JP5794662B2 - Waste melting treatment method - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a waste melting method using a shaft furnace type gasification melting furnace, in which wood chips are introduced to reduce the amount of coke used.

  In a shaft furnace type gasification melting furnace (hereinafter referred to as “gasification melting furnace”), various kinds of waste such as general waste, industrial waste, incinerated ash, excavated landfill waste, and sludge are melted. In gasification and melting furnaces, waste is put into the furnace together with coke and other auxiliary materials, and drying, preheating and heat are generated in the process of descending the drying / pretropical zone, pyrolysis zone, and combustion / melting zone in the gasification melting furnace It is decomposed, burned and melted and discharged as slag and metal.

  A furnace body 1 of a general gasification melting furnace shown in FIG. 4 includes a shaft portion 1 a and a lower morning glory portion 5, and a lower tuyere 3 for combustion / melting zone is provided at the lower end of the morning glory portion 5. Above this, an upper tuyere 2 for the pyrolysis zone is provided. Oxygen or oxygen-enriched air is supplied from the lower tuyere 3, and air is supplied as combustion gas from the upper tuyere 2.

  From the upper part of the furnace main body 1, waste, coke as a combustion aid, limestone as a basicity adjuster, etc. are charged into the furnace. For this charging, a charging device 9 having a seal valve is provided at the top of the furnace body 1, and a slag or metal outlet after melting the waste at the lower end of the furnace body 1. 11 is provided.

  In the above configuration, the waste 1 b charged in the furnace descends from the upper layer of the furnace body 1 through the dry / pre-tropical zone 6, the pyrolysis zone 7, and the combustion / melting zone 8. The coke bed 4 and the pyrolysis residue 12 which are coke grates are burned at a high temperature by oxygen supplied from the lower tuyere 3 or oxygen-enriched air, and this becomes a melting heat source. On the other hand, air is supplied from the upper tuyere 2 to mainly burn the thermal decomposition residue 12 of the waste, and the generated gas is used for drying / preheating and thermal decomposition of the waste. The molten waste is discharged from the tap 11 as a slag or metal melt.

  The high-temperature pyrolysis gas generated in the gasification melting furnace is introduced into the combustion chamber as a combustible gas from the gas pipe 10 at the top of the furnace body 1 and burned, and the combustion exhaust gas is introduced into the boiler through the exhaust pipe. After the waste heat is recovered, the temperature is adjusted in a temperature reducing tower, passed through a dust collector, and further, pollutants are removed in a catalytic reaction tower, and then discharged from a chimney.

In a gasification and melting furnace, coke bed derived from fossil fuel is used to form a coke bed at the bottom of the furnace and used as a heat source for melting. From the viewpoint of preventing global warming, gas is used to reduce CO ₂ derived from fossil fuels such as coal. Technology has also been proposed to reduce the amount of coke used in chemical melting furnaces.

For example, Patent Literature 1 discloses that biomass is used as an alternative to coke, which is a fossil fuel used for melting treatment of waste, to reduce the amount of coke used and to reduce CO ₂ load on the environment. A material melting treatment method is disclosed. This treatment method is an oxygen-free generated by putting pressure-molded biomass solids together with waste from the top of the furnace and reducing and burning together with waste with oxygen or oxygen-enriched air blown from the bottom of the furnace. With this combustion gas, biomass solids are carbonized by drying and dry distillation in a shaft furnace, a charcoal layer is formed at the lower part of the shaft furnace, and burned to form a heat source for melting. By this method, the coke consumption can be suppressed, so that the generation of CO ₂ originating from fossil fuel can be suppressed.

JP-A-2005-274122

  However, the technique of Patent Document 1 requires a biomass solid material obtained by mixing a biomass such as powdered wood with a binder and pressing and solidifying it. Therefore, a new facility is required for the pressure molding of biomass, and there is a problem that the pretreatment of the biomass takes time and the processing cost increases.

