United States Patent: 8968688
In a prior report, now accessible via:
Massachusetts Recovers Rare Earth Metals from Coal Ash | Research & Development | News; concerning: "US Patent Application 20130287653 - Recovery of Rare Earth Elements and Compounds from Coal Ash; 2013; Inventors: Prakash B. Joshi, et. al., MA; (Presumed Assignee of Rights: Physical Sciences, Incorporated", or, interestingly, just "PSI"); Abstract: Rare earth elements are recovered from coal ash";
we documented that a rather intriguing company in Massachusetts, often called just "PSI", had developed technology for recovering a class of elements that are appropriately known as "Rare Earth Elements" from Coal Ash.
In that report, we documented to a certain extent both how important and how rare the Rare Earth Elements actually are.
The only current domestic United States source of those "Elements" is a once-mothballed mine in California that only recently reopened as a result of our perceived vulnerability to potentially unfriendly, or at least politically and diplomatically unreliable, foreign sources of supply.
More about the situation can be learned via:
Going Critical: Being Strategic with Our Mineral Resources | Science Features; which reports: "Rare-earth elements are necessary components of more than 200 products across a wide range of applications, especially high-tech consumer products, such as cellular telephones, computer hard drives, electric and hybrid vehicles, and flat-screen monitors and televisions. Significant defense applications include electronic displays, guidance systems, lasers, and radar and sonar systems. ... Although the amount of REE used in a product may not be a significant part of that product by weight, value, or volume, the REE can be necessary for the device to function. ... . Beginning in 1990 and beyond, supplies of REEs became an issue as the Government of China began to change the amount of the REEs that it allows to be produced and exported. The Chinese Government also began to limit the number of Chinese and Sino-foreign joint-venture companies that could export REEs from China".
We remind you that we, in the United States of America, are equally dependent on foreign sources for our supply of virgin Aluminum metal and Aluminum ore, "bauxite", even though, as confirmed by the United States Department of Energy in our report of:
USDOE Says Coal Ash Could End Aluminum Ore Imports | Research & Development | News; concerning, in part: "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. Methods to obtain substantial amounts of aluminum, iron, and titanium from these wastes are presented. The primary purpose of our investigation is to find a process that is economically sound or one that at least will partially defray the costs of waste processing. 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";
by using known processes for doing so, we could make ourselves entirely independent in our supply of Aluminum by extracting it from Coal Ash. And, the United States Government just days ago confirmed the same to be true of Rare Earth Elements, via their issuance and allowance, in response to "US Patent Application 20130287653", of:
"United States Patent 8,968,688 - Recovery of Rare Earth Elements and Compounds from Coal Ash
Recovery of rare earth elements and compounds from coal ash - Physical Sciences, Inc.
Date: March 3, 2015
Inventors: Prakash B. Joshi, et. al., MA
Assignee: Physical Sciences Incorporated, Andover, MA
(We won't belabor the issue here. But, we refer you to our prior report of "US Patent Application 20130287653" for more information concerning "Physical Sciences Incorporated", or "PSI", and their rather "strategic" interests, and refer you as well to the above-cited report "Going Critical: Being Strategic with Our Mineral Resources". You should get some inkling from all of that as to why PSI would be interested in obtaining "Rare Earth Elements", and, why we all should care that they do - - especially if they're going to get them from Coal Ash, with the economic value to US Coal Country that would imply.)
Abstract: Rare earth elements are recovered from coal ash. The coal ash with rare earth elements can be treated with a mineral acid to form an aqueous mineral acid solution. The aqueous mineral acid solution can be extracted to form an organic solution that includes the rare earth salts. The organic solution can be mixed with water to form an aqueous solution that includes the rare earth salts. The rare earth elements are separated from the aqueous solution.
Claims: A method of recovering rare earth elements in a form of rare earth salts from coal ash, the method comprising: preprocessing coal ash to concentrate the coal ash; treating the concentrated coal ash that includes rare earth elements with a mineral acid to form an aqueous mineral acid solution that includes rare earth salts and an ash cake, wherein the ash cake is formed free of hazardous elements; evaporating the aqueous mineral acid solution to a concentrate; extracting the concentrated aqueous mineral acid solution to form an organic solution that includes the rare earth salts; mixing the organic solution with water to form a second aqueous solution that includes the rare earth salts; and separating the rare earth salts from the second aqueous solution.
The method ... wherein the mineral acid is nitric acid (and) wherein treating the concentrated coal ash further comprises: heating the mineral acid to approximately 90 C; and exposing the concentrated coal ash to the mineral acid for at least one hour.
