火龙果真空冷冻干燥的模拟分析和实验研究

为了准确预测冷冻干燥时间，本文基于传热传质理论，利用COMSOL软件对厚度为12 mm、半径为4 cm的红心火龙果片进行建模，模拟升华干燥阶段火龙果内部水蒸气流动耦合热质传递、火龙果温度分布特性、升华界面位移以及冰升华过程，预测升华周期，并通过实验验证模型的可靠性。结果表明：模拟值与实测值相吻合且误差较小，火龙果中心点温度模拟值与实测值绝对误差为0.9℃,火龙果含水率模拟值与实测值相对误差为1.2%,脱水速率模拟值与实测值相对误差为6.63%。本模型可以准确模拟升华干燥过程热质传递动态变化。通过模拟对比不同厚度火龙果片升华周期，同时考虑到冻干制品质量和产量，12 mm为红心火龙果片冻干最佳厚度。     

改进的分子筛脱水装置在页岩气脱水中的应用

页岩气开发过程中多在集气站进行脱水处理,工艺多采用三甘醇(TEG)脱水,但边远页岩气单井的开发需脱水后再进入外输管网。针对这类单井产气量小、工况不稳定等特点,若采用三甘醇脱水工艺,存在投资和运行成本增加、装置运行不稳定等问题。通过对重庆页岩气公司足202井的特点进行分析,综合比较了分子筛与三甘醇脱水装置的优缺点,并对工艺与设备进行了集成创新,提出了利用分子筛进行井口气脱水的新思路,研制出一套处理量为12×104 m^3/d的撬装分子筛脱水装置,并在现场进行了成功应用。分析结果表明,装置满足脱水需求,节省了投资和能耗。另外,装置在针对性和适用性上有许多亮点,在自动化和信息化方面进行了有益的尝试,可为类似天然气分子筛脱水系统的设计提供参考。     

图版修正法水露点测量技术在海上气田的应用

天然气水露点是衡量天然气质量的重要指标,鉴于传统水露点测量的不足,针对三甘醇脱水工艺,以接触塔出口平衡水露点、贫三甘醇质量分数及入口气温度的关系图为基础,提出了一种图版修正法水露点测量技术。测量前通过试验测试获得气田平衡水露点与实际水露点之间的偏差量。测量中通过采集三甘醇脱水系统中接触塔入口天然气温度以及贫三甘醇质量分数,代入已知的图版,获得平衡水露点,在平衡水露点基础上增加偏差量修正,获得测量水露点。为便于精确读图,开发出了测量软件。图版修正法水露点测量方法操作简便,测量精度高,在海上气田取得了良好的应用效果,可广泛推广使用。     

Sustainable value-added C_3 chemicals from glycerol transformations:A mini review for heterogeneous catalytic processes

It is of importance to convert glycerol, the primary by-product from biodiesel manufacturing, to various valuable C_3 chemicals, such as acrolein via dehydration, lactic acid, 1,3-dihydroxyacetone via oxidation,and 1,3-propanediol, allyl alcohol via hydrogenolysis. As compared to petroleum-based resources, C_3 chemicals from glycerol provide a benign, sustainable and atomically economic feature. Extensive heterogeneous catalysts have been designed, prepared and tested for these transformations. In recent five years,great progress, including high yields to target products over appropriate catalysts, insight into reaction mechanism and network, has been achieved. The present review systematically covers recent research progress on sustainable C_3 chemical production from catalytic glycerol transformations. We hope that it will benefit future research on transformations of glycerol as well as other polyols.     

Unique structure of fibrous ZSM-5 catalyst expedited prolonged hydrogen atom restoration for selective production of propylene from methanol

A unique mesostructured fibrous silica@ZSM-5 (HSi@ZSM-5) catalyst was synthesized via microemulsion ZSM-5 zeolite seed assisted synthesis method and successfully applied in enhanced propylene formation in methanol to olefin (MTO) process. Characterization of the catalysts were carried out by FESEM, TEM, XRD, TGA, N₂ adsorption-desorption, NH₃ and KBr probed FTIR. Catalytic performance of as-synthesized catalyst was examined using a micro-pulse reactor and compared with the commercial HZSM-5. The reaction mechanism was elucidated by in-situ methanol FTIR spectroscopy. It was found that HSi@ZSM-5 produced higher propylene selectivity (56%) and was stable for long time on stream (80 h), nearly three-fold higher than that of commercial HZSM-5. In addition, HSi@ZSM-5 displayed higher rate of methanol dehydration, surface methoxy species generation and olefin methylation, indicating that alkene catalytic cycle is the dominant reaction mechanism. The higher selectivity towards propylene was correlated to the existence of moderate acidity which impeded the formation of paraffins and polymethylbenzene intermediates. These observations are further supported by KBr probed FTIR findings which revealed negligible paraffinic carbon species on HSi@ZSM-5. Thus, the unique fibrous silica@ZSM-5 retarded coke deposition due to suppression of undesired side reactions thereby signifying intensified propylene formation, which is highly desirable in commercial MTO processes.     

