JP2017072341A - Method and apparatus for cooling gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus enabling exhaust gas from a waste melting furnace to be more surely cooled.SOLUTION: The method for cooling gas is provided in which exhaust gas exhausted from a waste melting furnace 2 is cooled by spraying cooling water in a first cooling tower 41 provided in a fluid channel of the exhaust gas, and the method includes (a) adjusting the spray amount of the cooling water so as to bring the temperature of exhaust gas cooled in the first cooling tower 41 close to target temperature, and (b) increasing the spray amount of the cooling water in accordance with rise of pressure in a furnace top part of the waste melting furnace 2.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a gas cooling method and a gas cooling device.

  In the waste melting furnace, exhaust gas containing dust is generated, so that exhaust gas is discharged after passing through a dust collector. If the hot exhaust gas is passed through the dust collector without cooling, the dust collector may be damaged. Therefore, the exhaust gas is cooled by a cooling device and then passed through the dust collector. For example, Patent Document 1 includes a cooling tower having a water spray nozzle therein and a flow rate control valve that controls the amount of spray from the water spray nozzle, and controls the flow rate control valve according to the temperature of exhaust gas that has passed through the cooling tower. A cooling device is disclosed.

JP-A-8-61653

  In a waste melting furnace, the outflow amount of exhaust gas varies greatly depending on various factors such as the type of waste, the state of waste accumulation, and the amount of waste. When the cooling device described above is applied to a waste melting furnace, the amount of heat flowing into the cooling tower along with the exhaust gas changes as the outflow amount of the exhaust gas from the waste melting furnace changes. It is necessary to adjust the amount of cooling water sprayed into the cooling tower. However, since the flow rate control valve of the cooling water is controlled according to the temperature of the exhaust gas on the downstream side of the cooling tower, it is delayed in adjusting the spray amount of the cooling water with respect to the temperature change of the exhaust gas on the downstream side of the cooling tower. Occurs. For this reason, when the outflow amount of the exhaust gas from the waste melting furnace increases rapidly, the adjustment of the spray amount of the cooling water is not in time, and there is a possibility that the high temperature of the exhaust gas on the downstream side of the cooling tower cannot be sufficiently suppressed.

  Therefore, this indication aims at providing the method and apparatus which can cool the exhaust gas from a waste melting furnace more reliably.

  A gas cooling method according to the present disclosure is a method of cooling exhaust gas by spraying cooling water in a cooling tower provided in a flow path of exhaust gas discharged from a waste melting furnace, and (a) cooled in the cooling tower. Adjusting the spray amount of the cooling water so that the temperature of the exhaust gas approaches the target temperature, and (b) increasing the spray amount of the cooling water in response to an increase in the pressure in the top of the waste melting furnace. .

  According to the gas cooling method according to the present disclosure, when the pressure in the top of the waste melting furnace (hereinafter referred to as “furnace top pressure”) is stable, the temperature of the exhaust gas cooled in the cooling tower is adjusted. The spray amount of the cooling water is adjusted so as to approach the target temperature. Thereby, since the spray amount of cooling water is optimized according to the temperature of the exhaust gas on the downstream side of the cooling tower, the exhaust gas from the waste melting furnace can be stably cooled. When the furnace top pressure rises, the amount of cooling water sprayed is increased accordingly. The furnace top pressure tends to correlate with the outflow amount of exhaust gas from the waste melting furnace, so by increasing the spray amount of cooling water as the furnace top pressure increases, according to the increase in outflow amount of exhaust gas. The amount of cooling water sprayed can be increased. Thereby, the spray amount of cooling water can be increased before the exhaust gas temperature on the downstream side of the cooling tower rises according to the increase in the outflow amount of the exhaust gas. For this reason, even if it is a case where the outflow amount of the exhaust gas from a waste melting furnace increases rapidly, the high temperature of the exhaust gas in the downstream of a cooling tower can fully be suppressed. Therefore, the exhaust gas from the waste melting furnace can be cooled more reliably.

  In said (b), when the pressure evaluation value correlated with the pressure rise in a furnace top part exceeds a threshold value, you may increase the spraying quantity of cooling water temporarily. If the spray amount of the cooling water is excessive, dust in the exhaust gas gets wet and accumulates in the cooling tower, which may make it difficult to continuously operate the cooling device. In contrast, when the pressure evaluation value exceeds the threshold value to increase the cooling water spray amount in response to the rise in the furnace top pressure, the cooling water spray amount becomes excessive. Can be suppressed. Therefore, the exhaust gas from the waste melting furnace can be cooled more reliably.

  In (b) above, the amount of increase in the amount of cooling water spray may be increased as the pressure evaluation value increases. As described above, the furnace top pressure tends to correlate with the amount of exhaust gas discharged from the waste melting furnace. Therefore, by increasing the amount of increase in the amount of cooling water sprayed as the pressure evaluation value increases, the amount of increase in the amount of cooling water sprayed as the amount of heat flowing into the cooling tower along with the exhaust gas increases. Can be increased. Therefore, the exhaust gas from the waste melting furnace can be cooled more reliably.

  In the above (b), the threshold value may be increased as the outflow amount of the exhaust gas from the waste melting furnace increases. In a state where the amount of exhaust gas flowing out from the waste melting furnace is large, the amount of heat flowing into the cooling tower is large, so the amount of cooling water sprayed is also large (hereinafter referred to as the “first state”). On the other hand, in a state where the amount of exhaust gas discharged from the waste melting furnace is small, the amount of heat flowing into the cooling tower is small, so the amount of cooling water sprayed is also small (hereinafter referred to as “second state”). That is, in the first state, more cooling water exists in the cooling tower than in the second state. For this reason, when the outflow amount of the exhaust gas increases in the first state, the temperature of the exhaust gas on the downstream side of the cooling tower tends not to rise as compared with the case where the outflow amount of the exhaust gas increases in the second state. On the other hand, when the threshold value is increased as the amount of exhaust gas discharged from the waste melting furnace increases, the start condition of (b) is narrower in the first state than in the second state. Thereby, in the 1st state, it is suppressed that the spraying quantity of cooling water becomes excessive. In the second state, it is suppressed that the amount of cooling water sprayed becomes too small. Therefore, the exhaust gas from the waste melting furnace can be cooled more reliably.

