WO1997004886A1

WO1997004886A1 - Dry method for separating particles

Info

Publication number: WO1997004886A1
Application number: PCT/US1995/014593
Authority: WO
Inventors: Kenneth I Savage
Original assignee: Kenneth I Savage
Priority date: 1995-07-28
Filing date: 1995-10-30
Publication date: 1997-02-13

Abstract

A method of separation of a pulverulent mixture of different solid substances into fractions (108, 114), one or more of which is upgraded as to the desired constituent. More particularly, the invention relates to the unidirectional blowing of a gaseous suspension of particles of differing specific gravities within an apparatus. Here the suspended particles are subjected to the pressures at the drag faces (106, 112) where a series of eddies form flowing counter to the main current. Distinct fractions are separated within housings (14, 16) via the flow of the eddies.

Description

DRY METHOD FOR SEPARATING PARTICLES

Field of Invention

This invention relates to a method for upgrading pulverulant particles into distinct fractions without the use of water.

Background - Description of Prior Art

This invention can be used on pulverulent particles in industry such as but not limited to the coal, food, or chemical industries/ particularly where the use of water is not desired. This invention is especially needed in the coal industry because impurities must be removed to stop air pollution. Present methods have serious drawbacks mainly because they rely on and pollute water.

Coal is the solid hydrocarbon burned as fuel to produce most electricity/ most cement/ a variety of chemicals, and most coke. All steel is made from coke. Coal must be ground to a fine pulverulant before industrial use. Ash and sulfur are major coal impurities. They remain bound to the coal hydrocarbon of these particles, reducing the coal's value. If still attached to coal that is burned they become pollutants. If left to transfer into coke they lower the value of steel. Therefore^"steps are taken to clean coal by separating the impurities from the hydrocarbon yielding an upgraded product. Until now all attempts to clean coal before burning relied upon the use of water in common, unpatented industrial processes. All suffer from any of these disadvantages:

(a) Each unit operation of the process requires a costly arrangement of cumbersome mechanical equipment.

(b) Typically at least five unit operations are needed.

(c) In each, vast amounts of water must be pumped into the coal making a slurry. This requires vast plumbing and electricity to transport.

(d) The water from each unit operation is now polluted requiring pH correction before discharge.

(e) The upgraded coal is now mixed with water. It must be de-watered by an energy intensive process of centrifuges and screens.

(f) Thermal dryers may then used to further remove water.

(g) The clean coal is now loaded for shipment. Charges include 10 to 30 percent weight of water still remaining.

(h) In winter this water will freeze the coal. Cars must be electrically warmed in thawing sheds. Costly de-icing chemicals must be sprayed on the cars before shipping.

(i) Water remains causing problems in coal use. When burned the thermal value of such coal is lowered up to 15%. Coke made from such coal is inferior. It increases the cost of making steel. Close monitoring is needed to avoid ruin of the walls of the retort in which the coke is made.

Because of these and other flaws, much coal is simply burned as is. The impurities degenerate into particulate matter and S02. Coal burning utility companies employ attempts to capture these pollutants.

Attempts to capture ash have these disadvantages:

(j) This unit operation alone requires a space about one half the size of the entire facility.

(k) Costly, energy consuming equipment such as electrostatic precipitators, cyclones, or bag houses must now be used to remove the ash. Attempts to capture S02 involve scrubbers and suffer from these disadvantages.

(1) Scrubbers require space which is larger than that needed for the entire original utility plant.

(m) This space with such vast equipment as lime slakers, S02 adsorbers, tanks, vats, and centrifuges.

(n) S02 is bonded to lime (CaO) within a water slurry in a web of piping. The solids formed readily adhere to the walls inside the pipes. Blockages are soon formed shutting down the entire scrubbers over 50 percent of the time.

(o) Each 100 mega watts of electricity results in 260,000 gallons of polluted water. The pH is restored in a third plant.

(p) Electricity is drained off to pump these slurries.

In summary what is needed is the dry method of this patent which employs a gaseous stream to separate impure particles.

