A method for cathodic protection of a drag conveyor inner runner component in a high-salinity water environment

Abstract

This invention discloses a cathodic protection method for the internal guide wheel component of a slag remover in a high-salt environment, comprising: selecting the type of sacrificial anode material according to the material of the internal guide wheel component to be protected and its service environment; selecting the protection current density required for cathodic protection of the internal guide wheel component according to the high-salt and high-temperature service conditions of the internal guide wheel component, and calculating the surface area of ​​the required sacrificial anode material accordingly; fabricating the sacrificial anode material according to the selected type and surface area of ​​the sacrificial anode material, and then installing the sacrificial anode material. This method can achieve corrosion protection for the internal guide wheel component of the slag remover.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical cathodic protection technology for thermal power plants, and relates to a cathodic protection method for the guide wheel component inside a slag removal machine in a high-salinity environment. Background Technology

[0002] As a crucial piece of equipment in the normal operation of thermal power plants, ash removal machines are widely used in boiler ash removal operations. The reliability of these machines not only affects the performance of the equipment itself but also the normal operating conditions of the boiler and other equipment, ultimately impacting the power generation efficiency and quality of the thermal power plant. Furthermore, due to the special working conditions of the ash removal machine, there is significant friction and wear between the ash, the chain, and the inner guide wheel. This leads to corrosion of the inner guide wheel, causing breakage and affecting production. Moreover, thermal power plants introduce desulfurization wastewater with high salt content into the existing ash slurry, further exacerbating corrosion of components during service. Existing materials only meet the engineering requirements before the introduction of desulfurization wastewater; however, with the introduction of desulfurization wastewater, components suffer from both corrosion and frictional wear, significantly reducing their service life. Therefore, to ensure the normal operation of the ash removal machine and safeguard the economic benefits of the thermal power plant, it is essential to find an effective process to protect the inner guide wheel of the ash removal machine and extend its service life.

[0003] Cathodic protection is a corrosion prevention process applicable to most metallic materials, but its application in the guide wheels of power plant slag removers is rare. Therefore, developing a cathodic protection process suitable for the guide wheels of slag removers in high-salinity environments is of great significance for achieving corrosion protection of the guide wheel components, saving costs, and ensuring safety. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a cathodic protection method for the guide wheel component inside a slag remover in a high-salt environment. This method can achieve corrosion protection for the guide wheel component inside the slag remover.

[0005] To achieve the above objectives, this invention discloses a cathodic protection method for the guide wheel component inside a slag remover in a high-salinity environment, comprising:

[0006] The type of sacrificial anode material is selected based on the material of the guide wheel component inside the slag remover being protected and its service environment;

[0007] Based on the high salt and high temperature service conditions of the inner guide wheel component of the slag remover, the protection current density required for the cathodic protection of the inner guide wheel component is selected, and the surface area of ​​the required sacrificial anode material is calculated accordingly.

[0008] The sacrificial anode material is manufactured according to the type and surface area of ​​the selected sacrificial anode material, and then the sacrificial anode material is installed.

[0009] The sacrificial anode material was chosen to be a zinc-aluminum alloy.

[0010] The zinc-aluminum alloy contains 5% Al by mass.

[0011] The area of ​​sacrificial anode material required per unit area of ​​cathode material is:

[0012]

[0013] U 阳极 =I×R 总

[0014] R 总 =R 阴极 +R 溶液 +R 焊接

[0015] I = s 阴极 ×i 阴极

[0016] s 阳极 =I÷i 阳极

[0017] Among them, R 阴极 ρ is the resistance of the cathode material (the material being protected). 阴极 L is the resistivity of the cathode material. 阴极 S is the length of the cathode material. 阴极 s is the cross-sectional area of ​​the cathode material. 阴极 i is the surface area of ​​the cathode material. 阴极 To protect the current density.

[0018] Protective current density i 阴极 30mA / m 2 .

[0019] To determine the required protection current density for cathodic protection, the guide wheel inside the slag remover, the anode material, the welding point, and the surrounding solution are considered as a complete circuit system. An equivalent circuit diagram of this complete circuit system is fitted, in which the anode material undergoes an oxidation reaction to provide electrons, and the cathode material, solution, and welding point undergo a reduction reaction to consume electrons. The surface area of ​​the sacrificial anode material required is calculated based on this.

