Coating Granulation by Rapid Expansion of Supercritical Fluid Solutions in a Fluidized Bed

采用超临界CO_2溶液快速膨胀法制粒粘结剂(石蜡)，在沸腾床中用二氧化硅微粒包覆玻璃微珠。通过超临界CO2溶液的快速膨胀沉积石蜡，将细小的二氧化硅颗粒加入到核心颗粒周围的层中。最初，由于粘附力，单个细小颗粒附着在核心颗粒上，然后由于粘结剂的沉积，通过固体桥联进行结合。包衣造粒稳定，无过度团聚现象。在低气速下，粘结剂沉积在附着在核心颗粒上的细小颗粒的包覆层上。这导致了通过对细小颗粒进行分层而形成均匀的涂层颗粒化。另一方面，在高气速下，在核心颗粒上有小颗粒和细小颗粒的层状分布，并在多孔颗粒上涂覆薄膜掩膜，以控制超临界CO2溶液在床内的快速膨胀。通过红色素释放率的测定和扫描电子显微镜的观察，考察了涂层的性能。结果表明，通过控制操作条件，可以控制释放速率。包衣过程中颗粒均为单分散，颗粒间无团聚现象。实验中对释药速率和包衣表面进行了分析。

The coating granulation by the rapid expansion of supercritical CO_2 solutions of binder (paraffin) was performed to coat the surface of core particles (glass beads) with fine silica particles in a fluidized bed. The deposition of paraffin by rapid expansion of supercritical CO_2 solutions incorporated fine silica particles into the layers around core particles. Initially individual fine particles are attached to the core particles due to the adhesion force and then are bounded by solid bridging due to the deposition of binder. A stable coating granulation was achieved without the excess agglomeration. At low gas velocity the binder material was deposited on the coating layer of fine particles adhered to the core particle. This leads to the uniform coating granulation by layering fine particles. On the other hand, at high gas velocity small agglomerates and fine particles are found to be layered on the core particles.In addition, porous particles were coated with film masking for releasing control by the rapid expansion of supercritical CO_2 solution in a fluidized bed. The coating characteristics was examined by the measurements of releasing rate of red pigment and SEM observation. It was found that the releasing rate can be controlled by controlling the operation condition. All the particles in mono-dispersion in the coating process with out agglomeration in granules. The releasing rate and the coating surface analysis was analyzed in the experiment.