Method and device for preventing corrosion of a smoke water heat exchanger

Abstract

This application relates to a corrosion prevention device for a flue gas heat exchanger. The device includes: an air preheater, a low-temperature flue gas absorber, a high-temperature flue gas bypass, and a flue gas baffle assembly. The high-temperature flue gas bypass is connected to both the flue gas pipe at the inlet of the air preheater and the low-temperature flue gas absorber, and is used to introduce the high-temperature flue gas before it flows into the air preheater into the low-temperature flue gas absorber. The low-temperature flue gas absorber includes a first melting chamber and a second melting chamber. The flue gas baffle assembly is located at the inlets of the first and second melting chambers and is used to control the opening and closing of the first and second melting chambers. This application solves the problem of easy corrosion in low-temperature flue gas heat exchange systems. The high-temperature flue gas bypass introduces the high-temperature flue gas before it flows into the air preheater into the low-temperature flue gas absorber, using high temperature to volatilize acidic substances deposited on the pipes in the low-temperature flue gas absorber. The low-temperature flue gas absorber is divided into different compartments to ensure normal operation of the low-temperature flue gas absorber while high-temperature flue gas is introduced.

Description

Technical Field

[0001] This application relates to the application of coal-fired power generating units, and in particular to methods and devices for corrosion prevention of flue water heat exchangers. Background Technology

[0002] When utilizing waste heat from boiler combustion, the low-temperature flue gas often corrodes the metal pipe walls of the heat exchange system due to its low temperature and the presence of sulfuric acid, water, and ammonium bisulfate. Typically, after a period of operation, the system experiences increased resistance and decreased heat exchange efficiency due to the deposition of acidic substances. As the corrosion of the metal pipe walls intensifies, holes appear in the pipes, severely impacting system operation and even affecting the entire unit's operation.

[0003] Currently, no effective solution has been proposed for the problem of corrosion in low-temperature flue water heat exchange systems in related technologies. Summary of the Invention

[0004] This application provides a method and apparatus for corrosion prevention of flue water heat exchangers, so as to at least solve the problem of easy corrosion of low-temperature flue water heat exchange systems in related technologies.

[0005] In a first aspect, embodiments of this application provide a corrosion protection device for a flue gas heat exchanger, the flue gas heat exchanger comprising: an air preheater, a low-temperature flue gas absorber, a high-temperature flue gas bypass, and a flue gas baffle assembly.

[0006] The air preheater is connected to the low-temperature flue gas absorber and is used to convert the incoming high-temperature flue gas into low-temperature flue gas and transfer the low-temperature flue gas to the low-temperature flue gas absorber.

[0007] The high-temperature flue gas bypass is connected to the flue gas pipe at the inlet of the air preheater and the low-temperature flue gas absorber, respectively, and is used to introduce the high-temperature flue gas before it flows into the air preheater into the low-temperature flue gas absorber.

[0008] The low-temperature flue gas heat absorber includes a first melting chamber and a second melting chamber;

[0009] The flue gas damper assembly is installed at the inlet of the first melting chamber and the second melting chamber, and is used to control the opening and closing of the first melting chamber and the second melting chamber.

[0010] In some embodiments, the flue gas heat exchange device includes: a high-temperature flue gas flow control regulating valve.

[0011] The high-temperature flue gas flow control valve is installed on the high-temperature flue gas bypass and is used to control the flow rate of high-temperature flue gas flowing into the low-temperature flue gas absorber through the high-temperature flue gas bypass according to the flue gas temperature in the low-temperature flue gas absorber.

[0012] In some embodiments, the low-temperature flue gas heat absorber further includes a third melting chamber and a fourth melting chamber, and the flue gas baffle group includes a first melting chamber baffle, a second melting chamber baffle, a third melting chamber baffle, and a fourth melting chamber baffle;

[0013] The first margin call baffle is used to control the opening and closing of the first margin call;

[0014] The second margin call baffle is used to control the opening and closing of the second margin call;

[0015] The third margin call baffle is used to control the opening and closing of the third margin call;

[0016] The fourth margin call baffle is used to control the opening and closing of the fourth margin call.

[0017] In some embodiments, the flue gas heat exchange device further includes: a low-temperature flue gas heater, a circulating cold water pipe, and a circulating hot water pipe.

[0018] Both the low-temperature flue gas heater and the low-temperature flue gas absorber are flue-water heat exchangers with internal pipes. The working medium inside the pipes is water, and the working medium outside the pipes is flue gas.

[0019] The internal pipes of the low-temperature flue gas absorber and the low-temperature flue gas heater are connected through the circulating cold water pipe and the circulating hot water pipe, respectively.

[0020] The cold water in the low-temperature flue gas heater flows into the low-temperature flue gas absorber through the circulating cold water pipe, absorbs the heat of the flue gas in the low-temperature flue gas absorber, and then flows back to the low-temperature flue gas heater through the circulating hot water pipe.

[0021] In some embodiments, the flue water heat exchange device further includes: a thermostatic pump and a cold water temperature measuring instrument.

