Development and application of an online sliver content detection device
In order to determine the sliver content in tobacco shreds in a timely fashion, an online detection device was developed based on a multistage winnower. The main components of the device are an air fan, an air velocity measurement system and a gas-solid fluidized chamber. The fluidised chamber is partitioned into two section: one with a cross-sectional area of 220 mm × 220 mm and the other with a cross sectional area of 35 mm × 35 mm: alternatively forming air passages wherein the air velocities are 4.0 - 4.5 m/s at the cross-sectional area of 35 mm × 35 mm and 0.5 - 1.0 m/s at 220 mm × 220 mm. Slivers drop down in the lower air velocity area due to their critical fluidisation velocity of 1.15 m/s, while tobacco shreds continuously rise up in the whole gas-solid fluidised chamber, thereby separating sliver from the tobacco shreds. The accuracy, precision, optimal sampling volume, and sampling frequency of the device were tested. The results showed that: (1) The measured levels well agreed with theoretical estimations with absolute errors ranging from 0.0079 % to 0.1881 % and relative errors from 0.2950 % to 0.8623 %. (2) The optimal sampling volume was 150 g and optimal number of repeated tests was 30. (3) The measured levels were accurate at different sliver content in tobacco shreds whereas an increase of sliver content did not influence the accuracy and precision when the sliver content was more than 3 %.