HK40067661A - Method and facility for continuous aeraulic separation of particulate materials consisting of a mixture of particles heterogeneous in both particle size and density - Google Patents

Description

Method and device for the continuous pneumatic separation of particulate material consisting of a mixture of particles of non-uniform particle size and density

Technical Field

The present invention relates generally to processes for grinding and pneumatically separating particulate materials, and more particularly to processes for separating particulate materials that are non-uniform in size, density and shape. The invention is applicable in a wide variety of fields and is particularly applicable to the treatment of ores, waste from construction and public works, plant or animal matter (e.g. biomass, food), electronic waste, etc.

Background

Referring to fig. 1, in order to separate different types of components from each other, the process for separating heterogeneous particulate material M generally comprises: a first grinding stage consisting of a combination of grinder B and classification CL1, the classification CL1 separating the particles according to size into the coarsest and finest particles until a certain particle size range is reached; and a second classification stage CL2 following the first grinding stage, the second classification stage CL2 being intended to separate the finest particles and/or particles having different properties (typically classification by density to separate the most dense particles from the least dense particles). In some applications, the most dense particles are the metals that are sought to be recovered from the scrap.

In this known method, the coarsest particles from the first separation step are reinjected at the mill inlet to be subdivided again.

A significant disadvantage of this approach is the continuing aspect of CL2, CL2 only works after the combined action of B and CL1 has been completed. In some cases this may lead to a reduced efficiency of the classification CL2 and to a high energy consumption for action B in combination with CL1, which action B has to process the whole material.

Disclosure of Invention

The present invention aims to remedy these drawbacks by a completely innovative approach.

The present invention aims to improve the existing methods for separating heterogeneous materials and, by a novel simultaneous combination of grinding and two pneumatic classifications, makes it possible to produce a fraction comprising particles classified according to both particle size and density and another fraction also classified according to particle size and density (e.g., one fraction having finer and denser particles and the second fraction having coarser and less dense particles).

To this end, according to a first aspect, the invention relates to a method for the continuous pneumatic separation of a particulate material consisting of a mixture of particles of non-uniform particle size and density, characterized in that it comprises the following steps:

(a) the particles of the abrasive material are present in the form of particles,

(b) a gas stream is generated that transports the milled particles,

(c) subjecting the gas stream to a first pneumatic separation in a first pneumatic separation unit in order to separate the particles contained in the gas stream into a first fraction consisting of the coarsest particles with variable density and a second fraction consisting of the finest particles,

(d) second pneumatic separation of the first fraction in a second pneumatic separation unit in order to separate the particles contained in the first fraction into a third fraction consisting of the coarsest and/or densest particles and a fourth fraction consisting of the finest and/or densest particles,

(e) reinjecting the third or fourth fraction at the grinding inlet, and

(f) and simultaneously recovering the second particle group and the fourth particle group or the third particle group respectively as output products.

The invention is implemented according to the embodiments and alternative embodiments disclosed below, which are to be considered individually or according to any technically feasible combination.

Advantageously, the first pneumatic separation comprises a dynamic classification associated with the recovery of the particles.

According to a preferred embodiment, the first fraction is recovered from the gas stream and mechanically conveyed to the gas stream feeding the second pneumatic separation unit.

Similarly, the second pneumatic separation comprises a dynamic classification associated with the recovery of the particles.

According to a particular aspect of the invention, the third fraction or the fourth fraction is recovered from the gas stream and conveyed mechanically or via the gas stream to the inlet of the grinding step.

More specifically, when the method is applied to the separation of particulate material comprising metallic material and non-metallic material lighter than the metallic material, step (e) comprises reinjecting at the grinding inlet a third fraction comprising particles of the finest particle size and having an increased proportion of metallic material relative to the initial particles, so as to recover a second fraction comprising particles of the finest particle size and having an increased proportion of non-metallic material relative to the initial particles, and a fourth fraction comprising particles of the coarsest particle size and having a minimum density and having an increased proportion of non-metallic material relative to the initial particles.

