Patent Application
20190336981
The invention relates to ferrite solids (filler) for a heavy liquid suspension, a method of preparation thereof from waste materials and use of ferrite as heavy liquid suspension solids.
Liquids of the density higher than the density of water, referred to as heavy liquids in mineral engineering, are utilized for enrichment of raw mineral materials, in particular bituminous coal and ores, e.g. iron ores, zinc-lead, manganese, tungsten, tin ores, non-metallic ores, and numerous other useful minerals. Use of heavy liquids in raw mineral material enrichment processes was described, for instance, in the patent descriptions Nos. PL40417 i PL46223, and in a publication by Laskowski T., Błaszczyński S., Ślusarek., titled “Wbogacanie kopalin w ciec
ach ci
żkich”, Śl
sk Editions, Katowice 1979. Such processes employ the effect of floating of grains on the liquid's surface with the density lesser than the density of the liquid, whereby a useful fraction of raw mineral materials and waste fraction are separated.
An example of a typical enrichment device employing a heavy liquid is the DISA type separator. Feed containing useful mineral products and waste is directed to the separator, where it is divided into a floating fraction and a sinking fraction within a separation chamber with a heavy liquid. The floating fraction is transferred downstream with the heavy liquid in the direction of a notch, where it is directed outside of the separator by means of a rake. Whereas the sinking fraction, after falling down to partitions of a lifting wheel, is lifted to certain height into a chute for discharging the sinking fraction.
The heavy liquid is delivered to the separators in two levels: slightly above the liquid level and in a lower portion of the separator below the liquid level. The heavy liquid flows over an overflow threshold and is directed outside the separator with the floating product. Heavy liquid circulation is closed. The heavy liquid is returned to the separator, and its depletion is made up with fresh liquid of suitable density.
There are two types of heavy liquids—homogenous and non-homogenous heavy liquids. Homogenous heavy liquids are characterized by constant density within the entire liquid volume regardless of the time. In general, these are chemical salt solutions. Non-homogenous (suspension) heavy liquids are mechanical aqueous suspension with very fine heavy mineral grains, which remain in water for some time as a suspension.
Heavy liquid suspension solids (fillers) include, for instance, magnetite—for enrichment of bituminous coals, and a magnetite (25%) and ferrosilicon (75%) mixture—for enrichment of zinc-lead ore. It is assessed that about 40 million tons of coal per year is enriched with heavy liquids in Polish coal treatment plants. As a rule, liquids of two characteristic densities are used: 1.5 g/cm3, in which coal with improved quality and environmental parameters (reduced ash, sulfur, chlorine content) is obtained, and 1.8 g/cm3, in which waste (the sinking product) is separated. At ore enrichment plants, a heavy liquid with the separation density equal to the limit maximum density of the waste components is used. In the case of the Polish zinc-lead ores the heavy liquid density at which the ore is enriched is about 2.85 g/cm3.
Solids of heavy liquid suspensions are finely ground solid grains of the density greater than 1 g/cm3, which can form a suspension in water. Fillers should be characterized by: the density twice higher than the highest density of a suspension liquid made therefrom, non-solubility in water, stability and ease of recovery. In the industrial practice, due to ease of recovery, magnetic solids, in particular fillers from magnetite and ferrosilicon, are mainly used. The basic requirements imposed on heavy liquids with magnetite solids were described in the Polish Standard No. PN-92/G-04601“Obciżniki ciec
y ci
żkiej
awiesinowej. Obciqżnik magnetytowy. Wymagania i badania”.
According to the above-indicated standard the magnetite fillers should fulfil the following requirements: filler density—minimum 4 g/cm3 for artificial magnetites and 4.5 g/cm3 for magnetite; magnetic component content—at least 90%; magnetic susceptibility—at least 40% for artificial magnetites and at least 70% for magnetite; granulometry—percentage of the particular outputs of magnetite size grades should be in the following ranges: 0-10% for a grade above 0.15 mm, 60-80% for a grade below 0.06 mm and 40-50% for a grade below 0.04 mm.
The solids for a heavy liquid used to date, i.e. magnetite and ferrosilicon, are very expensive, and as no cheaper substitute has been developed so far. Therefore, there is a need for a filler for heavy liquid suspensions with properties, which would not deviate from the filler used nowadays, and which would be more economical in use. Moreover there is a need to utilize ferrite-containing waste materials, for instance, metallurgical slags, steelwork dusts, coal combustion ashes and the ferromagnetic fraction of electronic waste.
