US2859957A - Sintering apparatus - Google Patents

Description

Nov. 11, 1958 o. ROLFSEN ETAL 2,859,957

.SINTERING APPARATUS Filed Oct. 4. 1955 2 Sheets-Sheer. 1'

Nov. 11, 1958 o. ROLFSEN ETAL 2,859,957

SINTERING APPARATUS Filed Oct. 4. 1955 I 2 Sheets-Sheet 2 u M w SlNTERlNG APPARATUS Ole Rolt'sen, Uslo, and Per Rolfsen, Rjukan, Norway Application October 4, 1955, Serial No. 538,472

Claims priority, application Sweden Dctober 13, 1954 12 Claims. (Cl. 266-21) The present invention relates to a water-cooled draught sintering apparatus of the conical type. Such sintering apparatus are disclosed in U. S. Patents 2,193,698 and 2,493,421. They comprise a grate rotating about an inclined axis and concentric therewith and having watercooled grate bars which interconnect water chambers rotating therewith and extending along the lower and upper edges, respectively, of the grate for supplying and discharging cooling water for the bars. In such apparatus the charging takes place in a position where the grate surface is largely horizontal, whereas the discharge of finished material takes place within a range where the grate surface is approximately vertical, and a circulation of cooling water through the individual grate bars is ensured by a thermo-syphon ettect, the bars having an ascending inclination from the inlet end to the outlet end with increasing steepness during the course of the process, and the water chambers at the lower and upper ends thereof having in known embodiments the form of complete annular passages and care being taken by means of suitable valve arrangements that the cooling water is constantly discharged from the top of the'outlct cham her only, so that the water flow in the grate system will in all places have an ascending course and therefore no pockets are formed in which air and steam bubbles might collect.

Due to the combined thermal, mechanical and chemical stresses on the grate bars apparatus or": this kind may, however, in many cases require rather frequent replacement of individual grate bars. This may occasion a relatively long interruption of the operation, especially because in order to provide a reliable seal the bars should not be mounted for individual replacement but should be welded to the walls of the water chambers. It is therefore desirable according to the present invention to effect an exchange of grate sections, so that when re quired, a section of the outer and inner chamber together with the appurtenant bars may be removed and a new similar section inserted, so that the apparatus may again be made ready for operation within a much shorter time than required for repairing the defective sec tion. However, here a difiiculty is encountered in that it is practically impossible to obtain a satisfactory permanent seal by using continuous annular conduits, due to the fact that the conduit sections and the grate bars are subjected to highly varying temperatures with consequent dissimilar expansion stresses. According to the present invention this difilculty is overcome by the fact that the water chambers are divided into hollow ring segments, each of which is closed at both ends and has an individual inlet and outlet, and which together with the appurtenant grate bars form separately detachable grate sections.

In order to minimize and often completely avoid formation of steam bubbles which might disturb the circulation in the hollow ring segments on the outlet side, these ringsegments are conveniently provided with outlets adjacent both ends thereof so that the water may flow rates Patent ice out by thermosyphon effect, irrespective of which end is highest at the moment.

In order, further, to avoid collection of steam in outlet conduits rotating with the grate and extending from the outlet ring segments to an outlet valve or the like, without having to use long conduits with a continuously ascending course, these segments may be connected to a ring conduit concentric to the axis of rotation of the grate and rotating with the same, which conduit is connected through further conduits to a valve device which constantly provides discharge substantially from the uppermost point of the ring conduit. The ring conduit is conveniently made polygonal with the connection conduits extending from the corners so that collection of steam in the ring conduit itself is avoided.

The use of hollow, closed ring segments may according to the invention be further utilized for reducing the expansion stresses. For this purpose the hollow ring segments may be mounted with a certain mutual clearance which permits expansion in the circumferential direction. Further the outer hollow ring segments may be supported in such a manner that they are capable of moving outwards independently of each other to a certain extent, so that they can yield to expansion of the grate bars.

A rotating frame-work structure may conveniently be used as a mounting structure for supporting the exchangeable grate sections. If the suction chambers below the grate are exchangeable, which may often he demanded, for example when dealing with gases having a corrosive or other detrimental effect on the walls of the chambers, the frame-work structure may conveniently include bars which extend under the grate and in parallel relation thereto and which support the suction chambers and carry dividing walls extending upwards to the bottom side of the grate so as effectively to separate the suction chambers. When using this embodiment the supporting structure may easily be spared from direct contact with the hot gases. Removal of the chambers may conveniently be effected in the upward direction on removal of the overlying grate sections.

