逆流超声波辅助提取过程的计算机仿真模拟研究

发布时间：2018-03-29 09:29

本文选题：超声波　切入点：仿真模拟　出处：《江苏大学》2017年博士论文

【摘要】：超声波辅助提取技术是一种安全、无毒、环保,并能够大幅度提高提取率以及降低能耗的新型绿色提取技术。超声波作为一种辅助提取手段被广泛应用于有效组分的提取工艺中,从而达到提高有效组分传质速率、加速提取进程和提高提取产率的目的。在超声波辅助提取设备中,由于声压在传播介质中分布的不均匀性,超声波大规模被应用于工业化生产时仍然存在放大设计的难题。大米蛋白具有合理的氨基酸组成、唯一的低变应原和高营养价值的优点,被公认为优质的谷物蛋白;米渣是大米生产糖浆过程的副产物,价格低廉且蛋白质含量丰富(一般在40%以上),是提取大米蛋白的理想蛋白源。本文首先借助COMSOL Multiphysics仿真模拟软件,通过对逆流超声波辅助提取设备中的声场、流体场、温度场和传质场进行计算,建立声场与流速、温度、传质之间相互耦合的多物理场仿真模型,考察超声波对提取有效成分的作用效果;第二选取米渣为原料,用逆流超声波辅助提取设备提取米渣蛋白,考察超声波对辅助提取米渣蛋白提取率的影响,依此结果验证仿真模拟预测提取效果的可行性;第三,基于混合物流体中声压场分布、流体速度和固体颗粒体积分数的变化,进一步探讨超声波辅助提取的机制;最后,利用声场的仿真模拟结果,在现有设备基础上,对辅助提取设备进行了简单的设计和讨论。本文得到的结论如下:⑴基于理想状态下的质量守恒定律、动量守恒定律和能量守恒定律,建立了粘性运动流体中的声波波动方程、运动方程、能量方程和传质微分方程,对逆流超声波辅助提取设备中的声场、流体场、温度场和传质场仿真模拟提供一定的理论基础。⑵逆流超声波在碱液中传播有益于有效成分的提取。基于超声波的传播对流体介质速度和温度的影响,利用COMSOL Multiphysics仿真模拟软件中的声场、流体场和温度场模块,建立辅助提取设备中的声场、流体场和温度场仿真模型,为超声波有效应用于辅助提取提供一定的理论指导。仿真模拟结果表明,声压振幅随超声波功率和频率的增加而增加,随传播距离的增加趋于平衡,空化效应更容易发生;超声波在流体介质中传播使得流体的速度增加,压强增大,涡量也显著增加,有利于混合效应产生;在脉冲工作模式下,超声波在0.08 mol/L的NaOH溶液中传播4 min,最高温度升高3.91°C。⑶超声波辅助提取米渣蛋白的试验结果表明,在米渣蛋白的提取过程中,施加超声波能够显著提高蛋白质提取率,最大可增加2.4倍。这种超声波显著改善提取过程的结果与超声波对物理场仿真模型所推测的结果相一致。且米渣蛋白提取率随碱液浓度、提取温度的增加而增加;随提取时间的延长先增加后趋于平衡;随固液比、间歇比和超声波功率的增加先增加后下降。氨基酸分析结果表明,超声波辅助提取的米渣蛋白,疏水性氨基酸、限制性氨基酸(赖氨酸和蛋氨酸)的含量增加。扫描电镜(SEM)、原子力显微镜(AFM)和傅立叶红外光谱(FT-IR)结果表明,超声波处理后,空化效应破坏了原料米渣粉和米渣蛋白的微观结构,具体表现为:米渣粉表面的多孔性增加、米渣蛋白的粒径变小、聚集体数量降低。这些微观结构的变化也表明了超声波在提取过程中有空化作用的发生,这与超声波声场有利于空化作用发生的仿真模拟结果是相符的。⑷超声波辅助提取的动力学研究结果表明,逆流超声波辅助提取大大降低了提取时间、提高了米渣蛋白提取率。在前20 min处理时间内,在所有考察因素水平下,米渣蛋白的提取率均是随处理时间显著增加。基于决定系数R2和均方根误差RMSE,非稳态动力学模型与试验数据之间的拟合较好。仿真模拟结果表明,设备中高声压场的形成有利于空化效应的发生、流体速度增加、固体颗粒充分悬浮,超声波辅助提取设备中的声场有利于米渣蛋白的提取。温度随时间的增加而增加,且温度的波动与脉冲工作模式密切相关。⑸基于COMSOL Mltiphysics仿真模拟软件的计算,对超声波辅助提取设备的尺寸、设备制作材料和超声波探头数量等因素对声场的影响进行了讨论分析。结果表明,为保证容器中具有正负交错的高声压场,超声波探头的尺寸与探头下方的作用管道直径不宜相差太大;选取阻抗较高的材料不锈钢作为设备制作材质,以保证有较强的反射波,与行波叠加形成随传播距离增加不衰反增的高声压场;两个超声波探头不管是平行排列还是120°交叉排列,频率和功率均显著影响声场中的声压分布,且与声压振幅呈正相关关系。这为以后超声波大规模的应用于工业化生产提供一定的理论指导。
[Abstract]:The ultrasonic assisted extraction technique is a safe, non-toxic, environmental protection, and can greatly improve the extraction rate and reduce the energy consumption of the new green extraction. Ultrasonic extraction technology as a means of assisted extraction is widely used in the effective component, so as to improve the effective components of the mass transfer rate, accelerate the extraction process and improve the extraction the yield of the products. In the ultrasonic assisted extraction equipment, because of uneven pressure distribution in the medium, the ultrasonic mass was being applied to industrial production still exists problem. The amplification design of rice protein has the advantages of reasonable amino acid composition, only low allergen and high nutritional value, is recognized as the quality of grain protein; rice residue is a by-product of rice syrup production process, low price and rich in protein (generally above 40%), is ideal for protein extraction of rice protein Source. This paper using COMSOL Multiphysics simulation software, based on the current ultrasonic assisted extraction equipment in the field, fluid field, temperature field and mass transfer calculation, the establishment of sound field and flow velocity, temperature, mass transfer between coupled multiphysics simulation model, the effects of ultrasonic wave on the effect of extracting effective ingredients from second meters; slag as raw material, ultrasonic assisted extraction equipment with countercurrent extraction of rice residue protein, rice dreg protein extraction rate of the effects of ultrasonic wave on extraction, and simulation results verify the feasibility of predicting the extraction effect; third, the distribution of sound pressure in the fluid mixture based on the change of fluid velocity and solid particle volume fraction, to further explore the mechanism of ultrasonic assisted extraction; finally, the simulation results using field simulation, based on existing equipment, the extraction equipment of a simple. Plan and discussion. The conclusions of this paper are as follows: firstly, the mass conservation law under the ideal condition based on the law of conservation law of conservation of energy and momentum, a wave equation in fluid viscous motion motion equation, energy equation and mass transfer differential equation of ultrasonic wave assisted countercurrent extraction equipment in the field, fluid field, temperature to provide a theoretical basis and field simulation of mass transfer field simulation. The ultrasonic countercurrent extraction in alkaline solution is beneficial