We've documented many times that the Ash which is co-produced by our economically essential use of Coal in the generation of truly reliable and genuinely affordable electric power can be and should be treated as a valuable resource.
Aside from it's indisputable and well-established utility as a raw material for the making of Portland-type cement and as a property-enhancing fine aggregate for blending into cement, to make stronger, more chemically resistant concrete, Coal Ash can also, as explained by our USDOE in:
West Virginia Coal Association | USDOE Says Coal Ash Could End Aluminum Ore Imports | Research & Development; concerning, in part, the USDOE reports:
"'Economic Metal Recovery from Fly Ash'; Symposium on Resource Recovery and Environmental Issues of Industrial Solid Wastes; 1981; Oak Ridge National Laboratory, USDOE; Abstract: Although most coal combustion ash produced in the United States is discarded as a waste, results are presented to show that fly ash can be an economical source of Al2O3, Fe2O3, and possibly several other metals, many of which are presently being imported"; and:
"Resource Recovery from Coal Residues; 73rd Annual Meeting of the American Institute of Chemical Engineers; 1980; Oak Ridge National Laboratory; USDOE; Abstract: Several processes are being developed to recover metals from coal combustion and conversion residues. Methods to obtain substantial amounts of aluminum, iron, and titanium from these wastes are presented. ... A cursory look at the content of fly ash enables one to see the merits of recovery of these huge quantities of valuable resources. The major constituents of fly ash of most interest are aluminum (14.8%), iron (7.5%), and titanium (1.0%). If these major elements could be recovered from the fly ash produced in the United States (60 million tons/year), bauxite would not have to be imported, iron ore production could be increased, and titanium production could be doubled";
serve as an economical ore of several valuable metals, with Aluminum predominant in volume. And, although our USDOE, some of it's precedent agencies, and other entities in the United States have, as seen for just one example in:
West Virginia Coal Association | Iowa Improves Recovery of Aluminum from Coal Ash | Research & Development; concerning: "United States Patent 4,362,703 - Process for Preparing Cryolite from Fly Ash; 1982; Assignee: Iowa State University Research Foundation; Abstract: Cryolite (Na3AlF6) as a source of aluminum is prepared from coal fly ash by reacting the aluminum oxide (Al2O3) in fly ash with phosphoric acid to form aluminum phosphate, which is then converted to sodium aluminate by reaction with sodium hydroxide, and the sodium aluminate is converted to cryolite by reaction with hydrofluoric acid (HF), or equivalent reagent providing H+ and F- ions. Aluminum is thereby obtained from fly ash in a preferred form (as cryolite) for use in producing metallic aluminum";
developed the necessary technologies to extract, for example, Aluminum, from Coal Ash, it is, as seen in our report of:
West Virginia Coal Association | China Extracts Aluminum Ore from Coal Ash | Research & Development; concerning: "China's Shenua to Produce Alumina from Coal Ash; 2011; China's Shenhua Group began construction Sunday of a coal ash-based alumina refinery in the Inner Mongolia autonomous region, the official Xinhua news agency said. ... At an aluminium conference in (China) earlier this month, (it was stated that) "fly ash ... will probably become the important alternative resource for alumina production in China";
China who are actually reducing such technologies to commercial, industrial practice.
As in our above citation of our report concerning "United States Patent 4,362,703 - Process for Preparing Cryolite from Fly Ash", technologies for recovering Aluminum, and most of the other available metals, from Coal Ash involve chemical extractions using solutions of acids or bases, or both, to first dissolve the metals and then precipitate their salts, which can then be refined using conventional processes.
However, such techniques aren't economically or technically suitable for the recovery of the Iron in Coal Ash, which, Iron compounds, as in the above-cited USDOE report: "Resource Recovery from Coal Residues; 73rd Annual Meeting of the American Institute of Chemical Engineers; 1980; Oak Ridge National Laboratory", comprises on average a significant "7.5%" of Coal Ash, and which, in fact, can interfere with the chemical extraction of Aluminum and other metals, aside from being present in high enough volumes to be itself worth recovering.