Gas ducts rotating with the grate may conveniently be passed from the suction chambers in a straight line directly to a fixed suction head, into which they open under an obtuse angle. Hereby the least possible change of direction of hot gas currents of high velocity will result, whereby the separation of dust is reduced and tube bends subjected to heavy wear from hot entrained particles are avoided. Besides, an arrangement of the gas ducts as described above will involve a small overall height, the more as a combined distributor and valve device may easily be placed centrally behind the suction head. The object of this valve device is to control the supply and outlet of cooling water.

Further details of the invention will appear from the following specification in connection with the accom panying drawings, which illustrate a particularly convenient embodiment.

Fig. 1 shows the apparatus in vertical longitudinal section.

Fig. 2 shows a quadrant of the apparatus, comprising four sectors, A, B, C and D with various parts removed from one sector to the next and viewed in the direction of the axis and in section along the line II--II in Fig. 1.

Fig. 3 shows a rotating valve head in section along the line Ill-III in Fig. 1.

In the embodiment shown the rotating part of the. apparatus includes a carrying structure. having a central stem. The latter comprises a central tube'll, which by plates 2 and 3 is connectedto supporting rings 4 and 5 respectively for channel iron supporting rings at the: top and at the bottom. Truss structures radiate from the stem in axial planes. Each of these comprises a radially extending bottom boom 6, a likewise radially extending top boom 7, to tie boom 8 extending along a generatrix of a cone with upwardly facing apex and an apex angle of 90 and coaxial to the tube 1, and finally pressure bars 9 and 10, joining at the connection point between the booms 7 and 8 and connecting the latter with the bottom boom 6 and extending at a right angle to the tie boom 8 and parallel to the stem axis respectively. In alignment with the bar 10 a ring 11 is attached to the bottom side of the boom 6. This ring is composed of section irons and carries an annular running rail 12, supported axially and radially on running rollers 13 and 14 respectively in such position that the stem forms an angle of 45 with the vertical direction. Fixed to the bottom side of the bottom booms 6 at the outer extremities thereof is a channel section ring 15 which may carry a toothed rim, a chain or a similar machine element, not shown, for driving the apparatus at the periphery.

The axially extending truss planes subdivided the rotating part of the apparatus into sectors, four of which are assumed to be included in each quadrant according to Fig. 2, so that the total number of sectors will be sixteen. On top of the ring 4 an annular row of suction sockets 16 is mounted, one for each sector. These extend along generatrixes of a cone coaxial with the stem and having an upwardly facing apex and an apex angle of 90 and terminate at their inner ends on a cylindrical surface coaxial with the axis of rotation. Inside the row a stationary suction head including a carrying ring 17 is provided, which by means of a sliding bearing 18 is supported on a flange on the socket row and in turn carries a cone 19 flush with the bottom side of the sockets. Axial ribs 20 connect the ring 17 rigidly with an upper ring 21, which by means of a sliding bearing 22 is supported on the top of the socket row. A suction duct 23 for outgoing gases is connected to the ring 21. At the ring 21 the suction head may be withheld against rotation by means of suitable straps or the like. These may at the same time serve to afford an adequate lateral support of the suction head with the outgoing gas duct, or a balancing with a counterweight may be used for this purpose.

The booms 6 and 7 carry annular supporting members 24 and 25 respectively for the grate. These have substantially Y-shaped cross-section and support the grate bars 26, 27 at a distance above the tie booms S. The bars 26 and 27 extend alternately along two cones having a common base circle along the outer ends of the bars, buthaving slightly different apex angles so that the bars will allow the aspirated air and combustion gases to pass between them throughout their length without the bars spreading too much at their outer extremities. On top of the bars the grate is flanked externally and internally by refractory lining plates 28 and 29 respectively, for example of cast iron, in the illustrated embodiment three such plates being provided in each sector. The linings are carried by ring segments 36 and 31 respectively of section iron, each of which extends over one sector and which are joined for example by bolts and flanges so as to form annular supporting rims. The outer supporting segments 30 are mounted on a plate 32, fixed on top of the bottom boom 6, whereas the segments 31 are carried by the channel iron ring 33 on top of the bottom boom 7. The bars 26 and 27 are composed of water-cooled tubes of suflicient diameter for withstanding the chemical and mechanical loads occurring during the sintering process. Outside the bottom edges of the linings 28 and 29 the bars are extended at both extremities in the form of thinner tubes 34, 35 and 36, 37, connected to an inner water chamber 38 and an outer water chamber 39, respectively. Thechambers 38 are located in a space confined between the support 25, the channel iron ring 33 and the supporting segment 31, whereas the chambers 39 are located in a space confined by the support 24, the plate 32 and the supporting segments 30. The chambers 38 and 39 are formed by cases in the form of hollow ring segments and closed at both ends, and both in the outer and in the inner row of water chambers one segment is provided in each sector. In each of the sectors the chamber 33 and the chamber 39 together with the appurtenant grate bars form a tight welded unit. The cases forming the chambers in each row have a slight tangential distance from each other so as to permit expansion.

