|Title of Invention
"A COUNTER-ROTATING ROTOR DEVICE FOR A COAL/MINERAL PULVERIZER"
|This invention relates to means for pulverizing coal or other mineralS by causing them to impact against rotating elaments which are specially contoured to maximize two objectives: 1) improved efficiency in pulverization of the material , particles at high production rateis; and 2) protection of the rotating elements themselves from wear by contact with the process material. The device is formed with counter-rotating rotors which are inverted with respect to each other. The rotors have specially contoured cl entente attached to their innar faces in concentric ring. The elements could be any one of four different embodiments or a combination of two or more different elements forming successive rings.
|TITLB OF THE IMVHNTIOH
BACKGROUND OP THE IHVETION
Coal pulverizers which prepare coal for firing boilers are needed to reduce coal to very fine grades with a substantial degree of reliability. It is important to produce coal which both burns efficiently and cleanly. Finer grades of coal are necessary to support boiler firing techniques which suppress nitrous oxide production. Finer coal burns more completely and produces less smog.
Various centrifugal type pulverizer machines operate on the concept of material being fed through an axial feed tube into the center of a high speed rotor with vanes that expel the coal or process material at high velocities. The material dissipates large amounts of enerqy on material banked walls or anvils causing size reduction. The Spokane Model 120 and the Bannac Ouopactor are in this class • However, none of these devices prevent wear of metal
partis due to uuLlifaiona of the materia.
Ways have been found to cause material to collide with itself, thus sparing wuar on metal parts. Santos, in U.S. Patent No. 4,366,929 describes a machine in which material is made to change direction rapic.ly and collide with other material. Weinert, in U.S. Patent No. 4,340,616, protects surfaces with a sufficient layer of material held by magnetic attraction.
Brown, et al in U.S. Patent No. 5,275/631 describes a coal pulverizer in the form of rotating ringa within which material banks up again*t the inside walls and then is thrown out against counter-rotating inverted rings which are self-protected in the
same way, combind with aerodynamic and electrostatic separators. The contents of U.S. Patent No. 5,275,631 are incorporated herein by reference thereto.
There are nany cage type mills which incorporate impacting members on counter-rotating rotors. Some of these depend on impacts of particles thrown between counter-rotating elements, with additive velocities at impact. Other.counter-rotating designs are aimed at producing interactive air movements for churning particles against one-another with little contact with wearable components. The latter group have been commercially successful only in limited throughput capacities up to 5 tons per hour. Their design principles have not scaled up efficiently, rotating at over 3000 RPM in order to move mostly air, which in turn moves particles.
The Nick:. U.S. Patent No. 5,009,371, issued in 1991, describes a disintegration chamber in which vortex zones of gas/solids mixture are formed within annular chambers defined by the front and rear edges of opposed blades. In some devices of this type as much as 60 percent of the reduction apparently takes place without the particles contacting the blades or impact members.
Earlier rotary disintegrators have depended solely on contact with rotary impact members. The Bint U.S. Patent No. 3,9497,144 is
of this type, using a particular configuration of rotor bars to impact particulate material. Hoe, as early as 1968, in U.S. Patent No. 3,411,724, describes a cage type disintegrator in which blades are angled 20 to 30 degrees and are "substantially concave" on the active surface in order to retain process material for wear resistance. Durek, in 1983, in U.S. Patent No. 4,406,409, describes a machine with four or more rows of concave scoops, angled at 20 tc 30 degrees for optimal impacting and particle retention* Hushoenborn, in 1985, describes angled impact elements with a "trailing profile of streamlined cross section" which is meant to eliminate "cavitation phenomena and hence reduces vortex formation and turbulences."
The use oil cage mills or other rotary disintegrators to produce the fine, superfine or ultrafine grades of pulverized coal, however, generally has not been done efficiently at the high production ratea required for feeding utility and large industrial boilers, that is 20 to 75 tons per hour. There is a need for a device which can both protect the metal parts from wear and can maximize efficient reduction of the process material at high rates to finer grades.
This invention relates to means for pulverizing coal or other minerals by causing them to impact against rotating elements which are specially contoured to maximize two objectives: 1) improved efficiency in pulverization of the material particles at high
production rates; and 2) protection of the rotating elements themselves from wear by contact with the process material.
The device is formed with counter-rotating rotors which are inverted with respect to each other. The rotors have specially contoured elements attached to their inner faces in concentric rings. The elements could be any one of four different embodiments or a combination of two or more different elements forming successive rings.
