JP2004271039A - Thermal decomposition gasifying melting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal decomposition gasifying melting system capable of dispensing with supply of auxiliary fuel or reducing it and reducing running cost. <P>SOLUTION: This thermal decomposition gasifying melting system is provided with a gasifying furnace 3 for burning an object to be burned partially to generate thermal decomposition gas and char by thermal decomposition, a melting furnace 6 for supplying air b for combustion to thermal decomposition gas and char from the gasifying furnace 3 for combustion and melting ash in the char to discharge as slag, and a dust collection device 10 for removing dust in combustion exhaust gas from the melting furnace 6. The combustion exhaust gas (g) from which dust is removed in the dust collection device 10 is mixed with air a for combustion to supply to the melting furnace 6. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pyrolysis gasification and melting system that pyrolyzes general waste and industrial waste and recovers ash as slag.
[0002]
[Prior art]
FIG. 6 is a schematic configuration diagram of a conventional pyrolysis gasification and melting system for treating general waste, industrial waste, and the like. As shown in the figure, burnable materials such as refuse and waste are supplied to a fluidized-bed gasifier 3 and gasified by pyrolysis in a state of insufficient air, and the generated pyrolysis gas and Combustion of char mainly composed of fuel carbon and ash in the melting furnace 6 obtains a high-temperature field and turns ash in the char into molten slag. In this process, garbage is reduced in volume, and dioxins are completely decomposed and rendered harmless at high temperatures.
[0003]
The combustion exhaust gas from the melting furnace 6 is completely burned in the secondary combustion chamber 7. Further, after the heat is recovered by the waste heat recovery boiler 8, it is quenched by the temperature reducing device 9 in order to prevent re-synthesis of dioxins, and is subjected to dust removal and desalination in a dust collector 10 provided with a bag filter. Released during.
[0004]
In the figure, 1 is a supply hopper, 2 is a dust supply device, 4 is an air diffuser, 5 is a flow path of a pyrolysis gas, 11 is a chimney, 12 is a combustion air blowing nozzle, 13 is a forced air blower, and 14a is an air flow rate. 15a is an air flow control valve, 16 is an oxygen concentration meter, a is fluidized air, b is combustion air, c is incombustible, d is slag, e is slaked lime, and f is dust.
[0005]
Regarding the combustion melting furnace, for example, the following Patent Documents 1 and 2 can be cited.
[0006]
[Patent Document 1]
JP 2001-289414 A
[Patent Document 2]
JP-A-10-54518
[Problems to be solved by the invention]
In order to make the temperature of the melting furnace equal to or higher than the melting point of the ash using only the combustion energy of the refuse, it is necessary to increase the heat load of the melting furnace and reduce the ratio of the amount of heat dissipated to the heat input. In order to increase the heat load of the melting furnace, it is necessary to reduce the size of the melting furnace, but if the melting furnace is reduced in size, it becomes impossible to secure the residence time required for burning the pyrolysis gas and char generated in the gasification furnace, Combustion efficiency and combustion temperature decrease.
[0009]
For this reason, a reduction in combustion efficiency is generally prevented by employing a swirling melting furnace and securing a residence time. The swirling melting furnace has a structure in which pyrolysis gas and char and air necessary for burning these combustible substances flow tangentially into the melting furnace. Further, by increasing the blowing velocity of the pyrolysis gas and the combustion air as much as possible, the combustion efficiency is improved by turbulent mixing, and a device is devised to complete the combustion reaction in a short time.
[0010]
The minimum heat value at which ash can be melted using only the combustion energy of refuse without using any auxiliary fuel is 1500 to 1800 kcal / kg at a throughput of 100 t / d. In order to completely burn the pyrolysis gas and the char in the melting furnace, it is necessary to increase the blowing speed of the pyrolysis gas and the combustion air as much as possible. If the calorific value of the refuse is always constant, the amount of the pyrolysis gas and the amount of combustion air will be constant, and the nozzle size that maximizes the flow velocity within the allowable range of the fan can be determined.
[0011]
However, the moisture of garbage varies with the season, and the calorific value changes accordingly. In addition, from the viewpoint of the service life of the equipment, it is required to design a furnace that assumes the heat generation of the refuse several decades from now. Therefore, it is essential to design a melting furnace that can cope with such a wide range of the heat generation of the refuse.
