连续超声反应器声场特性及分布规律研究
发布时间：2018-07-26 08:31
【摘要】：超声反应器是实现声化学反应及进行声化学研究的关键设备,是指在超声波的作用下进行声化学反应的系统。超声反应器具有操作简单,性能稳定优良和效率高等特点,其应用研究和开发日益受到人们的重视。本文以实验室的发明专利样机——连续式多频超声反应槽作为反应容器,以纯净水及酸化油体系为研究对象,探究超声反应器中声场特性随超声频率及组合、超声功率、流体中固含量的变化规律及其在反应器中的分布规律,旨在探究超声反应器中声场分布规律对最佳反应条件、声化学产率的重要影响,并为推动声化学技术由实验室规模向工业化应用提供指导。本论文主要工作及研究结果如下：(1)通过超声波声强测定仪对超声反应器的声场分布进行了测定,发现：长度宽度方向、轴向及平面处的声场有相似的分布规律,除换能器辐射面和器壁附近声强值较高外,总体声场分布均匀；流体流量(0-40L/h)和温差变化(25-40℃)对声场分布影响较小；反应器形状、换能器安装位置及超声功率对声场分布影响较大：靠近换能器辐射面的声强值较高,换能器输入功率增加时声强值也相应的明显变化；比较酸化油和纯水两种介质在连续超声反应器中同等实验条件下的声能分布规律,发现油体中声强衰减较大,这是油的粘滞系数较高所致,但整体声场分布规律与水介质中的相似。(2)在水体系中加入细小固体颗粒(活性炭),并维持在悬浮状态下,声强变化幅度缩小为7%(未加微细颗粒时变化幅度高达40%),可以明显改善声场分布均匀性。对活性炭颗粒粒径和添加量进行了考察,35kHz的反应器的测试结果表明：最佳颗粒粒径为200目(75μm),添加量为1.25kg/m3。在该条件下测定声强分布,发现之前辐射面附近和壁面处声压值不稳定的现象已不存在,其与超声的协同作用达到最佳值；声强随输入功率的变化更具规律性,这使得功率对超声反应器的作用更容易控制,为进一步改善传质反应提供了一定的措施。(3)以高酸值酸化油为原料进行生物柴油连续制备实验,得知在多频超声作用(15-25-35-40kHz),各输入功率200W条件下(醇油比6：1、催化剂(KOH)用量1.2%(质量分数)、反应时间54min、温度为室温等条件均相同),生物柴油产率(95.34%)较无超声辐射下产率(52.18%)提高了43.16%；较单频辐射(15kHz)时产率(87.95%)提高了7.39%,进一步验证了声强大小和声场分布均匀性对强化传质的重要性。(4)通过对超声场中的空化气泡运动方程进行数值模拟,发现：随超声频率增大,空化泡半径变化幅度减小,空化泡达到最大半径所需时间明显变长,空化效应减弱；随声强的增大,空化效应增强；粘度较大的流体对空化泡运动的阻尼作用更为明显,可通过增加输入功率的方式达到预定的声强或空化效果。本文研究结果表明,超声反应器内声强大小及其分布均匀性对强化传质过程意义重大。通过具体的生物柴油连续制备实验对所做声场分布描述进行了验证,并对超声场中空化泡的运动进行了相关的数值模拟,这些研究都为声化学反应器的性能优化提供了理论依据和技术参考。
[Abstract]:Ultrasonic reactor is the key equipment for the realization of sonochemical reaction and sonochemical research. It refers to the sound chemical reaction system under the action of ultrasonic wave. The ultrasonic reactor has the characteristics of simple operation, good performance stability and high efficiency. The application research and development of the ultrasonic reactor is paid more and more attention. This paper is based on the invention patent of the laboratory. The prototype, a continuous multi frequency ultrasonic reaction tank as a reaction vessel, takes pure water and acidified oil as the research object, and explores the characteristics of sound field in the ultrasonic reactor with ultrasonic frequency and combination, ultrasonic power, the law of the change of solid content in the fluid and the distribution rules in the reactor. The aim is to explore the distribution law of sound field in the ultrasonic reactor. The important influence of the optimum reaction conditions and the sound chemical yield is provided to promote the application of the acoustic chemistry technology from the laboratory scale to the industrial application. The main work and research results of this paper are as follows: (1) the sound field distribution of the ultrasonic reactor is measured by the ultrasonic intensity measuring instrument, and the direction of length, the axis and the plane are found. The sound field has a similar distribution law. The sound field distribution is uniform except the high acoustic intensity near the transducer and the wall of the transducer. The fluid flow (0-40L/h) and temperature difference (25-40 degrees) have little influence on the distribution of sound field; the shape of the reactor, the installation position of the transducer and the ultrasonic power have great influence on the distribution of sound field: near the transducer radiation The sound intensity of the surface is higher and the intensity of the transducer is increased. The sound energy distribution under the same experimental conditions in the acidified oil and the two kinds of pure water in the continuous ultrasonic reactor shows that the sound intensity attenuates greatly in the oil body, which is the result of the higher viscosity of the oil, but the distribution law of the whole sound field and the water. The similarity in the medium. (2) adding fine solid particles (active carbon) in the water system and maintaining the sound intensity in the suspension state, the amplitude of the sound intensity is reduced to 7% (when the change amplitude is up to 40% without fine particles), and the distribution uniformity of the sound