Application Of Microwave Energy Research Articles

Applications of microwave energy in gas production and tar removal during biomass gasification

Microwave heating has the potential to promote gas production and tar removal during biomass pyrolysis or gasification based on its advantageous characteristics such as rapid heating and selective heating.

Application of microwave energy for rapid fabrication of nano-hydroxyapatite reinforced polycaprolactone composite foam

This research work is aimed to utilize microwave energy for rapid fabrication of nano-hydroxyapatite (nHA) reinforced polycaprolactone (PCL) composite foam. Weight fraction of nHA and NaCl was fixed at 20% and 30%, by weight, respectively. The NaCl was acts as microwave absorber as well as the porogen agent in the composite. The interconnected porosity was induced by leaching of the NaCl particles from composite in an ultrasonicator bath. The influence of microwave process parameters such as microwave power and exposure time was studied on mechanical and microstructural feature of PCL/nHA composite foam.

Effects of Microwave Energy on Fast Compressive Strength Development of Coal Bottom Ash-Based Geopolymers

Microwave energy has been shown to be effective for geopolymer synthesis due to its fast and penetrative heating characteristics; however, the changes in the physicochemical properties of the geopolymer, resulting from the microwave irradiation, have not been fully elucidated. Therefore, this study is aimed at investigating the effect of the microwaving on the properties of coal bottom ash(CBA) geopolymers. We prepared geopolymer samples by casting a mixture of ground CBA and 14 M NaOH solution against cubic molds with a hand press machine, followed by pre-curing in a dry oven at 75 °C for 24 h and microwaving under various powers and durations. The compressive strength strongly depended on the moisture content, i.e., the strength increased from 21 to 65 MPa or higher as the moisture content decreased to critical values, after which the strength began to decrease. The results showed that microwave energy stimulated an additional geopolymerization by evaporating the redundant free water. This led to the strength gain, although the over-irradiation generated a high internal stress and poor structural integrity, which resulted in the strength loss. Therefore, the appropriate application of microwave energy is a promising option for synthesizing high-strength geopolymers in a cost- and time-effective manner.

Model-free adaptive control for microwave heating process with actuator saturation constraint

This study is concerned with the development of model-free adaptive control (MFAC) of microwave heating process for the industry application of microwave energy. Precise control of the material's time–temperature profile is essential for preventing thermal runaway. To achieve good tracking performance a data-driven MFAC with input constrain is proposed since it is hard to establish an accurate dynamic model of microwave heating process. The stability of the proposed MFAC algorithm is analyzed. The proposed techniques are implemented and tested on a simple one-dimension non-linear thermodynamics model of the heated product in microwave heating process and the microwave heating system in laboratory, respectively. Simulation and experimental results are presented to compare MFAC with and without considering power input constraint to demonstrate the performance of the proposed algorithms.

Effects of fish oil incorporation on the gelling properties of silver carp surimi gel subjected to microwave heating combined with conduction heating treatment

To understand the oil-protein interaction in silver carp surimi gel under microwave irradiation, the effects of fish oil (FO) incorporation on the gelling and microstructural properties of surimi gel subjected to microwave heating combined with conduction heating were investigated. Although FO incorporation into surimi gel disrupted the protein matrix, thereby decreasing (P < 0.05) the gel strength, the destructive behavior was remarkably remedied by microwave heating. The whiteness of the gel subjected to microwave heating was also elevated (P < 0.05) when the amount exceeded 6%. Furthermore, microwave heating significantly decreased (P < 0.05) the hardness, gumminess and chewiness of the gel, which indicated that a softer gel was obtained by this treatment. The results of expressible moisture content and T2 relaxation analysis confirmed that microwave heating facilitated the retention of water trapped in the protein network. The scanning electron microscope images revealed that microwave heating promoted the oil-protein interaction and triggered a more compact gel microstructure. Although lipid oxidation that inevitably occurred after FO enrichment of surimi gel increased, and the malondialdehyde content was effectively increased (P < 0.05) after microwave heating, it was apparent below the range for consumers acceptance. This study revealed that the gelling quality of surimi gel enhanced with nutritional FO could be improved by rational application of microwave energy for the fabrication of functional surimi-based seafoods.