[0020] Zinc-aluminum alloy at 60℃, Cl － The current efficiency in a mixed environment of desulfurization wastewater and slag water with a concentration of 20,000 mg / L reaches over 95%, and the self-corrosion potential is -1.123V. SCE The corrosion current reached 1.527 × 10⁻⁶. -4 A.

[0021] The zinc-aluminum alloy is prepared by melting and casting.

[0022] The present invention has the following beneficial effects:

[0023] The cathodic protection method for the guide wheel component of a slag remover in a high-saltwater environment, as described in this invention, involves selecting a novel zinc-aluminum alloy sacrificial anode material based on the material of the guide wheel. This zinc-aluminum alloy sacrificial anode material exhibits high electrochemical activity, a sufficiently negative working potential, high current efficiency, uniform corrosion morphology, automatic detachment of corrosion products, a low alloy element composition, simple production process, and low requirements for raw material impurity content. By pre-calculating the surface area of ​​the sacrificial anode material based on the size of the cathode material, the amount of anode material used can be reduced, costs can be saved, and safety can be increased. Attached Figure Description

[0024] Figure 1 Equivalent circuit diagram;

[0025] Figure 2 The graphs show the potentiodynamic polarization curves of the cathode and anode materials.

[0026] Figure 3 This is a macroscopic morphology diagram of the cathode material after intermittent immersion testing;

[0027] Figure 4 This is a macroscopic morphology diagram of the anode material after intermittent immersion testing;

[0028] Figure 5 This is a microscopic morphology diagram of the anode material after intermittent immersion testing. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, not all embodiments, and are not intended to limit the scope of the present invention. Furthermore, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion regarding the concepts disclosed in the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0030] The accompanying drawings show structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not drawn to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0031] The cathodic protection method for the guide wheel component of a slag remover in a high-salinity environment, as described in this invention, includes the following steps:

[0032] 1) Selection of sacrificial anode material;

[0033] The type of sacrificial anode material is selected based on the material of the guide wheel components inside the slag remover being protected and its service environment.

[0034] 2) Calculation of the sacrificial anode area;

[0035] refer to Figure 1 Based on the high-salt and high-temperature service conditions of the guide wheel component in the slag remover, the required protection current density i for cathodic protection of the guide wheel component is selected as 30 mA / m. 2 The guide wheel (cathode material), anode material, welding points, and surrounding solution of the slag remover are considered as a complete circuit system. An equivalent circuit diagram is obtained by fitting this system. In this circuit, the anode material undergoes an oxidation reaction to provide electrons, while the cathode material, solution, and welding points undergo reduction reactions to consume electrons. The shape and material of the cathode material are fixed. The current value I in the circuit is calculated based on the surface area of ​​the cathode material and the required protective current density. The resistance values ​​of the guide wheel, solution, and welding points are obtained through measurement and are fixed values ​​R in this system. 总 Based on the characteristics of a series circuit, the potential of the anode material is calculated using U=IR. Then, based on the potentiodynamic polarization curve of the anode material, the current density i at that potential is determined. 阳极 Finally, the surface area of ​​the required anode material is calculated.

[0036] In this embodiment, the sacrificial anode material is composed of Zn-Al, comprising 5% Al, ≤0.1% impurities, and the balance being Zn by mass percentage; the impurities are metal oxides remaining in the melt.

[0037] In this embodiment, the sacrificial anode material is at 60°C, Cl － The current efficiency in a mixed environment of desulfurization wastewater and slag water with a concentration of 20,000 mg / L reaches over 95%, and the self-corrosion potential is -1.123V. SCE The corrosion current was 1.527 × 10⁻⁶. -4 A.

[0038] In this embodiment, zinc is used as the raw material, and 5% aluminum by weight is added. The sacrificial anode material is prepared by smelting using a casting method.

[0039] To select a suitable sacrificial anode material, this experiment used three zinc alloys—Zn, Zn-5Al, and Zn-55Al—as anode materials.

[0040] Example 1

[0041] A zinc alloy sacrificial anode material suitable for the guide wheel component of a slag remover in a power plant, comprising the following components by weight percentage: Al: 5%, impurities ≤0.1%, and balance Zn.

