Claas Wagner

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

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.

Acoustic chemometric at-line characterization for monitoring particle size fractions in pneumatically conveyed biomass

Reliable on-line/at-line prediction of particle size fractions of biomass material is a process monitoring concern owing to inherent variation in particle size and difficulty in sampling of pneumatically ducted biomass material. A feasibility study on application of acoustic chemometrics for at-line prediction of size fractions of biomass material has been performed, with all models subjected to independent test set validation. This study serves as a platform for at-line characterization of biomass samples from a sampling device extracting biomass samples from pneumatic conveying systems (based on theory of sampling). A prestudy using complex biomass/plastic pellets mixtures was used to test reliability and robustness of the experimental setup. Promising prediction results were achieved (slope, relative root mean square error of prediction (RMSEPrel), and correlation coefficient (r2) were 1.08, 24.94%, and 0.90, respectively). The same experimental setup was adapted for quantitative prediction of coarse versus fine biomass mixtures (the main objective) with satisfactory results; slope = 0.96, r2 = 0.97, RMSEP(rel) = 11%. A case study was also performed showing the adverse effect of using nonrepresentative coarse versus fine biomass samples for calibration. It is concluded that acoustic chemometrics is a viable technique for at-line prediction of size fractions of representative biomass materials.