JP2019007718A - Waste melting furnace and operation method thereof - Google Patents

Abstract

To provide a waste melting furnace that can reduce running cost using a solid fuel including briquette coal.SOLUTION: A waste melting furnace has a fusion furnace part 4 that burns solid fuel including briquette coal by feeding gas containing oxygen from a tuyere 42, and melts waste or pyrolysis residues thereof. The gas has an oxygen concentration of 27-35 vol.%, and a cross-section flow rate at the bottom part 4A of the fusion furnace part 4 is maintained in a range of 0.07-0.18 m/seconds.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a waste melting furnace and an operation method thereof.

  As a method for treating general waste and industrial waste, a method of using solid fuel as a heat source and melting the waste in an industrial furnace is known. The melting treatment of waste has an advantage that not only the volume of waste can be reduced, but also incinerated ash and incombustible waste that have been finally disposed of by landfill can be recovered as resources such as slag and metal.

  As examples of solid fuel for a waste melting furnace, coke for blast furnace, and formed charcoal containing a carbonaceous material and a binder are known. In Patent Documents 1 and 2, using a binder containing a predetermined carbonaceous material and a lignin sulfonate having a number average molecular weight of 1100 or more, a coal for waste melting furnace having a high crushing strength even in a high temperature environment is obtained. Manufacturing techniques have been proposed.

Japanese Patent No. 5684420 Japanese Patent No. 5762653

  Coal charcoal as proposed in Patent Documents 1 and 2 is advantageous in terms of running cost as compared with the case where coke for blast furnace is used as the solid fuel of the waste melting furnace. However, it has been found that depending on the use conditions of the coal, the amount of the coal used for melting the waste increases and the running cost increases.

  In one aspect, an object of the present invention is to provide a method for operating a waste melting furnace capable of reducing running cost using a solid fuel containing coal. Another object of the present invention is to provide a waste melting furnace capable of reducing running cost using a solid fuel containing coal.

  In one aspect, the present invention provides a waste melting process including a melting step of burning solid fuel while supplying a solid fuel containing oxygen and gas containing oxygen to the bottom of the furnace, and melting the waste or its thermal decomposition residue. A method of operating a furnace, in the melting step, waste melting in which the oxygen concentration of the gas is maintained within a range of 27 to 35% by volume and the cross-sectional flow rate at the furnace bottom is within a range of 0.07 to 0.18 m / sec. A method for operating a furnace is provided.

  In this waste melting furnace operating method, in the melting step, the oxygen concentration of the gas supplied to the furnace bottom and the cross-sectional flow rate at the furnace bottom are maintained within a predetermined range. For this reason, it can suppress that the small piece of solid fuel scatters from a furnace bottom part, and can use solid fuel effectively as a fuel. Therefore, the running cost can be reduced by using solid fuel containing coal.

  The formed charcoal preferably includes a binder containing a charcoal material and lignin sulfonate. Thereby, the crushing strength of the coal becomes sufficiently high and a good grate function can be exhibited. Therefore, the waste or the thermal decomposition residue thereof can be melted more efficiently.

  The ratio of the amount of carbon scattered from the bottom of the furnace to the amount of carbon contained in the solid fuel supplied to the bottom of the furnace is preferably 20% by mass or less. As a result, the proportion of solid fuel scattered from the bottom of the furnace can be reduced, and the running cost can be further reduced.

  The above-mentioned waste melting furnace includes a shaft part having a waste charging inlet, a melting furnace part having a tuyere that is arranged by shifting the shaft part and the furnace core, and supplying the gas, and a lower part of the shaft part and a melting furnace The waste gasification melting furnace provided with the communication part which connects the upper part of a part may be sufficient. In this case, the operation method may include a pyrolysis step of drying and pyrolyzing waste in the shaft portion and the communication portion, and the melting step may be performed in the melting furnace portion.

  In another aspect, the present invention provides a waste melting furnace provided with a melting furnace section for supplying a gas containing oxygen from a tuyere to burn solid fuel containing coal and melting waste or a thermal decomposition residue thereof. A waste configured to maintain an oxygen concentration of the gas in a range of 27 to 35% by volume and a cross-sectional flow rate in a furnace bottom of a melting furnace in a range of 0.07 to 0.18 m / sec. A melting furnace is provided.

  The waste melting furnace supplies a gas having a predetermined oxygen concentration from the tuyere to the melting furnace section, and keeps the cross-sectional flow velocity at the furnace bottom of the melting furnace section within a predetermined range. For this reason, it can suppress that the small piece of solid fuel scatters from a furnace bottom part, and can use solid fuel effectively as a fuel. Therefore, the running cost can be reduced by using solid fuel containing coal.