[0012]
Since the combustion temperature of the refuse becomes maximum when the value of the air ratio (= supply air amount / theoretical air amount) is around 1, if the air ratio at the melting furnace outlet is designed to be 1, the combustion energy of the refuse is reduced. Maximum available. The theoretical amount of air is calculated from the amount and composition of combustible components in garbage, but generally has a correlation with the amount of heat generated, and the larger the amount of heat generated, the greater the amount of theoretical air. Every year, the calorific value of refuse tends to increase, and at present, a system capable of stably processing refuse having a calorific value of about 3000 kcal / kg is demanded. This is about twice the value of 1500 to 1800 kcal / kg, which is the amount of heat that can melt ash using only the combustion energy of refuse, and the theoretical amount of refuse air at this time is also about twice.
[0013]
In the gasification furnace, it is necessary to maintain the temperature at about 600 ° C. in order to thermally decompose the refuse. The amount of air required at this time is substantially constant regardless of the amount of heat generated by the refuse. This is because, as shown in FIG. 7, the partial heating value of the refuse in the gasification furnace depends on the air ratio (= supply air amount / theoretical air amount). The value of the air ratio required to maintain the temperature of the gasification furnace at about 600 ° C. may be smaller for refuse having a larger calorific value. That is, the refuse having a large amount of generated heat has a large theoretical air amount, but the value of the air ratio may be small. Therefore, the absolute value of the amount of air supplied to the gasifier does not depend on the refuse quality and is substantially constant.
[0014]
On the other hand, in the melting furnace, it is necessary to set the outlet air ratio of the melting furnace to about 1 in order to increase the temperature as much as possible. Therefore, the total amount of air supplied to the gasification furnace and the melting furnace needs to be equal to the theoretical air amount of the refuse. As described above, since the amount of air supplied to the gasification furnace is substantially constant regardless of the quality of the waste, the amount of combustion air supplied to the melting furnace increases as the amount of heat generated from the waste increases.
[0015]
In addition, since the amount of air supplied to the gasifier is almost constant regardless of the amount of heat generated by the waste, the amount of generated pyrolysis gas is also substantially constant, and the flow rate of the pyrolysis gas blown into the melting furnace depends on the quality of the waste. Is almost constant.
[0016]
On the other hand, the amount of combustion air supplied to the melting furnace depends on the amount of heat generated from the refuse, so that care must be taken in determining the nozzle dimensions. From the viewpoint of improving flammability, it is necessary to set the blowing flow rate to 50 m / s or more. However, when the nozzle size is determined at a flow rate of 50 m / s based on the refuse having the lowest calorific value, the highest calorific value is obtained. In the case of refuse, the flow velocity is about twice as high as 100 m / s, exceeding the capacity of the fan.
[0017]
Therefore, the nozzle size must be determined so that the flow rate is about 60 m / s for the waste with the highest heat generation. In this case, the flow rate for the waste with the lowest heat generation is about half, about 30 m / s. It becomes extremely small and flammability deteriorates. There is a correlation between the flow rate of the combustion air and the temperature in the melting furnace as shown in FIG. 2. When the flow rate is lower than 50 m / s, the temperature drops rapidly, and it becomes difficult to melt the ash.
[0018]
For this reason, conventionally, the temperature was increased using an auxiliary burner installed in a melting furnace to melt the ash. Originally, it should be possible to melt the ash only by the combustion energy of the garbage, but because of the deterioration of the flammability, it is necessary to supply auxiliary fuel, unnecessary fuel cost is generated, and the running cost is increased. There's a problem.
[0019]
SUMMARY OF THE INVENTION An object of the present invention is to provide a pyrolysis gasification and melting system that can solve the above-mentioned drawbacks of the prior art, can eliminate or reduce the supply of auxiliary fuel, and can reduce running costs.
