JP5767486B2 - Heat recovery plant and operation control method thereof - Google Patents

Description

  The present invention relates to a heat recovery plant (heat recovery facility) including a combustion furnace and a boiler that recovers heat generated in the combustion furnace. More specifically, the present invention relates to a technique for suppressing corrosion of metal components such as a boiler water pipe, an evaporator pipe, and a superheater pipe in a heat recovery plant.

  A heat recovery plant is a facility that generally includes a combustion furnace and a boiler, burns fuel, and generates high-temperature and high-pressure steam by the generated combustion heat and heat of exhaust gas. Steam generated in the boiler of the heat recovery plant is sent to a superheater or a steam turbine to be used for power generation, power, heating, or the like. Fuels for heat recovery plants include biomass (wood, seaweed, garbage, etc.), asphalt, and black liquor generated in the papermaking process, in addition to conventionally known coal and oil. The heat recovery plant has different forms depending on the fuel, and there are, for example, what are called coal boilers, waste incinerators, soda recovery boilers, and the like.

  Among heat recovery plants, especially in waste incineration plant boilers that use general waste as fuel, soda recovery boilers that use black liquor as fuel, and coal boilers that use coal as fuel, it is included in the ash generated when fuel is burned Corrosive components cause significant corrosion of metal components such as water tubes and superheater tubes that make up the boiler. Among these, in the waste incineration plant, the composition of general waste as fuel is miscellaneous and its properties fluctuate greatly. Therefore, the properties of the flue gas flowing into the boiler from the combustion furnace fluctuate. The corrosive environment inside changes. Therefore, a technique for indirectly detecting a corrosive environment in a boiler by detecting corrosion of metal parts of the boiler using an electrochemical measurement method in a waste incinerator has been proposed.

  The waste incinerator described in Patent Document 1 is an incinerator that burns garbage, a boiler that is located at the top of the incinerator and that recovers the heat of the flue gas flowing in from the incinerator, a corrosion detector, and a control Device. This corrosion detector is installed in an exhaust gas passage in the boiler, and detects a corrosive environment of the boiler by a change in electrical resistance between a pair of electrodes. The control device then operates the incinerator to reduce the severity of the corrosive environment based on the information from the corrosion detector (ie, the combustion air flow rate, the amount of water spray in the furnace, the dust feed rate, the grate feed rate) And at least one of the boiler inflow water amount and the boiler evaporation amount). As an example of specific control of the control device, when the corrosion signal exceeds a certain limit value, the furnace cooling air amount is increased to lower the exhaust gas temperature, the grate speed is reduced and the combustion air amount is reduced. It is described that the generation of molten salt is suppressed and the severity of the corrosive environment is reduced by reducing the amount of heat generated in the incinerator.

JP 2002-106822 A

  In the above-mentioned patent document 1, in order to reduce the severity of the corrosive environment, it is described that the exhaust gas temperature is lowered or the heat generation amount of the incinerator is reduced. In a waste incinerator that is a kind of heat recovery plant, the factors that corrode the metal components of the boiler vary depending on the type of incinerator, the type of garbage, and the operating conditions. Therefore, since the corrosive environment of the boiler is severe, reducing the exhaust gas temperature unnecessarily or reducing the heat generation amount of the incinerator may lower the processing efficiency more than necessary. In addition, an appropriate amount of waste must be maintained, and the amount of waste cannot be reduced unnecessarily. In other words, it is desirable from the viewpoint of maintaining high efficiency of the incinerator and saving energy to take appropriate measures in accordance with factors that have severely affected the corrosive environment of the boiler.

  Therefore, in the present invention, in a heat recovery plant equipped with a combustion furnace and a boiler, the corrosive environment in the boiler is monitored, and when the corrosive environment becomes severe, the factor is estimated and appropriate measures are taken. It aims at providing the technology which relieves the corrosive environment in a boiler.

  The heat recovery plant according to the present invention includes a combustion furnace for burning fuel, a boiler for recovering heat of combustion exhaust gas flowing from the combustion furnace, and an electric resistance between a pair of electrodes installed in an exhaust gas passage in the boiler. Corrosion detection means for detecting corrosion of metal parts of the boiler based on the change of the boiler, and monitoring the corrosion environment of the boiler based on information from the corrosion detection means, and detecting that the corrosion environment has become severe Corrosion environment monitoring means, and when the corrosive environment of the boiler becomes harsh, of the processing amount of the combustion furnace, the supply amount of combustion air to the combustion furnace, the amount of steam generated in the boiler, and the calorific value of fuel Based on at least one, the factors that caused the corrosive environment to become severe are estimated, and a policy determination means that determines measures to mitigate the corrosive environment based on the estimated factors, and In which and a driving control means for controlling the operation of the combustion furnace so as to mitigate environmental.

  Similarly, an operation control method for a heat recovery plant according to the present invention is an operation control method for a heat recovery plant including a combustion furnace for burning fuel and a boiler for recovering heat of combustion exhaust gas flowing from the combustion furnace. A corrosion detection step for detecting corrosion of metal parts of the boiler based on a change in electrical resistance between a pair of electrodes installed in the exhaust gas passage in the boiler, and information obtained in the corrosion detection step. A corrosion environment monitoring step for monitoring the corrosive environment of the boiler based on the detected corrosion environment, and detecting the amount of combustion in the combustion furnace when the corrosive environment of the boiler becomes severe, the combustion Based on at least one of the supply amount of combustion air to the furnace, the amount of steam generated in the boiler, and the calorific value of the fuel, a factor causing the harsh corrosion environment is estimated, and based on the estimated factor. A strategy determining step of determining a measures to mitigate corrosion environment Te, is intended to include the operation control step of controlling the operation of the combustion furnace so as to alleviate the corrosive environment based on the determined measure.

  According to the heat recovery plant and the operation control method thereof, the corrosive environment in the boiler is monitored based on the corrosion of the metal parts in the boiler that is constantly detected, and when the corrosive environment becomes severe, the factor is estimated, A strategy for mitigating the corrosive environment is determined based on the estimated factors. Therefore, it is possible to take an appropriate measure to alleviate the corrosive environment, and thereby it is possible to efficiently suppress the corrosion thinning of the boiler. Since no extra operation is performed in order to alleviate the corrosive environment, the amount of processing and efficiency are not reduced more than necessary, which can contribute to energy saving.