PTA装置醋酸脱水塔的动态模拟及控制策略分析

以PTA装置醋酸脱水塔为研究对象，在该醋酸脱水塔的稳态模型的基础上，通过建立的平衡级动态数学模型以及补充设置好的动态参数，利用Aspen Plus软件建立好动态模型。以Aspen Dynamics软件为工具，用回流流量控制灵敏板温度，塔釜再沸器热负荷与进料流量F ₁呈比例控制，模拟设计出了控制策略CS1。又为了保证在进料流量扰动时塔底醋酸浓度更加稳定，利用塔釜再沸器热负荷来控制塔釜醋酸浓度，设计出了控制策略CS2。将两种不同的控制策略对其动态响应进行分析比较，得出在相同目标条件下表现更优的控制策略，为实际生产和控制方案的设计提供方向和指导。     

Osmotic pretreatment for instant controlled pressure drop dried apple chips: Impact of the type of saccharides and treatment conditions

Instant controlled pressure drop (ICPD) is an emerging drying technique that can produce fruit chips with crispy texture. To improve the qualities of ICPD-dried apple chips, six types of saccharides with different polymerization were used for osmotic pretreatment on apple slices. Firstly, the effects of different saccharides on the osmotic behavior and texture of ICPD-dried apple chips were evaluated. Then, the effects of osmotic conditions of a selected saccharide, i.e. stachyose, on the qualities of ICPD-dried apple chips were studied. The results showed that sucrose, raffinose, and stachyose could significantly enhance the crispness of the ICPD-dried apple chips. In addition, the ICPD-dried apple chips pretreated with stachyose possessed the highest T_g (29.74?°C) and superior porous structure compared with pretreatments using the other saccharides. Moreover, limited color change (ΔE) was found in the samples pretreated with stachyose at 40?°C for 30?min, as well as higher retention of polyphenols. In conclusion, it is confirmed that the types of saccharides significantly influence the qualities of the ICPD-dried apple chips, and osmotic pretreatment at 40?°C for 30?min using stachyose was suggested for improving the overall quality of ICPD-dried apple chips.     

Application of osmotic dehydration and microwave drying to strawberries coated with edible films

Osmotic dehydration (OD) is one of the conventional methods to increase the shelf-life of vegetables and fruits. However, the operating conditions can adversely affect the organoleptic and nutritional quality of fresh products due to the high sugar uptake during processing and the loss of water-soluble constituents to the osmotic medium. The application of edible films has attracted interest due to their ability to reduce the entry of solutes and simultaneously increase the removal of water during OD treatments. Microwave (MW) is one of the most effective emerging technologies to accelerate dehydration processes in vegetable matrices. This aspect is particularly relevant in strawberries, given its high content in bioactive and nutritional compounds. Thus, the aim of this paper was to assess the influence of edible film application (alginate–lactate) in strawberry slabs during combined OD-microwaves dehydration processes. Samples of 1?cm thickness were treated with sucrose solution (60°Bx, 40?°C, 4?h) and then were dehydrated in a microwave oven (1.2?W/g). The application of alginate–lactate edible films resulted in similar weight and water losses but lower solids gain compared to uncoated samples during OD treatment. OD pre-treated MW-dried strawberry slabs with moisture contents up to 0.15?kg dry basis were obtained after 100?min of MW drying. Besides, the effective diffusional coefficient (D_e) was estimated for MW drying process, values ranged from 4.5 to 8.8 10^?10 m²/s when shrinkage effect was considered, and from 1.1 to 2.3 10^?9 m²/s for constant thickness assumption.     

集冷凝和离心分离功能于一体的天然气超音速旋流分离技术

天然气超音速旋流分离技术具有结构简单紧凑、无转动部件、可靠性高、无化学添加剂、投资和维护费用低等优点,工业应用前景广阔,但由于其过程的复杂性,理论研究还不成熟。为了推进该技术的大规模工业化应用,在介绍天然气超音速旋流分离器的结构及其工作原理的基础上,阐述了其旋流流动过程、内部凝结过程和内部流动过程等数值模拟的研究新进展,分析了近年来国内外有关的实验研究现状,总结了相关数值模拟和实验研究的进展,并对未来天然气超音速旋流分离技术亟待解决的关键问题进行了展望。研究结果表明:(1)目前关于超音速旋流分离器的数值模拟研究主要集中在旋流流动过程、内部凝结过程和内部流动过程等方面,并取得了一定成果;(2)国内对超音速旋流分离器的实验研究主要集中在低压实验,而在高压天然气的凝结机理及分离机理研究等方面则可能尚存在着一定的差距。结论认为:(1)解决超音速喷管的收缩段曲线和扩张段曲线的匹配、旋流器的结构优化设计与安装位置等问题,有助于气体凝结和提高气液分离效率;(2)开展符合天然气实际操作工况的高压实验,有助于探究天然气旋流分离的凝结和分离机理;(3)亟待在准确揭示高压天然气跨音速流动时其中水分及重烃的凝结机理和分离过程方面进行深入研究,确定影响分离性能的因素,以期为天然气旋流分离器的工程设计与应用奠定坚实的理论基础。