CA1249957A - Process for producing a coal-water mixture - Google Patents
Process for producing a coal-water mixtureInfo
- Publication number
- CA1249957A CA1249957A CA000473046A CA473046A CA1249957A CA 1249957 A CA1249957 A CA 1249957A CA 000473046 A CA000473046 A CA 000473046A CA 473046 A CA473046 A CA 473046A CA 1249957 A CA1249957 A CA 1249957A
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- Prior art keywords
- coal
- process according
- fraction
- feedstock
- particles
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- 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
- C10L1/00—Liquid carbonaceous fuels
- C10L1/32—Liquid carbonaceous fuels consisting of coal-oil suspensions or aqueous emulsions or oil emulsions
-
- 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
- C10L1/00—Liquid carbonaceous fuels
- C10L1/32—Liquid carbonaceous fuels consisting of coal-oil suspensions or aqueous emulsions or oil emulsions
- C10L1/326—Coal-water suspensions
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- Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Liquid Carbonaceous Fuels (AREA)
- Solid Fuels And Fuel-Associated Substances (AREA)
Abstract
PROCESS FOR PRODUCING A
COAL-WATER MIXTURE
ABSTRACT OF THE DISCLOSURE
A process for producing a coal-water mixture includes forming dilatant coal particles in an aqueous coal feedstock mixture by treatment with ozone and classifying the coal feedstock to form first and second coal feed streams each comprised of differently-classified coal particles. Separate surge vessels receive the coal particles to form separate feed streams. The distribution of coal particles in a liquid medium forming each coal feed stream is determined and an electrical signal is delivered to a microprocessor fox controlling the portions of each stream which are mixed together in the presence of a dispersing agent to form a coal-water mixture. The coal-water mixture is comprised of at least 65% by weight coal particles, preferably 70%. The coal content may be increased and flow properties of the coal-water mixture improved by removing a minus 2-micron particle fraction which is predominantly clay from feedstock and mixing a minus 2-micron fraction of coal particles with quantities of the first and second feed streams.
COAL-WATER MIXTURE
ABSTRACT OF THE DISCLOSURE
A process for producing a coal-water mixture includes forming dilatant coal particles in an aqueous coal feedstock mixture by treatment with ozone and classifying the coal feedstock to form first and second coal feed streams each comprised of differently-classified coal particles. Separate surge vessels receive the coal particles to form separate feed streams. The distribution of coal particles in a liquid medium forming each coal feed stream is determined and an electrical signal is delivered to a microprocessor fox controlling the portions of each stream which are mixed together in the presence of a dispersing agent to form a coal-water mixture. The coal-water mixture is comprised of at least 65% by weight coal particles, preferably 70%. The coal content may be increased and flow properties of the coal-water mixture improved by removing a minus 2-micron particle fraction which is predominantly clay from feedstock and mixing a minus 2-micron fraction of coal particles with quantities of the first and second feed streams.
Description
9S~
PROCESS FOR PROD~CING A
COAL-WATER MIXTURE
This invention relates to a process ~o produce a coal-water mixture comprised of coal particles in an aqueous liquid medium. More particularly9 the present invention relates to a process for producing a coal-water mixture from feedstock formed of coal particles which can be ground, freshly-mined coal or coal salvaged from sil~ ponds or other sources after processlng to remove clay3 shale9 pyrite and other minerals wherein the feed-stock is classified and/or treated to impart dilataney to the coalparticles and two or more feed streams comprised of differently-sized, e.g., classified, coal particles in a liquid mRdium are mixed together with a dispersing agent to form a coal-water mixture having at least 65% by weight coal particles.
One characteristic of the coal recovered from silt ponds is a substantial varia~ion to the coal particle size distribution in a flow stream on a day-to-day basis and possibly on an hour-to-hour basis. A substantial variation to the particle ~ize distribution of ultrafine sizes of freshly-mined coal can be expected when preparing feedstock for a process to form a coal-water mixture. The problem of variations to the particle size distribution oi the feedstock exists in all curren~ly-known methods for wet and dry grinding of coal.
In a paper entitled Rheolo~y of Hi~h Solids Coal-Water Mixture by D.R ~inger, J.E. Funk~ Jr. and J.E. Funk, Sr., 4th International Symposium on Coal Slurry Combustion, May 10-12, 3~57 1984, there is descrlbed thP "rheological proper~ies of a coal-water mixture having 9805% coal particles at 50 mesh or less depending on ~he particle-packLng efficiency which minimizes in~erstitlal porosity. An equation for optimum particle-packing efficiency is derived and an algori~hm developed calculating ~h~
porosity of real particle distribu~ions. The calculated poro-sity was checked by pressure filtration and measurement of porosity. The speciflc surfa~e area is also calculated by an algorithm. The data provides a family of particle size distri-butions wh~ch produce exceptional rheological properties pro-vided that a surfactant addition is effec~ive for dispersing the coal particles. It was found ~ha~ monospheres~ regardless of their size will usually pack to an average orthorhombic array o about ~0V/~ by volume. In order to shear, the structure must open or dilate to a cubic array where the porosity increases from 40% to about 48%. It was found that to prevent dilatancy, or interparticle collisions in shear, the system must be dilu~ed so that the interparticle spacing is at least IPS ~ r--3)D 9 where IPS is the interparticle spacing and D is the particle size.
The problem arises, however, as to the manner by which a coal-water mixture can be produced comprising at least, for example, 65% by weight coal particles and preferably 70% and up to about 82% by weight coal particles on an hourly and a day-to-day basis for reliable use. At about 65% by weight coal particles, a coal-water mixture requires the use of addi~ional fuel ~uch as a com~ustible gas when used in a power pl~nt. How-ever, the coal-wa~er mixture can be economically utilized. It is, howevery far more economical to provide a coal-water mixture with a coal-particles concentration of at least 70~ by weight coal particles. Above 82% by weight coal particles, mechanical problems can be expected to impede delivery of the coal-water mixture by piping networks, pumps and valves.
Feedstock for a coal-water mixture is usually an aqueous coal slurry about 20~ to 40% by weight coal particles.
The slurry must be dewatered to an extent sufficient to form a flowable coal-water mixture with at least 65% by weight coal and rheological properties, particularly viscosity that will not impede flow in pipelines at normal ambient temperatures, e.g., 0 C to 35 C. It has been discovered that dilatancy of coal particles can be effectively utilized for dewatering a mass of coal particles derived from an aqueous coal slurry.
It has also been discovered that dilatancy can be imparted to coal particles by increasing the ratio of surface area to mass whereby a dispersing agent in a subsequently-formed coal-water mixture functions in a surprising and far superior manner to enhance the flow characteristics of the mixture. The feedstock for the coal-water mixture can be made dilatant also by removing a clay constituent that is hydrophobic and prevents dilatancy.
According to the present invention there is provided a process for producing a coal-watex mixture, the steps including: producing an aqueous coal slurry comprised of granular coal feedstock which is greater then 50% by weight of ,f~h.~3Sr7 an aqueous liquid medium, forming :Erom the aqueous coal slurry at least first and second dilatant coal feed strea~s each comprised of a different size classification of the granular coal feedstock in aqueous liquid medium, the aqueous liquid medium of each of the feed streams being less than 50% by weight of the granular coal feedstock, and mixing together selected amounts of the first and second dilatant coal feed streams in the presence of a dispersing agent to from a coal-water mixture comprised of at least 65% by weight coal particles.
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 diagrammatic flow sheet of a practical installation for producing a coal-water mixture according to the present invention;
Fig. 2 is an elevational view of a preferred form of a dewatering device for use in the process of the present invention; and Fig. 3 is a diagrammatic flow sheet of a further installation for producing a coal-water mixture according to the present invention.
Feedstock conducted by line 10 for the process of the present invention may be freshly-mined coal or coal '55~q salvaged from silt ponds or other suitable sources. The feedstock is processed by conventional state-of-the art means.
