Increasing Microwave Power Research Articles

Microwave drying optimization and kinetic modeling of fly ash from municipal solid waste incineration

As a kind of hazardous waste, municipal solid waste incineration fly ash (MSWI FA) needs to be stored in a dry state in the process of landfill, transportation, and comprehensive utilization. Therefore, from the perspective of safety and sustainable development, it is necessary to dry as the pretreatment of MSWI FA. In this paper, MSWI FA drying experiments were carried out under different microwave power, different initial moisture content, and different particle size distribution conditions. The drying characteristics of MSWI FA were explored and the thin-layer drying kinetic model was used to explore the basic theory of the dynamics of MSWI FA drying process for the first time. The fitting analysis of the experimental data showed that the drying efficiency of MSWI FA increases gradually with the increase of microwave power and fly ash particle size, and the drying process of MSWI FA could be well represented by the Diffusion approach model (R2 greater than 0.99). Through Fick's second law calculation, it was found that when the microwave power was increased from 400w to 800w, the surface diffusion coefficient increased from 1.11 × 10-12 m2/s to 2.92 × 10-12 m2/s, which further showed that the microwave power has a significant effect on the drying efficiency of MSWI FA.

Effect of Microwave Leakage on Backward Current in an X-Band Dual-Mode RBWO Packaged With Permanent Magnet

In this article, the effect of microwave leakage into the diode region on the suppression of backward current in a relativistic backward wave oscillator (RBWO) operating at low magnetic field is investigated by the theoretical analysis, particle-in-cell (PIC) simulation, and experiments. The theoretical results show that some backward electrons are absorbed by the cathode holder due to microwave leakage, and as the microwave power increases, the microwave frequency increases, and the guiding magnetic field decreases, it will promote the absorption of electrons. The PIC simulations based on the first principle reveal that the leakage microwave partially suppresses the backward current and the suppression is enhanced when the incidence TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> is dominant. In the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${X}$ </tex-math></inline-formula> -band dual-mode RBWO packaged with permanent magnet experiments, a microwave pulse with the power of 3.9 GW, the frequency of 9.93 GHz, and the efficiency of 33% was measured when the diode voltage was 820 kV and diode current was 14.5 kA.

Synthesis And Characterization Of Carbon-Chitosan Composite Electrodes Based On Biomass Carbon Activated Using The Microwave Method

In this research, the synthesis and characterization of chitosan modified carbon composites based on biomass carbon has been carried out using the microwave method. Chemically activated carbon with 2.5% H3PO4 activator was stirred using a magnetic stirrer for 1 hour and allowed to stand for 24 hours. The carbon was then physically reactivated using a microwave for 20 minutes with a power variation of 800, 1000 and 1200 watts and a Scanning Electron Microscopy (SEM) test was carried out. After the SEM test, chitosan modified carbon was synthesized with a composition ratio of 1:1, 2:1 and 3:1 and the specific capacitance was measured using Galvanostatic Charge-Discharge (GCD) testing. The SEM test results analyzed using ImageJ software-based image processing methods show that the value of sphericity, pore size and carbon porosity decreases with increasing microwave power used. The optimum conditions based on the value of Sphericity, pore size and porosity were obtained at a variation of 800 watts of microwave power with values ​​of 0.952, 0.832 m, and 25.87%, respectively, which were included in the macropore size (&gt;50 nm). Because the higher the power used, the smaller the pore area and porosity. The electrode-specific capacitance values ​​were 3.4 x 10-1 F/g, 24.02 F/g, and 1.3 x 10-1 F/g, respectively. Electrodes with a ratio of 2:1 have the largest capacitance value, because they can be charged by an electric charge. The longer the charge-discharge process, the greater the capacitance value, so the curve will approach a more symmetrical isosceles triangle shape.

Examination of rehydration ratio, color properties and drying kinetics of microwave dried garlic (Allium sativum L.)

