United States Patent: 8728296

We submit today another dispatch further confirming the value inherent in Coal Fly Ash.

We've documented many times that valuable metals can be extracted from Coal Ash, primary among them Aluminum, all raw ore of which the United States now imports.

Another, more modestly important, metal, the ore of which the United States must import, but which can be extracted from Coal Ash, is Gallium.

 

As explained by the United States Geologic Survey, via:

http://minerals.usgs.gov/minerals/pubs/commodity/gallium/mcs-2013-galli.pdf; "Imports of gallium, which supplied most of U.S. gallium consumption, were valued at about $32 million" in 2012.

So, it's not of enough total value to meaningfully affect our balance of trade deficit; but, since the bulk of it is used in high-tech semiconductor applications, it is rather important, even strategic.

And, as we learned in:

China Extracts Aluminum Ore from Coal Ash | Research & Development | News; concerning in part  the news report: "China's Shenua to Produce Alumina from Coal Ash; December 19, 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. Shenhua plans to invest Yuan 135.8 billion ($21.4 billion) in the project, deputy manager Ling Wen is quoted as having said. Located in the Jungar coal mining areain Ordos city, the project will include a 6.6 GW power plant, an alumina plant and a gallium plant";

it is feasible to construct a facility that would be able to extract both Aluminum ore and Gallium from Coal Ash in a single, integrated process; and, thus, the extraction Gallium in concert with the vastly more important Aluminum would simply enhance the value of such an Aluminum "mining" enterprise; and, reduce even further our exposure to foreign sources of supply of strategic minerals and materials.

With regard to Shenhua's above-reported extraction of Gallium from Coal Ash, we documented in our report of:

China Uses CO2 to Recover High-Tech Metal from Coal Ash | Research & Development | News; concerning:  "US Patent Application 20130081954 - Method for Extracting Gallium from Fly Ash; April 4, 2013; Inventor: Dazhao Gu, et. al., China; Assignee: China Shenhua Energy Company, Ltd., Beijing; Abstract: Disclosed is a method for extracting gallium from fly ash, which comprises the following steps: crushing the fly ash and removing Fe by magnetic separation; then dissolving it by using hydrochloride acid to obtain hydrochloric acid leachate; adsorbing gallium contained in the hydrochloric acid leachate with macro-porous cationic resin, followed by eluting to obtain an eluent containing gallium; adding masking agent to mask ferric ion to obtain an eluent containing gallium after masking; adsorbing gallium in the eluent containing gallium after masking with macro-porous cationic resin, followed by eluting to obtain a secondary eluent; adding sodium hydroxide solution into the secondary eluent to react; filtering and removing precipitates after reaction, and then concentrating the filtrate and electrolyzing to obtain metal gallium. The method simplifies the process and improves extraction efficiency of gallium";

new technology Shenhua, the largest Coal-mining company in the world, had developed to accomplish that extraction of Gallium.

And, herein we learn that technical experts in the employ of our United States Government recently confirmed that Shenhua's process of "US Patent Application 20130081954" does represent real and practicable technology, via their issuance, as excerpted from the initial link in this dispatch, of:

"United States Patent 8,728,296 - Method of Extracting Gallium from Fly Ash

Patent US8728296 - Method for extracting gallium from fly ash - Google Patents

Date: May 20, 2014

Inventors: Dazhao Gu, et. al., China

Assignee: China Shenhua Energy Company Limited, Beijing

Abstract: Disclosed is a method for extracting gallium from fly ash, which comprises the following steps: crushing the fly ash and removing Fe by magnetic separation; then dissolving it by using hydrochloric acid to obtain hydrochloric acid leachate; adsorbing gallium contained in the hydrochloric acid leachate with macro-porous cationic resin, followed by eluting to obtain an eluent containing gallium; adding masking agent to mask ferric ion to obtain an eluent containing gallium after masking; adsorbing gallium in the eluent containing gallium after masking with macro-porous cationic resin, followed by eluting to obtain a secondary eluent; adding sodium hydroxide solution into the secondary eluent to react; filtering and removing precipitates after reaction, and then concentrating the filtrate and electrolyzing to obtain metal gallium. The method simplifies the process and improves extraction efficiency of gallium.

Claims: A method for extracting gallium from fly ash, comprising the following steps: a) crushing the fly ash to a size of 100 mesh or smaller, removing iron by wet magnetic separation such that the ferric oxides content in the fly ash is reduced to 1.0 weight % or less, then adding hydrochloric acid into the de-ironed fly ash for an acid-leaching reaction, and subjecting the reaction product to solid-liquid separation, so as to yield a hydrochloric leachate having a pH value in the range of 1-3; b) adsorbing gallium in the hydrochloric leachate by passing the same through a column loaded with a strongly acidic styrene-based cation-exchange resin; eluting the column with water or hydrochloric acid as an eluting agent when the adsorption reaches saturation to obtain a gallium-containing eluent; c) masking ferric ions in the gallium-containing eluent by a masking agent followed by passing the masked eluent through the column loaded with a strongly acidic styrene-based cation-exchange resin; eluting the column with water or hydrochloric acid as an eluting agent when the adsorption reaches saturation to obtain a second eluent; and d) adding an alkali solution into the second eluent, removing precipitates by filtering after reaction, and concentrating the filtrate till both gallium content and sodium hydroxide content (reach specified conditions).

The method ... wherein, in step a), the apparatus used for removing iron by wet magnetic separation is a vertical ring magnetic separator which 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 fly 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, and 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 ridge-like sharp angles. 

The method ... wherein the vertical ring magnetic separator further comprises a pulsating mechanism, which is coupled with the tailing bucket via a rubber plate (and) wherein the inductive medium is provided in the entire circle of the rotating ring.

