JP6914118B2 - Waste melting furnace and its operation method - Google Patents

Description

The present disclosure relates to a waste melting furnace and a method of operating the same.

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 waste melting treatment has the advantage that not only the volume of the waste can be reduced, but also the incineration ash and non-combustible waste that have been finally disposed of by landfill can be recovered as resources such as slag and metal.

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

Japanese Patent No. 5648420 Japanese Patent No. 5762653

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

An object of the present invention is to provide, in one aspect, a method of operating a waste melting furnace capable of reducing a running cost by using a solid fuel containing briquette. In another aspect, it is an object of the present invention to provide a waste melting furnace capable of reducing running costs by using a solid fuel containing briquette.

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

In this method of operating the waste melting furnace, the oxygen concentration of the gas supplied to the bottom of the furnace and the cross-sectional flow velocity at the bottom of the furnace are maintained within a predetermined range in the melting step. Therefore, it is possible to suppress the scattering of small pieces of solid fuel from the bottom of the furnace and effectively use the solid fuel as fuel. Therefore, the running cost can be reduced by using the solid fuel containing briquette.

The briquette preferably contains a binder containing a carbonaceous material and a lignin sulfonate. As a result, the crushing strength of the briquette 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 portion having a waste loading inlet, a melting furnace portion having a tuyere for supplying the gas, and a lower portion of the shaft portion and a melting furnace. It may be a waste gasification melting furnace provided with a communication part connecting to the upper part of the part. In this case, the operation method may include a thermal decomposition step of drying and thermally decomposing the 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 is a waste melting furnace provided with a melting furnace section in which a gas containing oxygen is supplied from a tuyere to burn a solid fuel containing molded charcoal to melt the waste or its thermal decomposition residue. The waste is configured to maintain the oxygen concentration of the gas in the range of 27 to 35% by volume and the cross-sectional flow velocity at the bottom of the melting furnace in the 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 bottom of the melting furnace section within a predetermined range. Therefore, it is possible to suppress the scattering of small pieces of solid fuel from the bottom of the furnace and effectively use the solid fuel as fuel. Therefore, the running cost can be reduced by using the solid fuel containing briquette.

The waste melting furnace includes a shaft portion that dries and thermally decomposes the waste charged from the waste loading inlet from the upstream side based on the waste flow direction, and the lower portion of the shaft portion and the melting furnace. A communication portion connecting the upper part of the portion and a melting furnace portion arranged by shifting the shaft portion and the furnace core may be provided in this order.

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

FIG. 1 is a vertical sectional view schematically showing an embodiment of a waste melting furnace. FIG. 2 is an enlarged vertical sectional view showing a melting furnace portion of the waste melting furnace of FIG. 1. FIG. 3 is a diagram schematically showing a change due to combustion of briquette. FIG. 3 (A) is a diagram schematically showing a solid fuel before combustion, and FIG. 3 (B) is a diagram schematically showing 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 of operating a waste melting furnace of the present invention burns a solid fuel while supplying a gas containing oxygen and a solid fuel containing molded charcoal to the bottom of the furnace, and the waste or a thermal decomposition residue thereof. Has a melting step of melting. In this melting step, the oxygen concentration of the gas supplied from the tuyere is maintained in the range of 27 to 35% by volume, and the cross-sectional flow velocity at the bottom of the furnace is maintained in the range of 0.07 to 0.18 m / sec. The waste melting furnace is provided with a tuyere at the bottom of the furnace for supplying a gas containing oxygen.

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

The solid fuel contains briquette. Briquette preferably contains a charcoal material and a binder. The coal material may contain at least one selected from coal, coke breeze, char, petroleum coke and fly ash. The mass ratio of the binder to the carbonaceous material may be 0.06 to 0.2. By mixing at such a mass ratio, the crushing strength of the briquette can be increased. Therefore, the 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 sulfonates.