The present inventors developed ferrite solids for heavy liquid suspensions, which could substitute the presently used magnetic fillers, such as the magnetite fillers. The ferrite solids not only constitute a cheaper equivalent of the presently used fillers for heavy liquids, but also they are environmentally friendly as they are manufactured from waste materials. Moreover, a method of preparation of ferrite solids comprises solely selective crushing and physical separation of waste materials. Due to metal malleability it is possible to isolate ferrite grains from metals contained in the waste. Thus, no environment unfriendly chemical agents are required for the treatment of the ferrite filler.
The invention is directed to a filler (solids) for a heavy liquid suspension comprising comminuted (fine-grained) ferrite of grain size no more than 0.6 mm, preferably 0.3 mm. In a preferred embodiment, the granulometric characteristic of the comminuted ferrite filler of the invention comprises the following ranges: 0-15% for particle size above 0.15 mm, 60-80% for particle size below 0.06 mm and 40-50% for particle size below 0.04 mm. Most preferably, the granulometric characteristic of the comminuted ferrite filler of the invention comprises the following values: 13.4% for particle size above 0.15 mm, 37.1% for particle size in the range of from 0.15 mm to 0.06 mm, 9.9% for particle size in the range below 0.06 mm to 0.04 mm, and 39.6% for the size grade below 0.04 mm.
In a preferred embodiment, the filler of the invention comprises comminuted ferrite acquired from waste materials, such as metallurgical slags, steelwork dusts, coal combustion ashes and, in particular, electronic waste, preferably from printed circuit boards (PCB), by selective comminution and mechanical classification methods.
The invention also provides a method of preparation of a ferrite filler for a heavy liquid suspension comprising steps of comminution and mechanical classification of a fraction, said method comprising the steps of
Preferably, the mechanical 0.2-2 mm classifier from step (a) of the method of the invention is a mechanical 1 mm classifier. A designation of the classifier means that in a given step of a method a classifier with a cut-off value selected from a described range or a classifier with the specifically indicated cut-off value may be used. Further preferably, in step (a) of the method of the invention a light fraction is seized by a light fraction separator located at the end of the classifier.
In a preferred embodiment, the method of the invention comprises further the steps
(c1) where the coarse fraction obtained in step (a) from the 0.2-2 mm classifier is comminuted in a crusher, preferably a roll crusher,
(c2) where the fraction comminuted in step (c1) is separated in a two-deck 2-5 mm and 0.2-2 mm classifier to form three fractions: the finest screened ferrite fraction directed to the electromagnetic separator with migrating magnetic field along with the screened fraction from step (a), a coarser ferrite fraction directed to the comminuter from step (c), and the coarsest fraction comprising a metallic fraction, which is isolated from the system along with the metallic fraction from step (e),
wherein said coarser ferrite fraction obtained in step (c2) is recycled to the two-deck 2-5 mm and 0.2-2 mm classifier used in this step.
Preferably, the two-deck 2-5 mm and 0.2-2 mm classifier from step (a2) is a two-deck 4 mm and 1 mm classifier.
In a preferred embodiment the method of the invention comprises step (a1), where the coarse fraction obtained in step (a) from the 0.2-2 mm classifier is further separated in the mechanical 5-8 mm classifier, wherein the screened fine fraction is directed to the crusher in step (c1), and the coarse fraction is subject to a further treatment comprising the steps of:
Preferably, step (a1) of the method of the invention is conducted in a mechanical 6.3 mm classifier. Also preferably, steps (a) and (a1) of the invention are conducted in a sole two-deck 5-8 mm and 0.2-2 mm classifier, more preferably in a 6.3 and 1 mm classifier. Further preferably, the two-deck 8-12 mm and 5-8 mm classifier from step (g) of the method of the invention is a two-deck 10 and 6.3 mm classifier, and the mechanical 5-8 mm classifier from step (i) of the method of the invention is a 6.3 mm classifier.
The method of the invention is preferably conducted in a continuous manner. In an alternative preferred embodiment the method of the invention is conducted in cycles (periodically).
The invention is also directed to a ferrite filler for a heavy liquid suspension manufactured by the method of the invention.
In a further aspect the invention provides the use of the comminuted ferrite as a filler (solids) for a heavy liquid suspension. In a preferred embodiment, according to the use of the invention, the ferrite is acquired from waste materials, such as electronic waste, metallurgical slags, steelwork dusts, coal combustion ashes, preferably from the electronic waste, more preferably from printed circuit boards, by means of techniques of selective comminution and mechanical classification.
