Title of Invention

"A POWER GRATE FOR PROCESS PLANT LIKE SHAFT KILN"

Abstract

A power grate for process plant like shaft kiln, which comprises a plurality of ellipsoidal shaped grate plates (4) of varying diameters having a central hole and circumferential teeth (5), characterised in that each of the said grate plates (4) being provided with atleast three dowel pins (3) and holes so as to engage and accept dowel pins of a corresponding grate plate, the said grate plates being removably fixed onto a base plate (1) having matching dowel pins (3) and a vertical central bolt (6,7,8), as to form a stepped ellipsoidal cone with inter-grate circumferential passages (24), the said stepped cone of grate plates being enclosed in a static stepped inverted conical frustum (16) and rotatably fixed by means such as groove (9) and key (13) onto a hub (2) mounted drive shaft (10) coupled (14) through a thrust bearing (11) to a conventional drive assembly (15), the static stepped frustum (16) being provided with a bottom cup (25) and material discharge means (26,27, 28) such as discharge cylinder (26), discharge funnel (27) and drive shaft stuffing box (28), the said static frustum (16) being provided for connecting to an air box (20, 23) of a kiln shell (22), the said base plate (1) being provided with an air cone (21) connected through an air duct (29) to the air header (19) of a conventional blower (18).

Full Text

The present invention relates to a power grate for process plant like shaft kiln. The power grate is a device for disintegrating and discharging process solid materials along with arrangements for distribution of process air in a process plant like the vertical shaft kiln for cement manufacture. In process plants wherein chemical transformation takes place with a counter current flow of air with pressure, there is likelihood of lump formation of process materials. In such conditions, the process equipment is required to meet three primary objectives. (a) Crushing of lumps to desired sizes (b) Better controlled discharge of process material (c) Efficient and optimum power transmission. Generally, the lump formation of process material is frequently observed in vertical shaft kiln and similar process equipments, but the output material needs to be crushed out for uniform discharge and further processing. In such process units the present invention of a power grate for process plant like shaft kiln will meet all these objectives efficiently. Hitherto known process equipment generally uses : (i) Reference may be made to Indian patent no. 150483. A rotary grate (a) ts shown in fig. 1a & 1b, of the drawings accompanying this specification. It is round, conical and stepped in shape fitted eccentrically in a cylindrical shell (b) held to a rotary shaft (c) with provision for air to be introduced into the process equipment through peripherial holes (d) provided circumferentially all along the matching grate plates. The disadvantages are : - The grate plates (a) as shown in fig. 1a & 1b of the drawings, are eccentrically mounted forming annular space all through out the cylindrical shell (b) placed outside. The assembly of this grate results in a circumferential single opening for discharge of material. The overhung load on the torque increasing device viz. reduction gear unit increases beyond the normal limit of the designed load. Moreover, the eccentricity of the grate causes uneven load on the costly torque increasing device (gear unit) beyond the designed limit. Again, due to single opening in the periphery, the downward movement of the bed of process material is not uniform and this is reflected in the top bed surface of the material with disturbances in the uniform counter current flow of air. For all these reasons it is difficult to design higher capacity vertical shaft kilns. (ii) Reference may be made to Indian patent no. 140502. A rotary grate (I) as shown in fig. 2 (a) & (b) of the drawings, comprising of a frame (II) held to a rotary shaft, a grate plate (I) supported on a said frame, the said grate plate having a plurality of holes (III) for discharge of clinker and introduction of air into the process equipment. Moreover, a plurality of cutting teeth (IV) are mounted on grate plate or the segments thereof, along with another crown provided eccentrically held to the center of the said grate plate extending upwardly towards an apex. The disadvantages are : It provides a flat rotary grate (I) as shown in fig. 2a & 2b of the drawings, having holes (III) and cutting edges (IV) which is not efficiently useful for all types of raw materials used for cement manufacture. It is because of clogging of holes (III) meant for both discharge of materials and air passage. Moreover, the cutting action of the grate as envisaged in the design does not seem to be operative