[0022] The cold water temperature measuring instrument is installed on the circulating cold water pipe and is used to obtain the temperature of the water flowing in the circulating cold water pipe;

[0023] The circulating cold water pipe and the circulating hot water pipe are connected by an intermediate connecting pipe, and the constant temperature pump is installed on the intermediate connecting pipe.

[0024] In some embodiments, the thermostatic pump is used to introduce water from the circulating hot water pipe into the circulating cold water pipe when the temperature of the water flow in the circulating cold water pipe is lower than a preset water flow temperature threshold, so that the water flow temperature in the low-temperature flue gas absorber is higher than the volatilization temperature of the first target acidic substance.

[0025] Secondly, embodiments of this application provide a method for preventing corrosion of a flue water heat exchanger, the method being applied to the flue water heat exchange device described in the first aspect, the method comprising:

[0026] Based on the flue gas temperature in the low-temperature flue gas absorber, the flow rate of high-temperature flue gas flowing into the low-temperature flue gas absorber through the high-temperature flue gas bypass is controlled, wherein the high-temperature flue gas in the high-temperature flue gas bypass is the high-temperature flue gas before flowing into the air preheater.

[0027] Based on preset rules, it is determined whether the acidic deposits in the first compartment need to be volatilized. Based on the determination result, the opening and closing of the first and second melting compartments, as well as the opening and closing of the corresponding circulating water inflow branch valves of the first and second melting compartments, are controlled.

[0028] In some embodiments, controlling the opening and closing of the first melting tank and the second melting tank based on the judgment result, and the opening and closing of the corresponding circulating water inflow branch valves of the first melting tank and the second melting tank, includes:

[0029] When it is necessary to volatilize the acidic deposits in the first compartment, the first melting compartment is opened and the second melting compartment is closed by the flue gas baffle group, and the circulating water inflow branch valve corresponding to the first melting compartment is closed and the circulating water inflow branch valve corresponding to the second melting compartment is opened, so that the flue gas temperature in the low-temperature flue gas absorber is higher than the volatilization temperature of the second target acidic substance.

[0030] In some embodiments, controlling the flow rate of high-temperature flue gas flowing into the low-temperature flue gas receiver through the high-temperature flue gas bypass, based on the flue gas temperature in the low-temperature flue gas receiver, includes:

[0031] Acquire the water flow data and flue gas data of the low-temperature flue gas absorber;

[0032] Based on a preset high-temperature flue gas flow control model, the flow rate of high-temperature flue gas flowing into the low-temperature flue gas absorber through the high-temperature flue gas bypass is determined according to the water flow data and the flue gas data.

[0033] In some embodiments, the high-temperature flue gas flow control model includes:

[0034]

[0035] Among them, Q gy The high-temperature flue gas flow rate is given in Nm³. 3 / h;Q 水 Q represents the flow rate of cold water in the low-temperature flue gas absorber, in kg / h. yT1 is the total flue gas flow rate of the low-temperature flue gas absorber, in kg / h; T2 is the cold water inflow temperature, in °C; T3 is the cold water outflow temperature of the low-temperature flue gas absorber, in °C; T4 is the total flue gas flow rate of the low-temperature flue gas absorber, in kg / h; T5 is the total flue gas flow rate of the low-temperature flue gas absorber, in kg / h; T6 is the total flue gas flow rate of yc The outlet flue gas temperature of the low-temperature flue gas absorber is expressed in °C (°C); T y ′ r The inlet flue gas temperature of the low-temperature flue gas absorber is expressed in °C (°C); T gy Temperature of the incoming high-temperature flue gas, in °C; C 水 C represents the specific heat of cold water, expressed in kJ / kg·℃. yc The specific heat of the outlet flue gas of the low-temperature flue gas absorber is expressed in kJ / Nm³·℃; C y ′ r The specific heat of the inlet flue gas of the low-temperature flue gas absorber is expressed in kJ / Nm³·℃; C yg The specific heat of the incoming high-temperature flue gas.

[0036] Units are kJ / Nm3·℃; η is the heat exchanger efficiency, in percentage.

[0037] Compared to related technologies, the anti-corrosion device for the flue gas heat exchanger provided in this application includes: an air preheater, a low-temperature flue gas absorber, a high-temperature flue gas bypass, and a flue gas baffle assembly. The high-temperature flue gas bypass is connected to the flue gas pipe at the inlet of the air preheater and the low-temperature flue gas absorber, respectively, and is used to introduce the high-temperature flue gas before it flows into the air preheater into the low-temperature flue gas absorber. The low-temperature flue gas absorber includes a first melting chamber and a second melting chamber. The flue gas baffle assembly is set at the inlet of the first melting chamber and the second melting chamber and is used to control the opening and closing of the first melting chamber and the second melting chamber. This solves the problem of easy corrosion of the low-temperature flue gas heat exchange system. By introducing the high-temperature flue gas before it flows into the air preheater into the low-temperature flue gas absorber through the high-temperature flue gas bypass, the solid sulfate particles and ammonium bisulfate particles deposited on the pipes in the low-temperature flue gas absorber can be volatilized by the high temperature. The flue gas duct where the low-temperature flue gas absorber is located is divided into different compartments, and the opening and closing of each melting chamber is controlled according to the acid deposition adhesion to ensure that the low-temperature flue gas absorber operates normally while introducing high-temperature flue gas. Attached Figure Description

[0038] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0039] Figure 1 This is a schematic diagram of a corrosion prevention device for a flue water heat exchanger according to an embodiment of this application;

[0040] Figure 2 This is a schematic diagram of a low-temperature flue gas heat absorber according to an embodiment of this application;

[0041] Figure 3 This is a schematic diagram of a low-temperature flue gas heat absorber and its internal piping according to an embodiment of this application;

[0042] Figure 4 This is a flowchart of a flue water heat exchanger corrosion prevention method according to an embodiment of this application.