In acknowledgment of those facts concerning Iron, the USDOE and one of it's contractors proposed, as in:
West Virginia Coal Association | Iowa Mines Metals from Coal Ash for the USDOE | Research & Development; concerning, in part: "'United States Patent 4,386,057 - Recovery of Iron Oxide from Coal Fly Ash'; 1983; Assignee: The United States of America; The U.S. Government has rights in this invention pursuant to Contract No. W-7405-ENG-82 between the U.S. Department of Energy and Ames Laboratory; Abstract: A high quality iron oxide concentrate, suitable as a feed for blast and electric reduction furnaces is recovered from pulverized coal fly ash. The magnetic portion of the fly ash is separated and treated with a hot strong alkali solution which dissolves most of the silica and alumina in the fly ash, leaving a solid residue and forming a precipitate which is an acid soluble salt of aluminosilicate hydrate. The residue and precipitate are then treated with a strong mineral acid to dissolve the precipitate leaving a solid residue containing at least 90 weight percent iron oxide";
first extracting an Iron-rich "magnetic portion" from the bulk of the Coal Ash, then treating that "magnetic portion" chemically to extract residual "silica and alumina", thus resulting in a product consisting almost entirely of pure Iron ore, "iron oxide", which could, we submit, be added to the natural Iron ore being fed into any conventional Iron or steel refinery.
And, herein, we learn that China has further established and developed the technology for extracting that Iron-rich "magnetic portion" from Coal Ash, thus making it available as an Iron Ore for further, conventional refining. As seen, with comment appended, in excerpts from the initial link in this dispatch to:
"United States Patent 8,505,735 - Vertical Ring Magnetic Separator for De-Ironing of Pulverized Coal Ash
August 13, 2013
Inventors: Jianguo Han, et. al., China
Assignee: China Shenhua Energy Company Limited, Beijing
Abstract: A vertical ring magnetic separator for de-ironing of coal ash comprises a rotating ring, an inductive medium, an upper iron yoke, a lower iron yoke), a magnetic exciting coil, a feeding opening, a tailing bucket and a water washing device. The feeding opening is used for feeding the coal ash to be de-ironed, and the tailing bucket is used for discharging the non-magnetic particles after de-ironing. The upper iron yoke and the lower iron yoke are respectively arranged at the inner and outer sides of the lower portion of the rotating ring. The water washing device is arranged above the rotating ring. The inductive medium is arranged in the rotating ring. The magnetic exciting coil is arranged at the periphery of the upper iron yoke and the lower iron yoke so as to make the upper iron yoke and the lower iron yoke to be a pair of magnetic poles for generating a magnetic field in the vertical direction, wherein the inductive medium is layers of steel plate meshes, each steel plate mesh is woven by wires, and ridge-shape sharp corners are formed at the edges of the wires. A method for magnetically separating and de-ironing of coal ash, utilizes the vertical ring magnetic separator for de-ironing of coal ash. By adopting the vertical ring magnetic separator and the method of magnetic separation for de-ironing, the de-ironing efficiency is improved by at least 20%.
(Note: The full patent document includes schematics to which the unabridged Abstract makes frequent reference. We can't include the schematics in this dispatch, though they will be accessible via the various links; and, we have thus edited our excerpts from the Abstract accordingly. The drawings make the description much more clear.)
Claims: A vertical ring magnetic separator for de-ironing of coal ash, wherein, the vertical ring magnetic separator comprises a rotating ring, an inductive medium, an upper iron yoke, a lower iron yoke, a magnetic exciting coil, a feeding opening, a tailing bucket and a water washing device, wherein the feeding opening is used for feeding the coal ash to be de-ironed, the tailing bucket is used for discharging the non-magnetic particles after de-ironing, the upper iron yoke and the lower iron yoke are respectively arranged at the inner and outer sides of the lower portion of rotating ring, the water washing device is arranged above the rotating ring, the inductive medium is arranged in the rotating ring, the magnetic exciting coil is arranged at the periphery of the upper iron yoke and the lower iron yoke, so as to make the upper iron yoke and the lower iron yoke to be a pair of magnetic poles for generating a magnetic field in the vertical direction, wherein the inductive medium is layers of steel plate meshes, each steel plate mesh is woven by wires, and the edges of the wires have prismatic sharp angles, and the vertical ring magnetic separator provides a magnetic field strength of at least 15,000 Gauss.
