同向旋转双螺杆挤出机相似放大参数优化深入探讨

采用FEM与正交试验设计相结合的方法,分别将20和72同向旋转双螺杆挤出机作为基准机型和目标机型,选用螺槽深度、螺杆转速和螺杆与机筒间隙作为试验因素,将产量、比能耗、最大剪切应力和平均停留时间作为评价指标,综合分析了不同几何参数对各个指标的影响,得出目标机型最优几何参数水平组合。     

Pellet layering: scale-up considerations using different kinds of processing equipment

Objective: In this study an aqueous suspension of poorly water-soluble HCT (hydrochlorothiazide) was layered on small spherical starter cores with a drug content in the final pellets of 30%. The aim was to compare different kinds of processing equipment (Wurster fluid-bed, CPS rotor fluid-bed and drum coater) in view of process efficiency, process duration and feasibility to scale-up.

Results: In a pilot scale drum coater, it was possible to achieve the desired LE (layering efficiency) and yield specifications (both >95%), but the process duration was at least 202?min. In the small scale Wurster fluid-bed machine, it was possible to reduce the process time for an optimized process from 67?min to 41?min. However, the acceleration of the process led to an increase of agglomerates and the same process took at least 114?min in the scale-up experiments. A small scale CPS rotor processor with a cone-shaped disc was superior to the conventional planar rotor disc design, regarding yield and agglomerates. This rotor process was both, fast and highly efficient (yield: 98.4%; LE: 99.3%). The high quality of the process was also observed for the pilot scale batches, in which neither considerable losses of drug (LE ≥ 98.6%) nor formation of agglomerates occurred. The absolute spray rate in this pilot scale process was 85?kg/h.

Conclusion: Best results were achieved with the CPS rotor technology. With a duration of 29?min (small scale) and 44?min (pilot scale) it was the fastest option to produce layered pellets.     

固液非均相硝化器内流体流动模型的研究

本文以火炸药生产中常用的固液非均相硝化器为模拟对象,建立并检验了该系统停留时间分布(RTD)的流动模型。在五个几何相似的模拟硝化器(碟底釜,体积为0.005～0.150m~3)内,研究了固液两相RTD的变化规律。研究结果为固液非均相硝化器的放大提供了理论和实验依据,具有较大的实际意义。     

碳纳米管:可控制备决定未来（英文）

在过去几十年中,碳纳米管由于其优异的物理和化学性质而备受关注,被认为是一个强有力的未来明星材料.尽管基于碳纳米管的诸多产品及应用实例相继浮现,但是碳纳米管所呈现出的实际性质与理论值之间依然存在较大差异,无法达到研究者的预期,这源自于目前尚未成熟的控制制备技术.碳纳米管的可控制备技术包括结构的精细控制方法和样品的宏量制备技术,这在很大程度上决定了碳纳米管的未来发展前景.基于此,本文概述了近几十年来研究者们在碳纳米管的精细结构控制、聚合状态设计和样品宏量制备等方面的主要进展,进一步指出了碳纳米管未来的可控制备技术必须与特定化的应用紧密结合,以迎接即将来临的产业化时代.     

Whole Cell Biotransformation of 5-(4-(2-(2-Pyridyl)methylamino)ethoxy)benzylidenethiazolidine-2,4-dione to its Benzyl Derivative Using a Yeast Reductase

Whole yeast cell reductive biotransformation of a benzylidene thiazolidinedione to its corresponding benzyl derivative has been scaled up from laboratory to small pilot plant scale. The fermentation conditions for the yeast Rhodotorula rubra were examined and cell titres increased by optimising the medium. Problems encountered in handling substrates of low water solubility are discussed. Various techniques are described for adapting the procedure for process scale operation using the general principles of process scale-up and integration. Liquid–liquid extraction using a dense solvent was performed on whole broth systems using a continuous flow liquid–liquid separator. Fatty acid impurities were removed using selective solvent extraction. © 1997 SCI.     

Scale Effects on Hydrodynamic and Mass Transfer Characteristics of External Loop Airlift Reactors

Gas hold-up and oxygen transfer have been investigated in two geometrically similar external loop airlift reactors of linear scale ratio of 2. In mass transfer experiments, the sampling location was found to be important as significantly different k_La values can be obtained. The variations of k_La with probe location have been explained in terms of non-uniform hydrodynamic properties and the results obtained have been validated by means of high speed video camera recordings. At higher gas flowrates, the gas hold-up was significantly higher in the large-scale reactor. It was found that in order to maintain the gas hold-up or k_La constant in both the small- and large-scale reactor, the small-scale reactor required 25% and 27% more power input per unit volume of liquid respectively. © 1997 SCI.     

Root culture using a mist culture system and estimation of scale-up feasibility

Normal root of Hyoscyamus niger was cultivated in four different culture systems; a flask, a stirred tank reactor, a mist bioreactor, and a unified mist bioreactor. The scopolamine/hyoscyamine contents of the roots in the various reactor configurations were at similar levels, but the growth rates were different. The dry weight of the root in the flask increased 21·4 times in 25 days, 12·9 times in the stirred tank reactor, and 4·76 times in the first mist bioreactor respectively. This low growth rate in the first mist bioreactor was probably due to limited nutrient supply of the air-carrier method. Root growth increased 9·29 times using the unified mist bioreactor in which mist can be sufficiently supplied without dilution of mist by air flow. It was estimated that a scale-up of over 10 dm³ of reactor volume would not be effective if the air-carrier method were used in a mist culture system.     

The use and profitability of hermetic technologies for grain storage among smallholder farmers in eastern Kenya

Hermetic storage technologies (HSTs) have been disseminated in Sub-Saharan Africa (including Kenya) to reduce grain storage losses among farmers. We carried out a study in three counties in eastern Kenya to assess the use and profitability of HSTs among farmers. Data were collected from 613 farmers using a semi-structured questionnaire and Kobo Toolbox via android tablets. Results showed an increase in use of HSTs among farmers from 53.7% in 2015 to 91.2% in 2017. PICS was the most used hermetic bags by farmers (84%) in 2017. Majority of farmers (73.5%) received training in the use of HSTs from extension agents and agro-dealers. About 40% of respondents purchased additional (one to five) bags after their first experience using them. The quantity of grain produced made up about half of the farmer’s decision to store. The primary reason (87%) farmers used hermetic bags was the need to manage insect pests. Maize and beans were the most produced and most stored crops; but maize was the most stored in HST. Grain price seasonality showed a near doubling effect between the lean and harvest seasons. Estimates of the return on investments (ROI) ranged between 13 and 80% for all crops and maize stored in hermetic bags had the highest ROI. Awareness and trainings are key in increasing adoption and proper use of HSTs.     

Scale-up of mixing in gassed multi-turbine agitated vessels

A mixing model previously developed for the determination of mixing time in gassed tanks stirred by multiple Rushton turbines (Vasconcelos et al., 1995) was verified for the additional scales of 0.39, 0.56 and 0.72 m vessel diameter. It is now shown that the single adjusted parameter previously required by the model, the air-induced axial velocity parameter v_ax, is scale-independent with an invariant value of 7 × 10^?2 m/s. Model simulations, with tank and turbine diameters and the number of stages as the only required parameters, deviate 5% on average from the experimentally determined mixing time t_0.05. The model is thus a valuable tool for scale-up of this type of vessels.