JP4377824B2 - Waste melting treatment method using biomass - Google Patents

Description

    The present invention relates to a method for melting waste such as general waste and industrial waste, and more particularly to a method for melting waste using biomass.

    As a method for treating waste such as landfill waste including earth and sand that has been dug up again after landfill processing once, after treating these wastes by general waste and industrial waste, or those obtained by drying, incineration, crushing, etc. These waste materials are melted in a shaft furnace type waste melting furnace and recycled as slag and metal.

  A shaft furnace type waste melting furnace is used as a method for melting waste (see Patent Document 1). As shown in FIG. 2, the furnace body 1 includes a shaft portion 1 a and a lower morning glory portion 5, and a lower tuyere 3 for a combustion melting zone is provided at the lower end of the morning glory portion 5. Has a plurality of upper tuyere 2 for the pyrolysis zone. Oxygen or oxygen-enriched air is supplied from the lower tuyere 3, and air is supplied from the upper tuyere 2 as a combustion support gas.

  At the top of the furnace body, there is provided a charging device 11 having a seal valve for charging waste to be treated, coke as a combustion aid, limestone as a basicity adjusting agent, etc. into the furnace. The lower end portion is provided with a slag and metal outlet 13 after melting the waste.

  In the above configuration, the charged waste 1b is dried from the upper layer of the melting furnace main body 1 and dried / pre-trophic 6 (about 300 to 400 ° C.), pyrolysis zone 7 (about 300 to 1000 ° C.), combustion and melting It melt-processes by passing through band 8 (about 1700-1800 ° C.).

  The coke 4 and the pyrolysis residue 14 are burned at a high temperature by the oxygen supplied from the lower tuyere 3 or oxygen-enriched air, and used as a heat source for melting. On the other hand, air is supplied from the upper tuyere 2 to mainly generate heat from waste. The decomposition residue 14 is combusted, and the waste gas is dried, preheated and thermally decomposed with the generated gas. The molten waste is discharged from the outlet 13 with slag and metal as melt.

  The high-temperature combustion exhaust gas rises as a counterflow through the waste bed in the shaft furnace, is introduced into the combustion chamber as a combustible gas from the exhaust gas pipe 12 at the upper part of the melting furnace body, and is combusted. After passing through the boiler and recovering waste heat, the temperature is adjusted in a temperature reducing tower and passed through a dust collector. Further, pollutants are removed in a catalytic reaction tower and then discharged from a chimney.

On the other hand, development for reducing CO ₂ derived from fossil fuels such as coal is being promoted from the viewpoint of preventing global warming. Also in the direct melting furnace equipment, coke derived from fossil fuel is used as a melting heat source, and therefore, a coke usage reduction technique capable of reducing the CO ₂ load on the environment has been proposed. For example, as a means to efficiently burn and melt the object to be processed with as little coke as possible, flammable dust (char) discharged from the top of the furnace is collected and loaded again into the melting furnace body via the tuyere. There is a method of entering (see Patent Documents 2 and 3), a method of crushing waste plastic, and charging from a tuyere or a large one from the furnace and using it as a heat source (see Patent Document 4).
JP 2001-90923 A JP-A-8-285250 JP 2001-21123 A JP 11-153309 A

Although the conventional tuyere blowing technology can reduce the coke consumption, the coke consumption is completely achieved by the gasification reaction of the fixed carbon, represented by C + CO ₂ → 2CO and C + H ₂ O → H ₂ + CO. In addition, since coke bets are formed from coke to maintain the grate function, there is a limit to the reduction of coke usage.

The present invention uses biomass as an alternative to coke derived from fossil fuels used for melting treatment of waste, thereby reducing the amount of coke used and reducing the CO ₂ load on the environment. The present invention provides a waste melting treatment method using the above.

In the waste melting method using biomass according to the present invention, waste is charged into a shaft furnace type waste melting furnace, oxygen or oxygen-enriched air is blown from the furnace bottom blower, and the waste is dried, heated In the waste melting treatment method that decomposes, burns, and melts , either woody biomass, biomass powder such as livestock manure / sewage sludge / human waste sludge, or powdered carbides thereof, or combustible dust scattered from the top of the melting furnace Or, a briquette that has been pressure-molded with the addition of a mixture of these is introduced together with waste from the top of the furnace, and reduced or burned together with waste with oxygen or oxygen-enriched air blown from the furnace bottom blowing tuyere. The biomass solids are carbonized by drying and dry distillation in the shaft furnace with oxygen combustion gas, and a charcoal layer is formed at the lower part of the shaft furnace. It performs the reduction combustion in the inner, characterized by a melting heat source for in the waste ash.

