US 3630502 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
United States Patent Inventor Werner Schmidt Frankfurt, Germany Appl. No. 26,989 Filed Apr. 9, 1970 Patented Dec. 28, 1971 Assignee Drnvo Corporation Pittsburgh, Pa. Priority Apr. 18, 1969 Germany P l9 19 668.0
APPARATUS FOR THE THERMAL TREATMENT OF SOLIDS Primary Examiner-John J. Camby Att0rneyParmelee, Utzler & Welsh ABSTRACT: Apparatus for the thermal treatment of solids in straight-traveling grates including a working path extending through a sintering machine where grate trucks are passed therethrough at one speed, and a conveying device for carrying the grate units back to the working path at a speed much greater than the work speed. An acceleration device is positioned at the end of the work path and is shaped to transfer a grate truck to the conveying device while at the same time accelerating the truck to the speed of the conveying device A deceleration device positioned at the end of the conveying device transfers a grate truck to the work path while decelerating it to the work path speed.
SHEET 1 BF 2 Q) FIG.
(b //v VEN TOR WE NER SCHMIDT A I lorneys PATENTED UEG28 I97! SHEET 2 BF 2 INVENTOR.
WERNER sum/0r W 47 g I A rrarneys APPARATUS FOR THE THERMAL TREATMENT OF SOLIDS The invention relates to an apparatus for the thermal treatment of solids in straight-traveling grates, where the grate units entering the no-load track through deflecting wheels are conducted back to the work path by means of conveyor devices.
For the thermal treatment of solids on traveling grates various systems are known. The form of construction of these machines chiefly used in the practice consists of an endless belt of individual grate trucks strung together, which are charged with the material to be treated at the loading point of the upper band. During the forward movement of the grate trucks on the upper band the material is then subjected to a thermal treatment. At the end of the upper band, the grate trucks are gripped by the so-called lowering wheel, tilted, emptied, conducted into the lower band, and at the end thereof seized by a so-called lifting wheel and again conducted onto the upper band. In this arrangement always more than half of the installed load surface is not utilized for the treatment process, so that due to the high-manufacturing costs of the grate trucks great investment costs per throughput unit are required.
Various suggestions have already been made for the better utilization of 1 the installed load surface. Thus designs of straight-traveling grates are known where the lower band of the above-described traveling grate machines is arranged parallel and at the same level alongside the upper band." After completion of the thermal treatment process on the first belt, the grate trucks are emptied by tilting, shifted laterally to the second belt, and charged with material. On the second belt there then occurs likewise a heat treatment process, which is completed at the end of the second belt. These traveling grate machines, however, have several disadvantages, which interfere with their practical use. Thus either only an intermittent operation is possible, which must be interrupted every time a grate truck is tilted, or expensive devices, e.g., means for pulling up the last grate truck before the tilting operation, are necessary to permit continuous operation. in addition, complicated shifting devices for the transport of the grate trucks from one belt to the other belt and an exactly matched control for all movements are required. Moreover, the trouble proneness due to the many movable parts and the rough operating conditions is great. The saving of the grate trucks of the lower band returning empty is offset by the cost of a complex operating system for the second belt.
Forms of construction of the straight traveling grates are also known where the grate trucks are emptied by tilting at the end of the upper band and rotated 180 by special devices, so that they enter the lower band with the load surface up. On the lower band the grate trucks are then again charged with the material discharged from the upper band, so that a heat treatment of the material occurs also on the lower band. After completion of this second heat treatment, the grate trucks are emptied, rotated 180, and returned to the upper band. This type can also operate so that the first heat treatment occurs on the lower band and the second heat treatment on the upper band, it being then necessary to convey the material into the charging device for the upper band by adequate transport devices. The difficulties in the operation of these traveling grates reside mainly in the complicated reversing mechanisms and the necessary capsulation against fouling from the dust raised at the discharge points. In addition, the discharge must either occur within the lowering wheels, and the transfer device for the material transport to the lower band must likewise be arranged within the lowering wheel, or additional transport devices are needed.
It has also been proposed to fit only the upper band and the lifting wheel of sintering machines with grate trucks, and to design the lower band, with the exception of a certain distance before the lifting wheel, only as return path for the emptied grate trucks. The gate trucks are then guided down onto the lower band at the end of the upper band by means of curve tracks. The lower band is arranged sloping down in the direction of the lifting wheel, so that the grate trucks pass through this section freely. This arrangement has the great disadvantage that the grate trucks impinge on the grate trucks present before the lifting wheel at considerable speed and are easily damaged. It has also been proposed to brake the grate trucks at the outlet of the curve track sharply by a braking device, whereby a better discharging and reduction of the impact was to be achieved, but also with this arrangement the impingement of the grate trucks is still so strong that damage is inevitable.