Sulfur and clay may be removed from the feedstock before use in the present process. If desired, batching of the feedstock may be carried out in a suitable vessel. The feedstock can be an aqueous coal slurry and delivered by line 10 to a vessel 11. In this embodiment, the feedstock is preferably at ambient temperature but can be supplied at an elevated temperature in the range of 140 F to 1~0 F. At an elevated temperature, the viscosity of the slurry is lower and the moisture content can be more easily controlled. Also, a slurry which is warm can be more thoroughly mixed with the ~ f~ 57 chemicals selec~ed to form a s~abilizing agent and a dispersing agent. Some of these chemicals have a liquidus temperature at about 140F. The process of ,he present invention is parti cularly useful to form and deliver a coal-~a~er mix~ure for use at a remo~e site at ambient temperature. The coal slurry in line lO is preferably formed by a mixture of bituminous coal particles 150 by 0 microns and water. The aqueous slurry pre-fPrably at about Z0%, usually not in excess of 40%, by weigh~
coal particles is treated with ozone in vessel ll. The ozone is fed by line 12 into the vessel ~o increase the ratio of the surface area to a mass~ This treatmen~ renders the coal of the slurry dilatant. The oxidizing action of the ozone on the surface of the coal particles causes pockmarks resembling the dimpled configuration of a golf ball. The treatment with ozone renders the coal dilatant. Impurities in the aqueous coal slurry in vessel ll, if present, are mostly clay with somR
pyrite that comprises a minus 2-micron size fraction. The minus 2-micron fraction will also include some, e.g., 7% by weight, carbon which is an insignificant carbon loss. It is to be unders~ood that the coal slurry in vessel ll can be treated with other agents to achieve dilatancy. If bituminous, the coal particles have a specific gravity of between 1.26 and 1.40 The ~reated slurry in vessel ll is delivered by a line 13 to a classifier 14 which is operated to deliver, in line 15, a first aqueous coal fraction comprised of ooal particles grea~er than 30 microns. Preferably, the first aqueous coal fraction is a 44 micron by lS0 micron coal particle fraction and a small amount of liquid medi~lm, e.g., l6% by wcight of thc fraction.
b ~ 3 5~
Usually, ~his first fraction will hc~ve flow characteristics of a semi-fluid slurry, e.g.~ we~ cake, and not a liquid. The lower siæe limit to the particles forming the first fraction is pre-ferably at 44 microns but can be larger, e.g. 9 50 to 60 microns.
The upper size limi~ to the coal par~icles of this fraction can be as large as 200 to 300 micxons; however particles of 150 microns o~ less are preferrecl. Line 15 is connected ~o deliver the first fraction of coal particles to a surge ve~sel 16. A
minus 30-micron fraction~ preferably the minus 44 micron, from classifi.er 14 is delivered by a linP 17 to a classifier 18.
Classifi~r 18 is operated to effect a sharp separation a~ 2 microns. The minus 2-micron fraction from ~lassifier 18 is delivered by line 19 to other apparatus for processing or dis-posal because this fraction contains a substantial amount of ash and, therefore, is not suitable to form part of a coal-water mixture. The remaining ~0 micron by 2 micron fraction of coal particles, preferably 44 by 2 micron fraction, from classifier 18 constitutes the second fraction of coal particles and is conveyed by line 21 for delivery to a surge vessel 22 This second fraction will usually have ~he characteristic of a flowable viscous slurry and, therefore, a dewatering device 23, described in greater detail hereinafter, is placed in line 21 to reduce t~le aqueous liquid component of the second frac~ion down to 30% or less by weight of the fraction, and thereby increasing the concentration of coal particles in the serond feed stream. The extracted aqueous liquid medium is discarded from the dewatering device by line 24. The liquid conducted by line 24 may be returned to vessel 11 for reuse ~o form additional quantities of the coal slurry.
~s~ 5~
Lines 15 and 21 are provided with par~icle-concentration monitors 25 and 26, respectively~ which deliver electrical signals in lines 25A and 26A to a m;croprocessor 27. The monitors 25 and 26 are well known in ~he art, per se, and may be a sonic, a nuclear or a product-saml)ling type of monitor.
The surge vessels 16 and 22 are used to deliver feed streams having a substantially uniform particle distribution in each feed stream. The di~eharge flow of ~he first aqueous coal fraction from surge vessel 16 is delivered to a flow controllPr 28 which may be a valve, but preferably a flow-assisting con-veyor or a proportioning flow ontroller driven ~y a variable speed motor which forms a control element 29. The discharge flow of the second aqueous coal fraction from surge vessel 22 is delivered to a flow controller 31 which also can be a valve, but preferably a flow-assisting conveyor or a proportioning flow controller driv~n by a variable speed motor which forms a control element 32. The control elements 29 and 32 respond to separate electrical signals derived from the microprocessor 27 on the basis of a program which utilizes the electrical signals from the monitor 25 and 26 and correspond to the concentration of coal paxticles in each of the first and seeond feed streams. The program also utilizes electrical signals fed to the microprocessor from volume-measuring or weighing devices 33 and 34 that form part of separate delivery sys~ems for the feed streams issuing from flow controllers 28 and 31, respectively~ After weighing, the separate feed streams are combilled in a mixer 35 to form a coal-wa~er mixtu?-e. rhe dewatering device 23 is operated to increase the coal particle concentration in the second fraction to the extent that when this fraction is combined with the first ~ 2~ 5~
fraction, the supply stream has a d,esired or greater than desired final particle concentra~ion of the coal-wa~er mixture.
According to the present invention, the coal-water mixture is comprised of at least 65% by weight coal particles and up to about 82% by weight coal particles. The dewatering device 23 is operated by a drive which can be controlled by an electrical signal from the microprocessor to assure that the combined quantities of aqueous media in the two fractions do not exceed the desired COnteTIt of aqueous media in the coal-water mi2ture.
It will usually be necessary to con~rol ex~raction of the aqueous medium by the dewatering device to compensate for quantities of aqueous media that form part of a surfactant such as a stabilizing agent and/or dispersing agent that is added to each of the first and second feed streams. Preferably, a water-soluble dispersing agent is added to the vessel forming the mixer containLng quantities of each feed stream.
The dispersing agent can be selected from the group consisting of lignosulfonate, condensed polynuclear hydrocarbons or alkoxylated amine. Preferably, the dispersing agent is a wa~er~soluble ethoxylated, propoxylated or ethoxylated propoxylated composition, which is mixed with the feed streams in mixer 35 to prevent physical separation of the coal particles in the coal-water mîxture. The coal particles in the coal-water mixture are compacted in the liquid medium which is delivered by line 36 to a storage tank or site for final usage such as a blast furnace, boiler or the like.
The px eferred dispersing agent will elimina~e the need for a stabilizing agent; however, a stabilizing agent can be 9~7 selected from the group consis~ing of attapulgite clay, branched macromolecules containing active carbonyl and hydroxyl groups.
To control the supply of a surfactant, e.g.~ dispersing agent, an electrical signal is delivered from the microprocessor in line 37 to a controller 389 e.g., a valve or pump, for con trolling ~he delivery of the surfa~tant from a tank 39 to the mixer 35. However, it is preferred to use t~nk 39 for s~pplying the preferred dispersing agent~ An elec~r~cal signal is also provided hy the microprocessor in line 41 for controlling a valve 42 in an aqueous fluid medium supply line 43 extending to the mixer 35. Fluld medium is added to the mixture in the mixer to adjust the density of coal particles in the final coal-water mixture to the desired ex~ent. The combine~ feed streams, absent a surfactant and addi~ional aqueous fluid medium from line 43 will typically comprise 20% to 25% by weight aqueous medium which is increased to the desired extent by the addi~ion of a dispersing agent, preferably in an aqueous medium~ and ~queous medium to produce a coal-water mixture having about 70% by weight solids.
While the foregoing description of the invention utilizes a two-stage classification, proportioning and blending of coal particles, it will now be apparent ~o those skilled in the art that three or more stages of classification can be used to produce a coal-water mixture. It is important to determine and control the distribution of coal particles within each size fraction, par~icularly che smaller size particles for subsequen~
mixing together of each fraction of coal par~icles. In this way, one can con~rol ~he particle size distribution and~ in ~urn, 3~i7 the density of the coal particles in t.he coal-water mixture derived from the process.