  Therefore, the present invention provides a waste melting method in a gasification melting furnace, in which wood chips are thrown into the furnace together with waste without pretreatment, and the amount of coke used can be reduced.

In the waste melting method of the present invention, waste is charged into a shaft furnace type waste melting furnace together with coke and limestone, and oxygen or oxygen-enriched air is blown from the furnace bottom blower to dry the waste, heat A waste melting treatment method that decomposes, burns, and melts. Wood chips are mixed with waste without pressure molding and charged into a furnace, and the wood chips are carbonized to form carbide particles on the coke bed. In a waste melting treatment method in which a ventilation resistance layer comprising layers is formed and equivalently substituted with coke and fixed carbon amount, the maximum part of the wood chip dimension is set to 100 mm or less, and the water content of the wood chip is input. The total amount is 2.5% by mass or less, and the wood chips are mixed in a ratio of 30% by mass or less with respect to the waste and charged into the furnace .

  Even if wood chips were simply put into the gasification melting furnace together with the waste, there was a situation where a sufficient coke reduction effect could not be obtained due to variations in the properties of the wood chips, but in the present invention it was completely carbonized. By producing the wood chip carbide, it is possible to secure a molten slag temperature equivalent to that when only the coke is operated, and to reduce the coke at an equivalent ratio by the fixed carbon amount of the wood chip.

  By setting the wood chip moisture content to 25% or less and the mixing ratio with the waste to 10 to 30%, the moisture evaporation time of the wood chip in the process of descending the gasification melting furnace is shortened, and the furnace The wood chip was quickly heated up to the bottom, making it possible to produce fully carbonized wood chip carbide.

  In addition, by setting the longest part of the wood chip size to 100 mm or less, it is possible to generate wood chip carbide that is sufficiently heated and heated up to the inside of the wood chip and completely carbonized to the inside of the chip. In this way, the present invention enables the generation of completely carbonized wood chip carbide by mixing wood chips with appropriate properties in an appropriate ratio with waste, and the coke is fixed carbon of the wood chips. The amount can be reduced at an equivalent rate.

  In addition, since the completely carbonized carbide descends in the furnace, and the carbide particle layer formed in the lower part of the gasification melting furnace functions as a ventilation resistance layer, the phenomenon that the furnace gas blows through the filler layer is also suppressed. It is definitely obtained.

It is a schematic diagram which shows the state by which the carbide particle layer was formed in the gasification melting furnace. It is a graph which shows the relationship between the water | moisture content in a wood chip | tip, and molten slag temperature. It is a graph which shows the relationship between a wood chip and a carbide particle layer. It is the schematic which shows an example of the conventional gasification melting furnace.

  The gasification / melting furnace shown in FIG. 1 is substantially the same as the conventional gasification / melting furnace shown in FIG. Compared with the conventional waste melting treatment method shown in FIG. 4, the present invention is different from the conventional waste melting treatment method in that the present invention mixes and introduces wood chips of appropriate properties with waste at an appropriate ratio. Although different from the waste melting method, the others are not substantially changed.

  When processing waste in a gasification and melting furnace, the waste and wood chips that have been put into the furnace together with a predetermined amount of coke and limestone auxiliary materials are dried by the high-temperature gas that flows oppositely as they descend in the furnace. , Pyrolyzed. The heat source for drying and pyrolysis of waste is the heat of combustion of waste by air blown from the upper tuyere 2 and the heat of combustion of coke by air blown from the lower tuyere 3 or oxygen-enriched air. used.

  The dry distillation residue resulting from pyrolysis and gasification of waste and wood chips is deposited on the upper surface of the coke bed 4 together with ash and incombustible components to form a carbide particle layer 13. The carbide particle layer 13 functioning as a ventilation resistance layer prevents the in-furnace gas such as the gas blown from the lower tuyere 3 or the dry distillation gas from being blown locally, and rectifies the gas flow.

