PULSATING INCINERATOR HEARTH

Abstract: The hearth (13) is suspended on a fixed frame (19) for movement in a limited short are arc to urge random size particles burning in a pile on the hearth in a predeterminded path intermittently across the surface of the hearth. Move­ ment is imparted to the hearth in periodic pulses preferably by inflating sets of air bags (53) mounted on the frame, which stroke the hearth to move it a short distance from an initial position to jar it against the frame, thus impelling the burning pile upon each stroke, and then returning the hearth to its intitial position. The hearth may also have a plurality of nozzles (34) connected to a source of air for delivering gently flowing air to the burning pile on the hearth.

Description: Background of the Invention This invention relates to a pulsating hearth for an incinerator, and is more particularly directed to such a hearth which is capable of concurrent intermittent moving and stoking of a pile of random size particles burning on the hearth. Incineration may provide acceptable means for disposing of waste, for heat processing of various materials, and for recovery of heat from burning refuse; however, the process of incineration has had imposed upon its use severe and substantial limitations. Some incinerators require removal of materials not fully combustible in prior art systems or burnable only with undesireable side effects or hazards; thus a sorting step is necessary for use of such processes and equipment. Other incinerators need shredded material for burning and that prerequisite also requires extra processing and equipment. Most prior art incinerators are incapable of meeting environmental standards, and require one or more of a wide range of auxiliary equipment, such as afterburners, scrubbers, precipitators and the like to make them function. Even with suitable pre-incineration processes and equipment and auxiliary environmental protection devices, full combustion of random refuse material is seldom achieved, because adequate oxygenation of the burning particles is required, although the burning cannot be so rapid as to make the fire too hot or permit excessive gasification or atomization of the burning particles or the products of combustion. Optimum non-polluting combustion requires close control of the time, turbulence and temperature of the burning process. The problem is further magnified when the refuse contains plastics, wet refuse and liquids and when unburned particles are permitted to escape from the main burning chamber. Preferably, the main burning chamber of an incinerator has a hearth floor. However, such a hearth has some inherent problems requiring solution for effective and efficient combustion of random refuse. The refuse on the hearth must receive an even distribution of oxygen for the material to burn. Air must be mixed with the burning material and dispersed. Air alone, particularly with high velocities, will entrain and lift burning particles before they are fully consumed. The uncontrolled rapid burning of the pile may also increase velocities. Such high velocities and the accompanying incomplete burning results in slagging and tends to clog up the incinerator floor, as well as to permit incompletely burned particulate and products of combustion to exit the main burning chamber of the incinerator before they are adequately consumed. Some incinerators have been constructed using a starved air principle in their main burning chamber, but in these devices the lack of oxygen does not permit the burning hydrocarbons to convert to water and carbon dioxide, thus carbon monoxide is frequently formed, representing a hazard to operating personnel and restricting use of such devices to very well ventilated areas. Additionally, it is often desired to control the rate and extent of the burn in the main combustion chamber, without either the risk of pollution or the loss of desired selected unburned or ash products. For example, in some incinerator processes it is desired to burn perhaps 75% of each particle, but no more, and return the mostly burned particles before it is entirely reduced to ash. In other processes, it is desired to burn off readily combustible coatings and retain substrata unburned and not damaged by heat. In these situations it is particularly useful to control both the rate of burning and the time that the particle to be burned is subject to the heat of combustion. EP-A-0 64 589 shows an improved and very efficient system for incinerating bulk refuse. In it appears an incinerator having a housing, an inlet opening and an outlet opening in said housing removed from said inlet opening, a fixed suspension frame and a superstructure for limited arcuate movement of said superstructure relative to said frame in a first direction from said inlet opening to said outlet opening, said superstructure including a central area thereon adapted to receive a pile of burning particles, and impelling means for stroking and stopping movement of said superstructure relative to said frame primarely in said first direction with a first speed or in a second direction opposite to said first direction to compel movement of said particles when arranged on said burning area responsive to each stroking and stopping of said superstructure. The arcuate pendelous motions moving the burning refuse from the inlet towards the outlet, while adequately accomplishing the problems