[0043] In the above figures, the meanings of the reference numerals are as follows:

[0044] 1. Low-temperature flue gas heat absorber; 2. Air preheater; 3. Dust collector; 4. Desulfurization tower; 5. Low-temperature flue gas heater; 6. Exhaust fan; 7. Chimney; 8. Thermostatic pump; 9. High-temperature flue gas flow control valve; 10. High-temperature flue gas bypass; 11. Circulating water inlet main valve; 12. Circulating water outlet main valve; 13. Circulating water cold water pipeline; 14. Circulating water hot water pipeline; 15. Circulating pump; 16. Cold water temperature measuring instrument; 90. Flue gas baffle assembly; 901. First melting chamber baffle; 902. Second melting chamber baffle. 903. Third melting chamber baffle; 904. Fourth melting chamber baffle; 91. First high-temperature flue gas control valve; 92. Second high-temperature flue gas control valve; 93. Third high-temperature flue gas control valve; 94. Fourth high-temperature flue gas control valve; 101. First melting chamber; 102. Second melting chamber; 103. Third melting chamber; 104. Fourth melting chamber; 111. First circulating water inflow branch valve; 112. Second circulating water inflow branch valve; 113. Third circulating water inflow branch valve; 114. Fourth circulating water inflow branch valve. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this application clearer, the application is described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0046] Obviously, the accompanying drawings described below are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without any inventive effort. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0047] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0048] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms “a,” “an,” “an,” “the,” and similar words used in this application do not indicate quantity limitation and may indicate singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units not listed, or may include other steps or units inherent to these processes, methods, products, or devices. The terms “connected,” “linked,” “coupled,” and similar words used in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. “Multiple” used in this application refers to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can represent: A alone, A and B simultaneously, and B alone. The character " / " generally indicates that the preceding and following objects are in an "or" relationship. The terms "first," "second," and "third" used in this application are merely to distinguish similar objects and do not represent a specific ordering of the objects.

[0049] This embodiment provides a corrosion prevention device for a flue water heat exchanger. Figure 1 This is a schematic diagram of a corrosion prevention device for a flue water heat exchanger according to an embodiment of this application, as shown below. Figure 1 As shown, the flue gas heat exchange device includes: an air preheater 2, a low-temperature flue gas absorber 1, a high-temperature flue gas bypass 10, and a flue gas baffle assembly 90.

[0050] Air preheater 2 is connected to low-temperature flue gas absorber 1 and is used to convert the incoming high-temperature flue gas into low-temperature flue gas and transfer the low-temperature flue gas to low-temperature flue gas absorber 1.

[0051] The high-temperature flue gas bypass 10 is connected to the flue gas duct at the inlet of the air preheater 2 and the low-temperature flue gas absorber 1, respectively, and is used to introduce the high-temperature flue gas before it flows into the air preheater 2 into the low-temperature flue gas absorber 1.

[0052] The low-temperature flue gas heat absorber 1 includes a first melting chamber and a second melting chamber. A flue gas baffle assembly 90 is disposed at the inlet of the first melting chamber and the second melting chamber and is used to control the opening and closing of the first melting chamber and the second melting chamber.

[0053] High-temperature flue gas (e.g., flue gas at 380-450℃) becomes low-temperature flue gas (e.g., flue gas at 110-160℃) after passing through air preheater 2. The temperature of the low-temperature flue gas is further reduced after passing through low-temperature flue gas absorber 1, and then flows sequentially through dust collector 3, desulfurization tower 4, low-temperature flue gas heater 5, induced draft fan 6, and chimney 7.

[0054] The low-temperature flue gas exiting the air preheater 2 contains sulfuric acid, ammonium bisulfate, and water vapor. This low-temperature flue gas flows into the low-temperature flue gas receiver 1. The low-temperature flue gas receiver 1 is a non-contact flue-water heat exchanger with internal heat exchange metal tubes. Cold water flows inside the tubes, while low-temperature flue gas flows outside. Therefore, as the low-temperature flue gas flows through the low-temperature flue gas receiver 1, the flue gas temperature gradually decreases while the water temperature gradually increases. At this time, the outer surface temperature of the heat exchange metal tube bundle in the low-temperature flue gas receiver 1 decreases, and the gaseous sulfuric acid and ammonium bisulfate in the flue gas become liquid and adhere to the metal tubes, causing relatively severe corrosion to the metal tube bundle.