[0042] The preparation method of the sacrificial anode material is as follows: According to the alloy formula, weigh the corresponding mass of alloying elements and melt them in a resistance furnace. Specifically, place zinc and aluminum in a preheated graphite crucible in the melting furnace, add charcoal covering agent, and set the temperature to 600℃. After the metal ingot melts, press the weighed Al wrapped in zinc foil into the zinc liquid using a bell jar and keep it at that temperature for 30 minutes. After it is completely melted, the power can be turned off. Then, add refining agent to refine the material, and stir to mix the alloy components evenly and fully alloy them. After the furnace temperature drops to 450℃, remove the slag, pour the casting, and allow it to cool naturally to form the desired shape.

[0043] Comparative Example 1

[0044] A zinc alloy sacrificial anode material suitable for the guide wheel component of a power plant slag remover comprises the following components by weight percentage: Zn: 100%, purity 99.5%.

[0045] Comparative Example 2

[0046] A zinc alloy sacrificial anode material suitable for the guide wheel component of a slag remover in a power plant comprises the following components by weight percentage: Al: 55%, Si: 1.6%, impurities ≤0.1%, and the balance being Zn.

[0047] Verification Example 1

[0048] Electrochemical dynamic polarization curves were tested on zinc alloy anode materials and cathode inner guide wheel materials (20CrMnTi) with different alloy contents prepared in Example 1, Comparative Example 1 and Comparative Example 2.

[0049] The cathode and anode materials were cut into blocks with dimensions of 10*10*3 mm to prepare electrochemical working electrode samples, with a test area of ​​1 cm². 2 The remaining surfaces are sealed with insulating glue.

[0050] The electrochemical test employed a three-electrode system: a saturated calomel electrode as the reference electrode, a 10*10*1mm platinum sheet electrode as the auxiliary electrode, and the sample to be tested as the working electrode. The electrolyte was desulfurization wastewater, in which Cl... - The concentration was 20000 mg / L, and the test temperature was 60℃.

[0051] The test sample was tested for open circuit points for 1200 seconds. The potentiodynamic polarization test range was ±0.3V at the open circuit point. The sensitivity was automatic and the scan speed was 0.05V / s.

[0052] Electrodynamic potential polarization curves of cathode and anode materials are as follows Figure 1 As shown, the fitting data results are shown in Tables 1 and 2.

[0053] Table 1

[0054]

[0055] Table 2

[0056]

[0057] Verification Example 2

[0058] Zinc alloy anode materials and cathode inner guide wheel materials (20CrMnTi) with different alloy contents prepared in Example 1, Comparative Example 1 and Comparative Example 2 were subjected to inter-immersion corrosion experiments, and the morphology of each sample after corrosion was observed.

[0059] The cathode material is made into a block with dimensions of 50*25*5mm using an electrical discharge wire cutting machine, and a φ3 through hole is made on one side using a drilling machine. A copper wire is used to connect to the cathode material, and the connection is sealed with insulating glue.

[0060] After determining that the potential energy of the selected zinc alloy meets the protection requirements of the slag removal machine components, the required sacrificial anode material area per unit area of ​​cathode material is calculated using the following formula.

[0061]

[0062] U 阳极 =I×R 总

[0063] R 总 =R 阴极 +R 溶液 +R 焊接

[0064] I = s 阴极 ×i 阴极

[0065] s 阳极 =I÷i 阳极

[0066] Among them, R 阴极 ρ is the resistance of the cathode material (the material being protected). 阴极 L is the resistivity of the cathode material. 阴极 S is the length of the cathode material. 阴极 s is the cross-sectional area of ​​the cathode material. 阴极 i is the surface area of ​​the cathode material. 阴极 Based on experience, the cathodic protection current density *i* in the slag removal machine system is determined to be 30 mA / m². 2 .

[0067] The required anode material area is calculated based on the formula, and the required area is cut out using an electrical discharge wire cutter. Copper wires are then used to connect the anode material to the cathode material, and finally, epoxy resin is used to encapsulate the anode material.

[0068] The wires connecting the anode and cathode materials are interconnected and placed on a rotating plate corrosion tester. The corrosion solution is Cl. - Desulfurization wastewater with a concentration of 20000 mg / L was treated with NaOH added to control the pH at 9, and the water bath temperature was set at 60℃. The corrosion method was rotary immersion. In one cycle, the sample was immersed in the corrosion solution for 60 seconds and exposed to air for 180 seconds, with a total operating time of 120 hours.