The invention also relates to a device for the continuous pneumatic separation of particulate material consisting of a mixture of particles of non-uniform particle size and density, characterized in that it comprises:

a grinder fed with a heterogeneous mixture of particles to be treated,

-means for generating a gas stream containing particles from the grinding at the outlet of the grinding mill,

a first pneumatic classifier receiving the gas stream and capable of producing a first group of particles comprising the coarsest particles with variable density and a second group of particles comprising the finest particles,

-a second pneumatic classifier receiving said first fraction and capable of producing a third fraction comprising the coarsest and/or most dense particles and a fourth fraction comprising the finest and/or least dense particles, and

-means for feeding the third or fourth fraction to the inlet of the mill.

Preferably, the first pneumatic classifier comprises a dynamic classifier associated with a particle recycler.

Advantageously, the device further comprises a duct for reinjection of the flow of clean air at the inlet of the grinding mill, at the outlet of the recuperator.

More specifically, means for mechanically conveying the particles of the first group to a diffuser inserted on the inlet duct of the second pneumatic classifier are also included.

According to a particular embodiment, the second pneumatic classifier comprises a second dynamic classifier associated with a second particle recycler.

According to a particular aspect, the apparatus further comprises a duct for re-injecting the flow of clean air at the outlet of the second particle recycler, at the inlet of the second dynamic classifier, or alternatively at the inlet of the mill if the fourth fraction is returned to the mill.

In addition, the apparatus includes means for mechanically or pneumatically conveying the particles from the third granule set or the fourth granule set to the inlet of the mill.

Drawings

Further advantages, objects and features of the invention will emerge from the following description, made for explanatory purposes and in no way limitative, with reference to the accompanying drawings, in which:

figure 1, already described in the introduction, is a general diagram of a method for separating heterogeneous particulate matter according to the prior art (a classified grinding phase, followed by a second classification phase),

fig. 2 is a first general diagram of a method for separating heterogeneous particulate matter according to the invention, in which case the third fraction is returned to the mill,

fig. 3 is a variant of fig. 2, in which case the fourth fraction is returned to the mill,

fig. 4 shows an example of an apparatus for implementing the method in fig. 2.

Detailed Description

It will be noted in the introduction that: the terms "coarse", "fine", "dense", "low density", and the like, alone or in association with comparative or relative terms, are to be measured in the perspective of one skilled in the art, i.e., as a characteristic, median or average value for a given particulate composition, covering ranges that may overlap in nature.

Referring first to fig. 2 and 3, a method for separating particulate material according to the present invention will be described.

In a manner common to both figures, the starting material M, optionally pre-fractionated by means of per se known means, is introduced into a grinder B which also receives a gas flow G (generally air or another gas) so as to produce a pneumatic flow F1, the pneumatic flow F1 containing particles in a relatively wide particle size range, having a maximum size of, for example, less than 500 μ M.

This stream F1 is applied to the inlet of a first classification unit CL1, the first classification unit CL1 serving to divide the particles into a stream F2 of the coarsest particles and a stream F3 of the finest particles.

Unlike the method according to the prior art, in which the stream F2 of the coarsest particles is directly redirected to the inlet of the mill, this stream F2 is here simultaneously subjected to a second classification (by particle size and/or by density) at the second classifier CL2, which second classifier CL2 produces a fourth stream F4 of the finest and/or least dense particles and a third stream F5 of the coarsest and/or most dense particles.

At this stage, the process can be carried out in two alternative embodiments, depending on the type of product to be treated and the target application.

Thus, in the first embodiment shown in fig. 2, the coarsest and/or densest particles (stream F5) are redirected towards the inlet of mill B, while stream F4 of the finest and/or densest particles is recovered as end product or intermediate product.

In the second embodiment shown in fig. 3, the finest and/or least dense particles (stream F4) are redirected to the inlet of mill B, while the coarsest and/or most dense particle stream F5 is recovered as the final or intermediate product.

