AU671321B2

AU671321B2 - An inlet for the delivery of a substance to be incinerated and a furnace having such an inlet

Info

Publication number: AU671321B2
Application number: AU52746/93A
Authority: AU
Inventors: Shigeru Saitoh
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-12-25
Filing date: 1993-12-24
Publication date: 1996-08-22
Anticipated expiration: 2013-12-24
Also published as: KR940015368A; SE9304272D0; JPH06193845A; KR0136736B1; SE9304272L; CA2110879A1; AU5274693A

Description

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION NAME OF APPLICANT(S): Shigeru SAITOH ADDRESS FOR SERVICE: DAVIES COLLISON CAVE Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

INVENTION TITLE: An inlet for the delivery of a substance to be incinerated and a furnace having such an inlet The following statement is a full description of this invention, including the best method of performing it known to me/us:- -1 a-

DESCRIPTION

FIELD OF THE INVENTION The invention of this application relates to an inlet for the delivery of a substance to be incinerated into a furnace, and to a furnace installed with the inlet, PRIOR ART In prior art furnaces, exhaust gases are generally removed by a chimney or expelled by a blow fan. Subsequently, where there is an open inlet for a substance to be incinerated, there exists an air flow from the inlet to the incineration chamber.

However, changes in the incineration process may cause a sudden reversal of 15 exhaust gas flow. In this situation, gases from the incineration chamber may flow to the inlet of the furnace. As the inlet provides for the delivery of substance to be incinerated, a dangerous situation can develop in relation to ignition of incoming substances. This can cause difficulties in the supply of substances to be incinerated.

To prevent reverse flow of the exhaust gas, the substance to be incinerated should be delivered continuously into the furnace and hence there must be disposed a device for continuously packing and supplying the substance to be incinerated into the inlet. When the inlet is packed with substance to be incinerated, reverse flow is suppressed.

Other disadvantages of furnaces of the prior art include generation of noxious and odorous gases, damage to the hearth caused by the incineration of certain kinds of substances, and incomplete combustion of substances.

SUMMARY OF THE INVENTION It is an objective of the present invention to provide a safe and efficient furnace having an inlet which prevents reverse flow of the exhaust gas and in which it is not necessary to supply the substance to be incinerated continuously.

Another objective of this invention is to provide a furnace which minimises 931223,pAopcr\gjnSAITO H.356,1 the emission of harmful or odorous gases, even if the substrate to be incinerated produces exhaust gases containing component' suc"- as HCI, SOx and NOx, and which further minimises the risk of damage to the bottom of the furnace by the flame or heat produced by combustion of plastic wastes having a high calorific value.

According to a first aspect of the present invention there is provided an inlet for delivering a substance to be incinerated into a furnace, the inlet comprising side walls, reverse flow suppressor means for suppressing the reverse flow of exhaust gas and at least one buffer disposed inside the side walls of the inlet, said at least one buffer being spaced from said reverse flow suppressor means and from said side walls of the inlet thereby providing a space between said at least one buffer and the side walls.

""BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a furnace having an inlet according to a first embodiment of the present invention; Fig. 2 shows an inlet according to a second embodiment of the present invention; Fig. 3 shows an inlet according to a third embodiment of the present S"invention; Fig. 4 shows an inlet according to a fourth embodiment of the present invention; and Fig. 5 shows an inlet according to a fifth embodiment of the present invention.

.DESCRIPTIONOF THE PREFERRED EMBODIMENT Embodiments of the present invention will be further explained in detail referring to the accompanying drawings.

Fig. 1 shows a furnace including an inlet for the delivery of the substance to be incinerated A. Also shown are side walls 4, a reverse flow suppressor part 3 and three buffers 5 disposed inside the side walls 4 of the inlet 1. Buffers 5 are secured by connecting members 6 so that the buffers 5 are not in direct contact with the side walls 4 or the reverse flow suppressor 3 and are spaced from the reverse flow suppressor 3 and the side walls 4 of the inlet 1, thereby providing a space between 931223,p:\oper\gjr4SAITOH.356,2 the buffers 5 and the side walls 4 of the inlet.

