WO2007098211A2

WO2007098211A2 - Gravimetric separation system and method

Info

Publication number: WO2007098211A2
Application number: PCT/US2007/004526
Authority: WO
Inventors: R.J. Smythe
Original assignee: 2082710 ONTARIO Ltd
Current assignee: 2082710 ONTARIO Ltd
Priority date: 2006-02-21
Filing date: 2007-02-21
Publication date: 2007-08-30
Anticipated expiration: 2008-08-21
Also published as: WO2007098211A3

Abstract

A method for separating components of a material includes assaying the material to determine the components and the specific gravity of at least one component. The material is ground into a heterogeneous gangue of predetermined particle size. Optionally, the particle size is determined according to Stokes' law. The gangue is delivered to a fluidizing bed having a gas permeable floor and a gas source delivering gas through the gas permeable floor at a predetermined gas flow rate, optionally corresponding to the terminal velocity of a component to be separated from the gangue. The gangue separates according to specific gravity and particles are extracted at a predetermined distance from the fluidizing bed.

Description

GRAVIMETRIC SEPARATION SYSTEM AND METHOD

Field of the Invention The present invention relates to systems and devices for material separation.

Specifically, the present invention is a device for using distinct terminal gravitational velocities to separate material such as coal by specific gravity and particulate diameter.

Background of the Invention

Mined fuels such as coal are often found mixed with other components. However, because these other components can often create pollution or cause adverse health effects when burned, fuels mixed with such components are disfavored or are typically burned in plants with elaborate chemical and mechanical scrubbers to reduce the emissions. It is known to refine such materials, but the costs of refining the fuels are typically impractical compared to the cost of the refined fuel and the alternative fuels available.

Summary of the Invention The present invention includes a material, separating system for separating the components found in mined coal. An embodiment of such a system includes a grinder to grind the mined coal into a heterogeneous gangue of predetermined particle size. A fluidizing bed includes a gas permeable floor and a gas source disposed vertically below the gas permeable floor. The gas source directs a flow of gas through the gas permeable floor at a predetermined gas flow rate. Optionally, gas dispersion plates are disposed between the gas source and the gas permeable floor. An extractor is disposed vertically above the fluidizing bed, the extractor adapted to extract particles of the gangue at a predetermined height vertically above the fluidizing bed. A method for separating components comprising mined coal includes assaying the mined coal and determining the specific gravity of at least one of the components comprising the mined coal. A particle size is calculated based on the specific gravity of at least one component. Optionally, the particle size is calculated based on the specific gravity of coal such that the calculated particle size provides different terminal velocities of the component and the coal based on the equation

T = K SG D²

where T is the terminal velocity, SG is the specific gravity, D is the diameter of the particles, and K is a constant accounting for at least the geometry of the particles.

The mined coal is ground into a heterogeneous gangue of the calculated particle size. Optionally, the gangue is mixed with a gaseous carrier prior to floating the gangue on the fluidizing bed. The gangue is floated on a fluidizing bed having a gas permeable floor through which gas is flows at a predetermined gas flow rate. The predetermined gas flow rate corresponds to the terminal velocity of the component at the calculated particle size. Particles of the gangue are extracted at a predetermined distance from the fluidizing bed.

In an optional embodiment in which multiple components each having a specific gravity are to be separated, the method may include repeating the steps of floating the gangue on a fluidizing bed and extracting particles, of the gangue at a predetermined distance from the fluidizing bed at multiple different predetermined gas flow rates. Optionally, a second particle size may be calculated based on a specific gravity of a component of the gangue and the gangue may be re-ground to the second particle size prior to repeating the steps of floating the gangue on a fluidizing bed and extracting particles of the gangue at a predetermined distance from the fluidizing bed at a different predetermined gas flow rate.

Brief Description of the Drawings

FIG. 1 is a flow chart of a method according to an embodiment of the present invention; FIG. 2 is a block diagram of a system according to an embodiment of the present invention;

FIG. 3 is a block diagram of a system according to an embodiment of the present invention;

FIG. 4 is a block diagram of a system according to an embodiment of the present invention.

Description

Reference is now made to the figures wherein like parts are referred to by like numerals throughout. Referring generally to FIGS. 1-4, the present invention is a method and system for separating components forming a heterogeneous gangue.

In the an optional embodiment, the material to be separated is assayed to determine at least one component in its composition. For example, in an optional embodiment applied to mined coal, the mined coal may be assayed to determine the undesired components and the desired components to be separated. In determining the composition of the material, the specific gravity of the components is determined experimentally or based on its chemical makeup.

