Incinerator ash collection system

Abstract

This technology provides a way to maintain the temperature of the exhaust gas discharged from the fluidized bed incinerator and flowing into the dust collector at an appropriate temperature, while simultaneously increasing the temperature of the preheated air supplied to the fluidized bed incinerator. This reduces the heavy metal content, allows for the collection of an appropriate amount of incinerated ash, and reduces the amount of auxiliary fuel used. [Solution] The incineration ash collection system 1 controls the opening and closing of the first control valve 21 to adjust at least one of the temperature of the first air flowing into the first heat exchanger 3 and the flow rate of the second air, based on the target exhaust gas temperature of at least one of the exhaust gas temperature at the exhaust gas inlet of the dust collector 4 and the exhaust gas temperature at the exhaust gas outlet of the dust collector 4, and the temperature of the first preheated air flowing out of the first heat exchanger 3 and into the fluidized incinerator 2.

Description

Technical Field

[0001] The present disclosure relates to a technique for collecting incineration ash from exhaust gas discharged by incinerating an incineration target in a fluidized incinerator using a dust collector.

Background Art

[0002] Patent Document 1 discloses an incineration system for sludge that produces incineration ash containing phosphorus that is reused as a resource and having a reduced content of heavy metals, which are harmful components. In this prior art, the pyrolysis gas generated by pyrolyzing the sludge and the incineration ash are separated by a cyclone (dust collector). Then, by heating the separated incineration ash in a heating furnace, unburned substances in the incineration ash are burned, and treated incineration ash containing phosphorus and having heavy metals removed and exhaust gas containing heavy metals are generated. Note that the temperature inside the dust collector during separation is 500°C or higher and 850°C or lower.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When removing arsenic, which is an example of a heavy metal, and selenium dioxide from exhaust gas discharged by incinerating an incineration target in a fluidized incinerator and collecting the incineration ash using a dust collector, the sublimation points of arsenic and selenium dioxide are typically around 613°C and around 315°C, respectively. Therefore, if the temperature inside the dust collector is higher than these sublimation points, it is possible to collect the incineration ash while reducing the content of heavy metals.

[0005] However, if the temperature of the exhaust gas flowing into the dust collector is more than a predetermined temperature above the sublimation point, the incinerated ash will melt and remain in the system, making it impossible to collect a sufficient amount of incinerated ash. Conversely, if the temperature of the exhaust gas flowing into the dust collector is more than a predetermined temperature below the sublimation point, even if a sufficient amount of incinerated ash is collected, it will not be possible to reduce the content of heavy metals (especially arsenic).

[0006] Therefore, it is preferable to maintain the temperature of the exhaust gas discharged from the fluidized bed incinerator and flowing into the dust collector at an appropriate temperature while reducing the heavy metal content and collecting an appropriate amount of incinerated ash. To maintain the temperature of the exhaust gas flowing into the dust collector at an appropriate temperature, a heat exchanger is installed between the fluidized bed incinerator and the dust collector to exchange heat between the exhaust gas discharged from the fluidized bed incinerator and the air used for combustion and fluidization in the fluidized bed incinerator. As a result, the air is preheated by the temperature rise, and this preheated air (preheated air) is supplied to the fluidized bed incinerator, thereby reducing the amount of auxiliary fuel used. Auxiliary fuel is fuel used to supplement the materials to be incinerated in order to burn them at an appropriate temperature in the fluidized bed incinerator, and city gas, heavy oil, kerosene, etc., are used.

[0007] However, the higher the temperature of the exhaust gas flowing into the dust collector (for example, above 613°C), the lower the temperature of the preheating air supplied to the fluidized bed incinerator. On the other hand, if the temperature of the preheating air is increased to reduce the amount of auxiliary fuel used, the temperature of the exhaust gas flowing into the dust collector decreases, making it impossible to maintain the temperature of the exhaust gas flowing into the dust collector at the appropriate level.

[0008] One objective of this disclosure is to provide a technology that can reduce the heavy metal content and collect an appropriate amount of incinerated ash while maintaining the temperature of the exhaust gas discharged from the fluidized bed incinerator and flowing into the dust collector at an appropriate temperature, thereby increasing the temperature of the preheated air supplied to the fluidized bed incinerator, and reducing the amount of auxiliary fuel used. [Means for solving the problem]

[0009] The first aspect of this disclosure relates to an incineration ash collection system that collects incineration ash from exhaust gas emitted after incinerating materials in a fluidized bed incinerator using a dust collector. The incineration ash collection system includes a first blower that supplies air, a first heat exchanger installed between the fluidized bed incinerator and the dust collector, which raises the temperature of the first air and lowers the temperature of the exhaust gas discharged from the fluidized bed incinerator through heat exchange between the first air (representing some or all of the air supplied by the first blower) and the exhaust gas discharged from the fluidized bed incinerator, and supplies first preheated air at a higher temperature than the first air to the fluidized bed incinerator while discharging first exhaust gas at a lower temperature than the exhaust gas, and a second heat exchanger installed at the exhaust gas outlet of the dust collector, which raises the temperature of the second air and lowers the temperature of the second exhaust gas discharged from the exhaust gas outlet of the dust collector through heat exchange between the second air (representing some or all of the air supplied by the first blower) and the second exhaust gas discharged from the exhaust gas outlet of the dust collector, and supplies second preheated air at a higher temperature than the second air to the first heat exchanger while discharging third exhaust gas at a lower temperature than the second exhaust gas, and The system comprises: a first pipe having one end connected to a first heat exchanger and the other end connected to a first connection point, supplying first air to the first heat exchanger; a second pipe having one end connected to a first blower and the other end connected to a first connection point of the first pipe; a second branch pipe having one end connected to the second pipe and the other end connected to a first connection point of the first pipe via a second heat exchanger, supplying second preheated air flowing out of the second heat exchanger to the first pipe; a first control valve provided in the second pipe between the first connection point and the second connection point between the second pipe and the second branch pipe, for adjusting the flow rates of second air and second preheated air flowing through the second branch pipe; and a control device connected to the first blower and the first control valve, respectively, for opening and closing the first control valve to adjust at least one of the temperature of the first air and the flow rate of the second air based on the target exhaust gas temperature of at least one of the temperature of the first exhaust gas and the temperature of the second exhaust gas and the temperature of the first preheated air.

[0010] A second aspect of this disclosure relates to an incineration ash collection system for collecting incineration ash from exhaust gas discharged after incinerating materials in a fluidized bed incinerator using a dust collector. The incineration ash collection system includes a first blower and a second blower for supplying air, a first heat exchanger provided between the fluidized bed incinerator and the dust collector, which raises the temperature of the first air (representing some or all of the air supplied by the first blower) and lowers the temperature of the exhaust gas discharged from the fluidized bed incinerator through heat exchange, and supplies first preheated air at a higher temperature than the first air to the fluidized bed incinerator while discharging first exhaust gas at a lower temperature than the exhaust gas, and a second heat exchanger provided at the exhaust gas outlet of the dust collector to the second blower. A second heat exchanger raises the temperature of the incoming air through heat exchange with the second exhaust gas discharged from the dust collector's exhaust outlet, while simultaneously lowering the temperature of the second exhaust gas, and discharges a second preheated air at a higher temperature than the incoming air and a third exhaust gas at a lower temperature than the second exhaust gas. A second heat exchanger is provided at the air outlet of the second heat exchanger and changes the temperature of the second air, which represents some or all of the air supplied by the first blower, through heat exchange with the second preheated air discharged from the air outlet of the second heat exchanger. A third heat exchanger that raises the temperature of the second air and lowers the temperature of the second preheated air, supplying a third preheated air at a higher temperature than the second air to the first heat exchanger; a first pipe that has one end connected to the first heat exchanger and the other end connected to a first connection point, supplying the first air to the first heat exchanger; a second pipe that has one end connected to a first blower and the other end connected to a first connection point of the first pipe; and a first distribution that has one end connected to the second pipe and the other end connected to a first connection point of the first pipe via the third heat exchanger, supplying the third preheated air flowing out of the third heat exchanger. The system includes a second branch pipe supplying to the main pipe, a first connection point, a first control valve provided in the second pipe between the second pipe and the second connection point of the second branch pipe for adjusting the flow rates of the second air and the third preheated air flowing through the second branch pipe, and a control device connected to the first blower and the first control valve, respectively, which controls the opening and closing of the first control valve to adjust at least one of the temperature of the first air and the flow rate of the second air based on the target exhaust gas temperature of at least one of the temperature of the first exhaust gas and the temperature of the second exhaust gas and the temperature of the first preheated air.

[0011] A third aspect of this disclosure, in addition to the first or second aspect, further has the following features: If the amount of air flowing into the fluidized bed incinerator is greater than or equal to a predetermined airflow rate required for combustion in the fluidized bed incinerator, the control device changes the set value of the rotation speed of the first blower fan to a value smaller than the current value until the target exhaust gas temperature is raised to an appropriate temperature.

[0012] A fourth aspect of this disclosure, in addition to the first or second aspect, further has the following features: If the amount of air flowing into the fluidized bed incinerator is less than a predetermined airflow rate required for combustion in the fluidized bed incinerator, the control device changes the set value of the rotation speed of the first blower fan to a value greater than the current value until the target exhaust gas temperature is reduced to an appropriate temperature.

