Waste treatment facilities and methods for operating waste treatment facilities

Abstract

This invention provides a waste treatment facility that enables reliable furnace operation for years to come by efficiently preheating and drying wet waste. [Solution] A waste treatment facility comprising: a heat treatment furnace for heat-treating waste; a pit for storing waste to be fed into the heat treatment furnace; a crane for agitating the waste fed into the pit and feeding it into the heat treatment furnace; a dryer for reducing the moisture content of a portion of the waste before it is fed into the pit using the heat generated in the heat treatment furnace; and a feeding mechanism for feeding the waste processed by the dryer into the pit.

Description

Technical Field

[0001] The present invention relates to a waste treatment facility and a method for operating a waste treatment facility.

Background Art

[0002] Conventionally, waste such as municipal solid waste collected by waste collection vehicles and transported to waste treatment facilities was uniformly put into a pit, stirred in the pit using a garbage crane, and after stirring, the waste was operated to be put into an incinerator. By leveling the quality of the waste by stirring, it is to suppress fluctuations in the combustion state of the waste input into the incinerator.

[0003] By the way, an incinerator is designed by determining the specifications of various facilities such as a boiler so that power generation with a power generation amount corresponding to the design value can be obtained with the assumed low calorific value of the waste as the basic design value. And it is designed so that it can be operated while maintaining stable combustion for 20 years, which is the service life.

[0004] However, due to the recent trend towards a recycling-based society, it is predicted that the quality of the waste collected in the future will decline due to the reduction in the use of plastics and the promotion of recycling. If the low calorific value of the waste drops significantly below the design conditions, it is assumed that it will be difficult to operate the incinerator stably.

[0005] In preparation for such a situation, it is assumed that wet waste is dried in advance using the waste heat generated in the incinerator and then incinerated.

[0006] Patent Document 1 discloses a vacuum dryer that dries sludge obtained by biologically treating organic waste such as sewage and night soil. It is a technology that efficiently uses waste heat by generating steam with the waste heat generated in the incineration process of the dried sludge and using the steam as the driving source of an ejector for decompression, which is a vacuum generation device of the vacuum dryer.

[0007] Patent Document 2 discloses a self-contained biomass treatment system in which high-moisture biomass such as manure, livestock manure, and sewage sludge is dried in a vacuum drying device to produce dried or low-moisture biomass, and the dried or low-moisture biomass is mixed with forestry and sawmill waste such as thinned wood and sawmill scraps and fed into a small-capacity biomass incinerator, which is attached to the vacuum drying device and has the capacity to generate power and heat source steam mainly by incinerating forestry and sawmill waste, thereby completing the biomass treatment by incineration, and the electricity and steam generated by the biomass incinerator are utilized as utilities for the vacuum drying device for drying manure and other biomass. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Special Publication No. 52-49911 [Patent Document 2] Japanese Patent Publication No. 2005-257211 [Overview of the project] [Problems that the invention aims to solve]

[0009] All of these technologies are configured to dry the entire amount of wet sludge to be treated before incineration or other processing.

[0010] However, drying the entire amount of waste collected by waste collection vehicles and placed in the pit using the waste heat from the incinerator would require the construction of extremely large-scale facilities, which could compromise economic efficiency.

[0011] Furthermore, not all collected waste is wet waste; some is easily combustible. Putting all waste into a pit and agitating it with a waste crane could actually increase the amount of wet waste.

[0012] The object of the present invention is to provide a waste treatment facility and a method for operating a waste treatment facility that enable good furnace operation for the future by efficiently preheating and drying wet waste. [Means for solving the problem]

[0013] To achieve the above objectives, the first characteristic configuration of the waste treatment facility according to the present invention is that the waste treatment facility comprises a heat treatment furnace for heat-treating waste, a pit for storing waste to be fed into the heat treatment furnace, a crane for agitating the waste fed into the pit and feeding it into the heat treatment furnace, a dryer for reducing the moisture content of a portion of the waste before it is fed into the pit using the heat generated in the heat treatment furnace, and a feeding mechanism for feeding the waste treated by the dryer into the pit.

[0014] By using a dryer that reduces the moisture content by utilizing the heat generated in the heat treatment furnace, a portion of the waste, i.e., the wet waste, is dried before being put into the pit. After drying, the waste is then fed into the pit using a feeding mechanism. This allows for efficient use of limited waste heat to dry the materials to be treated, even when the amount of plastics contained in the waste is reduced.