A particle size for the gangue is determined 100. In an optional embodiment, the particle size is determined 100 based on the specific gravities of the components of the material such that the desired components and the undesired 'components will have distinguishable terminal velocities. For example, in one such optional embodiment, the terminal velocities are determined by application of Stokes' Law:

T = K - SG - D²

where T is the terminal velocity, SG is the specific gravity of the component, D is the particle diameter, and AT is a constant accounting for at least particle geometry.

Optionally, K may also account for one or more of unit conversion, air density, temperature, air viscosity, particulate shape, and units of measure used. For example, at sea level, for a temperature of 70° F, where D is in microns and T is computed in inches/second, K = 0.00078 for irregular shapes and K = 0.00118 for spherical shapes. Based upon the determination of particle size, e.g. D in the equation given above, the terminal velocity for the components are determined 200.

A grinder 10 grinds 300 the material into a heterogeneous gangue with particles substantially the particle size. In an optional embodiment, the gangue may be mixed with a gaseous carrier, such as an inert gas. A system according to the present invention may include a fluidizing bed 20.

In an optional embodiment, the fluidizing bed 20 includes a gas permeable floor and a gas source. Gas is directed through the gas permeable floor at a known gas flow rate. Optionally, dispersion plates are disposed between the gas source and the gas permeable floor to create a substantially uniform gas flow rate throughout the gas permeable floor, in an optional embodiment, the present system and method take advantage of gravity acting against a fluidized bed of gangue. In one such optional embodiment, the gas flow rate is determined 400 based on the terminal velocities of the components to be separated. In such an optional embodiment, the gas is forced vertically upward or with a vertically upward component to act in the opposite direction as gravity.

The gangue is delivered to the fluidizing bed 20 and a fluidized bed of gangue is created 500 on the fluidizing bed by the gas flowing through the gas permeable floor. Optionally, the gas flow is substantially equal to the terminal velocity calculated 200 for a component to be separated from the gangue.

For example, in an optional embodiment, the fluidizing bed is a gas permeable conveyor belt moving through a substantially gas impermeable chamber. The fluidized bed is created 500 by distributing the gangue across the surface of the gas permeable conveyor belt which carries the over an upward flow of gas. The gas passing through the gas permeable floor of the fluidizing bed 20 causes the gangue to fluidize 500 and float over the gas permeable floor. Because the, gangue has a substantially uniform- particle size, i.e. the particle size calculated to provide distinguishable terminal velocities, the gangue separates into components according to specific gravity, where less dense components float at a different vertical location than denser components. Using the predetermined particle size, bands of float may be computed where such bands relate to the ranges of terminal velocity, T, into which the gangue could separate. Components having a terminal velocity less than or equal to the rate of the upward flow rate of the gas float above the fluidizing bed 20. Based on the terminal velocity calculations, an extractor 30 extracts 600 particles from the fluidized gangue to separate 800 the material into desired components and undesired components. In an optional embodiment, the extractor 30 may use an exhaust current directed orthogonal to the upward gas flow from the fluidizing bed 20 at a predefined distance from the fluidizing bed 20 to extract particles floating at that distance. It is contemplated that particles extracted could be undesired components or desired components, as shown in FIG. 2. That is, it is contemplated that the extracted particles could comprise the desired components and the gangue could contain the undesired components; or the extracted particles could comprise the undesired components and the gangue could contain the desired components. For example, in one optional embodiment, bands could be calculated for two desired components having terminal velocities of 3.5 inches/second and 8.0 inches/second. Knowing these terminal velocities and the gas flow rate, extractors could be set to extract the desired components from the fluidized bed, or extract the undesired components from the fluidized bed, to thereby separate 800 the desired components from the undesired components.

In an optional embodiment, the process may be staged with multiple iterations, such as shown in FIGS. 1, 3, and 4. That is, after a component is extracted, the remaining gangue may be floated at a different gas flow rate which would create different bands of particles above the fluidizing bed. The extractors could then extract a different component from the remaining gangue until the material is separated 800 into desired components and undesired components.

