Microwave Drying : Effects on Paper Properties

Kumar, Pawan; Mujumdar, Arun S.; Koran, Z.

doi:10.1080/07373939008959936

Cited by 6 publications

(5 citation statements)

References 1 publication

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“…Drying is one of the highest energy-consuming and most expensive processes in the pharmaceutical industry. Microwave irradiation has attracted much attention in different fields dedicated to studying benefits and drawbacks of microwaves as an unconventional source of heat − and has become a popular heating technique for various processes including synthesis, solution concentration and drying of food, − fruits, chemicals, , agricultural products, polymers, ceramics, pulp and paper, textiles, in mineral processing as well as in wood processing industries . Although drying of pharmaceutical powders with microwave heating has been shown to increase drying rates and product stabilities during the drying process, , application in the pharmaceutical industry is still limited.…”

Section: Introductionmentioning

confidence: 99%

A Facile Microwave-Mediated Drying Process of Thermally Unstable / Labile Products

Pinchukova

Voloshko

Shyshkin

et al. 2010

Org. Process Res. Dev.

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The drying behavior of (S)-N-acetylindoline-2-carboxylic acid, precipitated (1a, 17 wt %) and nonprecipitated (1b, 5 wt %), and N-acetyl-(S)-phenylalanine ((S)-2-acetamido-3-phenylpropanoic acid, 2), both pharmaceutical intermediates, and of cocarboxylase hydrochloride (thiamine pyrophosphate, 3), a coenzyme, a bioactive form of vitamin B 1 , being a thermolabile substance, has been determined in straightforward drying setups. The method of supplying energy to the system had a profound influence on the drying rate and on the internal temperature of the samples during drying. The drying time of (S)-N-acetylindoline-2-carboxylic acid (1b) with the low moisture content (5 wt %) could be reduced by a factor 4 using microwave irradiation instead of conventional heating, while keeping the sample temperature under 35 °C. N-Acetyl-(S)-phenylalanine(2) with a higher moisture content (22 wt %) demonstrated a decrease in drying time by a factor 2.5 to 4 depending on the applied microwave powers. A reduction in drying time of the precipitated (S)-N-acetylindoline-2-carboxylic acid (1a, 17 wt % moisture) by a factor 2 was demonstrated for drying at 150 W of microwave irradiation instead of using a water bath at 70 °C. A dramatically shorter drying time by a factor 10 was found for cocarboxylase hydrochloride (3, 15 wt % water) on lab-scale which could be reproduced on pilot-plant scale. To achieve with conventional heating similar drying times as under microwave irradiation for the four examples, extremely high energy inputs should be applied, necessitating extremely high temperature differences between the heating source and the sample. The results reveal that microwave irradiation is less energy-consuming and is particularly useful for effective drying of thermally unstable materials in short periods of time.

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Section: Introductionmentioning

confidence: 99%

A Facile Microwave-Mediated Drying Process of Thermally Unstable / Labile Products

Pinchukova

Voloshko

Shyshkin

et al. 2010

Org. Process Res. Dev.

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“…In this method, dehydration starts from product surface through convective heat transfer. The heat is then transferred inside the product through conduction (Kumar, Mujumdar, & Koran, ; Mujumdar, ). Since biological materials have low thermal conductivity, heat transfer in hot air flow method, due to strong dependence on conduction, faces some drawbacks (Akosman, ; Kocabiyik & Tezer, ).…”

Section: Introductionmentioning

confidence: 99%

Energy economy and kinetic investigation of sugar cube dehydration using microwave supplemented with thermal imaging

Hazervazifeh

Nikbakht

Moghaddam

et al. 2017

J Food Process Preserv

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High energy and time consumption in the dehydration of sugar cubes hinder its industrial commercialization. Microwave is employed to overcome the drawbacks of hot air drying. For microwave power 880 W, pulsing ratios 1.5, 2.5, 4.5, and 10 were applied to prevent thermal runaway and probable melting and caramelization. In order to monitor the spatial thermal variation of sugar cubes, thermal imaging was performed. Maximum effective diffusivity was measured to be 9.0905 × 10−8 m2/s, which belongs to pulsing ratio 2.5 and is 16 times larger than when hot air is used. Furthermore, the minimum specific energy consumption and minimum energy cost were calculated to be 314,192.45 J/g H2O and 0.179 × 10−3 $/g, respectively, which found in pulsing ratio 2.5. Technically speaking, regarding the critical temperatures of sugar cubes and energy economy, the study suggests pulsing ratio 2.5 for sugar cube dehydration using microwave power 880 W. Practical applications Sugar cube production line consists of several unit operations. Dehydration is the last operation commonly known as the major concern in industry due to high level of quality issues and energy aspects. At present, hot air drying is the common method in plants and is highly dependent on thermal conductivity of cubes which is very low. This method exerts notable costs to producers. Microwave technology as a solution is investigated in this research. Influencing parameters such as diffusivity, energy consumption, economy of energy, and kinetics are experimentally assessed and described. Based on the results obtained, the industry would have a full perception of using microwave radiation as a substitute for conventional hot air drying in order to resolve the challenges of energy, time, and costs.

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“…-1455 and radiation phenomena through the external materials surface, in presence of thermal gradients. However, microwave energy is transferred to the wood material through molecular interactions with electromagnetic field via conversions of electromagnetic energy into thermal energy [1][2][3].…”

Section: Introductionmentioning

confidence: 99%

Computational analysis of heat and mass transfer during microwave drying of timber

2016

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The need for improvement in engineering design and process optimization for microwave drying of wood has stimulated the development of computer simulation techniques to predict temperature and moisture history and distribution wood sample. A 3-D comprehensive heat and mass transfer model was developed to simulate the free liquid, vapor, and bound water movement including consideration of internal heat generation in microwave drying of yellow poplar specimens. The model was solved using the finite element analysis with FEMLAB software. The model predictions compared favorably with predicted and experimental solutions. The effect of changes of the most important parameters on the predictions of the model is also presented. The results showed that the variations of irradiation time, microwave power level and sample thickness played an important role in overall drying kinetics.

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Microwave Drying : Effects on Paper Properties

Cited by 6 publications

References 1 publication

A Facile Microwave-Mediated Drying Process of Thermally Unstable / Labile Products

A Facile Microwave-Mediated Drying Process of Thermally Unstable / Labile Products

Energy economy and kinetic investigation of sugar cube dehydration using microwave supplemented with thermal imaging

Computational analysis of heat and mass transfer during microwave drying of timber

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