field can be improved obviously. The particle size and addition of activated carbon particles are investigated and the test results of the 35kHz reactor are tested. The results show that the optimum particle size is 200 mesh (75 mu m) and the addition amount of 1.25kg/m3. is used to determine the sound intensity distribution under this condition. The phenomenon that the acoustic pressure is unstable near the surface of the radiation surface and the wall surface has not existed, and the synergistic effect of the acoustic intensity is the best. The sound intensity is more regular with the change of the input power, which makes the power to ultrasonic inverse. The function of the stress is easier to control and provides some measures to further improve the mass transfer reaction. (3) a continuous preparation experiment of biodiesel is carried out with high acid value acidified oil as raw material. It is known that under the multi frequency ultrasonic action (15-25-35-40kHz) and the input power of 200W (alcohol oil ratio 6:1, catalyst (KOH) dosage 1.2% (mass fraction), reaction time 54mi) N, with the same temperature as room temperature, the yield of biodiesel (95.34%) increased by 43.16% compared with that without ultrasonic radiation (52.18%), and the yield (87.95%) increased by 7.39% compared with single frequency radiation (15kHz). The importance of the sound intensity and the uniformity of sound field distribution to the mass transfer was further verified. (4) through the cavitation bubble movement in the ultrasonic field The numerical simulation of the equation shows that as the ultrasonic frequency increases, the radius of cavitation bubble decreases, the time required for the cavitation bubble to reach the maximum radius is obviously longer, the cavitation effect decreases, and the cavitation effect increases with the increase of sound intensity, and the damping effect of the fluid with larger viscosity is more obvious, and the input power can be increased by increasing the input power. The results show that the sound intensity and distribution uniformity in the ultrasonic reactor are of great significance to the enhancement of mass transfer process. The description of the sound field distribution is verified by the continuous preparation experiment of biodiesel, and the motion of the hollow bubble in the ultrasonic field is related. These studies provide theoretical basis and technical reference for the performance optimization of sonochemical reactors.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ052;O644.3
本文编号：2145444
[Abstract]:Ultrasonic reactor is the key equipment for the realization of sonochemical reaction and sonochemical research. It refers to the sound chemical reaction system under the action of ultrasonic wave. The ultrasonic reactor has the characteristics of simple operation, good performance stability and high efficiency. The application research and development of the ultrasonic reactor is paid more and more attention. This paper is based on the invention patent of the laboratory. The prototype, a continuous multi frequency ultrasonic reaction tank as a reaction vessel, takes pure water and acidified oil as the research object, and explores the characteristics of sound field in the ultrasonic reactor with ultrasonic frequency and combination, ultrasonic power, the law of the change of solid content in the fluid and the distribution rules in the reactor. The aim is to explore the distribution law of sound field in the ultrasonic reactor. The important influence of the optimum reaction conditions and the sound chemical yield is provided to promote the application of the acoustic chemistry technology from the laboratory scale to the industrial application. The main work and research results of this paper are as follows: (1) the sound field distribution of the ultrasonic reactor is measured by the ultrasonic intensity measuring instrument, and the direction of length, the axis