[0015] The second characteristic configuration is that, in addition to the first characteristic configuration described above, it includes a second pit where waste to be processed by the dryer is temporarily stored.

[0016] Even if some waste requiring drying cannot be dried immediately, temporarily storing it in the second pit prevents the undesirable situation of it mixing with wet waste in the pit where other waste is being introduced.

[0017] The third characteristic configuration is that, in addition to the first characteristic configuration described above, it includes a gas supply mechanism for supplying gas into the heat treatment furnace, and the dryer is equipped with an ejector section that utilizes the gas flow velocity of the gas supply mechanism to create negative pressure inside the dryer.

[0018] The inside of the dryer is depressurized by the negative pressure formed by the ejector part that utilizes the gas flow rate of the gas supply mechanism, and the moisture contained in the waste can be evaporated at a lower temperature.

[0019] The fourth characteristic configuration is that, in addition to the first characteristic configuration described above, the heat treatment furnace is a waste incinerator.

[0020] If the heat treatment furnace is an incinerator, even when the amount of plastics contained in the waste decreases, the wet waste can be efficiently incinerated in the incinerator after being dried in the dryer.

[0021] The fifth characteristic configuration is that, in addition to the first characteristic configuration described above, the heat treatment furnace is a melting furnace.

[0022] If the heat treatment furnace is a melting furnace, even when the amount of plastics contained in the waste decreases, the wet waste can be efficiently melted in the melting furnace after being dried in the dryer.

[0023] The first characteristic configuration of the operation method of the waste treatment facility according to the present invention is an operation method of a waste treatment facility, including a pit input step of inputting the waste collected in the waste treatment facility into a pit, a stirring step of stirring the waste stored in the pit with a crane, a furnace input step of inputting the waste stored in the pit into a heat treatment furnace with a crane, a heat treatment step of heat-treating the waste input into the heat treatment furnace in the input step, and a drying step of selecting the waste with a high moisture content among the waste collected in the waste treatment facility before the pit input step and drying it in a dryer that utilizes the waste heat of the heat treatment furnace, and in the pit input step, both the waste that has undergone the drying step and the waste that has not undergone the drying step are input into the pit.

[0024] The second characteristic configuration is that, in addition to the first characteristic configuration described above, in the drying step, a part of the waste is dried based on the moisture content of the collected waste measured by a moisture content sensor provided on the waste collection vehicle.

[0025] Since the moisture content sensor provided in the waste collection vehicle can determine the wet state of the collected waste, the waste carried into the site by the waste collection vehicle can be immediately dried without waiting for a separate subsequent determination process.

Effect of the Invention

[0026] As described above, according to the present invention, it has become possible to provide a waste treatment facility and an operation method of the waste treatment facility that enable good furnace operation in the future by efficiently drying wet waste with waste heat.

Brief Description of the Drawings

[0027] [Figure 1] Overall explanatory drawing of a garbage incinerator which is a waste treatment facility [Figure 2] Explanatory drawing of a plan view of a platform and a garbage pit [Figure 3] (a) is an explanatory drawing of a dryer, and (b) is an explanatory drawing of a vacuum device

Mode for Carrying Out the Invention

[0028] Hereinafter, a waste treatment facility and an operation method of the waste treatment facility according to the present invention will be described.

[0029] Hereinafter, as an example of a heat treatment furnace for heat-treating waste, an incinerator for incinerating garbage will be described As shown in FIG. 1, a stoker-type incinerator 1 includes a platform 3 into which a garbage collection vehicle 2 enters, a garbage pit 4 for accumulating the garbage collected by the garbage collection vehicle 2, a crane mechanism 5 for stirring the garbage in the garbage pit 4 and transferring the grasped garbage to a garbage input hopper 6, an incinerator main body 7, a waste heat boiler 8, an economizer 9, a desuperheating tower 10, a dust collector 11, an induced draft fan 12, a chimney 13, and the like.

[0030] By opening the waste input doors D, which are provided at waste input ports 4A and 4B to prevent odor leakage and ensure safety, the waste collected and transported by the garbage truck 2 is deposited into the waste pit 4.

[0031] The waste collected in the waste pit 4 is grasped by a crane mechanism 5 of the club bucket type, which is operated automatically or by an operator in the control room 5C, and transported to an opening formed at the upper end of the waste input hopper 6 before being dropped into it.

