US3255999A

US3255999A - Apparatus for the treatment of pulps

Info

Publication number: US3255999A
Application number: US380358A
Authority: US
Inventors: Weston David
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-01-21
Filing date: 1964-07-06
Publication date: 1966-06-14
Anticipated expiration: 1983-06-14

Description

June 14, 1966 D. WESTON 3,255,999

APPARATUS FOR THE TREATMENT OF PULPS Original Filed Jan. 21, 1959 //v l/EA/TOK 94 W0 M55 70 ByWfff flrraemevs United States Patent 4 Claims. (Cl. 259-2) This application is a division of US. application Serial No. 788,175, tiled January 21, 1959, now abandoned.

This invention relates to an apparatus for the application of reagents to finely divided particulate materials While the latter are suspended in a liquid pulp. More particularly, in its primary application the invention relates to the application of reagent to such materials in order to prepare the latter for a subsequent flotation step in which one or more constituents of the material are to be concentrated.

Certain materials are generally regarded as refractory to flotation. These include such materials as manganese oxides, iron oxides, oxidized sulphides of lead, copper and Zinc, and many others. Various attempts have been made to concentrate such materials by flotation and in general, although concentration can be achieved in most cases, reagent consumption is high and recoveries and grades of concentrate are comparatively low, so that economically acceptable operation of such processes has in general not been satisfactory. One feature of many such materials is that in many cases in addition to naturally occurring slimes, reduction of the material to an appropriate stage of mineral liberation involves the production of a considerable additional quantity of slimes, which it' has heretofore been necessary to eliminate prior toflotation, resulting in a substantial amount of the head value of the material being lost with the slimes which are eliminated.

It has recently been shown that in at least some instances it is possible to float slimes through the use of exorbitantly high concentrations of reagent or through the use of certain special reagents with a very long period of conditioning. Neither system can be regarded as economically satisfactory as long conditioning times are costly both in power consumption and in capital cost and maintenance cost of the plant involved. Where flotation of slimes is achieved by the use of exorbitantly high reagent concentrations, the cost of the reagent consumed is frequently higher than the worth of the values recovered from the slimes.

The present invention provides a means for activating refractory materials, and in particular materials associated with slimes in a much shorter period of time than has heretofore been possible, and with greatly reduced reagent consumption. The invention, while leading to outstanding benefits in relation to refractory ores and slimes, is generally applicable to all types of material and is capable of producing reduction of reagent consumption and/ or increases of recovery and/ or grade in almost all cases.

Broadly speaking, the invention is based upon the novel conception that reagent. may successfully and rapidly be applied to refractory particles, including slimes, by firstly having the reagent in finely subdivided form in a physical condition in which at least during its period of application it is capable of existing as a liquid phase separate from the liquid of the pulp, and secondly by the maintenance in such particles of reagent at least during the period of application thereof of a level of energy in re- 3,255,999 Patented June 14, 1966 going concept is put into practice by suspending the particulate material to be treated in a first liquid to form a pulp, and establishing and maintaining within the said pulp a localized zone of concentrated reagent activity into which the reagent is fed as a finely divided mechanical dispersion in the form of a second liquid which is immiscible with said first liquid at least to the extent necessary to maintain the droplets of reagent as a sepical dispersion of the reagent.

lation to the particulate material being treated suflicient to override the existing interaction of forces at the solid liquid interface between the particles of material and I the pulp liquid.

Broadly speaking according to the invention, the forearate phase for the conditioning period, while the pulp is progressively passed through said zone.

The level of available energy possessed by the particles of reagent may be influenced in many difierentways. To begin with, the formation of a finely divided mechanical dispersion creates available energy at the surface of the reagent particles which is of a higher order of potential the smaller the particles. This energy is in very many cases sufficient to overcome the existing forces of the solid liquid interface of the particles of material. Where a higher level of available energy is required, this may be supplied within the zone of concentrated reagent activity by elevation of temperature, pressure, or both, by raising the kinetic energy of the pulp within said zone by agitation or the creation of conditions of elevated or extreme turbulence, by the application of sonic, supersonic or ultrasonic vibration, or where applicable, the application of static or alternating electrostatic or electromagnetic fields. Alternatively to the foregoing or in conjunction therewith, the available energy of the reagent particles may be increased by introducing the reagent as a water soluble substance dissolved in a water insoluble vehicle. In this case, as the reagent droplets become mixed with the liquid of the pulp the water soluble reagent within the droplets will seek to distribute itself on either side of the interface boundary; and there will thus be established surrounding each droplet a zone of high reagent concentration during the period of conditioning, the concentration of reagent within such zone being sufiicient to overcome the forces acting at the solid liquid interface of particles to be treated.

