Incinerator

Abstract

Comminuted waste fuel or material is injected into the incinerator at the bottom thereof through a conduit. Centrally arranged in this conduit, at the discharge end thereof is a second auxiliary fuel conduit which is provided at its termination end within the first conduit with a plurality of fuel discharge orifices which are directed radially outwardly and upwardly towards the discharge end of the first conduit. The incinerator also includes provision for a separator wherein the baffles and bottom disc are cooled by means of circulating air which is then discharged from the disc portion of the separator in a tangential direction complementing the direction of rotation of the cyclone within the incinerator.

Description

BACKGROUND OF THE INVENTION

This invention relates to improvements in incinerators and has particular application to incinerators of the cyclone type which are used to burn comminuted waste material.

DESCRIPTION OF THE PRIOR ART

In many conventional cyclone incinerators, the reduced garbage and refuse is supplied to the combustion chamber via a primary air supply conduit. Exemplary of this is the incinerator disclosed in U.S. Pat. 3,566,809 which issued on Mar. 2, 1972 in the name of Ecology Industries, Inc. wherein the primary air carrying the comminuted waste fuel is injected under pressure into the bottom of the combustion chamber through a discharge pipe. The pipe at its discharge end is surrounded by an annular ring burner, the function of which is to ignite the waste fuel or material issuing from the discharge pipe. The problem inherent in this type of ignition system resides in the fact that the flame from the annular ring burner must penetrate into the core of the discharge stream of primary air and comminuted waste fuel in order to effect a proper primary combustion. Since the velocity of the primary air and waste material is relatively high the mass flow of the auxiliary fuel flowing through the jets or orifices in the annular ring burner must also be relatively high. The problem here is that the primary burner, because of its annular construction, necessarily must in surrounding the discharge pipe, cover a large surface area and consequently be provided with a large number of auxiliary fuel jets or orifices which are spaced relatively close to one another for mutual flame support. This has the effect of reducing the mass flow of the auxiliary fuel which is available in order to properly penetrate the primary air and waste fuel or material.

Many incinerators today are provided with what is termed a separator which is located downstream of the discharge vent of the combustion chamber. Basically, the separator is cage-like in appearance and similar to that disclosed in the Ecology patent aforesaid. The primary purpose of the separator is to further reject uncombusted and non-combustible materials from the combustion gases passing therethrough. This rejected material is either recycled for combustion in the chamber or withdrawn as reject in the ash-sump. Because of the completion of combustion and maximizing of temperature, the cyclone effect within the chamber decays materially at a point where its centrifugal action is most needed. This is not readily cured by the provision of secondary air inlet ports in the walls of the incinerator opposite the separator since the swirling action is most required at the periphery of the lower baffle disc where a void has been left by the natural action of the gases in passing this obstruction during its upward flow. Further, most separators are water cooled which, in addition to causing serious maintenance and water treatment problems, effectively reduces the operating temperature thereof below the melting point of glass particulate material which otherwise would adhere thereto and drop off in the form of slag.

SUMMARY OF THE INVENTION

I have found that the foregoing combustion disadvantages can be overcome or minimized by providing for a co-axial burner and primary air-waste system wherein the burner is centrally positioned and the conduit for the primary air and waste fuel or material is arranged thereabout. The advantage of positioning the burner centrally and the waste fuel supply conduit thereabout is that better ignition of the waste fuel is achieved by virtue of the fact that the flame from the central burner can penetrate the waste stream more efficiently. Further, because the burner is centrally located, its fuel jets are much closer together and thus are mutually flame supporting to a far greater degree than is the case with ring burners. This permits the fuel jets of the central burner to be of a greater diameter than the jets of a ring burner and hence the novel construction permits a far greater mass flow of auxiliary fuel through each jet of the central burner for any given total mass flow, with a resultant improved degree of penetration of flame through the waste fuel stream.

I have also found that providing the inner wall of the primary air supply conduit with one or more ribs, vanes or baffles arranged in a fashion to impart a whirling motion to the waste material passing therethrough, such as a helix, produces a more intimate mixing of the primary combustion air with the waste fuel. Additionally, it is a function of these radial deflector vanes to separate non-combustible metal and glass particulate components of the waste by centrifugal force from the main stream of the flame issuing from the co-axial burner. Metal particles drop out of the stream of products of combustion into an ash sump and fine glass particles are caused to adhere to combustion chamber walls of the incinerator which is operating at temperatures above glass fusion temperature. This glass coating on the combustion chamber walls continuously flows down or drops from the walls (as molten slag) into the ash sump. The trapping and conversion of fine glass particles to molten slag reduces pollution by preventing escape of particulate from the combustion chamber with the products of combustion.

