JP4276559B2 - 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 waste melting furnace and recycled as slag and metal.

Waste to a method of melting treatment, e.g., a shaft furnace type of waste melting furnace is used (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 2 for a combustion melting zone is provided at the lower end of the morning glory portion 5, and above that Has a plurality of upper tuyere 3 for the pyrolysis zone. Oxygen or oxygen-enriched air is supplied from the lower tuyere 2, and air is supplied from the upper tuyere 3 as a combustion support gas.

  In the upper part of the furnace main 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 bottom end of the main body 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 to the dry pre-tropical zone 6 (about 300 to 400 ° C.), the pyrolysis zone 7 (about 300 to 1000 ° C.), the combustion / melting zone. 8 (about 1700-1800 ° C.) to be melt processed.

  The coke 4 and the pyrolysis residue 14 are burned at a high temperature by the oxygen supplied from the lower tuyere 2 or oxygen-enriched air and used as a heat source for melting. On the other hand, air is supplied from the upper tuyere 3 to mainly generate heat from waste. The decomposition residue 14 is combusted, and the generated gas is used for drying / preheating and thermal decomposition of the waste. 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 the exhaust heat, the temperature is adjusted in the temperature reducing tower and passed through the dust collector. Further, after the pollutant is removed in the catalytic reaction tower, it is discharged from the chimney.

In this method, when the waste ash is melted in the shaft furnace type melting furnace, the waste is dried and dry-distilled (pyrolysis) by the high-temperature combustion gas rising from the bottom of the furnace, and the volatile matter is in the upper part of the furnace. Residue after pyrolysis, mainly composed of fixed carbon that has been exhausted as flammable gas and has not been volatilized and is carbonized, descends to the bottom of the furnace. It reacts with the supplied oxygen 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. As it scatters and the one that reaches the bottom of the furnace burns and disappears immediately, it does not form a combustion grate like coke, so it is difficult to produce hot slag metal, its In order to maintain the melting, there was no other way to maintain the melting by adding coke or sending fuel gas or oxygen from the tuyere. Therefore, the fossil fuel must be used anyway, and as a result, CO ₂ was discharged.

Therefore, a coke usage reduction technique capable of reducing the CO ₂ load on the environment has been proposed even in a direct melting furnace facility. 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 the tuyere or a large one from the top of the furnace and using it as a heat source (see Patent Document 4).

Further, for example, the waste melting furnace described in Patent Document 5 also uses a supplementary fuel mainly composed of coke as a melting heat source of waste in the shaft furnace, although the structure is partially different, and CO ₂ derived from fossil fuel. The same kind of problem is involved in the sense of discharging.

For example, also in the waste melting furnace described in Patent Document 6, auxiliary fuel such as LNG or kerosene is used to maintain melting. Even in these systems, the amount of LNG, kerosene, etc. for maintaining stable melting increases, and it is not possible to expect a significant reduction in CO ₂ emissions resulting from fossil fuels.
JP 2001-90923 A JP-A-8-285250 JP 2001-21123 A JP 11-153309 A JP-A-5-346221 JP-A-10-132242

  In response to these problems, it is conceivable to use biomass such as charcoal as a melting heat source in a shaft furnace type melting furnace. However, it is indispensable to form a high-temperature grate at the bottom of the shaft furnace for the shaft furnace type waste melting process. To form the grate, when using biomass, crushing and heating Pre-processing such as compression molding is required, or only high-strength biomass needs to be selected. This is because biomass that has not been pretreated or has low strength is pulverized again as it descends the shaft furnace and is scattered outside the furnace on the upflow in the shaft furnace.

  In addition, although it is possible to blow powdery biomass from the lower tuyere, in that case, it is necessary to crush it to a size suitable for airflow conveyance, and a device for crushing the biomass is required. Maintenance costs for consumable parts of the crusher were necessary. That is, in order to reduce the amount of coke used by using bulk biomass and powdery biomass, there are restrictions on the installation location, region, raw material, economic aspect, and the like.

Therefore, in the present invention, as an alternative to coke, LNG, kerosene, etc. derived from fossil fuels used in the melting treatment of shaft furnace type waste, a wide variety of biomass is used to reduce coke consumption. In addition, the present invention provides a waste melting treatment method using biomass that can reduce the CO ₂ load on the environment.

  The waste melting method using biomass according to the present invention is a waste melting method in which waste is charged into a shaft furnace type waste melting furnace, and the waste is dried, pyrolyzed, burned, and melted. Even if the biomass is insufficient, the waste generated from the combustion of the waste at the bottom of the furnace with the air, oxygen, or oxygen-enriched air that is thrown in along with the waste from the top of the furnace and blown from the blower tuyeres at the bottom of the furnace Due to the oxyfuel gas, the massive and strong biomass that partially exists forms a grate-like layer at the lower part of the shaft furnace. Others pulverize before reaching the lower part of the shaft furnace, get on the upward flow in the shaft furnace, and scatter from the upper part of the furnace together with combustible gas and combustible dust caused by combustible waste. A dust remover is installed on the downstream side of the furnace to collect the scattered biomass and combustible dust, and the mixture of the collected biomass and dust is fed into the furnace together with air, oxygen and oxygen-loaded air from the lower tuyere of the shaft furnace. By blowing it in and burning it in front of the lower tuyere, the powdered material can be directly converted into a melting heat source.