For the supply and discharge of cooling water, in the lower part of the apparatus a stationary cylindrical valve housing 40 is provided, which is located coaxially with respect to the rotating unit and which by means of a dividing wall 41 is subdivided into two spaces, which are connected to a supply conduit 42 and a discharge conduit 43 respectively. Throughout the major part of the valve housing the dividing wall 41 extends diametrically'therein, but at the top it extends to the cylindrical wall on the outlet side and here the valve housing terminates in a connecting socket 44, which with a sliding seal forms a connection between the supply chamber and a rotating distributing chamber 45, from which connecting conduits 46 extend for feeding the individual outer water chambers 39. At the outer ends the conduits 46 are continued by thinner conduits 47, which to a certain extent are flexible and which are passed in a bend outside the plate 32. Each conduit 46 is provided with a flange connection 48 inserted therein, and its end portion which extends in parallel relation to the grate is connected to a socket 49 on the case 39. The conduit is here passed through the supporting segment 30 in sealed relation within a wide stuffing box 50. Adjacent each end of each of the water chambers 38 on the outlet side of the grate a pipe socket 51 parallel to the axis is passed from the water chamber through the appurtenant supporting segment 31 by means of a stuffing box 52 which at the same time forms a connection to a corresponding socket 53 on a conduit 54, which extends in a closed ring around the whole apparatus in the form of a polygon, the corners of which are located at the sector borders. From each corner of the polygon a conduit 55 extends to a valve housing 56, which forms a sliding seal with the outer face of the housing 4t). By means of walls 57 extending in axial planes between the outlet openings of the conduit 55 the valve housing 56 is divided into an annular row of chambers. The housing 40 has on the upwardly facing side of the cylindrical surface an axially extending slot 58, through which the outlet chamber thereof is connected successively to the chambers of the surrounding rotating row, and is thus constantly at any moment connected to the uppermost point of the annular conduit 54.

It may be convenient to make the cooling water circulate in an entirely closed system for reducing the risk of corrosion.

of the grate bars so that the various suction chambers are effectively separated from each other. By means of stuffing boxes 65 at their inner ends each of the suction boxes 60 is connected to a tube socket 66. Each of these sockets is placed in alignment with one of the sockets 16 and connected thereto at its inner end. They may conveniently have a cross-section varying smoothly from circular to rectangular shape. In front of the inlet to each of the sockets 66 a gate is mounted which consists of a supporting ring 67 having a pivoted closing flap 68, which by means of a suitable mechanism not shown in the drawings, can be manipulated so that it remains closed throughout the unloaded portion of the grate at the start of the process and is thereafter opened gradually. They may also, if desired, be used for controlling the air flow in operation.

Across an opening 69 in the outer wall immediately above the bottom of each box, an external flap valve 70 is mounted in such a manner that it is normally held in a closed position by means of a spring 71, but is opened by the action of a stationary cone, indicated diagrammatically at 72, in the substantially vertical position of the grate or shortly after this position. Thereby ashes and other solids will automatically be discharged from the suction box.