In order for the droplets of the reagent dispersion to be maintained as a separate'liquid phase during passage through the zone of concentrated reagent activity it is not necessary that the reagent droplets be entirely immiscible with the pulp liquid, it is only necessary that there be sufficient immiscibility that a phase boundary between the two liquids is preserved for a final period which corresponds at least to the time it takes: the reagent particle to pass through the zone. This may in some cases be extremely short, i.e. of the order of a few milliseconds. In the absence of a conventional term to express the required degree of immiscibility, the required degree is referred to herein as being effective immiscibility, the reagent being described as effectively immiscible with the pulp liquid.

It will be appreciated that as in all operations which relate to the treatment of naturally occurring materials the treatment of any particular material will involve an appropriate selection of the reagents and the conditions of application thereof in order to secure the best and most economical results.

Various ways are available in which to form a mechan- One suitable method is to form such dispersion in a stream of air or other gas inert to the proposed conditioning operation by means of a fog nozzle. The resulting air dispersion may then be introduced to the zone of concentrated reagent activity in the pulp either in the body of the pulp, or to the air intake of a flotation machine or in various other ways, a number of which will be hereinafter described. Instead of forming the dispersion in a stream of air or inert gas, it may be found desirable to introduce the dispersion in a stream of soluble gas such as carbon dioxide. Alternatively, the reagent may be introduced by means of a steam line either by forming a mechanical suspension of droplets in the steam itself where the reagent is substantially insoluble in steam or does not vaporize therein, or in the case where the reagent is soluble or unstable in steam or vaporizes at the temperatures of the steam line, simply by feeding the reagent in metered quantities to the steam so that as the steam condenses within the zone of concentrated reagent activity the reagent is left as a mechanical dispersion in the pulp as it condenses. It will be appreciated that introduction of the reagent in a steam line will produce a very high degree of kinetic energy in the zone of concentrated reagent activity owing to the shock waves produced by the condensing steam.

Instead of using air or gas or vapor as a vehicle for the dispersion of reagent, such dispersion may be formed utilizing a liquid vehicle, the latter being either a liquid readily miscible with the liquid of the pulp, water, or pulp liquid which is recycled, e.g., from a filtration or other dewatering stage of the process involved. Such dispersion can be formed by means of high speed mechanical impellers placed in the feed line or by forcing concurrent streams of the reagent and vehicle through appropriately designed mixing chambers of conventional construction. It is important particularly where liquid vehicles are used that the formation of the dispersion take place as closely as possible to the point of introduction of the dispersion to the zone of concentrated reagent activity in the pulp, so that the surface energy created on the dispersed droplets has as little time as possible to dissipate before introduction thereto. The use of emulsifying agents and other surface active agents to promote dispersion is to be avoided as the latter tend to maintain intact the face boundary between the dispersed reagent and the vehicle with the consequence that the surface energy produced by the creation of the dispersion is in effect neutralized and is not available to assist in the displacement of the solid liquid interface at the surface of the particles of material. In order to distinguish the type of dispersions preferred in the practice of the present invention from stabilized dispersions such as colloids and emulsions which have been stabilized with surface active agents, I refer herein to such dispersions as are preferred in the practice of the invention as dynamic dispersions.

A preferred manner of employing the present invention embodies the formation of the zone of concentration of reagent activity within one or more mixing chambers placed in a line through which the pulp is fed by appropriate means. A preferred application of energy to the said zone in this instance is through the use of a concentration of ultrasonic energy provided by ringing a number of supersonic generators around the outside of the mixing chamber as will hereinafter be described. In this instance the feed lines for the dispersion of reagent will enter the mixing chamber at the throat thereof, and the application of ultrasonic energy may be made just prior to or just after the introduction of the reagent dispersion or both. A particular advantage of this embodiment of the invention resides in the fact that the use of ultrasonic frequencies within the relatively small enclosed space of the mixing chamber tends to disassociate particles of slime from larger particles of particulate material to which they may be adhering, and thus said particles become freed for independent application to them of the reagent.