  In the waste melting treatment method, when the ash content in the waste is melted in the shaft furnace type melting furnace, the waste is dried and dry-distilled (pyrolyzed) by the high-temperature combustion gas rising from the bottom of the furnace, and the volatile content is reduced. Is discharged as combustible gas from the upper part of the furnace, and the residue after pyrolysis mainly composed of fixed carbon that has not been volatilized and is carbonized falls to the bottom of the furnace, and the lower stage blows in front of the lower blower tuyeres at the bottom of the furnace. It reacts with oxygen supplied from the tuyere and burns at a high temperature to become a melting heat source that melts the ash in the waste. However, most of the combustibles in waste are paper, plastic, etc., and are finely divided by dry distillation. Therefore, residues containing fixed carbon after dry distillation are in a larger proportion than the top of the furnace due to gas flow. Since it scatters, there is not much ratio which burns as a melting heat source at the furnace bottom.

  However, in the waste melting treatment method using biomass according to the present invention, the solid biomass charged into the furnace is dried, carbonized and carbonized (coking) by carbonization (coking) by dry distillation as in the case of waste. For example, in the case of wood, the proportion of fine particles is small, and most of it falls to the furnace bottom and can be used as a heat source for melting. Therefore, when using coke derived from fossil fuel as an auxiliary melting heat source together with waste, the fixed carbon content after dry distillation of the biomass solidified product functions as an alternative to the melting heat source.

  The biomass solidified product can be used as a heat source for melting at the furnace bottom by pressing powdery biomass into briquettes to suppress fine granulation even after drying and dry distillation in the furnace. When biomass is pressure-molded, the lignin, cellulose, and hemicellulose in the biomass are converted into oil by frictional heat or external heat, and the oil becomes a binder. By further pressurizing, the oil reaches the entire molded product and becomes dense. The strength of the molded product can be increased.

  In addition, when using biomass powders such as livestock manure, sewage sludge, human waste sludge, etc., or powdered carbides carbonized by carbonization (coking) as a biomass solidified product, these biomasses alone In the case where pressure molding is impossible, powdery woody biomass, preferably sawdust is added as a binder, and pressure molding can be performed to obtain the strength of the molded product without pulverization in the melting furnace. It can be used as a heat source for melting to melt waste ash at the bottom of the furnace.

  Also, by solidifying the biomass solidified in advance into solid carbide, it can be stably lowered to the bottom of the furnace and used as a heat source for melting regardless of the heat history in the drying / dry distillation zone in the melting furnace. It becomes. That is, it is possible to obtain sufficient strength even in the hot state by performing the carbonization process at a carbonization temperature and a temperature rising rate suitable for the type of solid carbide.

  In addition to woody biomass, tar pitch binder, plastic, water, starch, lignin, cellulose, hemicellulose, or a mixture thereof can be added as a binder. For example, when the powdered carbide is solidified, if the oil necessary for obtaining a sufficient strength of the solid is insufficient, an appropriate amount of a tar pitch binder is preferably added as a binder.

When manufacturing a briquette by press-molding biomass, it is heated so that the solid temperature of the biomass is 50 ° C. to 350 ° C., and pressurized at a pressure of about 0.5 t to 5 t / cm ² . For example, a double roll molding machine is used as the molding machine. The solid temperature by heating is that the lignin, cellulose, and hemicellulose components in the biomass become oily, and a temperature of 50 ° C. or higher is necessary to become a binder. On the other hand, if it exceeds 350 ° C., thermal decomposition starts during molding, Since it expand | swells by the production | generation of gas, shaping | molding becomes difficult and the intensity | strength of solidified material falls.

  Also, the briquette obtained by pressure molding is about 500 ° C. or higher in a rotary kiln or coke oven, and the carbonization time becomes longer when the carbonization temperature is low. Therefore, it is preferably carbonized at a carbonization temperature of 800 ° C. or higher in order to improve productivity. Therefore, it can be carbonized (coked) and used as a carbide. In order to use biomass solids in a waste melting furnace, it is necessary to set the particle size of the biomass solids to 20 mm or more (4 cc or more in volume), thereby forming a coke bed and the function of the grate Thus, it is possible to ensure the liquid permeability of the melt and the breathability of the combustion gas at the bottom of the furnace.

