CA1330427C - Method and apparatus for separating clay from and then dewatering ultra fine coal - Google Patents
Method and apparatus for separating clay from and then dewatering ultra fine coalInfo
- Publication number
- CA1330427C CA1330427C CA000580930A CA580930A CA1330427C CA 1330427 C CA1330427 C CA 1330427C CA 000580930 A CA000580930 A CA 000580930A CA 580930 A CA580930 A CA 580930A CA 1330427 C CA1330427 C CA 1330427C
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- Prior art keywords
- coal
- clay
- dilatant
- mass
- aqueous
- Prior art date
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Classifications
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L9/00—Treating solid fuels to improve their combustion
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/01—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons
- B01D33/03—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons with vibrating filter elements
- B01D33/0307—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons with vibrating filter elements with bag, cage, hose, tube, sleeve or the like filtering elements
- B01D33/0315—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons with vibrating filter elements with bag, cage, hose, tube, sleeve or the like filtering elements arranged for inward flow filtration
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/01—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons
- B01D33/03—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons with vibrating filter elements
- B01D33/0346—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons with vibrating filter elements with flat filtering elements
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/01—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons
- B01D33/03—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons with vibrating filter elements
- B01D33/0346—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons with vibrating filter elements with flat filtering elements
- B01D33/0353—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons with vibrating filter elements with flat filtering elements self-supporting
- B01D33/0369—Filters with filtering elements which move during the filtering operation with translationally moving filtering elements, e.g. pistons with vibrating filter elements with flat filtering elements self-supporting with curved filtering elements
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/04—Filters with filtering elements which move during the filtering operation with filtering bands or the like supported on cylinders which are impervious for filtering
- B01D33/042—Filters with filtering elements which move during the filtering operation with filtering bands or the like supported on cylinders which are impervious for filtering whereby the filtration and squeezing-out take place between at least two filtering bands
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/35—Filters with filtering elements which move during the filtering operation with multiple filtering elements characterised by their mutual disposition
- B01D33/37—Filters with filtering elements which move during the filtering operation with multiple filtering elements characterised by their mutual disposition in parallel connection
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/44—Regenerating the filter material in the filter
- B01D33/46—Regenerating the filter material in the filter by scrapers, brushes nozzles or the like acting on the cake-side of the filtering element
- B01D33/463—Regenerating the filter material in the filter by scrapers, brushes nozzles or the like acting on the cake-side of the filtering element nozzles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/44—Regenerating the filter material in the filter
- B01D33/48—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps
- B01D33/50—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps with backwash arms, shoes or nozzles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/58—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element
- B01D33/62—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element for drying
- B01D33/64—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element for drying by compression
- B01D33/646—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element for drying by compression by pressure rollers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D36/00—Filter circuits or combinations of filters with other separating devices
- B01D36/02—Combinations of filters of different kinds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D37/00—Processes of filtration
- B01D37/03—Processes of filtration using flocculating agents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03B—SEPARATING SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS
- B03B1/00—Conditioning for facilitating separation by altering physical properties of the matter to be treated
- B03B1/04—Conditioning for facilitating separation by altering physical properties of the matter to be treated by additives
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03B—SEPARATING SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS
- B03B9/00—General arrangement of separating plant, e.g. flow sheets
- B03B9/005—General arrangement of separating plant, e.g. flow sheets specially adapted for coal
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/35—Filters with filtering elements which move during the filtering operation with multiple filtering elements characterised by their mutual disposition
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/58—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/58—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element
- B01D33/62—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element for drying
- B01D33/64—Handling the filter cake in the filter for purposes other than for regenerating the filter cake remaining on the filtering element for drying by compression
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/70—Filters with filtering elements which move during the filtering operation having feed or discharge devices
- B01D33/76—Filters with filtering elements which move during the filtering operation having feed or discharge devices for discharging the filter cake, e.g. chutes
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Organic Chemistry (AREA)
- Solid Fuels And Fuel-Associated Substances (AREA)
- Liquid Carbonaceous Fuels (AREA)
Abstract
A~STRACT OF THE DISCL08URE
A ~ethod ~nd ~pparatu~ rOr dewatering nn aqueous coal slurry include~ impnrting high ~hear rorc~s to th~ aqueous coal slurry in the presence o~
peptizing agent to render co~l particle~ hydrophobic by stripping clay ~ro~ th~ oo~l particles ~nd peptizing th- clay in th- aqu30u- medium Or thu lurry IhO alurry 1- -par~tlng tu rooover coal partlcle~ ana th~ agusou~ m diu~ i~ draining medlum ~rom th~ hydrophobic curfacQ of the coal particles
A ~ethod ~nd ~pparatu~ rOr dewatering nn aqueous coal slurry include~ impnrting high ~hear rorc~s to th~ aqueous coal slurry in the presence o~
peptizing agent to render co~l particle~ hydrophobic by stripping clay ~ro~ th~ oo~l particles ~nd peptizing th- clay in th- aqu30u- medium Or thu lurry IhO alurry 1- -par~tlng tu rooover coal partlcle~ ana th~ agusou~ m diu~ i~ draining medlum ~rom th~ hydrophobic curfacQ of the coal particles
Description
METHOD AND APPARATUS FOR SEPARATING CIAY
~= ~Rl~ ~L'rRA PINE
BACKGROUND OF THE INVENTION
1. Field of the Invention: This Invention relates to a method and apparatus for dewatering ultra fine coal and more particularly to dewatering an aqueou~ coal ~lurry after separating peptized clay from coal particlec in a slurry thereof.
~= ~Rl~ ~L'rRA PINE
BACKGROUND OF THE INVENTION
1. Field of the Invention: This Invention relates to a method and apparatus for dewatering ultra fine coal and more particularly to dewatering an aqueou~ coal ~lurry after separating peptized clay from coal particlec in a slurry thereof.
2- S~ElE~i~e Of the Prior Art: In United Statss patent 4,537,599 there 1~ di6010~ed a proce~
for removing sulfur and ash, particularly clay and pyrite from the surface of coal particles. A peptized ~-~lurry of coal particle~ is treated to separate clay and pyrite from the coal and weaken chemically bonded contaminant~ on the coal sur~ace. The clay and pyrite particle~ are disper~ed as a colloid in an aqueous med~um Or the slurry. To maintain the colloldal ~uspension, the pH Or the slurry is adjusted by the addition of a normalizer. The slurry is then beneficated in a centrifuge and in froth-flotation cell~ to recover coal particle~ greater than two microns. Thereafter, an aqueous coal slurry is again for~ed and the pH is ad~usted to maintain contaminants as colloids in the aqueous medium of the slurry during treatment with ~onic energy and ozone. Thereafter, the aqueou6 coal slurry with the aqueous medium , :-1 ~:
- ` 1 330427 .1, .
containing colloidal conta~inants i~ classified to again ~eparate coal par~icles ~ro~ conta~inantfi.~
The cleaned coal product xecovered from this process can be used for diverse purpo8es, one use as di~closed in U.S. Patent No. 4,662,894, 18 as a ~eed stock for the preparation of a coal water mixture.
The cleaned coal product iB first separated so that coal particles of different size classifications form two or more coal feed streams which are delivered to :`
separate surge vessels in a liquid medium. The feed stream comprised Or coal particles having the smallest size are again classified to di~card a minu~ two micron fract~on which i~ compri3ed mainly of contaminants, particularly clay, and thereafter selected quantitie~ o~ each of the coal ~eed streams are mixed together in the presence of a dispersing agent to form a coal-water mixture.
It is a time consuming and costly, particularly in terms of energy requirements, to -~ 20 reduce the water content of a mass of coal particles, ~i~ particularly in instances where the coal particles . ~ after cleaning to remove clay and pyrite are to`be ~ used in the form of a feed stock having a low moisture ,~ content for any of diverse purposes such as for a ~? ``,~ 2S coal-water mix. The moisture content of the cleaned coal after classification in ~he centrifuge according to the process of U.S. Patent No. 4,537,599, is usually about 32% to 36% by weight and no significant moisture reduction occurs even after several days residence in storage. When an aqueous coal water slurry is dewatered in a conventional belt press, it was found that the moisture content was about 36%
SUMMARY OF THE INVENTION
According to the present invention there is provided a method of treating clay contaminated ultra fine coal particles wherein the method includes the steps of forming an aqueous slurry of clay contaminated ultra fine coal particles, mechanically stripping clay contaminants from the surfaces of the coal particles while subdividing the size of the clay contaminant to clay platelets, peptizing the clay platelets to imp~rt a state of discreetness in the aqueous slurry, , :
,;
collecting a mass of dilatant coal particles in a superimposed rélation upon a dilatant coal layer, the dilatant coal layer being defined by forming an aqueously permeable barrier comprised of a dilatant coal layer of collected coal particles from the slurry upon a barrier, using the dilatancy of the dilatant coal mass in combination with an applied force for dewatering the coal mass by draining aqueous medium along with peptiz,ed clay platelets~from the coal mass: and recovering the, coal mass.
The apparatus of the present invention provides for dewatering an aqueous coal slurry, wherein the apparatus includes a vessel for an aqueous slurry of clay contaminated coal particles, means for supplying a peptizing agent to the `` 1 330427 vessel r means for imparti~g high shear forces to the aqueous medium in the vessel sufficient to separate clay contaminant from the coal surface and subdivide the clay from clay platelets for peptizing the latter, means including an aqueously permeable barrier for forming a dilatant coal layer, means for dewatering a coal mass collected on the dilatant coal layer, and means for recovering the dewatered coal mass.
The present invention also provides a novel coal product produced according to the aforesaid method. The coal product is preferably comprised of coal particles predominately within a size range of 37 and 2 microns.