as there is no distinct relative motion between the cutting edges of the grate and the lumps of process material. If there is no lump formation there will be no control of discharge of process material in this type of grate. The main objective of the present invention is to provide a power grate for process plant like shaft kiln which will avoid eccentricity and remove the drawbacks of sudden torque increase in the torque increasing device (reduction gear unit) and thereby prevent sudden damage of the torque increasing unit due to the increase in overhung load. Another objective of the present invention is to provide increased rate of discharge of process materials for the same number of revolutions. Still another objective of the present invention is to have a better grip for crushing of lumps of process material in the crushing zone. Yet another objective of the present invention is to provide higher capacity discharge with low torque requirement by which cost of the torque increasing unit (reduction gear) can be reduced. Another objective of the present invention is to provide process air inlet above the crushing zone for uniform distribution of air throughout the process equipment. The present invention of power grate basically comprises of elliptical shaped segmental plates housed co-centrically inside an inverted stepped frustum cone. Segmental plates contain number of circumferential passages effecting uniform distribution of process air at desired zones along with normal passage for air at the upper zone from header and air box. Novelty in this system is enabling design of higher capacity process plants like the vertical shaft kiln because of incorporation of elliptical segmental grate housed inside an inverted frustum of cone which effects plural openings for both disintegrated process materials and flow of counter-current process air inside the plant along with uniform material travel at the upstream unit. The plural opening effects larger discharge of process material along with maintenance of uniform bed level of materials at up-stream and also results in uniform distribution of process air inside the plant. In figures 3, 4 and 5 of the drawings accompanying the specification are shown the details of the power grade of the present invention : Fig. (3) shows the plan (3a) & elevation (3b) of grate assembly. The various parts are: 1. Base Plate 2. Hub 3. Dowel Pin 4. Grate Plate 5. Teeth 6. Central Bolt 7. Hexagonal Nut 8. Square Head 9. Groove 10. Drive Shaft 11. Thrust bearing 12. Broom 13. Key 21. Air Cone 24. Circumferential Passage 27. Discharge Funnel. Fig. (4) shows the elevation showing assembly. The various parts are : 1. Base Plate 2. Hub 3. Dowel Pin 4. Grate Plate 6. Central Bolt 7. Hexagonal Nut 8. Square Head 9. Groove 10. Drive Shaft 11. Thrust Bearing 12. Broom 13. Key 14. Coupling 15. Drive Assembly 16. Stepped Frustum 18. Blower 19. Air Header 20. Air Box 21. Air Cone 22. Kiln Shell 23. Holes for air in Air Box 24. Circumferential Passage 25. Bottom Cup 26. Discharge Cylinder 27. Discharge Funnel 28. Stuffing Box 29. Air Duct Fig. (5) shows the plan (5a) and elevation (5b) of grate and surrounding shell. The various parts are : 1. Base Plate 8. Square Head 21 .Air Cone 2. Hub 9. Groove 24. Circumferential Passage 3. Dowel Pin 10. Driving Shaft 25. Bottom Cup 4. Grate Plate 12.Broom 26. Discharge Cylinder 5. Teeth 13.Key 29.Air Duct 6. Central Bolt 16. Stepped Frustum 7. Hexagonal Nut 17. Annular Opening As illustrated in figure 3(b) the grate assembly comprises of a mild steel base plate (1) consisting of hub (2), three dowel pins (3) above which the casted grate plates (4) of elliptical shape having teeth (5) rest having holes for locating dowel pins (3). The whole assembly of the grate plate is secured to the base plate (1) through a carbon steel bolt (6), the square head (8) of which rest in the groove (9) of the base plate (1) and the grate plate (4). Each of the grate plates will have provision for dowel pins. The base plate with hub is provided with a set of brooms (12). The base plate with hub is connected with the driving shaft (10) through a set of key (13). As shown in figure 4, the driving end of the shaft is connected to coupling (14), through a thrust bearing (11) which is being supported on a suitable structure (not shown in figures). The coupling is connected to a drive assembly (15) consisting of reduction gear unit and a variable speed motor connected by a chain sprocket or belt drive system. The grate assembly is surrounded by an inverted conical stepped frustum (16) comprising of teeth made of steel. In figure 5, the plan shows the grate and the surrounding shell (22) showing two annular section openings (17) for discharge of material. Process air is provided through a system of blower (18), air duct (29), air header (19) to an air box (20) and to an air cone (21). The air box (20) is directly fitted through a flange to surrounding shell (22). The main process equipment is fitted above the air box (20) by a flange joint . The air box is provided with plurality of holes \ for the process equipment. The grate plates contain a number of circumferential passages (24) effecting uniform distribution of process air from air cone (21) along with normal passage for air at the upper zone from header (19) and air box (20). The air cone (21) is fixed on the bearing housing (11). A bottom cup (25) is joined through a flange to the bottom flange of the surrounding shell (22). Surrounding the bottom cup (25), there is a discharge cylinder (26) and a discharge funnel (27) all flanged together for discharge of the process material. In the bottom inclined plate of the discharge funnel (27), a stuffing box (28) is provided through which the rotating shaft (10) passes. Accordingly the present invention provides a power grate for process plant like shaft kiln, which comprises a plurality of ellipsoidal shaped grate plates (4) of varying diameters having a central hole and circumferential teeth (5), characterised in that each of the said grate plates (4) being provided with atleast three dowel pins (3) and holes so as to engage and accept dowel pins of a corresponding grate plate, the said grate plates being removably fixed onto a base plate (1) having matching dowel pins (3) and a vertical central bolt (6,7,8), as to form a stepped ellipsoidal cone with inter-grate circumferential passages (24), the said stepped cone of grate plates being enclosed in a static stepped inverted conical frustum (16) and rotatably fixed by means such as groove (9) and key (13) onto a hub (2) mounted drive shaft (10) coupled (14) through a thrust bearing (11) to a conventional drive assembly (15), the static stepped frustum (16) being provided with a bottom cup (25) and material discharge means (26,27, 28) such as discharge cylinder (26), discharge funnel (27) and drive shaft stuffing box (28), the said static frustum (16) being provided for connecting to an air box (20, 23) of a kiln shell (22), the said base plate (1) being provided with an air cone (21) connected through an air duct (29) to the air header (19) of a conventional blower (18). In an embodiment of the present invention the rotating grate assembly and static frustum provide annular discharge openings (17). In another embodiment of the present invention the grate assembly is located co-centrically with the driving shaft. In yet another embodiment of the present invention the ellipsoidal shaped grate plates used have a ratio of minor diameter to major diameter in the range of 1.015 to 1.035. In still another embodiment of the present invention the bottom of the base plate (1) is provided with brooms (12). In a further embodiment of the present invention process air is provided through a cylindrical air box, having plurality of holes, fixed through flange over the inverted conical frustum having teeth. The present invention provides a power grate for process equipment like shaft kiln which comprises of a stepped, conical, ellipsoidal shaped grate assembly surrounded by stepped inverted conical frustum having teeth. Each grate plate having circumferential teeth. The grate plates being positioned through dowel pins of the corresponding grate plates below or on the base plate. The grate plates are secured by a common bolt to the base plate. The base plate is provided with brooms. The said grate assembly rotates inside a surrounding inverted stepped conical shell provided with teeth to obtain relative motion between grate and shell for crushing and discharge of process material. The rotation with torque transmission being effected by a drive assembly comprising of a driving shaft secured to the base plate of grate assembly through a set of keys, thrust bearing and being coupled to an appropriate reduction gear unit and a prime mover through a chain sprocket or belt drive system. When the shaft rotates with grate assembly, the process material discharges through the double annular sectional opening obtained due to ellipsoidal section of the stepped conical grate along the horizontal axis. The ratio of minor diameter and the major diameter is variable and ranges from 1.015 to 1.035 depending upon the design capacity. The discharge of material is controlled by a bottom cup and brooms provided in the said grate assembly, finally passing through discharge cylinder and discharge chute, wherein the required process air is being fed from a blower to a header through air duct to an air box, having plurality of holes directly secured through flange joint over the surrounding shell of the grate assembly. The process equipment like shaft kiln can be