[0055] To avoid corrosion of the metal tube bundle, this embodiment introduces a high-temperature flue gas bypass 10 at the flue gas inlet side of the low-temperature flue gas receiver 1. This high-temperature flue gas bypass directly introduces the high-temperature flue gas before it flows into the air preheater 2 into the low-temperature flue gas receiver 1. The high temperature can volatilize the solid sulfate particles and ammonium bisulfate particles deposited on the pipes in the low-temperature flue gas receiver 1, thereby solving the problem of metal pipe corrosion.

[0056] To ensure the normal operation of the low-temperature flue gas absorber 1 while introducing high-temperature flue gas, the flue duct where the low-temperature flue gas absorber 1 is located is divided into different melting chambers. Based on preset rules, it is determined whether the acidic deposits in the first chamber need to be volatilized. Based on the determination results, the opening and closing of each melting chamber, as well as the opening and closing of the corresponding circulating water inflow branch valves for each chamber, are controlled.

[0057] In some embodiments, the flue gas heat exchange device includes: a high-temperature flue gas flow control regulating valve 9, which is installed on the high-temperature flue gas bypass 10 and is used to control the flow rate of high-temperature flue gas flowing into the low-temperature flue gas absorber 1 through the high-temperature flue gas bypass 10 according to the flue gas temperature in the low-temperature flue gas absorber 1.

[0058] The flow rate of high-temperature flue gas flowing into low-temperature flue gas absorber 1 through high-temperature flue gas bypass 10 is determined by the flue gas temperature in low-temperature flue gas absorber 1.

[0059] Optionally, the flow rate of high-temperature flue gas flowing into the low-temperature flue gas absorber through the high-temperature flue gas bypass can be determined by using a preset high-temperature flue gas flow control model.

[0060] The high-temperature flue gas flow control model includes:

[0061]

[0062] Among them, Q gy This refers to the flow rate of high-temperature flue gas, in Nm³. 3 / h;Q 水 Q represents the flow rate of cold water in the low-temperature flue gas absorber, expressed in kg / h. y T1 is the total flue gas flow rate of the low-temperature flue gas absorber, in kg / h; T2 is the cold water inlet temperature, in °C; T3 is the cold water outlet temperature of the low-temperature flue gas absorber, in °C; T4 is the total flue gas flow rate of the low-temperature flue gas absorber, in kg / h; T5 is the total flue gas flow rate of the low-temperature flue gas absorber, in kg / h; T6 is the total flue gas flow rate of the yc The outlet flue gas temperature of the low-temperature flue gas absorber is expressed in °C (T). y ′ r T represents the inlet flue gas temperature of the low-temperature flue gas absorber, in °C. gy Temperature of the incoming high-temperature flue gas, in °C; C 水 C represents the specific heat of cold water, expressed in kJ / kg·℃. yc C represents the specific heat of the outlet flue gas of the low-temperature flue gas absorber, expressed in kJ / Nm³·℃. y ′ r C represents the specific heat of the inlet flue gas of the low-temperature flue gas absorber, expressed in kJ / Nm³·℃. yg η represents the specific heat of the incoming high-temperature flue gas, in kJ / Nm3·℃; η is the heat exchanger efficiency, in %.

[0063] In some embodiments, the low-temperature flue gas absorber further includes a second melting chamber 102, a third melting chamber 103, and a fourth melting chamber 104, and the flue gas baffle group 90 includes a first melting chamber baffle 901, a second melting chamber baffle 902, a third melting chamber baffle 903, and a fourth melting chamber baffle 904.

[0064] The first margin call baffle 901 is used to control the opening and closing of the first margin call 101; the second margin call baffle 902 is used to control the opening and closing of the second margin call 102; the third margin call baffle 903 is used to control the opening and closing of the third margin call 103; and the fourth margin call baffle 904 is used to control the opening and closing of the fourth margin call 104.

[0065] Figure 2 This is a schematic diagram of a low-temperature flue gas heat absorber according to an embodiment of this application, as shown below. Figure 2As shown, the flue located at 1 is divided into four compartments of equal volume (first melting compartment 101, second melting compartment 102, third melting compartment 103, and fourth melting compartment 104). Each melting compartment is equipped with a corresponding high-temperature flue gas control valve. The high-temperature flue gas entering the first melting compartment 101 is controlled by the first high-temperature flue gas control valve 91, the high-temperature flue gas entering the second melting compartment 102 is controlled by the second high-temperature flue gas control valve 92, the high-temperature flue gas entering the third melting compartment 103 is controlled by the third high-temperature flue gas control valve 93, and the high-temperature flue gas entering the fourth melting compartment 104 is controlled by the fourth high-temperature flue gas control valve 94.

[0066] When it is necessary to volatilize the acidic deposits in the first compartment, open the high-temperature flue gas flow control regulating valve 9, the first melting chamber baffle 901, and the first high-temperature flue gas control valve 91; close the second melting chamber baffle 902, the third melting chamber baffle 903, the fourth melting chamber baffle 904, the second high-temperature flue gas control valve 92, the third high-temperature flue gas control valve 93, and the fourth high-temperature flue gas control valve 94. Simultaneously, keep the second circulating water inflow branch valve 112, the third circulating water inflow branch valve 113, and the fourth circulating water inflow branch valve 114 open, while closing the first circulating water inflow branch valve 111 to cut off the corresponding cold water absorption heat, ensuring that the high-temperature flue gas temperature in this compartment is higher than the volatilization temperature of ammonium bisulfate, thus achieving the purpose of volatilizing the acidic deposited particles. After a preset time T, close the corresponding first melting chamber baffle 901 and open the other three melting chamber baffles to achieve corrosion prevention. Figure 3 This is a schematic diagram of a low-temperature flue gas absorber and its internal piping according to an embodiment of this application, where 12 is the main valve for circulating water outflow.

