Flue gas waste heat recovery device and using method thereof

Abstract

The invention discloses a flue gas waste heat recovery device, relates to industrial energy-saving equipment, and aims to improve the anti-corrosion effect of a flue gas heat exchanger during waste heat recovery. Comprising a flue gas humidification heat exchanger, a flue gas heat exchanger, an air humidification heat exchanger, a booster water pump, an in-water neutralization device, a flow control valve, an air hygrometer, a flue gas hygrometer, an air humidification heat exchanger atomizer, a flue gas humidification heat exchanger atomizer and a water tank, and the low-temperature side of the flue gas heat exchanger is used for circulating a low-temperature medium which exchanges heat with flue gas. The invention further discloses a using method of the flue gas waste heat recovery device. The flue gas condensate water is used for humidifying flue gas or combustion-supporting air, the pH value of the condensate water of the flue gas heat exchanger is adjusted, the service life of the flue gas heat exchanger is prolonged, flue gas waste heat recovery is improved, the purpose of corrosion prevention of the flue gas heat exchanger is achieved, meanwhile, flue gas pollutant emission is reduced, and the flue gas dew point temperature is increased.

Description

Technical Field

[0001] The invention relates to industrial energy-saving equipment, and in particular to a flue gas waste heat recovery device and a use method thereof. Background Art

[0002] The combustion process of natural gas boilers generally produces nitrogen oxides, and some produce sulfur dioxide. Flue gas waste heat recovery is an effective means to improve the energy efficiency of boilers. However, the condensed water produced in this recovery process has a pH value of about 4.6 due to the dissolution of acidic substances in the flue gas in water, which is corrosive to ordinary heat exchangers.

[0003] Using condensed water to humidify flue gas or combustion air is a wet waste heat recovery technology, also known as steam pump flue gas waste heat recovery technology. It is usually used to increase the flue gas condensation temperature, thereby providing conditions for recovering the flue gas latent heat under higher cold source temperature conditions. Patent CN 109268820 B reduces the combustion temperature by humidifying combustion air and fuel gas to achieve the purpose of reducing the production of nitrogen oxides. At present, there is no technology on the market that adjusts the pH value of condensed water by humidifying flue gas or combustion air to achieve corrosion protection of heat exchangers. Increasing the pH value of condensed water is of great significance for extending the service life of heat exchanger materials or coatings. Summary of the invention

[0004] In order to extend the service life of a flue gas heat exchanger, prevent the corrosion of the flue gas heat exchanger, reduce the emission of flue gas pollutants and increase the dew point temperature of the flue gas, the present invention provides a flue gas waste heat recovery device and a use method thereof.

[0005] A flue gas waste heat recovery device in the present invention comprises a flue gas humidifying heat exchanger, a flue gas heat exchanger, an air humidifying heat exchanger, a booster water pump, a water neutralization device, a flow control valve A, a flow control valve B, a flow control valve C, an air thermometer and hygrometer, a flue gas temperature and humidity meter, a pH detector, a four-way valve A, a four-way valve B and a water tank. The flue gas humidifying heat exchanger and the air humidifying heat exchanger are direct heat exchangers. The water inlet of the flue gas humidifying heat exchanger is connected to the flow control valve B, the smoke outlet of the flue gas humidifying heat exchanger is connected to the smoke inlet on the high temperature side of the flue gas heat exchanger, the flue gas temperature and humidity meter is arranged between the flue gas humidifying heat exchanger and the flue gas heat exchanger, the water outlet of the flue gas heat exchanger is connected to one end of the water neutralization device, and the pH detector is connected to the flue gas humidifying heat exchanger. The meter is arranged between the flue gas heat exchanger and the water neutralization device, the other end of the water neutralization device is connected to the inlet of the booster water pump, the outlet of the booster water pump is connected to one end of the four-way valve A, the other three ends of the four-way valve A are respectively connected to one end of the flow control valve A, the flow control valve B and the flow control valve C, the other end of the flow control valve C is connected to one end of the four-way valve B, the other three ends of the four-way valve B are respectively connected to the water inlet of the water tank, the water outlet of the flue gas humidifying heat exchanger and the water outlet of the air humidifying heat exchanger, the water inlet of the air humidifying heat exchanger is connected to the flow control valve A, the air temperature and humidity meter is arranged at the exhaust port of the air humidifying heat exchanger, and the low-temperature side of the flue gas heat exchanger is used for circulating the low-temperature medium for heat exchange with the flue gas.