mentioned inbefore, the motion of the hearth did not appear to assist the actual incinerator of the refuse in any particular manner. In order to achieve an adequate oxygenation of the burning pile without increasing velocities in the main burning chamber and to control the rate and extent of burning, also in any particular manner, said impelling means also provides said superstructure when moving in said first direction, with an upward component of motion. Further, said superstructure moves between first and second positions and from said first position to said second position in said first direction and said impelling means includes a fluid system with inflatable bags and means for rapidly inflating said bags on each stroking of said superstructure. Said superstructure has a yoke extending from one side thereof and said frame has a beam on each of opposed sides of said yoke defining predetermined positions für said movement of said superstructure relative to said frame, and wherein said stroking and stopping means comprises said air bags on one of said beams and impact cushion means on the other of said beams and whereby one of said beams has fluid-operating means for moving said yoke away from said impact cushion means. According to the invention, said fluid system has control means selectively operable to inflate said air bags to actuate said fluid means for moving said yoke away from said impact cushion means and beeing provided with timer means controlling the frequency at which the operation of said impelling means is repeated, and with means for controlling the strengths of the stroking movement of said superstructure. In using said control means the moving of said hearth is between a first position to a second position in said first direction by impacting said hearth when at said second position against a fixed object it is for instance possible to create a shuddering of said hearth while at said second position. The moving of said hearth in said first direction can be repeated at time intervals. These and other objects and advantages of the invention will become more apparent at this description proceeds, taken in conjunction with the accompanying drawings. Figure 1 is perspective view of an incinerator system embodying the pulsating hearth which is subject of the invention. Figure 2 is a perspective view of a pulsatable hearth embodying the invention. Figure 3 is a cross-sectional view of the hearth shown in Figure 2, along line 3 - 3 thereof, and, additionally showing the suspension frame and sealing structure. Figure 3a is a sectional view showing the sealing structure for retaining the hearth closed within the suspension frame. Figure 4 is a vertical sectional view of part of the hearth and frame structure, including the means for delivering impact to the pulsating hearth. Figure 5 is a top plan view of the structure shown in Figure 4. Figure 6 is a detail sectional view of the toggle structure for suspending the hearth from its suspension frame. Figure 7 is an elevational view of the structure shown in Figure 6. Figure 8 is a perspective view of part of a pulsating hearth, showing an alternative modified structure for use when two or more hearths are ganged for delivery of burning particles one hearth to the other. Figure 9 is a schematic representation of the desired impact and movement of the pulsations for the subject hearth over time and with acceleration. Figure 10 is a schematic representation of the compressed air delivery and control system for pulsating the hearth. Figure 11 is a detail top plan view of a corner of the hearth and suspension frame, showing an alternative modified impact cushioning structure. Figure 12 is a detail section view of an alternative modified suspension structure for carrying the hearth on its suspension frame. Figure 13 is an elevational view of the structure shown in Figure 6. Description of a Preferred Embodiment As shown in Figure 1, an incinerator system, having a main combustion chamber 10, into which refuse or other materials to be burned are charged, through an entry door 11, by means of a loading device 12, includes one or more hearths 13, upon which the refuse is to be burned. Products of combustion released by burning in the main combustion chamber 10 may be reburned in one or more afterburners 14, and, with or without further processing in a scrubber or other auxiliary equipment, exhausted to atmosphere through a stack 15. Ash created from burning in the main chamber 10 may be conveyed to an ash pit 16, where the ash may be removed by a collector system 17. In the present invention, particularly with reference to the structure shown in Figures 2-7 and 9-10, the main combustion chamber 10 has a hearth 13 which is capable of moving the burning material thereacross until it is ready for disposal. This moving hearth has a fixed frame 19 suspended from which are toggle members 20 carrying a movable superstructure 21. The superstructure 21 has a floor 22, side plates 23, large tubular channels 24, each defining a first set of air plenums 25, angular channels 26, which carry step plates 27, upon which a layer of fire bricks 28 are mounted, and small tubular channels 29, each defining a second set of air plenums 30, which are secured, as by welding, to the top wall of each of the large tubular channels 24. The central floor area 31 and end wall 32, which is preferably tapered, together with the side