(A "Gauss", as seen in:
Gauss (unit) - Wikipedia, the free encyclopedia; is the standard unit of measurement for the strength of a magnetic field. And, although "15,000 Gauss" is a pretty strong magnet, it still falls, for instance, well within the range of "medical magnetic resonance imaging machine"s. And, oher references inform that the electromagnets used to pick up junked cars and such in scrap yards can have strengths of about 20,000 Gauss. So, this is a practical sort of device.)
The vertical ring magnetic separator ... wherein the vertical ring magnetic separator further comprises a pressure balance chamber water jacket disposed adjacent to the magnetic exciting coil (and) wherein the magnetic exciting coil is flat wire solenoid coil which is double glass envelope enamelled aluminum (and) wherein the layer spacing of the steel plate meshes is 2-5 mm (and) wherein the layer spacing of the steel plate meshes is 3 mm.
(We're not reproducing all of the details. But, the sizes, materials of construction, and design of the thing are thoroughly specified and described.)
The vertical ring magnetic separator ... wherein the vertical ring magnetic separator further comprises a pulsating mechanism coupled with the tailing bucket via a rubber plate.
A method of magnetic separation for de-ironing of coal ash using the vertical ring magnetic separator according (as claimed above), wherein the method comprises:
a. preparing the coal ash into a slurry having a predetermined solid content;
b. magnetically separating the slurry by the vertical ring magnetic separator;
c. measuring the Fe content in the slurry after magnetically separating;
d. when the Fe content in the slurry is lower than or equal to a predetermined content, discharging the slurry; when the Fe content in the slurry is higher than the predetermined content, returning the slurry to the step b, and magnetically separating the slurry by the vertical ring magnetic separator once more.
The method ... wherein when magnetically separating the slurry by the vertical ring magnetic separator, the vertical ring magnetic separator provides a magnetic field strength of 15,000-20,000 Gauss.
The method ... wherein the method further comprises ... pressure-filtering the discharged slurry to a filtered cake.
The method ... wherein ... the coal ash is prepared into the slurry having a solid content of 20-40 wt %.
Background and Field: The present invention relates to a magnetic separation apparatus and method, and in particular relates to a vertical ring magnetic separator for de-ironing of coal ash and a method of magnetic de-ironing by using the magnetically separator.
The coal ash is a waste discharged from the coal-combustion power station.
The coal ash contains a number of components that can be utilized, such as aluminum oxide, silicon oxide and the like. These useful components, if being extracted, can facilitate a highly efficient complex utilization for the coal ash.
However, during extracting of the useful components of the coal ash, the existence of iron oxide contained in the ash will affect the purity of the extracts. Therefore, it is of great importance to remove iron from the coal ash, for improving the purity of the useful components and improving the complex utilization for the coal ash.
The method of magnetic separation generally used for removing iron from the coal ash is mainly dry magnetic separation, i.e. passing the coal ash through a powerful magnetic separator directly. However, in case of low content of iron impurities (when the content of iron oxide is lower than 5%) in the coal ash ...it is difficult to ... remove the iron impurities completely.
Currently, vertical ring magnetic separators are used to select from weak magnetic Iron ore for finally obtaining Iron ore having a certain grade as required. Therefore, their structure and magnetic field strength are designed with respect mainly to iron selecting, not de-ironing. The prior vertical ring magnetic separators have the circular rod shaped stainless steel media as magnetic media, which have relatively large spacing therebetween so as to avoid blocking of the medium rod by the iron ore during magnetically separating. However, during magnetic de-ironing from the coal ash, the spacing between the media is too large, thus the particles in the coal ash which have small granularity and relatively weak magnetism would pass through the media, rather than adsorb by the media, thus decreasing the effect of magnetic separation.