[0013] A fifth aspect of this disclosure has the following additional features in addition to the first or second aspect: The control device changes the set value of the opening degree of the first control valve to a value greater than the current value when the temperature of the first preheating air flowing into the fluidized bed incinerator is above a predetermined temperature and above the temperature upper limit.

[0014] The sixth aspect of this disclosure has the following additional features in addition to the first or second aspect: When the amount of air flowing into the fluidized bed incinerator is equal to or greater than a predetermined airflow rate required for combustion in the fluidized bed incinerator, the control device increases or decreases the set value of the rotation speed of the first blower fan to maintain the target exhaust gas temperature, and controls the opening and closing of the first control valve so that the temperature of the first preheated air reaches a predetermined temperature. [Effects of the Invention]

[0015] According to the technology disclosed herein, the temperature of the exhaust gas discharged from the fluidized bed incinerator and flowing into the dust collector is maintained at an appropriate temperature. Furthermore, the temperature of the preheated air supplied to the fluidized bed incinerator is increased. This makes it possible to reduce the heavy metal content and collect an appropriate amount of incinerated ash, as well as reduce the amount of auxiliary fuel used. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic diagram showing an example configuration of an incineration ash collection system according to an embodiment. [Figure 2] It is a flowchart showing a processing example of high-temperature dust collection control in an incineration ash collection system according to an embodiment. [Figure 3] It is a flowchart showing a processing example of high-temperature dust collection and low fuel consumption operation control in an incineration ash collection system according to an embodiment. [Figure 4] It is an explanatory diagram showing an example of state change of a control target in high-temperature dust collection control and high-temperature dust collection and low fuel consumption operation control of an incineration ash collection system according to an embodiment. [Figure 5] It is a schematic diagram showing a comparative example of an incineration ash collection system according to an embodiment. [Figure 6] It is a schematic diagram showing a comparative example of an incineration ash collection system according to an embodiment. [Figure 7] It is a comparison table showing the performance difference between a configuration example and a comparative example of an incineration ash collection system according to an embodiment. [Figure 8] It is a schematic diagram showing a configuration example of an incineration ash collection system according to other embodiments.

Embodiments for Carrying out the Invention

[0017] Referring to the accompanying drawings, an incineration ash collection system according to an embodiment of the present disclosure will be described. In addition, the same reference numerals are given to common elements in each figure, and duplicate explanations are omitted.

[0018] 1. Configuration Example of Incineration Ash Collection System 1-1. Overview FIG. 1 is a schematic diagram showing a configuration example of an incineration ash collection system 1 according to an embodiment. The incineration ash collection system 1 includes a fluidized incinerator 2, a first heat exchanger 3, a dust collector 4, a first blower 5, a second heat exchanger 6, a third heat exchanger 7, a second blower 8, an exhaust gas treatment device 9, an exhaust fan 10, a chimney 11, and a cooling water pump 12. The fluidized incinerator 2 (hereinafter simply referred to as the incinerator 2) generates a fluidized bed by flowing a fluid medium such as sand flowing into the furnace with air fed from the lower part of the furnace, and incinerates incineration objects such as sewage sludge and garbage input into the heated fluidized bed by stirring them together with the fluid medium. The incinerator 2 includes an air inlet 2A for allowing air to flow in and an exhaust gas outlet 2B for discharging exhaust gas generated during incineration of the incineration object.

[0019] The first heat exchanger 3 is provided between the incinerator 2 and the dust collector 4. The first heat exchanger 3 includes an exhaust gas inlet 3C through which exhaust gas discharged from the exhaust gas outlet 2B of the incinerator 2 flows in via a first duct 61. The first duct 61 is a pipe having one end connected to the exhaust gas outlet 2B of the incinerator 2 and the other end connected to the exhaust gas inlet 3C of the first heat exchanger 3.

[0020] Further, the first heat exchanger 3 includes a co-current side air inlet 3A and a counter-current side air inlet 3B. For example, as shown in FIG. 1, when the exhaust gas inlet 3C of the first heat exchanger 3 is provided at the upper part of the first heat exchanger 3, the co-current side air inlet 3A is provided at the upper part of the first heat exchanger 3, and the counter-current side air inlet 3B is provided at the lower part of the first heat exchanger 3. The co-current side air inlet 3A and the counter-current side air inlet 3B are connected to a first pipe 51. A part or all of the air supplied by the first blower 5 flows into the co-current side air inlet 3A and the counter-current side air inlet 3B connected to the first pipe 51 via a second pipe 52. The air flowing into the first heat exchanger 3 (co-current side air inlet 3A and counter-current side air inlet 3B) is also referred to as first air.

[0021] Furthermore, the first heat exchanger 3 is equipped with an air outlet 3D that increases the temperature of the first air by heat exchange between the first air flowing into the parallel-flow air inlet 3A and the counter-flow air inlet 3B and the exhaust gas flowing into the exhaust gas inlet 3C, and discharges preheated air (first preheated air) at a temperature higher than the temperature of the first air. In addition, the first heat exchanger 3 is equipped with an exhaust gas outlet 3E that lowers the temperature of the exhaust gas by heat exchange between the first air flowing into the parallel-flow air inlet 3A and the counter-flow air inlet 3B and the exhaust gas flowing into the exhaust gas inlet 3C, and discharges first exhaust gas at a temperature lower than the temperature of the exhaust gas. Furthermore, the parallel-flow air inlet 3A and the counter-flow air inlet 3B are provided for use when heat exchange between the exhaust gas and the first preheated air is performed in parallel flow, when heat exchange between the exhaust gas and the first preheated air is performed in counter-flow, and when heat exchange between the exhaust gas and the first preheated air is performed in both parallel and counter-flow.

[0022] The first heat exchanger 3 receives first air through the parallel-flow air inlet 3A and the counter-flow air inlet 3B connected to the first piping 51. The first air includes, for example, air that has been preheated by the second heat exchanger 6 (second preheated air) which is supplied by the first blower 5 via the second branch piping 52A and the second branch piping 52B, in part or all of the air.

[0023] The first pipe 51 is for supplying the first air to the first heat exchanger 3. One end of the first pipe 51 is connected to the parallel-flow air inlet 3A and the counter-flow air inlet 3B of the first heat exchanger 3, and the other end is connected to the first connection point a. The first connection point a is the end of the first pipe 51, and is also the end of the second branch pipes 52A and 52B, which are branches of the second pipe 52. The second pipe 52 is for supplying the air sent out from the first blower 5. One end of the second pipe 52 is connected to the first blower 5, and the other end is connected to the first connection point a of the first pipe 51. The second branch pipes 52A and 52B are for supplying the second preheated air flowing out of the second heat exchanger 6 to the first pipe 51. The second branch pipes 52A and 52B are connected at one end to the second pipe 52 and at the other end to the first connection point a of the first pipe 51 via the second heat exchanger 6. Details of the second branch pipes 52A and 52B will be described later.

[0024] The first heat exchanger 3 discharges first preheated air through an air outlet 3D. The first preheated air discharged from the air outlet 3D is supplied to the air inlet 2A of the incinerator 2 via a third pipe 53. The third pipe 53 is a pipe in which one end is connected to the air outlet 3D of the first heat exchanger 3 and the other end is connected to the air inlet 2A of the incinerator 2. The air inlet 2A is also referred to as the incinerator preheated air inlet 2A, and the air outlet 3D is also referred to as the incinerator preheated air outlet 3D.

[0025] In this way, the first heat exchanger 3 raises the temperature of the first air, which is part or all of the air supplied by the first blower 5, and lowers the temperature of the exhaust gas discharged from the incinerator 2 through heat exchange with the exhaust gas. It supplies first preheated air at a higher temperature than the first air to the incinerator 2 and discharges first exhaust gas at a lower temperature than the exhaust gas. By supplying the first preheated air discharged from the first heat exchanger 3 to the incinerator 2, the combustion efficiency of the incinerator 2 can be improved. Furthermore, when the flow rate of the first air is constant, the higher the temperature of the first preheated air, the more the amount of auxiliary fuel used in the incinerator 2 can be reduced.

[0026] The dust collector 4 has an exhaust gas inlet 4A into which the first exhaust gas discharged from the exhaust gas outlet 3E of the first heat exchanger 3 flows in via the second duct 62, and an exhaust gas outlet 4B into which the second exhaust gas, from which the incinerated ash contained in the first exhaust gas has been separated and removed, is discharged. In other words, the dust collector 4 separates and recovers solid components such as ash contained in the first exhaust gas and discharges the second exhaust gas from which the solid components such as ash have been removed. Accordingly, the dust collector 4 is equipped with an ash discharger 4C that separates and recovers the incinerated ash contained in the first exhaust gas. The second duct 62 is a pipe in which one end is connected to the exhaust gas outlet 3E of the first heat exchanger 3 and the other end is connected to the exhaust gas inlet 4A of the dust collector 4.

[0027] The first blower 5 is a blower that supplies air. The first blower 5 has a motor 5A that controls the rotation speed of the fan so that the airflow can be increased or decreased. The rotation speed of the fan by the motor 5A is controlled by a control device 100, which will be described later. An example of the first blower 5 is a fluid blower. Note that the method for increasing or decreasing the airflow of the first blower 5 is not limited to the motor 5A that controls the rotation speed of the fan, but may also be adjusted using an adjustment valve provided at the inlet or outlet of the first blower 5.

