Elbow Pipe Optimization for Power Plant

Application

Industry: Coal-Fired Power Plant
Capacity: 800MW * 3 units
Country: Taiwan

Problem

The plant constantly experienced pipe leakage in the elbow pipes of fly ash conveying pipelines at Economizer (ECO), Air Pre-Heater (APH), and Selective Catalytic Reactor (SCR) every 4 to 6 months. The conveying system is positive pressure type, so the leakage was visible and caused contamination in the nearby surroundings. The pipe bore is 5” (ID=100mm) with chrome alloy liner and R500mm curve radius. The pipes had been patched with concrete whenever leakage was observed, but obviously such solution has been proven to be futile.

Solution

Pipe leakage caused by erosive wear is a common pestering problem, which has a lot to do with particle velocity and hardness, solids loading ratio, and particle impact angle. These three parameters are subjected to the more complicated conditions of plant process and ash conveying system throughput design, thus, the simpler way to better withstand erosive wear is to improve the particle impact angle and pipe hardness.

Tai & Chyun recommended the plant to replace the original elbow pipe with inner ceramic-lined sleeve longer radius elbow pipe. By increasing the bend radius, the bend to pipe diameter ratio (D/d) is also increased, whereas the particle impact angle is decreased, and thus the erosive wear is kept to the minimum. The hardness of ceramic liner is 10 MOHS, which is higher than that of chrome alloy liner, 5 MOHS. The increased hardness of pipe liner material allows longer lifetime for the elbow pipe.

To ECO/SCR ash silo

SCR ash pipe

APH ash pipe

ECO/SCR/APH ash pipe to silo