Comparison of maize stover and wheat straw slurry flow in vertical pipes

The scale-up of biorefineries to compete with fossil fuel production is limited by the high overland transportation cost of lignocellulosic biomass. Pipeline hydro-transport of agri-cultural or forest residue biomass to biorefineries could be a cost-effective and sustainable solution to this problem. The upward flow of chopped maize stover (also known as corn stover) aqueous slurries through a vertical pipe section of a 29 m long, 50 mm diameter in a closed pipeline loop was studied. The frictional pressure drops of maize stover slurries were measured at several particle sizes (from <3.2-19.2 mm), slurry solid concentrations (5-40% [mass]), and slurry velocities (0.5-4.3 m s-1). The results were analysed and compared with wheat straw. For specific concentrations and flow rates, particle size, shape, and flexibility are the factors that most reduced drag, which was highest (by 32%) for the largest particle size of maize stover. For velocities >= 2.5 m s-1, maize stover suspensions (other than the 3.2 mm particle size) were more effective in reducing drag than wheat straw, whereas at lower velocities (<2.0 m s-1), wheat straw had more influence (other than the 19.2 mm). The results for critical concentrations for maximum drag reduction, onset velocity, threshold concentration for minimum onset velocity, and their variations with respect to particle size, particle type, and slurry concentrations provide new insights that require further investigation in larger diameter pipes. The results here will be bene-ficial for the design and operation of long-distance pipeline hydro-transport of biomass.(c) 2022 IAgrE. Published by Elsevier Ltd. All rights reserved.