JP2005201609A - Refuse gasification melting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refuse gasification melting system capable of reducing an amount of auxiliary fuel supplied to a gasification melting furnace even when a heating value of refuse is low. <P>SOLUTION: A bypass line 8 from a gasification furnace 1 bypassing a melting furnace 2 and connected to a secondary combustion furnace 3, and a return line 12 supplying soot and dust f collected by a dust collector 6 to the melting furnace 2 are provided in the gasification melting system. When a heating value of refuse becomes a set value or less, a supply destination of pyrolysis gas and char produced by the gasification furnace 1 is changed from the melting furnace 2 to the secondary combustion furnace 3 through the bypass 12, the soot and dust f collected by the dust collector 6 is supplied to the melting furnace 2 through the return line 12, and auxiliary fuel b is supplied to the melting furnace 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a waste gasification and melting system for treating municipal waste, for example, and more particularly to a technique for greatly reducing the amount of auxiliary fuel used when processing waste with a small calorific value in a waste gasification and melting furnace. It is.

  An example of a conventional refuse gasification melting furnace system is shown in FIG. Garbage is supplied to the gasification furnace 1 and reacts with separately supplied air a, so that a part of the garbage is burned and a thermal decomposition reaction occurs. In the gasifier 1, a pyrolysis gas composed of a combustible gas such as carbon monoxide and hydrogen, and char mainly composed of unburned carbon and ash are generated.

  The pyrolysis gas and char are supplied to the melting furnace 2 and react with the separately supplied combustion air a to obtain a high temperature field of 1300 ° C. or higher to melt the ash and collect it as slag e. The exhaust gas discharged from the melting furnace 2 is completely burned in the secondary combustion furnace 3 and is recovered by the waste heat boiler 4. In the temperature reducing device 5, the exhaust gas is rapidly cooled to 200 ° C. or less in order to prevent the regeneration of dioxins. On the upstream side of the dust collector 6, activated carbon c and slaked lime d are sprayed to remove hydrogen chloride and dioxins in the exhaust gas. The dust f is collected by the dust collector 6, and the cleaned exhaust gas is discharged from the chimney 7.

  In the waste gasification and melting furnace 2, ash can be melted without using the auxiliary fuel b when the waste heat generation amount is high. However, when the waste heat generation amount is low, the auxiliary fuel b is used to remove the ash. Need to melt.

  The lower limit of the lower heating value of waste that can melt ash without using auxiliary fuel b is about 6.7 to 7.5 MJ / kg. In urban areas, the lower heating value of waste is as high as 9 to 10 MJ / kg. The ash can be melted without using b. However, there are some areas where the calorific value is extremely low due to the different types and materials of garbage collection in each city. In addition, the calorific value may be low due to seasonal fluctuations in the water content in the garbage. Further, in the future, it is expected that the amount of heat generated from the incinerated waste will be reduced by promoting recycling. In this case as well, it is necessary to use a large amount of auxiliary fuel b in order to melt the ash.

Examples of this type of patent document include the following.
JP 11-118124 A

  As described above, the conventional waste gasification and melting system requires a large amount of auxiliary fuel when processing waste with a low calorific value, and thus has a drawback of high running costs.

  An object of the present invention is to solve such problems of the prior art and provide a waste gasification and melting system capable of reducing the amount of auxiliary fuel supplied to the gasification and melting furnace even when the amount of heat generated by the waste is low. is there.

  In order to achieve the above object, the present invention provides a gasification furnace for pyrolyzing waste, a melting furnace for melting pyrolysis gas and char generated in the gasification furnace to melt ash, and an exhaust gas from the melting furnace. The present invention is intended for a waste gasification and melting system equipped with a secondary combustion furnace that completely burns and a dust collector that collects soot in the exhaust gas from the secondary combustion furnace.

  The first means of the present invention includes a bypass line that bypasses the melting furnace from the outlet side of the gasifier and is connected to the inlet side of the secondary combustion furnace, and the dust collected by the dust collector. When the heat generation amount of the waste falls below the set value, the supply destination of the pyrolysis gas and char generated in the gasification furnace is switched from the melting furnace to the secondary combustion furnace through the bypass. In addition, the dust collected by the dust collector is supplied to the melting furnace through the return line, and auxiliary fuel is supplied to the melting furnace.

  The second means of the present invention is the first means, wherein a plurality of the dust collectors are installed along the flow direction of the exhaust gas, and, for example, slaked lime is provided upstream of the second and subsequent dust collectors from the upstream side. In this case, only the dust collected by the most upstream dust collector is supplied to the melting furnace.

