JP4191636B2 - Waste melting treatment method using bulk 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 bulk 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.

  For example, a shaft furnace type waste melting furnace is used as a method of melting waste (see Patent Document 1).

  As shown in FIG. 4, 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.

  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 with oxygen or oxygen-enriched air supplied from the lower tuyere 2 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.

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 plastics, 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.

Moreover, even with the waste melting furnace according Patent Document 6, an auxiliary fuel such as LNG or kerosene in order to maintain the melt. Even in these systems, the amount of LNG, kerosene, etc. is increased in order to maintain stable melting, and there is no substitute for discharging CO ₂ caused by fossil fuels. In general, it is conceivable to add a small amount of coke in order to maintain stable melting, but in that case, as described above, a problem substantially equivalent to that of the coke system occurs.
JP 2001-90923 A JP-A-8-285250 JP 2001-21123 A JP 11-153309 A JP-A-5-346221 JP-A-10-132242

The conventional tuyere blowing technique used in the coke bed type shaft furnace can reduce the coke consumption, but the fixed carbon content represented by C + CO ₂ → 2CO and C + H ₂ O → H ₂ + CO. The coke consumption cannot be completely suppressed due to the gasification reaction. In addition, in order to maintain the grate function of the coke bed formed of coke, it is necessary to supplement the coke, and there is a limit to the reduction of coke usage.

Also, in the gasification and melting method of the shaft furnace type that does not use other coke, auxiliary fuel is used from the acid feed port at the bottom of the furnace, or auxiliary fuel is used for homogenizing the slag. The generation of CO ₂ caused by fuel could not be suppressed.

As an alternative to coke, LNG, kerosene, etc. derived from fossil fuels used in the melting treatment of shaft furnace type waste, the present invention uses a massive biomass to form a high temperature grate at the bottom of the shaft furnace. The present invention provides a waste melting treatment method that uses bulk biomass that can be formed to reduce the amount of coke used and reduce the CO ₂ load on the environment.

  The waste melting method using bulk 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. , Oxygen or oxygen-enriched air blown from the furnace bottom blowing tuyere is charged with waste biomass from the top of the furnace together with waste, with a hot strength of 20 or more in CSR, which is a representative hot strength index The mass of biomass is raised by the oxygen-free combustion gas generated by reducing and burning waste at the bottom, and the ash content in the waste is melted by forming a grate-like layer at the bottom of the shaft furnace. And

Here, strength after high-temperature reaction: CSR is described in Table 4.23, Table 4.23 of 3rd edition Steel Handbook II, Steelmaking and Steelmaking (edited by the Japan Iron and Steel Institute). + is due to normal temperature rotation test) method, after 2 hours through gas 950 ° C. of CO ₂ gas to the sieved sample of about 20 mm, when the 600 rotates toward the reaction after the sample strength tester, to 10mm over It is shown in the ratio that stays.

  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. As it scatters and the one that reaches the bottom of the furnace burns and disappears quickly, it does not form a combustion grate like coke, so it is difficult to produce hot slag metal, 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, fossil fuel must be used anyway, and as a result, CO ₂ was discharged.

  Therefore, it is conceivable to directly feed massive biomass into the shaft furnace. However, this method has a drawback that it has little effect of functioning as a melting heat source of the shaft furnace, and requires a large amount of biomass input. Depending on the nature and dry distillation method of the bulk biomass, crystallization (graphitization, coking) has not progressed and the bulk biomass remains in a two-dimensional graphite structure. In the combustion process, partly separated into layers, not only the proportion of forming a grate in the lower part of the furnace is small, but even if a grate is formed, it is separated into layers by oxyfuel combustion blown from the tuyere However, there is a problem that a high temperature grate cannot be formed and the ratio that can contribute to high temperature melting is extremely low, and a large amount of input is required.

  Thus, experimentally, a mass biomass having various strengths, shapes, and origins was actually introduced into the shaft furnace, and the percentage of high yields that effectively became a high-temperature grate in the shaft furnace was calculated. FIG. 2 shows the relationship between the slag temperature, which is one of the operation indices of the CSR and the waste melting furnace. As a result of this experiment, it was found that there is the following law property.

  As for the hot strength of bulk biomass, the bulk biomass with a CSR of 20% or more reaches the bottom of the furnace regardless of the type, and the tuyere installed at the bottom of the furnace forms a high-temperature grate. It was confirmed by the observation situation from. As a result of forming a high-temperature grate at the bottom of the furnace, the discharged slag temperature could be stably operated at 1500 ° C. or higher.