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These features and advantages of the present invention as well as others will be more fully understood when the following description is read in light of the accompanying drawings in which: -Figure 1 is a schematic illustration of onearrangement of apparatus of the present invention which is also suitable to carry out the method thereof;
Figure 2 is a schematic illustration of a second . -embodiment of the apparatus of the present invention which is also suitable to carry out the method of the present invention:
Figure 3 is a schematic illustration of the third embodiment of the pxesent invention;
Figure 5 is a schematic illustration of a third ,- embo~diment of ths apparatus of the present invention which is also suitable to carry out the method thereof:
Figure 5 is an enlarged view in section of the coal ¦~; withdraw portion of a classifier included in the apparatus of ~ Figure 4; and } ~
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Figures 6, 7 and 8 are graphs illustrating the moisture reduction effect on dialant and hydrophobic coal particles according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to Figure 1, there is illustrated a mixing vessel 10 into which there is added a coal feed stock, which is indicated by reference numeral 12, the feed stock maya be freshly mined coal or coal salvage from silt ponds or other suitable sources. The feed stock can be an aqueous slurry, as for example, the underflow from a static thickener or other thickening device common to the practice of coal processing. Untreated ultra-fine coal may comprise the feed stock for the process and apparatus cf the present invention. Such coal generally has constituent components of: coal of varying purity; high ash impure coal or bone; clay and clay shales: pyrite/marcasite; and various other high ~ 20 ash carbonous and non-carbonous rocks and minerals.
"! If desired, the feed stock can be cleaned coal particles derived from other coal cleaning process after treatment for removal of any hydrocarbon containmen~ from the surfaces of coal particles that li 25 are to be peptized. Preferably the feed stock is made ~;
~ 6 ,, ~, ~' ~ ~ 330427 up of coal parti¢leB typically 100 me~h or les6 but can be ~ mesh or less, Tyler ~ries. The vessel 10 alQo receives water, if required, which is introduced by line 14 to form an aqueous slurry in the vessel to which there is al50 added a pept~zing agent by way of line 16. Preferably the aqueou~ coal slurry contains 25% to 35% solids by dry weight. The peptizing agent B i~ added as one ~tep in the ~orming o~ the aqueous coal slurry. Any one of a number of substances can form the peptizing agent, an example of one peptizing agent is sodium hexametaphosphate which i~ effective in a pH range of about 6.8 to about 8Ø Another peptizing agent which i~ not pH sensitive i6 ;~ Praestaminol which is available ~rom Stockhausen.
In the forming of the peptized coal slurry, a motor 18 i8 energized to rotate a mixer blade 20 that is submergQd in the tank. The mixer is operated for a pariod of time, usually at least 5 minute~ under operating condition6 that impart high shear for¢es to the coal water ~lurry. During the high ~hear mixing/peptizing period, a high degree~of aeration or air entrainment takes place including solubilizlng of air in the water of the slurry. Thus there ls , ~ , solubilized air in the water on the surface of the coal particles. The application o~ high shear ~orces ~`` ` i breaks the adhesion and ionic bonds which bond clay particles. The mixing o~ the ~lurry $n the peptizin~
vess21, peptizes the clay particle~ and deagglomeration occurs which render~ the individual coal impurities, other than clay, and clay particles into a state of discretenes~. The individual clay particles fall within a typical size range of between 0.68 to 2.0 micrometers and interact with a peptizing agent to effect an ionic exchange thereby imparting to the clay particles a strong negative electrokinetic i charge. The peptized clay particles become discrete and become suspended a~ a colloid in the a~sociated water of the slurry~ Under these conditions, the individual coal particles attain a state of di~cr~tene~ from clay and other coal impuxltles relea~ed ~rom the face surface~ Or the coal particle~.
Once ~ree of adhered clay, the coal particles are ~ rendered hydrophobic. In the event the selected 3~ peptizing agent requires a pH adiustment to the aqueous slurry, then according to the demands of the particular peptizing agent a suitable neutralizing agent is introduced into the vessel to bring about the requlred pH ad~ustment.
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The treated aqueous slurry is then discharged ~rom the ve~sel 10 by line 22 to a wet screening apparatus 24 having three tandem arranged vibrating screens 26, 28 and 30 where the aqueous phase along with peptized clay particleR and other undersized contaminants drain from the coal particles which remain on the screens. After the ini~ial drainage of a predominant liquid part of the aqueous -phase, the vibrating screen, imparts energy to the ~0 coal particles which are now in a state of dilatancy.
The energy cau~es an expulsion of 6urfac~ moisture from the coal particlqs along with clay particlas ~ associated therewith. It can be expected that the ;~ moistu~e content of the overflow product will be reduced from an initial 70-75~ moisture by weight down to 30-31% percent moisture content when discharged from the v,ibrating ~creens. The reduced moisture contènt i6 signiflcantly less than the usual 40% which is obtained without peptization and attendant clay , ~, .
desliming.
~- The wet screening apparatus illustrated in Figure 1 is of the type well known in the art and made by~Derrick Manufacturing Company of Buffalo, New York.
The three screen panels 26, 28 and 30 are mounted on a frame which is excited by a high speed vibrating motor ,'~
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- s 32. The ncreen panels preferably have screens having a 400 mesh (37um) ~ize. Typiaally, the ~creen panels vibrate at 3600 cyclGs per minutQ which is a hlgh frequency vibration having a low amplitude to rapidly S expel aqusous liquid including clay, which may be still pre~ent, from the coal particle~. The aqueous coal slurry is di~tributed acro~s the width of ths ~irst screen panel 27 by a head box 34. The screen panels are inclined to the horizontal in a manner such that the screening surfaces extend downwardly to a terminal end where the top screen product passes to an undarlying collector 36 which directs the top screen product to discharge line 38. The aqueous liquid ~- medium, peptized clay, other undersized contaminants and undersized coal particles pass through the screens ,;i ' , and are collected in an lnclined underlying tray 40 ~or di~¢harge from the machine by conduit 42.
The solids o~ the underflow are -37um fractions which can be discarded or when desired the re idual coal content can be recovered by treatment in froth flotation cells or in a hiqh ~peed centrl~uge.
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The peptizad condition of the underproduct greatly enhances the separation proces~ by froth c~lls. The coal is more amenable to the action of the frothing agent and the efficiency of coal recovery is improved.
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When a high speed centrifuge is used, a cut should be made at about 2, um because the clay is predominantly contained in the -2,, um fraction. To be economical feasible the plus 2, um. of the -37, um fraction must be mainly coal. The burden on the centrifuge is reduced due to the initial separation by the vibrating screens. In Figure 1 conduit 42 is illustrated schematically in which clay and other contaminants conducted by the conduit are discharged into a silt pond or a waste area generally indicated by reference numeral 44. The screen over product recovered from the vibrating screens is delivered by line 38 to a vibrating hopper 46 or if desired the top screen ~ product may be delivered first to a belt press 48.
I 15When the coal mass is delivered by line 38 from the vibrating screens to the vibrating hopper 46, the coal particles collect in a hopper chamber 50 wherein vibrating tubes 52 are arranged as fingers as ~; shown in Figure 1, extending along the height of the coal mass and angularly at the bottom portion to exit sites in one of two stopping bottom wall sections.
, , ,~ -The tubes 52 are perforated and packed with long grained filter media. A motor 54 coupled through an eccentric 56 to vibrator frame imparts low frequency large amplitude vibration to the tubes 52. The tubes ~::
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deliver liquid collected in the hopper chamber to drainage ports 58 which communicate with a drain box 60.
The hopper chamber 50 has an opening in the other sloping bottom walls which communicate with a discharge chamber 62 having helical flight attachments 64 on a shaft 66 driven by a motor 68. Coal particles , are carried by the flight attachments from the bottom of the hopper chamber to a discharge header box 70 for delivery by line 77. The incoming coal particles in line 38 typically have a moisture content of 30-31% by weight. After about 29 minutes treatment time in the vibrating hopper, the moisture content is reduced to ~;
~ 24% by weight. -j Energy can be imparted to the mass of coal in the hopper chamber 50 by other means than mechanically operative vibrator device. Such other means can take the form of perforated tubes extending in the coal mass in a manner similar to tubes 52. The ~:
perforated tubes connected with a header by which ~'~ 20 compressed air can be delivered to the tube and ~` exhausted through the perforated openings to the coal~ ,~
mass. Such streams of compressed air permeating the coal mass transfers sufficient energy to drive ~; moisture from the surface of the coal particles.
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When it i8 de3ired to speed up the ; dewatering process, the coal particles in line 38 are ~irst mixed with a ~mall quantity, typically 1%
ligninsolfunate by weight of coal particles in a 5 ribbon type mixer 74 and then the admixture of coal particles and ligninsolfunate are feed to the hopper 3' chamber 50. After about 10 minute~ treatment in the J vibrating hopper, the moisture content of the coal is reduced to about 24% by weight when discharged from s 10 the hopper. No further moisture reduction will occur beyond 10 minutes treatment time with the ligninsolfunate in the hopper 46. The ligninsolfunate has an affinity for carbon and tharefore drives ~-adhered moisture on the coal from the coal particles.
A surprising result reaides in the discovery that the removal of the clay renders the resulting coal particles particularly su$table for extruding operation~ to produce a product which can be more easily handled and shipped. Ultra fine clay containing coal without dewa~ering including de~liming, according to the present invention, cannot be extruded without a moi~ture reduction to below about 10% by weight and the addition of expensive lubricants and binders. The extruder is identified by ,~ .
~;; 25 reference numeral 76.
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The feed stream in line 38 can b~ fed alternatively to a chamber 78 of the belt press 48 and discharged under gravity onto a first endless belt 80 which carries the coal water burden beyond a rollQr 82A to a second endle~ belt 84. The belts 80 and 84 are sieve belt~ made of synthetic fiber so that liquid, particularly water, can freely pass from the coal particl~s on and between the belts on a horizontal drainage section 86 and in a roller pressing section 88B. Liquid draining from the belt~
is collected in a container 90. The coal and liquid mixture between the belts entering section 88A is subject to high pressurss and shearing forces as the belts pass along a tortuous path formed by rollers 88B
which aro connected to a ~uitable drive. Other rollers 88C and 88D as well as roller 88A are re~ovably mounted to control tensioning of the belts ;~ by actuators. The dewatered reed stream is discharged ~rom between the belts at 88E. The coal mass recovered fro~ the ~elt press is ready for u~e.
The hydrophobic characteristic of the mass ;~ of recovered coal particles from the vibration hopper or belt press even without the addition of ligninsolfunate undergoes an accelerated reduction to ,~.
