We've documented for you in a number of past reports that Coal Ash can serve as a viable, and valuable, source of Aluminum, or Aluminum Ore.
Those reports have included, for a few examples:
West Virginia Coal Association | Iowa Mines Metals from Coal Ash for the USDOE | Research & Development; concerning, in part: "United States Patent 4,397,822 - Process for the Recovery of Alumina from Fly Ash; 1983; Inventor: Marlyn Murtha, Iowa; Government Interests: The United States 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: An improvement in the lime-sinter process for recovering alumina from pulverized coal fly ash is disclosed. The addition of from 2 to 10 weight percent carbon and sulfur to the fly ash-calcium carbonate mixture increase alumina recovery at lower sintering temperatures";
West Virginia Coal Association | USDOE Says Coal Ash Could End Aluminum Ore Imports | Research & Development; concerning: "Resource Recovery from Coal Residues; 73rd Annual Meeting of the American Institute of Chemical Engineers; 1980; G. Jones, et. al.; Oak Ridge National Laboratory; USDOE; Abstract: Several processes are being developed to recover metals from coal combustion and conversion residues. 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".
Although more than thirty years old, the above report is especially significant, we think, since it demonstrates that if we could all just get our heads screwed on straight about the true value of Coal, and of Coal-use residuals, we could, since Aluminum is such a strategically important basic metal of commerce and industry, and, since we have no commercially-viable deposits of natural Aluminum Ore in the United States, and thus must import all of the non-recycled Aluminum our economy demands, put ourselves in a much, much more secure strategic and economic position relative to the rest of the world.
And, China, who - - as we've many times documented, as, for instance, in:
West Virginia Coal Association | China Makes "Huge Profits" from Coal Liquefaction | Research & Development; concerning: "'China Coal Producer Reaps Huge Profits From CTL Project'; Shenhua Group, China's largest coal producer, has made huge profits from its pilot coal-to-liquid (CTL) project in north China in the first three months of this year, a company executive said";
- - isn't, as we seem to be, embarrassed, or even repelled, by her Coal riches, and has no problem with openly and happily employing Coal to it's fullest and highest value, is, as seen in:
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'";
in the process of exploiting her better-than-free Coal Ash raw material resource for it's Aluminum content.
And, herein, we see that she has begun to develop the ways and means to do a better job of extracting Aluminum from Coal Ash, along with a co-product of some additional value.
Comment follows excerpts from the initial link in this dispatch to:
"United States Patent 7,871,583 - Recovery of Silica Followed by Alumina from Coal Fly Ash
(First, to get it out of the way, the "Silica" is, as seen in:
Silicon dioxide - Wikipedia, the free encyclopedia; "Silica is used primarily in the production of glass for windows, drinking glasses, beverage bottles, and many other uses. The majority of optical fibers for telecommunications are also made from silica. It is a primary raw material for many whiteware ceramics such as earthenware, stoneware, porcelain, as well as industrial Portland cement";
a product of some broad commodity use; and, although we can't document it specifically via concise reference, Silica can, just like whole Fly Ash, as seen in:
West Virginia Coal Association | Iowa Makes Coal Ash-reinforced Plastic Sewer Pipes | Research & Development; concerning: "United States Patent 8,043,548 - Polymer Mortar Composite Pipe Material and Manufacturing Method; 2011; Assignee: Iowa State University Research Foundation; Abstract: Composite material and plunger-cast pipe manufacturing method and system wherein the composite material includes waste, chemically unmodified PET material, one or more waste filler materials (e.g. ... waste coal combustion by-products)";
be used as a value-extending filler in some types of molded plastics. )
Date: January, 2011
Inventors: Qin Jinguo and Gu Songqing, China
Assignee: Pingshuo Industrial Limited, Shanxi Province
A process for recovery of silica and alumina from fly ash, in which, Si (Silicon) is leached out from the fly ash in the form of Na2SiO3 (Sodium Silicate, aka Water Glass) using a NaOH (Lye) solution ... followed by separation to obtain a Na2SiO3 solution and a residue having Al--Si ratio greater than or equal to 2; vaporizing the solution to obtain Na2SiO3 solutions of various concentrations, or producing silica by carbonation, and producing Al2O3 by prior art methods from residues obtained after alkali-leaching, ultimately producing filler or cement from the residue after the recovery of Al. The method permits recovery of Al2O3 directly from fly ash by removing Si before recovering the Al, which raises the Al-Si ratio of the residue after alkali-leaching and thus simplifies the recovery of Al2O3 and raises the rate of Al recovery from fly ash. The invention further includes calcining high Al coal gangue, kaolinite and middle-low-class bauxite at 900-1100C.
