Heat recovery system, heat recovery method, and combustion control device

Abstract

To provide a heat recovery system suppressing high-temperature corrosion by using a simple structure and improving heat recovery efficiency.SOLUTION: A heat recovery system includes: a combustion chamber; a heat exchanger to which combustion gas generated in the combustion chamber is supplied; and a combustion control device controlling an oxygen concentration of the combustion gas. The combustion chamber includes an oximeter measuring the oxygen concentration of the combustion gas, and the combustion control device controls the oxygen concentration so that differential pressure between divergence pressure of a contact part of the heat exchanger and oxygen partial pressure of the combustion gas becomes a specified value or smaller.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a heat recovery system, a heat recovery method, and a combustion control device, and more particularly to a combustion control device having a function of controlling an oxygen concentration in a combustion chamber, and a heat recovery system including the combustion control device. [Background technology]

[0002] Conventionally, in waste incineration facilities that incinerate waste such as municipal waste, there is known a heat recovery system that recovers and reuses heat generated during the incineration process. In such a heat recovery system, collected municipal waste is burned in an incinerator, and then the heat of the generated combustion gas is recovered by a heat exchanger such as an air preheater. The heat recovered by the air preheater is returned to the incinerator and used to raise the temperature of the combustion air, for example (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-24504 A Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional heat recovery systems, exhaust gas generated in an incinerator is further completely combusted in a re-burning chamber (secondary combustion chamber) to suppress the generation of harmful substances such as dioxins. At this time, the law requires that the exhaust gas be retained in the re-burning chamber at a temperature of 850°C or higher (preferably 900°C or higher) for more than two seconds. Therefore, the temperature of the combustion gas discharged from the re-burning chamber is also high, at 900°C or higher.

[0005] Here, if high-temperature gas of 900°C or more is directly supplied to a heat exchanger, there is a problem that the metal components constituting the heat exchanger (especially the parts that directly contact the high-temperature gas) will deteriorate due to high-temperature corrosion. High-temperature corrosion is corrosion that does not involve liquid water and occurs in a high-temperature environment. For this reason, in conventional heat recovery systems, it was necessary to lower the temperature of the high-temperature gas generated in the reburning chamber to a temperature at which high-temperature corrosion would not occur. It is also known that dioxin resynthesis occurs at approximately 400°C or higher. Therefore, in consideration of suppressing dioxin resynthesis, the combustion gas discharged from the reburning chamber was cooled to approximately 350°C before being supplied to the heat exchanger.

[0006] As described above, conventional heat recovery systems require heat recovery from combustion gas whose temperature has been reduced to around 350°C, and therefore generally use a steam boiler as a heat exchanger to ensure heat recovery efficiency. However, steam boilers require the operation of a qualified person (boiler engineer) because the vessel is highly pressurized, which leads to increased costs for maintenance and equipment upkeep.

[0007] An object of the present invention is to provide a heat recovery system having a simple structure, which suppresses high-temperature corrosion and improves heat recovery efficiency. [Means for solving the problem]

[0008] A heat recovery system according to an embodiment of the present invention includes a combustion chamber, a heat exchanger to which a combustion gas generated in the combustion chamber is supplied, and a combustion control device that controls an oxygen concentration of the combustion gas. The combustion chamber has an oxygen concentration meter that measures the oxygen concentration of the combustion gas. The combustion control device measures the oxygen concentration of the contact portion of the heat exchanger. dissociation The pressure difference between the partial pressure of oxygen in the combustion gas and the pressure in the combustion gas is equal to or less than a predetermined value. The oxygen concentration is controlled so as to satisfy the above condition.

[0009] In the heat recovery system, the combustion chamber may further include a thermometer for measuring a temperature of the combustion gas. In this case, the control device may determine the temperature of the combustion gas based on the temperature. dissociation The pressure may be calculated.

[0010] The heat recovery system may further include a gas supply device that supplies oxygen gas or an inert gas to the combustion chamber. In this case, the combustion control device may control the gas supply device in accordance with the oxygen concentration.

[0011] The heat recovery system may further include an air flow rate adjusting device that adjusts the amount of air supplied to the combustion chamber. In this case, the combustion control device may control the air flow rate adjusting device in response to the oxygen concentration.

[0012] In the heat recovery system, the heat exchanger may be a vacuum or non-pressure type hot water heater.

[0013] The heat recovery system may further include a cooling chamber to which the combustion gas that has passed through the heat exchanger is supplied.

[0014] The heat recovery system may further comprise an incinerator supplying primary combustion gases to the combustion chamber.

[0015] In the heat recovery system, the oxygen concentration meter may be a laser type oxygen concentration meter.

[0016] In one embodiment of the present invention, a heat recovery method includes measuring an oxygen concentration of a combustion gas generated in a combustion chamber, and calculating an oxygen concentration of a contact part of a heat exchanger connected to the combustion chamber. dissociation The present invention also includes controlling the oxygen concentration so that a pressure difference between the partial pressure of oxygen in the combustion gas and the pressure in the exhaust gas is equal to or less than a predetermined value, and supplying the combustion gas in which the oxygen concentration has been controlled to the heat exchanger.

[0017] The heat recovery method may further include measuring a temperature of the combustion gas. dissociation The pressure may be calculated based on the temperature.

[0018] The heat recovery method may use a vacuum type or non-pressure type hot water heater as the heat exchanger.

