Papers by Keyword: Microwave Drying

Abstract: The drying process that is responsible for ensuring the coffee quality, reduces the moisture of the coffee bean thus avoiding unwanted microorganisms. Traditional drying methods take between 16 and 45 hours to dry coffee beans, which results in high operational costs. Therefore, the application of the microwave drying technique is a possible alternative, as it can reduce drying periods by four times. In this study, the main goal was to evaluate the heating kinetics and distribution of a single coffee bean due to microwaves to verify its heterogeneity. Initially, a single coffee bean was designed and inserted into a monomode microwave cavity. The geometry of the coffee bean was simplified as a semi-ellipsoid with its diameters measured experimentally and with four different curvatures at the edges. As a result of the numerical simulations, the temperature distribution on the coffee bean over time was obtained as well as the average temperature and temperature at its center. The heating kinetics plot described a linear curve for every geometry, having a higher inclination in the sharp edge and decreasing as the curvature increases. Also, when comparing the average and center temperatures, the temperature in the center is 107.58 °C and the average temperature of the coffee bean is 96.09 °C, which corroborates the fact that the microwave heating occurs from inside out. In conclusion, the microwave heating in coffee beans is heterogeneous, starting in its center, favoring the mass transfer phenomenon during drying and can be influenced by the sharpness of the coffee beans edges.

Abstract: Drilled cuttings contaminated by non aqueous drilling fluids are the major waste from oil well drilling activities. More restrictive environmental legislation has led to the search for alternative technologies to promote cuttings decontamination according to the law. The mixture of cuttings and fluid returning from the well goes through a set of separation equipments, called solids control systems, in order to recover the drilling fluid for reuse. The cuttings from the solids control system must be decontaminated before they can be discharged into the sea. Microwave heating has been studied over the past few years as an alternative to promote the decontamination of this waste and has been shown to be a promising technology. This work aimed to investigate fundamental aspects of microwave heating and drying of drilled cuttings. The heating curve of two different drilling fluids commonly employed in well-drilling operations was obtained. The kinetics of drying of cuttings contaminated with these drilling fluids was also investigated. It was evaluated the behavior of organic phase and water removal in the microwave drying process.

Abstract: Building construction drying using high-frequency electromagnetic radiation (EMW), or microwave technology (MW), is gaining more usage in practise. It is the quickest way of eliminating water content in construction (wall, ceiling, etc.). Microwave is a term for a part of the electromagnetic radiation of 300 MHz to 300 GHz frequency with a wavelength from 1 mm to 1 m. The frequency of 2,45 GHz and 122 mm wavelength is used for technical practice. Due to the effect of MW radiation a different homogeneity of temperature field can be observed.This article discusses the spreading of the temperature field depending on the water volume and thereby the amount of mass moisture of the material (silica fume). Temperature fields will be shown by the thermo camera at certain time cycles of heating.

Abstract: The present study was aimed to investigate the effect of microwave drying on the anti-diabetic potential of the leaves of Aquilaria subintegra and Aquilaria malaccensis with regard to its efficacy by local herbalists in the treatment of diabetes frailties. The drying process was carried out at 50, 100 and 150 W, and the drying curves were developed to analyse the drying characteristics of both species of Aquilaria leaves. Solid-liquid extraction was done by using ethanol as solvent prior to in-vitro analysis of the inhibition activity on α-amylase. Following that, HPLC and FTIR were done to support findings on the antidiabetic compounds of the leaves extract. The results indicated that an increase in power level will reduce the drying time during microwave treatment. Findings showed that both species of Aquilaria leaves extract could remarkably inhibit the activity of α-amylase and provide a rationale for the use of the leaves in the treatment of diabetes mellitus.

Abstract: This paper presents the effect of drying methods on chemical and functional properties of Jerusalem artichoke (Helianthus tuberosus L.) powders. To prepare the Jerusalem artichoke powders, the slices of Jerusalem artichoke were dried in hot-air oven at 60°C, in microwave oven with 200 W, under open-air sun and under shade until moisture content of approximately 10% (dry basis) was reached. In addition, blanching was used in order to investigate the influence of pre-treatment. The contents of total phenolic, total sugar, reducing sugar and water-holding capacity of Jerusalem artichoke powders prepared by different drying methods were analyzed. The results showed that both blanching and drying method affected these properties of Jerusalem artichoke powders significantly (p<0.005).

Abstract: Combination of oven and microwave and only oven are two ways to study municipal sludge,and it investigates whether different size, microwave drying pretreatment, pretreatment time and oven temperature characteristics have effect on drying characteristics. The results shows that: using microwave to dry sludge need short time, the drying rate is fast, combination of oven and microwave has higher drying rate and lower energy consumption than only oven.

Abstract: A fractal model simulate the internal structure of the sludge, and on the model deduce that fractal dimension is D and the corresponding pore is r, the porosity is P. Determine the rate in the air-blast and microwave drying and calculate its different fractal dimension under different ages. The results showed that: the fractal dimension and its rate of water loss has a good correlation. Fractal dimension can describe a certain amount of sludge pore channels and internal cell rupture can cause that which would accelerate the evaporation of bound water. Microwave and the excessive energy of air-blast can be caused by temperature changes in the structure of the sludge that could change the structure of sludge.

Abstract: The experiments are designed to study influence of different loading mass and microwave power on drying kidney beans. A conclusion is obtained that all the two factors significantly affect dehydration and power consumption. When the power level increased, the dehydration rate increased while the drying energy consumption decreased. The same water loss will consume more energy when the moisture content is less than about 300 (w%,d.b.). The sensory quality of the dried samples decreased with increase first-stage of power and second-stage power when the power was more than 1.6kW/kg and 1.0kW/kg.

Abstract: Applying microwave heating and impinging hot-air is one of the most interesting methods to increase the higher drying rates of rubberwood drying based on acceptable quality. A maximum microwave power level of 200W at a frequency of 2.45GHz with maximum working temperature of 70°C, only hotair (70°C) and combined microwave (200W) - hotair (70°C) were choosed to evaluate the effect of rubberwood drying by different width sizes (1, 2, 3 and 4 in.) by 46 in. length by 1 in. thick. In all cases, the drying time is reduced significantly from 168 h to less than 8-15 h in various wood widths and resulted in saving to an extent of about 91% of drying time from initial moisture content ranges of 73%-49% to 15% percent of moisture level. Drying stresses from prong test no found during drying and total color of rubberwood changed after high temperature drying is a natural surface when compared to fresh wood. The values of six strength compared to the reference values are concentrated in the ranges of 16.9-23.9 (11.0)MPa for shearing strength parallel to grain, 4291.1-6701.6 (4350)N for hardness, 73.3-110.2 (66.0)MPa for MOR, 7059.5-12856.7 (9240.0) MPa for MOE, 27.2-14.3 (5.0)MPa for compressive strength perpendicular to grain and 60.6-35.7 (32.0)MPa for compression strength parallel to grain. These results show that it is possible to develop a drying process for rubberwood using microwave-hot air in investigating further in this area.

Abstract: The morphological structure and properties of wet natural rubber (NR) granulates dried by microwave were studied, which compared with wet NR granulates dried by hot-air. The results show that the molecular weight of NR dried by microwave is higher than that of NR dried by hot-air, and the molecular weight distribution of NR dried by microwave is narrower than that of NR dried by hot-air. The wet NR granules dried by microwave are rough on surfaces and the cutting traces produced during the processing remained on surfaces; whereas the wet NR granules dried by hot-air are smooth on surfaces resulted from melt adhered, and the cutting traces disappeared; the thermal-oxidative resistance of NR vulcanizates dried by microwave improved significantly.