AU690286B2 - Method of incinerating and melting wastes and apparatus therefor - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICA~TION STANDARD PATENT Applicanit: Shinroku NISHIYAMA Invention Title: METHOD OF INCINERATING AND MELTING WASTES AND APPARATUS THEREFOR The following statement is a full description of this invention, including the best method of performing it known to me/us: -2- METHOD OF TREATING WASTES AND APPARATUS THEREFOR Background of the Invention Field of the Invention The present invention relates to a method of treating wastes and apparatus therefor, and particularly to a method and apparatus for treating combustible material, such as plastic products, paper products, woods, or rubber products and incombustible material including metal products.

Prior Art In recent times, the amount or urban waste has greatly increased due to a change of life style and a general movement of the population toward towns and cities.

An important problem in the disposal of waste lies in reducing its volume. Another problem often encountered is that urban waste nowadays often includes harmful materials.

Because harmful materials generally efflux from the waste, when simply buried under the ground, it has become common practice to incinerate the waste.

20 Typically, the ash of urban waste, including that known as fly ash is collected by a bag-filter of a collector and is generally disposed of by being buried underground either under reclaimed land or under construction sites or the like prior to civil engineering and construction work such as, for example, concrete work.

However, ashes are generally fine powders which absorb dioxins and other residue of incineration often includes incombustible heavy metals, and therefore there are problems in transferring such ash and residue, not the least of which include transportation, handling and treatment costs.

Additionally, there is a high possibility that the ash may be scattered in the wind during treatment and transfer.

Further, where ash and residue are simply buried underground, harmful materials included in, adsorbed or absorbed to the ash are drawn out therefrom by rain and RA4 underground water thereby causing public pollution.

S:P19711:15/1/98 3 Therefore, it is necessary or at least desirable that disposal of ash should be carried out with care.

The overall quantity of ash and residue is increasing quickly even though wastes are disposed of by incineration to reduce their volume, simply because the volume of urban waste is increasing too rapidly. Further, where ash and residue are simply buried underground, harmful materials retained in the ashes are likely to be drawn out due to rain and underground water.

Recently, laws and rules concerning disposal of urban and industrial wastes have been enacted, which appear to S•require waste be disposed of via a second treatment after incineration.

As a method of further decreasing the volume of ash and residue and resolving the problem of harmful materials being o drawn out, it has been proposed to melt the ash and residue.

Proposed methods of melting the ash and residue have included the use of plasma-electric melting, high frequency electric melting, and heat melting by burners.

20 It has been found that it is technically difficult to use an electric furnace since the waste to be incinerated and melted may generally include nonferrous materials.

Large scale plasma-electric furnaces are very expensive and have high installation costs.

Therefore, it has been proposed to provide a method of melting ashes by means of conventional heat furnaces having a burner which uses, for example, gaseous, liquid or solid fuel. Such burner type heating means has become popular recently because it may generate high temperatures, may have high heat efficiencies, low running costs and easy burning control.

The burner may use an LPG, an NLG or other fuels, and the air for burning the fuel may be supplied by means of an air compressor such as a centrifugal turbine pump or a vane pump and them mixed with the fuel.

This manner of combustion may generate a high S:P19711:15/1/98 pe~s* ~aaRerrrraau~---~11--- 4 temperature which melts ashes, but it is difficult to control generation of a CO gas. Generation of CO gas means that dioxins, which are closely connected with CO gas, cannot be controlled.

Additionally, this latter method is based on the concept that incineration of wastes is generally carried out in a process which is quite distinct from the melting process of the ash. As a result, there may be additional problems such as, for example, that it generally is 10 necessary to provide two distinct remotely located disposing e.

installations, one for incinerating the wastes and the other for melting the ashes thereof and that the costs for transferring of the wastes and ashes and also the fuel costs become high thus making the method very expensive.

Further, the molten waste or slag is fragile after cooling and therefore there is no ready way to dispose of it :except, for exalmple, to take it to reclaimed land and bury it under the ground.

SUMMARY OF THE INVENTION An object of the present invention is to address one or more of the above identified problems of the prior art.