[0019] The heat recovery method may further include supplying the combustion gas that has passed through the heat exchanger to a cooling chamber.

[0020] The heat recovery method may further include supplying primary combustion gas generated in an incinerator to the combustion chamber.

[0021] In the heat recovery method, the oxygen concentration may be measured by a laser type oxygen concentration meter.

[0022] A combustion control device according to an embodiment of the present invention includes a storage unit for storing a control program and a processor for executing the control program. The control program acquires a temperature inside a combustion chamber, and calculates a temperature of a contact part of a heat exchanger by using the temperature. dissociation The oxygen concentration in the combustion chamber is obtained, and the oxygen partial pressure of the combustion gas generated in the combustion chamber is calculated using the oxygen concentration. dissociation The processor determines whether a pressure difference between the combustion chamber and the internal pressure of the combustion chamber is equal to or less than a predetermined value, and when the pressure difference is not equal to or less than the predetermined value, controls the oxygen concentration inside the combustion chamber.

[0023] In the combustion control device, the control program further includes a step of: when the pressure difference exceeds the predetermined value, the oxygen partial pressure is dissociation and determining whether the oxygen partial pressure is higher than the dissociation When the oxygen partial pressure is higher than the pressure, the oxygen concentration inside the combustion chamber is reduced, and the oxygen partial pressure is dissociation When the pressure is lower than the pressure in the combustion chamber, the processor may be caused to perform a process to increase the oxygen concentration within the combustion chamber. [Brief description of the drawings]

[0024] [Figure 1] 1 is a block diagram showing a configuration of a heat recovery system according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram showing a configuration of a heat exchanger in the heat recovery system according to one embodiment of the present invention. [Diagram 3] FIG. 4 is a flowchart showing an example of control of a combustion control device in the heat recovery system according to one embodiment of the present invention. [Figure 4] FIG. 2 is a diagram showing a configuration of a heat exchanger in the heat recovery system according to one embodiment of the present invention. [Diagram 5] 1 is a block diagram showing a configuration of a heat recovery system according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the present invention can be implemented in various forms without departing from the gist of the present invention, and should not be interpreted as being limited to the description of the embodiments exemplified below. In the drawings, the width, thickness, shape, etc. of each part may be shown diagrammatically compared to the actual form in order to make the explanation clearer, but these are merely examples and do not limit the interpretation of the present invention. In this specification and each drawing, elements having the same functions as those described with respect to the previous drawings may be given the same reference numerals, and duplicate explanations may be omitted.

[0026] (First embodiment) [Heat recovery system configuration] Fig. 1 is a diagram showing an example of a heat recovery system 100 according to an embodiment of the present invention. The heat recovery system 100 of this embodiment includes an incinerator 110, a combustion chamber 120, a heat exchanger 130, a cooling chamber 140, and a combustion control device 150. However, the system configuration shown in Fig. 1 is merely an example of the heat recovery system 100. Although not shown, other equipment may be provided, such as a garbage pit for accumulating collected garbage, an ash pit for accumulating ash generated in the incinerator, and a filter-type dust collector for collecting fine ash contained in the combustion gas.

[0027] The incinerator 110 is a facility that incinerates waste 202, such as municipal waste, that is brought in. The incinerator 110 converts the waste 202 into ash and renders it harmless through incineration processing. In this embodiment, a stoker-type incinerator is used as the incinerator 110, but is not limited to this. When the waste 202 is incinerated in the incinerator 110, primary combustion gas 204 is generated. The primary combustion gas 204 generated in the incinerator 110 is supplied to the combustion chamber 120.

[0028] The combustion chamber 120 is a facility for reburning the primary combustion gas 204 generated in the incinerator 110. In this embodiment, the primary combustion gas 204 supplied from the incinerator 110 stays in the combustion chamber 120 at a temperature of 950° C. for 2 seconds. In the combustion chamber 120, the unburned gas contained in the primary combustion gas 204 is burned, thereby completely burning the combustion gas. The secondary combustion gas 206 generated by complete combustion in the combustion chamber 120 is supplied to the heat exchanger 130 via a flue (not shown). Although not shown in FIG. 1, the combustion chamber 120 may be provided with a blower for blowing air and a damper for adjusting the amount of air supplied from the blower.

[0029] In this embodiment, the oxygen concentration meter 122 is disposed inside the combustion chamber 120. Specifically, the oxygen concentration meter 122 is disposed near the exhaust port inside the combustion chamber 120. However, the oxygen concentration meter 122 is not limited to being disposed near the exhaust port, and may be disposed at any position suitable for measuring the oxygen concentration. For example, the oxygen concentration meter 122 may be disposed in a flue connecting the combustion chamber 120 and the heat exchanger 130.

[0030] The oxygen concentration meter 122 measures the oxygen concentration contained in the secondary combustion gas 206. In this embodiment, a laser type oxygen concentration meter is used as the oxygen concentration meter 122, so it is possible to measure the oxygen concentration of the secondary combustion gas 206 in real time. Furthermore, a thermometer 124 is disposed inside the combustion chamber 120. In this embodiment, the combustion chamber 120 is configured to measure the indoor temperature of the combustion chamber 120 (i.e., the gas temperature of the secondary combustion gas 206) in real time. As described above, the combustion chamber 120 is suitable for measuring the oxygen concentration and indoor temperature with high accuracy because the combustion gas remains therein for at least 2 seconds. The roles of the oxygen concentration meter 122 and the thermometer 124 will be described later.