For example, in one such optional embodiment , the gangue is processed in an iterative series of steps, with each iteration of the process directed to separating a band of components having a higher terminal velocity. For example, if it is known that undesired components have terminal velocities of 3.0 inches/second and 7.5 inches/second, while desired components have terminal velocities of 3.5 inches/second and 8.0 inches/second, the method could be conducted with four iterations, starting with a gas flow rate of 3.0 inches/second to extract the first undesired material, then a gas flow rate of 3.5 inches/second to extract the first desired material, then a gas flow rate of 7.5 inches/second to extract the second undesired material, then a gas flow rate of 8.0 inches/second to extract the second desired material.

In an optional embodiment in which material is reprocessed, it is contemplated that the gangue may be re-ground prior to each fluidization 500 such as shown in FIG. 4. It is also contemplated that, in an optional embodiment at least a portion of the extracted component may be added back to the gangue before or after re-grinding the remaining gangue to extract additional particles until the extracted component or components or the remaining gangue, whichever contains the desired component or components, contains a desired concentration of the desired component.

While certain embodiments of the present invention have been shown and described it is to be understood that the present invention is subject to many modifications and changes without departing from the spirit and scope of the claims presented herein.

Claims

I CLAIM:

1. A system for separating components comprising mined coal comprising: a grinder adapted to grind said mined coal into a heterogeneous gangue of predetermined particle size; a fluidizing bed including a gas permeable floor; a gas source disposed vertically below said gas permeable floor, said gas source adapted to direct a flow of gas through said gas permeable floor at a predetermined gas flow rate; and an extractor disposed vertically above said fluidizing bed, said extractor adapted to extract particles of said gangue at a predetermined height vertically above said fluidizing bed.

2. The system of claim 1 further comprising gas dispersion plates disposed between said gas source and said gas permeable floor.

3. A method for separating components comprising mined coal comprising: assaying said mined coal and determining the specific gravity of at least one of said components comprising said mined coal; calculating a particle size based on the specific gravity of said at least one component; grinding said mined coal into a heterogeneous gangue of said calculated particle size; forming a fiuidized bed of said gangue on a fluidizing bed having a gas permeable floor through which gas is flows at a predetermined gas flow rate, said predetermined gas flow rate corresponding to the terminal velocity of said component at the calculated particle size; and extracting particles of said gangue at a predetermined distance from said fluidizing bed.

4. The method of claim 3 further comprising mixing said gangue with a gaseous carrier prior to forming a fluidized bed of said gangue.

5. The method of claim 3 further comprising calculating said particle size based on the specific gravity of coal such that said calculated particle size provides different terminal velocities of said component and said coal based on the equation r= K SG- D² where T is the terminal velocity, SG is the specific gravity, D is the diameter of said particles, and K is a constant accounting for at least the geometry of said particles.

6. The method of claim 3 wherein multiple components each having a specific gravity are to be separated, further comprising repeating said steps of forming a fluidized bed of said gangue and extracting particles of said gangue at a different predetermined gas flow rate.

7. The method of claim 6 further comprising: calculating a second particle size based on a specific gravity of a component of said gangue; and re-grinding said gaπgue to said second particle size prior to repeating said steps of forming a fluidized bed of said gangue and extracting particles of said gangue at a different predetermined gas flow rate.

8. A method for separating components comprising mined coal comprising: assaying said mined coal and determining the specific gravity of at least one of said components comprising said mined coal; calculating a particle size based on the specific gravity of said at least one component and the specific gravity of coal such that said calculated particle size provides different terminal velocities of said component and said coal based on- the equation

T = K SG- D² where T is the terminal velocity, SG is the specific gravity, D is the diameter of said particles, and AT is a constant accounting for at least the geometry of said particles; grinding said mined coal into a heterogeneous gangue of said calculated particle size; forming a fluidized bed of said gangue on a fluidizing bed having a gas permeable floor through which gas is flows at a predetermined gas flow rate, said predetermined gas flow rate corresponding to -the terminal velocity of said component at the calculated particle size; and extracting particles of said gangue at a predetermined distance from said fluidizing bed.

9. The method of claim S further comprising mixing said gangue with a gaseous carrier prior to forming a fiuidized bed of said gangue.

10. The method of claim 8 wherein multiple components each having a specific gravity are to be separated, further comprising repeating said steps of forming a fiuidized bed of said gangue on a fluidizing bed and extracting particles of said gangue at a different predetermined gas flow rate.

11. The method of claim 10 further comprising: calculating a second particle size based on a specific gravity of a component of said gangue; and re-grinding said gangue to said second particle size prior to repeating said steps of forming a fiuidized bed of said gangue on a fluidizing bed and extracting particles of said gangue at at a different predetermined gas flow rate.