When bulk biomass with a CSR of less than 20% is used, it means that most bulk biomass is pulverized by CO ₂ hot gas by gasification from the inside, and it was charged from the top of the furnace. High-temperature grate cannot be formed like coke because lump biomass is pulverized in the process of descending in the shaft furnace and eventually scatters or disappears immediately after reaching the bottom of the furnace . As a result, the slag temperature dropped and eventually slag could not be discharged, making it impossible to continue operation.

  Therefore, it is necessary to adjust the CSR to be at least 20% or more by adjusting the bulk biomass to be input. Some of the charcoal, etc. that have been subjected to carbonization and carbonization after compression molding of charcoal and sawdust, satisfy these standards.

  In addition, it can be confirmed that the poultry manure and wood chips derived from industrial waste have reached the bottom of the furnace if the pressure molding conditions and dry distillation conditions are adjusted so that the CSR is 20% or more. It was. In addition, the CSR of general blast furnace coke is about 70%, and even with biomass, it can be achieved further by optimizing the heating molding and dry distillation conditions, but the running cost increases, so economical operation is possible. I can't. Therefore, it is desirable to adjust so that the CSR of biomass is 20% or more and 70% or less, but from FIG. 2, when CSR exceeds 40%, the slag temperature becomes about 1550 ° C, and the CSR is increased. It can also be seen that the contribution to the slag temperature is small. Therefore, the most economical operation can be realized by adjusting the CSR of biomass to 20% or more and 40% or less.

  At present, the disposal of building waste is a problem, and most of the waste is incinerated as it is or only at a low level of recovering its thermal energy. Since a large amount of wood is contained in building waste, it is pulverized, compression molded, and then subjected to dry distillation treatment. As a high-temperature grate of the shaft furnace, it is discarded at the bottom of the furnace without being pulverized in the melting furnace. It can be used as a melting heat source for melting the ash content of the product.

  In order to efficiently use the massive biomass solid as a substitute for coke in the waste melting furnace, it is efficient to adjust the particle size of the massive biomass to 20 mm or more. Since fine particles of 20 mm or less burn out immediately after reaching the bottom of the furnace, a high-temperature grate cannot be formed like coke. As a result, a hot grate is formed under the shaft furnace, and the liquid permeability of the melt and the breathability of the combustion gas at the bottom of the furnace can be ensured by the function of the grate. On the other hand, when the thickness is 100 mm or more, the biomass having a lower strength than the blast furnace coke is likely to be cracked in the conveyance process and in the furnace, and on the contrary, often has a small diameter at the bottom of the furnace. Therefore, the particle size of the massive biomass is desirably 100 mm or less.

In addition, it is efficient that the cold strength of the bulk biomass is 50% or more with the drum strong skin DI ₁₅ which is a general strength standard. For drum strength DI ₁₅ , as described in JISK2151, the sample is loaded into a specified drum testing machine, rotated at a specified speed at a specified speed, and then the yield on a sieve with a 15 mm sieve. It is expressed as a ratio.

FIG. 3 shows the results of experiments conducted by the inventors on the relationship between the drum strength DI ₁₅ and the slag temperature. According to FIG. 3, when DI ₁₅ is 50% or more, the slag temperature can be maintained at about 1500 ° C.

When bulk biomass with a DI ₁₅ strength of less than 50% is used, a significant portion is finely divided when passing through a transport or transport device, and a yield of 20 mm or more that can form a high-temperature grate at the bottom of the shaft furnace is obtained. It becomes small and the addition ratio of the massive biomass for inevitably maintaining sufficient melting increases. Of course, even if the input amount is increased, the CO ₂ -free bulk biomass is finally converted into steam energy by waste heat recovery and contributes to the prevention of global warming as electric power by the steam turbine. It was difficult to say that it contributed effectively to the suppression of the use of fossil fuels for melting heat sources, which is the original purpose of this patent. Accordingly, cold strength of massive biomass, the drum strength DI ₁₅ which is a measure of the general strength of 50% or more is effective, and further, slag in Figures 3, DI _l5 with 70% Since the temperature is almost constant, producing more than 70% of biomass is uneconomical as a melting heat source. Therefore, it is desirable that the drum strength DI ₁₅ of the bulk biomass be 50% or more and 70% or less.

