关键词: 无水醋酸钠, 超声谱, 图像法, 结晶, 粒度分布, 测量

Abstract:

The crystallization process is an energy-efficient solid-liquid separation and purification technology in chemical unit operation, which is widely used in food, medicine, dye and other production processes. The crystallization of sodium acetate was studied by ultrasound, image and optical turbidimetry simultaneously, in which the crystal size distribution (CSD) was obtained by ultrasonic forward model combined with the optimum regularization technique (ORT) algorithm. By implementing a series of experiments at various stirring and cooling rates, the crystallization temperature and particle size were measured, and the crystal shape was also determined via image analysis. The results showed that the faster cooling rate the higher crystal growth rate, and the faster stirring rate promoted crystal growth at the initial stage but the average size decreased due to particle wear and breakage in the later stage. The crystallization temperature detected by ultrasonic method was slightly lower than that of optical turbidimetry under the same condition but the deviation was within 15%. In addition, the crystal growth and the morphology had been directly observed and characterized by the image method, which yielded a close trend with ultrasonic method, and the deviation of median diameter measured by these two methods was less than 15% once the crystal precipitated steadily. As a whole, the optical methods are more suitable for local characteristic measurement in the early stage compared with the ultrasonic method, and the latter is more appropriate for probing the continuous process of particle size change.

Key words: sodium acetate, ultrasonic spectra, image method, crystallization, particle size distribution, measurement