  According to the inventors' experiment, in order for the input biomass to form a high-temperature grate at the lower part of the shaft furnace, the input biomass, such as charcoal or the like that has been carbonized and subjected to dry distillation treatment after compression molding of charcoal and sawdust In the case of chicken manure or wood chips caused by industrial waste, it is known that it is necessary to install a crushing device and a pressure heating molding device and to adjust the operating conditions. Thus, when using biomass in a waste melting furnace, to maintain a high-temperature grate, both powdery biomass and bulk biomass consume energy, and need to be molded, crushed, etc., and effective use of energy In view of the above, it is desired to use biomass more broadly and economically.

  Therefore, in the present invention, a dust remover such as a cyclone is provided at the shaft furnace outlet, and the dust combustible dust is blown together with air, oxygen, or oxygen-enriched air from the tuyere to reach the furnace bottom. A wide range of biomass can be used by burning the scattered biomass powder at the bottom of the shaft furnace furnace, suppressing consumption of the high-temperature grate at the bottom of the furnace, and using it as a heat source for melting.

  Furthermore, in that case, the biomass powder scattered outside the furnace is finely divided in the process of descending in the shaft furnace, and when scattered from the shaft furnace, the particle size is suitable for air current conveyance of about 100 μm, and processing such as crushing is not possible. It is unnecessary. According to the present invention, among the biomass charged into the furnace, biomass capable of forming a high-temperature grate forms a high-temperature grate at the lower part of the furnace, and biomass that cannot be formed is blown from the tuyere after being scattered outside the furnace. By burning in front of the tuyere and becoming a heat source for melting, more efficient use of biomass becomes possible.

  At this time, the oxygen concentration at the lower tuyere is preferably 25% or more for efficient melting, and conversely, even if it is 40% or more, the melting temperature cannot be raised. This is because the gas temperature in the vicinity of the tuyere rises when the oxygen concentration is increased, but when it reaches the 2000 degree level, the gas dissociation reaction and the endothermic reaction become active, and the temperature does not rise any further. The increase in the oxygen concentration is about 40% efficient in order to suppress the use of expensive oxygen.

  Furthermore, in order to efficiently burn the powdery biomass blown from the tuyere in front of the lower tuyere, it is effective to keep the oxygen ratio at the lower tuyere appropriate.

  According to the experiments by the inventors, when the oxygen ratio is less than 1, some of the biomass blown from the lower tuyere does not burn, and these rise in the furnace and burn at the upper tuyere. Or re-scatter. That is, the biomass blown from the lower tuyere is not effectively used. In that case, by adjusting the amount of biomass introduced from the top of the furnace, the amount collected in the dust remover, that is, the amount of biomass blown from the lower tuyere can be easily controlled.

In addition, when the biomass to be input has a shape that makes it difficult to form a high-temperature grate such as a building waste material chip, the amount of CO ₂ emitted from fossil fuels can be reduced by using the minimum coke. It is possible to perform a melting process with a minimum of. Here, the minimum is the minimum amount for maintaining the high-temperature grate, and according to the experiments by the inventors, about 1% of the waste to be treated is sufficient. Even in this case, the amount of use is greatly reduced as compared with the conventional case. Furthermore, even biomass that cannot form a high-temperature grate by itself can be used as a heat source for melting by using it with coke, so it is effective from the two aspects of reducing the amount of fossil fuel used and utilizing a wide range of energy.

According to the present invention, in a shaft furnace type waste melting furnace, the consumption of fossil fuels such as coke, LNG, and kerosene required to maintain high temperature melting is greatly increased by introducing CO ₂ -free biomass. Therefore, it is possible not only to directly suppress the generation of CO ₂ derived from fossil fuels but also to effectively use a wide range of biomass-derived fuels. In addition, if steam recovery power generation with a boiler is performed at the latter stage of the melting furnace, conversion to electric energy is also possible. As a result, (1) the power consumption in the site can be reduced, the amount of power purchased can be suppressed, and (2) power By transmitting power to a company or the like, power generation using fossil fuel by an electric power company or the like is indirectly suppressed, and as a result, generation of CO ₂ originating from fossil fuel can be suppressed.