  According to a third means of the present invention, in the first or second means, a separation device that can be separated by, for example, mass is provided in the middle of the return line, and the ash mainly composed of incinerated fly ash and molten fly ash by the separation device. And the ash mainly composed of the incinerated fly ash is supplied to the melting furnace.

  According to a fourth means of the present invention, in the first to third means, a metal recovery line in which a metal separation device is installed is connected to the gasification furnace, and the metals from the incombustibles discharged from the gasification furnace. Is recovered, and the recovered non-combustible material that does not contain metals is supplied to the melting furnace together with the soot and dust.

 According to the first means, if the amount of generated heat of the waste is equal to or greater than the set value, it is operated as a normal gasification and melting furnace, and in addition to the pyrolysis gas and char generated in the gasification furnace, some auxiliary Ash can be melted stably by using fuel or without using auxiliary fuel. In addition, when the amount of heat generated from the waste falls below the set value, the amount of auxiliary fuel used increases when operated as a normal gasification and melting furnace. By supplying the soot dust burned in the next combustion furnace and collected by the dust collector to the melting furnace and melting it using the auxiliary fuel, the amount of auxiliary fuel used is kept constant, The running cost can be reduced by reducing the amount used.

According to the second means, in addition to the effects of the first means, it is possible to supply only the generated ash to the melting furnace. An increase in melting point due to an increase in basicity (= CaO / SiO ₂ ) can be suppressed, and stable melting can be performed.

 According to the third means, in addition to the effects of the first and second means, incinerated fly ash produced by incineration and molten fly ash produced by melting the incinerated fly ash in a melting furnace are separated. As a result, only the incinerated fly ash can be supplied to the melting furnace, so that the concentration of chlorine and heavy metals contained in the molten fly ash can be prevented.

According to the fourth means, in addition to the effects of the first, second, and third means, non-combustible materials other than the metal recovered in the gasification furnace, that is, ceramics or glass mainly composed of SiO ₂ . The basicity of the material to be melted can be lowered by mixing the substance and the soot containing a large amount of CaO recovered by the dust collector. Lowering the basicity has the effect of lowering the melting point and enabling more stable melting.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram of a waste gasification and melting system according to the first embodiment of the present invention. FIG. 1 (a) shows a flow during normal operation, and FIG. 1 (b) shows a flow during melting furnace bypass operation. It is a figure which shows a flow.

  Waste such as municipal waste is supplied to the gasification furnace 1 and reacts with the separately supplied combustion air a, so that part of the waste is burned and a thermal decomposition reaction occurs. In the gasifier 1, a pyrolysis gas composed of a combustible gas such as carbon monoxide and hydrogen, and char mainly composed of unburned carbon and ash are generated.

  The pyrolysis gas and char are supplied to the melting furnace 2 and react with the separately supplied combustion air a to obtain a high temperature field of 1300 ° C. or higher to melt the ash and collect it as slag e. The exhaust gas discharged from the melting furnace 2 is completely combusted by supplying the combustion air a in the secondary combustion furnace 3 and recovered by the waste heat boiler 4. In the temperature reducing device 5, the exhaust gas is rapidly cooled to 200 ° C. or less in order to prevent the regeneration of dioxins. On the upstream side of the dust collector 6, activated carbon c and slaked lime d are sprayed to remove hydrogen chloride and dioxins in the exhaust gas. The dust f is collected by the dust collector 6, and the cleaned exhaust gas is discharged from the chimney 7.

  In the waste gasification and melting system of the present invention, a bypass line 8 is provided so as to bypass the melting furnace 2 from the gasification furnace 1 to the secondary combustion furnace 3, and the bypass line 8 is connected to the bypass line 8 as shown in FIG. 1 partition plate 9a and a second partition plate 9b on the entrance side of the melting furnace 2 as shown in FIG.

  Furthermore, a return line 10 for returning the dust f collected by the dust collector 6 to the melting furnace 2 is provided, and a third partition plate 9c is installed in the middle thereof.

 In a normal gasification and melting operation in which the amount of heat generated from the waste is high, as shown in FIG. 1 (a), the bypass line 8 is closed by the first partition plate 9a, and the pyrolysis gas and char generated in the gasification furnace 1 are It flows into the melting furnace 2 and burns. In this normal gasification melting operation, the return line 10 is also closed by the third partition plate 9c.

