Deposition Velocities of Newtonian and Non-Newtonian Slurries in Pipelines

Abstract

Executive SummaryThe External Flowsheet Review Team (EFRT) expressed concern about the potential for Waste Treatment and Immobilization Plant (WTP) pipe plugging. Per the review's executive summary, "Piping that transports slurries will plug unless it is properly designed to minimize this risk. This design approach has not been followed consistently, which will lead to frequent shutdowns due to line plugging." To evaluate the potential for plugging, critical-velocity tests were performed on several physical simulants to determine if the design approach is conservative. Critical velocity is defined as the point where particles begin to deposit to form a moving bed of particles on the bottom of a straight horizontal pipe during slurry transport operations. The critical velocity depends on the physical properties of the particles, fluid, and system geometry.This report gives the results from critical-velocity testing and provides an indication of slurry stability as a function of fluid rheological properties and transport conditions that are typical of what the plant will see. The experimental results are compared to the WTP design guide on slurry-transport velocity in an effort to confirm minimum waste-velocity and flushing-velocity requirements as established by calculations and critical-velocity correlations in the design guide. The major findings of this testing are as follows:Experimental results indicate that for Newtonian fluids, the design guide is conservative. The design guide is based on the Oroskar and Turian (1980) correlation, a traditional industry-derived equation that focuses on particles larger than 100 m in size. Slurry viscosity has a greater effect on particles with a larger surface area to mass ratio, i.e. smaller particles. The increased viscous forces on small particles result in a smaller critical velocities. Since the Hanford slurry particles generally have large surface area to mass ratios, the reliance on such equations in the 24590-WTP-GPG-M-0058, Rev 0 design guide (Hall 2006) is conservative. Additionally, the use of the 95% percentile particle size as an input to this equation is conservative. The design guide specifies the use of the d 95 density, this term is ambiguous and needs clarification in the design guide. Nonetheless, this value is interpreted to mean the density of the d 95 particle. This density value is irrelevant for critical velocity calculations. Often this value is unknown, and Equation 1 of the 24590-WTP-GPG-M-0058, Rev 0 design guide (Hall 2006) will be used for design purposes. This equation calculates an average or composite density of all solids in the slurry. However, test results indicate that the use of an average particle density as an input to the equation is not conservative. Particle density has a large influence on the overall critical-velocity result returned by the correlation. The viscosity correlation used in the WTP design guide has been shown to be inaccurate for Hanford waste feed materials. Additionally, the recommendation of a 30% minimum margi...

Deposition Velocities of Non-Newtonian Slurries in Pipelines: Complex Simulant Testing

“…The first type of simulant was similar to the glass-bead simulants discussed in WTP-RPT-175 Rev. 0 (Poloski et al 2009). The simulant consists of glass beads with a nominal particle size of 150 µm in a kaolin/water slurry.…”

“…Lastly, a cross-sectional pipe tomogram of slurry conductivity was measured using a P2000 electrical-resistance tomography system manufactured by ITS. Further details of test apparatus can be found in WTP-RPT-175 Rev 0 (Poloski et al 2009). …”

Hanford Tank Farms Waste Certification Flow Loop Phase IV: PulseEcho Sensor Evaluation

“…The purpose of the PulseEcho system was to perform non-invasive, real-time ultrasonic detection and measurement of sediment mobility and accumulation in pilot-scale pulse jet mixing vessels and the WTP M1 series initiative test loop (Poloski et al 2009a and2009b;Yokuda et al 2009). The PulseEcho system was successful in detecting solids mobility in both applications.…”

“…This simulant is the same as that used by Poloski et al (2009a) during the M1 issue resolution. SS has a density of ~8 g/cm 3 and a broad distribution with a significant portion of the particles falling in the range of 10 to 30 microns.…”

“…For simplicity, the data in these tables are classified into Newtonian and non-Newtonian slurries. To facilitate data comparison, the data in these tables are presented in a format similar to that used previously (Poloski et al 2009aand 2009b, Bontha et al 2010a) to facilitate easy comparison of the data. Presented below is a description of the methods and approaches used to generate the data in these tables.…”