[0067] In some embodiments, the flue gas heat exchange device further includes: a low-temperature flue gas heater 5, a circulating cold water pipe 13, and a circulating hot water pipe 14.

[0068] Both the low-temperature flue gas heater 5 and the low-temperature flue gas absorber 1 are flue-water heat exchangers with internal pipes. The working medium inside the pipes is water, and the working medium outside the pipes is flue gas.

[0069] The internal pipes of the low-temperature flue gas absorber 1 and the low-temperature flue gas heater 5 are connected by circulating cold water pipe 13 and circulating hot water pipe 14, respectively.

[0070] The cold water in the low-temperature flue gas heater 5 flows into the low-temperature flue gas absorber 1 through the circulating cold water pipe 13. After absorbing the heat of the flue gas in the low-temperature flue gas absorber 1, it flows back to the low-temperature flue gas heater 5 through the circulating hot water pipe 14.

[0071] Cold water is sprayed inside the wet desulfurization tower 4. After the flue gas flows through the wet desulfurization tower 4, the temperature is around 50℃. When this part of the flue gas flows into the low-temperature flue gas heater 5, the flue gas temperature rises while the water temperature drops. In this way, the low-temperature flue gas absorber 1 absorbs the heat from the flue gas, and the low-temperature flue gas heater 5 releases the heat from the low-temperature flue gas absorber 1 back into the flue gas, thereby achieving the purpose of "eliminating white smoke".

[0072] Eliminating white smoke: When the flue gas temperature inside a power plant chimney is relatively low, a large amount of white water vapor will appear in the flue gas, just like boiling water. This white water vapor looks like the smoke from a chimney when cooking with firewood, which can easily lead people to mistakenly believe that the white water vapor is dirty smoke. In order to avoid misunderstanding by the surrounding residents, it is necessary to eliminate this white 'smoke'.

[0073] When the low-temperature flue gas heat absorber 1 and the low-temperature flue gas heater 5 are used in combination, the low-temperature flue gas heat absorber 1 recovers waste heat, while the low-temperature flue gas heater 5 utilizes waste heat. It should be noted that the waste heat recovered by the low-temperature flue gas heat absorber 1 can also be used for other purposes, such as heating condensate water, heating return water, primary or secondary cold air from the boiler, etc. The low-temperature flue gas heater 5 is also a heat exchange device used to release the waste heat recovered by the low-temperature flue gas heat absorber 1. Depending on the application, different heat exchanger types and materials can be selected for the low-temperature flue gas heat absorber 1 and the low-temperature flue gas heater 5.

[0074] In some embodiments, the flue water heat exchange device further includes: a thermostatic pump 8 and a cold water temperature measuring instrument 16.

[0075] The cold water temperature measuring instrument 16 is installed on the circulating cold water pipe 13 to obtain the temperature of the water flowing in the circulating cold water pipe 13;

[0076] The circulating cold water pipe 13 and the circulating hot water pipe 14 are connected by an intermediate connecting pipe, and the thermostatic pump 8 is installed on the intermediate connecting pipe.

[0077] In some embodiments, the thermostatic pump 8 is used to introduce water from the circulating hot water pipe 14 into the circulating cold water pipe 13 when the temperature of the water flow in the circulating cold water pipe 13 is lower than a preset water flow temperature threshold, so that the water flow temperature in the low-temperature flue gas absorber 1 is greater than the volatilization temperature of the first target acidic substance.

[0078] Optionally, the primary target acidic substance is sulfuric acid, and the formula for calculating the volatilization temperature of sulfuric acid is as follows:

[0079]

[0080] Among them, t sld t represents the temperature at which sulfuric acid is deposited in flue gas, in °C. ldβ is the water vapor dew point of the flue gas, in °C; β is a constant related to the excess air coefficient a, where β = 129 when a = 1.4 and β = 121 when a = 1.2; S and A are the converted sulfur and ash contents. This refers to the proportion of fly ash in the total ash content.

[0081] The lower the temperature of the metal pipe wall, the faster the sulfuric acid corrosion. When the temperature of the cold water in the circulating cold water pipe 13 is too low, the thermostatic pump 8 is operated to divert a portion of the hot water in the circulating hot water pipe 14 into the circulating cold water pipe 13, thereby controlling the temperature of the cold water flowing into the low-temperature flue gas absorber 1 to be above the sulfuric acid volatilization temperature, keeping it basically constant within the safe temperature range. This can prevent a large amount of sulfuric acid from condensing and slow down the corrosion of the metal pipe wall.

