EP2420326A1

EP2420326A1 - Method for the dry beneficiation of wollastonite ores

Info

Publication number: EP2420326A1
Application number: EP09843413A
Authority: EP
Inventors: Valery Mikhailovich Snezhko; Maxim Viktorovich Kuryshkin; Alexey Alexandrovich NOSACHEV
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-04-17
Filing date: 2009-08-27
Publication date: 2012-02-22
Also published as: WO2010120204A1; RU2383398C1; CN102239014A

Abstract

The invention relates to benefication of mineral deposits and can be used for benefication of wollastonite ores. According to the inventive method for dry benefication of wollastonite ore, which comprises primary and secondary crushing of the ore, drying of the material, X-ray fluorescent separation of the crushed material, classification of the material according to grain-size categories, magnetic separation on a belt conveyor, magnetic separation on a roll-type separator in order to remove impurities from wollastonite concentrate of various grain sizes, grinding, as well as extraction of flour particles of the material, the drying of the material is performed between the primary and secondary crushing stages, the X-ray fluorescent separation is performed after the secondary crushing, the classification according to grain-size categories is performed immediately after the X-ray fluorescent separation by sequentially carrying out impact grinding, magnetic separation on a belt conveyor and air sizing, followed by magnetic separation on a roll-type separator; the extraction of flour particles of the material is performed at the primary and secondary crushing stages and during the impact grinding of the ore, wherein all extracted flour particles are supplied to one of the rolls of the roll-type magnetic separator; the wollastonite concentrate of one or more grain sizes can be dried, which is followed by electrostatic separation of the dried concentrate in order to remove impurities therefrom, followed by air sizing of the product obtained after electrostatic separation in order to divide it into fractions with different grain size; one or more product fractions can be additionally ground, which is followed by removal of the electrostatic charge. The amount of wollastonite that goes into waste is reduced and the quality of the final product is improved.

Description

Technical field

The invention relates to benefication of mineral deposits and can be used for benefication of wollastonite ores.

