Numerical Simulation of NO_x Emission Characteristics of a Cyclone Boiler with Slag-Tap Furnace

Abstract

In order to optimize the parameters of boilers and realize the burning of pure, high-alkali coal, the velocity field, temperature field, and component distribution characteristics of a new cyclone boiler with slag-tap furnace were numerically studied using ANSYS software. The influence law of the over-fire air rate on the NO x emission of the cyclone boiler with slag-tap furnace was established, and the optimal over-fire air rate was determined. The renormalization-group k−ε double equation model was used to simulate the gas phase flow, the discrete phase model was used to compute the gas−solid two-phase flow, and the high-alkali coal combustion model was revised based on experimental data. The results show that the overall aerodynamic field in the entire boiler with slag-tap furnace is favorable, the flue gas is completely formed, and the cyclone burners in a staggered and reversed arrangement can enhance combustion. The temperature near the wall of the cyclone can reach 1700−2100 K, which satisfies the requirements of a liquid slag discharge. The temperature under various over-fire air rate conditions can allow the high-alkali coal to burn normally and ensure fluidization of its ash. The greater the over-fire air rate, the lower the average temperature in the furnace and the lower the NO x concentration at the outlet of the furnace. Considering that it is not easy to fluidize the ash of high-alkali coal when the average temperature in the cyclone boiler with slag-tap furnace is very low, an over-fire air rate of 10% is selected for the optimal air-staged combustion scheme.

Numerical Study and Hydrodynamic Calculation of the Feasibility of Retrofitting Tangentially Fired Boilers into Slag-Tap Boilers

“…Therefore, high-temperature flue gas fills the entire combustion chamber quickly. This is consistent with the results in the literature [15]. Given the relatively concentrated combustion area in the slag-tap boiler, the maximum combustion temperature is high, reaching 2306.8 K. Different from the tangentially fired boiler, the flue gas temperature remains high near the water-cold wall in the combustion chamber of the slag-tap boiler.…”

“…It reveals that pulverized coal enters the cyclone burners via the primary air inlet. Under the effect of tangential secondary air, the pulverized coal particles swirl along the cyclone burners wall, prolonging their residence time in the cyclone burners [15]. When the pulverized coal proceeds into the combustion chamber, it intermingles with particles from other cyclone burners, ensuring thorough filling of the combustion chamber with flue gas.…”

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

“…However, research on the flow characteristics of vertical cyclone burner systems is currently limited. Many previous studies ,, have primarily concentrated on optimizing combustion in the cyclone liquid boiler furnace using numerical simulations. However, there is a dearth of experimental research on the resistance characteristics of coal transport pipelines, which calls for a more comprehensive experimental analysis.…”

Experimental Investigation on Combustion and NOx Formation Characteristics of Low-Ash-Melting-Point Coal in Cyclone Furnace

“…In contrast, the slag tapping cyclone furnace is quite suitable for the combustion of low-ash-melting-point coal. 3 In the cyclone furnace, the molten ash formed by the combustion of low-ash-melting-point coal will deposit on the wall of the cyclone barrel under the action of a strong swirling effect and eventually be discharged in the form of liquid slag. The formed slag layer can insulate and protect the refractory material, which promotes the stable and safe operation of the cyclone furnace.…”

“…For example, as a kind of low-ash-melting-point coal, the typical Zhundong coal with a melting point between 1100 and 1200 °C has attracted the attention of many scholars. , Unfortunately, the combustion of low-ash-melting-point coal is likely to cause serious fouling and slagging problems in pulverized coal boilers and circulating fluidized bed boilers. In contrast, the slag tapping cyclone furnace is quite suitable for the combustion of low-ash-melting-point coal . In the cyclone furnace, the molten ash formed by the combustion of low-ash-melting-point coal will deposit on the wall of the cyclone barrel under the action of a strong swirling effect and eventually be discharged in the form of liquid slag.…”