Preferred embodiments of the present invention may facilitate a reduction in the volume of wastes through treatment with a low cost of fuel, may provide high temperature resolution of the dioxin problems and may provide easy disposal of the molten waste after vitrification.

The present invention provides a method of treating wastes comprising the steps of: charging a first batch of wastes into a rotary furnace through an opening provided in one end of said rotary furnace; incinerating said batch at a temperature from 800 0 C to 1200 0 C by means of an oxygen burner, using an oxygen gas R having a density of more than 50%, and a fuel, so as to S:P19711:15/1/98 I reduce the volume of the batch of wastes; then charging an additional batch of wastes into said rotary furnace through said opening and incinerating said additional batch in the same way as the first batch, then, if necessary, repeating the previous step of charging and incinerating an additional batch one or more times, until a predetermined quantity of wastes has been incinerated into ash and residue and accumulated in the furnace, then melting the ash and residue accumulated in the furnace 10 at a temperature of more than 16000C to form molten material and discharging the molten material from an opening provided S"in an opposite end of the furnace for disposal and drawing exhaust gases generated during the incineration and melting steps from said opening on said opposite end of the furnace and directing the exhaust gases to a dust collector for cleaning.

The present invention also provides a method of treating wastes comprising the steps of: charging a first batch of wastes into a rotary furnace 20 through an opening provided in one end of said rotary furnace; incinerating said batch at a temperature from 8000C to 12000C by means of an oxygen burner, using an oxygen gas having a density of more than 50%, and a fuel, so as to reduce the volume of the batch of wastes; then charging an additional batch of wastes into said rotary furnace through said opening and incinerating said additional batch in the same way as the first batch, then, if necessary, repeating the previous step of charging and incinerating an additional batch one or more times until a predetermined quantity of wastes has been incinerated into h and residue and accumulated in the furnace, then transferring the accumulated ash and residue to a melting furnace then melting the transferred ash and residue in the melting furnace at a temperature of more than 16000C S:P19711:15/1/98 6 o o o to form molten material for vitrification and discharging the molten material frem the melting furnace and drawing exhaust gases generated during the incineration and melting steps from an opening in the melting furnace and from an opening in an opposite end of the rotary furnace and directing the exhaust gases to a dust collector for cleaning.

It is preferred that the method further comprises the step of: charging soda ash (Na 2

CO

3 into the furnace during the melting step.

It is also preferred that the method further comprises the step of: charging a solid fuels selected from cokes, coal and charcoal in the form of powder or lump into the furnace prior to the incineration step and/or the melting step for assisting incineration and/or melting.

Preferably the charging step is enabled by means of waste throwing means.

The present invention extends to an apparatus for treating wastes comprising: a rotary furnace rotatable about a longitudinal axis thereof and tiltable about a horizontal axis which intersects the longitudinal axis at right angles, said rotary furnace having an opening at each respective end thereof, charging means for sequentially supplying discrete batches of wastes into the rotary furnace through one of said openings thereof, to enable sequential charging and incineration of discrete batches of wastes for accumulation of a predetermined quantity of ash and residue from incineration in the furnace; an oxygen burner using an oxygen gas of 50% density and a fuel, provided at said one opening of the rotary furnace to open and close said one opening thereof, said burner being constructed to melt the accumulated ash and residue at r: h /ij' r )A4 K P C

T.

S:P19711:15/1/98 o -I I~B~-~PUUB- 7 a temperature of more than 1600 0 C for vitrification, and a dust collector connected to an exhaust duct which is connected to another of said openings of the rotary furnace for cleaning exhaust gas generated through incineration and melting processes within the furnace.

It is preferred that soda ash (Na 2

CO

3 is charged into the furnace to mix with the waste during melting.

It is also preferred that the fuel comprises a solid fuel selected from coke, coal and charcoal in the form of powder or lump, and wherein said fuel is charged into the furnace prior to the incineration step or the melting step ololo S"to assist incineration and/or melting.

It is further preferred that the apparatus further Scomprises a crusher for crushing waste disposed upstream of charging means.

Preferably the charging means comprises a waste o• ••throwing means.