The object of the invention is illustrated by the drawing, wherein:
The inventors have unexpectedly found that the ferrite recovered from the waste materials has properties, which make possible its use as a filler (solids) for heavy liquid suspensions. In a preferred embodiment, the starting material for the manufacture of a ferrite filler is a ferromagnetic fraction obtained from a magnetic separator, which separates the electronic waste components pre-comminuted in a hammer crusher into two fractions: a magnetic (also, ferromagnetic) and non-magnetic fraction. The ferromagnetic fraction, referred also to as feed, apart from steel components and ferrite, comprises a significant amount of undesirable components (plastics, films, copper wires, aluminum, and the like). However, the starting material for the manufacture of the ferrite filler may comprise any ferrite-containing waste material, preferably, the material containing more than 50% of ferrite, in particular metallurgical slag, steelwork dusts, coal combustion ashes.
A method of ferrite filler preparation of the invention from waste materials is based on the process of selective crushing, milling and mechanical classification (separation) and magnetic separation. The method provides the highest degree of ferrite recovery. The exemplary systems for carrying out the method of the invention are shown on
The screened fractions separated on a deck screen, i.e. fractions of the size smaller than 1 mm, are in the next step subject to separation in an electromagnetic separator with migrating magnetic field, where after separating a non-magnetic fraction (contaminants), a ferrite fraction, which constitutes a filler for a heavy liquid suspension, is obtained. The electromagnetic separator with migrating magnetic field (defined also as the electromagnetic separator with running magnetic field) is an essential element of the separation system, since it removes ultimately undesired non-magnetic fractions. It should be also emphasized that in the case of the method of the invention, other types of electromagnetic separators, for instance belt separators, will not separate non-magnetic contaminants with sufficient efficiency. In the implementation of the method of the invention a magnetic separator was used as described in the publication by Hycnar J. J., Kochański B., Tora B., “Otrymywanie i właściwości pyłu magnetyc
nego
uboc
nych produktów spalania w
gli”, Inżynieria mineralna, July-December 2012. However, in order to separate magnetic contaminants from finely grained ferrite, magnetic separators described in the patent descrptions PL59502B1, U.S. Pat. Nos. 1,933,995, 8,715,494, and US20130256233 may also be used.
The top fractions separated on a deck screen, i.e. with grains of the size greater or equal to 1 mm, are milled in a ball mill. Instead of the ball mill, other finely grinding mills, such as a bead, tower, quern, stream, ultrasound mill etc. may be used. Fraction obtained by milling is recycled to the screen to be separated again. In this system, metallic fraction of the grain size larger than 1 mm is removed periodically.
The system for conducting the method of the invention is further provided with a light fraction separator, such as a pneumatic separator. It is located at the end of the screen, to enable separation of fine non-magnetic fractions (e.g. dusts), but at the same time enable earlier screening-off the fine ferrite fractions.
The system described above for ferrite filler production may be expanded using additional elements, which improve efficiency of the process and enable greater control of ferrite filler properties (e.g. granulometric characteristics). The example of the system is shown in
Due to the use of roll crushers, grains of ferrite are subjected to comminution, and the remaining metal (steel and aluminium) grains are compressed and increase their size. It is therefore easily possible to separate them from the comminuted ferrite grains.
The comminuted fraction is passed from the roll crusher to a two-deck screen with cut-off values of 4 and 1 mm. The ferrite fraction separated therewith with grain sizes less than 1 mm is then forwarded to a magnetic separator with migrating magnetic field, the ferrite fraction of the grain sizes of 1-4 mm is forwarded to a ball mill to be further comminuted and directed again to the two-deck screen, and the fraction with grain sizes above 4 mm is a metallic fraction to be eliminated from the system for other uses.
The optimum system for conducting the method of the invention is presented in the diagram in
The method of the invention is advantageous in that it enables controlling sizes of the obtained grains. It is also possible to control the amount of the ferrite fraction obtained by the method of the invention.
The manufacturing process conducted according to the diagram presented on
Operation of the system in the batch mode comprises screening the determined amount of the material on the screen, while the screened fractions are collected in receptacles, and subsequently each fraction is subject to comminution and classification in suitable systems, as presented in
The ferrite fillers obtained by the above-described process have properties close to the properties of the presently used heavy liquid fillers, such as the magnetite (MP) and ferrosilicon (SiFe) fillers.