In this study, color values and rehydration ratios of dried garlic slices at four different microwave power (300W, 450W, 600W and 700W) were determined. Thin layer drying models were used for drying kinetics. It was determined that L* and b* values were lower and a* values were higher in microwave-dried garlic compared to fresh garlic slices. It was observed that the C* (Chroma) and h (hue angle) values of garlic decreased as the microwave power increased compared to fresh garlic. It was determined that the rehydration ratio decreased significantly with increasing microwave power. Therefore, the highest rehydration ratio was detected in the garlic samples applied at 300W. Moisture ratio (MR) versus time calculated as a result of microwave drying was compared with 5 (Lewis, Page, Henderson, and Pabis, Midilli et al. and Logarithmic) drying models in the literature. R2 (coefficient of expression), χ2 (chi-square) and RMSE (root mean square error) were calculated by SPSS and nonlinear regression analysis of dried garlic samples. It was determined that the highest R2 (0.994-0.998, the lowest RMSE (0.016-0.022) and χ2 (0.00033-0.00064) values belonged to the Lewis model.

Evaluation of Thermal and Drying Characteristics of Dried Hazelnut (Corylus avellana L.) Shell Waste

As a biomass fuel, the hazelnut shell must be milled into sawdust and dried to contain a certain amount of moisture. For this purpose, calorific value, drying rates, thermal values, moisture diffusion, activation energy, and energy consumption at the end of the drying of the hazelnut shell, which is dried in the conveyor belt and microwave dryer, were calculated. The total minimum energy consumed by the hazelnut shell at the end of the experiment in microwave drying was measured as 0.2 kWh for 460 W and 4.65 kWh at 80°C drying temperature in conveyor belt drying until the final moisture value reached 1.1±0.8% wet basis at the end of the experiment. The effective diffusivity of moisture of hazelnut shell changed from 4.13×10-7 to 1.89×10-6 m2 s-1, and the activation energy was found as 2.275 W g-1 in microwave drying. The effective diffusivity of moisture of hazelnut shell changed from 6.39×10-7 to 9.21×10-7 m2 s-1, and the activation energy was found as 19 kJ / mol in the conveyor belt drying. In general, the diffusion coefficient increased with increasing air temperature and decreased with increasing microwave power. At the end of the experiments, the temperature in the product was measured as 72°C in microwave drying and 73.5°C in conveyor belt drying. According to these values, it has been determined that the most suitable drying system for waste disposal was the microwave drying system. The calorific value was measured as 20028.52 kJ/kg in conveyor belt drying and 20036.76 kJ/kg in microwave drying. Microwave drying yielded better results with an increase of 2.72%.

Microwave-assisted pyrolysis derived biochar for volatile organic compounds treatment: Characteristics and adsorption performance

Biochar derived from corn stalk doping with activated carbon was produced by microwave-assisted pyrolysis and applied to sorb volatile organic compounds (VOCs: benzene and o-xylene). Specific surface area (SSA), total pore volume (TPV) and micropore volume (MV) of microwave biochar increased with increasing microwave power with the maximum values 325.2 m2·g−1, 0.181 mL·g−1 and 0.1420 mL·g−1, respectively. Adsorption capacities of benzene and o-xylene on microwave biochar ranged 6.82–54.75 mg·g−1 and 7.43–48.73 mg·g−1, which were separate positively related with SSA, TPV, and MV. Benzene adsorption was mainly dominated by surface interaction and partition mechanisms, while o-xylene adsorption was governed by pore filling. The adsorption capacities of microwave biochar for benzene and o-xylene decreased by only 0.30% and 0.99% on the 5th cycle that illustrated the reasonably good reusability of microwave biochar. The results of this research demonstrate that microwave biochar is a promising adsorbent for VOCs removal.

Study on Microstructure Evolution of Oolitic Hematite during Microwave Fluidization Roasting

To explore the microstructure evolution of oolitic hematite during microwave fluidization roasting, COMSOL multiphysics and scanning electron microscopy (SEM)–energy-dispersive spectrometry (EDS) were used to simulate and explore the microstructure evolution. The simulation results indicated that with the extension of microwave heating time and the increase of microwave power, the surface temperature in the particle model progressively increased, and the heating rate of hematite was the fastest, followed by quartz and apatite; simultaneously, the temperature stress and difference between the three mineral interfaces in the model were increased. The SEM–EDS results illustrated that there were microcracks at the interface between iron minerals and gangue minerals, such as quartz and apatite, and the microcracks were more obvious at the interface between iron minerals and quartz minerals. With the extension of microwave treatment time, the microcracks were gradually extended and expanded inward along the outer edge of oolitic and gradually formed in the core of the oolitic structure. Appropriately increasing the roasting temperature, prolonging the roasting time, and increasing the CO concentration made the particle surface more loose and rough, and produced more cracks and pores, while the ore surface presented a honeycomb morphology.