Only two patents bear any similarity to this one. Their methods are not applicable to coal and they are not used in the coal industry. Because both upgrade a material by a dry method of particle separation, they will be reviewed here. U.S. Patent No. 4,321,134 to Leschonski et al, 1982, describes a system of sieves and screens to dry sort two or more polydispersed components. The initial separation would not work on coal. This is because the hydrocarbon is tightly, physically bound to the ash and sulfur molecules. Coal is not made up of the polydispersed components as required by Leschonski.

U.S. Patent No. 3,263,808 to Schwartz, 1966, describes a process and apparatus for upgrading iron ore. Here a main gaseous stream of larger, heavier iron particles are caused to penetrate and pass through a wall, or plane of pressure formed by gases flowing toward each other. At each such plane of intersection, the lighter and smaller particles are diverted at right angles to their previous direction line. The Schwartz patent was designed for iron ore particles which penetrate the gaseous planes. The lighter, noniron particles are swept along with the feed stream. Because cσal particles are of a lower specific gravity than iron, they would not penetrate the gaseous stream. Instead they would be swept along with the noncoal particles. No cleaning or separation would result. Therefore neither patent is used in the coal industry.

Objects and Advantages

Accordingly, several objects of the present invention are to provide the following advantages over prior art:

(a) It requires only a small amount of mechanical equipment.

(b) Only two unit operations are needed.

(c) Because no water is used no slurry is produced and no plumbing is needed. Only minimal electric power is needed because a blower transports the dry particles.

(d) No water is used. Therefore none is polluted requiring correction.

(e) No screens and centrifuges are needed for dewatering.

(f) Thermal dryers are not needed.

(g) Shipping charges will be 10 to 30 percent lower due to the absence of water.

(h) Expensive de-icing chemicals and heated thawing sheds will not be needed to prevent freezing.

(i) The coal cleaned by this patent is free of water upon delivery. It's efficiency is thus improved. The thermal value of coal which is burned is increased up to 30 percent. The coke made from dry coal is improved. It reduces the cost of producing steel. Only minimal monitoring is needed of the walls of the retort in which the coke is made.

The present patent can readily be utilized at either the site where mined or at the site where used by the consumer. This will greatly reduce the amount of equipment upon which utility companies depend to capture ash and sulfur after burning coal.

This invention has the following advantages over prior methods to capture ash:

(j) Space requirements will be greatly reduced.

(k) Energy consuming, expensive ash removal equipment such as electrostatic precipitators, cyclones, or bag houses can be greatly reduced.

This invention will reduce the dependence upon scrubbers for the capture of S02 by providing the following advantages:

(1) Space required for scrubbers will be greatly reduced.

(m) Scrubber equipment can be greatly reduced.

(n) Coal with some 50 percent less sulfur will now be burned. Far less CaO will be needed to make the slurry. Less solids will be formed, reducing the blockages. Scrubbers will operate with only scheduled shutdowns.

(o) Less sulfur burned means less water pollution. The plant where the pH of the water is restored can be greatly reduced.

(p) Because the slurry will be diluted, much less electric power will be drained off to pump the slurry.

It is the object of this invention is to provide a method for cleaning the ash and sulfur from coal by using a dry method which is not dependent upon myriads of costly, space and energy consuming mechanical equipment which ultimately pollute water.

Other and further important objects of this invention will become more apparent from the following description, particularly when taken in connection with the accompanying drawings.

Drawing Figures

In the drawings herein like numerals are employed to designate the same structure elements:

FIGURE 1 is a diagrammatic plan side view exemplifying apparatus which may be employed to practice the method of this invention, a

FIGURE 2 is an top elevational view of the same apparatus. Reference Numerals In Drawings:

10 conduit 64 opening

12 intake valve 66 legs

14 housing 68 base plate

16 housing 70 collector

18 feed hopper 72 funnel

20 valve 74 valve

22 legs 76 opening

24 base plate 78 legs

26 entry wall 80 base plate

28 opposite wall 82 conduit

30 end wall 84 blower

32 end wall 86 conduit

34 horizontal cover 88 plate

36 damper 90 legs

38 funnel 92 base plate

40 valve 94 motor

42 opening 96 plate

44 legs 98 legs

46 base plate 100 base plate

48 entry wall 102 entrained feed

50 opposite wall 104 moving bed

52 end wall 106 drag face

54 end wall 108 fractionated solids

56 horizontal cover 110 moving bed

58 damper 112 drag face

60 funnel 114 fractionated solids.