A lower part of the side walls of the inlet 1 forms part of the incineration chamber 7 and therefore it is preferable to line part of the side walls 4 with fireproof refractory) materials, at least where very high temperatures are generated.

A hearth particle inlet 8 is formed between inlet 1 and external wall 9.

Hearth particle inlet 8 may be adjoined to or separated from the inlet 1 and is in communication with an oblique furnace hearth 10. Hearth particles B flow as a layer cn the oblique hearth 10 and form a layered furnace particle bed 12.

The hearth particles B forming the particle bed 12 move downwardly across oblique hearth 10 under gravity but controlled by friction, so that there is maintained a constant bed formation as the particles descend, without reverse upward floating of particles.

.omo The upper surface of the hearth particle bed 12 forms a slope having a predetermined angle of rest depending on the quality, shape, and size of the particles 15 B. Particle bed 12 flows down to the bottom edge of the furnace hearth 10, which has a slope angle substantially the same as the angle of rest of the upper surface of the particle bed 12.

In the oblique hearth 10, especially towards its lower end, there is disposed air holes 11 which allow the supply of air for combustion in the furnace.

The substance A to be incinerated falls from the inlet 1 onto the particle bed 12 and is burned in the combustion zone 7 with the aid of air supplied through the combustion promoting holes 11.

The walls forming the combustion zone 7 are preferably covered with fireproof refractory) lining materials.

The substance or substances to be incinerated are incinerated in the combustion zone 7. The products of combustion mixwith the hearth particles moving downwardly as the particle bed 12 and form a mixture D.

The mixture D passes through a lower part of the furnace 13, and thence outlet 14, and onto a mixture removal means, preferably a movable plane member.

In this embodiment, the mixture removal means is a belt conveyor 15 and belt 16.

The mixture D falls onto one end of belt 16 which is mounted on the belt 931223,p:\oper\gjnSATOH.356,3 -4conveyor The mixture D is then moved toward the recovery box 17 as the belt 16 is activated and deposited into the recovery box.

The hearth particles are separated, if necessary, from the mixture D through a sieve, for recycling use.

Between the lower outlet 14 and tiu belt 16, a constant angle of rest is formed by the aforementioned mixed hearth particles D. This angle of rest of the mixed hearth particles is preferably substantially the same as that of the pure hearth particles B forming the particle bed 12 of the furnace.

The combustion mixture D delivered from the lower outlet 14 will never spread out of the area defined by the angle of rest of the combustion mixture D and the distance between the lower outlet 14 and belt 16. Subsequently, if the area of the belt is designed a little larger than the defined area, the combustion mixture D i'"'"does not overflow the sides of belt 16.

15 Further, the distance between the lower outlet 14 and the belt 16 may be designed to be changeable if needed.

Although in this embodiment, the movable plane member is indicated as a conveyor belt, the movable plane member may be a caterpillar or rotating table.

An exhaust gas extraction means is applied to the combustion zone 7.

The combustion gases rise up an exhaust chamber 19 lined with fireproof refractory materials and pass to a chimney or smokestack (not shown) via an exhaust .oo.oi pipe 20, a cooling wash tower 21, an exhaust pipe 22, and an extraction fan 23.

A portion of the high temperature combustion gases produced in the :...combustion zone 7 is recycled back to the combustion zone through the holes 11 disposed in the hearth 10 via conduit 25, circulating fan 26, and conduit 27. This recycled gas may be mixed with fresh air introduced from a fresh air intake 28 before entering the combustion zone 7. A greater amount of fresh air is introduced where necessary to promote combustion in the combustion zone.

The cross-section of the furnace may be any shape including a cylinder, a square, a quadriiateral or other shape. The cross-section of the inlet 1 is preferably a circle, an oval, a regular square, or a square, but can be any other shape having an opening at its center which allows the substance to be incinerated to descend 931223,p:\ oper\gjnSA ITO H.356,4 naturally by gravity.

The reverse flow suppressor 3 has an opening through which passes the substance to be incinerated. The reverse flow suppressor 3 is constructed to prevent reverse flow of the combustion gas or the produced exhaust gas toward the inlet.