  The waste melting furnace has a shaft part for drying and thermally decomposing waste charged from the waste inlet from the upstream side with respect to the distribution direction of the waste, a lower part of the shaft part, and a melting furnace. You may provide the communication part which connects the upper part of a part, and the melting furnace part arrange | positioned by shifting a shaft part and a furnace core in this order.

  In one aspect, the present invention can provide a method for operating a waste melting furnace capable of reducing running costs using a solid fuel containing coal. In another aspect, the present invention can provide a waste melting furnace capable of reducing running costs using a solid fuel containing coal.

FIG. 1 is a longitudinal sectional view schematically showing an embodiment of a waste melting furnace. 2 is an enlarged longitudinal sectional view showing a melting furnace part of the waste melting furnace of FIG. FIG. 3 is a diagram schematically showing changes due to combustion of coal. FIG. 3A schematically shows a solid fuel before combustion, and FIG. 3B schematically shows a state after partial combustion. FIG. 4 is a graph showing the results of Examples 1 and 2 and Comparative Examples 4 and 5. FIG. 5 is a graph showing the results of Reference Example 1.

  In some embodiments, the method for operating a waste melting furnace according to the present invention burns solid fuel while supplying solid fuel containing oxygen-containing gas and coal to the bottom of the furnace, and waste or a pyrolysis residue thereof. A melting step of melting In this melting step, the oxygen concentration of the gas supplied from the tuyere is maintained within the range of 27 to 35% by volume, and the cross-sectional flow rate at the furnace bottom is within the range of 0.07 to 0.18 m / sec. The waste melting furnace includes tuyere for supplying a gas containing oxygen at the bottom of the furnace.

  The oxygen concentration of the gas is a volume ratio in a standard state (0 ° C., 101.325 kPa), and the cross-sectional flow velocity at the furnace bottom is obtained by dividing the gas flow rate in the standard state by the cross-sectional area of the furnace bottom. The cross-sectional area of the furnace bottom is the cross-sectional area of the internal space when the furnace bottom is cut by a horizontal plane having a height at which the bottom tuyere is provided.

  Solid fuel contains coal. The formed charcoal preferably contains a charcoal material and a binder. The carbonaceous material may contain at least one selected from coal, powdered coke, char, petroleum coke, and fly ash. The mass ratio of the binder to the carbon material may be 0.06 to 0.2. If mixed at such a mass ratio, the crushing strength of the coal can be increased. Therefore, scattering of solid fuel can be further suppressed.

  Examples of the binder include a hydrophilic polymer having a benzene ring and at least one functional group selected from the group consisting of a sulfo group, a hydroxyl group, and a carboxyl group in the molecular structure. Preferred hydrophilic polymers include lignin sulfonate.

  A commercial item can be used for lignin sulfonate. The number average molecular weight of the lignin sulfonate may be, for example, 1000 or more, or 1400 or more, from the viewpoint of improving the crushing strength of the coal. From the viewpoint of availability, the number average molecular weight of the lignin sulfonate may be, for example, 10,000 or less, or 8000 or less. The number average molecular weight in the present disclosure is determined from a polystyrene standard calibration curve using gel permeation chromatography. Examples of the lignin sulfonate include magnesium lignin sulfonate, calcium lignin sulfonate, and sodium lignin sulfonate.

The shape of the charcoal is not particularly limited, and may be, for example, a columnar shape or a Macek shape. The density of the charcoal may be, for example, 1.0 to 2.0 g / ml. The particle size A ₁ [mm] of the coal is, for example, 30 mm or more. The particle diameter A ₁ [mm] of the coal is calculated by the following formula (1) by converting the volume V ₁ [ml] of the coal into a true sphere having the same volume.
A ₁ = 2 × ((V ₁ × 3/4 / π) ^1/3 ) × 10 (1)

  The waste melting furnace of this invention can be used suitably for the above-mentioned operation method. In some embodiments, the waste melting furnace has a tuyere that supplies a gas containing oxygen to the bottom of the furnace, and a gas containing oxygen is supplied from the tuyere to burn solid fuel containing coal. And a melting furnace section for melting the waste or its thermal decomposition residue. This waste melting furnace is configured to maintain the oxygen concentration of the gas within a range of 27 to 35% by volume and the cross-sectional flow velocity at the bottom of the melting furnace within a range of 0.07 to 0.18 m / sec. . The method for obtaining the oxygen concentration and cross-sectional flow velocity of the gas supplied from the tuyere is as described above.

  The waste melting furnace has a shaft part for drying and thermally decomposing waste charged from the waste inlet from the upstream side with respect to the distribution direction of the waste, a lower part of the shaft part, and a melting furnace. A waste gasification melting furnace may be provided that includes a communication part that connects the upper part of the part, and a melting furnace part that is arranged by shifting the shaft part and the furnace core in this order. If it is such a waste gasification melting furnace, the thermal decomposition process which dries and thermally decomposes waste in a shaft part and a communicating part can be performed, and a melting process can be performed in a melting furnace part.

