Claims:We claim:
1. A method for recovery of low ash coal from high ash coal, the method comprising:
grinding raw coal fines in a ball mill for grinding the coal particles to liberate an organic matter of coal particles from associated inorganic mineral matter and to generate new fresh surfaces of the coal particles;
simultaneously aadding alcohol to modify the surfaces of the coal particles through the process of esterification;
after the grinding and simultaneously mixing of alcohol, preparing a slurry in an agitator by adding water;
conditioning the slurry with collector to further improve the hydrophobicity of the coal particles;
adding the hydrophobic liquid to the slurry under condition of intense agitation to disperse hydrophobic liquid droplets which collide with the coal particles, so that the hydrophobic liquid droplets come up to the surface of the slurry carrying along with organic matter of the coal particles;
skimming off the organic matter using a scraper so as to collect the organic matter in a tray;
filtering, by a vaccum fitler, the collected organic matter which is clean coal to remove liquid; and
drying the filtered organic matter to obtain low ash coal.
2. The method as claimed in claim 1, wherein the grinding is performed from 150 to 300 seconds.
3. The method as claimed in claim 1, wherein the alcohol is ethanol.
4. The method as claimed in claim 1, wherein preparing a slurry in an agitator by adding water comprising agitating the agitator for 5 minutes at impeller speed of 1800 revolutions per minute (rpm).
5. The method as claimed in claim 1, wherein the collector is dodecane.
6. The method as claimed in claim 1, wherein conditioning the slurry with collector is carried out for 5 minutes.
7. The method as claimed in claim 1, wherien the light hydrophobic liquid is pentane.
8. The method as claimed in claim 1, wherein after adding a light hydrophobic liquid to the slurry, conditioning of the slurry is carried out for 5 minutes. , Description:TECHNICAL FIELD
[0001] The present disclosure relates to provide a method to recover low ash coal particles from high ash raw coal fines effectively.
BACKGROUND
[0002] Background description includes information that may be useful in understanding the present subject matter. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed subject matter, or that any publication specifically or implicitly referenced is prior art.
[0003] Raw coal fines are often subjected to beneficiation processes to remove excessive impurities before being sold to market. Generally, fines account for around 20?weight% of the raw coal feed in a typical hard coking coal processing plant in India (Mackinnon and Swanson, 2010) and up to 40?weight% of raw coal feed on a worldwide basis (Aplan and Arnold, 1991). At present, processes that might be considered (alone or in combination) for fine coal cleaning and for the recovery of organic matter from coal particles include: (a) Dense medium separation (b) froth flotation (c) selective flocculation and (d) liquid agglomeration. Among these four techniques froth flotation is widely used for fine size fractions (typically?<0.5?mm). However, froth flotation does not work very effectively for very fine (<~100 mesh) coal especially in the presence of clay slimes. Use of dense media cyclones is not very feasible because of inefficiency and difficulty in recovery of expensive magnetite used as the heavy media. Furthermore, efficient operation of dense medium cyclones requires precise control of the density of the heavy medium slurry. On the other hand, liquid agglomeration techniques appear to be quite promising in recovering the fine coal from waste streams and refuse ponds. Among the beneficiation methods,
[0004] One of the technique in removing inorganic impurities from coal fines is using oil agglomeration, which has received considerable amount of appreciation in the field of coal beneficiation. Removing inorganic impurities such as clay, sand, stone and minerals could be achieved based on the differences between the surface properties of organic and inorganic constituents of coal particles. Oil agglomeration is a complex process affected by many factors, such as the nature and amount of oil, nature of coal fines, residence time of mixture, intensity of agitation, pH of solution, and ionic strength of aqueous medium. In a typical oil agglomeration process, the addition of liquid, also known as collecting or bridging liquids, to the coal water slurry leads to the agglomeration of coal particles because of the capillary interfacial forces. For the liquid selected, the sample is not only required to be capable of effectively recovering the organic matter of coal particles in feed, but also simultaneously reject the inorganic mineral particles. In this way, the coal particles would adhere naturally to the oil droplet, leaving mineral particles in the water phase. The fine coal particles attach to each other through bridging oil droplets and form larger coal particles (can be from 2 to 5 mm) through the collision between the oil droplets.
OBJECTS OF THE DISCLOSURE
[0005] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed hereinbelow.
[0006] A general object of the present disclosure is to determine a method to recover low ash coal particles from high ash raw coal fines effectively. Low ash clean coal is the main purpose for the present disclosure. The parameters chosen for the present disclosure are liberation size, surface hydrophobicity, clean coal yield and ash of the clean coal.
[0007] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.
SUMMARY
[0008] This summary is provided to introduce concepts related to for recovery of low ash coal from high ash coal. 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.
