GB1596515A - Separating solid materials - Google Patents

Description

(54) SEPARATING SOLID MATERIALS (71) We, KNIPPI "NIPRORUDA", of 205, Boulevard Al.Stamboliski, Sofia, Bulgaria, a Research Institute, organized under the Laws of Bulgaria, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a method of and apparatus for the mechanical separation of solid materials, more particularly but not exclusively of aluminium-containing slags, by means of controlled crushing or crumbling and selective screening. The metal or aluminium content of the preferred material to be treated may vary in a wide range, e.g.

from 1 to 99%.

In metallurgical processes a large variety of products (e.g. slag, dross and clinker) is obtained, often consisting of large lumps and containing a mixture of metal granules, linked to non-metallic inclusions. These products are conventionally treated by crumbling, crushing, milling and screening.

The methods and equipment used heretofore, have however the following drawbacks: crushers easily break down; the separation methods often fail to achieve the necessary selectivity of separation; and too frequently metal particles present are ground too finely, which leads to considerable losses of the metal. Thus, for example, during metallurgical melting of secondary alluminium alloys a large quantity of waste slag is produced which contains a high percentage of aluminium in the form of metal inclusions and oxides.

Existing methods of treatment are of the dry type, and the most novel of them feature the autogenous crushing of aluminium-containing slag in semi-autogenous mills of the "AEROFALL"-type wherein the slag is fed to the mill in separate batches being thereafter crushed for 8 to 10 hours. During this period the mill is supplied with air, heated to 80"C in an appropriate heater, in order to obtain complete drying of the slag. Tbe mill is also supplied with steel balls, sized from 80 to 120 mm. A fine product is continuously separated through a lattice, mounted in the cylindrical part of the mill. In order to separate this powderlike product, powerful aspirating units comprising ventilators and sleeve-type filters are used.The remaining aluminium-containing product is periodically discharged for which purpose the mill must be stopped, the metallic product extracted together with the steel balls, then sifted through a special grid in order to separate the balls which are finally fed back to the mill.

Though most novel, this methods with the remaining methods-is not yet perfect, featuring the following fundamental drawbacks: The process requires a complete drying of the slag and is a batch process; it requires effective dust removal involving sophisticated equipment; there are large losses of aluminium metal in the powder product and also from the tiny oxide particles released at the periodical discharge of the metallic product; the purity of the fine product is unsatisfactory which impairs its utilization; it is necessary to separate the steel balls at the completion of each working cycle and to return them to the mill; and, finally, the mechanization and automation of the process present many difficulties.

The known wet processes are used only with the so called salt-aluminium slags (i.e.

low metallic aluminium content-up to 20%; small particles sized not more than 8-10 mm, and high salt content). The purpose of these methods is to dissolve and regenerate the salts contained in the salt-slags. The drawbacks of the known salt-methods are as follows: the field of application is fairly restricted; there is no means of separation of metallic and non-metallic (oxide) fractions; and the mixed aluminium product obtained is of limited use.

Among the equipment for the mechanical separation of large-sized materials one can cite rotary-screen units, wherein screening to predetermined sizes only can be effected with insignificant crumbling of the weaker component, while in some rotary-screen equipment, additional accessories can be inserted, e.g. ribs or chains. These accessories can only improve the mixing of the material and its autogenous crushing and crumblingwhich is far from complete.

Rod-type mills are also known, wherein only the grinding of different materials can be implemented; normally these mills contain grinding materials having maximum dimensions of 40 to 60 and 10 to 15 mm. The main drawback of these mills is the incomplete crumbling and the rather difficult discharge of the larger sized product. In addition, rod-type mills are almost unable to ensure selectivity of grinding or classification of the material.

An aim of this invention is to provide a method of and apparatus for the mechanical separation of large-sized materials, including aluminium-containing slag, by means of simultaneous and selective crumbling and screening operations, particularly for the treatment of large-sized mineral products of metallurgical processes, e.g. slag, dross and clinker and more specifically, but not exclusively, the treatment of all sorts of aluminium slag (e.g. dry and salted). Embodiments of the invention may provide for a continuous processing and complex utilization of the treated materials, ensuring a good separation selectivity and high quality of the products, the process being fully mechanized with prospects for its complete automation.