Background art

A known method for benefication of wollastonite ores comprises dry crushing of the ore in an inertial cone crusher or an autogenous grinding mill similar to "Aerofol" and air sizing into categories of 1.0 and 0.071 mm: category +1.0 mm is sent to recrushing, category - 0.071 mm is extracted as final wollastonite product and category- 1.0+0.071 mm is sent to magnetic separation, obtaining garnet concentrate. Prior to extraction of wollastonite concentrate the non-magnetic product is subjected to friction electrification, heating it to a temperature of 150-170°C in an electric tube furnace and then cooling it down to a temperature of 100-110°C on the tray of a vibration feeder. The wollastonite concentrate is extracted by means of electrostatic separation with simultaneous extraction of calcite concentrate and quartz product, setting the electric field intensity in the range of 3.5-10⁵-3.9-10⁵ V/m, see RU 2002513C1 .
The disadvantages of the described known method consist in its complexity caused by the need to perform thermal treatment in strictly specific temperature conditions, and in the low quality of the vendible product, which is obtained as two sorts of wollastonite concentrate. The first sort of concentrate, which is obtained by air sizing of the material of category -0.071 from crushed initial ore, has high contents of calcite and gannet that contaminate the wollastonite product. In addition, the method of friction electrification used for separation of the material and extraction of the second sort of concentrate does not allow obtaining a high-quality vendible product.
Another known method for dry benefication of wollastonite ore comprises dry crushing of the ore, X-ray fluorescent separation of the crushed material, grinding and classification of the beneficated material according to grain-size categories with subsequent magnetic and electrostatic separation in order to remove the impurities and subsequent grinding of the obtained wollastonite concentrate.
In the described known method, prior to grinding of the ore which is performed in an inertial cone crusher or a grinding mill "Aerofol", the ore is subjected to screening with size-grading, whereupon category +50 mm is sent to recrushing, category -10 mm is sent to grinding and categories 20+10 mm and -50+20 mm are sent to X-ray fluorescent separation; pieces with low content of wollastonite are removed to tailings, whereupon the beneficated ore and grain-size category -10 mm are subjected to grinding in an inertial cone crusher until obtaining -3 mm, which is then used to extract -0.1 mm grain-size category by means of air sizing, thus obtaining the first wollastonite concentrate with wollastonite content of 85%, whereas grain-size category - 3+0.1 mm is put through a magnetic separator, producing garnet-pyroxene concentrate, and the non-magnetic product is sent to a rotary high-speed mill, using the ground material to extract grain-size category -0.063 mm by means of air sizing, thus obtaining the second wollastonite concentrate with at least 90% of wollastonite content, whereupon the grain-size category -0.5+0.063 mm is subjected to magnetic separation, extracting grains of garnet and pyroxene which are opened during further grinding, as well as tool iron, while the non-magnetic material in the form of calcite, quartzite and wollastonite is dried and separated in a two-stage electrostatic separator, where needle-shaped wollastonite drifts towards the high-voltage electrode, while the admixtures, having a rounder and slightly elongated form, push away from the high-voltage electrode and go to the quartz-wollastonite concentrate. Elongated needle-shaped grains of wollastonite are supplied to a disintegrator, where they are ground to grain-size category -0.040 mm, thus obtaining the third wollastonite concentrate with wollastonite content of 90%, see RU 2142348 C1 .
A serious disadvantage of the described known method consists in the low quality of the vendible product. The described known method produces three wollastonite concentrates. The first wollastonite concentrate WCT-1, obtained through air sizing of products of crushing of the initial ore, cannot be regarded as a wollastonite concentrate, since it does not pass through magnetic or electrostatic separation and contains the entire range of impurities (garnets, calcites, pyroxenes, quartzites etc.), which are present in the initial ore. In fact, it is the product of crushing of the initial ore down to grain-size category of-0.1 mm.
The second wollastonite concentrate WCT-2 obtained according to the described known method is in fact a calcite-wollastonite concentrate, since it is extracted prior to electrostatic separation, and the contents of calcite and other non-magnetic impurities in this concentrate are greater than or equal to the contents of these impurities in the ore, which has a negative impact on the quality of the vendible product.
According to the described known method, air sizing is used to extract material of grain-size category - 3+0.1 mm, which is then sent to magnetic and electrostatic separation. The air sizing method is known to be effective for separation of particles of materials with identical or similar density. Experiments that were conducted in the conditions of the described known method showed that the specified material comprises mineral particles of different density and therefore it is virtually impossible to obtain material strictly within the specified grain-size range of- 3+0.1 mm by means of air sizing. Usually the final contents include particles larger than 3 mm and, most importantly, quite a lot of particles smaller than 0.1 mm. Contemporary magnetic and electrostatic separators cannot provide high-quality purification of wollastonite (elimination of admixtures) with such wide grain-size range (-3+0.1 mm) of the material, which also contains high amounts of small particles (smaller than 0.1 mm).
In addition, the upper limit of the grain-size category of the material supplied to the first stage of magnetic separation is significantly greater than the limit of grain size of the material that provides maximum liberation of attachments of minerals. After passing through the magnetic separator, the material that contains high amount of particles with unliberated mineral attachments either goes to the final product and contaminates it after regrinding, or goes to the waste, reducing the extraction of wollastonite from the ore.
Another known method for benefication of wollastonite ore comprises primary crushing of the ore during the first stage, directly followed by X-ray fluorescent separation, which separates the bare (empty) rock - the tailings. Directly after the X-ray fluorescent separation the remaining ore (without the tailings) is dried and then subjected to secondary crushing. Then the material is divided into grain-size categories, the classification involving only screening of the material. After the screening the material with grain-size category of +dp is sent to regrinding, material with grain-size category of 1 < dmax/ dmin ≤ 5 is subjected to magnetic separation, first on a belt conveyor and then on a roll-type magnetic stator. Material that has grain-size category - 0.1 dp after the screening is extracted as the final product after air sizing. Directly after the magnetic separation and extraction of the tool iron, garnet, pyroxene etc. the electric separation is performed, see RU 2292963 C1 .
This engineering solution has been taken as a prototype of the present invention.
The prototype method has several disadvantages.
Since the X-ray fluorescent separation is performed directly after the primary (first) crushing of the ore, there is significant output of wollastonite into tailings (about 20-25%). Flour particles of the material are collected only during the screening and are not collected during preceding crushing stages, which results in loss of the wollastonite-iferous material.
Flour particles of the material are selected as the final product (Voksil M100 and Voksil A) immediately after the screening, without passing through the magnetic or electrostatic separation. As a result, the product contains a lot of impurities (garnets, calcites, pyroxenes, quartzites etc.) that are present in the initial ore.
The lack of additional drying of the material prior to electrostatic separation causes agglomeration of particles of the material; in addition, the presence of moisture during electrostatic separation prevents polarization of the material particles, thus lowering the quality of separation.
It also should be noted that the prototype method does not include the step of removing electrostatic charge from wollastonite particles, which they acquire during electrostatic separation and grinding; this results in coupling of particles due to interaction of opposite poles and thus lowers the product quality.