As the lignin sulfonate, a commercially available product can be used. 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 briquette. From the viewpoint of availability, the number average molecular weight of the lignin sulfonate may be, for example, 10,000 or less, or 8,000 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 briquette is not particularly limited, and may be, for example, a columnar shape or a Masek shape. The density of the briquette may be, for example, 1.0 to 2.0 g / ml. The particle size A ₁ [mm] of the briquette is, for example, 30 mm or more. The particle size A ₁ [mm] of the briquette _{is calculated by the following formula (1) by converting the volume V 1} [ml] of the briquette into spheres of the same volume.
A ₁ = 2 x ((V ₁ x 3/4 / π) ^1/3 ) x 10 (1)

The waste melting furnace of the present invention can be suitably used 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 the gas containing oxygen is supplied from the tuyere to burn a solid fuel containing molded charcoal. It is provided with a melting furnace unit for melting the waste or its thermal decomposition residue. In this waste melting furnace, the oxygen concentration of the gas is maintained in the range of 27 to 35% by volume, and the cross-sectional flow velocity at the bottom of the melting furnace is maintained in the range of 0.07 to 0.18 m / sec. .. The method of obtaining the oxygen concentration and the cross-sectional flow velocity of the gas supplied from the tuyere is as described above.

The above-mentioned waste melting furnace has a shaft portion that dries and thermally decomposes the waste charged from the waste loading inlet from the upstream side based on the waste flow direction, and the lower portion of the shaft portion and the melting furnace. It may be a waste gasification melting furnace including a communication portion connecting the upper part of the portion and a melting furnace portion arranged with the shaft portion and the core shifted in this order. In such a waste gasification melting furnace, a thermal decomposition step of drying and thermally decomposing the waste can be performed at the shaft portion and the communicating portion, and a melting step can be performed at the melting furnace portion.

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

FIG. 1 is a vertical cross-sectional view schematically showing a waste gasification melting furnace, which is an embodiment of a waste melting furnace. The method of operating the waste melting furnace according to the embodiment can be carried out using this waste gasification melting furnace. The waste gasification melting furnace 10 shown in FIG. 1 mainly includes a shaft portion 2, a communication portion 5 having a carbonized grate portion 3, and a melting furnace portion 4. The shaft portion 2 dries the waste and thermally decomposes it in a reducing atmosphere. In the communication portion 5, the carbonized grate portion 3 further thermally decomposes the waste from the shaft portion 2 to carbonize the waste. The melting furnace section 4 burns and melts the thermally decomposed waste.

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

The shape of the shaft portion 2 may be, for example, a cylinder or a rectangle. A waste loading inlet 21 for charging waste into the furnace is formed in the upper part of the shaft portion 2. The type of waste is not particularly limited and may be either general waste or industrial waste. It is also possible to treat simple substances or mixtures of shredder dust (ASR), excavated waste, incinerator ash, etc., or mixtures of these with combustible waste. The waste filling layer 100 is formed in the shaft portion 2 by the waste. The dry-distilled waste and char may be put in together with the waste from the waste loading inlet 21.

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

The communication portion 5 has a rectangular vertical cross-sectional shape, and the carbonized grate portion 3 is arranged along the bottom surface thereof. The carbonized grate portion 3 further thermally decomposes the waste dried and thermally decomposed by the shaft portion 2. The carbonized grate unit 3 has a function as a device for thermally decomposing (dry distillation) the waste and a function as a supply device for supplying the carbonized waste to the melting furnace unit 4. The carbonized grate portion 3 is formed by alternately combining a movable carbonized grate and a fixed carbonized grate in a stepped or inclined shape.

Each movable carbonized grate is configured to reciprocate in the lateral direction at a constant pitch by a driving device 31 (31a, 31b) such as a fluid pressure cylinder (see the double-headed arrow in FIG. 1). By such a combination of the movable carbonized grate and the fixed carbonized grate, the waste on the carbonized grate portion 3 can be extruded from the upstream side to the downstream side while being agitated.

The carbonization grate portion 3 has a two-stage structure consisting of a supply carbonization grate 3A on the upper stage side and a dry distillation carbonization grate 3B on the lower stage side. The supply carbonized grate 3A is located directly below the shaft portion 2 so as to directly receive the load of the waste filled in the shaft portion 2. The supply carbonization grate 3A further thermally decomposes the waste so that the carbonization of the waste dried and thermally decomposed at the shaft portion 2 proceeds, and pushes out and supplies the waste to the dry distillation carbonization grate 3B.

The dry distillation carbonization grate 3B is provided adjacent to the supply carbonization grate 3A, and further thermally decomposes the waste from the supply carbonization grate 3A to generate carbonization. In this way, the thermal decomposition step of the waste is performed in the carbonized grate portion 3 of the shaft portion 2 and the communication portion 5. The carbonization carbonization grate 3B extrudes the thermally decomposed (carbonized) waste into the opening 46 of the melting furnace section 4.