OBJECTS OF THE INVENTION
An object of this invention is to improve the technology of pulverizing coal and other minerals.
A further object of this invention is to provide more efficient means for pulverizing coal and other minerals to fine, superfine and ul.trafine grades.
Still another object of this invention is to produce a coal pulverizer which is economical to manufacture, reliable in operation and easy to maintain.
Yet a further object of this invention is provide for a coal pulverizer having counter-rotating elements •
To provide for counter rotating elements incorporating a variety of formis causing material to conically bank up against the rings is another object of this invention.
Still yet i\ further object of this invention is to provide for counter-rotating •l^m^nts which are contoured to both protect the elements from collision wear and to maximize collision efficiency.
d yet still another object of this invention is to provide for a coal pulverizing device which combines specially contoured elements and banned up elements in a. series of successive rings.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other attendant advantages and objects of this
invention Will become obvlus them the following dotailed description and accompanying drawings in which;
Fig. 1 is a plan view of specially contoured counter-rotating sets of elements, showing vector line seta which illustrate (A) particle trajectory paths and (B) radial vector lines along which centrifugal force acts;
Pig, 2 is a partial cross sectional view through the rotor set of Pig. 1, incorporating the novel features of this invention;
Fig. 3 is a side cross sectional view of a rotor set illustrating three forms of counter-rotating ring elements;
Fig. 4 is a top view of one embodiment inner rotor elements;
Fig. 5 is a cross sectional view of a second embodiment of the counter-rotating ring elements;
Fig. 6 is a cross sectional view of a third embodiment of the counter-rotating ring elements;
Fig. 7 is t. cross sectional view of a fourth embodiment of the counter-rotating ring elements; and
Fig. 8 is a perspective view of a pulverizer unit.
LED DESCRIPTION OF THE DRAWINGS
Now referring to Figs. 1 through 8 there are shown the preferred embodiments of the invention. Fig. 8 shows a typical coal pulverizer device having a center feed pipe 30 through which coal is fed to the pulverizer unit 10. Adjacent to the feed pipe 30 is a channel 40 for the influx of air, as seen in Figs. 2, 3 and 8. When exiting the feed pipe 30 the coal is fed into a pair of counter-rotating rotors 26 and 28. Generally these rotors 26 and 28 are cup shapisd and have diameters such that one cup 26 fits inside the other cup 28.
The rotors 26 and 28 are mounted facing each other and have their centers positioned on the same axis. The upper rotor is carried on the hollow shaft 38 which surrounds the central feed pipe 30. The hallow shaft is rotated by a motor 20. The lower rotor is mounted on a separate shaft 24 which is rotated by a separate motor 22. The separate motor control of these rotors provides for counter-rotation of the rotors with respect to each other.
The interior of the rotors is formed by attaching a series of elements to the rotor base plate. These elements can vary in size, shape and character for producing different results.
One embodiment of these rotor elements is shown in Fig. 2. Coal or other material is fed into the pulverizer through a center feed pipe 30. ??he coal lands on the spinning lower rotor 12. Some fine coal 13 banks up against ring 14, which assures that no coal will be thrown beneath the second circle of elements 17.
As shown in Fig. 4, sets of specially contoured elements 15 and 17 are arranged in concentric ring patterns causing the feed material to be centrifugally accelerated. The feed material which lands on lower rotor 12 is captured in the contour of elements 15. The material then slides off the first set of specially contoured elements 15, driven by centrifugal acceleration of the lower rotor 12.
Prior to departing from the rotational influence of elemental 15 the feed material is accelerated to the full rotational speed of the elements 15 and thereby the rotor. Therefore, the particles reach the maxim-am velocity of the rotor 12 before impacting on second set of specially contoured elements 17.
Elements 17 are mounted on the upper rotor 18 which is rotating in the opposite direction relative to the lower rotor 12. The resulting addition of opposite velocities provides the opportunity for highly destructive impacting of particles as they are thrown from elements 15 to elements 17.
Now referring to Fig. 1, to maximize the value of these destructive impacts, elements 17 are contoured along curvature X according to a curve generated by a continuous series of perpendiculars to the angles of incidence of particles thrown along the tangents of preceding ring of elements 15, Elements 15 by contrast are contoured along curvature V according to a curve generated by a continuous series of perpendiculars to tangents from the inside wall of the center feed pipe 30. Curve X of elementS 17 and curve V of elements 15 will be substantially the same.