Summary of the invention

It is an object of the present invention to reduce the amount of wollastonite that goes into waste and improve the quality of the final product.
According to the inventive method for dry benefication of wollastonite ore, which comprises primary and secondary crushing of the ore, drying of the material, X-ray fluorescent separation of the crushed material, classification of the material according to grain-size categories, magnetic separation on a belt conveyor, magnetic separation on a roll-type separator in order to remove impurities from wollastonite concentrate of various grain sizes, grinding, as well as extraction of flour particles of the material, the drying of the material is performed between the primary and secondary crushing stages, the X-ray fluorescent separation is performed after the secondary crushing, the classification according to grain-size categories is performed immediately after the X-ray fluorescent separation by sequentially carrying out impact grinding, magnetic separation on a belt conveyor and air sizing, followed by magnetic separation on a roll-type separator; the extraction of flour particles of the material is performed at the primary and secondary crushing stages and during the impact grinding of the ore, wherein all extracted flour particles are supplied to one of the rolls of the roll-type magnetic separator; the wollastonite concentrate of one or more grain sizes can be dried, which is followed by electrostatic separation of the dried concentrate in order to remove impurities therefrom, followed by air sizing of the product obtained after electrostatic separation in order to divide it into fractions with different grain sizes: one or more product fractions can be additionally ground, which is followed by removal of the electrostatic charge.
The applicant has not found any sources of information containing data on engineering solutions identical to the present invention, which enables to conclude that the invention conforms to the criterion "Novelty" (N).
Realization of the features of the invention provides a significant decrease of wollastonite waste, since the X-ray fluorescent separation is performed after the second (secondary) crushing. Loss of wollastonite is also reduced due to the fact that flour particles of the material are extracted at all crushing stages and during impact grinding, not only during screening as in the prototype. In addition, the fact that flour particles of the material are subjected to magnetic or, additionally, electrostatic separation reduces the amount of impurities in the product. The quality of electrostatic separation and, therefore, of the product is improved due to additional drying of the material before the separation, because it reduces agglomeration of the material particles.
The applicant has not found any sources of information containing data on the influence of the features of the invention on the technical result produced by the invention, which enables to conclude that the invention conforms to the criterion "inventive Step" (IS).

Brief description of the drawings

The invention is further explained, by way of example, with reference to the drawing that shows a flow diagram of the process, in which:

1 -: ore;
2 -: primary crushing;
3 -: drying;
4 -: secondary crushing;
5 -: X-ray fluorescent separation;
6 -: tailings;
7 -: grinding (impact);
8 -: magnetic separation (belt conveyor);
9 -: tool iron and strong magnetic admixtures;
10 -: air sizing;
11 -: magnetic separation (roll-type separator);
12 -: 1^st roll;
13 -: 2^nd roll;
14 -: cyclone;
15 -: garnet-pyroxene concentrate (GPC);
16 -: wollastonite concentrate (WCT1);
17 -: garnet-pyroxene concentrate (GPC);
18 -: wollastonite concentrate (WCT1);
19 -: drying;
20 -: electrostatic separation;
21 -: quartz-calcite concentrate (QCC);
22 -: air sizing;
23, 24, 24 -: wollastonite concentrate (WCT2);
26 -: grinding in a disintegrator;
27 -: removal of electrostatic charge;
28 -: wollastonite concentrate (WCT3).