(So, the process also results in production of a solid waste that, like raw Fly Ash, can be used as a component of Concrete, a "filler or cement from the residue after the recovery of Al". The final sentence, about "calcining high Al coal gangue, kaolinite and middle-low-class bauxite" seems a somewhat separate, though related, issue; and, we're surprised it's inclusion. almost as an aside, was allowed to stand by the patent examiners. But, it serves to further confirm the value of Coal-associated minerals.)
Claims: A process for recovering silica and alumina from coal fly ash, comprising:
a) alkali-leaching Si from fly ash at 70-150 C with a NaOH solution (as specified), then separating a Na2SiO3 solution from a residue ... .
b) concentrating the Na2SiO3 solution by vaporization, or obtaining silica by carbonation; and:
c) producing Al2O3 from the residue ... .
The process ... wherein the fly ash is activated by one or more of the following steps:
The process ... wherein the fly ash is activated by one or more of the following steps:
a) roasting-activating the fly ash,
b) steeping fly ash in H2SO4 (Sulfuric Acid) solution,
c) steeping fly ash in NaOH solution.
The process ... wherein the fly ash is a high Al coal gangue, a kaolinite or middle-low-class bauxite, and further comprises activating the fly ash at 900-1100 C.
The process ... further comprising producing filler or cement using the residue created after producing Al2O3.
The process ... wherein the fly ash is a high Al coal gangue, a kaolinite or middle-low-class bauxite, and further comprises activating the fly ash at 900-1100 C.
The process ... further comprising producing filler or cement using the residue created after producing Al2O3.
(Note that the "carbonation" specified as an alternative would likely be accomplished with the help of good old CO2; and, it lead to the production of an intermediate byproduct, sodium carbonate/bicarbonate, which can be further processed for recycling back into the system. That's a technical refinement a bit beyond the scope of our reportage herein, but which is addressed to some extent in the full Disclosure.)
Background and Field: The present invention refers to fine utilization of fly ash, and particularly to a process for recovery of silica and alumina from fly ash, and more specifically refers to a process in which silica is firstly recovered from fly ash, remaining an Al - Si ratio greater than or equal to 2, then metallurgical alumina is produced with prior art, the residue of which is used as a filler or to produce cement.
Fly ash is .. a mineral resource.
Fly ash is .. a mineral resource.
It generally contains about 15-40% Al2O3 and mostly above 40% SiO2, even above 40% Al2O3 and about 50% SiO2 in high Al fly ash.
More than 3 hundred million tons of fly ash are discharged ... each year in China, wherein 1 hundred million ton is no less than high aluminum fly ash. If resources from high aluminum fly ash that is being abandoned can be fully recovered, more than 30 million tons of Al2O3 can be produced each year, which is far higher than the total production of Al2O3 today in China (and, it) is therefore ... important for the sustainable development of an aluminum industry in China to develop and use the resources of high Al fly ash.
(The statement that more "than 3 hundred million tons of fly ash are discharged ... each year in China" seems likely to be a tad on the high side, to us. Industry stats don't have anything to do with the process and technology, as certified to be viable by our expert US patent examiners, however.)
The method of recovering Al2O3 from fly ash can be divided into acid methods and alkali methods. With acid processing, damage to SiO2 can be avoided while Al oxide is efficiently recovered from fly ash. But when leaching Al2O3, the disadvantage of acid processing is that a number of soluble impurities such as Fe, Ti, Mg contained in the fly ash are introduced into the solution, so post-treatment must be added; another disadvantage is that apparatus of the acid method needs better acid-corrosion-resistance, so it is rather difficult to make the reaction facility; Another disadvantage regarding the acid process for recovery of Al2O3 from fly ash includes high energy consumption and the necessary cost for environmental protection.