  The combustion gas of coke and combustible carbonization residue reaches the maximum temperature at the upper end of the coke bed 4 formed in the lower part of the furnace, the ash is melted in this region, and the molten material drops in the voids of the coke bed 4 forming a grate. . The dripped melt is temporarily stored in a liquid pool at the bottom of the furnace, and is intermittently discharged by opening the hot water outlet 11.

  In the present invention, the waste to be treated in the gasification melting furnace is a waste that has been conventionally melt-treated, such as general waste, industrial waste, excavated waste, incinerated ash, sludge and the like.

  The wood chip is not particularly limited, and the chip manufacturer can use a cutting chip that has been cut, a crushed chip that has been crushed into a rod shape, or a sawdust of about 1 mm that can be used as a by-product when the chip is produced. . The wood chip preferably has a maximum dimension of 100 mm or less.

  Table 1 shows the fixed carbon concentration of various carbides, and the operation results sample is operated with a wood chip having a maximum part size of 100 mm or less and a mixing ratio of 10% by mass with waste (hereinafter, “%” is “% by mass”). It is the example which implemented.

  In Table 1, the fixed carbon in the operation sample and dry distillation test sample of wood chip carbide is 77 to 84% by mass, the fixed carbon concentration is almost equal to that of coke, and the dimension of the maximum part of the wood chip is 100 mm or less. If so, it can be completely carbonized and the heat source function equivalent to coke can be substituted.

  Table 2 shows the results of examining the conditions of wood chips that can ensure the same molten slag temperature (1350 ° C. or higher) as in the operation of 3.4% coke fixed carbon, which is the actual operation of coke.

  As shown in the stable operation performance limit (base condition) in Table 2, coke fixed carbon is 2% (input amount 2.5% × fixed carbon amount ratio (0.808) = 2%), wood chip mixing ratio 10 Under the test conditions of%, the wood chip moisture content was changed to 10%, 20%, and 25%, and the molten slag temperature was confirmed.

  As a result, when the moisture content of the wood chip is 25% and the fixed carbon content of the wood chip is 1.4% (fixed carbon in the wood chip 13.6% × input ratio 0.1 = 1.4%), coke A molten slag temperature equivalent to that at the time of fixed carbon 3.4% operation could be secured.

  From this, 1.4% of fixed carbon in wood chips is (3.4%-fixed amount of coke 2% = fixed carbon amount of wood chips 1.4% = fixed carbon of coke 1.4%). It was found that wood chips and coke can be replaced with equal amounts of fixed carbon because they could be replaced with the same amount as fixed carbon of 1.4%.

  In FIG. 2 in which the operation at a wood chip mixing ratio of 10% by mass (size of 100 mm or less) was carried out to determine the relationship between the moisture in the wood chip and the molten slag temperature, the moisture in the wood chip changed its chip properties. When the water content exceeds 25% by mass, the temperature is below the molten slag control temperature, and there is a situation where stable operation is hindered. It is necessary to. Since this is a value at a wood chip mixing ratio of 10%, it can be seen that there is no problem even if the amount of water in the wood chips is 25% × 10% = 2.5% of the total amount of waste to be added.

  As shown in FIG. 3, it is preferable that the input amount of the wood chip is a mixing ratio of 30% by mass or less with respect to the waste to be input. However, when the waste itself contains components that generate dry distillation residue, the thickness of the carbide particle layer varies depending on the type of waste (especially the amount of fixed carbon contained in the waste). There is. Therefore, as shown in FIG. 3, it is preferable that the mixing ratio is 10 to 30% by mass with respect to the waste to be charged in consideration of the fluctuation range of the layer thickness based on the type of waste. FIG. 3 exemplifies the thickness of the carbide particle layer (based on a fixed carbon amount) in the case of waste with a large amount of fixed carbon and waste with a small amount of fixed carbon in association with the input amount of wood chips. It is an example of the result confirmed by actually conducting a test. As can be seen from this result, even when wood chips are not charged, there are fluctuations in the amount of dry distillation residue corresponding to a layer thickness of 25 to 40 mm depending on the type of waste. An appropriate range of the amount is 10 to 30% by mass.