In operation the whole frame-work with grate and suction boxes rotates in the direction of the arrows shown in the drawings, while the grate is continuously charged in front of an ignition device not shown in the drawing. The charging takes place when the grate is substantially in a horizontal position, and removal of sintered matter takes place when the grate is in a substantially vertical position, preferably so that the grate is covered somewhat more than 180. Suction is maintained through the duct 23, so that an air current will flow continuously downwards through the grate for maintaining the combustion. If desired, the suction head above the cone 19 as well as the suction conduit 23 may be provided with radial dividing walls so as to form a plurality of passages, whereby it will be possible while omitting the flaps 68, if desired, to adjust the air current through the various portions of the grate differently and in particular to shut off the air current through the uncovered portion, and/or to collect outgoing gases of different temperatures and/ or compositions from different stages of the process. At the same time the grate is supplied with cooling water, under pressure if desired, from the supply conduit 42 through the distributing chamber 45, and the water flows through the grate bars in parallel-connected upward currents straight to the annular conduit 54, in which the water, while still flowing upwards, continues to the uppermost point of this conduit, which point has an outlet connection through the valve housing 56 to the discharge conduit 43. Therefore, during each revolution every portion of the grate will perform a temperature cycle on its way from the charging point to the removal point, conveniently so that the combustion zone successively approaches the grate, thereby causing an increase of the temperature thereof, whereafter the aspired air current after the combustion process has approximately been terminated will cool the material as well as the grate on the last part of the path to the point of removal. Due to the heating of the grate a natural circulation occurs in the individual constantly upwardly sloping grate bars, and this effect is increasing during the operating cycle due to the increasing steepness of the bars. With an embodiment like that shown in the drawings an interruption of the circulation consequent to local formation of steam cannot occur, since the water flow both in the interior of the grate bars and in the conduits leading therefrom, is constantly passing upwards through the conduit portions 34, 36 and through the respective hollow ring segments 38-to the end which is uppermost at the moment, and therefrom further through the annular conduit 54 to the uppermost point of the latter, where the entire water current is joined anew, thereby entraining any steam bubbles which might occur. This effect will be ensured even if due to some disturbance in operation the rotation should cease so that the final burning of the material must be effected in a stationary condition of the grate.

Since due to the flexibility of the pipe portion 47 and its course through the stufling box 50 the individual outer water chamber sections 39 have a certain mobility outwards and inwards in the supporting segments 3% independently of each other, the grate is to a great extent spared for mechanical stress caused by elongation and shortening of the bars during heating and cooling, which Since the gas ducts 66, 16 from the suction boxes 60 I extend in straight lines to the suction head 1921, and the gas currents are here deflected at an obtuse angle only on their way to the gas outlet duct 23, the conveying system is spared to a high degree as it is not likely to be subjected to excessive tear from hot suspended particles in pipe bends. Besides, as mentioned above, the solids collected in the box 60 will be discharged through the valve 70 each time the treatment of the overlying material has been finished.

Further, the embodiment shown, in which the connecting conduits from the annular conduits 54 of the water system on the outlet side of the grate are passed between gas outlet conduits 66 of the individual sections to a centrally positioned outlet valve behind the gas outlet, permits the apparatus to be made extremely low in height.

If now a grate section is to be replaced, the flange connection 48 in the supply conduit concerned is disconnected, and likewise the coupling box 52 on the two outlet sockets 53, and the appurtenant supporting ring segments 30 and 31. The supporting ring segment 30 may hereafter be lifted together with the outer extremity of the grate section, While the segment 31 is displaced upwardly along the sockets 53, whereafter the grate section as a whole may be lifted out from its supports 24, 25, and drawn out together with the ring segment 30. It may thereafter, if required, even be detached from the ring segment 3% by opening the stuffing box 5%? and disnecting a coupling in the conduit inside the same.

On removal of the grate section with appurtenant supporting segments it is possible, if necessary, even to replace the underlying suction box 60. In that case the external ash valve 70 as well as the internal mounting ring 67 are at first dismantled and then the box is de tached from the vertical stems of the tie booms supportting the box, whereafter the box can be lifted off these tie booms 8 and the supports 24, 25.

The various stages of dismantling have largely been indicated from one sector to the other in the sequence AD in Fig. 2, except that even certain fixed parts have been removed in the showing of sector D, and that for the simplicity of illustration the sector B shows the grate section to remain in position on removal of the carrying segments, which will of course not normally occur when using the embodiment described.

The invention can of course be carried out in various other ways than those shown with reference to the embodiment illustrated. Thus, in apparatuses with a great width of the grate it may be convenient to provide an additional support for the grate bars in one or more points intermediate their ends, for example in the form of detachable transverse supporting bars for the individual grate sections. Further, it is for example possible instead of passing the outgoing gases inwards in directions parallel to the grate to an upwardly extending gas discharge duct, to pass them largely at right angles to the grate to a downward gas discharge duct, which, if desired, may be provided with a cyclone separator. In the latter case it may even be contemplated to place the rotating valve for the supply and discharge of water centrally within or on top of the rotating supporting structure, and to pass the conduits connecting the valve to the outer row of hollow ring segments, between the suction ducts.