  Hereinafter, an embodiment of a waste melting furnace and an operation method thereof will be described with reference to the drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and a duplicate description is omitted.

  FIG. 1 is a longitudinal sectional view schematically showing a waste gasification melting furnace which is an embodiment of a waste melting furnace. The operation method of the waste melting furnace which concerns on one Embodiment can be implemented using this waste gasification melting furnace. A waste gasification melting furnace 10 shown in FIG. 1 includes a shaft portion 2, a communication portion 5 including a carbonized fire grate portion 3, and a melting furnace portion 4 as main components. The shaft part 2 is thermally decomposed while drying waste in a reducing atmosphere. In the communication part 5, the waste from the shaft part 2 is further thermally decomposed by the carbonization grate part 3, and the waste is carbonized. The melting furnace unit 4 burns and melts the pyrolyzed waste.

  The shaft portion 2 and the melting furnace portion 4 are disposed so as to relatively shift the furnace core in the lateral direction. The opening portion 23 on the bottom side of the shaft portion 2 and the opening portion 46 on the upper side of the melting furnace portion 4 Are connected by the communication part 5. The carbonized grate portion 3 forms the bottom surface of the communication portion 5 and is arranged in a step shape.

  The shape of the shaft portion 2 may be, for example, a cylindrical shape or a rectangular shape. A waste inlet 21 for charging waste into the furnace is formed at the upper portion of the shaft portion 2. The kind of waste is not particularly limited, and may be any of general waste and industrial waste. Shredding dust (ASR), excavated waste, incinerated ash, or the like, or a mixture of these and combustible waste can be treated. A waste filling layer 100 is formed in the shaft portion 2 by the waste. From the waste inlet 21, the carbonized waste and char may be introduced together with the waste.

  On the upper side of the shaft portion 2, an in-furnace gas discharge port 22 is formed for discharging gas generated by thermal decomposition of waste and gas blown into the furnace. An opening 23 is formed at the lower end of the shaft portion 2, and the waste that descends in the shaft portion 2 due to its own weight is introduced from the opening 23 into the communication portion 5. In the shaft part 2, the waste gas is generated by heat exchange when the gas containing oxygen blown from the carbonization grate part 3 and the melting furnace part 4 and the gas generated in the furnace pass through the waste packed bed 100. Drying and pyrolysis of the product proceed.

  The communicating portion 5 has a rectangular longitudinal cross-sectional shape, and the carbonized fire grate portion 3 is disposed along the bottom surface thereof. The carbonized grate part 3 further thermally decomposes the waste dried and thermally decomposed by the shaft part 2. The carbonization grate unit 3 has a function as a device for pyrolyzing (dry distillation) waste and a function as a supply device for supplying the carbonized waste to the melting furnace unit 4. The carbonization grate part 3 is formed by combining a movable carbonization grate and a fixed carbonization grate alternately in a staircase shape or an inclined shape.

  Each movable carbonization grate is configured to reciprocate at a constant pitch in the lateral direction by a drive device 31 (31a, 31b) such as a fluid pressure cylinder (see double arrows in FIG. 1). By combining such a movable carbonization grate and a fixed carbonization grate, waste on the carbonization grate unit 3 can be pushed out from the upstream side to the downstream side while stirring.

  The carbonization grate part 3 has a two-stage structure including a supply carbonization grate 3A on the upper stage side and a dry distillation carbonization grate 3B on the lower stage side. The supply carbonization grate 3 </ b> A is located directly below the shaft portion 2 so as to directly receive a load of waste filled in the shaft portion 2. The supply carbonization grate 3A further thermally decomposes the waste so that carbonization of the dry and pyrolyzed waste at the shaft portion 2 proceeds and supplies the waste by pushing it to the dry distillation carbonization grate 3B.

  The dry distillation carbonization grate 3B is provided adjacent to the supply carbonization grate 3A, and further generates a carbide by further pyrolyzing the waste from the supply carbonization grate 3A. In this manner, a waste pyrolysis step is performed in the carbonized grate portion 3 of the shaft portion 2 and the communication portion 5. The dry distillation carbonization grate 3 </ b> B pushes the pyrolyzed (carbonized) waste to the opening 46 of the melting furnace section 4.

  The movable carbonization grate of the supply carbonization grate 3A is driven by the first drive unit 31a, and the movable carbonization grate of the dry distillation carbonization grate 3B is driven by the second drive unit 31b. Thus, by providing the first and second driving devices 31a and 31b independently of each other, the driving, stopping, and driving speed of the carbonization grate 3A, 3B can be controlled independently. As a result, the carbonization grate 3A, The waste conveyance speed by 3B can also be controlled independently.

