Microwave Metal Interaction Research Articles

Enhanced pyrolysis of woody biomass under interaction of microwave and needle-shape metal and its production properties

Pyrolysis is one of the routes to value-added utilization of biomass, and the pyrolysis process can be enhanced with microwave heating, especially in the presence of catalyst. However, the catalysts used for biomass pyrolysis are usually in form of powder or grain, which leads to a problem that the catalysts are hard to separate from bio-char after the pyrolysis process. Based on this issue, the development of an enhanced microwave-assisted pyrolysis method without catalyst is of great significance. Therefore, this study proposes the method of microwave-enhanced pyrolysis of woody biomass via the interaction of microwave and needle-shape metal (iron-wire). In the paper, the pyrolysis characteristics and kinetic behaviors in the presence and in the absence of iron-wire were investigated, using pine sawdust and the mixture of biomass components as the material. Moreover, the properties of pyrolysis products with and without microwave-metal interaction were characterized, and the mechanism of microwave-metal interaction on the enhancement of pyrolysis was also analyzed. The results showed that the value of Ea reduced by 50% with microwave-metal interaction and the process under microwave-metal interaction was more conducive to the generation of bio-gas, with the yield of 62.43 wt%. Microwave-metal interaction increased ID/IG value of bio-char from 0.69 to 0.92, indicating an improvement of graphite degree, and decreased the content of aromatic compounds in bio-oil by 11.8%. The enhanced pyrolysis process is due to the increased electromagnetic distribution density after the insertion of iron wire into microwave and even microwave discharge occurred at the initial stage.

Characteristics and kinetic analysis of pyrolysis of forestry waste promoted by microwave-metal interaction

In the present work, a method of pyrolyzing forestry waste (FW) under microwave-metal interaction was proposed. The kinetic analysis of the process was carried out using a microwave thermogravimetric analyzer. The mechanism of FW pyrolysis under microwave-metal interaction was discussed from the perspective of microwave-induced metal discharge and non-discharge processes. The initial pyrolysis temperature Ti reduced, and the maximum pyrolysis rate Rm and pyrolysis characteristic index S increased by employing a method where microwave and metal were coupled. The number of metals inserted also significantly affected the pyrolysis behavior. Rm in the presence of one metal was 92.3% higher than that recorded in the absence of metal. The results of kinetic analysis revealed in the presence of metal, the activation energies at 400 W and 560 W were 51.7% and 57.5% lower, respectively, than the activation energy recorded in the absence of metal. Multiple effects of light, heat, and plasma produced by microwave-induced discharge caused the local pyrolysis of FW. The promotion of FW pyrolysis in the non-discharge stage was primarily caused by the microwave absorption of carbon into heat and the conversion of current on the metal surface into Joule heat.

Effect of Input Power and Process Time on Conversion of Pure and Mixed Plastics into Fuels Through Microwave-Metal Interaction Pyrolysis

This study investigated the effect of input power and process time on microwave-metal interaction pyrolysis of pure plastics (PS, PP, LDPE) and their blends into liquid and gaseous fuels. The microwave power and time were varied to pyrolyze 20 g of each sample in an iron coil. The pure PS underwent maximum conversion into fuels followed by PP and LDPE. Under optimized microwave power (2100–2500 W), PS produced 88.7% oil after 19 min of reaction time, PP produced 54.65% oil at 23 min of reaction time and LDPE produced 30.15% oil after 26 min of reaction time. Pure PS and PP showed high conversion efficiency of 95.40% and 95.10%, respectively, into liquid and gaseous fuels. Pure LDPE showed only 54.30% conversion into fuels by producing large quantity of waxy residue. In blended form, PS-PP blend revealed highest conversion of 65.67% into fuels followed by PS-PP-LDPE blend (57.23%), PS-LDPE blend (46.52%) and PP-LDPE blend (28.08%). Based on mass balance and percentage conversion, PS-PP blend showed maximum conversion of 96.25% whereas PP-LDPE showed minimum conversion of 74.99%. Higher microwave powers within optimal range produced better yield of liquid fuel in shorter time periods. The pyrolytic oils contained some useful aromatic and aliphatic hydrocarbons (C8–C16).

On Processing and Characterization of Cu–Mo-Based Castings Through Microwave Heating

In the present work, the processing of microwave castings of Cu–Mo-based materials was carried out using microwave heating at 2.45 GHz and 900 W. Three sets of castings were developed inside microwave applicator cavity with three different compositions such as Cu + 10% Mo, Cu + 30% Mo and Cu + 50% Mo by volume percentage. A mechanism describing microwave metal interaction has been established. Microstructure analysis study of developed castings revealed the formation of small equiaxed grains with uniform dispersion of Mo particles in Cu-based metal matrix. The presence of Cu64O, Cu6Mo5O18 and MoO2 elements phases was observed during phase analysis of microwave processed composite castings. Vicker’s microhardness study analysis revealed that the Cu + 50% Mo-based casting exhibited maximum Vicker’s microhardness of order 120.8 ± 9 HV, which was approximately 2.7 times that of microwave processed Cu-based castings. The higher percentage of Mo particles inside Cu-based matrix resulted in an increase in electrical resistivity of the casting.

