Comparison of Drag Reduction Characteristics During Hydro-Transport of Comminuted Wood Chips Through Pipelines

Highlights Found evidence for drag reduction in comminuted wood chip slurry and quantified it. Fine wood chip slurries show flow behavior like agricultural residue slurries. Established upper and lower limits in the drag reduction regime for fine wood chip slurries. Identified three flow regimes in fine wood chip slurries, akin to pulp fiber and agri-residue slurries. Abstract. Pipeline hydro-transportation of forest residues helps in reducing the biomass feedstock's delivered cost compared to truck transport. This can subsequently help in establishing large-scale biorefineries. There is limited research on wood chips and water slurry transport through pipelines. In addition, there is no study on the comparison of flow regimes of wood chips and agricultural residue slurries. This research experimentally investigated the flow behavior of slurries made of milled wood chips and water. Experiments were carried out in a 25.5 m long, 50 mm diameter closed-circuit pipe loop test setup to measure horizontal pressure gradients. Pressure gradients were measured for wood particle sizes ranging from 1.3 to 3.2 mm, saturated mass concentrations ranging from 5% to 35%, and bulk velocities ranging from 0.5 to 5.0 m/s. The findings indicate evidence of drag reduction behavior in wood residue slurries with small particle sizes (< 2.6 mm) and aspect ratios (4–6). A 22% decrease in pressure drop was obtained, compared to water, when pumping 1.3 mm wood residues at a bulk velocity of 3.4 m/s and a saturated mass concentration of 25%. Comparing pressure drop values from tests on earlier research on agricultural residue slurry suggests similar flow behavior. However, the maximum drag reduction in wood residue slurries was 33% lower than that reported for agricultural residues. The findings from this study will be crucial in refining wood residue hydro-transport for cost-effective biomass conversion and for the development of large-scale biorefineries on woody biomass. Keywords: Biomass slurry, Drag-reduction, Flow regimes, Forest residues, Hydro-transport, Toms effect.