~1~ 25 the moi~ture content. Upon expo-~ure to the ;~
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atmosphere, a constant rate drying period is initiated during which the ~ur~ace o~ the aoal mass i~ entirely wet. Evaporation takes place at whatever rate is dictated by the surrounding conditions of air temperature, humidity and replacement ratQ o~ air and coal particle moisture. An upward change in the temperature of the cake whether induced internally or by external means, results in an expansion of the solubilized air. This re~ult~ in creation of internal pressure on the entrained moisture in capillaries and interspaces between coal particle~. Net effect of this is to accelerate the capillary migration, or wicking of the internal moi6ture toward the surface o~
the coal mass and in turn, the reduction of time required ~or the evaporative proces~ to be totally ef~ective.
1~ The wet screening apparatu~ i8 ~urpri~ingly ¦~ ef~ective and produced a dramatic reduction to the water content to the top ~creen product. Prior to the :, present invention, it was not possible to reduce the water content of a clay contaminated mass of -100 mesh 150, um~ coal parti¢}es recovered from an aqueous ~lurry below about 40% by welght. ~oreover, a more surprising result is the'dramatic decrease of the ash content of the variouR fraction~ of the minus -100 :~, ~ 15 ,~
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me~h (-150, um) scre~n over-produ~t when oompar~d with a wet sieve analysi~ of a peptized head sample of the feed to a Derrick f creen equipped to ~eparate at a nominal 400 mesh or 37,um. The results are qiven in s Table I.
TABLE I
Weiaht ~rY A~h . Over- , Over-Mesh Head Sam~le Product Head Sam~le Product Size ~~ ~ Cu~. ~ Cum. _% _ Cum. % Cu 1oax325 32.1 32.1 66.0 66.0 15.9 15.9 8.2 8.2 325X400 5.1 37.210.6 76.6 17.2 16.1 11.6 8.7 400XSO0 5.7 42.96.0 82.6 20.3 16.6 12.9 9.0 - 500 57.1 100.017.4 100.0 45.6 32.1 39.8 14.4 Wet sieve analyse~ ~how the transfer of the highf2r ash clay and other minus 37,u.m. impuritie3 to the screen ! under product by way of the passage of the aqueous solution through the screen openings. This can be een by comparison of the dry a~h content of the ecreen over product fractions with those of ~he under .
product fSractions. The results are giv~n in Table II.
.~
. 20 TABLE II
Weiqht Dry Ash ~:~ Over- Under- Over- Under-Mesh Proauct Product Product P~oduct Size - % Cum. % Cum. % Cum. % __Cum. -~: 100X325 66.0, 66.0 0.1 0.1 8.2 8.2 11.7 ~}1.7 325X400 10.6 76.6 0.6 0.7 11.~ 8.7 13.4 13.1 400X5006.0 82.6 5.7 6.4 12.9 9.O 20.7 19.8 :
~ 25 - 50017.4 100.0 93.6 100.0 39.8 14.4 45.8 45.4 ., ,~
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In thi~ teet the cumulative recovery of coal value~ in the plus 25, um fraction of the feed as calculated on an ash halance basis was found to be 99.2%.
In Figure 2 there i8 illustrated a further embodiment of the present invention, in which vessel 10, like the embodiment of Figure 1, recaives coal feedstock, water and a peptizing agent from supply lines 12, 14 and 16, respectively. The feed stock is ~ixed under high shear ~orces by motor 18, and the mixing process is carried out for a sufficient period of time to peptize clay particles which are driven from the surface of the coal particle#. The mixture i~ delivered from the vessel 10 to a head box of a vibrating sieve bend 94 where the aqueous phase including peptized clay and undersized solids drain to a collection pan 96 from the mass of coal particles on curved screen a~ssmbly 98. The screen assembly i~
vibratsd by drive motor 100 at a high frequency, e.g.
3600 cycles per minute at a low amplitude motion. The under product including an aqueous phase i~ carried away by a drain line 102. The over-product from sieve ~- bend 98 is delivered by way of a hopper collector 104 : ~
to a pug mill 106. The fraction in drain line 102 is ; delivered to a vibrating screen as~embly 108 which can ~~
be the ~ame as ~creen a~sembly 24 described ,"~
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.. ,~ , ,.. ,.,~, ~ ,.. ,~:., ,, ~.,.,,,.. ` ;-hereinbaforQ and shown in Figure 1. The screen over- --~ product i~ delivered by line 110 to the pug mill 10~.
'l This arrangement of apparatu~ has the advantage of offering a greater re~idence t~me by the underflow in line 102 on a vibrator screen 108 so that the moisture ~j on the face surfaces of the coal particles can be acted upon for a longer period of time as the coal ;! particles pass along the vibrating screens. The product fed to the pug mill 106 i8 mixed with ~ 10 ligninsolfunate, a binder or other agent delivered by ¦~ line 112 to the pug mill and mixed therein w~th the coal particle~. The product discharged from the pug mill is delivered by line 114 to vibrating hopper 116.
After dewatering in hopper 116, the coal particles form into 8uitable extruded shapes by extruder 118 for shipment. In~tead of extruder 118, if desired, the product ~rom the vibrating hopper can be feed to a rotating peltatizum drum, disc or pin mixer where the coal particles are agglomerated into pellets.
In Figure 3, like the embodiments of Figures 1 and 2, vessel 10 receives coal feedstock, water, and a peptizing agont from supply lines 12, 14 and 16, -~
~-~ respectively.i Mixing occurs under high shear force ~-; conditions produced by blade 20 driven by motor 18.
The coal ~lurry is delivered by line 22 to a vibrating ~ ' ~
~ 18 :~ ' `,'~
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~ ~ 1 330427 ~creen a~embly 120 which i8 the same as screen as~embly 24. The screen under products can be discarded by line 122 and the screen over product i~
deliver~d to a pug mill 124 which includes a helical mixing blade 126. Ligninsolfunate is mixed with the coal particles in the pug mill to speed up the dewaterlng process. Aqueous liquid drains from the coal slurry in the pug mill by line 130. $he coal particles can then be treated according to e~bodiments 10 of Figures 1 and 2 downstream of assembly 24. ~ -In the embodiment of the invention ~hown in Figures 4 and 5, like the embodiments of Figures 1, 2 and 3, a vessel 10 receives coal feedstock, water and peptizing agent in lines 12, 14 and 16 respectively.
The feedstock, initial pulping water and peptizing agent are introduced into the peptizing tank to produce a slurry having rrom 10% to 45% dry solids.
The slurry i~ mixed ~or a period of time, under condition~ imparting high shear ~orces to the coal . ~ ~
'~ 20 particle~. Usually a mixing time of at least 5 ~ minute~ i8 required. Should the peptizing ; agent be pH sensitive, then a pH adjust~ent is ~ade to the aqueous coal slurry by the addition of a suitable neutralizing agent before the addition of the peptizing agent. This is particularly true when ,3.':. 19 l i',~
.
sodium hexametapho~phate 1~ u~ed. Other peptizinq agents whlch are not pH dependent are well known and can be selected for use~ As explained previQusly, th~
mixing of the slurry in the peptizing Ve88Ql ~ peptize~
the clay particles and deagglomeration occurs which renders the individual coal impurities other than clay and clay particles ~nto a state of di~creteness. The individual clay particle~ fall within a typ~cal aize range of between 0.68 to 2.0 micrometers and interact with a peptizing agent to effect an ionic exchange I thereby imparting to the clay particles a strong negative electrokinetic charge. The peptized clay particle~ become discrete and become su~pend~d a~ a colloid in the a~sociatQd water of the slurry.
The peptize slurry after mixing, i8 transferred by line 22 to a dilution tank 132 wherein ~ .
the percent of dry solids making up the coal wa~er slurry is ad~ustsd by lowering the percent to permit :
unhindered settling of unpeptized particles larger than the point of classification size as well as unhindered upward migration of water, clay and such other particles of coal and associated unpeptized material that are smaller in particle size than the , . I ~ , . :
chosen point of classification. Typically, it is desired to adjust the solid content of the slurry with . ~:~
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the addltion of water from supply line 134 whereby the dry solid content iB a maximum o~ 10 percent but not 1eB8 than 2.5 percent. Solids are kept in solution in dilution tank by means of stirring blades 136 driven by motor 138. The slurry from the dilution tank i8 then delivered by a flow line connected to a metering pump 140 into an upcurrent classif~er 142. The point , of entry in the classifier by the diluted coal water i slurry i8 at the site of dispersion dispenser 144.
10 The dispenser is a generally conical member having the ~-apex thereof directed upward whereby a alurry entering the slassifier proceed~ against the inter conical wall o~ the disper~er 80 that the slurry rebounds and is directed toward the truncated conical bottom 146 of the upcurrent classifier. The dispen~er ¢an take the for~ of a rotating perforated arm driven by the velocity of the aqueous slurry exiting from the perforations~
~he slurry introduction procedure provides guiding for the particles of coal to settle in the manner o~ a sediment. Water with peptized clay as a ~ ., i collold thereln along with ~mall coal particles`and '~,;; other ~lner~l~ of lesser size mlgrate to a point of cla~siflcation along a rever~e coar~e of travel and pass upwardly towards the discharge opening 148 at the . '~
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1 330~27 /
top of the classifier. The classifier iB constructed 80 as to siphon off the ef~luent in a guie~cent and controlled manner. Since the settled coal particle~
and non-clay mineral particles are rendered dilatant and hydrophobic in the peptization process as opposed to a non-dilatant, hydrophilic properti~ of clay and of a mixture o~ al~y, coal and others assoclated mi~eral~. The ~ettled partlcle~ in th~ truncated conical bottom 146, of the classifier arrange themselves in a manner conducive to the exclusion of the presence of water and its accompanying peptized clay load impo~ed by the overlying column of liquid.