The Comparison of Microwave Thawing and Ultra-High-Pressure Thawing on the Quality Characteristics of Frozen Mango.

As one of the popular tropical fruits, mango has a relatively short shelf life due to its perishability. Therefore, post-harvest losses are always a topic of concern. Currently, freezing is a common approach to extending mango shelf life. In relation, it is also critical to select a proper thawing process to maintain its original quality attributes. In this study, microwave thawing, and ultra-high-pressure thawing were investigated, and traditional thawing methods (air thawing and water thawing) were compared as references. The thawing time, quality attributes, and sensory scores of frozen mangoes were evaluated. Compared to traditional methods, innovative thawing methods can extensively shorten thawing time. These things considered, the thawing time was further decreased with the increase in microwave power. Additionally, microwave thawing enhanced the quality of mangoes in terms of less color change and drip loss and reduced loss of firmness and vitamin C content. Microwave thawing at 300 W is recommended as the best condition for thawing mangoes, with the highest sensory score. Current work provides more data and information for selecting suitable thawing methods and optimum conditions for frozen mango to minimize losses.

Dynamic analysis of moisture, dielectric property and microstructure of ginger slices during microwave hot-air flow rolling drying

This study investigates the drying process of ginger slices using the microwave hot air rolling bed drying (MHARD) method, in terms of measuring drying kinetic change, moisture state and migration, dielectric characteristics, and color changes. The low-field nuclear magnetic resonance (LF-NMR) signal of free, immobilized, and bound water analysis indicates that during the drying of the sample, the drying rate followed a typical “rapid rise-steady-decline” trend in the “preliminary-constant rate-falling rate” stages, respectively. The LF-NMR result shows the content of free water ( A 23 ) in the ginger slices decreased gradually during the drying. Meanwhile, bound water ( A 21 ) content and immobilized water ( A 22 ) content firstly increased and subsequently decreased, because of the microwave and hot air, the movement of water molecules accelerated and the binding force weakened, and then bound water ( A 21 ) and immobilized water ( A 22 ) decreased. On the other hand, both dielectric constant ( ε ′ ) and loss factor ( ε ″ ) of the sample decreased gradually with the decrease in moisture content and logarithmic models were established to describe this correlation. In the preliminary drying stage, although increased microwave power led to a higher drying rate, it resulted in significant damage to the microstructure and compromised the color profile of the final dehydrated ginger slices. This research aims to discuss the mechanism of ginger slides dehydration using the MHARD technique to produce a final product with high quality. • Microwave hot air rolling drying (MHARD) can improve ginger drying uniformity. • Microwave and hot air can accelerate drying rate and optimize the drying process. • Microstructure and color can be damaged by microwave power and hot air temperature. • Inner moisture migrated outwards and gradually distributed evenly during MHARD. • Dielectric properties are affected by moisture content, especially free water.

Kinetics and Characterization of Microalgae Biofuel by Microwave-assisted Pyrolysis Using Activated Carbon

The reaction kinetics and the effect of power on microwave-assisted pyrolysis (MAP) in converting microalgae to biofuel were investigated to determine the decomposition mechanism and then characterize the best product. The resulting product consisted of three phases, namely liquid phase (bio-oil), solid residue (char), and uncondensable gas products. The results showed that the optimal increase in microwave power obtained was 20.57% with a 600-watt microwave power condition, a reaction time of 20 minutes, a microwave absorber to microalgae ratio of 1:6, and a heating rate of 25.96 K/min (600 watts). The reaction kinetics evaluated in the best condition showed a second-order reaction with activition energy (Ea) and pre-exponential factor (A) at 35.5971 kJ/moles and 2,606.75/minute, respectively. The characteristics of the biofuel product obtained were 1.01 gr/mL density, viscosity 10.97 cP, and pH 9.30. In addition, based on GC-MS analysis, the bio-oil contained aliphatic, aromatic, phenol, FAME, and polycyclic aromatic hydrocarbon (PAH) organic compounds. These results indicate that MAP has the potential to be developed as an alternative production process for biofuels.