In the embodiment of Fig. 1, the reverse flow suppressor 3 takes the form of a funnel shaped hopper having an opening at its center. In the embodiment of Fig.2 the reverse flow suppressor 3 includes a peripheral shoulder 32 disposed about the opening of the reverse flow suppressor 3. This embodiment also includes spaced baffles 31 disposed around the inner peripheral part of the side wall 4 of the inlet 1.

The buffers 5 have openings at their center through which the substance to be incinerated falls down by gravity.

S.:io The buffers are configured and positioned so that the gaps between the buffers 5 and the side walls 4 are relatively small, as is the space between the 15 uppermost buffer and the reverse flow suppressor part 3. The shapes of the buffers correspond to the shapes of the inlet 1 and side walls 4.

The buffers 5 may be used singly or plurally. Where a plurality of buffers are used, each of the buffers 5 may be formed in the same size and the same shape, as *shown in Fig. 1 and Fig. 2. Alternatively as shown in Fig. 3, the buffers 5 may be variously sized. The buffers 5 may be shaped in the form of circle, square, or other Ssection shape cylinder or annular member having an opening at its center.

The buffers 5 may take the form of a truncated hollow cone as in an upside down lamp-shade like shape as shown in Fig. 4 or an upright lamp-shade like shape as shown in Fig. 5. A buffer may also take the form of a plate having an opening at its center.

The size and the shape of the buffers 5 may be same or different and the buffers may be disposed in any order.

Further the buffers may have apertures if desired.

Fig. 2-Fig. 5 show various forms of reverse flow suppressors 3 and buffers Other embodiments of the reverse flow suppressor 3 and the buffers 5, which are not shown may be used. These include a plate having an opening at its center, and any combination of the aforementioned buffers and/or rev-erse flow suppressors 931223,p:\oper\gjnSAITOH.356,5 -6alone or in combination with other shapes.

The distance between the buffers 5 and reverse flow suppressor 3 may be fixed or variable.

To simplify the illustration, angle or bracket members for fixing the buffers are omitted in Fig. 2-Fig. The size of the opening disposed at the center of each buffer 5 is determined to allow the free fall therethrough of the substance to be incinerated. The size of the outer edge of each buffer 5 is smaller than the size of the inside diameter of the side walls 4 thus forming a space between the side walls 4 and the buffer 5 for allowing the reverse flow of the combustion gas.

When the substance to be incinerated enters inlet 1 and falls by gravity, it collides with the buffers 5 and imparts a physical shock to the buffers 5. It is oooo therefore preferable to fix each buffer member 5 firmly to the side walls through the connecting member 6, preferably by shock absorbing means.

15 Examples of substances to be incinerated are plastics which have a high calorific value, substances the burning of which produces odorous, noxious, or corrosive gases, such as HCI, SOx, and NOx, and general waste or any other *..**combustible materials.

Materials suitable for use as hearth particles B include crushed rocks, stones, comparatively coarse sands, pieces of iron, and other materials which are durable against the high temperature, and form voids therebetween to allow air flow through o oor S"the particle hearth bed 12. The mean diameter of the hearth particles may be from to 20cm, or more preferably from 1cm to .i :The inlet of this invention has been explained as applied to a furnace having a hearth particle bed, but it is not restricted to the explained embodiments. It is also applicable to other conventional furnaces.

That is to say, the objectives and advant'ges of this invention are achieved when it is applied to a conventional furnace not in tailed with a particle hearth bed but installed with conventional hearth bed, or to a furnace not fitted with an exhaust gas extraction system, or not fitted with a fresh air supply system.

The furnace is constructed such that when the substance A to be incinerated enters the inlet 1 of the furnace then it falls freely and evenly and readily reaches 931223,p:\opergjn,5A TOH.356,6 -7the combustion chamber 7.

Where abnormal combustion takes place the combustion chamber and reverse flow of the exhaust gas towards the inlet 1 of the furnace occurs, the reverse flow of the exhaust gas is dampened by the reverse flow suppressor 3 disposed at the inlet 1 of the furnace, and by the buffer or buffers 5 located within the inlet 1. Therefore the possibility of exhaust gas being forced out through the inlet is removed to significantly diminish.

