Active anti-corrosion air preheater

Abstract

The utility model belongs to the technical field of boiler air preheaters, and discloses an active anti-corrosion air preheater. According to the technical scheme, the heat exchanger is composed of an outer shell assembly, heat exchange element boxes and heat exchange elements, wherein the heat exchange element boxes and the heat exchange elements are divided into a plurality of trapezoidal bins; sacrificial anode structures formed by active metal blocks are fixed to the lower ends of the outer shell assembly, the trapezoidal bin grids, the heat exchange element box and the heat exchange element respectively, and the sacrificial anode structures and the outer shell assembly, the trapezoidal bin grids, the heat exchange element box and the heat exchange element are of an integrated structure. As the sacrificial anode structures which are formed by the active metal blocks and are integrated with the outer shell assembly, the trapezoidal bin grids and the heat exchange element are respectively fixed at the lower end parts of the outer shell assembly, the trapezoidal bin grids and the heat exchange element which form the air preheater structure, and electrochemical corrosion occurs preferentially, the carbon steel structure assembly of the air preheater is protected; the purposes of prolonging the service life of the air preheater, reducing operation faults and improving the heat exchange efficiency are achieved.

Description

Technical Field

[0001] The utility model belongs to the technical field of air preheaters, and relates to an air preheater used for waste heat recovery in the flue gas discharge process of thermal power plants. Background Art

[0002] An air preheater (abbreviation: APH) is one of the indispensable core equipment of a power station boiler, which consists of an external shell and a central rotor. The external shell is static, and the central rotor is divided into several trapezoidal compartments, and heat exchange elements are installed in the compartments. An air preheater is a device that uses the heat of flue gas to heat air. Generally, it rotates counterclockwise. The boiler flue gas flows vertically down through the air preheater, and the central rotor rotates to carry the heat of the flue gas and radiate and release heat into the air duct. The heat of the flue gas first passes through the primary air duct, and the heat of the flue gas heats the primary air and sends it to the coal mill, becoming the power for coal powder preheating and conveying; then the heat of the flue gas passes through the secondary air duct, and after heating the secondary air, it is sent to the boiler for combustion, increasing the air temperature at the inlet of the boiler burner, achieving the effect of improving the utilization rate of coal combustion and energy conservation and environmental protection.

[0003] The main component of coal is C, and it is mixed with N and S. Therefore, when coal burns, it will produce a mixed flue gas of CO2, CO, SO2, SO3, NO, and NO2 (nitrogen oxides NO X ). SO3 in the flue gas will further react with the water vapor in the flue gas to form sulfuric acid vapor. When the flue gas flows into the denitration reactor, the escaped ammonia NH3 in the denitration and sulfuric acid vapor will react to form ammonium bisulfate. When the temperature is lower than the acid dew point temperature, sulfuric acid and ammonium bisulfate in the flue gas will be in a liquid state, and the flue gas temperature at the inlet and outlet of the lower end of the air preheater is between 230°C and 110°C, which is exactly in the section where the acid dew point temperature is formed. Sulfuric acid vapor and ammonium bisulfate will form acidic condensates with the coal ash particles in the flue gas. This condensate strongly adheres to the compartment plates, central rotor, and heat exchange element layer at the lower end of the air preheater, resulting in chemical corrosion of the air preheater.

[0004] To prevent corrosion of components such as the outer shell of the air preheater, trapezoidal bin compartments, heat exchange element boxes and heat exchange elements installed in the bins, the current anti-corrosion method is to apply an organic anti-rust paint on the surfaces of the outer shell and trapezoidal bin compartments that make up the air preheater, and apply an enamel coating on the cold-end heat exchange elements. The above anti-corrosion methods all belong to passive anti-corrosion; the organic anti-rust paint on the outer shell and bin of the air preheater will oxidize rapidly when exposed to high-temperature flue gas, especially the acid-corrosive components in the flue gas will quickly dissolve the organic anti-rust paint; applying an inorganic enamel coating on the heat exchange elements is a complex process, energy-consuming at high temperatures, and has a high production cost. Due to the poor thermal conductivity of the enamel coating, its heat exchange efficiency is greatly affected. During the installation of the finished product, porcelain chipping is likely to occur. When the high-pressure steam soot blower is used for on-line soot blowing during the operation of the air preheater, the enamel coating will be severely damaged, resulting in serious corrosion and blockage of the heat exchange elements, greatly affecting the service life of the air preheater. Summary of the Invention

[0005] The purpose of the present invention is to provide an air preheater that can effectively and actively resist corrosion, thereby reducing the chemical corrosion of the air preheater caused by harmful flue gases such as sulfuric acid vapor and ammonium bisulfate formed during the combustion of coal.

[0006] The technical solution for realizing the above-mentioned utility model patent is as follows:

[0007] An actively anti-corrosive air preheater is composed of an outer shell assembly, and is divided into several trapezoidal bin compartments, heat exchange element boxes installed in the bins and heat exchange elements. Its characteristics are:

[0008] At the lower end of the outer shell assembly, trapezoidal bin compartment, heat exchange element box or / and heat exchange element, a sacrificial anode structure composed of active metal blocks integrally fixed therewith is provided.

[0009] In the structure of the above-mentioned actively anti-corrosive air preheater,

[0010] - The sacrificial anode structure fixed to the outer shell assembly includes a wire electrically connected to the outer shell assembly and a sacrificial anode structure fixed to the other end of the wire;

[0011] - A steel core with one or both ends exposed is buried in the middle of the sacrificial anode structure.

