Claims:WE CLAIM:
1. A coal crusher (100) for enhanced maceral liberation, the coal crusher (100) comprising:
a base plate (12);
a roller cover assembly (2) mounted over the base plate (12);
a feeding hopper assembly (1) mounted on a top of the roller cover assembly (2);
a pair of rollers (6, 7) housed in the roller cover assembly (2) housing, each roller of the pair of rollers (6, 7) includes a grooved pattern (8), the pair of rollers (6, 7) having:
profile pitch (p): 50mm - 60mm,
depth of cut (d): 2mm- 5mm,
angle of cut: 82-87 degree; and
a driving mechanism for driving the pair of rollers (6, 7).
2. The coal crusher (100) as claimed in claim 1, wherein feeding to the feeder hopper assembly (1) controlled by deploying a standard vibratory crusher.
3. The coal crusher (100) as claimed in claim 1, wherein grooved pattern (8) enables the shear crushing of coal particles.
4. The coal crusher (100) as claimed in claim 1, wherein the driving mechanism is a geared motor (3).
5. The coal crusher (100) as claimed in claim 1, wherein shaft (9) each roller (6, 7) is coupled to the driving mechanism of the geared motor (3) via a synchronous pulley (6).
6. The coal crusher (100) as claimed in claim 1, wherein a gap between the pair of rollers (6, 7) is 0.5 mm.
7. The coal crusher (100) as claimed in claim 6, wherein the gap is achieved by adjusting screws (13).
8. The coal crusher (100) as claimed in claim 1, wherein the rollers (6, 7) are supported on springs (14).
9. The coal crusher (100) as claimed in claim 1, wherein the coal crusher (100) rests on the base plate (12) is supported by frame (17).
10. The coal crusher (100) as claimed in the preceding claims is housed in a crusher cover (16), the crusher cover (16) having a cut-off switch (18).
, Description:COAL CRUSHER FOR ENHANCED MACERAL LIBERATION
FIELD OF INVENTION
[001] The present invention relates generally to the roller crusher used for comminution of ores. More specifically, it relates to a specially designed roller crusher for enhanced maceral liberation of coal particles which improves the coking potential of coal.

BACKGROUND OF THE INVENTION

[002] For producing pig iron in blast furnaces, coke is utilized as a major fuel and reducing agent. The coke making process accounts for majority of the costs involved in a steel plant. Thus, driving various research activities for cost reduction either coal or process research. In coke making process, coal is being converted into coke which is highly porous strong structure with almost 90% of carbon. The coke making process can be written broadly into the following steps-
- Coal sourcing/ Coal beneficiation
- Coal blending
- Coal crushing
- Coal Charging in the oven
- Heating of coal mass in the absence of air
- Pushing and collection of coke
- Quenching the hot coke produced
- Transport to blast furnace for use

[003] Though, majorly the quality of coke depends upon the chemical structure of the coal. But, by improving different processing and operational variables the coking potential of coals can be enhanced. One variable considered in this art is crushing of the coal particles. Coals are organic detrital sedimentary rocks originating from a variety of plant material and different tissues along with dispersion of mineral matter. Embedded together the coal forms a highly heterogeneous structure. The structure of coal can be understood by dividing the same into three macerals (vitrinite, inertinite, liptinite) and ash/mineral constituents. The macerals compositions are the categories which can be underlined for understanding coking potential of coal. The vitrinite contributes majorly for defining the coking potential of a coal. But it’s just not the presence of the macerals that contribute in the coke making, the positioning or the way they are dispersed plays an important role in coke making.

[004] Vitrinite and exinite are viscoelastic solids. When force is applied to them, there are superimposed an elastic deformation, a temporary deformation with a gradual return to the initial state on release, and a permanent viscous deformation which can be considerable for vitrinites of medium rank if shattering of the particle can be avoided. During coke making, as the temperature rises the viscoelasticity of these macerals contributes towards the softening and thereby better coking. But the exposure of the vitrinites in normal conditions can be restricted due to either the tectonic movements or due to the industrial mining & crushing processes which shatters/breaks the particle in a random manner and the thereby results in the lower coking properties.

[005] To take best advantage of the property of vitrinites, application of stresses in the tangential parallel planes is important. The cutting nature or bodily shear forces when applied on to the particles opens up the particles along the maceral boundaries producing elongated vitrinites along with efficient breakage of inertinites. Present invention takes into account that slower deformation and strain rates when applied to the particles of the coal in tangential parallel planes can result in better reactivity of the coal during the coke making.