The movable carbonized grate of the supply carbonized grate 3A is driven by the first drive device 31a, and the movable carbonized grate of the dry distillation carbonized grate 3B is driven by the second drive device 31b. By providing the first and second drive devices 31a and 31b independently of each other in this way, the drive, stop and drive speed of the carbonized grate 3A and 3B can be controlled independently, and as a result, the carbonized grate 3A, The waste transport speed by 3B can also be controlled independently.

The carbonized grate portion 3 can supply air toward the waste on the carbonized grate portion 3 through the gap between the carbonized grate and / or the air vent (not shown) formed in the carbonized grate. It is composed. That is, the carbonized grate portion 3 also serves as a blower for blowing air for drying and thermal decomposition of waste into the furnace. On the back surface side of the supply carbonization grate 3A and the carbonization carbonization grate 3B, a first recovery chamber 32a for recovering fine carbonized waste when it falls from a gap between the carbonization grate. And the second collection chamber 32b are arranged respectively.

A blower pipe 33a is connected to the first collection chamber 32a. The blower pipe 33a is provided with a flow rate control valve 33b for adjusting the flow rate of air, and a blower device 36 for supplying air is connected to the upstream side of the flow rate control 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 control valve 33b. The air supplied to the first recovery chamber 32a is introduced into the furnace through the gap of the supplied carbonized grate 3A and / or the air vent formed in the carbonized grate.

A blower pipe 34a is connected to the second collection chamber 32b. The blower pipe 34a is provided with a flow rate control valve 34b for adjusting the flow rate of air, and a blower device 36 for supplying air is connected to the upstream side of the flow rate control 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 control valve 34b. The air supplied to the second recovery chamber 32b is introduced into the furnace through the gaps in the dry distillation carbonized grate 3B and / or the air vents formed in the carbonized grate.

The communication portion 5 above the melting furnace section 4 is provided with an auxiliary material charging inlet 41 for supplying solid fuel containing briquette into the melting furnace section 4. The solid fuel may contain coke, carbides of biomass, etc. in addition to briquette. In addition to the solid fuel, limestone or the like as a basicity adjusting agent may be supplied from the auxiliary material charging inlet 41.

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

In addition to the solid fuel and the like from the auxiliary material charging inlet 41, the thermal decomposition residue of the waste dried and carbonized through the shaft portion 2 and the communication portion 5 is supplied to the melting furnace portion 4 from the opening 46. Will be done. The thermal decomposition residue of the supplied waste is further pyrolyzed in the melting furnace section 4. At least a part of the waste supplied to the melting furnace unit 4 may not be thermally decomposed.

A packed bed 101 is formed by carbonized waste on the sedimentary layer 102 in the melting furnace section 4. The solid fuel containing the briquette charged from the auxiliary material charging inlet 41 passes through the filling layer 101 and is deposited on the furnace bottom portion 4A below the melting furnace portion 4 to form the deposited layer 102. The furnace bottom portion 4A is composed of a columnar 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 deposit layer 102 formed in the internal space.

At the bottom 4A of the furnace, the fixed carbon of the thermal decomposition residue of the solid fuel and the waste is burned by supplying a gas containing oxygen from the tuyere 42. The heat of combustion melts the ash and non-combustible components contained in the waste or its thermal decomposition residue. In this way, the melting step of melting the waste or the decomposition residue thereof is performed in the melting furnace unit 4. The high-temperature gas generated in the thermal decomposition step and the melting step may be discharged from the gas discharge port 22 in the furnace, the waste heat may be recovered by a device such as a boiler, and then detoxified and discharged.

The bottom portion 4A of the melting furnace portion 4 is provided with a hot water outlet 44 for discharging molten matter (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 to the outside of the furnace can be cooled and solidified to obtain slag and metal.