to the dissemination of effective components. The influence of ultrasonic propagation of fluid velocity and temperature based on the simulation software of the sound field by using COMSOL Multiphysics simulation, flow field and temperature field module, an auxiliary extraction equipment in the field. The fluid field and temperature field simulation model, provide some theoretical guidance for the effective application in ultrasonic assisted extraction. The simulation results show that the sound pressure amplitude with ultrasonic wave Increase the power and frequency increases with the increase of propagation distance tends to balance, cavitation occurs more easily; the ultrasonic propagation velocity of the fluid increases in the fluid medium, the pressure increases, the vorticity increases obviously, is conducive to the mixed effect; the pulse working mode, 4 min ultrasonic propagation in 0.08 NaOH solution in mol/L, the highest temperature of 3.91 DEG C. by ultrasonic assisted extraction of rice residue protein test results show that the extraction process of rice residue protein, ultrasonic wave can significantly improve the extraction rate of protein, the maximum increase of 2.4 times. This is consistent with the process of ultrasonic ultrasonic significantly improved results that extraction of physical field simulation the results of the model. And the extraction rate of rice residue protein with the alkali concentration, extraction temperature increases; with prolonging extraction time increases firstly and then tends to balance; with the solid-liquid ratio, the ratio of intermittent and The increase in ultrasonic power increased first and then decreased. The amino acid analysis results show that the ultrasonic assisted extraction of rice residue protein, hydrophobic amino acids, limiting amino acids (lysine and methionine) content increased. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and Fu Li leaves red spectra (FT-IR) results show that after ultrasonic treatment, cavitation destroyed the microstructure of raw materials of rice residue powder and rice residue protein, specific performance: the porous powder on the surface of rice residue increased, rice residue protein has smaller particle size, the number of aggregates decreased. These changes of microstructure also shows that ultrasonic cavitation occurs in the extraction process this, and ultrasonic field simulation for cavitation occurred. The results are consistent with the results of kinetic study showed that ultrasonic assisted extraction, countercurrent ultrasonic assisted extraction can greatly reduce the extraction time and improve the Rice residue protein extraction rate. In min before 20 time, all the factors in the level, the extraction rate of rice protein was significantly increased with treatment time. The coefficient of determination R2 and root mean square error of RMSE based on the fit between the non steady state dynamic model with the experimental data well. The simulation results show that the equipment high pressure is conducive to the formation of cavitation occurs, fluid velocity increases, the solid particles in suspension, ultrasonic assisted extraction equipment in the field is favorable to extraction of rice residue protein. The temperature increased with time, and the temperature and pulse wave mode are closely related. The calculation simulation software based on COMSOL Mltiphysics the ultrasonic assisted extraction, the size of the equipment, materials and equipment of ultrasonic probe number and other factors on the field are discussed. The results show that, in order to ensure the container out There are positive and negative pressure loudly staggered, effect of the tube size and the bottom of the probe ultrasonic probe diameter should not be too large difference; selection of high impedance material of stainless steel equipment as the production of the material, to ensure a strong reflection, the formation of enduring pressure increased loudly with the propagation distance increasing and traveling wave superposition; two ultrasonic probes whether parallel or 120 degrees cross arrangement, frequency and power significantly affects the pressure distribution in the field, and is associated with the sound pressure amplitude was positively relationship. For the future application of ultrasonic in large-scale industrial production to provide a theoretical guide.

【学位授予单位】：江苏大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ936

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