The arrangement of a special brake device, operating on the principle of the friction wheel, just before the lifting wheel in the lower band did bring a certain improvement, but still suffers from technical inadequacies.
A method different from the above-cited state of the art for improving traveling grates provides passing the grate units, supplied by the lowering wheel to the lower band, to the lifting wheel by means of a conveying device. The return then occurs at a speed which is much greater than the speed of the grate units on the working track. The transfer of the grate units from the working belt to the no-load track occurs preferably with gear wheels which seize the grate units by rolls mounted on the shaft, transporting them so that in the descent they do not touch the preceding or following grate unit. Having arrived on the no-load track, the grate unit is seized by drive pins of a conveying device, e.g., two endless chains running parallel, and are taken along at a speed about lO-l5 times greater (referred to that of the working track).
Although it is possible by the cited proposal to reduce the total surface and hence the total weight of the grate units by about 35 percent and to avoid wear of the grate units at their transverse side by impingement during the descent in the zone of the lowering wheel, it suffers from considerable. disadvantages. The most important is that the comparatively slowly lowered grate units are seized by drive pins of the conveying devices running 10 to 15 times faster and are thus exposed to the effect of forces which do not occur in normal operation. Therefore an unbearably high wear occurs, or else the construction of the grate units involves an actually unnecessarily high expense.
This invention avoids the above-mentioned disadvantages. It relates to an apparatus for the thermal treatment of solids on straight traveling grates where the grate units entering the no load track through deflecting wheels are guided back from the beginning to the end of the no-load track, with the aid of conveying devices at a much greater speed than that which they have during the thermal treatment, and is characterized by a device which accelerates the grate unit at the end of the work belt for transfer to the conveying device from working speed to return speed, and a device which decelerates the grate unit at the end of the no-load track for transfer to the work track from return speed to work speed.
The devices for acceleration and deceleration of the speed of the grate units have preferably the form of levers or else of specially shaped cam plates mounted in pairs on a shaft. When using levers, the acceleration or deceleration of the grate units can be achieved in that the rotary shaft of the levers itself executes an accelerated or decelerated movement. Preferably, however, the lever pairs, as well as the cam plates, are mounted on a shaft suspended outside the center of circle defined by the deflection path, so that at constant rotary movement of the shaft the acceleration or deceleration of the grate units is attained due to the varying circumferential speed of the contact points between the rolls of the grate units and the levers or cam plates. In the apparatus according to the invention for the thermal treatment of solids, the upper band of the traveling grate may be designed as working belt and the lower band as no-load belt, or the upper band may be designed as no-load belt and the lower band as working belt.
Synchronism is provided between the conveying device and the device for the transfer of the grate units to the working belt. A simple possibility suitable for this consists in that the conveying device and device for the transfer of the grate units are driven by means of the same assembly and that difierent speeds are brought about by different transmission ratios.
Other details and advantages of the invention will become apparent as the following description of certain present preferred embodiments thereof proceed.
In the accompanying drawings I have shown certain present preferred embodiments of this invention in which:
FIG. 1 is a side elevation, partly in schematic, ofa traveling grate where the work path is arranged in the upper band and the no-load track in the lower band. Also shown are devices in accordance with the present invention for accelerating and decelerating the grate units, such devices being shown as specially designed levers.
FIG. 2 is a side elevation view, partly in schematic, of a traveling grate where the work path is arranged in the lower band and the no-load track in the upper band. Also shown are devices in accordance with the present invention for accelerating and decelerating the grate units.
FIG. 3 is a side elevation view, partly in schematic, of a traveling grate where the work path is arranged in the upper band and the no-load track in the lower band. Also shown are cam devices in accordance with the present invention for accelerating and decelerating the grate units.
FIG. 4 is a side elevation view, partly in schematic, of a traveling grate where the work path is arranged in the lower and the no-load track in the upper band. Also shown are cam devices in accordance with the present invention for accelerating and decelerating the grate units.