The invention now having been described in some of its broader aspects, a better understanding of its application may be had by reference to the following detailed explanation of its application by means both of conventional apparatus and of novel apparatus particularly adapted to carry it out. The application of the invention will be described in conjunction with the accompanying drawing wherein:

FIG. 1 is a diagrammatic view of suitable apparatus for the formation of the zone of concentrated reagent activity within a mixing chamber placed in a line through which the pulp is flowing;

FIG. 2 is a diagrammatic illustration of a specially designed mixing chamber which is adapted to provide for application of supersonic or other energy to the material both before and after introduction of the reagent.

In FIGS. 1 and 2 are illustrated novel alternative forms of apparatus which are particularly adapted to carry out the method of the present invention.

Referring particularly to FIG. 1, the mixing chamber is connected by means of a rubber flange 81 to a line 82 through which is being fed a pulp of the material to be treated preferably at a high solids liquid ratio (i.e.

up to 70-75% solids). The mixing chamber 80 is also connected to discharge line 33 through the rubber flange 84. A plurality of nozzles 85 supplied by

lines

86 and 87 are directed into the interior of the mixing chamber 80 adjacent the inlet end thereof while the body of the mixing chamber 80 is surrounded with the generators 88 which consist of a plruality of ultrasonic vibration generators, or which may alternatively be generators of any other selected form of high energy oscillation. In operation, the incoming reagent dispersion from nozzles 85 is intimately mixed and dispersed in the pulp coming into chamber 80 from line 82. As this mixing action is taking place, the energy from the generator 88 will be assisting both the mixing action and by the release of energy within the pulp, the association of the reagent with the particles of mineral. A typical application for an apparatus of the type illustrated in FIG. .1 is that of the treatment of manganese or hematite ore from a tailings dam with tall oil for subsequent flotation.

In FIG. 2, a special unit is illustrated adapted to be connected by rubber flanges 9t and 91 in a line carrying pulp of a material to be treated. The device illustrated has an-inlet duct 92 leading to a venturi throat 93, which in turn leads into the expansion chamber 94. Ultrasonic generators 95 are situated around the inlet duct 92 to disassociate slimes within the pulp from larger particles to which these slimes may be adhering. A plurality of nozzles 96 are directed into the throat of the venturi 93, these nozzles 96 being supplied by the two

supply lines

97 and 98. The zone of concentrated reagent activity is formed within the expansion chamber 94 where the high turbulence not only produces efi'lcient mixing of the reagent dispersion with the pulp, but also builds up high electrostatic forces and mechanical forces due to the friction produced within the pulp. The latter action may be augmented by means of pulse generators 99 placed around the expansion chamber generating as may be appropriate either ultrasonic, high frequency electrostatic or electromagnetic pulses. In many cases steam may be used as the vehicle for the reagent dispersion adding to the available energy in the zone of concentrated reagent activity both by elevating the temperature and in the production of shock waves as it condenses.

In addition to its use which has already been described in some detail for purposes of conditioning refractory materials for flotation operations, the method of the present invention lends itself to a variety of other applications. For instance, in the conditioning of magnetite for wet magnetic separation, the reagent sodium silicate may be introduced through line 96 as a dispersion either in air or in water, and the application of sodium silicate to the particles of the pulp which takes place in the zone of concentrated reagent activity which is present in the expansion chamber 94 produces a complete dispersion of the magnetite allowing each particle of the pulp to move independently under the influence of the magnetic field in the subsequent magnetic separation step.

With suitable modifications to enable the handling of corrosive materials, an apparatus such as that illustrated in FIG. 2 may be used in the employment of the process of the invention in order to carry out a leaching operation.

As is well known, conventional leaching involves the use of great volumes of liquid and long hold-up times. The reason for this is that in order to achieve adequate wetting of the material to be leached a relatively large volume of water is considered necessary. In order to maintain reagent costs Within economic limits, the concentration of reagent in the leaching baths is comparatively low. As a result, the solution time of the soluble constituents of the material being leached is correspondingly long. By utilizing the method of the present invention, it is possible to disperse a small volume of relatively concentrated reagent throughout a mass of relatively dense pulp so that the reagent is available throughout the mass at a relatively high concentration. It is further possible by the application of external energy such as ultrasonic vibration to overcome the air solid and air liquid interfaces which are the result of imperfect wetting with the effect that not only is the leaching time reduced to the point where the solution of the materials to be leached can take place almost immediately, but this result is achieved with a minimum amount of dilution so that the total volume of solution resulting from the leach is very materially reduced and the values in such solutions are very materially more concentrated than is presently possible by conventional methods.