OBJECTIVE

[006] The prime objective of the present invention is to break the coal particles in a shear mode by application on surficial and bodily shear forces.

[007] Another object of the invention is to achieve particle size distribution for stable coal cake.

[008] Another object of the invention is to achieve enhanced liberation of the coal macerals.

[009] Another object of the invention is to improve the rheological characteristics of coal.

PRIOR ART

[0010] United States Patent US4168806 provides a roll crushing mill of the type having a frame with two rotatably disposed crushing rolls parallel and in opposition to one another forming therebetween a crusher gap are both deflectable relative to one another, each roll being mounted on a rotary shaft, each shaft being mounted on a carriage, and the carriages being swingably pivoted on the frame.

[0011] United States Patent US4382561 provides a vertical roller mill that includes a grinding table positioned for rotation around a vertical axis and two upright grinding rollers resting on their peripheral grinding surfaces on the grinding table for grinding material thereon. Each of the grinding rollers is rotatably mounted on a respective fixed horizontal shaft connected at one end to a common, central frame and at the other end to a draw bar. Preferably, the draw bar is regulated by a hydraulic cylinder secured in a bracket which is anchored in the mill foundation.

[0012] Chinese Patent reference CN2036065 provides - The utility model relates to a large coal breaking device which is special for a coal delivering system in an electric station. The utility model is designed for eliminating the coal blockage phenomenon of a grating grid. The roll type coal breaker can mechanize the coal breaking in the coal delivering system. Consequently, labor conditions of workers are improved, and labor strength is reduced. The utility model has the advantages of high production efficiency, safe operation, high reliability, reasonable structure, convenient installation. The utility model is composed of a frame, a protecting cover, a traveling mechanism and a breaking mechanism. The breaking mechanism comprises a breaking roll with a cutter head. The rolling, cutting and breaking of large coals are realized through the rotating of the breaking roll. The utility model runs safely and reliably through a machine-electricity double overload protection, and the roll type coal breaker has the advantages of reasonable structure, simple installation, etc.

[0013] Chinese Patent reference CN2642398 provides - A gear two-roll crusher arranged at entry of coal bunker in coal mine well can crush the coal on working surface, which is characterized in that: the crushing rolls comprises two horizontal shafts and multiple gear teeth arranged along axial direction of two shafts; the gear teeth with four-teeth structure comprises active buck-billed gear sleeves and ring gears; the gear sleeves are connected at their both ends and then fixed on the ring gear with bolts. The gear teeth are assembled with flat keys and horizontal shafts. Adjacent gear teeth are assembled with a deflection angle of 15 degrees along horizontal shaft circumference. Teeth tips of gear teeth on two horizontal shafts form two relative helical lines, which ensure mandatory feeding and discharging. Two shafts make relative rotation to crush materials with gear teeth. The utility model has compact structure and is suitable for the narrow and bad environment in coalmine well. The gear sleeves made of hard and wearing cast steel have duck-billed structures. The gear sleeves have high crushing capability and interchangeability. The gear sleeves can be exchanged at any time, which is convenient, economical and practical.

[0014] Japanese Patent reference JP2009142809 provides - PROBLEM TO BE SOLVED: To provide a roller type grinder capable of increasing a production amount of fine powder while performing a stable conventional operation with a large-sized machine when grinding adhesive substances such as limestone (CaCO3). SOLUTION: The roller type grinder is used for grinding raw material by performing relatively turnably operation in the circumferential direction with a plurality of grinding rollers 2 disposed at predetermined intervals around the center line and base members 1 continuously disposed in the circumferential direction around the center line for grinding the material between the plurality of rollers 2. In the grinder, the grinding rollers 2 are flat rollers with a smooth surface, and the base members 1 are grooved bases formed with slit grooves 6 in the crossing direction to the turning direction in the circumferential direction at predetermined pitches on an annular grinding surface grinding the material while biting it between the grinding rollers 2.

