Effect of Solubles on Disintegration of Distiller's Spent Grain Compacts During Superheated Steam Drying

Drying of densified spent grain in superheated steam (SS) may cause breakage and disintegration of the product in the initial stage of SS drying. The present work investigated the effect of solubles (0, 10, 30, 50, and 70% solubles) on the percentage change in length, diameter, volume; hardness; and the asymptotic modulus (E_A) of the cylindrical compacts during SS drying. An increase in dimensions along with a decrease in hardness and E_A of the compact was observed immediately after exposing it to SS. We observed a 47% increase in length and 12% increase in diameter for compacts having 0% solubles during the first five seconds of SS drying; however, when the soluble content increased to 70%, the percentage increase in length and diameter became 12 and 2%, respectively. Also, with an increase in the amount of solubles in the compact, a considerable increase in the hardness and E_A of the compact was observed. The study also aimed to find suitable explanatory variables for predicting the hardness and E_A of the compact using a stepwise forward regression method.     

Drying Characteristics In Superheated Steam Drying at Reduced Pressure

The superheated steam drying at reduced pressure is performed, and the effects of operational conditions such as drying pressure and temperature on the drying characteristics are examined. In order to obtain the basic guideline for the design of the superheated steam dryer at reduced pressure, the heat flux to sample was calculated and the optimal conditions were estimated.

After the sample temperature reached at the boiling point, the temperature was maintained at the boiling point and the drying rate became almost constant. Once the sample was dried out, the temperature suddenly increased up to the drying gas temperature. From the calculation of combined heat flux, the followings were found. The contribution of radiative heat transfer to the combined heat flux became larger as the drying pressure was lower. The combined heat flux had a maximum value against the drying pressure. The optimum drying pressure, which gave the maximum heat flux, became lower as the drying gas temperature decreased. It was found that reduction in the drying pressure is effective for the enhancement in drying performance.     

Drying Characteristics In Superheated Steam Drying at Reduced Pressure

Abstract

The superheated steam drying at reduced pressure is performed, and the effects of operational conditions such as drying pressure and temperature on the drying characteristics are examined. In order to obtain the basic guideline for the design of the superheated steam dryer at reduced pressure, the heat flux to sample was calculated and the optimal conditions were estimated.

After the sample temperature reached at the boiling point, the temperature was maintained at the boiling point and the drying rate became almost constant. Once the sample was dried out, the temperature suddenly increased up to the drying gas temperature. From the calculation of combined heat flux, the followings were found. The contribution of radiative heat transfer to the combined heat flux became larger as the drying pressure was lower. The combined heat flux had a maximum value against the drying pressure. The optimum drying pressure, which gave the maximum heat flux, became lower as the drying gas temperature decreased. It was found that reduction in the drying pressure is effective for the enhancement in drying performance.     

Drying Foodstuffs with Superheated Steam

Abstract

A thin-layer superheated steam drier was constructed with the objective of determining the drying characteristics, drying rates, and the effect of superheated steam on product quality in thin-layers. Results from superheated steam drying experiments with sugar-beet pulp, potatoes, Asian noodles, and spent grains indicate that drying times and rates increase with increasing steam temperature. For sugar-beet pulp it was also found that these changes were more significant than increases seen by hot-air drying under the same conditions and that drying rates were not affected by velocity for hot air but were increased for superheated steam. When quality aspects were examined, superheated steam dried Asian noodles saw both beneficial changes to recovery, adhesiveness, and gumminess while parameters of maximum cutting stress, resistance to compression, and surface firmness saw deleterious effects. Spent grains saw high levels of starch gelatinization and retention of fibre content.

     

Enhancement of Properties of Diverse Grades of Paper by Superheated Steam Drying

Abstract:

Studies from this laboratory have documented significant changes in properties when paper is dried in superheated steam rather than, as in all current processes, in air. Extending these investigations to additional important pulp types, recycled pulps, and filled papers, and using commercial furnishes from mills, has identified further grades of paper for which drying in superheated steam enhances key properties. For bleached chemithermomechanical pulps and blends with kraft pulp, as used for tissue and toweling, strong paper resulted with 10% higher bulk. Linerboard from 100% recycled old corrugated containers (OCC) is obtained with various strength properties increased by up to 21% with no densification, actually a 4% increase in bulk. Linerboard from high-yield (55–67%) virgin kraft pulps shows a 23 to 37% increase in strength and toughness. Filled papers containing 0–10% clay can be produced with the same brightness but 23% higher tensile index when dried in superheated steam.     

