METHOD FOR BENEFICIAL PROCESSING OF COAL USING PHASE SELECTIVE ORGANO GELATORS

TECHNICAL FIELD
[0001] The present disclosure, in general, relates to the beneficiation process for coal particles, in particular a method for beneficial processing of coal using phase-selective organogelators (PSOG).
BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Beneficiation of coal is a process of reducing ash content present in coal in form of different minerals such as quartz; clay minerals such as kaolinite, illite, etc.; feldspar; carbonates such as calcite, siderite and dolomite; and sulphide minerals such as pyrite and the like in order to maximize the carbon content at a feasible cost.
[0004] Generally, different methods of beneficiation based on the difference in properties, such as density, surface hydrophobicity, electrical conductivity, magnetic conductivity, etc., of coal and mineral matter are utilized. Among the available density-based processes, dense media bath, jigs (batac jig, baum jig, etc.) and dense media cyclone are commonly used for beneficiation of coarse coal. Apart from these methods, spirals, water only cyclone, vorsyl separator, and the like methods are used in the fine size range of coal. Further, in the ultrafine size range, advanced gravity separators, say reflux classifier, Kelsey jig, teeter bed separator, fluidized bed separator, and so forth, are popularly used.
[0005] However, almost all the gravity-based separators get influenced by the difference in the density of coal and ash particles. Hence, the efficiency of these separators reduces with the increase in Near Gravity Materials (NGM) which is found in high proportion in high ash coals. Because of these reasons, other alternate beneficiation methods are also used.
[0006] One such method is froth flotation which is widely used for fine coal beneficiation. In this method, coal flotation makes use of the natural hydrophobicity of the carbonaceous matter in coal. For instance, air bubbles are introduced in the coal-water suspension where they get attached to the hydrophobic particles and carry them to the froth phase. In froth flotation method, the mineral matter in raw coal is comprised of hydrophilic minerals which stay wetted in the suspension and are removed later. Also, reagents play a very important role in flotation as they have the tendency to alter the surface properties as well as make the process more selective. Based on the usage, different types of reagents such as collectors, frothers, promoters, depressants, and the like, can be used in flotation. But, this increases the overall cost of the flotation process and makes the process very hard to control at the commercial scale.
[0007] Another beneficiation method practiced based on the differences in surface properties of coal and mineral matter in an aqueous suspension is oil agglomeration. In this method, very dense lumpy agglomerates of coal particles are formed in an aqueous solution by addition of a bridging liquid like hydrophobic oils. However, the method is applicable only in the size range where flotation becomes ineffective, i.e., below 75 micron/-200 mesh. Furthermore, the addition of oil in large amounts makes the process uneconomical.
[0008] Hence, the above-mentioned existing beneficiation methods are not able to achieve the maximum recovery of clean coal from raw coal deposits and lack in some way or the other. Also, in view of the degrading quality of raw coal deposits, some new beneficiation methods based on advanced as well as innovative technology are required to be developed.
[0009] Nowadays, many hydrophobic oils such as diesel, kerosene etc. are used in beneficiation of coal during different processes, viz., floatation, oil agglomeration, etc., based on the hydrophobic nature of both oil and coal. However, there are methods of recovery of oil from different kinds of aqueous solutions as in the case of marine oil spills. Marine oil spills, which occur because of accidents during oil drilling in the sea or oil shipping (accounts for a third of global maritime trade), as well as natural causes such as volcanic eruption in the seabed, is a serious environmental problem with severe adverse consequences for the marine ecosystem. Accordingly, there is a lot of interest in developing new methods for marine oil-spill recovery. Commonly used methods are bio-remediation (WO2001002086A1, IN200400964I1, AU198310534A and IN236474B) use of oil adsorbents (CN103936919A, CN103877952A, CN107556772A, CN105315431A, and EP75384A1), use of dispersants (CN104962238A, CN104962239A, CN106964299A, WO2003006147A2, EP21571A1 and CN105694817A), and oil gelation (JP9151369A, KR336175B, KR2002022335A and KR2001073581A). Among the methods used for oil spill recovery, the method of oil gelation is based on the hydrophobic nature of oil & high hydrophilic tendency of saline water.