[0028] The second heat exchanger 6 is equipped with an air inlet 6A into which second air, representing some or all of the air supplied by the first blower 5, flows in via a second branch pipe 52A that branches off from the second pipe 52. The second branch pipe 52A is a pipe whose one end is connected to the second pipe 52 and whose other end is connected to the air inlet 6A of the second heat exchanger 6. The second heat exchanger 6 is also equipped with an exhaust gas inlet 6C into which second exhaust gas discharged from the exhaust gas outlet 4B of the dust collector 4 flows in via a third duct 63. The third duct 63 is a pipe whose one end is connected to the exhaust gas outlet 4B of the dust collector 4 and whose other end is connected to the exhaust gas inlet 6C of the second heat exchanger 6.

[0029] Furthermore, the second heat exchanger 6 includes an air outlet 6B that increases the temperature of the second air by heat exchange between the second air flowing into the air inlet 6A and the second exhaust gas discharged from the exhaust gas outlet 4B of the dust collector 4 and flowing into the exhaust gas inlet 6C, thereby releasing preheated air (second preheated air) at a temperature higher than the temperature of the second air, and an exhaust gas outlet 6D that decreases the temperature of the second exhaust gas by heat exchange between the second air flowing into the air inlet 6A and the second exhaust gas flowing into the exhaust gas inlet 6C, thereby releasing third exhaust gas at a temperature lower than the temperature of the second exhaust gas.

[0030] In this way, the second heat exchanger 6 raises the temperature of the second air and lowers the temperature of the second exhaust gas by exchanging heat between the second air (second air) supplied by the first blower 5 via the second branch pipe 52A, which branches off from the second pipe 52. As a result, the second heat exchanger 6 can supply second preheated air, which is at a higher temperature than the second air, to the first heat exchanger 3 via the second branch pipe 52B and the first pipe 51. The second heat exchanger 6 also discharges third exhaust gas, which is at a lower temperature than the second exhaust gas.

[0031] Let's consider the first air flowing into the first heat exchanger 3. As shown in Figure 1, the first pipe 51 through which the first air flows is connected to the second pipe 52 and the second branch pipe 52B. In other words, the first air is a mixture of air flowing out of the second pipe 52 and air flowing out of the second branch pipe 52B. The air flowing out of the second pipe 52 is the air supplied by the first blower 5 that flows through the second pipe 52 but does not flow into the second branch pipe 52A and instead flows towards the first pipe 51; that is, it is the air flowing through the second pipe 52 excluding the second air that flows into the second branch pipe 52A. The air flowing out of the second pipe 52 is also called the third air. The air flowing out of the second branch pipe 52B is the second preheated air, which is obtained by preheating some or all of the air supplied by the first blower 5 (the second air) with the second heat exchanger 6.

[0032] The third heat exchanger 7 is equipped with an air inlet 7A through which air supplied by the second blower 8 (fourth air) flows in via the fifth pipe 55. The fifth pipe 55 is a pipe whose one end is connected to the second blower 8 and whose other end is connected to the air inlet 7A of the third heat exchanger 7. The third heat exchanger 7 is also equipped with an exhaust gas inlet 7C through the fourth duct 64 through which the third exhaust gas discharged from the exhaust gas outlet 6D of the second heat exchanger 6 flows in. The fourth duct 64 is a pipe whose one end is connected to the exhaust gas outlet 6D of the second heat exchanger 6 and whose other end is connected to the exhaust gas inlet 7C of the third heat exchanger 7.

[0033] Furthermore, the third heat exchanger 7 includes an air outlet 7B that increases the temperature of the fourth air by heat exchange between the fourth air flowing into the air inlet 7A and the third exhaust gas flowing into the exhaust gas inlet 7C, and discharges preheated air (third preheated air) at a temperature higher than that of the fourth air, and an exhaust gas outlet 7D that decreases the temperature of the third exhaust gas by heat exchange between the fourth air flowing into the air inlet 7A and the third exhaust gas flowing into the exhaust gas inlet 7C, and discharges fourth exhaust gas at a temperature lower than that of the third exhaust gas.

[0034] In this way, the third heat exchanger 7 raises the temperature of the fourth air and lowers the temperature of the third exhaust gas through heat exchange between the fourth air supplied by the second blower 8 and the third exhaust gas air, and can supply the third preheated air, which is at a higher temperature than the fourth air, to locations that require heating (e.g., equipment, piping). The third heat exchanger 7 also discharges the fourth exhaust gas, which is at a lower temperature than the third exhaust gas.

[0035] Furthermore, the third heat exchanger 7 may be provided with a parallel flow air inlet and a counterflow air inlet, similar to the first heat exchanger 3. In this case, in the heat exchange between the third exhaust gas and the fourth air, one of the following is selected based on the advantages of heat exchange and the low-temperature corrosion temperature of the internal materials: performing the heat exchange between the third exhaust gas and the fourth air in parallel flow, performing the heat exchange between the third exhaust gas and the fourth air in counterflow, or performing the heat exchange between the third exhaust gas and the fourth air in both parallel and counterflow. In addition, the third preheated air, which is at a higher temperature than the fourth air supplied by the second blower 8, is supplied to heat utilization equipment and devices. Applications of the third preheated air include supplying it to the chimney 11 via the sixth pipe 56 to prevent the generation of white smoke when released into the atmosphere, and supplying the third preheated air to the duct 66 that flows into the exhaust fan 10 via a pipe branched from the sixth pipe 56 to raise the temperature of the exhaust gas discharged from the exhaust gas treatment device 9 and remove deposits from the duct 66 and the equipment.

[0036] As described above, the second blower 8 is a blower that supplies the fourth air. The second blower 8 has a motor 8A that controls the rotation speed of the fan so that the airflow of the fourth air can be increased or decreased. The rotation speed of the fan by the motor 8A is controlled by the control device 100, which will be described later. An example of the second blower 8 is a supply fan. Note that the method for increasing or decreasing the airflow of the second blower 8 is not limited to the motor 8A that controls the rotation speed of the fan, but may also be adjusted using an adjustment valve provided at the inlet or outlet of the second blower 8.

[0037] The exhaust gas treatment device 9 is a device that removes air pollutants such as sulfur oxides and soot contained in the fourth exhaust gas. The fifth exhaust gas, from which the air pollutants contained in the fourth exhaust gas have been removed by the exhaust gas treatment device 9, is exhausted to the outside through the chimney 11 by the exhaust fan 10.

[0038] The cooling water pump 12 is an example of a refrigeration system. Cooling water is an example of a refrigeration system. By spraying the cooling water supplied by the cooling water pump 12 into the incinerator 2, the temperature inside the incinerator 2 can be lowered.

[0039] 1-2. Specific Examples This section describes in detail an example configuration for maintaining the exhaust gas temperature of the dust collector 4 at an appropriate temperature. The appropriate temperature is defined as a temperature that includes around 613°C, the sublimation point of arsenic, an example of a heavy metal. Furthermore, this section describes in detail an example configuration for controlling the temperature of the first preheating air supplied to the incinerator 2 from the first heat exchanger 3 in order to maintain or improve the combustion efficiency within the incinerator 2. Note that if the flow rate of the first preheating air supplied to the incinerator 2 is constant, increasing the temperature of the first preheating air can reduce the amount of auxiliary fuel used in the incinerator 2. Below, assuming a combustion temperature of the incinerator 2 of 850°C and a standard reference temperature of 650°C for the first preheating air flowing into the incinerator 2, the method of reducing the amount of auxiliary fuel used in the incinerator 2 by raising the temperature of the first preheating air to 700°C will be described in detail. Note that the flow rate of the first preheating air is also referred to as the first preheating air volume or the incinerator inlet air volume.

[0040] Specifically, the incineration ash collection system 1 is equipped with multiple measuring instruments and multiple control valves. The multiple measuring instruments include multiple thermometers for measuring temperature and multiple airflow meters (also called flow meters) for measuring airflow. The multiple thermometers include a first thermometer 31, a second thermometer 32, a third thermometer 33, a fourth thermometer 34, and a fifth thermometer 35. The multiple airflow meters include a first airflow meter 41, a second airflow meter 42, a third airflow meter 43, and a fourth airflow meter 44.

[0041] The first thermometer 31 is attached to the second duct 62 near the exhaust gas inlet 4A of the dust collector 4 and measures the temperature of the first exhaust gas flowing into the exhaust gas inlet 4A of the dust collector 4. The second thermometer 32 is attached to the third duct 63 near the exhaust gas outlet 4B of the dust collector 4 and measures the temperature of the second exhaust gas discharged from the exhaust gas outlet 4B of the dust collector 4. The third thermometer 33 is attached to the third piping 53 and measures the temperature of the first preheated air flowing out from the preheated air outlet 3D of the first heat exchanger 3 and into the incinerator 2. The fourth thermometer 34 is installed between the first connection point a shown in Figure 1 and the first heat exchanger 3 in the first piping 51 connected to the co-flow side air inlet 3A and the counter-flow side air inlet 3B of the first heat exchanger 3, and measures the temperature of the first air, which is a mixture of the air flowing out from the second piping 52 (third air) and the second preheated air flowing out from the second branch piping 52B. The fifth thermometer 35 is installed in the first duct 61 near the exhaust gas inlet 3C of the first heat exchanger 3 and measures the temperature of the exhaust gas flowing into the exhaust gas inlet 3C of the first heat exchanger 3.