[0012] Compared with the prior art, the active anti-corrosion air preheater provided by the present utility model has a sacrificial anode structure formed by active metal blocks integrally fixed to the lower ends of its outer shell assembly, trapezoidal compartments or / and heat exchange elements. The sacrificial anode structure is made of active metal materials. When it is connected to the air preheater structure components, an electrochemical corrosion reaction occurs preferentially, protecting the carbon steel structure components of the air preheater and achieving the purpose of effectively reducing the chemical corrosion of the air preheater caused by sulfuric acid vapor and ammonium bisulfate formed during the combustion of coal. Thus, the service life of the air preheater is increased, operation failures are reduced, and the heat exchange efficiency is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 FIG. is a schematic structural diagram of the active anti-corrosion air preheater provided by the present utility model;

[0014] Figure 2 FIG. is a schematic structural diagram of the compartment structure of the air preheater;

[0015] Figure 3 FIG. is a schematic structural diagram of the element box of the air preheater;

[0016] Figure 4 For forming Figure 3 FIG. is a schematic structural diagram of the frame of the element box of the air preheater shown;

[0017] Figure 5 FIG. is a schematic structural diagram of the heat exchange element of the air preheater;

[0018] Figure 6 FIG. is a schematic structural diagram of the sacrificial anode structure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The following further details the structure and working principle of the active anti-corrosion air preheater provided by the present utility model with reference to the accompanying drawings:

[0020] As shown in Figure 1 , 2 , 3, 4 and 5, FIG. is a schematic structural diagram of the active anti-corrosion air preheater provided by the present utility model. Its structure includes an outer shell assembly 1 and a central rotor compartment assembly 3 fixed therein by a shaft 2. Among them, the central rotor compartment assembly is composed of 48 trapezoidal compartments 31 (the number of compartments can be designed according to needs) each having a fan angle of 7.5 degrees as shown in Figure 2 . In the trapezoidal compartments, there are three groups of heat exchange element boxes 32, namely the first, second and third groups A1, A2 and A3, and they are arranged in two layers, upper and lower, as shown in Figure 3 . And the heat exchange element box 32 is composed of several groups as fixed in a frame 51 as shown in Figure 4 ​Figure 5 It is composed of a vertical corrugated plate 52 with the structure shown. Sacrificial anode structures 4 made of active metal blocks are fixedly arranged at the lower ends of the external housing assembly 1, trapezoidal bin 31, heat exchange element box 32 and heat exchange element respectively and are integrally formed therewith.

[0021] During the operation of the rotary air preheater, sacrificial anode structures 4 made of magnesium-based, zinc-based or aluminum-based, which are more active than iron element, are fixedly arranged at the outer shell of the air preheater, the lower ends of the bin plates, the lower ends of the element boxes and the lower ends of the heat exchange elements and are integrally formed therewith. When the sulfuric acid vapor and ammonium bisulfate in the flue gas entering the air preheater are in a liquid state at a temperature lower than the dew point temperature, the condensates of sulfuric acid vapor, ammonium bisulfate and flue gas particles adhere to the bin plates, the outer shell and the heat exchange element layer at the lower end of the air preheater. At this time, the acidic condensates first react electrochemically with the metals in the magnesium-based, zinc-based and aluminum-based alloys that make up the sacrificial anode structure 4, so as to effectively avoid or slow down the electrochemical corrosion of the metal iron that makes up the outer shell of the air preheater, the lower ends of the bin plates, the lower ends of the element boxes and the heat exchange elements, achieving the purpose of active corrosion resistance of the air preheater.

[0022] In the structure of the above-mentioned active corrosion-resistant air preheater,

[0023] - The sacrificial anode 4 fixed to the above-mentioned external housing assembly is connected to the external housing of the air preheater 1 through a connecting wire 43; the sacrificial anode structure 4 is fixed on a steel structure platform 6, and multiple sacrificial anode structures 4 can be connected to the external housing assembly 1;

[0024] - The sacrificial anode structures (magnesium-based, zinc-based or aluminum-based) 4 on the trapezoidal bin 2, heat exchange element box 5 and heat exchange element 52 are riveted to their corresponding structures respectively to achieve a low-resistance fixed connection between the two.

[0025] - In order to further reduce the resistance between the sacrificial anode structure 4 and the trapezoidal bin 2, heat exchange element box 5 and heat exchange element to which it is riveted, as Figure 6 shown, a steel core 41 with one or both ends exposed is buried in the middle of the above-mentioned sacrificial anode structure 4, and the steel core is used for electrical connection between the trapezoidal bin 2, heat exchange element box 5 and heat exchange element.

Claims

1. An active anti-corrosion air preheater, which consists of an external housing assembly, and heat exchange element boxes and heat exchange elements that are divided into several trapezoidal compartments and installed in the compartments, is characterized in that: A sacrificial anode structure composed of active metal blocks integrally fixed to the lower ends of the external housing assembly, trapezoidal compartments, heat exchange element boxes or / and heat exchange elements is provided.

2. The active anti-corrosion air preheater according to claim 1, wherein: The sacrificial anode structure fixed to the external housing assembly includes a wire electrically connected to the external housing assembly and a sacrificial anode structure fixed to the other end of the wire.

3. The active anti-corrosion air preheater according to claim 1, characterized in that: A steel core with one or both ends exposed is buried in the middle of the sacrificial anode structure.

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