[0032] A hydraulic dust supply device P is provided at the bottom of the waste input hopper 6, and the waste filled in the waste input hopper 6 is pushed into the incinerator body 7. The waste filled in the waste input hopper 6 functions as a sealing mechanism that blocks the inflow of outside air from the waste input hopper 6 into the furnace chamber formed in the incinerator body 7, and the furnace chamber is maintained at a negative pressure by induction by the induced draft fan 12.

[0033] The furnace chamber formed in the incinerator body 7 includes a primary combustion chamber 7A equipped with a stoker mechanism ST and a secondary combustion chamber 7B for the complete combustion of the exhaust gas produced in the primary combustion chamber 7A, with multiple water tubes of the waste heat boiler 8 embedded in the wall of the secondary combustion chamber 7B.

[0034] The steam generated in the waste heat boiler 8 is superheated in the superheater 8H, supplied to the steam turbine T, and used to generate electricity in the generator G. The exhaust gas, which has been completely combusted in the secondary combustion chamber 7B, is heat-exchanged with combustion air in an economizer 9 located along the flue, cooled by water injection in a cooling tower 10, then neutralized by injection, collected by a dust collector 11, and finally exhausted through the chimney 13.

[0035] Garbage truck 2 enters platform 3 after being weighed by weighing scale W, and loads the garbage into garbage pit 4 through the input opening. Platform 3 is equipped with multiple input openings, including input opening 4A with a dumping box for garbage truck 2A without a dumping function, input opening 4B for garbage truck 2B with a dumping function, and input opening 4C equipped with a crusher for bulky waste. In Figure 1, the above multiple input openings are shown to be arranged vertically, but in reality, the above multiple input openings are installed on the same floor.

[0036] As shown in Figure 2, in order to maintain good combustion of waste in the primary combustion chamber 7A, the system is equipped with a dryer 20 that uses the waste heat from the incinerator to reduce the moisture content of a portion of the waste before it is put into the waste pit 4, and an input mechanism that puts the waste processed by the dryer 20 into the pit 4. Reference numeral 2I denotes the entrance to platform 3, and reference numeral 2O denotes the exit 2O of platform 3.

[0037] Some garbage trucks 2D(2) that enter platform 3 do not put the collected garbage into the garbage pit 4, but instead put the garbage into the hopper 21A of the dryer 20 located to the side of the garbage pit 4. These garbage trucks 2D are those that collect wet garbage such as kitchen waste and food waste with a high moisture content, and if the characteristics of the garbage can be determined in advance from the garbage collection route, the garbage is put directly into the hopper 21A of the dryer 20 instead of the garbage pit 4. The garbage is dried by the dryer 20 and discharged, then put into the garbage pit 4 via the input mechanism. The input mechanism can be an input chute made of concrete or steel plate, or a screw conveyor mechanism.

[0038] Furthermore, the garbage truck 2D is equipped with a moisture content sensor that uses microwaves or the like, and if the moisture content of the collected garbage can be automatically detected as wet garbage, the garbage is directly fed into the hopper 21A of the dryer 20 instead of the garbage pit 4.

[0039] When the dryer 20 is in operation, if a garbage truck 2D brings in wet waste, it cannot be fed into the dryer 20 and must wait. To prepare for such situations, a second pit 41 is provided where waste scheduled to be processed by the dryer 20 is temporarily stored. When the drying process by the dryer 20 is completed, the waste is grasped by the crane mechanism 5 and fed into the hopper 21B of the dryer 20. Even if some of the waste that requires drying cannot be dried immediately, temporarily storing it in the second pit 41 prevents the undesirable situation of it being mixed with wet waste in the pit 4 where other waste is fed. The standard value for the moisture content of waste that requires drying should be set for each facility, taking regional characteristics into consideration, and there is no need to set an absolute standard value common to multiple facilities. However, for example, if waste with a moisture content exceeding 60% is dried, it is easier to obtain the effect of increasing the heat output in the incinerator due to drying.

[0040] Figure 3(a) shows an example of a dryer 20 for vacuum drying of wet waste. The dryer 20 includes a hopper 21B (hopper 21A is omitted), a dryer body 22, a vacuum device 23, an air supply blower 24, an exhaust gas supply mechanism 25, an outlet 26, and the like.