FIG. 2 is an enlarged vertical sectional view showing a melting furnace portion 4 of the waste gasification melting furnace 10 of FIG. 1. In the solid fuel deposit layer 102 in the bottom 4A of the melting furnace unit 4, carbon is mainly gasified around the combustion reaction region 102A in which the carbon contained in the solid fuel is mainly burned 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 the formula (2), and the main reaction in the gasification reaction region 102B is represented by the formula (3). In the present embodiment, the boundary line of the gasification reaction region 102B of the combustion reaction region 102A is clearly shown for ease of understanding, but these regions may not be clearly defined. That is, the reaction of the formula (2) may proceed mainly in the vicinity of the tuyere 42, and the ratio of the reaction of the formula (3) to the tuyere 42 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, which 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 oxygen-containing gas supplied from the tuyere 42 becomes too small, the combustion reaction region 102A shrinks, and it becomes difficult for the combustion reaction of the formula (2) to proceed sufficiently at the center of the furnace bottom 4A. .. As a result, the temperature of the bottom 4A of the furnace is lowered, and the melting of the waste or the thermal decomposition residue thereof tends to be difficult to proceed. From this point of view, the cross-sectional flow velocity of the oxygen-containing gas is 0.07 m / sec or more. From the viewpoint of promoting the combustion of solid fuel and improving the amount of waste processed, the cross-sectional flow velocity of the oxygen-containing gas supplied from the tuyere 42 is preferably 0.09 m / sec or more, more preferably 0.09 m / sec or more. It is 0.1 m / sec or more.

On the other hand, if the cross-sectional flow velocity of the oxygen-containing gas becomes too large, the amount of scattered solid fuel pieces 52a increases from the sedimentary 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 charging inlet 41 peeled off, and debris generated by the collapse of the solid fuel. From the viewpoint of reducing the amount of scattered small pieces 52a, the cross-sectional flow velocity of the oxygen-containing gas supplied from the tuyere 42 is 0.18 m / sec or less. From the viewpoint of sufficiently reducing the amount of scattered small pieces 52a and effectively utilizing the solid fuel, the cross-sectional flow velocity of the oxygen-containing gas at the bottom 4A of the furnace is preferably 0.16 m / sec or less, more preferably 0. It is .14 m / sec or less.

A tuyere 42 is provided in the bottom portion 4A of the melting furnace portion 4. The tuyere 42 has a configuration capable of supplying a mixed gas of air and oxygen from the oxygen generator 43 as a gas containing oxygen. The gas supply amount and the oxygen concentration from the tuyere 42 are adjusted by the flow rate control valve 47a for adjusting the air flow rate and the flow rate control valve 47b for adjusting the oxygen supply amount. By adjusting the supply ratio of air and oxygen, the oxygen concentration of the gas supplied from the tuyere 42 can be adjusted. The amount of gas supplied and the oxygen concentration are not limited to such examples, and may be performed by other means. For example, a three-way valve for adjusting the supply ratio of air and oxygen and a flow rate control valve for adjusting the flow rate of gas may be provided on the downstream side of the three-way valve.

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

The bottom 4A of the furnace does not have to be cylindrical. For example, when the internal space of the furnace bottom portion 4A is a square columnar shape, the cross-sectional flow velocity of the gas can be obtained by the following formula (5). In equation (5), A indicates 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 the short side of the cross section when cut on a horizontal plane is shown. When the cross section is square, L1 = L2.
Cross-sectional flow velocity [m / sec] = A / (L1 × L2) (5)

The cross-sectional flow velocity of the oxygen-containing gas at the bottom 4A of the furnace 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 cut in the horizontal plane at the height at which the lowermost tuyere 42 is provided in the furnace bottom portion 4A. It is calculated.

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

The briquette 50 contained in the solid fuel forming the sedimentary layer 102 shown in FIG. 1 is burned by oxygen contained in the gas. Here, the coal material 52 contained in the briquette 50 tends to be less affected by the oxygen concentration of the gas than the binder 54. That is, the binder 54 tends to have a higher combustion rate than the carbonaceous material 52 as the oxygen concentration of the gas increases. Therefore, if the oxygen concentration of the gas becomes too high, the binder 54 burns before the carbonaceous material 52 and disappears. Then, as shown in FIG. 3B, the small piece 52a remains. The small pieces 52a not bound by the binder 54 tend to scatter from the sedimentary layer 102 more easily than those bound by the binder 54.

From the viewpoint of reducing the amount of scattered small pieces 52a, the oxygen concentration in the gas containing oxygen 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 required for combustion of the solid fuel increases, so that the temperature at the bottom 4A of the furnace tends to decrease. In particular, when the oxygen concentration is 26.5% by volume or less, the consumption of solid fuel increases sharply. Therefore, the running cost tends to increase. From such a viewpoint, the oxygen concentration in the oxygen-containing gas is 27% by volume or more, preferably 29% by volume or more.

