JP4814621B2 - Waste disposal method - Google Patents

Description

The present invention, by heating dry distillation of organic waste such as biomass, directed to waste treatment method for obtaining a combustible gas and carbides.

In recent years, with the ratification of the Kyoto Protocol, there are high demands for CO ₂ reduction, and there are increasing demands for the use of renewable energy such as biomass.

  Gasification by heating dry distillation is attracting attention as a method of effectively using biomass. When biomass is heat-distilled, carbides are obtained together with gas. However, the chlorine contained in the biomass generated dioxins in the product gas, preventing the use of the gas. That is, organic chlorine compounds such as dioxin cause corrosion of equipment and may have an adverse effect on the human body.

  In addition, gas obtained by heat-distilling biomass contains oils such as tar and light oil, which may cause troubles such as clogging and condensing light oil when the temperature of the gas decreases. .

  In the case of gasification by heating dry distillation in order to effectively use other organic waste such as waste plastic, dioxin, tar, light oil, etc. contained in the gas are problematic as in the case of biomass.

  On the other hand, Patent Document 1 discloses a technique for decomposing and suppressing dioxins in combustion exhaust gas by first decomposing dioxins with a catalyst layer and adsorbing the remaining dioxins with an activated carbon layer. However, in the technique of Patent Document 1, when reducing dioxin contained in a combustible gas such as a product gas by heating and dry distillation of organic waste, hydrocarbon gas other than dioxin is also decomposed in the catalyst layer, and soot is generated. Since it occurs, it closes immediately. Moreover, in the activated carbon layer, tar and light oil other than dioxin are adsorbed and the activity of the activated carbon cannot be maintained. In order to sustain it, it is necessary to always use new activated carbon, which increases operating costs.

Patent Document 2 discloses a technique for removing char (solid carbon particles) contained in a gas with a ceramic filter in a generated gas treatment method for a waste treatment furnace. However, tar and light oil are included in the gas. If present, it is likely to become blocked.
JP 2003-33628 A JP 2005-24193 A

The problem to be solved by the present invention is to efficiently produce organic chlorine compounds such as tar, light oil, char, and dioxin contained in gas obtained by heating and distilling organic waste such as biomass at low cost. An object of the present invention is to provide a waste treatment method that can be removed and that can effectively use carbides obtained by heating and carbonization.

The waste treatment method of the present invention is a waste treatment method in which organic waste is heated and distilled in a carbonization furnace to obtain a combustible gas and a carbide, and the gas obtained from the carbonization furnace is cooled to 80 ° C to 150 ° C. The tar, light oil, and organic chlorine compound contained in the gas are misted, and then the tar, light oil, char, and organic chlorine compound contained in the gas are obtained from the dry distillation furnace, and are heated to 80 ° C to 150 ° C. It is characterized by purifying the gas and / or improving the calorific value of the carbide by contacting with the cooled carbide and adsorbing it on the self-covered carbide.

  As described above, the present invention is characterized by adsorbing the tar, light oil, char and organic chlorine compound contained in the gas to the carbide using the carbide obtained by heating and distilling the organic waste. To do.

  That is, the carbide obtained from the carbonization furnace has numerous pores generated in the process of volatilization of organic components, and has the property of adsorbing impurities such as tar, light oil, char, and organic chlorine compounds. Therefore, by allowing gas to pass through and contact with the carbide, impurities contained in the gas can be adsorbed and the gas can be purified.

