| Electrical capacitance tomography(Electrical Capacitance Tomography,ECT)can obtain the projection data of the measured object field under different viewing angles in a non-contact manner and reconstruct the corresponding medium distribution image according to the dielectric constant distribution of the medium.It has a simple structure,With the advantages of low cost,high flexibility,and real-time reconstruction,this article uses ECT technology to observe and study the phenomenon of gas-solid fluidization in a fluidized bed,and conduct a series of studies on the phenomenon of bubble movement and the movement trajectory of coal particles.The advantages and disadvantages of different ECT image reconstruction algorithms are analyzed and compared,and the LBP non-iterative algorithm used in the test conditions of this article is selected for research work;the three-dimensional model of the ECT sensor is modeled through the Comsol simulation software.The electric potential distribution and the empty full field capacitance are studied.It is found that the electric potential of the field near the excitation electrode is higher,and the capacitance value of the electrode plate close to the excitation electrode is the highest.At the same time,it is found that as the dielectric constant increases,the full field capacitance between different plates increases approximately in a linear relationship;The sensor area near the electrodes is very sensitive and more sensitive to changes in permittivity in the field.The experimental work provides theoretical basis and foundation.Based on the ECT technology,the bubble motion behavior in the Geldart Class B aggravated mass separation fluidized bed was measured and studied.Combined with the ECT measurement method and the Matlab image processing technology,a method for the bubble parameter measurement using the ECT technology was developed,and Geldart was proposed.The predictive model of bubble size in type B aggravated fluidized bed,analyzes the influencing factors of bubble size;it is found that under different bed material heights,the influence of gas velocity on bubble diameter shows regularity.Different ECT measurement plane bubbles The overall diameter of the gas increases with the increase of the fluidizing gas velocity.When the gas velocity increases to a certain level,the growth trend of the bubble size tends to be gentle;the relationship between the bubble size and the bed height is still unclear,and the bed height factor The influence of bubble diameter cannot be directly reflected.Combined with the bubble size model,Models of bubble movement velocities are further established.The established bubble size and ascent rate model was compared and validated with a traditional empirical model.It has been found that the established bubble motion model can more accurately predict the size and position of bubbles.To modify the traditional Darton bubble size model to make it suitable for bubble size prediction under the ECT measurement environment in a class B particle fluidized bed.It provides a theoretical basis for understanding the movement behavior of bubbles.Using ECT technology to trace the movement of coal particles,it is found that the movement characteristics of coal particles under different conditions are different.For the greater the gas velocity,the greater the range and amplitude of the movement of coal particles in the bed.The density of coal particles increases,the trajectory of coal particles in the bed is greatly affected by gravity,and the motion state of coal particles tends to be stable;different shapes of coal particles move in different ways,and the continuity of rod-shaped coal particles in the bed Stronger,flaky coal particles are greatly affected by friction,drag in the bed,etc.;the floating and sinking of coal particles is judged and captured by ECT technology,and the changes in axial concentration in the bed measured by ECT are used for coal particles.The float-sink test to get the bed sorting density. |
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