Why is it required for ash transport in power plants?
The medium conveyed through pneumatic ash removal pipelines in power plants is dry fly ash or slag, characterized by high flow velocities and high particle hardness. Under prolonged erosive conditions, conventional carbon steel pipes or wear-resistant cast steel pipes exhibit particularly severe wear at bends, tees, reducers, and downstream of valves, leading to rapid thinning of the pipe walls or even perforation.
The lining of wear-resistant ceramic pipelines typically employs alumina ceramic (with an Al₂O₃ content ≥95%), which exhibits a Mohs hardness of up to 9.0-second only to diamond-in terms of hardness, and possesses wear resistance 10–20 times greater than that of conventional carbon steel. This means that under identical ash transport operating conditions, the service life of the pipelines can be significantly extended; data indicate that the service life of wear-prone components, such as elbows, can be increased by 5–8 times, and in certain application scenarios, the service life may exceed 10 years compared to conventional steel pipes.
Common structural types
The most commonly used type in power plant ash transport systems is the surface-mounted wear-resistant ceramic pipeline, which typically features a three-layer structure:
|
top class |
Material/Construction |
act on |
|
outer sphere |
Q235 or Q345 carbon steel pipes (wall thickness typically ≥6–8 mm) |
Provides structural strength and pressure resistance, facilitating welding or flange connections. |
|
Adhesive layer |
High-temperature resistant inorganic adhesive (thickness ≥ 2 mm) |
The ceramic sheets are firmly bonded to the inner wall of the steel pipe; once cured, they exhibit impact resistance and are resistant to aging. |
|
inside liner |
High-purity alumina ceramic sheets (typical thickness: 5–8 mm) |
Directly withstands abrasive wear from dust and powder, providing core wear-resistant protection. |
Ceramic plates are typically arranged using interlocking protrusion-and-recess patterns or staggered joint arch connections, ensuring zero seams at the pipe-end junctions, with inner walls that are flat and smooth (surface roughness ≤ ±0.2 mm), thereby reducing flow resistance of the material and the risk of dust accumulation causing pipe blockage.
Key performance indicators for power plant operating conditions
According to the power plant bidding technical specifications and product data, wear-resistant ceramic pipelines used for ash transport are typically required to meet the following specifications:
Ceramic content: The Al₂O₃ content is typically required to be ≥95% to ensure hardness and density.
Ceramic hardness: Rockwell hardness HRA ≥ 85, and microhardness HV ≥ 1000.
Temperature Resistance: In power plant applications-such as dry ash removal and ash conveying in economizers-the operating temperatures are typically high, necessitating the selection of high-temperature resistant inorganic adhesive systems. Conventional products can operate continuously below 350 °C, while some improved variants can withstand temperatures up to 500 °C.
Connection method: Supports flange connections or direct welding of the outer steel pipe, facilitating integration with existing on-site pipelines.
Key Considerations for Model Selection and Operation & Maintenance
Although wear-resistant ceramic piping offers an extended overall service life, certain details should still be considered during model selection and operational use:
Adhesion quality is critical: the fixation of ceramic plates relies on the adhesive layer. If the inner wall of the steel pipe is not thoroughly degreased and descaled, or if the adhesive curing process is inadequate, it may lead to delamination or detachment of the ceramic plates. Once detached, localized areas of the plates can rapidly suffer from scouring and wear.
Temperature Matching: Different adhesive systems have different maximum temperature ratings. If there are temperature fluctuations or localized high temperatures in the ash conveying pipeline, it is essential to select an adhesive system whose temperature rating matches the operating conditions to prevent the adhesive layer from failing under high temperatures.
Local repair: When a single ceramic tile is found to be cracked or detached, it can be promptly replaced individually; there is no need to replace the entire pipe segment, which can further reduce long-term maintenance costs.
https://www.chenyiceramic.com/ceramic-lined-pipe/ash-handling-pipe.html