wall edges 33, of the hearth, are preferably covered with refractory material. For burning of some materials, it is possible to fabricate the entire hearth superstructure 21 from steel or similar material, which preferably may be water cooled. Passages 30a are preferably formed in the neutral area along the inside walls of the large tubular channels 24 to permit circulation of air within the space defined by the floor 22, side plates 23, tubular channels 24 and 29 and step plates 27. Air may be admitted to the interior of the hearth 13 through air holes 24a formed in the exterior walls of the large tubular channels 24, and those air holes 24a may be in fluid communication with ducts (not shown) connected to air blowers for delivery of air to the interior of the hearth 13. Depending upon the length and number of hearths 13 used, the hearths may be pitched or tilted in the direction of ash pit 16 to encourage gravity flow of materials burning on the hearth and to provide a longer stroke of the hearth pulsations, in a manner to be described. For example, in a three hearth system, the first hearth (closest to the entry door 11, may be pitched about 1 inch per foot of hearth length, the second hearth may be pitched about 1/4 inch per foot of length, and the third hearth may be only slightly tilted. The degree of tilt is one means for controlling the rate of flow across the burning area 31 of the hearth, and other means will be described hereafter. Extending through the large and small channels 24 and 29, respectively, and the aligned step plates 27 and between fire bricks 28 are a series of nozzle pipes 34, which are of a sufficient length to reach and open into the central floor area 31 of the hearth 13 where burning is intended to take place. The nozzle pipes 34 each have a series of ports 35 in communication with their related plenums 25 and 30, respectively, and one end of each of these nozzle pipes also have a removable plug 36, accessible through the frame 19, to permit them to be reamed for cleaning purposes upon removal of the plugs. These nozzle pipes 34 may also be slightly pitched toward the central burning area 31, preferably about 3 o -6 o , to inhibit lodging of ash particles therein and for self-cleaning by the gently flowing air passing through the nozzle pipes. The upper end of the frame 19 carries shelf-like angle plates 37, which extend over the upper wall of the small channels 29 to prevent escape of small burning particles from the central burning area 31. These plates 37 also each carry along their longitudinal edges a bracket 38 to which is connected a pair of spring-like sealing arms 39, and the outside walls of the small channels 29 each carry along their edges a longitudinally extending bracket 40, to which is connected in upstanding sealing strip 41 spring fit between the spring sealing arms 39 (see Figure 3a). At the charging end of the hearth 13, the exterior of the superstructure 21 (see Figure 4) has another seal bracket 38a carrying double finger spring strips 41a rubbing against an extension 19a of the frame 19 for sealing the end of the moving hearth in a manner similar to the hearth side arms 39 - strip 41 described above. Angular plates 37 also have depending therefrom a plurality of toggle members 20, which may comprise toggle brackets 42 mounted to the frame 19, through each of which extends a first pivot axle pin 43, and toggle links 44 are pivotally connected to each of said axle pins 43. The other end of each of said toggle links 44 have pivotally secured thereto a second pivotal axle pin 45, and the side plates 23 and large channels 24 have connected, as by welding, to their outside walls a toggle lug 46, which is pivotally secured to the second pivotal axle pin 45. These toggle lugs 46 may be suitably reinforced by angle plates 47 secured to the outside walls of the large tubular channels 24. At the charging end of the hearth 13, the large channels 24 each extend beyond the end of the hearth to form a U-shaped yoke 50. Likewise, the suspension frame 19 is extended to provide an air bag frame which consists of a header beam 51 on one side of the yoke 50 and an impact beam 52 on the other side of the yoke. The header beam 51 has spaced apart along its length a plurality of like air bags 53, each of which is secured inflatable to that beam by a bracket 54 facing one side of the yoke 50. Yoke 50 has secured thereon in alignment with the air bags 53 push plates 55. The impact beam 52 has arranged along its length, preferably in alignment with each of the header beam air bags 53, carried on the impact beam by brackets 56, another set of air bags, the end air bags 57 of which set are enclosed in a cushioning frame 58 and the central air bags 59 of which set are exposed. The side of the yoke 50 facing the impact beam 52 has impact plates 60 aligned with the impact beam air bags 57 and 59. Spacing and aligning of the header and impact beams 51 and 52, respectively, relative to the yoke 50, may be set and maintained by rods 61 secured one end to each of said beams. Stops 62, preferably mounted on the respective beams 51 and 52, may be provided adjacent each of said air bags 53 and 57 and 59, respectively. Arms 63 may be secured to the header beam 51 for carrying thereon an accummulator tank 64, which may contain compressed air. Preferably, upper walls 65 of the burning area 31 consist of a body of refractory and are tapered from