Low ~requency, high amplitude vibrations, generated by a vibrator 150 driven by motor 142 are imposed on the ~;~
conical bottom 146 which serves as an inducement to the resi~tance of the introduction of water into the ~ettled material at the conical bottom. To eliminate the possibility of rat holing, it may be necessary in some in~tances to install an inverted cone in the , .
interior of the conical bottom 80 as to create an annular opening between the cone and conical bottom 146 of a proper width through which settled particles can pass in their downward movement towards a . .
di~charge conveyor screw assembly 154 which draws off ,~ 25 quantities of coal particles from the classifier.
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1 330~27 As best shown in Figure 5, an upset cone 156 i~ fit into the interior of the conical bottom of the separ~tor in a opaced relation from the conical bottom ~ 146 to form angular opening b~tween the two cones.
¦ 5 The width of the opening i~ selected 80 that cone particles can pass in their downward movement towards a discharge assembly ~54. As the settled particles bscome compacted in the annular gap, free water ~ migrates to the interface between the compacted mass J, 10 and the surface of the conical bottom. Further, dewatering i6 achieved by a series of horizontally arranged annular rings 158 and 160 which are installed as shown in Figure 5 on the cone 156 and annular ~ bottom 146, respectively, to interrupt the continuity i 15 o~ the flow path. The rings may be packed with non-corroding metal wool so as to provide an unobstructed free passage for captured water to exit at the ring through a portal opening in the side wall of the classifier. Each ring will produce a con6tant discharge of water from the classifier.
Point size of classification is a function of the vertical distance between the point of dispersion~distribution and the veloclty of the upward moving column of water and its load of colloidal clay and ultra fine particles. In turn, velocity is a ~::
~ 23 :~
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function of the area dimensions of the vessel, percent o~ dry solids in ~he ~lurry and volumetric rate of introduction of slurry into the up-current cla~ifying vessel. ~ince the characteristic of each raw feedstock and the ~arket requirements for the end product to be recovered from it are site specific and the largest size clay platelet i8 smaller that 2,um, A
cla3sification point of 2,um for most coal6 should prove desirable. However, higher points of classification, such as lOum and even as large as 25, um, may be found more suitable to effect the desired degree of ash reduction to be attained in the process.
Ash reduction i6 limited to the total of the ash of the clay minerals that can be peptized. In the ma;ority of coal6, this should be sufficient to reduce ~ the ash in the finished product to a point acceptable -¦ to the market place. Since pyrite occurs as circular l platelets in all ~izes in ultra-fine raw coal, all free pyrite in the peptized slurry of a finer size than the point of classification will report to the tailings ~ and the ~ulfur content of the recovered product will 3: be commensurately reduced.
The effect of rendering the recovered -~ particles dilatant and hydrophobic along with ,~ .
:
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, 91~.. ` ' ' , , compaction through vibration allowG removal of the product ~rom the classi~ier at an initial molsture level of about 27 percent as compared to a moisture content of about 34 percent should the produc~ be repulped and then dewatered in a high speed centrifuge. Recovery by centrifuging of an unpeptized -100 mesh (-150, um) feedstock produces a cake having a minimum of 40 percent moisture and more likely in the range of 50 percent to 60 percent moi~ture. By way of comparison, the moisture content of the underflow from an up-current classifier feed of an ultra-fine unpeptized raw coal slurry will rarely be less than 65 percent.
Within the initial hour after di~charge from the vessel, natural drainage will eli~inate all of the free water. During this period and continuing thereafter until all of the unbound water has been eliminated, the evaporation phenomenon i6 in effect.
For example, without thermal assist the moisture content o~ a layer of product 1/2" to 3/4" thick will be reduced at the rate of 1.2 percent per hour until air dry equilibrium is reached.
If thie product is mixed with a small amount - of ligninsolfunate and then exposed to the ambient atmosphere in a layer of similar thickness without ::
/
moving air, the natural evaporation phenomenon reault~
in a reduction of the remaining unbound moisture at the rat~ o~ 3.6 percent per hsur.
It is nece~ary to understand that ultra-fine coal that has been ~tripped of all clay through the peptization proce~s has entirely dirferent physical characteristics than those of a normal coal/clay association. In addition to the dewatering 0 phenomenon, this change in characteri~tics permits the reforming of ultra-fine coal into larger, more q marketable forms by extrusion, pelletizing or pressing. Generally, this i6 not presently i economically po~sible with unpeptized ultrafine coal.
i 15 In the graph of Figure 6, a drying test is demon~trated by a comparison bet.ween peptized and -~ ;
unpeptlzed centrifuge cakes about 3/4" ln thlckne~
wlthout the addition of ligninsolfunate in a 115 ; degrees F forced air atmosphere. As can be seen from Figure 6, graph line 162 indicates the per cent reduction of moisture in a processed cake comprised of dilatant coal particles and graph line 164 shows a reduction to moisture contact of a raw cake comprised .
of coal particles that are not dilatant. A
dramatically increased amount of moisture is drawn .; ~ ' ~ .
~ .
*rom the dilatant coal p~rticles as can be seen ~rom a comparison of graph lines 168 and 170. The percent of the moisture content in the proces~ed cake wa8 ~ound to decrease a~ shown by graph line 168 to about 2 percent within about 3 1/2 hour~ after processing according to the present invention. An unprocessed filter cake did not obtain a corrQsponding percent moisture content until about 14 hours after treatment as shown by graph line 170.
Figure 7 illustrate~, by two sets of graph curves, the percent redu¢tion to the moisture conten~
of a peptized classifier coal product in a drying test wherein the ambient temperature was 75 degrees F.
I average in static atmo~pheric air. Graph line 172 ¦ 15 shows the dramatic reduction to the percent of the moisture content in the classifier product which i8 mixed with one percent by weight ligninsol~unate as ~,; compared with graph line 174 which 6hsw6 the percent I~- reduction to the moisture content in the same Gla~sifier product but without the addition of lignin~olfunate. There was about a 47% moisture ~;~ reduction to the treated peptized product within the !~ first five hours as compared with only about~a 13%
reduction during the ~ame time period of an untreated peptized product. Similarly, the percent o~ moisture ``~
``:::
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~ 33~4~7 in the classifier product treated with lignin~olfunate dropped rapidly as can be ~een by graph line 176 a~
compared with graph line 17a which shows the percont of moi ture content of the classifiar product without the addition of ligninsolfunate.
In F~gure 8, the e~ect of heated forced air at 360 degrees F. verses so degrees F. a~blent still air on the moisture reduction of a peptized extruded classi~ier product i~ ~h~wn by pairs of graph lines.
In the drying test depicted by the graph lines o~
Figure 8, classifier product samples are treated with ~- one percent ligninsolfunate. One sample was exposed ~- to forced air at 350 degrees F, while another sample ~- was exposed to still air at 90 degrees F. ambient.
The percent reduction o~ moi~ture content in the ~ forced air classifier product is shown by graph line ¦~ 180, and it can be seen that within the first lO ~-~
~` minutes, a very dramatic moisture reduction occurs as compared with the ~oisture reduction of the classifier 20 product in still air as shown by graph line 182. The ~
effect on the moisture content of the classifier ~;
product under forced air condition shows that within , ~ about 15 minutes as depioted by graph line 184 there t ~ was a percent moisture reduction that could not be I ~ 25 achieved in still air until about a lapsed time of 30 ~ ~ 28 1 330~7 ,~.
or more minutes as depicted by graph line 186. Thus, a~ can be clearly under~tood by tho~e skilled ln the art, the effect of lignin~olfunate greatly Qnhance~
the ~peed at which dawatering of the mas~ of coal particles occurs.
While the present invention has been described in connection with the pre~erred embodiment of the various figures, it is to be understood that other similar embodiments may be used or modification~ .-and additions may be made to the described e~bodiment for performing the same function of the present invention without deviating therefrom. Therefore, the pre~ent invention ~hould not be limited to any ~ingle embodiment, but rather construed in breadth and ~cope in accordance with the recitation of the appended claims.
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for removing sulfur and ash, particularly clay and pyrite from the surface of coal particles. A peptized ~-~lurry of coal particle~ is treated to separate clay and pyrite from the coal and weaken chemically bonded contaminant~ on the coal sur~ace. The clay and pyrite particle~ are disper~ed as a colloid in an aqueous med~um Or the slurry. To maintain the colloldal ~uspension, the pH Or the slurry is adjusted by the addition of a normalizer. The slurry is then beneficated in a centrifuge and in froth-flotation cell~ to recover coal particle~ greater than two microns. Thereafter, an aqueous coal slurry is again for~ed and the pH is ad~usted to maintain contaminants as colloids in the aqueous medium of the slurry during treatment with ~onic energy and ozone. Thereafter, the aqueou6 coal slurry with the aqueous medium , :-1 ~:
- ` 1 330427 .1, .
containing colloidal conta~inants i~ classified to again ~eparate coal par~icles ~ro~ conta~inantfi.~
The cleaned coal product xecovered from this process can be used for diverse purpo8es, one use as di~closed in U.S. Patent No. 4,662,894, 18 as a ~eed stock for the preparation of a coal water mixture.
The cleaned coal product iB first separated so that coal particles of different size classifications form two or more coal feed streams which are delivered to :`
separate surge vessels in a liquid medium. The feed stream comprised Or coal particles having the smallest size are again classified to di~card a minu~ two micron fract~on which i~ compri3ed mainly of contaminants, particularly clay, and thereafter selected quantitie~ o~ each of the coal ~eed streams are mixed together in the presence of a dispersing agent to form a coal-water mixture.
It is a time consuming and costly, particularly in terms of energy requirements, to -~ 20 reduce the water content of a mass of coal particles, ~i~ particularly in instances where the coal particles . ~ after cleaning to remove clay and pyrite are to`be ~ used in the form of a feed stock having a low moisture ,~ content for any of diverse purposes such as for a ~? ``,~ 2S coal-water mix. The moisture content of the cleaned coal after classification in ~he centrifuge according to the process of U.S. Patent No. 4,537,599, is usually about 32% to 36% by weight and no significant moisture reduction occurs even after several days residence in storage. When an aqueous coal water slurry is dewatered in a conventional belt press, it was found that the moisture content was about 36%
SUMMARY OF THE INVENTION
According to the present invention there is provided a method of treating clay contaminated ultra fine coal particles wherein the method includes the steps of forming an aqueous slurry of clay contaminated ultra fine coal particles, mechanically stripping clay contaminants from the surfaces of the coal particles while subdividing the size of the clay contaminant to clay platelets, peptizing the clay platelets to imp~rt a state of discreetness in the aqueous slurry, , :
,;
collecting a mass of dilatant coal particles in a superimposed rélation upon a dilatant coal layer, the dilatant coal layer being defined by forming an aqueously permeable barrier comprised of a dilatant coal layer of collected coal particles from the slurry upon a barrier, using the dilatancy of the dilatant coal mass in combination with an applied force for dewatering the coal mass by draining aqueous medium along with peptiz,ed clay platelets~from the coal mass: and recovering the, coal mass.