  In the above (b), the pressure evaluation value may be calculated based on at least one of the pressure in the furnace top and the in-furnace differential pressure of the waste melting furnace. In this case, the furnace top pressure can be accurately evaluated.

  In the above (a), the change in the spray amount of the cooling water according to the change in the temperature of the exhaust gas may be made smaller as the temperature of the exhaust gas becomes lower than the target temperature. Due to the increase in the amount of cooling water sprayed, the temperature of the exhaust gas greatly decreases after the execution of the above (b), and may be greatly separated to the negative side with respect to the target temperature (hereinafter referred to as “third state”). That said.) When the third state occurs due to the execution of (b), the spray amount of the cooling water is greatly reduced in the subsequent (a). If the spray amount of the cooling water is greatly changed in (a) above, a state in which the temperature of the exhaust gas repeats excessively on the plus side and the minus side with respect to the target temperature (hereinafter referred to as “hunting”) is likely to occur. Become. On the other hand, if the change in the spray amount of the cooling water according to the change in the temperature of the exhaust gas is made smaller as the temperature of the exhaust gas becomes lower than the target temperature, the above (a) after the third state has occurred. , The change width of the spray amount of the cooling water is reduced. For this reason, generation | occurrence | production of the said hunting is suppressed. Therefore, the exhaust gas from the waste melting furnace can be cooled more reliably.

  In the above (a) and (b), the amount of cooling water sprayed is adjusted by the opening degree of the valve provided in the cooling water supply pipe, and the opening degree of the valve is adjusted as the temperature of the exhaust gas decreases. The upper limit value may be lowered. Also in this case, the occurrence of the hunting is more reliably suppressed. Therefore, the exhaust gas from the waste melting furnace can be cooled more reliably.

  During the execution of (b), (a) may be interrupted. With this configuration, the control content can be simplified.

  A gas cooling apparatus according to the present disclosure is provided in a flow path of exhaust gas discharged from a waste melting furnace, and a cooling tower for cooling exhaust gas by spraying cooling water, and a temperature of the exhaust gas cooled in the cooling tower. Control to adjust the spray amount of cooling water so as to approach the target temperature, and control to increase the spray amount of cooling water as the pressure in the top of the waste melting furnace increases And a controller configured to.

  According to the present disclosure, the exhaust gas can be cooled even when the amount of heat of the exhaust gas increases temporarily.

It is a schematic diagram which shows schematic structure of a waste melting facility. It is a hardware block diagram of a controller. It is a flowchart which shows the execution procedure of a gas cooling method. It is a graph which shows the relationship between the temperature of waste gas, and the upper limit of a valve opening degree. It is a graph which shows the relationship between the temperature of exhaust gas, and a proportional gain. 4 is a graph showing a relationship between a supply amount of combustion gas and a first threshold value H. It is a graph which shows the relationship between pressure evaluation value (DELTA) PV and increase amount (DELTA) MV of the spray amount of cooling water. 3 is a graph showing the results of Example 1. 6 is a graph showing the results of Comparative Example 1.

  Hereinafter, embodiments will be described in detail with reference to the drawings. In the description, the same elements or elements having the same functions are denoted by the same reference numerals, and redundant description is omitted.

[Waste melting equipment]
First, an outline of the waste melting facility 1 according to the present embodiment will be described with reference to FIG. The waste melting facility 1 is a facility for performing gasification melting treatment on general waste, industrial waste, etc. (hereinafter simply referred to as “waste”). For example, the waste melting facility 1 includes a waste melting furnace 2, a combustion chamber 3, a gas cooling device 4, a dust collector 5, an induction fan 6, and a chimney 7.

  The waste melting furnace 2 thermally decomposes and gasifies the combustible material in the waste under a reducing atmosphere to melt ash and incombustible materials. The waste melting furnace 2 includes a furnace body 20, an inlet 20a, a gas outlet 20b, a hot water outlet 20c, at least one tuyere 21, and pressure sensors B1 and B2.

  The furnace body 20 has a shape extending in the vertical direction, and forms a waste W storage space. The side wall of the furnace body 20 has, for example, a cylindrical shape, and a tapered portion 20d having an inner diameter that decreases in the downward direction is formed in the lower portion thereof. The size of the furnace body 20 can be appropriately set according to the processing capacity of the waste melting furnace 2.

  The charging port 20 a is formed in the upper part of the waste melting furnace 2. The gas discharge port 20b is formed in the upper part of the waste melting furnace 2 around the charging port 20a. The outlet 20 c is formed at the bottom of the furnace body 20.

  At least one tuyere 21 is provided in the lower part of the furnace body 20. The tuyere 21 is connected to an oxygen-containing gas supply source (not shown). The waste melting furnace 2 may have a plurality of upper tuyere 22 and a plurality of lower tuyere 23 as at least one tuyere 21. The upper tuyere 22 and the lower tuyere 23 are lined up and down. The plurality of upper tuyere 22 are arranged so as to surround the inside of the furnace body 20, and the plurality of lower stage tuyere 23 are also arranged so as to surround the inside of the furnace body 20.

  The pressure sensor B <b> 1 is provided in the furnace top of the waste melting furnace 2. The top of the furnace means a portion located above the waste W in a state where the waste W is charged to the maximum extent in the furnace body 20. As an example, the pressure sensor B <b> 1 is provided around the loading port 20 a in the upper part of the furnace body 20.

  The pressure sensor B <b> 2 is provided in a portion where the waste W is deposited in the waste melting furnace 2. As an example, the pressure sensor B <b> 2 is provided below the side wall of the furnace body 20. The pressure sensor B <b> 2 may be provided between the lower tuyere 23 and the upper tuyere 22 on the side wall of the furnace body 20.

