Combustion Characteristics of 500 t/d Mechanical Grate Waste Incinerator and Effects of Secondary Wind Ratio on Coking of the Throat

In view of the characteristics of high ash content, low calorific value, and susceptibility to coking during the incineration power generation process, this study examines a mechanical grate waste incinerator with a daily treatment capacity of 500 t in Laishui, Baoding, Hebei Province, as the research object and explores the component characteristics of village and town domestic waste through sampling and analysis. The fly ash, bottom slag, throat wall coke, and ash soil components in the waste incinerator are sampled, and their ash melting points are measured. Based on the structural characteristics of the waste incinerator and the composition and calorific value of local domestic waste, FLIC and Ansys Fluent software are utilized to simulate the water evaporation, volatile release, volatile combustion, and coke incineration processes along the grate movement direction, as well as the distribution of the temperature field, velocity field, and concentration field in the furnace. The simulated results are compared and analyzed with the measured data. Considering the coking part, coke block shape, and coking degree in the furnace, the main factors affecting coking in the waste incinerator are analyzed. The risk and degree of coking in the equipment are reduced by adjusting the secondary air ratio between the front and rear arches. The ash melting point test results indicate that the hemispherical temperature and flow temperature of the ash samples in the furnace are slightly lower than those of the ash soil composition and the treated fly ash, which are close to 1 200 °C. The primary component in the furnace coke sample is pyroxene, accounting for 51%, followed by calcium (sodium) feldspar and orthoclase feldspar, accounting for 30%. The simulation results demonstrate that when the wind speed of the front arch and the wind speed of the back arch is 41 m/s and 38 m/s, respectively, the gas flow field and temperature field distribution in the throat and the front and rear arch areas in the furnace are optimized, the gas erosion of the front arch and the reflux zone at the throat are improved, and the suppression effect on the coking phenomenon is maximized. The research findings provide important guidance and engineering application value for predicting and mitigating coking in waste incinerators, improving boiler thermal efficiency, and enhancing operational economy.