The present invention further extends to an apparatus for treating wastes comprising: 20 a rotary furnace rotatable about a longitudinal axis thereof and tiltable about a horizontal axis which intersects the axis at right angles said rotary furnace having an opening at each respective end thereof, charging means for supplying batches of waste into the rotary furnace through one of said openings thereof, to enable sequential charging and incineration of the waste discrete batches for accumulation of a predetermined quantity of ash and residue from incineration in the furnace; an oxygen burner using an oxygen gas of 50% density and a fuel, provided at said one opening of the rotary furnace to open and close one opening thereof, a melting furnace for receiving said accumulated ash and residue from the rotary furnace and for melting same, a melting oxygen burner using an oxygen gas of density and a fuel, provided with the melting furnace and S:P19711:15/1/98

I

ul lmar~- 8 constructed to melt said accumulated ash and residue of the waste received from the rotary furnace at a temperature of more than 1600'C, for vitrification; a dust collector connected to an exhaust duct which is connected to another of said openings of the rotary furnace and another exhaust duct which is connected to the opening of the melting furnace for cleaning the exhaust gas generated through incineration and melting.

According to preferred aspects of the present 0 invention, it becomes possible not only to charge and incinerate wastes by means of an oxygen burner using an oeeee S"oxygen gas of 50% density, so as to reduce their volume, but by sequentially charging and incinerating small batches in the furnace, it is possible to accumulate ash and residue to a predetermined quantity prior to melting them in the furnace.

Utilisation of an oxygen burner using an oxygen gas of 050% density for the incineration of the wastes, may not only promote more complete incineration of the wastes, but may oo also increase the density of oxygen in the atmosphere of the rotary furnace thereby producing an exhaust gas which has a low density of CO gas. Additionally, dioxins are being resolved at high operating temperatures from 8000C to 12000C. Therefore, it may be possible to control dioxins even though the exhaust gas is discharged into the air through a dust collector.

Further, repeated charging and incineration of the small batches of wastes may make it possible not only to carry out reduction of their volume, but also to preheat the rotary furnace with combustible wastes, particularly any kinds of plastic rubbish having a high calorific power, so as to save fuel costs associated with raising the temperature of the rotary furnace to that suitable for melting the ashes of the wastes.

Furthermore, by utilising an oxygen burner which may L\ generate very high operating temperatures, it may become S:P19711:15/1/98 i'- 9 possible to heat and melt the ash and residue which have been accumulated in the furnace, to a temperature of more than 1600 0 C, thereby to vitrify same. Soda ash is generally added to the melt prior to vitrification. During melting, the provision of an oxygen burner using an oxygen gas of density, enhances the level of oxygen density in the rotary furnace thereby lowering the level of CO in the exhaust gas.

This means that it may be possible to reduce the quantity of or prevent harmful materials generally found in the exhaust :0 gas, which are produced due to the CO gas, from discharging via the dust collector.

oo* Incombustible materials other than the ash and residue, such as metal, may be melted at very high temperatures and .involved in the vitrified ashes.

Preferred embodiments of the present invention have the advantages of reducing the volume of the waste by charging and incinerating sequentially discrete batches of waste in the furnace until a predetermined quantity of ash and residue accumultes therein and then said accumulated ash 20 and residue is melted. This operation utilises a single rotary furnace into which small batches of waste are incinerated sequentially and this provides savings in heating costs of the rotary furnace in that the calorific power of the waste is used to raise the temperature within the rotary furnace to high temperatures (generally exceeding about 1600 0 C) generally used for the melting step.

Further, since incineration and melting of the waste is carried out by means of an oxygen burner using an oxygen gas of 50% density, it may be possible not only to incinerate the fuel (for example an LPG) completely, but also to reduce the generation of CO by increasing the density of oxygen in the rotary furnace so as to prevent production of dioxins and resolve the dioxins through the incineration and melting at a very high temperature so that scattering of the harmful materials in the ash may be prevented.

I Furthermore, the ash and residue may be vitrified at a S:P19711:15/1/98 -L I B~IIBI~T~L" 1~ 10 very high temperature (about more than 1600 0 C) and when such ,itrified waste is buried underground, any harmful materials therein are unlikely to discharge into the ground due to rain and underground water.