  The waste melting furnace 2 configured as described above operates as follows. First, a layer (coke bed C) of red-hot carbon-based combustible material (for example, coke) is formed at the bottom of the waste melting furnace 2. In this state, the charging port 20a of the waste melting furnace 2 receives a mixture of waste and a carbon-based combustible material into the furnace body 20. Waste and carbon-based combustible materials charged into the furnace body 20 from the charging port 20a are deposited on the coke bed C. In this state, oxygen-containing gas is blown into the tuyere 21. For example, air having a higher oxygen concentration (oxygen-enriched air) is blown into the lower tuyere 23 and air is blown into the upper tuyere 22.

  The coke bed is maintained at the bottom of the furnace body 20 by the oxygen-containing gas blown into the lower tuyere 23, and the high-temperature gas generated in the coke bed rises in the furnace body 20. Waste and carbon-based combustible materials are partially combusted by the oxygen-containing gas blown into the upper tuyere 22, and the gas generated thereby rises in the furnace body 20. Hereinafter, the high-temperature gas rising in the furnace is collectively referred to as “furnace gas”.

  The waste in the furnace body 20 descends while facing the upward flow of the furnace gas. In this process, heat exchange is performed between the furnace gas and the waste, and the drying of the waste and the thermal decomposition of the waste are promoted. By the pyrolysis, the combustible component of the waste is gasified, rises in the furnace body 20 together with the furnace gas, and is discharged from the gas discharge port 20b. Hereinafter, the gas discharged from the gas discharge port 20b is referred to as “exhaust gas”.

  Residual components that have not been gasified in the pyrolysis further descend in the furnace body 20. This residual component includes a pyrolysis residue (carbide), ash, incombustibles, and the like. The pyrolysis residue (carbide) collects on the bottom side of the furnace body 20 along the tapered portion 20d of the furnace body 20, and forms a carbide particle layer (so-called char layer) on the coke bed. Ash and incombustibles are melted in the coke bed and collected at the bottom of the furnace body 20. The melt collected at the bottom of the furnace body 20 is intermittently taken out from the tap 20c and collected as slag, metal, and the like.

  The combustion chamber 3 burns the exhaust gas discharged from the gas discharge port 20b of the waste melting furnace 2. The combustion chamber 3 includes a combustion chamber main body 30, an exhaust gas inlet 30a, an exhaust gas outlet 30b, and at least one combustion gas inlet 31.

  The combustion chamber main body 30 has a shape extending in the vertical direction, and forms an exhaust gas storage space. In the combustion chamber main body 30, a burner (not shown) is provided for burning combustible components in the exhaust gas.

  The exhaust gas inlet 30a is provided in the lower part of the side wall of the combustion chamber main body 30, and is connected to the gas outlet 20b of the waste melting furnace 2 via the duct D1. The exhaust gas outlet 30 b is provided in the upper part of the combustion chamber main body 30.

  At least one combustion gas inlet 31 is provided on the side wall of the combustion chamber body 30 between the exhaust gas inlet 30a and the exhaust gas outlet 30b. The combustion gas inlet 31 is connected to the oxygen-containing gas supply source A. The oxygen-containing gas (hereinafter referred to as “combustion gas”) is, for example, air, and the supply source A is, for example, a blower. The combustion chamber 3 may have a primary combustion gas reception port 31 a and a secondary combustion gas reception port 31 b as at least one combustion gas reception port 31. The secondary combustion gas receiving port 31b is provided above the primary combustion gas receiving port 31a.

  The combustion chamber 3 may have at least one flow rate sensor F that detects the flow rate of the combustion gas supplied from the supply source A to the combustion gas receiving port 31. For example, the combustion chamber 3 may have flow sensors F1 and F2 as at least one flow sensor F. The flow sensor F1 detects the flow rate of the combustion gas supplied from the supply source A to the primary combustion gas receiving port 31a. The flow rate sensor F2 detects the flow rate of the combustion gas supplied from the supply source A to the secondary combustion gas receiving port 31b.

  The combustion chamber 3 configured as described above operates as follows. The exhaust gas receiving port 30 a receives the exhaust gas discharged from the gas discharge port 20 b of the waste melting furnace 2 into the combustion chamber main body 30. The primary combustion gas inlet 31a and the secondary combustion gas inlet 31b each receive combustion gas. The amount of combustion gas supplied to the primary combustion gas receiving port 31a and the secondary combustion gas receiving port 31b is adjusted according to the amount of exhaust gas discharged from the gas discharge port 20b. Specifically, the amount of combustion gas supplied to the primary combustion gas receiving port 31a and the secondary combustion gas receiving port 31b is increased as the amount of exhaust gas discharged from the gas discharge port 20b increases.

  The exhaust gas that has entered the combustion chamber body 30 from the exhaust gas inlet 30a is mixed with the combustion gas that has entered the combustion chamber body 30 from the primary combustion gas inlet 31a and is burned by the burner. Thereafter, the exhaust gas rises in the combustion chamber main body 30 and further mixes with the combustion gas that has entered the combustion chamber main body 30 from the secondary combustion gas receiving port 31b. As a result, the combustible component remaining in the exhaust gas is further burned. The exhaust gas after combustion is discharged from the exhaust gas outlet 30b.

  The gas cooling device 4 cools the exhaust gas discharged from the exhaust gas outlet 30 b of the combustion chamber 3. Details of the gas cooling device 4 will be described later. The dust collector 5 removes dust in the exhaust gas cooled by the gas cooling device 4. A specific example of the dust collector 5 is a filtration dust collector that adsorbs dust with a filter cloth. The induction ventilator 6 pumps the exhaust gas that has passed through the dust collector 5 to the downstream side. The exhaust gas pumped downstream by the induction fan 6 is discharged from the chimney 7 through a denitration tower (not shown) filled with a denitration catalyst.

[Gas cooling device]
Next, the gas cooling device 4 will be described in detail. The gas cooling device 4 includes at least one cooling tower 40, at least one temperature sensor T, and a controller 80.