[0006] A flue gas waste heat recovery device in the present invention, wherein a plurality of flue gas humidifying heat exchanger atomizers are arranged in the flue gas humidifying heat exchanger, and the flue gas humidifying heat exchanger atomizers are connected to the water inlet of the flue gas humidifying heat exchanger.

[0007] A flue gas waste heat recovery device in the present invention, wherein a plurality of air humidifying heat exchanger atomizers are arranged in an air humidifying heat exchanger, and the air humidifying heat exchanger atomizers are connected to the water inlet of the air humidifying heat exchanger.

[0008] A flue gas waste heat recovery device in the present invention, wherein the flue gas heat exchanger is an indirect heat exchanger.

[0009] A flue gas waste heat recovery device in the present invention, wherein the warm medium is heat network return water.

[0010] A flue gas waste heat recovery device in the present invention, wherein the low-temperature medium is a heat pump working fluid.

[0011] The method for using the flue gas waste heat recovery device of the present invention comprises the following steps:

[0012] (1) Connect the flue gas inlet of the flue gas humidifying heat exchanger to the flue gas outlet of the boiler, connect the air outlet of the air humidifying heat exchanger to the air inlet of the boiler, start the boiler and keep it running, let the low-temperature medium flow through the flue gas heat exchanger, and then start the booster pump, flow control valve A, flow control valve B and flow control valve C;

[0013] (2) Determine whether the boiler is running. If the boiler is running, proceed to step (3); if the boiler is stopped, stop the low-temperature medium from flowing through the flue gas heat exchanger and close the booster pump, flow control valve A, flow control valve B and flow control valve C;

[0014] (3) detecting the value of the pH detector to determine whether the pH value is greater than or equal to the target value;

[0015] (4) If the pH value in step (3) is greater than or equal to the target value, then detecting whether the air humidity value reaches 100%;

[0016] (5) If the pH value in step (3) is less than the target value, the amount of condensed water and the air humidity value of the air humidifying heat exchanger are detected to determine whether the amount of condensed water in the air humidifying heat exchanger has reached a maximum value or whether the air humidity value is greater than or equal to 99%;

[0017] (6) If the air humidity value in step (4) reaches 100%, the amount of condensed water entering the air humidifying heat exchanger is reduced through the flow control valve A, and the process returns to step (2); if the air humidity value in step (4) does not reach 100%, the amount of condensed water entering the flue gas humidifying heat exchanger 1 is reduced through the flow control valve B, and the process returns to step (2);

[0018] (7) If the amount of condensed water in the air humidifying heat exchanger in step (5) reaches the maximum value or the air humidity value is greater than or equal to 99%, continue to detect whether the air humidity value is equal to 100%; if the amount of condensed water in the air humidifying heat exchanger in step (5) does not reach the maximum value and the air humidity value is less than 99%, increase the amount of condensed water in the air humidifying heat exchanger and return to step (2);

[0019] (8) If the air humidity value in step (7) is equal to 100%, the amount of condensed water in the air humidifying heat exchanger is reduced and the process returns to step (5); if the air humidity value in step (7) is less than 100%, the amount of condensed water in the flue gas humidifying heat exchanger is detected to see whether it has reached a maximum value;

[0020] (9) If the amount of condensed water in the flue gas humidifying heat exchanger reaches the maximum value in step (8), return to step (2); if the amount of condensed water in the flue gas humidifying heat exchanger does not reach the maximum value in step (8), increase the amount of condensed water in the flue gas humidifying heat exchanger and return to step (2).

