JP2004301494A - Waste melting method - Google Patents

Abstract

Provided is a waste melting treatment method capable of suppressing consumption of coke, injecting a larger amount of dust into a furnace bottom than in the past, and maintaining the temperature of the melt by the heat of dust combustion. .
SOLUTION: A combustion melting furnace 16 is provided in the vicinity of the bottom of the shaft furnace melting furnace 1, and the furnace bottom of the combustion melting furnace 16 and the furnace bottom of the shaft furnace melting furnace 1 are communicated with each other. Fine combustible waste or an intermediate product thereof is charged from the port 17 and burned and melted. The combustion exhaust gas is introduced into the melting zone 8 of the shaft furnace type melting furnace 1 and used as a heat source for melting.
[Selection diagram] Fig. 1

Description

  The present invention relates to a general waste, an industrial waste, and a treated product obtained by drying, incineration, crushing, and the like thereof (an incinerated ash or a landfill waste including a once-landfilled ash and a sediment reclaimed again. The present invention relates to a waste melting method for improving the combustion / melting efficiency and reducing operating costs when burning and melting waste such as waste and sludge in a shaft furnace waste melting furnace.

  In recent years, most waste has been disposed of in an incinerator system, but the incineration system has disadvantages such as requiring a disposal site for incinerated ash. In particular, in a metropolitan area, it is difficult to secure a disposal site for incinerated ash.Therefore, the method of melting the incinerated ash after incineration of the waste and reducing the volume, or directly melting the waste There is a growing need for methods of recycling as slag and metal.

  As a method of directly melting waste, for example, there is a shaft furnace type waste melting furnace (see Patent Document 1). As shown in FIG. 5, the furnace body 1 comprises a shaft portion 1a and a lower bosh section 5, a lower tuyere 2 for a combustion melting zone is provided at the lower end of the bosh section 5, and above the lower section. It has a plurality of upper tuyeres 3 for the pyrolysis zone.

  The lower tuyere 2 supplies oxygen or oxygen-enriched air, and the upper tuyere 3 supplies air as a combustion supporting gas.

  At the upper part of the furnace main body, a charging port 11 for charging waste to be treated, coke as an auxiliary agent, limestone as a basicity adjusting agent, etc. into the furnace is provided. A slag and metal slag port 19 after the melting process is provided.

  In the above configuration, the charged waste 1b is melted through the drying zone 6, the thermal decomposition zone 7, and the combustion melting zone 8 from the upper layer of the melting furnace main body 1.

  The coke 4 and the pyrolysis residue 14 are burned at a high temperature by the oxygen or oxygen-enriched air supplied from the lower tuyere 2 to serve as a heat of fusion, while air is supplied from the upper tuyere 3 to mainly generate waste heat. The decomposition residue 14 is burned, and the waste gas is dried and thermally decomposed with the generated gas. The molten waste is discharged from the slag port 19 as slag and metal 18.

  The high-temperature combustion exhaust gas is raised as a counter flow in a bed of waste in the shaft furnace, and is recovered as combustible gas from the exhaust gas pipe 12 at the upper part of the melting furnace main body or supplied to the combustion chamber. Combustion air is supplied to the combustion chamber via an air supply pipe, and is burned in the chamber. The flue gas is introduced into the boiler through the flue gas pipe, and after collecting the exhaust heat, the temperature is adjusted in a cooling tower and passed through a dust collector, and further, after removing pollutants in a catalytic reaction tower, a chimney Is discharged from

At this time, combustible dust (char) discharged from the furnace top is collected as a means to reduce the coke as a fuel source as much as possible and to efficiently burn and melt the object to be treated, and then to the smelting furnace body again. There is a method of charging through a mouth (see Patent Literatures 2 and 3), a method of crushing waste plastic, and charging from a tuyere or a large one from around the furnace (see Patent Literature 4). What is blown may be not only collected dust and waste plastics but also crushed combustibles such as general waste RDF fuel.
JP 2001-90923 A JP-A-8-285250 JP 2001-21123 A JP-A-11-153309

  When the fine combustible waste such as collected char and waste plastic described in the patent document or the intermediate treated product is blown into the furnace main body through the tuyere, the following problem occurs. .