The oxygen concentration in the oxygen-containing gas supplied from the tuyere 42 is 27 to 35% by volume, preferably 29 to 33% by volume. As a result, it is possible to reduce the amount of solid fuel required to secure the temperature in the melting furnace unit 4 while suppressing the scattering of the solid fuel in the melting furnace unit 4. Therefore, the amount of solid fuel used can be 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 detection unit 48 can measure the concentrations of carbon monoxide and carbon dioxide in the melting furnace unit 4. Based on these measured values and the amount of gas blown from the tuyere 42, the amount of carbon consumed by the above formulas (2) and (3) can be calculated. The amount of carbon scattered from the bottom 4A by subtracting the total amount of carbon consumed by the formulas (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 reducing the ratio of the solid fuel scattered from the bottom 4A and further reducing the running cost, the ratio of the amount of carbon scattered from the bottom 4A to the amount of carbon contained in the solid fuel is preferably 20% by mass. It is less than or equal to, more preferably 15% by mass or less. From the viewpoint of further reducing the consumption of the solid fuel, the ratio of the amount of carbon consumed by the reaction of the formula (2) to the amount of carbon contained in the solid fuel is preferably 40% by mass or more, more preferably 50. It is mass% or more.

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

The waste gasification melting furnace 10 suppresses the scattering of small pieces 52a of solid fuel from the bottom portion 4A of the melting furnace portion 4, and the solid fuel can be effectively used as fuel. Therefore, the running cost can be reduced by using the solid fuel containing briquette.

Although some embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, the above-mentioned waste melting furnace is provided with a communication portion having a carbonized grate portion, but may be a vertical waste melting furnace without 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 of coke for blast furnace and briquette>
(Comparative Example 1)
Using ordinary blast furnace coke (particle size: 20 to 80 mm) as solid fuel, a waste gasification melting furnace equipped with a shaft portion as shown in FIG. 1, a communication portion provided with a carbonized grate portion, and a melting furnace portion. I drove. The high calorific value of coke for blast furnace is as shown in Table 1. General waste was charged from the waste inlet of the shaft, and coke for blast furnace was charged as solid fuel from the auxiliary material inlet. The operation was performed so that the height of the waste at the shaft portion and the temperature of the melt discharged from the hot water outlet at the bottom of the furnace (about 1360 ° C.) were substantially constant. The oxygen concentration of the gas supplied from the tuyere at the bottom of the furnace and the cross-sectional flow velocity at the bottom of the furnace are as shown in Table 1. The amount of solid fuel (coke for blast furnace) used and the amount of calorific value required to completely melt a unit mass of waste in a steady state were determined. The results are 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 briquette prepared as follows was used instead of the coke for blast furnace as the solid fuel.

As a liquid binder, a commercially available magnesium lignin sulfonate aqueous solution (manufactured by Nippon Paper Co., Ltd., trade name: Sun Extract M100, number average molecular weight: 3000) and commercially available powdered coke (moisture: 20% by mass, particle size: 3 mm or less) are used. Got ready. After drying the coke breeze in a dryer, an aqueous solution of magnesium lignin sulfonate was mixed with the coke powder 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 coke breeze.

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

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

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

The oxygen concentration of the gas supplied from the tuyere at the bottom of the furnace and the cross-sectional flow velocity of the gas at the bottom of the furnace are as shown in Tables 2 and 3. The oxygen concentration and the cross-sectional flow velocity are the values when the gas is converted into the standard state, respectively. The calorific value of the solid fuel required to melt a unit mass of waste in a steady state was determined. In addition, the concentrations of carbon monoxide and carbon dioxide were measured by a gas detector installed above the tuyere. Based on these measured values and the amount of gas blown from the tuyere, the amount of carbon consumed by the above formulas (2) and (3) was calculated. The amount of carbon scattered from the bottom of the furnace is calculated by subtracting the total amount of carbon consumed by equations (2) and (3) from the amount of carbon contained in the solid fuel supplied to the waste gasification and melting furnace. did. In addition, the consumption ratio and the scattering ratio of each carbon were calculated. The results are as shown in Tables 2 and 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 coke for a blast furnace, the running cost cannot be reduced.