[0010] Since coal like oil is also naturally hydrophobic in nature because of its high organic content, there is a need for a method of coal gelation which is fundamentally derived from the concept of oil gelation.
OBJECTS OF THE DISCLOSURE
[0011] In view of the foregoing limitations inherent in the state of the art, some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed hereinbelow.
[0012] It is a general object of the present disclosure to provide a method for the beneficiation of different varieties of coal to produce maximum recovery. This will help in the better utilization of different varieties of coal deposits such as low volatile coking coals, deep seam coal deposits, highly mineral matter disseminated coal deposits, oxidized coal, weathered coals, etc.
[0013] It is yet another object of the present disclosure to carve the way forward for an appropriate use of the solid wastes generated in the coal preparation plants by providing a feasible beneficiation route at acceptable ash and yield. It will help in conserving the limited and highly valued reserves of hydrophobic oil like diesel, kerosene etc. for the future.
[0014] It is yet another object of the present disclosure to provide an alternative to hydrophobic oils which are used for beneficiation of coal.
[0015] It is also an object of the present disclosure to provide a method of treating coal of varying ash and washability characteristics.
[0016] It is a further object of the present disclosure to provide a method for beneficiation of coal particles that is simple and easy as compared to the prior techniques.
SUMMARY
[0017] This summary is provided to introduce concepts related to a method for beneficial processing of coal using phase-selective organogelators (PSOG). The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0018] In an embodiment, the present disclosure relates to a method of beneficiation process for coal. The method beings with mixing a feed coal with water in a conditioning tank to form a coal slurry; followed up with adding a reagent with the coal slurry in the conditioning tank, where the reagent is a polymeric derivative of nitrogen-based compounds which acts as a phase-selective organo-gelators (PSOG) in the dosage of 0.5% to 1% of the weight of the feed coal; then mixing the reagent with the coal slurry for a stipulated time in the conditioning tank; and finally transferring the coal slurry into a settling tank for allowing the coal slurry to settle down so as to form two distinct layers: one gel-like thick mass layer with being comprised beneficiated clean coal and other suspended aqueous layer of high ash mineral matter.
[0019] In an aspect, the mixing of the feed coal and the water is carried out at a ratio between the feed coal and the water ranging from 1:9 to 1:4 (by wt/wt).
[0020] In an aspect, the polymeric derivative of the nitrogen-based compounds belongs to the class of the phase selective organo-gelators (PSOG).
[0021] In an aspect, the stipulated time for mixing of the reagent with the coal slurry corresponds to the quantity of the feed coal.
[0022] In an aspect, after settling down to form two distinct layers, the method includes separating the two distinct layers through one of decanting off the aqueous layer of high ash mineral matter or filtering or screening off of the thick gel layer of the clean coal.
[0023] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
[0024] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and methods that are consistent with the subject matter as claimed herein, wherein:
[0025] FIG. 1 illustrates a coal gelation environment for a coal gelation process in accordance with an embodiment of the present disclosure;
[0026] FIG. 3 illustrates a graphical representation of adsorption of PSOG/Gelator molecule on the surface of the coal analyzed through Fourier-transform infrared spectroscopy (FTIR) technique; and
[0027] FIG. 2 illustrates the method of beneficiation processing of coal in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION
[0028] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0029] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0030] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes”, “consisting” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0031] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0032] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0033] Embodiments explained herein pertain to a new beneficial process for coal particles through the method of coal gelation using phase selective organagelators (PSOG) chemicals. Generally, coal in nature occurs in association with mineral matter commonly referred to as the ash content of coal. While coal is hydrophobic in nature, ash is hydrophilic. Utilizing this difference in surface properties of coal and ash particles, a method of coal gelation has been proposed herein in the present disclosure. In this method, PSOG molecules which have the ability to selectively congeal organic molecules/particles from a biphasic mixture has been used. These PSOGs, when added to a mixture/slurry of coal and water, selectively attaches themselves to the more hydrophobic coal particles leading to the formation of coal agglomerates. Whereas on the other hand, the ash articles remain in the suspension & therefore separation of coal particles from ash particles take place efficiently and easily.
