CA1053388A - Method and apparatus for separating a solid from a slurry by flotation - Google Patents
Method and apparatus for separating a solid from a slurry by flotationInfo
- Publication number
- CA1053388A CA1053388A CA225,824A CA225824A CA1053388A CA 1053388 A CA1053388 A CA 1053388A CA 225824 A CA225824 A CA 225824A CA 1053388 A CA1053388 A CA 1053388A
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- CA
- Canada
- Prior art keywords
- slurry
- gas
- separating
- solid
- passage
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
- B03D1/00—Flotation
- B03D1/14—Flotation machines
- B03D1/1443—Feed or discharge mechanisms for flotation tanks
- B03D1/1462—Discharge mechanisms for the froth
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
- B03D1/00—Flotation
- B03D1/14—Flotation machines
- B03D1/24—Pneumatic
- B03D1/247—Mixing gas and slurry in a device separate from the flotation tank, i.e. reactor-separator type
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- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Biotechnology (AREA)
- Paper (AREA)
- Physical Water Treatments (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
In a flotation process for separating a mineral from a slurry, air is inserted into the slurry to form bubble-solid aggregates between the chemical conditioning of the slurry and the separating vessel.
The air is fed into the slurry through closures which are preferably located above the level of the surface of the slurry is the separating vessel so that they do not become clogged when the process has stopped.
In a flotation process for separating a mineral from a slurry, air is inserted into the slurry to form bubble-solid aggregates between the chemical conditioning of the slurry and the separating vessel.
The air is fed into the slurry through closures which are preferably located above the level of the surface of the slurry is the separating vessel so that they do not become clogged when the process has stopped.
Description
3~8~
This invention relates to a flotation ~rocess in which a solid, such as a mineral 9 in the form of a slurry is conditioned by addition of chemicals and is pumped into a separating vessel from the conditionin~ f receptacles subject to the addition of a gas~ particularlY
of air, and a foam containing the bubble-solid aggre~ates formed by the introduction of gas is separated from the ; slurryg for example by stripping it off the surface of ,i the slurry. Moreover, the invention relat,e,s to a plant for carrying out this process. The invention is particularly applicable to treatment of a slurry containing coal.
` By using flotation in accordance with the invention solids ~rom drainage can be floated. In particular flotation according to the invention can be used for refining minerals, particularly coal, from slurries ~Ihich contain another dross besides the minerals.
Inert gases are suitable for introduction having the ~ -advantage that they do not change the surfaces of the solid parts. On a large industrial scale, however, air is generally introduced into the slurry.
- .:
In the usual flotation processes, there are three actions largely distinct ~rom one another. The solid particles Present in aqueous suspension or brought into suspension are made water-repellent selectively by conditioning the slurry by using organic or inorganic reagents. Bubbles o~ gas are produced in the conditioned slurry by the inserted gas, to which bubbles the solids to be separated may be attached~iunder certain conditions so that bubblea of gas-solid a~gregates are formed in the slurry. These~aggregates are then made to float in the -~
separating vessels, v~he~re a stable three-phase foam is
This invention relates to a flotation ~rocess in which a solid, such as a mineral 9 in the form of a slurry is conditioned by addition of chemicals and is pumped into a separating vessel from the conditionin~ f receptacles subject to the addition of a gas~ particularlY
of air, and a foam containing the bubble-solid aggre~ates formed by the introduction of gas is separated from the ; slurryg for example by stripping it off the surface of ,i the slurry. Moreover, the invention relat,e,s to a plant for carrying out this process. The invention is particularly applicable to treatment of a slurry containing coal.
` By using flotation in accordance with the invention solids ~rom drainage can be floated. In particular flotation according to the invention can be used for refining minerals, particularly coal, from slurries ~Ihich contain another dross besides the minerals.
Inert gases are suitable for introduction having the ~ -advantage that they do not change the surfaces of the solid parts. On a large industrial scale, however, air is generally introduced into the slurry.
- .:
In the usual flotation processes, there are three actions largely distinct ~rom one another. The solid particles Present in aqueous suspension or brought into suspension are made water-repellent selectively by conditioning the slurry by using organic or inorganic reagents. Bubbles o~ gas are produced in the conditioned slurry by the inserted gas, to which bubbles the solids to be separated may be attached~iunder certain conditions so that bubblea of gas-solid a~gregates are formed in the slurry. These~aggregates are then made to float in the -~
separating vessels, v~he~re a stable three-phase foam is
- 2 -.
~S3388 ~roduced. The foam can be stripped from the surface of the slurry without destroying the adherent solids which are thus discharged.
On the one hand conditions must be created in which attachment o~ the solid particles to the gas bubbles due to creation of contact forces which exceed the repulsive forces. On the other hand the bubble-solid aggregates once formed must be fur-ther treated under conditions which avoid the creation of excessive breakdown of these aggregates.
.; 10 lilhile, for attachment of the solids, in practice only the mechanical and the hydrodynamic forces and occasiona]Ly also electrical forces too, can be influenced technically, the separatin~ forces are largely determined by the mechanisms of flow chiefly in the separating vessels. In particular heavily turbulent flow leads to undesirable destruction of the said three-phase aggregates.
A process of this kind is disclosed in German Specification No. 1,922~610. With this known process the slurry is added to chemicals in a conditioning vessel and then suppliea to the separating vessels formed like a - cyclone by means of an air drive. As a result of the cyclone-like movement of the slurry, turbulence occurs in the separating vessels. This leads to the formation of bubbles of gas and to the attachment of the solids.
For this reason in the know~ process the formation of the three-phase aggregates only takes place in the separating vessel.