The method ... wherein exposing the concentrated coal ash further comprises additional heating of a resulting solution formed when exposing the concentrated coal ash to the mineral acid to generate a more concentrated mixture (and) wherein the extracting the concentrated aqueous mineral acid solution further comprises: mixing the concentrated aqueous mineral acid solution with tributyl phosphate and kerosene; and removing the organic solution from the concentrated aqueous mineral acid solution such that the rare earth salts are substantially removed along with the organic solution.
The method ... wherein extracting the concentrated aqueous mineral acid solution further comprises performing a dry extraction, a liquid extraction, or any combination thereof (and) wherein the dry extraction comprises performing continuous extraction of rare earth salts with tributyl phosphate (and) wherein the liquid extraction comprises: mixing a volume of tributyl phosphate and kerosene equal to a volume of the concentrated aqueous mineral acid solution; and removing the organic solution from the concentrated aqueous mineral acid solution.
The method ... further comprising exposing the concentrated coal ash to a magnetic treatment such that the concentrated coal ash separates into a substantially magnetic portion and a substantially non-magnetic portion of the concentrated coal ash.
(With regards to the above, see our report of:
China Recovers Iron Ore from Coal Ash | Research & Development | News; concerning: "United States Patent 8,505,735 - Vertical Ring Magnetic Separator for De-Ironing of Pulverized Coal Ash; 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".)
The method ... wherein separating the rare earth salts comprises an ion exchange separation using either anion or cation exchange (and) wherein the ion exchange separation leads to rare earth salt mixtures suitable to be converted to mixtures of rare earth oxides and rare metals, the mixtures of rare earth oxides and rare metals are used to make catalysts, magnets, and phosphors.
(Concerning the above, for further information see our prior report of "US Patent Application 20130287653".)
The method ... wherein extracting the concentrated aqueous mineral acid solution forms a second aqueous mineral acid solution (and) further comprising distilling the second aqueous mineral acid solution to recover mineral acid.
(As above, the process allows for the economical recovery of some of the needed reagents.)
The method ... further comprising: recovering the ash cake from the concentrated aqueous mineral acid solution; and using the ash cake in building or road construction materials.
(With regards to the above claim, see, for one example, our report of:
More Coal Fly Ash Facts for Highway Engineers | Research & Development | News; concerning: "Fly Ash Facts for Highway Engineers; American Coal Ash Association; DTFH61-02-X-00044; (for the) Federal Highway Administration; Report Number: FHWA-IF-03-019; June 13, 2003".)
Background and Field: The invention relates generally to recovery of rare earth elements and/or compounds from coal ash.
Rare earth elements can be fundamental to emerging green energy technologies in the United States (e.g., permanent magnet motors for wind turbines and disk drives, hybrid car batteries, compact fluorescent lighting, and/or displays in all types of consumer/defense electronics), as well as other usages such as industrial catalysts for refining heavier crude oil, automobile catalytic converters, and/or as alloying elements. Presently, rare earth elements can be obtained through mining.
Coals from certain regions of the world can be particularly rich in rare earth elements, approaching a total concentration of about 1000 parts-per-million ("ppm"). The combustion of coal in power plants for energy generation concentrates non-volatile minerals in the ash by about ten times, to about 10,000 ppm, or on the order of approximately 1%. Coal ash can be the product of burning coal. Coal ash can be comprised of fly ash and bottom ash. Fly ash can be ash that rises with flue gases. Bottom ash can be ash that is found at the bottom of a furnace. Fly ash can be collected before the flue gases reach chimneys of power plants.
Accounting for process yield and variability in rare earth element content, if rare earth elements are extracted from coal ash, a reasonable fraction of currently available fly ash (e.g., about 10-15%) can be adequate to meet rare earth elements demand in the United States.
Summary: Advantages of the invention include recovering rare earth elements from coal ash.
Another advantage of the invention includes economical production of rare earth elements and/or compounds from alternative, non-mineral raw materials. Another advantage of the invention is the ability to build reliable production capabilities and/or supply chain for rare earth elements and/or byproducts.
Another advantage of the invention is processing fly ash to recover rare earth materials, particularly heavier rare earths, more economically and energy-efficiently per kilogram of rare earth elements than from processing and extracting mineral resources.
(The indication is, that, we can recover rare earth elements "more economically and energy-efficiently" from our domestic Coal Ash than we can from imported natural mineral ores.)
Another advantage includes the beneficiation of coal ash, which is an abundant waste material, for recovering economically useful and marketable industrial materials that include rare earth elements as a significant component.
Another advantage includes energy efficient extraction of rare earth elements, which can save energy use by about 75% relative to conventional mining per unit weight of rare earth elements produced.
In one aspect, the invention involves a method of recovering rare earth elements from coal ash. The method involves treating coal ash that contains rare earth elements with a mineral acid to form an aqueous mineral acid solution. The aqueous mineral acid solution is extracted to form an organic solution that includes the rare earth salts. The organic solution is mixed with water to form an aqueous solution that includes the rare earth salts. The rare earth elements are recovered by separating the rare earth elements from the aqueous solution.
