Process and apparatus for separating anthracite or bituminous from refuse

A process for separating Anthracite and low quality carbon from refuse. Crushed refuse is admixed with water from a water storage source. The admixture is transferred to a first cyclone separator to divide the admixture into a refuse rich slurry stream and a carbonaceous rich slurry stream. The refuse rich slurry stream is dewatered through a vibrating screen and the water collected sent to the raw feed sump source. The carbonaceous rich slurry is directed to a second cyclone separator to separate low quality carbon from high quality carbon, the high quality carbon is transferred to a third cyclone separator used to separate the media water therefrom. The separated media water is returned via a siphon leg to the raw feed sump, and the dewatered high quality Anthracite is available for markets requiring higher quality carbon.

FIELD OF THE INVENTION

The present invention relates to the energy field and, more particularly, to a process and apparatus for separating Anthracite from refuse.

BACKGROUND OF THE INVENTION

Since the early 1800's, coal has been valued for its energy content, and substantial quantities of Anthracite was mined and processed to produce coal of various sizes. The coal was separated from mining refuse, and huge mounds of tailings were produced; mine tailings being the material left over after the process of separating the valuable energy rich ore. Tailings processed once or twice by previously known methods are presumed to be uneconomical to further process.

Known processes for separating coal from refuse is the use of a heavy media cyclone separator which relies on centrifugal forces in conjunction with a slurry to achieve separation. The slurry carries a specific gravity which is controlled by adding finely-pulverized magnetite ore to the tailings. The separator produces an overflow which is carbon-rich and an underflow which is rich in refuse. The carbon-rich overflow is dewatered and is rinsed with fresh water to produce a clean coal output and a magnetite-rich underflow slurry. The underflow slurry from the cyclonic separator is also dewatered and rinsed with fresh water to produce a refuse-rich reject material and a magnetite-rich underflow. The magnetite-rich underflow from both the coal-rich and refuse-rich dewatering screens is then passed through magnetic separators which separate the magnetite ore from its water carrier. While the prior art process is intended to prevent losses of magnetite, substantial losses of magnetite occur. Magnetite-enriched heavy medium cyclonic separation techniques are not economical. The magnetite-enriched heavy medium cyclonic separation process includes the requirement of a substantial amount of fresh water and a significant capital investment for the magnetic separators and the ongoing cost of magnetite.

A magnetite-enriched heavy medium cyclonic separation process is disclosed in U.S. Pat. No. 2,726,763. Coal separation processes which use other types of medium are disclosed in U.S. Pat. Nos. 2,701,641; 2,649,963; 2,860,252; 3,031,074; 2,819,795; 4,203,831; and 4,252,639. Separating cyclones are disclosed in one or more of the preceding patents and the following U.S. Pat. Nos. 2,724,503; 3,353,673; 4,164,467; 3,887,456; 4,175,036; 4,226,708; 3,379,308; and 3,902,601. Multiple stage cyclones are disclosed in one or more the following patents: U.S. Pat. Nos. 3,926,787; 4,802,976; 4,830,741; 4,865,740; 5,108,608; 5,277,368; and 10,399,123.

Applicant is the inventor named in U.S. Pat. No. 4,364,822, issued on Dec. 21, 1982, entitled “Autogenous Heavy Medium Process and Apparatus for Separating Coal from Refuse”, the contents of which are incorporated herein by reference. The disclosure was directed to an autogenous non-magnetic heavy medium cyclonic separator in combination with ancillary equipment.

In the process, raw input from mine tailings was screened and mixed with a heavy medium to form an aqueous based slurry feedstock. The feed stock slurry flows through a primary cyclonic separator which causes a coal rich portion to exit its overflow and a refuse rich portion to exit its underflow. The underflow is screened and the fines are subsequently processed to yield carbonaceous matter. While the above referenced process and apparatus provided beneficial results, the process failed to recognize the ability to separate the coal refuse into channels of inert rock, low quality carbon, and high quality Anthracite.