  On the other hand, the calorific value of the carbide is improved by adsorption of tar, light oil, char and the like. By burning this carbide in a combustion furnace and using it as a heat source necessary for gasification and dry distillation, it is not necessary to regenerate by heating and purchase a new one by replacement, which is necessary when using general activated carbon. It can be covered and is optimal in terms of energy and cost. By burning the carbide, the adsorbed dioxins and the like can be decomposed, and the influence on the environment is small. Further, in the case of biomass, the volatile component occupies the majority of the combustible component, and conventionally, the carbonized material obtained by heating dry distillation has a problem that its calorific value is lower than that of fossil fuels such as coal. According to this, since tar, light oil, char and the like are adsorbed on the carbide, a high calorific value of the carbide is obtained, and the utility value as an alternative fuel for fossil fuel is increased. In particular, in the case of coal-fired power generation, it has been difficult to use biomass fuels due to the problem of increased crushing power energy due to the fibers of (woody) biomass. Is possible. Of course, the purified gas can be burned in a combustion furnace to be used as a heat source for a dry distillation furnace, or used as an alternative fuel for fossil fuels.

  In the present invention, steam can be blown into the carbonization furnace to improve the activity of the carbide. By blowing steam, fine residual volatile matter on the surface of the carbide is removed, and the activity of the carbide is improved.

  Further, in the present invention, it is preferable to fill the adsorption tower with the carbide to be brought into contact with the gas and to use the adsorption tower as a moving bed. That is, the carbide that has adsorbed impurities in the adsorption tower gradually deteriorates, and the carbide that has adsorbed a certain amount of impurities loses its activity, so that the deteriorated ones are sequentially discharged out of the system and replenished with newly generated carbides. Like that. Specifically, it is possible to always maintain the activity of the packed bed by replenishing from the top of the packed bed of carbide in the adsorption tower and sequentially withdrawing from the lower part of the packed bed. Furthermore, by letting the gas flow in a counterflow, the outlet gas reacts with new carbides, prevents the adsorbate from re-scattering, and maintains a high adsorption power.

In the present invention, the gas obtained from the carbonization furnace is cooled to 80 ° C. to 150 ° C. , and tar, light oil, and organic chlorine compounds are misted and then brought into contact with the carbide . By cooling the gas and misting the impurities in this way, the impurities are easily adsorbed on the carbide. The cooled gas can be passed through a dust removing device to remove dust components, and then contact with the carbide.

  Further, in the present invention, oxygen or air and steam are blown into the gas obtained from the carbonization furnace and reformed at 800 ° C. to 1400 ° C., and after reducing the tar content and light oil content, it can be brought into contact with the carbide. . By doing this, when there are many impurities such as tar and light oil relative to the amount of carbide generated, tar, light oil and dioxin can be reduced by modifying the gas, and the amount suitable for the generated carbide The optimum system can be established.

  Moreover, in this invention, the carbide | carbonized_material obtained from the dry distillation furnace can be used for adsorption | suction, after passing a sieve apparatus and removing a fine particle. That is, if fine particles (fine powdered carbides) are present in the carbide, it will lead to blockage of the adsorption tower and scattering of fine powdered carbide in the adsorption tower. Therefore, it is preferable that the fine particles are removed and then introduced into the adsorption tower.

  According to the present invention, by using the carbide obtained from the carbonization furnace for the adsorption of impurities, tar, light oil, char and organic chlorine compounds contained in the gas obtained from the carbonization furnace can be efficiently produced at low cost. The gas can be purified by removal.

  Further, since the calorific value of the carbide is improved by adsorption of tar, light oil, char, etc., it can be used as an alternative fuel for fossil fuel, and can be used effectively.

Embodiments of the present invention will be described below based on examples shown in the drawings. In the following description, an embodiment including only a part of the configuration of the present invention will be described.

  FIG. 1 is an apparatus configuration diagram showing a first embodiment of the present invention. This embodiment is a basic form of the present invention, in which biomass is treated as organic waste.

  In FIG. 1, biomass is crushed to a certain size or less so as to complete gasification and dry distillation within the residence time of the dry distillation furnace 1, and then charged into the dry distillation furnace 1. And biomass is heat-distilled at 300 to 1000 degreeC with the carbonization furnace 1, and a combustible gas and a carbide | carbonized_material are obtained. As the dry distillation furnace 1 shown in FIG. 1, for example, a direct heating type rotary kiln can be used. In this case, biomass is heated to dry distillation by introducing combustion air or oxygen and partially combusting a combustible gas. In addition, an indirect heating type rotary kiln, a shaft furnace, a fluidized bed furnace, or the like can be used.