Effect of reaction time and microwave power on coil temperature during microwave-metal interaction pyrolysis of plastics

Rapid rise in production of plastic waste has posed a threat to environment due to its nonbiodegradable nature. In recent years, microwave assisted pyrolysis of plastic waste has emerged as a promising solution toward reduction of waste and recovery of value-added products and fuels. Previous works on microwave-metal interaction pyrolysis estimated only the peak value of coil temperature at a constant microwave power without monitoring complete reaction. The current study was directed toward investigating the effect of reaction time and variable microwave power on the coil temperature during microwave-metal interaction pyrolysis of plastics. The experiment was performed on individual plastics PS (polystyrene), PP (polypropylene) and LDPE (low density polyethylene) for comparative analysis. Pyrolysis was carried out for a reaction time of 30 minutes at different values of microwave power in the range of 500-2500 W. Type K thermocouple was used to monitor temperature of metal coil. Fluctuation in temperature of coil was found to be a consequence of interaction of coil and thermocouple with the microwaves. Maximum heating rate was observed in the first 5 minutes of microwave exposure. The slopes of average temperature versus microwave power were found to be nearly equal estimated as: PS = 0.24 °C/W, PP = 0.20 °C/W, LDPE = 0.18 °C/W, which indicated consistency in heating process for each plastic, achieved by the current set-up. Further, it was inferred that nature of plastic pyrolyzed had insignificant influence on coil temperature due to absence of direct contact between plastic and the coil.

Production of highly upgraded bio-oil by microwave–metal interaction pyrolysis of biomass in a copper coil reactor

ABSTRACTIn this study, highly upgraded bio-oil was produced by microwave–metal interaction pyrolysis of water hyacinth biomass. A copper coil was used as a microwave receiver and heat generating antenna. The pyrolysis of biomass was carried out with and without using a cement catalyst. The fractional amounts of the as-produced bio-oil, biogas, and biochar were determined in terms of catalyst mass, reaction time, and the gauge of the copper coil antenna. In cement catalyzed pyrolysis, the water hyacinth was converted into 20% bio-oil and 31% combustible gases with overall conversion efficiency of 66%. In the case of uncatalyzed pyrolysis, the overall conversion efficiency remained below 60% with 10% bio-oil. The biomass to catalyst ratio of 5:1, 25 min of reaction time and 2.5 mm gauge of wire were predicted as optimum conditions for the pyrolysis process. The bio-oil was further analyzed through chromatography–mass spectrometry (GC-MS) while the gaseous products were analyzed through chemical testing and combustibility analysis. Significant difference in the chemical composition of the bio-oils, produced using catalytic and noncatalytic microwave–metal interaction pyrolysis, was noticed in these investigations. The oil product of the catalyzed and uncatalyzed pyrolysis contained 11.6% and 9.418% hydrocarbons, respectively. Similarly, oxygen content in the oil was measured about 14.73% and 16.66%, respectively. Also, unlike the thermal or thermo-catalytic pyrolysis, the bio-oil product of the microwave–metal interaction pyrolysis was found immiscible with water.

Effect of metal coil on product distribution of highly upgraded bio-oil produced by microwave-metal interaction pyrolysis of biomass

The microwave-metal interaction pyrolysis technique has great potential of producing highly upgraded bio-oils from the biomass. In this study, the heat of the sparking metals in a microwave oven was utilized to pyrolyze the biomass into bio-oil, biogas and char. Using this technique, highly upgraded preliminary bio-oil was produced from the water hyacinth biomass. The effect of the metal type and gauge size on the product quality and composition was investigated by using different heat generating antennas. The bio-oil, obtained with each metal coil, was analyzed with Gas chromatography–mass spectrometry (GC–MS) technique. The gaseous products were characterized using spot test and combustibility analysis. Significant difference in the chemical composition of the bio-oils, produced with different metal coils, was noticed in these investigations. For all the tested metals, the oxygen and hydrocarbon content in the oil product was found significantly lower than those obtained through conventional pyrolysis. Also, unlike the thermal or thermo-catalytic pyrolysis, the bio-oil product of the microwave-metal interaction pyrolysis did not contain any water content.

Cement catalyzed conversion of biomass into upgraded bio-oil through microwave metal interaction pyrolysis in aluminum coil reactor

Metal objects spark in the microwaves, exposing metals to melting point temperatures. The resulting heat can be utilized for the pyrolysis of biomass into upgraded bio oil. In this work pyrolysis was carried out both in the presence and absence of catalyst and the upgradation of bio oil was found the combine action of microwave heating, microwave effects and the catalytic activity of cement. Catalytic pyrolysis of biomass was carried out by mixing powdered biomass with fine powder of cement and placing the resulting mixture in an aluminum coil located in the baked clay reactor followed by its exposure to the microwaves. In this process aluminum coil was used as microwave receiving and heat generating antenna. All these experiments were carried out in a modified domestic microwave oven. The amount of product fractions like bio-oil, biogas and biochar was determined in terms of the mass of catalyst, time of reaction and the gauge of aluminum wire used for the preparation of coil. The bio oil obtained under the optimum conditions was analyzed using Gas chromatography mass spectrometry and the gaseous product was analyzed using chemical tests. Significant difference was observed in the chemical composition of bio oils prepared by catalytic and non-catalytic processes. Further, the oxygen contents of both types of the bio oil were found less than those to be obtained by conventional pyrolysis.

