Thermal conductivity and heat transfer characteristics of biomass slurry and coal water slurry

Carbonaceous material slurry gasification technology is one of the key approaches for achieving clean and efficient energy utilization, with slurry preheating playing a critical role in improving gasification efficiency. In this study, biomass （corn straw fermentation residue）, Shaanxi Shenfu coal, and Xinjiang Zhundong coal were selected as the research objects to systematically measure their thermal conductivity and the heat transfer performance of their corresponding slurries. At room temperature, the thermal conductivities of the biomass disc, Shenfu coal, and Zhundong coal are 0.1556 W·m⁻¹·K⁻¹, 0.1196 W·m⁻¹·K⁻¹, and 0.1929 W·m⁻¹·K⁻¹, respectively. Within the mass fraction range of 51% to 59%, the Shenfu coal slurry exhibits the minimal thermal conductivity, whereas the Zhundong coal slurry demonstrates the maximal thermal conductivity, with biomass slurry occupying an intermediate position. Notably, the thermal conductivity of the slurry decreases in correlation with an increase in mass fraction. At a mass fraction of 59%, the thermal conductivities of the biomass slurry, Shenfu coal slurry, and Zhundong coal slurry are 0.3601 W·m⁻¹·K⁻¹, 0.3589 W·m⁻¹·K⁻¹, and 0.4049 W·m⁻¹·K⁻¹, respectively. Traditional formulas inadequately capture the heat transfer dynamics of complex slurries containing solid particles. This is attributed to the fact that during the flow process, solid particles disrupt the thermal boundary layer through the synergistic effects of Saffman lift force and thermophoretic force and particle collisions, while acting as heat transfer carriers to enhance heat transfer. Based on these mechanisms, This study establishes a Nusselt number correlation equation applicable to high-concentration slurry laminar flow in a straight tube, and the temperature rise calculated using this correlation shows good agreement with the experimental results.