Effect of intermittent microwave convective drying on physicochemical properties of dragon fruit.

The study was carried out to investigate the effect of Intermittent microwave convective drying (IMCD) on the overall quality of dried dragon fruit in terms of total phenolic content, color change, and rehydration ratio. Three levels of microwave power (200-600W) and a temperature of 60°C for hot air were applied alternately throughout the process with three levels of pulse ratio such as 1:10, 1:20, and 1:40, respectively. The total phenolic content of the dragon fruit slice obtained by IMCD was ranged between 5.750 and 6.575mg GAE/g dry weight. Within the experimental range of process variables under IMCD conditions, the drying efficiency, color change, and rehydration ratio of the dried dragon fruit slices were 15.287-51.930%, 18.643-24.847, and 1.908-3.239, respectively. The Weibull model scale (α) parameter was found to vary between - , while the shape (β) parameter was found to vary between . The Weibull model parameters were shown to decrease with increasing microwave power at constant pulse ratio. The IMCD method produced a dried dragon fruit slices with reduced color changes and higher total phenolic content and rehydration ratio values. This investigation would contribute to the development of effective drying techniques for increased food quality and product consistency in the drying of diverse fruits and vegetables.

Modeling of process and analysis of drying characteristics for natural TiO2 under microwave heating

In this paper, factors affecting the microwave drying characteristics of rutile TiO2 were discussed, and the data were fitted with nine common thin layers drying kinetic models. The results demonstrate that the drying efficiency of rutile TiO2 shows a positive relationship with microwave power. With a microwave power increase from 320W to 640W, the drying time is shortened by 35.7%. The microwave drying efficiency presents a positive relationship with initial moisture content. With a moisture content increase from 2% to 12%, the average drying rate increased from 0.009%·s−1 to 0.054%·s−1. Additionally, the microwave drying efficiency is positively correlated with the initial mass when the initial mass is below 45 g. Otherwise, the microwave drying efficiency is negatively correlated with the initial mass. Besides, kinetic models were used to understand the microwave drying process of nature rutile TiO2. The results show that the Modified Page model agrees well with the experimental data, and the fitting parameters are consistent with the law of matching degree. The demonstration of microwave drying techniques can be applied effectively and efficiently to the treatment processing of drying of the raw materials of metallurgy and chemical industry with the theoretical and scientific basis.

Effects of Stepwise Microwave Synergistic Process Water Recirculation During Hydrothermal Carbonization on Properties of Wheat Straw

In this study, wheat straw (WS) was treated using two-step synergistic techniques, which were process water recirculation (PWR) during hydrothermal carbonization (HTC) and microwave energy activation (MEA). The physicochemical properties of solid and liquid products during the process of HTC PWR were characterized. The temperature-rising properties, yields, and fuel properties of hydrochar after MEA were explored. Then the optimal technique conditions were explored. When HTC PWR was twice, the carbon content (55.59%) and higher heating value (21.72 MJ/kg) were the highest, and the ash content (1.93%) and the O/C and H/C ratios were the lowest. When HTC PWR was three times, the fixed carbon content, mass yield, and energy yield were the highest: 18.53%, 58.25%, and 71.84%, respectively. Many more carbon microspheres and pores appeared on the surface of hydrochar after PWR, which could improve the fuel characteristics and mass yield. After HTC PWR, the concentration of organic acids and HMF in liquid by-products increased, which was conducive to the increase of carbon content and mass yield. The best effect was HTC PWR twice or three times. With the increase of microwave power or the extension of microwave activation duration, the temperature-rising properties of hydrochar significantly increased, and the mass and energy yields decreased. The volatile contents of hydrochar decreased and their fixed carbon contents and HHV increased with the increase of microwave power. The properties of hydrochar could be improved when MEA was 900 W or 1000 W for 4 min. Therefore, MEA had significant effects on the properties of hydrochar after different PWR conditions.