[0009] The present disclosure relates to a method for recovery of low ash coal from high ash coal. The method includes grinding raw coal fines in a ball mill for grinding the coal particles to liberate an organic matter of coal particles from associated inorganic mineral matter and to generate new fresh surfaces of the coal particles; simultaneously aadding alcohol to modify the surfaces of the coal particles through the process of esterification; after the grinding and simultaneously mixing of alcohol, preparing a slurry in an agitator by adding water; conditioning the slurry with collector to further improve the hydrophobicity of the coal particles; adding the hydrophobic liquid to the slurry under condition of intense agitation to disperse hydrophobic liquid droplets which collide with the coal particles, so that the hydrophobic liquid droplets come up to the surface of the slurry carrying along with organic matter of the coal particles; skimming off the organic matter using a scraper so as to collect the organic matter in a tray; filtering, by a vaccum fitler, the collected organic matter which is clean coal to remove liquid; and drying the filtered organic matter to obtain low ash coal.
[0010] In an aspect, the grinding is performed from 150 to 300 seconds.
[0011] In an aspect, the alcohol is ethanol.
[0012] In an aspect, the preparing of a slurry in an agitator by adding water is performed by agitating the agitator for 5 minutes at impeller speed of 1800 revolutions per minute (rpm).
[0013] In an aspect, the collector is dodecane.
[0014] In an aspect, the conditioning of the slurry with collector is carried out for 5 minutes.
[0015] In an aspect, the light hydrophobic liquid is pentane.
[0016] In an aspect, after adding a light hydrophobic liquid to the slurry, the conditioning of the slurry is carried out for 5 minutes.
[0017] 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.
[0018] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.
[0019] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system and/or methods in accordance with embodiments of the present subject matter are now described, by way of example only, and with reference to the accompanying figures, in which:
[0021] FIG. 1 illustrates a method for recovery of low ash coal from high ash coal, in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION
[0022] In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.
[0023] While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.
[0024] The terms “comprises”, “comprising”, “includes” or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, device or method that includes a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or apparatus proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or method.
[0025] In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the disclosure may be practised. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.
[0026] Hereinafter, a description of an embodiment related to a method of recovery of low ash coal from high ash coal. In an aspect, raw coal fines are grinded to liberate an organic matter of coal particles from associated inorganic mineral matter and to generate new fresh particle surfaces of the coal particles. Simultaneously, alcohol is also added to modify the surface of the coal particles through the process of esterification. With same pre-treated raw fine coals, slurry is prepared by adding water followed by conditioning with a collector to further improve the hydrophobicity of the coal particles. Then, a light hydrophobic liquid is added to the slurry, in which the coal particles are suspended. In particular, the light hydrophobic liquid is added under condition of intense agitation to disperse liquid into small droplets, which collide with the fine particles. These light hydrophobic liquid droplets carry the captured organic matter of the coal particles which are hydrophobic, and bring it to the surface of the slurry. The organic matter reporting to the liquid phase are skimmed off by a scraper and collected in a tray. Then, the collected organic matter which is clean coal, was filtered and dried followed by weight and ash analysis.
[0027] FIG. 1 illustrates a method 100 of recovery of low ash coal from high ash coal, according to an embodiment of the present disclosure. The order in which the method 100 is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any appropriate order to carry out the method 100 or an alternative method. Additionally, individual blocks may be deleted from the method 100 without departing from the scope of the subject matter described herein.
[0028] At block 102, the method 100 includes grinding raw coal fines in a ball mill for grinding the coal particles to liberate an organic matter of coal particles from associated inorganic mineral matter and to generate new fresh surfaces of the coal particles. In an aspect, 250 grams of raw coal fines (-0.5 mm) is taken in a ball mill for grinding the coal particles to generate new fresh surfaces. Speed of the ball mill is maintained at 30 rpm. The particle size distribution analysis of raw coal fines indicates that 90% of the particles are passing 200 microns. From the microscopic analysis, it is found that 90% of the organic matter of coal particles will be liberated from the associated inorganic mineral impurities at a size of 75 microns. In order to liberate organic matter from coal particles grinding was carried out for different time period (T1, T2, T3). Table 1 shows the results of 90% particle size passing at different grinding time. Time T2 shows that 90% of the particles are below 72 microns which is favourable time to liberate minerals from coal particles.
Table 1
Grinding time (min) 90% passing size (microns)
T1 (0- 150 sec) 120
T2 (150-300 sec) 72
T3(300-450 sec) 70

[0029] At block 104, the method 100 includes simultaneously aadding alcohol to modify the surfaces of the coal particles through the process of esterification. In an aspect, contact angle of the raw coal fines is 37°. The alcohol of 15 ml is added simultaneously during grinding to modify the oxidised surface of the coal by the process of esterification. Around four different types of alcohols are used to improve the contact angle of the coal particles. From the Table 2, it can be seen that alcohol A3 shows the maximum improvement of contact angle.