 When the amount of heat generated from the waste is low, the bypass line 8 is used as shown in FIG. 2B, so that the inlet side of the melting furnace 2 is closed by the second partition plate 9b and generated in the gasification furnace 1. The pyrolysis gas and char that have been passed through the melting furnace 2 are sent to the secondary combustion furnace 3. In the secondary combustion furnace 3, air a is separately supplied, and the pyrolysis gas and char are completely combusted.

 The dust f collected by the dust collector 6 is sent to the melting furnace 2 through the return line 12, and the auxiliary fuel b is supplied to the auxiliary burner to keep the inside of the melting furnace 2 at 1300 ° C. or more and melt the ash. . The exhaust gas from the melting furnace 2 flows into the secondary combustion furnace 3 and is completely burned together with the pyrolysis gas and char from the gasification furnace 1.

  Fig. 2 shows the relationship between the amount of waste heat and the required auxiliary fuel. In normal gasification and melting operation, auxiliary fuel is not necessary when the amount of heat generated by the waste is sufficiently high, but when the heat generation amount decreases, the amount of auxiliary fuel used increases monotonously as shown by the solid line. On the other hand, when the pyrolysis gas and char generated in the gasification furnace are not sent to the melting furnace but burned in the secondary combustion chamber, the amount of exhaust gas in the melting furnace does not depend on the composition of the waste or the amount of heat generated, and the Depends on the amount of auxiliary fuel required. Therefore, the amount of auxiliary fuel charged into the melting furnace is always constant as shown by the dotted line, regardless of the amount of heat generated by the waste.

  Here, as shown in the figure, when the heat generation amount of the waste used is higher than the value of the heat generation amount of the waste where the solid line and the dotted line intersect, the normal gasification and melting operation produces a supplementary fuel amount. Although it can be reduced, the amount of supplementary fuel can be reduced by operating with the melting furnace bypassed for waste with less calorific value. Therefore, it is possible to minimize the amount of auxiliary fuel used by switching between the normal gasification melting operation and the melting furnace bypass operation according to the heat generation amount of the waste to be used.

 In this embodiment, when only municipal waste is treated, the calorific value is as high as about 7500 kJ / kg, and no supplementary combustion is required in normal gasification and melting operation. On the other hand, the waste generated by mixing municipal waste with sewage sludge, sludge, human waste, etc. has a low calorific value of about 5000 kJ / kg, and a large amount of auxiliary combustion is required for normal gasification and melting operation. Therefore, when the operation was switched to the melting furnace bypass operation shown in Fig. 1 (b), the amount of auxiliary fuel could be reduced to about 1/2.

 FIG. 3 is a system diagram of a refuse gasification melting system according to the second embodiment of the present invention. In this embodiment, two dust collectors 6a and 6b are installed along the flow direction of the exhaust gas, and the dust f collected by the upstream first dust collector 6a is collected. In the second dust collector 6b on the downstream side, a desalting agent such as slaked lime d is supplied to remove hydrogen chloride in the exhaust gas.

 In this embodiment, two dust collectors 6 are installed. However, it is possible to install three or more dust collectors 6. In short, a plurality of dust collectors 6 are installed along the flow direction of exhaust gas. In addition, the desalting agent is blown on the upstream side of the second and subsequent dust collectors 6 from the upstream side, and only the dust f recovered by the most upstream dust collector 6 is supplied to the melting furnace 2. It ’s fine.

As a result, even when the concentration of hydrogen chloride in the exhaust gas is high and the exhaust gas treatment is necessary, the melting point is increased due to the increase in the melted material due to mixing of desalting agents such as slaked lime and the increase in basicity (= CaO / SiO ₂ ). The rise can be suppressed.

 FIG. 4 is a system diagram of a refuse gasification melting system according to the third embodiment of the present invention. In the present embodiment, a separation device 10 is provided in the middle of the return line 12, and the separation device 10 generates ash mainly composed of incineration fly ash generated by incineration and incineration fly ash by melting in the melting furnace 2. Separated into ash mainly composed of molten fly ash. Therefore, ash mainly composed of incinerated fly ash can be supplied to the melting furnace 2 and ash mainly composed of molten fly ash can be taken out of the system as waste dust g. Concentration of contained chlorine and heavy metals in the system can be prevented.

 As shown in Fig. 5, the particle size and specific gravity of incineration fly ash and molten fly ash differ greatly, so it is easy to completely separate them by gravity (mass) separation or centrifugation. is there.