62 valve 116 gas

Description - Fig. 1 and Fig. 2

As shown in the drawings suitable apparatus for practicing the method of my invention comprises a feed conduit 10, the axis of which preferably lies at an angle to the horizontal plane. Said conduit 10 is provided at its free end with an intake valve 12 for for the controlled admission of air or other gas suitable for transporting the pulverulent solid mixture is into the successive housings, a housing 14 and a housing 16 are shown, and forming drag faces on the pulverulent solids mixture that is to be separated into fractions. Such a pulverulent solid mixture is introduced into conduit 10 by means of a feed hopper 18 and a suitable valve 20 for metering the feed at a proper rate that will, in correlation with the rate of flow of the gas through conduit 10, insure the entrainment of the solids in the gas flow. Said hopper 18 is supported on four legs 22 and base plate 24, or any other suitable manner.

The straight run of conduit 10 is connected beyond the feed hopper 18 into the straight portion, or entry way into the opposite end of which is connected a housing section 14 having a common axis with conduit 10. Said conduit 10 may be flared for connection at its further end with housing 14, also coaxial with the conduit 10.

In the drawings, a housing 14 has an entry wall 26 sloped at angle A with the horizontal, an opposite wall 28 sloped at angle B with the horizontal which are interconnected with two vertical end walls 30 and 32, an cover 34 which has an adjustable transverse partition or a damper 36 to control the gases to the drag face, the walls extend downward to a funnel shaped portion 38 which has a valve 40 connected to opening 42. Said walls 26 and 28 of housing 14 may be at an angle from generally 30 to 90 degrees with the horizontal and angle A is generally greater than angle B. Said housing 14 is provided with a valve 40 which has a means to empty fractions of the separated pulverulent through an opening 42. Gases and partially upgraded pulverulent continue beyond damper 26 and enter housing 16. Said housing 14 is supported on four legs 44 and a base plate 46 or in any other suitable manner. In the drawings, a housing 16 has an entry wall 48 sloped at angle C with the horizontal, an opposite wall 50 sloped at angle D with the horizontal which are interconnected with two vertical end walls 52 and 54, an cover 56 which has an adjustable transverse partition or a damper 58 to control the gases to the drag face, the walls extend downward to a funnel shaped portion 60 which has a valve 62 connected to opening 64. Said walls 48 and 50 of housing 16 may be at an angle from 30 to 90 degrees with the horizontal and angle C is generally greater than angle D. Said housing 16 is provided with a valve 62 which has a means to empty fractions of the separated pulverulent through opening 64. Gases and further upgraded pulverulent continue beyond damper 58 and enter an upgraded solids collector 70. Said housing 16 is supported on four legs 66 and a base plate 68 or in any other suitable manner.

Gases and upgraded pulverulent enter an collector 70 which may be a cyclone or a bag house or other suitable means in any combination. The upgraded pulverulent is retained or collected in said collector 70. The walls of collector 70 extend downward to a funnel portion 72 which is provided with a valve 74 to remove upgraded pulverulent through opening 76. Said collector 70 is supported on four legs 78 and base plate 80 or in any other suitable manner.

The clean gases continue through conduit 82 to the suction end of a blower 84 and exit through conduit 86. Said blower is attached by plate 88 which is supported by four legs 90 and a base plate 92 or in any other suitable manner.

A motor 94 is attached to plate 96 which is supported by legs 98 and base plate 100 or in any other suitable manner.

