Abstract:
This paper used a micro differential pressure sensor to collect bed pressure signals at different axial positions in a two-dimensional vibrating fluidized bed. The original pressure signals were decomposed by using nonlinear signal analysis methods to reconstruct the bubble response pressure signals. The influence of bubble motion on the evolution of bed flow patterns is accurately characterized with image analysis methods. The law of pressure distribution at different axial positions of the bed layer was studied. The pressure signals induced by vibration airflow excitation in the form of multiple bubble responses were decomposed and reconstructed, and the time-domain and frequency-domain characteristics of the response pressure signals were identifed and extracted. A method for evaluating the evolution of bed flow patterns was proposed by calculating and analyzing the entropy changes of bubble response pressure signals. The separation characteristics of −6+1 mm fine coal in a vibrating fluidized bed were studied. The results indicate that the main frequency of the response pressure signal caused by bubbles was 3 Hz. The peak power spectral density of the bubble response pressure signal increased with the axial height of the bed increased. However, the main frequency of the pressure signal disappeared, and the frequency band widened under larger operating parameters, which consisted with the behavior of bubble movement. The variation law of the bed flow pattern was characterized by analyzing the Shannon entropy of the response pressure signal. The Shannon entropy of the signal under various vibration parameters shows a trend of first decreasing and then increasing with the increase of gas velocity. The fluidization state of the bed flow is in the order of non-uniform fluidization, uniform fluidization, and severe fluidization. When
f=20 Hz,
A=2 mm, and
v=16 cm/s, the porosity distribution in the middle and lower parts of the bed is uniform. The coalescence behavior of bubbles is suppressed under the synergistic effect of vibration and airflow with the increase of the axial height of the bed. The frequency of bubble rupture is relatively high, and more small-sized bubbles are concentrated in the upper part of the bed. It was found that under the optimal fluidized state, the sorting effect of −6+1 mm fine coal was relatively good, with a fine coal ash content of 8.3% and a yield of 87% by studying the ash content and yield distribution of fine coal after selection.