[0041] The dryer body 22 is divided into a drying chamber 22B for wet waste equipped with agitator blades 22A that are rotated by a motor M, and a heating jacket 22C that supplies heat into the drying chamber 22B from the outside. As a waste heat supply source that provides heat to the heating jacket 22C, a portion of the steam generated by the waste heat boiler 8 and a portion of the exhaust gas before it is exhausted from the chimney 13 are used.

[0042] First, open the lid of the hopper 21 and put in the wet waste, then close the lid. Activate the vacuum device 23 to create a negative pressure environment in the drying chamber 22B (for example, 0.5 × 10⁻⁶). 5The pressure is maintained at approximately PaA. By creating a negative pressure environment in the drying chamber 22B, the boiling point of water can be lowered to 70-90°C. Next, by supplying residual heat to the heating chamber 22C, the drying chamber 22B is heated to 70-90°C, and the stirring blades 22A are rotated forward to promote the drying of the wet waste. After drying, air is supplied from the air supply blower 24 to cool the dried, high-temperature waste and to release the pressure in the drying chamber 22B. Finally, the outlet 26 is opened and the stirring blades 22A are rotated in reverse to discharge the dried waste into the waste pit 4.

[0043] Figure 3(b) illustrates a vacuum device 23 attached to the dryer 20. The vacuum device 23 includes a suction port 23a attached to the drying chamber 22B and a gas inlet 23b into which a portion of the steam generated in the waste heat boiler 8 flows. The gas flow path from the suction port 23a forms an intake chamber that bends 90 degrees internally and is arranged to communicate with a diffuser 23d, which is a widening diffusion flow path. A nozzle 23C is formed at the tip of the gas flow path that flows in from the gas inlet 23b and is positioned to protrude from the bend in the gas flow path from the suction port 23a.

[0044] The vacuum device 23 described above functions as an ejector, converting a portion of the pressure energy of the steam injected from the nozzle 23C into kinetic energy, which increases its speed. The humid gas from the drying chamber 22B that flows into the intake chamber comes into contact with the steam, which becomes the driving fluid, and receives kinetic energy, resulting in a mixing action. The mixed gas consumes the kinetic energy of the steam in the diffuser, reducing its speed while recovering its pressure, and is then sent out to the discharge port 23e.

[0045] The gas discharged from the outlet 23e is guided to the incinerator via the exhaust gas supply mechanism 25 and used as primary and secondary combustion air. Since the gas discharged from the outlet 23e contains air from the drying chamber 22B, it may be configured to be dehumidified by a dehumidifier in the exhaust gas supply mechanism 25 before being guided to the incinerator. Furthermore, if the air content is low, instead of using it as combustion air, it can be blown into the incinerator 7 for high-temperature treatment to process odors generated from the waste, and then released into the atmosphere after odor treatment. In other words, the vacuum device 23 is equipped with an exhaust gas supply mechanism 25 that supplies gas to the incinerator, and the dryer 20 becomes an ejector section that creates negative pressure inside the dryer 20 by utilizing the gas flow velocity of the steam generated in the waste heat boiler 8.

[0046] The vacuum device 23 described above may be replaced with a water-sealed vacuum pump or exhaust blower, configured to exhaust humidified gas from the drying chamber 22B. In this case as well, the exhaust gas is dehumidified via the exhaust gas supply mechanism 25 and then used as primary and secondary combustion air for the incinerator.

[0047] Alternatively, the dryer body 22 may be formed as a single unit without dividing it into a drying chamber 22B and a heating chamber 22C, and the heat source gas from the residual heat supply source may be supplied directly into the dryer body 22. In this case, it is preferable to supply the heat source gas to the dryer body 22 after removing the moisture contained in the heat source gas using a dehumidification mechanism.

[0048] In the embodiment described above, an example was explained in which a dryer is provided to reduce the moisture content of a portion of the waste before it is put into the pit 4 by utilizing the waste heat of the incinerator. However, the target of drying by the dryer is limited to wet waste, and may also be waste that has been put into the pit 4. For example, the pit 4 may be equipped with a sensor capable of detecting moisture content, such as an infrared sensor, and the waste of blocks that are determined to have a high moisture content may be put into the dryer 20 using the crane mechanism 5.

