 张凡凡; 杨陈仪敏; 张怡晴
Original assignee: 中国矿业大学
Priority date: 2021-10-28
Filing date: 2022-10-20
Publication date: 2023-05-04
Also published as: CN114705593A

Abstract

A test system and method for a dynamic interaction force between flotation particles and bubbles, relating to the technical field of sensitive force test research, and solving the problem in the prior art that a measurement device is high in price and is mostly suitable for a fluid dynamics condition of a low Reynolds number. The test system comprises a motion driving unit, a displacement sensor (2), a bubble generation unit, a mechanical test unit, an image monitoring unit and a signal acquisition and processing unit; the motion driving unit is connected to the bubble generation unit and can move in a vertical direction; the displacement sensor (2) is connected to the motion driving unit; the mechanical test unit is provided below the bubble generation unit; the image monitoring unit is provided on a side of the mechanical test unit; the signal acquisition and processing unit is electrically connected to the displacement sensor (2), the mechanical test unit, and the image monitoring unit, respectively. The present invention is flexible in operation and controllable in costs.

Description

Test system and test method for dynamic interaction force between flotation particles and air bubbles

technical field

The invention relates to the technical field of sensitivity test research, in particular to a test system and test method for dynamic interaction force between flotation particles and air bubbles.

Background technique

Flotation is widely considered to be the most effective means of sorting and upgrading fine-grained minerals and coal, and achieves selective separation between target minerals and gangue particles according to the difference in physical and chemical properties of the particle surface. Flotation pulp is a complex multiphase system composed of water, mineral particles, air bubbles and flotation agents. Hydrophobic particles adhere to air bubbles to form air flocs and float up to become concentrate products, while hydrophilic particles remain in the pulp to be Discharged into tailings products.

As the basic action unit in flotation, the interaction between particles and air bubbles directly determines the flotation process and the efficiency of sorting. Generally speaking, the interaction between particles and bubbles is controlled by the surface force and fluid force between particles and bubbles. It is of great scientific significance to study the interaction force between particles and bubbles and clarify its interaction mechanism. It can be used for low-rank coal, oxidized coal It provides theoretical guidance for the strengthening of the separation process of difficult floating coal and complex refractory minerals.

Since the 1930s, the interaction between particles and bubbles has attracted widespread attention from scholars at home and abroad, and a series of experimental techniques have gradually emerged to detect their interaction force, with AFM (Atomic Force Microscope, Atomic Force Microscope) being the most widely used. widely. AFM relies on colloidal probe technology to detect the bending amount of the microcantilever through laser signals to obtain the interaction force between particles and bubbles. The force resolution is as high as 0.1nN, but AFM is only suitable for microscopic particles at lower approach speeds The Reynolds number is generally less than 10-2, which is far lower than the hydrodynamic parameters in flotation.

Therefore, it is extremely necessary to develop a sensitive test system that can accurately measure the interaction force between flotation-sized particles and air bubbles in a wider speed range.

Contents of the invention

In view of the above analysis, the embodiment of the present invention aims to provide a test system and test method for the dynamic interaction force between flotation particles and air bubbles, which is used to solve the problem that the existing force measurement equipment is expensive and is mostly suitable for low Reynolds number fluid dynamics. problems under current conditions.

On the one hand, the present invention provides a dynamic interaction force test system between flotation particles and air bubbles, including a motion drive unit, a displacement sensor, a bubble generation unit, a mechanical test unit, an image monitoring unit, and a signal acquisition and processing unit. The driving unit is connected with the bubble generating unit and can move in the vertical direction, the displacement sensor is connected with the motion driving unit, the mechanical testing unit is arranged under the bubble generating unit, and the image monitoring unit is arranged On the side of the mechanical testing unit, the signal acquisition and processing unit is electrically connected to the displacement sensor, the mechanical testing unit, and the image monitoring unit, respectively.

Further, the motion drive unit is used to drive the air bubbles to approach the sample, and the measuring contact of the displacement sensor is connected to the motion drive unit for collecting the dynamic voltage signal generated by the displacement change of the motion drive unit. The test unit is used to detect the micro-deformation in the process of interaction between flotation particles and air bubbles, and convert the micro-deformation into electrical signals.