FIG. 6 is a system diagram of a refuse gasification melting system according to the fourth embodiment of the present invention. In the present embodiment, a metal recovery line 13 is provided between the gasification furnace 1 and the melting furnace 2, and a metal separation device 11 is installed in the middle thereof. Then, the metal separator 11 separates and recovers the metal i such as iron or aluminum from the incombustible material h discharged from the gasification furnace 1, and the non-combustible material excluding the metal, that is, ceramic or glass SiO _2. By supplying the main substance and the soot f containing a large amount of CaO recovered by the dust collector 6 together to the melting furnace 2, the basicity of the material to be melted can be lowered.

There is a correlation as shown in FIG. 7 between the basicity (CaO / SiO ₂ ) of the material to be melted and the melting point of ash, and the melting point is lowered by lowering the basicity, so that more stable melting is possible.

 In the second to fourth embodiments, the control for switching between the normal operation in which the melting furnace 2 is not bypassed and the operation in which the melting furnace 2 is bypassed according to the amount of heat generated by the garbage is the same as in the first embodiment. It is the same.

It is a systematic diagram of the refuse gasification melting system concerning a 1st embodiment of the present invention. It is a figure which shows the relationship between the emitted-heat amount of garbage and the amount of auxiliary fuel at the time of normal gasification melting operation and melting furnace bypass operation. It is a systematic diagram of the refuse gasification melting system which concerns on the 2nd Embodiment of this invention. It is a systematic diagram of the refuse gasification melting system which concerns on the 3rd Embodiment of this invention. It is a figure which shows the relationship between the particle diameter and specific gravity of combustion fly ash, molten fly ash, and slaked lime. It is a systematic diagram of the refuse gasification melting system which concerns on the 4th Embodiment of this invention. It is a figure which shows the relationship between the basicity of to-be-melted material, and melting | fusing point of ash. It is a systematic diagram of the conventional refuse gasification melting system.

Explanation of symbols

1: gasification furnace, 2: melting furnace, 3: secondary combustion furnace, 4: waste heat boiler, 5: temperature reduction device, 6: dust collector, 6a: first dust collector, 6b: second Dust collector, 7: chimney, 8: bypass line, 9a: first partition plate, 9b: second partition plate, 9c: third partition plate, 10: separation device, 11: metal separation device, 12: Return line, 13: Metal recovery line, a: Combustion air, b: Auxiliary fuel, c: Activated carbon, d: Slaked lime, e: Slag, f: Dust, g: Waste dust, h: Incombustible, i: Metals .

Claims (4)

A gasification furnace for pyrolyzing waste, a melting furnace for burning pyrolysis gas and char generated in the gasification furnace to melt ash, a secondary combustion furnace for completely burning exhaust gas from the melting furnace, In a refuse gasification and melting system equipped with a dust collector that collects dust in the exhaust gas from the secondary combustion furnace,
A bypass line that bypasses the melting furnace from the outlet side of the gasifier and is connected to the inlet side of the secondary combustion furnace;
Providing a return line for supplying the dust collected by the dust collector to the melting furnace;
When the heating value of the waste falls below the set value, the pyrolysis gas and char generated in the gasification furnace are switched from the melting furnace to the secondary combustion furnace through the bypass and collected by the dust collector. A refuse gasification and melting system is characterized in that supplied dust is supplied to the melting furnace through the return line and auxiliary fuel is supplied to the melting furnace.   2. The refuse gasification and melting system according to claim 1, wherein a plurality of the dust collectors are installed along the flow direction of the exhaust gas, and a desalting agent is blown on the upstream side of the second and subsequent dust collectors from the upstream side. A refuse gasification and melting system, wherein only the dust collected by the most upstream dust collector is supplied to the melting furnace.   3. A refuse gasification and melting system according to claim 1, wherein a separation device is provided in the middle of the return line, and the separation device separates the ash mainly composed of incinerated fly ash and the ash mainly composed of molten fly ash. A refuse gasification and melting system, characterized in that ash mainly composed of incineration fly ash is supplied to a melting furnace. The refuse gasification and melting system according to any one of claims 1 to 3, wherein a metal recovery line with a metal separator installed in the middle is connected to the gasification furnace, and metal is obtained from incombustibles discharged from the gasification furnace. A waste gasification and melting system that collects waste and supplies non-combustible materials that do not contain metals after recovery to the melting furnace together with the dust.

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