Other advantages of the present invention will be understood from the description of the embodiment on the basis of the drawings.

BRIEF DISCRIPTION OF DRAWINGS 10 The drawings show a preferred embodiment of a method of treating wastes and an apparatus therefore, wherein: 0Figure 1 is a vertical view of an arrangement plan of 0* the apparatus for treating waste according to a first embodiment, Figure 2 is a sectional side view of a rotary furnace o according to the first embodiment, Figure 3 is a front view of the apparatus for treating waste according to a second embodiment, Figure 4 is a plan view of the apparatus for treating 20 and melting waste according to the second embodiment.

Figure 5 is a front view showing operations of a rotary furnace and a melting furnace according to the second embodiment, Figure 6 is a side view of the rotary furnace and le melting furnace according to the second embodiment, Figure 7 is a sectional view of an important portion of the rotary furnace according to the second embodiment, and Figure 8 is a front view showing operations of the melting furnace according to the second embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS A first embodiment of a method of treating waste and apparatus therefor according to the present invention will be described in detail with reference to the drawings.

A method of the invention comprises the steps of charging a first batch of waste, by waste throwing means, in S:P19711:15/1/98 lli^~l ~TI 11 the form of a waste thrower 3 from one opening la of openings la and Ib provided at each ojective end of a rotary furnace 1, incinerating the batch of waste at a temperature from 800 0 C to 1200 0 C, by means of an oxygen burner 2 using an oxygen gas having a density of more than and a fuel such as an NLG or an LPG, so as to reduce its volume, charging an additional batch of waste and incinerating said additional batch, and if necessary repeating the previous steps several times, until a 0 predetermined quantity of waste has been incinerated into ash and residue and accumulated in the furnace, thereafter •melting the accumulated ash and residue of the incinerated waste pooled in the rotary furnace 1 by means of the oxygen burner 2 at a high temperature of more than 16000°C, so that the melted ash and residue may be vitrified, discharging the vitrified ash and residue from another opening Ib of the rotary furnace 1 provided at the opposite end of the furnace for disposal, and introducing an exhaust gas generated in the incinerating and melting processes from said another 20 opening Ib of the rotary furnace 1 to a dust collector 7 for cleaning the gas.

It is preferred that the melting temperature is more than 1600°C, in order to vitrify the ash and residue completely, but it is sufficient that the temperature reaches around the said value since vitrification conditions vary.

It is also preferred that materials such as, for example, soda ash (Na 2 C0 3 glass collets, and limestone, be charged to mix with the waste at this melting stage so as to achieve a good vitrification.

In the above method, it is possible to charge at least one solid fuel such as, for example, coke or charcoal at the time of charging the waste.

The use of the solid fuel in combination reduces consumption of oxygen and LPG at the time of incineration and melting of the waste.

5:P19711:15/1/98

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12 Generally oxygen and LPG are expensive and hence the overall costs may be reduced. Further, it is not necessary to raise the temperature of the waste above that for incineration other than to the temperature for melting.

Of course, the solid fuel may be utilised in the melting process as an assistant energy source in order to raise the temperature of the rotary furnace and ash.

Now, the apparatus for treating waste according to a preferred embodiment of the invention will be described.

Figure 1 shows an arrangement plan of the apparatus and Figure 2 is a sectional side view of the rotary furnace.

The numeral 1 denotes a rotary furnace 1 having a body of substantially cylindrical cross-section and its detailed construction is as shown in Figure 2. The rotary furnace 1 15 has openings la and ib at respective ends thereof, is rotatable about a central longitudinal axis thereof and is tiltable about a horizontal axis which is substantially to the central axis (see the phantom lines in Figure The inside wall of the rotary furnace 1 is lined with firebricks S 20 which have a heat resistance temperature of more than 1600 0

C.