The apparatus of the present invention provides for dewatering an aqueous coal slurry, wherein the apparatus includes a vessel for an aqueous slurry of clay contaminated coal particles, means for supplying a peptizing agent to the `` 1 330427 vessel r means for imparti~g high shear forces to the aqueous medium in the vessel sufficient to separate clay contaminant from the coal surface and subdivide the clay from clay platelets for peptizing the latter, means including an aqueously permeable barrier for forming a dilatant coal layer, means for dewatering a coal mass collected on the dilatant coal layer, and means for recovering the dewatered coal mass.
The present invention also provides a novel coal product produced according to the aforesaid method. The coal product is preferably comprised of coal particles predominately within a size range of 37 and 2 microns.
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These features and advantages of the present invention as well as others will be more fully understood when the following description is read in light of the accompanying drawings in which: -Figure 1 is a schematic illustration of onearrangement of apparatus of the present invention which is also suitable to carry out the method thereof;
Figure 2 is a schematic illustration of a second . -embodiment of the apparatus of the present invention which is also suitable to carry out the method of the present invention:
Figure 3 is a schematic illustration of the third embodiment of the pxesent invention;
Figure 5 is a schematic illustration of a third ,- embo~diment of ths apparatus of the present invention which is also suitable to carry out the method thereof:
Figure 5 is an enlarged view in section of the coal ¦~; withdraw portion of a classifier included in the apparatus of ~ Figure 4; and } ~
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Figures 6, 7 and 8 are graphs illustrating the moisture reduction effect on dialant and hydrophobic coal particles according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to Figure 1, there is illustrated a mixing vessel 10 into which there is added a coal feed stock, which is indicated by reference numeral 12, the feed stock maya be freshly mined coal or coal salvage from silt ponds or other suitable sources. The feed stock can be an aqueous slurry, as for example, the underflow from a static thickener or other thickening device common to the practice of coal processing. Untreated ultra-fine coal may comprise the feed stock for the process and apparatus cf the present invention. Such coal generally has constituent components of: coal of varying purity; high ash impure coal or bone; clay and clay shales: pyrite/marcasite; and various other high ~ 20 ash carbonous and non-carbonous rocks and minerals.
"! If desired, the feed stock can be cleaned coal particles derived from other coal cleaning process after treatment for removal of any hydrocarbon containmen~ from the surfaces of coal particles that li 25 are to be peptized. Preferably the feed stock is made ~;
~ 6 ,, ~, ~' ~ ~ 330427 up of coal parti¢leB typically 100 me~h or les6 but can be ~ mesh or less, Tyler ~ries. The vessel 10 alQo receives water, if required, which is introduced by line 14 to form an aqueous slurry in the vessel to which there is al50 added a pept~zing agent by way of line 16. Preferably the aqueou~ coal slurry contains 25% to 35% solids by dry weight. The peptizing agent B i~ added as one ~tep in the ~orming o~ the aqueous coal slurry. Any one of a number of substances can form the peptizing agent, an example of one peptizing agent is sodium hexametaphosphate which i~ effective in a pH range of about 6.8 to about 8Ø Another peptizing agent which i~ not pH sensitive i6 ;~ Praestaminol which is available ~rom Stockhausen.
In the forming of the peptized coal slurry, a motor 18 i8 energized to rotate a mixer blade 20 that is submergQd in the tank. The mixer is operated for a pariod of time, usually at least 5 minute~ under operating condition6 that impart high shear for¢es to the coal water ~lurry. During the high ~hear mixing/peptizing period, a high degree~of aeration or air entrainment takes place including solubilizlng of air in the water of the slurry. Thus there ls , ~ , solubilized air in the water on the surface of the coal particles. The application o~ high shear ~orces ~`` ` i breaks the adhesion and ionic bonds which bond clay particles. The mixing o~ the ~lurry $n the peptizin~
vess21, peptizes the clay particle~ and deagglomeration occurs which render~ the individual coal impurities, other than clay, and clay particles into a state of discretenes~. The individual clay particles fall within a typical size range of between 0.68 to 2.0 micrometers and interact with a peptizing agent to effect an ionic exchange thereby imparting to the clay particles a strong negative electrokinetic i charge. The peptized clay particles become discrete and become suspended a~ a colloid in the a~sociated water of the slurry~ Under these conditions, the individual coal particles attain a state of di~cr~tene~ from clay and other coal impuxltles relea~ed ~rom the face surface~ Or the coal particle~.
Once ~ree of adhered clay, the coal particles are ~ rendered hydrophobic. In the event the selected 3~ peptizing agent requires a pH adiustment to the aqueous slurry, then according to the demands of the particular peptizing agent a suitable neutralizing agent is introduced into the vessel to bring about the requlred pH ad~ustment.
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The treated aqueous slurry is then discharged ~rom the ve~sel 10 by line 22 to a wet screening apparatus 24 having three tandem arranged vibrating screens 26, 28 and 30 where the aqueous phase along with peptized clay particleR and other undersized contaminants drain from the coal particles which remain on the screens. After the ini~ial drainage of a predominant liquid part of the aqueous -phase, the vibrating screen, imparts energy to the ~0 coal particles which are now in a state of dilatancy.
The energy cau~es an expulsion of 6urfac~ moisture from the coal particlqs along with clay particlas ~ associated therewith. It can be expected that the ;~ moistu~e content of the overflow product will be reduced from an initial 70-75~ moisture by weight down to 30-31% percent moisture content when discharged from the v,ibrating ~creens. The reduced moisture contènt i6 signiflcantly less than the usual 40% which is obtained without peptization and attendant clay , ~, .
desliming.
~- The wet screening apparatus illustrated in Figure 1 is of the type well known in the art and made by~Derrick Manufacturing Company of Buffalo, New York.
The three screen panels 26, 28 and 30 are mounted on a frame which is excited by a high speed vibrating motor ,'~
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- s 32. The ncreen panels preferably have screens having a 400 mesh (37um) ~ize. Typiaally, the ~creen panels vibrate at 3600 cyclGs per minutQ which is a hlgh frequency vibration having a low amplitude to rapidly S expel aqusous liquid including clay, which may be still pre~ent, from the coal particle~. The aqueous coal slurry is di~tributed acro~s the width of ths ~irst screen panel 27 by a head box 34. The screen panels are inclined to the horizontal in a manner such that the screening surfaces extend downwardly to a terminal end where the top screen product passes to an undarlying collector 36 which directs the top screen product to discharge line 38. The aqueous liquid ~- medium, peptized clay, other undersized contaminants and undersized coal particles pass through the screens ,;i ' , and are collected in an lnclined underlying tray 40 ~or di~¢harge from the machine by conduit 42.
The solids o~ the underflow are -37um fractions which can be discarded or when desired the re idual coal content can be recovered by treatment in froth flotation cells or in a hiqh ~peed centrl~uge.
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The peptizad condition of the underproduct greatly enhances the separation proces~ by froth c~lls. The coal is more amenable to the action of the frothing agent and the efficiency of coal recovery is improved.
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When a high speed centrifuge is used, a cut should be made at about 2, um because the clay is predominantly contained in the -2,, um fraction. To be economical feasible the plus 2, um. of the -37, um fraction must be mainly coal. The burden on the centrifuge is reduced due to the initial separation by the vibrating screens. In Figure 1 conduit 42 is illustrated schematically in which clay and other contaminants conducted by the conduit are discharged into a silt pond or a waste area generally indicated by reference numeral 44. The screen over product recovered from the vibrating screens is delivered by line 38 to a vibrating hopper 46 or if desired the top screen ~ product may be delivered first to a belt press 48.
I 15When the coal mass is delivered by line 38 from the vibrating screens to the vibrating hopper 46, the coal particles collect in a hopper chamber 50 wherein vibrating tubes 52 are arranged as fingers as ~; shown in Figure 1, extending along the height of the coal mass and angularly at the bottom portion to exit sites in one of two stopping bottom wall sections.
, , ,~ -The tubes 52 are perforated and packed with long grained filter media. A motor 54 coupled through an eccentric 56 to vibrator frame imparts low frequency large amplitude vibration to the tubes 52. The tubes ~::
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deliver liquid collected in the hopper chamber to drainage ports 58 which communicate with a drain box 60.
The hopper chamber 50 has an opening in the other sloping bottom walls which communicate with a discharge chamber 62 having helical flight attachments 64 on a shaft 66 driven by a motor 68. Coal particles , are carried by the flight attachments from the bottom of the hopper chamber to a discharge header box 70 for delivery by line 77. The incoming coal particles in line 38 typically have a moisture content of 30-31% by weight. After about 29 minutes treatment time in the vibrating hopper, the moisture content is reduced to ~;
~ 24% by weight. -j Energy can be imparted to the mass of coal in the hopper chamber 50 by other means than mechanically operative vibrator device. Such other means can take the form of perforated tubes extending in the coal mass in a manner similar to tubes 52. The ~:
perforated tubes connected with a header by which ~'~ 20 compressed air can be delivered to the tube and ~` exhausted through the perforated openings to the coal~ ,~
mass. Such streams of compressed air permeating the coal mass transfers sufficient energy to drive ~; moisture from the surface of the coal particles.