[0034] FIG. 1 illustrates a coal gelation environment 100 for coal gelation process in accordance with an embodiment of the present disclosure. The coal gelation environment 100 shown in FIG. 1 should not be construed as a limitation for structural elements or components. Those skilled in the art can appreciate that the structural components or elements shown in FIG. 1 are represented for the purpose of explanation of the present disclosure.
[0035] Referring to Fig. 1, the coal gelation environment 100 includes a grinding mill 102 in which raw coal or feed coal is fed from an inlet 102-2. Once the feed coal is fed to the grinding mill 102, the grinding mill 102 grinds the feed coal to form fine particles of the feed coal. After grinding of the feed coal, the feed coal is converted into a feed size of 80% passing 100 mesh or 150 µm.
[0036] The feed coal, after grinding, is moved from out from an output 102-4 of the grinding mill 102 to a coal inlet 104-2 of a conditioning tank 104. The amount of feed coal fed into the conditioning tank 104 depends on the pulp density of the coal slurry to be prepared and in this case, it is varied from 10% to 20% solids on weight by weight basis. After adding the feed coal into the conditioning tank, a suitable amount of water is fed into the conditioning tank 104 through a water inlet 104-4 for mixing with the feed coal. In an aspect, the amount of the water fed into the conditioning tank 104 corresponds to the amount of feed amount present in the conditioning tank.
[0037] Once the feed coal and the water are fed into the conditioning tank 104, mixing blades 104-6, provided inside the conditioning tank 104, are set into motion for mixing the feed coal with water so as to form a coal slurry. In an aspect, the rotation speed of the mixing blades 104-6 is kept at a standard known revolution per minutes (rpm). Also, the standard speed is maintained constant throughout the process for proper mixing of the feed coal and water so as to form coal slurry.
[0038] After formation of the coal slurry, a calculated amount of reagent from the reagent tank 106 is added, from a reagent input 104-8 to the conditioning tank 104. In an aspect, the dosage of the reagent in the conditioning tank 104 is varied in between from 0.5% to 1% of the weight of the coal feed. In an aspect, the reagent in the present disclosure includes, but not limited to, a polymeric derivative of nitrogen-based compounds like urea/amide based containing more than 10 carbon atoms in the hydrocarbon chain.
[0039] After the addition of reagent in conditioning tank 104, the mixing blades 104-6 provided inside the conditioning tank 104 are again set to the motion for mixing the reagent with the coal slurry. During the mixing, the coal particles because of their inherently hydrophobic nature get attached to the reagent molecules through the bridging mechanism and form a black gel-like layer containing most of the coal particles.
[0040] This gel-like layer is moved from the conditioning tank 104 to a settling tank 108 where the gel-like layer is allowed to settle down for an adequate time so that a first thick black gel-like layer comprising of the coal particles is separated from a second layer mostly greyish brown in color. The second layer is formed outside the first layer due to the presence of high ash mineral matter in the gel-like layer received from the conditioning tank 104. In an aspect, only two parameters which are varied during the gelation of coal particles are reagent dosage and pulp density of the coal slurry, whereas all other parameters are almost kept constant.
[0041] Once a clear-cut demarcation is obtained between both the first and second layers, then the aqueous suspension of the mineral matter is decanted or filtered slowly leaving behind the gel layer of coal. Both the first and second layers are then transferred to different trays, namely mineral matter tray 110 and clean coal tray 112, and subjected to filtration and drying.
[0042] Thus, the subject matter disclosed herein provides a method wherein phase-selective organogelators (PSOG) molecules which have the ability to selectively congeal organic molecules/particles from a biphasic mixture has been used. These PSOGs when added to a mixture/slurry of coal and water, they selectively attach themselves to the more hydrophobic coal particles leading to the formation of coal agglomerates, whereas on the other hand, the ash articles remain in the suspension. The aqueous suspension of the ash particles is decanted or filtered slowly leaving behind the gel layer of coal. Both the layers are then transferred to different trays and subjected to filtration and drying. The coal gel layer thus obtained is filtered and dried and weighed to calculate the yield after which ash analysis is done to determine product ash and thus separation of coal particles from ash particles take place easily and efficiently.