This process has the disadvantage that the flow ~;
conditions in the separating vessel can either be adjusted only for optimum formation of the three-phase aggregates or only for the optimum formation of the foam. In any case an impaired yield results in relation to the optimum - .. . . . . . .
yield of solid matter. ~loreover, a disproportionate a~ount of gas is required because a predominant part r.lust be separated out o~ the slurry as surplus gas and conducted away in a controlled manner ~; 5 It is further known to displace the formation o~ bubbles into the separating vessels and to close the gas inlet pipes by porous means, at the openings of which the gas bubbles are ~ormed (U.S. Patent Speci~ication No. 3,218,519). The gas flows out in all directions at `! 10 these closures, ~specially upwards and downwards. This has the disadvantage that the openings can easily be clogged with the solid particles o~ the slurry especially when stopping ~lotation but also during operation.
Moreover, the gas bubbles and the conditions under which the solid particles attach to the gas bubbles cannot be ` ;
controlled to produce optimum flow conditions, because they are determined by the formation of foam in the separating vessel. -~
. .
Finally, it is known to undertake ~ormation o~
the gas bubbles in a special fluid separately from the slurry, said fluid then being added to the flotation slurry in the separating vessel. Since the mixture of the ~luid and the slurry is carried out in the flotation compartment, it is necessary to provide stirring mechanisms-in the flotation compartment. These enable the ~ormation of ~oam to take place but also produce heavy turbulence which leads to the destruction of bubbie-solid aggregates. Moreover such flotation compartments are relatively expensive to manufacture because o~ the stirring devices. Further in the known process the formation of gas bubbles is undertaken electrically. High operating costs are there~ore involved in this process.
~ 4 ~
.. . . . .. .. . . . . ~ - .... . . . ..... . . . . .
S3~
The invention is based on the aim Or carrying out the formation of bu~bles and the ~ormation of the bubble-solid aggregates under o~timum mechanical and hydrodynamic conditions and to facilitate formation of the foam in the slurry under optimum conditions.
- According to the invention in one aspect, there is provided a flotation process in which a solid, such as a mineral~ in the form of a slurry is conclitioned by addition of chemicals, and is pumped past porous closures through which gas from a delivery pipe is injected into the slurry in streams directed substantially at right angles to the direction of flow of the gas-containing slurry, thus forming bubble-solid aggregates which are pumped with the slurry into a separating vessel in which a foam containing the bubble-solid aggregates is separated from the slurry.
According to the invention, in another aspect, there is provided a plant for separating a solid from a slurry by flotation, comprising means for conditioning the 20~ slurr~Y with chemicals~ a device for the introduction of gas . .
connected to receive slurry from the conditioning means and having a passage pipe for the slurry and at least one gas inlet provided with a penetrable closure arranged substantially parallel to the direction of flow of the ~5 slurry in the passage pipe, and a separating vessel, to ~ -receive slurry from the device for the introduction of gas, In the process according to the invention the conditioned slurry as a whole is subjected to the intro-duction of gas in a separate location fro~ the conditioning and the separating vessels. Thus the formation of bubble-solid aggregates also takes place. This occurs in a zone 1~5~3~
~or the introduction o~ gas, which the entire slurry flows through a~ter its conditioning. As a result the slurry alre~dy contains the gas bubbles loaded with the solid matter at the entrance to the separating vessels. Thus the formation of foam can be carried out under conditions of floi7 whereby no separating forces are developed which are larger than the forces ~hich hold the solid particles to the bubbles, The process according to the invention thus has the advantage that, on the one hand, the size of the formed gas bubbles and the probability with which solid matter attaches to the bubbles can be optimised by adjustment to the conditions of the slurry, of the porosity of the gas delivery pipe shutters and of the conditions of flow in,and the dimensions of, the zone of gas introduction and, on the other hand, the formation of foam and the discharge of the foam can be improved in the separating vessels by providing conditions of flow which protect the ;~
bubble-solid aggregates. As a result a considerable .
~ 20 increase in the quantity produced is achieved, with coal ~-, said increase reaching, for example, quantities discharged of 85~ and more in a flotation unit. Moreover, the `~
capital expense is lowered by the abolition of stirring devices in the separating vessels. The spatial separation of the formation of bubbles and the attachment of the solid matter to the bubbles from the separation of the . .
bubble-solid aggregates from the slurry has the further .
advantage,of a better utilisation of the space available for treatment. -The saving in energY caused by the abolition of the stirring device and the short time for flotation is of substantial importance in the proces~ according ~' .
~533~
to the invention because the proportion o~ surplus ~as or air can be substantially lowered. In addition the period of flotation is reduced considerably.
3ecause of its ability to adjust the size of the bubbles to the solid matter, the process according to the invention can be successfully used for ~oating very fine solid matter~ On this rests, among other things, the adaptability of the process for flotation of impurities from drainage.
l`he direction of the gas delivery pipe in relation to the direction of flow o~ the slurry avoids clogging of the openings in the porous means, In one embodiment of the invention gas delivery pipe closures are arranged with their plane in the direction of flow o~ the pumped slurry. Also the plane of the openings runs parallel to`the direction of flow of the : , slurry.
Sintered means can be used in the process according to the invention-as gas delivery pipe closures, ..
~ 20 the pore width being up to 50 ~ Alternatively orifice , plates may be used, the diameter of the orifice being 5, 10, 20 and 50~u .
It is useful to arrange for the introduction of gas above the level of the surface of the slurry in the separating vessels. Then if the flotation is stopped under these circumstances, sedimentation of the solid particles on the porous surface of the closures from which the gas comes out, cannot take place. In this way blockages are prevented~
It is use~ul to implement the process according to the invention so that the conditioned slurry flows do~ ~ards and is thus acted on by gas and so that the , ~ ~
~1533~
! slurr~ is conducted through a curved pipe to the separating vessels. In this Way it is possible to avoid turbulence which can destroy or damage the bubble-solid aggregates in the slurry.