[0020]
[Means for Solving the Problems]
In order to achieve the above object, a first means of the present invention is to provide a gasification furnace which partially burns an object to be burned, such as general waste or industrial waste, and generates a pyrolysis gas and char by being pyrolyzed. ,
A melting furnace that supplies combustion air to the pyrolysis gas and the char from the gasifier and burns it, melts the ash in the char and discharges it as slag;
It is intended for a pyrolysis gasification and melting system including a dust collecting device for removing dust from the combustion exhaust gas from the melting furnace.
[0021]
Then, the combustion exhaust gas dedusted by the dust collector is mixed with combustion air and supplied to the melting furnace.
[0022]
According to a second aspect of the present invention, in the first aspect, the combustion air and the combustion gas are mixed so that a flow rate of a mixture of the combustion air and the combustion exhaust gas into the melting furnace is maintained at 50 m / s or more. The supply amount of the combustion exhaust gas is adjusted.
[0023]
A third means of the present invention is characterized in that, in the first means or the second means, the combustion exhaust gas is supplied from an outlet of an induction ventilator provided on an outlet side of the dust collector. .
[0024]
According to a fourth aspect of the present invention, in the first to third aspects, the dust discharged from the dust collector is supplied to a melting furnace along with the combustion exhaust gas. .
[0025]
According to a fifth aspect of the present invention, in the first to third aspects, the incombustible substance discharged from the gasification furnace is supplied to the melting furnace together with the combustion exhaust gas. is there.
[0026]
In a sixth aspect of the present invention, in the first to third aspects, the dust discharged from the dust collector and the incombustibles discharged from the gasifier are accompanied by the combustion exhaust gas. It is characterized in that it is supplied to a melting furnace.
[0027]
According to the present invention, it is possible to properly maintain the blowing flow rate from the combustion air injection nozzle, which was difficult with only the combustion air, so that the flammability of the pyrolysis gas and the char and air in the melting furnace can be maintained. It does not invite the deterioration. Therefore, it is possible to eliminate or reduce the supply of the auxiliary fuel required in the prior art, and it is possible to reduce the calorific value at which the ash can be melted only by the combustion energy of the object to be burned such as refuse, Since the supply of auxiliary fuel is unnecessary or can be reduced, the running cost can be reduced.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a pyrolysis gasification and melting system according to the first embodiment. This system is a combination of a fluidized bed gasifier 3 and a swirling melting furnace 6, and a secondary combustion chamber 7 is provided at the latter stage of the melting furnace for complete combustion of combustion exhaust gas. Further, a waste heat recovery boiler 8 for recovering heat from the combustion exhaust gas and a temperature reducing device 9 for adjusting the exhaust gas temperature in order to suppress the resynthesis of dioxins are provided. A bag filter, which is a filtration type dust collector, is provided as the dust collector 10, and slaked lime e is supplied as a desalinating agent upstream of the bag filter.
[0029]
The general refuse introduced into the supply hopper is supplied to a fluidized-bed gasification furnace 3 by a dust supply device 2, and is fluidized by fluidized air a supplied from an air diffuser 4 installed at the bottom of the gasification furnace 3. Fluidize with. In this process, the refuse is partially burned and pyrolyzed to generate pyrolysis gas and char mainly composed of unburned carbon and ash. The incombustibles c are discharged from the bottom of the gasification furnace 3.
[0030]
The generated pyrolysis gas and char are sent to the swirling melting furnace 6 through the flow path 5 and react with the separately supplied combustion air b to burn. The inside of the melting furnace 6 is maintained at a temperature higher than the melting temperature of the ash, and the ash in the char is melted and collected as slag d.
[0031]
The combustion exhaust gas is completely burned in the secondary combustion chamber 7, heat is recovered by the waste heat recovery boiler 8, and then the temperature of the combustion exhaust gas is reduced by the temperature reducing device 9 in order to suppress the resynthesis of dioxins. Further, the flue gas g, which is detoxified and desalted by the dust collecting device 10 and detoxified, passes through the induction ventilator 20, and a part of the flue gas g is supplied to the melting furnace 6 by the flue gas recirculation fan 17, and the remaining combustion is performed. The exhaust gas is emitted from the chimney 11. The dust f is discharged from the dust collector 10. If the above-mentioned discharge pressure of the induction ventilator 20 is used, no additional fan is required.