  FIG. 4 is a graph showing a change in furnace temperature with an increase in the amount of combustible dust. When blowing the dust, if the amount of the blown dust is relatively small, as shown in FIG. 4A, the furnace temperature is high, the particle size of the dust is sufficiently smaller than coke, and the specific surface area is large. It is fast and contributes to reducing coke consumption.

  However, in order to further increase the amount of blown dust and further suppress coke consumption, dust blown at room temperature deprives the coke bed of sensible heat due to the initial temperature rise of the solid, and is shown in FIG. 4B. As the position of the maximum temperature rises, the temperature decreases and the coke bed cannot maintain a sufficient temperature.To continue the operation, it is necessary to increase the oxygen enrichment and increase the oxygen concentration. In addition, coke cannot not only reduce the amount of dust dust to be blown, but also cannot achieve a total energy reduction of coke and oxygen enrichment, so that a sufficient effect cannot be obtained. Further, when the oxygen enrichment amount is increased and the oxygen concentration is not increased, the temperature of the melt also decreases, and it becomes difficult to continue the operation, so that the reduction of coke by dust injection has a limit.

  Therefore, the present invention effectively burns the dust blown into the furnace bottom, suppresses the consumption of coke than before, and allows the blown amount of dust blown into the furnace bottom to be blown more than before, so that the heat of dust combustion An object of the present invention is to provide a waste melting treatment method capable of maintaining the temperature of a melt.

  The present invention relates to a waste melting treatment method for melting waste in a shaft furnace melting furnace and discharging as a melt, wherein a combustion melting furnace is provided near a furnace bottom of the shaft furnace melting furnace. The furnace bottom of the shaft furnace type melting furnace is communicated with the furnace bottom of the shaft furnace type melting furnace, and the combustion exhaust gas of the combustion melting furnace is introduced into a melting zone of the shaft furnace type melting furnace to be used as a heat source for melting.

  Further, the present invention provides a waste melting treatment in which waste is melted in a shaft furnace type melting furnace, and the melt is discharged through a heat retention furnace adjacent to the melting furnace main body and communicating with the furnace bottoms. In the method, the combustion exhaust gas of the heat retaining furnace is introduced into a melting zone of the shaft furnace type melting furnace through a communication passage between the shaft furnace type melting furnace and the heat retaining furnace, and is used as a melting heat source and a heating source of the melt. It is characterized by.

  ADVANTAGE OF THE INVENTION This invention can suppress consumption of coke conventionally by burning a dust in the combustion melting furnace or heat retention furnace connected to the waste melting furnace. Further, the amount of dust blown into the furnace bottom can be blown more than before.

When discharging the melt continuously, it was necessary to supply auxiliary fuel to a heat storage furnace for heat storage and homogenization.However, heat can be maintained using dust as a heat source, and the self-energy of garbage can be used. Therefore, auxiliary fuel for the heat retaining furnace at the time of continuous hot water supply becomes unnecessary, operation costs and CO ₂ generation can be suppressed, heating efficiency in the melting furnace main body can be improved, and operating costs can be reduced.

  Further, according to the present invention, fine combustible waste and intermediate products thereof can be treated together.

  Further, in the case of reduction combustion, the heavy metal in the melt can be sufficiently reduced and volatilized because the contact time with the reducing gas can be prolonged, and the content ratio of the heavy metal which becomes a problem when recycling the melt can be reduced. .

  In the combustion melting furnace or the heat retention furnace, unlike blowing into a coke bed, the combustion of dust is maintained by securing a necessary combustion space. When burning at an air ratio of 1 or more with respect to the theoretical combustion air of dust, secure a space in which oxygen almost disappears, and when the combustion gas temperature reaches the maximum, introduce combustion gas into the heat retention part of the melt to keep heat. I do. The ash in the dust is melted by the combustion of the dust, and is captured on the wall surface by centrifugal force generated by swirling, or merged with the melt melted in the shaft furnace and discharged.

  When operating at an air ratio of 1 or more, the exhaust gas introduced into the furnace bottom contains oxygen, which burns coke and waste at the furnace bottom with a high-temperature oxygen-containing gas and effectively contributes to the melting of ash in the waste. However, even if the amount of dust to be blown is large, it is possible to reduce the amount of coke calorie according to the amount of dust calorie.

