Abstract: For the pipes of coal gasification black water treatment system, due to the high contents of both solid particles and corrosive elements in the flowing fluid media, and their high temperature and high-pressure difference working environment, the inner surface of the pipes are extremely vulnerable to corrosion and erosive wear, thus affecting their service life. In the paper, the computatioanal fluid dynamics method was used to study the erosion behaviors of the solid-liquid two-phase flow pipeline in the coal gasification black water system. And the influence rules of flow velocity and solid particle size on the erosion rates of the pipes were also investigated. Meanwhile, two modified elbows with blind pipe and vortex chamber were analyzed respectively to extend the service life. Results indicated that the primary erosion failure positions of the tested pipeline located in the structural abrupt position, such as the extrados of the elbow and the Variable diameter pipe. The flow behaviors of continuous liquid phase inside the pipeline and the impact effect of the discrete solid particles on the pipe wall played a great role in the pipeline erosion. Both the erosion rates of the elbows and variable diameter pipe increased as the fluid velocity increased; however, the influence rules of solid particle size on the erosion rate were not monotonic. A vortex chamber added to the elbow decreased the maximum erosion rate, thus alleviating erosive wear of the elbow and prolonging its service life.