WO1992020967A1

WO1992020967A1 - Incinerator

Info

Publication number: WO1992020967A1
Application number: PCT/AU1992/000190
Authority: WO
Inventors: William Scholer
Original assignee: Scholer Incineration Co Pty Ltd
Priority date: 1991-05-10
Filing date: 1992-04-27
Publication date: 1992-11-26

Abstract

A natural draught incinerator (10) having a primary combustion chamber (16) joined to a stack (13) by means of a tortuous path. Positioned along said path are baffles (48) and a water trap (52). The water level (14) of the trap (52) is adjusted in order to control the flow of gas through the incinerator (10) and thereby control the combustion process in the combustion chamber (16). Sensors (65, 66, 67) are provided in the outlet passage (43) of the chamber (16), which sensors (65, 66, 67) via a pivotally mounted weir (60), govern the height of the water level (14) and therefore the cross-sectional area of the passage above the water level (14).

Description

INCINERATOR Field of the Invention The present invention pertains to waste incinerators and more particularly to a naturally forced draft incinerator having a tortuous flue gas passageway between the furnace and the stack, and which is and which is operable to control the flow rate of gas in order to control the rate of combustion and therefore the temperatures associated therewith.

Background Art The combustion furnace of a waste incinerator produces ash and flue gases. The flue gases have ash and particulate waste intrained in them. The need exists for an incinerator which economically and efficiently removes intrained solids from the flue gases. Still further industrial incinerators are provided with an artificial forced draft combustion air supply and are generally fed air at a continuous rate fed. These features can contribute to the incomplete combustion of the waste and promote toxic gas release.

Known commercial incinerators are generally complex and have large numbers of moving parts. This increases the alntenence costs as well as the capital expenditure in respect of the installation of the incinerator. Due to the complexity of the incinerators, excessive numbers of operating staff are required. Additional equipment such as fans is also required.

A still further disadvantage of known industrial incinerators, is the starved air mode at which they operate. These low temperatures create back pressures within the incinerator thereby inhibiting the flow of gases through the incinerator.

Known incinerators do not adjust spontaneously to the combustion requirements of materials having different calorific content which can constitute the waste being delivered to the combustion chamber. Still further, known incinerators do not respond to changing conditions within the incinerator between ignition and advanced combustion. Accordingly known incinerators do not operate at optimum temperature and performance, which can result in incomplete destruction of the waste, including semi-toxic and highly toxic material. Object of the Invention

The object of the invention is to provide an incinerator having a tortuous passageway between the furnace and the stack, which substantially ameliorates the above disadvantages.

SUBSTITUTE SHEET Summary of the Invention A natural draft incinerator is provided having a furnace and a stack. Interposed between the furnace and the stack is a tortuous flue passageway. The tortuous passageway includes a water trap. The water level within the trap is adjusted to control the flow rate of gas through the incinerator.

Brief Description of the Drawings Figure 1 is a schematic cross-sectional side elevation of an alternate embodiment of the incinerator of the present invention; and Figure 2 is a cross-sectional top plan view of the incinerator as viewed through lines Q-Q of Figure 2.

Best Mode and other Embodiments of the Invention As shown in the accompanying drawings, an incinerator 10 includes a tortuous passageway 11 between the furnace 12 and the stack 13. Waste material is introduced into the furnace through a vertically counter-weighted guillotine type door. The waste material (or other fuel) falls through a chute 15 and continues downward into the furnace combustion chamber 16. The incinerator 10 is loaded with a desired volume prior to or after ignition. Accordingly the incinerator is volumetrically loadable. The furnace is lined with a refractory material 17 such as high alumina fire brick laid in high alumina fire clay and may include extended joints to eliminate spoiling and thermal shock damage. Opposing walls of the combustion chamber 18,19 include venturi air cones 20. Two or more air cones 20 may be provided on each of the opposing walls. The air cones 20 may be pivotable or multi-directional and are open to atmosphere. The floor of the combustion chamber 16 is in the form of a discharge grate 21. The discharged grate includes two downward sloping, hinged sections 22 which together form a generally "V" shaped bottom which opens downwardly and from the centre 23. Waste may be automatically or manually fed through the guillotine door at the front of the unit, or through a gravity-drop chute which passes through the vaulted or arched roof of the primary combustion chamber. The combustion chamber 16 is normally filled to capacity with waste then ignited, either manually or automatically. The resulting partial vacuum in the combustion primary and secondary chambers causes a natural forced draft excess air entry through the multi-directional cones 20, of atmospheric pressure at high velocity which penetrates the burning material and feeds oxygen to the exiting combustion case. Primary air