As shown in Figure 1 (omitted in Figure an oxygen burner 2, which uses an oxygen gas of 50% density and a fuel, is provided at the opening la of the rotary furnace 1 to open and close the opening la. The construction of the burner 2 is well known and therefore its detailed description is omitted here. Tilt of the rotary furnace 1 is carried out in order to discharge the molten and vitrified waste from the opening lb after the melting operation is completed. The oxygen burner 2 is removed from the opening la when the materials including the waste and additives are thrown into the rotary furnace 1. The numeral ic denotes rails for supporting rotation of the rotary furnace i.

The numeral 3 denotes waste throw means in the form of FA a waste thrower for transferring and supplying waste into S:P19711:15/1/98 13 the rotary furnace 1 when the oxygen burner 2 opens the opening la.

The waste thrower 3 is constructed to mix and throw soda ash, limestone, glass pellets and other materials including ash and residue of waste transferred from other waste incineration locations.

Further, as shown in Figure i, the waste thrower 3 is constructed so as to move from a position facing the opening la of the rotary furnace 1 to a waste supplying position for receiving the waste, and to throw the waste received therein as it is inclined by means of an air cylinder, into the S: rotary furnace 1 which has been tilted so that the opening la faces upwardly.

The numeral 4 denotes a bucket lift for supplying waste 15 to the waste thrower 3 when positioned in the waste supplying position. Beneath the bucket lift 4, a crusher is arranged so that the waste conveyed by a dump truck may be thrown in the crusher 5 and that the crushed wastes may be supplied to the bucket 4.

20 A duct faces the opening lb of the rotary furnace 1 and exhaust gas is directed to a cooling tower in the form of a water cooling tower 6. After the exhaust gas is cooled in the cooling tower 6, it is directed to a dust collector 7.

Between the cooling tower 6 and the dust collector 7, a powder supplier 8 adds, for example, slaked lime to the exhaust gas so as to cause a reaction between the slake lime and some constituents of the exhaust gas, for example, S02.

The dust collector 7 is of a type having a bag-filter, the construction of which is well known, and therefore its detailed description is omitted here.

The waste materials for treatment are urban wastes (combustible and incombustible materials), their ashes, shredder dust (such as automobile) and so forth.

As mentioned above, since heat in the rotary furnace 1 is maintained throughout the operation in which discrete RAZ, batches of waste are thrown, incinerated and accumulated, S:P19711:15/1/98 ~IIIPQI III IIIL11~~1- 14 the fuel cost for heating the rotary furnace 1 at a high temperature for melting can be reduced by 30%-40%.

Next, a second embodiment of the invention will be described.

In the second embodiment, the furnace for incineration and melting is separated. Figures 3 and 4 show the apparatus for incineration and melting. Numeral 101 denotes a rotary furnace and its detailed construction will be described hereinafter on the basis of Figures 5 through 7.

The waste materials for treatment are, for example, urban waste, the ashes thereof, shredder dusts (automobile scrap), and sludge or ooze in the river and sea. Figure 6 shows a Se:: plan view of the apparatus for incinerating and melting the waste and Figure 8 shows a state in which the molten material or slag is discharged from the melting furnace.

As shown in Figures 3 and 4, the numeral 103 denotes a pre-duster to which the exhaust gas from the rotary furnace 101 is provided to enable the dust in the exhaust gas to be removed thereby. The pre-duster 103 is of well known 20 construction using a mesh. The numeral 104 denotes a first water cooled cooling tower where the exhaust gas passing through the pre-duster 103 is cooled.

The numeral 105 denotes a second water cooled cooling tower for cooling the exhaust gas and it is constructed so as to also function as a desulfuriser by providing for mixing and feeding of powder such as unslaked lime. The numeral 106 denotes a dust collector housing having a bagfilter for removing fine dust and fly ash. The fine dust filtered by the bag-filter is made to fall to a conveyor by means of a vibrator which operates periodically. The dust is collected by the conveyor for transfer to a hopper arranged next to the melting furnace, which is referred to hereinafter. Then, the fine dust is melted with the ash discharged from the rotary furnace 101. The dust collector 102 in the present invention, refers to the apparatus in which such a removing operation is carried out.