According to one aspect of the present invention, there is provided a method of treating solids to obtain thereby a coarse product fraction and a fine product fraction, in which the solids are treated in three successive stages, the first and third stages involving selective screening of the solids while they are being sprayed with a liquid, and the second stage including selective mechanical crumbling.

According to another aspect of the present invention, there is provided an apparatus for treating solids to obtain a coarse product fraction and a fine product fraction which apparatus comprises a rotatable, generally cylindrical body divided into three contiguous chambers, wherein (a) the cylindrical walls of the first and third chambers are formed with a plurality of sieves; (b) the second chamber contains means for selectively crumbling material fed thereto; (c) the division between the second and third chambers is in the form of a perforated disc screen; (d) the first and third chambers are provided with means for spraying a liquid onto material contained therein; and (e) the apparatus is adapted to operate with the longitudinal axis of said generally cylindrical body inclined to the horizontal.

The method of mechanical separation of large-sized materials and particularly of aluminium-containing slag preferably involves the materials and slag being submitte'd to mechanical crumbling and screening in conditions of intensive water-spraying to separate a coarse (metal) fraction from the fine (oxide) fraction. Iron inclusions in the coarse (metal) fraction can be extracted by means of magnetic separation, being dried thereupon.

With aluminium-containing slag, drying of this fraction may be carried out by autogenous means, the dried aluminium-metal product being further submitted to metallurgical treatment through a remelting process.

The fine oxide-containing fraction, separated by means of screening, may also undergo magnetic separation, and may afterwards be dewatered and dried.

With aluminium-containing slag the drying of the product may be done autogeneously the product being further submitted to a chemical treatment.

Water separated during the dehydration of the fine fraction after desliming may be recycled or-if salts are present therein used for salt-extraction.

The equipment according to the invention is a rotatable three chamber cylindrical body which generally will be tilted along its axis, wherein the cylindrical walls of the first and third chambers are formed with several sieves or screens disposed with their axes mutually in parallel and so that a particle passing through any one of the sieves travels transversely to the cylindrical axis of the chamber. By such a disposition the jamming of the screen openings is successfully avoided, ensuring meanwhile an adequate screening selectivity. Means are provided for spraying a liquid onto material within the first and third chambers.

The openings in the screens are preferably relatively small-advantageously ranging from 2 to 5 mm, but the maximal size of the solid material e.g. slag to be treated may be up to 300 mm. In practice we believe that there is no equipment known with such a material size to screen openings ratio, i.e.

more than 100.

The second chamber, conveniently taking about 1/2 of the cylindrical body's length, advantageously has a smooth cylindrical inner surface and is provided at its downstream end with a perforated disc screen preferably with a broad central opening. The second chamber can contain from 3 to 10 metal rods and the perforated disc screen ensures a better passage for the smaller particles thus avoiding their overcrumbling.

The disc also serves to retain the crumbling rods within the second chamber. Thus, only the crushing of low-hardness mineral-inclusions is effected, e.g. the oxide fraction without crushing the larger particles of greater hardness, that is the mineral or metallic fraction.

To the main features of the equipment as a whole, it may be added that changing the angle of tilt along the longitudinal axis of the equipment regulates the crumbling rate so that predetermined throughput rates can be achieved.

The method and apparatus of the invention can be used to ensure the selective crumbling and screening of metallurgical process products, minerals, etc., thereby providing additional quantities of metals and other raw materials at low investment rate and ensuring for example an efficient separation of metallic aluminium from aluminium and other compounds, as well as providing high-quality aluminium and iron products.

The method and apparatus are expected to have wide application for the treatment of various materials containing components of different hardness, the treatment of metallurgical products and some minerals, and furthermore, provides the possibility for continuous technological processing and complex utilization of mechanically-separated materials and particularly aluminium slag.