Curvature X may also be offset in multiple places along tangent lines as shown in elements 17A, in order to provide a more shallow pocket for retained material.
Pulverized material is retained with centrifugal force in the pockets formed by curve X and curve Y in elements 17. The retained material provides a barrier against wear of element 17 in the impact zone of curve X. The extension of form at E on element 17 prolongs the wear life of element 17 along the line where curve x intersects curve z. On the opposite side of element 17, in the area of curve Y, the exposed portion of element 17 is protected from impacting particles by the proximate element 17.
Curve £ represents the ourved angle ef repooc of the partioles imposed centrifugally against element 17. It is generated by a continuous series of 60 degree angles to radii of the rotating system.
As shown i:i Fig. 4, successive circular sets of elements 19 and 20 are constructed to perform according to the same considerations, as are elements 15, though on a slightly reduced scale in the latter case.
The final rings in the pulverizer may be constructed in a variety of ferns. In the embodiment shown in Fig. 3, process material banks up in conical form against ring 21, providing abrasion surfaces for further reduction of oncoming particles as well as protection to the ring 21. Abrasive reduction of the process material is desired in these distal rings since fine
particles of coal are less easily reduced to still smaller sizes by impacting than a::e larger particles.
A* shown in Fig. 3, rings 21 and 22 also serve to change the flow pattern of in-process material: material passing from elements 15 to elements 17 to elements 19 to elements 21 is arrayed in a series of rotating vertical spray*. Ring 21 reduces the verticality, and ring 22 converts it completely to a horizontal spray.
The remaining series of distal rings may all be cone rings as similar to elements 21 and 22, that is they cause process material to be conically banked up against the ring for abrasive reduction. However, the ditital rings may be any of several alternative ring forms one of which is illustrated in Fig. 3.
In Fig. 3, process material thrown from ring 21 impacts on counter-rotatincj ring 22. Some of the process material bounces out of ring 22 prior to being re-accelerated in the opposite direction. Such material continues to be abraded through contact with the conically banked material on counter-rotating oone ring element 23.
The material impacted on counter-rotating cone ring element 23 is centrifugally accelerated up the slope of the cone, until it passes through a aeries of apertures in the wall of said ring, thereby being accelerated fully to the rim speed of said ring 23. The material thsn impacts on another ring element 24/ also of the cone ring variety, similar to rings 21 and 22, and so on, through multiple rings.
Fig. 5 illustrates another embodiment of ring form in which a series of notched N and bars B are arranged at intervals around the circumference of each ring and serving to accelerate process material tc full rim speed.
Fig. 6 illustrates yet another embodiment of ring form in which a series of notches N are arranged around the circumference of each ring to accelerate process material to full rim speed. Adjacent to the bottoms of said notches N, a ring K of steel or other hardened material is affixed. Said ring K serves to maintain evenness in the surface of the cone of banked-up material. In the absence of ring K a furrowing of the cone would result from banking of material to alternating rim heights between said notches N and unnotched circumferential segments between said notches. The resulting unevenness represents discontinuity in the effective abrading surfaces.
In Fig. 7, platforms P provide base surfaces for cones of banked-up proceus material. Said platforms P permit close proximity and interposing of successive rings while providing space for locating holes G on upper rotor disc U and lower rotor disc L. These holes G permit movement of gases between the interior and exterior of the rotor set.
Exiting the rotating system in a horizontal spray finely reduced particles may be either directly inserted into a rising air flow for transport or imparting against a surrounding series of impact blocks 41 as shown in Fig. 8.
A counter-rotating rotor debvic for a coal/mineral pulverizer,
a center feed pipe;
an upper rotor having a bottom surface;
a first rotation means for rotating said upper rotor connected to a
a lower rotor having a top surface, said lower rotor facing said
upper rotor and rotating in an opposite direction relative to said
a second rotation means for rotating said lower rotor connected to
a first plurality of irregularly shaped elements which are contoured
with a curvature defined by a continuous series of perpendiculars
of dimensions approaching zero said perpendiculars relative to
tangents from an inside wall of said feed pipe and for retention of a
material barrier when said material is centrifugally accelerated;
wherein said elements outwardly extend from said top surface of
said lower rotor; and
a second plurality of irregularly shaped contoued elements • contoured each increment of said contour being defined by a series of perpendiculars to the line of impact of particles that exit an immediately preceding plurality of irregularly shaped members wherein the impact of said particles is maximized and further curved for retention of process material.wherein said elements outwardly extend from either said bottom surface of said upper rotor or said top surface of said lower rotor.
