【作者】 赵小进；

【导师】 黄永春；

【作者基本信息】 广西工学院 ， 生物化工， 2010， 硕士

【摘要】 氢氧化钙和二氧化硫中和反应是糖厂亚硫酸法澄清工艺的主要反应,该过程要求氢氧化钙和二氧化硫反应迅速、完全,从而使糖液中的亚硫酸根离子和钙离子含量较低,形成的亚硫酸钙沉淀颗粒均匀、比表面大,对蔗汁中的非糖份吸附能力强,使白砂糖具有更好的品质。但是由于现行工艺的缺点,常常会导致产品白砂糖中二氧化硫残留量偏高,以至于降低了白砂糖的品质。因此,找到一种简单有效的提高亚硫酸法澄清效果的辅助手段成为制糖工业的一个热点。近来,超声波作为一种清洁、有效的辅助手段被用来研究强化糖厂亚硫酸法澄清工艺。作为超声强化蔗汁澄清研究的基础工作,本文在前人研究的基础上,研究超声波对氢氧化钙和二氧化硫中和反应的影响,主要研究内容如下:(1)研究了超声参数如超声作用功率、超声作用时间、超声探头深入溶液距离等对水溶液中亚硫酸和氢氧化钙中和反应过程的影响。结果表明与磁力搅拌反应相比较而言,超声作用可以显著降低溶液中Ca2+和SO32-的残留量,且所有参数对反应都有影响。超声作用的最佳条件是:超声功率97.5W,超声作用时间1min,超声探头深入距离1.4cm。(2)研究了超声参数如超声作用功率、超声作用时间、超声探头深入溶液距离等对亚硫酸钙晶粒形态的影响。研究结果表明超声作用能使亚硫酸钙晶粒更小、更均匀,拥有更大的比表面积;对反应结束后形成的亚硫酸钙晶粒而言,晶粒体积越大,超声作用对其影响越明显。(3)研究了超声作用对氢氧化钙和亚硫酸中和反应生成亚硫酸钙晶粒过程诱导期的影响。研究结果表明超声作用可以明显缩短亚硫酸钙晶粒形成过程的成核诱导期;理论推导结果表明超声作用能够影响亚硫酸钙晶粒形成过程是因为其能够降低溶液的表面张力,增强溶液中粒子的扩散作用。(4)研究了超声作用对不同浓度的氢氧化钙溶液、亚硫酸溶液表面张力和电导率的影响。研究结果表明超声作用能够降低溶液的表面张力,增加溶液的电导率,证明了前面理论推导结果的正确性。(5)研究了通入氮气对超声空化作用的影响以及空化作用的强弱对亚硫酸钙晶粒形成过程的影响。研究结果表明通入氮气能够增强超声空化作用;超声空化作用对亚硫酸钙晶粒形成过程起促进作用。更多还原

【Abstract】 The neutralization reaction of calcium hydroxide and sulfur dioxide is the main reaction of cane juice clarification process in cane sugar mill which sulfurous acid methods are applied. According to the industrial need, in order to obtain White sugar with high quality,all the following should match: calcium hydroxide and sulfur dioxide should react fast and completely, therefore the remains of Ca2+ and SO32- in the sugar juice are little; the calcium sulfite crystals formed should be uniform and possess high specific surface area, therefore the crystals have strong adsorption capacity in absorbing non-sugar impurities. But the present technology has some disadvantages, the remains of SO32- in white sugar are often high, which reduces the quality of the products and depresses the competitiveness of sugar factory. For that reason, finding a method which has great efficiency and simple process is the hotspot in sugar-making industry. Lately, ultrasound as a clean、effective means is studied to enhance the cane juice clarification process. As the basic research of cane juice clarification process enhanced by ultrasonic treatment, based on previous works, the influence of ultrasonic treatment on the neutralization reaction of calcium hydroxide and sulfur dioxide is studied. The main contents of studies were as follow:1. The influences of ultrasonic parameters such as ultrasonic power、ultrasonic treatment time and horn immersion depth on the reaction of calcium hydroxide and sulfur dioxide were analyzed. The results showed that compared with magnetic stirring, the residuals of Ca2+ and SO32- was decreased significantly and all of the ultrasound parameters affected the results. The optimum conditions were as follows:ultrasound power 97.5W,ultrasonic treatment time 1min,horn immersion depth 1.4cm.2. The influences of ultrasonic parameters such as ultrasonic power、ultrasonic treatment time and horn immersion depth on the morphology of calcium sulfite formed were analyzed. The results showed that the crystal morphology changes with ultrasonic treatment. Compared with natural reaction and reaction with magnetic stirring, the calcium sulfite crystals obtained by ultrasound treatment was smaller in size and more uniform in shape and possessed higher specific surface area. In addition, to the calcium sulfite already formed, the bigger the crystals were, the more influence ultrasonic treatment had.3. The influence of ultrasonic treatment on primary nucleation of calcium sulfite was studied. The results showed that ultrasonic treatment decreased the induction period significantly, and based on the classical theory of nucleation, ultrasonic treatment could decrease surface tension and enhance diffusion of particles in the solution.4. The influence of ultrasonic treatment on the properties of calcium hydroxide solution and sulfurous acid solution with different concentrations was investigated. The result showed that ultrasonic treatment reduced surface tension and increased electrical conductivity of these solutions, therefore the result obtained by the classical theory was verified.5. The change of cavitation effect was study by adding nitrogen,and the influence of ultrasonic treatment that had different cavitation intensity on the crystallization process was investigated. The results showed that adding nitrogen enhanced the ultrasonic cavitation effect, and ultrasonic cavitation effect accelerated the crystallization process of calcium sulfite.更多还原