The method, when applied to the reprocessing of aluminium slag, ensures the dilution of any salts present in the slag and enables their regeneration using the exothermic effect for drying the aluminium product.

The apparatus ensures the mechanical separation of large-sized materials by means of crymbling and screening. It features a compact design and construction which may enable considerable savings to be made e.g.

in the fields of transportation, construction, labour and power consumption. The final technical, technological and economical effect may be substantially higher than the sum of the effects provided by the three chambers if they were considered as independent apparatus or elements.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figures 1 and 2 show illustrative diagrams of the method in accordance with the invention; Figure 3 is a front view of one embodiment of apparatus in accordance with the invention; Figure 4 is a cross-section along the line YY of Figure 3; and Figure 5 is a plan view of this embodiment.

The apparatus shown in Figures 3 to 5 comprises a cylindrical body I including three rotatable cylindrical working chambers 1, II and III. Between the chambers II and III a perforated element or screen 4 is mounted.

The outer side of the cylindrical body features two wheels 2 (shroud wheels) and a gear rim 3 fixed thereon. The shroud wheels 2 rest on four freely rotating rollers 5, while the drive of the gear rim is effected by means of a reducer 6 and an electrical motor 7. The rollers 5, the reducer 6 and the motor 7 are mounted on a frame 8. The chambers I and III each include a plurality of mutually parallel sieves 13 mounted in their cylindrical walls, which sieves act as selective screening sieves. Means (not shown) for spraying a liquid, e.g. water, onto the material within chambers I and III are provided. The chamber II has a smooth cylindrical inner surface.

The screen underflow products A pass through the sieves 13 and are withdrawn from the apparatus through chutes 9 and 10, each of which is adjacent to the cylindrical wall of the respective one of chambers I and III. The screen overflow product B passes longitudinally through all three chambers and is evacuated through chute 11. The apparatus is operated as follows: The material AB intended for reprocessing procedures is supplied to the chamber I of the body 1 which is slightly and axially sloped downwardly in the direction of material flow. Under the effect of the rotary motion of this chamber, the preliminary screening of the feedstock is implemented.

Fines pass into chute 9 while the larger particles are fed to chamber II which contains means, in the form of 3 to 10 steel rods for selective mechanical crumbling of the larger particles. The weight and diameter of the rods are selected so as not to crush large-generally metallic-particles but just to crumble down the non-metallic or softer inclusions, this being achieved by a slight cascading or tumbling motion of the rods within the material. The material thus treated is passed through the perforated element or screen 4 and, through its central opening, flows to the chamber III. The final separation of the crumbled fine materials (as a screen underflow product) from the large particles (the screen overflow product) takes place in this chamber.The screen underflow products are evacuated from the apparatus via the chutes 9 and 10, while the screen overflow products are evacuated through the chute 11. The intensive spraying of a liquid, e.g. water, into chambers I and III aids the crumbling of soft agglomerates and their selective screening from harder inclusions.

Figures 1 and 2 are flow diagrams illustrating the method of this invention. In Figure 1, the starting material (e.g. ores mixed with, e.g., slag) is free of magnetic inclusions. It is supplied to apparatus such as that described above with reference to Figures 3, 4 and 5, where it undergoes mechanical separation by selective screening under intensive water spraying, and mechanical crumbling. The screen overflow product (indicated by a "+" sign) consisting of relatively hard particles is then dewatered to give a final coarse fraction.

The screen underflow products (indicated by a "-" sign) consisting of relatively soft particles are then dewatered to give a final fine fraction and a suspension. The suspension is then purified to give a slime and pure water, the latter being recycled to the apparatus where it is sprayed onto the material within the first and third chambers.