S:P19711:15/1/98 s15 A density measuring instrument (not shown in the drawings) for measuring the density of oxygen in the exhaust gas, is provided in the duct connected to the dust collector 106 and the measured data fed back to a controller. A control valve for an oxygen burner, which is referred to hereinafter, can be controlled by means of said controller so that the oxygen in the rotary furnace 101 normally exceeds at least 6%.

As shown in Figures 5 through 7, the rotary furnace 101 is constructed to be substantially cylindrical having openings 101a and 101b at each respective end thereof, and rotatably supported by a frame 108 about a central longitudinal axis P1. The oxygen burner 109 for using an oxygen gas having a density of 50% and fuel, for example, 15 LPG, is provided at the opening la of the rotary furnace 101 to open and close the opening la in a well known suitable manner.

The oxygen burner 109 provides a regulator for regulating a mixing ratio of the fuel (LPG) and the oxygen gas of the predetermined density and as well as their volumes, and the burner is so constructed as to be controlled by the density measuring instrument for measuring the density of the oxygen gas, which is referred to hereinbefore.

The numeral 110 denotes charging means in the form of a waste throwing means which is constructed to push industrial waste in an upper hopper 111 into the rotary furnace 101 by means of an air cylinder. In this case, the air cylinder housing is made of ceramics material having a high heat resistance. Further, an exhaust duct 112 is arranged to face the opening lb of the rotary furnace 101 and is connected to the pre-duster 103.

A small melting furnace 113 is disposed beneath the rotary furnace 101 for receiving the ash and residue including incombustible materials which are made to fall from the rotary furnace 101 when the rotary furnace 101 is S:P19711:15/1/98 16 tilted. The melting furnace 113 is provided with an oxygen burner 114 which uses an oxygen gas of more than 50% density and a fuel such as LPG. The oxygen burner 114 is arranged on a lid of the melting furnace, which lid is constructed to be closed and opened, and the burner radiates its flame downwardly. The burner, however, may be disposed at any other suitable position such as the side wall of the melting furnace 113.

The melting furnace 113 is mounted on a base cart having wheels movable on rails, so that the molten materials or slag may be moved to another place where they can, for S: example, be cast into granules or pellets by sudden cooling treatment. Figure 8 illustrates the discharge of the molten materials or slag into a ladle 115 at said another place.

15 Treatment of the wastes are carried out as follows: First, a first batch of waste is charged by charging means in the form of a transporter 110 into the rotary furnace 101 from the opening 101a.

Then, the opening 101a is closed by the burner 109 and 20 combustible materials of the waste are incinerated with the fuel of LPG and the oxygen gas having a density of more than 50%. The combustible materials are burnt and the ash thereof and the incombustible materials of the waste are stored and accumulated in the rotary furnace 101. An additional batch of waste is charged, incinerated and stored and accumulated in the rotary furnace.

Further, discrete batches of waste may be charged, accumulated and stored in the rotary furnace until a predetermined quantity of waste has been incinerated into ash and residue and accumulated in the furnace.

The caloric powers of the combustible materials and the fuel for the burner 109, preheat the incombustible materials for melting.

The exhaust gas generated in the incineration process is introduced to the dust collector 102 having a bag-filter, %via the duct which is connected to the opening 101b of the S:P19711:15/1/98 -I I 17 rotary furnace 101, and then discharged to the air. The density of oxygen in the exhaust gas of the rotary furnace is maintained at the volume that sufficiently exceeds 6% (the guidelines of the Japanese Ministry of Health and Welfare). At the same time, the value of CO in the exhaust gas may be lowered under 50ppm, which is set in the guidelines of the Japanese Ministry of Health and Welfare.

After incineration, the burner 109 is stopped and removed from the rotary furnace 101 and the rotary furnace 101 is tilted for transferring the accumulated ash and residue and residue including incombustible materials (metals and sludge) into the melting furnace 113 at the high .temperature of about 300'C to 600 0

C.

In the melting furnace 113, a burner 114, which s provides a mechanism for spraying an oxygen gas having a density of more than 50%, and a regulator for mixing the fuel of LPG and the oxygen gas, heats the accumulated ash and residue including incombustible materials at the very high temperature of about 15000C to 16000C, so as to melt S 20 these materials. Incineration using a high density of oxygen gas (more than 50% density) may assist in keeping the density of oxygen in the melting furnace 113 high so as to greatly reduce generation of CO.

