Corrosion-resistant flue gas condensing heat exchanger with built-in magnesium-based sacrificial anode protection device

Abstract

The utility model discloses an anti-corrosion flue gas condensing heat exchanger with built-in magnesium-based sacrificial anode protection device, belongs to flue gas condensing heat exchanger anticorrosion technical field, solves the corrosion problem of acidic condensate, and specifically includes heat exchanger casing, and the both ends of heat exchanger casing are provided with flue gas inlet and flue gas outlet respectively, the bottom of heat exchanger casing is provided with condensate discharge port and magnesium-based sacrificial anode block, magnesium-based sacrificial anode block is used as anode, and heat exchanger casing is used as cathode, and the acidic condensate formed with flue gas condensation constitutes electrochemical corrosion protection loop, in the utility model, heat exchanger casing is horizontal pressure vessel, as the protected main body, usually is made of carbon steel, after flue gas passes through heat exchanger casing, condenses into acidic condensate under the cooling effect of heat exchange tube bundle, and acidic condensate acts as electrolyte, and oxidation reaction occurs with magnesium-based sacrificial anode block, through the self-sacrifice of anode, continuously inhibits the corrosion of heat exchanger body, prolongs the service life of equipment.

Description

Technical Field

[0001] This utility model relates to the field of corrosion protection technology for flue gas condensing heat exchangers, and in particular to a corrosion-resistant flue gas condensing heat exchanger with a built-in magnesium-based sacrificial anode protection device. Background Technology

[0002] The flue gas from industrial boilers, gas-fired boilers, and other equipment contains a large amount of heat energy. By using a flue gas condensation heat exchanger to reduce the flue gas temperature below the dew point, the latent heat of vaporization released by water vapor condensation can be recovered, significantly improving the efficiency of heat energy utilization. However, the sulfur and nitrogen elements in the fuel, after combustion, produce sulfur oxides and nitrogen oxides that dissolve in the condensate to form highly corrosive acidic liquids such as sulfuric acid, sulfurous acid, and nitric acid. These liquids cause severe electrochemical corrosion to the metal walls of the heat exchanger (usually made of carbon steel), leading to equipment perforation and leakage, and significantly shortening the equipment's lifespan.

[0003] Currently, the main anti-corrosion methods include: using high-grade stainless steel (such as 316L) or duplex stainless steel, the disadvantage of which is that the cost is extremely high; using non-metallic materials (such as glass tubes and fluoroplastic tubes), the disadvantage of which is that the heat exchange efficiency is low and the structural strength is insufficient; applying anti-corrosion coatings to the metal surface, but the coatings have pinhole defects or are easy to peel off under thermal stress, and once damaged, local corrosion is aggravated.

[0004] Sacrificial anode cathodic protection is a mature electrochemical corrosion protection technology widely used in shipbuilding, underground pipelines, and other fields. Applying this technology to the corrosion protection of flue gas condenser heat exchangers also provides good protection. Therefore, there is an urgent need for a targeted, highly integrated, and cost-effective built-in corrosion protection solution. Utility Model Content

[0005] To address the shortcomings of existing technologies, this utility model provides a corrosion-resistant flue gas condensing heat exchanger with a built-in magnesium-based sacrificial anode protection device. The purpose is to actively protect the main metal of the heat exchanger by using a built-in replaceable magnesium-based sacrificial anode, thereby fundamentally solving the corrosion problem of acidic condensate.

[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows: A corrosion-resistant flue gas condensing heat exchanger with a built-in magnesium-based sacrificial anode protection device includes a heat exchanger shell, with a flue gas inlet and a flue gas outlet respectively provided at both ends of the heat exchanger shell; The bottom of the heat exchanger shell is equipped with a condensate drain port and a magnesium-based sacrificial anode block; the magnesium-based sacrificial anode block serves as the anode, and the heat exchanger shell serves as the cathode, forming an electrochemical corrosion protection circuit with the acidic condensate formed by flue gas condensation.