In Figure 2, the starting material is an aluminium-containing slag which has iron inclusions. This material is supplied to apparatus such as that described above with reference to Figures 3, 4 and 5, where it undergoes mechanical separation by selective screening under intensive water spraying, and mechanical crumbling. The screen overflow products (indicated by a "+" sign) and the screen underflow products (indicated by a "" sign) are subjected to magnetic separation, leading to the recovery of iron scrap from both underflow and overflow products. A final coarse fraction is obtained after magnetic separation treatment of the screen overflow product.The residue from the magnetic separation treatment of the screen underflow products is then dewatered, giving a final fine fraction and a suspension of ultrafine particles which is then subjected to a precipitation step to give further material constituting part of the final fine fraction and water which can be recycled to the apparatus if it is chemically pure, or which, if it contains dissolved salts, can be regenerated prior to recycling.

To illustrate the invention, the following examples are given: Example 1: A batch of 100 tons of dry aluminium slag, sized up to 200 mm, is supplied to the apparatus of Figures 3 to 5 for mechanical separation by selective crumbling and screening in conditions of intensive water-spraying and screening, resulting in the separation of the metal fraction from the oxide fraction. The metal fraction is submitted to magnetic separation, whereupon two products are obtained: a metallic aluminium product-56 tons, sized between 3 and 250 mm and having an aluminium content of 28%; and an iron product amounting to 14.0 tons, sized between 3 and 250 mm and iron content: Fe= 78%.

The separated oxide fraction in the form of a suspension is submitted to magnetic separation, resulting in fine iron particles amounting to 1.0 ton sized smaller than 3 mm and iron content of 66%. The nonmagnetic oxide-fraction is dehydrated in a spiral classifier, resulting in aluminium-containing oxides amounting to 26.0 tons, sized between 0.08 mm and 3 mm with aluminium content of 63%.

The water separated from the oxides is submitted to mechanical treatment to remove impurities, whereupon aluminium slag (oxide) is obtained amounting to 3.0 tons, being sized at 0.08 mm and at an aluminium content of 31%.

The products thus obtained are used in the following way: as per the metallic aluminium product-for obtaining pig aluminium: the iron, including the fine fraction is used as feedstock for the iron & steel industry; the aluminium oxide, incl. the aluminium slag, is used for the manufacturing of technical aluminium sulphate; and finally, the residual waters are utilized for recycling in the process of this invention.

Example 2: A batch of 100 tons of salted aluminium slag is supplied to the apparatus shown in the drawings for mechanical separation by crumbling and screening in intensive water-spraying conditions, resulting in the separation of metallic and oxide fractions and salted solutions. The metal fraction is submitted to magnetic separation resulting in two products: an aluminium product amounting to 7 t., and sized larger than 3 mm with an aluminium content of 78%, and an iron product amounting to 6 tons, sized larger than 3 mm, with an iron content of 80%.

The separated oxide-fraction in a suspension-form is submitted to magnetic separation, resulting in iron fines amounting to 0.5 ton, sized smaller than 3 mm and having an iron content of 64%. The non-magnetic oxide fraction is dehydrated in a spiral classifier, resulting in aluminium-containing oxides amounting to 3.6 tons, sized smaller than 3 mm with an aluminium content of 58%.

The liquid (aqueous salt solution) separated from the oxides is submitted to a purification from magnetic impurities therein, being afterwards submitted to crys tallisation in order to regenerate the salts according to known methods.

The products obtained are used by the following way: the metallic aluminium product is used for obtaining pig aluminium; the iron is used as a feedstock for the iron & steel industry; the aluminium-containing oxide-for the production of technical aluminium sulphate; and the residual salted watersfor the production of salts.

The yield of the products obtained depends upon the nature of reprocessed aluminium slag.

WHAT WE CLAIM IS: 1. A method of treating solids to obtain thereby a coarse product fraction and a fine product fraction, in which the solids are treated in three successive stages, the first and third stages involving selective screening of the solids while they are beinng sprayed with å liquid, and the second stage including selective mechanical crumbling.

