Direct Heating Process Research Articles

Solar-thermal cold-wall chemical vapor deposition reactor design and characterization for graphene synthesis

Manufacturing processes are often highly energy-intensive, even when the energy is primarily used for direct heating processes. The required energy tends to derive from local utilities, which currently employ a blend of sources ranging from fossil fuels to renewable wind and solar photovoltaics, among others, when the end manufacturing need is thermal energy. Direct solar-thermal capture provides a compelling alternative that utilizes renewable energy to reduce greenhouse gas emissions from industrial processes, but one that has rarely been employed to date. In this study, a 10 kWe custom-built high flux solar simulator (HFSS) that closely approximates the solar spectrum produces a heat flux distribution with an adjustable peak between 1.5 and 4.5 MW/m2. The HFSS system is coupled to a cold-wall chemical vapor deposition (CVD) system that is equipped to automate graphene synthesis while providing safe operation, precise control, and real-time monitoring of process parameters. A numerical heat transfer model of a thin copper substrate is derived and validated to compute the substrate’s temperature profile prior to the synthesis process. The peak substrate temperature is correlated to the HFSS supply current and vacuum pressure, as it serves as a critical design parameter during graphene synthesis. We report the synthesis of high-quality graphene films on copper substrates with an average Raman peak intensity ratio ID/IG of 0.17. Backscattered electron microscopy reveals a characteristic grain size of 120 μm, with an area ratio of 16 when compared to that of low-quality graphene on copper. The reported solar-thermal CVD system demonstrates the ability to produce a high-value product, namely, graphene on copper, directly from a renewable energy resource with process control and automation that enables synthesis under a variety of conditions.

UV-enhanced conductive and dielectric properties in KTN crystal

We observe enhancements of both conductive and dielectric properties under UV illumination by using a ferroelectric absorber, potassium tantalate niobate (KTa1-xNbxO3, KTN). The UV-generated electron-hole pairs weaken the intrinsic ferroelectric polarization while enhance the conductive property. The UV-induced heat effect causes the enhancement of the dielectric property. The results are further confirmed by the maximal rectification ratio which shows an opposite trend between the direct heating process and the UV illumination. Our results are useful for better understanding of ferroelectric properties under UV illumination and the development of new optoelectronic devices.

Energy consumption and atmospheric emissions from refined petroleum in Mexico by 2030

One of the basic needs for a country’s economic development is to cover the major fuel demand, and both energy consumption and environmental impacts resulting from the production of such fuels need to be fast and reliable. The purpose of this paper is to contribute to an estimate of energy consumption and atmospheric emissions of some of the pollutant species reported by Pemex Refinacion under different projections. The predictive estimate model was applied considering four different gasoline demand scenarios, as well as different refining technology options to satisfy fuel consumption needs, based on production yields: four different types of refineries, three types of crude oils and eight different processes. Emission estimates were determined applying emission factors, both for the type of fossil fuel energy source used in the direct heating processes for vapor generation, as well by using electric energy. Results show that the equivalent energy consumption relative to the total processes crude is greater in complex refineries (full conversion); however, a greater conversion efficiency allows a smaller volume of crude consumption needed to satisfy the fuel demand with lower emissions relative to other types of technologies. Mexico’s possible refineries need to adapt themselves to different operation scenarios, such as changes in the crude’s yield, the quality of the product, variations in the prices of the crude and of the refined products. Therefore, is important to develop and apply perspectives than maximize productivity and minimize energy consumption, reducing air emissions, in constant change scenarios. Finally, the problem would then be evaluating which would be more convenient to obtain a greater socio-economic benefit: reduce emissions to the atmosphere or to lower operation costs of the refinery.