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

FIG. 4 is a graph showing the relationship between the cross-sectional flow velocity of the bottom of the furnace 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 results of FIG. 4, it is predicted that when the cross-sectional flow velocity exceeds a predetermined value (about 0.12 m / sec), the proportion of scattered carbon 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 squares method, the straight line shown in FIG. 4 was obtained. A relationship was obtained. From this result, it was found that if the cross-sectional flow velocity at the bottom of the furnace is 0.18 m / sec or less, the rate of peeling and scattering can be maintained at 20% by mass or less.

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

<Evaluation of combustion rate>
(Reference example 1)
The combustion rate was evaluated by performing thermogravimetric analysis of coke breeze and lignin sulfonate contained in the briquette used in Example 1 described above. The thermogravimetric analysis was performed at 1000 ° C. assuming the temperature of the bottom of the waste melting furnace. Analysis was performed for the cases where the atmosphere of thermogravimetric analysis was oxygen concentration of 21% by volume, 30% by volume, and 37% by volume, respectively. The results were as shown in FIG.

As shown in FIG. 5, when the oxygen concentration was around 30% by volume, the burning rates of coke breeze and lignin sulfonate were almost the same. On the other hand, when the oxygen concentration increased to around 37% by volume, the burning rate of lignin sulfonate became considerably higher than the burning rate of coke breeze. At the bottom of the waste melting furnace, when the burning rate of lignin sulfonate becomes higher in this way, the binder lignin sulfonate burns first, and the remaining coke breeze scatters from the bottom of the furnace as small pieces. It is presumed that it will be easier.

2 ... Shaft part, 3 ... Carbonized grate part, 3A ... Supply carbonized grate (carbonized grate), 3B ... Dry distillate carbonized grate (carbonized grate), 4 ... Melting furnace part, 4A ... Furnace bottom part, 5 ... Communication Part 10 ... Waste gasification and melting furnace, 21 ... Waste loading inlet, 22 ... In-furnage gas outlet, 23 ... Opening, 31 ... Drive device, 32a ... First recovery chamber, 32b ... Second recovery chamber, 36 ... blower, 41 ... auxiliary material inlet, 42 ... tuyere, 43 ... oxygen generator, 44 ... hot water outlet, 45 ... inverted conical base, 46 ... opening, 47a, 47b ... flow control valve, 48 ... Gas detector, 50 ... Molded charcoal, 52 ... Carbon material, 52a ... Small pieces, 54 ... Binder, 100 ... Waste packing layer, 101 ... Filling layer, 102 ... Deposit layer, 102A ... Combustion reaction region, 102B ... Gasification reaction region.

Claims (5)

A method of operating a waste melting furnace having a melting step of burning the solid fuel while supplying a gas containing oxygen and a solid fuel containing molded charcoal to the bottom of the furnace to melt the waste or its thermal decomposition residue.
The briquette contains a carbonaceous material and a binder containing lignin sulfonate.
A method for operating a waste melting furnace, in which the oxygen concentration of the gas is maintained in the range of 27 to 35% by volume and the cross-sectional flow velocity at the bottom of the furnace is maintained in the range of 0.07 to 0.18 m / sec in the melting step. The method for operating a waste melting furnace according to claim 1, 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. The waste melting furnace includes a shaft portion having a waste loading inlet, a melting furnace portion having a tuyere for supplying the gas, and a lower portion of the shaft portion and the above. It is a waste gasification melting furnace equipped with a communication part that connects to the upper part of the melting furnace part.
It has a thermal decomposition step of drying and thermally decomposing the waste in the shaft portion and the communication portion.
The method for operating a waste melting furnace according to claim 1 or 2 , wherein the melting step is performed in the melting furnace section. A waste melting furnace provided with a melting furnace section that supplies a gas containing oxygen from a tuyere to burn a solid fuel containing briquette and melts the waste or its thermal decomposition residue.
The briquette contains a carbonaceous material and a binder containing lignin sulfonate.
A waste melting furnace configured to maintain the oxygen concentration of the gas in the range of 27 to 35% by volume and the cross-sectional flow velocity at the bottom of the melting furnace in the range of 0.07 to 0.18 m / sec. .. From the upstream side, based on the waste distribution direction
The shaft part that dries and thermally decomposes the waste charged from the waste loading inlet,
A communication portion that connects the lower portion of the shaft portion and the upper portion of the melting furnace portion, and
The waste melting furnace according to claim 4 , further comprising the shaft portion and the melting furnace portion arranged so as to be displaced from the core in this order.

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