2. A method according to claim 1, wherein the spraying liquid is water.

3. A method according to claim I or 2,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (32)

**WARNING** start of CLMS field may overlap end of DESC **. particles are then dewatered to give a final fine fraction and a suspension. The suspension is then purified to give a slime and pure water, the latter being recycled to the apparatus where it is sprayed onto the material within the first and third chambers. In Figure 2, the starting material is an aluminium-containing slag which has iron inclusions. This material is supplied to apparatus such as that described above with reference to Figures 3, 4 and 5, where it undergoes mechanical separation by selective screening under intensive water spraying, and mechanical crumbling. The screen overflow products (indicated by a "+" sign) and the screen underflow products (indicated by a "" sign) are subjected to magnetic separation, leading to the recovery of iron scrap from both underflow and overflow products. A final coarse fraction is obtained after magnetic separation treatment of the screen overflow product.The residue from the magnetic separation treatment of the screen underflow products is then dewatered, giving a final fine fraction and a suspension of ultrafine particles which is then subjected to a precipitation step to give further material constituting part of the final fine fraction and water which can be recycled to the apparatus if it is chemically pure, or which, if it contains dissolved salts, can be regenerated prior to recycling. To illustrate the invention, the following examples are given: Example 1: A batch of 100 tons of dry aluminium slag, sized up to 200 mm, is supplied to the apparatus of Figures 3 to 5 for mechanical separation by selective crumbling and screening in conditions of intensive water-spraying and screening, resulting in the separation of the metal fraction from the oxide fraction. The metal fraction is submitted to magnetic separation, whereupon two products are obtained: a metallic aluminium product-56 tons, sized between 3 and 250 mm and having an aluminium content of 28%; and an iron product amounting to 14.0 tons, sized between 3 and 250 mm and iron content: Fe= 78%. The separated oxide fraction in the form of a suspension is submitted to magnetic separation, resulting in fine iron particles amounting to 1.0 ton sized smaller than 3 mm and iron content of 66%. The nonmagnetic oxide-fraction is dehydrated in a spiral classifier, resulting in aluminium-containing oxides amounting to 26.0 tons, sized between 0.08 mm and 3 mm with aluminium content of 63%. The water separated from the oxides is submitted to mechanical treatment to remove impurities, whereupon aluminium slag (oxide) is obtained amounting to 3.0 tons, being sized at 0.08 mm and at an aluminium content of 31%. The products thus obtained are used in the following way: as per the metallic aluminium product-for obtaining pig aluminium: the iron, including the fine fraction is used as feedstock for the iron & steel industry; the aluminium oxide, incl. the aluminium slag, is used for the manufacturing of technical aluminium sulphate; and finally, the residual waters are utilized for recycling in the process of this invention. Example 2: A batch of 100 tons of salted aluminium slag is supplied to the apparatus shown in the drawings for mechanical separation by crumbling and screening in intensive water-spraying conditions, resulting in the separation of metallic and oxide fractions and salted solutions. The metal fraction is submitted to magnetic separation resulting in two products: an aluminium product amounting to 7 t., and sized larger than 3 mm with an aluminium content of 78%, and an iron product amounting to 6 tons, sized larger than 3 mm, with an iron content of 80%. The separated oxide-fraction in a suspension-form is submitted to magnetic separation, resulting in iron fines amounting to 0.5 ton, sized smaller than 3 mm and having an iron content of 64%. The non-magnetic oxide fraction is dehydrated in a spiral classifier, resulting in aluminium-containing oxides amounting to 3.6 tons, sized smaller than 3 mm with an aluminium content of 58%. The liquid (aqueous salt solution) separated from the oxides is submitted to a purification from magnetic impurities therein, being afterwards submitted to crys tallisation in order to regenerate the salts according to known methods. The products obtained are used by the following way: the metallic aluminium product is used for obtaining pig aluminium; the iron is used as a feedstock for the iron & steel industry; the aluminium-containing oxide-for the production of technical aluminium sulphate; and the residual salted watersfor the production of salts. The yield of the products obtained depends upon the nature of reprocessed aluminium slag. WHAT WE CLAIM IS:

1. A method of treating solids to obtain thereby a coarse product fraction and a fine product fraction, in which the solids are treated in three successive stages, the first and third stages involving selective screening of the solids while they are beinng sprayed with å liquid, and the second stage including selective mechanical crumbling.