[0007] In this scheme, the heat exchanger shell is a horizontal pressure vessel, which is the main body to be protected and is usually made of carbon steel. After the flue gas passes through the heat exchanger shell, it condenses into acidic condensate under the cooling effect of the heat exchange tube bundle. The acidic condensate acts as an electrolyte and reacts with the magnesium-based sacrificial anode block to form an oxidation reaction. Through the self-sacrifice of the anode, the corrosion of the heat exchanger body is continuously inhibited, resulting in a thorough protection effect and extended equipment life.

[0008] Furthermore, the magnesium-based sacrificial anode block includes a steel metal core and a magnesium alloy anode. The magnesium alloy anode has a hollow rod-shaped structure, and a steel metal core is pre-embedded in the center of the hollow rod-shaped structure along the axial direction. An installation interface is provided at the bottom of the heat exchanger shell, and the steel metal core is fixed in the installation interface.

[0009] In this design, a magnesium alloy anode is wrapped around a steel core, allowing the magnesium alloy anode to fully contact the condensing acidic condensate and effectively provide electrochemical protection.

[0010] Furthermore, one end of the steel metal core extends from the tail of the magnesium alloy anode, and the outer surface of the extended end is machined with external threads; a flange seat is installed at the mounting interface, and the inner hole of the flange seat is machined with internal threads; the steel metal core is installed on the flange seat through threaded engagement, and the side of the steel metal core that wraps around the magnesium alloy anode faces the inside of the heat exchanger shell, and the steel metal core uses the thread action to make the end face of the magnesium alloy anode abut against the mounting interface.

[0011] In this design, the external thread of the steel metal core is screwed into the internal thread of the flange seat. After the steel metal core is tightened, the magnesium alloy anode is pulled tight, making it fit tightly against the end face of the mounting interface. This achieves close contact between the magnesium alloy and the heat exchanger shell, ensuring the flow of electrons between them during chemical protection.

[0012] Furthermore, the ends of the steel metal core are welded to the shell metal around the mounting interface, forming a conductive weld at the welding position. The steel metal core and the heat exchanger shell are electrically connected through the conductive weld.

[0013] In this design, the conductive weld further enhances the electrical connection between the steel core and the mounting interface, ensuring a low-resistance connection.

[0014] Furthermore, the magnesium alloy anode is immersed in the acidic condensate formed by the condensation of flue gas.

[0015] Furthermore, an inspection hole is provided at the top of the heat exchanger shell.

[0016] In this design, the access hole is used by maintenance personnel to enter the equipment for inspection and maintenance.

[0017] Furthermore, the magnesium alloy anode is made of MgAZ63B magnesium alloy.

[0018] Furthermore, the heat exchanger shell contains several heat exchange tube bundles; the two ends of the heat exchange tube bundles are connected by two tube sheets; the two tube sheets are respectively provided with a cooling medium inlet and a cooling medium outlet.

[0019] Furthermore, the number of magnesium-based sacrificial anode blocks is several.

[0020] In this scheme, multiple magnesium-based sacrificial anode blocks are evenly arranged to ensure that the entire protected inner surface receives a uniform protective current.

[0021] The beneficial effects of this utility model are: This utility model provides a corrosion-resistant flue gas condensing heat exchanger with a built-in magnesium-based sacrificial anode protection device. Utilizing electrochemical principles, the magnesium anode actively and continuously inhibits corrosion of the heat exchanger body through self-sacrifice, providing thorough protection and extending equipment lifespan several times over. It allows the heat exchanger body to use inexpensive carbon steel instead of expensive stainless steel, significantly reducing manufacturing costs. Maintenance costs are limited to periodically replacing low-cost magnesium anode blocks. It prevents increased thermal resistance caused by corrosion products (rust scale) depositing on the heat exchange surface, ensuring long-term stability of heat exchange efficiency.