[0031] A gas supply device 126 is also connected to the combustion chamber 120 of this embodiment. The gas supply device 126 is connected to the combustion control device 150, and supplies oxygen gas or an inert gas (e.g., nitrogen gas) to the combustion chamber 120 according to the control of the combustion control device 150. As described below, the combustion control device 150 is configured to measure the oxygen concentration inside the combustion chamber 120, and adjust the oxygen concentration when a predetermined condition is satisfied. At that time, the gas supply device 126 functions as a supply source of oxygen gas or inert gas to the combustion chamber 120.

[0032] The heat exchanger 130 is a facility that recovers heat from the secondary combustion gas 206 supplied from the combustion chamber 120. Specifically, in this embodiment, a vacuum type hot water heater is used as the heat exchanger 130. The vacuum type hot water heater is structured to reduce the pressure inside a container to a pressure lower than atmospheric pressure, reduce the pressure of heat transfer water (water used as a heat transfer medium) to boil, and use the heat of the steam to extract hot water.

[0033] 2 is a diagram showing the configuration of the heat exchanger 130 in the heat recovery system 100 of one embodiment of the present invention. As described above, the heat exchanger 130 is a vacuum type hot water heater. In the heat exchanger 130, the inside of the housing 131 is divided into a heating chamber 132 and a heat exchange chamber 133. A secondary combustion gas 206 sent from the combustion chamber 120 is supplied to the heating chamber 132. The secondary combustion gas 206 supplied to the heating chamber 132 is used to heat the heat transfer water 134 filled in the heat exchange chamber 133, and then discharged as a combustion gas 208.

[0034] The metal member constituting the inner wall of the heating chamber 132 has a role of transferring heat of the secondary combustion gas 206 to the heat exchange chamber 133 while being exposed to the high-temperature secondary combustion gas 206. In this embodiment, the part of the heat exchanger 130 (here, a vacuum type hot water heater) that comes into direct contact with the secondary combustion gas 206 is called the "contact part". The contact part is preferably made of an alloy material containing iron, which has excellent heat resistance and heat conductivity. For example, S-TEN steel (registered trademark), which has high corrosion resistance against sulfuric acid and hydrochloric acid, may be used as the metal material constituting the contact part.

[0035] The heat exchange chamber 133 is decompressed below atmospheric pressure. Therefore, the heat transfer water 134 boils at a reduced pressure at about 80°C to generate steam. A heat exchange section 135 is disposed above the heat transfer water 134, and heat exchange is performed using the heat of the generated steam. The heat exchange section 135 has a water supply pipe 136, to which water is supplied from an inlet 136a and hot water is obtained from an outlet 136b. The steam whose temperature has been reduced by the heat exchange is exhausted from an exhaust port 131a provided at the top of the housing 131.

[0036] In this embodiment, the high-temperature (e.g., 950°C) secondary combustion gas 206 discharged from the combustion chamber 120 can be directly supplied to the heat exchanger 130. In other words, unlike the conventional technology, it is not necessary to cool the secondary combustion gas 206 discharged from the combustion chamber 120 to about 350°C before supplying it to the heat exchanger 130. Therefore, it is not necessary to use a steam boiler as in the conventional technology, and heat can be recovered with high efficiency even if a heat exchanger such as a hot water heater is used.

[0037] In addition, the vacuum type hot water heater is not subject to boiler regulations because the inside of the housing 131 is in a reduced pressure state. Therefore, unlike the conventional technology that uses a steam boiler, there is no need to appoint a boiler engineer to manage the heat exchanger 130. In this way, the heat recovery system 100 of this embodiment can use a hot water heater that is not subject to boiler regulations as the heat exchanger 130, and therefore the costs required for maintenance and equipment upkeep can be reduced.

[0038] Returning to the explanation of Fig. 1, the combustion gas 208 that has passed through the heat exchanger 130 is supplied to the cooling chamber 140. The cooling chamber 140 is a facility for lowering the temperature of the combustion gas 208 to about 350°C. A water injection device (not shown) is provided in the cooling chamber 140, and the temperature of the combustion gas 208 is reduced by injecting water into the container. The combustion gas 210 whose temperature has been reduced in the cooling chamber 140 is sent to other downstream equipment (for example, a filter-type dust collector) via a flue (not shown).

[0039] Through the above-described flow, heat can be recovered from the combustion gas (specifically, the secondary combustion gas 206) generated by the incineration treatment of the waste 202. At this time, in this embodiment, the combustion control device 150 controls the oxygen concentration of the secondary combustion gas 206 inside the combustion chamber 120. Specifically, the combustion control device 150 adjusts the oxygen concentration inside the combustion chamber 120 using measurements acquired from the oxygen concentration meter 122 and the thermometer 124 arranged in the combustion chamber 120. By adjusting the oxygen concentration, the oxygen partial pressure of the secondary combustion gas 206 inside the combustion chamber 120 is controlled. This point will be described in detail below.

[0040] [Operation of combustion control device] In the heat recovery system 100 of this embodiment, the combustion control device 150 includes at least a processor and a storage unit, and executes a control program stored in the storage unit by the processor to perform combustion control of the combustion chamber 120. However, in addition to the combustion control of the combustion chamber 120, the combustion control device 150 may also execute control of other components constituting the heat recovery system 100.