While gaseous fuel is the preferred fuel, my novel co-axial burner is also capable of including a further back-up or secondary co-axial fuel supply conduit for an oil atomizer. This secondary fuel supply conduit can be arranged co-axial within the auxiliary fuel conduit and put into use when the primary auxiliary fuel supply is exhausted or for some reason not operating. I have also found that by positioning a conically shaped screen about the auxiliary fuel supply conduit just below the burner, the screen effectively shields the auxiliary fuel ignition point from the stream of high velocity waste and primary air. The screen permits a small fraction of air to penetrate to the root of the flame front to assist in flame propagation through small eddy currents of air which stabilize the auxiliary flame at its root.

I have also devised a novel air cooled separator which permits it to function at a temperature sufficiently high to permit the adherence thereto of glass particulate material for build-up and drop-off as slag which is collected in the ash-sump. Further, I have found that the cooling air can be advantageously discharged from the bottom of the disc of the separator as what I term as tertiary air. The tertiary air is jetted about the separator in a direction complementary to the direction of the cyclone flow. This tertiary air discharge enhances the rejection of passage of particulate matter carried by the combustion gases by virtue of the fact that a whirling air centrifugal effect is centrally created at a point proximate the incinerators discharge vent.

BRIEF DESCRIPTION OF THE DRAWINGS

In drawings which illustrate various embodiments of my improvements to incinerators,

FIG. 1 is a vertical section of the incinerator taken along line I--I of FIG. 4,

FIG. 2 is a more detailed vertical section of a co-axial auxiliary fuel conduit and outer comminuted waste and air supply conduit which is similar to that shown in FIG. 1,

FIG. 3 is a more detailed vertical section of the separator shown in FIG. 1, and

FIG. 4 which is illustrated on the same sheet of drawings as FIG. 2, is a plan view of the separator taken along the line IV--IV of FIG. 1 which also shows in partial cut-away section the secondary air inlet ports taken along lines A--A and B--B of FIG. 1.

DETAILED DESCRIPTION

Referring to FIG. 1, the incinerator 10 is generally cylindrical in shape and has an inwardly tapering bottom portion. The incinerator may be supported by any suitable means such as base frame 11. The combustion chamber of the incinerator comprises primary combustion chamber 12 and secondary combustion chamber 12a thereabove. A centrally located discharge vent 13 is located at the top of the incinerator. The upper portion of the incinerator is connected to suitable chimney or flue means (not shown). Connected to the top of the incinerator and extending downwardly into the combustion chamber from the discharge vent 13 is separator 15.

The walls of the incinerator 10 are constructed from fire brick inner wall 16, insulating block intermediate wall 17 and outer metal wall and framework 18. A plenum 19 surrounds the incinerator walls and is supplied with secondary air from an air pressure supply source (not shown). The secondary air is fed tangentially from plenum duct 20 through port 21 to thereby create a cyclone effect within the plenum. Through heat exchange, the secondary air is preheated and discharged into the combustion chamber through secondary air inlet ports 22 as seen in FIGS. 1 and 4. Flame nozzle 23 is provided and extends through the walls of the incinerator in the secondary combustion chamber 12a. Incoming fuel for flame nozzle 23 is advantageously mixed with air withdrawn from the plenum through piping 24. Inspection or observation ports 25 and 26 are also provided in the walls of the incinerator.

The lower or bottom section of the incinerator is provided with a vertically arranged and centrally located outer comminuted waste and primary air supply conduit 27 which is in communication with waste and primary air feed pipe 28 connected to a waste material source and primary air pressure supply (not shown). Co-axial with and internally positioned in supply conduit 27 is the primary burner and auxiliary fuel supply conduit generally indicated at 29. A water quenching bath is maintained below the upper end of supply conduit 27 at 30, the level of which is regulated by a conventional water level control device generally indicated at 31. Rejected particulate material and slag collected in the water bath or ash-sump is withdrawn therefrom in any conventional manner (not shown). Access door 14 is provided for periodic maintenance and repair.

Ignition of the burner portion of the auxiliary fuel supply conduit 29 is effected by means of a retractable high energy ignitor 32. Flame scanner 33 is positioned above the ignitor.