[0043] An exemplary adsorption of PSOG/gelator molecule on the surface of the coal analyzed through Fourier-transform infrared spectroscopy (FTIR) technique is shown in FIG. 2
[0044] FIG. 3 illustrates example method 300 for implementing coal gelation environment 100. The order in which the method 300 is described is not intended to be construed as a limitation, and any number of the described method blocks may be combined in any order to implement the method 300, or an alternative method. Furthermore, method 300 may be implemented by processing resource or computing device(s) through any suitable hardware, non-transitory machine-readable instructions, or combination thereof.
[0045] At block 302, the method includes mixing a feed coal with water in a conditioning tank to form a coal slurry.
[0046] At block 304, the method includes adding a reagent with the coal slurry in the conditioning tank. In an aspect, the reagent is a polymeric derivative of nitrogen-based compounds which acts as a phase-selective organo-gelators (PSOG) in the dosage of 0.5% to 1% of the weight of the feed coal.
[0047] At block 306, the method includes mixing the reagent with the coal slurry for a stipulated time in the conditioning tank.
[0048] At block 308, the method includes transferring the coal slurry into a settling tank for allowing the coal slurry to settle down so as to form two distinct layers: one gel-like thick mass with being comprised beneficiated clean coal and other suspended aqueous layer of high ash mineral matter.
[0049] Thus, with the implementation of the subject matter described herein, the present disclosure provides a process for the beneficiation of different varieties of coal to produce maximum recovery. This will help in the better utilization of different varieties of coal deposits such as low volatile coking coals, deep seam coal deposits, highly mineral matter disseminated coal deposits, oxidized coal, weathered coals, etc. In addition to this, the present disclosure provides an enhanced scope of beneficiation of the coal by-products which are generated during the coal washing process.
[0050] Currently, only a small fraction of these by-products, such as coal tailings, coal middlings, and rejects, are utilized in power production while most of them are discarded or left over. This is a big environmental concern due to problems like water pollution, soil pollution, air pollution, shortage of land by coal preparation plants, coal mine fires etc. in the nearby areas of coal mines and preparation plants. In view of these issues, the present disclosure carves the way forward for an appropriate use of these solid wastes generated in the coal preparation plants by providing a feasible beneficiation route at acceptable ash and yield. Finally, the present disclosure will help in conserving the limited and highly valued reserves of hydrophobic oil like diesel, kerosene, etc., for the future.
[0051] Further, those skilled in the art can appreciate that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.
[0052] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
[0053] While the foregoing describes various embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof. The scope of the present disclosure is determined by the claims that follow. The present disclosure is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
EXPERIMENTAL DATA
[0054] The following examples are provided to illustrate the present disclosure and are not meant to comprise a limitation thereto.
[0055] The two coal samples used in the present invention were obtained from a coal preparation plant during a normal working day. One sample is of low ash while the other is of high ash and designated as coal A & B in this work. Their proximate analysis & washability analysis are given in Table 1 & 2 respectively.

Table 1: Proximate analysis of the coal samples
Coal A Coal B
Moisture, % 1.43 1.52
Volatile matter, % 17.69 18
Fixed Carbon % 55.08 34
Ash % 25.8 46.4

Table 2: Washability analysis of the coal samples
Coal A Coal B
Sp. Gravity Cumulative
Ash % Cumulative
Wt. % Cumulative
Ash % Cumulative
Wt. %
-1.3 3.86 12.48 10.84 0.09
1.3-1.4 6.04 31.57 15.17 1.10
14.-1.5 9.73 50.28 27.61 10.05
1.5-1.6 11.03 60.25 31.29 41.93
1.6-1.7 12.20 65.33 34.54 63.36
1.7-1.8 13.47 70.46 36.48 72.47
1.8-1.9 14.27 73.77 37.97 78.82
1.9-2.0 14.95 76.93 40.47 84.79
+2.0 25.72 100.00 44.72 100.00

[0056] Among the surface property-based beneficiation methods of coal, oil gelling agent can bridge the coal particles into gel type aggregates for convenient recovery. The traditional oil solidifying agents have been studied widely in recent decades, such as the derivatives of polyvinyl alcohol, soybean protein, sorbitol, and chitosan. These reagents can very well work for oil recovery but not much for coal as coal is a solid material and less hydrophobic than oil. For good recovery of coal from mineral matter, strong selectivity of the reagent is required which cannot be possible with the naturally occurring materials. Some high amphiphile molecules with high charge density as well as a high hydrophobic character due to the presence of large no. of carbon atoms is a must. This is possible with the PSOGs which can create entangled 3D supramolecular networks through intermolecular self-assembly usually driven by the specific non-covalent interactions like hydrogen bonding, p-p stacking, electrostatic interaction, and van der Waals forces, etc. The entangled networks can entrap fine coal particles to realize effective gelation or immobilization. Because of the capability of PSOGs of gelating more hydrophobic particles preferentially over other hydrophilic particles in a given two-phase mixture derives their name as phase selective organogelators.