[0041] In this embodiment, the combustion control device 150 adjusts the oxygen partial pressure of the secondary combustion gas 206 by controlling the oxygen concentration of the secondary combustion gas 206 generated in the combustion chamber 120. dissociation The oxygen partial pressure is adjusted so that the pressure difference between the pressure of the combustion gas 202 and the oxygen partial pressure of the secondary combustion gas 206 is equal to or less than a predetermined value. dissociation It is the difference between the oxygen partial pressure and the oxygen pressure, and is expressed as a positive value. For example, from the oxygen partial pressure dissociation The absolute value of the pressure subtracted can be used as the differential pressure.

[0042] In this embodiment, the secondary combustion gas 206 is at a high temperature of 800° C. or more, and therefore, metal materials in contact with the secondary combustion gas 206 are deteriorated by high-temperature corrosion. α O β The reaction equation for high-temperature corrosion is expressed as follows:

[0043]

number

[0044] In this case, the free energy (ΔG) of equation (1) is expressed by equation (2).

[0045]

number

[0046] Here, ΔG 0 is the standard free energy of formation (also called the standard Gibbs energy of formation), R is the gas constant, T is the absolute temperature, α x is the activity of x, P O2 is the partial pressure of oxygen.

[0047] The redox reaction of high-temperature corrosion is determined by the value of ΔG in equation (2). That is, if ΔG is negative, the reaction of equation (1) proceeds and the metal element M is oxidized. Conversely, if ΔG is positive, the reverse reaction of equation (1) proceeds and the oxide MαOβ is reduced. In other words, when ΔG = 0, the redox reaction of the metal element M is in equilibrium.

[0048] The partial pressure of oxygen when ΔG=0 (P O2 ) is a metal element M and an oxide M α O β is the oxygen partial pressure at which equilibrium occurs. dissociation It's called pressure. dissociation Pressure (P O2 ) is expressed by equation (3).

[0049]

number

[0050] In other words, when metal element M exists in a gas containing oxygen, the oxygen partial pressure of the gas is dissociation When the pressure exceeds 1000 K, the metal element M is oxidized to form the oxide M. α O β Conversely, if the oxygen partial pressure of the gas is dissociation Below this pressure, the oxide M α O β is reduced to metal element M. This means that the oxygen partial pressure of the gas is dissociation This means that when the pressure is consistent with that of the metal element M, it will not be oxidized and will not be subject to high temperature corrosion.

[0051] In equation (3), the standard free energy of formation (ΔG0) is a value specific to the substance. Therefore, dissociation Pressure is also a value specific to the material. However, as is clear from equation (3), dissociation The pressure changes depending on the temperature. In other words, if the standard free energy of formation of a metal component and the temperature are known, the dissociation Therefore, the calculated pressure of the metal member can be calculated. dissociationIt can be seen that high-temperature corrosion of the metal members can be suppressed by matching the oxygen partial pressure of the gas in contact with the metal members.

[0052] Therefore, in this embodiment, the oxygen concentration of the secondary combustion gas 206 is controlled to reduce the amount of oxygen in the contact area of ​​the heat exchanger 130. dissociation By making the pressure of the combustion control device 150 equal or approximately equal the oxygen partial pressure of the secondary combustion gas 206, the oxidation-reduction reaction at the contact portion of the heat exchanger 130 is brought into equilibrium. dissociation By keeping the pressure difference between the partial pressure of the combustion gas 204 and the oxygen partial pressure of the secondary combustion gas 206 at a predetermined value or less, deterioration of the heat exchanger 130 due to high-temperature corrosion can be suppressed.

[0053] At the contact portion of the heat exchanger 130 dissociation The range of the pressure difference between the partial pressure of the secondary combustion gas 206 and the partial pressure of oxygen in the secondary combustion gas 206 should be appropriately selected depending on the extent to which deterioration of the heat exchanger 130 should be suppressed. dissociation A threshold value (predetermined value) may be set to 10% (preferably 5%, more preferably 3%) of the pressure difference, and when the pressure difference is equal to or less than the threshold value, it may be determined that the oxidation-reduction reaction of the contact portion of the heat exchanger 130 is in equilibrium. dissociation The oxygen concentration may be controlled so that the oxygen partial pressure of the secondary combustion gas 206 falls within a range of ±10% (preferably 5%, and more preferably 3%) based on the pressure.

[0054] Since the material of the contact part of the heat exchanger 130 is known in advance, if the temperature can be specified, the dissociationThe oxygen partial pressure of the secondary combustion gas 206 can be obtained. Furthermore, if the oxygen concentration of the secondary combustion gas 206 (i.e., the oxygen concentration inside the combustion chamber 120) and the gas flow rate are known, the oxygen partial pressure of the secondary combustion gas 206 can be obtained. For this reason, in this embodiment, an oxygen concentration meter 122 is disposed near the exhaust port of the combustion chamber 120 to measure the oxygen concentration of the secondary combustion gas 206. The gas flow rate can be measured using the temperature measured by a thermometer 124 and the pressure inside the combustion chamber 120 measured by a pressure gauge (not shown).