2. A method according to claim 1, wherein the spraying liquid is water.

3. A method according to claim I or 2,

wherein the solids are produced by a metallurgical process.

4. A method according to claim 3, wherein the solids are slag or clinker.

5. A method according to claim 1, 2, 3 or 4 wherein either or both of the fine and the coarse product fractions are subjected to magnetic separation.

6. A method according to any preceding claim, wherein the product fractions are dried.

7. A method according to any preceding claim, in which the liquid used to spray the solids is collected and recycled.

8. A method according to any preceding claim, wherein the liquid which is used to spray the solids is collected and subjected to a salt-extraction process.

9. A method according to any preceding claim, wherein the solids comprise aluminium-containing slag.

10. A method according to any preceding claim, wherein the selective screening is performed with screens having openings in the range of from 2 to 5 mm.

11. A method according to claim 10 wherein the solids initially consist of particles up to 300 mm. in size.

12. A method according to any preceding claim, wherein the mechanical crumbling is carried out by the action of tumbling rods.

13. A method according to any preceding claim, wherein the first and third stages are carried out in chambers the walls of which are formed with a plurality of lamellar sieves.

14. A method according to claims 12 and 13, wherein opposite ends of a chamber containing the tumbling rods are in direct communication with said chambers for carrying out the first and third stages.

15. A method according to claim 14, wherein solids which have been treated in the tumbling rod chamber pass through a perforated disc screen having a central opening into the downstream one of said chambers.

16. A method according to claim 13, 14 or 15, wherein the throughflow product from the lamellar sieves constitutes the fine product fraction.

17. A method substantially as hereinbefore described with reference to, and as illustrated by, Figure 1 or 2 of the accompanying drawings.

18. A method substantially as hereinbefore described with reference to Figures 3, 4 and 5 of the accompanying drawings.

19. A method substantially as described in either of the foregoing examples.

20. An apparatus for treating solids to obtain a coarse product fraction and a fine product fraction which apparatus comprises a rotatable. generally cylindrical body divided into three contiguous chambers, wherein (a) the cylindrical walls of the first, and third chambers are formed with a plurality of sieves; (b) the second chamber contains means for selectively crumbling material fed thereto; (c) the division between the second and third chambers is in the form of a perforated disc screen; (d) the first and third chambers are provided with means for spraying a liquid onto material contained therein; and (e) the apparatus is adapted to operate with the longitudinal axis of said generally cylindrical body inclined to the horizontal.

21. An apparatus as claimed in claim 30 wherein said perforated disc screen has a central aperture.

22. An apparatus as claimed in claim 20 or 21, wherein said second chamber is adapted to function as a tumbling or rotating mill.

23. An apparatus as claimed in claim 22, wherein said second chamber contains a plurality of metal rods.

24. An apparatus as claimed in claim 23, wherein said second chamber contains from 3 to 10 metal rods.

25. An apparatus as claimed in any one of claims 20 to 24, wherein the openings in said sieves are in the range of from 2 to 5 mm.

26. An apparatus as claimed in any one of claims 20 to 25, wherein said second chamber has a smooth cylindrical inner surface.

27. An apparatus as claimed in any one of claims 20 to 26, wherein said three chambers are mounted at a slight inclination to the horizontal so that the third chamber is slightly lower than the first chamber.

28. An apparatus as claimed in any one of claims 20 to 27, wherein the inclination of the three chambers to the horizontal is adjustable.

29. An apparatus as claimed in claim 20 and substantially as hereinbefore described.

30. An apparatus substantially as hereinbefore described with reference to, and as illustrated in, Figures 3, 4 and 5 of the accompanying drawings.

31. A material whenever treated by a method or in an apparatus as claimed in any preceding claim.

32. A material as claimed in claim 31, which has been produced from an aluminium-containing slag.