Microwave assisted pyrolysis of plastic waste for production of fuels: a review

This paper presents an overview of advantages of microwave assisted pyrolysis of waste plastics together with its limitations. It has been established that microwave induced pyrolysis can be used to get value added chemicals and fuels through its numerous noted advantages in contrast to conventional pyrolysis. The process has the potential for fast, volumetric and selective heating of plastics for the recovery of energy. The limitation in the use of dielectric material as absorbent in plastic pyrolysis has been highlighted. Special focus has been given to the constraints encountered in the accurate measurement of temperature and uniform heating in microwave assisted pyrolysis. A new alternative method based on microwave-metal interaction in the pyrolysis of plastic waste has been presented. Further it has been realized that proper investigation and understanding of microwave process shortcomings is fundamental to the successful implementation of the technology and at the same time provide a sustainable environment in the endeavor for waste to energy mission.

Wavelength tunable TFBG based microwave sensor using surface plasmon resonance

A noble idea is used to propose a wavelength tunable tilted Fiber Bragg Gratings based microwave sensor using surface plasmon resonance. The Bragg wavelength shifts linearly about 6pm/°C, due to the temperature change. This temperature variation occurs because of the microwave–metal interaction at cladding layer of the optical fiber based proposed sensor. The wavelength tuning can be achieved by using tilted Fiber Bragg Gratings. To use the wavelength sources of 850nm, 1310nm and 1550nm, tiled Fiber Bragg Gratings with grating periods of 293.65nm, 452.56nm and 535.47nm respectively are required in the same fiber with certain distances among them.

Microwave-metal Interaction Pyrolysis of Waste Polystyrene in a Copper Coil Reactor

Waste polystyrene was pyrolyzed into substituted aromatic compounds in a microwave oven using a copper coil reactor. The copper coil acts as an antenna and heat-generating object. The rate of reaction was found to be dependent on the size, shape, and form of the metal antenna. The pyrolysis products were found to contain 85% oily liquid, 10–12% gases, and char residue. The amount of gas was calculated by taking the difference. The liquid products were analyzed by using gas chromatography-mass spectrometry and found that it contains substituted benzene in addition to polycyclic aromatics and condensed ring aromatic compounds.

The conversion of waste polystyrene into useful hydrocarbons by microwave-metal interaction pyrolysis

Waste polystyrene was pyrolyzed at temperatures as high as the melting point of aluminum into styrene and other substituted aromatic compounds. This temperature was attained by the interaction of microwaves with aluminum in the form of a tightly coiled wire, strips, and cylinder. The rate of reaction was found to depend on the size, shape and form. The reaction was faster for the coil, slower for strips and negligible for the cylindrical form. The yields of pyrolysis were also found to depend on size, shape and form of the metal. The products of the pyrolysis were found to contain 88 wt % liquid, 9–10 wt % gases and residual char. The liquid portion was collected using cold traps and measured, whereas the amount of gas was obtained by taking difference. The liquid portion was analyzed using GC/MS and found that it contains substituted benzene in addition to polycyclic aromatics and condensed ring aromatics. The gases were identified using acetylide formation and Baeyer's test. The products, formation, mechanism of the reaction, and nature of products are discussed.

Co-liquefaction of Makarwal coal and waste polystyrene by microwave–metal interaction pyrolysis in copper coil reactor

A novel method for the co-pyrolysis of waste polystyrene with coal was investigated. This method is based on high temperature obtained by microwave copper interaction. This pyrolysis is believed to be the combine action of the high temperature, microwaves interaction and the active species produced during the process. The metal antenna may also catalyze the pyrolysis process and affect the nature of products. This is a faster method of the co-pyrolysis and gives 66% oily liquid which was a mixture of tar and oil, 10% aqueous liquid mainly composed of sulfides, 6% gases and 18% residues. The liquid product was collected using cold traps and the amount of gas was obtained by taking difference. The oily liquid product was analyzed using GC–MS and found that it contains mainly aromatic compounds in a narrow range. The range of products and product formation is also discussed in this communication.

Microwave–metal interaction pyrolysis of polystyrene

A novel method for the pyrolysis of waste polystyrene was investigated which was based on high temperature by microwave–metal interaction. This interaction may also catalyze the pyrolysis process and affect the nature of products. Polystyrene was rapidly pyrolyzed under microwave while placing in a batch type reactor containing a cylindrical mesh of iron. The iron mesh generates heat in the range of 1100–1200 °C which converts polystyrene into 80% liquid, 15% gas and 5% char residue. The liquid product was collected using cold traps and the amount of gas was obtained by taking difference. The liquid product was analyzed using GC/MS and found that it contains styrene in addition to polycyclic aromatics and condensed ring aromatic compounds. The products formation is also discussed.