Uterine adenosarcoma in a patient following microwave endometrial ablation: a case report

In Japan, almost six million women are said to be suffering from menorrhagia. Microwave endometrial ablation (MEA) is a minimally invasive and effective surgical treatment for dysfunctional uterine bleeding using the application of microwave energy to the endometrium. Its popularity has been increasing over time in many countries because of its safety and simplicity. Recently, a number of cases of medical complications after MEA have been reported. Here, the authors present the first reported case of adenosarcoma diagnosed in a woman, five years after treatment with MEA. This finding highlights the need for gynecologists to use caution and perform close patient follow-up for a prolonged time period after MEA.

Conventional and microwave-assisted pyrolysis of gumwood: A comparison study using thermodynamic evaluation and hydrogen production

The application of microwave energy in biomass pyrolysis has gained increasing interest due to its fast, volumetric, selective and efficient heating. However, the dominance may be levelled off if the energy and exergy efficiencies of overall system are taken into consideration. Hence, based on the lab-scale experimental data (at 600, 700 and 800 °C), energy and exergetic assessment of pyrolysis-derived gas, char and oil from gumwood under conventional and microwave heating were investigated in this work. The results showed that at each temperature, the corresponding energy and exergy rates of gas under microwave heating were found to be 23% and 26%, respectively, higher than those of conventional one. Meanwhile, the values for char were around 46%. This was mostly because microwave-derived pyrolysis product contained more gaseous and char products compared to the conventional process. In contrast, opposite trend was noticed for bio-oil due to the reduction of oil yield in pyrolysis product. It was demonstrated that the total energy and exergy value of individual pyrolysis products were significantly influenced by the energy and exergy content of individual component. For example, the increment rate of energy and exergy values of H2 and CH4 were sufficiently higher than the decrement rate of energy and exergy values of CO and CO2 with the increase of temperature; the total values were consequently increased at the elevated temperature. For the case of char and oil, the energy and exergy rate were decreased with temperature due to the reduction of individual product yield. Pyrolysis system efficiency (PSE), the overall performance indicator used in this study, of the microwave-assisted process was 13.5% higher than that of the conventional process. Moreover, the experimental results were further analysed with the conduct of a hydrogen plant simulation using Aspen Plus™ whose results confirmed that an improved performance of microwave heated system was achieved by producing 120 gH2/kg gumwood, 15% higher compared to that of conventional system.

OPTIMIZATION OF GINGER OLEORESIN EXTRACTION FROM FRESH GINGER BY USING MICROWAVE - ASSISTED ENERGY

Nowadays, the active compounds from natural products are interested in not only research fields but also industrial area. Steam distillation is widely employed for the isolation of bioactive substances from natural sources. However, the process is usually long time consuming, high energy consumption and unwanted chemicals can be entrained with the main products. Microwave-assisted extraction is now recognized as an efficient extraction technique that dramatically reduces extraction time, increases yields and higher quality of the extracts can be obtained. The aim of this study is evaluation of the major factors affected by operating parameters such as concentration of solvent, radiation time, ratio of microwave power to material, volume of solvent on yield of products by microwave-assisted extraction. In addition, comparison between traditional extraction methods and microwave-assisted extraction is also carried out. The results show that application of microwave energy for the extraction of active substances from fresh ginger have faster heating, reduce thermal gradients and extraction time.