~ , , ~ ; 12 .,~
When it i8 de3ired to speed up the ; dewatering process, the coal particles in line 38 are ~irst mixed with a ~mall quantity, typically 1%
ligninsolfunate by weight of coal particles in a 5 ribbon type mixer 74 and then the admixture of coal particles and ligninsolfunate are feed to the hopper 3' chamber 50. After about 10 minute~ treatment in the J vibrating hopper, the moisture content of the coal is reduced to about 24% by weight when discharged from s 10 the hopper. No further moisture reduction will occur beyond 10 minutes treatment time with the ligninsolfunate in the hopper 46. The ligninsolfunate has an affinity for carbon and tharefore drives ~-adhered moisture on the coal from the coal particles.
A surprising result reaides in the discovery that the removal of the clay renders the resulting coal particles particularly su$table for extruding operation~ to produce a product which can be more easily handled and shipped. Ultra fine clay containing coal without dewa~ering including de~liming, according to the present invention, cannot be extruded without a moi~ture reduction to below about 10% by weight and the addition of expensive lubricants and binders. The extruder is identified by ,~ .
~;; 25 reference numeral 76.
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The feed stream in line 38 can b~ fed alternatively to a chamber 78 of the belt press 48 and discharged under gravity onto a first endless belt 80 which carries the coal water burden beyond a rollQr 82A to a second endle~ belt 84. The belts 80 and 84 are sieve belt~ made of synthetic fiber so that liquid, particularly water, can freely pass from the coal particl~s on and between the belts on a horizontal drainage section 86 and in a roller pressing section 88B. Liquid draining from the belt~
is collected in a container 90. The coal and liquid mixture between the belts entering section 88A is subject to high pressurss and shearing forces as the belts pass along a tortuous path formed by rollers 88B
which aro connected to a ~uitable drive. Other rollers 88C and 88D as well as roller 88A are re~ovably mounted to control tensioning of the belts ;~ by actuators. The dewatered reed stream is discharged ~rom between the belts at 88E. The coal mass recovered fro~ the ~elt press is ready for u~e.
The hydrophobic characteristic of the mass ;~ of recovered coal particles from the vibration hopper or belt press even without the addition of ligninsolfunate undergoes an accelerated reduction to ,~.
~1~ 25 the moi~ture content. Upon expo-~ure to the ;~
, ~
,~
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atmosphere, a constant rate drying period is initiated during which the ~ur~ace o~ the aoal mass i~ entirely wet. Evaporation takes place at whatever rate is dictated by the surrounding conditions of air temperature, humidity and replacement ratQ o~ air and coal particle moisture. An upward change in the temperature of the cake whether induced internally or by external means, results in an expansion of the solubilized air. This re~ult~ in creation of internal pressure on the entrained moisture in capillaries and interspaces between coal particle~. Net effect of this is to accelerate the capillary migration, or wicking of the internal moi6ture toward the surface o~
the coal mass and in turn, the reduction of time required ~or the evaporative proces~ to be totally ef~ective.
1~ The wet screening apparatu~ i8 ~urpri~ingly ¦~ ef~ective and produced a dramatic reduction to the water content to the top ~creen product. Prior to the :, present invention, it was not possible to reduce the water content of a clay contaminated mass of -100 mesh 150, um~ coal parti¢}es recovered from an aqueous ~lurry below about 40% by welght. ~oreover, a more surprising result is the'dramatic decrease of the ash content of the variouR fraction~ of the minus -100 :~, ~ 15 ,~
"
me~h (-150, um) scre~n over-produ~t when oompar~d with a wet sieve analysi~ of a peptized head sample of the feed to a Derrick f creen equipped to ~eparate at a nominal 400 mesh or 37,um. The results are qiven in s Table I.
TABLE I
Weiaht ~rY A~h . Over- , Over-Mesh Head Sam~le Product Head Sam~le Product Size ~~ ~ Cu~. ~ Cum. _% _ Cum. % Cu 1oax325 32.1 32.1 66.0 66.0 15.9 15.9 8.2 8.2 325X400 5.1 37.210.6 76.6 17.2 16.1 11.6 8.7 400XSO0 5.7 42.96.0 82.6 20.3 16.6 12.9 9.0 - 500 57.1 100.017.4 100.0 45.6 32.1 39.8 14.4 Wet sieve analyse~ ~how the transfer of the highf2r ash clay and other minus 37,u.m. impuritie3 to the screen ! under product by way of the passage of the aqueous solution through the screen openings. This can be een by comparison of the dry a~h content of the ecreen over product fractions with those of ~he under .
product fSractions. The results are giv~n in Table II.
.~
. 20 TABLE II
Weiqht Dry Ash ~:~ Over- Under- Over- Under-Mesh Proauct Product Product P~oduct Size - % Cum. % Cum. % Cum. % __Cum. -~: 100X325 66.0, 66.0 0.1 0.1 8.2 8.2 11.7 ~}1.7 325X400 10.6 76.6 0.6 0.7 11.~ 8.7 13.4 13.1 400X5006.0 82.6 5.7 6.4 12.9 9.O 20.7 19.8 :
~ 25 - 50017.4 100.0 93.6 100.0 39.8 14.4 45.8 45.4 ., ,~
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In thi~ teet the cumulative recovery of coal value~ in the plus 25, um fraction of the feed as calculated on an ash halance basis was found to be 99.2%.
In Figure 2 there i8 illustrated a further embodiment of the present invention, in which vessel 10, like the embodiment of Figure 1, recaives coal feedstock, water and a peptizing agent from supply lines 12, 14 and 16, respectively. The feed stock is ~ixed under high shear ~orces by motor 18, and the mixing process is carried out for a sufficient period of time to peptize clay particles which are driven from the surface of the coal particle#. The mixture i~ delivered from the vessel 10 to a head box of a vibrating sieve bend 94 where the aqueous phase including peptized clay and undersized solids drain to a collection pan 96 from the mass of coal particles on curved screen a~ssmbly 98. The screen assembly i~
vibratsd by drive motor 100 at a high frequency, e.g.
3600 cycles per minute at a low amplitude motion. The under product including an aqueous phase i~ carried away by a drain line 102. The over-product from sieve ~- bend 98 is delivered by way of a hopper collector 104 : ~
to a pug mill 106. The fraction in drain line 102 is ; delivered to a vibrating screen as~embly 108 which can ~~
be the ~ame as ~creen a~sembly 24 described ,"~
;~
.. ,~ , ,.. ,.,~, ~ ,.. ,~:., ,, ~.,.,,,.. ` ;-hereinbaforQ and shown in Figure 1. The screen over- --~ product i~ delivered by line 110 to the pug mill 10~.
'l This arrangement of apparatu~ has the advantage of offering a greater re~idence t~me by the underflow in line 102 on a vibrator screen 108 so that the moisture ~j on the face surfaces of the coal particles can be acted upon for a longer period of time as the coal ;! particles pass along the vibrating screens. The product fed to the pug mill 106 i8 mixed with ~ 10 ligninsolfunate, a binder or other agent delivered by ¦~ line 112 to the pug mill and mixed therein w~th the coal particle~. The product discharged from the pug mill is delivered by line 114 to vibrating hopper 116.
After dewatering in hopper 116, the coal particles form into 8uitable extruded shapes by extruder 118 for shipment. In~tead of extruder 118, if desired, the product ~rom the vibrating hopper can be feed to a rotating peltatizum drum, disc or pin mixer where the coal particles are agglomerated into pellets.
In Figure 3, like the embodiments of Figures 1 and 2, vessel 10 receives coal feedstock, water, and a peptizing agont from supply lines 12, 14 and 16, -~
~-~ respectively.i Mixing occurs under high shear force ~-; conditions produced by blade 20 driven by motor 18.
The coal ~lurry is delivered by line 22 to a vibrating ~ ' ~
~ 18 :~ ' `,'~
~j ~
~ ~ 1 330427 ~creen a~embly 120 which i8 the same as screen as~embly 24. The screen under products can be discarded by line 122 and the screen over product i~
deliver~d to a pug mill 124 which includes a helical mixing blade 126. Ligninsolfunate is mixed with the coal particles in the pug mill to speed up the dewaterlng process. Aqueous liquid drains from the coal slurry in the pug mill by line 130. $he coal particles can then be treated according to e~bodiments 10 of Figures 1 and 2 downstream of assembly 24. ~ -In the embodiment of the invention ~hown in Figures 4 and 5, like the embodiments of Figures 1, 2 and 3, a vessel 10 receives coal feedstock, water and peptizing agent in lines 12, 14 and 16 respectively.
The feedstock, initial pulping water and peptizing agent are introduced into the peptizing tank to produce a slurry having rrom 10% to 45% dry solids.
The slurry i~ mixed ~or a period of time, under condition~ imparting high shear ~orces to the coal . ~ ~
'~ 20 particle~. Usually a mixing time of at least 5 ~ minute~ i8 required. Should the peptizing ; agent be pH sensitive, then a pH adjust~ent is ~ade to the aqueous coal slurry by the addition of a suitable neutralizing agent before the addition of the peptizing agent. This is particularly true when ,3.':. 19 l i',~
.
sodium hexametapho~phate 1~ u~ed. Other peptizinq agents whlch are not pH dependent are well known and can be selected for use~ As explained previQusly, th~
mixing of the slurry in the peptizing Ve88Ql ~ peptize~
the clay particles and deagglomeration occurs which renders the individual coal impurities other than clay and clay particles ~nto a state of di~creteness. The individual clay particle~ fall within a typ~cal aize range of between 0.68 to 2.0 micrometers and interact with a peptizing agent to effect an ionic exchange I thereby imparting to the clay particles a strong negative electrokinetic charge. The peptized clay particle~ become discrete and become su~pend~d a~ a colloid in the a~sociatQd water of the slurry.
The peptize slurry after mixing, i8 transferred by line 22 to a dilution tank 132 wherein ~ .
the percent of dry solids making up the coal wa~er slurry is ad~ustsd by lowering the percent to permit :
unhindered settling of unpeptized particles larger than the point of classification size as well as unhindered upward migration of water, clay and such other particles of coal and associated unpeptized material that are smaller in particle size than the , . I ~ , . :
chosen point of classification. Typically, it is desired to adjust the solid content of the slurry with . ~:~
.:
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the addltion of water from supply line 134 whereby the dry solid content iB a maximum o~ 10 percent but not 1eB8 than 2.5 percent. Solids are kept in solution in dilution tank by means of stirring blades 136 driven by motor 138. The slurry from the dilution tank i8 then delivered by a flow line connected to a metering pump 140 into an upcurrent classif~er 142. The point , of entry in the classifier by the diluted coal water i slurry i8 at the site of dispersion dispenser 144.