Drying Kinetics of Instant Asian Noodles Processed in Superheated Steam

The objective for this work was to develop a novel technique for creating instant noodles by determining the drying kinetics of noodles undergoing simultaneous drying and processing using superheated steam. The mathematical model of moisture ratio was differentiated to determine the drying rates of noodles during processing. There was a constant rate drying period for all temperatures at a steam velocity of 1.5 m/s but there was no constant rate drying period at a steam velocity of 0.5 m/s. The constant rate drying period suggested by measurement of internal noodle temperature is much longer and well defined for all processing conditions than from the drying curves. The constant drying rate period, was nearly 200 s at 110°C but decreased to 50 s at 150°C. Equilibrium moisture content isobars were determined from mass changes during superheated steam processing. It was determined that isotherm equations for equilibrium moisture content in hot air systems may be utilized to model isobars in superheated steam systems.     

Drying of Fish Press-Cake with Superheated Steam in a Pilot Plant Impingement System

Drying tests for pine sawdust and mackerel press-cake with hot air and with superheated steam were carried out in a pilot impingement cylindrical dryer. Wet particles move axially along the dryer, adjusting the inclination of the equipment, whereas hot gases circulate in cross-flow against the particles, forming a corotational impingement front. Feed rate and residence time of solids were studied experimentally as a function of dryer inclination for hot air and superheated steam as drying media. Drying rates and heat and mass transfer coefficients were found to increase at shorter residence times and higher gas temperatures. Dried mackerel press-cake with superheated steam resulted in a product with high moisture removal and very low losses of the valuable omega-3 fatty acids.     

Evaluation of Three Semi-empirical Models for Superheated Steam Vacuum Drying of Timbers

Superheated steam drying at sub-atmospheric pressure (SSV) has been successfully employed in Europe and Asia for drying some types of timbers, showing that drying time could be reduced by 50% with respect to conventional drying without significant losses in the quality of the final product. This reduction is the consequence of a different heat and mass transfer control mechanism. Since SSV drying is carried out in absence of gaseous air, diffusion of the generated vapor is not a limiting factor and drying rate becomes more dependent on heat transference. Therefore, classical interpretation of timber drying as a process based on moisture migration control is not applicable to SSV. This work is targeting the development and validation of a simplified semi-empirical model for SSV drying of timbers. Mathematical representation of the proposed model is uncomplicated and straightforward to apply, and the comparison between model predicted and experimental data showed a high degree of agreement under variable drying conditions.     

Evaluation of Three Semi-empirical Models for Superheated Steam Vacuum Drying of Timbers

Abstract

Superheated steam drying at sub-atmospheric pressure (SSV) has been successfully employed in Europe and Asia for drying some types of timbers, showing that drying time could be reduced by 50% with respect to conventional drying without significant losses in the quality of the final product. This reduction is the consequence of a different heat and mass transfer control mechanism. Since SSV drying is carried out in absence of gaseous air, diffusion of the generated vapor is not a limiting factor and drying rate becomes more dependent on heat transference. Therefore, classical interpretation of timber drying as a process based on moisture migration control is not applicable to SSV. This work is targeting the development and validation of a simplified semi-empirical model for SSV drying of timbers. Mathematical representation of the proposed model is uncomplicated and straightforward to apply, and the comparison between model predicted and experimental data showed a high degree of agreement under variable drying conditions.     

Use of Superheated Steam Drying to Increase Strength and Bulk of Papers Produced from Diverse Commercial Furnishes

ABSTRACT

Studies from this laboratory have documented significant changes in properties when paper is dried in superheated steam rather than, as in all current processes, in air. Extending these investigations to additional important pulp types, to recycled pulps and to filled papers, using commercial furnishes from mills, has identified further grades of paper for which drying in superheated steam enhances key properties. For bleached chemithermomechanical pulps and blends with kraft pulp as used for tissue and toweling, strong paper resulted, with 10% higher bulk. Linerboard from 100% recycled old corrugated containers (OCC) is obtained with various strength properties increased by up to 21% with no densification, actually a 4% increase in bulk. Linerboard from high-yield (55–67%) virgin kraft pulps show 23 to 37% increase in strength and toughness. Filled papers containing 0–10% clay can be produced with the same brightness but about 23% higher tensile index when dried in superheated steam.     