The valves 20, 40, 62 and 74 are of the type well known in the art, which when rotated either continuously or intermittently permit passage of pulverulent material while at the same time in any rotary position substantially preventing passage of gases. Said valves may be operated manually or automatically in any desired sequence by suitable means (not shown). Operation-Figs. 1 and 2

In the operation of a system such as illustrated in the drawings, the gas blower 84 forms the primary, and usually the only, means for creating gas flow through the system. With the blower 84 in operation, the valve 12, damper 36 and damper 58 are adjusted to give the desired volume rates of flow and pressure gradients across the drag faces, or planes of resistance that are set up within the housings 14 and 16, as will presently be described. The feed of the pulverulant solid mixture through the feed hopper 18 into the conduit 10 is such as to insure entrainment of the mixture in the first stream of air, or other gas, flowing unidirectionally, as indicated by an arrow 102, into housing 14.

Due to the somewhat reduced gas velocity in housing 14, some of the pulverulent solids will form a moving bed as indicated by an arrow 104. At the confluence of the main gas flow and the moving bed of entrained pulverulant mixture a phantom drag face of resistance forms as indicated by dashed line 106. Some of the fractionated pulverulent will be drawn past damper 36 and into housing 16 as indicated by an arrow 108.

As will later be explained in connection with the specific example, a first fraction of the pulverulent solid mixture that is generally unable to be drawn past damper 20 and remains in container 14 is collected in funnel 38 and is removed through opening 42.

As said pulverulent 108 enters housing 16 some will from a moving bed of entrained pulverulant mixture as indicated by arrow 110. Due to the suction effect of blower 84 the main flow of gas will continue into collector 70. At the confluence of the main gas flow and the moving bed of entrained pulverulant mixture a phantom drag face of resistance, as indicated by dashed line 112 is set up within housing 16.

Due to the suction effect of the blower 84 some of the fractionated pulverulent solids will be drawn past damper 58 and into collector 70 as indicated by arrow 108. The residual portion of the pulverulent solid mixture that remains after separation of the secondary fraction at plane of drag resistance 48 is drawn off through funnel 60 and opening 64. The further fractionated pulverulent solids 114 are collected in collector 70 and removed through valve 74 and opening 76.

Other housings may be used to further upgrade the pulverulent solids.

Examples

The following examples will serve to illustrate the application of the method of my invention to the upgrading of a coal mixture, but it should be understood that this example is merely by the way of exemplification and is not intended to limit the scope of my invention in any way.

The starting material was a mined product from the Kittanning Seam coal crushed to a pulverulent such that substantially all of the particles would pass through a 28-mesh screen. Where mesh units are given herein, they will be understood to refer to the Tyler Standard Screen Scale Series and to mean the number of meshes per linear inch. A minus (-) sign means that the pulverulent will pass through the specified mesh, while a plus (+) sign means that the pulverulent will stay on the specified mesh screen.

The typical measure of improved quality in coal is the reduction in sulfur content and reduction in ash content.

A mined product is a coal mixture containing a gradation of coal quality from particles that are almost completely ash to those particles which are completely free of ash with a mixture of sulfur in all of these particles.

On the basis of 100 pound of run-of- ine coal as starting material, the following screen analysis will serve to illustrate weight distribution, sulfur assay, ash assay in accordance with the following table: Screen Fractions Weight Ash Assay Sulfur Assay Pass Retain pound kg wt % wt %

-28 +60 52.0 23.6 18.36 5.02

-60 +150 25.5 11.1 21.50 4.47

-150 23.5 10.7 23.64 4.98

Total 100.0 45.4 20.37 4.88

EXAMPLE ONE The run-of-mine starting material was fed into the feed conduit 10 through feed hopper 18 at a rate of 1 lbs. per minute. With the blower 84 in operation and valve 12 and dampers 36 and 52 properly adjusted, a stream of air was drawn through valve 12 into container 14 at a linear rate of over 6,000 f.p.m., and a weight rate of about 2 lbs. per min. of air on the basis of a feed of 1 lbs. per min. of run-of-mine. This gave a saturation ratio (R) of 0.5. R is the ratio of weight of feed/weight of air.

At the end of the run of 100 lbs. of run-of-mine coal, the following data were found:

Primary Fraction 24.0 lbs. total weight of pulverulent product. Assay 9.24 % Ash and 2.52 % sulfur. This entire fraction was then subjected to a single sizing operation, using a 60-mesh screen, with the following results:

+60 mesh subfraction, 10.0 lb., which was of high quality material of 8.50 % ash and 2.48 % sulfur.