  Further, in the combustion melting furnace, unlike blowing into a coke bed, there is no coke or waste other than dust, so oxygen supplied to the melting furnace together with dust is used only for combustion of dust. If the supplied oxygen is measured by a flow meter and the dust is measured by a weigh scale or a cut-out volume, strict control of the air ratio can be easily performed. Furthermore, if a thermometer or a gas analyzer is installed in the combustion section, the combustion state can be monitored, and more precise control can be performed.

When the reduction combustion is performed at an air ratio of less than 1 with respect to the theoretical combustion air of the dust, the dust is burned, and a space for substantially completing the gasification reaction represented by CO ₂ + C → 2CO is secured, and the dust is substantially gasified. Then, the combustion gas is introduced into the heat retaining section of the melt to perform heat retention and to reduce and volatilize heavy metals in the melt.

  If the air ratio to the theoretical combustion air of dust is less than 0.5, oxygen becomes insufficient even in reduction combustion, and dust cannot be gasified, but if the combustion exhaust gas temperature is maintained higher than the melt temperature, it is introduced into the furnace bottom. By this time, the temperature of the dust solid can be raised, and the operation becomes possible. Since the reduced exhaust gas burned to the bottom of the furnace has a sufficiently high temperature and is stably burned at high temperature at the tip of the tuyere with air supplied from the lower tuyere or oxygen-enriched air, it effectively contributes to the melting of ash in the waste. Even if the amount of dust to be introduced is large, it is possible to reduce the amount of coke heat corresponding to the amount of dust heat.

  FIG. 1 is a cross-sectional view of the waste melting furnace of the present embodiment. The same components as those of the waste melting furnace shown in FIG.

  In FIG. 1, the waste charged from the furnace top is dried in the drying zone 6 of the shaft portion 1a, and falls into the thermal decomposition zone 7 and the combustion melting zone 8 together with coke. Air is blown from the upper tuyere 3 for the pyrolysis zone, and the dried and partially pyrolyzed waste is mainly burned.

  Oxygen-enriched air is blown from the lower tuyere 2 for the combustion melting zone, and the coke mainly forming the coke bed 4 and the pyrolysis residue 14 of some waste are burned at a high temperature of 1500 ° C. or higher, and the waste Is melted and discharged as a melt 18 at 1400 ° C. or higher from a slag port 19 installed in the hearth 10.

  Combustible dust and air or oxygen-enriched air are blown from a combustible dust injection tuyere 17 provided in a combustion melting furnace 16 communicating with the hearth section 10 of the waste melting furnace 1 to form a combustible dust combustion melting furnace. A high-temperature combustion of 1400 ° C. or more is performed at the combustion furnace outlet temperature in the combustion furnace 16, and the exhaust gas is exhausted to the coke bed 4 through the connection port. It burns together with the combustion residue 4 and some waste residue 14 and contributes as a heat source for melting. Even when the exhaust gas from the combustion and melting furnace is not flammable, it can be used as a heat source for melting and heating the combustion residue in the furnace due to the high-temperature exhaust gas.

Table 1 shows a comparison between the present invention and a conventional example.

  As shown in Table 1, in Conventional Example 2, combustible dust was blown at 50 kg / h during operation at a waste treatment amount of 1000 kg / h with coke added at 50 kg / h without adding the combustible dust of Conventional Example 1. Since the combustible content in combustible dust is equivalent to 20 kg / h in coke, the amount of coke added can be reduced to 30 kg / h, but the temperature of the melt is stably maintained at 1400 ° C or more due to the delay in combustion of combustible dust. In order to do so, the oxygen concentration of the combustion supporting gas blown from the tuyere for the combustion melting zone had to be adjusted from 30% to 40% by adding the pure oxygen amount.