The gas obtained from the carbonization furnace 1 contains H ₂ , CO, and CH ₄ as main components, and also contains tar, light oil, char, dioxin, and the like. The gas obtained from the carbonization furnace 1 is then introduced into the adsorption tower 2.

  The adsorption tower 2 contains the carbide obtained from the carbonization furnace 1, and this carbide forms a packed bed 2a. Then, when the gas obtained from the dry distillation furnace 1 passes through the packed bed 2a, tar, light oil, char, dioxin and the like contained in the gas are adsorbed and removed by the carbide of the packed bed 2a. The refined gas is used in gas utilization facilities such as commercial power generation boilers, gas turbines, and furnace burners.

  In this embodiment, the adsorption tower 2 is used as a moving bed in order to maintain the adsorption capacity of the adsorption tower 2 at a high level. That is, the carbide obtained from the carbonization furnace 1 is indirectly cooled with cooling water at the conveyor 3 at the carbonization furnace outlet, and then transferred to the carbide hopper 4 at the top of the adsorption tower 2. Are sequentially inserted. On the other hand, carbides that have adsorbed impurities and have decreased activity are sequentially discharged from the bottom of the adsorption tower 2 by the screw conveyor 6. Thus, by making the adsorption tower 2 into a moving bed, the activity of the carbide of the packed bed 2a can be maintained at a high level. The supply device 5 disposed between the carbide hopper 4 and the adsorption tower 2 preferably has a so-called double seal valve structure by providing two rotary valves as shown in FIG. That is, when supplying carbide into the adsorption tower 2, if air leaks to the gas side, abnormal combustion or the like may be caused. Therefore, it is preferable to supply after replacing with nitrogen or the like. The supply device 5 may be a combination of a swing valve, a ball valve, a gate valve, a rotary valve, and a screw.

  The carbide discharged by the screw conveyor 6 has a reduced activity as an adsorbent, but the calorific value is improved by adsorbing tar, light oil, char and the like. Therefore, it can be effectively used as an alternative fuel for fossil fuels used for commercial power generation.

  FIG. 3 shows an example of the structure of the adsorption tower, (a) is a longitudinal sectional view, and (b) is a transverse sectional view. In this example, the space partitioned by the louver 2b is filled with carbide to form a packed bed 2a. The gas is passed horizontally. Since the louver 2b is inclined upward, the carbide does not leak out.

  FIG. 4 shows an example of the structure of the adsorption tower, (a) is a longitudinal sectional view thereof, and (b) is an AA sectional view of (a). In this example, the carbide moves in the space partitioned by the plate 2c having holes that do not spill carbide. This moving layer (filling layer 2a) of carbide is disposed so as to close the front surface of the main body, and the gas enters from the hole of the plate 2c and flows upward after coming into contact with the carbide. The moving layer of carbide is installed obliquely and moves downward by gravity by discharging from the lower part. The moving bed is installed while being folded in a plurality of height directions, and the gas is gradually purified every time it passes through the moving bed of carbide.

  FIG. 5 shows still another structural example of the adsorption tower, in which (a) is a longitudinal sectional view and (b) is a transverse sectional view. In this example, a plurality of cylinders 2d with holes are arranged, and the cylinder 2d is filled with carbide to form a packed bed 2a. Gas is introduced from below and discharged from above. The hole opened in the cylinder 2d is set to a size that prevents the carbide from leaking out.

