GB2261939A - Incinerator - Google Patents

Abstract

An incinerator comprises a generally cylindrical chamber (212) rotatable about an axis below which material is to be burnt. Elongate apertured gas delivery means (239, 239') are entrant the chamber (212) so as to direct a gas stream into space below the axis of rotation of the chamber (212). The gas serves to promote combustion and/or to cool the chamber periphery provided by drum (212). The incinerator may include an internal heat shield (253) to shield the drum (212). <IMAGE>

Description

INCINERATOR This invention relates to incinerators, particularly for burning waste products.

Refuse disposal presents problems for local communities and authorities. Tips are unsightly, often dangerous, generally environmentally damaging. Disposal by in-filling does not significantly reduce dangers, nor potential for environmental damage, and does not produce usable land for many years, if ever. Incineration is generally accepted as the best solution, and large incinerators are known for such purposes. Those of socalled rocking-hearth type have hearth segments that move in order to translate material as it is consumed.

Generally, both in capital-cost and operating time, incineration is considered to be expensive.

It is an object of this invention to provide incineration equipment that is conducive to efficient processing of refuse.

According to one aspect of this invention, an incinerator comprises a generally cylindrical chamber rotatable about an axis below which material is to be burnt, and elongate apertured gas delivery means extending into the chamber so as to direct a gas stream into space below said axis, the gas serving for combustion-promotion and/or chamber periphery cooling purposes.

Such elongate apertured gas delivery means are advantageous in that they may be arranged to direct gas into the chamber from spaced locations along the internal length of the chamber. Preferably the gas delivery means are operative to direct gas into the chamber at locations spaced along a major proportion of the internal length of the chamber.

A A serious disadvantage of prior incinerators is that effective combustion is only achieved at the entrance to the chamber.

In other aspects the invention provides alternative methods for incinerating refuse.

It is advantageous for the gas delivery means to be operative to direct gas from below and preferably also from one side of the chamber, preferably the side towards which the chamber's bottom moves when rotated.

Preferred gas delivery means are elongate apertured means which suitably comprise one or more tubes, each tube having one or more gas outlets. Gas delivery means from a side of the chamber are suitably directed downwards and sideways into material to be burnt generally effectively from below as the chamber rotates.

The incinerator will be provided with an exhaust gas outlet, which preferably has associated means for positively drawing gas from the interior of the chamber, which gas drawing means is most preferably operative to withdraw as much or more volume as introduced into the chamber by operation of the gas- delivery means.

A suitable exhaust gas outlet is generally tubular and extends further into the chamber at its top than at its bottom, the chamber being rotatable about the outlet. Inward extension of the outlet into the chamber can be eccentric of the axis of rotation of the chamber with its topmost greatest extent closer to the top of the chamber than its lowest extent is to the bottom of the chamber. A tapering slot along the outlet from its inward-upmost extension may be eccentric to one side of a vertical through the axis of the outlet, a lower edge thereof then conveniently carrying the gas delivery tube. Internally, the exhaust outlet preferably has heat exchanger tubes, some about its inner periphery.

Preferably the incinerator is provided with a heat shielding means, spaced from the internal periphery of the chamber to shield the chamber periphery from the combustion products. Such heat shielding means are advantageous in that they may allow omission of a refractory lining for the chamber periphery, which thus substantially reduces manufacturing costs and facilitates maintenance of -the incinerator. Suitable heat shielding means are of double-walled construction to allow passage of cooling fluid therethrough.

Preferably the chamber is rotatable about any heat shielding means.

In some embodiments the chamber includes walling or a partition, which may or more preferably may not rotate with the chamber, to define a part of the chamber to which burning is to be substantially confined.

Preferably the chamber includes an arcuate partition and at or near the spaced edges of the partition serving to define a part of the chamber for combustion. In this regard, preferably gas delivery means are operative to direct gas from the chamber periphery into that part of the chamber, suitably between spaced edges of an arcuate partition such as described above.

In such embodiments where walling or a partition is included, preferably means are also provided for cooling the partition. In this respect, most preferably the partition is of double-walled construction to allow passage of cooling fluid therethrough. Most preferably a partition also provides a heat shielding means for the internal periphery of the chamber.

The incinerator chamber may take various forms.

In some embodiments, the chamber is of a solid-wall construction and the internal periphery of the chamber wall is provided with baffles, suitably axially spaced annular fins, which preferably extend substantially around the internal circumference of the chamber, for example to assist in deflecting combustion material from chamber walls. In this embodiment, gas delivery means are also preferably operative to direct gas into the chamber from the baffles suitably by provision of gas delivery means in spaces provided between at least some of the baffles such as the spaced fins described above.