directly secured over the top flange of the air box. The present invention provides stepped conical ellipsoidal grate assembly having teeth in each grate plate inside a surrounding stepped inverted conical frustum which will produce two annular sectional opening for discharge and better grip of lumps of process material for crushing. Where as in the previous eccentric stepped inverted cone grate plates, there is only one annular sectional opening resulting in lower discharge per revolution in comparison to an elliptical power grate of similar size, as in the present invention. Because of the eccentric rotation of the previous stepped inverted cone grate the crushing action takes place on one side across the plates and the surrounding shell, thereby generating uneven moments on the driving shaft thereby demanding larger torque for lesser discharge. In case of the present invention, the ellipsoidal grate assembly located co-centrically with the driving shaft creates two opposite crushing zones of progressive lapping area due to inverted frustum surrounding the grate unlike cylindrical shell in both the prior art Indian patent no. 150483 & 140502. By incorporating the above inventive features in the present invention it enables novelty of uniform reduced torque requirement, higher rate of discharge, better process air distribution and uniform flow of process materials on the upstream unit. In another embodiment of the present invention, the required process air is provided through a cylindrical air box having plurality of holes directly secured through flange over the stepped inverted conical frustum having teeth. The material after processing but before being discharged may contain lumps of assorted size that will enter the grate assembly zone above which the air box is continuously supply air uniformly all through out the periphery of the air box through plurality of holes into the process equipment. The assorted process material will be trapped between the grate plates and stepped inverted conical frustum and crushing action will start due to the relative motion and elliptical shape of the grate plates. The grate plate rotates at a uniform speed co-centrically with the driving shaft while the grate plates due to its elliptical shape gradually hold the material and crush the material due to change of axes from minor to major in two distinct areas for the rotation of the grate assembly. Due to reduction of sizes and gravity, the material will start flowing gradually downward while new assorted materials will take its place uniformly. This uniformity of flow of process material will clearly be reflected at the top bed of the process material in the process equipment. This will also enable uniform air distribution all through out the kiln due to uniform discharge. The discharge is regulated through a set of broom and bottom cup provided just below the grate assembly zone. The material will get discharged through the annular space of bottom cup to a discharge cylinder and discharge chute. The discharge rate can be controlled by controlling the rotational movement of the driving shaft which is connected to a variable speed motor through a reduction gear unit. Where as in the previous eccentric stepped inverted cone grate plates, there is only one annular sectional opening resulting in lower discharge per revolution in comparison to an elliptical power grate of similar size. Due to its eccentric rotation, the crushing action takes place on one side across the plates and the surrounding shell, thereby generating uneven moments on the driving shaft. In case of rotary grate, the grate plate has a plurality of holes for discharge of clinker and introduction of air into the process equipment. If there is no lump formation there will be no control of discharge of process material in this type of grate. Moreover, a plurality of cutting teeth are mounted on grate plate for size reduction of lumps of process material. In case of both the prior art, the grate plate has to carry whole load due to process material and hence moment on the shaft is greater resulting in larger torque requirement for lesser discharge. The present invention provides stepped conical ellipsoidal grate assembly located co-centrically with the driving shaft having teeth in each grate plate inside a surrounding stepped inverted conical frustum produces two opposite discharge openings and two opposite crushing zones as shown in fig.5, and shares the load due to process material by both the grate and surrounding shell. Due to two opposite crushing zones and sharing of load, moments occurring on the driving shaft are balanced and minimized. The follow example gives illustrative experimental results and data and should not be construed to limit the scope of the invention. Example 1 We have carried out