  FIG. 6 is a longitudinal sectional view showing still another structural example of the adsorption tower. In this example, the inside of the adsorption tower 2 is filled with carbide to form a packed bed 2a. In this case, when the gas is introduced from the wall surface of the adsorption tower 2, the gas flows along the wall surface and does not flow through the central portion of the packed bed 2a, so that the adsorption effect is reduced. Therefore, as shown in FIG. 6, it is preferable to blow gas into the center of the carbide of the packed bed 2a. More preferably, the duct 7 is placed in the center of the packed bed 2a, and gas is introduced downward. When the duct is directed upward, the carbides that have entered the duct are not discharged, and an adsorbed amount of impurities exceeding the allowable amount may be adsorbed, leading to blockage.

In such an adsorption tower 2, if the flow rate of the gas passing through the packed bed 2a is too high, impurities in the gas cannot be sufficiently adsorbed. Therefore, the flow rate of the gas passing through the packed bed 2a is set to 0.05 to 1.0 m / s. The residence time of the gas in the packed bed 2a is 1 sec to 30 sec. Moreover, the temperature of the carbide | carbonized_material of the filled layer 2a shall be 80 to 150 degreeC. As described with reference to FIG. 1, the carbide produced in the carbonization furnace 1 is cooled by the conveyor 3 at the furnace outlet. However, if the temperature of the carbide is high, the conveying device up to the adsorption tower 2 is hindered. Moisture in the gas condenses on the surface, impairing adsorption performance.

  In addition, although the process of biomass was demonstrated in this Example, you may make it mix and process waste plastics and other organic waste with biomass.

  FIG. 7 is an apparatus configuration diagram showing a second embodiment of the present invention. In this embodiment, a configuration in which high-temperature steam is blown into the dry distillation furnace 1 is added to the configuration of the first embodiment.

  By blowing high-temperature steam (about 100 ° C. to 400 ° C.) into the carbonization furnace 1, fine residual volatile components on the surface of the carbide are removed, and the activity of the resulting carbide is improved. By using the carbide having improved activity in the adsorption tower 2, the adsorption capacity of the adsorption tower 2 is improved.

  When gasification and carbide activation (activation) are performed simultaneously in the dry distillation furnace 1 as described above, it is desirable to put a nozzle into the dry distillation furnace 1 and spray the vapor directly on the carbide after the carbide is generated.

  FIG. 8 is an apparatus configuration diagram showing a third embodiment of the present invention. In this embodiment, a carbonization furnace is provided separately from the dry distillation furnace.

  In FIG. 8, biomass is heated and gasified at a low temperature of about 300 ° C. to 600 ° C. in the former carbonization furnace 1a, and carbide remaining after gasification is further heated at a high temperature of about 600 ° C. to 1000 ° C. in the latter carbonization furnace 1b. I try to heat it. In the carbonization furnace 1a and the carbonization furnace 1b provided in two stages, steam is blown together to increase the pores of the carbide and improve the adsorption ability of the carbide.

  FIG. 9 is an apparatus configuration diagram showing a fourth embodiment of the present invention. In this embodiment, all or a part of the carbide discharged by adsorbing impurities in the adsorption tower 2 is used as a heat source necessary for gasification and dry distillation of biomass in the dry distillation furnace 1. .

  In FIG. 9, a part of the carbide discharged from the screw conveyor 6 at the bottom of the adsorption tower 2 is put into the combustion furnace 8, and the combustion exhaust gas is used as a heat source for gasification and dry distillation in the dry distillation furnace 1. The dry distillation furnace 1 shown in FIG. 9 is an indirect heating (external heating type) rotary kiln or shaft furnace, and performs gasification and dry distillation of biomass using high-temperature combustion exhaust gas from the combustion furnace 8 as a heat source. The combustion exhaust gas after being used as a heat source for the dry distillation furnace 1 is subjected to exhaust heat treatment after exhaust heat recovery and exhaust gas treatment.

  In FIG. 9, instead of burning the carbide in the combustion furnace 8, the purified gas may be burned in the combustion furnace 8 and used as a heat source for the dry distillation furnace 1.