If desired, the valve may be placed so high that the conduits from the top row of the hollow ring segments can be passed directly to the valve without using an annular conduit, but in that case the advantage of a low overall height must be dispensed with.

Likewise the invention is easily applicable for a concave grate, i. e. for such embodiments in which the grate surface forms the interior surface of an inclined cone with downwardly facing apex. Finally the main features of the invention may be used for grate structures having a central rotating shaft, which may especially be contemplated for relatively small units.

If the cooling water is passed straight on in upward currents from the hollow ring sections the apparatus accord ingtothe invention may, if desired, at the same time serve as a heater for the production of steam.

-We claim:

1. A draught sintering apparatus comprising a conical grate having an inclined axis and mounted for rotation about said axis, said grate comprising a plurality of independently mounted sections each provided with an upper and a lower water chamber respectively provided with a water outlet and a water inlet, each of said sections including a plurality of hollow grate bars each communicating with said upper and lower water chambers, said sintering apparatus further including common water supply and discharge means to which the water inlet and outlet of each of said sections is connected during rotation of said grate, whereby when replacement of some of said hollow grate bars becomes necessary the independently mounted sections carrying such bars can be Wholly removed without dismantling of the entire apparatus due to the independent mounting of said sections.

2. A draught sintering apparatus according to claim 1, including a ring conduit rotatable with said grate and connected with the water outlet of each of said sections, and a plurality of discharge conduits connected with said ring conduit, said common water discharge means including a valve device selectively closing off all of said discharge conduits other than that which is uppermost at a given time.

3. A draught sintering apparatus according to claim 2, wherein said valve device comprises a housing rotatable with said grate and subdivided into a plurality of chambers each communicating with a respective discharge conduit, and a stationary housing including an inlet zone communicating with the water chambers of the sections through their water inlets and a discharge zone provided with an aperture positioned to communicate with the chamber of said housing corresponding to the uppermost section.

4. A draught sintering apparatus according to claim 3, wherein said stationary housing is disposed within said rotatable housing and is divided longitudinally into said inlet zone and said outlet zone, said aperture of said outlet zone being provided in the stationary housing wall, said rotatable housing being provided with a plurality of radial dividing walls forming a sliding seal with said stationary housing, said inlet zone of said stationary housing communicating with a distributing chamber rotating with said grate and communicating with said water inlets of said lower water chambers of said sections.

5. A draught sintering apparatus according to claim 1, wherein each of said sections forming the conical grate is spaced slightly from adjacent sections so as to permit expansion of said sections in circumferential direction.

6. A draught sintering apparatus according to claim 1,

7 including supporting means for each of said sections forming the conical grate and supporting said sections so that each is capable of independent radial displacement due to expansion of its respective grate bars.

7. A draught sintering apparatus'according to claim 6, including a rotatable truss structure carrying said supporting means, and a suction box for each section carried by said truss structure, said truss structure including bars ex-- tending under said grate parallel thereto between adjacent suction boxes and dividing walls extending upwardly from said bars to the underside of .said grate.

' 8. A draught sintering apparatus according to claim 7, including a central stationary suction head, and a suction duct extending from each suction box straight to said central suction head, each suction duct opening into said central suction head at an obtuse angle.

9. A draughtsintering apparatus according to claim 8, including a discharge gate normally closing each of said suction boxes, and means for opening each of said gates during each revolution, whereby ashes collected in said suction boxes will be discharged.

10. A draught sintering apparatus according to claim 1, wherein both end portions of each of said hollow grate bars is of reduced diameter, said reduced end portions being bent relative to the intermediate portion and being located outside the lateral confines of the grate surface;

said common water discharge means including a valve device selectively closing off all of said discharge conduits other than that which is uppermost at a given time.

References Cited in the file of this patent UNITED STATES PATENTS 2,193,698 Rolfsen Mar. 12, 1940- 2,493,421 Rolfsen Jan. 3, 1950 FOREIGN PATENTS 7,026 Australia Q Apr. 26, 1927 Great Britain June 17, 1941

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