Further, the image monitoring unit is used to observe the interaction process of the flotation particles and air bubbles and measure the three-phase contact periphery and dynamic contact angle, and the signal acquisition and processing unit is used to acquire the generated images and dynamic voltage signals, and convert the voltage The signal is transformed into a "displacement-time" curve and a "force-time" curve.

Further, the motion drive unit includes an electric motor, a controller, and a translation platform, the electric motor is connected to the translation platform, the controller is electrically connected to the electric motor, and controls the electric motor to drive the The displacement stage moves up and down.

Further, the bubble generation unit is used to generate millimeter-scale bubbles, and specifically includes a syringe, a hose and a capillary, and the syringe communicates with the capillary through the hose.

Further, the capillary is arranged vertically, one end of the capillary is connected to the displacement platform, and the other end is a free end.

Further, the mechanical testing unit includes a transparent liquid tank, a resistance bridge force sensor and a sample holding part, the resistance bridge force sensor is arranged in the transparent liquid tank, and the sample holding part is connected to the resistance bridge force sensor. Connect the free end of the sensor.

Further, the sample holding part is located directly below the capillary.

Further, the signal acquisition and processing unit includes a differential amplifier, a data acquisition card and a PC terminal, the differential amplifier is used to amplify the voltage signal generated by the resistance bridge force sensor, and the amplified voltage signal is combined with the displacement sensor to generate The voltage signals are collected by the data acquisition card and transmitted to the PC terminal, and the PC terminal converts the two voltage signals into a "force-time" curve and a "displacement-time" curve respectively.

In another aspect, the present invention provides a method for testing the dynamic interaction force between flotation particles and air bubbles, using the above-mentioned dynamic interaction force test system between flotation particles and air bubbles, the steps include:

Step 1: Place a series of weights of known mass on the sample holding part connected to the resistance bridge force sensor, record the generated voltage value, draw the standard curve of force and voltage, and obtain the linear relationship between force and voltage;

Step 2: Place solid particles to be measured on the sample holding part connected to the resistance bridge force sensor, and use a syringe to generate a millimeter-sized air bubble at the free end of the capillary connected to the displacement stage;

Step 3: Control the electric motor to drive the stage to move up and down, so that the air bubbles at the free end of the capillary approach the particle surface at a certain speed along the z-axis, and return to the initial position after contacting the air bubbles;

Step 4: Process the voltage signal on the PC to convert the dynamic voltage signal generated by the displacement sensor into a "displacement-time" curve; use low-pass filtering to process the dynamic voltage signal, and use the "force-voltage" standard obtained in the calibration step Curve, convert the dynamic voltage signal into a "force-time" curve; combine the "displacement-time" curve with the "force-time" curve to obtain a "force-displacement" curve;

Step 5: The image analysis software on the PC reads the image sequence recorded by the image monitoring unit, measures the length of the three-phase contact line and the dynamic contact angle at different times, and realizes the direct observation of the dynamic process of the interaction between particles and bubbles.

Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

(1) The present invention allows users to study the interaction between two colloids (such as particles and bubbles, bubbles and bubbles) under dynamic and equilibrium conditions.

(2) The present invention is suitable for studying the influence of hydrodynamic conditions on the interaction force. The motion drive unit of the present invention provides a large vertical displacement, which can achieve millimeter-level motion displacement in a very short time compared with the commercial AFM whose maximum z-direction displacement is only 20 μm. The approaching/retracting speed can be changed in the range of μm/s to mm/s, realizing the measurement of the interaction force between floating particles and air bubbles in a wider speed range.

(3) The high-speed data acquisition card selected by the present invention has a sampling frequency as high as 10kHz and a higher time resolution. Such features enable users to accurately track the entire process of approaching, contacting, and separating particles and air bubbles.

(4) The present invention integrates a CMOS camera for monitoring, photographs and records the entire interaction process, and can simultaneously realize the simultaneous measurement of the interaction force between particles and air bubbles, the three-phase contact periphery, and the dynamic contact angle.