  In the heat recovery plant, the pair of electrodes of the corrosion detection means is disposed upstream of the boiler metal parts in the exhaust gas passage, and the corrosion detection means cools the pair of electrodes. It is preferable that a cooling mechanism for setting the pair of electrodes to the same temperature as the surface temperature of the metal component is provided. Similarly, in the operation control method of the heat recovery plant, in the corrosion detection step, the pair of electrodes are arranged on the upstream side of the boiler metal parts in the exhaust gas passage, and the pair of electrodes is the metal It is preferable to maintain the same temperature as the surface temperature of the component.

  According to the heat recovery plant and the operation control method thereof, when the corrosion of the metal parts of the boiler is indirectly detected by the pair of electrodes, the pair of electrodes are placed in an environment closer to the metal parts of the boiler. Corrosion of parts can be detected with higher accuracy.

  In the heat recovery plant, the corrosion detection means may include one or a plurality of dummy tubes disposed around the pair of electrodes. Similarly, in the operation control method of the heat recovery plant, in the corrosion detection step, one or a plurality of dummy tubes may be disposed around the pair of electrodes.

  According to the above heat recovery plant and its operation control method, the presence of the dummy tube causes the pair of electrodes to be placed in a fluid environment closer to the fluid environment in which the boiler metal parts are placed. Can be detected with higher accuracy.

  In the heat recovery plant, the corrosion environment monitoring means detects that the corrosion environment has become severe when the corrosion rate included in the information from the corrosion detection means continues to exceed a certain threshold. It may be constituted as follows. Similarly, in the operation control method of the heat recovery plant, the corrosion environment becomes severe when the corrosion rate of the metal parts of the boiler continues to exceed a threshold value in the corrosion environment monitoring step. May be detected.

  In the heat recovery plant, the policy determining means may include one or more of an increase / decrease in the processing amount of the combustion furnace, an increase / decrease in the supply amount of combustion air to the combustion furnace, and an increase / decrease in the processing speed of the combustion furnace. The combination may be configured to be determined as a strategy. Similarly, in the operation control method of the heat recovery plant, in the policy determination step, among the increase / decrease in the processing amount of the combustion furnace, the increase / decrease in the supply amount of combustion air to the combustion furnace, and the increase / decrease in the processing speed of the combustion furnace One or more combinations may be determined as a strategy.

  Alternatively, the heat recovery plant further includes a pit for storing fuel to be input to the combustion furnace, and a stirring unit for stirring the pit, and the policy determining unit is configured to increase / decrease the processing amount of the combustion furnace, the combustion One or more combinations of increase / decrease in the amount of combustion air supplied to the furnace, increase / decrease in the processing speed of the combustion furnace, and increase in the stirring frequency of the pits may be determined as a strategy. Similarly, in the operation control method of the heat recovery plant, the heat recovery plant further includes a pit for storing fuel to be input to the combustion furnace, and a stirring means for stirring the pit, and in the policy determination step, One of an increase / decrease in the processing amount of the combustion furnace, an increase / decrease in the supply amount of combustion air to the combustion furnace, an increase / decrease in the processing speed of the combustion furnace, and an increase in the agitation frequency of the pit for storing fuel to be input to the combustion furnace Alternatively, a plurality of combinations may be determined as a strategy.

  In the heat recovery plant, the policy determining means determines whether the corrosive environment is based on a change in the processing amount, a change in the steam amount, and an air ratio calculated based on the combustion air supply amount and the calorific value. Severe factors may be estimated. Similarly, in the operation control method of the heat recovery plant, in the policy determination step, a change in the processing amount, a change in the steam amount, and an air ratio calculated based on the combustion air supply amount and the heat generation amount, Based on the above, the factor that the corrosive environment becomes severe may be estimated.

  According to the present invention, the corrosive environment in the boiler is monitored based on the constantly detected corrosion of the metal parts in the boiler, and when the corrosive environment becomes severe, the factor is estimated, and based on the estimated factor Measures to mitigate the corrosive environment are determined. Therefore, it is possible to take an appropriate measure to alleviate the corrosive environment, and thereby it is possible to efficiently suppress the corrosion thinning of the boiler.

It is the schematic which shows the whole structure of the waste incinerator which concerns on one Embodiment of the heat recovery plant of this invention. It is a figure which shows typically the structure of a corrosion detection apparatus. It is a figure which shows arrangement | positioning of the superheater pipe | tube and corrosion sensor in a boiler. It is a figure which shows arrangement | positioning of the superheater pipe | tube in a boiler, a corrosion sensor, and a dummy pipe | tube. It is a block diagram which shows the control structure which concerns on the corrosive environment monitoring of a garbage incinerator. It is a flowchart which shows the flow of the corrosion environment monitoring process by a corrosion environment monitoring part. It is a flowchart which shows the flow of the front | former stage of the process which determines the policy for relieving the corrosive environment by a policy determination part. It is a flowchart which shows the flow of the back | latter stage of the process which determines the policy for relieving the corrosive environment by a policy determination part.

  Below, the case where the heat recovery plant which concerns on this invention is applied to the refuse incinerator as the example is demonstrated.

(Garbage incinerator 10)
As shown in FIG. 1, a waste incinerator 10 is a so-called stoker-type combustion furnace 11 that combusts garbage as fuel, and high-temperature and high-pressure steam by combustion heat generated in the combustion furnace 11 and retained heat of combustion exhaust gas. A boiler 19 to be generated is integrally provided. The waste incinerator 10 includes a steam turbine 71 and a generator 70 for generating power using waste heat of the waste incinerator 10 and a pit 60 in which waste to be input to the waste incinerator 10 is stored. It is installed. The pit 60 is provided with a crane 61 and its control device 62 for agitating the dust stored in the pit 60 and supplying it to the incinerator 10.