[0069] Macroscopic images of the cathode and anode materials after inter-immersion experiments are shown below. Figure 2 and Figure 3 As shown, the microstructure of the anode material is as follows: Figure 4 As shown.

[0070] Verification Example 3

[0071] Intermittent immersion corrosion experiments were conducted on zinc alloy anode materials and cathode inner guide wheel materials (20CrMnTi) with different alloy contents prepared in Example 1, Comparative Example 1 and Comparative Example 2. The mass difference and corrosion rate of each sample before and after corrosion were calculated.

[0072] After the indirect immersion corrosion test was completed, the cathode and anode materials were separated. The samples were then repeatedly rinsed with deionized water and dried until no crystalline salts were precipitated on the surface.

[0073] The cathode material was placed in dilute hydrochloric acid and ultrasonically vibrated for 10 minutes to remove surface corrosion products. Then, it was cleaned with deionized water and alcohol and weighed to calculate the mass loss.

[0074] The anode material was placed in a saturated ammonium acetate solution and ultrasonically vibrated for 5 minutes to remove surface corrosion products. Then, it was cleaned with deionized water and alcohol and weighed to calculate the mass loss.

[0075] The quality of the anode and cathode materials before and after the immersion test is shown in Tables 3 and 4.

[0076] Table 3

[0077]

[0078] Table 4

[0079]

[0080] Based on the cathodic weight loss before and after the intermittent immersion experiment, the corrosion rate of the cathode material per unit area per unit time can be calculated. The calculation formula is shown below, and the calculation results are shown in Table 5.

[0081]

[0082] Where m1 is the mass before the experiment; m2 is the mass after the experiment; Δm3 is the mass of the blank control; S is the sample surface area; T is the experimental time; D is the sample density; and R is the corrosion rate.

[0083] Table 5

[0084]

[0085] Table 6

[0086]

[0087]

[0088] Based on the test results of Verification Examples 1, 2 and 3, when Al: 5%, Zn: balance, and impurity content ≤ 0.1%, the sacrificial anode material has better cathodic protection effect in practical applications.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A cathodic protection method for the guide wheel component inside a slag remover in a high-salinity environment, characterized in that, include: The type of sacrificial anode material is selected based on the material of the guide wheel component inside the slag remover being protected and its service environment; Based on the high salt and high temperature service conditions of the inner guide wheel component of the slag remover, the protection current density required for the cathodic protection of the inner guide wheel component is selected, and the surface area of ​​the required sacrificial anode material is calculated accordingly. The sacrificial anode material is manufactured according to the type and surface area of ​​the selected sacrificial anode material, and then the sacrificial anode material is installed. The area of ​​sacrificial anode material required per unit area of ​​cathode material is: Among them, R 阴极 The resistance of the cathode material, L is the resistivity of the cathode material. 阴极 S is the length of the cathode material. 阴极 s is the cross-sectional area of ​​the cathode material. 阴极 i is the surface area of ​​the cathode material. 阴极 The cathode protection current density, s 阳极 i is the surface area of ​​the anode material. 阳极 The protective current density of the anode. The potential of the anode; The sacrificial anode material was chosen to be a zinc-aluminum alloy. The zinc-aluminum alloy contains 5% Al by mass. To determine the required protection current density for cathodic protection, the equivalent circuit diagram of the complete circuit system is fitted, taking the guide wheel inside the slag remover, the anode material, the welding point, and the surrounding solution as a complete circuit system.

2. The cathodic protection method for the guide wheel component of a slag remover in a high-salinity environment according to claim 1, characterized in that, Protective current density i 阴极 30mA / m 2 .

3. The cathodic protection method for the guide wheel component of a slag remover in a high-salinity environment according to claim 1, characterized in that, Zinc-aluminum alloy at 60℃, Cl － The current efficiency in a mixed environment of desulfurization wastewater and slag water with a concentration of 20,000 mg / L reaches over 95%, and the self-corrosion potential is -1.123V. SCE The corrosion current reached 1.527 × 10⁻⁶. -4 A.

4. The cathodic protection method for the guide wheel component of a slag remover in a high-salinity environment according to claim 1, characterized in that, The zinc-aluminum alloy is prepared by melting and casting.

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