[0049] As an example of a feeding mechanism for loading waste processed in the dryer 20 into the pit, an agitator blade 22A and an outlet 26 incorporated in the dryer 20 were given. However, a conveyor mechanism for transporting the dried waste discharged from the outlet 26 to the pit 4, or a waste chute made of concrete or steel plate that is inclined downwards toward the pit 4, may also be used.

[0050] A melting furnace can be used as an example of a heat treatment furnace for heat-treating waste. For example, the present invention may be applied to a rotary surface melting furnace, which has a waste storage section between an inner cylinder and an outer cylinder that rotate relative to each other, guides the waste into a furnace chamber formed inside the inner cylinder by relative rotation, melts the waste from the surface with a burner provided on the furnace ceiling, and discharges it as molten slag from a slag outlet formed in the center of the furnace bottom, or to an electric ash melting furnace of the electric resistance type or plasma type.

[0051] As described above, the present invention provides a method for operating a waste treatment facility, comprising: a pit input step of putting the waste collected at the waste treatment facility into a pit; a stirring step of stirring the waste stored in the pit with a crane; a furnace input step of putting the waste stored in the pit into a heat treatment furnace with a crane; a heat treatment step of heat treating the waste put into the heat treatment furnace in the input step; and a drying step prior to the pit input step, in which waste with a high moisture content is selected from the waste collected at the waste treatment facility and dried using a dryer that utilizes the heat generated in the heat treatment furnace, wherein in the pit input step, both waste that has undergone the drying step and waste that has not undergone the drying step are put into the pit.

[0052] As described above, by using a dryer that reduces the moisture content by utilizing the waste heat from the heat treatment furnace, a portion of the waste before it is put into the pit, i.e., wet waste, is dried, and the dried waste is then put into the pit by the input mechanism. This allows for efficient use of limited waste heat to dry the materials to be treated, even when the amount of plastics contained in the waste is reduced.

[0053] It should be noted that the embodiments described above are merely examples of the present invention, and the specific configuration of each part can be appropriately modified and designed within the scope of achieving the effects of the present invention. [Explanation of Symbols]

[0054] 1: Heat treatment furnace (incinerator) 2: Garbage truck 3: Platform 4: Garbage pit 5: Crane mechanism 20: Dryer 21: Hoppa 22A: Agitator blade 22B: Drying room 22C: Heated Jacket 23: Vacuum equipment 41: Second Pit

Claims

1. It is a waste treatment facility, A heat treatment furnace for heat-treating waste, A pit where waste to be fed into the heat treatment furnace is stored, A crane that agitates the waste placed in the pit and then feeds it into the heat treatment furnace, A dryer is used to reduce the moisture content of a portion of the waste before it is placed in the pit, by utilizing the heat generated in the heat treatment furnace. A waste treatment facility comprising: a feeding mechanism for feeding waste processed by the aforementioned dryer into a pit.

2. The waste treatment facility according to claim 1, further comprising a second pit for temporarily storing waste to be processed in the aforementioned dryer.

3. The system includes a gas supply mechanism that supplies gas into the heat treatment furnace, The waste treatment facility according to claim 1, wherein the dryer is equipped with an ejector section that uses the gas flow velocity of the gas supply mechanism to form a negative pressure inside the dryer.

4. The waste treatment facility according to claim 1, wherein the heat treatment furnace is an incinerator.

5. The waste treatment facility according to claim 1, wherein the heat treatment furnace is a melting furnace.

6. A method for operating a waste treatment facility, A pit loading process in which waste collected at the aforementioned waste treatment facility is loaded into a pit, A stirring step is performed in which the waste stored in the pit is stirred by a crane, A furnace loading process in which the waste stored in the aforementioned pit is loaded into a heat treatment furnace using a crane, A heat treatment step in which the waste introduced into the heat treatment furnace in the aforementioned furnace loading step is heat-treated, Prior to the pit loading process, a drying process is performed in which a portion of the waste collected at the waste treatment facility, sorted based on its moisture content, is dried using a dryer that utilizes the heat generated in the heat treatment furnace. Equipped with, A method for operating a waste treatment facility in which, in the pit input step, both waste that has undergone the drying step and waste that has not undergone the drying step are input into the pit.

7. A method for operating a waste treatment facility according to claim 6, wherein in the drying process, a portion of the waste is dried based on the moisture content of the collected waste measured by a moisture content sensor installed on a waste collection vehicle.

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