  The combustion furnace 11 of the garbage incinerator 10 is provided with a main combustion chamber 14 whose inner wall is made of a refractory. A hopper 12 and a chute 13 are provided on the upstream side of the main combustion chamber 14 in the conveyance direction (left side of FIG. 1, hereinafter, simply referred to as “upstream side”). Garbage charged from the hopper 12 is supplied to the main combustion chamber 14 through the chute 13. At the bottom of the main combustion chamber 14 and in the vicinity of the dropping position of the waste introduced from the hopper 12, a feeder for sending the waste to the downstream side in the conveying direction (right side of the paper in FIG. 1, hereinafter, simply referred to as "downstream side"). 41 is provided. The feeder 41 is an extruding member that pushes dust and moves it downstream, and includes a feeder drive device 42 that moves the feeder 41 from the upstream side to the downstream side. For example, a hydraulic cylinder or the like can be used as the feeder driving device 42. By changing the moving speed or moving amount of the feeder 41 by the feeder driving device 42, it is possible to adjust the amount of waste sent to the stalker 15 (that is, the waste processing amount V).

  A stoker 15 (grate) is laid at the bottom of the main combustion chamber 14 and downstream of the feeder 41. Further, an exhaust chute 18 is provided on the bottom surface of the main combustion chamber 14 and downstream of the stoker 15. The stoker 15 is provided with a dry stoker 15a that dries garbage, a combustion stoker 15b that burns garbage, and a post-combustion stoker 15c that burns unburned matter in ash in order from the upstream side. The stalker 15 includes a stalker driving device 16 that reciprocates the stalker 15 between the upstream side and the downstream side. As the stalker driving device 16, for example, a hydraulic cylinder or the like can be used. By the reciprocating motion of the stalker 15, the dust on the stalker 15 moves from the upstream side to the downstream side. Further, by changing the reciprocating speed of the stalker 15 by the stalker driving device 16, the moving speed of the trash on the stalker 15 (that is, the processing speed of trash) and the combustion position of the trash can be adjusted.

  Primary combustion air (hereinafter, simply referred to as “primary air”) is sent from below the stalker 15 to the main combustion chamber 14 through the stalker 15. For this purpose, a primary air supply path 65 for supplying primary air to the main combustion chamber 14 opens below the stoker 15. The primary air supply path 65 is provided with a blower 66 for supplying primary air, a flow rate control valve 67 for controlling the flow rate of primary air, and a flow meter 68 for detecting the flow rate of primary air. Further, secondary combustion air (hereinafter referred to as “secondary air”) is sent from the upstream ceiling 14 a and the downstream ceiling 14 b of the main combustion chamber 14. For this purpose, in the main combustion chamber 14, secondary air is supplied to the upstream ceiling 14a located above the dry stoker 15a and the combustion stoker 15b and to the downstream ceiling 14b located above the rear combustion stoker 15c. The secondary air supply path 75 for opening is opened. The secondary air supply path 75 is provided with a blower 76 that feeds secondary air, a flow rate control valve 77 that controls the flow rate of the secondary air, and a flow meter 78 that detects the flow rate of the secondary air. Yes.

  A boiler 19 is provided on the downstream side of the combustion exhaust gas generated in the main combustion chamber 14. The upper part of the rear combustion stoker 15 c and the discharge chute 18 of the main combustion chamber 14 communicates with the radiation chamber 20 of the boiler 19. In the boiler 19, an exhaust gas flow path including chambers of the radiation chamber 20, the second flue 21, and the third flue 22 is formed in order from the upstream side to the downstream side in the conveyance direction of the combustion exhaust gas. In the radiation chamber 20, an exhaust gas flow path is formed from below to above. In the second flue 21, an exhaust gas flow path from the upper side to the lower side is formed. In the third flue 22, an exhaust gas flow channel is formed from below to above. An exhaust port 29 connected to the exhaust passage 28 is provided at the upper end of the third flue 22. The exhaust passage 28 is provided with an exhaust gas treatment facility for detoxifying the exhaust gas. The exhaust gas treatment facility includes a bag filter 81, a reheater 82, an exhaust gas treatment device 83, an induction fan 84, and the like. The combustion exhaust gas in the boiler 19 and the exhaust gas discharged from the boiler 19 to the exhaust passage 28 are released to the atmosphere through the chimney by the operation of the induction blower 84.

  A plurality of water pipes 23 are provided on the wall portion defining the radiation chamber 20 and the second flue 21 of the boiler 19. These water tubes 23 are made of carbon steel. The water pipe 23 is connected to a boiler drum 24 provided in the upper part of the third flue 22, and waste heat recovery water sent from the boiler drum 24 flows in the water pipe 23. The upper part of the boiler drum 24 is connected to the superheater 25, and steam is sent from the boiler drum 24 to the superheater 25. The amount of steam sent from the boiler drum 24 to the superheater 25 (that is, the main steam amount F) is measured by a steam flow meter 39 provided on the downstream side of the superheater 25. The superheater 25 includes a superheater tube 27 that recovers heat from the combustion exhaust gas in the third flue 22 and further superheats the steam sent from the boiler drum 24 to a high temperature and high pressure. The superheater tube 27 is made of stainless steel. The superheater pipe 27 is circulated in the third flue 22, and the end thereof is connected to a steam turbine 71 that drives the generator 70.

  Next, the flow of the waste treatment by the waste incinerator 10 having the above configuration will be described. Garbage thrown into the hopper 12 by the crane 61 provided in the pit 60 is supplied into the main combustion chamber 14 of the combustion furnace 11 through the chute 13. Garbage supplied to the main combustion chamber 14 is sent onto the dry stoker 15 a by the feeder 41. Garbage on the dry stoker 15a is dried by the primary air and the radiant heat of the main combustion chamber 14, and eventually ignites. The ignited garbage is sent to the combustion stoker 15b. Combustible gas is generated from the ignited garbage by pyrolysis. This combustible gas rides on the primary air and moves to the gas layer above the main combustion chamber 14, and flame burns with the secondary air in this gas layer. Due to the heat radiation accompanying this flame combustion, the temperature of the garbage further increases. A part of the ignited garbage burns on the combustion stoker 15b, and the remaining unburned portion is sent to the post-combustion stoker 15c. The unburned waste is burned on the post-combustion stoker 15c, and the incineration ash remaining after the combustion is further sent to the downstream side and discharged from the discharge chute 18 to treat the incineration ash (not shown). ).