As will be explained in greater detail hereinafter, the dilatant pro~er~y of the coal part:icles forming the second feed s~ream grea~ly enhances the removal of the aqueous medium from the feed stream through the use of the dewatering device 23.
However, to assure a desired carbon conLent in ~he final coal-water mixture and optimize the particle packing, particularly by the use of smaller coal particles to fill inner spaces in the coal-water mixture, it is desired to introduce a minus 2-micron coal fraction to replace the minus 2-micro~ fraction that was discarded in line 19. The replacement fraction should, of course, colaprise essentially only coal particles which can be derived by both processing of a small subflow from one of the first or second feed stream in a ball mill~ The feed stream which is selected to provide the subflow to the ball mill can vary from time-to-time based on an oversupply of one particular coal fraction due to an ever-changing coal particle size distribution forming ~he feed-stock. Thus, for example, should a feedstock throughout a period of time contain an overabundant supply Of coal particles within the size range of 44 by 150 microns, then the first feed stream is selected to form the subflow to the ball mill. Thereafter, should the feedstock contain an overabundant supply of coal particles within the size range of 2 by 44 microns9 ~hen the seoond feed s~ream will be selected to form the subfLow to the ball mill.
Depending upon th~ source of the f~edstock, a continuing over-abundan~ supply of ? by 44 micron coal particles is likely to occur.
To avoid depleting of the 44 by 150 micron coal particle fraction, _~_ ~ ~96~57 a ball mill is used ~o reduce an oversize coal fraction or a separate supply of coal is used to produce make-up quantities of the insufficient coal particle fraction. Make-up quantities of a coal particle fraction are treated to impart dilatancy as described hereinbefore. Make up quantities for the first coal particle fraction are delivered to the surge-holding vessel 16 by line 44 and make-up quantities of the second coal particle fraction are delivered to the surge-hold.i~g vessel 22 by line 45.
In Fig. 1, a subflow of the first feed stream in line 15 is delivered by line 46 ~hrough ~ three-way valve 47 to a header pipe 48 extending to a ball mill 49. A subflow of the second feed stream in line 21 is directed by line 51 to valve 47 which can be positioned to deliver a partial flow of the second fraction to header pipe 48 and thence to ball mill 49. A minus
PROCESS FOR PROD~CING A
COAL-WATER MIXTURE
This invention relates to a process ~o produce a coal-water mixture comprised of coal particles in an aqueous liquid medium. More particularly9 the present invention relates to a process for producing a coal-water mixture from feedstock formed of coal particles which can be ground, freshly-mined coal or coal salvaged from sil~ ponds or other sources after processlng to remove clay3 shale9 pyrite and other minerals wherein the feed-stock is classified and/or treated to impart dilataney to the coalparticles and two or more feed streams comprised of differently-sized, e.g., classified, coal particles in a liquid mRdium are mixed together with a dispersing agent to form a coal-water mixture having at least 65% by weight coal particles.
One characteristic of the coal recovered from silt ponds is a substantial varia~ion to the coal particle size distribution in a flow stream on a day-to-day basis and possibly on an hour-to-hour basis. A substantial variation to the particle ~ize distribution of ultrafine sizes of freshly-mined coal can be expected when preparing feedstock for a process to form a coal-water mixture. The problem of variations to the particle size distribution oi the feedstock exists in all curren~ly-known methods for wet and dry grinding of coal.
In a paper entitled Rheolo~y of Hi~h Solids Coal-Water Mixture by D.R ~inger, J.E. Funk~ Jr. and J.E. Funk, Sr., 4th International Symposium on Coal Slurry Combustion, May 10-12, 3~57 1984, there is descrlbed thP "rheological proper~ies of a coal-water mixture having 9805% coal particles at 50 mesh or less depending on ~he particle-packLng efficiency which minimizes in~erstitlal porosity. An equation for optimum particle-packing efficiency is derived and an algori~hm developed calculating ~h~
porosity of real particle distribu~ions. The calculated poro-sity was checked by pressure filtration and measurement of porosity. The speciflc surfa~e area is also calculated by an algorithm. The data provides a family of particle size distri-butions wh~ch produce exceptional rheological properties pro-vided that a surfactant addition is effec~ive for dispersing the coal particles. It was found ~ha~ monospheres~ regardless of their size will usually pack to an average orthorhombic array o about ~0V/~ by volume. In order to shear, the structure must open or dilate to a cubic array where the porosity increases from 40% to about 48%. It was found that to prevent dilatancy, or interparticle collisions in shear, the system must be dilu~ed so that the interparticle spacing is at least IPS ~ r--3)D 9 where IPS is the interparticle spacing and D is the particle size.
The problem arises, however, as to the manner by which a coal-water mixture can be produced comprising at least, for example, 65% by weight coal particles and preferably 70% and up to about 82% by weight coal particles on an hourly and a day-to-day basis for reliable use. At about 65% by weight coal particles, a coal-water mixture requires the use of addi~ional fuel ~uch as a com~ustible gas when used in a power pl~nt. How-ever, the coal-wa~er mixture can be economically utilized. It is, howevery far more economical to provide a coal-water mixture with a coal-particles concentration of at least 70~ by weight coal particles. Above 82% by weight coal particles, mechanical problems can be expected to impede delivery of the coal-water mixture by piping networks, pumps and valves.
Feedstock for a coal-water mixture is usually an aqueous coal slurry about 20~ to 40% by weight coal particles.
The slurry must be dewatered to an extent sufficient to form a flowable coal-water mixture with at least 65% by weight coal and rheological properties, particularly viscosity that will not impede flow in pipelines at normal ambient temperatures, e.g., 0 C to 35 C. It has been discovered that dilatancy of coal particles can be effectively utilized for dewatering a mass of coal particles derived from an aqueous coal slurry.
It has also been discovered that dilatancy can be imparted to coal particles by increasing the ratio of surface area to mass whereby a dispersing agent in a subsequently-formed coal-water mixture functions in a surprising and far superior manner to enhance the flow characteristics of the mixture. The feedstock for the coal-water mixture can be made dilatant also by removing a clay constituent that is hydrophobic and prevents dilatancy.
According to the present invention there is provided a process for producing a coal-watex mixture, the steps including: producing an aqueous coal slurry comprised of granular coal feedstock which is greater then 50% by weight of ,f~h.~3Sr7 an aqueous liquid medium, forming :Erom the aqueous coal slurry at least first and second dilatant coal feed strea~s each comprised of a different size classification of the granular coal feedstock in aqueous liquid medium, the aqueous liquid medium of each of the feed streams being less than 50% by weight of the granular coal feedstock, and mixing together selected amounts of the first and second dilatant coal feed streams in the presence of a dispersing agent to from a coal-water mixture comprised of at least 65% by weight coal particles.
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 diagrammatic flow sheet of a practical installation for producing a coal-water mixture according to the present invention;
Fig. 2 is an elevational view of a preferred form of a dewatering device for use in the process of the present invention; and Fig. 3 is a diagrammatic flow sheet of a further installation for producing a coal-water mixture according to the present invention.
Feedstock conducted by line 10 for the process of the present invention may be freshly-mined coal or coal '55~q salvaged from silt ponds or other suitable sources. The feedstock is processed by conventional state-of-the art means.
Sulfur and clay may be removed from the feedstock before use in the present process. If desired, batching of the feedstock may be carried out in a suitable vessel. The feedstock can be an aqueous coal slurry and delivered by line 10 to a vessel 11. In this embodiment, the feedstock is preferably at ambient temperature but can be supplied at an elevated temperature in the range of 140 F to 1~0 F. At an elevated temperature, the viscosity of the slurry is lower and the moisture content can be more easily controlled. Also, a slurry which is warm can be more thoroughly mixed with the ~ f~ 57 chemicals selec~ed to form a s~abilizing agent and a dispersing agent. Some of these chemicals have a liquidus temperature at about 140F. The process of ,he present invention is parti cularly useful to form and deliver a coal-~a~er mix~ure for use at a remo~e site at ambient temperature. The coal slurry in line lO is preferably formed by a mixture of bituminous coal particles 150 by 0 microns and water. The aqueous slurry pre-fPrably at about Z0%, usually not in excess of 40%, by weigh~
coal particles is treated with ozone in vessel ll. The ozone is fed by line 12 into the vessel ~o increase the ratio of the surface area to a mass~ This treatmen~ renders the coal of the slurry dilatant. The oxidizing action of the ozone on the surface of the coal particles causes pockmarks resembling the dimpled configuration of a golf ball. The treatment with ozone renders the coal dilatant. Impurities in the aqueous coal slurry in vessel ll, if present, are mostly clay with somR
pyrite that comprises a minus 2-micron size fraction. The minus 2-micron fraction will also include some, e.g., 7% by weight, carbon which is an insignificant carbon loss. It is to be unders~ood that the coal slurry in vessel ll can be treated with other agents to achieve dilatancy. If bituminous, the coal particles have a specific gravity of between 1.26 and 1.40 The ~reated slurry in vessel ll is delivered by a line 13 to a classifier 14 which is operated to deliver, in line 15, a first aqueous coal fraction comprised of ooal particles grea~er than 30 microns. Preferably, the first aqueous coal fraction is a 44 micron by lS0 micron coal particle fraction and a small amount of liquid medi~lm, e.g., l6% by wcight of thc fraction.
b ~ 3 5~
Usually, ~his first fraction will hc~ve flow characteristics of a semi-fluid slurry, e.g.~ we~ cake, and not a liquid. The lower siæe limit to the particles forming the first fraction is pre-ferably at 44 microns but can be larger, e.g. 9 50 to 60 microns.
The upper size limi~ to the coal par~icles of this fraction can be as large as 200 to 300 micxons; however particles of 150 microns o~ less are preferrecl. Line 15 is connected ~o deliver the first fraction of coal particles to a surge ve~sel 16. A
minus 30-micron fraction~ preferably the minus 44 micron, from classifi.er 14 is delivered by a linP 17 to a classifier 18.
Classifi~r 18 is operated to effect a sharp separation a~ 2 microns. The minus 2-micron fraction from ~lassifier 18 is delivered by line 19 to other apparatus for processing or dis-posal because this fraction contains a substantial amount of ash and, therefore, is not suitable to form part of a coal-water mixture. The remaining ~0 micron by 2 micron fraction of coal particles, preferably 44 by 2 micron fraction, from classifier 18 constitutes the second fraction of coal particles and is conveyed by line 21 for delivery to a surge vessel 22 This second fraction will usually have ~he characteristic of a flowable viscous slurry and, therefore, a dewatering device 23, described in greater detail hereinafter, is placed in line 21 to reduce t~le aqueous liquid component of the second frac~ion down to 30% or less by weight of the fraction, and thereby increasing the concentration of coal particles in the serond feed stream. The extracted aqueous liquid medium is discarded from the dewatering device by line 24. The liquid conducted by line 24 may be returned to vessel 11 for reuse ~o form additional quantities of the coal slurry.
~s~ 5~
Lines 15 and 21 are provided with par~icle-concentration monitors 25 and 26, respectively~ which deliver electrical signals in lines 25A and 26A to a m;croprocessor 27. The monitors 25 and 26 are well known in ~he art, per se, and may be a sonic, a nuclear or a product-saml)ling type of monitor.
The surge vessels 16 and 22 are used to deliver feed streams having a substantially uniform particle distribution in each feed stream. The di~eharge flow of ~he first aqueous coal fraction from surge vessel 16 is delivered to a flow controllPr 28 which may be a valve, but preferably a flow-assisting con-veyor or a proportioning flow ontroller driven ~y a variable speed motor which forms a control element 29. The discharge flow of the second aqueous coal fraction from surge vessel 22 is delivered to a flow controller 31 which also can be a valve, but preferably a flow-assisting conveyor or a proportioning flow controller driv~n by a variable speed motor which forms a control element 32. The control elements 29 and 32 respond to separate electrical signals derived from the microprocessor 27 on the basis of a program which utilizes the electrical signals from the monitor 25 and 26 and correspond to the concentration of coal paxticles in each of the first and seeond feed streams. The program also utilizes electrical signals fed to the microprocessor from volume-measuring or weighing devices 33 and 34 that form part of separate delivery sys~ems for the feed streams issuing from flow controllers 28 and 31, respectively~ After weighing, the separate feed streams are combilled in a mixer 35 to form a coal-wa~er mixtu?-e. rhe dewatering device 23 is operated to increase the coal particle concentration in the second fraction to the extent that when this fraction is combined with the first ~ 2~ 5~
fraction, the supply stream has a d,esired or greater than desired final particle concentra~ion of the coal-wa~er mixture.
According to the present invention, the coal-water mixture is comprised of at least 65% by weight coal particles and up to about 82% by weight coal particles. The dewatering device 23 is operated by a drive which can be controlled by an electrical signal from the microprocessor to assure that the combined quantities of aqueous media in the two fractions do not exceed the desired COnteTIt of aqueous media in the coal-water mi2ture.
It will usually be necessary to con~rol ex~raction of the aqueous medium by the dewatering device to compensate for quantities of aqueous media that form part of a surfactant such as a stabilizing agent and/or dispersing agent that is added to each of the first and second feed streams. Preferably, a water-soluble dispersing agent is added to the vessel forming the mixer containLng quantities of each feed stream.
The dispersing agent can be selected from the group consisting of lignosulfonate, condensed polynuclear hydrocarbons or alkoxylated amine. Preferably, the dispersing agent is a wa~er~soluble ethoxylated, propoxylated or ethoxylated propoxylated composition, which is mixed with the feed streams in mixer 35 to prevent physical separation of the coal particles in the coal-water mîxture. The coal particles in the coal-water mixture are compacted in the liquid medium which is delivered by line 36 to a storage tank or site for final usage such as a blast furnace, boiler or the like.
The px eferred dispersing agent will elimina~e the need for a stabilizing agent; however, a stabilizing agent can be 9~7 selected from the group consis~ing of attapulgite clay, branched macromolecules containing active carbonyl and hydroxyl groups.
To control the supply of a surfactant, e.g.~ dispersing agent, an electrical signal is delivered from the microprocessor in line 37 to a controller 389 e.g., a valve or pump, for con trolling ~he delivery of the surfa~tant from a tank 39 to the mixer 35. However, it is preferred to use t~nk 39 for s~pplying the preferred dispersing agent~ An elec~r~cal signal is also provided hy the microprocessor in line 41 for controlling a valve 42 in an aqueous fluid medium supply line 43 extending to the mixer 35. Fluld medium is added to the mixture in the mixer to adjust the density of coal particles in the final coal-water mixture to the desired ex~ent. The combine~ feed streams, absent a surfactant and addi~ional aqueous fluid medium from line 43 will typically comprise 20% to 25% by weight aqueous medium which is increased to the desired extent by the addi~ion of a dispersing agent, preferably in an aqueous medium~ and ~queous medium to produce a coal-water mixture having about 70% by weight solids.
While the foregoing description of the invention utilizes a two-stage classification, proportioning and blending of coal particles, it will now be apparent ~o those skilled in the art that three or more stages of classification can be used to produce a coal-water mixture. It is important to determine and control the distribution of coal particles within each size fraction, par~icularly che smaller size particles for subsequen~
mixing together of each fraction of coal par~icles. In this way, one can con~rol ~he particle size distribution and~ in ~urn, 3~i7 the density of the coal particles in t.he coal-water mixture derived from the process.
As will be explained in greater detail hereinafter, the dilatant pro~er~y of the coal part:icles forming the second feed s~ream grea~ly enhances the removal of the aqueous medium from the feed stream through the use of the dewatering device 23.