According to the present invention, in a coke bed type melting furnace using coke as a grate, since the coke consumption can be suppressed, not only the generation of CO ₂ derived from fossil fuels can be suppressed, but also the amount of waste treated in the melting furnace is reduced. It is possible to use a fuel derived from biomass without causing it. Further, if steam recovery power generation by a boiler is performed at the latter stage of the melting furnace, conversion to electric energy is possible, and as a result, generation of CO ₂ originating from fossil fuel can be suppressed. Further, in a melting furnace other than the coke bed type, a melting heat source can be stably supplied to the bottom of the furnace regardless of the properties of the waste, so that a stable melting process is possible.

  FIG. 1 is a diagram showing a waste melting treatment facility according to the present invention, which is substantially the same as the conventional waste melting treatment facility shown in FIG. 1, and the same components are denoted by the same reference numerals and description thereof is omitted. . The operation according to the present invention is greatly different from the conventional one in that the coke derived from fossil fuel is replaced with biomass, but the others are not substantially changed.

  Biomass is classified by the FAO (International Food and Agriculture Organization). In the present invention, woody biomass such as forest land residue, thinned wood, unused trees, lumber residue, construction waste, rice straw, rice husks, and papermaking Biomass biomass, agricultural residues, livestock manure, unused biomass resources such as food waste, or carbides after their dry distillation treatment are used.

  For example, in the case of woody biomass, the woody biomass is pulverized and heated at 150 to 350 ° C. to form a biomass molded product. This biomass molded product is used as a dry distillation furnace for dry distillation in a rotary kiln or coke oven. It is manufactured by doing.

  The shaft furnace type waste melting furnace 1 shown in FIG. 1 is charged with waste, coke, limestone, and biomass solids, and is discarded by blowing air from the upper blower tuyere 2 and oxygen-enriched air from the lower blower vent 3. The product was melt processed.

As the biomass solid, sawdust generated during wood processing was heated so that the solid temperature was about 200 ° C., and a briquette having a diameter of about 40 mm was formed by pressure molding at about 1 t / cm ² . For comparison, a test using coal coke as a heat source was also conducted. Table 1 shows the operating conditions and results when using the biomass solidified product and coal coke.

In each case, the upper air flow rate (air) is 350 Nm ³ / h, the lower air flow rate (air) is 250 Nm ³ / h, and the oxygen concentration is lower, the lower acid feed amount (pure oxygen) is 60 Nm ³ / h. Blasting is a constant condition with an oxygen concentration of 36.3%, and when using biomass solidified, the amount of fuel used is 180 kg / waste t against 40 kg / waste t of coal coke in anticipation of its volatile content. Operated at.

  Although the amount of waste was slightly reduced to 800 kg / h compared to when coal coke was used, as a result of the test, the biomass solidified product was operated without any change in melting capacity compared to coal coke used as a conventional heat source. It was confirmed that it was possible.

The biomass solidified product is produced by heating sawdust generated during wood processing so that the solid temperature becomes about 200 ° C., and forming a briquette having a diameter of about 40 mm by pressure molding at about 1 t / cm ^2. Table 1 shows the operating conditions and results using carbides charged in a carbonization furnace and carbonized at 800 ° C. for 20 hours.

The operating conditions, the upper air volume (air) 350 Nm ³ / h, the lower air volume (air) 250 Nm ³ / h, oxygen to enrich, and lower air volume (pure oxygen) 60 Nm ³ / h, the lower blade Blowing at the mouth is a constant condition with an oxygen concentration of 36.3%, and when using solidified biomass, the volatile content is as low as that of coal coke. It operated with the thing t.

  As a result of the test, the amount of waste treated was 850 kg / h, which was the same as when using coal coke, and the discharge temperature of the melt was also equivalent to that of coal coke. That is, it was confirmed that the solidified product of biomass solidified product can be operated without any change in melting capacity compared to coal coke that has been used as a heat source.