-60 mesh subfraction, 14.0 lbs., which may be of marketable material of 9.76 % ash and 2.55 % sulfur.

Combined Secondary Fraction 76.0 lbs. total weight of pulverulent product. Assay, 23.89 % ash and 5.62 % sulfur. This entire fraction was then subjected to a single sizing operation, using a 60-mesh screen with the following results:

+60 mesh subfraction, 42.0 lbs. which is suitable for recirculation through the system,

-60 mesh subfraction, 34.0 lbs. which may be considered tails and sent to discard. The overall yield based upon the totals of the subfractions of 10.0 lbs. and 14.0 lbs. amounting to 14.0 lbs. and assaying 9.24 % ash and 2.52 % sulfur represent a direct recovery of 14.0 percent with a recycle load of 42.0 lbs. per 100 lbs. of feed.

EXAMPLE TWO The run-of-mine starting material was fed into the feed conduit 10 through feed hopper 18 at a rate of 1 lbs. per minute. With the blower 84 in operation and valve 12 and dampers 36 and 52 properly adjusted, a stream of air was drawn through valve 12 into container 14 at a linear rate of over 9,000 f.p.m., and a weight rate of about 3 lbs. per min. of air on the basis of a feed of 1 lbs. per min. of run-of-mine. This gave a saturation ratio (R) of 0.33. R is the ratio of weight of feed/weight of air.

Primary Fraction 51.3 lbs. total weight of pulverulent product. Assay 11.21 % ash and 3.06 % sulfur. This entire fraction was then subjected to a single sizing operation, using a 150-mesh sieve, with the following results:

+150 mesh subfraction, 32.3 lb., which was of high quality material of 9.12 % ash and 2.97 % sulfur.

-150 mesh subfraction, 19.0 lbs., which may be of recirculation material of 14.77 % ash and 3.21 % sulfur.

Combined Secondary Fraction 48.7 lbs. total weight of pulverulent product Assay, 30.02 % ash and 6.80 % sulfur.

This entire fraction was then subjected to a single sizing operation, using a 150-mesh screen with the following results:

+150 mesh subfraction, 44.2 lbs. which is suitable for recirculation through the system,

-150 mesh subfraction, 4.5 lbs. which may be considered tails and sent to discard. The overall yield based upon the totals of the subfraction of 32.3 lbs. and assaying 9.12 % ash and 2.97 % sulfur represent a direct recovery of 32.3 percent with a recycle load of 63.2 lbs. per 100 lbs. of feed.

Summary, Ramifications, and Scope

Accordingly, the reader will see that the separation of coal by this method can be used easily and conveniently accomplished. Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. For example, the housings for the moving beds can have other shapes, such as but not limited to circular, oval, trapezoidal, triangular, etc.: the dampers can have other configurations: the openings between the bins may be continuous or noncontinuous, etc.

Thus the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.

Claims

ClaimsI claim as my invention

1. In a method for the upgrading a mixture of dry discrete particles of various sizes and densities, the steps of providing a gas-suspended moving bed mixture of discrete particles of such a mixture of a particle size generally less than 1/4 inch (6 mm), wherein an upgraded fraction of the dry discrete particles flows parallel with the same direction as the gas, feeding said mixture of discrete particles into one of said moving bed mixtures, feeding said gas to flow over the moving bed mixture, setting up a face of drag with the gas flowing over the moving bed mixture of discrete particles, collecting a primary fraction from said mixture of discrete solid particles which has moved parallel with the gas flow, collecting as a secondary fraction that portion of said mixture of discrete particles that remains in moving bed, sizing said primary and secondary fractions into subfractions, combining subfractions into upgraded product, recirculation and reject streams.

2. In a method as defined by claim 1, wherein the primary fraction from the first moving bed becomes the feed to a second moving bed, the flow of gas from the first moving bed becomes the gases that produce the drag face for the second moving bed, collecting a third fraction from said mixture of discrete solid particles which has moved parallel with the gas flow, collecting as a fourth fraction that portion of said mixture of discrete particles that remains in the second moving bed, sizing said secondary, third and fourth fractions into subfractions, combining subfractions into upgraded products, recirculation streams and rejection streams.