Provision of such baffles is also advantageous as it allows for location of gas delivery means at the chamber wall and thus to be underneath combustion material in use.

In some alternative embodiments gas delivery means are entrant from one end of the chamber, preferably the end opposite to entry provisions for material to be burnt. In any event, it is preferred that delivered gas is expected to be deflected from the inner drum periphery into or further onto material being burnt.

The gas delivery tube may be at or adjacent to one edge of an elongate exhaust gas outlet provision which may be entrant the combustion chamber, from either end. Preferably the exhaust gas outlet provision has increasing exhaust gas entry capability from one end, i.e. preferably with decrease from the in-chamber end of the exhaust gas provision. Provision of an exhaust gas outlet at the same end of the chamber as entry provisions for material to be burnt can be advantageous in assisting to promote combustion at that end of the chamber, by drawing gas to the entry provisions.

In another embodiment, the chamber is provided with a downwardly directed partition and may be at or near a lower edge thereof serving to define a sectoral part of the chamber to which burning is substantially confined, with lower gas delivery means to direct gas downwardly and sidewardly thereinto. Exhaust gas provision may suitably be upwardly and sidewardly offset eccentric with the chamber and generally above such sectoral combustion chamber part, conveniently with the partition depending therefrom. Upper gas delivery means may also be associated with a part of such exhaust gas provision adjacent the chamber wall and directed generally downwards or along that wall. A suitable exhaust gas provision is generally tubular and has access for combustion products from below and above at least the main burning region.

Specific implementation for this invention will now be described, by way of examples, with reference to the accompanying drawings, in which: Figure 1 is a simplified side view of one embodiment; Figure 2 is a simplified end view of the first embodiment; Figure 3 is a bottom view of the exhaust outlet for the Figures 1 & 2 embodiment; Figure 4 is a simplified side view of another embodiment; Figure 5 is a section/end view thereof; Figure 6 is a simplified diametrical crosssectional view of another embodiment; Figure 7 is a sectional view; and Figure 8 is a simplified side view of the Figures 6 and 7 embodiment.

In Figures 1 to 3, an incinerator 10 has a combustion chamber as a drum 12 of generally circular cylindrical form, say up to ten metres diameter and thirteen metres long, or larger if desired. The drum 12 has circular peripheral tracks 14A,B,C,D,E, spaced along its length for rotation on its side by engagement with wheels or rollers 16,18 correspondingly subscripted A-E, of which there are two (eg 16A,lSA) per track and of which at least one is driven, see motor 20 and common shafts 22,24. There will be a suitable lower framework (not shown) or equivalent for supporting the shafts 22,24. The periphery 34 of the drum 12 is generally of unapertured plate form between the drive tracks 14.

Combustion-promoting gas, normally air, which may further have some drum cooling effect, is delivered into the lower part of the drum 12 by a delivery tube 39 fed by a fan 37 and having outlets or nozzles 35 directed (36) towards a lower part of material 30 to be burnt.

The drum 12 has at one end 40 a loading entry 42 shown with a lower inclined chute 44 which in this embodiment is fed from a conveyor 46. Alternatively, material 30 may be stored in a storage hopper (not shown) positioned above chute 44, a wall or floor of the hopper being openable or removable to allow material 40 to exit the hopper and enter the drum 12 directly at end 40, without need of a conveyor. (The material 30 has preferably been sorted, selected say- by sifting/using magnets to remove materials for recycling, prior to entry into the drum 12.) At its other end 50, the drum 12 in this embodiment has an exhaust gas outlet provision indicated generally at 52 and comprising a circular cylindrical exit flue pipe 54 typically extending through the drum end 50, conveniently with a suitable simple clearance at 56 for the drum 12 to rotate about the flue pipe 54.

The flue pipe 54 typically incorporates an exhaust gas cleaning stage 57, say of electrostatic type, and an exhaust fan stage 59.

Inward extent 60 of the exhaust gas provision 52 is shown of greater diameter than the flue pipe 54 and eccentric relative thereto and to the drum 12 with a top extent 62 much greater, in fact most of the length of the drum 12, than its bottom extent 64, thus presenting a sloping exhaust gas entry 66. Ash removal will be from below the bottom extent 64 at the drum end 50.

Inward extent 60 of the exhaust provision 52 has a downwardly directed opening or slot 61 for entry of gaseous products of combustion. The slot 61 is wider at most inward end, indeed tapers down back from that end.

The slot 61 is also shown with its edges 63A,B at different levels as consistent with the slot width extending mainly in the direction of rotation 'of the drum 12, see Figure 3 for greater divergence from the drum axis by the edge 63B. The other edge 63A carries the air delivery tube 39. The air delivery tube 39 could, of course, go to its fan 37 through clearance 56 if large enough rather than as shown through the remainder of the exhaust provision 52.

