New Nozzle Study Of Superfine Particles Preparation Using Supercritical Fluids Technology

Some recent research works of producing superfine particles using supercritical fluid (SCF) technology have been summarized in this paper. How to increase the output of superfine particles is also a bottleneck problem which should be solved urgently in the field by using supercritical fluid technology. Moreover, the size of nozzle and the structure of nozzle are the key to solve the problem. The work of designing the nozzle based on the deep analysis and research will widen the applied field of this task and make a key step for solving this problem. In the meaning it has prominent value and significance in the engineering.By analyzing the atomization mechanism and the characteristics of different nozzle structures, a kind of axial extendable and adjustable nozzle was designed. This type nozzle includes single passage, muti-passages with different blend mode. Single passage nozzle was designed for RESS method. Muti-passages with blend-outside mode nozzle was designed for ASES method, with blend-inside mode nozzle one was designed for SEDS method and blend-inside and outside mode one nozzle was designed for improved SEDS method. All of them make use of the gap of two adjustable conic surfaces to jet the material. The traditional fixed structure of nozzle is changed into loop-gap one, and the loop-gap size can be adjusted outside the precipitator. So this type nozzle can be axially extended. And intensity calculation had been done for nozzle primary components, such as cover, movable ring and static ring. Their primary structure sizes were confirmed.Based on the gas-liquid flowing theory and analyzing the flowing characteristics of the flow-field in nozzle, a calculated model was established for numerical simulation. Using Fluent software, the author simulated the inside flow-field of two passages with blend-outside and blend-inside mode nozzles respectively. The effect regulation to the inside flow-field of structure parameters have been studied. The result indicated that, for the two passages with blend-outside mode nozzle, supercritical fluid flow length before blending should not be too long, as supercritical fluid flow resistance was augmented and the gas-to-liquid flow rate ratio was minished. So the structure of two passages with blend-outside mode nozzle had been improved. Estimative standard and fuzzy estimative method were put forward for the flow-field distributing of improved nozzle. Based on simulating results, nozzle structure had been optimized and suitable technics conditions for nozzle were gained. For the two passages with blend-inside nozzle, a suitable jet angle value existed which was advantage to the flow-field distributing of nozzle and mixing effect before jetting. The whole numerical simulation process had offered a guide for the optimizing of nozzle structure.