  The carbonization grate unit 3 can supply air toward the waste on the carbonization grate unit 3 through a gap between the carbonization grates and / or a blow hole (not shown) formed in the carbonization grate. It has a configuration. That is, the carbonization grate portion 3 also serves as a blower that blows air for drying and pyrolyzing waste into the furnace. On the back side of the carbonization grate 3A and the carbonization grate 3B, a first collection chamber 32a for collecting fine particles of the carbonized waste that has fallen from the gaps between the carbonization grate. And the second recovery chamber 32b are respectively disposed.

  A blower pipe 33a is connected to the first recovery chamber 32a. The air supply pipe 33a is provided with a flow rate adjusting valve 33b for adjusting the air flow rate, and an air blowing device 36 for supplying air is connected to the upstream side of the flow rate adjusting valve 33b. The air from the blower 36 is supplied to the first recovery chamber 32a through the blower pipe 33a after the flow rate is adjusted by the flow rate adjusting valve 33b. The air supplied to the first recovery chamber 32a is introduced into the furnace through the gaps in the supply carbonization grate 3A and / or the blow holes formed in the carbonization grate.

  A blower pipe 34a is connected to the second recovery chamber 32b. The air supply pipe 34a is provided with a flow rate adjusting valve 34b for adjusting the air flow rate, and an air blowing device 36 for supplying air is connected to the upstream side of the flow rate adjusting valve 34b. The air from the blower 36 is supplied to the second recovery chamber 32b through the blower pipe 34a after the flow rate is adjusted by the flow rate adjusting valve 34b. The air supplied to the second recovery chamber 32b is introduced into the furnace from the gaps in the dry distillation carbonization grate 3B and / or the blow holes formed in the carbonization grate.

  The communication part 5 above the melting furnace part 4 is provided with a secondary material inlet 41 for supplying solid fuel containing coal to the melting furnace part 4. The solid fuel may contain coke, biomass charcoal, or the like in addition to coal. In addition to the solid fuel, limestone as a basicity adjusting agent may be supplied from the auxiliary material inlet 41.

  The melting furnace part 4 has an inverted truncated cone part (so-called morning glory part) 45 that forms a constriction part on the communication part 5 side, that is, the upper part. The inclination angle of the inverted truncated cone part 45 with respect to the horizontal direction may be greater than 75 °, for example.

  In addition to the solid fuel from the auxiliary material inlet 41, the melting furnace section 4 is supplied with the pyrolysis residue of the waste that has been dried and carbonized through the shaft section 2 and the communication section 5 from the opening 46. Is done. The supplied pyrolysis residue of the waste is further pyrolyzed in the melting furnace section 4. In addition, at least a part of the waste supplied to the melting furnace unit 4 may not be thermally decomposed.

  On the deposited layer 102 in the melting furnace section 4, a packed layer 101 is formed by carbonized waste. The solid fuel containing coking coal charged from the auxiliary material inlet 41 passes through the packed bed 101 and is deposited on the furnace bottom 4A at the lower part of the melting furnace 4 to form a deposited layer 102. The furnace bottom portion 4A is configured by a cylindrical internal space, and a plurality of tuyere 42 are arranged side by side in the circumferential direction. A gas containing oxygen for combustion is supplied from the tuyere 42 to the solid fuel deposition layer 102 formed in the internal space.

  In the furnace bottom portion 4A, by supplying a gas containing oxygen from the tuyere 42, solid carbon and fixed carbon as a pyrolysis residue of waste are burned. The ash and incombustible components contained in the waste or its thermal decomposition residue are melted by the combustion heat. In this way, a melting step for melting the waste or its decomposition residue is performed in the melting furnace section 4. Note that the high-temperature gas generated in the pyrolysis step and the melting step may be discharged from the furnace gas discharge port 22, recovered after waste heat with an apparatus such as a boiler, and then discharged after being detoxified.

  The furnace bottom portion 4A of the melting furnace portion 4 is provided with a hot water outlet 44 for discharging a melt (that is, slag and metal). The hot water outlet 44 has an opening / closing mechanism (not shown) so that the melt can be stored and discharged in a reducing atmosphere, and the melt is discharged intermittently. The melt discharged outside the furnace can be cooled and solidified to obtain slag and metal.

