Development of correlations for the flow of agricultural residues as slurries in pipes for Bio-refining

Abstract

Pipeline hydrotransport of agricultural residue in a carrier liquid could be an economically viable alternative to replace truck delivery of biomass materials, as well as encouraging the increase in scale of bio-refineries. The feasibility of this concept, together with friction loss behaviour and corresponding mechanisms of biomass slurry flows through pipelines, was previously studied by the authors. A 50 mm diameter, 25 m long pipeline facility was used to measure the longitudinal pressure gradient of wheat straw and corn stover slurries over a range of particle dimensions, slurry solid mass fractions, and slurry velocities. Econometric software and a nonlinear least square regression model were used to analyse the measured pressure gradients and an empirical correlation was proposed to predict slurry pressure gradients as a function of slurry specifications and operating conditions. The correlation was then modified using scale-up methods to account for the effects of pipe diameter. The pressure gradient was found to be proportional to the pipe diameter to the power of −1.2. The final correlation was able to predict the longitudinal pressure gradient of the flow of agricultural residues (i.e., non-wood fibres) as biomass slurries in pipes and, with a small uncertainty (<10%), could be applied to design commercial pipelines to hydraulically transport various agricultural residue biomass slurries. This knowledge of the slurry flow pressure gradient is essential to specify slurry pumps, determine the number of booster stations, and estimate the capital and operational costs of a slurry pipeline. • Slurries of agricultural residue biomass were pumped into a closed-circuit pipeline. • Slurry longitudinal friction losses in the pipe were measured over a range of variables. • Econometric software and an NLS regression model were used to analyse measurements. • An empirical correlation was developed based on measurements and scale-up methods. • An empirical correlation can predict slurry pressure drop for all sizes of pipes.