[0015] Chinese Patent reference CN205684106 provides - The utility model provides a cement clinker roll crusher, includes the frame, the frame includes left and right support of broken case and broken case, the crushing roller including roller and roller shell, has first, second and the broken tooth of third roller shell in the outer fringe of roller shell, have first, second tooth in small, broken bits in the broken tooth millet of roller shell and separate first, second and the third tooth's socket, the second is located first tooth in small, broken bits and the broken intertooth space of second roller shell with the first tooth's socket of the broken intertooth space of third roller shell, and the second tooth's socket is located first, second intertooth space in small, broken bits, and the third tooth's socket is located broken tooth of third roller shell and second intertooth space in small, broken bits, the first tooth's socket of the broken intertooth space of third and first roller shell is located broken tooth of third roller shell and first intertooth space in small, broken bits, and the second tooth's socket is located second tooth in small, broken bits and the broken intertooth space of first roller shell, and the third tooth's socket is located first, second intertooth space in small, broken bits, staggers in first, the second in the broken tooth millet of roller shell of adjacent roller shell and the position of third tooth's socket, the right -hand member splined connection of broken roller drive mechanism and roller. Crushing effect is good, stable in operation.

[0016] Chinese Patent reference CN206285976 provides - The utility model discloses a roll -type crusher roller includes cylindrical roller roller cylindrical surface is equipped with two along the axial, and the recess internal fixation has an easy abrasive brick with the upper groove, the hardness of easy abrasive brick material is less than the hardness of roller material so that easily wear and tear than the roller. The utility model discloses because the hardness of easy abrasive brick material is less than the hardness of roller material therefore easily weares and teares than the roller in the recess, in the course of the work, make in the recess surface of easy abrasive brick always be less than the surface of roller through wearing and tearing to make the roller always form crude surface, always keep the frictional force of needs, it is stand wear and tear, need often not change the roller like current roller breaker, improved the life of roller, production efficiency has also been improved to the while, has reduced the use maintenance cost. The utility model discloses simple structure, it is convenient to manufacture.

SUMMARY OF THE INVENTION

[0017] The present disclosure relates to a coal crusher (100) for enhanced maceral liberation, the coal crusher (100) includes a base plate (12); a roller cover assembly (2) mounted over the base plate (12); a feeding hopper assembly (1) mounted on a top of the roller cover assembly (2); a pair of rollers (6, 7) housed in the roller cover assembly (2) housing, each roller of the pair of rollers (6, 7) includes a grooved pattern (8), the pair of rollers (6, 7) having: profile pitch (p): 50mm - 60mm, depth of cut (d): 2mm- 5mm, angle of cut: 82-87 degree; and a driving mechanism for driving the pair of rollers (6, 7).

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0018] Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings of the exemplary embodiments and wherein:
Fig 1: Isometric elevation of the closed assembly of the crusher
Fig 2: Isometric view of the crusher with the outer cover opened
Fig 3: Front view of the crusher
Fig 4: Right side view of the crusher
Fig 5: Left side view of the crusher
Fig 6: Top view of the assembly
Fig 7: Bottom view of the assembly
Fig 8: Roller schematic
Fig 9: Roller assembly

[0019] The figure(s) depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

[0020] The present invention, now be described more specifically with reference to the following specification.

[0021] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures.

[0022] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.

[0023] When stress is applied to the particles the micro cracks gets activated as the stress waves propagate through the medium. The fracture of the particles is highly dependent on the force field and the duration of stress application. Present mills can be broadly classified as impact-attrition, compression-attrition, or attrition mills based on the forces. Highest strain rates are induced in the impact mills. These kinds of mills the momentum is transferred from the rotating media on to the particles. Mostly all the impact mills transfer their high inertia on to the particles to cause fracture. As a result, high stress values are applied on to a particle for a smaller residence time and the crack growth happens randomly through the media and non-uniform product is obtained depending on the parent particle. This kind of the behavior can be seen typically in mills which operate on impact phenomena; hammer mills, ball mills, rod mills, jet mills etc. Conventionally coke plant operations deploy hammer mills for coal processing due to low maintenance and stabilized operations.

[0024] Lowering the strain rates can result in controlled product size and better energy efficiency. In roller mills, the strain rates applied are of a magnitude less than those in the impact mills. When the stresses applied on to the particle are predominantly of compressive nature along with the rolling motion, can cause particle to break by a combination of compression and attrition. This mechanism is the most efficient method of particle breakage as the losses are less due to lower effective operating volumes. Mills present in the market are of roller types both horizontal roller mills and vertical roller mills. The mills generally deploy hydraulic or spring forces in order to press the particles and break under compression. The product obtained from these mills have good sphericity as compared to the impact mills due to the affective attrition component of the forces acting on the particles.