[0021] A flue gas waste heat recovery device and a method of using the same disclosed in the present invention have at least the following beneficial effects: the present invention utilizes condensed water to humidify flue gas or air and adjusts the pH value of condensed water; the principle is simple, the operation is convenient, and the anti-corrosion effect on the flue gas heat exchanger is significant; the flue gas dew point temperature is increased, the temperature requirement for the low-temperature medium is reduced, the heat exchange effect of the flue gas heat exchanger is enhanced, and the pollution of the environment to the flue gas pollutants is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The schematic diagram of the structure of the flue gas waste heat recovery device in the present invention is shown;

[0023] Figure 2 A flow chart showing the method of using the flue gas waste heat recovery device in the present invention is shown.

[0024] Reference numerals:

[0025] 1-Flue gas humidifying heat exchanger; 2-Flue gas heat exchanger; 3-Air humidifying heat exchanger; 4-Boosting water pump; 5-Water neutralization device; 6-pH detector; 7-Flow control valve A; 8-Flow control valve B; 9-Flow control valve C; 10-Air temperature and humidity meter; 11-Flue gas temperature and humidity meter; 12-Air humidifying heat exchanger atomizer; 13-Flue gas humidifying heat exchanger atomizer; 14-Water tank; 15-Four-way valve A; 16-Four-way valve B. DETAILED DESCRIPTION

[0026] The present disclosure will now be discussed with reference to several exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and thus implement the present disclosure, rather than implying any limitation on the scope of the present disclosure.

[0027] As used herein, the term "including" and variations thereof are to be interpreted as open-ended terms meaning "including but not limited to." The term "based on" is to be interpreted as "based, at least in part, on." The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment." The term "another embodiment" is to be interpreted as "at least one other embodiment."

[0028] As used herein, the term "including" and its variants are to be interpreted as open-ended terms meaning "including but not limited to". The term "based on" is to be interpreted as "based at least in part on". The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment". The term "another embodiment" is to be interpreted as "at least one other embodiment". The orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal" and the like is based on the orientation or position relationship shown in the accompanying drawings. These terms are mainly for better describing the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation. In addition, in addition to being used to indicate an orientation or position relationship, some of the above terms may also be used to indicate other meanings, such as the term "upper" may also be used to indicate a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to the specific circumstances. In addition, the terms "install", "set", "provided with", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be an internal connection between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances. In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, "plurality" means two or more.

[0029] like Figure 1 As shown, the present invention discloses a flue gas waste heat recovery device, including a flue gas humidifying heat exchanger 1, a flue gas heat exchanger 2, an air humidifying heat exchanger 3, a booster water pump 4, a water neutralization device 5, a flow control valve A7, a flow control valve B8, a flow control valve C9, an air temperature and humidity meter 10, a flue gas temperature and humidity meter 11, an air humidifying heat exchanger atomizer 12, a flue gas humidifying heat exchanger atomizer 13, a pH detector 6, a four-way valve A15, a four-way valve B16 and a water tank 14, a plurality of flue gas humidifying heat exchanger atomizers 13 are arranged inside the flue gas humidifying heat exchanger 1, and are evenly arranged above the inside of the flue gas humidifying heat exchanger 1 to enhance the atomization effect, a plurality of air humidifying heat exchanger atomizers 12 are arranged inside the air humidifying heat exchanger 3, and are evenly arranged above the inside of the air humidifying heat exchanger 3 to enhance the atomization effect, wherein the air humidifying heat exchanger atomizer 12 and the flue gas humidifying heat exchanger atomizer 13 are both atomizing nozzles.

[0030] The flue gas humidifying heat exchanger 1 is provided with a flue gas inlet, a flue gas outlet, a water inlet and a water outlet.

[0031] The high temperature side of the flue gas heat exchanger 2 is provided with a flue gas inlet and a flue gas outlet, and the low temperature side of the flue gas heat exchanger 2 is provided with a low temperature medium inlet and a low temperature medium outlet.

[0032] The air humidifying heat exchanger 3 is provided with an air inlet, an air outlet, a water inlet and a water outlet.

