Modeling intraparticle transports during propylene polymerizations using supported metallocene and dual function metallocene as catalysts: Single particle model

Two improved multigrain models (MGMs) for preparing homopolypropylene and long chain branched polypropylene via propylene polymerization using silica-supported metallocene or dual function metallocene as catalysts are presented in this paper. The presented models are used to predict the intraparticle flow fields involved in the polymerizations. The simulation results show that the flow field distributions involve dare basically identical. The results also show that both the two polymerization processes have an initiation stage and the controlling step for them is reaction-diffusion-reaction with the polymerization proceeding. Furthermore, the simulation results show that the intra particle mass transfer resistance has significant effect on the polymerization but the heat transfer resistance can be ignored

一种测量石蜡相变乳液过冷度的新方法:平衡态比容法

石蜡相变乳液是集储热与传热于一体的新型功能流体,具有广阔的应用前景。但石蜡相变乳液在降温时会出现过冷现象,极大降低了其储热与传热的性能。采用差示扫描量热法(DSC)测量石蜡相变乳液的过冷度受到升/降温速率的影响,且升/降温速率越大,测得过冷度越大。本文提出一种测量石蜡相变乳液过冷度的方法——平衡态比容法。该方法通过测量石蜡相变乳液在不同温度下的比容,以确定乳液中石蜡粒子在升/降温过程中的相变温度,并进一步求解石蜡相变乳液的过冷度。实验结果表明,本研究提出的平衡态比容法能准确测量石蜡相变乳液的过冷度,并从比容变化的角度揭示石蜡相变乳液过冷现象的机理。国家自然科学基金项目(21606185

一种测量石蜡相变乳液过冷度的新方法:平衡态比容法

石蜡相变乳液是集储热与传热于一体的新型功能流体,具有广阔的应用前景。但石蜡相变乳液在降温时会出现过冷现象,极大降低了其储热与传热的性能。采用差示扫描量热法(DSC)测量石蜡相变乳液的过冷度受到升/降温速率的影响,且升/降温速率越大,测得过冷度越大。提出一种测量石蜡相变乳液过冷度的方法——平衡态比容法。该方法通过测量石蜡相变乳液在不同温度下的比容,以确定乳液中石蜡粒子在升/降温过程中的相变温度,并进一步求解石蜡相变乳液的过冷度。实验结果表明,本研究提出的平衡态比容法能准确测量石蜡相变乳液的过冷度,并从比容变化的角度揭示石蜡相变乳液过冷现象的机理。国家自然科学基金项目(21606185

制油方法和精炼过程对麻疯籽油品质的影响

为更好地了解油脂加工过程对麻疯籽油品质的影响,对比研究了浸出和压榨2种制油方法对麻疯籽油理化指标、脂肪酸组成的影响,并研究了浸出麻疯籽油在精炼过程中的品质变化。结果表明:2种制油方法制备的麻疯籽油在理化指标上存在较大差异,但在脂肪酸组成上并没有显著差异;与压榨法相比,浸出法制备的麻疯籽油具有较高的酸值、碘值、过氧化值、皂化值以及磷脂含量;麻疯籽油中的主要甘三酯为LOO(17.86%),LLO(16.02%),POL(14.06%),POO(7.14%),LLP(6.58%),OOO(6.44%),St OL(6.38%);此外,精炼对麻疯籽油的主要脂肪酸组成基本没有影响,但精炼后麻疯籽油的酸值、过氧化值、碘值和皂化值均明显降低