the overhanging shelf-like plates 37 toward the edges of the underlying bricks 28, and, like the refractory bodies 32 and 33 are suitably secured to the superstructure 21 by means of refractory anchors 66. Ganged Hearths In very large incinerators or where a longer incineration time is desired, similar hearths 13 may be ganged in line along their longitudinal axes by use of the structure shown in Figure 8, providing a central burning area 71 on a first hearth, which feeds burning material to a second hearth like the hearth 13, having a central burning area 31, shown in Figure 2. Such ganging of hearths is achieved by extending rods 72 and a plate 73 from the side edge and its underlying structure of a typical pulsatable hearth 13 (shown in Figure 2) and covering the rods and plate with a body of refractory material 75. These rods 72, plate 73 and body 75 are arranged over the next adjacent hearth, e.g. the aforementioned structure is elevated and extends over the tapered wall 32 (see Figure 2) on the next adjacent hearth. Piles of particles burning in the central burning area 71 are shuffled thereacross onto the body of refractory material 75, as shown in Figure 8, where they fall onto the next adjacent hearth, for example, onto the central burning area 31 of the hearth shown in Figure 2. Preferably, each of the pulsating hearths have their own suspension and means for delivering pulsating strokes to the hearths, as described herein. Impact Cushions As shown in Figure 11, an impact bumper 80, preferably a sheet of rubber of about 40 durometer having a typical thickness of about 3 inches, may be substituted for the end air bags 57 and their cushioning frames 58 (shown in Figures 4 and 5), but secured to the brackets 56 shown. A bumper plate 81, aligned with the impact bumper 80, may be mounted on the plate 60 secured to the yoke 50. In this arrangement, impact plate 81 on yoke 50 is thrust and bounced against bumper 80 on the impact beam 52, compressing the impact bumper to a typical thickness of about 1 inch during the thrust of each initial pulsation stroke. In all cases, even with this modified impact bumper arrangement, the central air bags 59 are preferably present and inflated for returning the yoke 50 from its stroked position to its initial stroking position shown in Figures 4 and 5. Stroking System Stroking of the hearth(s) 13 by movement of the yoke 50 from its initial position, i.e. against the header beam 51, thrust against the impact beam 52, and returning the stroked yoke to its initial position, may be accomplished by use of the stroking system shown in igure 10. In this system, compressed air is delivered from a compressor (not shown) from the "IN" side of the line through an inlet valve into conduit 101, which may have therein a filter, and is regulated by a regulator 111. This conduit 101 may also have a valve and pressure guage and a pressure switch therein. The conduit 101 is in flow communication with a branch conduit 102, which may be connected through a flexible hose 112, where the conduit 102 divides into two legs, one leg of which having another regulator 111 and a pressure guage and value, and the other leg of which may also have a valve, both legs being connected to the accummulator or air receiver tank 64, which may have a pressure guage therein and a blow-down valve at the extreme end thereof. Parallel conduits 103 lead from the tank 64 to three way solenoid valves 105. The solenoid valves 105 also have exhaust lines 104 extending therefrom. Air lines 106 connect each of the solenoid valves 105 to each of the air bags 53. Thus, when the solenoid valves 105 are open from the tank 64 to the air bags 53, air will rush into and very rapidly inflate the air bags 53, causing them to expand immediately and kick the yoke 50. Preferably, these solenoid valves 105 are adjustable within a range of about 5-150 lbs. and are adapted to open at about 80 psi. Compressed air is also delivered through conduit 101 to another branch conduit 107, which has another regulator 111 therein, and which connects to bumper and return air bag conduit 108, through a flexible hose 112 and a check valve. This conduit 108 connects with parallel conduits 109 leading to central air bags 59 and also has a relief line, having therein a pressure guage, and relief and control valves, terminating in mufflers 113 exhausting to atmosphere. Also connected to the conduit 101 through a regulator 111, flexible hose and check valve is the impact cushion conduit 110, leading to the end impact cushioning air bags 57, and this line also may have therein a pressure guage and relief valve. Preferably, pressure is steadily maintained in these impact cushioning air bags 57, so that only as they lose pressure is air injected into them. Air entering the bags 59 is not admitted with a surging action, as is the case with air bags 53 where the air is rapidly injected into those bags, and the filling of bags 59 is only sufficient to move the yoke 50 from its thrust position against the impact beam 52 back to its initial position against the header beam 51. The exhaust lines 104 lead from the solenoid valves 105 to a collector conduit 114 which terminates in a relief valve exhausting the conduit 114 to atmosphere through a muffler 113. When the yoke 50 is stroked by air bags 53, the movement of the yoke may activate a limit switch 115, which closes the solenoid valves 105 and opens the bags 