[0032]
The combustion air b supplied to the melting furnace 6 is taken in by a forced air blower 13 and measured by an air flow meter 14a, and the amount of air is controlled by an air flow regulating valve 15a so that the melting furnace 6 has a predetermined temperature or higher. The fuel is injected from the combustion furnace air blowing nozzle 12.
[0033]
The combustion air b is reduced in accordance with the decrease in the waste quality and the waste supply amount during operation, and the combustion exhaust gas g extracted from the downstream of the dust collector 10 is supplied to the combustion furnace air injection nozzle 12 for the melting furnace. Is controlled so that the blowing velocity of the nozzle portion is always 50 m / s or more (preferably 60 to 80 m / s).
[0034]
The amount of exhaust gas supplied to the melting furnace 6 is measured by an exhaust gas flow meter 14 g, and the oxygen concentration in the combustion exhaust gas is constantly measured by an oxygen concentration meter 16. The measurement data of the air flow meter 14a, the exhaust gas flow meter 14g, and the oximeter 16 are input to the arithmetic / control device 18, and the control signal from the arithmetic / control device 18 causes the melting furnace 6 to have a predetermined air ratio and temperature. In this way, the opening of the air flow control valve 15a and the exhaust gas flow control valve 15g is controlled.
[0035]
Since the amount of air supplied to the gasification furnace 3 is substantially constant regardless of the quality of the refuse, the amount of combustion air supplied to the melting furnace 6 increases as the amount of heat generated from the refuse increases. In addition, since the amount of air supplied to the gasification furnace 3 is substantially constant regardless of the amount of heat generated by the refuse, the amount of generated pyrolysis gas is also substantially constant, and the flow rate of the pyrolysis gas blown into the melting furnace 6 is determined by the quality of the refuse. It is almost constant irrespective of this.
[0036]
On the other hand, the amount of combustion air supplied to the melting furnace 6 varies depending on the calorific value of the refuse, but it is necessary to set the blowing velocity to 50 m / s or more in order to improve the combustibility. The nozzle size is determined such that the flow rate of the combustion air is 60 m / s based on the assumed highest heat generation amount of dust. In this case, the refuse having the lowest calorific value has a flow velocity of about 30 m / s, which is about half, so that the flammability deteriorates.
[0037]
There is a correlation between the flow velocity of the combustion air and the temperature in the melting furnace as shown in FIG. 2, and it has been found that when the flow velocity is lower than 50 m / s, the temperature rapidly decreases. In the present invention, by supplying a part of the combustion exhaust gas g as the combustion air a to the combustion air blowing nozzle 12, the blowing flow rate can be kept optimal.
[0038]
Therefore, the deterioration of the combustion properties of the pyrolysis gas and the char and the air in the melting furnace 6 does not occur. In addition, it is possible to eliminate the need for supplying the auxiliary fuel, which is required in the related art, and it is possible to reduce the calorific value at which the ash can be melted only by the combustion energy of the refuse.
[0039]
FIG. 3 is a schematic configuration diagram of a pyrolysis gasification and melting system according to the second embodiment. The present embodiment is different from the first embodiment in that an ejector 19 is provided on the supply path of the combustion exhaust gas g, and the combustion exhaust gas g supplied to the melting furnace 6 entrains the dust f collected by the dust collector 10. Is supplied to the melting furnace 6 through the blowing nozzle 12. According to the present embodiment, the dust supply nozzle and the dust transport air fan required in the related art can be omitted.
[0040]
FIG. 4 is a schematic configuration diagram of a pyrolysis gasification and melting system according to the third embodiment. The present embodiment differs from the second embodiment in that the combustion exhaust gas g supplied to the melting furnace 6 is accompanied by the incombustible material c discharged from the gasification furnace 3 and supplied to the melting furnace 6. .
[0041]
Waste ash is a highly basic ash with little silicon oxide or aluminum oxide, and most of the non-combustible material c is silicon oxide. Therefore, supply the non-combustible material c to the melting furnace 6 to reduce the basicity. Can be. Since the melting point is lowered by lowering the basicity in this way, the melting becomes easy and reliable. Further, according to the present embodiment, the incombustible material supply nozzle and the incombustible material conveying air fan which are required in the related art can be omitted.