[0033] The water inlet of the air humidifying heat exchanger 3 is connected to the flow control valve A7 through a water pipe, and the air humidifying heat exchanger atomizer 12 is connected to the water inlet of the air humidifying heat exchanger 3, so that the flow control valve A7 is connected to the air humidifying heat exchanger atomizer 12 through a water pipe. The water inlet of the flue gas humidifying heat exchanger 1 is connected to the flow control valve B8 through a water pipe, and the flue gas humidifying heat exchanger atomizer 13 is connected to the water inlet of the flue gas humidifying heat exchanger 1, so that the flow control valve B8 is connected to the flue gas humidifying heat exchanger atomizer 13 through a water pipe. The flue gas inlet of the flue gas humidifying heat exchanger 1 is connected to the flue gas outlet of the boiler, and the flue gas outlet of the flue gas humidifying heat exchanger 1 is connected to the flue gas inlet of the flue gas heat exchanger 2 through a flue. A flue gas temperature and humidity meter 11 is set on the flue to detect the temperature and humidity values ​​of the flue gas in the flue gas humidifying heat exchanger 1 in real time, and finally the flue gas is discharged through the flue gas outlet of the flue gas heat exchanger 2.

[0034] The upper air outlet of the air humidifying heat exchanger 3 is connected to the boiler air inlet, and the left air inlet of the air humidifying heat exchanger 3 is connected to the environment. Air flows in from the air inlet and is discharged from the air outlet. An air thermometer and hygrometer 10 is provided on the air channel of the air outlet to detect the temperature and humidity values ​​of the air in the air humidifying heat exchanger 3 in real time.

[0035] The air humidifying heat exchanger atomizer 12 is arranged on the upper side of the air humidifying heat exchanger 3, and the flue gas humidifying heat exchanger atomizer 13 is arranged on the upper side of the flue gas humidifying heat exchanger 1. One end of the four-way valve A15 is connected to the booster water pump 4 through a water pipe, and the booster water pump 4 is connected to one end of the water neutralization device 5 through a water pipe, and the other end of the water neutralization device 5 is connected to the water outlet of the flue gas heat exchanger 2 through a water pipe. The pH detector 6 is installed on the water pipe connecting the water neutralization device 5 and the flue gas heat exchanger 2 to detect the pH value of the condensed water in real time. The condensed water is neutralized by acid and alkali through the neutralization device 5, so as to achieve efficient and environmentally friendly treatment of the condensed water, and prevent pollutants from entering the air humidifying heat exchanger 3 and the flue gas humidifying heat exchanger 1 to cause corrosion to them.

[0036] The other three ends of the four-way valve A15 are connected to one end of the flow control valve A7, the flow control valve B8 and the flow control valve C9 respectively through water pipes, and the other ends of the flow control valve A7, the flow control valve B8 and the flow control valve C9 are connected to the air humidifying heat exchanger atomizer 12 in the air humidifying heat exchanger 3, the flue gas humidifying heat exchanger atomizer 13 in the flue gas humidifying heat exchanger 1 and one end of the four-way valve B16 respectively through water pipes, and the other three ends of the four-way valve B16 are connected to the flue gas humidifying heat exchanger 1, the water tank 14 and the air humidifying heat exchanger 3 respectively through water pipes.

[0037] During operation, the low-temperature medium is introduced from the low-temperature medium inlet of the flue gas heat exchanger 2, and is discharged from the low-temperature medium outlet of the flue gas heat exchanger 2 after passing through the flue gas heat exchanger 2. The flue gas exchanges heat with the low-temperature medium, and the flue gas is reduced to a dew point temperature or below to form condensed water. The formed condensed water flows from the water outlet of the flue gas heat exchanger 2 into the water pipe and enters the water neutralization device 5. Before the condensed water enters the water neutralization device 5, the pH detector 6 detects the pH value of the condensed water in real time. After the condensed water is neutralized by acid and alkali in the water neutralization device 5, it enters the booster water pump 4. The booster water pump 4 The water is pressurized, and then the condensed water flows into the flow control valve A7, the flow control valve B8 and the flow control valve C9 respectively through the four-way valve A15. The flow control valve A7 and the flow control valve B8 control the flow of the condensed water and then flow into the air humidifying heat exchanger atomizer 12 in the air humidifying heat exchanger 3 and the flue gas humidifying heat exchanger atomizer 13 in the flue gas humidifying heat exchanger 1 through the water pipe respectively. A certain number of the air humidifying heat exchanger atomizer 12 and the flue gas humidifying heat exchanger atomizer 13 are opened as needed to atomize the condensed water.

