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Representative Sampling of Suspended Particulate Materials in Horizontal Ducted Flow: Evaluating the Prototype ‘EFsampler’

Claas Wagner and Kim H Esbensen

The ‘EF-sampler’ is a newly developed sampler for suspended particulate materials in horizontal pneumatic conveying systems, designed for maximum possible compliance with the Theory of Sampling (TOS). Hitherto no sampler for this deployment location exists on the market that ensures representative samples as defined by TOS. Because of confinement of the pressurised ducted flow and because of gravitative and flow segregation, unbiased sampling constitutes a serious challenge. In addition to the primary demand for representativeness, interference with the material flow needs to be minimized in order to prevent clogging effects and/or possible pressure surges. We here disclose all design principles of the ‘EF-sampler’ and validate a 1/3-scale prototype in a pneumatic test facility by presenting our first test campaign results. Testing focuses on assessing sampling representativeness (accuracy and precision) using wheat flour and pulverized alumina as the major test materials, both spiked with LDPE plastic pellets in the role as trace constituents, extraneous material or contaminants. Input pellet concentration levels served as nominal reference values for the accuracy evaluation. Test parameters include airflow rate, sample LDPE pellet concentration and different cross-cutting sampler velocities. Results show that the patented EF-sampler prototype enables to extract fit-for-purpose samples with a relative inaccuracy <5% for the stated test materials, which is highly acceptable for this most-difficult deployment context. Sampler velocity and especially the material flow dilution status impact the accuracy of sample extraction, while precision remains constantly good for all test conditions. The prototype EF-sampler is not a universal sampler, since it is designed to require situation-dependant adjustments based on specific material heterogeneity and flow regime characteristics. However, the first test campaign results on two widely different materials show conclusively that it accommodates a wide field of potential applicability for many similar types of materials.