The details, further features and advantages of the invention are shown in the follo-~ing description of several embodiments with reference to the accompanying drawings, in which:-Figure 1 shows a plant for carrying out the -process according to the invention schematically, ~igure 2 shows a chamber ~or the introduction of gas according to one embodiment of the invention, ~igure 3 shows a device for introduction of gas according to another embodiment of the invention, and 1g ~igure 4 shows a modified version of the device for the introduction of gas sho~m in ~igure 3.
Referring to Figure 1, a slurry containing solld matter is conditioned in conditioning receptacles 1 containing stirring apparatus, i e. chemicals are added to the slurry making the solid matter to be water-repellent.
In flo~ation Or coal, pine oil, for example, is used. The conditioned slurry flows through pipes 2, through ball valves 3 into a Mono pump 4. The pump is provided v~ith ~ a PJV transmission and forces the slurry through pipes 5 and 6. In pipe 6 there is an inductive flowmeter. The slurry then arrives in the device for the introduction of gas generallY designated 7.
The device 7 ~or the introductlon of gas has a gas inlet 9. This conducts air. The air reaches the gas inlet 9 via an oil separator 19, a pressure-relief valve 20, a ~loat element flowmeter 21 and a check valve 23. A
pressure ~auge 22 makes it possible to read off the press~re .
,, . . . , : , .
.. ., : : : : . . . : . :,.
33~
in the gas inlet 9.
In the device 7, bubbles of gas of suitable diameter are formed in the slurry flowing through, as will be described hereinafter, At the same time attachment of the wate~-repellent solid matter to these bubbles of gas takes place, The s1urry loaded with the bubbles of gas or the bubble-solid aggregates is supplied to a separating vessel 12 below by means o~
a curved pipe 11. This takes the form of a compartment shaped like an injection moulding box in which the formation of foam is accomplished, On the surrace 25 of the slurry situated in the separatin~ vessel 12 a stiff foam is formed which is stripped o~f by a circulating discharge conveyor belt 14 into the overflow 15. The concentrated solid matter can be dra~m off at 17.
The slurry in the separating vessel 12 weakened by the concentration of the solid matter at the overflo1N
15 with whatever solid particles which are not water-repellent,~ flows through a valve 13 to an outlet 18.
Referring to Figure 2, the device 7 for the introduction of gas consists of a chaMber 43, a lo~er region of which has a rectangular cross-section of, for example 9 mm.
width and depth and 50 MM. length and is covered by a closure in the form of a screen 44. Air for the slurry is supplied to the chamber at an inlet 42, Various screens with differing orifice diameters can be used. Screens with orifice diameters of 5, 10, 20 and 40f~ are required for flotation of bituminous coal.
In the said lowerregion of the chamber 43, there are two zones of differing widths on the surface defined by the plane of the screen of the slurry flowing _ 9 _ ~ ~S;~333~
at 45. One zone 47 contains a mixture of slurry and bubbles of gas, while the previous zoné 46-only contains the slurry. The zone 47, which contains a concentration of bubbles of gas~ i9 where the formation of gas bubbles- ~' solid aggregates takes place. The space taken by the zone 47 becomes smaller with increasing slurry velocity and ; decreaslng gas velocity. The height of the mixture M ow varies between 4J 5 and 8 mm. The diameter of the screen openings and the surface tension of the water in which the solid matter is contained have a negligibly small influence on the formation of the zones.
~igure 3 shows an alternative embodiment of th'e device 7. The gas inlet 9 is secured to a metal sintered member 30. The front sides 31 and 33 of the sintered metal member are retained between a seal in'the form of a guide ' ;memb~er 35 ànd~à sécond seal~32. The slntered member is of hollow cylinder shape. ~It can have a length of 100 mm.
,, -and a diameter~of~30 mm. Gas flows only out of the pores which open out on'the sleeve surfaces 36 of the sintered member. ~ince the plane of thé pores lies largely in the sleeve surface, the gas streams at right angles to the direction of the arrow 37, which shows the path of the - M ow of the slurry. The sintered member 30 as well as - . : , . .
'- ~ ' its seals32 and 35 are surrounded by a casing pipe 38.
Thus the casing pipe 38 encompasses an annulus 39, in - : :: : : ~ .
which the zone for the introduction Or gas is formed. `~
:: :
~ igure 4, in which the same reference numerals designate parts corresponding to those of Figure 3, shows a further embodlment of the devlce 7. ~he casing pipe 38 ~30 has two chambers 40 or 41 for the introduction of gas.
-- ~creens corresponding to the embodiment according to '~
Flgure 2 act to enclose these chambers; sintered members, ... . . ~
l~S331~
hov~ever~ can also bs used as closure~s.
The embodiment according to Figure 3 is dis~in~uished from the embodiment according to Fi~ure 4 in that, in the latter, gas is introduced into the streaM
of slurry in the annulus 39 both from outside and from inside, but which, in the former, it is introduced exclusively from inside. In the embodiment according to Figure 2 the introduction of gas takes place only from outside.
The sintered members can consist of ceramic material~ }Iowever, matal sintered members based on bronze are especially suitable. Some characteristics of such sintered members suitable for carrying out the process according to the invention in coal flotation are as 1 5 follows:-Designa- Particle max. pore Porosity tion size range pore width closed open mm. width~ range % S~;
~ ~ ,.