As mentioned above, since the accumulated ash and residue including incombustible materials are preheated in the rotary furnace 101 and continued to be reheated in the melting furnace 113, the fuel cost for melting can be reduced by 30%-40%, in comparison with a conventional system in which the waste and incombustible materials are at least once cooled to room temperature and heated again for melting.

Further, at the time of melting, glass pellets are charged into the melting furnace 113 in order to strengthen the molten materials or slag and may provide sufficient strength to the molten materials or slag to facilitate Sforming, for example, dressing tiles for a pavement. The S:P19711:15/1/98 II II IIIIUIRI1I~-31YlsCI~ Clla~ll~- l 18 ratio of the glass pellets to the molten materials is 1 to 3, preferably. However, the ratio may be chosen as desired, for example, 4 to 1, 1 to i, or 1 to 3.

A hood and a duct are provided on the melting furnace 113 and the exhaust gas is introduced therefrom to the preduster 103 of the dust collector 102 for dust collection, and the cleaned gas issuing from the dust collection process is discharged to the air. Further, generation of CO may be reduced greatly with the incineration step utilising high density oxygen.

Where an inert gas such as nitrogen is used in ocombination with the oxygen gas of 50% density, it becomes Sopossible to produce the atmosphere in which it is difficult to generate a chemical reaction. As a result, the 15 generation of dioxins which appear to be produced under many o conditions is reduced.

In the claims which follow and in the preceding summary of the invention, except where the context requires ee S: otherwise due to express language or necessary implication, 20 the word "comprising" is used in the sense of "including", ie the features specified may be associated with further *features in various embodiments of the invention.

*.go S S S:P19711:15/1/98

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Claims (13)

1. A method of treating wastes comprising the steps of: charging a first batch of wactes into a rotary furnace through an opening provided in one end of said rotary furnace; incinerating said batch at a temperature from 800 0 C to 1200 0 C by means of an oxygen burner, using an oxygen gas having a density of more than 50%, and a fuel, so as to reduce the volume of the batch of wastes; then charging an additional batch of wastes into said rotary furnace through said opening and incinerating said additional batch in the same way as the first batch, then, 15 if necessary, repeating the previous step of charging and incinerating an additional batch one or more times, until a predetermined quantity of wastes has been incinerated into ash and residue and accumulated in the furnace, then melting the ash and residue accumulated in the furnace S" 20 at a temperature of more than 160 0 C to form molten material and discharging the molten material from an opening provided in an opposite end of the furnace for disposal and drawing S°exhaust gases generated during the incineration and melting steps from said opening on said opposite end of the furnace and directing the exhaust gases to a dust collector for cleaning.

2. A method of treating wastes comprising the steps of: charging a first batch of wastes into a rotary furnace through an opening provided in one end of said rotary furnace; incinerating said batch at a temperature from 8000C to 12000C by means of an oxygen burner, using an oxygen gas Shaving a density of more than 50%, and a fuel, so as to 5:P19711:15/l/98 I arrrr*rrr*-~~-l 20 reduce the volume of the batch of wastes; then charging an additional batch of wastes into said rotary furnace through said opening and incinerating said additional batch in the same way as the first batch, then, if necessary, repeating the previous step of charging and incinerating an additional batch one or more times until a predetermined quantity of wastes has been incinerated into ash and residue and accumulated in the furnace, then transferring the accumulated ash and residue to a melting furnace then melting the transferred ash and residue in the melting furnace at a temperature of more than 16000C to form molten material for vitrification and discharging the molten material from the melting furnace and drawing •exhaust gases generated during the incineration and melting 15 steps from an opening in the melting furnace and from an oe.. opening in an opposite end of the rotary furnace and directing the exhaust gases to a dust collector for o cleaning. e•:

3. The method of treating wastes as claimed in claim 1 or claim 2 further comprising the step of: S: charging soda ash (Na2CO 3 into the furnace during the melting step.