Novel Drying Process Assisted by Microwave to Iron Ore Pelletizing

Drying has became critical to iron ore pellet production, due to increasing inability to withdrawal moisture from the green pellets, especially faced by goethitic iron ore producers. Most of the existing pelletizing furnaces do not support increase heating rates nor changes in furnaces length, without compromise pellet quality. The present study evaluates an innovative alternative for the actual fully convective drying process composed by an up-draught drying (UDD) and down-draught drying stage (DDD), through the application of microwave energy to assist the existing process. In the present work, the process was simulated in a pot grate where industrial parameters can be simulated. The microwave generator (power input of 10 MW and 915 MHz) was connected in a traditional static pot grate at the hood by a microwave conductor. The experiments show elimination of the over-wet zone at the upper layer of pellet observed at the traditional process. A reduction greater than 7% of the moisture in UDD was achieved, while the convective process adds extra moist to the green pellets modifying the pellet shape.

Microwave irradiation on pore morphology of coal powder

An innovative microwave irradiation device is developed to investigate effect of microwave irradiation on pore morphology of coal powder. This device with several distinguished highlights, such as real-time infrared temperature measurement, gas replacement, process parameters controls, and large size samples testing. Specifically, results of effect of temperature (25–300 °C) and microwave power (1–6 kW) on pore morphology was evaluated by the mercury intrusion porosimetry method. The pore connectivity decreases at first then increased with incremental processing temperature or microwave power. The percolation threshold increases with increased heating temperature or microwave power. The total pores volume increases with increased processing temperature or microwave power. The total specific surface area increases firstly then decreases with increased temperature or microwave power. These suggest that effect of microwave irradiation on pore morphology is obvious. Several possibilities for microwave energy application in the field were discussed, including drilling borehole from the ground to the payzone, drilling up-hole or down-hole from the roadway to the payzone, drilling borehole along the coalbed. The process economics were also discussed. It implies that as a new technology microwave energy may have the potential for the degassing coal seams.

Comparison of machining performance of microwave post-heated WC insert with dry, wet and MQL cutting in turning operation

ABSTRACTThis paper describes the application of microwave energy to enhance the machining performance of tungsten carbide tool insert in order to reduce the use of cutting fluids. Application of cutting fluids increases the machining costs, which include fluid consumption, maintenance and disposal costs. Health hazards for workers, environmental issues and economic aspects of cutting fluid motivate researchers to move towards coolant-free machining. This study aimed to minimize the dependency on cutting fluid during machining and to suggest a suitable alternative to improve the performance of tungsten carbide tool insert. Microwave post-treatment of tungsten carbide tool insert is the emerging technique in which the tool insert is subjected to microwave irradiation at a frequency of 2.5 GHz. In the present investigation, turning operations have been performed on AISI 1040 steel (American Iron and Steel Institue) using microwave-treated insert under dry cutting environment and untreated insert using dry, wet and minimum quantity lubrication (MQL) cutting environment. Variation of tool wear and surface roughness has been experimentally investigated in this study to evaluate the machining performance. Tool wear mechanism and chip morphology have been analysed using scan electron microscopy. The results indicate that microwave-treated insert achieved better performance than fresh tungsten carbide (WC/Co) inserts used in dry, wet and MQL cutting conditions.

Assessment of microwave-assisted alkali pretreatment for the production of sugars from banana fruit peel waste

ABSTRACTThe current investigation deals with the application of microwave energy to facilitate alkali (NaOH) pretreatment on banana peel waste (BPW) to achieve optimal reducing sugar. We studied the effect of microwave power (100 to 600 W) and irradiating time (1 to 6 min) on composition and reducing sugar content of BPW. The enzymatic hydrolysis of microwave-assisted alkali-pretreated BPW at 600 W for 2 min gave the maximum reducing sugar (0.561 g/g) of dry biomass waste. Atomic force microscopy revealed that the surface of all BPW was changed noticeably when microwave-assisted alkali pretreatment was employed. X-ray diffraction study revealed a 5-fold increment in the degree of crystallinity in optimal microwave alkali-treated samples (54.45%) as compared to the untreated sample (10.55%). Overall, the microwave-assisted alkali pretreatment removed a significant amount of hemicelluloses and lignin and led to a high amount of sugar production, suggesting microwave heating pretreatment as a potential alternative to conventional methods to achieve maximal reducing sugars.