  The shaft furnace waste melting furnace is more efficient by burning waste at the upper tuyere to generate a heat source for drying and blowing oxygen-enriched air for combustion melting from the lower stage. It becomes possible to reduce the addition amount of massive biomass. In that case, at the upper tuyere level, garbage and massive biomass are mixed, but since the massive biomass of 20% or more in CSR has a dense structure, air blowing from the upper tuyere is selective. Since the waste will burn, inevitably, the ratio of the bulk biomass to the garbage falling below the upper tuyere can be increased, so by using the upper tuyere, the ratio of the massive biomass input more efficiently It can be lowered and becomes more economical.

  In addition, 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 increased. 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.

In addition, the block biomass described in these inventions can also be used in a range where both the hot strength CSR and the cold strength DI ₁₅ are lower than the blast furnace coke. Considering only economic efficiency, the lower the hot strength CSR and the cold strength DI ₁₅ , alleviate the restrictions on the molding conditions, material quality, and dry distillation conditions of the bulk biomass, and the production cost can be reduced. Therefore, in order to operate economically, it is necessary to reduce the strength level of the biomass. In this case, the biomass input from the top of the furnace is pulverized while being exposed to high temperature in the furnace, and finally In addition, there is biomass that is scattered outside the furnace with the gas in the furnace. In such a case, a dust removal device such as a cyclone is installed at the shaft furnace outlet, and the dust once burned out of the furnace is blown out with the oxygen or oxygen-enriched air from the tuyere. Since it burns in front of the tuyere and contributes as a heat source for melting, it becomes possible to more efficiently reduce the amount of bulk biomass added. In addition, the dust-removed gas flows into the combustion chamber on the downstream side of the dust remover and becomes the main component of gas combustion. Will be achieved.

  In addition, the amount of biomass solids to be input needs to be 3% or more of the waste processing amount on a solid carbon basis in order to make the addition amount of coke zero.

  In the shaft furnace type waste melting furnace, the current blast furnace coke can be operated at a level of 3%, but in the case of biomass solids, it is charged and charged according to the ratio of dry distillation and gasification in the furnace. It is necessary to add. In other words, biomass solids that have been pre-distilled at a very high temperature of 1200 degrees are hardly gasified in the furnace, and can be sufficiently operated at an addition amount of about 3%. Although it is inexpensive, it will be gasified by about 10% in the furnace, so it is necessary to add 20% extra for the amount of charging / addition in anticipation of partial pulverization. Become. Of course, it is not economically preferable to add more biomass than necessary, and it is desirable that the added amount be about 10%.

  At this time, this bulk biomass charging method requires the following charging method in order to maximize the effect. It is to alternately stack garbage and bulk biomass. In general, a shaft furnace type charging method uses a furnace top charging device having a seal structure to charge auxiliary materials such as garbage, coke, and limestone. At this time, the garbage and the auxiliary material may be charged from the same hopper or from different lines. At the time of charging, massive biomass that is relatively colder than coal coke may be destroyed by mutual collision and friction, and it may not be possible to efficiently form a high-temperature grate below the shaft. Therefore, by alternately charging with compressible garbage, mutual collision and friction can be suppressed and destruction of massive biomass can be prevented. This means that when the garbage and the auxiliary material have separate lines, the garbage and the auxiliary material are always charged alternately. In addition, when charging waste and auxiliary materials into the furnace at the same time, when putting it into the hopper in the charging device, stack the bulk biomass on the waste and charge it into the furnace as it is. This is possible.

According to the present invention, in a shaft furnace type waste melting furnace, consumption of fossil fuels such as coke, LNG, and kerosene required to maintain high temperature melting by introducing a CO ₂ -free biomass molding In addition to being able to suppress CO ₂ generation derived from fossil fuels directly, if steam recovery power generation using a boiler is performed at the latter stage of the melting furnace, conversion to electrical energy is possible. 1) Power consumption in the office can be reduced, the amount of power to be purchased can be suppressed, and (2) power generation using fossil fuels such as power companies is indirectly suppressed by transmitting power to power companies, etc. As a result, generation of CO ₂ originating from fossil fuel can be suppressed.

  Also, in melting furnaces other than the coke bed type, it is possible to maintain a high-temperature grate stably at the bottom of the furnace regardless of the properties of the waste by adding bulk biomass, so excessive amounts of LNG, kerosene, etc. A stable melting process is possible without using it for stool.