  FIG. 1 is a diagram showing a waste melting treatment facility for carrying out the method according to the present invention, which is exactly the same except that a dust remover 15 is provided at the shaft furnace outlet in addition to the conventional waste melting treatment facility shown in FIG. It is. Therefore, the same components are denoted by the same reference numerals and description thereof is omitted. FIG. 1 is basically the same as that which has already been put into practice for injecting combustible dust, and is sufficiently feasible in terms of equipment. In the dust remover 15, biomass powder scattered from the melting furnace main body 1 and combustible dust due to waste are simultaneously collected and blown from the lower tuyere 2 through the dust blowing device 16.

  An experiment was conducted in which waste, limestone, and biomass were charged into a shaft furnace type waste melting furnace, and the waste was melted by blowing air from the upper blower tuyere and oxygen-enriched air from the lower blower tuyere.

  Biomass was obtained by crushing driftwood collected from the river to 100 mm or less after drying in the sun, charging into a carbonization furnace, and carbonizing carbonized at 1000 ° C. for 5 hours in an oxygen-free atmosphere.

Since the raw material is driftwood, the size is wide, from logs with a diameter of about 200 mm to twigs with a diameter of about 2 mm, etc. When 20 mm sieving and hot strength CSR measurement were performed, the results were as shown in Table 1. . Here, the hot strength CSR is described in Table 4.23 on page 202 of the 3rd edition Steel Handbook II, Steelmaking and Steelmaking (edited by the Japan Iron and Steel Institute) (hot standing reaction + normal temperature). In the shaft furnace type waste melting furnace, the higher this value is, the easier it is to form a high-temperature grate at the lower part of the shaft furnace. According to the experimental results of the inventors, it has been found that a CSR of 20 or more is sufficient to form a high-temperature grate at the lower part of the shaft furnace.

A test using this biomass carbide was conducted, and for comparison, a test using coke as a heat source was also conducted. The operating conditions and test results are shown in Table 2.

  As shown in Table 2, the slag temperature can be operated at 1500 ° C. or higher under either condition. In addition, the amount of dust collected increased as the biomass was scattered, and it was found that they were blown from the lower tuyere and were effectively used as a heat source. In addition, the biomass used this time is 90% of fixed oxygen, which is almost equivalent to coke. When the same amount is charged, the slag temperature is almost the same, so it can be seen that this biomass can be replaced with 100% coke. .

This example is an example of mixed use of building waste material chips and coke. The building waste chip was a chip of about φ10 mm × 100 mm, and was placed in the furnace without performing the dry distillation operation. Table 3 shows the operating conditions and results.

In the actual test, the amount of building waste chips charged from the top of the furnace was adjusted so that the slag temperature would be about the same as when using only coke, and the results shown in Table 3 were obtained. . If conditions are set and relatively high quality bulk biomass is available, it can naturally be used instead of coke. In this example, the amount of CO ₂ emitted due to fossil fuel cannot be reduced to zero, but it can be reduced to 1/3 compared to the conventional case. In this example, coke and biomass are mixed in advance and supplied into the furnace from one hopper. However, separate hoppers may be installed and charged separately in the 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: Lower tuyere 3: Upper tuyere 4: Coke 5: Morning glory 6: Drying zone 7: Pyrolysis zone 8: Combustion melting zone 10: Furnace bottom 11: Charger 12: Exhaust gas pipe 13: Outlet 14: Thermal decomposition residue 15: Dust remover 16: Dust blower 17: Biomass

Claims (6)

Waste is provided in a shaft furnace type waste melting furnace that has upper and lower tuyere and blows air for drying waste from the upper tuyere and oxygen or oxygen-enriched air for combustion melting from the lower tuyere In addition, in the waste melting method, the biomass is charged and the waste is dried, pyrolyzed, burned, and melted.
Biomass with a strength in bulk present in part by the oxygen-free combustion gas generated by reducing the combustion of waste in a shaft furnace lower portion, and forming a layer of grate in a shaft furnace bottom, and the other ones, the shaft before reaching the furnace bottom portion than the shaft furnace top by the upward flow of the shaft furnace, is scattered together with the combustible gas and combustible dust, the mixture of the collected biomass and dust in dust collector installed in the shaft furnace downstream side A waste melting treatment method using biomass, which is blown together with oxygen or oxygen-enriched air from the lower tuyere of the shaft furnace and burns in front of the lower tuyere to directly convert the powdered material into a melting heat source . The waste melting treatment method using biomass according to claim 1, wherein the lower tuyere has an oxygen concentration of 25% to 40% . The amount of biomass input from the top of the furnace is adjusted so that the amount of combustible dust collected by the dust remover falls within a range of a certain ratio to the amount of oxygen blown from the lower tuyere. A waste melting method using biomass according to claim 1 or 2 . The waste melting treatment method using biomass according to any one of claims 1 to 3, wherein coke and biomass are mixed and charged into a melting furnace . The waste melting method using biomass according to any one of claims 1 to 4, wherein coke and biomass are each charged into a melting furnace alone . The waste melting treatment method using biomass according to any one of claims 4 and 5, wherein the charge amount of coke is 2.5% or less of the waste treatment amount on a solid carbon basis. .

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