As described, the air usually flows from the inlet to the combustion chamber by the aid of the reverse flow suppressor 3, the buffers 5, by forced extraction by the extraction fan, the circulating fan, and by the aid of the chimney.

As exhaust gas is substantially prevented from being blown out through the inlet 1, it is possible to deliver substance A to be incinerated intermittently, rather than continuously. This eliminates the need for a separate device to ensure continuous supply of substance A.

15 The hearth particles B supplied from the hearth particle inlet 8 fall by gravity, reach the oblique furnace bottom 10 and form a layer on this hearth. This layer is the particle bed 12. This particle bed 12 slides down the slope of the furnace bottom the surface of the particle bed forms a slope having an angle of rest depending on the hearth particles used.

The substance A to be incinerated on the hearth particle bed 12 is incinerated .i by air introduced from the air intake 28 for promoting combustion. This air enters S"the combustion chamber via apertures 11 and through the hearth particle bed 12.

Air also enters via the inlet 1. By the action of air entering via holes 11, less of the :heat produced by the incineration of the substance A will be transmitted to the furnace bottom The combustion promoting air introduced from the air intake 26 is mixed with exhaust gas from the conduit 25 kept at high temperature. Consequently the combustion efficiency is increased.

In the combustion zone 7, the substance A is incinerated producing exhaust gas and the products of combustion C. The products C are mixed with the hearth particles B to form the combustion mixture D.

The combustion mixture D falls by gravity through the outlet 14 disposed at 931223,p\oper\gj,AITOH.356,7 -8the bottom 13 of the furnace at the belt conveyor The combustion mixture D is deposited at one end of the belt conveyor and is carried to the other end of the belt conveyor and dropped into the combustion mixture container 17. The combustion mixture D may be separated by the sieve to obtain recycled hearth particles if desired.

The combustion mixture D, a mixture of the hearth particles B and the combustion products C, is deposited on one end of the belt conveyor and forms a stable slope of angle f rest 'etween the outlet 14 and the belt conveyor 16.

Therefc" 2, even if the belt 16 stopped for some reason the combustion mixture D stays still and the combustion mixture may not flow and drop out of the belt.

The invention has been explained in relation to a furnace having a hearth particle bed but as is clear from the description of this specification, the invention "of this application is applicable to other conventional furnaces and the functions and the advantages of this invention may there be accomplished.

EMBODIMENTS

A detailed embodiment of the invention, will now be explained in more detail.

The furnace is gen-ially in accordance with Figure 1.

The inside cross-section of the inlet for the substance to be incinerated is

M

2 and the shape of the inlet is a rectangle. The length of the side walls is meter.

9*9999 The reverse flow suppressor 3 is disposed at the top edge of the sidewalls 4, and extends inwardly and downwardly at an angle of 38 degrees with respect to horizontal to 0.35 meter below the top of the sidewall, extending inwardly 0.45 meter from the sidewall.

The inside diameter of the opening of the reverse flow suppressor is 0.6 meter.

The first buffer 5 is a square shaped ani, :.ar member having a square opening at its center. The outer width is 1.1 meter, the inner width is 0.6 meter and the height is 0.2 meter. This buffer 5 is spaced 0.4 meter below the lower end of the reverse flow suppressor 3 and spaced 0.2 meter from the sidewalls being supported from the reverse flow suppressor 3 and fixed by the connecting member 6.

931223,p:\oper\gj5SAITOH.356,8 -9- The second buffer 5 is disposed 0.25 meter below the first buffer 5, and spaced 0.2 meter from the sidewalls 4. The third and fourth buffers 5 are similarly disposed 0.25 meters below the previous buffer in each case and spaced 0.2 meters from the sidewalls 4. The buffers are fixed relatively to each other and to the sidewalls by the connecting members 6.

The effective opening of ihe inlet is a 0.6 x 0.6 meter square opening, the average velocity of the combustion air introduced from this opening is 0.2 Nm/sec.

Therefore the volume of the air introduced into the combustion chamber is 0.072 Nm3/sec.

The substance to be incinerated is typically fed at a rate of about for general waste.