At the same time, the finest particle stream F3 is recovered to form another final or intermediate product.

For example, the embodiment of FIG. 2 may be applied to the recovery of metal products from starting materials consisting of waste materials (e-waste; waste from general manufacturing, construction, public works, etc.). Thus, by continuously feeding the starting material to the mill and by rapidly (because simultaneously) extracting the lightest particles (here non-metallic materials: polymers, various minerals, etc.) still in their coarse state from the treated stream, a particularly cost-effective method is obtained for obtaining particles at stream F3 that are both fine and much more concentrated (denser) than the metal of the starting material.

Thus, the stream F3 forms essentially the sought end product or intermediate product.

Stream F4, consisting of minerals, polymers, etc., as the case may be, also forms another end product or intermediate product resulting from the treatment, which can be suitably reused, for example supplied to the recovery industry, according to its nature and the target application.

The embodiment of fig. 3 applies in particular to the following cases: in this case, the fraction that is most needed from the initial product is the fraction with the lowest density, which is the case, for example, when the husks are to be recovered as fuel. In this case, the rapid extraction of the coarsest and most dense fraction F5 (here the husks, which may for example be palletized to form a fuel) makes it possible to recover, at flow F3, an intermediate or final product of fine particle size and low density (here the inner part of the fruit is converted into a powder, for example for food applications).

Referring now to fig. 4, an example of an apparatus for recovering from scrap material containing both metal and non-metal having a density less than that of the metal, a group of substantially metallic particles having a fine particle size on the one hand, and a group of substantially non-metal particles having a coarser and less dense particle size on the other hand, will be described.

The apparatus first comprises a grinder 100 (grinder B in fig. 2) which receives at an inlet (e.g. a pneumatic conveyor, not shown) a particulate material 102, for example electronic waste material pre-ground in an initial step, not shown, in a particle size of for example between 0 and 10 mm.

The mill also receives a stream of clean or low dust gas (typically air) via a duct 104 for conveying the particles to the outlet of the mill 100.

The mill can be implemented according to any known technique and one known grinding method (compression, impact, grinding, depending on the nature and size of the starting material to be ground and the fineness sought) and is designed to reduce the initial fragments into a powder having a particle size generally less than about 500 μm. As a general rule, this maximum particle size is chosen to ensure an effective physical separation between the metallic and non-metallic particles in the particulate material, avoiding as far as possible the presence of particles containing both metallic and non-metallic materials.

The particles at the outlet of the mill are conveyed by the gas flow passing through the mill into a duct 150 (flow F1) to a first pneumatic separation stage 200, which here comprises a dynamic turbo classifier 210 of a type known per se, associated with one or more recyclers 220 (for example cyclone(s), cartridge filters, bag filters) known per se) of the particles contained in the air.

The classifier 210 illustratively includes a rotor 212, the rotor 212 including blades 214 rotating at a regulated speed above a collection hopper 216.

The air flow F1 conveying the particles is conveyed through the peripheral space 218 in the form of a frustoconical ring between the outer wall of the separator and the hopper 216 via the base of the apparatus. The particles are subjected to the combined effect of centrifugal force, aerodynamic entrainment and gravitational descent at the blades 214 of the rotor, so that eventually the finest particles pass through the rotor and emerge in the air flow into the upper outlet duct 250 of the separator, and the coarsest particles are retained outside the rotor and accumulate at the bottom of the hopper, from where they are extracted, for example via a honeycomb screen 230.

