MICROWAVE SINTERING OF ENGINEERING SPOIL CERAMSITE: MULTI-PHYSICS MODELING AND TEMPERATURE FIELD OPTIMIZATION

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Microwave sintering of engineering spoil into ceramsite presents a sustainable alternative to traditional high-temperature kiln processes. By converting construction and excavation waste into lightweight aggregate, this technology supports resource recycling and environmentally responsible construction practices. However, challenges such as temperature nonuniformity and inefficient energy utilization limit its large-scale industrial application. This study addresses these challenges by developing a comprehensive multi-physics modeling framework to analyze the energy conversion process and temperature evolution during microwave sintering.

Multi-Physics Coupled Modeling Framework

A three-dimensional electromagnetic–thermal–radiation coupled model was developed to simulate the microwave sintering process of ceramsite. The model integrates electromagnetic wave propagation, thermal conduction, and radiative heat transfer mechanisms to capture the complex interactions occurring during heating. Experimental validation confirmed the model’s accuracy in predicting temperature distribution and heating behavior, providing a reliable tool for investigating energy transfer and temperature field development in microwave-assisted sintering systems.

Role of Silicon Carbide Susceptor in Hybrid Heating

The introduction of a silicon carbide (SiC) susceptor significantly improves heating efficiency and temperature uniformity. Due to the relatively low dielectric loss of ceramsite materials, direct microwave absorption is limited. The SiC susceptor acts as an auxiliary heating element, converting microwave energy into thermal energy and transferring heat to surrounding ceramsite particles. This hybrid heating mechanism reduces temperature gradients and enhances overall sintering stability.

Temperature Evolution and Heat Transfer Mechanisms

The temperature field evolves through different dominant heat transfer mechanisms during the sintering process. At lower temperatures (below 800 °C), localized microwave-induced hotspots result in uneven heating patterns. As the temperature increases beyond 1000 °C, radiative heat transfer becomes the primary mechanism, promoting more uniform temperature distribution across the material. This transition highlights the importance of considering both electromagnetic and radiative effects when designing microwave sintering systems.

Influence of Particle Size and Microwave Power

Parametric analysis revealed that ceramsite particle size and microwave power significantly influence heating uniformity and energy efficiency. Smaller particles (1 cm) produce more uniform temperature distributions, while larger particles (3 cm) are susceptible to uneven heating due to electric field intensity variations. Regarding power input, lower microwave power improves temperature uniformity but increases energy consumption, whereas higher power reduces energy usage but worsens temperature gradients. A moderate microwave power of 3 kW was identified as the optimal operating condition for balancing energy efficiency and thermal uniformity.

Scale-Up Strategies and Hotspot Mitigation

To address industrial-scale challenges, the study proposed an enclosed susceptor design with multi-layer ceramsite arrangements. Among tested configurations, a two-layer structure achieved optimal heat exchange, reducing the temperature coefficient of variation (COV-T) by 21.1% compared to a single-layer setup. Additionally, rotational heating of the susceptor was introduced to mitigate hotspot formation. This dynamic heat redistribution mechanism significantly improves temperature uniformity, achieving a COV-T value of 0.014 at 1240 °C. Thermal flux analysis indicates that alternating radiative heat exchange between the rotating susceptor and ceramsite particles is the key mechanism behind the enhanced uniformity.

Global Civil Engineering Awards

#MaterialsEngineering
#CircularEconomy
#LightweightAggregates
#EnergyEfficiency
#CivilEngineeringResearch
#IndustrialSintering
#GreenMaterials
#ConstructionInnovation
#ThermalModeling

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