3. In a method as defined by claim 1 wherein the primary fraction from each successive multiple housings becomes the feed and moving bed for the next housing, collection of a fraction from each housing, sizing each said multiple fractions or combination of fractions, combining subfractions into upgraded products, recirculation streams and rejection streams.

4. In a method for the upgrading a mixture of dry discrete particles of various sizes and densities, the steps of providing a gas-suspended moving bed mixture of discrete particles of such a mixture of a particle size generally less than 1/4 inch (6 mm), wherein an upgraded fraction of the dry discrete particles flows parallel with the same direction as the gas, feeding said mixture of discrete particles into one of said moving bed mixtures, feeding said gas to flow over the moving bed mixture, setting up a face of drag with the gas flowing over the moving bed mixture of discrete particles, having the walls of the housings at a variable angle from 30 degrees to nearly vertical, collecting a primary fraction from said mixture of discrete solid particles which has moved parallel with the gas flow, collecting as a secondary fraction that portion of said mixture of discrete particles that remains in moving bed, sizing said primary and secondary fractions into subfractions, combining subfractions into upgraded product, recirculation and reject streams.

5. In a method as defined by claim 4, wherein the primary fraction from the first moving bed becomes the feed to a second moving bed, the flow of gas from the first moving bed becomes the gases that produce the drag face for the second moving bed, collecting a third fraction from said mixture of discrete solid particles which has moved parallel with the gas flow, collecting as a fourth fraction that portion of said mixture of discrete particles that remains in the second moving bed, sizing said secondary, third and fourth fractions into subfractions, combining subfractions into upgraded products, recirculation streams and rejection streams.

6. In a method as defined by claim 4 wherein the primary fraction from each successive multiple housing becomes the feed and moving bed for the next housing, collection of a fraction from each housing, sizing each said multiple fractions or combination of fractions, combining subfractions into upgraded products, recirculation streams and rejection streams.

7. In a method for the upgrading a mixture of dry discrete particles of various sizes and densities, the steps of providing a gas-suspended moving bed mixture of discrete particles of such a mixture of a particle size generally less than 1/4 inch (6 mm), wherein an upgraded fraction of the dry discrete particles flows parallel with the same direction as the gas, feeding said mixture of discrete particles into one of said moving bed mixtures, feeding said gas to flow over the moving bed mixture, setting up a face of drag with the gas flowing over the moving bed mixture of discrete particles/ having the entry walls of the housings at a variable angle from 45 degrees to nearly vertical, having the opposite walls of the housings at a variable angle from 30 degrees to nearly vertical, collecting a primary fraction from said mixture of discrete solid particles which has moved parallel with the gas flow, collecting as a secondary fraction that portion of said mixture of discrete particles that remains in moving bed, sizing said primary and secondary fractions into subfractions, combining subfractions into upgraded product, recirculation and reject streams.

8. In a method as defined by claim 7, wherein the primary fraction from the first moving bed becomes the feed to a second moving bed, the flow of gas from the first moving bed becomes the gases that produce the drag face for the second moving bed, collecting a third fraction from said mixture of discrete solid particles which has moved parallel with the gas flow, collecting as a fourth fraction that portion of said mixture of discrete particles that remains in the second moving bed, sizing said secondary, third and fourth fractions into subfractions, combining subfractions into upgraded products, recirculation streams and rejection streams.

9. In a method as defined by claim 7 wherein the primary fraction from each successive multiple housing becomes the feed and moving bed for the next housing, collection of a fraction from each housing, sizing each said multiple fractions or combination of fractions, combining subfractions into upgraded products, recirculation streams and rejection streams.

10. In a method as defined by claims 1 thru 9 wherein the said mixture of dry discrete particles is coal.

11. In a method as defined by claims 1 thru 10 wherein the said gas is air, nitrogen, carbon dioxide, argon, sulfur dioxide or any mixture of these gases.