[0082] For example, the system operates under the following conditions: at full load, the total flue gas volume is 2,260,000 Nm³ / h, the flue gas moisture content is 6.02%, the inlet flue gas temperature of component 2 is 438℃, and component 1 is arranged in a counter-current manner with inlet and outlet flue gas temperatures of 150℃ and 125℃, and inlet and outlet water temperatures of 70℃ and 90℃. Table 1 is a flue gas parameter table according to an embodiment of this application, and the specific parameters are shown in Table 1:

[0083] Table 1

[0084]

[0085]

[0086] When the unit operates at low load, the total flue gas volume decreases, causing the inlet water temperature of the low-temperature flue gas receiver 1 to drop below 70°C. The metal wall temperature of the low-temperature flue gas receiver 1 also drops below the deposition temperature of sulfuric acid and ammonium bisulfate, leading to significant corrosion. At this time, the thermostatic pump 8 is activated to return a portion of the hot water to the cold water to maintain the cold water temperature entering the low-temperature flue gas receiver 1 at 70°C, thus mitigating the impact of sulfuric acid corrosion on the low-temperature flue gas receiver 1.

[0087] Keep pipes 112, 113, and 114, and their corresponding pipes 902, 903, and 904 open, while closing pipe 111 and its corresponding pipe 901. Simultaneously, keep pipes 92, 93, and 94 closed and open pipes 9 and 91. At this point, high-temperature flue gas enters pipe 101 through pipe 10. Calculations show that the high-temperature flue gas flow rate is 10587 Nm³ / h, accounting for 1.87% of the total flue gas volume. At this time, the mixed temperature of the flue gas exiting pipe 1 is 120℃, the inlet and outlet water temperatures are 70℃ and 90℃ respectively, and the flue gas temperature in pipe 101 is 438℃, far exceeding the deposition temperatures of sulfuric acid and ammonium bisulfate (67.4℃ and 184℃ respectively). The acidic corrosion deposits already attached to the metal pipe wall are vaporized and carried away by the flue gas. Alternating the introduction of high-temperature flue gas into pipes 101, 102, 103, and 104 will completely solve the corrosion problem of sulfuric acid and ammonium bisulfate on pipe 1.

[0088] The aforementioned device introduces high-temperature flue gas, which flows into the air preheater, through a high-temperature flue gas bypass into the low-temperature flue gas receiver. This high temperature volatilizes solid sulfate and ammonium bisulfate particles deposited on the pipes of the low-temperature flue gas receiver, solving the problem of easy corrosion in the low-temperature flue water heat exchange system. The flue duct containing the low-temperature flue gas receiver is divided into different compartments, and the opening and closing of each compartment is controlled according to the acid deposition situation to ensure the normal operation of the low-temperature flue gas receiver while introducing high-temperature flue gas. When the temperature of the cold water in the circulating water cooling pipe 13 is too low, the thermostatic pump 8 diverts a portion of the hot water in the circulating water hot water pipe 14 into the circulating water cooling pipe 13, thereby controlling the temperature of the cold water flowing into the low-temperature flue gas receiver 1 to above the sulfuric acid volatilization temperature, preventing excessive condensation of sulfuric acid and slowing down the corrosion of the metal pipe walls.

[0089] This embodiment provides a method for preventing corrosion of a flue water heat exchanger, which is applied to the aforementioned flue water heat exchange device. Figure 4 This is a flowchart of a flue gas heat exchanger corrosion prevention method according to an embodiment of this application, such as... Figure 4 As shown, the process includes the following steps:

[0090] Step S401: Based on the flue gas temperature in the low-temperature flue gas absorber, control the flow rate of high-temperature flue gas flowing into the low-temperature flue gas absorber through the high-temperature flue gas bypass, wherein the high-temperature flue gas in the high-temperature flue gas bypass is the high-temperature flue gas before flowing into the air preheater.

[0091] To avoid corrosion of the metal pipe bundle, the high-temperature flue gas before flowing into the air preheater 2 is directly introduced into the low-temperature flue gas receiver 1 through the high-temperature flue gas bypass 10. This can volatilize the solid sulfate particles and ammonium bisulfate particles deposited on the pipes in the low-temperature flue gas receiver 1 through high temperature, thereby solving the problem of metal pipe corrosion.

[0092] In some embodiments, step S401 specifically includes:

[0093] Step S4011: Obtain water flow data and flue gas data from the low-temperature flue gas absorber.

[0094] The water flow data includes: cold water flow rate, cold water inlet temperature, and cold water outlet temperature in the low-temperature flue gas absorber.

[0095] The flue gas data includes: total flue gas flow rate of the low-temperature flue gas absorber, outlet flue gas temperature, inlet flue gas temperature, temperature of high-temperature flue gas flowing in through high-temperature flue gas bypass 10, specific heat of outlet flue gas, specific heat of inlet flue gas, and specific heat of inlet high-temperature flue gas.

[0096] Step S4012: Based on the preset high-temperature flue gas flow control model, determine the flow rate of high-temperature flue gas flowing into the low-temperature flue gas absorber through the high-temperature flue gas bypass according to the water flow data and flue gas data.

