WO1994007087A1

WO1994007087A1 - Plant for incinerating waste material

Info

Publication number: WO1994007087A1
Application number: PCT/DK1992/000279
Authority: WO
Inventors: Siegfried Binner
Original assignee: Volund Ecology Systems AS
Current assignee: Volund Ecology Systems AS
Priority date: 1992-09-15
Filing date: 1992-09-15
Publication date: 1994-03-31
Anticipated expiration: 1995-03-15
Also published as: AU2773992A

Abstract

In a refuse-incinerating plant of the kind comprising: a) a rotary kiln (1); and b) an after-burning device (4, 7) situated at the material-discharge end (2) of said rotary kiln (1) and having means for supplying air (11) for the after-burning process and means (10) for removing burned-out refuse, the novel features are: c) that said after-burning device comprises at least one grate (7) adapted to move material received from said material-discharge end (2), at least part of said grate (7) being placed below said material-discharge end (2); and d) that said means for supplying air (11) for the after-burning process is/are adapted to introduce said air above and/or below said grate (7). With this arrangement, highly economical incineration of e.g. hospital waste containing infectious material is achieved without risk of some of the material not being completely sterilized.

Description

PLANT FOR INCINERATING WASTE MATERIAL

TECHNICAL FIELD

The present invention relates to a refuse-incinerating plant of the kind set forth in the preamble of claim 1.

BACKGROUND ART

The international patent application WO 89/09364, vide esp. Figs. 7-9, describes a refuse-incinerating plant comprising a rotary kiln 33 discharging into a slag shaft or com¬ bustion shaft 35 or 16, to which secondary air for burning the unburnt residue from the rotaty kiln is supplied.

The use of such a slag shaft or combustion shaft does, however, entail a risk of caking of the slag coming from the rotaty kiln, with consequent disadvantages, such as an incomplete combustion of the material in those parts of the shaft, in which the air current is slowed down by caked or lumpy material, and - not least - difficulties in removing the slag from the shaft.

DISCLOSURE OF THE INVENTION

It is the object of the present invention to provide a refuse-incinerating plant of the kind referred to above, with which it is possible to ensure a substantially more complete burning-out of all components of the waste material to be incinerated than hitherto possible, while at the same time avoiding caking of the burnt material with the consequent disadvantages mentioned above, and this object is achieved with a plant, according to the present invention also exhibiting the features set forth in the characterizing clause of claim 1. Thus, the feature set forth in item c of claim 1 ensures that the material coming from the rotary kiln is kept in constant movement until it leaves the grate, thus preventing any caking, and - due to the feature set fort in item d - at this point the combustion will be complete, leaving no unburnt or un-sterilized residue likely to cause problems, such as in the case of surgical waste, that may contain disease- carrying material.

Advantageous embodiments of the plant according to the present invention, the effects of which are explained in the following detailed portion of the present specifi¬ cation, are set forth in claims 2-5.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present specifi¬ cation, the present invention will be explained in more detail with reference to the drawings, in which Figure 1 is a vertical longitudinal sectional view of the discharge end of a rotary kiln constituting a part of an exemplary embodiment of a plant according to the invention, the sectional plane being indicated by the line I-I in Figure 2, and Figure 2 is a vertical transverse sectional view of the part shown in Figure 1, taken along the plane shown by the line II-II in Figure 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The rotary kiln 1, of which only the discharge part 2 is shown, is in a well-known manner adapted to be rotated about a slightly inclined axis 3, and - likewise in a well-known manner - to support the burning of waste material 5 having been introduced at its inlet end (not shown) . The rotary kiln 1 discharges the waste material 5, which may or may not be completely burned-out after having passed through the kiln, into the lower part of an after-burning chamber 4, as indicated by the arrow 6 falling down onto an inclined grate 7.

In the exemplary embodiment shown, the grate 7 is connected to means (not shown) for actuating the grate 7 in a manner to facilitate the movement of the material received from the rotary kiln 1 towards the lower end of the grate, from where it falls down as indicated by an arrow 9 onto a diagrammatically indicated conveyor 10, with which the material is conveyed to e.g. a loading station (not shown) for lorries or railway waggons with a view to transporting the material to some place where it may be deposited or recycled. Preferably, the grate 7 is of the kind described in GB patent No. 2,120,764, the contents of which should be regarded as being included in the present specification by the present reference.

Air for combustion for the material moving along the grate 7 is preferably supplied from below the grate as indicated by an arrow 11, so as to reduce the tendency for small particles to fall down between the bars of the grate before they are completely burnt-out.

The direction 12 of movement of material on the grate 7 is preferably opposed to the direction 13 of movement of the lower part of the rotary kiln 1, thus ensuring that the material 5 will fall down onto the grate 7 as high up as possible on the latter and hence move through a maximum distance on it.

In operation, the operating parameters, such as the input of waste material in tons per hour, the supply of air for primary and secondary combustion in cubic metres per hour and the speed of rotation of the rotary kiln 1, are ad¬ justed to give nearly complete combustion at the exit from the kiln 1, the combustion process being completed on the grate 7.

It is, of course, possible to adjust the operating para¬ meters so as to give complete combustion at the exit from the rotary kiln 1 and to dispense with the grate 7, but tests have shown that this would result in a reduction in throughput and a consequent reduction in revenue consider¬ ably costlier than adding the grate 7 to the plant.

Tests have also been conducted with a grate placed upstream of the rotary kiln, but the results have shown that such a plant is unsuitable for incinerating e.g. surgical waste from hospitals containing infectious matter, as small particles of the material tend to fall through the upstream grate before having had time to be heated to safe steril¬ izing temperatures.

LIST OF PARTS

Claims

C L A I M S

1. Refuse-incinerating plant of the kind comprising a) a rotary kiln (1) , and b) an after-burning device (4,7) situated at the material-discharge end (2) of said rotary kiln (1) and having means for supplying air (11) for the after¬ burning process and means (10) for removing burned- out refuse, characterized in c) that said after-burning device comprises at least one grate (7) adapted to move material received from said material-discharge end (2) , at least part of said grate (7) being placed below said material-dis- charge end (2) , and d) that said means for supplying air (11) for the after¬ burning process is/are adapted to introduce said air above and/or below said grate (7) .

2. Plant according to claim 1, characterized in that said means to supply air (11) for the after-burning process is/are adapted to introduce at least the major proportion of said air below said grate (7) .

3. Plant according to claim 1 or 2, characterized in that said grate (7) is inclined downwardly towards its discharge end.

4. Plant according to any one or any of the claims 1-3, characterized in that said grate (7) is adapted to be vibrated or shaken or otherwise actuated in a manner to produce or facilitate movement of said material.

5. Plant according to any one or any of the claims 1-4, characterized in that said grate (7) is placed transversely of the axis (3) of said rotary kiln (1) and adapted to support or cause movement of material received therefrom in a direction (12) opposite the direction (13) , in which the lower part of the rotary kiln (1) moves during rotation thereof.