  As shown in the schematic diagram of FIG. 1, the carbide particle layer 13 is preferably formed on the upper surface of the coke bed 4 formed in the lower part of the furnace. Since oxygen or oxygen-enriched air is blown into the coke bed 4, the carbide particle layer 13 is formed to be positioned above the lower tuyere 3.

  The carbide particle layer 13 formed on the coke bed is a carbide particle layer in which carbonized wood chip carbonization residue is fine and has few voids, and therefore functions as a ventilation resistance layer when gas in the furnace passes through. Become.

The combustible carbide particle layer 13 is sequentially burned by the coke bed 4 from the lower layer side. In the present embodiment, in order for the carbide particle layer 13 to function effectively as a ventilation resistance layer for the in-furnace gas, the layer thickness is preferably 40 to 80 mm. As shown in FIG. 3 , when the layer thickness is smaller than 40 mm, the in-furnace gas blow-through phenomenon cannot be sufficiently suppressed. On the other hand, when the layer thickness is larger than 80 mm, the pressure loss of the filler layer increases and it becomes difficult to blow air from the tuyere.

  As described above, according to the waste melting treatment method of the present invention, wood chips are mixed with waste materials and co-raw materials such as coke, and then charged into the waste layer formed in the furnace. By forming the carbide particle layer, this carbide particle layer functions as a ventilation resistance layer, and the flow of the gas in the furnace is rectified, so that the contact between the gas in the furnace and the waste is made more uniform, and the heat Exchange efficiency is improved. As a result, even if coke as a heat source is not added excessively, complete melting can be achieved by the amount of heat of the pyrolysis residue of waste and the amount of heat of a small amount of coke. That is, since the heat exchange efficiency is improved by rectifying the gas by the carbide particle layer, it is possible to reduce the amount of coke used for drying and dry distillation of waste other than melting such as ash. .

Moreover, since the flow of the in-furnace gas is rectified by the formation of the carbide particle layer, the occurrence of the blow-in phenomenon of the in-furnace gas can be suppressed. That is, the blow-through phenomenon that occurs in the past is considered to occur as a result of inefficient drying and dry distillation of the waste. On the other hand, in the present invention, wood chips having a predetermined moisture content or less are disposed of as waste. By mixing and charging a predetermined amount to form a carbide particle layer 13 and rectifying the gas, waste can be efficiently dried and dry-distilled, and as a result, the occurrence of a blow-through phenomenon can be suppressed. Become.

1: Furnace body 1a: Shaft portion 1b: Waste 2: Upper tuyere 3: Lower tuyere 4: Coke bed 5: Morning glory 6: Drying / pre-tropical zone 7: Pyrolysis zone 8: Combustion / melting zone 9: Equipment Entry device 10: Gas pipe 11: Outlet 12: Thermal decomposition residue 13: Carbide particle layer

Claims (1)

Waste melting process in which waste is dried, pyrolyzed, combusted, and melted by introducing oxygen or oxygen-enriched air into the shaft furnace waste melting furnace together with coke and limestone, and blowing oxygen or oxygen-enriched air from the blower at the bottom of the furnace there is provided a method,
Wood chips are mixed with waste without pressure molding and charged into the furnace, and the wood chips are carbonized to form a ventilation resistance layer consisting of carbide particle layers on the coke bed, and coke and fixed carbon content In the waste melting treatment method equivalently replaced by
The maximum part of the wood chip size is set to 100 mm or less, the moisture content of the wood chip is set to 2.5% by mass or less of the total amount of waste, and the wood chip is mixed at a rate of 30% by mass or less with respect to waste. Then , the waste melting treatment method , which is charged into a furnace .

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