Man Zhang

With the global energy transition and large-scale renewable integration, thermal power units are shifting from base-load to peak-shaving roles, but deep peak shaving may cause combustion instability and increased emissions. High-temperature solid-particle thermal storage offers a low-cost and wide-temperature-range solution for enhancing unit flexibility. This study proposes a flue-gas-driven solid-particle thermal storage system in which high-temperature flue gas extracted from the furnace directly heats solid particles through a multi-stage suspension preheating process. An industrial-scale suspension preheater was modeled using the Computational Particle Fluid Dynamics (CPFD) method to investigate gas–solid flow and heat transfer for quartz sand with different particle sizes and cement raw meal. The effects of particle size and thermophysical properties on particle motion, temperature evolution, gas–solid heat transfer coefficient, and flow-field characteristics were systematically analyzed. The results show that the outlet flue-gas temperature was approximately 705–725 K under the investigated conditions. For quartz sand, the particle outlet temperature decreased from approximately 715 K to 660 K as the particle size increased from 0.45–0.55 mm to 1.45–1.55 mm. The gas–solid heat transfer coefficient of quartz sand remained relatively stable, mainly ranging from approximately 450 to 900 W/(m²·K), whereas that of fine raw meal was approximately 1750–2600 W/(m²·K). Larger quartz sand particles also exhibited more pronounced wall attachment because of their higher inertia. These results demonstrate the potential applicability of suspension-preheater-based direct flue-gas heating for high-temperature solid-particle thermal energy storage and provide quantitative information for the design and operation of such systems.

Under China’s “dual carbon” goals (carbon peaking and carbon neutrality), the utilization of high-chlorine coal faces significant challenges due to its abundant reserves in regions such as Xinjiang and its notable environmental impacts. This study systematically investigates the combustion characteristics, environmental risks, and control strategies for high-chlorine coal. Key findings reveal that chlorine release occurs in three distinct stages, namely low-temperature desorption, medium-temperature organic bond cleavage, and high-temperature inorganic decomposition, with release kinetics governed by coal metamorphism and the reaction atmosphere. Chlorine synergistically enhances mercury oxidation through low-activation-energy pathways but exacerbates boiler corrosion via chloride–sulfate interactions. Advanced control technologies—such as water washing, calcium-based sorbents, and integrated pyrolysis–gasification systems—demonstrate substantial emission reductions. However, challenges remain in addressing high-temperature corrosion and optimizing multi-pollutant synergistic control. This study provides critical insights into the clean utilization of high-chlorine coal, supporting sustainable energy transitions.

High-temperature solid granules are by-products produced by various industrial processes and contain an obvious quantity of waste heat. Therefore, recovering their heat can not only reduce energy costs but also prevent polluting the environment, which has a significantly valuable sense of sustainable development. Computational fluid dynamics (CFD) technology is widely used to solve challenges involving heat recovery, which can simulate the heat and mass transfer processes of the gas–solid two-phase flow. Herein, a review about the mass flow analysis methods, including the Euler–Euler and Euler–Lagrange methods, as well as heat transfer mechanisms, covering heat conduction, heat convection and heat radiation, is made. Meanwhile, the bases of numerical models, mass flow and heat transfer are also summarized. In addition, at the end of the paper, a prospect about this research field is proposed. This article not only reviews common research methods but also summarizes relevant new models and methods that have emerged in recent years. Based on existing work, it both fully demonstrates the widespread application of CFD technology in the field of recovering heat from high-temperature solid granule fields and summarizes the development trends and further utilization prospects of the technology.

Due to the rapid growth of the global economy, energy consumption has been steadily increasing, leading to increasing issues such as energy shortages and environmental concerns. Biomass energy, a critical renewable energy source, plays a vital role in advancing low-carbon energy development and resource sustainability. In this study, experiments were conducted to study the migration of C, H, and N elements of corn straw during the microwave heating process, and the effects of residence time, heating temperature, and microwave power were also investigated. The results showed that when the temperature rose, both the proportion of C and H elements fluctuated slightly. Specifically, when the temperature rose from 75 °C to 275 °C, there was a 1.02% increase in the proportion of the C element and a 0.25% decrease in the proportion of the H element. Residence time appeared to be a significant factor influencing the changes in C, H, and N elements. For a 40 min residence time, the proportion of the C element increased from 31.77% to 35.36%, while the proportion of the H element decreased from 4.50% to 3.83%. When there was an increase in the microwave power between 160 W and 200 W, higher temperatures were reached in the samples, leading to the carbonization process of corn straw being more complete. Consequently, the proportion of the C element rose with extended residence time, whereas the proportion of the H element decreased as the residence time increased.

When the load of Circulating Fluidized Bed (CFB) boiler changes dynamically, the accumulation and consumption of residual char causes a large inertia and hysteresis in the boiler combustion system. Therefore, accurate estimation of the residual char in the boiler is of great significance to the control system and improve the combustion efficiency. Based on the Computational Particles Fluid Dynamics (CPFD) method, a numerical simulation of the variable load process of CFB boiler was carried out, and the dynamic changes of the residual char inventory were analyzed by combining the coal feed, ash discharge, and furnace calorific value. The results showed that after CFB boiler reached stable operation, the residual char fluctuated from 11,000 kg to 16,000 kg, accounting for about 3.7% of the total bed material, and the residual char was in a dynamic balance. During the load-up phase, the average residual char was 17,500 kg, and during the load-down phase, the average residual char was 15,000 kg. In the process of load dynamic change, reasonable residual char stock can ensure the boiler load from one steady state to another steady state rapid transition.