In the traditional magnetic separation applications, the structure of vertical ring magnetic separators are configured to be fed from its upper portion and discharged from its lower portion. However, during de-ironing of the coal ash, as the iron-containing mineral have a relatively weak magnetism, if such upper portion feeding means is employed, it is possible for the iron-containing mineral to penetrate through the media under gravity, rather than being adsorbed, thus further decreasing the effect of magnetic de-ironing.
Summary: The vertical ring magnetic separator of the invention for de-ironing from coal ash comprises a rotating ring, an inductive medium, an upper iron yoke, a lower iron yoke, a magnetic exciting coil, a feeding opening, a tailing bucket and a water washing device, wherein the feeding opening is used for feeding the coal ash to be de-ironed, the tailing bucket is used for discharging the non-magnetic particles after de-ironing, the upper iron yoke and the lower iron yoke are respectively arranged at the inner and outer sides of the lower portion of the rotating ring, the water washing device is arranged above the rotating ring, the inductive medium is arranged in the rotating ring, the magnetic exciting coil is arranged at the periphery of the upper iron yoke and the lower iron yoke so as to make the upper iron yoke and the lower iron yoke to be a pair of magnetic poles for generating a magnetic field in the vertical direction, wherein the inductive medium is layers of steel plate meshes, each steel plate mesh is woven by wires, and the edges of the wires have prismatic sharp angles.
The present invention further provides a method for magnetic de-ironing of coal ash with the above-said vertical ring magnetic separator ... .
By means of the magnetic separation apparatus and the method of the present invention, in case of relatively low content of Fe impurities in the coal ash, the Fe impurities are removed more completely. Compared with the prior method for de-ironing of coal ash, the Fe removing efficiency is improved by at least 20%, thus significantly relieving the burden of de-ironing from solution in the subsequent processes, thereby reducing the production cost and improving the production efficiency."
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The point of it all is "reducing the production cost and improving the production efficiency" of "the subsequent processes" which extract Aluminum, the primary product, and other metals from the Coal Ash.
There isn't anything truly revolutionary in this invention. As noted above, in our prior report concerning "United States Patent 4,386,057 - Recovery of Iron Oxide from Coal Fly Ash", the potential was long ago identiftied.
And, as reported by the US EPA, in:
http://www.epa.gov/osw/nonhaz/
more than forty percent of conventionally-mined Iron ore is treated and concentrated by magnetic separation processes as a standard practice.
But, China's Shenhua have improved and adapted the already existing technology to make it more applicable to Coal Ash.
There is no indication herein, and we have so far found no separate reference indicating, what they intend to do with the extracted Iron ore compounds.
However, as can be learned via:
UPDATE 1-China's July iron ore imports hit record high | Reuters; "'China's July Iron Ore Imports Hit Record High'; August 8, 2013; July imports reach 73.14 million tons, up 17 pct on month";
China has to import a lot of the Iron ore they need, so there would be a ready domestic market for it.
On the other hand, as can be learned from the United States Geologic Survey, via:
http://minerals.usgs.gov/
our domestic conventional Iron ore production, combined with recycling, pretty much balances out our consumption; so, the development of new United States sources of Iron ore isn't quite the pressing issue here that it is in China.
However, since the Iron needs in any case to be removed from Coal Ash, prior to processing the Coal Ash for the recovery of Aluminum and other metals, that would almost be like "found money", wouldn't it? And, sales of co-produced Iron ore would serve to reduce the final costs of Aluminum ore and Aluminum, and other metals, like Gallium, ultimately produced from Coal Ash.
And, it all would serve to further increase the value of our by far most abundant and most valuable domestic fossil energy resource, Coal; and, to put more United States citizens to work; and, maybe, to give us something we could actually export and maybe earn ourselves a little foreign exchange with.