FIG. 2 is an enlarged longitudinal sectional view showing the melting furnace section 4 of the waste gasification melting furnace 10 of FIG. In the deposition layer 102 of the solid fuel in the furnace bottom portion 4A of the melting furnace unit 4, the carbon is mainly gasified around the combustion reaction region 102A in which carbon contained in the solid fuel burns and the combustion reaction region 102A. There is a gasification reaction region 102B. The main reaction in the combustion reaction region 102A is represented by Expression (2), and the main reaction in the gasification reaction region 102B is represented by Expression (3). In this embodiment, in order to facilitate understanding, the boundary line of the gasification reaction region 102B of the combustion reaction region 102A is clearly shown, but these regions may not be clearly defined. That is, the reaction of the equation (2) mainly proceeds in the vicinity of the tuyere 42, and the ratio of the reaction of the equation (3) to the equation (2) may gradually increase as the distance from the tuyere 42 increases.
C + O ₂ → CO ₂ (2)
C + CO ₂ → 2CO (3)

  The combustion reaction region 102A is formed in the vicinity of the tuyere 42 that is relatively rich in oxygen, and the gasification reaction region 102B is formed in a portion farther from the tuyere 42 than the combustion reaction region 102A. If the cross-sectional flow velocity of the gas containing oxygen supplied from the tuyere 42 becomes too small, the combustion reaction region 102A is reduced, and the combustion reaction of the formula (2) does not proceed sufficiently at the center of the furnace bottom 4A. . As a result, the temperature of the furnace bottom portion 4A is lowered, and the melting of the waste or its thermal decomposition residue tends to hardly proceed. From such a viewpoint, the cross-sectional flow velocity of the gas containing oxygen is 0.07 m / second or more. From the viewpoint of promoting the combustion of solid fuel and improving the throughput of waste, the cross-sectional flow rate of the gas containing oxygen supplied from the tuyere 42 is preferably 0.09 m / second or more, more preferably It is 0.1 m / second or more.

  On the other hand, if the cross-sectional flow velocity of the gas containing oxygen becomes too large, the amount of scattered solid fuel small pieces 52a increases from the deposited layer 102 in which the combustion reaction region 102A and the gasification reaction region 102B are formed. The small piece 52a includes, for example, a part of the solid fuel supplied from the auxiliary material loading port 41 that has been peeled off, a fragment that is generated by the collapse of the solid fuel, and the like. From the viewpoint of reducing the amount of scattering of the small pieces 52a, the cross-sectional flow velocity of the gas containing oxygen supplied from the tuyere 42 is 0.18 m / sec or less. From the viewpoint of effectively reducing the amount of scattering of the small pieces 52a to effectively use the solid fuel, the cross-sectional flow rate of the gas containing oxygen in the furnace bottom 4A is preferably 0.16 m / sec or less, more preferably 0. .14 m / sec or less.

  A tuyere 42 is provided at the furnace bottom 4A of the melting furnace section 4. The tuyere 42 is configured to be able to supply a mixed gas of air and oxygen from the oxygen generator 43 as a gas containing oxygen. The supply amount of gas from the tuyere 42 and the oxygen concentration are adjusted by a flow rate adjustment valve 47a that adjusts the flow rate of air and a flow rate adjustment valve 47b that adjusts the supply amount of oxygen. By adjusting the supply ratio of air and oxygen, the oxygen concentration of the gas supplied from the tuyere 42 can be adjusted. Note that the gas supply amount and the oxygen concentration are not limited to such examples, and may be performed by other means. For example, a three-way valve that adjusts the supply ratio of air and oxygen, and a flow rate adjustment valve that adjusts the flow rate of gas may be provided downstream of the three-way valve.

By adjusting the amount of gas supplied from the tuyere 42, the cross-sectional flow velocity in the furnace bottom 4A can be adjusted. When the furnace bottom portion 4A is a cylindrical internal space, the cross-sectional flow velocity of the gas can be obtained by the following equation (4). In equation (4), A represents the gas flow rate [m ³ / sec] when converted to the standard state, and L represents the inner diameter [m] at the height at which the lower tuyere 42 is provided. . When there are a plurality of tuyere 42, the gas flow rate is a total value of the gas flow rate supplied from each tuyere 42.
Cross flow rate [m / ^{s] = A / (π × L} 2/4) (4)

The furnace bottom 4A may not be cylindrical. For example, when the internal space of the furnace bottom 4A has a quadrangular prism shape, the gas cross-sectional flow velocity can be obtained by the following equation (5). In Equation (5), A represents the gas flow rate [m ³ / sec] when converted to the standard state, and L1 and L2 represent the internal space at the height at which the lower tuyere 42 is provided. The length [m] of the long side and short side of a cross section when cut along a horizontal plane is shown. Note that when the cross section is a square, L1 = L2.
Sectional flow velocity [m / sec] = A / (L1 × L2) (5)

  The cross-sectional flow rate of the gas containing oxygen in the furnace bottom 4A is 0.07 to 0.18 m / sec, preferably 0.09 to 0.16 m / sec, and more preferably 0.1 to 0.14 m / sec. Seconds. When the diameter of the furnace bottom portion 4A changes in the height direction, the cross-sectional flow velocity is based on the cross-sectional area of the internal space when the furnace bottom portion 4A is cut by a horizontal plane at the height where the bottom tuyere 42 is provided. Calculated.

  FIG. 3 is a diagram schematically showing changes due to combustion of the coal 50 contained in the solid fuel. FIG. 3A schematically shows the formed coal 50 included in the solid fuel before combustion, that is, from the auxiliary material inlet 41. The formed charcoal 50 contains a plurality of carbon materials 52 and a binder 54 that binds the plurality of carbon materials 52 to each other. The binder 54 contains lignin sulfonate as a main component.

  The formed coal 50 contained in the solid fuel forming the deposited layer 102 shown in FIG. 1 is burned by oxygen contained in the gas. Here, the charcoal material 52 contained in the coal 50 tends to be less susceptible to the influence of the oxygen concentration of the gas than the binder 54. That is, the binder 54 tends to have a higher combustion rate than the carbon material 52 when the oxygen concentration of the gas increases. For this reason, if the oxygen concentration of the gas becomes too high, the binder 54 burns before the carbon material 52 and disappears. Then, as shown in FIG. 3B, the small piece 52a remains. The small pieces 52 a that are not bound by the binder 54 tend to be scattered from the deposited layer 102 as compared with those that are bound by the binder 54.

  From the viewpoint of reducing the amount of scattering of the small pieces 52a, the oxygen concentration in the oxygen-containing gas is 35% by volume or less, preferably 33% by volume or less. On the other hand, if the oxygen concentration becomes too low, the amount of gas necessary for the combustion of the solid fuel increases, so the temperature at the furnace bottom 4A tends to decrease. In particular, when the oxygen concentration is 26.5% by volume or less, the consumption of solid fuel increases rapidly. For this reason, running costs tend to increase. From such a viewpoint, the oxygen concentration in the gas containing oxygen is 27% by volume or more, and preferably 29% by volume or more.

  The oxygen concentration in the gas containing oxygen supplied from the tuyere 42 is 27 to 35% by volume, preferably 29 to 33% by volume. Thereby, the solid fuel required for ensuring the temperature in the melting furnace part 4 can be reduced while suppressing the scattering of the solid fuel in the melting furnace part 4. Therefore, the amount of solid fuel used is reduced, and the running cost can be sufficiently reduced.

  Returning to FIG. 1, a gas detection unit 48 capable of detecting the concentrations of carbon monoxide and carbon dioxide is installed above the tuyere 42 of the melting furnace unit 4. The gas detector 48 can measure the concentrations of carbon monoxide and carbon dioxide in the melting furnace section 4. Based on these measured values and the amount of gas blown from the tuyere 42, the amount of each carbon consumed by the above equations (2) and (3) can be calculated. The amount of carbon scattered from the furnace bottom portion 4A by subtracting the total amount of carbon consumed by the equations (2) and (3) from the amount of carbon contained in the solid fuel supplied from the auxiliary material inlet 41 Can be calculated.

  From the viewpoint of further reducing the running cost by reducing the ratio of the solid fuel scattered from the furnace bottom portion 4A, the ratio of the amount of carbon scattered from the furnace bottom portion 4A to the carbon amount contained in the solid fuel is preferably 20% by mass. Or less, more preferably 15% by mass or less. From the viewpoint of further reducing the consumption of solid fuel, the ratio of the amount of carbon consumed by the reaction of formula (2) to the amount of carbon contained in the solid fuel is preferably 40% by mass or more, more preferably 50%. It is at least mass%.

  As the gas detector 48, a commercially available gas sensor capable of detecting hydrogen gas and methane gas can be used. The gas detection unit 48 may be provided with a sensor unit capable of detecting the concentrations of hydrogen gas and methane gas inside the melting furnace unit 4, or sampling equipment such as a pipe is installed in the melting furnace unit 4 for sampling. The gas may be measured with a commercially available gas sensor.

  The waste gasification melting furnace 10 can prevent the small pieces 52a of the solid fuel from scattering from the furnace bottom 4A in the melting furnace section 4, and can effectively use the solid fuel as fuel. Therefore, the running cost can be reduced by using solid fuel containing coal.

  As mentioned above, although several embodiment of this invention was described, this invention is not limited to the said embodiment at all. For example, the above-described waste melting furnace includes a communication portion having a carbonization grate portion, but may be a vertical waste melting furnace that does not include such a communication portion.

  Hereinafter, the contents of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

<Comparison between coke for blast furnace and coking coal>
(Comparative Example 1)
A waste gasification melting furnace using ordinary blast furnace coke (particle size: 20 to 80 mm) as a solid fuel, a shaft portion as shown in FIG. 1, a communicating portion having a carbonized grate portion, and a melting furnace portion Drove. Table 1 shows the higher heating value of the blast furnace coke. General waste was charged from the waste inlet of the shaft and blast furnace coke was charged as a solid fuel from the auxiliary material inlet. The operation was performed so that the height of the waste in the shaft portion and the temperature of the melt discharged from the tap at the bottom of the furnace (about 1360 ° C.) were substantially constant. Table 1 shows the oxygen concentration of the gas supplied from the tuyeres at the bottom of the furnace and the cross-sectional flow rate at the bottom of the furnace. In a steady state, the amount of used solid fuel (blast furnace coke) and calorific value required to completely melt unit mass of waste were determined. The results were as shown in Table 1.

(Comparative Example 2)
The waste gasification and melting furnace was operated in the same manner as in Comparative Example 1 except that the coking coal prepared as follows was used as the solid fuel instead of blast furnace coke.

  As a liquid binder, commercially available magnesium lignin sulfonate (manufactured by Nippon Paper Industries Co., Ltd., trade name: Sun Extract M100, number average molecular weight: 3000) and commercially available powder coke (moisture: 20% by mass, particle size: 3 mm or less). Got ready. After the powder coke was dried in a drier, an aqueous solution of magnesium lignin sulfonate was blended and mixed to prepare a mixture. The mixing ratio at this time was 22.5 parts by mass of the magnesium lignin sulfonate aqueous solution with respect to 100 parts by mass of the powder coke.

Water was added to the prepared mixture to prepare a molding raw material containing about 10% by mass of water. This molding raw material was supplied to a double roll molding machine to produce a charcoal. The charcoal produced was screened using a sieve having a mesh opening of 30 mm to obtain a charcoal having a volume of about 120 cm ³ . Table 1 shows the higher heating value of the coal. In the same manner as in Comparative Example 1, the amount of solid fuel (coal charcoal) required for melting the unit mass of waste and the calorific value in the steady state were determined. The results were as shown in Table 1.

  As shown in Table 1, in terms of calorific value, the coal coal of Comparative Example 2 consumed 1.2 times or more solid fuel compared to the blast furnace coke of Comparative Example 1. For this reason, it was confirmed that the running cost of the waste melting furnace cannot be reduced simply by replacing the solid fuel with the blast furnace coke by the coal.

<Effects of cross-sectional flow velocity at furnace bottom and oxygen concentration of gas supplied from tuyere>
(Examples 1-3, Comparative Examples 3-6)
Using the same coal as the coal used in Comparative Example 2, a small waste gasification and melting furnace having the same configuration as in FIG. 1 was operated. Specifically, a model experiment was performed in which the coal was charged from the auxiliary material inlet 41 of FIG. 1 and the coal was burned in the furnace bottom 4A.

  The oxygen concentration of the gas supplied from the tuyeres at the bottom of the furnace and the cross-sectional flow velocity of the gas at the bottom of the furnace were as shown in Tables 2 and 3. The oxygen concentration and the cross-sectional flow rate are values when the gas is converted into a standard state, respectively. In the steady state, the calorific value of the solid fuel required for melting the unit mass of waste was determined. Moreover, the concentration of carbon monoxide and carbon dioxide was measured by a gas detection unit installed above the tuyere. Based on these measured values and the amount of gas blown from the tuyere, the amount of each carbon consumed by the above formulas (2) and (3) was calculated. Calculate the amount of carbon scattered from the bottom of the furnace by subtracting the total amount of carbon consumed by Equation (2) and Equation (3) from the amount of carbon contained in the solid fuel supplied to the waste gasification and melting furnace. did. Moreover, the consumption rate and the scattering rate of each carbon were calculated. The results were as shown in Table 2 and Table 3.

(Comparative Example 7)
The waste melting furnace was operated in the same manner as in Comparative Example 6 except that the same blast furnace coke as in Comparative Example 1 was used as the solid fuel. The results are shown in Table 3. Since Comparative Example 7 uses blast furnace coke, the running cost cannot be reduced.

  In Examples 1 to 3, the total value (kg / h) of the consumed carbon amount and the scattered carbon amount was smaller than that of Comparative Example 3. From this, it was confirmed that Examples 1-3 can reduce the consumption of solid fuel.

  FIG. 4 is a graph showing the relationship between the cross-sectional flow velocity at the furnace bottom portion and the ratio of scattered carbon in Examples 1 and 2 and Comparative Examples 4 and 5 in which the oxygen concentration of the gas supplied from the tuyere is 30% by volume. . From the result of FIG. 4, when the cross-sectional flow velocity becomes a predetermined value (about 0.12 m / sec) or more, it is predicted that the ratio of carbon to be scattered increases linearly. Therefore, when the correlation between the cross-sectional flow velocity and the ratio of scattered carbon was obtained from the three data of Example 2 and Comparative Examples 4 and 5 excluding the data of Example 1 by the least square method, the straight line shown in FIG. A relationship was obtained. From this result, it was found that if the cross-sectional flow velocity at the furnace bottom is 0.18 m / sec or less, the rate of separation and scattering can be maintained at 20 mass% or less.