[0038] The air flows in from the air inlet of the air humidifying heat exchanger 3 through the air duct, and exchanges heat with the condensed water flowing out of the air humidifying heat exchanger atomizer 12 in the air humidifying heat exchanger 3, and is humidified at the same time, and then the air flows out from the air outlet of the air humidifying heat exchanger 3 to the boiler. The boiler flue gas flows in from the flue gas inlet of the flue gas humidifying heat exchanger 1, and exchanges heat with the condensed water flowing out of the flue gas humidifying heat exchanger atomizer 13 in the flue gas humidifying heat exchanger 1, and is humidified at the same time, and then the flue gas flows out from the flue gas outlet of the flue gas humidifying heat exchanger 1, flows into the flue gas inlet on the high temperature side of the flue gas heat exchanger 2 through the flue, and after exchanging heat with the low temperature medium in the flue gas heat exchanger 2, it is discharged from the flue gas outlet on the high temperature side of the flue gas heat exchanger 2.

[0039] The present invention uses flue gas condensate to humidify flue gas and air for heat exchange, adjusts the temperature and humidity of flue gas and air, and the flue gas temperature and humidity meter 11 and the air temperature and humidity meter 10 detect the temperature and humidity values ​​of the corresponding flue gas and air in real time, and then adjusts the pH value of the condensate to the target value, thereby achieving the purpose of preventing the flue gas condensate from corroding the flue gas heat exchanger 2, forming a virtuous circle.

[0040] The excess condensed water in the air humidifying heat exchanger 3 and the flue gas humidifying heat exchanger 1 flows into the four-way valve B16 through the water outlets of the air humidifying heat exchanger 3 and the flue gas humidifying heat exchanger 1, and then flows into the water tank 14 through the water inlet of the water tank 14. The excess condensed water pressurized by the booster water pump 4 flows into the flow control valve C9 for flow control, and then also flows into the water tank 14 through the four-way valve B16.

[0041] Among them, the flue gas humidifying heat exchanger 1 and the air humidifying heat exchanger 3 are direct heat exchangers, and the flue gas heat exchanger 2 is an indirect heat exchanger, which improves the working efficiency.

[0042] It should be noted that direct heat exchanger and indirect heat exchanger are general technical terms.

[0043] Direct heat exchangers refer to heat exchangers in which the heating medium and the heated medium do not exchange heat through the heating surface, but through direct contact. This type of heat exchanger avoids the heat resistance of dirt on the heat transfer partition and its two sides. As long as the contact between the fluids is good, there is a higher heat transfer rate. Compared with indirect heat exchangers that exchange heat through the heating surface, it generally has the characteristics of saving manufacturing equipment materials and high heat exchange efficiency.

[0044] Indirect heat exchange refers to a form of heat exchange in which the heat exchange media do not directly contact each other. Compared with direct heat exchange, this heat exchange method does not require mixing before heat exchange and separation after heat exchange, which saves production costs in terms of time and process and improves production efficiency.

[0045] The low-temperature medium that exchanges heat with the flue gas in the flue gas heat exchanger 2 can be heat network return water, heat pump working fluid or other media that can achieve equivalent effects, which is beneficial to system circulation and environmental protection.

[0046] like Figure 2 As shown, Q a Indicates the amount of condensed water in the air humidifying heat exchanger 3; Q a Max represents the maximum amount of condensed water in the air humidifying heat exchanger 3; Q g Indicates the amount of condensed water in the flue gas humidification heat exchanger 1; Q g Max indicates the maximum amount of condensed water in flue gas humidifying heat exchanger 1.

