Numerical Optimization Study of Combustion and Heat Transfer Characteristics in Municipal Solid Waste Incinerators.

The efficient and clean utilization of urban waste can substitute for partial fossil fuels and reduce total carbon emissions. Fuel combustion is divided into three stages. Before the fire, the fuel is put into the furnace to reach the preparation stage of the fire temperature, the combustion stage takes place after the ignition temperature is reached, and finally, the combustion is completed. This article employs numerical simulation methods to comprehensively study the effects of various factors on the combustion characteristics of waste in a mechanical grate incinerator, including the inclination angle of the front arch, fuel properties, height of the front and rear arches, air distribution methods, and speed of the grate chain rotation. The results indicate that when the rear arch angle is set at 25°, the airflow distribution within the furnace is uniform and the high-temperature flue gas exhibits an ideal "L" shaped flow, achieving favorable characteristics of airflow distribution inside the furnace. With this structure, the airflow from the rear arch can adequately penetrate deep into the front arch area, thereby forming an efficient T-shaped combustion flame.

Experimental Study on Gas-Solid Two-Phase Flow Characteristics of a Vertical Cyclone Combustor System.

According to the design and operational parameters of the cyclone liquid slag-discharging boiler, an experimental platform for the cyclone burner was designed and constructed in a cold state based on the principle of similarity. The experimental study investigated the effects of parameters, such as swirl-vane angles, coal concentration, operating parameters, and particle size, on the flow distribution and vertical riser resistance characteristics of the vertical cyclone burner. The results showed that there were differences in flow distribution among the cyclone burners, and the most uniform flow distribution was achieved when the swirl-vane angle of the primary air was 30°. The concentration of pulverized coal significantly influenced the pressure drop in the vertical ascending section, which increased with higher concentrations of pulverized coal. When the concentration of pulverized coal remains constant, the pipeline pressure drop is minimized at a primary air velocity of 7.5 m/s. As the secondary wind speed increased, the pressure drop consistently rose; when the secondary wind speed is 22 m/s, the pressure drop of the pipeline is the maximum; however, excessively high secondary wind speeds were found to be detrimental to the formation of an optimal aerodynamic field in the burner. Furthermore, when the pulverized coal concentration was held constant, materials with larger particle sizes exhibited the highest pressure drop. When the particle size increases from 50 to 150 µm, the pressure drop of the vertical riser segment also increases. Finally, based on the Barth additional pressure drop theory, the pressure drop formula of the vertical riser is fitted by a dimensional analysis method, and the correlation formula of the pressure drop test of gas-solid two-phase flow in the vertical riser is obtained.