[0057] As per the dosages of PSOG and pulp density, a good number of experiments were performed using different combinations. The results for both the coals were encouraging & shown in Tables 3 & 4 respectively.
Table 3: Coal gelation results for sample Coal A.
S. No. PSOG (wt.% of feed) Pulp density (wt./wt.%) Feed ash% Product ash% Yield%
1 0.5 10 25.8 13.23 42.41
2 0.5 15 25.8 13.55 42.06
3 0.5 20 25.8 13.75 41.87
4 0.75 10 25.8 14.01 45.62
5 0.75 15 25.8 14.2 43.44
6 0.75 20 25.8 14.26 46.80
7 1.0 10 25.8 14.76 46.04
8 1.0 15 25.8 14.81 46.77
9 1.0 20 25.8 14.95 47.32

Table 4: Coal gelation results for sample Coal B.
S. No. PSOG (wt.% of feed) Pulp density (wt./wt.%) Feed ash% Product ash% Yield%
1 0.5 10 44.25 20.43 35.62
2 0.5 15 44.25 20.65 35.12
3 0.5 20 44.25 21.73 34.96
4 0.75 10 44.25 23.08 37.83
5 0.75 15 44.25 23.11 37.09
6 0.75 20 44.25 23.74 38.46
7 1.0 10 44.25 23.48 38.21
8 1.0 15 44.25 24.91 35.67
9 1.0 20 44.25 24.78 34.79

[0058] The analysis of the results shows that coal gelation is a better method of beneficiation for different types of coal irrespective of their nature and ash content. The highest yield obtainable for the low ash coal is more than 47% at a product ash of 14-15%. While the highest yield obtainable for high ash coal is more than 38% at a product ash of 23-24%.

WE CLAIM:

1. A method for beneficiation processing of coal, comprising:
mixing a feed coal with water in a conditioning tank (104) to form a coal slurry;
adding a reagent with the coal slurry in the conditioning tank (104), wherein the reagent is a polymeric derivative of nitrogen-based compounds which acts as a phase-selective organo-gelators (PSOG) in the dosage of 0.5% to 1% of the weight of the feed coal;
mixing the reagent with the coal slurry for a stipulated time in the conditioning tank (104); and
transferring the coal slurry into a settling tank (108) from the conditioning tank (104) for allowing the coal slurry to settle down so as to form two distinct layers: one gel-like thick mass layer with being comprised beneficiated clean coal and other suspended aqueous layer of high ash mineral matter.
2. The method as claimed in claim 1, wherein the mixing of the feed coal and the water is carried out at a ratio between the feed coal and the water ranging from 1:9 to 1:4 (by wt/wt).
3. The method as claimed in claim 1, wherein the polymeric derivative of the nitrogen-based compounds belongs to the class of the phase selective organo-gelators (PSOG).
4. The method as claimed in claim 1, wherein the stipulated time for mixing of the reagent with the coal slurry corresponds to the quantity of the feed coal.
5. The method as claimed in claim 1, comprising separating the two distinct layers through one of:
decanting off the aqueous layer of high ash mineral matter, or
filtering or screening off of the thick gel layer of the clean coal.