SUBSTITUTESHEET (the remaining 10%) is introduced under the grates insuring final and complete combustion. The rate of combustion can be slowed by spraying water into the combustion chamber 16. Water or steam may also be sprayed into the incinerator 10, up to any location prior to the water trap 52. Rate slowing is advantageous in the combustion of highly volatile synthetic matter such as plastic and hazardous materials. The oxygen disassociated from the spray water and slower burn rate facilitates the treatment of certain types of toxic or pathological wastes and waste gases given off by plastics, chemicals and synthetics. After the combustion process is complete, the hinged grate 21 opens, resulting in the discharge of the remaining ash into an ash hopper and/or conveyor 25 located beneath the combustion chamber. Alternatively the remaining ash is manually raked out into bins.

As shown, the first ascending vertical passageway 32 includes a series of vertical ceramic or steel plates 43. The vertical passageway 32 leads into a first vaulted chamber 44 which preferably Includes an auxiliary fuel burner 45. The first vaulted chamber 44 leads through a descending and narrowing vertical passageway 46 and around a baffle 47 to an array of staggered and upright ceramic or metal plates 48. The staggered plates 48 are separated from the first ascending vertical passageway 32 by a partition 49 which also supports one end of the vertical plates 43. As seen more clearly 1n Figure 2, the vertical plates 43 are generally parallel with respect to one another, but the staggered plates 48 are not. Both sets of steel plates 43,48 are heated by the hot flue gases which pass over them. The plates 43,48 in turn, radiate and further heat the ash and entrained solids which pass in proximity to them or impinge on them. While the flow of flue gas over the vertical plates 43 is relatively laminar or uniform, the flow of flue gas around the staggered plates 48 is more turbulent owing to the staggered and non- parallel relationship of the plates 48. This further contributes to the efficiency and effectiveness of the combustion process with respect to the entrained solids. Flue gas which has passed over the staggered plates 48 is introduced through a second ascending vertical passageway 49 into a second vaulted chamber 50. The plates 43 and 48 burn carbon material passing the plates 43 and 48. The second vaulted chamber 50 also includes an optional auxiliary burner 51. The second vaulted chamber 50 directs flue gas downward through a second descending vertical passageway 51 toward a recirculating water collector 52. Note

SUBSTITUTE SHEET that the second descending passageway 51 narrows in the lower region 53, and that the side wall 54, like the baffle 47 includes both an inwardly tapering section 55 and an inclined bottom portion 56, which together contribute to the flow shaping and venturi effect of these portions of the tortuous passageway 11. Thus, flue gases are impinged on the recirculating water collector 52, whereby ash and solids are deposited into the water in the basin 57. Overflow from the basin is collected in a trough 58 and fed into external settling tanks 59 for further collection and disposal. After interaction with the recirculating water trap 52, the cleaned flue gases pass into the stack 13 for discharge into the atmosphere.

Preferably the above described incinerator operates within the range of 800°C to 1400°C.

Preferably, the cones 20 have a length approximately equal to the inlet (larger) diameter, with the outlet (smaller) diameter being approximately half the inlet diameter. These ratios may be varied by up to 20% without significant fall off in efficiency.