and the plane are found. The sound field has a similar distribution law. The sound field distribution is uniform except the high acoustic intensity near the transducer and the wall of the transducer. The fluid flow (0-40L/h) and temperature difference (25-40 degrees) have little influence on the distribution of sound field; the shape of the reactor, the installation position of the transducer and the ultrasonic power have great influence on the distribution of sound field: near the transducer radiation The sound intensity of the surface is higher and the intensity of the transducer is increased. The sound energy distribution under the same experimental conditions in the acidified oil and the two kinds of pure water in the continuous ultrasonic reactor shows that the sound intensity attenuates greatly in the oil body, which is the result of the higher viscosity of the oil, but the distribution law of the whole sound field and the water. The similarity in the medium. (2) adding fine solid particles (active carbon) in the water system and maintaining the sound intensity in the suspension state, the amplitude of the sound intensity is reduced to 7% (when the change amplitude is up to 40% without fine particles), and the distribution uniformity of the sound field can be improved obviously. The particle size and addition of activated carbon particles are investigated and the test results of the 35kHz reactor are tested. The results show that the optimum particle size is 200 mesh (75 mu m) and the addition amount of 1.25kg/m3. is used to determine the sound intensity distribution under this condition. The phenomenon that the acoustic pressure is unstable near the surface of the radiation surface and the wall surface has not existed, and the synergistic effect of the acoustic intensity is the best. The sound intensity is more regular with the change of the input power, which makes the power to ultrasonic inverse. The function of the stress is easier to control and provides some measures to further improve the mass transfer reaction. (3) a continuous preparation experiment of biodiesel is carried out with high acid value acidified oil as raw material. It is known that under the multi frequency ultrasonic action (15-25-35-40kHz) and the input power of 200W (alcohol oil ratio 6:1, catalyst (KOH) dosage 1.2% (mass fraction), reaction time 54mi) N, with the same temperature as room temperature, the yield of biodiesel (95.34%) increased by 43.16% compared with that without ultrasonic radiation (52.18%), and the yield (87.95%) increased by 7.39% compared with single frequency radiation (15kHz). The importance of the sound intensity and the uniformity of sound field distribution to the mass transfer was further verified. (4) through the cavitation bubble movement in the ultrasonic field The numerical simulation of the equation shows that as the ultrasonic frequency increases, the radius of cavitation bubble decreases, the time required for the cavitation bubble to reach the maximum radius is obviously longer, the cavitation effect decreases, and the cavitation effect increases with the increase of sound intensity, and the damping effect of the fluid with larger viscosity is more obvious, and the input power can be increased by increasing the input power. The results show that the sound intensity and distribution uniformity in the ultrasonic reactor are of great significance to the enhancement of mass transfer process. The description of the sound field distribution is verified by the continuous preparation experiment of biodiesel, and the motion of the hollow bubble in the ultrasonic field is related. These studies provide theoretical basis and technical reference for the performance optimization of sonochemical reactors.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ052;O644.3
【参考文献】
相关期刊论文 前1条
1 王双维;冯若;史群;;小尺度混响场中超声化学效应的研究[J];自然科学进展;1992年03期
，本文编号：2145444
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