High-thermal-conductivity filler based on waste biomass carbon: Design and performance evaluation of a heat-dissipating compound for cable ducts

During operation, cable ducts generate a large amount of Joule heat due to the current-carrying conductors; inadequate heat dissipation can accelerate insulation aging and reduce current-carrying capacity. Traditional cable duct filling slurries (such as cement-based or low-thermal-conductivity polymer-based materials) have low thermal conductivity and struggle to meet the heat dissipation requirements of high-voltage, high-capacity cables. In this study, corn cob powder—a agricultural waste product—was used as raw material to prepare highly thermally conductive biomass carbon (CC) through high-temperature carbonization. This carbon material was then introduced as a functional filler into the cable duct grout system, and the study systematically investigated its effects on the grout's thermal conductivity, workability, and actual heat dissipation performance within the ducts. The study shows that when the CC content is 10 wt%, the thermal conductivity of the slurry reaches 0.383 W/(m·K), which is 14.7 times that of air; the flowability remains at 150 mm, meeting the requirements for pumped construction; in transient heat dissipation tests, the peak temperature was 7°C lower than that of air-filled systems; under laboratory high-temperature thermal shock simulation conditions (heat source at 200°C), the steady-state temperature of the slurry remained stable at 100–110°C. Finite element simulations indicate that the slurry with this formulation can significantly increase cable current-carrying capacity across all climatic conditions (−40°C to 40°C); under extreme high-temperature conditions of 40°C, the current-carrying capacity reached 504 A, representing a 25.7% increase over traditional air-filled cables. This study provides an environmentally friendly, low-cost, and high-performance material solution to overcome the heat dissipation bottleneck in cable ducts, holding significant engineering implications for the capacity expansion, retrofitting, and safe operation of urban power grids.