The air at 300 "C flows from the bottom of the furnace at a rate of 0.33 Nm 3 /sec, the combustion is promoted with the heat flow.

Under these conditions the combustion occurs.

15 When the combustion ash or the exhaust gas are forced in the reverse dt-ection, the reverse exhaust gas or ash flow is deflected to the lateral direction at the lowest buffer. If not deflected fully at the first buffer, subsequent buffers may deflect the flow to the lateral direction. When deflected, the ash or exhaust ga. Is returned to the combustion chamber through idle spaces disposed along the side walls of the furnace. Thus reverse flow is generally prevented.

On the other hand, prior art furnaces operated under the same condition s S' described above can be difficult to operate because the combustion ash or th:e exhaust gas may be forced back against the intake air flow every few seconds.

ADVANTAGES OF THE INVENTION The reverse flow suppressor and the buffers absorb reverse flow of exhaust gases. Thus, it is not necessary to accumulate the substance to be incinerated in the inlet of the furnace for preventing the exhaust gas reverse flow. It also becomes unnecessary to supply the substance to be incinerated continuously. Further, it becomes unnecessary to use a packing device for forcing the substance to be incinerated into the inlet, which is usually used in this type of incineration furnace.

As the substance to be incinerated may be supplied into the combustion 931223p:\oper\gjnAIOH.356,9 chamber periodically the substance can remain in tl: mbustion chamber for a longer period of time, and more complete combustion is accomplished. Even if the furnace is a small incineration furnace, it is possible to obtain a higher combustion efficiency incineration furnace.

Furthermore this furnace provides a safe and efficient furnace which prevents scattering harmful, noxious or odorous gases, even if the substrate to be incinerated produces exhaust gases containing, for example, HCI, SOx and NOx. The furnace also reduces damage to the bottom of the furnace by the flame or the heat produced by combustion of plastic wastes having a high calorific value.

931223,p:\oper\ gjnAirro H.356,

Claims

1. An inlet for delivering a substance to be incinerated into a furnace, the inlet comprising side walls, reverse flow suppressor means for suppressing the reverse flow of exhaust gas and at least one buffer disposed inside the side walls of the inlet, said at least one buffer being spaced from said reverse flow suppressor means and from said side walls of the inlet thereby providing a space between said at least one buffer and the side walls.

2. A furnace comprising an inlet according to claim 1 and further including: side walls extending below said inlet; a hearth particle inlet; further side walls extending below said hearth particle inlet; *means defining a hearth disposed under said walls, on wkich hearth particles 15 flow and form a hearth particle bed, the surface of said particle bed having a slope whose angle is an angle of rest of the hearth particles; a lower part of the side walls, and the hearth defining an incineration zone; :0 an incineration mixture outlet disposed adjacent to the incineration zone; a movable plane member disposed under said outlet which removes the incineration mixture from the furnace, whereby the incineration mixture forms a slope having a slope angle of an angle of rest of the mixture of the hearth particles and incineration products; exhaust gas extraction means; and incineration air supply means. 931223,p:\oper\gjnSAITOH.356,11 4 0 12

3. An inlet for a furnace substantially as hereinbefore described with reference to the drawings. -teps- features,-composit-ions--nd-cmpeu-nds-ise4e3scdhri---ee to or indicated in the specification and/or claims p ication, individually or collectively, and. combinations of any two or more ofsaid steps or 0* 0* DATIED this TWENTY FOURTH day of DECEMBER 1993 Shigeru SAITOH by DAVIES COLLISON CAVE Patent Attorneys for the applicant(s) S 0* S S S 55 S S I ABSTRACT The invention of this application provides an inlet for delivering a substance to be incinerated into a furnace, the inlet comprising side walls, reverse flow suppressor means for suppressing the reverse flow of exhaust gas and at least one buffer disposed inside the side walls of the inlet, said at least one buffer being spaced from said reverse flow suppressor and means from said side walls of the inlet thereby providing a space between said at least one buffer and the side walls. Also provided is a furnace utilising said inlet for substance and further comprising a movable layered heath particle bed, the surface of the particle bed having a slope whose angle is the angle of rest of the hearth particles. 6 *a 931224,p\Aper\gjnSAITOH.356,12