B 0 --45 -0.045 10 0 - 10 30-3325-28 B 045-075 0.045-0.075 25 15 - 25 32-36 27-30 B 045- 1 00045-0.1 ~ 50 10 - 50 35-38 28-31 B 1 - 2 0.1 - 0.2 60 20 - 60 36-3931-34 B 3 - 4 0.3 - 0O4 1 501 00 -1 50 34-3830-33 In flotation of coal with pine oil, the surface tension determined by the proportion of pine oil may be `
the decisive factor affecting the size of the bubbles produced with these sintered members. At 6.7 cm3/m3 the t bubbles m~y be produced in sizes of 0.5 mm.up to limiting values of 0.2 mm, The flow velocity can have a relatively low influence on the size of the minute bubbles.
The size of the minute bubbles is in turn the decisive factor affecting the hydroaynamic ratios and for -~
the adherence of the solid particles to the minute bubbles~
"
'.
~IL05331~
The following values are ~or sintered metal members:-Pore ; width range:0-10 15-25 10-50 20-60100-150 ` 5 Porosity25-28 27-30 38-31 31-3430-33 open ; With sintered members with the said length of ~ 100 mm~and an outer diameter of 30 mm.a fill pipe with an inner diameter at the point of the annulus of 42 mm.
is used.
While the effect of changes in the width of the pores in the embodiment on the quantity of solid matter yielded in weight per cent is negligible up to a pore width of 50/~ , there occurs a reduction in the quantity yielded f`or an air to slurry ratio of 0.6 : 0,4 with increasing pore width, For the said flotation of bltuminous coal with pineoil there is apparently an - optimum amount of air on the one hand and of quantity yîelded on the other hand, whereby there exists linear dependence. ;
The finer the grain of the suspended solid matter the finer the size of the minute bubbles will be, ;~
- As regards the clearance bet~een the surface of the sintered member and the fill pipe, the result with two-sided aeration (Figure 4) and a clearance of 8 mm is just as good as with half clearance and one-sided aeration, `
With an increasing amount of gas the difference in the embodiment becomes greater.
The device 7 for the introduction of gas should be so formed that the slurry is introduced to the gas as homogenously as possible perpendicular to the direction .-~ 53~8 o flo~v in the cross-section of flow. In the embodiment according to ~igure 1 the device for the introduction of gas lies sli~htly above the level of the slurry designated 25 in the separatin~ vessel 12. Therefore a curved pipe 11, e.g a tube, must be used for the insertion of the aerated slurry into the separating vessel 12. The rnost uniform distribution possible of bubbles should be maintained in the tube in order to avoid coalescence in the turbulent flow. Surprisingly9 however, such coalescence hardly ever occurs in the curved tube In the actual separating vessel 12, there is a substantially laminar flow which in turn leads to a quick and complete separation of the loaded bubbles of air from the slurry and of the solid matter contained therein which is not water-repellent.
The danger of blockage of the pores in the -device 7 for the introduction of gas is avoided since the said device 7 is located above the level 25 and the gas rays come out at right angles to the direction of M ow of the slurry.
.
- In operation the slurry is conditioned in the receptacles 1. After adjustment of the respective quantities of slurry and air supplied to the M otation slurry, the velocity of the circulating foam discharge conveyor belt 14 is adjusted so that a foam zone of a certain height is formed above the slurry. The height of the slurry level 25 in the separating vessel 12 is regulated by the adjustment of the over~low 50.
The amount of slurry, air and solid matter are limited by the volume of the separating vessel 12.
If a vessel 12 is used with a capacity of 27 litres9 then ~ ;
up to 1100 cm3 of slurry per second can travel through.
~ 1~5338~
If this ar,~ount is increased then an increasing turbu-lence on the surface of the SeparatinCJ vessel 12 will arise, which leads to destruction of the gas bubbles- ~ -solid aggregates. Large amounts of foam whicll result S from large amounts of air-solid matter or slurry cause the time period for which the foam remains i.n the ~ separating vessel 12 to become too short in some circumstances. ', m An .increase in the velocity of the conveyor belt above an optimum amount results in the foam being beaten by the paddles arranged on the conveyor belt and thus a lower amount o~ solicl matter is discharged.
Smaller amounts of foam and also the time period for which the foam remains in the separating vessel being -~
too long cause partial disintegration of the bubble-solid aygregate.
~ .
,
~S3388 ~roduced. The foam can be stripped from the surface of the slurry without destroying the adherent solids which are thus discharged.
On the one hand conditions must be created in which attachment o~ the solid particles to the gas bubbles due to creation of contact forces which exceed the repulsive forces. On the other hand the bubble-solid aggregates once formed must be fur-ther treated under conditions which avoid the creation of excessive breakdown of these aggregates.
.; 10 lilhile, for attachment of the solids, in practice only the mechanical and the hydrodynamic forces and occasiona]Ly also electrical forces too, can be influenced technically, the separatin~ forces are largely determined by the mechanisms of flow chiefly in the separating vessels. In particular heavily turbulent flow leads to undesirable destruction of the said three-phase aggregates.
A process of this kind is disclosed in German Specification No. 1,922~610. With this known process the slurry is added to chemicals in a conditioning vessel and then suppliea to the separating vessels formed like a - cyclone by means of an air drive. As a result of the cyclone-like movement of the slurry, turbulence occurs in the separating vessels. This leads to the formation of bubbles of gas and to the attachment of the solids.
For this reason in the know~ process the formation of the three-phase aggregates only takes place in the separating vessel.
This process has the disadvantage that the flow ~;
conditions in the separating vessel can either be adjusted only for optimum formation of the three-phase aggregates or only for the optimum formation of the foam. In any case an impaired yield results in relation to the optimum - .. . . . . . .
yield of solid matter. ~loreover, a disproportionate a~ount of gas is required because a predominant part r.lust be separated out o~ the slurry as surplus gas and conducted away in a controlled manner ~; 5 It is further known to displace the formation o~ bubbles into the separating vessels and to close the gas inlet pipes by porous means, at the openings of which the gas bubbles are ~ormed (U.S. Patent Speci~ication No. 3,218,519). The gas flows out in all directions at `! 10 these closures, ~specially upwards and downwards. This has the disadvantage that the openings can easily be clogged with the solid particles o~ the slurry especially when stopping ~lotation but also during operation.