(cooling tower)
The cooling tower 40 is provided in the flow path of the exhaust gas discharged from the waste melting furnace 2, and cools the exhaust gas by spraying cooling water. The cooling tower 40 may be connected to the waste melting furnace 2 without passing through a heat exchanger such as a boiler, or may be connected to the waste melting furnace 2 via a heat exchanger such as a boiler. . Below, the case where the cooling tower 40 is connected to the waste melting furnace 2 without passing through a heat exchanger is demonstrated. The gas cooling device 4 may have one cooling tower 40 or two or more cooling towers 40. For example, the gas cooling device 4 includes a first cooling tower 41 and a second cooling tower 42 as at least one cooling tower 40.

  The first cooling tower 41 includes a tower body 43, an exhaust gas inlet 43a, an exhaust gas outlet 43b, and a spray device 45. The tower main body 43 has a shape extending in the vertical direction and forms an exhaust gas storage space. The exhaust gas inlet 43a is provided in the upper part of the tower main body 43, and is connected to the exhaust gas outlet 30b of the combustion chamber 3 through the duct D2. The exhaust gas outlet 43 b is provided in the lower part of the side wall of the tower body 43.

  The spraying device 45 sprays cooling water on the upper part in the tower main body 43. The cooling water may be any liquid as long as the exhaust gas can be cooled by vaporization. A specific example of the cooling water is water. Domestic wastewater or plant wastewater may be used as cooling water.

  For example, the spray device 45 includes at least one spray nozzle N1, a pump P1, and a valve V1. At least one spray nozzle N1 is provided in the upper part in the tower main body 43, and is connected to the cooling water supply source S via the liquid feeding pipe L1. The pump P1 and the valve V1 are provided in the liquid feeding pipe L1. The pump P1 pumps cooling water from the supply source S to the spray nozzle N1. The pump P1 may adjust the pressure at which the cooling water is pumped according to the input of the control signal. The valve V1 adjusts the opening degree of the flow path in the liquid feeding pipe L1 according to the input of the control signal. The spray nozzle N1 ejects the cooling water supplied from the supply source S in the form of a mist.

  The exhaust gas inlet 43 a of the first cooling tower 41 receives the exhaust gas sent from the exhaust gas outlet 30 b of the combustion chamber 3 into the tower body 43. The exhaust gas flows downward through the tower body 43 and is sent out from the exhaust gas outlet 43b. In the process of passing through the tower body 43, the exhaust gas is cooled by touching the cooling water ejected from the spray nozzle N1.

  Similar to the first cooling tower 41, the second cooling tower 42 includes a tower body 46, an exhaust gas inlet 46 a, an exhaust gas outlet 46 b, and a spray device 47. The exhaust gas inlet 46a is provided in the upper part of the tower body 46, and is connected to the exhaust gas outlet 43b of the first cooling tower 41 via the duct D3. The exhaust gas outlet 46b is provided in the lower part of the side wall of the tower main body 46, and is connected to the dust collector 5 through the duct D4.

  As with the spray device 45, the spray device 47 has at least one spray nozzle N2, a pump P2, and a valve V2. At least one spray nozzle N2 is provided in the upper part in the tower main body 46, and is connected to the cooling water supply source S via the liquid feeding pipe L2. The pump P2 and the valve V2 are provided in the liquid feeding pipe L2.

  The exhaust gas inlet 46 a of the second cooling tower 42 receives the exhaust gas sent from the exhaust gas outlet 43 b of the first cooling tower 41 into the tower body 46. The exhaust gas flows downward in the tower body 46 and is sent out from the exhaust gas outlet 46b. In the process of passing through the tower body 46, the exhaust gas is further cooled by touching the cooling water ejected from the spray nozzle N2. Since the exhaust gas cooled in the first cooling tower 41 flows into the second cooling tower 42, the heat resistance of the tower body 46 may be lower than the heat resistance of the tower body 43.

(Temperature sensor)
The temperature sensor T detects the temperature of the exhaust gas cooled in the cooling tower 40. The gas cooling device 4 may have one temperature sensor T or two or more temperature sensors T. For example, the gas cooling device 4 includes temperature sensors T1 and T2 as at least one temperature sensor T. The temperature sensor T1 is provided in the duct D3, for example, and detects the temperature of the exhaust gas discharged from the first cooling tower 41. The temperature sensor T2 is provided in the duct D4, for example, and detects the temperature of the exhaust gas discharged from the second cooling tower 42.

(controller)
The controller 80 controls to adjust the spray amount of the cooling water so that the temperature of the exhaust gas cooled in the cooling tower 40 approaches the target temperature, and responds to an increase in pressure in the top of the waste melting furnace 2. And controlling to increase the spray amount of the cooling water.

  When the gas cooling device 4 has a plurality of cooling towers 40, the controller 80 controls the amount of cooling water sprayed in each cooling tower 40. For example, the controller 80 controls the amount of cooling water sprayed by the spraying device 45 of the first cooling tower 41 and the amount of cooling water sprayed by the spraying device 47 of the second cooling tower 42.

  The target temperature of the exhaust gas discharged from the first cooling tower 41 and the target temperature of the exhaust gas discharged from the second cooling tower 42 can be set individually. For example, the target temperature of the first cooling tower 41 is 250 to 300 ° C., and the target temperature of the second cooling tower 42 is 150 to 200 ° C.

  Hereinafter, a specific configuration example of the controller 80 will be described. The controller 80 includes a temperature data acquisition unit 81, a pressure data acquisition unit 82, a pressure evaluation value calculation unit 83, an increase amount calculation unit 84, a valve control unit 85, and a control switching unit 86 as functional modules. .

  The temperature data acquisition unit 81 acquires detection values by the temperature sensors T1 and T2 as temperature data of the exhaust gas cooled in the cooling tower 40.

  The pressure data acquisition unit 82 acquires detection values by the pressure sensors B1 and B2 as pressure data in the waste melting furnace 2.