It will be appreciated from the foregoing that the present invention provides a novel, effective apparatus for the application of reagent to particulate materials where the latter are in the form of a pulp. It will further be appreciated that the invention is one of broad application and that it is not to be construed as being limited merely to the specific applications which have been given herein by way of illustration.

What is claimed is:

1. An apparatus for the application of reagents to particulte minerals, said particulate minerals being in the form of a slurry or pulp, said apparatus comprising a hollow casing providing a mixing chamber for said slurry or pulp, an inlet port communicating with said mixing chamber by means of which said slurry or pulp enters said mixing chamber, an outlet port communicating with said mixing chamber by means of which said slurry or pulp is discharged from said mixing chamber, flexible connection means associated with said inlet and outlet ports whereby said casing may be connected in a fluid line to vibrate substantially independently of said line, at least one nozzle mounted to said casing forward of said inlet port with the discharge end of the nozzle directed into the mixing chamber of said casing, a first and second supply means connected to said nozzle to controllably supply two separate reagent components to said nozzle, said nozzle being adapted in operation to form and project into the mixing chamber of said casing a dynamic dispersion of one of said reagent components in the other and establish a zone of concentrated reagent activity in said mixing chamber, and means mounted at the exterior of said casing forward of said nozzle and surrounding the mixing chamber confining said zone of reagent activity for applying high frequency oscillation to said zone of concentrated reagent activity established by the dynamic dispersion projected by said nozzle.

2. The apparatus of claim 1, including means mounted on the exterior of said casing between the inlet port and said nozzle for applying ultrasonic vibration to the particulate minerals flowing past said nozzle.

3. The apparatus of claim 1, wherein the hollow casing is formed to provide a venturi forward of said inlet port which leads into an expansion chamber comprising said mixing chamber, wherein said at least one nozzle forward of said inlet port is directed through said casing at the venturi thereof into said expansion chamber whereby to establish a concentrated zone of reagent activity within said expansion chamber forward of said nozzle, and wherein the high frequency oscillation means is mounted about the expansion chamber containing said zone of concentrated reagent activity.

4. The apparatus of claim 3 including means mounted on the exterior of said casing between the inlet port and the venturi for applying ultrasonic vibration to the particular mineral flowing past said nozzle.

References Cited by the Examiner UNITED STATES PATENTS Westbrook 2592 WALTER A. SCHEEL, Primary Examiner. JOHN M. BELL, Assistant Examiner.

Claims

1. AN APPARATUS FOR THE APPLICATION OF REAGENTS TO PARTICULATE MINERALS, SAID PARTICULATE MINERALS BEING IN THE FORM OF A SLURRY OR PULP, SAID APPARATUS COMPRISING A HOLLOW CASING PROVIDING A MIXING CHAMBER FOR SAID SLURRY OR PULP, AN INLET PORT COMMUNICATING WITH SAID MIXING CHAMBER BY MEANS OF WHICH IS SLURRY OR PULP ENTERS SAID MIXING CHAMBER, AN OUTLET PORT COMMUNICATING WITH SAID MIXING CHAMBER BY MEANS OF WHICH SAID SLURRY OR PULP IS DISCHARGED FROM SAID MIXING CHAMBER, FLEXIBLE CONNECTION MEANS ASSOCIATED WITH SAID INLET AND OUTLET PORTS WHEREBY SAID CASING MAY BE CONNECTED IN A FLUID LINE TO VIBRATE SUBSTANTIALLY INDEPENDENTLY OF SAID LINE, AT LEAST ONE NOZZLE MOUNTED TO SAID CASING FORWARD OF SAID INLET PORT WITH THE DISCHARGE END OF THE NOZZLE DIRECTED INTO THE MIXING CHAMBER OF SAID CASING, A FIRST AND SECOND SUPPLY MEANS CONNECTED TO SAID NOZZLE TO CONTROLLABLY SUPPLY TWO SEPARATE REAGENT COMPONENTS TO SAID NOZZLE, SAID NOZZLE BEING ADAPTED IN OPERATION TO FORM AND PROJECT INTO THE MIXING CHAMBER OF SAID CASING A DYNAMIC DISPERSION OF ONE OF SAID REAGENT COMPONENTS IN THE OTHER AND ESTABLISH A ZONE OF CONCENTRATED REAGENT ACTIVITY IN SAID MIXING CHAMBER,