The pipeline flow of coal‐in‐oil suspensions

The flow behavior of coal‐in‐oil suspensions at velocities up to ca. 20 ft./sec. has been investigated in a one‐inch d. experimental pipeline. Detailed data are presented for a bituminous and a subbituminous coal (effective size < 700 microns) entrained in two oils (μ = 5.6 and 46.7 ep. at 25°C. respectively); coal concentrations in the suspensions ranged > 70% w/w. At flow velocities greater than 2 ft./sec. and coal concentrations below 50% w/w, the suspensions were found to move as relatively homogeneous (or quasi‐homogeneous) fluids, and pressure gradients followed the usual friction factor/Reynolds number relationship. But no satisfactory correlations could be established for flow at < 2 ft./sec., which is influenced by significant settling, or for the behavior of suspensions containing > 50% w/w coal. In the latter case, laminar flow obtained at all velocities and the suspended particles tended to concentrate near the pipe axis (and to move along it as a definite ‘core'’. One effect of this phenomenon is a substantial reduction in the apparent viscosity of the suspension.