53 to bleeding to atmosphere through exhaust line 104 and conduit 114. When the yoke 50 has been thrown toward the impact beam 52 and bounced against the cushion air bags 57, the central bags 59 are filled through line 109, thus returning the yoke 50 to its initial position against the air bags 53 on header beam 51. The strength of the throw and its cushioning may be controlled by the pressure and sizing of conduits and components of the compressed air delivery system. The interval between strokes can be controlled by timer mechanism opening and closing the solenoid valves 105. Modified Suspension Members The toggle members 20, shown in Figures 6 and 7, are intended to provide free suspension of the hearth superstructure 21 from its suspension frame 19 and uninhibited movement in a short limited arc, usually not more than 4-8 inches, with sufficient momentum to impell the load of random size burning particles randomly arranged in piles on the hearth and stoke the pile, thus moving the particles forward across the hearth and rearranging the piles. This free suspension and uninhibited swinging in the fashion described requires free movement of the toggle members in such a way that the floor has relatively frictionless movement in a defined arc without canting the hearth to jam its swing. The toggle links 44 pivotally arranged, preferably aided by swivel bearing joints 43a, as shown in Figure 6, is one means to provide such movement. Another means is shown in Figures 12 and 13, where modified toggle members 120 comprise cable links 121 suspended between pairs of pivotable bearing pulleys 123, one of the pair mounted on the toggle bracket 42 and the other of the pair carried by the toggle lug 46. Acceleration Curve By means of the structure and system described above, the desired acceleration of the yoke 50 and its connected hearth 13 may be achieved. A typical acceleration curve, measured over time and distance, is shown in Figure 9. When the air bags 53 are inflated by opening of the solenoid valves 105, at point A on the Figure 9 graph, the yoke is moved to point B of maximum positive acceleration on its forward stroke. When the yoke 50 first hits the impact beam 52 at point B, negative acceleration begins, at which time the yoke has reached its maximum stroke, but the particles continue to be propelled forwardly, and the yoke 50 bounced against the impact beam 52 at point D, yielding to the return of the yoke 50 pushed off by the return air bags 59 until the yoke has come to rest against the header beam 51 and its air bags 53 then deflated at point E. This stroke measurement has been recorded on chart paper marked in centimeters, and with reference to the curve one centimeter of the chart represents about 0.2 second real time for the entire acceleration stroke, and the rate of acceleration was 0.053g per centimeter of chart paper. The rapid and traumatic acceleration and the aftershock following the build-up of momentum is demonstrated by the Figure 9 acceleration curve, and such acceleration force is required to sufficiently overcome inertia for movement of the particles and rearranging them in order to achieve both adequate combustion and travel.

Claims: An incinerator hearth for an incinerator, having a housing, an inlet opening and an outlet opening in said housing removed from said inlet opening comprising a fixed suspension frame (13) and a superstructure suspended for a limited arcuate movement of said superstructure relative to said frame (19) in a first direction from said inlet opening (21) to said outlet opening, said superstructure including a central area thereon adapated to receive a pile of burning particles, and impelling means for stroking and stopping movement of said superstructure (21) relative to said frame (19) primarely in said first direction with a first speed or in a second direction opposite to said first direction to compel movement auf said particles when arranged on burning area responsive to each stroking and stopping of said superstructure, whereby said stroking and stopping means includes a fluid system with inflatable airbags (53, 57, 59) and means for rapidly inflating said bags on each stroking of said superstructure (21), which has a yoke (50) extending from one side thereof and said frame (19) has a beam (51, 52) on each of opposed sides of said yoke (50)defining predetermined positions for said movement of said superstructure (21) relative to said frame (19), and wherein said stroking and stopping means comprises said airbags (57, 59) on one of said beams (52) and impact cushion means (53) on the other of said beams (51) and whereby one of said beams (51, 52) has fluid operating means for moving said yoke (50) away from said impact cushion means, charaterized in that, said fluid system has control means selectively operable to inflate said air bags (57, 59) and to actuate said fluid means for moving said yoke (50) away from said impact cushion means (53). The incinerator hearth recited in claim 1, further charaterized by timer means controlling the frequency at which the operation of said impelling means is repeated. The incinerator hearth recited in claim 2, further characterized by means for controlling the strengths of the stroking movement of said superstructure.

Inventors: BASIC, JOHN N. SR.
Applicants: BASIC, JOHN N. SR.
Application year: 1984
Main classification: F23G5
IPC codes: F23J1, F23L1, F23G5, B65G27