[0042]
FIG. 5 is a schematic configuration diagram of a pyrolysis gasification and melting system according to the fourth embodiment. This embodiment is different from the second embodiment in that both the dust f and the non-combustible material c are supplied to the melting furnace 6. According to the present embodiment, the dust supply nozzle, the dust fan for transporting dust, the non-combustible material supply nozzle, the air fan for transporting non-combustible material, and the like, which are required in the related art, can be omitted.
[0043]
Although the case of refuse has been described in the above embodiment, the present invention is also applicable to the case of treating other burnable materials such as industrial waste.
[0044]
【The invention's effect】
By applying the present invention, it is possible to always maintain good flammability of the melting furnace, and achieve stable operation of the melting furnace, that is, stable flow of slag. Further, conventionally, it is necessary to supply an auxiliary fuel to refuse having a low calorific value. However, the present invention can reduce the amount of the auxiliary fuel. Furthermore, the minimum value of the calorific value of refuse that can be stably melted without the supply of auxiliary fuel can be reduced, and economical operation becomes possible.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a pyrolysis gasification and melting system according to a first embodiment of the present invention.
FIG. 2 is a characteristic diagram showing a relationship between a combustion air blowing velocity and a melting furnace temperature.
FIG. 3 is a schematic configuration diagram of a pyrolysis gasification and melting system according to a second embodiment of the present invention.
FIG. 4 is a schematic configuration diagram of a pyrolysis gasification and melting system according to a third embodiment of the present invention.
FIG. 5 is a schematic configuration diagram of a pyrolysis gasification and melting system according to a fourth embodiment of the present invention.
FIG. 6 is a schematic configuration diagram of a conventional pyrolysis gasification and melting system.
FIG. 7 is a characteristic diagram showing a relationship between an air ratio and (consumption heat generation) / (refuse heat input).
[Explanation of symbols]
1: supply hopper, 2: dust supply device, 3: gasifier, 4: diffuser tube, 5: flow path, 6: melting furnace, 7: secondary combustion chamber, 8: waste heat recovery boiler, 9: temperature reduction Apparatus, 10: dust collector, 11: chimney, 12: combustion air blowing nozzle, 13: push blower, 14a: air flow meter, 14g: exhaust gas flow meter, 15a: air flow control valve, 15g: exhaust gas flow control Valve, 16: Oxygen meter, 17: Circulating fan, 18: Operation / control device, 19: Ejector, a: Fluidized air, b: Combustion air, c: Noncombustible, d: Slag, e: Slaked lime, f : Dust, g: combustion exhaust gas

Claims (6)

A gasification furnace that partially burns the material to be burned and generates pyrolysis gas and char by being pyrolyzed;
A melting furnace that supplies combustion air to the pyrolysis gas and the char from the gasification furnace and burns, melts the ash in the char and discharges it as slag;
In a pyrolysis gasification and melting system equipped with a dust collector that removes combustion exhaust gas from the melting furnace,
A pyrolysis gasification and melting system, wherein the combustion exhaust gas dedusted by the dust collector is mixed with combustion air and supplied to the melting furnace. 2. The pyrolysis gasification and melting system according to claim 1, wherein the flow rate of the mixed gas of the combustion air and the combustion exhaust gas into the melting furnace is maintained at 50 m / s or more. A pyrolysis gasification and melting system, wherein the supply amount of the gas is adjusted. The pyrolysis gasification and melting system according to claim 1 or 2, wherein the combustion exhaust gas is supplied from an outlet of an induction ventilator provided on an outlet side of the dust collector. . The thermal decomposition gasification and melting system according to any one of claims 1 to 3, wherein the dust discharged from the dust collector is supplied to a melting furnace together with the combustion exhaust gas. Cracking gasification melting system. The pyrolysis gasification and melting system according to any one of claims 1 to 3, wherein incombustible substances discharged from the gasification furnace are supplied to the melting furnace together with the combustion exhaust gas. Pyrolysis gasification melting system. 4. The pyrolysis gasification and melting system according to claim 1, wherein the dust discharged from the dust collector and the incombustible discharged from the gasification furnace are entrained in the combustion exhaust gas. 5. A pyrolysis gasification and melting system characterized by being supplied to a melting furnace.

Images