[0022] The system requires no external power supply, operates autonomously, has no over-protection risk, and is safe and reliable in operation. The magnesium anode is consumed slowly, typically requiring inspection and replacement only every 1-3 years, reducing maintenance frequency and ensuring a long maintenance-free period. Its simple structure and ease of implementation, integrating the anode internally, result in a compact design that doesn't occupy extra space. The threaded connection makes replacement quick and easy. Attached Figure Description

[0023] Figure 1 This is a top view of an anti-corrosion flue gas condensing heat exchanger with a built-in magnesium-based sacrificial anode protection device according to this utility model; Figure 2 This is a front view of an anti-corrosion flue gas condensing heat exchanger with a built-in magnesium-based sacrificial anode protection device according to this utility model. Figure 3 for Figure 2 A magnified view of a portion of region A in the middle; Figure 4 This is a side view of an anti-corrosion flue gas condensing heat exchanger with a built-in magnesium-based sacrificial anode protection device according to the present invention.

[0024] Figure label: 1. Heat exchanger shell; 11. Flange seat; 2. Heat exchanger tube bundle; 3. Tube sheet; 4. Flue gas inlet; 5. Flue gas outlet; 6. Cooling medium inlet; 7. Cooling medium outlet; 8. Condensate discharge port; 9. Magnesium-based sacrificial anode block; 91. Steel metal core; 92. Magnesium alloy anode; 10. Mounting interface; Detailed Implementation The present invention will be further described below with reference to the accompanying drawings and specific embodiments, and the specific implementation of the present invention will be described in order to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific implementation. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious. All inventions utilizing the concept of the present invention are within the scope of protection.

[0025] like Figures 1-4 As shown, this embodiment provides a corrosion-resistant flue gas condensing heat exchanger with a built-in magnesium-based sacrificial anode protection device. By incorporating a replaceable magnesium-based sacrificial anode, it actively protects the main metal of the heat exchanger, fundamentally solving the corrosion problem of acidic condensate. Specifically, it includes: Heat exchanger shell 1, condensate drain 8 and magnesium-based sacrificial anode block 9; The heat exchanger shell 1 is a horizontal pressure vessel, serving as the protected main body, and is typically made of carbon steel. A flue gas inlet 4 and a flue gas outlet 5 are located at both ends of the heat exchanger shell 1. A condensate discharge port 8 and a magnesium-based sacrificial anode block 9 are located at the bottom of the heat exchanger shell 1. After passing through the heat exchanger shell 1, the flue gas condenses into an acidic condensate under the cooling effect of the heat exchange tube bundle 2. The acidic condensate acts as an electrolyte, the magnesium-based sacrificial anode block 9 serves as the anode, and the heat exchanger shell 1 serves as the cathode, forming an electrochemical corrosion protection circuit with the acidic condensate formed by the flue gas condensation.

[0026] like Figure 3 As shown, the magnesium-based sacrificial anode block 9 includes a steel metal core 91 and a magnesium alloy anode 92. The magnesium alloy anode 92 is a hollow rod-shaped structure, with the steel metal core 91 embedded in the center of the hollow rod-shaped structure along the axial direction. An installation interface 10 is provided at the bottom of the heat exchanger shell 1, and the steel metal core 91 is fixed within the installation interface 10. The magnesium alloy anode 92 is wrapped around the steel metal core 91, allowing the magnesium alloy anode 92 to fully contact the condensed acidic condensate, effectively providing electrochemical protection.

[0027] One end of the steel metal core 91 extends from the tail of the magnesium alloy anode 92, and the outer surface of the extended end is machined with external threads. A flange seat 11 is installed at the mounting interface 10, and the inner hole of the flange seat 11 is machined with internal threads. The steel metal core 91 is installed on the flange seat 11 through threaded engagement. The side of the steel metal core 91 that wraps around the magnesium alloy anode 92 faces the inside of the heat exchanger shell 1. The threaded action of the steel metal core 91 causes the end face of the magnesium alloy anode 92 to abut against the mounting interface 10. The external thread of the steel metal core 91 is screwed into the internal thread of the flange seat 11. After the steel metal core 91 is tightened, it pulls the magnesium alloy anode 92 taut, making it tightly against the end face of the mounting interface 10, achieving close contact between the magnesium alloy and the heat exchanger shell, and ensuring the flow of electrons between them during chemical protection.