Effect of tea polyphenols on the retrogradation of sweet potato starch

淀粉老化会导致淀粉基食品变硬、弹性减小,严重缩短这些产品的货架期。本文通过X-射线衍射、质构分析、色泽分析和傅立叶变换红外光谱等方法检测甘薯淀粉样品在长期储存过程中(80d)的结构和特性变化,研究茶多酚对甘薯淀粉的抗老化效果。纯甘薯淀粉在放置80d之后,硬度接近初始硬度的30倍,而加入9WT.%茶多酚之后,硬度增大趋势得到明显的抑制,80d之后淀粉胶体硬度不足初始硬度的4倍。实验结果显示,茶多酚可抑制甘薯淀粉形成结晶结构,延缓其结晶过程,从而降低甘薯淀粉胶体的硬度,减小胶体的硬度和色泽变化。这说明茶多酚可有效抑制甘薯淀粉的老化。Retrogradation in cooked starch based products significantly shortens the shelf life of these products as they become firm and less elastic during storage.In this work,the effect of tea polyphenols( TPs) on the retrogradation of sweet potato starch during long- term storage( 80d) was evaluated by characterizing sweet potato starch sample using X- ray diffraction( XRD),texture profile analysis( TPA),color analysis,and Fourier transform infrared spectroscopy( FT- IR).After storage for 80 d,the hardness of pure sweet potato starch increased to about30 times of initial hardness.While for sweet potato starch with 9wt.% TPs,the normalized hardness was less than 4.The experimental results showed that TPs retard the recrystallization of starch,resulting in decrease in the hardness of sweet potato starch gel.The variations of hardness and color of the sweet potato starch gel were also limited by the addition of TPs.The results suggested that the retrogradation of sweet potato starch was inhibited by TPs

Comparison between REA model and thin layer drying model based on strip drying kinetics

为了获得最适用于烟草干燥的动力学模型,达到设计、优化和控制烟草干燥过程的目的,采用湿度发生器联用热重技术(TGA)研究了65 ℃ &RH; 15%, 75 ℃ & RH 10%和85℃& RH 5%条件下片烟的干燥动力学行为,并利用REA (Reaction engineering; approach)以及8种经验或半经验的薄层干燥模型分别对不同温湿度条件下的片烟干燥行为进行模拟。结果表明:①干燥温度越高,相对湿度越小时,片烟; 的干燥速率越快,平衡含水率越低;②REA模型预测的片烟干燥动力学曲线与实验曲线能够很好地吻合,尤其是在含水率由20%降至12%阶段;8种薄层干燥; 模型中Two; term模型拟合出的R~2值最大,均方根误差(RMSE)最小,是描述片烟干燥行为较合适的模型;③薄层干燥模型仅仅是获得特定温湿度条件下相对应的动; 力学参数,而REA模型是将温度和湿度作为变量引入模型中,模型中的动力学参数可以描述任意温湿度条件下的片烟干燥动力学行为;④REA模型构造简单,预; 测准确快速,较Two term模型更具有普适性、实用性。In order to select a kinetic model best fit for the design, optimization; and control of tobacco drying process, the drying kinetic behavior of; tobacco strips under the conditions of 65 ℃ & RH 15%, 75 ℃ & RH10%, 85 ℃; & RH 5% was investigated with a humidifier combined with TGA; (Thermogravimetric analyzer). The drying behavior of tobacco strips was; simulated by REA (Reaction engineering approach) model and eight; selected thin layer drying models (semi-empirical or empirical). The; results showed that: 1) With the rise of temperature and decrease of; humidity, the drying rate of strips raised and the equilibrium moisture; content of strips lowered. 2) The drying kinetic curves predicted by REA; model well agreed with experimental curves, especially at the stage when; the moisture content decreased from 20% to 12%. Among eight thin layer; drying models, Two term model was the best for predicting the drying; behavior of strips with the highest R~2 (determination coefficient) and; the lowest RMSE (root mean square error). 3) Thin layer drying model; reflected only the kinetic parameters corresponding to specified drying; conditions, while in the REA model the temperature and humidity served; as variables, it enabled the kinetic parameters in REA model to describe; the drying kinetic behavior at any drying condition. 4) REA model was; simple in structure, fast and accurate in prediction, more universal and; practical than Two term model.福建中烟工业有限公司科技项