[0042] The first airflow meter 41 is attached to the second pipe 52 and measures the airflow rate of the air supplied by the first blower 5 that flows into the second pipe 52. The second airflow meter 42 is attached to the second branch pipe 52A, which branches off from the second pipe 52, and measures the airflow rate of the second preheated air obtained by heat exchange with the second air that flows into the second heat exchanger 6. The third airflow meter 43 is attached to the fifth pipe 55 and measures the airflow rate of the fourth air supplied by the second blower 8 that flows into the third heat exchanger 7. The fourth airflow meter 44 is attached to the air pipe 54 located between the first blower 5 and the incinerator 2 and measures the airflow rate of the air supplied by the first blower 5 that flows into the air pipe 54 that branches off from the second pipe 52.

[0043] In the example described above, the airflow rate supplied to the incinerator 2 by the first blower 5 is expressed as the sum of the airflow rate flowing into the second pipe 52 and the airflow rate flowing into the air pipe 54 branched from the second pipe 52.

[0044] Now, let's consider the amount of air flowing into the incinerator 2. If the amount of air flowing into the incinerator 2 is F, the airflow rate of the air flowing into the second pipe 52 is F1, the airflow rate of the air (second air) flowing into the second branch pipe 52A which is branched from the second pipe 52 is F2, and the airflow rate of the air flowing into the air pipe 54 installed between the first blower 5 and the incinerator 2 is F4, then the amount of air F flowing into the incinerator 2 is expressed by the formula F = F1 + F4. Flow rate, air volume, and airflow rate all mean the same thing and are also called mass flow rate or standard conditions.

[0045] The air flowing into the second heat exchanger 6 (second air) passes through the second branch pipe 52A, which is branched off from the second pipe 52, the second heat exchanger 6, and the second branch pipe 52B in that order, and then through the first pipe 51. Therefore, the airflow rate F2 of the second air is included in F1, so the total airflow rate F remains unchanged at F = F1 + F4. In other words, the airflow rate F2 of the air flowing through the second pipe 52 is the same as the airflow rate of the first air flowing through the first pipe 51.

[0046] The air flowing into the air piping 54 is used to cool various parts of the incinerator 2 and as a seal to prevent backflow, and is supplied into the incinerator 2. The air supplied to the incinerator 2 is the sum of the air supplied for flowing to the air inlet 2A of the incinerator 2 and the amount of air required for combustion of the material to be incinerated into the incinerator 2 (standard airflow rate). Therefore, the airflow rate (amount of air required for flowing) F1 supplied by the first blower 5 and the amount of air F (amount of air required for combustion) flowing into the incinerator 2 are each adjusted to a predetermined airflow rate that is greater than the standard airflow rate.

[0047] Let's consider the case where the airflow rate supplied by the first blower 5 is a predetermined rate. In this case, the temperature of the exhaust gas discharged from the exhaust gas outlet 4B of the dust collector 4 can be adjusted by increasing or decreasing the airflow rate supplied by the first blower 5. Also, if the flow rate of the first air flowing into the first heat exchanger 3 is increased, the amount of heat exchange between the exhaust gas flowing into the first heat exchanger 3 and the first air increases, so the temperature of the first exhaust gas discharged from the first heat exchanger 3 decreases. On the other hand, if the flow rate of the first air flowing into the first heat exchanger 3 is decreased, the amount of heat exchange between the exhaust gas flowing into the first heat exchanger 3 and the first air decreases, so the temperature of the first exhaust gas discharged from the first heat exchanger 3 increases. Therefore, the airflow rate supplied by the first blower 5 is set to a predetermined rate that is greater than the amount of air (standard airflow rate) required for the combustion of the materials to be incinerated into the incinerator 2, and is adjusted to increase or decrease the temperature of the first exhaust gas.

[0048] The multiple control valves include a first control valve 21, a second control valve 22, a third control valve 23, a fourth control valve 24, and a fifth control valve 25.

[0049] The first control valve 21 is installed in the second pipe 52 between the first connection point a, which is the end of the first pipe 51, and the second connection point b, which is the connection point between the second pipe 52 and the second branch pipe 52A. Therefore, the first control valve 21 adjusts the flow rate of the second air flowing into the second heat exchanger 6. In other words, the first control valve 21 adjusts the flow rate of the second air flowing through the second branch pipe 52A and the flow rate of the second preheating air flowing through the second branch pipe 52B. This makes it possible to adjust the flow rate of the second preheating air contained in the first air flowing through the first pipe 51. In addition, another control valve may be installed in at least one of the second branch pipe 52A and the second branch pipe 52B. By adjusting the opening degree of the other control valve, the flow rate of the second air can be adjusted more precisely. The flow rate of the second air can be adjusted by adjusting the opening of another control valve. Alternatively, the first control valve 21 may be provided in at least one of the second branch pipe 52A and the second branch pipe 52B, rather than in the second pipe 52.

[0050] Specifically, by reducing the opening value of the first control valve 21 from its current value, the flow rate of air preheated by the second heat exchanger 6 (second preheated air) increases. In this case, the first air flowing through the first pipe 51 contains both the second preheated air preheated by the second heat exchanger 6 and air that has not been preheated by the second heat exchanger 6, so the temperature of the first air rises above the temperature before the opening value of the first control valve 21 was reduced. As a result, the temperature of the first air flowing into the first heat exchanger 3 increases, and the temperature of the first preheated air that flows out of the first heat exchanger 3 and into the incinerator 2 through the third pipe 53 after exchanging heat with the exhaust gas discharged from the incinerator 2 can be increased.

[0051] On the other hand, if the opening value of the first control valve 21 is increased from its current value, the flow rate of the air preheated by the second heat exchanger 6 (second preheated air) decreases. In this case, the temperature of the first air drops below the temperature before the opening value of the first control valve 21 was increased. As a result, the temperature of the first air flowing into the first heat exchanger 3 decreases, and the temperature of the first preheated air that flows out of the first heat exchanger 3 and into the incinerator 2 through the third pipe 53 after exchanging heat with the exhaust gas discharged from the incinerator 2 can be lowered.

[0052] Thus, the first control valve 21 is used to raise or lower the temperature of the first preheated air flowing into the incinerator 2.

[0053] The second control valve 22 adjusts the ratio of the flow rate of the first air flowing into the parallel-flow side air inlet 3A of the first heat exchanger 3 to the flow rate of the first air flowing into the counter-flow side air inlet 3B.

[0054] The third control valve 23 is installed in the seventh pipe 57, one end of which is connected to the incinerator 2 and the other end of which is connected to the cooling water pump 12. The third control valve 23 adjusts the amount of cooling water sprayed into the incinerator 2. Specifically, to increase the amount of cooling water sprayed into the incinerator 2 and lower the temperature of the exhaust gas flowing into the first heat exchanger 3, the setting value of the opening degree of the third control valve 23 is adjusted to a value greater than the current value. On the other hand, to decrease the amount of cooling water sprayed into the incinerator 2 and raise the temperature of the exhaust gas flowing into the first heat exchanger 3, the setting value of the opening degree of the third control valve 23 is adjusted to a value less than the current value.

[0055] The fourth control valve 24 is located in the air piping 54 between the fourth airflow meter 44 and the first blower 5. One end of the air piping 54 is connected to the incinerator 2 and the other end is connected to the first blower 5. The other end of the air piping 54 may be connected by branching off from the second piping 52. The air flowing into the air piping 54 is used for cooling and purging various parts of the incinerator 2 and is adjusted to a constant airflow rate in response to increases or decreases in the airflow rate supplied from the first blower 5. In this case, the set airflow rate of the air flowing into the air piping 54 is adjusted by controlling the opening of the fourth control valve 24 based on the value of the fourth airflow meter 44.

[0056] The fifth control valve 25 adjusts the amount of exhaust gas (the fifth exhaust gas) discharged to the outside based on the pressure fluctuations of the incinerator 2. If it is desired to further increase the amount of exhaust gas (the fifth exhaust gas) discharged to the outside, instead of adjusting the fifth control valve 25, the rotation speed of the exhaust fan 10 may be increased.

[0057] Furthermore, the incineration ash collection system 1 includes a control device 100. The control device 100 is connected to each of the following: a plurality of thermometers (first thermometer 31 to fifth thermometer 35), a plurality of airflow meters (first airflow meter 41 to fourth airflow meter 44), a plurality of control valves (first control valve 21 to fifth control valve 25), the motor 5A of the first blower 5, and the motor 8A of the second blower 8. The control device 100 is connected to each of the aforementioned plurality of devices using electrically communicable wiring or the like. A computer or other computing device is an example of the control device 100.

[0058] The control device 100 controls the opening and closing of the control valve to maintain the exhaust gas temperature of the dust collector 4 at an appropriate temperature, based on multiple temperature information obtained from multiple thermometers and multiple airflow information obtained from multiple airflow meters.

