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含毒油籽双液相浸取和脱溶过程放大的动力学与实验模拟

Dynamics and Experimental Simulation in the Scale-up of Leaching and Desolventization of Toxic Oilseeds with Two-Liquid-Phase Solvent

【作者】 包宗宏

【导师】 史美仁;

【作者基本信息】 南京工业大学 , 化学工程, 2003, 博士

【摘要】 菜籽和棉籽提取油脂后的粕富含蛋白质,是饲料和食品蛋白质的潜在来源。现行预榨浸出工艺只提取油脂,菜籽和棉籽中的毒素硫代葡萄糖甙(简称硫甙)或棉酚留在粕中,使粕中蛋白质资源不能合理利用。加拿大多伦多大学Rubin等人提出的甲醇-己烷双液相溶剂(TPS)浸取技术可在获取高质量菜油的同时得到无毒饼粕。本课题组把TPS浸取技术移植、改进用于加工中国的高硫甙菜籽和棉籽,菜粕和棉粕均达到饲料标准。 TPS浸取技术从实验室研究到工业化应用,有许多问题需要探索和解决。本文对TPS浸取含毒油籽(菜籽和棉仁)工艺放大过程中的若干问题进行了研究。具体内容包括: 1 TPS浸取油菜籽的动力学研究 有关TPS浸取油菜籽动力学数据极少且不一致,本文对含碱助剂TPS浸取油菜籽动力学数据进行了系统完整的测定。温度范围15~50℃;菜籽破碎质量平均粒径0.32~0.427mm;甲醇相溶剂比4~6ml/g;己烷相溶剂比2~4 ml/g;浸取时间2~210min。研究结果表明: (1)菜籽破碎粒径和浸取温度对菜油和硫甙浸取率的影响明显。粒径越小,浸取速率越快;温度越高,浸取速率越快;浸取时间越长,浸取率越大。 (2)甲醇相溶剂比和己烷相溶剂比对菜籽浸取的影响明显。甲醇相溶剂比越大,硫甙浸取速率越快,浸取率越大。己烷相溶剂比越大,菜油浸取速率越快,浸取率越大。 (3)TPS浸取模型的建立和应用。对TPS浸取菜油和硫甙的传质机理进行了分析,建立了菜油和硫甙的液-液-固浸取数学模型。采用非线性回归分析,确定了模型参数与浸出条件之间的定量关系。324个实验点浸取率的计算值与测定值平均绝对偏差在0.01-0.028之间,表明模型良好地描述了TPS浸取行为。用浸出模型计算了操作条件对模型参数和浸出率的影响。结果表明,各种浸出条件的影响并不完全相同。模型计算的菜油和硫甙在固相内扩散系数与浸出温度的关系符合Arrhenius方程。南京工业大学博士学位论文摘要2多级TPS并流浸取油菜籽模拟研究 中国菜籽硫贰含量高,需要在提油后用多级甲醇溶剂洗涤才能达到饲料标准。为简化流程,降低溶剂消耗,本文提出提油与脱毒同时进行的多级TPS并流浸取菜籽流程,并用串级实验进行了模拟,证实并流浸取设想是可行的。主要内容是: (I)操作参数的优选。级数是影响浸取效果的主要因素之一,级数越多,浸取效果越好。实验条件下,使用4级浸取即可以达到粕中残油<l .0%、硫贰含量<3。。mol/g的手旨标。己烷相溶剂比对油脂浸取效果有很大影响,在40一50℃,己烷相溶剂比为2较适宜。甲醇相溶剂比对硫贰脱除效果影响很大,甲醇相溶剂比为33较适宜,甲醇相水含量以10v%为宜。 (2)油脂浸出器理论级计算模型的建立。针对TPS并流浸出破碎油菜籽的浸出过程,建立了油脂浸出器理论级计算模型。模型关联了各股物料相对流率、油脂在各流股的相平衡参数,考虑了菜粕对两相溶剂的夹带返混作用,计及了浸取级效率。若己知浸出要求和浸出条件,通过模型计算可求出完成浸出任务所需的浸出器理论级数。若己知浸出结果,通过模型计算可知该浸出器的两相溶剂返混程度和平均级效率。用串级实验测定值对浸出器理论级模型进行了验证,计算值与实验值吻合良好。根据TPS并流浸出的特性,这种逐级计算模型可用于浸出过程的计算,可估算理论级数、溶剂返混状况和平均级效率,可为工程设计或实际生产提供参考数据。3 TPS浸出粕脱溶小试和中试研究 TPS浸出粕脱溶性能研究尚未见报道。根据TPS浸出粕特点,本文提出TPS浸出粕脱溶工艺的选择应采用三步脱溶法:先进行机械挤压预脱溶,再采用两级间接加热设备脱溶至成品。气 (1)小试脱溶实验。机械挤压压强为SMPa左右时,TPS浸出菜粕和棉粕的含溶量可分别降到0.45和0.38 kg/kg干粕。在常压厢式固定床干燥器脱溶时,加热空气流速0.4m/s,料层厚度smln,菜粕在354K下的脱溶速率为7.0 x10’kg/s.m’·,临界湿含量为0.48kg溶剂/kg干粕;棉粕在364K下的脱溶速率为10.5xlo‘kg/5.mZ’,临界湿含量为0.62kg溶剂/kg干粕。 (2)中试脱溶实验。物料在卧式内外加热低速螺旋推进脱溶器(HCD)内南京工业大学博士学位论文摘要的运动状况可视为活塞流,可得到脱溶均匀的粕。干粕出料速率与HCD螺旋推进转速呈直线关系,由此可确定HCD的产率。 在常压和脱溶温度低于100℃条件下,用两级HCD串联脱溶可得合格脱溶粕。在第一级脱溶时,只要提供足够的传热面积,可方便地把TPS浸出粕中总溶剂残留量降至170以下。在第二级脱溶时,入HCD棉粕的溶剂含量、脱溶温度、脱溶时间、逆流通过脱溶器的惰性气体流量等操作条件对脱溶后棉粕中的溶剂残留量均有影响,可把TPS棉粕中甲醇和己烷的残留量分别降至1 000和60Om眺g以下。脱溶条件相同时,脱除己烷易于脱除甲醇。因此,可以把甲醇残留量作为棉粕的脱溶控制指标。只要甲醇残留量不超标,己烷残留量就不会超标。 (3)建立HCD传质单元模型。基于HCD内物料平衡、相平衡、动力学方程等提出的HCD传质单元模型,关联了脱溶器的传质单元数和操作条件与脱溶效果之间?