What is needed is an economical process for refining coal mine tailings that is environmentally friendly.

SUMMARY OF THE INVENTION

Disclosed is a process and equipment for separating Anthracite from refuse. The process employs three cyclone separators staged to recover low and high quality carbon. The carbon rich overflow from a first cyclone separator reports to a second cyclone separator where the underflow is a low quality carbon and the overflow is high quality Anthracite. The carbon rich overflow reports to a third cyclone separator which separates the solids from the slurry. The water from the third cyclone separator is continuously circulated until the density reaches 1.35 or 1.45 (dirty H20) specific gravity, at which point fresh water is added and dirty water removed to a tailings pond, vacuum press, or a centrifuge to be clarified and reused. The process admixes coal refuse having an approximate size of less than ⅜″×0″ with water from a water storage source into a feedstock slurry. The feedstock slurry is transferred to a first cyclone separator to divide the feedstock slurry into a refuse rich underflow stream and a carbonaceous rich overflow stream. The underflow stream is dewatered through a vibrating screen, and the collected water is recirculated to the main feed sump. The carbonaceous rich slurry is directed to a second cyclone separator to further separate low quality carbon from high quality carbon, the low quality carbon available for a market that uses the lower quality (i.e. Cogen Industry). The high quality Anthracite slurry is transferred to a third cyclone separator to separate solids from the slurry, the separated media is returned to the main feed sump, and the dewatered high quality Anthracite is available for markets requiring the higher quality carbon.

An objective of the invention is to recover high quality Anthracite from refuse in mine tailings, thought otherwise to be too expensive and difficult to recover.

Another objective of the invention is to teach a three stage refuse process, summarized as a first cyclone separator for rejecting the bulk of inert fireproof rock, a second cyclone separator for separating high quality carbon from low quality carbon, and a third cyclone separator to separate circulating media water from the high quality carbon.

It is another objective of the instant invention to provide an improved coal separation process that is environmentally friendly using recycled water.

Yet another object of the instant invention is to reduce the need for ancillary equipment and manpower to separate low quality carbon from high quality carbon.

Yet another objective of the invention is to teach a highly efficient process for the recovery of carbon.

Yet still another objective of the invention is to provide an inexpensive method for concentrating rare earth elements.

An advantage of the process is the minimum amount of energy necessary for operation because the separation is achieved at relatively low specific gravities and relatively low pressures.

Another advantage of the process is that no additives are required, and has a low operating cost.

Another advantage of the process is the minimal amount of equipment and make-up water required.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A typical pile of tailings comprises coal and refuse. For instance, a typical pile may comprise up to 20% by weight of coal with the balance being refuse. As used herein, the term coal is intended to mean Anthracite or Bituminous coal, and the term refuse is intended to mean a variety of inorganic matter such as rocks, shale, slate, clay, and the like, which is mined along with the coal. Referring to the figures in general, in the processes, refuse10which may comprise less than 20% coal by weight, is crushed and screened to an approximate size range of less than ⅜″×0″, The crushed refuse is admixed with water14drawn from a water source forming an admixture16. The admixture16is transferred into a first cyclone separator18constructed and arranged to divide the admixture16into a refuse rich slurry stream20and a carbonaceous rich slurry stream22. Preferably, as further described herein, the cylindrical shaped cyclone separators have a continuous sidewall shaped to adjust acceleration/centrifugal force of the slurry stream. A first cyclone separator18has a continuous sidewall30depending from a top wall32forming a chamber34therein. An upper section36formed by the sidewall30expanding from a first diameter, as measured by the size of the top wall32expanding outwardly to a middle section38forming a second diameter40, as measured along the widest portion of the sidewall30. The admixture16is admitted through an inlet42formed tangentially in the sidewall30, wherein acceleration is slowed and then rapidly increased upon entering a third section44, wherein the sidewall30is formed into a conical shape diminishing in diameter from the middle section38to a first apex46to expel a refuse rich slurry50containing inert rock. The refuse rich slurry50is passed over a vibrating screen52for dewatering. Water54collected from the dewatering step is directed to the raw feed sump12for reuse, and the inert rock51with about 80% ash content is discharged. Because of the cylindrical shape, a substantial deceleration and acceleration is imparted to the solids as they circulate in the chamber at any given radius.