  The pressure evaluation value calculation unit 83 calculates a pressure evaluation value that correlates with a pressure increase in the top of the waste melting furnace 2. The pressure evaluation value calculation unit 83 may calculate a pressure evaluation value based on at least one of the pressure in the top of the waste melting furnace 2 and the in-furnace differential pressure. The in-furnace differential pressure is a differential pressure generated between two points arranged in the vertical direction due to a pressure loss when the in-furnace gas passes through the waste. For example, the pressure evaluation value calculation unit 83 uses the value detected by the pressure sensor B1 as the pressure in the furnace top portion and the difference between the detection values from the pressure sensors B1 and B2 as the pressure difference in the furnace, and uses these to calculate the pressure evaluation value. May be.

  The increase amount calculation unit 84 calculates the increase amount of the opening degree of the valves V1, V2. The increase amount calculation unit 84 may set the increase amount of the opening degree of the valves V1, V2 to be large as the pressure evaluation value increases.

  The valve control unit 85 adjusts the opening degree of the valves V1 and V2 so that the detection value acquired by the temperature data acquisition unit 81 approaches the target temperature (hereinafter referred to as “control a”).

  The control switching unit 86 switches the control content by the valve control unit 85 in accordance with the increase in the pressure in the top of the waste melting furnace 2. For example, the control switching unit 86 performs a valve operation to increase the opening degree of the valves V1 and V2 (hereinafter referred to as “control b”) in accordance with an increase in the pressure in the top of the waste melting furnace 2. The content of control by the control unit 85 is switched. At this time, the valve control unit 85 may increase the opening degree of the valves V <b> 1 and V <b> 2 by the increase amount calculated by the increase amount calculation unit 84. The control switching unit 86 performs valve control so that the control b is temporarily executed when the pressure evaluation value calculated by the pressure evaluation value calculation unit 83 exceeds a threshold (hereinafter referred to as “first threshold”). The control content of the unit 85 may be switched. The valve control unit 85 may interrupt the control a when executing the control b.

  The controller 80 may further include an upper limit setting unit 87 and a control gain setting unit 88. The upper limit value setting unit 87 lowers the upper limit values of the opening degrees of the valves V1, V2 as the temperature of the exhaust gas cooled in the cooling tower 40 decreases. For example, the upper limit value setting unit 87 decreases the upper limit value of the opening degree of the valves V1 and V2 as the temperature data acquired by the temperature data acquisition unit 81 decreases.

  As the temperature of the exhaust gas cooled in the cooling tower 40 becomes lower than the target temperature, the control gain setting unit 88 reduces the change in the spray amount of the cooling water according to the change in the temperature of the exhaust gas. For example, the control gain setting unit 88 reduces the proportional gain of the control a by the valve control unit 85 in response to the detection value acquired by the temperature data acquisition unit 81 being lower than the target temperature.

  The controller 80 may further include a combustion gas data acquisition unit 89 and a threshold value calculation unit 90. The combustion gas data acquisition unit 89 acquires detection values obtained by the flow sensors F1 and F2.

  The threshold calculation unit 90 sets the first threshold. The threshold value calculation unit 90 may increase the first threshold value as the amount of exhaust gas discharged from the waste melting furnace 2 increases. As described above, the amount of combustion gas supplied to the primary combustion gas receiving port 31a and the secondary combustion gas receiving port 31b is adjusted according to the amount of exhaust gas discharged from the gas discharge port 20b. For this reason, the detection values by the flow sensors F1 and F2 correlate with the outflow amount of the exhaust gas from the waste melting furnace 2. Therefore, the threshold value calculation unit 90 may increase the first threshold value as the detection values by the flow sensors F1 and F2 acquired by the combustion gas data acquisition unit 89 increase.

  As shown in FIG. 2, the controller 80 includes a circuit 100 having one or more processors 93, a memory 94, a storage 95 (storage medium), an input / output port 96, and an input unit 97. . The input / output port 96 acquires detection values from the pressure sensors B1 and B2, the temperature sensors T1 and T2, and the flow rate sensors F1 and F2, and outputs control signals to the valves V1 and V2 and the pumps P1 and P2. The input unit 97 is connected to the input / output port 96 and receives input from the operator. The input unit 97 includes, for example, an operation switch, a keyboard, a mouse, a touch panel, or the like. The input unit 97 may be connected to the input / output port 96 via a network line, for example.

  The storage 95 records a program for causing the gas cooling device 4 to execute a gas cooling method. The storage 95 may be anything that can be read by a computer. Specific examples include a hard disk, a nonvolatile semiconductor memory, a magnetic disk, and an optical disk. The memory 94 temporarily stores the program loaded from the storage 95, the calculation result of the processor 93, and the like. The processor 93 configures each functional module described above by executing a program in cooperation with the memory 94.

  Note that the hardware configuration of the controller 80 is not necessarily limited to the configuration of each functional module by a program. For example, each functional module of the controller 80 may be configured by a dedicated logic circuit or an ASIC (Application Specific Integrated Circuit) in which the logic modules are integrated.

[Gas cooling method]
Next, a gas cooling procedure executed by the gas cooling device 4 will be described as an example of the gas cooling method.

  As shown in FIG. 3, the controller 80 first executes step S01. In step S01, the temperature data acquisition unit 81 acquires the detection value by the temperature sensor T1 as the temperature of the exhaust gas cooled in the first cooling tower 41, and the temperature sensor T2 as the temperature of the exhaust gas cooled in the second cooling tower 42. Get the detection value by.

  Next, the controller 80 executes step S02. In step S02, the upper limit setting unit 87 sets the upper limit of the opening degree of the valves V1, V2. For example, the upper limit value setting unit 87 decreases the upper limit value of the opening degree of the valve V1 in accordance with a decrease in the value detected by the temperature sensor T1 (the temperature of the exhaust gas cooled in the first cooling tower 41). The upper limit value of the opening degree of the valve V2 is lowered in accordance with a decrease in the value detected by the sensor T2 (the temperature of the exhaust gas cooled in the second cooling tower 42). The upper limit value of the opening degree of the valves V1, V2 can be set by a preliminary experiment, simulation, or a combination thereof.

  FIG. 4 is a graph showing an example of setting an upper limit value of the opening degree of the valves V1, V2. The horizontal axis in FIG. 4 indicates the temperature of the exhaust gas cooled in the cooling tower 40, and the vertical axis indicates the upper limit value of the opening degree of the valves V1, V2. As shown in FIG. 4, the upper limit setting unit 87 may change the upper limits of the opening degrees of the valves V1, V2 in a stepped manner in accordance with the temperature of the exhaust gas.