In the 1960's, a soda lime sintering method was used to recover Al2O3 from fly ash in Poland and an experimental plant which produced ten thousand tons of Al2O3 and 100 thousand tons of cement each year was built up there.
The method of recovering Al2O3 from fly ash can be divided into acid methods and alkali methods. With acid processing, damage to SiO2 can be avoided while Al oxide is efficiently recovered from fly ash. But when leaching Al2O3, the disadvantage of acid processing is that a number of soluble impurities such as Fe, Ti, Mg contained in the fly ash are introduced into the solution, so post-treatment must be added; another disadvantage is that apparatus of the acid method needs better acid-corrosion-resistance, so it is rather difficult to make the reaction facility; Another disadvantage regarding the acid process for recovery of Al2O3 from fly ash includes high energy consumption and the necessary cost for environmental protection.
In the 1960's, a soda lime sintering method was used to recover Al2O3 from fly ash in Poland and an experimental plant which produced ten thousand tons of Al2O3 and 100 thousand tons of cement each year was built up there.
(We've mentioned a variation, or relative, of the "soda lime sintering method", known as the "cal-sinter process" or "lime-sinter process", previously, as for one example in our introductory reference to our earlier report of "United States Patent 4,397,822 - Process for the Recovery of Alumina from Fly Ash", and might address it again in future reports. The newer methods for extracting Aluminum ore from Coal Ash, as represented by the process of our subject, sound more efficient; and, the "soda lime" and "cal-sinter" processes might be considered out of date. But, note that, at one time, in Poland, Aluminum and cement were being produced on an industrial basis, using that basic technique, from Coal Fly Ash.)
In the 1980's, Metallurgy Institute of Anhui Province and Hefei Cement Institute in China declared the achievement of recovering Al2O3 from fly ash by sintering limestone and dissolving Na2CO3 and producing cement with the residue.
This achievement passed the expert examination in March 1982. The process of recovering Al2O3 from fly ash by soda lime sintering, and producing cement with the residue studied by Building Material Institute of Ningxia Autonomous District was examined by Technology Committee of Ningxia Autonomous District in September 1987. The examination of the project entitled "Industrialization of recovery Al2O3 and producing cement from fly ash", which was (further) researched and developed ... in Inner Mongolia Autonomous Region ... and a pilot study of nearly 5000 ton-class was completed ... .
But the process of treating high Si and Al-containing fly ash by alkali methods normally has such disadvantages as high complexity, high time consumption, large quantities of processing materials, large investment of facility, high energy consumption and high cost. Furthermore the amount of residue is several times that of fly ash; the market coverage of cement made from the residue is limited; the comprehensive economic efficiency and the level of synthetic utilization are low. All of these factors inhibit the use of alkali methods in synthetic utilization of fly ash.
Summary: An object of the present invention to provide a process for recovering silica and alumina from fly ash, in which silica is firstly recovered from the fly ash ... , then metallurgical alumina is produced using conventional methods. A residue can be used to produce filler or cement."
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In other words, we can extract Aluminum ore and industrially useful Silica from Coal Ash; and, the residue from those extractions can be consumed in the manufacture of Cement.
Sounds like that might pretty much take care of any Coal Ash "disposal" issues we might have, doesn't it?
And, according to our own United States Department of Energy, in our above-cited report concerning "Resource Recovery from Coal Residues", such extraction of Aluminum from the Coal Ash we have available to us could put an end to our dependence on foreign sources of supply for that strategically important metal.
In any case, surprising as it might be, China has gone on to develop even more efficient ways of extracting Aluminum from Coal Ash; and, we will address those more recent developments in coming reports.
The upshot of it all is, though, that:
The solid residues co-produced by our economically essential use of Coal in the generation of abundant and truly affordable electric power constitute a valuable mineral resource.
That is the way we need to start thinking of, and treating, Coal Ash.