Hydraulic analysis (referred to as water analysis) is a method of indirectly measuring the particle size composition by measuring the sedimentation velocity of the particles.
Commonly used water analysis methods: gravity sedimentation method, rising water flow method and centrifugal sedimentation method.
Measurement object: material less than 0.1 mm.
Measurement conditions: Under free-settling conditions, the solid volume concentration of the suspension was less than 3%.
To prevent particle agglomeration, a dispersing agent such as 0.01-0.02% water glass is usually added.
Settling water analysis
A relatively simple and reliable method of sedimentation is the elutriation method. The basic principle of the elutriation method is to use the method of gradually shortening the settling time to elute the various grade materials from fine to coarse and gradually.
The elutriation water analysis device is also called the Baring sedimentation analyzer, as shown in Figure 2-1.
Baring settlement analyzer
step:
(1) Calculate the time t used for the sedimentation of the ore particles of particle size d in water;
(2) Pour the slurry into the cup (6:1 ratio of slurry to solid), add water to zero mark, and stir. (Volume concentration < 3%).
(3) standing, sedimentation, through the t period, the siphon is used to absorb all the pulp in the upper part of h (less than the graded particle size);
(4) adding water to the cup, repeat the above steps until the aspirate liquid does not contain less than the graded particle size;
(5) Drying, weighing, and testing.
Features:
Simple and reliable, but time consuming and labor intensive.
Ascending water flow method
principle
Using the same amount of rising water, different rising water velocities are generated in the different diameters of the grading pipes, and the granules with different particle sizes are divided into several granules according to their different settling velocities.
Device
As shown in the figure, a set of four-tube water separators, in addition to the main working part classification pipe, there are water supply devices, water glass adding devices, feeding devices and overflow receiving devices.
Continuous water separator:
Graded tube diameter
Determined by the amount of water supplied and the graded particle size. If the sectional area of ​​the classification pipe is A, the water supply amount is Q, and the inner diameter of the classification pipe is D, the following relationship exists:
Where D is the diameter of the tube.
In each of the classification pipes, the particles whose sedimentation velocity v0 is larger than the upward flow velocity va in the pipe settles, and the particles smaller than va enter the next classification pipe and are sequentially classified. The particles that remain suspended in each of the classification tubes are the critical particle size of the classification.
The sample for each water analysis is about 50g, and is placed in a glass cup with a stirrer. The water is filled with water in each of the classification tubes and the continuous tube before the mine is opened, and the tube clamp is opened to make the slurry flow into each of the classification tubes. Under normal circumstances, the feeding time is about 1.5h. After 2h, the stirring is stopped. After about 6h, the water supply is stopped (according to whether the overflow water is clear or not). Then, the soft rubber tube at the lower end of each classification tube is clamped with a clip, and the products of each size are washed and discharged in order of thickness, and a series of treatments such as clarification, filtration, drying, weighing, and testing are performed.
The continuous water separator can obtain multi-stage products at one time, and the operation is simple. As long as the work is normal (the bubbles in the tube are released in time and the ore particles are not blocked), the obtained result is more accurate, but the water analysis time is longer.
Centrifugal sedimentation
Principle: The classification process is carried out in a centrifugal force field. The radial settling velocity of the particles in the cyclone water separator can still be obtained by the Stokes formula, and only the centrifugal acceleration is used to replace the gravity acceleration.
The device used in the centrifugal sedimentation method: a series cyclone classifier, also called a cyclone water separator, has the structure as shown. It consists of an inverted (bottom opening vertical) hydrocyclone connected in series and parallel.
Figure of the working system of the cyclone water analyzer
The cyclone water analysis method is a method for hydraulic analysis of fine-grained grade (-0.074 mm) materials in a centrifugal force field. The analysis process is carried out in five hydrocyclones connected in series, and the grit chamber of the hydrocyclone is vertically oriented. Upper, the overflow port is facing downward, the overflow pipe of the former cyclone is the feed pipe of the next cyclone, and the grit chamber of the cyclone is connected with the container containing the discharge valve. When the water analysis operation is performed, the discharge valve is closed.
When the material is subjected to particle size analysis by the cyclone water analysis method, the primary ore amount is about 1000 g. The mineral water is adjusted into pulp to make the ore particles fully loose, and the amount of pulp is usually less than 150mL. The slurry is given to the ore container, filled with water, and placed on the pipeline, then the valve is closed, the water pump is started, and the flow valve is opened to the maximum position. After the water flows through the cyclones, starting from the No. 1 cyclone, the air and debris in the cyclone are discharged one by one through the underflow valve, and the underflow valve is closed. Open the valve to the ore container and let the ore enter the cyclone within 5 minutes. Adjust the flow of water to make the reading of the rotameter from large to small, up to the required value. Record the time and complete the water analysis process within 30 minutes. When the water is dissolved, the flow rate is adjusted to the maximum value. Starting with the No. 5 cyclone, the graded product in the underflow vessel was removed one by one and the pump was turned off. Each of the obtained products was dried, metered, and the yield of each fraction was calculated.
The movement state of the slurry and particles in the hydrocyclone is shown in Figure 5-2-3. After the slurry is tangentially given to the cyclone, it rotates at a high speed, and is promoted by the subsequent continuous slurry. Next, the slurry enters the top container where the solid particles are strongly disturbed and tend to return to the cone portion. During the return process, the particles are also in a state of high-speed rotational motion, so they are subjected to the action state of the cyclone to the centrifugal inertial force. For particles larger than the separation granularity, the centrifugal inertia force is large, and the rotation is upward. In the flowing stream layer, returning to the top container, the particles smaller than the separation particle size are subjected to a small centrifugal inertia force, and the flow layer is rotated downward in the middle, and finally discharged from the lower overflow pipe to enter the next cyclone. in.
Diagram of the movement of pulp and particles in a hydrocyclone
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