United States Patent Application: 0130115149

As we've documented previously a number of times, as for just one example in our report of:

West Virginia Coal Association | USDOE Says Coal Ash Could End Aluminum Ore Imports | Research & Development; which included, among others, separate reference to:

"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"; and:

"Economic Metal Recovery from Fly Ash; Symposium on Resource Recovery and Environmental Issues of Industrial Solid Wastes; 1981; T.M. Gilliam, et. al.; 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, Fe2/O3, and possibly several other metals, many of which are presently being imported. Although several metal recovery processes were studied, only the two of greatest economic potential and widest applicability were given detailed economic evaluation; the direct acid leach of ash with HCl (a minimum treatment process) and a pressure digestion-acid leach (a maximum recovery process). Results show that both methods can remove from fly ash all metals that would otherwise be available for release to the environment after disposal and that a major portion of the leached metals can be separated in saleable form. Economic analyses indicate that the direct acid leach process is most attractive";

our own United States Government, more than three decades ago, through the USDOE, not only confirmed that Coal Ash was such an abundant source of Aluminum that it could enable us to stop importing Aluminum ore, all of which we need is now imported, by the way; but, also identified the most efficient way, an "acid leach ... with HCl", of recovering Aluminum ore from Coal Ash.

And, as we reported 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";

China is actually doing something with and about the knowledge that Coal Ash is a rich source of Aluminum; using a technology that, as can be learned in the full Disclosure of:

West Virginia Coal Association | China Extracts Metallurgical Grade Aluminum Ore from Coal Ash | Research & Development; "Method For Preparing Metallurgical-Grade Alumina By Using Fluidized Bed Fly Ash; Publication Number: WO/2011/134398; International Application Number: PCT/CN2011/073371; 2011; Applicants: China Shenhua Energy Company Limited, et. al., Beijing; Abstract: Provided a method for preparing metallurgical-grade alumina by using fluidized bed fly ash";

is just such an "acid leach ... with HCl" method of recovering Aluminum ore from Coal Ash, as established three decades ago by our US Government as being the most efficient means of effecting such recovery.

Now, herein, via excerpts from the initial link in this dispatch, we see that China has just asked the United States Government, as well, to assign them the United States rights to employ "acid leach" technology to extract Aluminum ore, "Alumina", from Coal Ash:

"United States Patent Application 20130115149 - Method for Preparing Metallurgical-Grade Alumina by Using Fluidized Bed Fly Ash

METHOD FOR PREPARING METALLURGICAL-GRADE ALUMINA BY USING FLUIDIZED BED FLY ASH - CHINA SHENHUA ENERGY COMPANY LIMITED

Patent US20130115149 - Method for preparing metallurgical-grade alumina by using fluidized bed fly ash - Google Patents

Date: May 9, 2013

Inventors: Zhaohua Guo, et. al., China

Assignee: China Shenhua Energy Company Limited, Beijing

Abstract: Provided a method for preparing metallurgical-grade alumina by using fluidized-bed fly ash, comprising: a) removing iron by wet magnetic separation after crushing the fly ash; b) reacting the fly ash after magnetic separation with hydrochloric acid to obtain a hydrochloric leachate; c) passing the hydrochloric leachate through macro-porous cationic resin to deeply remove iron to obtain a refined aluminum chloride solution; d) concentrating and crystallizing the refined aluminum chloride solution to obtain an aluminum chloride crystal; and e) calcining the aluminum chloride crystal to obtain the metallurgical-grade alumina. The method is simple, the procedure is easy to be controlled, the extraction efficiency of alumina is high, the production coast is low, and the product quality is steady.

(Note: This process is for the recovery of Alumina from "fluidized-bed fly ash", which could be somewhat different in physical makeup from Fly Ash that results from conventional pulverized Coal-fired boilers, due to differences in combustion temperature and other factors. The essential elements of composition will remain basically the same, although their relative proportions could vary, as could the compounds in which they are bound. All of that could affect the applicability of this process to Coal Ash arising from different sources. Certainly, we have experts in our various Coal Country educational institutions and power generation corporations who could advise anyone genuinely interested on the particulars.)

Claims: A method for preparing metallurgical-grade alumina by using fluidized-bed fly ash, comprises the following steps:

a) crushing the fly ash to a size of 100 mesh or smaller, adding water therein to prepare a slurry having a solid content of 20-40 wt %, removing iron from the slurry by wet magnetic separation, such that Fe content of the fly ash is reduced to 1.0 wt % or less, and filtering the slurry to obtain a filtered cake;

(Note, concerning this initial claim, that, in our above citation of the USDOE's report, "Resource Recovery from Coal Residues", our government also acknowledged, many decades ago, that Coal Ash was a potential source of Iron. We just didn't do anything about it.)

b) adding hydrochloride acid into the filter cake from step a) to react the fly ash with the hydrochloride acid, and then subjecting the reaction product to solid-liquid separation and rinse to yield a hydrochloric leachate having a pH value in the range of 1-3;

c) passing the hydrochloric leachate through a column loading with a macro-porous cationic resin to further remove iron to obtain a refined aluminum chloride solution;

d) subjecting the refined aluminum chloride solution to vacuum concentration, then cooling the concentrated solution for crystallization, and conducting solid-liquid separation to obtain aluminum chloride crystal; and:

e) calcining the aluminum chloride crystal at a temperature in the range of 900-1200 C for 1-4 hours to obtain the metallurgical-grade alumina; or calcining the aluminum chloride crystal at a temperature in the range of 300-500 C for 1-2 hours, then at an elevated temperature in the range of 900-1100 C for additional 1-3 hours to obtain the metallurgical-grade alumina. 