[0025] Toothed rolls can also be found in the prior art, these rolls have the capability of applying the load on the particles in a manner that both impact and compression forces are transferred. Some of these mills are able to produce the tangential parallel forces as discussed in the previous sections but the magnitude of the stress is very high which makes the nature of these mills as impact. Due to this nature these mills are deployed for large lump reductions and predominantly used in the primary crushing applications.
[0026] In terms of coke making the granulometry of the particles is of great importance, particularly in the case of stamp charged coke making. Stamp charged coke making uses the crushed coal and transforms the powder into a cake by application of energy. This is then fed into the coke ovens for processing. The particle size for coke making is also highly dependent on the heating rates that exist in the coke oven batteries. Generally, the sizes considered for the particles should be -3mm in size in order to match with the plastic layer thickness generated due to the heating rates. The size of the particles should not be very fine which will create an unstable cake and also non-participation in the coke making.

[0027] Impact mills like hammer mills can produce the particle size distributions but the nature of the forces shatters the reactive macerals. The impact mills like ball mills create very fine product. The compression mills can produce a controlled particle size distribution but the directionality of forces along with the magnitude again produces grain with higher sphericity and elongation of the reactive macerals is not observed.

[0028] Above mentioned constraints make the equipment selection for the coal crushing in terms of coke making tricky. These constraints considered along with better liberation of the coal particles leaves no choice for the machines which could produce both the particle size distribution and enhanced liberation by the principles stated in the background.

[0029] To overcome the problems associated with the prior art, a coal crusher 100 is provided. Fig. 1 illustrates an isometric elevation of a closed assembly of the coal crusher 100 in accordance with an embodiment of the present disclosure. In an embodiment, the coal crusher 100 includes the following components:

- 1: Feeding hopper assembly
- 2: Roller cover assembly
- 3: Geared Motor
- 4: Synchronous belt
- 5: Synchronous Pulley
- 6: Roller -1
- 7: Roller-2
- 8: Groove pattern
- 9: Roller Shaft
- 10: Housing assembly
- 11: Shaft Hub and bearing
- 12: Base plate
- 13: Adjusting Screws
- 14: Spring
- 15: Discharge chute
- 16: Crusher cover assembly
- 17: Base frame
- 18: Cut off safety switch

[0030] Fig. 2 illustrates an isometric view of the coal crusher 100 with outer cover opened. Fig. 3 illustrates front view of the coal crusher 100. Fig. 4 illustrates right side view of the coal crusher 100. Fig. 5 illustrates left side view of the coal crusher 100. Fig. 6 illustrates top view of the closed assembly of the coal crusher 100. Fig. 7 illustrates bottom view of the closed assembly of the coal crusher 100. Fig. 8 and Fig. 9 respectively illustrates a roller schematic and a roller assembly having 6: Roller -1, 7: Roller-2, 8: Groove pattern, and 9: Roller Shaft.

[0031] Referring collectively to Figs. 1-9, a working associated with the coal crusher 100 will now be described in the foregoing description. In the presented coal crusher 100, the material is fed from the hopper assembly 1 between the rollers 6,7. In an embodiment, the feeding needs to be controlled by deploying a standard vibratory crusher the discharge of which can feed the hopper assembly 1. In an example, the rollers 6,7 have special groove patterns 8 which enables the shear crushing of the particles. The rollers 6,7 are locked on to the periphery of the shaft 9. The shafts are 9 powered on one end by geared motors 3 via a synchronous belt 5 and pulley system 6 and are supported by the bearing hub 10. The rollers 6,7 are provided required speed for the crushing of the coal particles. The roller 6, 7 includes profile pitch (p): 50mm - 60mm, depth of cut (d): 2mm- 5mm, angle of cut: 82-87 degree.

[0032] Due to the rotation of the rollers 6,7 and the coefficient of friction of coal particles, the coal is drawn between the rollers 6,7. The particles are crushed by mechanisms as described in previous sections. Entire roller assembly is enclosed by cover assembly 2 for controlling the dust. The roller 7 is supported by two springs 14 for accounting the occasional hard mineral constituents and to provide necessary compression for drawing particles between the rollers 6,7. The gap between the rollers 6,7 can be adjusted by adjusting screws 13 provided on the left roller 7. The gap settings for the crushing are crucial and should be altered considering the groove profiles 8 of the crusher.