A solar reactor for bio-diesel production from Pongamia oil: Studies on transesterfication process parameters and energy efficiency

Abstract Over exploitation of non-renewable energy reserves will lead to increase in price of petroleum fuels. Therefore there is a need for suitable and sustainable substitutes (renewable resource) for conventional fuels. In this study, an efficient and environmental friendly method for production of bio-diesel from Pongamia (Karanja) oil has been developed using a solar reactor. During the experimental study, the maximum temperature attained by the pongamia oil during the transesterification process was 64.1°C. The transesterification reaction was studied by varying different parameters such as reactant flow rate (5-20 LPH), stirring speed (150-450 r·min-1), catalyst loading (0.5 wt% -2 wt%) and methanol to oil ratio (3:1 to 15:1). The maximum biodiesel yield was 83.11% at a flow rate of 5 LPH, stirring speed of 350 rpm, a methanol to oil ratio of 15:1, catalyst loading of 1wt % and reaction time of 270 min. The physical and chemical properties of biodiesel was analyzed as per American Society for Testing Materials (ASTM) standards and it had density of 938 kg·m-3, viscosity (28.7 cSt), acid value (9.45 mg KOH·(g oil)-1) and flash point (215°C). The energy efficiency of solar heating process was determined by comparing the net energy ratio of direct heating process and solar heating process. For solar heating the net energy ratio (NER) was found to be 31.85 against 5.73 for direct heating. Similarly, net energy efficiency index was calculated for 10 kg production scale and was found to be increasing when scaled up which means that the solar heating process is more effective even in scaled up production.

Economic analysis of solar thermal system for melting of ice at high altitude regions using Scheffler solar concentrator

ABSTRACT The present paper deals with the economic investigation of hot water generation from melting of ice through Scheffler solar concentrator at high altitude regions like Leh Ladakh in India. For determination of the cost incurred per litre in terms of the Indian Currency, several factors have been studied and evaluated. In all three examined cases, for every respective case, the undeviating technique is adopted. The experimentation is performed in the atmospheric conditions of National Institute of Technology, Kurukshetra, Haryana, India. Exclusive economics of yearly cost per litre is achieved for the generation of hot water from ice at high altitudes by making use of direct heating process.

Rational design of a functionalized aluminum metal-organic framework as a turn-off fluorescence sensor for α-ketoglutaric acid.

A 3D metal-organic framework (MOF) called Al-DUT-5-N2H3 (1) (DUT: Dresden University of Technology) was prepared hydrothermally using Al(iii) salt and a hydrazinyl functionalized linker called 2-hydrazinyl-[1,1'-biphenyl]-4,4'-dicarboxylic acid (BPDC-N2H3). Material 1 was successfully characterized by X-ray powder diffraction (XRPD), FT-IR spectroscopy, N2 sorption (BET) experiment, thermogravimetric analysis (TGA), EDX and FE-SEM analyses. The activated form of material 1 (called 1') was achieved by a direct heating process. Material 1' was successfully employed for the solution-phase fluorescence detection of α-ketoglutaric acid (α-KG). It showed high detection performance even when there were other competitive analytes present in the mixture. Material 1' is the first MOF-based fluorescent turn-off sensor for the detection of α-KG. The response time for α-KG is exceptionally low (60 s) as compared to any other reported α-KG sensor. The limit of detection (LOD) was found to be 0.61 μM, which is far better as compared to any other reported sensor for α-KG to date. The mechanism for α-KG sensing was thoroughly investigated and proposed to be PET (photoinduced electron transfer) process by TD-DFT (time-dependent DFT) calculations.

Transparent, Highly Stretchable, Rehealable, Sensing, and Fully Recyclable Ionic Conductors Fabricated by One‐Step Polymerization Based on a Small Biological Molecule