  Combustion exhaust gas generated by the combustion of garbage in the main combustion chamber 14 flows from the main combustion chamber 14 into the boiler 19. The combustion exhaust gas flowing into the boiler 19 moves to the third flue 22 through the radiation chamber 20 and the second flue 21, and is discharged from here through the exhaust port 29 to the exhaust passage 28. The exhaust gas discharged from the boiler 19 is rendered harmless through each exhaust gas treatment facility provided in the exhaust passage 28 and released to the atmosphere. The waste heat recovery water flowing in the water pipe 23 of the boiler 19 recovers the waste heat of the radiation chamber 20 or the second flue 21 and returns to the boiler drum 24 in a state where part of the waste heat is vaporized to become steam. Part of the waste heat recovery water that has returned to the boiler drum 24 that has become steam is sent from the boiler drum 24 to the superheater pipe 27 of the superheater 25 and is superheated. The steam that has become higher temperature and pressure in the superheater 25 is sent to the steam turbine 71 to drive the generator 70.

  In the above-described waste treatment flow by the waste incinerator 10, a part of the volatile components and incineration ash generated in the main combustion chamber 14 are accompanied by the combustion exhaust gas, and the radiation chamber 20 of the boiler 19 communicated with the main combustion chamber 14. To the second flue 21 and the third flue 22. A part of the accompanying volatile components and incineration ash adheres to and accumulates on the water pipe 23 and the superheater pipe 27. The attached ash has high corrosivity and corrodes the water pipe 23 and the superheater pipe 27. Therefore, the refuse incinerator 10 includes a corrosion detection device 30 for detecting the corrosion state of at least one of the water pipe 23 and the superheater pipe 27. The refuse incinerator 10 according to this embodiment includes a corrosion detection device 30 for detecting the corrosion state of the superheater tube 27. The corrosion detection device 30 is configured to detect the metal parts of the boiler 19 (here, the superheater tube 27) based on a change in electrical resistance between a pair of electrodes (the sample electrode 45 and the counter electrode 47) installed in the exhaust gas passage in the boiler 19. It is configured to detect corrosion.

(Corrosion detection device 30)
FIG. 2 is a schematic configuration diagram schematically showing the configuration of the corrosion detection device 30. As shown in FIG. 2, the corrosion detection device 30 includes a corrosion sensor 31, an electrochemical measurement device 32, a terminal device 33, a blower 34, a flow rate regulator 35, and a valve 36. The blower 34 and the flow rate regulator 35 constitute a cooling mechanism 37 that cools the electrodes.

The corrosion sensor 31 includes a long cylindrical protective tube 40 made of stainless steel. The protective tube 40 is formed with a cooling passage 40a for flowing cooling air through its inner wall. One end of the sample electrode 45, the reference electrode 46, and the counter electrode 47, which are detection units, is exposed in the boiler 19 on the peripheral surface on the distal end side of the protective tube 40. These electrodes are embedded in the protective tube 40 via a sleeve made of an insulating material such as a ceramic material. The corrosion sensor 31 is inserted into the wall 19 a of the boiler 19, and the tip detection part is located in the boiler 19. It is desirable that the insertion depth D of the protective tube 40 be adjustable. In the corrosion sensor 31 according to the present embodiment, in order to detect corrosion of the superheater tube 27, the detection part of the corrosion sensor 31 is in the third flue 22 and is upstream of the superheater tube 27 in the transport direction of the exhaust gas. Is located. As shown in FIG. 3, the protective tube 40 is preferably arranged so that the interval between the superheater tube 27 and the protective tube 40 and the interval between the superheater tubes 27 are each W ₁ . In other words, the protective tube 40 is arranged so that the interval between the superheater tube 27 and the protective tube 40 is equal to the interval between the superheater tubes 27. More desirably, as shown in FIG. 4, one or a plurality of dummy tubes 38 (pseudo tubes) are arranged around the protective tube 40. The dummy tube 38 is for placing the protective tube 40 in an exhaust gas flow environment similar to the superheater tube 27. Therefore, the dummy pipe 38 has the same outer diameter as the superheater tubes 27, and are arranged at the same interval as superheater tubes 27 distance between (W _1, W ₂₎ from the dummy tube 38 and protective tube 40 It is desirable. Further, the dummy tube 38 may be provided with a cooling mechanism (not shown) for bringing the dummy tube 38 to a temperature close to that of the superheater tube 27.

  The sample electrode 45 is a rod-shaped member made of the same material as the target member whose corrosion state is to be detected. The sample electrode 45 according to the present embodiment is made of the same stainless steel or carbon steel as the superheater tube 27. A sample electrode lead wire 51 made of platinum and a sample electrode thermocouple 53 are connected to the sample electrode 45 in the protective tube 40. In addition to the sample electrode thermocouple 53, the protection tube 40 detects the temperature of the gas around the protection tube 40 and the protection tube thermocouple 56 for detecting the temperature of the tip of the protection tube 40. And a thermocouple 57 for gas temperature.

  The reference electrode 46 is provided with a dome-shaped mullite-made Tamman tube 46a, and the Tamman tube 46a is filled with an electrolyte serving as a solvent (a mixture of NaCl, KCl, etc., in a 1/10 molar ratio of AgCl), and the Tamman tube 46a. Is closed by a lid 46b. Further, a spiral silver wire 46c is enclosed in the Tamman tube 46a, and the silver wire 46c is electrically connected to a reference electrode lead wire 54 made of platinum through a through hole formed in the lid 46b. Has been.

  The counter electrode 47 is a rod-shaped member made of platinum. A counter electrode lead wire 55 made of platinum in the protective tube 40 is electrically connected to the counter electrode 47.

  The lead wires 51, 54, 55 connected to the electrodes 45, 46, 47 are led out of the base end portion of the protective tube 40 located outside the boiler 19 through the protective tube 40, and subjected to electrochemical measurement. It is electrically connected to the device 32. Similarly, the sample electrode thermocouple 53, the protective tube thermocouple 56, and the gas temperature thermocouple 57 are drawn out to the outside of the base end portion of the protective tube 40 through the protective tube 40, and are electrically connected to the flow rate regulator 35. It is connected to the. Further, a blower 34 for sending cooling air to the cooling passage 40 a in the protective tube 40 is connected to the proximal end portion of the protective tube 40.