KURUTMA SICAKLIĞI VE MİKRODALGA GÜCÜNÜN HİNDİ GÖĞÜS DİLİMLERİNİN KALİTE ÖZELLİKLERİNE ETKİLERİ

In this study, spiced turkey slices were dried at different temperatures (60 and 70°C) and microwave powers (0, 180 and 360 W at fixed product weight) and physical, chemical, microbiological and sensory quality characteristics of these dried slices were determined. The turkey slices dried at these conditions had an average moisture content of 25%, an aw value of 0.72, a pH value of 6.02, and a thiobarbituric acid reactive substance (TBARS) value of 15.77 µmol MDA/kg. It was determined that the cutting force value of the samples increased to 56.14 N depending on the temperature increase and to 59.12 N depending on the increase in microwave power. In addition, it was found that the L* value of the samples decreased significantly (p &amp;lt; 0.01) as the microwave power increased. Furthermore, the microbial quality was better in samples applied at 70°C drying temperature and 360 W microwave power.

Implementation of Ambipolar Polysilicon Thin-Film Transistors with Nickel Silicide Schottky Junctions by Low-Thermal-Budget Microwave Annealing.

In this study, the efficient fabrication of nickel silicide (NiSix) Schottky barrier thin-film transistors (SB-TFTs) via microwave annealing (MWA) technology is proposed, and complementary metal-oxide-semiconductor (CMOS) inverters are implemented in a simplified process using ambipolar transistor properties. To validate the efficacy of the NiSix formation process by MWA, NiSix is also prepared via the conventional rapid thermal annealing (RTA) process. The Rs of the MWA NiSix decreases with increasing microwave power, and becomes saturated at 600 W, thus showing lower resistance than the 500 °C RTA NiSix. Further, SB-diodes formed on n-type and p-type bulk silicon are found to have optimal rectification characteristics at 600 W microwave power, and exhibit superior characteristics to the RTA SB-diodes. Evaluation of the electrical properties of NiSix SB-TFTs on excimer-laser-annealed (ELA) poly-Si substrates indicates that the MWA NiSix junction exhibits better ambipolar operation and transistor performance, along with improved stability. Furthermore, CMOS inverters, constructed using the ambipolar SB-TFTs, exhibit better voltage transfer characteristics, voltage gains, and dynamic inverting behavior by incorporating the MWA NiSix source-and-drain (S/D) junctions. Therefore, MWA is an effective process for silicide formation, and ambipolar SB-TFTs using MWA NiSix junctions provide a promising future for CMOS technology.

Effect of Microwave Pretreatment on Some Properties of Bamboo (Gigantochloa apus) for Bioethanol Production

Pretreatment of lignocellulosic biomass plays an essential role in bioethanol production as an alternative biofuel. This process reduces biomass recalcitrance in order to improve cellulose digestibility for saccharification and further fermentation reactions. In this study, microwave (MW) pretreatment was done on bamboo (Gigantochloa apus) to investigate the resulting physicochemical properties and bioethanol produced. Bamboo was irradiated in the microwave at different power (100-600 Watt) and irradiation time (5-20 minutes) followed by Water Soluble content (WSC) and lignin analysis. Simultaneous saccharification and fermentation (SSF) using cellulase enzyme was also done in five different treatment combinations (C1-C5) to investigate the effect of produced reducing sugar and bioethanol. The result shows that increasing MW power and irradiation time could decrease WSC gradually. The lowest WSC of 0.3% was obtained at 600-Watt MW power and 20 minutes irradiation time. Lignin content decreased from 18.9% to 16.0% concerning increasing irradiation time from 5 to 20 minutes under 300-Watt MW power. SEM images show that partial disruption and micro-scale pores existed in pretreated samples. The highest amount of ethanol was obtained at 24 hours fermentation for pretreated bamboo at 300-Watt MW power for 15 minutes followed by cellulase enzyme addition. The overall results showed that microwave pretreatment is a prospective method for future bioethanol production from bamboo due to effective WSC reduction and lignin degradation in a relatively short period of time.

