To reveal the distribution characteristics of the arc-plasma and the behavior of the flow field and further analyze the relationship between external parameters and arc behavior, this study conducts a numerical simulation of a coaxial dual-chamber plasma generator based on Magneto Hydro Dynamics (MHD) theory. The research investigates the correlations among arc voltage, cathode spot distribution, and airflow parameters with the axisymmetric model by incorporating coupled calculations of the flow field and electromagnetic field. The simulation results indicate that arc voltage is relatively insensitive to radial airflow; within the studied parameter range, fluctuations in radial airflow pressure have a maximum impact of only 4.2% on arc voltage. In contrast, arc voltage exhibits a strong positive correlation with axial airflow velocity, and a fitted correlation equation has been obtained. Temperature and velocity distribution analyses show that the maximum nozzle temperature exceeds 3500 K, ensuring sufficient ignition capability for low-quality coal and stable combustion performance. Moreover, the results confirm that, under proper airflow configuration, the coaxial dual-chamber structure enables plasma igniters to achieve both high power and extended electrode lifespan. It reveals the anti-ablation mechanism of this structure, namely, the alternating sweeping effect of the two gas flows—the axial flow primarily controls the output power, while the radial flow regulates the arc root position through periodic fluctuations, thereby preventing single-point erosion and extending the electrode lifespan. Furthermore, the study further identifies the balance point between the two gas flows through optimized design experiments, providing theoretical support for future research on the long-term durability of plasma generators.

Improving coal adaptability of plasma ignition systems is of significant importance for assisting power plants in energy conservation, emission reduction, and achieving the dual-carbon goals. To address issues such as unstable combustion and flameout encountered during the operation of existing staged plasma burners when igniting lean coal with low volatile content, this study employs a numerical simulation approach. First, a three-dimensional mesh model of the staged plasma burner is established, incorporating the Realizable k-ε turbulence model, the P1 radiation model, and a pulverized coal combustion model with Two-competing-rates model for volatile matter release and kinetics/diffusion-limited model for char combustion. Subsequently, mesh independence verification is conducted by comparing temperature parameter differences among models with low, medium, and high mesh densities to ensure the reliability of the selected mesh. Following this, the control variable method is applied to sequentially investigate the effects of three critical operational parameters—plasma power, primary air velocity, and pulverized coal concentration—on lean coal combustion process within the staged plasma burner. Finally, the operational parameters of the plasma burner are optimized to resolve ignition and combustion issues associated with lean coal. The results demonstrate that plasma power is the key factor affecting lean coal ignition. To achieve stable ignition and combustion of lean coal in the plasma burners, the plasma power should not be less than 150 kW. Primary air velocity affects the combustion temperature during the initial ignition stage, with an optimal range identified between 22 to 25 m/s. Pulverized coal concentration is a crucial factor for successful lean coal ignition; maintaining a relatively high concentration is necessary to ensure stable ignition and combustion, with a recommended concentration not lower than 0. 3 kg/kg. This research provides direct and important theoretical guidance and a practical basis for power plants to optimize the operational strategies of existing plasma burners, safely and economically utilize lean coal, reduce fuel costs, and lower carbon emissions. It holds positive implications for promoting fuel flexibility and facilitating the green, low-carbon transformation of coal-fired power plants.

Facing the increasingly strict requirements of industrial flue gas emission in China, this paper designed a new type of cyclone-tube demister to overcome the low removal efficiency of fine droplets that particle size less than 20 μm by wave-plate demister. The flow of flue gas in the cyclone tube demister was numerically simulated by using Euler-Lagrangian method, using rigid spherical water drops instead of fog drops. And the RNG k-ε model and DPM model were used for the alternating coupling calculation of continuous phase and discrete phase. The performance changes of the cyclone-tube demister under different flow velocities were studied. Based on the simulation experiment of orthogonal design, the influence of the structural parameters of the cyclone-tube demister on the demisting performance was studied. The simulation results of basic structure cyclone-tube demister show that, under the flow rate of 3~7 m/s, the removal efficiency of droplets with diameter greater than 20 μm is more than 99%; the removal efficiency of droplets with a diameter of 10~20 μm is above 86.5%; the removal efficiency of droplets with a diameter of 2~10 μm is above 51.3%; when the pressure drop is 61.4~321.3 Pa, it can significantly improve the removal efficiency of fine droplets. By analyzing the results of orthogonal simulation test, it is found that the increase of a and the decrease of d are beneficial to improve the removal efficiency of droplets. With the increase of a, d and H, the pressure drop of flue gas flowing through the demister will be increased. The optimum structure with demister efficiency of 2~10 μm as index is d=100 mm, H=2000 mm, a=900°, the optimum structure with demister efficiency of 10~20 μm as index is d=100 mm, H=1600 mm, a=900°, the optimum structure with the pressure drop as index d=100 mm, H=2400 mm, a=540° are obtained. The cyclone-tube demister proposed in this study can significantly improve the removal efficiency of fine droplets, which is of great significance to the ultra clean emissions of coal-fired power plants.