The carbonaceous rich slurry stream22is drawn from an outlet60through a transfer line62to a second cyclone separator68. The second cyclone separator68has a continuous sidewall70depending from top wall72forming a chamber74therein. An upper section76is formed by the sidewall70depending from a first diameter, as measured by the size of the top wall72, with a uniform diameter to a lower section78. The admixture, being a carbonaceous rich slurry stream22, is admitted through an inlet80formed tangentially in the sidewall70, wherein acceleration maintained and then rapidly increased upon entering the lower section78, wherein the sidewall70is formed into a conical shape, diminishing in diameter along the length of the lower section78to a second apex82for expelling a low quality carbon84with about 45% ash content. The high quality Anthracite slurry90is drawn from the vortex. The high quality carbon exits the second cyclone separator68through an intake92and transfer line94. A cylindrical type of cyclone is to be contrasted with a tapered or variable acceleration type, wherein the shell has a depending frusto-conical or tapered portion of substantial length and a relatively small included cone angle. Because of the conical shape, the acceleration forces increase on the particles as they circulate and advance.

The high quality Anthracite slurry stream90is drawn through the transfer line94to a third cyclone separator100. The third cyclone separator100has a continuous sidewall102depending from a top wall104forming a chamber106therein. An upper section108is formed by the side all102depending along a first diameter, as measured by the size of the top wall104maintaining a uniform diameter to a lower section110. The high quality Anthracite slurry90is admitted through an inlet96formed tangentially in the sidewall102, wherein acceleration is maintained and then rapidly increased upon entering the lower section110. The sidewall102is formed into a conical shape, diminishing in diameter along the length of the lower section110to a third apex114used for expelling dewatered high quality Anthracite118with about 12% ash content. The third cyclone100operates to separate the high quality Anthracite slurry90from the media water120drawn from an intake112of the cyclone separator100through a transfer line122for recycling to the raw feed sump12with about 90% return of the media water120. According to this preferred embodiment of the present invention, the above-described process will operate efficiently in a continuous manner to separate carbon of different qualities from refuse provided certain process conditions are observed. For instance, for Anthracite coal it is important that the specific gravity of the water is measured through the water storage source. For Anthracite coal having a specific gravity of about 1.75, the density of the water should be maintained in a range of about 1.35 and 1.45 specific gravity.

The specific gravity of the medium tends to increase after the process has been operating in the steady state for a period of time. In order to control the specific gravity of the medium within the desired range upstream of the first cyclone separator, the recirculating media is constantly monitored with a density gauge so that appropriate action can be taken to maintain the specific gravity within the desired range. For instance, if the specific gravity should increase beyond the desired limit, it can be reduced by bleeding media water out of the system and adding fresh water. If the specific gravity should drop below the desired lower level, it can be increased by increasing the particulate matter in the crushed Anthracite material make up.

In a preferred embodiment, the feedstock slurry is supplied at a static pressure in a range of about 10 psi to about 20 psi at a volumetric flow rate in a range of about 2,000 gpm.

The process disclosed herein is directed to separating Anthracite coal and a low quality carbon from refuse. Since Anthracite coal separation is known to be more difficult than Bituminous coal separation, the process should be effective on Bituminous coal. While some adjustments in operating conditions will have to be made to compensate for the different specific gravity of bituminous coal, such adjustments should be apparent to those skilled in the art in light of the present disclosure.

The term “coupled” is defined as connected, although not necessarily directly, and not necessarily mechanically. The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one,” but it is also consistent with the meaning of “one or more” or “at least one.” The term “about” means, in general, the stated value plus or minus 5%. The use of the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or the alternative are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or.”

All patents and publications mentioned in this specification are indicative of the levels of those skilled in the art to which the invention pertains. It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and figures included herein.