AbstractTo date, various stretchable conductors have been fabricated, but simultaneous realization of the transparency, high stretchability, electrical conductivity, self‐healing capability, and sensing property through a simple, fast, cost‐efficient approach is still challenging. Here, α‐lipoic acid (LA), a naturally small biological molecule found in humans and animals, is used to fabricate transparent (>85%), electrical conductivity, highly stretchable (strain up to 1100%), and rehealable (mechanical healing efficiency of 86%, electrical healing efficiency of 96%) ionic conductor by solvent‐free one‐step polymerization. Furthermore, the ionic conductors with appealing sensitivity can be served as strain sensors to detect and distinguish various human activities. Notably, this ionic conductor can be fully recycled and reprocessed into new ionic conductors or adhesives by a direct heating process, which offers a promising prospect in great reduction of electronic wastes that have brought acute environmental pollution. In consideration of the extremely facile preparation process, biological available materials, satisfactory functionalities, and full recyclability, the emergence of LA‐based ionic conductors is believed to open up a new avenue for developing sustainable and wearable electronic devices in the future.

Formation of Large-scale Coronal Loops Interconnecting Two Active Regions through Gradual Magnetic Reconnection and an Associated Heating Process

Abstract Coronal loops interconnecting two active regions (ARs), called interconnecting loops (ILs), are prominent large-scale structures in the solar atmosphere. They carry a significant amount of magnetic flux and therefore are considered to be an important element of the solar dynamo process. Earlier observations showed that eruptions of ILs are an important source of CMEs. It is generally believed that ILs are formed through magnetic reconnection in the high corona (>150″–200″), and several scenarios have been proposed to explain their brightening in soft X-rays (SXRs). However, the detailed IL formation process has not been fully explored, and the associated energy release in the corona still remains unresolved. Here, we report the complete formation process of a set of ILs connecting two nearby ARs, with successive observations by STEREO-A on the far side of the Sun and by SDO and Hinode on the Earth side. We conclude that ILs are formed by gradual reconnection high in the corona, in line with earlier postulations. In addition, we show evidence that ILs brighten in SXRs and EUVs through heating at or close to the reconnection site in the corona (i.e., through the direct heating process of reconnection), a process that has been largely overlooked in earlier studies of ILs.

Aromatic constituents and their changes of Illicium verum processed by different heating methods

The aromatic constituents and their changes of Illicium verum during different heating processes and the practical applications were investigated in this study. Results of gas chromatography-mass spectrometry (GC–MS), gas chromatography olfactometry (GC–O) and corresponding sensory assessment showed that trans-anethole was the most representative and important component of aromatic volatiles in Illicium verum, which would cover up the scents of other ingredients. Furthermore, these results implied that the volatilization of trans-anethole reached the maximum at 100 °C during direct heating process and at 160 °C during frying heating process, which showed high similarity in sensory evaluation. The present study would provide the theory base for maximum utilizing the flavor of Illicium verum in food processing.

Pathways of F region thermospheric mass density enhancement via soft electron precipitation

AbstractThe efficiencies of pathways of thermospheric heating via soft electron precipitation in the dayside cusp region are investigated using the coupled magnetosphere‐ionosphere‐thermosphere model (CMIT). Event‐based data‐model comparisons show that the CMIT model is capable of reproducing the thermospheric mass density variations measured by the CHAMP satellite during both quite and active periods. During the 24 August 2005 storm event (Kp = 6−) while intense Joule heating rate occurs in the polar cusp region, including soft electron precipitation is important for accurately modeling the F region thermospheric mass density distribution near the cusp region. During the 27 July 2007 event (Kp = 2−) while little Joule heating rate occurs in the polar cusp region, the controlled CMIT simulations suggest that the direct pathway through the energy exchange between soft electrons and thermospheric neutrals is the dominant process during this event, which only has a small effect on the neutral temperature and mass density at 400 km altitude. Comparisons between the two case studies show that the indirect pathway via increasing the F region Joule heating rate is a dominant process during the 24 August 2005 storm event, which is much more efficient than the direct heating process.