Table 2
Grinding time (min) Alcohols Dosage (ml) Contact angle (degree)
T2 (150 – 300 sec) A1(Methanol) 15 45
A2(Propanol) 15 48
A3(Ethanol) 15 66
A4(Pentanol) 15 41
Note: Contact angle of Raw coal fines was 37 degree

[0030] At block 106, after the grinding and simultaneously mixing of alcohol, the method 100 includes preparing a slurry in an agitator by adding water. In particular, the same coal is taken in an agitator of 2.5 litre volume. 2000 ml of water is then added and agitated for 5 minutes at higher impeller speed of 1800 rpm to provide intense agitation and mixing.
[0031] At block 108, the method 100 includes conditioning the slurry with collector to further improve the hydrophobicity of the coal particles. The collector was added to further enhance the hydrophobicity of the coal particles. Four different types of collectors were used. Table 3 shows the contact angle of the coal particles after the treatment with different collector. Collector C4 shows maximum contact angle. The step of conditioning with collector was done for next 5 minutes.
Table 3
Grinding time (min) Alcohol Collector Dosage (ppm) Contact angle (degree)
T2 (150 – 300 sec) A3(Ethanol) C1(Kerosene) 100 79
C2(Diesel oil) 100 72
C3(Synthetic collector (Nalco)) 100 75
C4(Dodecane) 100 86

[0032] At block 110, the method 100 includes adding the hydrophobic liquid to the slurry under condition of intense agitation to disperse hydrophobic liquid droplets which collide with the coal particles, so that the hydrophobic liquid droplets come up to the surface of the slurry carrying along with organic matter of the coal particles. In particular, 200 ml of light hydrophobic liquid is added to the slurry, and conditioned for next 5 minutes. After that, the impeller speed is slowed down to 1000 rpm and kept constant for next 2 minutes, to allow the hydrophobic liquid to come up to the surface of the slurry carrying along with the hydrophobic coal particles. Following that, impeller speed is brought down to zero, and the slurry remain undisturbed for next one minute. The hydrophobic liquid phase is formed on the top of the slurry carrying hydrophobic low ash coal particles.
[0033] At block 112, the method 100 includes skimming off the organic matter using a scraper so as to collect the organic matter in a tray. In an aspect, the skimming off is performed manually.
[0034] At block 114, the method 100 includes filtering, by a vaccum fitler, the collected organic matter which is clean coal to remove liquid.
[0035] At block 116, the method 100 includes drying the filtered organic matter to obtain low ash coal. In particular, the fitler ornaic matter is dried in air oven followed by weight and ash analysis. Table 4 shows the yield-ash results with different light hydrophobic liquids. It can be seen that maximum yield (46%) with least ash (9.1%) is achieved using liquid O1.
Table 4
Grinding time (min) Alcohol Collector Hydrophobic liquid Hydrophobic liquid dosage (ml) Yield (%) Ash (%)
T2 (150 – 300 sec) A3(Ethanol) C4(Dodecane) O1(Pentane) 200 46 9.1
O2(Hexane) 200 42 10.2
O3 (Butanol) 200 35 10.1
O4(Heptane) 200 25 11
O5(Octane) 200 13 16.7

[0036] Accordingly, with the present disclosure, pre-treatment of coal particles followed by low ash particles from raw coal fines is conducted by varying different parameters such as grinding time, alcohols, collectors and light hydrophobic liquid. 150 to 300 seconds (T2) of grinding is observed to be sufficient to liberate the organic constituents of the coal particles. During grinding, alcohol is also added simultaneously to improve the contact angle of the coal particles. Out of the four tested alcohol, maximum improvement of contact angle is observed using ethanol (A3). The coal slurry is prepared with the same pre-treated coal. Four different types of collectors are used to further enhance the hydrophobicity of the particles. Dodecane (C4) is more effective in improving the contact angle of the particles. For separation of low ash particles from raw coal fines, light hydrophobic liquid was added. Out of the five liquid tested, pentane was found to produce maximum yield (46%) with least ash (9.1%).
Equivalents:
[0037] The specification has described a method of recovery of low ash coal form high ash coal. The illustrated steps are set out to explain the exemplary embodiments shown, and it should be anticipated that on-going technological development will change the manner in which particular functions are performed. These examples are presented herein for purposes of illustration, and not limitation. Further, the boundaries of the functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternative boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the disclosed embodiments. Also, the words "comprising," "having," "containing," and "including," and other similar forms are intended to be equivalent in meaning and be open-ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.
[0038] Finally, the language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based here on. Accordingly, the embodiments of the present invention are intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.