塑料的干燥及其设备

介绍塑料干燥的特点，方法和干燥设备的原理，结构及选用。     

DEVELOPMENT OF NEW DRYING TECHNOLOGY AND EQUIPMENT FOR MEDICAL PLASTERS

Study was made of the trends in drying medical plaster leucomass by means of an organic solvent using different heating methods. Based on the research made, a new drying technology and efficient thermal drying equipment have been developed, which are introduced into industry.     

DRYING TECHNOLOGY IN AGRICULTURE AND FOOD SCIENCE

ABSTRACT

The retentions of alcohol dehydrogenase (ADH) activity during drying and storage were investigated at various temperatures and relative humidities for various carbohydrate solutions. The highest retention of ADH activity after drying was obtained for the mixture of trehalose and methyl-β-cyclodextrin. For a single dried droplet, the effects of humidity on the storage stability of ADH were reversed between the trehalose solution and the blend of trehalose and methyl-β-cyclodextrin. However, the addition of methyl-β-cyclodextrin decreased the residual activity of ADH during storage. The carbohydrate matrix structure after drying might influence mainly the storage stability of ADH encapsulated in the mixed carbohydrate of trehalose and methyl-β-cyclodextrin.     

PET片材挤出设备与工艺

结合实际工作，分原料预处理，熔融挤出，片材成型，牵引收卷四部分介绍了ＰＥＴ片材的挤出设备与加工工艺。     

DRYING KINETICS AND PARTICLE RESIDENCE TIME IN SPRAY DRYING

A unique experimental equipment for extensive trials on the spray drying kinetics and particles residence time involving “in situ” analysis of the properties of continuous and dispersed phases was designed, built, and tested. Advanced experimental techniques (including laser techniques) to determine current parameters of spray drying process (temperature, humidity, moisture content) and current structure of spray (particle size distribution, particle velocities, etc.) were employed. Full scale spray drying tests of baker's yeast and maltodextrin enabled identification of the effect of process parameters on drying kinetics and spray residence time in the tower. Quantitative relationship describing spray drying kinetics as a function of atomization ratio and drying agent temperature were determined. The experimental results proved that spray residence time was controlled by atomization ratio and airflow rate. Drying kinetics in spray drying process is presented for the first time in the literature.     

DRYING KINETICS AND PARTICLE RESIDENCE TIME IN SPRAY DRYING

ABSTRACT

A unique experimental equipment for extensive trials on the spray drying kinetics and particles residence time involving “in situ” analysis of the properties of continuous and dispersed phases was designed, built, and tested. Advanced experimental techniques (including laser techniques) to determine current parameters of spray drying process (temperature, humidity, moisture content) and current structure of spray (particle size distribution, particle velocities, etc.) were employed. Full scale spray drying tests of baker's yeast and maltodextrin enabled identification of the effect of process parameters on drying kinetics and spray residence time in the tower. Quantitative relationship describing spray drying kinetics as a function of atomization ratio and drying agent temperature were determined. The experimental results proved that spray residence time was controlled by atomization ratio and airflow rate. Drying kinetics in spray drying process is presented for the first time in the literature.     

DEVELOPMENT OF NEW DRYING TECHNOLOGY AND EQUIPMENT FOR MEDICAL PLASTERS

Study was made of the trends in drying medical plaster leucomass by means of an organic solvent using different heating methods. Based on the research made, a new drying technology and efficient thermal drying equipment have been developed, which are introduced into industry.     

HEAT AND MASS TRANSFER IN IMPINGEMENT DRYING

ABSTRACT

In industrial drying applications, efficient transfer of heat and mass between a drying medium and the material being dried is very critical for the overall economics of the operation. Impinging jets are therefore widely used for their enhanced tmnsport characteristics, especially for drying of continuous sheets of materials such as paper and textiles. In such applications, a thin sheet of material, as wide as 6m in cross machine direction, speeds at velocities as high as 90 km/hr under high velocity jets emerging from a confining surface parallel to the material surface. Many variables and effects need to k considered for proper design of such impinging jet systems: nozzle geometry and size, nozzle configuration, location of exhaust pons, nozzle-to-surface separation, jet-to-jet separation, cross flow, jet exit velocity and surface motion. For permeable materials, additional enhancement of heat and mass transfer that occur when some of the impinging gas is removed through the material makes this option an atmctive one.