[0055] In this embodiment, a thermometer 124 is disposed inside the combustion chamber 120 to measure the temperature inside the combustion chamber 120. Therefore, the combustion control device 150 determines the temperature of the contact part of the heat exchanger 130 based on the temperature obtained from the thermometer 124. dissociation For example, when the heat recovery system 100 is operated intermittently instead of continuously, the temperature of the secondary combustion gas 206 changes when the temperature of the combustion chamber 120 increases and decreases. Even in this case, the pressure at the contact portion of the heat exchanger 130 can be obtained by measuring the temperature of the combustion chamber 120 in real time. dissociation It is possible to obtain the change in pressure following the change in the temperature inside the combustion chamber 120. Therefore, if the heat recovery system 100 is operated intermittently, even if the temperature of the combustion chamber 120 is rising or falling, dissociation By changing the oxygen partial pressure in response to the change in pressure, high temperature corrosion of the contact area can be suppressed.

[0056] In addition, when the heat recovery system 100 is operated continuously, or when there is no need to take into account the temperature rise or fall of the combustion chamber 120, the temperature of the contact portion of the heat exchanger 130 is assumed to be constant. dissociation In this case, it is not necessary to know the temperature inside the combustion chamber 120, and the thermometer 124 can be omitted.

[0057] As described above, the combustion control device 150 in the heat recovery system 100 of this embodiment controls the oxygen concentration of the secondary combustion gas 206 generated in the combustion chamber 120, thereby reducing the amount of oxygen in the contact area of ​​the heat exchanger 130. dissociationThe oxygen concentration of the secondary combustion gas 206 (oxygen concentration in the combustion chamber 120) is adjusted so that the pressure difference between the pressure in the combustion chamber 120 and the oxygen partial pressure of the secondary combustion gas 206 is equal to or less than a predetermined value. This makes it possible to suppress deterioration due to high-temperature corrosion of the contact portion of the heat exchanger 130 caused by the secondary combustion gas 206 (the portion of the heat exchanger 130 that contacts the secondary combustion gas 206).

[0058] [Control flow of combustion control device] Fig. 3 is a flow chart showing an example of the control of the combustion control device 150 in the heat recovery system 100 of one embodiment of the present invention. The control shown in Fig. 3 is executed by a processor included in the combustion control device 150 executing a control program stored in a storage unit. Note that Fig. 3 shows an example in which the control program is executed periodically at a predetermined interval, but the control program may be executed continuously by loop processing.

[0059] 3, when the control program is executed, the combustion control device 150 acquires the temperature inside the combustion chamber 120 from the thermometer 124 (step S301). In this embodiment, the temperature inside the combustion chamber 120 is set to 950°C. That is, the temperature of the secondary combustion gas 206 generated in the combustion chamber 120 can be considered to be 950°C.

[0060] Next, the combustion control device 150 controls the temperature of the contact part in the heat exchanger 130 based on the acquired temperature. dissociation In this embodiment, since a steel material such as S-TEN steel is used as the material for the contact portion, the standard free energy of formation is known. Therefore, if the temperature can be obtained, the standard free energy of formation of the contact portion can be calculated by the above-mentioned formula (3). dissociation The pressure can be calculated. dissociation However, the present invention is not limited to this example. For example, the temperature and dissociation A look-up table is prepared that corresponds to the temperature and pressure, and the look-up table is used to select the temperature and pressure based on the obtained temperature. dissociation The pressure may be acquired.

[0061] dissociationAfter calculating the pressure, the combustion control device 150 acquires the oxygen concentration inside the combustion chamber 120 from the oxygen concentration meter 122 (step S303). In this embodiment, a laser type oxygen concentration meter is used as the oxygen concentration meter 122, so that the oxygen concentration inside the combustion chamber 120 can be measured in real time. The oxygen concentration meter 122 is disposed so as to measure the oxygen concentration near the exhaust port of the combustion chamber 120. Therefore, the oxygen concentration measured by the oxygen concentration meter 122 can be regarded as the oxygen concentration of the secondary combustion gas 206 generated in the combustion chamber 120.

[0062] Next, the combustion control device 150 calculates the oxygen partial pressure of the secondary combustion gas 206 based on the acquired oxygen concentration (step S304). Since the shape of the combustion chamber 120 and the like are known and the temperature inside the combustion chamber 120 has already been acquired, the gas flow rate of the secondary combustion gas 206 in the area where the oxygen concentration meter 122 is arranged can also be calculated. Therefore, if the oxygen concentration can be acquired, the oxygen partial pressure of the secondary combustion gas 206 can be found by calculation. However, this is not the only example, and if the gas flow rate is known, a reference table that associates oxygen concentrations with oxygen partial pressures may be prepared in advance, and the oxygen partial pressure may be acquired from the reference table based on the acquired oxygen concentration.

[0063] Through the above process, the oxygen partial pressure of the secondary combustion gas 206 and the contact point of the heat exchanger 130 dissociation After determining the oxygen partial pressure and dissociation The differential pressure between the oxygen partial pressure and the oxygen partial pressure is calculated, and it is determined whether the calculated differential pressure is equal to or lower than a predetermined value (i.e., whether the oxygen partial pressure is dissociation In this embodiment, the combustion control device 150 determines whether the oxygen partial pressure and the pressure are within a predetermined range (step S305). dissociation When the pressure difference between the dissociation By this determination process, the combustion control device 150 determines whether the oxygen partial pressure of the secondary combustion gas 206 is equal to or lower than the oxygen partial pressure of the contact area of ​​the heat exchanger 130. dissociation It is possible to know whether the pressure is in equilibrium or not.