  The blower 34 is provided with a flow rate regulator 35 for controlling the flow rate from the blower 34. A valve 36 for adjusting the amount of air is provided between the blower 34 and the cooling passage 40a. As described above, the flow rate regulator 35 is connected to the thermocouple 53, and the valve 36 is opened so that the temperature of the sample electrode 45 becomes equal to a predetermined temperature in accordance with the output from the thermocouple 53. And the flow rate of the cooling air from the blower 34 is controlled. In the present embodiment, the temperature of the sample electrode 45 is controlled to be equal to the temperature of the gas around the corrosion sensor 31 detected by the gas temperature thermocouple 57, that is, the temperature of the superheater tube 27. As a result, the environment in which the sample electrode 45 is placed and the environment in which the superheater tube is placed can be brought into the same state, so that the corrosion state of the superheater tube 27 can be estimated more accurately.

  The electrochemical measuring device 32 is a device that measures the corrosion rate of the sample electrode 45 by a known electrochemical impedance method. Specifically, the electrochemical measuring instrument 32 detects a current flowing through the reference electrode for each frequency by causing a weak AC signal of various frequencies to flow through the sample electrode 45 and the counter electrode 47 using a frequency response analyzer. The frequency response characteristic of the impedance with the reference electrode 46 is obtained. The frequency response characteristics of this impedance converge on the low frequency side (f-0) and the high frequency side (f + ∞), and the difference between these convergence values corresponds to the polarization resistance (impedance) at the interface of the sample electrode 45. The electrochemical measuring instrument 32 obtains the polarization resistance (impedance) at the interface of the sample electrode 45 from the frequency response characteristic of the impedance described above based on the relationship as described above.

  Further, the corrosion rate and the polarization resistance at the interface of the sample electrode 45 have a correlation that the corrosion rate decreases depending on the reciprocal of the polarization resistance. In the terminal device 33, the correlation between the polarization resistance of the member made of the same material as the sample electrode 45 and the corrosion rate obtained in advance is stored in advance, and this correlation and the polarization resistance obtained by the electrochemical measuring device 32 are stored. Based on the above, the corrosion rate of the sample electrode 45 is calculated. The terminal device 33 accumulates the calculated corrosion rates and integrates the accumulated corrosion rates to detect the corrosion amount of the sample electrode 45. By detecting the corrosion rate and corrosion amount of the sample electrode 45 in this way, the corrosion rate and corrosion amount of the superheater tube 27 can be estimated. The corrosion rate and the corrosion amount of the superheater tube 27 estimated using the corrosion sensor 31 as described above are transmitted from the terminal device 33 of the corrosion detection device 30 to the central control device 100.

(Central control device 100)
The operation of the garbage incinerator 10 having the above configuration is controlled by the central controller 100. FIG. 5 is a block diagram showing a control configuration for monitoring the corrosive environment of the waste incinerator. In FIG. 5, a configuration for monitoring a corrosive environment of the boiler 19 to be described later and determining a measure for mitigating the corrosive environment is described in detail, and the others are omitted. As shown in FIG. 5, the central control device 100 includes an operation control unit 101 that controls the operation of the waste incinerator 10, functional units of a corrosive environment monitoring unit 102 and a policy determining unit 103 described later, and a database 105. ing. The central control device 100 is a so-called computer, and can have functions as the above-described functional units by executing a predetermined program. In the central control device 100, in order to always keep track of the status of the main combustion chamber 14, the boiler 19, the pit 60, the generator 70, etc. of the operating combustion furnace 11, various operations are performed. Process variables are provided. Specifically, a temperature sensor and a pressure sensor for measuring the temperature and pressure of the combustion gas layer in the main combustion chamber 14 are provided, and these detection signals are output to the central controller 100. In addition, a temperature sensor and a pressure sensor for measuring the temperature and pressure of each part of the radiation chamber 20 of the boiler 19 and the second and third flues 21 and 22 are provided, and these detection signals are sent to the central controller. 100 is output. Further, the flow meter 68 from the primary air supply amount f _a is, the flow meter 78 from the secondary air supply amount, the main steam flow F from the steam flow meter 39 is generated in the boiler 19, are respectively output to the central control unit 100 The Further, the corrosion detection device 30 outputs information on the corrosive environment (that is, the corrosion rate and the corrosion amount of the superheater tube 27) to the central control device 100. In addition, the operation amount of the feeder driving device 42 and the stalker driving device 16, the amount of dust supplied from the pit 60, the power generation amount C of the generator 70, the amount of dust detected in the exhaust passage 28, and the chloride provided in the exhaust passage 28 The hydrogen chloride concentration detected by the hydrogen sensor 86, the oxygen concentration detected by the oxygen sensor 87 provided in the exhaust passage 28, and the like are input to the central controller 100.

  As described above, various process variables related to the operation of the waste incinerator 10 are constantly input to the central controller 100 from each part in the waste incinerator 10, and information on the corrosive environment is always input from the corrosion detection device 30. . The central controller 100 temporarily stores in the database 105 together with various information related to the operation of the refuse incinerator 10 and information related to the corrosive environment received along with time information. Then, the operation control unit 101 of the central controller 100 performs control calculation for the purpose of maintaining the amount of steam that stabilizes the power generation amount of the generator 70, optimizing the exhaust gas properties, and mitigating the corrosive environment in the boiler 19. And a control signal for optimizing them comprehensively is transmitted to each operation device in the waste incinerator 10. The corrosion environment monitoring unit 102 of the central control device 100 monitors the corrosion environment of the boiler 19 based on information on the corrosion environment obtained from the corrosion detection device 30 during the operation control of the operation control unit 101.

  Here, FIGS. 6, 7, and 8 show the flow of the corrosive environment monitoring process by the corrosive environment monitoring unit 102 of the central control device 100 and the flow of the process for determining the policy for mitigating the corrosive environment by the policy determining unit 103. The description will be given with reference. FIG. 6 is a flowchart showing the flow of the corrosive environment monitoring process by the corrosive environment monitoring unit, FIG. 7 is a flowchart showing the flow before the process of determining the policy for mitigating the corrosive environment by the policy determining unit, and FIG. It is a flowchart which shows the flow of the back | latter stage of the process which determines the policy for relieving the corrosive environment by a part.

