Erosion wear mechanisms of coal-water-slurry (CWS) ceramic nozzles in industry boilers

Al2O3/(W, Ti)C ceramic composites were prepared for the use of coal-water-slurry (CWS) nozzles in industry boilers. The erosion rates of the CWS ceramic nozzles were measured. Eroded bore surfaces of the nozzles was examined by scanning electron microscopy. Finite element method (FEM) was used as a means of numerically evaluating temperature, temperature gradient, thermal stress and its distribution inside the ceramic nozzle. Results showed that the primary wear mechanisms of the CWS ceramic nozzle exhibited polishing action in the inner center hole and thermal shock damage with chipping at exit. The temperature, temperature gradient and thermal stress at exit surfaces of the CWS ceramic nozzle were higher than those of other parts of the nozzle. Greater temperature gradient and higher thermal stress were the main reason that caused the failure of the exit surface of the CWS ceramic nozzle.