ПРИМЕНЕНИЕ МИКРОВОЛНОВОГО ИЗЛУЧЕНИЯ В ДОБЫВАЮЩЕЙ МЕТАЛЛУРГИИ

ПРИМЕНЕНИЕ МИКРОВОЛНОВОГО ИЗЛУЧЕНИЯ В ДОБЫВАЮЩЕЙ МЕТАЛЛУРГИИ

Microwave Soil Treatment Improves Weed Management in Australian Dryland Wheat

Abstract. Herbicide resistance has prompted the development of a chemical-free weed management practice in no-till farming systems. In this study, we examined the effect of pre-emergence microwave (MW) soil treatment for weed management in a no-till wheat production system in Australia. One-time MW soil treatment (2.45 GHz, 600 W, 120 s) was applied to plots that were arranged in a randomized complete block design with five replicates. The MW energy was projected through a horn antenna with aperture dimensions of 5.5 cm × 11 cm into the topsoil (0 to 6 cm) horizon. The applied MW energy density in the treated plots (2.6 m2), which was calculated by Simpson’s numerical surface integral approximation, was approximately 560 J cm-2. This achieved an increase in soil temperature of about 75°C to 80°C. This temperature induced a 65% to 80% reduction in weed establishment through thermal devitalization of the weed seedbank, compared to the untreated control plots. In addition, a substantial increase in wheat grain yield of 39.2% was achieved through MW energy application (7.8 t ha-1) compared to non-MW conditions (5.6 t ha-1). In summary, this non-chemical weed management strategy promises to effectively control herbicide-resistant weeds and sustain dryland wheat yields. Keywords: Microwave energy, Soil, Weed Suppression, Wheat.

第 5 回電磁波エネルギー応用セミナー -マイクロ波科学 基礎と応用の報告-

第 5 回電磁波エネルギー応用セミナー -マイクロ波科学 基礎と応用の報告-

Application of Microwave Energy for Biodiesel Production using Waste Cooking Oil

An experimental study has been carried out to produce biodiesel from different kinds of feedstock. Operating parameters have been optimized with respect to percentage yield of production and viscosity. The most common method for production of biodiesel is transesterification. Palm, karanja, mahua, linseed and castor oil are among the few of the non-edible oils. Along with this waste cooking oil can also be considered as non-edible oil as it is mostly thrown away. The process of transesterification depends on various factors like reaction temperature, stirring rate, molar ratio, amount of catalyst and reaction time. Depending upon the acid value, the number of steps of transesterification was determined. If free fatty acid is greater than 2.5% then two step transesterificaton is carried out. Karanja and mahua oil undergo two-step process because of high FFA content. The main objective of the study was to optimize the reaction parameters for production of biodiesel from different kinds of oil based on kinematic viscosity and percentage of yield obtained.

Microwave energy application to combustion synthesis: A comprehensive review of recent advancements and most promising perspectives

Microwave heating fundamentally differs from other heating techniques as the consequence of its unique characteristic of being based on the electromagnetic energy transfer from the microwaves source to the interacting material, which according to its electric, dielectric, and magnetic properties can convert the absorbed energy into heat. This peculiar heating mechanism is at the basis of plenty of unquestionable advantages that were reported during the last three decades in most of the different branches of chemistry as well as materials science, thus including also combustion synthesis. After a brief overview of the microwave heating fundamentals as well as of the different components constituting the scientific microwave applicators, all the most significant and recent advancements in the use of microwaves as energy source in both solid-state as well as solution combustion synthesis processes will be comprehensively reviewed, highlighting the unique opportunities arising from the coupling of these two energy efficient techniques. Moreover the possible employment of less conventional frequencies as well as the use of new-generation solid state generators will be critically discussed also in the framework of scaling-up and microwave reactor design considerations.