  First, as shown in FIG. 6, the corrosion environment monitoring unit 102 of the central controller 100 acquires the corrosion rate from the information related to the corrosion environment (step S1), and compares the corrosion rate and the corrosion rate threshold ( Step S2). The corrosion rate threshold value is set in the central controller 100 in advance. If the corrosion rate is equal to or lower than the corrosion rate threshold (NO in step S2), the corrosion environment monitoring unit 102 records in the database that the corrosion environment is not severe (step S3). On the other hand, if the corrosion rate is greater than the corrosion rate threshold (YES in step S2), the corrosion environment monitoring unit 102 records in the database that the corrosion environment is severe (step S4). Here, “the corrosive environment is severe” means a combustion state of the combustion furnace 11 in which the corrosion of the metal parts of the boiler 19 is remarkably accelerated.

Subsequently, the corrosive environment monitoring unit 102 reads the information stored in the database and calculates the duration L of the severe corrosive environment (step S5). Further, the corrosive environment monitoring unit 102 compares the calculated duration L with the allowable duration L ₀ (step S6). The allowable continuation time L ₀ (time) is an arbitrary value in the range of 1 to 12, and is set in the central control device 100 in advance. If the duration L of the severe corrosive environment is longer than the allowable duration L ₀ (YES in step S6), the corrosive environment monitoring unit 102 determines a policy for mitigating the corrosive environment by the policy determining unit 103 described next. Is started (step S7). The duration L of the severe corrosive environment is less than or equal to the allowable duration L ₀ , but if the severe corrosive environment suddenly appears and the corrosion rate is extremely high, the garbage stored in the pit 60 There are cases where many corrosive substances or substances that generate corrosive substances exist locally. Therefore, in such a case, the central control device 100 instructs the control device 62 of the crane 61 that stirs the pit 60 to increase the agitation frequency of the pit 60 in order to homogenize the garbage thrown in from the hopper 12. Is preferable.

As shown in FIGS. 7 and 8, measures determining unit 103 that initiated the processing for determining the measures to mitigate the corrosive environment, first, a waste processing amount V _T before the current waste throughput V and the time T Obtain them (step S11) and compare them. Note that the time T before the waste throughput V _T, a waste processing amount when a significant acceleration of the corrosion rate is not detected, a waste treatment amount before T time from the present. T (time) is an arbitrary value in the range of 1 to 24, and is set in the central controller 100 in advance. However, instead of the waste processing amount V _T before T time, the steady state waste processing amount V ₀ is set in the central controller 100 in advance, and the current waste processing amount V and the steady state waste processing amount V ₀ are set as follows. May be compared.

If the current waste treatment amount V is significantly increased from the waste treatment amount V _T before T time, it is estimated that the factor of the corrosion rate acceleration is an increase in the waste treatment amount V. Therefore, the policy determination unit 103 determines that the current waste processing amount V is larger than the waste processing amount V _T before time _T by a tolerance ΔV or more (YES in step S12), that is, the waste processing amount is remarkably large. If it has increased, a measure for decreasing the primary air supply amount and the secondary air supply amount and reducing the waste treatment speed and the waste treatment amount is determined (step S13). The tolerance ΔV is an arbitrary value and is set in the central controller 100 in advance. Then, the operation control unit 101 causes the operation devices of the flow rate control valves 67 and 77, the stalker driving device 16, and the feeder driving device 42 to adjust the operation amount in accordance with the policy determined by the policy determining unit 103. As a result, the combustion position of the garbage and the distribution of the combustion air supply amount are optimized, the volatilization amount of the incineration ash is reduced, and the corrosive environment is mitigated.

On the other hand, if the difference between the waste processing amount V _T before the current waste throughput V and the time T is equal to or smaller than the allowable difference [Delta] V (NO at step S12), the other words, when there is no significant increase in waste throughput V is It is speculated that the cause of the acceleration of the corrosion rate is other than the increase or decrease of the waste treatment amount V. Therefore, the policy determining unit 103 evaluates changes in the main steam amount F and the primary air ratio A in order to search for other factors.

If there is no significant increase in waste throughput V (NO at step S12), the strategy determination unit 103 acquires a main steam amount F _T before the current main steam quantity F and the time T (step S14). Here, the “main steam amount F” refers to the flow rate of steam detected between the superheater outlet and the steam turbine. In the waste incinerator 10 according to the present embodiment, the main steam amount F is the flow rate of steam detected by the steam flow meter 39. However, the main steam amount F may be the flow rate of steam detected by a flow meter provided between the boiler drum 24 and the superheater 25 and between the superheater 25 and the steam turbine 71. Absent. Incidentally, previously set in the central control unit 100 of the main steam flow F ₀ of previously steady state instead of the main steam flow F _T before T time, the main steam flow F ₀ of the current main steam quantity F and the steady state May be compared.

Further, the policy determining unit 103 calculates the current primary air ratio A (step S15). Primary air ratio A, the primary air supply amount f _a is the calculated by dividing the theoretical air amount of the fuel (primary air ratio A = primary air supply rate f _a / theoretical air quantity). The theoretical air amount is the amount of air necessary for completely burning the fuel, and for example, an approximate expression estimated from the calorific value of the fuel is shown. The calorific value of the fuel can be derived from the exhaust gas temperature and the amount of steam. This way, the theoretical air amount obtained by the primary air supply amount f _a detected by the primary air flow meter 68, it is possible to determine the primary air ratio A. Thus the primary air ratio A calculated based on the calorific value of the primary air supply amount f _a and the fuel is indicative of the excess and deficiency of primary air supply amount f _a.

The strategy determination unit 103 is configured to compare the current and the main steam flow F _T before the main steam flow F and the time T (step S16, S20), the primary air ratio A and the primary air ratio A as needed The threshold A _S is compared (step S22), the factor that accelerated the corrosion rate is estimated, and a policy suitable for the estimated factor is determined. The threshold value A _S of the primary air ratio A is an arbitrary value in the range of 0.7 to 1.2, and is set in the central controller 100 in advance.

If the difference between the main steam flow F _T before the current main steam quantity F and the time T is equal to or smaller than the allowable difference [Delta] F (NO in step S16), and that is, when there is no significant decrease in the main steam flow F is, T There is little or no change in the heat input and combustion gas layer temperature from the combustion state before the time. In this way, there are many factors that cause corrosive substances and corrosive substances in the garbage when there is no significant increase or decrease in the waste treatment amount V and no significant increase or decrease in the main steam amount F. It is estimated that Therefore, in such a case, it is effective to increase the agitation frequency of the pits 60 in order to homogenize the dust introduced from the hopper 12. Therefore, when the main steam amount F does not significantly increase or decrease (NO in step S16), the policy determining unit 103 determines a policy for increasing the agitation frequency of the pit 60 (step S17). Then, a command is issued to the control device 62 of the crane 61 that stirs the pit 60 to increase the stirring frequency of the pit 60.

Further, when there is a significant increase or decrease in the main steam amount F (YES in step S16), the heat input amount and the combustion gas layer temperature are changed from the combustion state before T time. If the current main steam amount F is increased from the main steam flow F _T before T time than tolerance [Delta] F (YES in step S20), i.e., when the main steam flow F has increased significantly, The amount of heat input and the combustion gas layer temperature are rising. Thus, the factor of acceleration of the corrosion rate when there is no significant increase / decrease in the waste treatment amount V and the main steam amount F is significantly increased, is the incineration ash containing the corrosion-causing substances due to the increase in the temperature of the combustion field. It is estimated that the amount of generation is increased. Therefore, when the main steam amount F is remarkably increased, the policy determining unit 103 determines a policy for decreasing the waste processing amount and increasing or decreasing the primary air supply amount according to the primary air ratio A. Specifically, if the main steam amount F is significantly increased (YES in step S20) and the primary air ratio A is smaller than 1 (YES in step S21), the amount of waste is reduced and the primary air supply amount. Is reduced (step S23). Further, when the main steam amount F is remarkably increased (YES in step S20) and the primary air ratio A is 1 or more (NO in step S21), the policy determining unit 103 reduces the waste treatment amount and primary. The air supply amount is increased (step S24). Then, the operation control unit 101 causes the feeder driving device 42 and the flow rate control valve 67 to adjust the operation amount according to the policy determined by the policy determination unit 103. As a result, the temperature of the combustion field is lowered and the amount of burned garbage is reduced, so that the amount of incinerated ash generated is reduced and the corrosive environment can be mitigated.

Further, when the current main steam amount F has decreased from the main steam amount FT before the time _T by the tolerance ΔF or more (NO in step S20), that is, when the main steam amount F has significantly decreased. The amount of heat input, the amount of heat generated, and the temperature of the dust combustion gas layer are decreased. For this reason, there is no significant increase or decrease in the waste treatment amount V and the factor of acceleration of the corrosion rate when the main steam amount F is remarkably reduced is an increase in the amount of incinerated ash transported by the supplied primary air or secondary air. It is estimated that. Therefore, in order to reduce the severity of the corrosive environment, it is effective to reduce the gas flow rate in the boiler 19 by suppressing the supply amount of primary air or secondary air that is a carrier medium for incineration ash. . Therefore, (YES at step S22) strategy determination unit 103, the main steam flow F is significantly reduced (NO in step S20), and when the primary air ratio A is greater than the threshold A _S, the primary air supply A policy for reducing the value is determined (step S25). Then, the operation control unit 101 causes the flow control valve 67 to adjust the operation amount according to the policy determined by the policy determination unit 103. On the other hand, measures determining unit 103, the main steam flow F is greatly reduced (NO at step S20), and the primary air ratio A is less than or equal to the threshold value A _S (NO at step S22), and the secondary air A measure for reducing the supply amount is determined (step S26). Then, the operation control unit 101 causes the flow control valve 77 to adjust the operation amount according to the policy determined by the policy determination unit 103.

  As described above, in the waste incinerator 10, the corrosive environment is monitored by the corrosive environment monitoring unit 102 of the central controller 100. When the corrosive environment becomes severe, the policy determining unit 103 estimates a factor that the corrosive environment becomes severe and determines a measure for mitigating the corrosive environment based on the estimated factor. Furthermore, the operation is performed such that the corrosive environment is alleviated by executing the determined measure by the operation control unit 101. Thereby, in the refuse incinerator 10, since the combustion state which accelerates | stimulates corrosion can be suppressed, suppression of the corrosion thinning of the metal component of the boiler 19 can be anticipated. In addition, the policy determining unit 103 of the central control device 100 estimates factors that make the corrosive environment severe, and determines a policy for mitigating the corrosive environment according to the estimated factors. Therefore, no wasteful and effective measures can be taken. Therefore, since the operation performance of the waste incinerator 10 is not lowered more than necessary to alleviate the corrosive environment, it is possible to contribute to maintenance of an appropriate amount of processing and energy saving.

  The preferred embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and various design changes can be made as long as they are described in the claims. is there.

For example, in the embodiment described above, measures determining unit 103 of the central control unit 100 is mainly waste throughput V, the main steam flow F, based on the primary air supply amount f _a, and the power generation amount C, the corrosive environment Although the policy for reducing the severity is determined, the factors for determining the policy are not limited to the above. For example, in addition to the above, the policy determining unit 103 adds the secondary air supply amount detected by the secondary air flow meter 78, the hydrogen chloride concentration detected by the hydrogen chloride sensor 86, and the dust amount detected by the exhaust passage 28. The acceleration factor of the corrosion rate may be estimated by taking into account one or a combination of the dust layer temperature detected by the temperature sensor and the combustion gas temperature.

  Further, for example, in the above-described embodiment, the corrosion detection device 30 estimates the corrosion state of the superheater pipe 27 in order to obtain information related to the corrosive environment of the boiler 19, but the corrosion detection device 30 is the water pipe 23 or the superheater. The corrosion state of the pipe 27 and the water pipe 23 may be estimated. Furthermore, when the corrosion state of the water pipe 23 is estimated by the corrosion detection device 30, the corrosion sensor 31 may be disposed in either the radiation chamber 20 or the second flue 21.

  In addition, although this embodiment demonstrated the case where the corrosion detection apparatus 30 was used with the waste incinerator 10, it does not limit a use location to the waste incinerator 10. FIG. For example, if the plant has an environment in which deposits containing high-temperature molten salt accumulate on metal parts and corrode metal parts, such as a soda recovery boiler and coal fired boiler, the heat recovery plant according to the present invention and its operation A control method can be applied. Moreover, the configuration of the waste incinerator 10 is merely an example, and can be applied even if the configuration is different from the above-described configuration. Furthermore, the present invention is not limited to the embodiments described above, and the configuration can be changed, added, or deleted without departing from the spirit of the present invention.