In the form of construction according to FIG. I, grate trucks 2 traverse the sintering path arranged in the upper band of the sintering machine I. The drive occurs through a driving wheel or wheel pair 3, which engages in the rolls 4 disposed on the axles of the grate trucks 2. At the end of the sintering path, the first grate truck is seized by the device 5 designed as a lever, separated from the grate truck chain, and accelerated on the deflection track 6 from working speed to the speed corresponding to the conveying device 7. The design of lever 5 and of the grate truck axles by rolls 4 is such that an acceleration of the grate truck beyond the intended speed due to gravitation cannot take place. In fact, if the acceleration caused by gravitational forces would be greater than intended, roll 4 of the rear grate truck axle would run up on the flank away from the direction of movement of lever 5 and thereby prevent too great an acceleration of the grate truck. Moreover, the arm of lever 5 may be designed widened toward the pivot, so that at the point of the deflection track 6 at which the gravitational forces would cause an acceleration beyond the desired speed the distance between front and rear rolls 4 is practically filled by the lever 5 and thus absolute positive conduction of the grate truck exists.
The grate truck, having arrived on the no-load track 8, is seized by the drive pin 9 at the roll 4 and dragged on the no-load track at practically constant speed, which may be about lO-l5 times the speed of the trucks on the sintering path. At the end thereof, the grate truck is transferred to lever 10, whose circumferential speed at the takeup point of the grate truck is practically identical with the return speed thereof. On the way leading through the deflecting track 11 back to the sintering path the circumferential speed of the contact point between roll 4 of the grate truck and lever 10, and hence the speed of the grate truck itself, decreases continually, so that it is in the end taken up by the driving wheel 3 at working speed and pressed against the preceding grate truck chain.
Wheel 12 has a separating function, i.e., it is to prevent that due to inevitable differences in tensile strength of the sinter, two or even more grate trucks are pulled off by the lever S at the individual abutment points of the grate trucks. The separating wheel 12 may be unnecessary if, for example, pellets are fired or if the device according to the invention is applied to processes where large area intercrescence of the charge is not to be expected. Then, however, provision must be made by suitable measures, e.g., by inclination of the work track, that the cohesion of the individual grate units is preserved.
The design of the device according to the invention illustrated in FIG. 2 differs from that of FIG. I by interchange of the position of the work belt and of the no-load track. The various shapes, configurations, and parts of the apparatus correspond to those explained in reference to FIG. 1. However, for the device for transferring the grate truck to the conveyor, the form of a fork 10 is advisable.
In the form of construction of the apparatus of the invention according to FIG. 3, cam plates 13 and 14, having specially arranged guide strips 15 and 16, take over the function of the levers 5 and 10. The use of the cam plates 13 and 14 as devices for the acceleration or deceleration of the speed of the grate trucks 2 involves the advantage that the drive wheel 3 (as per FIG. 1 or 2) and the separating wheel (as per FIG. 1 or 2) can be dispensed with. Because of the shape of their flanks, the cam plates 13 and 14 also take over the driving and separating function. Lastly, for the form of construction here shown only one roll or respectively one roll pair 4 is required at the front axle of the grate truck.
In the device according to FIG. 4, the working track is in the lower band and the no-load track 8 with conveying device 7 in the upper hand of the traveling grate. The function of the cam plates 13 and 14 corresponds to that described in FIG. 3. In this case the guide strips 15 and 16 (as per FIG. 3) are not necessary.
The apparatus according to the invention for the thermal treatment of solids is applicable to the sintering of ores and ore concentrates, to the firing of pellets of any origin, to the calcining of any substances, and to drying and cooling processes.
1. Apparatus for use in the thermal treatment of solids comprising:
a work path extending through a treatment zone;
' traveling grate units for carrying solids through the treatment zone;
power means for driving the grate units at one speed along the work path;
no-load track means for carrying empty units back to the work path at a speed greater than the work speed;
first elongated revolvable transfer means arranged at the discharge end of the work path for engaging and transferring the grate units from the work path to the no-load track means and for accelerating the units to the no-load track speed; and
second elongated revolvable transfer means arranged at the feed end of the work path for engaging and transferring the grate units from the no-load track means to the work path and for decelerating the units to the work path speed.
2. Apparatus as set forth in claim 1 wherein said first transfer means includes a rotatable lever member arranged at the end portion of the work path and shaped to engage a grate unit to guide same onto the no-load track; and said second transfer means includes a rotatable lever member arranged at the beginning portion of the work path and shaped to engage a grate unit to guide same onto the work path.
3. Apparatus as set forth in claim 1 wherein said first transfer means includes a rotatable cam member arranged at the end portion of the work path and shaped to engage a grate unit to guide same onto the no-load track; and said second transfer means includes a cam member arranged at the beginning portion of the work path and shaped to engage a grate unit to guide same onto the work path.
4. Apparatus as set forth in claim 1 wherein said work path is arranged above said no-load track means.
5. Apparatus as set forth in claim I wherein said no-load track means is arranged above said work path.
6. Apparatus as set forth in claim 3 wherein the cam member of said second transfer means forms said power means by being shaped to drive the grate units along the work path.