2. A counter rotating rotor debvic for a coal /mineral pulverizer as claimed in claim 1, wherein said upper and lower rotors have coincidental centerpoints and both said first and second pluralities of irregularity shaped elements are symmetrically and equidistantly spaced relative to said centerpoints of said upper and lower rotors.
3. A counter rotating debvic for a coal/ mineral pulverizer as claimed in claim 2, having multiple radial rings of elements similar to said second plurality of irregularly shaped elements, spatially outwardly mounted on said top surface of said lower rotor wherein a portion of said radial rings are mounted to said bottom surface of said upper rotor and radially alternate with a portion of said multiple radial rings mounted on said top surface of said lower rotor.
4. A counter rotating debvic for a coal /mineral pulverizer as claimed in claim 3, having a plurality of outer rings mounted at one end to said upper rotor or said lower rotor and having an outer unmounted rim, said outer rings radially alternating between upper and lower rotors.
5. A counter rotating rotor debvic for a coal/mineral pulverizer as
claimed in claim 4, wherein said outer rings has an annular
inner ring affixed near said outer unmounted rim of said outer ring, such that processed material is held within said ring in a conical pattern due to centrifugal acceleration wherein said outer unmounted rim of said outer rings is notched, a surface of said notch being continuous with said annular ring, said continuous surface being perpendicular with said axis of rotation.
6. A counter rotating rotor debvic for a coal/ mineral pulverizer as claimed in claim 4, having a plurality of bars affixed at intervals to said outer rings and wherein said outer rings are notched on said outer unmounted rim immediately adjacent to each of said plurality of bars such that a surface of said bars is continuous with a surface of said notch and said continuous surface is parallel to said axis of rotation.
7. A counter rotating rotor debvic for a coal /mineral pulverizer as claimed in claim 4, having a platform extending radially inward from said outer rings, said platform being located near the mounting edge of said outer rim and wherein said upper and lower rotors have small orifices located at intervals for venting of gases.
8. A counter rotating rotor debvic for a coal/mineral pulverizer as claimed in any one of claims 5, 6 or 7, having an axial material feed tube having a feeder end, for introducing material and air in between said upper and lower rotors, said feeder end being rotatably connected within a bore in the center of said upper rotor.
9. A counter-rotating rotor debvic for a coal/mineral pulverizer as defined in claim 1, comprising an upper rotor having a bottom surface;
a first rotation means for rotating said upper rotor connected to a pulverizer;
a lower rotor having a top surface, said lower rotor facing said upper rotor and rotating in an opposite direction relative to said upper rotor;
a second rotation means for rotating said lower rotor connected to said pulverizer;
a first plurality of concentric rings mounted at one end to said
bottom surface of said upper rotor and having an unmounted
a second plurality of concentric rings mounted at one end to said
top surface of said lower rotor and having an unmounted outer
wherein said first and second pluralities of concentric rings are
radially alternating and positioned in a spaced apart relationship
relative to each other such that material is retained against said
rings in a conical pattern due to centrifugal acceleration.
10. A counter-rotating .debvic a coal/mineral pulverizer as claimed in claim 9 comprising an annular inner ring affixed to an inner surface of said concentric rings near said unmounted outer rim and wherein said unmounted outer rim of said first and second plurality of concentric rings is notched, said notch being perpendicular to said annular inner ring.
. 11. A counter-rotating debvic for a coal/mineral pulverizer as claimed
in claim 9 comprising a plurality of bars affixed at intervals to said concentric rings and wherein said unmounted outer rim of said concentric rings is notched adjacent to said plurality of bars such that a surface of said bars is continuous with a surface of said notches.
12. A counter-rotating debvic or a coal/mineral pulverizer as claimed in claim 9 comprising a platform attached to an inner surface of said concentric rings near said mounted end of said concentric rings and said upper and lower rotor having orifices located at intervals for venting of gases.
13. A counter-rotating rotor debvic for a coal/ mineral pulverizer substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.
|Indian Patent Application Number
|PG Journal Number
|Date of Filing
|Name of Patentee
|DAVID KEPLER BROWN
|11232 MIDLOTHIAN TNPK., BOX 141, RICHMOND, VIRGINIA 23235, UNITED STATE OF AMERICA.
|PCT International Classification Number
|PCT International Application Number
|PCT International Filing date