The method ... wherein in step b), the concentration of the hydrochloride acid is ... 20-30 wt %; the molar ration of HCL contained in the hydrochloride to alumina contained in the fly ash is ...preferably 4.5:1-6:1. 

The method ... wherein in step b), the reaction temperature is ... preferably 130-150 C; the reaction time is 0.5-4.0 hours, preferably 1.5-2.5 hours; the reaction pressure is ...preferably 0.3-1.0 MPa.

(The conditions of temperature and pressure are not severe, and the concentration of the HCl itself isn't that high, although you need a good bit of it, relative to the alumina content of the Coal Ash. It is, or can be, though, as Shenhua describes in the full Disclosure, recoverable, and can be filtered, regenerated and recycled in the process.)

The method ... wherein the macro-porous cationic resin is selected from styrene resins or acrylic resins (as specified).

The method ... wherein hydrochloride gas generated in step e) is (captured and recycled, and) wherein in step b), a mother liquid obtained after the solid-liquid separation is recycled (as specified). 

The method ... wherein in step a), a vertical ring magnetic separator is used for removing iron by wet magnetic separation, 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 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, 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 prismatic sharp angles. 

The method ... wherein the upper iron yoke and the lower iron yoke are formed integrally, and are arranged, in a plane perpendicular to the rotating ring, to surround the inner and outer sides of the lower portion of the rotating ring (and) wherein the vertical ring magnetic separator further comprises a pressure balance chamber water jacket disposed adjacent to the magnetic exciting coil (and) wherein the steel plate mesh has a medium layer spacing (as specified).

(They actually go into considerable detail about the recovery of Iron from the treated Coal Ash. It's an economical thing to do both because the Iron is a product of some value, and, the Iron would otherwise interfere with the recovery of the Alumina.)

Background and Field: The present invention relates to a comprehensive utilization of fluidized-bed fly ash and in particular relates to a method for preparing metallurgical-grade alumina by using the fluidized-bed fly ash. 

Fly ash ... contains a number of components that can be utilized, for example, circulating fluidized-bed fly ash usually contains about 30 to 50 percent by weight of alumina. Nowadays, as the bauxite resources become gradually rare, it is an efficient way to extract valuable materials, such as alumina from the fly ash and provide a highly comprehensive utilization for the fly ash, which is of great social and economic benefits. 

By now, methods used for extracting alumina from fly ash are basically divided into two categories, acid leaching method and alkali leaching method. Further, the alkali leaching method may be divided into limestone (soda-lime) sintering method and sodium carbonate sintering method. The limestone (soda-lime) sintering process is such a method that the fly ash is mixed with limestone (soda-lime) and the mixture is calcined to be activated at a very high temperature (1320-1400 C), thereby alumina and silicon dioxide contained in the fly ash react respectively with limestone (soda-lime) to form calcium aluminate and dicalcium silicate. The calcined ash was leached with sodium carbonate solution and filtered to remove unwanted substances, thus the calcium aluminate enters the solution in the form of sodium metaaluminate, from which, after desilicification and carbon precipitation (or seed precipitation) treatments, aluminum hydroxide is thereby obtained. Subsequently, the obtained aluminum hydroxide is calcined to obtain alumina product. Moreover, after the filtering treatment, the dicalcium silicate turns into silicium-calcium slag which may be employed as raw material for cement.

Summary: The object of the invention is to provide an improved method for preparing metallurgical-grade alumina by using the fly ash as the raw material. The method is simple, the production cost is low, and the product quality is steady."

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We'll close our excerpts there since the remainder of the Disclosure is given over to comparisons of the Disclosed process and the prior-art "limestone (soda-lime) sintering process"; the design and operation of the Iron separation process; and, presentation of example operations. And, please note that our excerpts, edited for the sake of concision, don't fully document all of the chemistry involved.

Concerning the "limestone (soda-lime) sintering process", which might be more applicable to the recovery of Aluminum from pulverized Coal-fired boiler Ash, as opposed to the fluidized bed Ash specified herein, see, for one example, our report of:

West Virginia Coal Association | Iowa Mines Metals from Coal Ash for the USDOE | Research & Development; which contains information about such sintering processes, such as: "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".

As far as using the residual Coal Ash "slag"  "as raw material for cement", as Shenhua herein specifies, see for only one example:

West Virginia Coal Association | Standard Oil Converts Coal Conversion Residues into Cement | Research & Development; concerning: "United States Patent 4,174,974 - Process for Converting Coal Ash Slag into Portland Cement; 1979; Assignee: Standard Oil Company of Indiana; Abstract: Disclosed is a manufacturing process for converting coal ash slag from a slagging coal gasifier into a marketable cement product having the characteristics and qualities of portland cement".

However, Aluminum is an important elemental component of Cement. And, since the Ash herein would be depleted of Aluminum subsequent to the treatment specified by our subject, "United States Patent Application 20130115149 - Method for Preparing Metallurgical-Grade Alumina by Using Fluidized Bed Fly Ash", a supplemental source of it, such as dirt-common aluminosilicate shale, might be needed to add to the residual Ash remaining after such Aluminum extraction so that it can be more effectively consumed in a cement-making process.

In any case, we have herein official, formal explanation of a process for the profitable extraction of commercial-grade Aluminum ore from Coal Ash, a process that has likely already been reduced to industrial practice at "a coal ash-based alumina refinery in the Inner Mongolia autonomous region".

Isn't it worthy of at least some consideration to build such "a coal ash-based alumina refinery", based on this or alternative processes, or three or four of them, in West Virginia, Pennsylvania, Kentucky, Ohio and other states in US Coal Country, and, thereby, while we put some more Americans to work in good-paying jobs, put an end to our economically debilitating, and potentially crippling, near-total national reliance on foreign sources of supply for a metal as strategically critical as Aluminum?


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