(5) The present invention has higher flexibility. During the test, the bubble/particle size can be changed more flexibly by replacing capillary tubes and sample holders of different sizes, which overcomes the requirement of the upper limit of the particle/bubble size (100 μm) due to the limitation of the diameter of the cantilever in the traditional AFM test. By replacing different types of sample holding parts, the measurement of the interaction force between different samples (particles and particles, bubbles and bubbles) can also be realized.

(6) Compared with commercial integrated force measurement equipment such as AFM, the present invention has the advantages of flexible operation and controllable cost.

Description of drawings

Fig. 1 is a structural schematic diagram of the interaction force testing system of the present invention.

Reference signs:

11-electric motor; 12-controller; 13-transition stage; 14-fixed stage; 2-displacement sensor; 31-syringe; 32-hose; 33-capillary; 41-transparent liquid tank; 42-resistance bridge force sensor ; 43-sample clamping part, 44-passive vibration isolation table; 51-CMOS camera; 52-LED light source; 61-differential amplifier; 62-data acquisition card; 63-PC terminal.

Detailed ways

The preferred embodiments of the present invention will be specifically described below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and together with the embodiments of the present invention are used to explain the principles of the present invention and are not intended to limit the scope of the present invention.

Example 1

A specific embodiment of the present invention, as shown in Fig. 1 , discloses a kind of dynamic interaction force test system (hereinafter referred to as " mutual force test system ") between flotation particle and air bubble, comprises motion drive unit, displacement sensor 2, Bubble generating unit, mechanical testing unit, image monitoring unit and signal acquisition and processing unit. The motion driving unit is connected with the bubble generating unit and can move in the vertical direction, the displacement sensor 2 is connected with the motion driving unit, the mechanical testing unit is arranged under the bubble generating unit, and the image monitoring unit is arranged at the side of the mechanical testing unit, The signal acquisition and processing unit is electrically connected with the displacement sensor 2, the mechanical testing unit and the image monitoring unit.

The motion drive unit is used to drive the air bubbles close to the sample. The measuring contacts of the displacement sensor 2 are connected with the motion drive unit for collecting the dynamic voltage signal generated by the displacement change of the motion drive unit. The mechanical test unit is used to detect the micro-deformation in the process of interaction between flotation particles and air bubbles, and convert the micro-deformation into electrical signals.

The image monitoring unit is used to observe the interaction process between flotation particles and air bubbles, and measure the three-phase contact periphery and dynamic contact angle. The signal acquisition and processing unit is used to acquire the generated images and dynamic voltage signals, and convert the voltage signals into "displacement-time" curves and "force-time" curves.

The motion drive unit is used to drive the air bubbles to approach, contact and move away from the flotation particles at a certain speed. Specifically, the motion drive unit includes an electric motor 11 , a controller 12 , a displacement stage 13 and a fixed stage 14 . The translation platform 13 is connected to the fixed platform 14 , the electric motor 11 is connected to the translation platform 13 , and the controller 12 is electrically connected to the electric motor 11 . The controller 12 is used to control the electric motor 11 to drive the translation stage 13 to move up and down, and the moving speed can be changed in the range of μm/s to mm/s.

Exemplarily, the fixed platform 14 is provided with a guide rail in the vertical direction, and the displacement platform 13 is slidably connected with the guide rail. The rotation of the motor 13 drives the lead screw to rotate and then drives the displacement bar 13 to move vertically along the fixed table 14 .

In this embodiment, the displacement sensor 2 is fixed by a bracket, and its measuring contact is connected to the displacement platform 13 of the motion drive unit, and is used to collect the dynamic voltage signal generated by the linear displacement change of the displacement platform 13 . The update speed of the displacement sensor 2 is 0.3ms/time, the displacement resolution can reach 2μm, and the dynamic voltage signal generated is proportional to the linear displacement change.