Moreover, the gas bubbles and the conditions under which the solid particles attach to the gas bubbles cannot be ` ;
controlled to produce optimum flow conditions, because they are determined by the formation of foam in the separating vessel. -~
. .
Finally, it is known to undertake ~ormation o~
the gas bubbles in a special fluid separately from the slurry, said fluid then being added to the flotation slurry in the separating vessel. Since the mixture of the ~luid and the slurry is carried out in the flotation compartment, it is necessary to provide stirring mechanisms-in the flotation compartment. These enable the ~ormation of ~oam to take place but also produce heavy turbulence which leads to the destruction of bubbie-solid aggregates. Moreover such flotation compartments are relatively expensive to manufacture because o~ the stirring devices. Further in the known process the formation of gas bubbles is undertaken electrically. High operating costs are there~ore involved in this process.
~ 4 ~
.. . . . .. .. . . . . ~ - .... . . . ..... . . . . .
S3~
The invention is based on the aim Or carrying out the formation of bu~bles and the ~ormation of the bubble-solid aggregates under o~timum mechanical and hydrodynamic conditions and to facilitate formation of the foam in the slurry under optimum conditions.
- According to the invention in one aspect, there is provided a flotation process in which a solid, such as a mineral~ in the form of a slurry is conclitioned by addition of chemicals, and is pumped past porous closures through which gas from a delivery pipe is injected into the slurry in streams directed substantially at right angles to the direction of flow of the gas-containing slurry, thus forming bubble-solid aggregates which are pumped with the slurry into a separating vessel in which a foam containing the bubble-solid aggregates is separated from the slurry.
According to the invention, in another aspect, there is provided a plant for separating a solid from a slurry by flotation, comprising means for conditioning the 20~ slurr~Y with chemicals~ a device for the introduction of gas . .
connected to receive slurry from the conditioning means and having a passage pipe for the slurry and at least one gas inlet provided with a penetrable closure arranged substantially parallel to the direction of flow of the ~5 slurry in the passage pipe, and a separating vessel, to ~ -receive slurry from the device for the introduction of gas, In the process according to the invention the conditioned slurry as a whole is subjected to the intro-duction of gas in a separate location fro~ the conditioning and the separating vessels. Thus the formation of bubble-solid aggregates also takes place. This occurs in a zone 1~5~3~
~or the introduction o~ gas, which the entire slurry flows through a~ter its conditioning. As a result the slurry alre~dy contains the gas bubbles loaded with the solid matter at the entrance to the separating vessels. Thus the formation of foam can be carried out under conditions of floi7 whereby no separating forces are developed which are larger than the forces ~hich hold the solid particles to the bubbles, The process according to the invention thus has the advantage that, on the one hand, the size of the formed gas bubbles and the probability with which solid matter attaches to the bubbles can be optimised by adjustment to the conditions of the slurry, of the porosity of the gas delivery pipe shutters and of the conditions of flow in,and the dimensions of, the zone of gas introduction and, on the other hand, the formation of foam and the discharge of the foam can be improved in the separating vessels by providing conditions of flow which protect the ;~
bubble-solid aggregates. As a result a considerable .
~ 20 increase in the quantity produced is achieved, with coal ~-, said increase reaching, for example, quantities discharged of 85~ and more in a flotation unit. Moreover, the `~
capital expense is lowered by the abolition of stirring devices in the separating vessels. The spatial separation of the formation of bubbles and the attachment of the solid matter to the bubbles from the separation of the . .
bubble-solid aggregates from the slurry has the further .
advantage,of a better utilisation of the space available for treatment. -The saving in energY caused by the abolition of the stirring device and the short time for flotation is of substantial importance in the proces~ according ~' .
~533~
to the invention because the proportion o~ surplus ~as or air can be substantially lowered. In addition the period of flotation is reduced considerably.
3ecause of its ability to adjust the size of the bubbles to the solid matter, the process according to the invention can be successfully used for ~oating very fine solid matter~ On this rests, among other things, the adaptability of the process for flotation of impurities from drainage.
l`he direction of the gas delivery pipe in relation to the direction of flow o~ the slurry avoids clogging of the openings in the porous means, In one embodiment of the invention gas delivery pipe closures are arranged with their plane in the direction of flow o~ the pumped slurry. Also the plane of the openings runs parallel to`the direction of flow of the : , slurry.
Sintered means can be used in the process according to the invention-as gas delivery pipe closures, ..
~ 20 the pore width being up to 50 ~ Alternatively orifice , plates may be used, the diameter of the orifice being 5, 10, 20 and 50~u .
It is useful to arrange for the introduction of gas above the level of the surface of the slurry in the separating vessels. Then if the flotation is stopped under these circumstances, sedimentation of the solid particles on the porous surface of the closures from which the gas comes out, cannot take place. In this way blockages are prevented~
It is use~ul to implement the process according to the invention so that the conditioned slurry flows do~ ~ards and is thus acted on by gas and so that the , ~ ~
~1533~
! slurr~ is conducted through a curved pipe to the separating vessels. In this Way it is possible to avoid turbulence which can destroy or damage the bubble-solid aggregates in the slurry.
The details, further features and advantages of the invention are shown in the follo-~ing description of several embodiments with reference to the accompanying drawings, in which:-Figure 1 shows a plant for carrying out the -process according to the invention schematically, ~igure 2 shows a chamber ~or the introduction of gas according to one embodiment of the invention, ~igure 3 shows a device for introduction of gas according to another embodiment of the invention, and 1g ~igure 4 shows a modified version of the device for the introduction of gas sho~m in ~igure 3.