  Next, the controller 80 executes step S03. In step S03, the control gain setting unit 88 sets the proportional gain of the control a. For example, the control gain setting unit 88 reduces the proportional gain of the control a by the valve control unit 85 in response to the detection value acquired by the temperature data acquisition unit 81 being lower than the target temperature. The value of the proportional gain according to the temperature of the exhaust gas can be set by preliminary experiment, simulation, or a combination thereof.

FIG. 5 is a graph showing an example of setting the proportional gain. The horizontal axis in FIG. 5 indicates the temperature of the exhaust gas cooled in the cooling tower 40, and the vertical axis indicates the proportional gain. In the example of FIG. 5, when the temperature of the exhaust gas is equal to or higher than Tθ2, the proportional gain is set to K2. When the temperature of the exhaust gas is equal to or lower than Tθ1 which is lower than Tθ2, the proportional gain is set to K1. The temperature Tθ2 is lower than the target temperature REF, and the proportional gain K1 is lower than the proportional gain K2. When the temperature of the exhaust gas is a value between the temperature Tθ2 and the temperature Tθ1, the proportional gain K is set by the following equation.
K = (K2−K1) / (Tθ2−Tθ1) × (T−Tθ1) + K1

  Next, the controller 80 executes step S04. In step S04, the valve control unit 85 adjusts the opening degrees of the valves V1 and V2 so that the detection values obtained by the temperature sensors T1 and T2 approach the target temperature. For example, the valve control unit 85 adjusts the opening degree of the valves V1 and V2 by PID control using the proportional gain set in step S03. At this time, the valve control unit 85 sets the opening degree of the valves V1, V2 to be equal to or less than the upper limit value set in step S03.

  Next, the controller 80 executes step S05. In step S05, the pressure data acquisition unit 82 acquires detection values by the pressure sensors B1 and B2 as pressure data in the waste melting furnace 2.

  Next, the controller 80 executes Step S06. In step S06, the combustion gas data acquisition unit 89 acquires detection values by the flow sensors F1 and F2 as data correlated with the outflow amount of the exhaust gas from the waste melting furnace 2.

Next, the controller 80 executes Step S07. In step S07, the pressure evaluation value calculation unit 83 calculates a pressure evaluation value. As an example, the pressure evaluation value calculation unit 83 calculates a pressure evaluation value based on the pressure in the furnace top of the waste melting furnace 2 and the in-furnace differential pressure. Specifically, the pressure evaluation value calculation unit 83 calculates the pressure evaluation value ΔPV by the following equation.
ΔPV = | current P1−previous P1 | + | (current P1−current P2) − (previous P1−previous P2) |
P1: Detection value by pressure sensor B1 P2: Detection value by pressure sensor B2

  Next, the controller 80 executes Step S08. In step S08, the threshold calculation unit 90 calculates the first threshold. The threshold value calculation unit 90 may increase the first threshold value as the amount of exhaust gas discharged from the waste melting furnace 2 increases. For example, the threshold value calculation unit 90 increases the first threshold value as the total value of the detection values obtained by the flow sensors F1 and F2 increases. The first threshold value corresponding to the outflow amount of the exhaust gas can be set by preliminary experiments, simulations, or a combination thereof.

  FIG. 6 is a graph showing an example of setting the first threshold value H. The horizontal axis in FIG. 6 indicates the total value (combustion gas supply amount) of the flow sensors F1 and F2, and the vertical axis indicates the first threshold value H. As shown in FIG. 6, the threshold value calculation unit 90 may change the first threshold value H in a stepped manner according to the supply amount of the combustion gas. The threshold calculation unit 90 may individually set the first threshold H for the first cooling tower 41 and the first threshold H for the second cooling tower 42. For example, the threshold value calculation unit 90 may make the first threshold value H for the first cooling tower 41 larger than the first threshold value H for the second cooling tower 42.

  Next, the controller 80 executes step S09. In step S09, the control switching unit 86 checks whether or not the pressure evaluation value ΔPV is equal to or less than the threshold value. When it is determined that the pressure evaluation value ΔPV is equal to or less than the threshold value, the controller 80 confirms whether or not a stop command is input by the operator (step S13). If no stop command is input, the controller 80 returns the process to step S01. Thereby, adjusting the opening degree of valve | bulb V1, V2 so that the detection value by temperature sensor T1, T2 approaches target temperature (the said control a) is performed continuously.

  When it determines with pressure evaluation value (DELTA) PV exceeding the threshold value in step S09, the controller 80 performs step S10-S12 before execution of step S13.

  In step S10, the increase amount calculation unit 84 calculates the increase amount ΔMV of the opening degree of the valves V1, V2. The increase amount calculation unit 84 may set the increase amount ΔMV larger as the pressure evaluation value ΔPV increases. The increase amount calculation unit 84 may individually set the increase amount ΔMV for the first cooling tower 41 and the increase amount ΔMV for the second cooling tower 42. For example, the threshold value calculation unit 90 may make the increase amount ΔMV for the first cooling tower 41 larger than the increase amount ΔMV for the second cooling tower 42. The value of the increase amount ΔMV corresponding to the outflow amount of the exhaust gas corresponding to the pressure evaluation value ΔPV can be set by preliminary experiment, simulation, or a combination thereof.

  FIG. 7 is a graph showing a setting example of the increase amount ΔMV. The horizontal axis in FIG. 7 indicates the pressure evaluation value ΔPV, and the vertical axis indicates the increase amount ΔMV. As shown in FIG. 7, the increase amount ΔMV may be changed stepwise according to the pressure evaluation value ΔPV.