Here, we review the above effects and offer predictive correlations from literature which may be used in the design of high velocity impinging jet systems.     

涤纶细旦POY生产新设备与新工艺

简要介绍了由德国 Neumag公司引进的涤纶超细纤维生产设备的基本特征 ,对利用该设备生产单丝线密度介于 0 .8～ 1.2之间的细旦 POY及其后加工工艺进行了详细的探讨。     

OPTIMAL CONTROL OF THE PRIMARY AND SECONDARY DRYING STAGES OF BULK SOLUTION FREEZE DRYING IN TRAYS

The problem of operating a tray freeze dryer to obtain a desired final bound water content in minimum time is formulated as an optimal control problem with the use of the rigorous unsteady state mathematical model of Sadikoglu and Liapis [9] that has been found to describe satisfactorily the experimental dynamic behavior of the primary and secondary drying stages of bulk solution freeze drying of pharmaceuticals in trays. The heat input to the material being dried and the drying chamber pressure are considered to be control variables. Constraints are placed on the system state variables by the melting and scorch temperatures during primary drying, and by the scorch temperature during secondary drying. Necessary conditions of optimality for both the primary and secondary drying stages are derived and presented, and an approach for constructing the optimal control policies that would minimize the drying times for both the primary and secondary drying stages, is presented. The theoretical approach presented in this work was applied in the freeze drying of skim milk, and significant reductions in the drying times of primary and secondary drying were obtained, when compared with the drying times obtained using the operational policies reported in the literature, by using the optimal control policies constructed from the theory presented in this work. Furthermore, it is shown that the optimal control policy leads to the desired in practice result of having at the end of secondary drying temperature and bound water concentration profiles (in the dried layer) whose gradients are very small. It is also shown that by using the optimal control policy and an excipient capable of increasing the melting temperature without affecting product quality, one can significantly reduce the drying time of the primary drying stage.     

OPTIMAL CONTROL OF THE PRIMARY AND SECONDARY DRYING STAGES OF BULK SOLUTION FREEZE DRYING IN TRAYS

Abstract

The problem of operating a tray freeze dryer to obtain a desired final bound water content in minimum time is formulated as an optimal control problem with the use of the rigorous unsteady state mathematical model of Sadikoglu and Liapis [9] that has been found to describe satisfactorily the experimental dynamic behavior of the primary and secondary drying stages of bulk solution freeze drying of pharmaceuticals in trays. The heat input to the material being dried and the drying chamber pressure are considered to be control variables. Constraints are placed on the system state variables by the melting and scorch temperatures during primary drying, and by the scorch temperature during secondary drying. Necessary conditions of optimality for both the primary and secondary drying stages are derived and presented, and an approach for constructing the optimal control policies that would minimize the drying times for both the primary and secondary drying stages, is presented. The theoretical approach presented in this work was applied in the freeze drying of skim milk, and significant reductions in the drying times of primary and secondary drying were obtained, when compared with the drying times obtained using the operational policies reported in the literature, by using the optimal control policies constructed from the theory presented in this work. Furthermore, it is shown that the optimal control policy leads to the desired in practice result of having at the end of secondary drying temperature and bound water concentration profiles (in the dried layer) whose gradients are very small. It is also shown that by using the optimal control policy and an excipient capable of increasing the melting temperature without affecting product quality, one can significantly reduce the drying time of the primary drying stage.     