[0028] The end of the steel metal core 91 is welded to the shell metal around the mounting interface 10, and a conductive weld is formed at the welding position. The steel metal core 91 and the heat exchanger shell 1 are electrically connected through the conductive weld, which further enhances the electrical connection between the steel metal core and the mounting interface 10 and ensures a low-resistance connection.

[0029] Magnesium alloy anode 92 is immersed in acidic condensate formed by flue gas condensation.

[0030] The heat exchanger shell 1 has an inspection hole at the top, which is used by maintenance personnel to enter the equipment for inspection and maintenance.

[0031] The material of magnesium alloy anode 92 is MgAZ63B magnesium alloy.

[0032] The heat exchanger shell 1 contains several heat exchange tube bundles 2; the two ends of the heat exchange tube bundles 2 are connected by two tube sheets 3; the two tube sheets 3 are respectively provided with a cooling medium inlet 6 and a cooling medium outlet 7. The tube sheets 3 can be made of low-cost carbon steel.

[0033] The number of magnesium-based sacrificial anode blocks 9 is several. Multiple magnesium-based sacrificial anode blocks 9 are evenly arranged to ensure that the entire protected inner surface receives a uniform protective current.

[0034] The working principle of this embodiment is as follows: Flue gas flow: High-temperature flue gas (approximately 120-200℃) enters the shell side of the heat exchanger from flue gas inlet 4, scouring and sweeping across the outer wall of the heat exchange tube bundle 2. The flue gas is cooled by the cooling water inside the tubes, and its temperature gradually decreases. When the flue gas temperature drops below the dew point (approximately 50-60℃), the water vapor in the flue gas begins to condense, forming an acidic condensate (pH 2-4), which drips and accumulates at the bottom of the shell.

[0035] Cooling water flow: Low-temperature cooling water enters the heat exchange tube bundle 2 (i.e., the heat exchanger tube side) from the cooling medium inlet 6, flows through the interior of all heat exchange tube bundles 2, absorbs the heat of the flue gas outside the tubes and becomes hot water, and flows out from the cooling medium outlet 7.

[0036] Electrochemical protection process: The acidic condensate accumulated at the bottom of the heat exchanger shell 1 acts as an electrolyte, connecting the magnesium alloy anode 92 and the heat exchanger shell 1. Since magnesium has a much higher chemical reactivity than iron (carbon steel), a potential difference is formed between the two, constituting a galvanic cell.

[0037] Anodic reaction (occurring on magnesium alloy anode 92): Acidic condensate causes an oxidation reaction on the magnesium alloy surface, releasing electrons; Mg - 2e - → Mg 2+ (Magnesium alloy dissolution) Electrons are transferred from the magnesium alloy anode 92 to the steel metal core 91. Through the conductive weld, the electrons continuously flow from the anode to the protected shell metal, making the whole anode and thus protected. Corrosion is completely suppressed, and the corrosion attack is entirely borne by the replaceable magnesium alloy anode.

[0038] Cathodic reaction (occurring on the surface of the shell, tube sheet, and tube bundle): 2H + + 2e - → H2↑ or O2 + 2H2O + 4e - →4OH - .