[0047] The method for using the flue gas waste heat recovery device of the present invention comprises the following steps:

[0048] (1) Connect the flue gas inlet of the flue gas humidifying heat exchanger 1 to the flue gas outlet of the boiler, connect the air outlet of the air humidifying heat exchanger 3 to the air inlet of the boiler, start the boiler and keep it running, and let the low-temperature medium flow through the flue gas heat exchanger 2, then start the booster pump 4, flow control valve A7, flow control valve B8 and flow control valve C9;

[0049] (2) Determine whether the boiler is running. If the boiler is running, proceed to step (3); if the boiler is stopped, stop the low-temperature medium from flowing through the flue gas heat exchanger 2 and close the booster pump 4, flow control valve A7, flow control valve B8 and flow control valve C9;

[0050] (3) detecting the value of the pH detector 6 to determine whether the pH value is greater than or equal to the target value;

[0051] (4) If the pH value in step (3) is greater than or equal to the target value, then detecting whether the air humidity value reaches 100%;

[0052] (5) If the pH value in step (3) is less than the target value, the amount of condensed water and the air humidity value of the air humidifying heat exchanger 3 are detected to determine whether the amount of condensed water of the air humidifying heat exchanger 3 has reached a maximum value or whether the air humidity value is greater than or equal to 99%;

[0053] (6) If the air humidity value in step (4) reaches 100%, the amount of condensed water entering the air humidifying heat exchanger 3 is reduced through the flow control valve A7, and the process returns to step (2); if the air humidity value in step (4) does not reach 100%, the amount of condensed water entering the flue gas humidifying heat exchanger 1 is reduced through the flow control valve B8, and the process returns to step (2);

[0054] (7) If the amount of condensed water in the air humidifying heat exchanger 3 in step (5) reaches the maximum value or the air humidity value is greater than or equal to 99%, continue to detect whether the air humidity value is equal to 100%; if the amount of condensed water in the air humidifying heat exchanger 3 in step (5) does not reach the maximum value and the air humidity value is less than 99%, increase the amount of condensed water in the air humidifying heat exchanger 3 and return to step (2);

[0055] (8) If the air humidity value in step (5) is equal to 100%, the amount of condensed water in the air humidifying heat exchanger 3 is reduced, and the process returns to step (5); if the air humidity value in step (7) is less than 100%, the amount of condensed water in the flue gas humidifying heat exchanger 1 is detected to see whether it has reached a maximum value;

[0056] (9) If the amount of condensed water in the flue gas humidifying heat exchanger 1 reaches the maximum value in step (8), return to step (2); if the amount of condensed water in the flue gas humidifying heat exchanger 1 does not reach the maximum value in step (8), increase the amount of condensed water in the flue gas humidifying heat exchanger 1 and return to step (2).

[0057] After the boiler is turned on, the flue gas waste heat recovery device is operated, and the low-temperature medium flows into the low-temperature side of the flue gas heat exchanger 2, and forms condensed water after heat exchange with the flue gas.

[0058] Check the boiler status. If the boiler is running, check the pH value of the pH detector 6. If the boiler is not running, stop the flue gas waste heat recovery device.

[0059] If the pH value is greater than or equal to the target value, the value of the air temperature and humidity meter 10 is detected. If the air humidity value reaches 100%, the amount of condensed water flowing into the air humidifying heat exchanger 3 is reduced through the flow control valve A7, and a certain number of air humidifying heat exchanger atomizers 12 are closed to avoid oversaturation, and the boiler operation status is checked to determine whether the flue gas waste heat recovery device is continuously operated, that is, if the boiler is operating, the flue gas waste heat recovery device is continuously operated, and if the boiler stops operating, the flue gas waste heat recovery device is also stopped; if the air humidity value is less than 100%, the amount of condensed water flowing into the flue gas humidifying heat exchanger 1 is reduced through the flow control valve A8, and a certain number of flue gas humidifying heat exchanger atomizers 13 are closed to reduce pollutant emissions, and the boiler operation status is checked to determine whether the flue gas waste heat recovery device is continuously operated, that is, if the boiler is operating, the flue gas waste heat recovery device is continuously operated, and if the boiler stops operating, the flue gas waste heat recovery device is also stopped.

[0060] If the pH value detected by the pH detector 6 is less than the target value, the amount of condensed water in the air humidifying heat exchanger 3 and the humidity value of the air thermometer and hygrometer 10 are detected. If the amount of condensed water in the air humidifying heat exchanger 3 reaches the maximum value or the air humidity value detected by the air thermometer and hygrometer 10 is greater than or equal to 99%, continue to observe whether the humidity value of the air thermometer and hygrometer 10 reaches 100%; if the amount of condensed water in the air humidifying heat exchanger 3 does not reach the maximum value and the humidity value of the air thermometer and hygrometer 10 is less than 99%, the amount of condensed water flowing into the air humidifying heat exchanger 3 is increased through the flow control valve A7, and a certain number of air humidifying heat exchanger atomizers 12 are opened, the boiler operating status is checked, and it is determined whether the flue gas waste heat recovery device is continuously operated, that is, if the boiler is running, the flue gas waste heat recovery device is continuously operated, and if the boiler stops running, the flue gas waste heat recovery device is also stopped.