[0059] Furthermore, the airflow rate supplied by the first blower 5 is adjusted so that the amount of air F flowing into the incinerator 2 is greater than the standard airflow rate. Provided that the amount of air F is the predetermined airflow rate, the control device 100 controls the rotation speed of the motor 5A of the first blower 5 to adjust the airflow rate supplied by the first blower 5, thereby increasing or decreasing the airflow rate supplied by the first blower 5 and maintaining the exhaust gas temperature of the dust collector 4 at an appropriate temperature.

[0060] For example, if the amount of first air preheated in the first heat exchanger 3 is increased, the amount of heat exchanged between the exhaust gas flowing into the first heat exchanger 3 and the first air increases, thus increasing the amount of heat exchanged on the exhaust gas side. In this case, the temperature of the first exhaust gas discharged from the first heat exchanger 3 decreases. On the other hand, if the amount of first air preheated in the first heat exchanger 3 is decreased, the amount of heat exchanged between the exhaust gas flowing into the first heat exchanger 3 and the first air decreases, thus decreasing the amount of heat exchanged on the exhaust gas side. In this case, the temperature of the first exhaust gas discharged from the first heat exchanger 3 increases. Therefore, the amount of air F flowing into the incinerator 2 is set to be greater than or equal to the amount of air required for the combustion of the material to be incinerated (standard airflow rate), and is adjusted to raise or lower the temperature of the first exhaust gas.

[0061] The following describes in detail an example of control in the control device 100.

[0062] 2. Control Examples First, let's consider how the control device 100 controls the exhaust gas temperature of the dust collector 4 to an appropriate temperature. The exhaust gas temperature of the dust collector 4 includes the temperature of the first exhaust gas flowing into the dust collector 4, which is obtained by the first thermometer 31, and the temperature of the second exhaust gas discharged from the dust collector 4, which is obtained by the second thermometer 32. In other words, the control device 100 determines whether the temperature of at least one of the target exhaust gases, the temperature of the first exhaust gas and the temperature of the second exhaust gas, is at an appropriate temperature. This allows the control device 100 to determine whether it is necessary to adjust the temperature of the first exhaust gas flowing into the second duct 62.

[0063] Next, we consider a method of supplying the first preheated air flowing out of the first heat exchanger 3 to the incinerator 2 at a temperature higher than the current temperature, while maintaining the exhaust gas temperature of the dust collector 4 at an appropriate temperature. The temperature of the first preheated air flowing into the incinerator 2 is obtained by the third thermometer 33. Since the amount of auxiliary fuel used in the incinerator 2 can be determined by obtaining the temperature of the first preheated air, the amount of auxiliary fuel used may be adjusted to reduce it based on the temperature of the first preheated air.

[0064] According to an example of control in the control device 100, two types of control are performed: one to maintain the dust collector 4 at a high temperature (high-temperature dust collection control), and another to maintain the dust collector 4 at a high temperature while reducing the amount of auxiliary fuel used in the incinerator 2 (high-temperature dust collection / low-fuel-consumption operation control). The details of each control are described below. Note that the high-temperature dust collection / low-fuel-consumption operation control is also simply called "low-fuel-consumption operation control."

[0065] 2-1. High-temperature dust collection control Figure 2 is a flowchart showing an example of high-temperature dust collection control in the incineration ash collection system 1 according to the embodiment.

[0066] In step S001, the control device 100 determines whether the amount of air F flowing into the incinerator 2 is equal to or greater than a predetermined airflow rate. If it is determined that the amount of air F is equal to or greater than the predetermined airflow rate (step S001; Yes), the process proceeds to step S002. Otherwise (step S001; No), the process proceeds to step S011. Note that the predetermined airflow rate is greater than the amount of air required for combustion (reference airflow rate).

[0067] In step S002, the control device 100 determines whether at least one of the target exhaust gas temperatures—the temperature of the first exhaust gas flowing into the dust collector 4 and the temperature of the second exhaust gas flowing out of the dust collector 4—is within the control temperature range. If it is determined that the target exhaust gas temperature is within the control temperature range (step S002; Yes), the process proceeds to step S005. Otherwise (step S002; No), the process proceeds to step S003.

[0068] The control temperature range, as shown in Figure 4(A), for example, represents the range between the upper limit of the target exhaust gas temperature and the lower limit of the target exhaust gas temperature. The upper limit of the target exhaust gas temperature is set, for example, based on the heat resistance temperature of the dust collector 4 relative to the target exhaust gas temperature. The lower limit of the target exhaust gas temperature is set, for example, based on the sublimation temperature of the target heavy metal. In the example shown in Figure 4(A), the upper limit of the target exhaust gas temperature is set at 625°C, and the lower limit of the target exhaust gas temperature is set at 613°C. If the target exhaust gas temperature is within the control temperature range, it can be said that the target exhaust gas temperature is being maintained at an appropriate temperature.

[0069] Here, in the process of controlling the temperature of the target exhaust gas, it is assumed that the temperature of the first preheating air will decrease as the target exhaust gas temperature rises, and the temperature of the first preheating air will increase as the target exhaust gas temperature decreases. When the temperature of the first preheating air rises, it is necessary to ensure that it does not exceed a predetermined temperature upper limit. Therefore, in step S005, the control device 100 determines whether the temperature of the first preheating air flowing out of the first heat exchanger 3 is above the temperature upper limit. If it is determined that the temperature of the first preheating air is above the temperature upper limit (step S005; Yes), the process proceeds to step S021. Otherwise (step S005; No), the process proceeds to the low-fuel-consumption operation control shown in Figure 3. The temperature upper limit is set, for example, based on the heat resistance temperatures of the first heat exchanger 3, the third piping 53, and the incinerator 2. In the example shown in Figure 4(B), the temperature upper limit is set to 720°C. The temperature of the first preheating air is also called the incinerator inlet temperature.

[0070] If the temperature of the first preheated air flowing out of the first heat exchanger 3 is above the temperature limit, it is necessary to reduce the temperature of the first preheated air to below the temperature limit. Therefore, in step S021, the control device 100 changes the set value of the opening degree of the first control valve 21 to a value greater than the current value (open direction). By increasing the opening degree of the first control valve 21, the flow rate of the second air flowing into the second heat exchanger 6 decreases, and the temperature of the first air flowing into the first heat exchanger 3 decreases. As the temperature of the first air decreases, the temperature of the first preheated air flowing out of the first heat exchanger 3 decreases. After that, the process returns to the start and control is performed until the temperature of the first preheated air falls below the temperature limit. This allows high-temperature dust collection to be performed while maintaining the target exhaust gas temperature at an appropriate temperature.

[0071] Let's consider the case where, in step S001 described above, it is determined that the air volume F is less than a predetermined airflow rate (step S001; No). In this case, since it is necessary to make the air volume F equal to or greater than the predetermined airflow rate, the control device 100 changes the setting value of the rotation speed of the fan of the first blower 5 to a value greater than the current value in step S011. In other words, the rotation speed of the fan of the first blower 5 is set so that the air volume F flowing into the incinerator 2 is equal to or greater than a predetermined airflow rate, which is greater than the standard airflow rate.

[0072] Consider the case where, in step S002 described above, it is determined that the target exhaust gas temperature is not within the control temperature range (step S002; No). In this case, if the target exhaust gas temperature is lower than the target exhaust gas temperature lower limit, it means that the air flow rate supplied by the first blower 5 is high. When the air flow rate supplied to the first heat exchanger 3 is high, the amount of heat exchange also increases, and the amount of heat exchange on the exhaust gas side increases, so the temperature of the first exhaust gas discharged from the first heat exchanger 3 decreases. Therefore, in step S003, the control device 100 determines whether the target exhaust gas temperature is lower than the target exhaust gas temperature lower limit. If it is determined that the target exhaust gas temperature is lower than the target exhaust gas temperature lower limit (step S003; Yes), the process proceeds to step S012. Otherwise (step S003; No), the process proceeds to step S004.

[0073] If, in step S003 described above, it is determined that the target exhaust gas temperature is higher than the lower limit of the target exhaust gas temperature (step S003; No), and the target exhaust gas temperature is higher than the upper limit of the target exhaust gas temperature (step S004; Yes), the flow rate of air supplied to the first heat exchanger 3 by the first blower 5 is increased to increase the amount of heat exchange and lower the temperature of the first exhaust gas discharged from the first heat exchanger 3. If it is determined that the target exhaust gas temperature is higher than the upper limit of the target exhaust gas temperature (step S004; Yes), the process proceeds to step S013. Otherwise (step S004; No), the process returns to the start and control is performed until the target exhaust gas temperature falls within the control temperature range.

[0074] In step S012, the control device 100 changes the set value of the fan speed of the first blower 5 to a value smaller than the current value. This reduces the flow rate of air supplied to the first heat exchanger 3 by the first blower 5, decreasing the amount of heat exchange and raising the temperature of the first exhaust gas discharged from the first heat exchanger 3. In step S013, the set value of the fan speed of the first blower 5 is changed to a value larger than the current value. As described above, this increases the flow rate of air supplied to the first heat exchanger 3 by the first blower 5, increasing the amount of heat exchange and lowering the temperature of the first exhaust gas discharged from the first heat exchanger 3. After the execution of step S012 or step S013, the process proceeds to step S015.