In some embodiments, the coal ash can be exposed to a magnetic treatment such that the coal ash separates into a substantially magnetic portion and a substantially non-magnetic portion of the coal ash.
In various embodiments, extracting the aqueous mineral acid solution forms a second aqueous mineral acid solution. The second aqueous mineral acid solution can be distilled to recover mineral acid.
Detailed Description: A method of processing coal ash can be used to recover rare earth elements in order to, for example, meet critical rare earth element materials needs. The method can employ a closed looped schema e.g., certain materials, such as aqueous mineral acid, can be reused rather than discharged as waste. Since materials are reused, the closed-loop schema can have a lower environmental impact than, for example, mining for rare earth elements.
The method can utilize waste ash, e.g., ash that follows coal combustion, as a resource for rare earth elements. The method can allow beneficiating the waste ash while simultaneously recovering rare earth elements.
Rare earth elements principally include the lanthanide series of the periodic table, but the term can also incorporate scandium and yttrium that are not true lanthanides. Exemplary rare earth elements, include: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc) and yttrium (Y). Rare earth elements can include light rare earth elements, medium rare earth elements, and/or heavy rare earth elements. Exemplary light rare earth elements include Sc, La, Ce, Pr, Nd, and Pm. Exemplary medium rare earth elements include Sm, Eu, and Gd. Exemplary heavy rare earth elements include Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y.
Rare earth elements that are recovered from coal can have a number of applications. For example, some of these coals contain Y, a heavy rare earth element that can be used in compact fluorescent light bulbs. The coals can also contain Nd, a light rare earth element that can be used in permanent magnet motors in hybrid vehicles, wind turbines, and computer disk drives. Other applications for rare earth elements can include, for example, use in aerospace components, high refractive index glass, flint, batteries, catalysts, polishes, lasers, x-ray machines and capacitors.
In some embodiments, fly ash is used to extract the rare earth elements (as opposed to coal ash, which contains both fly ash and bottom ash). Although fly ash and coal ash are not necessarily the same, any of the preceding and/or foregoing methods applied to fly ash can be applied to coal ash and vice versa. In various embodiments, any of the preceding and/or foregoing methods applied to fly ash and/or coal ash can also be applied to bottom ash.
Process parameters (e.g., time, temperature, concentration) are nominal values and can be optimized by one of ordinary skill in the art to improve the yields for rare earth elements from coal ash, depending on, for example, the concentration of rare earth elements in the coal ash.
Ash cake that can be formed in the process of recovering rare earth elements (e.g., the solid residue after mineral acid digestion) can be free of hazardous elements ... (and, the) ash cake formed in this process as a by product can be more environmentally friendly and therefore can be used in applications such as a building or road construction material".
Not only can we recover strategically important rare earth elements, elements critical for some high-tech applications and which must otherwise be imported, from our domestic US Coal Ash, we can do so in a way that has "a lower environmental impact than ... mining for" those "rare earth elements".
Just as our United States Department of Energy confirmed in our above-cited report 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"; and, separately, in our report of:
USDOE 2009 CO2 to Gasoline | Research & Development | News; concerning: "United States Patent 7,592,291 - Method of Fabricating a Catalytic Structure; 2009 Inventors: Harry Rollins, et. al., Idaho; Assignee: Battelle Energy Alliance, LLC, Idaho Falls, ID (USDOE Idaho National Laboratory); Abstract: A precursor to a catalytic structure comprising zinc oxide and copper oxide (and, a) method of hydrogenating a carbon oxide using the catalytic structure is also disclosed, as is a system that includes the catalytic structure. Government Interests: The United States Government has certain rights in this invention pursuant to Contract No. DE-AC07-05ID14517 between the United States Department of Energy and Battelle Energy Alliance, LLC. ... Carbon dioxide gas (CO2) may be converted into liquid fuels such as, for example, hydrocarbon molecules of between about 5 and about 12 carbon atoms per molecule (e.g., gasoline) through multi-step reactions";
the byproducts arising from our economically-essential use of Coal in the generation of abundant and affordable electric power could enable the United States of America to free itself from harmful and dangerous reliance on foreign sources of supply for both strategically critical metals and liquid hydrocarbon fuels; herein, our United States Government further confirms that Coal byproducts, Coal Ash, can, as well, free us from equally-dangerous reliance on foreign sources of supply for the "Rare Earth Elements" that are crucial to many cutting-edge and high-tech industrial and military applications.
Coal and the byproducts of it's use could and should now be viewed and treated as domestic material resources of stunning, almost blinding, value. How and why the truth of that is kept secret and how it isn't, as it were, shouted from the mountain tops of the Mountain State - and all the other Coal-producing, and all the Coal-using, states in the United States of America - is beyond comprehension.