The ferrite fillers of the invention exhibit magnetic properties close to the MP and SiFe fillers available on the market. Studies conducted by the inventors concerning magnetic properties of the ferrite fillers revealed that they have magnetic susceptibility not much lower than the industrial magnetite and fulfil requirements of the relevant standard.
The inventors conducted also the studies concerning assessment of stability of the heavy liquids obtained with the ferrite fillers. The sedimentation tests allow to conclude that suspensions made from the magnetite and ferrite filler behave similarly.
The examination of the properties of ferrite made by method of the invention reveal that it may be used as a filler for heavy liquid suspensions. It may be used alone or in combination with available fillers such as magnetite.
Feed in the ferromagnetic fraction electronic waste was subjected to the process of selective comminuting in roll crushers, ball mill and screening the ferromagnetic fraction along with dedusting. The studies lead to obtaining the optimum scheme of isolating the ferrite fraction presented in
In this system, it is necessary to combine a roll crusher with a screen equipped with sieves of a size larger or equal to the lower limit of the size grade of the feed. In this way, from the feed having granulometric characteristic of 6.3-25 mm, the product of 0-28 mm is obtained, from which a metallic ferrite-free fraction of 10-28 mm is screened off. The 6.3-10 mm fraction is subjected to crushing in a roll crusher in system II and classification in the one-deck screen, where a metallic fraction of 6.3-12 mm and a ferrite fraction of 0-6.3 mm are obtained. Both fractions from the second and third screens are combined and recycled to the first screen, where 0-1 and 1-6.3 mm grain fractions are screened off. The 1-6.3 mm fraction is subject to the subsequent crushing in a roll crusher (system III) and screening in the 4 and 1 mm sieves. The contaminated 1-4 mm ferrite fraction is collected in a charging hopper and milled in a periodically operating ball mill. The chart shown in
Properties of the filler of the invention made from the ferrite fraction (OF) and, for the comparison, the fillers used in industry: magnetite (MP) and ferrosilicon (Si—Fe) filler are examined.
Results of the examination of humidity, and density and bulk density are presented in Table 1.
Results of the examination were presented in Table 2 and in
In the case of a ferrite filler, its preparation process allowed to obtain the contents of particular size grades close to the magnetite filler.
To determine the magnetic properties of the ferrite obtained by the method of the invention and the industrial fillers: magnetite (MP) and ferrosilicon (Si—Fe) the following measuring methods were used:
a) magnetometry of the vibrating sample;
b) Mössbauer spectroscopy
c) magnetic separation.
The examination was conducted at the ambient temperature (20° C.=293 K)
By means of a precision vibrating magnetometer, magnetization measurements of samples in the function of the magnetic field intensity generated by an electromagnet were conducted. Plots of this relationship for the particular samples are presented in
To refer the results to the standard PN-92/G-04601, values of magnetization for Si—Fe, MP and OF samples were compared at the magnetic field intensity of 3 kOe (which corresponds to 240 kA/m listed in the standard) with the magnetization value at the same field intensity for the sample of the industrial magnetite (MP). In this way, values of relative magnetic susceptibility for these samples relative to magnetite were obtained. The corresponding values for magnetization and relative susceptibility are listed in Table 3.
The above results demonstrate that the ferrite filler samples obtained from processing of the magnetic fraction from the printed circuit boards have the magnetic susceptibility not much lower than the industrial magnetite and fulfil standard requirements in this field.
The remaining examination confirmed also the corresponding properties of the ferrite filler (data not presented).
The suspensions were prepared according to the requirements of the standard. The calculated amount of the filler was weighed, placed in a cylinder and water at the temperature of 20° C. was poured to obtain precisely 0.5 dm3 of the suspension. The suspensions were then mixed and left for 30 minutes to thoroughly wet the grains of the filler. Immediately before the measurement the suspensions were once again mixed thoroughly and, at the start of a stop-watch readings of the turbidity level at the height scale were recorded. In the first phase, the readings were taken every 5 seconds, and subsequently every 10 and 20 seconds. The last measurement was made after 4 minutes of sedimentation.
The measurement was based on reading of the height of the border between the clear water layer, and the concentrating suspension layer. In the case of suspensions where the border was invisible, the sediment height was read.
The results of the sedimentation tests are presented in
Analysis of the results of the sedimentation tests leads to a conclusion that the suspensions behave similarly. The values of the final concentrations, and weight and volume parts of the sediments are on the same level (data not presented).
| Number | Date | Country | Kind |
|---|---|---|---|
| PL420048 | Dec 2016 | PL | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2017/058527 | 12/29/2017 | WO | 00 |