  FIG. 10 is an apparatus configuration diagram showing a fifth embodiment of the present invention. In this embodiment, the gas obtained from the carbonization furnace 1 is cooled and then introduced into the adsorption tower 2.

10, the temperature of the gas obtained from the carbonization furnace 1 is about 300 ° C. to 800 ° C., which is cooled to a combination by Ri 80 ° C. to 150 DEG ° C. in the cooling tower 10 cooling water spraying system with boiler 9 . However, it is preferable to maintain at a temperature equal to or higher than the condensation temperature of the vapor in the gas determined by the moisture of the biomass to be treated and the amount of cooling water sprayed in the cooling tower 10. By cooling the gas, tar, light oil, dioxin and the like contained in the gas are misted, and these are easily adsorbed on the carbide in the adsorption tower 2. On the other hand, when the gas temperature is high, tar, light oil, dioxin and the like once adsorbed by the adsorption tower 2 are separated again, and sufficient adsorption performance cannot be obtained. When moisture condenses, the carbide absorbs moisture, and sufficient adsorption performance for tar, light oil, dioxin, etc. cannot be obtained.

  In order to maximize the dioxin adsorption capacity, the gas is cooled below the moisture condensation temperature, the moisture is condensed, and then the gas is reheated with a reheater (not shown), The temperature is raised to a temperature at which moisture does not condense in 2, and then introduced into the adsorption tower 2. Thus, adsorption at a low temperature can be performed, and the adsorption capacity can be utilized to the maximum.

Although not shown in FIG. 10, a dust removing device such as an electrostatic precipitator, a bag filter, or a cyclone is disposed at the rear stage of the cooling tower 10, and dust components are removed before being introduced into the absorption tower 2. You can also. The dust concentration at the outlet of the dust removing device is preferably 100 mg / Nm ³ or less. This can reliably prevent the adsorption tower 2 from being blocked.

  FIG. 11 is an apparatus configuration diagram showing a sixth embodiment of the present invention. In this embodiment, a reforming furnace 11 is added to the configuration of FIG.

  In FIG. 11, in the reforming furnace 11, oxygen or air and steam are blown into the gas obtained from the dry distillation furnace 1, and the tar content, light oil content and dioxin in the gas are reduced.

The reforming temperature is set to 800 to 1400 ° C., the gas temperature at the outlet of the reforming furnace 11 is measured, and oxygen or air and the amount of steam are adjusted so that the temperature becomes a target value. By this reforming, tar and light oil are converted into gases such as CO, CO ₂ , H ₂ , CH ₄ , H ₂ O, and char. Dioxins are also partially decomposed and reduced. If the reforming temperature is less than 800 ° C., reforming is insufficient, and if it exceeds 1400 ° C., tar content, light oil content and dioxin can be further reduced. , H ₂ , the gas calorie is lowered and the gas volume is increased, so that the utility value of the gas is lowered.

  Further, in this embodiment, the gas is cooled by the boiler 9 and the cooling tower 10 at the rear stage of the reforming furnace 11, the remaining amount of tar, light oil and dioxin depending on the reforming temperature of the reforming furnace 11, and cooling By adjusting the adsorption capacity depending on the temperature, the removal ability of tar, light oil and dioxin can be controlled in response to changes in the properties of the biomass to be treated, that is, changes in the properties and amount of the resulting carbide.

  FIG. 12 is an apparatus configuration diagram showing a seventh embodiment of the present invention. In this embodiment, biomass and other wastes such as waste plastic are processed in separate systems, and the configuration for this is added to the configuration of FIG.

  Wastes other than biomass, such as waste plastics, contain a large amount of chlorine, so a large amount of dioxin is contained in the gas obtained during gasification. On the other hand, the obtained carbide is often powdered (or granulated powdery) and is difficult to use for gas purification in the adsorption tower 2.

