Flow of suspensions in pipelines

Slurry pipelines are used in many industrial applications. Several parameters are often needed by the operator, including critical deposit velocity, solids concentration, and particle velocity profiles. This chapter first reviews important formulas used to predict critical deposit velocity both in Newtonian and non-Newtonian (power-law) carrier fluids. Various methods to measure local velocity and solids concentration profiles in slurry pipelines are discussed. Local solids concentration can be measured by sample withdrawal technique. However, the sample should be withdrawn at isokinetic conditions. Sampling downstream of tees and elbows can, result in significant errors in measuring solids concentration. Gamma-ray absorption methods can be used; however, two scans are needed to obtain local solids concentration. Bulk velocity of conductive slurries can be obtained using magnetic flowmeters mounted on a vertical section of the pipe. Local particle velocity can be obtained using conductivity probes. NMR methods can be used to measure concentration and particle velocity profiles but are limited to small-diameter pipes. Vertical solids concentration of coarse slurries flowing in a horizontal pipeline exhibits a positive gradient near the bottom of the pipe. Traditional models to predict these profiles are given, and new mathematical models and computer software to determine these profiles are introduced.