The bubble generation unit is used to generate millimeter-scale bubbles, and specifically includes a syringe 31, a hose 32 and a capillary 33, the syringe 31 and the capillary 33 communicate through the hose 32, the hose 32 is provided with a stop valve, and the capillary 33 is vertically arranged. One end thereof is connected with the displacement platform 13, and the other end is a free end. Using the syringe 31 can generate a millimeter-sized bubble at the free end of the capillary 33. After the bubble is generated at the free end of the capillary 33, close the stop valve to avoid shrinking or disappearing of the bubble in the backflow of the airflow, so that the bubble is in a stable volume state.

The mechanical testing unit is used to detect micro-deformation in the process of interaction between flotation particles and air bubbles, and specifically includes a transparent liquid tank 41, a resistance bridge force sensor 42, a sample clamping part 43 and a passive vibration isolation table 44, and the resistance bridge force sensor 42 is set In the transparent liquid tank 41 , the sample holding part 43 is connected to the free end of the resistance bridge force sensor 42 . Preferably, the resistive bridge force sensor 42 has a measuring range of -40mN～+40mN, a force resolution of μN level, and the dynamic voltage signal generated is proportional to the normal pressure. The passive vibration isolation table 44 is used to isolate micro-vibration and reduce interference.

Specifically, the transparent liquid tank 41 is arranged below the motion drive unit, and the sample holding part 43 is positioned directly below the capillary 33, so that when the capillary 33 moves downwards driven by the displacement stage 13, the air bubbles generated at the free end of the capillary 33 The sample held by the sample holding part 43 can be just touched. The transparent liquid tank 41 is placed on the passive shock isolation table 44, and the resistance bridge force sensor 42 is erected on the bottom of the transparent liquid tank 41 through installation. One end of the resistance bridge force sensor 42 is fixedly connected with the mounting frame, and the other end is used for setting the sample holder. The free end of the holding member 43.

The image monitoring unit includes a CMOS camera 51 and an LED light source 52, which are used to observe the interaction process between floating particles and air bubbles. Parameters such as the brightness of the LED light source 52 and the frame rate of the CMOS camera 51 can be adjusted according to the test conditions. In this embodiment, the CMOS camera 51 and the LED light source 52 are respectively arranged on both sides of the transparent liquid tank 41 .

The signal acquisition and processing unit includes a differential amplifier 61 , a data acquisition card 62 and a PC terminal 63 , the differential amplifier 61 is electrically connected to the signal input terminal of the data acquisition card 62 , and the output terminal of the data acquisition card 62 is electrically connected to the PC terminal 63 . The differential amplifier 61 is used to amplify the voltage signal generated by the resistance bridge force sensor 42. The amplified voltage signal and the voltage signal generated by the displacement sensor 2 are collected by the data acquisition card 62 and transmitted to the PC terminal 63. The circuit voltage signal is converted into a "force-time" curve and a "displacement-time" curve respectively. In addition, the PC terminal 63 is also used to receive the image taken by the CMOS camera 51 of the image monitoring unit, and the image can be processed to obtain the three-phase contact periphery and dynamic contact angle during the interaction between the flotation particles and the air bubbles.

It should be noted that the mutual force testing system of this embodiment can also realize the measurement of the interaction force between different samples (particles and particles, air bubbles and air bubbles) by replacing different types of sample holding parts.

Exemplarily, when measuring the interaction force between particles, the particles can be directly stuck to the bottom of the capillary 33, understandably, a clamping part capable of clamping the particles can also be connected to the lower end of the fixed table 14 , driven by the displacement stage 13, the particles on the surface are brought close to or away from the particles on the sample holding part 43, so as to realize the measurement of the interaction force between particles.

Exemplarily, when measuring the interaction force between air bubbles, an air bubble can be injected into the upper end of the sample holding part 43, understandably, a syringe can also be held by the sample holding part 43, and the A bubble, driven by the displacement stage 13, makes the bubble generated by the upper capillary 33 approach or move away from the bubble on the cantilever end of the resistance bridge force sensor 42, so as to realize the measurement of the interaction force between the bubble and the bubble.