The water trap 52 has a water level 14 governed by the movable weir wall 60. The wall 60 is pivotally mounted via a shaft 61. An external motor 62 operates a linkage 63 to cause pivotting of the wall 60 to adjust the height of the water level 14. By adjusting the height of the water level 14 relative to the portion 56, the orifice opening 64 defined therebetween can be adjusted In area In order to adjust the flow rate of gas through the incinerator 10. The motor 62 is controlled by sensors 65, 66 and 67. The sensor 65 is responsive to temperature and detects the temperature of the gas entering the secondary combustion chamber provided by the chamber 44. The sensor 66 is HCL responsive while the sensor 67 is an opacity sensor. If any one of the parameters being monitored by the sensors 65 to 67, is outside of a particular range, the water level 14 is adjusted by movement of the weir wall 60. For example, when the incinerator 10 is initially ignited, it is advantageous to slow the rate of flow of gas through the incinerator 10 in order to retain heat within the incinerator 10. This is achieved by raising the water level 14 and reducing the area of the orifice opening 64. As temperatures rise within the incinerator 10, and the sensor 65 responds thereto, the water level 14 is lowered to permit the flow rate of gas through the incinerator 10 to increase. As various materials of different calorific value are encountered by the

SUBSTITUTE SHEET combustion process, the water level 14 is adjusted so that the temperature and treatment of the combustion process is maintained at an optimum level. The sensor 66 again will interact with the motor 62 to adjust the water level 14 to slow or increase the combustion rate down. Similarly, if the excessive carbon is being produced and detected by the sensor 67, the water level 14 is raised to slow the combustion rate. The sensors 65 to 67 could also operate sprays which deliver water into the combustion chamber 16 as discussed previously. The sprays would co-operate with the water level 14 to control the combustion rate. The above described preferred embodiment has the advantage of providing for the unrestricted flow of gases through the incinerator ameliorating problems in respect of back pressures. Still further, the above described incinerator 10 is responsive to varying combustion parameters such as temperature, and acidity and opacity of the gases exiting from the primary combustion chamber.

It should be appreciated that the above discussed means of controlling the gas flow rates through the incinerator control the combustion process as opposed to preventing natural gas flow through the incinerator. Still further the above described preferred embodiment has the capacity to run at the optimum temperature with respect to the materials contained in the combustion chamber.

SUBSTITUTE SHEET

Claims

CLAIMS :

1. An incinerator comprising: a combustion chamber; a stack; a tortuous passageway through which combustion gases pass from said chamber to said stack; a water trap having a water level defining at least part of said passageway; and means to control the height of said water level to vary the cross-sectional area of said passage at said water trap.

2. The incinerator of claim 1 further including central means to detect a condition of said gas, and wherein the control means is responsive to said sensor.

3. The incinerator of claim 2 further including water spray means to deliver water to the interior of said chamber, and wherein the flow rate of water passing through said spray means is controlled by said sensor means.

4. The incinerator of claim 1, 2 or 3 wherein the control means includes a weir, the height of which is adjustable to govern the height of said water level.

5. The incinerator of claim 4 further including settling tank means, and means to circulate the water between said water trap and settling tank means to extract ash and solid material from said water.

6. The incinerator of any one of claims 1 to 5 further including baffles in said passage.

7. The incinerator of any one of claims 1 to 6 further including a plurality of cones to deliver air to the interior of said combustion chamber.

8. The incinerator of any one of claims 1 to 7 further including a floor defining at least part of said chamber; and wherein said floor is openable to enable ash to be delivered from the interior of said chamber.

9. The incinerator of any one of claims 1 to 8 wherein said combustion chamber is a primary combustion chamber, and said incinerator includes a secondary combustion chamber downstream in the direction of travel of said gas, from said primary combustion chamber.

SUBSTITUTE SHEET

10. An incinerator substantially as hereinbefore described with reference to the accompanying drawings.

SUBSTITUTE SHEET