In operation, material 30 to be burnt enters the drum 12 down the chute 44 conveniently from the conveyor 46 or a hopper (not shown) and is burned generally at 70 under the gas entry 66, in fact below the level of the bottom 64 of the exhaust gas outlet provision 52.

Combustion is promoted by gas, usually air, blown through the tube 39 and out of the jets 35, then swirling through the material being burnt and to some extent up the side of the drum, which will assist in aerating input material, also having it tumble while burning and the drum 12 is rotated. Such tumbling, and turbulence for the injected air, can be further aided by provision of baffles on the interior of the drum 12, normally of short length and staggered relationship.

It is useful to have the exhaust fan 59 operating to remove at least as much volume, preferably more, than the fan 37 injects, and it may well be advantageous to close down the material entry 42 to some extent if not altogether except at a letterbox-like entry to the chute 44, say by a suitable adjustable flap (not shown).

The inner and outer surfaces of the inward exhaust gas provision 60 may be coated with heat insulation such as suitable refractory or ceramic material, if need be. The exhaust gas exit 54 may have an alkali/acid stripping stage additional to, or instead of, the electrostatic precipitator stage 57.

Such stripping suitably involves spraying a solution, suitably an acidic/alkaline solution, conveniently through a venturi-type nozzle, into the hot stream of exhaust gas for reaction with pollutants entrained therein (such as hydrocarbons, oxides of nitrogen and sulphur etc). Removal of the polluted or spent solution (or vapour) is then assisted by, say, sorption/sorption of the solution/pollution in an appropriate medium, (or media), such as a solid, particularly a peat-based adsorbent, for example, followed by drying the medium for recycling. Such stripping procedures may be adapted for treatment of exhaust gases generally and comprise another aspect of the present invention.In this embodiment, the adsorbent is suitably supplied to an upper region of the exhaust gas exit 54 and allowed to fall under gravity through the stream of exhaust gas, which is directed from a lower region of the exit 54.

As an alternative to use of a peat-based adsorbent, the exhaust gas provision may include a filtration means for retaining spent solution from the stripping stage and allow passage of stripped gas from the exhaust gas exit. Suitable filtration means are of foam rubber type. Alternatively the spent solution (or vapour) may be entrained in a fast flowing liquid (typically water) to retain an acidic/alkaline vapour whilst allowing passage of stripped gas to the exhaust gas exit.

Steam pipe provisions are indicated in outline at 72 in Figure 1 within the inward extension 60 and exiting the exhaust provision 54 for taking off useful heat in the exhaust gases. A preferred arrangement is indicated at 72A in Figure 2 for heat exchanger tubes over the interior surface of the inward extension 60 of the exhaust outlet provision.

Turning to Figures 4 and 5, exhaust gas provision 152 as shown offset upwardly and sideways of the axis of the drum 112 with an entry opening 161 above and directed towards the main burning region near the material input end of the drum 112. Depending from the tubular exhaust gas provision 152 is a partition 153 defining a sectoral burning chamber below the exhaust entry opening 161 and having a gas, normally air, delivery tube 139 that is fan fed and has outlet nozzles 135 directed sideways and downwards into the sectoral burning chamber. Extending sideways from the tubular exhaust gas provision 152 is another input for another gas, normally air, delivery tube 155 having generally downwardly directed outlet nozzles 158 also into the sectoral burning chamber.

Figure 4 also indicates steam generation via a water entry tube 180 and steam exit 181 tube in the exhaust provision 152.

It will be noted that the exhaust provision 152 is shown of double-walled construction, as also are the partition 153 supporting the lower aerating delivery tube 139 and the support for the upper aerating delivery tube 155. Air (or other fluid) cooling between that double-walling and heat shielding at least facing the sectoral burning chamber assists maintaining structural stability and cooling of exhaust gases. Heated air from circulation through the double-walling can be used to run a boiler.

An advantageous feature of exhaust gas treatment processors is for sudden quenching from around 900"C to about 80"C as that significantly reduces various sulphurous and nitrous oxides.

Figure 6 shows provision of an alternative arcuate partition 253 in a drum 212 of generally circular cylindrical form. The partition 253 is of double-walled construction to allow passage of cooling fluid therethrough. The partition 253 thus provides a heat shield to shield a major proportion of the chamber wall from the combustion products. Spaced edge margins 254 and 255 define a part 257 of the chamber to which burning is to be substantially confined. The partition 253 is adapted to remain stationary whilst the drum 212 rotates around it, on rollers 216 such as previously described.Gas delivery means comprise apertured tubes 239 and 239' to direct gas downwardly and sidewardly to deflect from the drum 212 back into the chamber through the spaced edge margins 254 and 255, thereby serving to promote combustion in the chamber and to assist cooling of the periphery of drum 212 as it rotates past the edge margins.