Referring to Figure 1, a slurry containing solld matter is conditioned in conditioning receptacles 1 containing stirring apparatus, i e. chemicals are added to the slurry making the solid matter to be water-repellent.
In flo~ation Or coal, pine oil, for example, is used. The conditioned slurry flows through pipes 2, through ball valves 3 into a Mono pump 4. The pump is provided v~ith ~ a PJV transmission and forces the slurry through pipes 5 and 6. In pipe 6 there is an inductive flowmeter. The slurry then arrives in the device for the introduction of gas generallY designated 7.
The device 7 ~or the introductlon of gas has a gas inlet 9. This conducts air. The air reaches the gas inlet 9 via an oil separator 19, a pressure-relief valve 20, a ~loat element flowmeter 21 and a check valve 23. A
pressure ~auge 22 makes it possible to read off the press~re .
,, . . . , : , .
.. ., : : : : . . . : . :,.
33~
in the gas inlet 9.
In the device 7, bubbles of gas of suitable diameter are formed in the slurry flowing through, as will be described hereinafter, At the same time attachment of the wate~-repellent solid matter to these bubbles of gas takes place, The s1urry loaded with the bubbles of gas or the bubble-solid aggregates is supplied to a separating vessel 12 below by means o~
a curved pipe 11. This takes the form of a compartment shaped like an injection moulding box in which the formation of foam is accomplished, On the surrace 25 of the slurry situated in the separatin~ vessel 12 a stiff foam is formed which is stripped o~f by a circulating discharge conveyor belt 14 into the overflow 15. The concentrated solid matter can be dra~m off at 17.
The slurry in the separating vessel 12 weakened by the concentration of the solid matter at the overflo1N
15 with whatever solid particles which are not water-repellent,~ flows through a valve 13 to an outlet 18.
Referring to Figure 2, the device 7 for the introduction of gas consists of a chaMber 43, a lo~er region of which has a rectangular cross-section of, for example 9 mm.
width and depth and 50 MM. length and is covered by a closure in the form of a screen 44. Air for the slurry is supplied to the chamber at an inlet 42, Various screens with differing orifice diameters can be used. Screens with orifice diameters of 5, 10, 20 and 40f~ are required for flotation of bituminous coal.
In the said lowerregion of the chamber 43, there are two zones of differing widths on the surface defined by the plane of the screen of the slurry flowing _ 9 _ ~ ~S;~333~
at 45. One zone 47 contains a mixture of slurry and bubbles of gas, while the previous zoné 46-only contains the slurry. The zone 47, which contains a concentration of bubbles of gas~ i9 where the formation of gas bubbles- ~' solid aggregates takes place. The space taken by the zone 47 becomes smaller with increasing slurry velocity and ; decreaslng gas velocity. The height of the mixture M ow varies between 4J 5 and 8 mm. The diameter of the screen openings and the surface tension of the water in which the solid matter is contained have a negligibly small influence on the formation of the zones.
~igure 3 shows an alternative embodiment of th'e device 7. The gas inlet 9 is secured to a metal sintered member 30. The front sides 31 and 33 of the sintered metal member are retained between a seal in'the form of a guide ' ;memb~er 35 ànd~à sécond seal~32. The slntered member is of hollow cylinder shape. ~It can have a length of 100 mm.
,, -and a diameter~of~30 mm. Gas flows only out of the pores which open out on'the sleeve surfaces 36 of the sintered member. ~ince the plane of thé pores lies largely in the sleeve surface, the gas streams at right angles to the direction of the arrow 37, which shows the path of the - M ow of the slurry. The sintered member 30 as well as - . : , . .
'- ~ ' its seals32 and 35 are surrounded by a casing pipe 38.
Thus the casing pipe 38 encompasses an annulus 39, in - : :: : : ~ .
which the zone for the introduction Or gas is formed. `~
:: :
~ igure 4, in which the same reference numerals designate parts corresponding to those of Figure 3, shows a further embodlment of the devlce 7. ~he casing pipe 38 ~30 has two chambers 40 or 41 for the introduction of gas.
-- ~creens corresponding to the embodiment according to '~
Flgure 2 act to enclose these chambers; sintered members, ... . . ~
l~S331~
hov~ever~ can also bs used as closure~s.
The embodiment according to Figure 3 is dis~in~uished from the embodiment according to Fi~ure 4 in that, in the latter, gas is introduced into the streaM
of slurry in the annulus 39 both from outside and from inside, but which, in the former, it is introduced exclusively from inside. In the embodiment according to Figure 2 the introduction of gas takes place only from outside.
The sintered members can consist of ceramic material~ }Iowever, matal sintered members based on bronze are especially suitable. Some characteristics of such sintered members suitable for carrying out the process according to the invention in coal flotation are as 1 5 follows:-Designa- Particle max. pore Porosity tion size range pore width closed open mm. width~ range % S~;
~ ~ ,.
B 0 --45 -0.045 10 0 - 10 30-3325-28 B 045-075 0.045-0.075 25 15 - 25 32-36 27-30 B 045- 1 00045-0.1 ~ 50 10 - 50 35-38 28-31 B 1 - 2 0.1 - 0.2 60 20 - 60 36-3931-34 B 3 - 4 0.3 - 0O4 1 501 00 -1 50 34-3830-33 In flotation of coal with pine oil, the surface tension determined by the proportion of pine oil may be `
the decisive factor affecting the size of the bubbles produced with these sintered members. At 6.7 cm3/m3 the t bubbles m~y be produced in sizes of 0.5 mm.up to limiting values of 0.2 mm, The flow velocity can have a relatively low influence on the size of the minute bubbles.