[0097] In some embodiments, the high-temperature flue gas flow control model includes:

[0098]

[0099] Among them, Q gy This refers to the flow rate of high-temperature flue gas, in Nm³. 3 / h;Q 水 Q represents the flow rate of cold water in the low-temperature flue gas absorber, expressed in kg / h. y T1 is the total flue gas flow rate of the low-temperature flue gas absorber, in kg / h; T2 is the cold water inlet temperature, in °C; T3 is the cold water outlet temperature of the low-temperature flue gas absorber, in °C; T4 is the total flue gas flow rate of the low-temperature flue gas absorber, in kg / h; T5 is the total flue gas flow rate of the low-temperature flue gas absorber, in kg / h; T6 is the total flue gas flow rate of the yc The outlet flue gas temperature of the low-temperature flue gas absorber is expressed in °C (T). y ′ r T represents the inlet flue gas temperature of the low-temperature flue gas absorber, in °C. gy Temperature of the incoming high-temperature flue gas, in °C; C 水 C represents the specific heat of cold water, expressed in kJ / kg·℃. yc C represents the specific heat of the outlet flue gas of the low-temperature flue gas absorber, expressed in kJ / Nm³·℃. y ′ r C represents the specific heat of the inlet flue gas of the low-temperature flue gas absorber, expressed in kJ / Nm³·℃. yg η represents the specific heat of the incoming high-temperature flue gas, in kJ / Nm3·℃; η is the heat exchanger efficiency, in %.

[0100] Step S402: Determine whether the acidic deposits in the first compartment need to be volatilized according to preset rules. Based on the determination result, control the opening and closing of the first and second melting compartments, as well as the opening and closing of the corresponding circulating water inflow branch valves of the first and second melting compartments.

[0101] In some embodiments, step S402, based on the judgment result, controls the opening and closing of the first melting tank and the second melting tank, as well as the opening and closing of the corresponding circulating water inflow branch valves of the first melting tank and the second melting tank, including:

[0102] When it is necessary to volatilize the acidic deposits in the first compartment, the first melting compartment is opened and the second melting compartment is closed by controlling the flue gas damper group, and the circulating water inflow branch valve corresponding to the first melting compartment is closed and the circulating water inflow branch valve corresponding to the second melting compartment is opened, so that the flue gas temperature in the low-temperature flue gas absorber is higher than the volatilization temperature of the second target acidic substance.

[0103] Optionally, the second target acidic substance is ammonium bisulfate, and the formula for calculating the volatilization temperature of ammonium bisulfate is as follows:

[0104]

[0105] Among them, t ABS C is the volatilization temperature of ammonium bisulfate in flue gas, expressed in °C. NH3 ammonia slip concentration in flue gas, unit: ppm; C SO3 This represents the ammonia escape concentration in the flue gas, expressed in ppm.

[0106] Using the above method, the high-temperature flue gas bypass introduces the high-temperature flue gas before it flows into the low-temperature flue gas receiver into the low-temperature flue gas receiver. The high temperature can volatilize the solid sulfate particles and ammonium bisulfate particles deposited on the pipes of the low-temperature flue gas receiver. The flue where the low-temperature flue gas receiver is located is divided into different compartments, and the opening and closing of each compartment is controlled according to the acid deposit adhesion to ensure that the low-temperature flue gas receiver operates normally while high-temperature flue gas is introduced, thus solving the problem of easy corrosion of the low-temperature flue water heat exchange system.

[0107] It should be noted that the steps shown in the above process or in the flowchart of the accompanying figures can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0108] Those skilled in the art should understand that the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0109] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A corrosion prevention device for a flue gas heat exchanger, characterized in that, The corrosion protection device for the flue gas heat exchanger includes: an air preheater, a low-temperature flue gas absorber, a high-temperature flue gas bypass, a high-temperature flue gas flow control valve, and a flue gas damper assembly. The air preheater is connected to the low-temperature flue gas absorber and is used to convert the incoming high-temperature flue gas into low-temperature flue gas and transfer the low-temperature flue gas to the low-temperature flue gas absorber. The high-temperature flue gas bypass is connected to the flue gas pipe at the inlet of the air preheater and the low-temperature flue gas absorber, respectively, and is used to introduce the high-temperature flue gas before it flows into the air preheater into the low-temperature flue gas absorber. The low-temperature flue gas heat absorber includes a first melting chamber and a second melting chamber; The flue gas damper assembly is installed at the inlet of the first melting chamber and the second melting chamber, and is used to control the opening and closing of the first melting chamber and the second melting chamber; The high-temperature flue gas flow control valve is installed on the high-temperature flue gas bypass and is used to control the flow rate of high-temperature flue gas flowing into the low-temperature flue gas absorber through the high-temperature flue gas bypass according to the flue gas temperature in the low-temperature flue gas absorber.

2. The apparatus according to claim 1, characterized in that, The low-temperature flue gas heat absorber also includes a third melting chamber and a fourth melting chamber, and the flue gas baffle group includes a first melting chamber baffle, a second melting chamber baffle, a third melting chamber baffle and a fourth melting chamber baffle; The first margin call baffle is used to control the opening and closing of the first margin call; The second margin call baffle is used to control the opening and closing of the second margin call; The third margin call baffle is used to control the opening and closing of the third margin call; The fourth margin call baffle is used to control the opening and closing of the fourth margin call.