4. The method of treating wastes as claimed in any one of claims 1 or 3, further comprising the step of: charging a solid fuels selected from cokes, coal and charcoal in the form of powder or lump into the furnace prior to the incineration step and/or the melting step for assisting incineration and/or melting. A method of treating wastes as claimed in any one of the preceding claims wherein the charging step is enabled by means of waste throwing means.

S:P19711:15/1/98 21

6. An apparatus for treating wastes comprising: a rotary furnace rotatable about a longitudinal axis thereof and tiltable about a horizontal axis which intersects the longitudinal axis at right angles, said rotary furnace having an opening at each respective end thereof, charging means for sequentially supplying discrete batches of wastes into the rotary furnace through one of said openings thereof, to enable sequential charging and incineration of discrete batches of wastes for accumulation of a predetermined quantity of ash and residue from incineration in the furnace; i: an oxygen burner using an oxygen gas of 50% density and a fuel, provided at said one opening of the rotary furnace 15 to open and close said one opening thereof, said burner .being constructed to melt the accumulated ash and residue at a temperature of more than 1600 0 C for vitrification, and Sga dust collector connected to an exhaust duct which is *6e* •connected to another of said openings of the rotary furnace for cleaning exhaust gas generated through incineration and melting processes within the furnace.

7. The apparatus for treating wastes as claimed in claim 6, wherein soda ash (Na 2 COs) is charged into the furnace to mix with the waste during melting.

8. The apparatus for treating wastes as claimed in claims 6 and 7, wherein the fuel comprises a solid fuel selected from coke, coal and charcoal in the form of powder or lump, and wherein said fuel is charged into the furnace prior to the incineration step or the melting step to assist incineration and/or melting.

9. The apparatus for treating wastes as claimed in any one of claims 6 to 7, further comprising: S:P19711:15/1/98 U Llllilllc ~-arars~ -ana~m~- I-il -r~ 22 a crusher for crushing waste disposed upstream of charging means.

Apparatus for treating wastes as claimed in any one of claims 6 to 9 wherein the charging means comprises a waste throwing means.

11. An apparatus for treating wastes comprising: a rotary furnace rotatable about a longitudinal axis thereof and tiltable about a horizontal axis which intersects the axis at right angles said rotary furnace having an opening at each respective end thereof, 9charging means for supplying batches of waste into the rotary furnace through one of said openings thereof, to 15 enable sequential charging and incineration of the waste discrete batches for accumulation of a predetermined quantity of ash and residue from incineration in the S• furnace; an oxygen burner using an oxygen gas of 50% density and 99 20 a fuel, provided at said one opening of the rotary furnace to open and close one opening thereof, a melting furnace for receiving said accumulated as ashen and residue from the rotary furnace and for melting same, a melting oxygen burner using an oxygen gas of density and a fuel, provided with the melting furnace and constructed to melt said accumulated ash and residue of the waste received from the rotary furnace at a temperature of mo'e than 1600 0 C, for vitrification; a dust collector connected to an exhaust duct which is connected to another of said openings of the rotary furnace and another exhaust duct which is connected to the opening of the melting furnace for cleaning the exhaust gas generated through incineration and melting. S:P19711:15/1/98 23

12. A method of treating wastes substantially as hereinbefore described with reference to any one or more of the accompanying drawings.

13. Apparatus for treating wastes substantially as hereinbefore described with reference to any one or more of the accompanying drawings. Dated this 15th day of January 1998 o e ee e e *e e e e e S* SHINROKU NISHIYAMA By their Patent Attorneys GRIFFITH HACK S:P19711:15/1/98 Abstract of the Disclosure The method of and apparatus for incinerating and melting wastes are incinerating the wastes and melting the same with the incombustible materials in the wastes continuously. Namely, throwing wastes in a rotary furnace, incinerating the wastes at a temperature from 800 C to 1,200" C, and melting the ashes of the wastes together with the remaining to be vitrified at a temperature of more than 1,600' C, by means of a burner of oxygen type for using an oxygen gas having a density of more than 50%, and a fuel. The exhaust gas generated in the incineration and melting processes is introduced to a dust collector for cleaning the same. 9