This separator with powders containing metal and non-metal makes it possible to carry out a first recovery of fine particles (fines) in the outflow air flow in the top part, these fine particles having a proportion of metal particles that is significantly greater than the proportion of metal particles in the initial ground product, and therefore these fine particles having a lower proportion of non-metal particles, while the coarsest particles are recovered at the bottom of the separator 210 and extracted via a honeycomb sieve 230 to simultaneously undergo a second classification as will be described hereinafter (flow F2)

The conduit 250 is connected to the inlet of a particle recycler 220, the particle recycler 220 being, for example, one or more cyclones, cartridge filters or bag filters, the parameters of which are adjusted to remove a majority of the fines suspended therein from the air stream. As mentioned above, these particles are fine particles with an increased proportion of metal and form the first product resulting from the treatment. These particles are recovered via honeycomb screen 240 to form the final product or directed (arrow 242) to another process (stream F3).

The air flow at the outlet of the particle recycler 220 flows in a duct 251 to a heat exchanger 260 and then to a blower 270, which blower 270 generates an air flow in the mill and in the separation station 200. This air stream, which can be kept with a very small amount of particles, is re-injected at the inlet of the mill 100 via the conduit 253. It should be noted that the heat exchanger 260 makes it possible to cool the air before it returns towards the mill inlet, in particular when the mill, due to its working principle, produces a significant increase in the temperature of the air flow and of the conveyed particles (grinding heat).

The dynamic turbo classifier 210 is advantageously of the type having an adjustable separation threshold, and is for example selected to allow a particle size at the inlet of up to 5 mm, wherein the adjustable particle size separation threshold is between 3 and 400 μm.

The first separating station 200 is functionally connected to a second separating station 300, the second separating station 300 here also comprising a dynamic turbo classifier 310 of a type known per se, the dynamic turbo classifier 310 being combined with one or more further particle recyclers 320, preferably of the same type as the recycler 220.

More specifically, the fraction F2 consisting of the coarsest metallic and non-metallic particles from the honeycomb screen 230 associated with the classifier 210 is conveyed by gravity or a mechanical conveyor (line 231) and injected via a diffuser 335 into the air flow conveyed into a duct 350, the duct 350 feeding the bottom of the classifier 310. The classifier 310 advantageously has the same structure as the classifier 210; this structure will not be described again, since such classifiers are known per se. The classifier is configured such that the coarsest and/or densest particles are kept outside the turbine and accumulate at the bottom of the hopper. They are collected by the honeycomb screen 330 and reinjected at the inlet of the mill 100 via gravity or mechanical transfer line 450 (stream F5).

The finest and/or least dense particles are present in the air stream in the top portion of classifier 310. This air flow is conveyed via a duct 351 to a particle recycler 320, from which the particle recycler 320 extracts the particles, where the second product resulting from the treatment, i.e. the relatively coarse and low-density powder with an increased proportion of non-metals, obtained by the device is formed. The latter accumulates at the bottom and is extracted via a honeycomb sieve 340 to be conveyed and, for example, packed for recycling (stream F5). The top portion of the recuperator 320 is connected by a conduit 352 to a blower 370, the blower 370 generating an air flow through the station 300, and the outlet of the blower is connected by conduits 353, 354 to the diffuser 335 described above.

The dampers 510, 520, 530, 540 can be controlled separately:

to allow fresh air to be supplied to the mill via duct 104,

so as to allow the supply of air to the diffuser 335 via the duct 354,

in order to allow the pneumatic surplus (exendent reaulique) coming from the blower 270 to be discharged into the atmosphere via a filtering station 500 (of a type known per se) for removing the last particles,

so as to allow the pneumatic surplus from the blower 370 to be discharged to the atmosphere via the filtering station 500 in the same way.

Thus, by a specific combination of grinding and simultaneous two-stage classification, the apparatus in fig. 4 allows to obtain, particularly efficiently and economically, without using separate particle size classification and classification steps by density, a fraction (F3) on the one hand and a fraction (F4) on the other hand, wherein the fraction (F3) contains the finest particles and has a significantly increased metal proportion, and the fraction (F4) contains relatively coarse and low-density particles and has a significantly increased non-metal proportion. It is to be understood that the detailed description of the inventive subject matter, given by way of illustration only, is in no way limiting and that technical equivalents are also included within the scope of the invention.