[0061] If the humidity value of the air thermometer and hygrometer 10 is 100%, the amount of condensed water flowing into the air humidifying heat exchanger 3 is reduced through the flow control valve A7, and a certain number of air humidifying heat exchanger atomizers 12 are closed, and then the amount of condensed water and the air humidity value of the air humidifying heat exchanger 3 are detected to determine whether the amount of condensed water in the air humidifying heat exchanger 3 has reached the maximum value or whether the air humidity value is greater than or equal to 99%, until the humidity value of the air thermometer and hygrometer 10 is less than 100%. At this time, check whether the amount of condensed water in the flue gas humidifying heat exchanger 1 has reached the maximum value; if the humidity value of the air thermometer and hygrometer 10 is less than 100%, directly check whether the amount of condensed water in the flue gas humidifying heat exchanger 1 has reached the maximum value.

[0062] If the amount of condensed water of the flue gas humidifying heat exchanger 1 reaches the maximum value, check the operating status of the boiler to determine whether the flue gas waste heat recovery device is continuously operated, that is, if the boiler is operating, continue to operate the flue gas waste heat recovery device, and if the boiler stops operating, then the flue gas waste heat recovery device is also stopped; if the amount of condensed water of the flue gas humidifying heat exchanger 1 does not reach the maximum value, increase the amount of condensed water flowing to the flue gas humidifying heat exchanger 1 through the flow control valve B8, and open a certain number of flue gas humidifying heat exchanger atomizers 13, check the operating status of the boiler to determine whether the flue gas waste heat recovery device is continuously operated, that is, if the boiler is operating, continue to operate the flue gas waste heat recovery device, and if the boiler stops operating, then the flue gas waste heat recovery device is also stopped.

[0063] It can be seen that the present invention can increase the pH value of the condensed water to the target value, thereby achieving the purpose of preventing the flue gas condensed water from corroding the flue gas heat exchanger 2, forming a virtuous cycle.

[0064] It should be noted that when the amount of condensed water in the flue gas humidification heat exchanger 1 and the air humidification heat exchanger 3 reaches the maximum value, the adjustment capacity of the device reaches its limit. At this time, it is still possible that the pH value does not reach the target value, but at this time the pH value is already greater than the initial value, that is, the pH value is increased. The purpose of the present invention of reducing corrosion to the flue gas heat exchanger 2 by increasing the pH value, extending the service life and reducing pollutant emissions can still be achieved.

[0065] Those skilled in the art will appreciate that the above-mentioned embodiments are specific examples for implementing the present disclosure, and in actual applications, various changes may be made thereto in form and detail without departing from the spirit and scope of the present disclosure.

Claims

1. A flue gas waste heat recovery device, characterized in that: The invention comprises a flue gas humidifying heat exchanger, a flue gas heat exchanger, an air humidifying heat exchanger, a booster water pump, a water neutralization device, a flow control valve A, a flow control valve B, a flow control valve C, an air thermometer and hygrometer, a flue gas temperature and humidity meter, a pH detector, a four-way valve A, a four-way valve B and a water tank, wherein the flue gas humidifying heat exchanger and the air humidifying heat exchanger are direct heat exchangers, the water inlet of the flue gas humidifying heat exchanger is connected to the flow control valve B, the smoke outlet of the flue gas humidifying heat exchanger is connected to the smoke inlet on the high temperature side of the flue gas heat exchanger, the flue gas temperature and humidity meter is arranged between the flue gas humidifying heat exchanger and the flue gas heat exchanger, the water outlet of the flue gas heat exchanger is connected to one end of the water neutralization device, and the pH detector is arranged between the flue gas heat exchanger and the water and device, the other end of the water neutralization device is connected to the inlet of the booster water pump, the outlet of the booster water pump is connected to one end of the four-way valve A, the other three ends of the four-way valve A are respectively connected to the flow control valve A, the flow control valve B and one end of the flow control valve C, the other end of the flow control valve C is connected to one end of the four-way valve B, the other three ends of the four-way valve B are respectively connected to the water inlet of the water tank, the water outlet of the flue gas humidifying heat exchanger and the water outlet of the air humidifying heat exchanger, the water inlet of the air humidifying heat exchanger is connected to the flow control valve A, the air thermometer and hygrometer are arranged at the exhaust port of the air humidifying heat exchanger, and the low-temperature side of the flue gas heat exchanger is used to circulate the low-temperature medium for heat exchange with the flue gas.