10 The dispenser is a generally conical member having the ~-apex thereof directed upward whereby a alurry entering the slassifier proceed~ against the inter conical wall o~ the disper~er 80 that the slurry rebounds and is directed toward the truncated conical bottom 146 of the upcurrent classifier. The dispen~er ¢an take the for~ of a rotating perforated arm driven by the velocity of the aqueous slurry exiting from the perforations~
~he slurry introduction procedure provides guiding for the particles of coal to settle in the manner o~ a sediment. Water with peptized clay as a ~ ., i collold thereln along with ~mall coal particles`and '~,;; other ~lner~l~ of lesser size mlgrate to a point of cla~siflcation along a rever~e coar~e of travel and pass upwardly towards the discharge opening 148 at the . '~
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top of the classifier. The classifier iB constructed 80 as to siphon off the ef~luent in a guie~cent and controlled manner. Since the settled coal particle~
and non-clay mineral particles are rendered dilatant and hydrophobic in the peptization process as opposed to a non-dilatant, hydrophilic properti~ of clay and of a mixture o~ al~y, coal and others assoclated mi~eral~. The ~ettled partlcle~ in th~ truncated conical bottom 146, of the classifier arrange themselves in a manner conducive to the exclusion of the presence of water and its accompanying peptized clay load impo~ed by the overlying column of liquid.
Low ~requency, high amplitude vibrations, generated by a vibrator 150 driven by motor 142 are imposed on the ~;~
conical bottom 146 which serves as an inducement to the resi~tance of the introduction of water into the ~ettled material at the conical bottom. To eliminate the possibility of rat holing, it may be necessary in some in~tances to install an inverted cone in the , .
interior of the conical bottom 80 as to create an annular opening between the cone and conical bottom 146 of a proper width through which settled particles can pass in their downward movement towards a . .
di~charge conveyor screw assembly 154 which draws off ,~ 25 quantities of coal particles from the classifier.
~ 22 , ~
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1 330~27 As best shown in Figure 5, an upset cone 156 i~ fit into the interior of the conical bottom of the separ~tor in a opaced relation from the conical bottom ~ 146 to form angular opening b~tween the two cones.
¦ 5 The width of the opening i~ selected 80 that cone particles can pass in their downward movement towards a discharge assembly ~54. As the settled particles bscome compacted in the annular gap, free water ~ migrates to the interface between the compacted mass J, 10 and the surface of the conical bottom. Further, dewatering i6 achieved by a series of horizontally arranged annular rings 158 and 160 which are installed as shown in Figure 5 on the cone 156 and annular ~ bottom 146, respectively, to interrupt the continuity i 15 o~ the flow path. The rings may be packed with non-corroding metal wool so as to provide an unobstructed free passage for captured water to exit at the ring through a portal opening in the side wall of the classifier. Each ring will produce a con6tant discharge of water from the classifier.
Point size of classification is a function of the vertical distance between the point of dispersion~distribution and the veloclty of the upward moving column of water and its load of colloidal clay and ultra fine particles. In turn, velocity is a ~::
~ 23 :~
/
function of the area dimensions of the vessel, percent o~ dry solids in ~he ~lurry and volumetric rate of introduction of slurry into the up-current cla~ifying vessel. ~ince the characteristic of each raw feedstock and the ~arket requirements for the end product to be recovered from it are site specific and the largest size clay platelet i8 smaller that 2,um, A
cla3sification point of 2,um for most coal6 should prove desirable. However, higher points of classification, such as lOum and even as large as 25, um, may be found more suitable to effect the desired degree of ash reduction to be attained in the process.
Ash reduction i6 limited to the total of the ash of the clay minerals that can be peptized. In the ma;ority of coal6, this should be sufficient to reduce ~ the ash in the finished product to a point acceptable -¦ to the market place. Since pyrite occurs as circular l platelets in all ~izes in ultra-fine raw coal, all free pyrite in the peptized slurry of a finer size than the point of classification will report to the tailings ~ and the ~ulfur content of the recovered product will 3: be commensurately reduced.
The effect of rendering the recovered -~ particles dilatant and hydrophobic along with ,~ .
:
';
, 91~.. ` ' ' , , compaction through vibration allowG removal of the product ~rom the classi~ier at an initial molsture level of about 27 percent as compared to a moisture content of about 34 percent should the produc~ be repulped and then dewatered in a high speed centrifuge. Recovery by centrifuging of an unpeptized -100 mesh (-150, um) feedstock produces a cake having a minimum of 40 percent moisture and more likely in the range of 50 percent to 60 percent moi~ture. By way of comparison, the moisture content of the underflow from an up-current classifier feed of an ultra-fine unpeptized raw coal slurry will rarely be less than 65 percent.
Within the initial hour after di~charge from the vessel, natural drainage will eli~inate all of the free water. During this period and continuing thereafter until all of the unbound water has been eliminated, the evaporation phenomenon i6 in effect.
For example, without thermal assist the moisture content o~ a layer of product 1/2" to 3/4" thick will be reduced at the rate of 1.2 percent per hour until air dry equilibrium is reached.
If thie product is mixed with a small amount - of ligninsolfunate and then exposed to the ambient atmosphere in a layer of similar thickness without ::
/
moving air, the natural evaporation phenomenon reault~
in a reduction of the remaining unbound moisture at the rat~ o~ 3.6 percent per hsur.
It is nece~ary to understand that ultra-fine coal that has been ~tripped of all clay through the peptization proce~s has entirely dirferent physical characteristics than those of a normal coal/clay association. In addition to the dewatering 0 phenomenon, this change in characteri~tics permits the reforming of ultra-fine coal into larger, more q marketable forms by extrusion, pelletizing or pressing. Generally, this i6 not presently i economically po~sible with unpeptized ultrafine coal.
i 15 In the graph of Figure 6, a drying test is demon~trated by a comparison bet.ween peptized and -~ ;
unpeptlzed centrifuge cakes about 3/4" ln thlckne~
wlthout the addition of ligninsolfunate in a 115 ; degrees F forced air atmosphere. As can be seen from Figure 6, graph line 162 indicates the per cent reduction of moisture in a processed cake comprised of dilatant coal particles and graph line 164 shows a reduction to moisture contact of a raw cake comprised .
of coal particles that are not dilatant. A
dramatically increased amount of moisture is drawn .; ~ ' ~ .
~ .
*rom the dilatant coal p~rticles as can be seen ~rom a comparison of graph lines 168 and 170. The percent of the moisture content in the proces~ed cake wa8 ~ound to decrease a~ shown by graph line 168 to about 2 percent within about 3 1/2 hour~ after processing according to the present invention. An unprocessed filter cake did not obtain a corrQsponding percent moisture content until about 14 hours after treatment as shown by graph line 170.
Figure 7 illustrate~, by two sets of graph curves, the percent redu¢tion to the moisture conten~
of a peptized classifier coal product in a drying test wherein the ambient temperature was 75 degrees F.
I average in static atmo~pheric air. Graph line 172 ¦ 15 shows the dramatic reduction to the percent of the moisture content in the classifier product which i8 mixed with one percent by weight ligninsol~unate as ~,; compared with graph line 174 which 6hsw6 the percent I~- reduction to the moisture content in the same Gla~sifier product but without the addition of lignin~olfunate. There was about a 47% moisture ~;~ reduction to the treated peptized product within the !~ first five hours as compared with only about~a 13%
reduction during the ~ame time period of an untreated peptized product. Similarly, the percent o~ moisture ``~
``:::
:~
~ 33~4~7 in the classifier product treated with lignin~olfunate dropped rapidly as can be ~een by graph line 176 a~
compared with graph line 17a which shows the percont of moi ture content of the classifiar product without the addition of ligninsolfunate.
In F~gure 8, the e~ect of heated forced air at 360 degrees F. verses so degrees F. a~blent still air on the moisture reduction of a peptized extruded classi~ier product i~ ~h~wn by pairs of graph lines.
In the drying test depicted by the graph lines o~
Figure 8, classifier product samples are treated with ~- one percent ligninsolfunate. One sample was exposed ~- to forced air at 350 degrees F, while another sample ~- was exposed to still air at 90 degrees F. ambient.
The percent reduction o~ moi~ture content in the ~ forced air classifier product is shown by graph line ¦~ 180, and it can be seen that within the first lO ~-~
~` minutes, a very dramatic moisture reduction occurs as compared with the ~oisture reduction of the classifier 20 product in still air as shown by graph line 182. The ~
effect on the moisture content of the classifier ~;
product under forced air condition shows that within , ~ about 15 minutes as depioted by graph line 184 there t ~ was a percent moisture reduction that could not be I ~ 25 achieved in still air until about a lapsed time of 30 ~ ~ 28 1 330~7 ,~.
or more minutes as depicted by graph line 186. Thus, a~ can be clearly under~tood by tho~e skilled ln the art, the effect of lignin~olfunate greatly Qnhance~
the ~peed at which dawatering of the mas~ of coal particles occurs.
While the present invention has been described in connection with the pre~erred embodiment of the various figures, it is to be understood that other similar embodiments may be used or modification~ .-and additions may be made to the described e~bodiment for performing the same function of the present invention without deviating therefrom. Therefore, the pre~ent invention ~hould not be limited to any ~ingle embodiment, but rather construed in breadth and ~cope in accordance with the recitation of the appended claims.
