Evaluation of Combustion Grate Damage: A Comprehensive Review of Grate Deterioration in Biomass Power Plants

Abstract

Biomass-fired power plants in the VSPP scale increasingly rely on agricultural and woody residues, yet grate components frequently experience premature failure that leads to unplanned outages and high maintenance costs. This study provides a quantitative evaluation of grate-bar degradation mechanisms using long-term operational data, in-situ temperature measurements, and metallurgical characterization. Surface temperatures of 1000–1200 °C and radiative heat fluxes of 65–78 kW/m^² were identified as the dominant thermal drivers of overheating, particularly in zones intermittently exposed during fuel-bed collapse. A six-year dataset from a 9.9-MW reciprocating-grate power plant, supplemented by laboratory material analysis and combustion-zone mapping, was used to identify the controlling failure modes. The results show that persistent primary-air (PA) maldistribution, unstable fuel-bed conversion, and periodic loss of ash/fuel coverage significantly increase radiative exposure and thermal cycling. Metallurgical examination revealed oxide-scale spallation, carburization, and creep deformation, consistent with thermomechanical–chemical mechanisms reported in prior studies. Although para-rubber woodchip contains relatively low concentrations of corrosive species, localized high-temperature oxidation and chloride-assisted attack were still observed, confirming that chemical effects—while secondary—accelerate degradation under fluctuating oxygen and temperature conditions. The study provides engineering recommendations for improving PA–SA distribution control, optimizing grate-motion strategies, and selecting alloys resistant to combined thermal fatigue and carburization. These findings offer a validated mechanistic framework explaining grate-bar failure in reciprocating-grate biomass systems and support more reliable, cost-effective operation of biomass power plants.