Use of Superheated Steam Drying to Increase Strength and Bulk of Papers Produced from Diverse Commercial Furnishes

Studies from this laboratory have documented significant changes in properties when paper is dried in superheated steam rather than, as in all current processes, in air. Extending these investigations to additional important pulp types, to recycled pulps and to filled papers, using commercial furnishes from mills, has identified further grades of paper for which drying in superheated steam enhances key properties. For bleached chemithermomechanical pulps and blends with kraft pulp as used for tissue and toweling, strong paper resulted, with 10% higher bulk. Linerboard from 100% recycled old corrugated containers (OCC) is obtained with various strength properties increased by up to 21% with no densification, actually a 4% increase in bulk. Linerboard from high-yield (55-67%) virgin kraft pulps show 23 to 37% increase in strength and toughness. Filled papers containing 0-10% clay can be produced with the same brightness but about 23% higher tensile index when dried in superheated steam.     

Effect of Fluidizing Particle on Drying Characteristics of Porous Materials in Superheated Steam Fluidized Bed under Reduced Pressure

The hygroscopic porous particle was used as the fluidizing particle for the superheated steam fluidized bed drying under reduced pressure. A relatively large material was immersed in the fluidized bed as the drying sample. The drying characteristics of the sample were examined experimentally and the results were compared with those in the case of inert particle fluidized bed.

The water transfer from the sample to the fluidizing particle bed in the case of hygroscopic porous particle facilitated the drying regardless of pressure and temperature in the drying chamber. The increment degree of the sample temperature at the earlier period of drying was smaller in the case of hygroscopic porous particle than in the case of inert particle, and the phenomenon was more remarkable in the case of superheated steam than in the case of hot air.     

Status and Developments of Drying Low Rank Coal with Superheated Steam in China

Superheated steam drying (SSD) of low rank coal (LRC) is applied to improve the heating value and thermal efficiency and to reduce greenhouse gas emissions and the danger of spontaneous combustion. It is essential to understand the fundamental aspects of drying LRC with superheated steam supported by funds in China and the development of clean coal technology. It is also important to promote the level of scientific technology relevant to safe energy strategies. The background of SSD based on China's unique energy structure and coal production situation are presented in this article. A comprehensive overview on progress and mechanisms of SSD is provided, including the status of drying technology supported by funds in China, distribution of project field and important research institutions, physical and chemical structure of water in coal, heat and mass transfer processes, mathematical models, and some results for wood, food, hot gas, etc., with particular reference to SSD in drying of LRC in China. There are still many challenges in the application of SSD of LRC in very large-scale power plants, drying equipment, and control technology. Advanced SSD sponsored by the fund project in China shows important significance to energy savings and reducing greenhouse gas emissions.     

Characteristics of Rice Dried in Superheated-Steam Fluidized-Bed

Characteristic properties of rice in a superheated-steam fluidized-bed dryer have been investigated using RVA, DSC, and SEM. The experimental results have shown that the reduction in moisture content from 41-42.5 to 25% d.b. using steam temperatures of 150-170°C was initially linear with drying time followed by the exponential decay when the moisture content was below 25% d.b. During the latter period, the water transport was controlled by the internal diffusion. Condensation of steam, along with the use of high temperature, enabled the development of gel layer as obvious from SEM. The formed gel layer caused the very low effective diffusivity when compared with the case of no gel formation in paddy kernel. The pasting properties and DSC measurements have shown that paddy dried at a higher temperature and a thinner bed depth provided a greater extent of gelatinization during the drying time, the first factor showing a profound effect. Kinetics of gelatinization is reasonably described by the zero-order reaction. For the paddy quality, the head rice yield was 70% higher than the reference value and color of white rice became yellow and low luminous after reducing moisture content to 18% d.b. The percentage of white belly was less than 1.5%.     