(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; 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".

for a full description of the Iron separation process being specified herein. Iron/Iron ore is present in high-enough quantities in some Coal Ash to make it's recovery worthwhile on a commercial basis, especially as a byproduct, like Gallium, from a process focused primarily on the extraction from the Coal ash of Aluminum. Otherwise, it needs to be removed inasmuch as is possible from the Ash prior to extracting Aluminum and Gallium, otherwise it interferes with the chemical processes.)

Background and Field: The present invention relates to a method for extracting metal gallium from fly ash and in particular relates to a method for extracting metal gallium from circulating fluidized-bed fly ash. 

Gallium is an important semiconductor material and widely used.

The price of gallium is very high in the international market and thus gallium has a bright prospect.

However, the reserve of gallium is low, only approximately 0.015% in the earth's crust. Gallium almost does not form minerals, but exists with other minerals in form of isomorphism. Therefore, extraction of gallium is considerably difficult.

The recent studies have shown that the fly ash obtained from some places contains a large amount of gallium which even overpasses the gallium level of mineral deposit. . . . As compared with the gallium contents of other resources, the fly ash deserves to be extracted for metal gallium as a raw material.

In light of different conditions of calcinations, the fly ash is classified into pulverized coal-fired boiler fly ash and circulating fluidized-bed fly ash. The pulverized coal-fired boiler fly ash is produced when coal is burned at a very high temperature (1400-1600 C.), in which alumina is in glassy state or present as a mineral form of mullite crystals or corundum crystals of hot aluminum mineral which make such alumina very stable. While the combustion temperature of circulating fluidized-bed fly ash is much lower than that of traditional pulverized coal-fired boiler fly ash, only about 850 C. Different combustion temperatures make a substantial difference in phase composition between the pulverized coal-fired boiler fly ash and circulating fluidized-bed fly ash, that is, amorphous kaolinite enters into the main phase composition of the circulating fluidized-bed fly ash, in which silicon dioxide, alumina and ferric oxide or the like possess excellent activity.

(Note that this process is intended, actually, for Coal Ash originating from "circulating fluidized-bed" boilers, which is different from fly ash originating our good old, more conventional pulverized Coal-fired boilers, but, which Coal-burning technology, as can be learned via:

http://www.fe.doe.gov/education/energylessons/coal/coal_cct4.html; and:

http://energy.gov/fe/science-innovation/clean-coal-research/advanced-combustion-technologies/fluidized-bed-technology;

has been and is being utilized in an increasing number of Coal-fired power plant installations. So, this Gallium extraction method is intended more for use as an adjunct to the newer generation of Coal-fired utility boilers. We remind you, though, as seen for one example in our report of:

Coal Ash a Superior Source of High-Tech Metal | Research & Development | News; concerning, in part: "United States Patent 4,643,110 - The Recovery of Gallium and Germanium from Coal Fly Ash; 1987"; 

thermo-chemical techniques have been established for the extraction of Gallium and other metals from Coal Ash originating in those older, more conventional Coal-fired boilers.)

Summary: The object of the invention is to provide an improved method for extracting metal gallium from circulating fluidized-bed fly ash. 

The method for extracting metal gallium from circulating fluidized-bed fly ash according to the invention comprises the following steps: 

a) crushing the fly ash to a size of 100 mesh or smaller, removing iron by wet magnetic separation such that the ferric oxides content in the fly ash is reduced to 1.0 wt % or less, then adding hydrochloric acid into the de-ironed fly ash for an acid-leaching reaction, and subjecting the reaction product to solid-liquid separation, so as to yield a hydrochloric leachate having a pH value in the range of 1-3; 

b) adsorbing gallium in the hydrochloric leachate by passing the same through a column loaded with a macro-porous cationic resin; eluting the column with water or hydrochloric acid as an eluting agent when the adsorption reaches saturation to obtain a gallium-containing eluent; 

c) masking ferric ions in the gallium-containing eluent by a masking agent followed by passing the masked eluent through the column loaded with macro-porous cationic resin; eluting the column with water or hydrochloric acid as an eluting agent when the adsorption reaches saturation to obtain a second eluent; and 

d) adding an alkali solution into the second eluent, removing precipitates by filtering after reaction, and concentrating the filtrate till both gallium content and sodium hydroxide content are 1 mol/l or more, then electrolyzing the concentrated filtrate to obtain metal gallium."

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Note that the process disclosed herein, though not well-reflected in our excerpts, is actually focused on an electrochemical process for recovering nearly-pure gallium. Most of the process steps specified in the Disclosure are targeted on obtaining an extract, a "filtrate" from Coal Ash, and, the "electrolyzing" that "filtrate" in order "to obtain metal gallium".

The Gallium obtained is very pure, and would be much more pure than that obtained by the thermochemical process disclosed in our above-cited report concerning, in part: "United States Patent 4,643,110 - The Recovery of Gallium and Germanium from Coal Fly Ash".

And, application of the technology disclosed by our subject herein,  "United States Patent 8,728,296 - Method of Extracting Gallium from Fly Ash", would be limited to those Coal-fired boilers using the fluidized bed combustion technique.

However, much as with Aluminum, as in our report of: 

USDOE Says Coal Ash Could End Aluminum Ore Imports | Research & Development | News;

and in the context of the above-cited US Geological Survey report:, which stated that "Imports of gallium (supply)most of U.S. gallium consumption",

we do make enough Coal Ash in the United States, that, via one technique or another, we could, if we wished, just as with Aluminum, put an end to our imports of strategically-important Gallium.


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