The size of the minute bubbles is in turn the decisive factor affecting the hydroaynamic ratios and for -~
the adherence of the solid particles to the minute bubbles~
"
'.
~IL05331~
The following values are ~or sintered metal members:-Pore ; width range:0-10 15-25 10-50 20-60100-150 ` 5 Porosity25-28 27-30 38-31 31-3430-33 open ; With sintered members with the said length of ~ 100 mm~and an outer diameter of 30 mm.a fill pipe with an inner diameter at the point of the annulus of 42 mm.
is used.
While the effect of changes in the width of the pores in the embodiment on the quantity of solid matter yielded in weight per cent is negligible up to a pore width of 50/~ , there occurs a reduction in the quantity yielded f`or an air to slurry ratio of 0.6 : 0,4 with increasing pore width, For the said flotation of bltuminous coal with pineoil there is apparently an - optimum amount of air on the one hand and of quantity yîelded on the other hand, whereby there exists linear dependence. ;
The finer the grain of the suspended solid matter the finer the size of the minute bubbles will be, ;~
- As regards the clearance bet~een the surface of the sintered member and the fill pipe, the result with two-sided aeration (Figure 4) and a clearance of 8 mm is just as good as with half clearance and one-sided aeration, `
With an increasing amount of gas the difference in the embodiment becomes greater.
The device 7 for the introduction of gas should be so formed that the slurry is introduced to the gas as homogenously as possible perpendicular to the direction .-~ 53~8 o flo~v in the cross-section of flow. In the embodiment according to ~igure 1 the device for the introduction of gas lies sli~htly above the level of the slurry designated 25 in the separatin~ vessel 12. Therefore a curved pipe 11, e.g a tube, must be used for the insertion of the aerated slurry into the separating vessel 12. The rnost uniform distribution possible of bubbles should be maintained in the tube in order to avoid coalescence in the turbulent flow. Surprisingly9 however, such coalescence hardly ever occurs in the curved tube In the actual separating vessel 12, there is a substantially laminar flow which in turn leads to a quick and complete separation of the loaded bubbles of air from the slurry and of the solid matter contained therein which is not water-repellent.
The danger of blockage of the pores in the -device 7 for the introduction of gas is avoided since the said device 7 is located above the level 25 and the gas rays come out at right angles to the direction of M ow of the slurry.
.
- In operation the slurry is conditioned in the receptacles 1. After adjustment of the respective quantities of slurry and air supplied to the M otation slurry, the velocity of the circulating foam discharge conveyor belt 14 is adjusted so that a foam zone of a certain height is formed above the slurry. The height of the slurry level 25 in the separating vessel 12 is regulated by the adjustment of the over~low 50.
The amount of slurry, air and solid matter are limited by the volume of the separating vessel 12.
If a vessel 12 is used with a capacity of 27 litres9 then ~ ;
up to 1100 cm3 of slurry per second can travel through.
~ 1~5338~
If this ar,~ount is increased then an increasing turbu-lence on the surface of the SeparatinCJ vessel 12 will arise, which leads to destruction of the gas bubbles- ~ -solid aggregates. Large amounts of foam whicll result S from large amounts of air-solid matter or slurry cause the time period for which the foam remains i.n the ~ separating vessel 12 to become too short in some circumstances. ', m An .increase in the velocity of the conveyor belt above an optimum amount results in the foam being beaten by the paddles arranged on the conveyor belt and thus a lower amount o~ solicl matter is discharged.
Smaller amounts of foam and also the time period for which the foam remains in the separating vessel being -~
too long cause partial disintegration of the bubble-solid aygregate.
~ .
,
Claims (12)
1. A flotation process in which a solid in the form of a slurry is conditioned by addition of chemicals, and is pumped past porous closures through which gas from a delivery pipe is injected into the slurry in streams directed substantially at right angles to the direction of flow of the gas-containing slurry, thus forming bubble-solid aggregates which are pumped with the slurry into a separating vessel in which a foam con-taining the bubble-solid aggregates is separated from the slurry.
2. A process according to claim 1, in which the closures on the gas delivery pipe are arranged with their plane in the direction of flow of the pumped slurry.
3. A process according to claim 1, in which sintered members are used as closures on the gas delivery pipe.
4. A process according to claim 2, in which the closures have orifice diameters of 5, 10, 20 and 40 or of pore widths up to about 50.
5. A process according to claim 1, 2 or 3, in which introduction of the gas is effected above the surface of the slurry In the separating vessels.
6. A process according to claim 1, 2 or 3, in which the conditioned slurry is directed downwards where it is thus introduced to gas and the aerated slurry is fed to the separating vessels through a curved pipe.
7. A plant for separating a solid from a slurry by flotation, comprising conditioning means for conditioning the slurry with chemicals, a device for introducing gas to said slurry, said device being connected to the conditioning means to receive slurry, said device having; a passage for conveying the slurry therethrough at least one gas inlet opening into said passage, a penetrable closure in said gas inlet and arranged substantially parallel to the direction of flow of the slurry in said passage and a separating vessel for receiving slurry from the device for the introduction of gas.
8. A plant according to claim 7, in which said passage of the device fox introducing gas is formed within a casing pipe which encompasses the closure of the gas inlet to form an annular passage for the slurry.
9. A plant according to claim 7 or 8, in which the gas inlet comprises a chamber surrounding said passage, its closure being arranged on the outside of the stream of slurry flowing through the pipe.
10. A plant according to claim 7, in which the device for the introduction of gas comprises a chamber in which the closure of the gas inlet pipe is located on one or both sides of the stream of slurry.