Compared with the prior art, the mutual force test system provided by this embodiment allows users to study the interaction between two colloids (such as particles and bubbles, bubbles and bubbles) under dynamic and equilibrium conditions. Suitable for studying the influence of hydrodynamic conditions on the interaction forces. The motion drive unit provides a relatively large vertical displacement (in the order of mm in this embodiment), compared with commercial AFMs whose maximum z-direction displacement is only 20 μm, millimeter-level motion displacement can be achieved in a very short time. The approaching/retracting speed can be changed in the range of μm/s to mm/s, realizing the measurement of the interaction force between floating particles and air bubbles in a wider speed range. The sampling frequency of the high-speed data acquisition card is as high as 10kHz, and it has high time resolution. This feature enables users to accurately track the entire process of approaching, contacting, and separating particles and bubbles. The integrated CMOS camera monitors and records the entire interaction process, which can simultaneously realize the simultaneous measurement of the interaction force between particles and bubbles, the periphery of the three-phase contact, and the dynamic contact angle. During the test, the bubble/particle size can be changed more flexibly by replacing capillary tubes and sample holders of different sizes, which overcomes the requirement of the upper limit of the particle/bubble size (100 μm) due to the limitation of the diameter of the cantilever in the traditional AFM test. By replacing different types of sample holding parts, the measurement of the interaction force between different samples (particles and particles, bubbles and bubbles) can also be realized. Compared with commercial integrated force measurement equipment such as AFM, it has the advantages of flexible operation and controllable cost.

Example 2

Another specific embodiment of the present invention discloses a method for testing the dynamic interaction force between flotation particles and air bubbles, using the dynamic interaction force test system between flotation particles and air bubbles in Example 1, the steps include:

Step 1: Place a series of weights of known mass on the sample holding part 43 connected to the resistance bridge force sensor 42, record the generated voltage value, draw a standard curve of force and voltage, and obtain a linear relationship between force and voltage.

Step 2: Place the solid particles to be measured on the sample holding part 43 connected to the resistance bridge force sensor 42 , and use the syringe 31 to generate a millimeter-sized air bubble at the free end of the capillary 33 connected to the displacement stage 13 .

Step 3: Use the controller 12 to control the electric motor 11 to drive the displacement table 13 to move up and down, so that the air bubbles at the free end of the capillary 33 approach the particle surface at a certain speed along the z-axis direction, and return to the initial position after contacting the air bubbles.

The displacement sensor 2 generates a dynamic voltage signal due to the displacement change, which is collected by the data acquisition card 62 and transmitted to the PC terminal 63; The acquisition card 62 collects and transmits to the PC terminal 63 ; the CMOS camera 51 photographs and records the interaction process between particles and air bubbles, and transmits the captured images to the PC terminal 63 .

Step 4: Process the voltage signal on the PC terminal 63 . According to the proportional relationship between displacement and voltage, the dynamic voltage signal generated by the displacement sensor 2 is converted into a "displacement-time" curve; the dynamic voltage signal is processed by low-pass filtering, and the dynamic The voltage signal is converted into a "force-time" curve; the "force-displacement" curve can be obtained by combining the "displacement-time" curve with the "force-time" curve.

Step 5: Use the image analysis software on the PC terminal 63 to read the picture sequence recorded by the CMOS camera 51, measure the length of the three-phase contact line and the dynamic contact angle at different times, and realize the direct observation of the dynamic process of the interaction between particles and bubbles.