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Claims (15)
1. A method of treating clay contaminated ultra fine coal particles, said method including the steps of:
forming an aqueous slurry of clay contaminated ultra fine coal particles;
imparting high shear forces to the slurry containing the clay contam.inated ultra-fine coal particles to strip clay contaminants from the surfaces of the coal particles and to subdivide the size of the clay contaminant to clay platelets without flocculating the ultrafine coal particles;
adding a sufficient amount of a peptizing agent to said slurry thereby peptizing the clay platelets to impart a state of discreetness in the aqueous slurry;
subjecting said peptized aqueous slurry to a size separator selected from the group consisting of a sieve having a barri~r layer of aqueous permeable unflocculated dilatant coal thereon, and a filt.er having a barrier layer of aqueous permeable unflocculated dilatant coal thereon, thereby forming a mass of dilatant coal particles;
using the dilatancy of said dilatant coal mass in combination with an applied force for dewatering the coal mass by draining aqueous medium along with discrete peptized clay platelets from the coal mass; and recovering the coal mass.
forming an aqueous slurry of clay contaminated ultra fine coal particles;
imparting high shear forces to the slurry containing the clay contam.inated ultra-fine coal particles to strip clay contaminants from the surfaces of the coal particles and to subdivide the size of the clay contaminant to clay platelets without flocculating the ultrafine coal particles;
adding a sufficient amount of a peptizing agent to said slurry thereby peptizing the clay platelets to impart a state of discreetness in the aqueous slurry;
subjecting said peptized aqueous slurry to a size separator selected from the group consisting of a sieve having a barri~r layer of aqueous permeable unflocculated dilatant coal thereon, and a filt.er having a barrier layer of aqueous permeable unflocculated dilatant coal thereon, thereby forming a mass of dilatant coal particles;
using the dilatancy of said dilatant coal mass in combination with an applied force for dewatering the coal mass by draining aqueous medium along with discrete peptized clay platelets from the coal mass; and recovering the coal mass.
2. The method according to claim 1 wherein said step of using the dilatancy of the dilatant coal mass includes treating the coal mass with an air flow for said dewatering.
3. The method according to claim 1 wherein said step of using the dilatancy of the dilatant coal mass includes treating the coal mass with mechanical energy for said dewatering.
4. The method according to claim 1 wherein said step of using the dilatancy includes drawing quantities of atmospheric air through the dilatant coal mass into a filter.
5. The method according to claim 1 wherein said peptizing agent comprises a sufficient amount of sodium hexametaphosphate to act as a peptizing agent.
6. The method according to claim 1 wherein said step of using the dilatancy includes treating said dilatant coal mass in a dewatering chamber.
7. The method according to claim 1 wherein said step of using the dilatency of the dilatant coal mass includes exposing the dilatant coal mass to an open atmosphere.
8. Apparatus for dewatering an aqueous coal slurry, said apparatus including a vessel for an aqueous slurry of clay contaminated coal particles;
means for supplying a peptizing agent to said vessel;
means for imparting high shear forces to the aqueous medium in said vessel sufficient to separate clay contaminant from the coal surface and subdivide the clay to clay platelets for peptizing the latter;
means including an aqueously permeable barrier for forming a dilatant coal layer:
means for dewatering a coal mass collected on said dilatant coal layer; and means for recovering said dewatered coal mass.
means for supplying a peptizing agent to said vessel;
means for imparting high shear forces to the aqueous medium in said vessel sufficient to separate clay contaminant from the coal surface and subdivide the clay to clay platelets for peptizing the latter;
means including an aqueously permeable barrier for forming a dilatant coal layer:
means for dewatering a coal mass collected on said dilatant coal layer; and means for recovering said dewatered coal mass.
9. Apparatus for dewatering an aqueous coal slurry, said apparatus including:
means for imparting high shear forces to the aqueous slurry sufficient to strip clay contaminants from the surfaces of the coal particles and subdivide the size of clay contaminants to clay platelets for peptizing the clay platelets; and pervious means having formed thereon a barrier layer of an aqueous permeable unflocculated dilatant coal and a filter made up of a barrier layer of aqueous permeable unflocculated dilatant coal to form a dewatered mass of coal particles.
means for imparting high shear forces to the aqueous slurry sufficient to strip clay contaminants from the surfaces of the coal particles and subdivide the size of clay contaminants to clay platelets for peptizing the clay platelets; and pervious means having formed thereon a barrier layer of an aqueous permeable unflocculated dilatant coal and a filter made up of a barrier layer of aqueous permeable unflocculated dilatant coal to form a dewatered mass of coal particles.
10. The apparatus according to claim 9 wherein said pervious means comprises a filter.
11. The apparatus according to claim 9 further including froth flotation cells to extract a minus 2 micron fraction to a tailings sump.
12. The apparatus according to claim 9 wherein said means for imparting high shear forces includes a vessel for containing a quantity of aqueous slurry of clay contaminated coal particles in an aqueous medium.
13. The apparatus according to claim 9 wherein said means for imparting high shear forces further includes a rotary impeller.
14. The apparatus according to claim 9 further including means operable with said barrier means for recovering said dewatered mass of coal particles.
15. The dewatered coal product according to the method consisting of the steps of:
forming an aqueous slurry of clay contaminated ultra fine coal particles;
imparting high shear forces to the slurry containing the clay contaminated ultra-fine coal particles to strip clay contaminants from the surfaces of the coal particles and to subdivide the size of the clay contaminant to clay platelets without flocculating the ultra-fine coal particles;
adding a sufficient amount of a peptizing agent to said slurry thereby peptizing the clay platelets to impart a state of discreetness in the aqueous slurry;
subjecting said peptized aqueous slurry to a size separator selected from the group consisting of a sieve having a barrier layer of aqueous permeable unflocculated dilatant coal thereon, and a filter having a barrier layer of aqueous permeable unflocculated dilatant coal thereon, thereby forming a mass of dilatant coal particles;
using the dilatency of said dilatant coal mass in combination with an applied force for dewatering the coal mass by draining aqueous medium along with discrete peptized clay platelets from the coal mass; and recovering the coal mass.
forming an aqueous slurry of clay contaminated ultra fine coal particles;
imparting high shear forces to the slurry containing the clay contaminated ultra-fine coal particles to strip clay contaminants from the surfaces of the coal particles and to subdivide the size of the clay contaminant to clay platelets without flocculating the ultra-fine coal particles;
adding a sufficient amount of a peptizing agent to said slurry thereby peptizing the clay platelets to impart a state of discreetness in the aqueous slurry;
subjecting said peptized aqueous slurry to a size separator selected from the group consisting of a sieve having a barrier layer of aqueous permeable unflocculated dilatant coal thereon, and a filter having a barrier layer of aqueous permeable unflocculated dilatant coal thereon, thereby forming a mass of dilatant coal particles;
using the dilatency of said dilatant coal mass in combination with an applied force for dewatering the coal mass by draining aqueous medium along with discrete peptized clay platelets from the coal mass; and recovering the coal mass.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US11266987A | 1987-10-22 | 1987-10-22 | |
| US112,669 | 1987-10-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1330427C true CA1330427C (en) | 1994-06-28 |
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ID=22345229
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000580930A Expired - Fee Related CA1330427C (en) | 1987-10-22 | 1988-10-21 | Method and apparatus for separating clay from and then dewatering ultra fine coal |
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| Country | Link |
|---|---|
| AU (1) | AU617698B2 (en) |
| CA (1) | CA1330427C (en) |
| DE (1) | DE3836064A1 (en) |
| FR (1) | FR2622203B1 (en) |
| GB (1) | GB2211440B (en) |
| IN (1) | IN170718B (en) |
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| DE19807116A1 (en) * | 1997-12-22 | 1999-06-24 | Roediger Anlagenbau | Process and plant for separating or separating heavy and light materials from a suspension |
| CN110593948B (en) * | 2019-09-18 | 2021-01-15 | 河南海光兰骏矿山技术有限公司 | Intelligent cleaning system for water bin coal water separation |
| CN115321859B (en) * | 2022-07-25 | 2023-05-26 | 武汉理工大学 | Method for separating superfine powder and nanoclay from limestone mine tailing mud |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1115694A (en) * | 1965-01-28 | 1968-05-29 | Huber Corp J M | Clay improvement |
| DK150272C (en) * | 1982-09-14 | 1987-10-05 | Jensen Ejnar & Soen As | DEVICE FOR CENTERING OF EXTENDED WASHING TOOLS TO BE TRANSFERRED TO A TRANSPORT BELT |
| WO1984001313A1 (en) * | 1982-09-29 | 1984-04-12 | Ilecard Pty Ltd | Recovery of solids from dispersions |
| DE3244898C2 (en) * | 1982-12-04 | 1985-04-11 | Chemische Fabrik Stockhausen GmbH, 4150 Krefeld | Process for the separation of mineral ultrafine grains from washing water of coal processing or from coal sludge |
| AU2650284A (en) * | 1983-03-03 | 1984-09-28 | Bp Australia Limited | Improvements relating to the dewatering of solid materials |
| US4537599A (en) * | 1983-04-28 | 1985-08-27 | Greenwald Sr Edward H | Process for removing sulfur and ash from coal |
| CA1249957A (en) * | 1984-02-21 | 1989-02-14 | Edward H. Greenwald, Sr. | Process for producing a coal-water mixture |
| US4662894A (en) * | 1984-08-13 | 1987-05-05 | Greenwald Sr Edward H | Process for producing a coal-water mixture |
-
1988
- 1988-10-20 AU AU24079/88A patent/AU617698B2/en not_active Ceased
- 1988-10-21 NZ NZ226661A patent/NZ226661A/en unknown
- 1988-10-21 GB GB8824760A patent/GB2211440B/en not_active Expired - Lifetime
- 1988-10-21 IN IN866/CAL/88A patent/IN170718B/en unknown
- 1988-10-21 CA CA000580930A patent/CA1330427C/en not_active Expired - Fee Related
- 1988-10-22 DE DE3836064A patent/DE3836064A1/en not_active Ceased
- 1988-10-24 FR FR8813878A patent/FR2622203B1/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| GB8824760D0 (en) | 1988-11-30 |
| GB2211440B (en) | 1992-04-22 |
| AU617698B2 (en) | 1991-12-05 |
| DE3836064A1 (en) | 1989-05-03 |
| FR2622203B1 (en) | 1994-04-15 |
| FR2622203A1 (en) | 1989-04-28 |
| NZ226661A (en) | 1991-05-28 |
| GB2211440A (en) | 1989-07-05 |
| IN170718B (en) | 1992-05-09 |
| AU2407988A (en) | 1989-04-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |