WO1982003085A1 - Processes for cleaning minerals and for producing stable suspensions/emulsions,particularly fuels comprising coal,oil,and water - Google Patents

Abstract

A carbon mud is stirred and can be subjected to cavitation under pressure by sound energy so as to be able to release and then separate the contaminating substances from the coal. The cleaned sludge is then subjected to cavitation under pressure by sound energy, subsequently reducing the size of the particles and releasing any residual contaminating substance including iron pyrites and ash. During the sound irradiation of the cleaned mud a small amount of oil is added to cause flocculation and spherical agglomeration of the coal and oil. The mixture of agglomerates and water is screened to extract most of the water, leaving approximately 10 to 40% of water in the carbon, the contaminating substances present in the extracted water also being discharged during the treatment. The spherical agglomerates are mixed with a certain amount of oil to produce a fuel of coal, oil and water and the mixture is still agitated, preferably irradiated by sound energy in order to subsequently reduce the size of the particles of coal and irrigate the subdivided coal mixture. Fuel stability is increased by combining distilled oil and residual oil in the process. In some cases heating the water used for the cleaned sludge also provides stability. A device enabling the method to be implemented is also described. The methods can be applied to a wide range of mineral slurries to stabilize these suspensions or dispersions.

Description

TITLE OF THE INVENTION

PROCESSES FOR CLEANING MINERALS AND FOR PRODUCING STABLE SUSPENSIONS/EMULSIONS, PARTICULARLY FUELS COMPRISING COAL, OIL, AND WATER

BACKGROUND OF THE INVENTION

The present invention evolves from the inventor's discoveries disclosed in his United States patent 3,941,552 and according to which a fuel in the form of a dispersion is made by mixing finely divided coal, oil, and water and subjecting the mixture to violent sonic agitation sufficient to cause cavitation in the mixture in order to effect a stability of the mixture, i.e., substantial shelf or storage life and the ability to use the fuel without in situ agitation equipment.

Earlier discoveries of the inventor, disclosed in his U.S. patents Re 25,324, 3,176,964, 3,344,766, 3,715,104 and 3,749,318, which pertain to apparatus and methods for producing emulsions, including fuels and for burning fuel emulsions also form the bases for the present invention. In this respect, as used herein, "emulsions" is intended to include emulsions having particulate matter in dispersion or suspension as a component thereof.

As noted in U.S. patent 3,941,552, the term "sonic" includes both audible and ultrasonic frequencies and can be effected by sonic generators such as an ultrasonic probe, or by so-called super mixers which cause violent agitation of liquid sufficient to cause cavitation, or by piston homogenizers operating at high pressures of 1000 to 4000 p.s.i. or higher effecting super mixing by means of liquid being ejected through a restriction to increase its velocity after which it impinges on a plate or ring at which time the pressure and/or impact causes violent agitation and cavitation. The same phenomenon, may be obtained in high-speed stirrers, controlled devices and liquid whistles, impact mills handling liquid, colloid mills and the like and in any device in which liquid is subjected to high shear and sudden pressure changes resulting in sonic agitation sufficient to cause cavitation.

As used herein, "sonifying" and "sonification" is intended to include the concept of agitation sufficient to cause cavitation.

In sonifying coal, oil, water mixtures it has been evidenced that with high back pressure in the container in which sonification occurs, while inducing cavitation of extreme intensity, chemical changes or exchanges are taking place between and among the three ingredients. Further, such intense cavitation will apparently stabilize all types of suspensions or dispersions, including those having only two components, such as a coal in water dispersion. Apparatus providing such back pressure during cavitation is disclosed in the inventor's U.S. patent 3,715,104 as well as in U.S. patent 3,941,552.

The use of sonic agitation to cause cavitation has now been determined to provide a very quick and economic method of agglomerating coal and oil within a water carrier and to produce agglomerates of such a nature as to mix with sufficient oil and water additives to form a stable coal, oil, water fuel without further sonification, although sonification is preferred to continue to reduce coal particle size for better burning.

In agglomerating oil and certain coal particulate, such as coal having lignite content, it was discovered that heating the water of the aqueous coal slurry to between 100 and 180 degrees Fahrenheit before agglomeration assured stability of the final fuel product. In this last respect, diminution of coal particulate prior to agglomeration by sonification of coal slurries also affects the separation of pyrites and ash from the coal and this has been found to be an excellent step in the beneficiation of the coal particulate making up the coal, oil, water fuels produced in accordance with the invention.

The stabilization effects of cavitation in the process of the invention appear to be applicable to a wide variety of mineral suspensions and dispersions and is very beneficial in fuel dispersions including coke, petroleum coke, peat, and charcoal, as well as coal, among the carbonaceous minerals having noncarbonaceous elements in their make up.

It has also been found that under the influence of cavitation, residual oil also acts as a stabilizer in the processes of the invention and, in this respect, in coal, oil, water fuels, it has been surprisingly effective to blend distillate and residual oils before adding the oil to the fuel mixture and before cavitation. Yet in other instances the use of distillate oil in an agglomeration step, for instance with the addition of residual oil in the final mixing step has produced the same stabilizing effect.

Moreover, the addition of residual oil in the final step has been found to have the additional benefit of having the viscosity of the resultant product (see U.S. Patent 3,846,087). The advantage of this art and the inventive concepts of this disclosure can be combined to provide an excellent fuel for use in place of No. 6 fuel oil.

The effects of cavitation in the processing of dispersions such as the fuels just discussed are so varied and are so beneficial in terms of fuel quality, production facility and economy that continuous in-line production of such fuels, utilizing the processes of the invention with in-line apparatus has become most desirable. In effecting such in-line production, the various phenomena occurring because of cavitation, agglomeration, coal benef iciation, separating steps and the like presented, at first, choice problems. That is to say, agglomeration has been thought to be the method by which coal is beneficiated and by which agglomerates are produced as a final product.

In the practice of the inventions of U.S. patent 3,914,552 the mixture of coal, oil, and water was balanced to avoid agglomeration because that phenomenon appeared to effect an undesirable instability in the final product. Furthermore, the elimination of sulfur oxides in the burning of the coal, oil, water fuel of the invention of that patent was accomplished by the addition of alkali to the mixture. Also, an initial step of coal beneficiation by agitation of a coal slurry and separating out the contaminants broken away from the coal particulate appeared to be the better alternative to agogolomeration.

SUMMARY OF THE INVENTION

To affect in-line commercial production of stable coal, oil, water fuels, the combining of coal beneficiation without agglomeration as a first step, with agglomeration as a second step, in the processes of the invention is effected. The beneficiation step is interrupted and the agglomeration step is modified to accommodate the basic, end result of a clean, stable fuel. Sonification is used to enhance both steps and, in the instance of agglomeration, to effect usable agglomerates which lose their identity as such in the final mixing step.

The in-line production methods of the invention have been found to facilitate improvement of the final product by accommodating the introduction of residual oil as a component of the coal, oil, water product and the use of heated components where desirable, for example.

One aspect of the present invention provides a method of separating particulate discrete minerals bonded together mechanically by making a slurry of the particles and subjecting the resulting slurry to such intense vibrating action as to produce cavitation within the slurry and the separation of the different components of the particles. From another aspect, the present invention provides a method for producing fuel comprising a mixture of coal, oil, and water which method includes the step of mixing particles of coal and impurities with water to form a slurry, exposing that slurry to such violent agitation as to cause cavitation so that the impurities are detached from the coal particles. The method also includes the step of separating the detached impurities from the slurry and using those impurities as a by-product, for example, in the production of aggregates. The cleaned coal slurry, after adjusting the water content is then mixed with oil and the mixture of coal, oil, and water is treated to form an emulsion. Most desirably, the treatment of the coal, oil, and water to produce an emulsion is that described in U.S. patent 3,914,552.

The agitation of the slurry of coal and water is most desirably affected sonically, and the slurry is exposed to an energy density of at least 3 watts per cm², but in any event sufficient energy density, in combination with a suitable frequency, as to cause cavitation and related to the range of particle size being treated.

According to another aspect of the invention, there are provided emulsions of coal and water with distillate oil or water with distillate oil which are emulsified and which are stabilized by blending a residual oil with the fuel.

In particular, one can obtain an emulsion using No. 2 fuel oil blended with a residual oil such as No. 4 or No. 6. The 4 or 6 oil (or mixtures of those and other residual oils) are generally in the proportion of lass than 10% by weight of the distillate oil. In an in-line production process, the present invention contemplates an optional first step of coarse grinding followed by separation of a major amount of the contaminants of the mineral being processed, followed by wet grinding followed by pre-sonification of the suspendant liquid and the particulate material to reduce the size of the particulate material and in case of coal, to further beneficiate the same by releasing from the coal particles, further particles of ash and other impurities not separated out in the first separation step.

Separation of the impurities from this slurry may then be effected, or while sonification of the slurry is taking place, agglomeration may be induced. A minimal amount of the agglomerating liquid is added to the sonified slurry and this mixture is continued to be agitated preferably by sonification sufficient to induce cavitation in the mixture. It has been found that with sonification in the agglomeration step, only small amounts of agglomerating liquid are required. After sonified agitation, the mixture may then be screened to separate out the suspendant liquid. Further bridging liquid may then be added to produce the final product.

As a first optional step in practicing the present invention in the production of coal, oil, water fuels, run of the mine coal is coarsely ground to between 20 and 60 mesh, sufficient to release most of the contaminants. Water is then added to make a slurry of about 10 to 60% by weight of water and the mixture is subjected to a conventional, separating process such as froth flotation, although sonification coupled with magnetic or centrifugal separation may be used, to remove the bulk of the contaminants. By treating this "coarse" grind there is virtually no loss of small particles which are not good candidates for conventional separating methods in a liquid medium but are good candi dates for the agglomeration process described herein.

In the process as it applies to the manufacture of coal, oil, water fuels, where the desired end product comprises 50% by weight coal, between 30% and 40% by weight of oil, and between 10% and 20% by weight of water, a slurry of coal particulate and water is derived from the initial steps with the coal being approximately 1/3 the weight of the aqueous mixture. That mixture is then sonified to break the ash and pyrites from the coal, and oil as the bridging liquid is added. Sonification of this mixture causes the coal and oil to agglomerate. This mixture is screened to separata out the remaining ash and as much water as desired from the agglomerated mass. Oil is then added to the agglomerated mass, which still retains some water, to the extent desired for the final product.

Depending upon the percentage of water in the agglomerated coal, final sonification or irradiation as it is also called, of the fuel with treatment by cavitation will cause some free water to be leached out of the complete mixture, and it has been found that the water content tends to migrate to the outside of the 'mixture. In other words, if the mixture is being conveyed through a pipe, there is a layer of water between the mixture and the bore of the pipe which facilitates the passage of this thixotropic liquid through the pipe.

The amount of water left in the agglomerated coal can be carefully controlled by the amount and type of oil which is introduced in the spherical agglomeration process just as the coal/water mixture is being irradiated and when the mixture is about to be further irradiated after the introduction of the oil as the agglomerating medium.

It has been noted that the requirement in terms of quantity of oil in the mixture for agglomeration when irradiation is used in the agglomeration steps is less than 10% oil by weight. The advantage of course is that the less oil used in the agglomeration step, the less expensive the process is. Additionally, in sonic irradiation the percentage of solids in the liquid can be much higher, thus, the advantage in the use of sonification in the process.

While the blending of distillate and residual oils for stability may be variously applied in the process, in the process incorporating agglomeration, it is preferred to use a distillate oil in the agglomeration step and residual oil or a blend of residual and distillate oil in the final mixing step.

In one application of heat in the process, it has been found beneficial to stabilization by using heated water in the agglomeration step, the temperature of the water being at least about 35°C.

DESCRIPTION OF THE DRAWINGS

Figure 1 is a flow diagram showing a coal benefaction process.

Figure 2 is a flow diagram showing a coal benefaction process in combination with an agglomeration process.

Figure 3 is a semi-diagrammatic showing of an ultrasonic reactor.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the process according to the invention disclosed in copending application serial number 109,117 filed October 6, 1980, which is a continuation of application serial no. 915,354 filed June 15, 1978, coal and water are delivered to an impact mill 10 or to some other appropriate grinding apparatus. Alternatively, and as indicated in the chain line in the flow chart, coal may be delivered to an impact mill 10a and water is added to the coal particles exiting impact mill 10a as, for example, at 12 to form a slurry. The slurry exiting mill 10, or that produced by the addition of water to the particles exiting mill 10a, is delivered to a tank 14 within which the slurry is subject to violent agitation in this particular embodiment by irradiating the slurry with sonic energy. The sonic vibrations may be generated by known technique, and particularly desirably the vibrations are generated by the utilization of equipment similar to that described in U.S. patent 3,941,552. Using a typical particle size of 50 to 100 microns or less the suitable vibrations have been found to have a frequency of between 500 and 50., 000 Hz and amplitudes ranging from about 2 x 10 to about 10 microns. The energy density should be of an order sufficient to produce effective cavitation within the volume of the slurry. It will be recognized that, dependent upon the density and other characteristics of the slurry, particularly the physical characteristics of the coal particles, the energy requirements will vary. The slurry is exposed to that radiation which will produce detachment of impurities bonded to the coal components of the particles and will simultaneously produce diminution of the particle size.

From the tank 14 the water and the coal and impuri ty components of the particles are delivered to a separation unit 16 in which the coal, pyrites and other impurities are separated. The denser impurities such as iron pyrites and silica are removed from the unit 16 as at 10 to be discarded or to be utilized in the manufacture of other products.

From unit 16 relatively pure coal and water is delivered to a dewatering unit 20 effective to reduce the quantity of the water in the slurry for further processing, such as in U.S. patent No. 3,941,552, or for feed stock, burning or other purposes.

When processed according to the teachings of U.S. patent 3,941,552, oil is added at input 22 to the mixture being delivered along line 24 that oil being added in an amount equal to about 60% by weight of the coal. The resultant mixture of coal, oil, and water is then delivered to a sonic treatment chamber 2.6 which conveniently is of the kind described in U.S. patent 3,941,552 where the mixture is subject to violent agitation to produce cavitation and to produce a virtually stable emulsion.

Alternatively, the agglomeration process may be induced in the sonic treatment chamber 26, in which case a much smaller amount of oil is added to the slurry, as shall be described.

Similarly, agglomeration may be induced in sonic reactor 14 and, in which event, separation may be effected in separation unit 16 or by screening as discussed below with reference to the process shown in Fig. 2.

Furthermore, a "cleaning" by separation may be performed after the first diminution step and the clean slurry presented to the reactor 14 for the agglomeration step.

While the processes of the invention are discussed mainly with relation to the production of coal, oil, water mixtures for fuels, it will be appreciated that utilization of sonification in conjunction with spherical agglomeration is not limited to coal, oil, water mixtures but is useful generally in the separation of solids from their suspendant liquid by the addition of a bridging liquid so the lyophobic particles separate from the suspension after agglomeration. lt is noted that if water is the suspendant liquid then an organic liquid, preferably insoluble in water, would be the bridging liquid and visa-versa. The object is that the bridging liquid will agglomerate with the solid in the suspendant liquid after which the agglomerated mass can be separated from the suspendant liquid.

It is within the purview of this invention to sonify the initial mixture of the suspendant liquid and solids and to again utilize sonification after the agglomerating medium is added and then preferably to again sonify any later mixture of the agglomerated mass with additional bridging medium. In this last respect, as more bridging liquid is added, the agglomerate disolve to become a part of the more liquid end product.

Specifically and with reference to Fig. 2, which diagramatically shows a process in which agglomeration is induced, the coal may first be coarsely ground and water is added and initial separation of contaminants with water is carried out by froth flotation, although other separation methods may be used such as sonification of the slurry and magnetic or centrifugal separation. The "clean" coal, water slurry is then subjected to a grinding operation to grind the coal to between 100 to 300 mesh.

If this first step is optionallly not carrried out, the suspendant liquid, water in this instance, may be fed from a water supply into a container and mixed with coal in particulate form preferably with a typical particle size of 50 to 100 microns or less, although larger particles sizes 200 microns or more may be used. The mixture preferably comprises 60% by weight of water and 40% by weight of coal. The mixture may be stirred by a propeller shown in phantom within the container in Fig. 1 and at any rate the slurry is pumped to an ultrasonic reactor of the type disclosed in U.S. Patent No. 3,941,552 and in U.S. Patent Nos. 3,715,104 and 3,749,318. Now the slurry is subjected to sonification, that is, to violent sonic agitation, with an intensity sufficient to cause cavitation and for a time sufficient to reduce the particle size of the coal particulate even further as a result of the pyrites including ash breaking away from the coal. To this slurry a small amount of the agglomerating medium may be added but in one preferred "in-line" process, the slurry may first be subjected to a separation step to eliminate the impurities broken away from the coal particulate. In either case the slurry is then pumped to a container where the relatively small amount of the agglomerating medium, in this instance between 1% and 370 by weight of the coal, is added to the slurry. In either case, the slurry with the agglomerating medium is then agitated or continued to be agitated and, according to the invention, preferably sonified again with sufficient intensity to cause cavitation.

The agglomeration step is very much enhanced by the use of sonfication, that is, it is quicker and less agglomerating medium has to be used than if agitation of less intensity is applied to the mixture.

The resultant mixture after sonification of the water/coal slurry and agglomerating oil medium comprises the agglomerated mass of coal and oil and. a mixture of water and ash which is lyophilic to the agglomerating medium but not to -water. The mixture is then screened so that the water and ash are screened out and the agglomerated mass of coal and oil is recovered.

The screened out water/ash may be brought back upstream through a separating step where the ash and water are separated and the water returned to the water supply to the initial container. In fact, however, the agglomerated mass also contains a small amount of water which is quite acceptable to the desirable qualities of the final product sought in this process, i.e., a coal, oil, water fuel with between 10% -

20% by weight of water. To the agglomerated mass is added oil sufficient to produce a blended coal, oil, water product consisting of oil and between 10% and 20% by weight of water. The coal, oil, water mixture may then be agitated or sonified again and then may be stored, piped, or used as a fuel. Sonification at this point in the process tends to separate out the water which tends to migrate to the outside of the mass, thus, to enhance pipe travel characteristics of the fuel.

There have been many experiments conducted in the laboratory involving the proportions of the constituent elements to be used in the above described process. Furthermore, experimentation has been carried out utilizing number 2 oil and number 6 oil both in the agglomerating and finalizing steps or in series (number 2 in one and number 6 in the other) with varying results in the end product as concerns viscosity and thixotropy. Similarly, the blending of residual and distillate oil in the process described without the agglomeration step has also produced desirable stability effects.

In one experiment, it was the object to determine whether spherical agglomeration would occur utilizing a number 2 oil in the agglomerating step. In that example 100 grams of coal having a particle size of approximately 70 microns was mixed with 200 grams of water in a blender. The resultant slurry was irradiated, i.e., sonified. To the resultant irradiated slurry first two grams of number 2 oil were added and the mixture was then irradiated. Agglomeration did not appear to occur. Two more grams of numbeτ 2 oil were added and the resultant mixture was again irradiated. No spherical agglomeration appeared to occur. Finally, two further grams, six in all, of number 2 oil were added and the resultant mixture was irradiated and spherical agglomeration did occur. This mixture was passed through a sieve where the water and ash, which has been separated from the coal, was separated out. To the agglomerated mass 40 grams of number 6 oil were added and the mixture was agitated. The resultant end product exhibited good thixotropic properties.

One fuel of this invention comprises a mixture of about 50% by weight coal particles of about 200 mesh size, 20% water, 25% No. 2 distillate oil, and 5% of No. 4 residual oil and is produced by first forming a slurry of water andcoal. Thereafter, the blended oils are united with the slurry of coal and water and the resultant mixture is subjected to agitation to cause the formation of an emulsion. The agitation may be sonic agitation or an homogenizer or other mixing means may be used.

Another fuel according to this aspect of the invention comprises only oil and water and is produced by blending 5% of No. 6 residual oil with 80% of No. 2 fuel oil and then admixing the resultant blend with water, the water comprising 15% by weight of the mixture. The mixture is then agitated to form an emulsion.

In each of the fuels described hereabove, the emulsion is stabilized by the addition of residual oil and appreciable shelf life is obtained in each instance.

Figure 3 is a semi-diagrammatic showing of an ultrasonic reactor 200. Ultrasonic vibrations from 20,000-22,000 Hz result from electricity at the same frequency which is shown coming in through wires. The vibration is in piezo-electric stack 210 to which is coupled the broad end 220 of a steel velocity transformer which tapers exponentially to a small end 230. It is this end which agitates the dispersion.

As discussed in U.S. patent 3,715,104, the reactor utilizes a sonic, or preferably ultrasonic, probe in confined space, such as a container 130. It is important that the space between the end face of the probe and the container wall 232 facing it be adjustable and that the channel between the space and wall be of uniform and small dimension so that liquid dispersions flowing between the plates are maintained in a thin or short path exposed to violent ultrasonic vibrations.

The container is provided with two liquid conduits, one coming in from the side and directed substantially across the space between the end of the probe and the wall, and the other conduit being axial. The flow of liquid across the plates makes is possible to have a somewhat extended zone of ultrasonic vibration as the probe end and container wall can be brought close together so that there are not such long paths through liquid as to attenuate seriously the force of the ultrasonic vibrations and in some cases that the amplitude of vibration approximate the spacing between probe end and wall.

The flow of liquid system across the probe and wall may either be under pressure, that is to say, where the liquid dispersion is pumped in, or it may flow by having the outlet under suction. It is, of course, possible to combine both methods. When pressure flow is used, it is sometimes desirable to increase the pressure downstream from the outlet conduit, which can be done by throttling or other means.

The pressure on the liquid medium in the zone of agitation, or in apparatus terms in the container, can vary, and in many cases a positive pressure is desirable.

It should be understood that the above is presented by way of example only and is not intended to limit the scope of the present invention, except as set forth in the appended claims.

Claims

WHAT IS CLAIMED IS

1. A method, of producing fuel comprising forming a slurry consisting of a dispersion of particles of coal and impurities bonded to said coal and water, exposing the slurry to a sufficiently intense vibrating action to produce cavitation within the slurry and to mechanically detach the impurities from said coal and to reduce the size of the particles, mechanically separating detached impurities from the slurry, and partially reducing but not fully separating the water content of the slurry.

2. A method of producing fuel comprising forming a slurry consisting of a dispersion of particles of coal and impurities bonded to said coal and water, exposing the slurry to violent agitation to produce cavitation within the slurry and to mechanically detach the impurities from said coal and to reduce the size of said particles, mechanically separating the detached impurities from the slurry and partially de-watering the coal/water slurry up to about 40% by weight of the coal, agglomerating the coal and oil, separating the agglomerates from a larger part of the water, adding oil to the partially de-watered agglomerate and then subjecting the resulting mixture to agitation to produce a stable emulsion.

3. The method of producing fuel according to Claim 1 wherein the oil is added in the process up to about 60% by weight of the coal.

4. The process for producing fuel comprising making a slurry of coal particulate and water, sonifying the slurry with sufficient intensity to causa cavitation, adding oil to the slurry during sonification thereof to thereby cause spherical agglomeration of the oil and coal portions of the mixture, screening out the water and any nonagglomerated particles from the coal particulate and adding oil to the agglomerate mass to form a stable fuel.

5. The process of Claim 4 in which the agglomerate mass and oil mixture is sonified.

6. The process of Claim 4 wherein run of the mine coal is first coarsely ground to 20 to 60 mesh to release contaminants therefrom, water is added to form a slurry and the slurry is subjected to a separation process in which water and contaminants are separated from the coal particulate, water is added to the particulate and this slurry is subjected to further grinding to bring the particulate size down to about 100-300 mesh, then the slurry is sonified in accordance with the process of claim 4.

7. A fuel consisting of coal, oil and water which has been sonified to form an emulsion, and in . which the oil consists of a mixture of a residual oil component and a distillate oil component, said residual oil component comprising means for stabilizing the emulsion and forming a part thereof, said coal comprising particulate which has been diminuated and from which impurities have been detached by sonifying the coal particulate in a water carrier.

8. A method of making a fuel comprising diminuting coal particulate in the process of a water carrier by sonifying the particulate and water under pressure, separating impurities broken away from the particulate, adding oil to the coal and water, and sonifying the resultant mixture consisting of coal, water, and oil.

9. Further stabilizing the fuel of Claim 8 by the admixture of residual oil in the mixture to constitute the emulsion as coal, water, and oil in which the oil consists of a distillate oil component and a residual oil component.

10. A method of producing fuel according to Claim 2 in which the water is heated prior to the agglomeration step to a temperature of at least about 35°C.