The biomass solidified product is mixed with sawdust generated at the time of wood processing together with charcoal of chicken dung (powder) in a weight ratio of 80:20 and heated to a solid temperature of about 200 ° C., and about 1 t / cm ^2. Table 1 shows the operating conditions and results obtained by forming a briquette having a diameter of about 40 mm by pressure molding, and further using the obtained briquette in a carbonization furnace and carbonized at 800 ° C. for 20 hours.

As operating conditions, the upper air flow rate (air) is 350 Nm ³ / h, the lower air flow rate (air) is 250 Nm ³ / h, and in order to enrich oxygen, the lower oxygen supply amount (pure oxygen) is 60 Nm ³ / h. The air blowing at the tuyere is a constant condition with an oxygen concentration of about 36.3%, and the volatile content of the biomass solidified product is as low as that of coal coke. The quantity was operated at 50 kg / waste t.

  As a result of the test, the amount of waste treated reached 830 kg / h, which is the same as when using coal coke, and the increased amount of ash in chicken manure carbide is very small compared to the amount of ash in waste. The discharge temperature was also equivalent to coal coke.

  That is, it was confirmed that the dry-distilled product of the mixed solidified product of biomass and chicken dung charcoal functioned as a heat source in the past, and the charcoal of chicken dung did not scatter and functioned as an alternative to coal coke at the furnace bottom.

The position of the lower tuyere is not particularly limited as long as oxygen or oxygen-enriched air can be blown into the charcoal layer 15 formed in the lower part of the shaft furnace.

It is a figure which shows the shaft furnace type waste melting equipment which enforces the operating method of this invention. It is a figure which shows the conventional shaft furnace type waste melting processing equipment.

Explanation of symbols

1: Melting furnace body 1a: Shaft portion 1b: Waste 2: Upper tuyere 3: Lower tuyere 4: Coke 5: Morning glory 6: Drying zone 7: Pyrolysis zone 8: Combustion melting zone 10: Hearth portion 11 : Charging device 12: exhaust gas pipe 13: outlet 14: pyrolysis residue 15: carbide layer

Claims (5)

In a waste melting treatment method in which waste is charged into a shaft furnace type waste melting furnace, oxygen or oxygen-enriched air is blown from the furnace bottom blower, and the waste is dried, pyrolyzed, burned, and melted.
Pressurized by adding woody biomass, biomass powder such as livestock manure, sewage sludge, human waste sludge, etc. or powdered carbides thereof, combustible dust scattered from the top of the melting furnace, or a mixture thereof An anoxic combustion gas generated by introducing briquettes with waste from the top of the furnace and reducing and burning with waste using oxygen or oxygen-enriched air blown from the bottom of the furnace. The biomass is characterized in that it is carbonized by drying and carbonization, forming a charcoal layer at the bottom of the shaft furnace, performing the reduction combustion in the charcoal layer, and using as a heat source for melting ash in waste Waste melting treatment method using In a waste melting treatment method in which waste is charged into a shaft furnace type waste melting furnace, oxygen or oxygen-enriched air is blown from a furnace bottom blower, and the waste is dried, pyrolyzed, burned, and melted.
Either a briquette obtained by pressure molding of biomass, or woody biomass, biomass powder such as livestock manure / sewage sludge / sewage sludge, or powdered carbides thereof, or combustible dust scattered from the top of the melting furnace, or these The solid carbide obtained by dry distillation of the briquette that was pressure-molded with the mixture of the above was added together with the waste from the top of the furnace, and reduced and burned with the waste with oxygen or oxygen-enriched air blown from the blower tuyeres at the bottom of the furnace With the generated oxygen-free combustion gas, the biomass solids are carbonized by drying and dry distillation in the shaft furnace, forming a charcoal layer at the bottom of the shaft furnace, and performing the reduction combustion in the charcoal layer, A waste melting treatment method using biomass, characterized by being a heat source for melting ash in waste. The biomass according to claim 1 or 2, wherein a tar / pitch binder, plastic, water, starch, lignin, cellulose, or a mixture thereof is added as an additive for pressure molding. Waste melting treatment method. The waste melting treatment method using biomass according to any one of claims 1 to 3, wherein a pressure is applied by heating to a solid temperature of 50 to 350 ° C during pressure molding . The biomass according to any one of claims 1 to 4, wherein the solid biomass subjected to pressure molding is subjected to prior dry distillation before charging into a waste melting furnace, and the dry distillation temperature is 500 ° C or higher. Waste melting treatment method using

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