DRYING OF CARROTS IN A FLUIDIZED BED. I. EFFECTS OF DRYING CONDITIONS AND MODELLING

Drying curves were determined in a mechanically agitated fluidized bed dryer, at temperatures between 70°C and 160°C, air velocities between 1.1 m/s and 2.2 m/s and stirring rates between 30 rpm and 70 rpm for batch drying of 3 kg lots of carrot slices, measuring the moisture content and shrinking of the particles in time. This was complemented by a study of the rate and degree of swelling of dried carrot particles in water between 20 and 75°C. Drying kinetics were modeled by Fick's second law, for which an optimal agreement with the experimental data was obtained when the effective diffusivity (D_e) was determined by a correlation based on the air velocity (v), the air temperature (T) and the dimensional moisture content of the carrot particles (X/X_o). Loss of carotenes is minimized when dehydration is carried out at about 130°C with a drying time below 12 min.     

DRYING OF CARROTS IN A FLUIDIZED BED. I. EFFECTS OF DRYING CONDITIONS AND MODELLING

ABSTRACT

Drying curves were determined in a mechanically agitated fluidized bed dryer, at temperatures between 70°C and 160°C, air velocities between 1.1 m/s and 2.2 m/s and stirring rates between 30 rpm and 70 rpm for batch drying of 3 kg lots of carrot slices, measuring the moisture content and shrinking of the particles in time. This was complemented by a study of the rate and degree of swelling of dried carrot particles in water between 20 and 75°C. Drying kinetics were modeled by Fick's second law, for which an optimal agreement with the experimental data was obtained when the effective diffusivity (D _e ) was determined by a correlation based on the air velocity (v), the air temperature (T) and the dimensional moisture content of the carrot particles (X/X _o ). Loss of carotenes is minimized when dehydration is carried out at about 130°C with a drying time below 12 min.     

THE USE OF AUXILIARIES IN DRYING TECHNOLOGY

ABSTRACT

In drying technology, the quality characteristics of the solid (its dispersibility, attrition resistance, etc.) are selectively adjusted by the use of auxiliaries. Typical auxiliaries include granulation aids for spray granulation and flow aids for solids with poor flow properties. Such auxiliaries are classified in the first part of this paper according to their mechanisms of action (eg. their adhesive effect, dispersion effect, bursting effect).

In the second part of the paper, an example will be used to illustrate the effect of auxiliaries. The effect of a binder (salt or polymer) on the drying of free-floating suspended droplets is investigated. The fracture resistance of the particles and the required drying time increase as the proportion of dissolved components increases.     

双色塑料异型材共挤工艺及设备

以螺丝刀双色透明塑料柄为例,介绍双色塑料异型材共挤工艺、设备及模具,成功地利用国产设备生产出合格产品。     

FREEZE DRYING WORLD UPDATE IN DRYING TECHNOLOGY

Spectral Sciences, Inc. is developing a multipoint humidity monitor for drying application in the pulp and paper industry. The humidity is measured by monitoring near-infrared optical absorption in the process stream atmosphere. An array of sensor heads distributed throughout the plant is linked by fiber optic cables to a single source/readout device which can be located in a control room hundreds of meters away. The sensor heads and cables are modular. allowing for raid installation and reconfiguration of a distributed sensor system in process control applications. The method used for quantifying the optical absorption provides substantial stability, accuracy, and signal processing advantages over standard wavelength scanning or band pass techniques. The laser diode's output wavelength is actively locked to the center of a water absorption line, thereby providing a constant monitor of water vapor concentration which is insensitive to all other species in the process stream. Wavelength modulation and second harmonic detection techniques are used to quantify the water vapor concentration. A simultaneous temperature measurement then permits an output of the absolute humidity or humidity ratio for process monitoring or control     

DRYING RESEARCH AND DEVELOPMENT IN THE GERMAN DEMOCRATIC REPUBLIC

A summary is given of papers published in the GDR in the field of drying including drying theory, dryer models, sensor development, and analysis of industrial dryers.

Today in the GDR more than 10 000 dryers using 280 000 TJ/a are operated. So drying research and development mainly is driven by practical considerations, but there are pure theoretical approaches to dryer modelling and development of sophisticated drying sensors of general intereet too.