3. The apparatus according to claim 1, characterized in that, The corrosion protection device for the flue gas heat exchanger also includes: a low-temperature flue gas heater, a circulating cold water pipe, and a circulating hot water pipe. Both the low-temperature flue gas heater and the low-temperature flue gas absorber are flue-water heat exchangers with internal pipes. The working medium inside the pipes is water, and the working medium outside the pipes is flue gas. The internal pipes of the low-temperature flue gas absorber and the low-temperature flue gas heater are connected through the circulating cold water pipe and the circulating hot water pipe, respectively. The cold water in the low-temperature flue gas heater flows into the low-temperature flue gas absorber through the circulating cold water pipe, absorbs the heat of the flue gas in the low-temperature flue gas absorber, and then flows back to the low-temperature flue gas heater through the circulating hot water pipe.

4. The apparatus according to claim 3, characterized in that, The corrosion protection device for the flue water heat exchanger also includes: a constant temperature pump and a cold water temperature measuring instrument. The cold water temperature measuring instrument is installed on the circulating cold water pipe and is used to obtain the temperature of the water flowing in the circulating cold water pipe; The circulating cold water pipe and the circulating hot water pipe are connected by an intermediate connecting pipe, and the constant temperature pump is installed on the intermediate connecting pipe.

5. The apparatus according to claim 4, characterized in that, The thermostatic pump is used to introduce water from the circulating hot water pipe into the circulating cold water pipe when the temperature of the water flow in the circulating cold water pipe is lower than a preset water flow temperature threshold, so that the water flow temperature in the low-temperature flue gas absorber is higher than the volatilization temperature of the first target acidic substance.

6. A method for preventing corrosion of a flue gas heat exchanger, characterized in that, The method is applied to the anti-corrosion device for a flue water heat exchanger according to any one of claims 1-5, and the method includes: Based on the flue gas temperature in the low-temperature flue gas absorber, the flow rate of high-temperature flue gas flowing into the low-temperature flue gas absorber through the high-temperature flue gas bypass is controlled, wherein the high-temperature flue gas in the high-temperature flue gas bypass is the high-temperature flue gas before flowing into the air preheater. Based on preset rules, it is determined whether the acidic deposits in the first compartment need to be volatilized. Based on the determination result, the opening and closing of the first and second melting compartments, as well as the opening and closing of the corresponding circulating water inflow branch valves of the first and second melting compartments, are controlled.

7. The method according to claim 6, characterized in that, The step of controlling the opening and closing of the first melting tank and the second melting tank based on the judgment result, as well as the opening and closing of the corresponding circulating water inflow branch valves of the first melting tank and the second melting tank, includes: When it is necessary to volatilize the acidic deposits in the first compartment, the first melting compartment is opened and the second melting compartment is closed by the flue gas baffle group, and the circulating water inflow branch valve corresponding to the first melting compartment is closed and the circulating water inflow branch valve corresponding to the second melting compartment is opened, so that the flue gas temperature in the low-temperature flue gas absorber is higher than the volatilization temperature of the second target acidic substance.

8. The method according to claim 6, characterized in that, The step of controlling the flow rate of high-temperature flue gas flowing into the low-temperature flue gas receiver through the high-temperature flue gas bypass, based on the flue gas temperature in the low-temperature flue gas receiver, includes: Acquire the water flow data and flue gas data of the low-temperature flue gas absorber; Based on a preset high-temperature flue gas flow control model, the flow rate of high-temperature flue gas flowing into the low-temperature flue gas absorber through the high-temperature flue gas bypass is determined according to the water flow data and the flue gas data.

9. The method according to claim 8, characterized in that, The high-temperature flue gas flow control model includes: Among them, Q gy The high-temperature flue gas flow rate is given in Nm³. 3 / h;Q 水 Q represents the flow rate of cold water in the low-temperature flue gas absorber, in kg / h. y T1 is the total flue gas flow rate of the low-temperature flue gas absorber, in kg / h; T2 is the cold water inflow temperature, in °C; T3 is the cold water outflow temperature of the low-temperature flue gas absorber, in °C; T4 is the total flue gas flow rate of the low-temperature flue gas absorber, in kg / h; T5 is the total flue gas flow rate of the low-temperature flue gas absorber, in kg / h; T6 is the total flue gas flow rate of yc The outlet flue gas temperature of the low-temperature flue gas absorber is expressed in °C (T'). yr The inlet flue gas temperature of the low-temperature flue gas absorber is expressed in °C (°C); T gy Temperature of the incoming high-temperature flue gas, in °C; C 水 C represents the specific heat of cold water, expressed in kJ / kg·℃. yc C' represents the specific heat of the outlet flue gas of the low-temperature flue gas absorber, expressed in kJ / Nm³·℃. yr The specific heat of the inlet flue gas of the low-temperature flue gas absorber is expressed in kJ / Nm³·℃; C yg η represents the specific heat of the incoming high-temperature flue gas, in kJ / Nm3·℃; η is the heat exchanger efficiency, in %.

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