  Further, the amount of combustible dust was increased to 100 kg / h in Conventional Example 3, and the combustible content in the combustible dust was equivalent to 40 kg / h in coke. The coke bed becomes smaller due to the reduced amount of coke added, there is not enough heat source to raise the solid temperature of combustible dust, and it promotes combustion delay of combustible dust. The temperature of the product dropped to 1400 ° C. or less, and it was difficult to continue stable melting. As shown in the graph of FIG. 4, as the amount of combustible dust increases, the maximum temperature of the combustion melting zone moves upward and the maximum temperature decreases. Therefore, the main cause is that the melt is cooled by the combustion gas in the dropping process. It is.

  On the other hand, in the present embodiment, the combustible dust is introduced into the combustible dust combustion / melting furnace 16 installed near the hearth of the shaft furnace type melting furnace together with air, and the combustible dust of the waste has a combustible content of 25 to 45%. Since the ash content is about 75 to 55% and contains a large amount of volatile matter, it receives heat radiation from the refractory wall in the combustion melting furnace, thereby enabling stable combustion.

  Example 1 shown in Table 1 is an example in which the amount of combustible dust and the amount of air and oxygen enriched from the tuyere for combustible dust are adjusted so that the air ratio becomes approximately 1.0 with respect to the amount of combustible dust. As shown in FIG. 3, high-temperature combustion of 1400 ° C. or more is possible at an air ratio of about 0.9 to 1.1 even with air having an oxygen concentration of 21%. Even at about 1.4, high-temperature combustion exhaust gas of 1400 ° C. or more can be generated.

  In Example 1, since the air ratio was 1 and the oxygen concentration was 30%, the combustion exhaust gas temperature of the combustible dust burned at a temperature exceeding 1500 ° C., and the ash in the combustible dust was melted. When the exhaust gas is guided, the exhaust gas is used as a heat source for melting ash in the waste charged from the upper part of the shaft furnace.

  From the lower tuyeres 2 for combustion and melting, the combustibles in the waste are dried, pyrolyzed and descend, and partially burn in the upper tuyeres 3 for the pyrolysis zone. Coke is burned at a high oxygen concentration of 30% to melt ash. At this time, since the combustion exhaust gas of the combustible dust is sufficiently higher than the melting temperature, the melt is not not only cooled but also effectively used as a heat source for melting. If the combustion ratio of the combustible dust injection tuyere 17 of the combustion melting furnace 15 to the combustible dust is reduced to 1 or less, high-temperature combustible gas is generated. The combustible gas is burned and becomes not only a heat source for melting, but also a high-temperature flue gas of combustible dust is introduced into the combustion melting zone, and the temperature in the vicinity of the lower tuyere 2 rises. Is no longer cooled by the combustion gas.

  If the combustion residence time of combustible dust in the combustion melting furnace is 0.5 seconds or more, preferably 1 second or more, the burning of the dust is almost completed. In addition, the combustion melting furnace is desirably swirling flow combustion, which can improve the flame holding properties of the flame, increase the residence time, and capture the ash in the dust on the wall surface of the combustion melting furnace, and can reduce the size of the combustion melting furnace. .

  The ash in the dust is melted during the combustion process, is captured on the combustion melting furnace wall and the combustion melting zone at the bottom of the shaft furnace, and is discharged together with the melt generated in the shaft melting furnace. The amount of coke used should be negligible if, according to the present invention, the amount of injected combustible dust and combustible fine waste can be completely replaced by the amount of coke calorie to secure a heat source for melting ash in the waste. Is also possible.

  Although the furnace shape is an example in which the bosh section 5 is formed in this embodiment, the amount of combustible dust injected into the combustion melting furnace is increased, and the cross-sectional area of the shaft furnace bottom is increased with the increase in the amount of exhaust gas. When doing so, it is possible to make the diameter the same as that of the shaft portion, and the morning glory portion is not always necessary.

  FIG. 2 is a sectional view of a waste melting furnace according to a second embodiment of the present invention. The same components as those of the waste melting furnace shown in FIG.

  In the case of continuously discharging a molten material in a waste melting furnace, a heat preservation furnace and a heat preservation heat source are usually required. That is, among the melts, those having a relatively low melting point start dropping from the combustion melting zone at about 1200 ° C. to 1300 ° C., but below the highest temperature point on the lower tuyere for the combustion melting zone, In addition to the lack of means for heating, the melt is cooled by the heat dissipation of the furnace body, so electric induction heating is used so that it can be heated during the dropping process, and a heat retaining furnace is provided at the outlet, and LPG and kerosene are provided. Heating is performed by an external source such as, for example, to prevent discharge failure and blockage due to a decrease in the temperature of the melt.