Effect of Time-Dependent Humidity Profiles from Air to Superheated Steam on Drying of a Wetted Starch Sphere

The effects of air humidity when drying with superheated steam (SHS) were examined considering displacement by SHS. A wetted raw starch sphere (ball) was used as the model material. It was found that the humidity profile strongly affects the mass change and properties of the products. The material became porous when it was dried with pure SHS from start to finish, which differs both from products dried with high-humidity air alone, and from products dried with air followed by SHS within a few minutes. A prediction method for adiabatic saturation temperature over a wide range of humidity is also proposed.     

Optimum Processing Conditions of Instant Asian Noodles in Superheated Steam

There is little information in the literature about what constitutes an acceptable instant noodle. To ascertain the commercial acceptability of superheated steam-processed instant noodles, a sampling of commercial products was undertaken. Noodles processed at a steam velocity of 1.5 m/s and at 125°C for 200 s, 130°C for 167 s, 135°C for 150 s, 140°C for 133 s, 150°C for 100 s, and a steam velocity of 1.0 m/s and 150°C for 133 s had acceptable color values (L* values greater than 63, a* values less than 0, and b* values above 20) and moisture at or below the safe storage limit. Superheated steam processed noodles were more firm and chewy than the commercial noodles. Adhesiveness, springiness, and resilience were generally the same for all noodle products. Breaking strength of superheated steam processed noodles was in the same range as the fried control and commercial products. Values varied from a low of 1121 ± 194 g/mm² for noodles processed at 150°C, 1.5 m/s, for 100 s to a high of 1575 ± 329 g/mm² for noodles processed at 140°C, 1.5 m/s, for 133 s. Starch gelatinization was greatest in the fried control samples and the least in the superheated steam processed samples (approximately 9% less).     

Computational Study of Impingement Jet Drying of Seeds Using Superheated Steam Based on Kinetic Theory of Granular Flow

A Eulerian model including the kinetic theory of granular flow (KTGF) and mass transfer in the period of saturated wet surface has been developed to simulate continuous drying of particulate solids using superheated steam in a radial impingement jet system. When applying this type of drying processes, the preliminary results obtained show good predictive ability of the Eulerian modeling based on KTGF. It is concluded that the present study and other works of modeling can be used to study the dynamics and control of this drying process and thus would facilitate the equipment design and scaling.     

过热蒸汽干燥技术的研究进展

过热蒸汽干燥技术具有安全、节能、环保等诸多优点,越来越受到广泛关注。对过热蒸汽干燥技术进行了简介,分析了其优缺点。总结了过热蒸汽干燥的理论研究进展,并对过热蒸汽干燥技术在食品、木材、纸张、污泥和和褐煤等物料的应用现状进行了综合评述。总而言之,过热蒸汽干燥技术是一种先进的干燥技术,具有广阔的应用前景。     

Modeling Microwave Vacuum Drying Kinetics and Moisture Diffusivity of Carrot Slices

Carrot slices of 3.5 mm thickness were dried in a laboratory microwave vacuum dryer at five different microwave power density levels of 2, 4.66, 7.33, 10, and 12.66 W/g and at three vacuum chamber pressure levels of 6.66, 19.98, and 33.3 kPa to 4-6% d.b. moisture content. Inside the dryer the sample holding plate was rotated with the speed of 4 rpm for uniform microwaves application. The drying rates were increased with the increase in microwave power density at all pressure levels and the Page model was found to be the most suitable model to predict the drying behavior of carrot slices at all process conditions. The Page model drying rate constant (k, min^-1) showed high correlation with microwave power density at constant pressure by a power law equation and showed a logarithmic relationship with the microwave power density and pressure. Similar to the drying rate constant, the average moisture diffusivity at constant pressure was found to be function of microwave power density by power law equation as well as was also dependent on the power density and pressure by a logarithmic relationship.     

Moisture Diffusivity in Food and Biological Materials

The spatial distributions of water content and temperature inside moist food or biological materials (native or manufactured) during drying are important in interpretation and prediction of quality changes. The dynamics of drying in modern devices is not simple—for instance, the process of intermittent drying—thus, a liquid diffusion model is expected to be the simplest and hopefully the very effective. In this article, some controversial aspects of the concept of the effective Fickian liquid moisture diffusivity are described and discussed. These discussions are intended to stimulate more interest in working toward a better rationalization of the liquid diffusion concept. It is suggested that such a parameter may even be called a “liquid depletion coefficient” instead to avoid confusion at the fundamental level. An improved alternative model from the effective liquid diffusion model is possible and some new ideas have been explored.