  The present invention prevents a corrosive environment of a boiler from becoming extremely severe without deteriorating the operation performance of the plant more than necessary in a heat recovery plant including a combustion furnace and a boiler that recovers waste heat during combustion. Useful for.

10 Waste incinerator (heat recovery plant)
DESCRIPTION OF SYMBOLS 11 Combustion furnace 12 Hopper 13 Chute 14 Main combustion chamber 15 Stoker 16 Stoker drive device 18 Discharge chute 19 Boiler 20 Radiation chamber 21 Second flue 22 Third flue 23 Water pipe 24 Boiler drum 25 Superheater 27 Superheater pipe 30 Corrosion detection Device 31 Corrosion sensor 39 Flow meter 41 Feeder 42 Feeder drive device 65 Primary air supply path 68 Primary air flow meter 75 Secondary air supply path 78 Secondary air flow meter 100 Central controller 101 Operation control section 102 Corrosion environment monitoring section 103 Measures Decision part

Claims (12)

A combustion furnace for burning fuel;
A boiler that recovers the heat of the flue gas flowing in from the combustion furnace;
Corrosion detection means for detecting corrosion of metal parts of the boiler based on a change in electrical resistance between a pair of electrodes installed in the exhaust gas passage in the boiler;
Corrosion environment monitoring means for monitoring the corrosion environment of the boiler based on information from the corrosion detection means, and detecting that the corrosion environment has become harsh,
When the corrosive environment of the boiler becomes severe, based on at least one of the processing amount of the combustion furnace, the supply amount of combustion air to the combustion furnace, the amount of steam generated in the boiler, and the heat generation amount of fuel A policy determination means for estimating factors that have caused the corrosive environment to become severe, and determining measures for mitigating the corrosive environment based on the estimated factors;
Operation control means for controlling the operation of the combustion furnace so as to mitigate the corrosive environment based on the determined policy ,
The corrosion sensing means, that comprise one or more dummy tubes disposed around the pair of electrodes, heat recovery plants. The pair of electrodes of the corrosion detection means are disposed upstream of the boiler metal parts in the exhaust gas passage,
The heat recovery plant according to claim 1, wherein the corrosion detection unit includes a cooling mechanism that cools the pair of electrodes to bring the pair of electrodes to the same temperature as the surface temperature of the metal component. The corrosive environment monitoring means detects that the corrosion rate included in the information from the corrosion sensing means when the state continues to exceed a certain threshold, corrosive environment has become severe, claim 1 or 2 The heat recovery plant described in 1. The policy determining means determines, as a policy, one or a combination of increase / decrease in the processing amount of the combustion furnace, increase / decrease in the supply amount of combustion air to the combustion furnace, and increase / decrease in the processing speed of the combustion furnace. Item 4. The heat recovery plant according to any one of Items 1 to 3 . The heat recovery plant further includes a pit for storing fuel to be input to the combustion furnace, and a stirring means for stirring the pit.
The policy deciding means includes one or more of an increase / decrease in the processing amount of the combustion furnace, an increase / decrease in the supply amount of combustion air to the combustion furnace, an increase / decrease in the processing speed of the combustion furnace, and an increase in the stirring frequency of the pits. determining combining as a measure, the heat recovery plant according to any one of claims 1-3. The policy deciding means estimates the factor that the corrosive environment becomes severe based on the change in the processing amount, the change in the steam amount, and the air ratio calculated based on the combustion air supply amount and the heat generation amount. The heat recovery plant according to any one of claims 1 to 5 . An operation control method for a heat recovery plant comprising a combustion furnace for burning fuel and a boiler for recovering heat of flue gas flowing in from the combustion furnace,
A pair of electrodes is installed in the exhaust gas passage in the boiler and one or more dummy tubes are installed around the pair of electrodes, and the metal parts of the boiler are changed based on a change in electrical resistance between the pair of electrodes. A corrosion detection step for detecting corrosion;
A corrosive environment monitoring step for monitoring the corrosive environment of the boiler based on the information obtained in the corrosion detecting step, and detecting that the corrosive environment becomes severe;
When the corrosive environment of the boiler becomes severe, based on at least one of the processing amount of the combustion furnace, the supply amount of combustion air to the combustion furnace, the amount of steam generated in the boiler, and the heat generation amount of fuel A policy determining step for estimating a factor that the corrosive environment becomes severe, and determining a policy for mitigating the corrosive environment based on the estimated factor;
An operation control step for controlling the operation of the combustion furnace to mitigate the corrosive environment based on the determined policy. In the corrosion detection step, the pair of electrodes is disposed upstream of the boiler metal part in the exhaust gas passage, and the pair of electrodes is maintained at the same temperature as the surface temperature of the metal part. The operation control method of the heat recovery plant according to claim 7 . 9. The corrosion environment monitoring step according to claim 7 or 8 , wherein when the corrosion rate of the metal parts of the boiler continues to exceed a threshold value, it is detected that the corrosion environment has become severe. Operation control method for heat recovery plant. In the policy determination step, one or a combination of increase / decrease in the processing amount of the combustion furnace, increase / decrease in the supply amount of combustion air to the combustion furnace, and increase / decrease in the processing speed of the combustion furnace is determined as a policy. heat recovery operation control method of the plant according to any one of claims 7-9. The heat recovery plant further includes a pit for storing fuel to be input to the combustion furnace, and a stirring means for stirring the pit.
In the policy determination step, increase / decrease in the processing amount of the combustion furnace, increase / decrease in the supply amount of combustion air to the combustion furnace, increase / decrease in processing speed of the combustion furnace, and agitation frequency of pits for storing fuel to be input to the combustion furnace The operation control method of the heat recovery plant according to any one of claims 7 to 10 , wherein one or a plurality of combinations among the increases is determined as a measure. In the policy determination step, the factor that the corrosive environment becomes severe is estimated based on the change in the processing amount, the change in the steam amount, and the air ratio calculated based on the combustion air supply amount and the heat generation amount. The operation control method of the heat recovery plant according to any one of claims 7 to 11 .

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