Production of aromatic hydrocarbons from microwave-assisted pyrolysis of municipal solid waste (MSW)

The microwave-assisted conversion of municipal solid waste (MSW) into value-added products would be a promising option to tackle MSW piles. The present work was intended to understand the effect of microwave power (300, 450, and 600 W) and graphite susceptor loading (10, 30, and 50 g) on MSW valorization. Response surface methodology was used to analyze the impact of input variables on product yields and energy consumption. The heating rate increased, and microwave energy consumption decreased with the increase in microwave power. An increase in susceptor quantity resulted in a reduction in heating rates and also energy consumption. Nearly 84–88 wt% of MSW was converted into gases (42–60%), oil (26–42%), and char (12–16%) products. The carbon number distribution of oil fraction is in the range of C5 to C20 with a high yield of carbon content (74–91%). A high yield of aromatic hydrocarbons (84.5%) was obtained at 600 W microwave power and 30 g of the susceptor. The char fraction is rich in carbon content (80–90%) with a reasonable pore area (111–152 m2/g). This work demonstrated the feasibility of MSW upgradation into value-added chemicals, materials, and energy-rich fuel products.

Drying kinetics and energy efficiency of microwave-dried lemon slices

In the current study, lemon slices were dried at various microwave powers (120, 350, 460, 600, and 700 W) to determine drying characteristics and energy efficiency. Drying rate and time were significantly affected by the increase in microwave power. The lowest and highest drying times were 8 and 54 minutes at 700 and 120 W, respectively. As microwave power increased, drying rate increased, and drying time decreased. Besides, the most suitable model to describe microwave drying curves of the lemon slice was obtained as the Page model. The values of Deff of the dried lemon slices were calculated between 3.61x10-9 and 3.41x10-8 m2s-1. The Ea of the lemon slices drying, calculated using Deff, and the rate constant obtained from the Page model were 4.39 Wg-1 and 6.04 Wg-1, respectively. Additionally, the higher the cumulative energy efficiency, the lower the specific energy consumption. The lowest specific energy consumption and the highest energy efficiency were calculated at 460 W. The 460 W drying power was the best power with 11 min of drying time, the highest energy efficiency, and the lowest specific energy consumption.

Effect of intermittent microwave drying on nutritional quality and drying characteristics of persimmon slices

The novelty of this paper was to evaluation the effect of intermittent microwave drying (IMD) on the nutritional quality and drying characteristics of persimmon slices. Persimmon slices were treated with IMD at the microwave power levels of 280, 350, 420, 490, and 560 W, and the drying characteristics, nutritional components, and sensory properties were determined and analyzed. The results showed that the drying process of persimmon slices could be divided into three stages; increasing speed, constant speed, and decreasing speed. Meanwhile, the higher the microwave power, the shorter the drying time and the higher the drying rate. With the increase of microwave power, the contents of soluble sugar, soluble tannin, vitamin C, and ash increased gradually, but had no obvious effect on the content of insoluble tannin, while the contents of soluble protein and vitamin E decreased gradually, and the overall acceptability score increased first and then decreased. In this study, the comprehensive scoring method was used for dried persimmon slices. The optimal microwave power for IMD persimmon slices was determined to be 490 W, which could effectively improve the drying rate and nutritional value, and has good sensory acceptability.

DRYING OF ZUCCHINI AND CARROT SLICES: INFLUENCE OF TISSUE STRUCTURE ON MASS TRANSFER PARAMETERS

The present work aimed mainly at investigating the influence of tissue structure on dehydration characteristics of zucchini and carrot. Microwave power levels of 100, 350, 550 and 750 W used to dehydrate the samples with thicknesses of 3, 5, 7 and 9 mm. The results showed that moisture removal from the slices occurred in a short accelerating period at the process beginning followed by a falling rate period. The moisture diffusivity increased with both increasing microwave power and the samples thickness where the average values for zucchini and carrot slices changed from 1.17×10-8 to 9.42×10-8 and from 0.73×10-8 to 5.51×10-8 m2 s-1, respectively. The average activation energy for zucchini and carrot slices varied in the range of 1.22–1.68 and 1.57–1.84 W g-1, respectively and decreased with increasing samples thickness.