However, to assure a desired carbon conLent in ~he final coal-water mixture and optimize the particle packing, particularly by the use of smaller coal particles to fill inner spaces in the coal-water mixture, it is desired to introduce a minus 2-micron coal fraction to replace the minus 2-micro~ fraction that was discarded in line 19. The replacement fraction should, of course, colaprise essentially only coal particles which can be derived by both processing of a small subflow from one of the first or second feed stream in a ball mill~ The feed stream which is selected to provide the subflow to the ball mill can vary from time-to-time based on an oversupply of one particular coal fraction due to an ever-changing coal particle size distribution forming ~he feed-stock. Thus, for example, should a feedstock throughout a period of time contain an overabundant supply Of coal particles within the size range of 44 by 150 microns, then the first feed stream is selected to form the subflow to the ball mill. Thereafter, should the feedstock contain an overabundant supply of coal particles within the size range of 2 by 44 microns9 ~hen the seoond feed s~ream will be selected to form the subfLow to the ball mill.
Depending upon th~ source of the f~edstock, a continuing over-abundan~ supply of ? by 44 micron coal particles is likely to occur.
To avoid depleting of the 44 by 150 micron coal particle fraction, _~_ ~ ~96~57 a ball mill is used ~o reduce an oversize coal fraction or a separate supply of coal is used to produce make-up quantities of the insufficient coal particle fraction. Make-up quantities of a coal particle fraction are treated to impart dilatancy as described hereinbefore. Make up quantities for the first coal particle fraction are delivered to the surge-holding vessel 16 by line 44 and make-up quantities of the second coal particle fraction are delivered to the surge-hold.i~g vessel 22 by line 45.
In Fig. 1, a subflow of the first feed stream in line 15 is delivered by line 46 ~hrough ~ three-way valve 47 to a header pipe 48 extending to a ball mill 49. A subflow of the second feed stream in line 21 is directed by line 51 to valve 47 which can be positioned to deliver a partial flow of the second fraction to header pipe 48 and thence to ball mill 49. A minus
2-micron coal fraction derive~ through the operation of the ball mill is fed by line 52 from a surge-holding vessel 53. A signal is delivered from valve 47 based on the position thereof to pro-vide a signal to the microprocessor whereby a partial subflow in lines 46 and 51, which occurs after the particle concentration monitors 25 and 26, respectively, insures that the quantity of coal particles in the partial flows from ~he first or sec~nd feed stream3 occurring at a fixed rate~ will update the storage of information in the microprocessor to accurately indicate the quantity and partial distribution size in each of the surge-holding vessels 16~ 22 and 53. This insures that the quantity of the minus 2-micron coaL fraction in surge-holding vessel 53 is controlled so that this particle size fraction does not exceed an overabundant supply of about 5% or less by dry weight of a i~
minus 2 micron coal frac~ 7 coal-water mixture.
:tnstead of deriving a subflow rom either the first or second feed stream for subdividing th~e coal particles to form a minus 2-micron coal particle fraction, it is preferred to use a supply of coal partlcles, particularly anthracite coal~ having a specific gravity of between 1.54 and i.80 and feeding this supply of coal particles to ball mill 49 to form a minus 2-micron coal fraction which is separately introduced into surge vessel 53 in quantities sufficient to form a 5% dry weight component to the coal forming the coal-water mixture. The discharge flow of the minus 2-micron coal fraction from surge-holding vessel 53 is delivered by lin~ 52 to a flow controller 54 which may be a valve but preferably a flow-assisting conveyor or proportioning flow controller driven by a variable speed motor which forms a control element 55. The program of the microprocessor 27 utilizes an electrical signal fed thereto from a volume-measuring or weighing device 56. After weighing, the minus 2-micron coal fraction is fed by line 57 to the mixer 35. In the final coal-water mixture, the plus 2-micron coal partic'les add significantly to ~he viscosity characteristic of the coal-water mixture. Specifically, the viscosity is generally increased over a temperature range of be~ween 0C and 35C by the addi~ion of the minus 2-micron coal par~icle fraction since these par~icles facilitate shear betwePn larger coal particles due ~o the "pockmarking" on the surface of the coal particles. The very favorable viscosity charac~eristics was discovered by laboratory ~ests which show that an unozonized 150 by 4 micron coaL-water mixture exhibited a viscosi~y of 4000 centipoise; whereas a coal-water mixture comprised o L50 by 2 ~4~
micron coal particles whi~h were treated with ozone, exhibited a viscosity of ~000 centipoise. The viscosity using ozonized coal particles of the coal-wa~er mixture at 3C was less than 900 centipolse. In view oE ~hLs discovery, i~ is desirable to cool the coal-water mixture wh;le mixing occurs in mixer 35.
For this purpose, a water-coolant jacket 58 is arranged to with-draw heat from the mixture in the vessel during the process by the use of a motor-driven mixer 59. The mixer 35 is supported on a base by load cells 61 which provide electrical signals corresponding to the weigh~ o the ma~erial in the mixer and are fed by line 62 to the microprocessor. The microprocessor also receives an electrical signal in line 63 from a volume-measuring device 64 such as a sonar or nuclear detector. The favorable viscosity property of the coal-water mixture is attributed to the increase in the ratio of surface area to mass characteristic of the coal particles. The flow properties of the coal-water mixture produced according to the present invention are improved further by the addition of a minus 2-micron fraction of coal particles. This enables an increase in the carbon content of the coal-water mixture as welL as improving the shear in the presence of a dispersing agent.
Turning, now,to Fig. 2 of the drawings, there is illustrated a preferred form of dewatering device to reduce the aqueous medium content of the second feed stream down to at least 30% or less by weight of the coal particles. Line 21 is preerably arranged verticall~ to discharge the second fraction below a water-pool level identiEied by reference numeral 70. The w~ter-pool level is contained within peripheral side walls 71 that extend
minus 2 micron coal frac~ 7 coal-water mixture.
:tnstead of deriving a subflow rom either the first or second feed stream for subdividing th~e coal particles to form a minus 2-micron coal particle fraction, it is preferred to use a supply of coal partlcles, particularly anthracite coal~ having a specific gravity of between 1.54 and i.80 and feeding this supply of coal particles to ball mill 49 to form a minus 2-micron coal fraction which is separately introduced into surge vessel 53 in quantities sufficient to form a 5% dry weight component to the coal forming the coal-water mixture. The discharge flow of the minus 2-micron coal fraction from surge-holding vessel 53 is delivered by lin~ 52 to a flow controller 54 which may be a valve but preferably a flow-assisting conveyor or proportioning flow controller driven by a variable speed motor which forms a control element 55. The program of the microprocessor 27 utilizes an electrical signal fed thereto from a volume-measuring or weighing device 56. After weighing, the minus 2-micron coal fraction is fed by line 57 to the mixer 35. In the final coal-water mixture, the plus 2-micron coal partic'les add significantly to ~he viscosity characteristic of the coal-water mixture. Specifically, the viscosity is generally increased over a temperature range of be~ween 0C and 35C by the addi~ion of the minus 2-micron coal par~icle fraction since these par~icles facilitate shear betwePn larger coal particles due ~o the "pockmarking" on the surface of the coal particles. The very favorable viscosity charac~eristics was discovered by laboratory ~ests which show that an unozonized 150 by 4 micron coaL-water mixture exhibited a viscosi~y of 4000 centipoise; whereas a coal-water mixture comprised o L50 by 2 ~4~
micron coal particles whi~h were treated with ozone, exhibited a viscosity of ~000 centipoise. The viscosity using ozonized coal particles of the coal-wa~er mixture at 3C was less than 900 centipolse. In view oE ~hLs discovery, i~ is desirable to cool the coal-water mixture wh;le mixing occurs in mixer 35.
For this purpose, a water-coolant jacket 58 is arranged to with-draw heat from the mixture in the vessel during the process by the use of a motor-driven mixer 59. The mixer 35 is supported on a base by load cells 61 which provide electrical signals corresponding to the weigh~ o the ma~erial in the mixer and are fed by line 62 to the microprocessor. The microprocessor also receives an electrical signal in line 63 from a volume-measuring device 64 such as a sonar or nuclear detector. The favorable viscosity property of the coal-water mixture is attributed to the increase in the ratio of surface area to mass characteristic of the coal particles. The flow properties of the coal-water mixture produced according to the present invention are improved further by the addition of a minus 2-micron fraction of coal particles. This enables an increase in the carbon content of the coal-water mixture as welL as improving the shear in the presence of a dispersing agent.