Claims

A dynamic interaction force test system between flotation particles and air bubbles, characterized in that it includes a motion drive unit, a displacement sensor (2), a bubble generation unit, a mechanical test unit, an image monitoring unit, and a signal acquisition and processing unit. The drive unit is connected with the bubble generation unit and can move in the vertical direction, the displacement sensor (2) is connected with the motion drive unit, the mechanical testing unit is arranged under the bubble generation unit, and the image The monitoring unit is arranged on the side of the mechanical testing unit, and the signal acquisition and processing unit is respectively electrically connected to the displacement sensor (2), the mechanical testing unit, and the image monitoring unit.
The dynamic interaction force test system between flotation particles and air bubbles according to claim 1, wherein the motion drive unit is used to drive air bubbles close to the sample, and the measuring contact of the displacement sensor (2) is connected to the The motion drive unit is connected to collect the dynamic voltage signal generated by the displacement change of the motion drive unit, and the mechanical test unit is used to detect the micro deformation during the interaction between the flotation particles and the air bubbles, and convert the micro deformation into electrical Signal.
The dynamic interaction force test system between flotation particles and air bubbles according to claim 1, wherein the image monitoring unit is used to observe the interaction process between flotation particles and air bubbles and measure the three-phase contact periphery and dynamic contact angle , the signal acquisition and processing unit is used to acquire generated images and dynamic voltage signals, and convert the voltage signals into "displacement-time" curves and "force-time" curves.
The dynamic interaction force test system between flotation particles and air bubbles according to claim 1, wherein the motion drive unit comprises an electric motor (11), a controller (12), and a displacement platform (13), so that Described electric motor (11) is connected with described displacement platform (13), and described controller (12) is electrically connected with described electric motor (11), and controls described electric motor (11) to drive described displacement platform (13) )Moving up and down.
The dynamic interaction force test system between flotation particles and air bubbles according to claim 4, wherein the air bubble generation unit is used to generate millimeter-scale air bubbles, specifically comprising a syringe (31), a hose (32) and A capillary (33), the syringe (31) communicates with the capillary (33) through the hose (32).
The dynamic interaction force test system between flotation particles and air bubbles according to claim 5, wherein the capillary (33) is vertically arranged, and one end of the capillary (33) is connected to the displacement platform (13) , and the other end is a free end.
The dynamic interaction force test system between flotation particles and air bubbles according to claim 5, wherein said mechanical test unit comprises a transparent liquid tank (41), a resistance bridge force sensor (42) and a sample holding part ( 43), the resistance bridge force sensor (42) is arranged in the transparent liquid tank (41), and the sample holding part (43) is connected to the free end of the resistance bridge force sensor (42).
The system for testing the dynamic interaction force between flotation particles and air bubbles according to claim 7, characterized in that the sample holding part (43) is located directly below the capillary (33).
The dynamic interaction force test system between flotation particles and air bubbles according to claim 7, wherein the signal acquisition processing unit includes a differential amplifier (61), a data acquisition card (62) and a PC terminal (63), The differential amplifier (61) is used to amplify the voltage signal generated by the resistance bridge force sensor (42), and the amplified voltage signal and the voltage signal generated by the displacement sensor (2) pass through the data acquisition card ( 62) Collect and transmit to the PC terminal (63), and the PC terminal (63) converts the two voltage signals into a "force-time" curve and a "displacement-time" curve respectively.
A method for testing the dynamic interaction force between flotation particles and air bubbles, characterized in that the dynamic interaction force test system between flotation particles and air bubbles according to claims 1-9 is used, and the steps include:

Step 1: Place a series of weights of known mass on the sample holding part (43) connected to the resistance bridge force sensor (42), record the generated voltage value, draw a standard curve of force and voltage, and obtain force and voltage linear relationship;

Step 2: Place solid particles to be measured on the sample holding part (43) connected to the resistance bridge force sensor (42), and use a syringe (31) to generate a millimeter-sized bubble;

Step 3: Control the electric motor (11) to drive the translation stage (13) to move up and down, so that the air bubbles at the free end of the capillary (33) approach the particle surface at a certain speed along the z-axis direction, and return to the initial position after contacting the air bubbles;

Step 4: Process the voltage signal on the PC terminal (63), convert the dynamic voltage signal generated by the displacement sensor (2) into a "displacement-time" curve; use low-pass filtering to process the dynamic voltage signal, and use the calibration step obtained The "force-voltage" standard curve converts the dynamic voltage signal into a "force-time" curve; combines the "displacement-time" curve with the "force-time" curve to obtain a "force-displacement" curve;

Step 5: The image analysis software on the PC terminal (63) reads the image sequence recorded by the image monitoring unit, measures the length of the three-phase contact line and the dynamic contact angle at different times, and realizes the direct observation of the dynamic process of the interaction between particles and bubbles .