With reference to FIG. 2, outer supply conduit 27 is preferably provided with ribs or baffles 34, the function of which is to impart to the waste fuel and primary air passing through annular passage 35 a whirling effect in order to facilitate proper intermixing of primary air with the waste fuel and to shape the resulting flame. As illustrated in FIG. 2, supply conduit 27 is flared at its discharge or termination end or it can be flared in a uniform and outwardly tapering fashion as illustrated in FIG. 1. Auxiliary fuel supply conduit 29 which is defined by inner and outer walls 60 and 61 terminates within the outer conduit 27 so that the auxiliary fuel issuing from first fuel discharge orifices 36 of the burner element portion 62 of conduit 29 are directed radially outwardly towards the discharge end of the outer supply conduit 27 as shown through the stream of waste fuel and primary air. A perforated screen or shield 50 is provided on the termination end of the supply conduit in order to enhance flame propagation of the auxiliary fuel.

While my novel waste fuel and burner arrangement need only have one conduit for the supply of auxiliary fuel, in the embodiment illustrated, I have made provision for an additional and co-axially arranged secondary fuel supply conduit 37. This secondary fuel supply conduit communicates with secondary fuel discharge orifices 38 of burner 63 which is arranged internally of discharge orifices 36 of burner 62. As illustrated, gaseous fuel is intended to be supplied through conduit 29 and liquid fuel such as oil through conduit 37. Since gas is the preferred fuel, in normal operation, conduit 37 and burner 63 are removed and the upper portion of wall 61 at burner 62 is capped by any suitable means. When conversion to oil firing is desired or necessary, the cap which is not illustrated is removed and conduit 37 and burner 63 are installed in the annular cavity defined by wall 36 and positioned as illustrated. Conduit 36 at its lower end is connected by suitable means to an oil supply (not shown).

Referring again to FIG. 1, it will be seen that ignition of the whirling waste fuel and primary air takes place at this point of introduction into primary combustion chamber 12. Further combustion takes place in secondary combustion chamber 12a through the added introduction of secondary air through ports 22 and flame injection from nozzle 23. As the products of combustion and particulate material carried thereby proceed upwardly, they are constrained through the positioning of disc 39 to move outwardly towards the walls of the incinerator.

The separator itself is formed from refractory material and basically comprises an annular manifold 41 surrounding discharge vent 13. The manifold is connected to disc 39 by a series of spaced, circumferentially arranged baffles 40. A series of interconnecting conduits 42, 43 and 44 are provided in the manifold, baffles and disc for the passage of tertiary air therethrough which air effectively cools the separator and then is advantageously discharged through tertiary air discharge orifices 47 into the combustion chamber in a tangential direction compatible with the direction of the cyclone air flow. Preferably, conduits 42, 43 and 44 are constructed from a stainless steel framework which serves as supporting members for baffles 40 and disc 39. As seen in FIG. 4, the baffles preferably are V-shaped in cross-section and include outer legs 45 which extend radially outwardly from the disc. The inner legs 46 of the baffles are located internally of the circumference of the disc and extend in a direction opposite to the direction of tertiary air discharge through orifices 47. The combined tertiary air discharge and baffle construction is such that the likelihood of particulate matter passing through the separator and thence through discharge vent 13 is minimized.

As illustrated in FIG. 1, inspection plate 48 is attached to the top of disc 39 and can be removed during shut down in order to permit interior inspection and repair to the combustion chamber.

Claims

What I claim as my invention is:

1. A co-axial burner for use in suspension burning incinerators of the cyclone type to burn comminuted waste material, comprising, an outer comminuted waste and primary air supply conduit and an inner co-axial auxiliary fuel supply conduit, the inner wall of said outer conduit being spaced apart from the outer wall of the auxiliary fuel supply conduit to thereby define an annular passage and to permit the flow of comminuted waste and primary air therethrough, said outer conduit having an outwardly flared discharge end and said auxiliary fuel supply conduit terminating within said outer conduit proximate the outwardly flared discharge end thereof, said auxiliary fuel supply conduit including at its termination end a burner element provided with a plurality of first fuel discharge orifices wherein said first orifices are circularly arranged and directed radially outwardly and upwardly from said fuel supply conduit towards the discharge end of said outer conduit and said first orifices are in communication with said fuel supply conduit.

2. A co-axial burner as claimed in claim 1, wherein said burner element is provided with a plurality of second fuel discharge orifices communicating with a secondary fuel supply conduit internally of said auxiliary fuel supply conduit, said second fuel dicharge orifices being positioned internally of said first fuel discharge orifices and wherein said second orifices are circularly arranged and directed radially outwardly and upwardly from said secondary fuel supply conduit towards the discharge end of said outer conduit.

3. A co-axial burner as claimed in claim 1, wherein said auxiliary fuel supply conduit at its termination end is provided with an upwardly and outwardly tapering annular and perforated shield.