Convective Drying Kinetics of Single Droplets of Aqueous Glucose

Conference Name:7th Asia-Pacific Drying Conference. Conference Address: Tianjin, PEOPLES R CHINA. Time:AUG, 2011.The convective drying kinetics of single droplets of aqueous glucose was measured using a single droplet drying rig. The effects of air temperature and velocity were evaluated. It was found that the droplet of aqueous glucose shrank uniformly, retaining a nearly spherical shape during drying. The normalized volume (d/d(0))(3) of the droplet decreased linearly with its moisture content. A constant-drying-rate-like period occurred when the moisture content of the droplet was higher than an amount of about 1.0 kg kg(-1) dry solid. The diameter of the droplet decreased sharply due to the evaporation of water, while its temperature remained at a wet-bulb-like temperature in this period. When the moisture content of the droplet was lower than the above-mentioned value, the drying transferred to a falling-drying-rate-period, during which the temperature of the droplet rose quickly and approached the air temperature as drying continued. The effect of air temperature on the drying of single droplets of aqueous glucose was more pronounced when compared with that of air velocity

Droplet drying behaviour of docosahexaenoic acid (DHA)-containing emulsion

National High Technology Research and Development Programme of China [2011AA100802-3]; Natural Science Foundation of Fujian Province of China [2011J05032]; Xiamen Kingdomway Group Company (China)Docosahexaenoic acid (DNA), one of the poly unsaturated fatty acids in omega-3 series, has attracted the attention of functional food industries due to its significant benefits to human health. DNA is often microencapsulated with modified starch and whey protein concentrate (WPC) to reduce oxidation, to improve stability during storage, and to mask any unpleasant odour. Spray drying is a common method to manufacture encapsulated powders. To the best of our knowledge, there is yet any work reported On the drying behaviour of the DNA emulsions. In fact, there is no reported literature on droplet drying behaviour, especially drying kinetics, for fish/algae oil in water emulsion system. Here, the drying behaviour of different kinds of DNA-containing emulsion droplets with varying concentrations and wall-materials were investigated via a single droplet drying device utilising the glass-filament approach to yield representative kinetics data. The changes of droplet size, moisture content, and droplet/particle temperature during drying were recorded, with the Reaction Engineering Approach (REA) employed to correlate the data. The related mechanisms were also discussed. The model has been shown to provide an accurate description of drying behaviour of different systems. This model can be implemented in dryer-wide simulation software to investigate large scale operations, thus the current work has provided the essential basis for future large scale explorations. (C) 2013 Elsevier Ltd. All rights reserved

Rheological behavior of agar solution in relation to the making of instant edible bird's nest products

Agar solution has been used in industry as a 'background' liquid material for the production of instant Edible Bird's Nest products. In this work, the rheological properties of agar solution were studied, especially the effect of shear rate, agar concentration and temperature, respectively, on the apparent viscosity of the agar solution. A HAAKE rotary viscometer was used. Results indicated that the agar solution exhibited shear-thinning behavior following the power law fluid model. Its apparent viscosity increased exponentially with an increase of solid concentration, and decreased with a rise of temperature. The independence of viscosity on temperature followed Arrhenius equation. Reasonable empirical correlations between the apparent viscosity of the agar solution for different temperatures, shear rates and different concentrations are proposed respectively. 漏 2012 De Gruyter

Phase diagram of aqueous two-phase system (ATPS) composed of polyethylene glycol (PEG) and gelatin

Conference Name:2nd International Conference on Chemical Engineering and Advanced Materials, CEAM 2012. Conference Address: Guangzhou, China. Time:July 13, 2012 - July 15, 2012.Phase diagram of aqueous two-phase system (ATPS) composed of polyethylene glycol (PEG) and gelatin is of paramount importance for the application of such system in microencapsulation of bioactive compounds. Phase separation of PEG/gelatin aqueous solution was investigated in the present work and the phase diagram of resultant ATPS was reported for the first time. The results show that phase separation will happen if the solid content of PEG/gelatin aqueous solution is higher than a critical value, resulting in an ATPS. The resultant ATPS consists of a low-density phase enriched in PEG and a dense phase enriched in gelatin. The phase compositions of the resultant ATPS were determined accurately using the method developed. The phase diagrams obtained show that higher solid content is required for the phase separation of PEG10,000/gelatin aqueous solution when compared with that of PEG20,000/gelatin one. And PEG is found to be more hydrophilic when compared with gelatin. 漏 (2012) Trans Tech Publications, Switzerland