2. A flue gas waste heat recovery device according to claim 1, characterized in that: A plurality of flue gas humidifying heat exchanger atomizers are arranged in the flue gas humidifying heat exchanger, and the flue gas humidifying heat exchanger atomizers are connected to the water inlet of the flue gas humidifying heat exchanger.

3. The flue gas waste heat recovery device according to claim 1, characterized in that: A plurality of air humidifying heat exchanger atomizers are arranged in the air humidifying heat exchanger, and the air humidifying heat exchanger atomizers are connected to the water inlet of the air humidifying heat exchanger.

4. The flue gas waste heat recovery device according to claim 1, characterized in that: The flue gas heat exchanger is an indirect heat exchanger.

5. The flue gas waste heat recovery device according to claim 1, characterized in that: The low-temperature medium is heat network return water.

6. The flue gas waste heat recovery device according to claim 1, characterized in that: The low-temperature medium is a heat pump working fluid.

7. A method for using the flue gas waste heat recovery device according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Connect the flue gas inlet of the flue gas humidifying heat exchanger to the flue gas outlet of the boiler, connect the air outlet of the air humidifying heat exchanger to the air inlet of the boiler, start the boiler and keep it running, let the low-temperature medium flow through the flue gas heat exchanger, and then start the booster pump, flow control valve A, flow control valve B and flow control valve C; (2) Determine whether the boiler is running. If the boiler is running, proceed to step (3); if the boiler is stopped, stop the low-temperature medium from flowing through the flue gas heat exchanger and close the booster pump, flow control valve A, flow control valve B and flow control valve C; (3) detecting the value of the pH detector to determine whether the pH value is greater than or equal to the target value; (4) If the pH value in step (3) is greater than or equal to the target value, then detecting whether the air humidity value reaches 100%; (5) If the pH value in step (3) is less than the target value, the amount of condensed water and the air humidity value of the air humidifying heat exchanger are detected to determine whether the amount of condensed water in the air humidifying heat exchanger has reached a maximum value or whether the air humidity value is greater than or equal to 99%; (6) If the air humidity value in step (4) reaches 100%, the amount of condensed water entering the air humidifying heat exchanger is reduced through the flow control valve A, and the process returns to step (2); if the air humidity value in step (4) does not reach 100%, the amount of condensed water entering the flue gas humidifying heat exchanger 1 is reduced through the flow control valve B, and the process returns to step (2); (7) If the amount of condensed water in the air humidification heat exchanger in step (5) reaches a maximum value or the air humidity value is greater than or equal to 99%, continue to detect whether the air humidity value is equal to 100%; If the amount of condensed water in the air humidifying heat exchanger in step (5) has not reached the maximum value and the air humidity value is less than 99%, the amount of condensed water in the air humidifying heat exchanger is increased and the process returns to step (2); (8) If the air humidity value in step (7) is equal to 100%, the amount of condensed water in the air humidifying heat exchanger is reduced and the process returns to step (5); if the air humidity value in step (7) is less than 100%, the amount of condensed water in the flue gas humidifying heat exchanger is detected to see whether it has reached a maximum value; (9) If the amount of condensed water in the flue gas humidifying heat exchanger reaches the maximum value in step (8), return to step (2); if the amount of condensed water in the flue gas humidifying heat exchanger does not reach the maximum value in step (8), increase the amount of condensed water in the flue gas humidifying heat exchanger and return to step (2).

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