  In steps S11 and S12, the control switching unit 86 switches the content of control by the valve control unit 85. For example, the control switching unit 86 switches the control content of the valve control unit 85 so as to temporarily increase the opening degree of the valves V1, V2 by the increase amount ΔMV calculated in step S10. Specifically, the control switching unit 86 switches the control content of the valve control unit 85 so that the opening degree of the valves V1, V2 is the opening degree obtained by adding the increase amount ΔMV to the previous opening degree (step S11). In that state, the passage of a predetermined time is waited (step S12). The predetermined time is preset by an actual machine test or simulation.

[Effect of this embodiment]
As described above, the gas cooling method according to the present embodiment is a method for cooling exhaust gas by spraying cooling water in the cooling tower 40 provided in the flow path of exhaust gas discharged from the waste melting furnace 2. (A) adjusting the spray amount of the cooling water so that the temperature of the exhaust gas cooled in the cooling tower 40 approaches the target temperature; (b) according to the increase in the pressure in the top of the waste melting furnace 2. Increasing the amount of cooling water spray.

  According to the gas cooling method according to the present embodiment, when the top pressure of the waste melting furnace 2 is stable, the cooling water is adjusted so that the temperature of the exhaust gas cooled in the cooling tower 40 approaches the target temperature. The spray amount is adjusted. Thereby, since the spray amount of cooling water is optimized according to the temperature of the exhaust gas on the downstream side of the cooling tower 40, the exhaust gas from the waste melting furnace 2 can be stably cooled. When the furnace top pressure rises, the amount of cooling water sprayed is increased accordingly. Since the top pressure tends to correlate with the outflow amount of the exhaust gas from the waste melting furnace 2, the increase in the outflow amount of the exhaust gas is increased by increasing the spray amount of the cooling water according to the increase in the top pressure. The amount of cooling water sprayed can be increased. Thereby, the spray amount of cooling water can be increased before the exhaust gas temperature on the downstream side of the cooling tower 40 rises according to the increase in the outflow amount of the exhaust gas. For this reason, even if it is a case where the outflow amount of the exhaust gas from the waste melting furnace 2 increases rapidly, the high temperature of the exhaust gas on the downstream side of the cooling tower 40 can be sufficiently suppressed. Therefore, the exhaust gas from the waste melting furnace 2 can be cooled more reliably.

  In said (b), when the pressure evaluation value correlated with the pressure rise in a furnace top part exceeds a threshold value, you may increase the spraying quantity of cooling water temporarily. If the spray amount of the cooling water is excessive, dust in the exhaust gas gets wet and accumulates in the cooling tower 40, which may make it difficult to operate the gas cooling device 4 continuously. In contrast, when the pressure evaluation value exceeds the threshold value to increase the cooling water spray amount in response to the rise in the furnace top pressure, the cooling water spray amount becomes excessive. Can be suppressed. Therefore, the exhaust gas from the waste melting furnace 2 can be cooled more reliably.

  In (b) above, the amount of increase in the amount of cooling water spray may be increased as the pressure evaluation value increases. As described above, the furnace top pressure tends to correlate with the outflow amount of the exhaust gas from the waste melting furnace 2. For this reason, by increasing the amount of increase in the amount of cooling water spray as the pressure evaluation value increases, the amount of cooling water spray increases as the amount of heat flowing into the cooling tower 40 along with the exhaust gas increases. The amount can be increased. Therefore, the exhaust gas from the waste melting furnace 2 can be cooled more reliably.

  In the above (b), the threshold value may be increased as the amount of exhaust gas flowing out from the waste melting furnace 2 increases. In a state where the amount of exhaust gas flowing out from the waste melting furnace 2 is large, the amount of heat flowing into the cooling tower 40 is large, so the amount of cooling water sprayed is also large (first state). On the other hand, in a state where the outflow amount of exhaust gas from the waste melting furnace 2 is small, the amount of heat flowing into the cooling tower 40 is small, so the spray amount of cooling water is also small (second state). That is, in the first state, there is more cooling water in the cooling tower 40 than in the second state. For this reason, when the outflow amount of the exhaust gas increases in the first state, the temperature of the exhaust gas on the downstream side of the cooling tower 40 tends not to rise as compared with the case where the outflow amount of the exhaust gas increases in the second state. On the other hand, if the threshold value is increased as the amount of exhaust gas discharged from the waste melting furnace 2 increases, the starting condition of (b) is narrower in the first state than in the second state. Thereby, in the 1st state, it is suppressed that the spraying quantity of cooling water becomes excessive. In the second state, it is suppressed that the amount of cooling water sprayed becomes too small. Therefore, the exhaust gas from the waste melting furnace 2 can be cooled more reliably.

  In the above (b), the pressure evaluation value may be calculated based on at least one of the pressure in the furnace top and the in-furnace differential pressure of the waste melting furnace 2. In this case, the furnace top pressure can be accurately evaluated.

  In the above (a), the change in the spray amount of the cooling water according to the change in the temperature of the exhaust gas may be made smaller as the temperature of the exhaust gas becomes lower than the target temperature. Due to the increase in the amount of cooling water sprayed, the temperature of the exhaust gas greatly decreases after the execution of the above (b), and there is a case where the temperature is greatly deviated to the minus side with respect to the target temperature (third state). When the third state occurs due to the execution of (b), the spray amount of the cooling water is greatly reduced in the subsequent (a). If the spray amount of the cooling water is greatly changed in the above (a), a state (hunting) in which the exhaust gas temperature repeats excessively on the plus side and the minus side with respect to the target temperature is likely to occur. On the other hand, if the change in the spray amount of the cooling water according to the change in the temperature of the exhaust gas is made smaller as the temperature of the exhaust gas becomes lower than the target temperature, the above (a) after the third state has occurred. , The change width of the spray amount of the cooling water is reduced. For this reason, generation | occurrence | production of the said hunting is suppressed. Therefore, the exhaust gas from the waste melting furnace 2 can be cooled more reliably.

  In (a) and (b) above, the spray amount of the cooling water is adjusted by the opening degree of the valves V1, V2 provided in the cooling water supply pipes L1, L2 (supply pipes), and the temperature of the exhaust gas is adjusted. The upper limit value of the opening degree of the valves V1 and V2 may be lowered as it becomes lower. Also in this case, the occurrence of the hunting is more reliably suppressed. Therefore, the exhaust gas from the waste melting furnace 2 can be cooled more reliably.