Turning, now,to Fig. 2 of the drawings, there is illustrated a preferred form of dewatering device to reduce the aqueous medium content of the second feed stream down to at least 30% or less by weight of the coal particles. Line 21 is preerably arranged verticall~ to discharge the second fraction below a water-pool level identiEied by reference numeral 70. The w~ter-pool level is contained within peripheral side walls 71 that extend
3~
around the outer edge of a stepped plate 72 having per~orated risers 73 arranged ~ransversely of the plate with respect to the length thereof. The sicle w~lls 71 and bottom plate 72 form a container that is incl;ned 0" to 3 to the horizontal by support columns 74 that are angularly arranged and constructed with an effective length to bring about the angular arrangement of the stepped plate wi~h respect to a support base 75. Preferably, the members 74 are supported at each of their opposite ends by hinge pins so that a drive 76 suppor~ed by the base and coupled to the stepped plate 72 can vibrate the plate at a selected frequency. Because the coal particles comprising the second fraction are dilat2nt, the vibratory action imparted to the stepped plate quickly forces entrained water to the surface of the second fraction within the dewatering device. A pool of wa~er will overlie the condensed solids and a discharge weir identified by reference numeral 77 is provided for removal of excess aqueous medium from the clewatering device. As appalent from Fig. 2, the weir is situated in the back wall of the dewatering device. The dewatering of ~he coal slurry continues throughout the time while the coal particles are advanced along the length of the pan from riser-to-riser. The length of the pan is selected commensurate with the desired extent to which the moisture content of the second fraction is to be reduced.
While the dewatering device illus~rated in Fig. 2 is useful for removing water from granular feedstocki per se, it is particularly useful fot- the dewatering process to reduce the residual moisture to a desired extent for ~he second feed stream in the produc~ion of the coal-water mix~ure. A minus 100-mesh centrifu~e cake of coal particles having a moisture con~ent o 50% may be reduced to a moisture con~ent of 28% through the use of ~he dewa~ering 35~
device shown in Fig. 2. The submerged feed to ~he dewatering device produces a smoo~h laminar movement zone of the coal cake without turbulenceO
In the embodimellt of l~ig. 3, feedstock comprising an aqueous coal slurry as des ribed previously, is delivered, preferably a~ an elevated temperature in the range of 140F ~o 180F by line 110 to a classifier 112. A coal slurry at ambient temperature can be used; however at an elevated temperature, the viscosity of thc slurry is lower and the moisture cont~nt can be used; however at an elevated temperature, the viscosity of the slurry is lower and the moisture content can be more easily con-trolled. Also, a slurry which is warm can be more thorou~hly mixed with the chemicals selected to form a stabilizing agent and a dispersing agent. Some of these chemicals have a liquidus ~emperature at about 140F~ Classifier 112 is operated to deliver, in line 114, a first aqueous coal fraction comprised of coal particles greater than 30 microns and a small amount of liquid medium. Usually, the first fraction will have flow characteristics of a semi-fluid slurry, e.g., wet cake, and not a li~uid. The lower size limit to the pa~ticles forming ~he first fraction is preferably at 30 microns but can be larger, e.g., 50 to 60 microns. The upper size limi~ to the coal particles of this fraction can be as large as 200 to 300 microns; however particles of 150 microns or less are preferred~ Line 114 is connected ~o deliver the first fraction of coal particles to a surge vessel 116. The minus 30 micron fraction from classifier 112 is delivered by line 118 to a classifiPr 120. Classifier 120 is operated to effec~ a sharp separation at 2 microns. ~he minus 2-_~_ micron frac~i.on rom classifier 120 :is delivered by line 122 toother apparatus for processing or di,posal when this fraction contains a substantial amount of ash and, therefore, is no~
suitabLe to fvrm part of a coal-water mixture. The remaining 30 micron by 2 micron fraction of coal particles from classifier 120 constitutes the second fraction of coal particles and is delivered by line 124 to a surge vessel 126. This second fraction will usualLy have the ch~racteristic of a flowable liquid slurry having low viscosity and, thereore, an in-line dewatering device 127 is placed in line 124 to increase the concentration of coal particles in the second feed stream by extracting liquid medium which is discharged from the process by line 1~7A.
The lines 114 and 124 are provided wi~h particle-concentration monitors 128 and 130, respectively, which deliver electrical signals in lines 128A and 130A in a microprocessor 132. The monitors 128 and 130 are well known in the art, per se, and may be a sonic, a nuclear or a product-sampling type of monitor.
The surge vessels are used to deliver feed streams having a substantiaLly uniform particle distribution in each feed stream. The discharge flow of ~he first aqueous coal fraction from surge vessel 116 is delivered to a flow controlLer 134 which may be a valve, but preerably a flow-ass;sting conveyor or a positive displacement pump driven by a variable speed mo~or which forms a control elemen~ 135. The discharge flow of the second aqueous coal fraction from surge vessel 126 is delivered to a flow controller 136 which also can be a valve, but preferaly a flow-assisting conveyor or a pOSLtiVe displacemen~ pump driven by a variable speed motor which forms a control element 137~ The ~L2~g~.~7 control elements 135 and 137 respond~ to separate electrical signals derived from the microprOCeSSQr 132 on the basis of a program which utlliges the electriccll signals from the monitors and correspond to the concen~ration of coal particles in each of the first and second feed streams. The program also utilizes electrical signals fed to the microprocessor from volume-measuring or weighing devices 138 and 139 that form part of 5eparate de~ivery systems for the feed streams issuing from flow controllerc 134 and 136, respectively. After weighing, the separate feed streams are combined in a mixer 140 to form a supply stream. The dewatering apparatus 127 is operated to increase the coal particle concentration in the second fraction ~o the extent that when t~is fraction is combined with the first fraction, the supply s~ream has a desired or grea~er than desired final particle concentration of the coal-water mixture. The final coal-water mixture is comprised of at least 65% by weigh~
coal particles and up to about 82% by weight coal particles.
The dewatering apparatus 127 is con~rolled by an electrical signal from the microprocessor to adjust the combined quantities of aqueous media in the supply stream. It will usually be necessary to control extraction of the aqueous medium by the dewatering apparatus to compensate for quantities of aqueous media that form part of a stabilizing agent that is added to each of the first and second feed streams.
Electrical signals are delivered from ~he microprocess in lines 141 and 142 to controllers 143 and 144, e.g., valves or pumps, for controlling the delivery of a dispersing agent from tank 145 to mixers 146 and 147. These mixers can be static, _.~
~ Jf~7 in line mixers prnvided in lines 114 and 124, 7-espectivPly, do~nstream of the monitors 128 and 130. The dispersing agen~
can be selected from the gro-lp consisting of lignosulfonate, ccndensed polynuclear hydrocarbons or alkoxylated amine. The dispersing agent is ~ixed with the feed stream in ~ blender 148 to prevent separation of the coal particles. The coal particles in the coal-water mi~ture are comp~cted in ~he ~iquid mediu which is delivered by line 149 to a storage tank or site for final us~ge such as a blast furnace, boiler or the like.
The stabilizing a~ent can be selected from the group consisting of attapulgite clay, branched macromolecules contain-ing active carbonyl and hydroxyl groups. An electrical signal is delivered from the microprocessor in line 150 to a controller 151, e.g., a valve or pump, for controlling the delivery of the stabilîzing agent from a tank 152 to the blender 148. An electrical signal is also provided by the microprocessor in line 153 for controlling a valve 154 in a supply fluid medium supply line 155 extending to the blender 148. Fluid medium is added to the mixture in the blender to adjust the densLty o~ coal particles in the final coaL-water mixture to the desired extent.
