Study On The Adsorption Of The Macroporous Resin For Ginkgo Flavonoids By Liquid-Solid Circulating Fluidized Bed

Separating gingko flavones with macroporous resins is now mainly operated in fixed bed or expanded bed. It has higher stability and is easy to be controlled of the fixed bed operation. When solid impurity existing in the bed, it is easy to be jammed. Expanded bed operation can decrease bed resistance. However, it has a disadvantage, which is that the adsorption, washing, elution and regeneration must be in switching operation. Comparing with fixed bed and expanded bed, liquid-solid circulating fluidized bed (LSCFB) has some advantages. For example, it is continuous in operation, fast in mass transfer, well in the contacting between liquid and solid and small in the axial backmixing extent. Main research content in this paper is as follows: particle axial holdup distribution, residence time distribution (RTD), liquid mixing behavior and the performance of absorption and separation of the macroporous resin for ginkgo Flavonoids.The axial solid holdup of the downcomer and the riser in the LSCFB had been measured firstly with conductivity meter and CCD. Experimental results show that the particle axial solid holdup of the dense area in the downcomer is between 0.35 and 0.55,and it is below 0.1 in the dilute area; The axial solid holdup in the riser is between 0.01 and 0.04 and the distribution is uniform. Investigation on the factors influencing the LSCFB fluid flow indicates that the larger the particle diameter is, the lower the dense area height will be. During the respective change of main fluid and assistant fluid, the particle circulating rate (Gs) increased first, and then decreased.In the residence time distribution (RTD) experiment of the downcomer, the dimensionless variance is about 0.1, the liquid backmixing coefficient is between 1.85×10-6 and 1.81×10-5, and the Bo value is between 10.4 and 16.9, so the bed is very stable, the flow pattern was similar to that of plug flow reactor (PFR). And in the RTD of the riser, the dimensionless variance is between 0.2 and 0.3, the liquid backmixing coefficient is between 1.48×10-3 and 2.96×10-3, the Bo value is between 5.65 and 7.44, so the results indicate that the riser is backmixing in an extent because of the existence of stagnant area and circulating flow.Investigations on the factors influencing the LSCFB adsorption indicate that it is favorable for LSCFB adsorption of a lower Uld, a higher Gs and a bigger charge. The results of LSCFB adsorption with the orthogonal test of four factors at three different levels gave the optimum experimental conditions: the particle size with 0.45～0.6mm diameter, the particle column height with 50 centimeter, Gs with 0.285 kg/m2·s and Uld with 0.15 mm/s.Finally, the riser desorption model and downcomer adsorption model were carried out. The results indicate that the riser desorption model can predict desorption process and the experimental value is inosculate to the calculated value; the downcomer adsorption model can predict adsorption process and the experimental value has some deviations from the calculated value because there will be a little backmixing when the macroporous resins fluidized in dense area.