【Abstract】 Rapeseed and cottonseed meal after they are squeezed for oil are potential protein resources for feed and food. Because of the toxic glucosinolates in rapeseed meal or gossypol in cottonseed meal, the rich protein in meals has not yet been utilized reasonably.Two-liquid phase solvent (TPS) extraction technique, invented by Rubin et al (University of Toronto), could obtain high-level rapeseed oil and toxin-free meal simultaneously. Our research group transplanted and improved the TPS technique in processing the Chinese rapeseed and cottonseed, obtained qualified meal.From bench test to commercial-scale application, TPS technique still has many problems to be investigated and solved. This dissertation studied the problems in dynamics and experimental simulation in the scale-up of leaching and desolventizing of toxic oil seeds (rapeseed and cottonseed) with TPS. The main issuers are as follows.1 Dynamic study in rapeseed TPS leachingThe dynamic data of rapeseed leaching by TPS in literature were rare and lack of consistence. This dissertation carried out a comprehensive investigation on rapeseed-leaching dynamics with TPS containing basic additives. The temperatures were 15-50; Ground rapeseed diameter 0.32-0.427mm; Ratio of methanol to rapeseed 4-6 ml/g; Ratio of hexane to rapeseed 2-4 ml/g; Leaching time 2-210 min. The results of the study showed that:(1) The effect of rapeseed particle size and temperature on leaching yields of oil and glucosinolates was obvious. The smaller the particle size, the quicker the leaching rate. The higher the temperature, the quicker the leaching rate, and the higher the leaching yield.(2) The effect of TPS ratio to rapeseed on leaching yield was obvious. The bigger the ratio of methanol to rapeseed, the quicker the glucosinolates-leaching rate and the higher the yield. The bigger the ratio of hexane to rapeseed, the quicker theoil-leaching rate and the higher the yield.(3) Foundation of TPS leaching model and its application. Mass transfer mechanism in leaching rapeseed by TPS had been analyzed and a liquid-liquid-solid leaching model was found. The quantitative expressions between model parameters and leaching conditions were determined by non-linear regression analysis. The dynamic data of leaching rate calculated by the model was identical with the 324 values determined by experiments. The dependence of diffusion coefficients both of oil and glucosinolates within rapeseed meal on temperature calculated by the model showed a good consistence with Arrhenius equation.2 Simulation of multistage cocurrent leaching of rapeseed with TPSThe glucosinolates content in Chinese rapeseed was in many times the Canadian’s rapeseed (conola) and a multistage methanol washing was needed after oil recovery. In order to simplify the process and decrease the solvent loss, a simplified process was proposed in the dissertation by uniting two-step processing, separately for the leaching of oil and gluconolates, into one, the multistage cocurrent leaching with TPS. To verify the feasibility of the idea, a cascade experiment were carried out.(1) Analysis of leaching factors and optimal leaching conditions. It was feasible to leach oil and remove glucosinolate simultaneously from Chinese rapeseed within a leaching apparatus. The number of stage was one of the main factors. The more the stages, the better the leaching result. In general, 4 theoretical stages would lead to a meal with residual oil below 1% and glucosinalates below 30 mol/g. In 40-50, the proper ratio of hexane to rapeseed was 2 ml/g. The proper ratio of methanol to rapeseed was 3.3 ml/g and water content in methanol phase was 10v%.(2) Foundation of theoretical stage model for liquid-liquid-solid three-phase cocurrent oil leacher. A model for calculation of theoretical stages in liquid-liquid-solid three phase leaching was proposed. The model correlated the relative flow rate of each stream entering and leaving the leacher and the equilibrium solubility of oil in each stream. The model also included the ba

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