  From the results shown in FIG. 4, Table 2 and Table 3, etc., the oxygen concentration of the gas supplied from the tuyere is 27 to 35% by volume, and the cross-sectional flow velocity at the furnace bottom is 0.07 to 0.18 m / sec. As a result, it was confirmed that the scattering of the solid fuel containing the coal was suppressed and the running cost of the waste melting furnace could be reduced.

<Evaluation of burning rate>
(Reference Example 1)
Thermogravimetric analysis of the powdered coke and lignin sulfonate contained in the coal coal used in Example 1 was performed to evaluate the combustion rate. The thermogravimetric analysis was performed at 1000 ° C. assuming the temperature at the bottom of the waste melting furnace. The analysis was performed in the case where the atmosphere of thermogravimetric analysis was an oxygen concentration of 21% by volume, 30% by volume, and 37% by volume. The result was as shown in FIG.

  As shown in FIG. 5, when the oxygen concentration was around 30% by volume, the burning rates of the powdered coke and the lignin sulfonate were almost the same. On the other hand, when the oxygen concentration was increased to around 37% by volume, the combustion rate of lignin sulfonate was considerably higher than the combustion rate of powdered coke. When the combustion rate of lignin sulfonate increases at the furnace bottom of the waste melting furnace, the lignin sulfonate, which is the binder, burns first, and the remaining powder coke is scattered from the furnace bottom as small pieces. It is assumed that it will be easier.

  2 ... Shaft part, 3 ... Carbonization grate part, 3A ... Supply carbonization grate (carbonization grate), 3B ... Carbonated carbonization grate (carbonization grate), 4 ... Melting furnace part, 4A ... Furnace bottom part, 5 ... Communication Parts, 10 ... waste gasification and melting furnace, 21 ... waste charging inlet, 22 ... gas outlet in the furnace, 23 ... opening, 31 ... drive device, 32a ... first recovery chamber, 32b ... second recovery chamber, 36 ... Air blower, 41 ... Sub-material inlet, 42 ... Tuyere, 43 ... Oxygen generator, 44 ... Hot water outlet, 45 ... Inverted truncated cone part, 46 ... Opening part, 47a, 47b ... Flow control valve, 48 ... Gas detection unit, 50 ... coal, 52 ... carbon, 52a ... small piece, 54 ... binder, 100 ... waste packed bed, 101 ... filled bed, 102 ... deposited bed, 102A ... combustion reaction region, 102B ... gasification reaction region.

Claims (7)

A method for operating a waste melting furnace comprising a melting step of burning the solid fuel while supplying a solid fuel containing oxygen and gas containing oxygen to the bottom of the furnace, and melting the waste or its thermal decomposition residue,
In the melting step, the waste melting furnace operating method wherein the oxygen concentration of the gas is maintained within a range of 27 to 35% by volume and the cross-sectional flow velocity at the furnace bottom is within a range of 0.07 to 0.18 m / sec.   The operation method of the waste melting furnace according to claim 1, wherein the forming charcoal includes a binder containing a charcoal material and lignin sulfonate.   The operation of the waste melting furnace according to claim 1 or 2, wherein the ratio of the amount of carbon scattered from the bottom of the furnace to the amount of carbon contained in the solid fuel supplied to the bottom of the furnace is 20% by mass or less. Method. The waste melting furnace includes a shaft part having a waste charging inlet, a melting furnace part having a tuyere arranged to shift the shaft part and a furnace core, and supplying the gas, and a lower part of the shaft part and the A waste gasification melting furnace comprising a communication part connecting the upper part of the melting furnace part;
A thermal decomposition step of drying and pyrolyzing the waste in the shaft portion and the communication portion;
The operation method of the waste melting furnace as described in any one of Claims 1-3 which performs the said melting process in the said melting furnace part. A waste melting furnace comprising a melting furnace section for supplying a gas containing oxygen from a tuyere to burn a solid fuel containing coal and melting the waste or its thermal decomposition residue,
A waste melting furnace configured to maintain an oxygen concentration of the gas in a range of 27 to 35% by volume and a cross-sectional flow rate in a furnace bottom of the melting furnace in a range of 0.07 to 0.18 m / sec. .   The waste coal melting furnace according to claim 5, wherein the forming coal includes a carbon material and a binder containing lignin sulfonate. From the upstream side, based on the distribution direction of the waste,
A shaft part for drying and thermally decomposing waste material charged from the waste material inlet;
A communication portion connecting the lower portion of the shaft portion and the upper portion of the melting furnace portion;
The waste melting furnace according to claim 5 or 6, comprising the melting furnace part arranged in this order by shifting the shaft part and the furnace core.

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