  The cold strength conventionally required in blast furnaces, etc., is not necessary as much as blast furnaces in shaft furnaces that handle waste that has no raceway in the vicinity of tuyere, and that waste is most likely to be destroyed during charging. In addition, since the furnace is in a reducing atmosphere and the temperature conditions in the shaft furnace are maintained at a relatively low temperature down to the bottom of the furnace compared to the blast furnace, the restrictions on hot strength are not as severe as those in the blast furnace. It has become possible to produce biomass in an inexpensive manner.

  FIG. 1 is a view showing a waste melting treatment facility for carrying out the method according to the present invention, which is substantially the same as the conventional waste melting treatment facility shown in FIG. Description is omitted. A dust remover 15 is installed between the melting furnace and the combustion chamber, and the scattered biomass collected therein is blown from the lower tuyere by the dust blowing device 16. These technologies can be applied directly to the technology that collects dust (char) caused by dust and blows it from the tuyere, which has already been put to practical use. The operation according to the present invention is greatly different from the conventional one in that coke derived from fossil fuel is replaced by bulk biomass, but the others are not substantially changed.

  An experiment in which waste, limestone, and massive biomass solidified material are charged into a shaft furnace type waste melting furnace, and the waste is melted by blowing air from the upper blowing tuyere and oxygen-enriched air from the lower blowing tuyere. Carried out.

  As the woody biomass solidified product, the following four types of molded products derived from compression-molded biomass were used. (1) Carbide obtained by heat compression molding sawdust from building waste, (2), (4) Two brands of commercial charcoal, (3) Chicken manure, (5) Commercial ogarite.

For comparison, a test using coke as a heat source was also conducted. Table 1 shows the properties of bulk biomass and coke, operating conditions, and results.

  As a result of the test, it has been confirmed that the bulk biomass of the above (1) and (2) can basically be operated almost the same as conventional coke. As a result, charcoal (2) has a slightly lower CSR compared to (1), lacks strength, and the amount added is about 25% higher than (1). By blowing inflammable dust collected from the mouth, the amount of bulk biomass added can finally be reduced to almost the same conditions.

  In addition, (3) chicken manure and (4) charcoal have CSR below 17, 13, and 20, and even if the tuyere is blown, a hot grate is not formed at the bottom of the furnace, Even if the addition amount was increased by about 60% compared to the conventional case, the slag temperature could not be maintained at a high temperature.

  The ogarite (5) is only compression-molded sawdust, but in this case, the slag temperature dropped rapidly immediately after switching from coke, and the operation could not be maintained.

It is a figure which shows the shaft furnace type waste melting equipment which enforces the operating method of this invention. In a shaft furnace type waste melting furnace, it is a figure which shows the relationship between hot reaction strength CSR of the fuel used as a melting heat source, and slag temperature. In shaft furnace type waste melting furnace is a diagram showing the relationship between cold strength DI ₁₅ and slag temperature of the fuel to be used as melting heat source. 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 blowing device 17: Bulk biomass

Claims (7)

And introducing waste into the waste melting furnace of the shaft furnace method, dry waste, pyrolysis, combustion, in a melt processing method of waste melting treatment, as a medium of high temperature grate forming the furnace bottom, 800 ° C. dry distillation was high-temperature strength after reaction at 1200 ° C. from: waste CSR is characterized by using waste amount of 3% or more than 10% of the bulk biomass is less than 70% 20% solid carbon-based fused Processing method.       The waste melt treatment method using bulk biomass according to claim 1, wherein the particle size of the bulk biomass is 20 mm or more and 100 mm or less. The waste melt treatment method using bulk biomass according to claim 1 or 2, wherein the cold strength of the bulk biomass is a typical drum strength index of DI ₁₅ of 50% or more.       The operating condition of the shaft furnace is that upper and lower tuyere are provided, waste drying air is blown from the upper stage, and oxygen-enriched air for combustion melting is blown from the lower stage. A waste melting method using the bulk biomass according to claim 1.       The oxygen concentration of a lower tuyere is 25%-40%, The waste melt processing method using the block biomass of any one of Claims 1-4 characterized by the above-mentioned.       Dust pulverized by massive biomass contained in the pyrolyzed gas or dust fine from waste is collected with a dust remover, and the collected combustible dust is enriched from the tuyere with oxygen or oxygen It blows with air, The waste melt processing method using the block biomass of any one of Claims 1-5 characterized by the above-mentioned. Charging method of bulk biomass, debris and massive biomass was charged into furnace alternately, in any one of claim 1 to 6, dust and massive biomass characterized by alternately stacking in a furnace The shaft furnace type waste melting method described.

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