Claims (13)

1. A method for continuous pneumatic separation of particulate material consisting of a mixture of particles of non-uniform particle size and density, characterized in that it comprises the steps of:

(a) the particles of the abrasive material are present in the form of particles,

(b) a gas stream is generated that transports the milled particles,

(c) subjecting the gas stream to a first pneumatic separation in a first pneumatic separation unit in order to separate the particles contained in the gas stream into a first fraction consisting of the coarsest particles with variable density and a second fraction consisting of the finest particles,

(d) second pneumatic separation of the first fraction in a second pneumatic separation unit in order to separate the particles contained in the first fraction into a third fraction consisting of the coarsest and/or densest particles and a fourth fraction consisting of the finest and/or densest particles,

(e) re-injecting the third or fourth fraction at the inlet of the mill, an

(f) Simultaneously recovering the second and fourth fractions or the third fraction, respectively, as output products.

2. The method of claim 1, wherein the first pneumatic separation comprises dynamic classification associated with recovery of the particles.

3. The method according to claim 1 or 2, wherein the first fraction is recovered from the gas stream and mechanically conveyed to the gas stream feeding the second pneumatic separation unit.

4. A method according to any one of claims 1 to 3, wherein said second pneumatic separation comprises dynamic classification associated with the recovery of said particles.

5. The method according to any one of claims 1 to 4, wherein the third or fourth fraction is recovered from the gas stream and conveyed mechanically or via the gas stream to an inlet of a milling step.

6. The method of claim 1 applied to the separation of particulate material comprising metallic material and non-metallic material lighter than the metallic material, wherein step (e) comprises reinjecting the third fraction at the grinding inlet to recover a second fraction comprising particles of the finest particle size and having an increased proportion of the metallic material relative to the initial particles, and a fourth fraction comprising particles of the coarsest particle size and having the smallest density and having an increased proportion of the non-metallic material relative to the initial particles.

7. An apparatus for continuous pneumatic separation of particulate material consisting of a mixture of particles of non-uniform particle size and density, said apparatus comprising:

-a grinder (100) fed with a heterogeneous mixture of particles to be treated,

-means (510, 104) for generating a gas stream (F1) containing particles from grinding at the outlet of the grinder,

-a first pneumatic classifier (200) receiving the gas stream and capable of producing a first group of particles (F2) containing the coarsest particles with variable density and a second group of particles (F3) containing the finest particles,

-a second pneumatic classifier (300) receiving said first fraction and capable of producing a third fraction (F5) comprising the coarsest and/or most dense particles and a fourth fraction (F4) comprising the finest and/or least dense particles, and

-means (450) for conveying the third fraction (F5) or the fourth fraction (F4) towards the inlet of the mill.

8. The apparatus of claim 7, wherein the first pneumatic classifier (200) comprises a dynamic classifier (210) associated with a particle recycler (220).

9. The apparatus according to claim 8, characterized in that it further comprises a duct (253) for reinjection of a flow of clean air at the inlet of the grinding mill (100), at the outlet of the recuperator (220).

10. The apparatus according to claim 8 or 9, characterized in that it further comprises means for mechanically conveying said particles of said first fraction (F2) to a diffuser (335), said diffuser (335) being inserted on an inlet duct (350) of said second pneumatic classifier (300).

11. The apparatus of any of claims 7 to 10, wherein the second pneumatic classifier (300) comprises a second dynamic classifier (310) associated with a second particle recycler (320).

12. The apparatus according to claim 11, characterized in that it further comprises a duct (353) for reinjection of a flow of clean air at the outlet of the second particle recycler (320), at the inlet of the second dynamic classifier (310), or alternatively at the inlet of the mill (100) in the case of a fourth fraction (F5) returned to the mill (100).

13. The apparatus according to claim 11 or 12, further comprising means for mechanically or pneumatically conveying particles from the third or fourth fraction to the inlet of the grinding mill (100).