[0033] The complete assembly of the coal crusher 100 rests on a base plate 12 which is supported by frame 17. The height of the frame 17 can be altered depending upon the discharge conditions. After the processing of the coal between the rollers 6,7, the crushed coal particles will fall onto to collection through the discharge chute 15. The completer crusher assembly is then covered by sheet metal cover assembly 16 with cut-off safety switch 18. The cover assembly provides additional safety for dust prevention and accidental human intervention. During the maintenance, the cutoff switch 18 restricts the start off motors.

[0034] The coal crusher 100 of the presented invention addresses all the bottlenecks present in the state of the art. The coal crusher 100 can process coal not only for the particle granulometry but enhanced liberation of macerals. Clearly when compared to the impact mills, pressure mills, or slow deformation rate mills, the coal crusher 100 has an edge in terms of liberation. The rollers 6,7 of the coal crusher 100 can apply forces on the tangential parallel planes of the particles. The shear force applied onto the particle are of two types; tangential or surficial shear and bodily shear force.

[0035] Unlike other prior arts, the coal crusher 100 of present invention has special groove profiles 8 which cause fracture of the particles in a manner so that the liberation can be achieved. The combination of both types of shear forces enables to maintain the granulometry desired for coke making. Due to the enhanced liberation of the particles, inferior grade coals can be effectively utilized in the coke making application. The introduction of the inferior grade coal in the coal blend can reduce the coke cost.

[0036] The coal crusher 100 of the present invention tackles the problem of slow deformation rates for coal crushing with respect to coke making applications. By applying the forces on the coal particles in a specified magnitude and direction better liberation of macerals along with particle size reduction is obtained.

[0037] The coal crusher 100 has the ability to apply force in to the coal particles in a specified direction and appropriate magnitude for enhanced maceral liberation. The coal crusher 100 setup is equipped with double rollers 6,7 with special grove profiling 8. The groove profiles 8 on the roller 6,7 are machined and case hardened for longer operational life. The rollers 6,7 are powered by individual motors 3 for rotation in opposite directions. Speed reduction of the rollers 6,7 is achieved by variable frequency drive and pulley 6 system. The pulleys 6 power the shaft 9 mounted on to the bearings 11 with dust casing. The rollers 6,7 are locked on to the shafts 9 by key arrangement. Position of One of the rollers 6,7 is fixed and the other is loaded by spring for accommodating harder minerals if present in the coal.

[0038] As mentioned earlier, gap adjustment between the rollers 6,7 is possible by adjustment screw 13 provided on movable roller. Complete roller assembly 6,7 is enclosed in an enclosure for dust prevention. The novelty of the equipment lies with the types of profiles that are used for making grooves 8 on to the roller 6,7 surfaces. In an example, the groove 8 is a triangular step with appropriate gap in between, which facilitates the shear breakage of the particles and at the same time generates enough traction to draw the particles within the rollers 6,7. The combination of these led to work in the smaller product size domain required for stamp charged coke making. Unlike the prior arts, the coal crusher 100 of the presented invention does not apply high compressive forces on the particles but applies a shear force on to the particles.

[0039] In an example, the particles in the coal crusher 100 can break either in these three conditions - a) By getting arrested between the grooves 8 of both the rollers 6,7, b) By getting arrested between the groove 8 of one and inclined surface of the other roller 6,7, c) By getting arrested between smooth surfaces of the rollers 6,7.

[0040] When the particle is subjected to condition (a) above, the fracture will be along the tangential planes and resulting in the coarse breakage of the particle. Due to the application of the bodily shear force as described, the vitrinite gets elongated until fracture point, by this time the breakage of the inertinites is already completed as they are most friable maceral. Resulting particles have elongated grains of exposed vitrinite along with the small inertinite portions.

[0041] When the particle is subjected to condition (b) above, the fracture of the particle will be caused by a joint action of shear forces on the body and on the surface on the particle. The resultant particle will have less number of elongated grains as compared to case (a) but good balance of the particle size distribution as fines will be generated due to the surficial shear forces.

[0042] When the particle is subjected to condition (c) above, the fracture will be mostly from the periphery of the particle, this breaks the parent particle from the surface while inducing shear strain on to the large particle. A particle goes through different combinations of case (a), case (b) and case (c), resulting in a product which is primarily broken in shear mode.

[0043] It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims.