THIN-LAYER DRYING BEHAVIOUR OF VEGETABLE WASTES FROM WHOLESALE MARKET

ABSTRACT

The thin-layer drying behaviour of vegetable wastes (as a mix of lettuce and cauliflower leaves) from wholesale market for a temperature range of 50-150^°C was determined. Drying of this material was found to take part only in the falling-rate period. The experimental data were fitted to the simple exponential model and the Page model. Both models have good prediction capability, Effective diffusion coefficient varied from 6.03*10^-9to 3.15*10^-8m3/s with an activation energy of diffusion of 19.82 kJ/mol. The temperature dependence of the effective diffusion coefficient was expressed by an Arrhenius-type relationship.     

FRUIT AND VEGETABLE POWDERS PRODUCTION TECHNOLOGY ON THE BASES OF SPRAY AND CONVECTIVE DRYING METHODS

ABSTRACT

The peculiarities of fruit and vegetable powders production technology based on spray & convective drying methods are shown.

The experimental data related to the drying kinetics of apple juice droplets as well as the production flow diagrams and the performance of a spray dryer intended for the treatment of hygroscopic pasty products are presented.     

KINETICS OF DRYING AND HYDRATION OF THE SCLEROGLUCAN POLYMER. A COMPARATIVE STUDY OF TWO CONVENTIONAL DRYING METHODS WITH A NEW DRYING PROCESS: DEHYDRATION BY SUCCESSIVE PRESSURE DROPS

The scleroglucan polysaccharides are mainly used in the petroleum industry but also have applications in the food, cosmetics and pharmaceutical industries. For most of these applications, the dissolution rate of hydrocolloïds is an important qualitative criterion. In this study, the kinetics of scleroglucan drying was investigated with the aim of improving the hydration capacity and the dissolution rate of the polymer. Two conventional methods (hot air and vacuum drying) were compared with a new drying process: dehydration by successive pressure drops, or DDS (Déshydratation par Détentes Successives). This process involves processing the polymer in a series of cycles that consist in placing it in desiccated air then subjecting it to an instantaneous (200 msec) decompression to a vacuum (50 mbar). Two parameters were varied: pressure (P: 4.5–7.5 bars) and processing time at this pressure (t = 5–10 sec). During each decompression, a certain quantity of water is eliminated by vaporisation, improving the diffusion of water by capillary action during hydration. Our results showed that processing time at high-pressure (P) has a significant effect on the drying kinetics. In contrast, processing pressure was not a critical parameter. The results showed that hot air and vacuum drying of scleroglucan are less effective techniques.     

植物单宁的应用及研究进展

植物单宁是自然界广泛分布的一类天然产物，具有结构类型的多样性和生物活性的广谱性，其在医药、食品、农业、材料、化工等多学科领域得到广泛的应用，已引起国内外研究者的普遍关注。本文就植物单宁近年来的研究与应用进展予以评述，旨在为新的活性成分研究及其资源的高效利用提供依据。     

植物单宁的应用及研究进展

植物单宁是自然界广泛分布的一类天然产物,具有结构类型的多样性和生物活性的广谱性,其在医药、食品、农业、材料、化工等多学科领域得到广泛的应用,已引起国内外研究者的普遍关注。本文就植物单宁近年来的研究与应用进展予以评述,旨在为新的活性成分研究及其资源的高效利用提供依据。     

多孔介质干燥机理在褐煤热力脱水中的应用

我国揭煤资源丰富,但是由于其水分高,导致了揭煤燃烧发电效率低下,不宜远距离运输.通过热力干燥可降低揭煤的水分含量,有利于揭煤运输和贮存,提高锅炉燃烧效率.从揭煤结构出发,提出其热力干燥过程的模型可将之视为多孔介质.分析了多孔介质的干燥过程特点,阐述了目前国内外的多孔介质干燥机理,总结了相关的多孔介质干燥模型,为多孔介质褐煤热力脱水模型化提供理论支持.     

微波辅助干燥技术的应用进展

微波辅助干燥是一种比微波干燥更有优势、应用前景更广的干燥技术，它结合了微波干燥和传统干燥技术的优点。本文主要阐述了微波辅助干燥的原理、特点以及在国内外的研究和应用现状。同时对该技术在陶瓷坯体干燥中的应用进行了分析。     

A CONTRIBUTION TO THE CHARACTERISTIC DRYING CURVE CONCEPT: APPLICATION TO THE DRYING OF PLASTER

ABSTRACT

Implicit equations relating the dimensionless drying rate to the reduced moisture content for porous non-hygroscopic slabs have been determined. This study is based on the receding evaporative front model and on the assumption of a parabolic moisture content profile in the diffusional zone of the wet region. The characteristic functions derived depend on the relative position of the receding evaporative front. Two cases were considered : the drying of thick products and the drying of thin products. It has been observed that the relationships corresponding to the C.D.C obtained for thick products depend on the initial. On the other hand, it was observed that experimental CDC. of plaster slabs determined for many thicknesses and various plaster textures depend strongly on these two parameters. Furthermore, the model presented gives good results only for thin products.     

虎杖白藜芦醇提取物的干燥方法研究

通过对虎杖白藜芦醇的提取物干燥方法的比较研究 ,筛选出真空冷冻干燥为虎杖白藜芦醇的最佳干燥方法 ,其回收率达 97.2 8%。     

DRYING KINETICS FOR SOME FRUITS: PREDICTING OF POROSITY AND COLOR DURING DEHYDRATION.

ABSTRACT

Drying kinetics of four fruits (prune, quince, fig and strawberry) were studied by using a simple mass transfer mathematical model involving a characteristic parameter (K) as a function of process variables. The model was tested with data produced in a laboratory air dryer, using non-linear regression analysis. The investigation involved three values of sample thickness (5, 10, 15mm) and three different air temperatures (50, 60, 70?°C).

The parameters of the model were found to be greatly affected by sample thickness and air temperature. The effect of moisture content on the porosity of three fruits (namely avocado, prune and strawberry) was also investigated. A simple mathematical model was used to correlate porosity with moisture content. It was found that porosity increased with decreasing moisture content.

Samples of three fruits (avocado, prune and strawberry) were investigated to estimate color changes during conventional drying at 70?°C. A first order kinetic model was fitted to experimental data with great success. It is found that the color of avocado and strawberry change while the color of prune remains the same.

Furthermore, the water sorption isotherms of three fruits (avocado, prune and strawberry) at 25° temperature were determined experimentally and the parameters at the GAB equation were evaluated by means of non-linear regression analysis. The use of the above equation produced a very good fit.     

喷雾闪蒸干燥在重质微细碳酸钙中的应用

介绍了重质微细碳酸钙的用途及生产方法,阐述了新技术喷雾闪蒸干燥的干燥原理、特点、工艺流程、设备及重质微细碳酸钙的产品质量指标,指明喷雾闪蒸干燥传热传质效果好,干燥速度快,自动化程度高,产品质量优,发展前景广阔。     

EFFECTS OF VARIOUS TREATMENTS ON THE DRYING KINETICS OF Muscatel GRAPES

ABSTRACT

The drying kinetics of Muscatel grapes at 60°C and a relative air humidity of 22% were determined after various pretreatments had been applied to the grapes. The pretreatment parameters varied were the chemical agent (potassium carbonate solution with or without olive oil, or sodium hydroxide solution); the duration of pretreatment; and the temperature and concentration of the solution. A 3 minute pretreatment with an aqueous solution of K₂CO₃ and olive oil at 60°C reduced drying time from about 80 h to 20 h. Optimal drying load corresponded to a single layer of almost close-packed grapes on each tray. The experimental drying kinetics were satisfactorily reproduced by a model in which both grape size and the effective coefficient of diffusion are functions of moisture content.     

CHANGE IN VIABILITY OF MAIZE DURING HIGH-TEMPERATURE DRYING

Germination and moisture content loss data were collected of maize with a moisture content ranging from 15 to 32% (w.b.), an air temperature from 40 to 75°C, and an exposure time from 0.5 to 180 minutes.

A germination-retention model was developed based on the normally distributed death-rate theory (NDD). The NDD model was combined with a concurrent-flow (CCF) dryer model, and tested against viability data of maize dried in a commercial two-stage CCF dryer. Acceptable agreement between the predicted and experimental viabilities was obtained.

The effect of the CCF dryer design, and of several operating parameters, on the loss of maize-seed viability was analyzed. Simulation with the NDD-CCF dryer model shows that high quality seed can be produced by drying at air temperatures well above 100°C.     

干燥方法对钛柱撑蒙脱石结构的影响

采用TiCl4水解法制备钛柱化剂,与蒙脱石离子交换后得到钛柱撑蒙脱石(Ti-pillared montmorillonite,Ti-PILM)。对制备的Ti-PILM采用室温风干(air drying,AD)、40℃烘干(common drying,CD)、乙醇清洗后风干(ethanol extraction drying,EAD)、室温条件下真空干燥(vacuum drying,VD)等方法干燥,并在不同温度下热处理。用XRD,IR,DTA-TG,N2等温吸附一脱附等技术对Ti-PlLM进行结构表征。结果表明：干燥方法对Ti-PILM的结构及热稳定性有较大的影响。采用AD和EAD干燥方法可以得到2．7nm左右大晶面间距Ti-PILM,且AD干燥的样品在500℃下有很好的稳定性,比表面达285．7m^2／g,具有介孔孔径且孔径分布窄。而经CD和VD方法干燥焙烧后．蒙脱石层间钛柱坍塌,导致Ti-PILM层状结构破坏,影响材料的热稳定性。     

EFFECTS OF HEATING METHODS ON VACUUM FREEZE DRYING

ABSTRACT

The heat and mass transfer during freeze drying of raw beef by different heating methods is studied theoretically and experimentally. The difference between radiant heating and microwave heating in freeze drying process has been analyzed. The results obtained are important for the selection of the heating methods in practical freeze dryers.     

EVALUATION OF DIFFERENT METHODS OF DRYING ON THE QUALITY OF OYSTER MUSHROOM (Pleurotus sp)

ABSTRACT

Mushrooms are extremely perishable and have a short shelf life period. To increase the post harvest lives, different methods of drying viz., sun diving, fluidized bed drying and thin layer drying with potassium metabisulphite (KMS) and blanching was done. The quality of mushroom dried in fluidized bed condition at 50°C for 80-120 minutes with 0.5 KMS was found to be superior to other drying methods. Rehydration ratio was also maximum in KMS treated mushroom and no significant difference at higher concentration. The treatment with KMS and blanching reduces the nutritive quality but improves the colour of the mushrooms when compared with sun dried samples. Storage of mushrooms after treatment with KMS at higher concentration (1.5%) reduces the microbial spoilage.     

中央供料和干燥系统在注塑行业中的应用

介绍注塑企业生产中的辅助设备一中央供料、干燥系统及其组成，如中央控制器、除湿干燥机、真空泵、上料机和色母计量机等。指出将中央供料、干燥系统应用于塑料加工业，可改善塑料制品质量，提高生产效率，节省人力和占地面积。对注塑企业的厂房规划和中央供料、干燥系统的设计提出一些建议。     

喷雾干燥在环保领域中的应用

环境保护是我国的基本国策之一,近年来呈蓬勃发展之势。本文主要介绍了喷雾干燥在半干法烟气脱硫、味精废水综合利用、造纸黑液处理等环保领域内的广泛应用。     

国产分子筛干燥技术的应用

介绍两套国产分子筛干燥装置的工艺流程和自检系统,并提出改进措施。     

喷雾干燥在环保领域中的应用

环境保护是我国的基本国策之一,近年来呈蓬勃发展之势.本文主要介绍了喷雾干燥在半干法烟气脱硫、味精废水综合利用、造纸黑液处理等环保领域内的广泛应用.