One-pot controllable synthesis of wurtzite CuInS2 nanoplates

Abstract Wurtzite CuInS 2 nanoplates have been synthesized using a simple one-pot colloidal chemical method, which is a direct heating process without any injection and pre-synthesis of any metal precursors. The transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) have been employed to characterize their morphology, crystalline phase, and composition, respectively. By changing the reaction conditions, such as reaction time, reaction temperatures and the Cu:In precursors ratio, the nanoplate thickness and composition can be tailored effectively. By monitoring the growth process of the as-obtained CuInS 2 nanoplates, it found that the monoclinic Cu 1.94 S nanocrystals were firstly formed and gradually transformed to CuInS 2 nanoplates with the increasing reaction time.

Нагрев для технологических операций

To heat the metal still more prevalent direct heating processes in electric power plants induction or contact heating. The paper shows the possibility of such electric installations for various processes, as well as the possibility of combining heating (serial or parallel) with other technological operations (combined treatment). Described the use of induction-hardening plants in research on hardening of hard alloys, as well as ways of sticking pieces exception when unloading them from the inductor. Shows the use of contact heating for quenching carbide and heating the electrolyte and by heating rolled before pressure treatment.

Optical properties and self-assembly of Ag2S nanoparticles synthesized by a one-pot method

Spherical silver sulfide (Ag2S) nanoparticles have been synthesized using a simple and one-pot route, which is a direct heating process using silver acetate and n-dodecanethiol as raw materials.Transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and selected area electron diffraction (SAED) were used to confirm the size, morphology and crystal structure of as-obtained Ag2S nanoparticles. The size of the products can be tuned by controlling the reaction time, and the growth process of the samples has been studied by employing UV–vis absorption spectra. Furthermore, these Ag2S nanoparticles have a high tendency to self-assemble into two- or three-dimensional superlattice structures. This one-pot approach may be extended to synthesis of other metal sulfides nanoparticles.

Effect of Cobalt Doping Concentration on the Crystalline Structure and Magnetic Properties of Monodisperse CoxFe3–xO4 Nanoparticles within Nonpolar and Aqueous Solvents

In this work, we investigate the effect of cobalt substitution on the size evolution, crystal structure, and magnetic properties of Fe3O4 nanoparticles. Monodisperse CoxFe3–xO4 nanoparticles were prepared, using a one-step method, by direct heating process of iron(III) and cobalt(II) acetylacetonates in high-boiling-point inert organic solvent. The quantities of precursors added were based on stoichiometric Fe/Co ratio of desired ferrite. Elemental analyses ICP-AES evidenced successful cobalt doping. The doped particles showed a cobalt-deficient composition. Transmission electron microscopy demonstrated the large changes of particle size as a function of cobalt doping. The magnetization measurements showed an unchanged saturation magnetization only up to x = 0.24, beyond which it significantly decreased. To make the as-synthesized nanoparticles suitable for biomedical applications, oleic acid ligands are exchanged with caffeic acid molecules leading to stable nanoparticles in physiological conditions.

A Facile “Dispersion–Decomposition” Route to Metal Sulfide Nanocrystals

In this paper, we demonstrate a simple and general "dispersion-decomposition" approach to the synthesis of metal sulfide nanocrystals with the assistance of alkylthiol. This is a direct heating process without precursor injection. By using inorganic metal salts and alkylthiol as the raw materials, high-quality Ag(2)S, Cu(2)S, PbS, Ni(3)S(4), CdS, and ZnS nanocrystals were successfully synthesized. The mechanism study shows that the reaction undergoes two steps. A key intermediate compound, metal thiolate, is generated first. It melts and disperses into the solvent at a relatively low temperature, and then it decomposes into metal sulfide as a single precursor upon heating. This method avoids using toxic phosphine agent and injection during the reaction process. The size and shape of the nanocrystal can be also controlled by the concentration of the reactant and ligands. Furthermore, the optical properties and assembly of the nanocrystals have also been studied. This report provides a facile, direct-heating "dispersion-decomposition" approach to synthesize metal sulfides nanocrystals that has potential for future large-scale synthesis.