[0064] If the determination in step S305 is YES, the oxygen partial pressure of the secondary combustion gas 206 and the contact area of ​​the heat exchanger 130 are dissociation If the result of step S305 is NO, the combustion control device 150 determines that the oxygen partial pressure is dissociation It is then determined whether the pressure is higher than the predetermined pressure (step S306).

[0065] If the determination in step S306 is YES, the combustion control device 150 reduces the oxygen concentration inside the combustion chamber 120 (step S307). Specifically, the combustion control device 150 controls the gas supply device 126 to supply a predetermined amount of inert gas into the combustion chamber 120. By supplying the inert gas, the oxygen concentration inside the combustion chamber 120 can be relatively reduced. If the determination in step S306 is NO, the combustion control device 150 increases the oxygen concentration inside the combustion chamber 120 (step S308). Specifically, the combustion control device 150 controls the gas supply device 126 to supply a predetermined amount of oxygen gas into the combustion chamber 120. By supplying the oxygen gas, the oxygen concentration inside the combustion chamber 120 can be relatively increased. In this way, the combustion control device 150 can monitor the oxygen concentration in the combustion chamber 120 in real time and control the oxygen concentration inside the combustion chamber 120 (i.e., the oxygen partial pressure of the secondary combustion gas 206).

[0066] When the supply of gas by the control process of step S307 or step S308 is completed, the combustion control device 150 returns the control process to step S301. Thereafter, the combustion control device 150 again performs the control process from step S301 onward, and adjusts the oxygen partial pressure and dissociation The control program continues to be executed until the pressure difference between the oxygen partial pressure and the combustion pressure becomes equal to or less than a predetermined value. dissociation When the pressure difference between the pressure in the intake duct and the pressure in the exhaust duct falls below the predetermined value, the determination in step S305 becomes YES, and the execution of the control program ends.

[0067] As described above, the heat recovery system 100 of this embodiment is equipped with the combustion control device 150, and thus can monitor the oxygen concentration inside the combustion chamber 120 (i.e., the oxygen partial pressure of the secondary combustion gas 206). In addition, the heat recovery system 100 is capable of monitoring the oxygen concentration inside the combustion chamber 120 (i.e., the oxygen partial pressure of the secondary combustion gas 206) calculated by the combustion control device 150 and the oxygen partial pressure of the contact part of the heat exchanger 130. dissociation The oxygen concentration in the combustion chamber 120 is controlled according to the result of comparing the oxygen partial pressure and dissociation The pressure can be kept within the same or approximately the same range as the pressure in the heat exchanger 130. As a result, the heat recovery system 100 can maintain an equilibrium state between the high-temperature secondary combustion gas 206 of about 950°C and the contact portion of the heat exchanger 130 even when the high-temperature secondary combustion gas 206 comes into contact with the contact portion of the heat exchanger 130. In this way, since heat exchange can be performed using the high-temperature secondary combustion gas 206, heat can be recovered with high efficiency even if a heat exchanger that is not subject to legal regulations, such as a hot water heater, is used. In other words, according to this embodiment, it is possible to provide a heat recovery system 100 that suppresses high-temperature corrosion with a simple structure and improves heat recovery efficiency.

[0068] In addition, the order of the control flow from step S301 to step S304 in FIG. 3 is not limited to this example. For example, the control flow in FIG. 3 may acquire the temperature after acquiring the oxygen concentration. In addition, in the control flow in FIG. 3, after acquiring the oxygen concentration and the temperature, dissociation The blood pressure and oxygen partial pressure may be calculated.

[0069] (Variation 1) In this embodiment, the contact portion of the heat exchanger 130 is heated by the control of the combustion control device 150. dissociation In the above description, the pressure difference between the partial pressure of oxygen in the secondary combustion gas 206 and the pressure difference between the partial pressure of oxygen in the secondary combustion gas 206 is set to a predetermined value or less. However, from the viewpoint of suppressing deterioration of the contact portion of the heat exchanger 130, the present invention is not limited to this example. For example, dissociation If the pressure exceeds the specified value, the pressure difference is kept below the specified value, and the oxygen partial pressure is dissociation In other words, the combustion control device 150 determines whether the oxygen partial pressure of the secondary combustion gas 206 is greater than the oxygen partial pressure of the contact portion of the heat exchanger 130. dissociationThe oxygen concentration of the secondary combustion gases 206 may be adjusted to be below pressure.

[0070] In this case, the contact parts of the heat exchanger 130 are always placed in a reducing atmosphere, so that deterioration of the contact parts due to high-temperature corrosion can be suppressed.

[0071] (Variation 2) In this embodiment, an example in which a vacuum type hot water heater is used as the heat exchanger 130 has been shown, but the present invention is not limited to this example. For example, an atmospheric pressure type hot water heater can also be used as the heat exchanger 130. The atmospheric pressure type hot water heater is structured to boil heat transfer water with the inside of the container open to the atmosphere, and to extract hot water by using the heat of the steam. The atmospheric pressure type hot water heater is also called a non-pressure type hot water heater, since no pressure is applied inside the container.

[0072] Fig. 4 is a diagram showing the configuration of the heat exchanger 130 used in the heat recovery system 100 of one embodiment of the present invention. Specifically, Fig. 4 shows the configuration of an atmospheric pressure type hot water heater 230 used as the heat exchanger 130. In the atmospheric pressure type hot water heater 230, the inside of a housing 231 is divided into a heating chamber 232 and a medium chamber 233. The heating chamber 232 is supplied with secondary combustion gas 206 sent from the combustion chamber 120. The secondary combustion gas 206 supplied to the heating chamber 232 is used to heat the heat transfer water 234 filled in the medium chamber 233, and then discharged as combustion gas 208.

