Drying of Porcine Dermal Tissue Via Pressure Swing Adsorption

Due to its close concordance with human tissue, porcine dermal tissues are often used as an acellular implant for skin regeneration in the field of tissue engineering. Generally, moisture within the dermal tissue has to be removed to preserve them until time for clinical applications. To investigate the drying kinetics of porcine dermal tissue under different drying conditions, a novel pressure swing adsorption dehydration (PSAD) system has been proposed for preliminary moisture removal. In this study, several process parameters were varied, namely, amplitude of pressure swing, depressurizing-pressurizing phase duration, and chamber temperature. In addition, a desiccant bed was incorporated to the experimental rig to maintain drying chamber humidity. Employing this pressure-swing drying technique, up to 50% of moisture from porcine dermal tissue could be easily removed within a relatively short period of time. Experimental results indicated that lower depressurized levels and higher frequency of pressure drops and chamber temperature improved dehydration rate. Color change for the dermal tissue was observed to be generally low, indicating low oxidation. Scanning electron microscopic study of the pore structure from pressure-swing adsorption dried dermal tissue showed samples having numerous internal channels. PSAD, therefore, has proven to be a highly effective drying technology to rapidly obtain partially dried dermal tissue while minimizing product quality deterioration.     

Drying Kinetics and Quality of Shrimp Undergoing Different Two-Stage Drying Processes

An innovative two-stage drying concept is presented in this article. The work considered drying of shrimp using a superheated steam dryer followed by a heat pump (SSD/HPD) or a hot air dryer (SSD/AD) both from drying kinetics and dried product quality points of view. The experiments were performed using the first-stage superheated steam drying temperature of 140°C while the second-stage heat pump drying (or hot air drying) was performed at 50°C. The moisture content of shrimp at the end of the superheated steam drying stage was varied between 30 and 40% (w.b.). The effect of tempering between SSD/HPD was also investigated. Shrinkage, color, rehydration behavior, texture (toughness and hardness), and microstructure of dried shrimp were measured. The results showed that SSD/HPD dried shrimp had much lower degree of shrinkage, higher degree of rehydration, better color, less tough and softer, and more porous than single-stage SSD dried shrimp. It was also found that SSD/AD gave redder shrimp compared to shrimp dried in a single-stage superheated steam dryer. No improvement in terms of shrinkage and rehydration behavior was observed, however.     

Drying Kinetics and Quality of Shrimp Undergoing Different Two-Stage Drying Processes

Abstract

An innovative two-stage drying concept is presented in this article. The work considered drying of shrimp using a superheated steam dryer followed by a heat pump (SSD/HPD) or a hot air dryer (SSD/AD) both from drying kinetics and dried product quality points of view. The experiments were performed using the first-stage superheated steam drying temperature of 140°C while the second-stage heat pump drying (or hot air drying) was performed at 50°C. The moisture content of shrimp at the end of the superheated steam drying stage was varied between 30 and 40% (w.b.). The effect of tempering between SSD/HPD was also investigated. Shrinkage, color, rehydration behavior, texture (toughness and hardness), and microstructure of dried shrimp were measured. The results showed that SSD/HPD dried shrimp had much lower degree of shrinkage, higher degree of rehydration, better color, less tough and softer, and more porous than single-stage SSD dried shrimp. It was also found that SSD/AD gave redder shrimp compared to shrimp dried in a single-stage superheated steam dryer. No improvement in terms of shrinkage and rehydration behavior was observed, however.     

Comparison of Water Blanching and High Hydrostatic Pressure Effects on Drying Kinetics and Quality of Potato

Abstract

Drying kinetics and quality parameters of potato cubes were evaluated as affected by high pressure processing and hot water blanching. The potato cubes in 1% citric acid solution as immersion medium were pressure treated at 400 MPa for 15 min. Hot water blanching was conducted in boiling water for 3 min. Drying kinetics and quality parameters (i.e., rehydrability, texture, color and apparent density) were assessed for the high pressure–treated and water-blanched samples and for dehydrated and rehydrated samples. Drying rates were found to be higher (p < 0.05) in the initial period of drying for the pressure treated samples. The Page model was found to better fit drying data of the thermally treated samples, and the two-terms model better described the drying behavior of high pressure–treated samples. High pressure–treated samples had a similar rehydrability to thermally treated samples. It was found that pressure–treated samples had a hardness value close to that of fresh samples, whereas thermal treatment resulted in a softer texture. After rehydration, samples of both treatments returned their texture before drying. The total color difference for the thermally blanched samples was higher (p < 0.05) than for pressure–treated samples before drying and after drying. High pressure–treated and dried potato cubes had a color close to that of fresh potato cubes. High pressure–treated and air-dried samples were found to have higher (p < 0.05) apparent density than thermally treated samples.     