Preferred embodiment

The method is implemented in the following way.
Wollastonite ore from Kain-Suu deposit (the Kyrgyz Republic) with wollastonite content 60-71% was used as raw material. Primary (first) crushing of the ore to grain size of 100-120 mm is performed in a jaw crusher. Then the material is dried with hot air in a container drier. After the drying the secondary crushing of the material is performed in a vibratory crusher to grain size of 30-40 mm. Then X-ray fluorescent separation of the material is performed, where pieces of ore with low content of wollastonite (less than 10%) are removed to tailings, and the beneficated ore is sent to classification according to grain-size categories, which is started by impact grinding in a rotary high-speed mill, followed by magnetic separation on a belt conveyor with pulley magnet, during which tool iron and strong magnetic admixtures are separated; the remaining material is divided into grain-size categories by means of air sizing.
Then magnetic separation on a roll-type magnetic separator is performed. In this particular example a two-roll separator is used. Larger material is supplied to one of the rolls, whereas smaller material is supplied to the other roll, as are the flour particles of the material, which are extracted by means of "Cyclone" device at the primary and secondary crushing stages and during impact grinding of the ore.
Larger weak-magnetic admixtures, namely garnet-pyroxene concentrate (GPC), as well as wollastonite concentrate (WCT1) of higher grain size, are removed from the first roll of the magnetic separator. Wollastonite content in WCT1 is at least 92 mass %, the average ratio of length of wollastonite grains to their diameter (L/D) is at least 10.
GPC and WCT1 with smaller grain size are extracted from the second roll. WCT1 can be regarded as final product, and the process according to claim 1 can be considered to be finished. GPT, which is a by-product, can be used as an abrasive material.
WCT1 can be subjected to additional drying in a tube drying furnace, whereupon electrostatic separation of dried wollastonite concentrate is performed, separating admixtures therefrom - quartz-calcite concentrate (QCC), which is a by-product and can be used, in particular, in pulp and paper industry. Wollastonite concentrate (WCT2) of various grain sizes obtained after the electrostatic separation has wollastonite content not lower than 96% and average ratio L/D not lower than 15.
WCT2 can be additionally ground in a disintegrator, whereupon electrostatic charge is removed from wollastonite crystals in an installation that creates horizontal electromagnetic field. Main elements of the installation are electrodes in the form of plates with supplied DC voltage of 25 kV.

Industrial applicability

The invention can be implemented by means of common factory equipment. In applicant's opinion, this enables to conclude that the inventions conform to the criterion "Industrial Applicability" (IA).

Claims

A method for dry benefication of wollastonite ore, which comprises primary and secondary crushing of the ore, drying of the material, X-ray fluorescent separation of the crushed material, classification of the material according to grain-size categories, magnetic separation on a belt conveyor, magnetic separation on a roll-type separator in order to remove impurities from wollastonite concentrate of various grain sizes, grinding, as well as extraction of flour particles of the material, characterized in that the drying of the material is performed between the primary and secondary crushing stages, the X-ray fluorescent separation is performed after the secondary crushing, the classification according to grain-size categories is performed immediately after the X-ray fluorescent separation by sequentially carrying out impact grinding, magnetic separation on a belt conveyor and air sizing, followed by magnetic separation on a roll-type separator, and the extraction of flour particles of the material is performed at the primary and secondary crushing stages and during the impact grinding of the ore, wherein all extracted flour particles are supplied to one of the rolls of the roll-type magnetic separator.
A method as claimed in claim 1,characterized in that the wollastonite concentrate of one or more grain sizes is dried, followed by electrostatic separation of the dried concentrate in order to remove impurities therefrom, followed by air sizing of the product obtained after electrostatic separation in order to divide it into fractions with different grain sizes.
A method as claimed in claim 2, characterized in that one or more product fractions are additionally ground and the electrostatic charge is removed.