Although the invention has been shown in connection with certain specific embodiments, it wiLl be readily apparent to those skilled in the art ~hat various changes in form and arrangement of parts may be made to suit requirements without departing from ~he spirit and scope of the invention.
i~
~_
around the outer edge of a stepped plate 72 having per~orated risers 73 arranged ~ransversely of the plate with respect to the length thereof. The sicle w~lls 71 and bottom plate 72 form a container that is incl;ned 0" to 3 to the horizontal by support columns 74 that are angularly arranged and constructed with an effective length to bring about the angular arrangement of the stepped plate wi~h respect to a support base 75. Preferably, the members 74 are supported at each of their opposite ends by hinge pins so that a drive 76 suppor~ed by the base and coupled to the stepped plate 72 can vibrate the plate at a selected frequency. Because the coal particles comprising the second fraction are dilat2nt, the vibratory action imparted to the stepped plate quickly forces entrained water to the surface of the second fraction within the dewatering device. A pool of wa~er will overlie the condensed solids and a discharge weir identified by reference numeral 77 is provided for removal of excess aqueous medium from the clewatering device. As appalent from Fig. 2, the weir is situated in the back wall of the dewatering device. The dewatering of ~he coal slurry continues throughout the time while the coal particles are advanced along the length of the pan from riser-to-riser. The length of the pan is selected commensurate with the desired extent to which the moisture content of the second fraction is to be reduced.
While the dewatering device illus~rated in Fig. 2 is useful for removing water from granular feedstocki per se, it is particularly useful fot- the dewatering process to reduce the residual moisture to a desired extent for ~he second feed stream in the produc~ion of the coal-water mix~ure. A minus 100-mesh centrifu~e cake of coal particles having a moisture con~ent o 50% may be reduced to a moisture con~ent of 28% through the use of ~he dewa~ering 35~
device shown in Fig. 2. The submerged feed to ~he dewatering device produces a smoo~h laminar movement zone of the coal cake without turbulenceO
In the embodimellt of l~ig. 3, feedstock comprising an aqueous coal slurry as des ribed previously, is delivered, preferably a~ an elevated temperature in the range of 140F ~o 180F by line 110 to a classifier 112. A coal slurry at ambient temperature can be used; however at an elevated temperature, the viscosity of thc slurry is lower and the moisture cont~nt can be used; however at an elevated temperature, the viscosity of the slurry is lower and the moisture content can be more easily con-trolled. Also, a slurry which is warm can be more thorou~hly mixed with the chemicals selected to form a stabilizing agent and a dispersing agent. Some of these chemicals have a liquidus ~emperature at about 140F~ Classifier 112 is operated to deliver, in line 114, a first aqueous coal fraction comprised of coal particles greater than 30 microns and a small amount of liquid medium. Usually, the first fraction will have flow characteristics of a semi-fluid slurry, e.g., wet cake, and not a li~uid. The lower size limit to the pa~ticles forming ~he first fraction is preferably at 30 microns but can be larger, e.g., 50 to 60 microns. The upper size limi~ to the coal particles of this fraction can be as large as 200 to 300 microns; however particles of 150 microns or less are preferred~ Line 114 is connected ~o deliver the first fraction of coal particles to a surge vessel 116. The minus 30 micron fraction from classifier 112 is delivered by line 118 to a classifiPr 120. Classifier 120 is operated to effec~ a sharp separation at 2 microns. ~he minus 2-_~_ micron frac~i.on rom classifier 120 :is delivered by line 122 toother apparatus for processing or di,posal when this fraction contains a substantial amount of ash and, therefore, is no~
suitabLe to fvrm part of a coal-water mixture. The remaining 30 micron by 2 micron fraction of coal particles from classifier 120 constitutes the second fraction of coal particles and is delivered by line 124 to a surge vessel 126. This second fraction will usualLy have the ch~racteristic of a flowable liquid slurry having low viscosity and, thereore, an in-line dewatering device 127 is placed in line 124 to increase the concentration of coal particles in the second feed stream by extracting liquid medium which is discharged from the process by line 1~7A.
The lines 114 and 124 are provided wi~h particle-concentration monitors 128 and 130, respectively, which deliver electrical signals in lines 128A and 130A in a microprocessor 132. The monitors 128 and 130 are well known in the art, per se, and may be a sonic, a nuclear or a product-sampling type of monitor.
The surge vessels are used to deliver feed streams having a substantiaLly uniform particle distribution in each feed stream. The discharge flow of ~he first aqueous coal fraction from surge vessel 116 is delivered to a flow controlLer 134 which may be a valve, but preerably a flow-ass;sting conveyor or a positive displacement pump driven by a variable speed mo~or which forms a control elemen~ 135. The discharge flow of the second aqueous coal fraction from surge vessel 126 is delivered to a flow controller 136 which also can be a valve, but preferaly a flow-assisting conveyor or a pOSLtiVe displacemen~ pump driven by a variable speed motor which forms a control element 137~ The ~L2~g~.~7 control elements 135 and 137 respond~ to separate electrical signals derived from the microprOCeSSQr 132 on the basis of a program which utlliges the electriccll signals from the monitors and correspond to the concen~ration of coal particles in each of the first and second feed streams. The program also utilizes electrical signals fed to the microprocessor from volume-measuring or weighing devices 138 and 139 that form part of 5eparate de~ivery systems for the feed streams issuing from flow controllerc 134 and 136, respectively. After weighing, the separate feed streams are combined in a mixer 140 to form a supply stream. The dewatering apparatus 127 is operated to increase the coal particle concentration in the second fraction ~o the extent that when t~is fraction is combined with the first fraction, the supply s~ream has a desired or grea~er than desired final particle concentration of the coal-water mixture. The final coal-water mixture is comprised of at least 65% by weigh~
coal particles and up to about 82% by weight coal particles.
The dewatering apparatus 127 is con~rolled by an electrical signal from the microprocessor to adjust the combined quantities of aqueous media in the supply stream. It will usually be necessary to control extraction of the aqueous medium by the dewatering apparatus to compensate for quantities of aqueous media that form part of a stabilizing agent that is added to each of the first and second feed streams.
Electrical signals are delivered from ~he microprocess in lines 141 and 142 to controllers 143 and 144, e.g., valves or pumps, for controlling the delivery of a dispersing agent from tank 145 to mixers 146 and 147. These mixers can be static, _.~
~ Jf~7 in line mixers prnvided in lines 114 and 124, 7-espectivPly, do~nstream of the monitors 128 and 130. The dispersing agen~
can be selected from the gro-lp consisting of lignosulfonate, ccndensed polynuclear hydrocarbons or alkoxylated amine. The dispersing agent is ~ixed with the feed stream in ~ blender 148 to prevent separation of the coal particles. The coal particles in the coal-water mi~ture are comp~cted in ~he ~iquid mediu which is delivered by line 149 to a storage tank or site for final us~ge such as a blast furnace, boiler or the like.
The stabilizing a~ent can be selected from the group consisting of attapulgite clay, branched macromolecules contain-ing active carbonyl and hydroxyl groups. An electrical signal is delivered from the microprocessor in line 150 to a controller 151, e.g., a valve or pump, for controlling the delivery of the stabilîzing agent from a tank 152 to the blender 148. An electrical signal is also provided by the microprocessor in line 153 for controlling a valve 154 in a supply fluid medium supply line 155 extending to the blender 148. Fluid medium is added to the mixture in the blender to adjust the densLty o~ coal particles in the final coaL-water mixture to the desired extent.
Although the invention has been shown in connection with certain specific embodiments, it wiLl be readily apparent to those skilled in the art ~hat various changes in form and arrangement of parts may be made to suit requirements without departing from ~he spirit and scope of the invention.
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Claims (23)
1. In a process for producing a coal-water mixture, the steps including:
producing an aqueous coal slurry comprised of granular coal feedstock which is greater then 50%
by weight of an aqueous liquid medium, forming from said aqueous coal slurry at least first and second dilatant coal feed streams each comprised of a different size classification of said granular coal feedstock in an aqueous liquid medium, the aqueous liquid medium of each of the feed streams being less than 50% by weight of the granular coal feedstock, and mixing together selected amounts of said first and second dilatant coal feed streams in the presence of a dispersing agent to form a coal-water mixture comprised of at least 65% by weight coal particles.
producing an aqueous coal slurry comprised of granular coal feedstock which is greater then 50%
by weight of an aqueous liquid medium, forming from said aqueous coal slurry at least first and second dilatant coal feed streams each comprised of a different size classification of said granular coal feedstock in an aqueous liquid medium, the aqueous liquid medium of each of the feed streams being less than 50% by weight of the granular coal feedstock, and mixing together selected amounts of said first and second dilatant coal feed streams in the presence of a dispersing agent to form a coal-water mixture comprised of at least 65% by weight coal particles.