[0075] If it is determined that the temperature of the first preheated air is above the temperature limit (step S015; Yes), in step S031, the control device 100 changes the set value of the opening degree of the first control valve 21 to a value greater than the current value (open direction), then returns to start and performs control until the target exhaust gas temperature is included in the control temperature range. Also, if it is determined that the temperature of the first preheated air is not above the temperature limit (step S015; No), the control device 100 returns to start and performs control until the target exhaust gas temperature is included in the control temperature range.

[0076] 2-2. Fuel-efficient driving control Figure 3 is a flowchart showing an example of low-fuel-consumption operation control in the incineration ash collection system 1 according to the embodiment.

[0077] Low-fuel-consumption operation control is performed when the conditions for the high-temperature dust collection control described above are met. Specifically, low-fuel-consumption operation control is performed on the following conditions: the amount of air F flowing into the incinerator 2 is equal to or greater than a predetermined airflow rate; the target exhaust gas temperature, which is the exhaust gas temperature of the dust collector 4, is included in the control temperature range; and the temperature of the first preheated air flowing out from the first heat exchanger 3 does not exceed the temperature upper limit.

[0078] In low-fuel-consumption operation control, the opening and closing of the first control valve 21 is controlled when the target exhaust gas temperature, which is the exhaust gas temperature of the dust collector 4, falls within the control temperature range. This allows the temperature of the first preheated air flowing out of the first heat exchanger 3 to be adjusted. Furthermore, by operating the system so that the temperature of the first preheated air flowing out of the first heat exchanger 3 and into the incinerator 2 is near the upper temperature limit, it becomes possible to reduce the amount of auxiliary fuel used in the incinerator 2 while maintaining the incineration temperature inside the incinerator 2. The details of an example of low-fuel-consumption operation control are described below.

[0079] In step S120, the control device 100 sets a temperature (low-fuel-consumption operation control temperature) that allows the temperature of the first preheated air flowing out of the first heat exchanger 3 to rise to a predetermined temperature, within a range where the temperature of the first preheated air does not exceed the temperature upper limit, thereby achieving low fuel consumption. The process then proceeds to steps S101 and S112. The low-fuel-consumption operation control temperature (determined temperature) is set to, for example, 700°C.

[0080] In step S101, the control device 100 determines whether the temperature of the first preheated air is below the low-fuel-consumption operation control temperature. If it is determined that the temperature of the first preheated air is below the low-fuel-consumption operation control temperature (step S101; Yes), the process proceeds to step S122. Otherwise (step S101; No), the process proceeds to step S102.

[0081] In step S122, the control device 100 changes the set value of the opening degree of the first control valve 21 to a value smaller than the current value (closed direction). As a result, the amount of air flowing into the second heat exchanger 6 increases, and the temperature of the first air flowing into the first heat exchanger 3 rises. The rise in the temperature of the first air increases the amount of heat exchanged, which reduces the amount of auxiliary fuel used in the incinerator 2. After step S122 is performed, the process proceeds to step S102.

[0082] In step S102, the control device 100 determines whether the temperature of the first preheated air flowing out of the first heat exchanger 3 is equal to or greater than the low-fuel-consumption operation control temperature limit. If it is determined that the temperature of the first preheated air is equal to or greater than the low-fuel-consumption operation control temperature limit (step S102; Yes), the process proceeds to step S121. Otherwise (step S102; No), the process returns to the start. The low-fuel-consumption operation control temperature limit is set to, for example, 715°C. The low-fuel-consumption operation control temperature limit is also simply referred to as the temperature limit.

[0083] In step S121, the control device 100 changes the set value of the opening degree of the first control valve 21 to a value greater than the current value (open direction). As a result, the amount of air flowing into the second heat exchanger 6 decreases, and the temperature of the first air flowing into the first heat exchanger 3 decreases. As the temperature of the first air decreases, the temperature of the first preheated air flowing out of the first heat exchanger 3 also decreases, preventing it from exceeding the heat resistance of various equipment (incinerator 2 and third piping 53). Therefore, this helps to prevent equipment failure. After step S121 is executed, the process proceeds to step S005A. Step S005A is the same process as step S005 of the high-temperature dust collection control described above, so the explanation is omitted here. If the conditions of step S005A are met (step S005A; Yes), the control device 100 turns off the low-fuel consumption operation control and switches to control of high-temperature dust collection control only. If the conditions of step S005A are not met (step S005A; No), the process returns to start.

[0084] The processing from step S112 onwards will now be explained. After transitioning from high-temperature dust collection control to low-fuel-consumption operation control, that is, after turning on low-fuel-consumption operation control, the target exhaust gas temperature of the dust collector 4 is maintained to be within the control temperature range. However, in the processing from step S101 onwards, when control is performed to increase the temperature of the first preheating air flowing out from the first heat exchanger 3, it is expected that the target exhaust gas temperature of the dust collector 4 will decrease. Therefore, in parallel with the temperature control of the first preheating air from step S101 onwards, control is performed to maintain the target exhaust gas temperature of the dust collector 4 at a high temperature. Note that the processing from step S112 onwards may be performed at periodic intervals using a timer.

[0085] Specifically, in step S112, the control device 100 changes the set value of the fan speed of the first blower 5 to a value smaller than the current value. This reduces the amount of air F flowing into the incinerator 2, thereby reducing the amount of auxiliary fuel used in the incinerator 2. Furthermore, by reducing the airflow of the first blower 5, the amount of heat exchanged in the second heat exchanger 6 decreases, and the amount of heat exchanged in the first heat exchanger 3 also decreases. Consequently, the cooling of the exhaust gas side of the first heat exchanger 3 is suppressed, and the target exhaust gas temperature of the dust collector 4 rises.

[0086] After step S112 is executed, the process executes steps S004A, S013A, and S003A. Steps S004A and S013A are the same controls as the high-temperature dust collection control. If the condition of step S003A is met (step S003A; Yes), that is, if the target exhaust gas temperature is lower than the control temperature lower limit, the control device 100 switches to control only high-temperature dust collection control, turning off the low-fuel-consumption operation control in order to prioritize raising the target exhaust gas temperature. If the condition of step S003A is not met (step S003A; No), the process returns to start.

[0087] 2-3. Examples of changes in the state of the controlled object Figures 4(A) to (E) are explanatory diagrams showing examples of changes in the state of the controlled objects in high-temperature dust collection control and low-fuel-consumption operation control of the incineration ash collection system 1 according to the embodiment. The controlled objects are the target exhaust gas temperature, the temperature of the first preheating air flowing into the incinerator 2, the amount of auxiliary fuel (heavy oil A) used in the incinerator 2, the amount of first preheating air, and the opening degree of the first control valve 21.

[0088] In the example shown in Figure 4, sludge with 80% moisture and 20% solid matter is incinerated at 850°C in incinerator 2 (fluidized bed incinerator). The inlet temperature of the dust collector 4 shown in Figure 4(A) is set as the target exhaust gas temperature, with an upper limit of 625°C and a lower limit of 613°C. In addition, the upper limit of the preheated air temperature at the inlet of incinerator 2 (temperature of the first preheated air), shown in Figure 4(B), is set to 720°C.

[0089] As shown in Figure 4, the incineration ash collection system 1 (control device 100) performs high-temperature dust collection control after the heating of each piece of equipment, when the target exhaust gas temperature is 615°C and the preheated air temperature of the incinerator 2 is 650°C. Furthermore, as shown in Figures 4(D) and (E), the control device 100 performs high-temperature dust collection and low-fuel consumption operation control by controlling the increase or decrease of the amount of air supplied by the first blower 5 and the opening and closing of the first adjustment valve 21.

[0090] In this case, the target exhaust gas temperature is maintained within the control temperature range (within the upper and lower limits of the target exhaust gas temperature), and the preheating air temperature at the inlet of incinerator 2 rises to 700°C and 715°C, which reduces the amount of auxiliary fuel used (see Figures 4(A), (B), and (C)).

[0091] 3. Effects According to the incineration ash collection system 1 of this embodiment, it is possible to reduce the heavy metal content and collect an appropriate amount of incineration ash while maintaining the target exhaust gas temperature of the dust collector 4 at an appropriate temperature. Furthermore, by making the temperature of the first preheated air flowing into the incinerator 2 higher, it becomes possible to reduce the amount of auxiliary fuel used in the incinerator 2.

[0092] Here, we consider the differences between the configuration example of the incineration ash collection system 1 according to the embodiment and the comparative example. Figures 5 and 6 are schematic diagrams showing a comparative example of the incineration ash collection system 1. In the comparative example of the incineration ash collection system 1, the second heat exchanger 6 is not included. In this case, in the comparative example shown in Figure 5, the temperature of the exhaust gas flowing into the dust collector 4 is maintained at an appropriate temperature of 615°C, the same as the incineration ash collection system 1 in Figure 1, but the temperature of the first preheated air flowing into the incinerator 2 is 517°C, which is lower than the 650°C in the incineration ash collection system 1 in Figure 1, and the amount of auxiliary fuel used in the incinerator 2 is 223 L / h, which is more than the 173 L / h in the incineration ash collection system 1 in Figure 1.