  During the execution of (b), (a) may be interrupted. With this configuration, the control content can be simplified. Note that (a) may be continued during the execution of (b).

  The cooling tower 40 may be connected to the waste melting furnace 2 without using a heat exchanger. In this case, when the outflow amount of the exhaust gas from the waste melting furnace increases rapidly, the accompanying increase in the amount of heat is not absorbed or alleviated in the heat exchanger. For this reason, in order to sufficiently suppress the high temperature of the exhaust gas, it is important to more reliably perform the cooling in the cooling tower 40. Therefore, the above-described action of sufficiently suppressing the high temperature of the exhaust gas on the downstream side of the cooling tower is further beneficial.

  Although the embodiment has been described above, the present invention is not necessarily limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, the gas cooling device 4 adjusts the spray amount of the cooling water sprayed in the cooling tower by adjusting the pressure of the pump provided in the cooling water supply pipe (pressure for pumping the cooling water). Also good.

  Further, the number of pressure sensors for measuring the pressure in the waste melting furnace 2 is not limited to two. For example, instead of the pressure sensor B2, pressure sensors may be arranged at the upper part, middle part, and lower part of the waste melting furnace 2, respectively.

[Example 1]
The waste melting equipment 1 was used to cool the exhaust gas by the above-described gas cooling procedure, and the opening degrees of the valves V1, V2 and the detected values of the temperature sensors T1, T2 were recorded.

[Comparative Example 1]
The waste melting equipment 1 was used to cool the exhaust gas by the gas cooling procedure in which the steps S10 to S12 were omitted, and the opening degrees of the valves V1 and V2 and the detected values of the temperature sensors T1 and T2 were recorded.

[Comparison results of Examples and Comparative Examples]
FIG. 8 is a graph showing the recording results of the opening degrees of the valves V1, V2 and the detected values of the temperature sensors T1, T2 in the first embodiment. FIG. 9 is a graph showing the recording results of the opening degrees of the valves V1, V2 and the detected values of the temperature sensors T1, T2 in Comparative Example 1. The horizontal axis of each graph is the elapsed time, which is the relative value of the opening degree of the valves V1, V2 and the magnitude of the detection values of the temperature sensors T1, T2. Time t0 in the figure is the time when the pressure evaluation value ΔPV exceeds the first threshold value H. Time t1 is 10 seconds after time t0. A broken line Ws1 is the opening degree of the valve V1, and a broken line Ws2 is the opening degree of the valve V2. A broken line Ts1 is a detection value of the temperature sensor T1, and a broken line Ts2 is a detection value of the temperature sensor T2.

  As shown in FIGS. 8 and 9, according to the first embodiment, the opening degree of the valves V <b> 1 and V <b> 2 is increased more quickly than after the time t <b> 0 compared to the first comparative example. For example, in FIG. 8, the opening degree of the valves V1 and V2 starts to increase immediately after the time t0, and reaches the upper limit at an elapsed time that is less than half of the elapsed time from the time t0 to the time t1. On the other hand, in FIG. 9, the opening degree of the valve V <b> 2 rises more slowly than in FIG. 8 and continues to rise after time t <b> 1. Further, a large increase in the opening degree was not confirmed for the valve V1. For this reason, according to Example 1, compared with the comparative example 1, the detected values of the temperature sensors T1 and T2 are kept low. For example, in FIG. 8, the detection value of the temperature sensor T2 does not exceed the reference value Tx, but in FIG. 9, the detection value of the temperature sensor T2 exceeds the reference value Tx. From the above results, it was confirmed that according to the above embodiment, the exhaust gas from the waste melting furnace 2 can be cooled more reliably.

  2 ... waste melting furnace, 4 ... gas cooling device, 41 ... first cooling tower (cooling tower), 42 ... second cooling tower (cooling tower), 80 ... controller.

Claims (10)

A method of cooling the exhaust gas by spraying cooling water in a cooling tower provided in a flow path of exhaust gas discharged from a waste melting furnace,
(A) adjusting the spray amount of the cooling water so that the temperature of the exhaust gas cooled in the cooling tower approaches the target temperature;
(B) A gas cooling method including increasing the spray amount of the cooling water in response to an increase in pressure in the top of the waste melting furnace.   2. The gas cooling method according to claim 1, wherein, in (b), when the pressure evaluation value correlated with the pressure rise in the furnace top exceeds a threshold value, the spray amount of the cooling water is temporarily increased.   3. The gas cooling method according to claim 2, wherein in (b), the amount of increase in the amount of spray of the cooling water is increased as the pressure evaluation value increases.   4. The gas cooling method according to claim 2, wherein, in (b), the threshold value is increased in accordance with an increase in the outflow amount of the exhaust gas from the waste melting furnace.   5. The gas according to claim 2, wherein, in (b), the pressure evaluation value is calculated based on at least one of a pressure in the furnace top portion and an in-furnace differential pressure of the waste melting furnace. Cooling method.   In (a), as the temperature of the exhaust gas becomes lower than the target temperature, the change in the spray amount of the cooling water according to the change in the temperature of the exhaust gas is reduced. The gas cooling method according to any one of claims.   In (a) and (b), the spray amount of the cooling water is adjusted by the opening degree of the valve provided in the cooling water supply pipe, and the temperature of the exhaust gas is lowered. The gas cooling method according to any one of claims 2 to 6, wherein an upper limit value of the degree of opening is lowered.   The gas cooling method according to any one of claims 2 to 7, wherein (a) is interrupted during the execution of (b). A cooling tower for cooling the exhaust gas by spraying cooling water, provided in a flow path of the exhaust gas discharged from the waste melting furnace;
Controlling the spray amount of the cooling water so as to bring the temperature of the exhaust gas cooled in the cooling tower close to a target temperature, and according to an increase in pressure in the top of the waste melting furnace A controller configured to perform control to increase the spray amount of the cooling water.   The gas cooling apparatus according to claim 1, wherein the cooling tower is connected to a waste melting furnace without a heat exchanger.

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