1、 Causes of root wear of wear-resistant beams
Due to the significant impact of the flow velocity of the sticking flow on the wear of water-cooled wall tubes, and when the material properties and concentration cannot be changed, reducing the sticking flow velocity will greatly reduce the wear rate of the water-cooled wall. To this end, wear-resistant beam technology has been introduced, as shown in Figure 3. During the descent of the wall sticking flow, it encounters a blocking beam, causing the flow velocity to decrease. In this process, some particles change the flow direction, resulting in a reduction in the number of particles in the wall sticking flow and further reducing wear. However, traditional wear-resistant beams cannot solve the problem of "inverted eight character" wear at the root of wear-resistant beams while reducing the wear rate of water-cooled walls on a large scale. The main reason is that the downward and upward materials attached to the wall form a "vortex" above the wear-resistant beam; After the downward material adheres to the wall and touches the wear-resistant beam, some of the material bounces back onto the heating surface. (As shown in Figure 4)
2、 Current market plan
1. Thermal spraying
For the arrangement of anti-wear beams in the dilute phase zone, the "inverted eight shaped" wear is relatively light, and can be combined with thermal spraying for anti-wear, which can achieve good anti-wear effect. Thermal spraying is a material surface strengthening and passive anti-wear technology widely used in the "four pipe" anti-wear and anti-corrosion applications in power plants. It uses gas, liquid, electric arc, plasma arc as heat sources to heat metal, alloy, ceramic, plastic and other powders to a molten or melted state, and adheres to the working surface with the help of flame thrust or compressed air injection, thereby forming a coating and achieving anti-wear and anti-corrosion effects. Thermal spraying requires a high level of construction technology, and during maintenance, it is necessary to arrange and plan reasonably to ensure the completion of thermal spraying work with quality and quantity guaranteed.
The relevant preparations and auxiliary coordination work (such as equipment debugging, scaffolding, lighting, etc.) must be in place before starting work, and the entire process must be tracked during construction to ensure the smooth progress of thermal spraying work. Surface rust removal and scale removal are very important steps in thermal spraying construction. If the surface treatment is not good, it is difficult to ensure the quality of later construction. Therefore, after the surface rust removal and scale removal are completed, professional personnel must be organized for acceptance, and if necessary, rework treatment must be carried out.
The use of welding wire in thermal spraying is crucial. The welding wire must undergo spectral analysis before entering the site, and the content of nickel, chromium, titanium and other alloys must meet the requirements. At the same time, the welding wire should be randomly inspected during construction to prevent construction personnel from using inferior materials as good ones during the thermal spraying process. Before the construction personnel apply the sealing paint, they must inspect the material (spectral analysis), strength, hardness, thickness, density, and uniformity of the hot spray coating. At the same time, they must check whether there is any obvious (excessive) damage to the heated surface during the hot spray process. When repairing or replacing the hot spray coating in the later stage, the original hot spray coating must be polished clean, otherwise it is prone to defects such as wrinkles, peeling, and post weld cracks in the new hot spray coating
2. Local areas adopt "deposition" technology
For the installation of wear-resistant beams in the dense phase zone, at the four corners of the furnace, and near the smoke window, thermal spraying technology is no longer able to meet the requirements for anti-wear. After testing and statistics, conventional thermal spraying technology has shown that the base material in these areas experiences "inverted eight character" wear for about 60-70 days. Therefore, we need to seek an anti-wear measure that can ensure the long-term operation of the unit.
The "deposition" technology (shown in Figure 5) is to deposit a layer of alloy material with a hardness higher than HRC45 on the surface of the heated surface, generally with a low thickness of 1.5mm or more, and the thickness can reach 4mm according to the wear and tear requirements. Compared to "thermal spraying" technology, "deposition" technology has the following advantages:
The surface of the deposited layer is smooth, without cracks or pores, and durable and wear-resistant. The thickness is much higher than that of the thermal spray coating and is controllable. Compared to the mechanical extrusion particle bonding of thermal spray coating, the deposited wear-resistant layer is a metallurgical bonding with high bonding strength while ensuring HRC55 or higher. In the case of the same thickness, the wear resistance life is three times that of the thermal spray coating. Generally, the deposited layer thickness is 2-3mm, and its wear resistance life is 6 to 9 times that of the thermal spray coating. The thickness of the deposited layer can be adjusted according to the user's requirements and the characteristics of the coal entering the furnace to ensure the anti-wear life, with a minimum of 3 years and a maximum of 5 years. Compared to the wear-resistant coating of thermal spraying, the deposited wear-resistant layer has strong repairability and weldability, and the easily worn areas of the "four pipes" can be repaired or thickened appropriately. Due to its metallurgical bonding, the anti-wear layer has minimal impact on the heat transfer of the water-cooled wall compared to thermal spray anti-wear and stepped anti-wear beams.
In summary, the "fusion deposition" technology has a significant effect when used alone or in combination with wear-resistant beams for wear prevention, or when preventing and treating the "inverted eight character" wear problem at the root of wear-resistant beams. It can be used on a large scale, especially in newly built units. However, for those that have been in production for a long time and have already used thermal spraying for anti-wear, the use of "deposition" technology should be cautious. In the case where the original thermal spraying layer is not polished clean, using "deposition" technology is quite risky and prone to cracking. Moreover, the construction speed of "deposition" technology is slow, there are few domestic construction manufacturers, and the cost is high.
3. Install wear-resistant protective tiles on the upper part of the wear-resistant beam
The installation of wear-resistant protective tiles on the upper part of the wear-resistant beam fundamentally solves the problem of "inverted eight shaped" wear at the root of the wear-resistant beam. This measure is more practical in solving the serious "inverted eight character" wear and tear above the wear-resistant beam in the dense phase zone of the furnace, the four corners of the furnace, and near the smoke window.
3、 Our company's plan
1. Above the root of the wear-resistant beam, a flexible special wear-resistant material (chromium mud) made of silicon crystal adhesive with a height of 4-6cm and a width of 1-2cm is used as a guide platform, with appropriate angles left to prevent "inverted eight type" wear;
2. Spray a 10cm, 2-3mm thick silicon crystal adhesive wear-resistant coating on the upper part of the diversion platform;
3. A 1-2mm thick wear-resistant coating of silicone gel is applied 10cm above the silicone gel coating;
4. Ensure effective anti-wear and erosion prevention of coarse, medium, and fine fly ash.
4、 Construction technology
1. First, clean up the debris at the root of the wear-resistant beam, repair the water wall and wear-resistant beam pits;
2. Weld the 2520 nail and calculate it reasonably;
3. Divide the silicone rubber flexible wear-resistant material into strips and strike them several times with a rubber hammer until the water seeps out; Smooth surface repair to ensure smooth flushing of fly ash;
4. Remove rust within 20cm of the upper water-cooled wall, and then evenly spray the silicon crystal adhesive anti-wear layer according to the thickness before and after.
5. After the construction is completed, the furnace can be started directly