[0093] As another comparative example, in the comparative example shown in Figure 6, the temperature of the first preheated air flowing into the incinerator 2 is 650°C, the same as the incineration ash collection system 1 in Figure 1, which is higher than the comparative example in Figure 5. The amount of auxiliary fuel used in the incinerator 2 is 173 L / h, the same as the incineration ash collection system 1 in Figure 1. However, due to heat exchange in the first heat exchanger 3, the exhaust gas temperature drops to 553°C, and the temperature of the exhaust gas flowing into the dust collector 4 is not maintained at an appropriate temperature, making high-temperature dust collection impossible.

[0094] Thus, in the comparative example of the incineration ash collection system 1, the exhaust gas temperature of the dust collector 4 and the temperature of the first preheated air flowing into the incinerator 2 are inversely related, with the other decreasing or increasing as one rises or decreases.

[0095] Let's consider the performance difference between the configuration example of the incineration ash collection system 1 according to the embodiment and the comparative example. Figure 7 is a comparison table showing the performance difference between the configuration example of the incineration ash collection system 1 according to the embodiment and the comparative example. Here, the comparative example of the incineration ash collection system 1 shown in Figure 5 will be referred to as the first comparative example, and the comparative example of the incineration ash collection system 1 shown in Figure 6 will be referred to as the second comparative example.

[0096] In the first comparative example, when the target exhaust gas temperature of the dust collector 4 is controlled to 615°C, the temperature of the first preheated air flowing into the incinerator 2 becomes 517°C. In contrast, the incineration ash collection system 1 according to this embodiment can maintain the target exhaust gas temperature of the dust collector 4 at an appropriate temperature while raising the temperature of the first preheated air flowing into the incinerator 2 to the standard 650°C. In this case, the amount of auxiliary fuel used in the incinerator 2 becomes 173 L / h, which is a reduction of 50 liters per hour compared to the amount of auxiliary fuel used in the first comparative example (223 L / h). In the second comparative example, the temperature of the first preheated air flowing into the incinerator 2 can be raised to the standard 650°C, but the target exhaust gas temperature of the dust collector 4 cannot be raised to 615°C.

[0097] The incineration ash collection system 1 allows for the maintenance of the target exhaust gas temperature of the dust collector 4 at an appropriate temperature while simultaneously adjusting the temperature of the first preheated air flowing into the incinerator 2. Furthermore, it enables a further reduction in the amount of auxiliary fuel used in the incinerator 2. The incineration ash collection system 1 also implements high-temperature dust collection and low-fuel-consumption operation control, raising the temperature of the first preheated air from the standard 650°C to 700°C, then 715°C, close to the upper limit of the equipment's operating temperature. This allows for a continuous reduction in the amount of auxiliary fuel used.

[0098] 4. Other Embodiments Figure 8 is a schematic diagram showing an example of the configuration of an incineration ash collection system 1A according to another embodiment. The incineration ash collection system 1A consists of an incinerator 2, a first heat exchanger 3, a dust collector 4, a first blower 5, a second heat exchanger 17, a third heat exchanger 16, a second blower 8, an exhaust gas treatment device 9, an exhaust fan 10, a chimney 11, and a cooling water pump 12. Note that the incinerator 2, dust collector 4, first blower 5, second blower 8, exhaust gas treatment device 9, exhaust fan 10, chimney 11, and cooling water pump 12 have the same configuration as in the embodiment described above, so their explanation is omitted here.

[0099] The first heat exchanger 3 will now be described. The configuration of the first heat exchanger 3 is the same as in the embodiment described above, and the difference from the embodiment described above is the air (first air) flowing into the first heat exchanger 3. Here, we will explain the details regarding the first air flowing into the first heat exchanger 3.

[0100] Specifically, the first heat exchanger 3 receives first air through the parallel-flow air inlet 3A and the counter-flow air inlet 3B connected to the first piping 51. The first air includes air (third preheated air) that has been preheated by the third heat exchanger 16 from some or all of the air supplied by the first blower 5 via the second branch piping 52A and the second branch piping 52B.

[0101] The first pipe 51 is for supplying first air to the first heat exchanger 3. One end of the first pipe 51 is connected to the parallel flow air inlet 3A and the counterflow air inlet 3B, and the other end is connected to the first connection point a. The first connection point a is the end of the first pipe 51, and is also the end of the second branch pipes 52A and 52B, which are branches of the second pipe 52. The second pipe 52 is for supplying air sent out from the first blower 5. One end of the second pipe 52 is connected to the first blower 5, and the other end is connected to the first connection point a of the first pipe 51. The second branch pipes 52A and 52B are for supplying the third preheated air that flows out of the third heat exchanger 16 to the first pipe 51 so that the third preheated air is included in the first air. The second branch pipe 52A and the second branch pipe 52B are connected at one end to the second pipe 52 and at the other end to the first connection point a of the first pipe 51 via the third heat exchanger 16.

[0102] The second heat exchanger 17 is equipped with an air inlet 17A into which air supplied by the second blower 8 (fourth air) flows in via the fifth pipe 55. The fifth pipe 55 is a pipe whose one end is connected to the second blower 8 and whose other end is connected to the air inlet 17A of the second heat exchanger 17. The second heat exchanger 17 is also equipped with an exhaust gas inlet 17C into which second exhaust gas discharged from the exhaust gas outlet 4B of the dust collector 4 flows in via the third duct 63. The third duct 63 is a pipe whose one end is connected to the exhaust gas outlet 4B of the dust collector 4 and whose other end is connected to the exhaust gas inlet 17C of the second heat exchanger 17.

[0103] Furthermore, the second heat exchanger 17 includes an air outlet 17B that increases the temperature of the fourth air by heat exchange between the fourth air flowing into the air inlet 17A and the second exhaust gas flowing into the exhaust gas inlet 17C, and discharges preheated air (second preheated air) at a higher temperature than the fourth air, and an exhaust gas outlet 17D that decreases the temperature of the second exhaust gas by heat exchange between the fourth air flowing into the air inlet 17A and the second exhaust gas flowing into the exhaust gas inlet 17C, and discharges third exhaust gas at a lower temperature than the second exhaust gas.

[0104] In this way, the second heat exchanger 17 raises the temperature of the fourth air and lowers the temperature of the second exhaust gas through heat exchange between the fourth air supplied by the second blower 8 and the second exhaust gas, and supplies second preheated air at a temperature higher than the fourth air to areas requiring heating (e.g., equipment, piping). The second heat exchanger 17 also discharges third exhaust gas at a temperature lower than the second exhaust gas.

[0105] Furthermore, the second heat exchanger 17 may be provided with a parallel flow air inlet and a counterflow air inlet, similar to the first heat exchanger 3. In this case, in the heat exchange between the second exhaust gas and the fourth air, one of the following is selected based on the advantages of heat exchange and the low-temperature corrosion temperature of the internal materials: performing the heat exchange between the second exhaust gas and the fourth air in parallel flow, performing the heat exchange between the second exhaust gas and the fourth air in counterflow, or performing the heat exchange between the second exhaust gas and the fourth air in both parallel and counterflow. In addition, the second preheated air, which is at a higher temperature than the fourth air supplied by the second blower 8, is supplied to the heat utilization equipment and devices. Applications of the second preheated air include supplying it to the chimney via the sixth pipe 56 to prevent the generation of white smoke when released into the atmosphere, and supplying it to the duct 66 that flows into the exhaust fan 10 via a pipe branched from the sixth pipe 56 to raise the temperature of the exhaust gas discharged from the exhaust gas treatment device 9 and remove deposits from the duct 66 and equipment. Furthermore, the second preheated air is used as a heat source to heat the first air that flows into the first heat exchanger 3.

[0106] The third heat exchanger 16 is equipped with an air inlet 16A into which second air, representing some or all of the air supplied by the first blower 5, flows in via a second branch pipe 52A that branches off from the second pipe 52. The second branch pipe 52A is a pipe whose one end is connected to the second pipe 52 and whose other end is connected to the air inlet 16A of the third heat exchanger 16. The third heat exchanger 16 is also equipped with an air inlet 16C into which second preheated air, discharged from the air outlet 17B of the second heat exchanger 17, flows in via a sixth pipe 56. The sixth pipe 56 is a pipe whose one end is connected to the air outlet 17B of the second heat exchanger 17 and whose other end is connected to the air inlet 16C of the third heat exchanger 16.

[0107] Furthermore, the third heat exchanger 16 includes an air outlet 16B that increases the temperature of the second air and discharges preheated air (third preheated air) at a higher temperature than the second air by heat exchange between the second air flowing into the air inlet 16A and the second preheated air flowing into the air inlet 16C, and an air outlet 16D that decreases the temperature of the second preheated air and discharges fifth air at a lower temperature than the second preheated air by heat exchange between the second air flowing into the air inlet 16A and the second preheated air flowing into the air inlet 16C.

[0108] In this way, the third heat exchanger 16 raises the temperature of some or all of the second air by heat exchange between some or all of the air (second air) supplied by the first blower 5 via the second branch pipe 52A branched from the second pipe 52 and the second preheated air flowing out from the second heat exchanger 17.

