SU64301A1 - Flotation machine - Google Patents

Description

Modern studies have established that the perfection of the design of flotation machines determines (the coefficient of use of the air introduced into them. A number of calculations carried out by many authors confirm that the surface of air bubbles dispersed in the pulp is mineralized to a very small extent. Even with the coefficient of surface mineralization of bubbles i, they can lift 10-30 times more (by weight) of the hard than it is.

Improved air utilization can be achieved by increasing the residence time of bubbles in the pulp (and, consequently, by increasing the number of collisions with mineral particles), by improving air dispersion and distributing bubbles across the volume of floated pulp by using reagents, increasing their flotation rate.

It mainly depends on the design of the machines.

Studies have shown that with:,; mechanical and pneumatic machines the residence time of bubbles in the pulp is extremely insignificant {from 2 to 10 seconds). Within all existing machines, their machines have a large number of upward pulp flows. A considerable part of the air bubbles is captured by these flows and rises to the surface with great speed. In airlift-type machines (Forrester, Southwest, Munro), the aerated pulp column rises very quickly, also contributing to a decrease in the residence time of bubbles in the pulp. For machines with mechanical agitation, the residence time of air is longer than that of purely pneumatic machines, not only because the former disperse the air better, but also because they communicate to the pulp a number of twists that reduce the vertical velocity of the air. However, the use of turbulent flows for the mind of the Bubble velocity of raising the bubbles has its negative CTOpGdbT, since it is difficult to create a uniform vortex field throughout the pulp volume and this requires a large amount of energy.

To increase the residence time of the air in the pulp, extraordinary measures such as increasing the depth of the machine are used.

up to several meters (for example, machines of the type of Brittany Pan-American), which is inevitably associated with an increase in the size and cost of the machine.

Drying, a natural defect of existing flotation machines is the presence of parallel movement of air bubbles and particles. In this case, the number of collisions of air bubbles and particles decreases dramatically.

It should be noted that in modern flotation machines small, usually well-mineralized bubbles linger down or rise very slowly.

The purpose of the present invention is to increase the residence time of air bubbles in the pulp and to increase the number of their collisions with particles of counter flows of pulp and rising bubbles.

In this case, air bubbles will rise in a uniform downward flow of pulp. The absolute speed of their ascent (even in a relatively shallow machine) will significantly decrease, and the number of collisions with mineral particles (and hence the degree of surface mineralization) will increase significantly. A counter movement at the same time will provide much more collisions than a parallel one that occurs in all modern machines.

The creation of laminar pulp flows must be accompanied by a significantly lower energy expenditure than the creation of turbulent flows.

Recent studies (I. Sven-Nilsson and M. A. Eygeles) have shown that mineralization of bubbles mainly depends on the duration of their contact with grains of floated minerals. However, with existing machines, this factor is spontaneously and is not available on its own — current adjustment. In the case of the application of the proposed machine, the contact time of the main mass of bubbles with mineral particles is easily controlled by changing the speed of the descending pulp flow.

There are known flotation machines equipped with a central tube with an impeller on a vertical axis and a system of tubes that evenly distribute the air supplied from the outside over the bath section.

The proposed flotation machine is equipped with one or several impellers placed inside the central tubes and guiding the slurry through the tube upwards and out of the visor covering it — into the bath against the air stream. This is meant to achieve the creation in the machine of the movement of the pulp, countercurrent upward air flow.

In FIG. 1 shows a flotation machine in schematic form and FIG. 2 - a section along a - a.

The proposed flotation machine consists of individual chambers made of iron or wood. Each chamber has a lower part in the form of a truncated pyramid 1. The axis 3 is fitted with impellers 4. A central tube 2 passes around the axis. A visor 5 is placed over the upper part of the tube. The flotation aerator can be made in various ways. For example, the action of a flotation aerator consisting of pipes 6 equipped with small rubber valves was recently tested. Tests have shown the full suitability of this design variant. Recently, the author has tested the possibility of using a simple iron pipe covered with thick (3-5 mm) rubber with holes in them as a flotation aerator. If such a flotation aerator is provided with a common reliable valve on the neck air supply and thus ensures that if the air supply is abruptly maintained, the pressure inside the flotaerator is equal to the external pressure of the pulp, then there is no clogging of the aero aerator, even if the machine runs for a long time without air supply to the aerial. Finally, you can put on pipes perforated rubber shirts of the type used in the Mac machine.

Air is supplied to each cell from the main line. At the outlet, a valve 7 and a tap S are installed, by means of which the air flow in each cell is regulated.

A pipe is connected to the flotation aerator from the water supply system to periodically clean the flotation aerator with water at a known pressure.

Power is supplied to the lower part of the central tube of the first chamber by the tube 9; in the remaining chambers, intermediate products are introduced in the same way via pipe 11.

Adjacent chambers communicate with each other by wide slits 12, in fact, they transform the bath of a machine from a large cell into a solid one. The main level of the pulp in the entire battery of cells is regulated normally (by shrewer or slats) at one point in the last chamber 10. In more detail, the height of the foam layer is determined by changing the air flow rate in the individual chambers.

Power is supplied to the lower part of the central tube.

The rotation of the impellers 4, located on axis 3, creates a circulation of pulp in the directions indicated by arrows in the drawing. In the central tube 2 there is an upward flow of pulp, in the zones of the flotation-aerator-descending.

Air bubbles emanating from the flotation aerator rise very slowly (due to the presence of counter flows of pulp). The presence of a counter-flow of bubbles and pulp will cause the maximum number of collisions of bubbles with particles, which can take a specified period of time.

A small part of the bubbles with a lower ascent rate than the average bubbles through which the machine is adjusted (apparently these will be the smallest bubbles and highly mineralized bubbles) will move downward from the flotation aerator and into the central tube, where upward flow will be quickly delivered into the upper layers of the pulp. Thus, in this machine, the well-mineralized bubbles are predominantly raised and the maximum stay in the pulp is not sufficiently mineralized. Such a selective approach to the rate of removal of bubbles from the pulp, depending on the degree of their mineralization, should also inevitably improve the use of air.

Foam removal can be carried out either from each chamber, or, using 1 the principle of counterflow of foam and pulp, only from the first; 1mery.

Subject invention

F; iotation iiaiuinia with a central Tpy6oii and an impeller on the vertical axis and a system of pipes that distribute the air supplied from the outside across the bath section, characterized in that, in order to create movement in the machine, countercurrent to the upward air flow distributed over the bath section pipes 6, one or several impellers 4, placed inside the central pipes 2 and guiding the slurry through pipe 2 upwards and from under the visor covering it 5 - into the bath against the air stream, are applied.