  Therefore, in this embodiment, waste plastic other than biomass is gasified in a separate system, and purification of the obtained gas is performed with carbide obtained from biomass. That is, waste plastic other than biomass is gasified in the gasification furnace 12, and the obtained gas is introduced into the adsorption tower 13 through the reforming furnace 11 and the cooling tower 10. The adsorption tower 13 is filled with carbide discharged from the bottom of the adsorption tower 2 of the biomass processing system, that is, carbide obtained from biomass. By setting it as such a structure, the gasification gas obtained from waste other than biomass can be refine | purified using the carbide | carbonized_material obtained from biomass.

  In the present embodiment, the carbide discharged from the bottom of the adsorption tower 13 of the processing system for waste plastics, etc. is charged into the combustion furnace 8 and used as a heat source for the dry distillation furnace 1.

  FIG. 13 is an apparatus configuration diagram showing an eighth embodiment of the present invention. In this embodiment, a sieve device 14 for removing fine particles in the carbide obtained from the carbonization furnace is provided in the configuration shown in FIG. 11, and this is the best example of a biomass processing device. .

  In FIG. 13, the sieving device 14 sieves carbides discharged from the conveyor 3 at the outlet of the carbonization furnace, and removes finely divided carbides having a particle size of less than 1 mm, for example. The carbide from which the fine carbide is removed is used for adsorption in the adsorption tower 2. On the other hand, the finely divided carbide is put into the combustion furnace 8 and used as a heat source of the dry distillation furnace 1.

Table 1 shows the results of measuring dioxins, solid carbon particles (char), and liquid hydrocarbons (tar content, light oil content) in the gas at the inlet and outlet of the adsorption tower in the apparatus shown in FIG.

  As shown in Table 1, it can be seen that all impurities are sufficiently removed by the adsorption tower.

BRIEF DESCRIPTION OF THE DRAWINGS It is an apparatus block diagram which shows 1st Example of this invention. It is a figure which shows the example of the valve structure for supplying a carbide | carbonized_material to an adsorption tower. The structural example of an adsorption tower is shown, (a) is the longitudinal cross-sectional view, (b) is a cross-sectional view. The other structural example of an adsorption tower is shown, (a) is the longitudinal cross-sectional view, (b) is AA sectional drawing of (a). Still another structural example of the adsorption tower is shown, in which (a) is a longitudinal sectional view and (b) is a transverse sectional view. It is a longitudinal cross-sectional view which shows the other structural example of an adsorption tower. It is an apparatus block diagram which shows 2nd Example of this invention. It is an apparatus block diagram which shows 3rd Example of this invention. It is an apparatus block diagram which shows 4th Example of this invention. It is an apparatus block diagram which shows 5th Example of this invention. It is an apparatus block diagram which shows 6th Example of this invention. It is an apparatus block diagram which shows 7th Example of this invention. It is an apparatus block diagram which shows 8th Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a Carbonization furnace 1b Carbonization furnace 2 Adsorption tower 2a Packing bed 2b Louver 2c Plate 2d Tube 3 Conveyor 4 Carbide hopper 5 Feeder 6 Screw conveyor 7 Duct 8 Combustion furnace 9 Boiler 10 Cooling tower 11 Reforming furnace 12 Gasification furnace 13 Adsorption tower 14 Sieve device

Claims (1)

In a waste treatment method in which organic waste is heat-distilled in a carbonization furnace to obtain a combustible gas and a carbide, the gas obtained from the carbonization furnace is cooled to 80 ° C. to 150 ° C., and tar contained in the gas , light oil and organic chlorine compounds after mist, tar contained in the gas, light oil, char and organic chlorine compounds is obtained from the dry distillation furnace, in contact with a carbide cooled to 80 ° C. to 150 DEG ° C. own A waste treatment method characterized by purifying gas and / or improving the calorific value of the carbide by adsorbing it to the carbide that can be covered by the method.

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