Numerical Simulation of Temperature Field and Stress Field of Electron Beam Brazing Stainless Steel Radiator

Aiming at the radiator with tube-to-plate structure applied usually in aeroplane, a two-dimensional model for finite element analysis was established in this work. By ANSYS software, the temperature field and stress field of electron beam brazing (EBB) 1Cr18Ni9Ti stainless steel radiator by two kinds of process were numerically simulated. The calculated results of temperature field show, by the stage-by-stage heating process, the uniform temperature distribution of radiator faying face was obtained. The temperature of most regions is between 1042~1051°C, which is in the range of brazing temperature. The calculation results of stress field indicate, for radial residual stress, the obvious stress concentration region was found in faying face by direct-heating process; while there was no stress concentration in faying face by stage-by-stage heating process. For circumferential residual stress, compared the stage-by-stage heating process with direct-heating process, the peak value of tensile stress reduces by 11.2%. Compared circumferential residual stress with radial residual stress by two kinds of brazing process, the peak value of circumferential tensile stress is higher than radial tensile stress. So the dangerous position of faying face is along circle direction, namely, the heating direction of scanning electron beam. Consequently, the temperature difference between different positions in faying face must be controlled well during heating. The reduction of temperature difference can fall the peak value of tensile stress and improve the distribution of residual stress.

Photoluminescence of hexagonal-shaped SiC nanowires prepared by sol–gel process

New hexagonal-shaped SiC nanowires were synthesized through a sol–gel and direct heating process. Electron microscopy, X-ray diffraction and Raman spectrum indicate the nanowires possess a β-SiC structure and have typical diameters of 50–100 nm and length up to several tens of micrometers. Two strong broad ultraviolet light emission peaks at about 290 and 396 nm are observed at room temperature from the hexagonal-shaped nanowires, which are excitated by 250 nm ultraviolet fluorescent light. Compared with the previous reports, the synthesized nanowires exhibit two larger buleshifts in the photoluminescence (PL) spectrum. The buleshift of former PL peak is attributed to the oxygen defects in SiO x layer and the second one is due to morphology and size confinement effects of the SiC nanowires. Memory effect may be responsible for the hexagonal shape formation of SiC nanowires during vapor–solid growth process.

Molecular dynamics study of the melting of nitromethane

Molecular dynamic studies of melting of nitromethane have been carried out using two methods: (1) void-nucleated melting with the gradual heating of the lattice and (2) equilibration of coexisting liquid and solid phases. The results are in near agreement with each other; the small difference is attributed to the hysteresis effect associated with the direct heating process. The values of the melting temperature Tm computed by using the intermolecular interaction potential of Sorescu et al. [J. Phys. Chem. B 104, 8406 (2000)] are found to be in good agreement with the experimental data at various values of pressure ranging from 1 atm to 30 kbar. The computed values of the melting temperature satisfy the Simon–Glatzel equation P(kbar)=aTmb+c, where a=1.597×10−5, b=2.322, c=−6.74, and Tm is in kelvin. A comparison of computed Tm with and without the presence of molecular vibrations reveals that Tm is insensitive to the intramolecular interaction term of the potential energy function, but depends strongly on the intermolecular interactions, particularly the Coulombic term (i.e., the partial charges on atoms).

Trace element mineral transformations associated with hydration and recarbonation of retorted oil shale

A laboratory study was conducted to evaluate the influence of hydration and recarbonation on the solidphase distribution of trace elements in retorted oil shale. The oil shale samples were retorted by the Paraho direct heating process and equilibrated with deionized—distilled water under controlled carbon dioxide conditions. A sequential extraction technique was then used to fractionate trace elements into soluble, KNO3-extractable (easily exchangeable), H2O-extractable (easily adsorbed), NaOh-extractable (organic), EDTA-extractable (carbonate), HNO3-extractable (sulfide), and residual (nonextractable silicate) phases. The chemical fractions present in retorted oil shale and hydrated and recarbonated retorted oil shale were compared to identify trace element mineralogical changes that may occur in retorted oil shale disposal environments.