Numerical study on the pipe flow characteristics of the cemented paste backfill slurry considering hydration effects

Abstract

Cemented paste backfill (CPB) plays a vital role in tailings management where the CPB slurry is hydraulically conveyed from the surface to underground voids in pipelines. To enhance transport efficiency, accurate prediction of their flow characteristics is always required during CPB design. The objective of this study is to investigate the flow characteristics of the CPB slurry by using computational fluid dynamics (CFD) method. In this method, a mixture model was utilized to represent the multi-phase characteristics of pipe flow and a reaction flow model was used to consider the hydration effect. The performance of the mixing model was verified using the experimental results and the influence of the cement hydration was discussed. A comprehensive sensitivity study was performed to investigate the coupled effect of the tailings-to-cement ratio (TCR), inlet velocity (IV), slurry concentration (SC) and particle size (PS). The results indicated that three zones were formed during pipe transportation due to the deposition of coarse tailings and the suspension of fine tailings. The velocity along the pipe cross-section was arch-like with a high velocity near the middle and low velocity near the wall. Cement hydration needs to be considered in the pipe system design and all influencing factors (TCR, IV, SC and PS) had important effects on the pipe flow of CPB transportation. The obtained results can provide guiding significance to the mining industry and backfill practitioners during the pipe system design.