experimental study after setting up the prototype of power grate in the vertical shaft kiln pilot plant. The following are the result of investigation : Investigation result (Table Removed) The above data obtained were uniformly consistent for adaptation in the scale up. The main advantages of the present invention are - (1) Total projected surface area of the grate plate is minimized and thereby the torque requirement is reduced. (2) By providing ellipsoidal section, two distinct crushing zones and two distinct discharge zones are obtained, thereby increasing the production rate. (3) The eccentricity of the grate plates is avoided. (4) Instead of cylindrical shell with ribs surrounding the grate assembly zone a stepped inverted conical frustum having teeth is provided which will give better gripping of lumps for the processed materials. (5) The surrounding stepped inverted conical frustum provides resistance to uncontrolled flow of materials due to gravity and at the same time support a part of the load column of process materials. (6) Air passages through grate assembly and the cylindrical air box having plurality of holes above the grate assembly zone ensures uniform air flow without clogging throughout the process equipment. (7) The present invention with ellipsoidal power grate with lesser surface area but double crushing and discharge zone along with surrounding stepped inverted conical frustum will enable design of higher capacity vertical shaft kiln or similar process equipments. We Claim: 1. A power grate for process plant like shaft kiln, which comprises a plurality of ellipsoidal shaped grate plates (4) of varying diameters having a central hole and circumferential teeth (5), characterised in that each of the said grate plates (4) being provided with atleast three dowel pins (3) and holes so as to engage and accept dowel pins of a corresponding grate plate, the said grate plates being removably fixed onto a base plate (1) having matching dowel pins (3) and a vertical central bolt (6,7,8), as to form a stepped ellipsoidal cone with inter-grate circumferential passages (24), the said stepped cone of grate plates being enclosed in a static stepped inverted conical frustum (16) and rotatably fixed by means such as groove (9) and key (13) onto a hub (2) mounted drive shaft (10) coupled (14) through a thrust bearing (11) to a conventional drive assembly (15), the static stepped frustum (16) being provided with a bottom cup (25) and material discharge means (26,27, 28) such as discharge cylinder (26), discharge funnel (27) and drive shaft stuffing box (28), the said static frustum (16) being provided for connecting to an air box (20, 23) of a kiln shell (22), the said base plate (1) being provided with an air cone (21) connected through an air duct (29) to the air header (19) of a conventional blower (18). 2. A power grate for process plant like shaft kiln as claimed in claim 1, wherein stepped, conical, ellipsoidal shaped power grate having teeth in each grate plate rotating inside a surrounding stepped inverted conical frustum provides two annular sectional discharge openings (17). 3. A power grate for process plant like shaft kiln as claimed in claim 1, wherein the ellipsoidal shaped grate is located co-centrically with the driving shaft. 4. A power grate for process plant like shaft kiln as claimed in claim 1, wherein the ellipsoidal shaped grate plates used have a ratio of minor diameter to major diameter in the range of 1.015 to 1.035. 5. A power grate for process plant like shaft kiln as claimed in claim 1, wherein the bottom of the base plate (1) is provided with brooms (12). 6. A power grate for process plant like shaft kiln as claimed in claim 1, wherein process air is provided through a cylindrical air box, having plurality of holes, fixed through flange over the stepped inverted conical frustum having teeth. 7. A power grate for process plant like shaft kiln substantially as herein described with reference to the example and figure 4 of the drawings accompanying this specification.

Documents:

404-DEL-2002-Abstract-(11-08-2008).pdf

404-del-2002-abstract.pdf

404-DEL-2002-Claims-(11-08-2008).pdf

404-DEL-2002-Claims-(28-08-2008).pdf

404-del-2002-claims.pdf

404-DEL-2002-Correspondence-Others-(11-08-2008).pdf

404-del-2002-correspondence-others.pdf

404-del-2002-correspondence-po.pdf

404-DEL-2002-Description (Complete)-(28-08-2008).pdf

404-del-2002-description (complete)-11-08-2008.pdf

404-del-2002-description (complete).pdf

404-del-2002-drawings.pdf

404-DEL-2002-Form-1-(28-08-2008).pdf

404-del-2002-form-1.pdf

404-DEL-2002-Form-18-(28-08-2008).pdf

404-del-2002-form-18.pdf

404-DEL-2002-Form-2-(11-08-2008).pdf

404-DEL-2002-Form-2-(28-08-2008).pdf

404-del-2002-form-2.pdf

404-DEL-2002-Form-3-(11-08-2008).pdf

404-del-2002-form-3.pdf