[0073] The heat transfer water 234 heated in the medium chamber 233 is supplied to the heat exchange section 235, and heat exchange is performed using the heat of the heated heat transfer water 234. The heat exchange section 235 has a water supply pipe 236, and water is supplied from an inlet 236a and hot water is obtained from an outlet 236b. A pump 237 is provided between the medium chamber 233 and the heat exchange section 235. The pump 237 serves to circulate the heat transfer water 234 between the medium chamber 233 and the heat exchange section 235.

[0074] In this embodiment, the high-temperature (e.g., 950°C) secondary combustion gas 206 discharged from the combustion chamber 120 can be directly supplied to the heat exchanger 130. In other words, unlike the conventional technology, it is not necessary to cool the secondary combustion gas 206 discharged from the combustion chamber 120 to about 350°C before supplying it to the heat exchanger 130. Therefore, it is not necessary to use a steam boiler as in the conventional technology, and high heat recovery efficiency can be ensured even if a heat exchanger such as a hot water heater is used.

[0075] In addition, the atmospheric pressure type hot water heater 230 has an opening 231a at the top of the housing 231, and the inside of the housing 231 is maintained at atmospheric pressure. Therefore, the internal pressure of the housing 231 of the atmospheric pressure type hot water heater 230 does not become high pressure, and the atmospheric pressure type hot water heater 230 is not subject to boiler regulations. Therefore, when the atmospheric pressure type hot water heater 230 is used as the heat exchanger 130, it is not necessary to assign a boiler engineer as a manager. In other words, since a hot water heater that is not subject to legal regulations can be used as the heat exchanger 130, the costs required for maintenance and equipment upkeep can be reduced.

[0076] (Variation 3) In the heat recovery system 100 of this embodiment, any heat exchanger other than the above-mentioned vacuum type hot water heater and atmospheric pressure type hot water heater can be used as the heat exchanger 130. In this embodiment, since the high-temperature secondary combustion gas 206 discharged from the combustion chamber 120 can be directly supplied to the heat exchanger 130, high heat recovery efficiency can be achieved regardless of the type of heat exchanger used.

[0077] (Variation 4) In the control flow shown in FIG. 3, in step S305, the oxygen partial pressure and dissociation The differential pressure between the oxygen partial pressure and the oxygen partial pressure is calculated, and it is determined whether the calculated differential pressure is equal to or lower than a predetermined value (i.e., whether the oxygen partial pressure is dissociation However, the present invention is not limited to this example. For example, in FIG. 3, step S305 may be omitted.

[0078] In this case, the combustion control device 150 performs the step S302 of dissociation In step S304, the oxygen partial pressure of the secondary combustion gas 206 is calculated. In step S306, the oxygen partial pressure is calculated as follows: dissociation Then, depending on the result of this determination, the combustion control device 150 executes the control process of step S307 or step S308 to increase or decrease the oxygen concentration in the combustion chamber 120. After controlling the oxygen concentration in this manner, the combustion control device 150 repeats the control process again from step S301.

[0079] The combustion control device 150 of this modification constantly executes the above-mentioned loop process to obtain the oxygen partial pressure and dissociation The results of the comparison with the oxygen partial pressure are fed back to dissociation This allows an equilibrium state to be maintained between the contact portion of the heat exchanger 130 and the secondary combustion gas 206 generated in the combustion chamber 120.

[0080] Second embodiment In the first embodiment, an example in which the oxygen concentration inside the combustion chamber 120 is adjusted using the gas supply device 126 has been described, but the present invention is not limited to this example. For example, the oxygen concentration inside the combustion chamber 120 can also be adjusted by using an air flow rate adjustment device such as a damper or a valve to adjust the amount of air supplied to the combustion chamber 120.

[0081] Fig. 5 is a block diagram showing the configuration of a heat recovery system 100a according to one embodiment of the present invention. In Fig. 5, the same elements as those in the heat recovery system 100 described in the first embodiment are given the same reference numerals and the description thereof will be omitted.

[0082] 5, the heat recovery system 100a of this embodiment includes a blower 127 and a damper 128. The blower 127 supplies air to the combustion chamber. The damper 128 is provided between the blower 127 and the combustion chamber 120, and adjusts the amount of air supplied to the combustion chamber 120. That is, the damper 128 functions as an air volume adjustment device that adjusts the flow rate of air supplied to the combustion chamber 120.

[0083] In this embodiment, the combustion control device 150a controls the damper 128. Specifically, the combustion control device 150a can adjust the amount of air supplied to the combustion chamber 120 by controlling the damper 128. That is, the combustion control device 150a can adjust the oxygen concentration inside the combustion chamber 120 by adjusting the amount of air supplied to the combustion chamber 120. For example, referring to the control flow shown in FIG. 3 in the first embodiment, the combustion control device 150a can lower (step S307) or raise (step S308) the oxygen concentration inside the combustion chamber 120 by controlling the damper 128 according to the determination in step S306. In this way, the combustion control device 150a can monitor the oxygen concentration in the combustion chamber 120 in real time and control the oxygen concentration inside the combustion chamber 120 (i.e., the oxygen partial pressure of the secondary combustion gas 206).