  According to the present embodiment, in FIG. 2, if the combustible dust discharged from the furnace top and collected by the dust remover is blown into the heat retaining furnace 15 from the combustible dust blowing tuyere 17 to serve also as a combustion melting furnace, By circulating and using the combustible dust that is part of the waste as a heat source, it is possible to maintain the heat of the molten material and even heat the molten material, eliminating the need for external heat sources such as electricity, LPG, and kerosene. In addition, it effectively acts as a melting heat source for the combustion melting portion of the shaft furnace.

  Furthermore, when continuously discharged, the properties of the molten slag vary, but this structure dissolves undissolved substances, homogenizes the properties, and traces a small amount of The heavy metals contained therein are gasified and volatilized, and more homogeneous and harmless slag can be produced.

  The furnace shape is an example in which the slag discharge port is formed immediately below the combustion melting furnace in the present embodiment, but unoxidized dust from the combustion melting furnace is directly discharged from the slag discharge port. In order to prevent slag, it is also possible to install a slag outlet on the downstream side (right side in FIG. 2) of the combustion melting furnace.

1 is a sectional view of a waste melting furnace according to a first embodiment. FIG. 6 is a sectional view illustrating a second embodiment of the present invention. It is a graph which shows the relationship between the air ratio at the time of combustible dust combustion, and the exit temperature of a combustion melting furnace. It is a graph which shows the furnace temperature change by the increase in the amount of combustible dust. It is sectional drawing of the conventional waste melting furnace.

Explanation of reference numerals

1: Melting furnace body 1a: Shaft portion 1b: Waste 2: Upper tuyere 3: Lower tuyere 4: Coke 5: Bosh section 6: Drying zone 7: Pyrolysis zone 8: Combustion melting zone 10: Furnace floor 11 : Inlet 12: Exhaust gas pipe 14: Pyrolysis residue 15: Heat retention furnace 16: Combustion melting furnace 17: Tuyere for blowing combustible dust 18: Melt (slag)
19: Slag port

Claims (10)

In a waste melting treatment method of melting waste in a shaft furnace type melting furnace and discharging it as a melt,
A combustion melting furnace is provided near the bottom of the shaft melting furnace, and the furnace bottom of the combustion melting furnace is communicated with the furnace bottom of the shaft melting furnace. A waste melting treatment method characterized by being introduced into a melting zone of a melting furnace and used as a heat source for melting.   The waste melting treatment method according to claim 1, wherein combustible dust discharged from the top of the shaft furnace type melting furnace is collected, charged into a combustion melting furnace and burned and melted.   The waste melting treatment method according to claim 1 or 2, wherein the fine combustible waste, an intermediate treatment product thereof, or waste plastic is charged into a combustion melting furnace and burned and melted.   The method according to any one of claims 1 to 3, wherein swirling combustion is performed in a combustion melting furnace.   The waste melting treatment method according to any one of claims 1 to 4, wherein reduction combustion is performed in a combustion melting furnace. In a waste melting treatment method of melting waste in a shaft furnace type melting furnace and discharging the melt through a heat retention furnace adjacent to the melting furnace body and communicating with the furnace bottoms,
The combustion exhaust gas of the heat retaining furnace is introduced into a melting zone of a shaft furnace type melting furnace through a communication path between the shaft furnace type melting furnace and the heat retaining furnace, and is used as a melting heat source and a heating source of a melt. Waste melting method.   The waste melting treatment method according to claim 6, wherein combustible dust discharged from the top of the shaft furnace type melting furnace is collected, charged into a heat retention furnace, and burned and melted.   The waste melting treatment according to any one of claims 6 to 7, wherein the fine combustible waste, an intermediate treatment product thereof, or waste plastic is charged into a heat retaining furnace and burned and melted. Method.   The method according to any one of claims 6 to 8, wherein swirling combustion is performed in a heat retaining furnace. The method according to any one of claims 6 to 9, wherein reduction combustion is performed in a heat retaining furnace.

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