Figure 7 shows possible construction of a wall of a drum 212. Here the drum 212 is provided with surface formations comprising axially spaced annular fins 216, which extend substantially around the circumference of the internal surface of the drum 212. The fins 216 are arranged spaced along substantially the internal length of the drum. The illustrated fins 216 have various heights and/or thickness, and are advantageous in deflecting combustion material from the periphery of drum 212 to assist in reducing temperature rise thereof.

In the illustrated embodiment gas delivery means comprising apertured tubes 239 are arranged between at least some of the spaced fins 216. (Whilst Figure 6 shows two gas delivery tubes 239, 239' clearly more tubes may be accommodated between the spaced fins 216, as shown in Figure 7). This is most advantageous in that combustion is facilitated since gas is directed into the chamber from underneath the material to be burnt.

In Figure 8 an incinerator 210 has a combustion chamber as a drum 212 of generally cylindrical form, of the type shown in the Figures 6 and 7. The drum 212 is rotatable by engagement of drum peripheral tracks in wheels or rollers such as previously described. The drum 212 has surface formations on its internal periphery as illustrated in Figure 7.

Combustion-promoting gas is delivered into the lower part of the drum 212 by delivery tubes 239 and 239' fed by a fan 237, and each having outlets or nozzles directed towards the material 230 to be burnt.

The delivery tubes 239, 239' are located at or near the edge margins 254, 255 of the partition 253 which delimits the part of the chamber to which burning is to be confined. A loading entry (such as previously described) for refuse is illustrated.

In this embodiment the exhaust gas outlet provision is indicated generally at 250, at the same end of drum 212 as the loading entry 240 and will include an exhaust gas cleaning stage such as previously described.

Location of the gas outlet provision 250 at this end of the drum 212 is advantageous in that it helps to draw combustion gases towards the loading entry 240, to promote combustion of the fresh refuse. An as outlet 251 for the ash produced from combustion of refuse is provided at the other end of the drum 212.

In use, refuse enters the drum 212 at 240, as combustion-promoting gas is delivered from tubes 239 and 239'. As the drum 212' is rotated, the refuse material is burnt and tumbles about in the lower region of the drums, deflecting from fins 216 on the inner surface of the drum 212. The arcuate partition 253 is effective to shield a major proportion of the drum 212 from the burning material, such that the burning material need only contact the drum 212 of fins 216 in the part of the chamber which is delimited by edge margins 254 and 255 of the partition 253.

Clearly various additional gas delivery pipes may be included, as desired, although it is preferred that gas delivery be effected at least from the bottom of the chamber and preferably also from one side of the chamber.

Claims (13)

1. An incinerator comprising a generally cylindrical chamber rotatable about an axis below which material is to be burnt and elongate apertured means entrant the chamber so as to direct a gas stream into space below said axis, the gas serving to promote combustion and/or to cool the chamber periphery.

2. An incinerator according to Claim 1 comprising heat shielding means spaced inwardly from the internal surface of the chamber.

3. An incinerator according to Claim 2 wherein the heat shielding means is of double-walled construction to allow passage of cooling fluid therethrough.

4. An incinerator according to Claim 2 or 3 wherein the heat shielding means are stationary and the chamber is rotatable about the heat shielding means.

5. An incinerator according to Claim 1 which includes walling or partition means delimiting part of the chamber to which burning is to be substantially confined.

6. An incinerator according to Claim 5 wherein the chamber includes arcuate heat shielding means having respective edge margins which constitute the said walling or partition means.

7. An incinerator according to Claim 5 or 6 wherein gas delivery means are arranged to direct gas into the part of the chamber to which burning is to be substantially confined.

8. An incinerator according to Claim 7 including gas delivery means arranged to direct gas downwards and/or sidewardly into material to be burnt.

9. An incinerator according to any preceding claim wherein the internal surface of the chamber is provided with surface formations for deflecting combustion material.

10. An incinerator according to Claim 9 wherein the internal surface of the chamber is.provided with spaced surface formations and gas delivery means are accommodated in at least some of the spaces defined by adjacent formations.

11. An incinerator according to claim 9 or 10 wherein the formations comprise axially spaced annular baffles.

12. An incinerator according to any preceding claim having an exhaust outlet and associated means for positively drawing gas to the outlet from the interior of the chamber.

13. An incinerator substantially as hereinbefore described and illustrated with reference to the accompanying Figures 1 to 8.