[0084] The embodiments of the present invention and their modifications can be combined as appropriate as long as they are not mutually inconsistent. A heat recovery system according to the above-described embodiment, in which a person skilled in the art appropriately adds or removes components or modifies the design, or adds or omits a process or modifies conditions, is included in the scope of the present invention as long as it includes the gist of the present invention.

[0085] Furthermore, even if there are other effects and advantages different from those brought about by the aspects of the above-mentioned embodiment, those which are clear from the description in this specification or which can be easily predicted by a person skilled in the art are naturally understood to be brought about by the present invention. [Explanation of symbols]

[0086] 100, 100a... heat recovery system, 110... incinerator, 120... combustion chamber, 122... oxygen concentration meter, 124... thermometer, 126... gas supply device, 127... blower, 128... damper, 130... heat exchanger, 131... housing, 131a... exhaust port, 132... heating chamber, 133... heat exchange chamber, 134... heat transfer water, 135... heat exchange section, 136... water supply pipe, 136a... inlet, 136b... outlet, 14 0...cooling chamber, 150, 150a...combustion control device, 202...waste, 204...primary combustion gas, 206...secondary combustion gas, 208...combustion gas, 210...combustion gas, 230...atmospheric pressure hot water heater, 231...casing, 231a...opening, 232...heating chamber, 233...medium chamber, 234...heat transfer water, 235...heat exchange section, 236...water supply pipe, 236a...inlet, 236b...outlet, 237...pump

Claims

1. A combustion chamber; a heat exchanger to which the combustion gas generated in the combustion chamber is supplied; A combustion control device for controlling an oxygen concentration of the combustion gas; Equipped with The combustion chamber has an oxygen concentration meter for measuring an oxygen concentration of the combustion gas, The combustion control device is a heat recovery system that controls the oxygen concentration so that the pressure difference between the dissociation pressure of a contact portion that is part of the heat exchanger and comes into contact with the combustion gas and the oxygen partial pressure of the combustion gas is equal to or less than a predetermined value.

2. The combustion chamber further includes a thermometer for measuring a temperature of the combustion gas. The heat recovery system according to claim 1 , wherein the combustion control device calculates the dissociation pressure based on the temperature.

3. The combustion chamber further includes a gas supply device for supplying oxygen gas or an inert gas to the combustion chamber, The heat recovery system according to claim 1 or 2, wherein the combustion control device controls the gas supply device in accordance with the oxygen concentration.

4. The combustion chamber further includes an air flow rate adjusting device for adjusting the amount of air supplied to the combustion chamber. The heat recovery system according to claim 1 or 2, wherein the combustion control device controls the air volume regulator in accordance with the oxygen concentration.

5. The heat recovery system according to claim 1 , wherein the heat exchanger is a vacuum or non-pressure type hot water heater.

6. The heat recovery system according to claim 1 , further comprising a cooling chamber to which the combustion gas that has passed through the heat exchanger is supplied.

7. 7. The heat recovery system of claim 1, further comprising an incinerator that supplies primary combustion gases to the combustion chamber.

8. The heat recovery system according to claim 1 , wherein the oxygen concentration meter is a laser type oxygen concentration meter.

9. Measure the oxygen concentration of the combustion gas generated in the combustion chamber, controlling the oxygen concentration so that a pressure difference between a dissociation pressure of a part of a heat exchanger connected to the combustion chamber that comes into contact with the combustion gas and an oxygen partial pressure of the combustion gas is equal to or less than a predetermined value; supplying the combustion gas, the oxygen concentration of which has been controlled, to the heat exchanger.

10. further comprising measuring a temperature of the combustion gas; The heat recovery method according to claim 9 , wherein the dissociation pressure is calculated based on the temperature.

11. The heat recovery method according to claim 9 or 10, wherein a vacuum type or non-pressure type hot water heater is used as the heat exchanger.

12. The heat recovery method according to any one of claims 9 to 11, further comprising: supplying the combustion gas that has passed through the heat exchanger to a cooling chamber.

13. 13. The method of claim 9, further comprising supplying primary combustion gas generated in an incinerator to the combustion chamber.

14. The heat recovery method according to claim 9 , wherein the oxygen concentration is measured by a laser type oxygen concentration meter.

15. A combustion control device including a memory unit that stores a control program and a processor that executes the control program, The control program includes: Obtain the temperature inside the combustion chamber, Obtaining an oxygen concentration inside the combustion chamber; Calculating the oxygen partial pressure of the combustion gas generated in the combustion chamber using the oxygen concentration; Calculating a dissociation pressure of a contact portion of a part of a heat exchanger that contacts the combustion gas using the temperature; determining whether a differential pressure between the oxygen partial pressure and the dissociation pressure is equal to or less than a predetermined value; A combustion control device that causes the processor to control the oxygen concentration inside the combustion chamber when the pressure difference is not equal to or less than the predetermined value.

16. The control program further comprises: When the differential pressure is not equal to or less than the predetermined value, it is determined whether the oxygen partial pressure is higher than the dissociation pressure; 16. The combustion control device according to claim 15, wherein the processor is configured to execute a process of decreasing the oxygen concentration inside the combustion chamber when the oxygen partial pressure is higher than the dissociation pressure, and increasing the oxygen concentration inside the combustion chamber when the oxygen partial pressure is lower than the dissociation pressure.

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