[0109] Furthermore, the air supplied by the second blower 8 (fourth air) serves as a heat source for heating the first air flowing into the first heat exchanger 3 with the third preheated air preheated by the second heat exchanger 17. Since this affects the temperature of the third preheated air flowing out of the third heat exchanger 16, the temperature of the second preheated air is adjusted by increasing or decreasing the airflow rate of the fourth air supplied by the second blower 8. The method for increasing or decreasing the airflow rate of the fourth air supplied by the second blower 8 is not limited to the motor 8A that controls the fan speed, but may also be adjusted using an adjustment valve provided at the inlet or outlet of the second blower 8.

[0110] The incineration ash collection system 1A includes a control device 100. The control device 100 is connected to each of the following: a plurality of thermometers (first thermometer 31 to sixth thermometer 36), a plurality of airflow meters (first airflow meter 41 to fourth airflow meter 44), a plurality of control valves (first control valve 21 to fifth control valve 25), the motor 5A of the first blower 5, and the motor 8A of the second blower 8. The control device 100 is connected to each of the aforementioned plurality of devices using electrically communicable wiring or the like. A computer or other computing device is an example of the control device 100.

[0111] The various controls performed by the control device 100 (high-temperature dust collection control, high-temperature dust collection and low-fuel consumption operation control) are the same as those performed in the embodiment described above. Therefore, in the incineration ash collection system 1A according to the other embodiment, the various controls of the control device 100 are realized by replacing "second heat exchanger 6" with "second heat exchanger 17", "third heat exchanger 7" with "third heat exchanger 16", and "second preheated air" with "third preheated air" in the description from section "1-2" onward of the incineration ash collection system 1 according to the embodiment described above. [Explanation of Symbols]

[0112] 1,1A…Incineration ash collection system, 2…Fluidized incinerator, 2A…Preheating air inlet, 2B…Exhaust gas outlet, 3…First heat exchanger, 3A…Parallel flow air inlet, 3B…Counterflow air inlet, 3C…Exhaust gas inlet, 3D…Air outlet, 3E…Exhaust gas outlet, 4…Dust collector, 4A…Exhaust gas inlet, 4B…Exhaust gas outlet, 4C…Ash discharger, 5…First blower, 5A…Motor, 6…Second heat exchanger, 6A…Air inlet, 6B…Air outlet, 6C…Exhaust gas inlet, 6D…Exhaust gas outlet, 7…Third heat exchanger, 7A…Air inlet, 7B…Air outlet, 7C…Exhaust gas inlet, 7D…Exhaust gas outlet, 8…Second blower, 8A…Motor 9…Exhaust gas treatment device, 10…Exhaust fan, 11…Chimney, 12…Cooling water pump, 16…Third heat exchanger, 16A…Air inlet, 16B…Air outlet, 16C…Air inlet, 16D…Air outlet, 17…Second heat exchanger, 17A…Air inlet, 17B…Air outlet, 17C…Exhaust gas inlet, 17D…Exhaust gas outlet, 21…First control valve, 22…Second control valve, 23…Third control valve, 24…Fourth control valve, 25…Fifth control valve, 31…First thermometer, 32…Second thermometer, 33…Third thermometer, 34…Fourth thermometer, 35…Fifth thermometer, 36…Sixth thermometer, 41…First airflow meter, 42…Second airflow meter, 43…Third airflow meter, 44…Fourth airflow meter, 51…First piping, 52…Second piping, 52A, 52B…Second branch piping, 53…Third piping, 54…Air piping, 55…Fifth piping, 56…Sixth piping, 57…Seventh piping, 61…First duct, 62…Second duct, 63…Third duct, 66…Duct, 100…Control device

Claims

1. An incineration ash collection system that collects incinerated ash from exhaust gas emitted after incinerating materials in a fluidized bed incinerator using a dust collector, A first blower that supplies air, A first heat exchanger is provided between the fluidized bed incinerator and the dust collector, and through heat exchange between the first air, which represents some or all of the air supplied by the first blower, and the exhaust gas discharged from the fluidized bed incinerator, the temperature of the first air is increased and the temperature of the exhaust gas is decreased, and a first preheated air at a higher temperature than the first air is supplied to the fluidized bed incinerator, while the first exhaust gas at a lower temperature than the exhaust gas is discharged, A second heat exchanger is provided at the exhaust gas outlet of the dust collector and, through heat exchange between the second air, which represents part or all of the air supplied by the first blower, and the second exhaust gas discharged from the exhaust gas outlet of the dust collector, raises the temperature of the second air and lowers the temperature of the second exhaust gas, and supplies second preheated air at a temperature higher than the temperature of the second air to the first heat exchanger and discharges third exhaust gas at a temperature lower than the temperature of the second exhaust gas, A first pipe having one end connected to the first heat exchanger and the other end connected to a first connection point, which supplies the first air to the first heat exchanger, A second pipe, one end of which is connected to the first blower and the other end of which is connected to the first connection point of the first pipe, A second branch pipe, one end of which is connected to the second pipe and the other end of which is connected to the first connection point of the first pipe via the second heat exchanger, supplies the second preheated air flowing out of the second heat exchanger to the first pipe, A first control valve is provided in the second pipe between the first connection point and the second connection point between the second pipe and the second branch pipe, and adjusts the flow rate of the second air and the second preheated air flowing through the second branch pipe. A control device connected to the first blower and the first control valve respectively, which controls the opening and closing of the first control valve to adjust at least one of the temperature of the first air and the flow rate of the second air based on the target exhaust gas temperature of at least one of the temperature of the first exhaust gas and the temperature of the second exhaust gas and the temperature of the first preheated air, Equipped with An incineration ash collection system characterized by the following features.

2. An incineration ash collection system that collects incinerated ash from exhaust gas emitted after incinerating materials in a fluidized bed incinerator using a dust collector, A first blower and a second blower that supply air, A first heat exchanger is provided between the fluidized bed incinerator and the dust collector, and through heat exchange with the exhaust gas discharged from the fluidized bed incinerator, it raises the temperature of the first air, which represents some or all of the air supplied by the first blower, and lowers the temperature of the exhaust gas, and supplies first preheated air at a higher temperature than the first air to the fluidized bed incinerator and discharges first exhaust gas at a lower temperature than the exhaust gas, A second heat exchanger is provided at the exhaust gas outlet of the dust collector, and raises the temperature of the air supplied by the second blower through heat exchange with the second exhaust gas discharged from the exhaust gas outlet of the dust collector, while lowering the temperature of the second exhaust gas, and discharges a second preheated air at a temperature higher than the temperature of the air and a third exhaust gas at a temperature lower than the temperature of the second exhaust gas, A third heat exchanger is provided at the air outlet of the second heat exchanger and raises the temperature of the second air, which represents part or all of the air supplied by the first blower, by heat exchange with the second preheated air discharged from the air outlet of the second heat exchanger, while lowering the temperature of the second preheated air, thereby supplying a third preheated air at a higher temperature than the second air to the first heat exchanger. A first pipe having one end connected to the first heat exchanger and the other end connected to a first connection point, which supplies the first air to the first heat exchanger, A second pipe, one end of which is connected to the first blower and the other end of which is connected to the first connection point of the first pipe, A second branch pipe, one end of which is connected to the second pipe and the other end of which is connected to the first connection point of the first pipe via the third heat exchanger, supplies the third preheated air flowing out of the third heat exchanger to the first pipe, A first control valve is provided in the second pipe between the first connection point and the second connection point between the second pipe and the second branch pipe, and adjusts the flow rate of the second air and the third preheated air flowing through the second branch pipe. A control device connected to the first blower and the first control valve respectively, which controls the opening and closing of the first control valve to adjust at least one of the temperature of the first air and the flow rate of the second air based on the target exhaust gas temperature of at least one of the temperature of the first exhaust gas and the temperature of the second exhaust gas and the temperature of the first preheated air, Equipped with An incineration ash collection system characterized by the following features.

3. An incineration ash collection system according to claim 1 or 2, The control device is configured to change the set value of the fan speed of the first blower to a value smaller than the current value until the target exhaust gas temperature is raised to an appropriate temperature, if the amount of air flowing into the fluidized bed incinerator is equal to or greater than a predetermined airflow rate required for combustion in the fluidized bed incinerator. An incineration ash collection system characterized by the following features.

4. An incineration ash collection system according to claim 1 or 2, The control device is configured to change the set value of the fan speed of the first blower to a value greater than the current value if the amount of air flowing into the fluidized bed incinerator is less than a predetermined airflow rate required for combustion in the fluidized bed incinerator, until the target exhaust gas temperature is reduced to an appropriate temperature. An incineration ash collection system characterized by the following features.

5. An incineration ash collection system according to claim 1 or 2, The control device is configured to change the setting value of the opening degree of the first control valve to a value greater than the current value when the temperature of the first preheating air flowing into the fluidized bed incinerator is above a predetermined temperature and above a temperature upper limit. An incineration ash collection system characterized by the following features.

6. An incineration ash collection system according to claim 1 or 2, The control device is configured to maintain the target exhaust gas temperature by increasing or decreasing the set value of the rotation speed of the first blower fan when the amount of air flowing into the fluidized bed incinerator is equal to or greater than a predetermined airflow rate required for combustion in the fluidized bed incinerator, and to control the opening and closing of the first control valve so that the temperature of the first preheated air reaches a predetermined temperature. An incineration ash collection system characterized by the following features.

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