2. The process according to claim 1 wherein said step of forming includes removing a minus 2-micron particle fraction from the coal feedstock.
3. The process according to claim 1 wherein said step of forming includes discarding a minus 2-micron particle fraction from the coal feedstock.
4. The process according to claim 1 wherein said step of forming includes increasing the ratio of surface area to mass of coal particles comprising the coal feedstock.
5. The process according to claim 4 wherein said step of forming further includes removing a minus 2-micron particle fraction from the coal feedstock.
6. The process according to claim 1 wherein said step of forming includes contacting particle of the coal feedstock with an oxidizing agent to increase the ratio of surface area to mass of coal particles.
7. The process according to claim 6 wherein said step of forming the coal feedstock further includes removing a minus 2-micron particle fraction.
8. The process according to claim 1 wherein said step of forming includes forming depressed areas in the surfaces of coal particles of the coal feedstock.
9. The process according to claim 8 wherein the ratio of surface area to mass of coal particles is increased by about 5% to 7%.
10. The process according to claim 2 including the further step of producing 2 microns or less granular coal particles and supplying a controlled portion of said 2 microns or less granular coal particles for said step of mixing.
11. The process according to claim 1 wherein said step of producing at least first and second coal feed streams includes forming said first coal feed stream by processing said coal feedstock in a first classifier, forming said second coal feed stream by processing a residual coal feed stream from said first classifier in a second fraction from the second classifier, and dewatering the second coal feed stream.
12. The process according to claim 11 wherein said step of dewatering includes feeding said second coal feed stream onto a first sieve belt and thereafter subjecting the second feed stream to pressure and shear forces in a roller pressing section of a belt press.
13. The process according to claim 11 wherein said step of dewatering includes feeding said second stream to the lower end of an upwardly-inclined stepped plate having transverely-extending attachments, and vibration of said stepped plate to advance said second fraction upwardly from attachment-to-attachment to separate aqueous medium from the second feed stream.
14. The process according to claim 13 wherein said step of dewatering further includes arranging said upwardly-incluined stepped plate at an angle to the horizontal of between 0 to 3.
15. The process according to claim 14 wherein said step of producing the coal feedstock includes increasing the ratio of surface area to mass of coal particles.
16. In a process for producing a coal-water mixture, the steps including:
producing an aqueous coal slurry comprised of granular coal feedstock which is greater than 50%
by weight of an aqueous liquid medium, forming at least first and second dilatant coal feed streams each comprised of a different size classification of said granular coal feedstock in a aqueous liquid medium, the aqueous liquid medium of each coal feed streams being less than 50% by weight of the granular coal feedstock, combining selected amounts of said first and second dilatant coal feed streams, and mixing the combined amounts of dilatant coal feed streams with a dispersing agent in effective quantities to form a coal-water mixture having a viscosity that gradually increases throughout a temperature range of 0 C. to 35 C., said coal-water mixture being comprised of at least 65% by weight coal particles.
producing an aqueous coal slurry comprised of granular coal feedstock which is greater than 50%
by weight of an aqueous liquid medium, forming at least first and second dilatant coal feed streams each comprised of a different size classification of said granular coal feedstock in a aqueous liquid medium, the aqueous liquid medium of each coal feed streams being less than 50% by weight of the granular coal feedstock, combining selected amounts of said first and second dilatant coal feed streams, and mixing the combined amounts of dilatant coal feed streams with a dispersing agent in effective quantities to form a coal-water mixture having a viscosity that gradually increases throughout a temperature range of 0 C. to 35 C., said coal-water mixture being comprised of at least 65% by weight coal particles.
17. A process for separating a slurry comprised of a fluid medium fraction and a dilatant granular material fraction, said process including the steps of:
forcing the fluid medium fraction toward the top of the slurry at the lower end of the stepped plate by the application of mechanical energy thereto, and advancing the dilatant granular material fraction upwardly along the plate from the fluid medium at the top of the slurry.
forcing the fluid medium fraction toward the top of the slurry at the lower end of the stepped plate by the application of mechanical energy thereto, and advancing the dilatant granular material fraction upwardly along the plate from the fluid medium at the top of the slurry.
18. The process according to claim 17 wherein said upwarly-inclined stepped plate extends at an angle to the horizontal of between 0 and 3 .
19. The process according to claim 17 including the further step of securing transversely-extending attachments to said upwardly-inclined stepped plate to retain quantities of the dilatant granular material fraction while advance upwardly from attachment-to-attachment along said plate.
20. The process according to claim 19 wherein said attachments includes openings to drain fluid material from granular material retained on the stepped plate by the attachments.
21. The process according to claim 17 including the further step of controlling the level of fluid medium retained on the said upwardly-inclined stepped plate.
22. The process according to claim 17 wherein said step of forcing the fluid medium fraction includes vibrating said stepped plate.
23. The process according to claim 17 wherein said step of advancing the dilatant material includes vibrating said stepped plate.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/581,538 US4521218A (en) | 1984-02-21 | 1984-02-21 | Process for producing a coal-water mixture |
| US581,538 | 1984-02-21 | ||
| US64583384A | 1984-08-13 | 1984-08-13 | |
| US645,833 | 1991-01-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1249957A true CA1249957A (en) | 1989-02-14 |
Family
ID=27078352
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000473046A Expired CA1249957A (en) | 1984-02-21 | 1985-01-29 | Process for producing a coal-water mixture |
Country Status (6)
| Country | Link |
|---|---|
| KR (1) | KR920009623B1 (en) |
| CA (1) | CA1249957A (en) |
| DE (1) | DE3505776A1 (en) |
| ES (1) | ES8607375A1 (en) |
| FR (1) | FR2559777B1 (en) |
| IT (1) | IT1206729B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5171148A (en) * | 1989-06-30 | 1992-12-15 | Ethicon, Inc. | Dental inserts for treatment of periodontal disease |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU617698B2 (en) * | 1987-10-22 | 1991-12-05 | Edward Harris Greenwald Sr. | Method and apparatus for separating clay from and then dewatering ultra fine coal |
| DE4000363A1 (en) * | 1990-01-09 | 1990-05-17 | Hartmann Helmut | Maintaining bulk flow properties of solid-liq. mixt. - by repeating component ratio determn. followed by corrective addn. of sepd. material |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4416666A (en) * | 1979-10-26 | 1983-11-22 | Alfred University Research Foundation Inc. | Coal-water slurry and method for its preparation |
-
1985
- 1985-01-29 CA CA000473046A patent/CA1249957A/en not_active Expired
- 1985-02-18 ES ES85540502A patent/ES8607375A1/en not_active Expired
- 1985-02-19 IT IT8519563A patent/IT1206729B/en active
- 1985-02-20 DE DE19853505776 patent/DE3505776A1/en not_active Ceased
- 1985-02-21 KR KR1019850001079A patent/KR920009623B1/en active IP Right Grant
- 1985-02-21 FR FR8502490A patent/FR2559777B1/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5171148A (en) * | 1989-06-30 | 1992-12-15 | Ethicon, Inc. | Dental inserts for treatment of periodontal disease |
Also Published As
| Publication number | Publication date |
|---|---|
| KR920009623B1 (en) | 1992-10-22 |
| ES8607375A1 (en) | 1986-05-16 |
| FR2559777A1 (en) | 1985-08-23 |
| KR850006447A (en) | 1985-10-05 |
| FR2559777B1 (en) | 1987-12-11 |
| ES540502A0 (en) | 1986-05-16 |
| IT1206729B (en) | 1989-05-03 |
| DE3505776A1 (en) | 1985-08-22 |
| IT8519563A0 (en) | 1985-02-19 |
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