[0039] Discharge and Maintenance: The generated Mg²⁺ ions are discharged from the condensate drain along with the condensate. Regularly check the consumption of the magnesium alloy anode 92 through the maintenance manhole. When it is worn down to the point where replacement is necessary, simply stop the machine, unscrew the old anode, and replace it with a new one to restore full protection. (When replacing the magnesium-based sacrificial anode block, first remove the old conductive weld seam, then remove the old magnesium alloy anode 92. After installing the new magnesium alloy anode 92, the steel metal core 91 in the center of the new magnesium alloy anode 92 must be reliably welded to the installation interface to form a new conductive weld seam. The weld joint should be treated with anti-corrosion measures to ensure the effectiveness of the cathodic protection system. Before installation, wrap sealing tape or apply high-temperature sealant to the threads of the new magnesium alloy anode to ensure a tight seal.)

[0040] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of this invention, and should be understood that the scope of protection of this invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on these technical teachings disclosed in this invention without departing from the essence of this invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A corrosion-resistant flue gas condensing heat exchanger with a built-in magnesium-based sacrificial anode protection device, characterized in that: It includes a heat exchanger shell (1), and the two ends of the heat exchanger shell (1) are respectively provided with a flue gas inlet (4) and a flue gas outlet (5); The bottom of the heat exchanger shell (1) is provided with a condensate discharge port (8) and a magnesium-based sacrificial anode block (9); the magnesium-based sacrificial anode block (9) serves as the anode, and the heat exchanger shell (1) serves as the cathode, forming an electrochemical corrosion protection circuit with the acidic condensate formed by flue gas condensation. The magnesium-based sacrificial anode block (9) includes a steel metal core (91) and a magnesium alloy anode (92). The magnesium alloy anode (92) is a hollow rod-shaped structure, and the steel metal core (91) is embedded in the center of the hollow rod-shaped structure along the axial direction. The bottom of the heat exchanger shell (1) is provided with an installation interface (10), and the steel metal core (91) is fixed in the installation interface (10). One end of the steel metal core (91) extends from the tail of the magnesium alloy anode (92), and the outer surface of the extended end is machined with external threads; a flange seat (11) is installed at the position of the mounting interface (10), and the inner hole of the flange seat (11) is machined with internal threads; the steel metal core (91) is installed on the flange seat (11) by threaded engagement, and the side of the steel metal core (91) that wraps around the magnesium alloy anode (92) faces the interior of the heat exchanger shell (1), and the steel metal core (91) makes the end face of the magnesium alloy anode (92) abut against the mounting interface (10) through the thread action.

2. The corrosion-resistant flue gas condensing heat exchanger with built-in magnesium-based sacrificial anode protection device according to claim 1, characterized in that: The end of the steel metal core (91) is welded to the shell metal around the mounting interface (10), and a conductive weld is formed at the welding position. The steel metal core (91) and the heat exchanger shell (1) are electrically connected through the conductive weld.

3. The corrosion-resistant flue gas condensing heat exchanger with built-in magnesium-based sacrificial anode protection device according to claim 1, characterized in that: The magnesium alloy anode (92) is immersed in the acidic condensate formed by flue gas condensation.

4. The corrosion-resistant flue gas condensing heat exchanger with built-in magnesium-based sacrificial anode protection device according to claim 1, characterized in that: The heat exchanger shell (1) has an inspection hole at the top.

5. The corrosion-resistant flue gas condensing heat exchanger with built-in magnesium-based sacrificial anode protection device according to any one of claims 2 to 4, characterized in that: The magnesium alloy anode (92) is made of MgAZ63B magnesium alloy.

6. The corrosion-resistant flue gas condensing heat exchanger with built-in magnesium-based sacrificial anode protection device according to any one of claims 1 to 4, characterized in that: The heat exchanger shell (1) is provided with a number of heat exchange tube bundles (2); the two ends of the heat exchange tube bundles (2) are connected by two tube sheets (3); the two tube sheets (3) are respectively provided with a cooling medium inlet (6) and a cooling medium outlet (7).

7. The corrosion-resistant flue gas condensing heat exchanger with built-in magnesium-based sacrificial anode protection device according to any one of claims 1 to 4, characterized in that: The number of the magnesium-based sacrificial anode blocks (9) is several.

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