A Comparative Study of Pork Drying Using Superheated Steam and Hot Air

Drying with superheated steam and hot air were comparatively studied for pork. Transport, physical, and chemical properties, i.e., effective diffusivity, color, microstructure, and rehydration ability, were investigated. The experimental results have shown that the decrease of pork moisture content in an early drying time was more rapid in superheated steam than in hot air and appeared to be lower in a latter time. The pork surface as examined by SEM was noticeably different for the samples dried by superheated steam and hot air. The fewer pores at the surface of superheated steam-dried pork caused a slower water penetration into the interior during rehydration, in addition to the lower drying rate. The color of the product from superheated steam was a relatively more intense brown than that obtained from hot air as presented by a lower L? value and a higher a? value.     

变压吸附的实质

变压吸附是利用分子筛筛分机理的特性来实现气体分离的。由于分子运动自由程的不同,气体分子通过分子筛的孔向孔内扩散时所受阻力不同,导致在孔内扩散速率不同,宏观上这种分离体现为气体被固定于分子筛的孔内部被"吸附"。实际操作时,不断采取"加压吸附-减压脱附"循环方式,因此被形象地称为"变压吸附",其实质是基于分子筛孔本身的筛分机理,并非吸附机理。通过变压吸附的机理分析,我们确定了分子筛孔径的选择方法,同时分析了变压吸附过程的影响因素。     

A Comparative Study of Pork Drying Using Superheated Steam and Hot Air

Drying with superheated steam and hot air were comparatively studied for pork. Transport, physical, and chemical properties, i.e., effective diffusivity, color, microstructure, and rehydration ability, were investigated. The experimental results have shown that the decrease of pork moisture content in an early drying time was more rapid in superheated steam than in hot air and appeared to be lower in a latter time. The pork surface as examined by SEM was noticeably different for the samples dried by superheated steam and hot air. The fewer pores at the surface of superheated steam-dried pork caused a slower water penetration into the interior during rehydration, in addition to the lower drying rate. The color of the product from superheated steam was a relatively more intense brown than that obtained from hot air as presented by a lower L* value and a higher a* value.     

变压吸附过程的数学模拟

变压吸附过程的数学模拟崔群姚虎卿（南京化工大学，南京２１０００９）关键词变压吸附（ＰＳＡ）数学模拟１前言变压吸附过程具有常温操作、易于自控、可获得高纯度产品等特点。广泛用于炼油和石油化工过程尾气的回收等系统，如用于炼油厂放空气和合成氨厂弛放气的Ｈ２...     

氢气变压吸附提纯单元改造探讨

中国石油吉林石化公司乙烯厂乙烯装置氢气变压吸附提纯单元(PSA单元)是与原300kt/a乙烯装置一同开车的单元,设计能力和吸附组分完全按照原300kt/a装置所产生氢气产量和组分而确定。装置700kt/a改扩建完成后,氢气产量和组分发生了很大变化,同时,PSA单元所存在的尾氢流量波动过大问题一直是制约裂解炉炉温控制的瓶颈。因此,2008年对PSA单元进行技术改造,使其处理能力和尾氢运行平稳率得到明显提高。     

A Comparative Study of Low-Pressure Superheated Steam and Vacuum Drying of a Heat-Sensitive Material

Using carrot cubes as a model heat-sensitive material, experimental investigations were conducted to examine the drying kinetics and various quality parameters of the dried product undergoing both low-pressure superheated steam and vacuum drying. Effects of operating parameters such as pressure and temperature on the drying characteristics as well as quality attributes, i.e., volume, shrinkage, apparent density, color, and rehydration behavior, of the dried product underwent the two drying processes were also evaluated and compared. Although low-pressure steam drying required longer dwell time to achieve the same final moisture content than vacuum drying, some of the quality attributes were superior to those obtained in vacuum drying.     

A Comparative Study of Low-Pressure Superheated Steam and Vacuum Drying of a Heat-Sensitive Material

Abstract

Using carrot cubes as a model heat-sensitive material, experimental investigations were conducted to examine the drying kinetics and various quality parameters of the dried product undergoing both low-pressure superheated steam and vacuum drying. Effects of operating parameters such as pressure and temperature on the drying characteristics as well as quality attributes, i.e., volume, shrinkage, apparent density, color, and rehydration behavior, of the dried product underwent the two drying processes were also evaluated and compared. Although low-pressure steam drying required longer dwell time to achieve the same final moisture content than vacuum drying, some of the quality attributes were superior to those obtained in vacuum drying.     

Vacuum Pressure Swing Adsorption to Produce Polymer-Grade Propylene

We have evaluated the Vacuum Pressure Swing Adsorption (VPSA) technology to separate propane–propylene streams to produce polymer-grade propylene. Zeolite 4A is used as kinetic adsorbent since propylene diffuses much faster than propane. A single VPSA process is able to produce propylene with purity higher than 99.6%. However, propylene recovery is only 67% and therefore a second stage is used. In this VPSA unit, zeolite 4A with smaller crystal radius is employed to reduce kinetic limitations. The second VPSA (tail unit) produces purified propane and recovers propylene that is recycled to the feed of the first VPSA (front unit). Linking these two VPSA units allows us to produce polymer-grade propylene (PGP) recovering 95.9% of the propylene. Comparing the performance of this process with distillation, there is a significant decrease in the separation volume. However, further efforts are necessary to reduce the power consumption of VPSA which is still slightly higher than for distillation.     

变压吸附技术应用小结

简述了采用变压吸附技术从合成氨弛放气中回收氢气的工艺过程及取得的效益。     

Effect of Osmotic Pretreatment on Hot Air Drying Kinetics and Quality of Chilean Papaya (Carica pubescens)

The effect of osmotic pretreatment on the mass transfer kinetics and quality of dried rehydrated Chilean papaya was researched. Osmotic treatments were sucrose solutions of 40, 50, and 60% w/w and dried at 60°C; non-pretreated samples were dried at different temperatures (40, 60, and 80°C). Quality parameters were analyzed: proximal composition, rehydration ratio, water-holding capacity, color, vitamin C content, firmness, and microstructure. Non-pretreated samples showed a clear turgor loss, color loss. and low ascorbic acid retention when rehydrated. Osmotic pretreatment improved the quality of rehydrated papayas, showing higher ascorbic acid retention and best firmness and color. Microstructure is better preserved in the pretreated papayas than in the non-pretreated samples, although this difference is minimal.     

变压吸附分离技术的研究进展

简述了变压吸附技术在分离净化方面的应用,及其在分离提纯高沸点组分中的研究进展,寻求进一步拓展变压吸附技术的应用领域,开发新型工业装置的途径     

变压吸附技术在氢回收中的应用

介绍了变压吸附(PSA)技术在回收电石法聚氯乙烯生产过程的精馏尾气中氢气的原理及应用,阐述了变压吸附技术的工艺流程及其分离原理,分析了采用此技术后的环境和经济效益。     

变压吸附数值模拟的研究

从变压吸附的控制方程入手,分析了瞬时平衡模型、线性推动力模型以及孔扩散模型,并对软件化模拟变压吸附系统进行了论述。利用三维流体力学模拟软件,可以模拟并优化吸附塔的气体分布器及其他塔内件,优化程控阀的流体力学性能;利用一维流体力学模拟软件,可以对变压吸附系统管网仿真与优化。利用大型商用软件对变压吸附系统进行从微观的流动细节模拟到宏观的运行状态模拟,是变压吸附数值模拟和系统优化的发展方向。     

Purple-Fleshed Sweet Potato Cubes Drying in a Microwave-Assisted Spouted Bed Dryer

Purple-fleshed sweet potatos (PFSP) were loaded into a laboratory-scale, microwave-assisted spouted bed with a coating of sodium alginate (SA) of 0, 0.2%, 0.4%, 0.8% (w/w) for both steam-blanching pretreated and fresh-cut raw samples. The drying curves, rehydration ratio, and maximum penetrating forces were studied for final products; color changes and anthocyanin level were also taken into consideration. It was concluded that coating processing forms barriers to moisture content, which changes the dielectric properties of PFSP cubes and shortens the drying time; however, coating PFSP cubes with SA did not lead to a porous microstructure in the final products. The final hardness was high and rehydration ratio was low. Steam-blanching was helpful for color and anthocyanin-level retention compared with raw samples. In sum, microwave-assisted spouted bed (MWSB) drying of PFSP cubes is not an ideal processing method, even with coating treatment, but blanching is an approach to obtain products with high anthocyanin level and fine purple color.     

变压吸附(PSA)空分制氧技术进展

论述了 PSA法空分制氧分子筛的开发现状和制氧工艺的进展 ,为 PSA法空分制氧今后的发展提出了研究方向     

变压吸附工艺的研究与进展

论述了国外变压吸附在气体分离研究及技术的最新进展 ,对其工艺流程设计存在的问题进行了阐述 ,并分析了变压吸附工艺的应用及发展方向。