11. A plant according to claim 8, in which the pene-trable closure is in the form of an elongated body of sintered material having a pair of oppositely disposed ends, sealing means for sealing said oppositely disposed ends, said gas inlet extending through one of said sealing means to admit gas to said elongated body, the other of said sealing means being formed as a guide element for guiding the stream of slurry through said passage.
12. A plant according to claim 11, in which the sintered member consists of a sintered metal base on bronze.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19742420482 DE2420482A1 (en) | 1974-04-27 | 1974-04-27 | METHOD AND SYSTEM FOR FLOTATION |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1053388A true CA1053388A (en) | 1979-04-24 |
Family
ID=5914146
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA225,824A Expired CA1053388A (en) | 1974-04-27 | 1975-04-24 | Method and apparatus for separating a solid from a slurry by flotation |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA1053388A (en) |
| DE (1) | DE2420482A1 (en) |
| GB (1) | GB1512565A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5096572A (en) * | 1990-03-12 | 1992-03-17 | Board Of Control Of Michigan Tech. University | Froth flotation |
| US5249688A (en) * | 1990-03-12 | 1993-10-05 | Board Of Control Of Michigan Technological University | Froth flotation apparatus |
| US5266240A (en) * | 1991-03-20 | 1993-11-30 | Servicios Corporativos Frisco, S.A. De C.V. | Flotation reactor with external bubble generator |
| US5431286A (en) * | 1994-01-06 | 1995-07-11 | Inco Limited | Recirculating column flotation apparatus |
| WO2008037086A1 (en) * | 2006-09-28 | 2008-04-03 | Hydro Processing & Mining Ltd. | Apparatus and method for efficient particle to gas bubble attachment in a slurry |
Families Citing this family (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH614636A5 (en) * | 1976-04-12 | 1979-12-14 | Swemac Sa | Process and installation for the elimination, by flotation, of impurities in the form of solid particles contained in a liquid |
| DE3111506C2 (en) * | 1981-03-24 | 1986-01-09 | Bergwerksverband Gmbh, 4300 Essen | Gas injection device for flotation systems |
| SE8104198L (en) * | 1981-03-24 | 1982-09-25 | Bergwerksverband Gmbh | DEVICE FOR INCORPORATING GAS IN A LIQUID OR IN A MIXTURE OF LIQUID AND SOLID SUBSTANCE |
| DE3641940A1 (en) * | 1986-12-09 | 1988-06-23 | Kloeckner Humboldt Deutz Ag | Flotation cell |
| US5814210A (en) * | 1988-01-27 | 1998-09-29 | Virginia Tech Intellectual Properties, Inc. | Apparatus and process for the separation of hydrophobic and hydrophilic particles using microbubble column flotation together with a process and apparatus for generation of microbubbles |
| US5078921A (en) * | 1988-10-21 | 1992-01-07 | The Deister Concentrator Company, Inc. | Froth flotation apparatus |
| DE3918025A1 (en) * | 1989-06-02 | 1990-12-06 | Bergwerksverband Gmbh | FLOTATION APPARATUS |
| DE3918213A1 (en) * | 1989-06-03 | 1990-12-06 | Dorfner Gmbh & Co Kaolin Und K | Sepn. of solid particles suspended in liq. - involves tank with inlet pipe with curved guide vanes |
| DE4022831C2 (en) * | 1990-07-18 | 2000-07-06 | Deutz Ag | Device for gassing liquids |
| ZA919256B (en) * | 1990-11-23 | 1992-11-25 | Atomaer Pty Ltd | Gas particle formation |
| DE4210571C1 (en) * | 1992-03-12 | 1993-09-16 | Dieter 8500 Nuernberg De Hompf | |
| DE19518631C1 (en) * | 1995-05-20 | 1996-08-29 | Kali & Salz Ag | Pneumatic flotation plant for solid suspensions |
| CA2596329C (en) | 2005-02-01 | 2015-07-14 | The University Of Newcastle Research Associates Limited | Method and apparatus for contacting bubbles and particles in a flotation separation system |
| CN111545354B (en) * | 2018-02-06 | 2021-10-01 | 安徽理工大学 | Improved flotation system and flotation process for refractory minerals |
| CN109759243B (en) * | 2019-01-31 | 2020-07-03 | 中国矿业大学 | Column sorting device and method for mineralization-flotation separation |
-
1974
- 1974-04-27 DE DE19742420482 patent/DE2420482A1/en active Granted
-
1975
- 1975-04-22 GB GB1652875A patent/GB1512565A/en not_active Expired
- 1975-04-24 CA CA225,824A patent/CA1053388A/en not_active Expired
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5096572A (en) * | 1990-03-12 | 1992-03-17 | Board Of Control Of Michigan Tech. University | Froth flotation |
| US5249688A (en) * | 1990-03-12 | 1993-10-05 | Board Of Control Of Michigan Technological University | Froth flotation apparatus |
| US5266240A (en) * | 1991-03-20 | 1993-11-30 | Servicios Corporativos Frisco, S.A. De C.V. | Flotation reactor with external bubble generator |
| US5431286A (en) * | 1994-01-06 | 1995-07-11 | Inco Limited | Recirculating column flotation apparatus |
| WO2008037086A1 (en) * | 2006-09-28 | 2008-04-03 | Hydro Processing & Mining Ltd. | Apparatus and method for efficient particle to gas bubble attachment in a slurry |
| US8281932B2 (en) | 2006-09-28 | 2012-10-09 | Hydro Processing & Mining Ltd. | Apparatus and method for efficient particle to gas bubble attachment in a slurry |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2420482A1 (en) | 1975-11-13 |
| DE2420482B2 (en) | 1979-01-18 |
| DE2420482C3 (en) | 1979-09-20 |
| GB1512565A (en) | 1978-06-01 |
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