Simultaneous application of microwave energy and hot air to whole drying process of apple slices: drying kinetics, modeling, temperature profile and energy aspect

Drying kinetics, modeling, temperature profile and energy indices were investigated in apple slices during drying by a specially designed microwave-hot air domestic hybrid oven at the following conditions: 120, 150 and 180 W microwave powers coupled with 50, 60 and 70 °C air temperatures. Both sources of energy were applied simultaneously during the whole drying processes. The drying process continued until the moisture content of apple slices reached to 20% from 86.3% (wet basis, w.b). Drying times ranged from 330 to 800 min and decreased with increasing microwave power and air temperatures. The constant rate period was only observed at low microwave powers and air temperatures. Two falling rate periods were observed. Temperature of apple slices sharply increased within the first 60 min, then reached equilibrium with drying medium and finally increased at the end of the drying process. In order to describe drying behavior of apple slices nine empirical models were applied. The Modified Logistic Model fitted the best our experimental data (R 2 = 0.9955–0.9998; χ 2 = 3.46 × 10−5-7.85 × 10−4 and RMSE = 0.0052–0.0221). The effective moisture and thermal diffusivities were calculated by Fick’s second law and ranged from 1.42 × 10−9 to 3.31 × 10−9 m2/s and 7.70 × 10−9 to 12.54 × 10−9 m2/s, respectively. The activation energy (Ea) values were calculated from effective moisture diffusivity (Deff), thermal diffusivity (α) and the rate constant of the best model (k). The Ea values found from these three terms were similar and varied from 13.04 to 33.52 kJ/mol. Energy consumption and specific energy requirement of the hybrid drying of apple slices decreased and energy efficiency of the drying system increased with increasing microwave power and air temperature. Apples can be dried rapidly and effectively by use of the hybrid technique.

A comparative property investigation of lithium phosphate glass melted in microwave and conventional heating

The present study addresses the application of microwave (MW) energy for melting lithium phosphate glass. A comparative analysis of the properties is presented with glasses melted in conventional resistance heating adopting standard methods of characterization. The density of the glass was found less in MW heating. The glass transition temperature was recorded as 3–10\({^{\circ }}\hbox {C}\) lower in MW prepared glass than in conventional glass. Micro-hardness is found to be improved in case of MW heating. Maximum forward power was recorded less than 2 kW with an average power \(\sim \)1 kW during melting of 40 g glass in MW furnace. MW forward and reflected power measured during melting in the MW cavity was elaborated. Total melting time was within 2 h 30 min in MW heating, whereas it was 6–7 h in resistive heating. Total power consumed was \(\sim \)5 kWh in MW heating and \(\sim \)14 kWh in resistance heating.

Application of Microwave Energy for Production of Iron Nuggets from the Pudo Iron Ore using ‘Pito’ Waste and its Blend with HDPE as Reductant

The local steel industry is currently facing stiff competition from South East Asia and elsewhere for high grade scrap iron, culminating in a ban by central Government on the export of ferrous scrap. In this work we investigate the potential for producing high grade iron nuggets from the Pudo iron ore in the Upper West Region of Ghana, using carbonaceous materials generated from locally available ‘pito’ waste and its blend with high density polyethylene (HDPE) as reductant. Composite pellets of the ore containing various blends of uncharred ‘pito’ and charred ‘pito’ waste with HDPE were irradiated in a domestic microwave oven and the extent of reduction was determined after 40 min of irradiation. It was observed that highly carburised premium grade iron nuggets can be produced from the Pudo iron ore using ‘pito’ waste (both charred and uncharred) and its blends with HDPE as reductant. The measured extent of reduction ranged from about 47 % to about 96 %, suggesting that the Pudo iron ore is a potential source of iron from which premium grade metallic iron can be produced commercially to feed the local steel industry. From the point of view of chemical reactivity, it appears the effect of hydrogen is more pronounced than the amount of fixed carbon in the ‘pito’ waste and this effect was felt in all the HDPE-‘pito’ waste blends utilised for the investigation. Accordingly dry ‘pito’ waste may be used directly with HDPE as reductant without the need to char the biomass. Keywords: Reduction, Pudo Iron Ore, Waste Biomass, Pito Waste, Extent of Reduction