High-temperature Tube Furnace Research Articles

Pore-fracture structures and seepage flow characteristics during spontaneous coal combustion based on CT 3D reconstruction

To study the evolution characteristics of the pore-fracture structures and seepage properties of coal in the process of spontaneous combustion, a high-temperature tube furnace was used to heat the coal samples. The coal samples were scanned using Xray-CT scanning technology, and the CT 3D reconstruction technology was used to extract the 3D pore structure and equivalent pore network model of each group of coal samples. Firstly, the specific surface area and volume of pore cleavage is statistically characterized; the change rules of Ep, Et, Lc, and Cn are quantitatively analyzed. At 200 °C, the coal body produces a large number of pore fractures, the development of coal samples is more significant, and the pore-specific surface area and the number of pore throats reached their maximum value. In addition, the changes of fractal dimension, porosity, connectivity, and permeability of coal with temperature were discussed, and the best permeability of the coal was achieved at 200 °C. The connectivity and permeability were weakened with the further increase of temperature, and the structural changes had a close influence on the gas seepage pressure and seepage flow rate. The results of the study provide important engineering guidance for deepening fire prevention in coalfields.

Pore-fracture structures and seepage flow characteristics during spontaneous coal combustion based on CT 3D reconstruction

To study the evolution characteristics of the pore-fracture structures and seepage properties of coal in the process of spontaneous combustion, a high-temperature tube furnace was used to heat the coal samples. The coal samples were scanned using Xray-CT scanning technology, and the CT 3D reconstruction technology was used to extract the 3D pore structure and equivalent pore network model of each group of coal samples. Firstly, the specific surface area and volume of pore cleavage is statistically characterized; the change rules of Ep, Et, Lc, and Cn are quantitatively analyzed. At 200 °C, the coal body produces a large number of pore fractures, the development of coal samples is more significant, and the pore-specific surface area and the number of pore throats reached their maximum value. In addition, the changes of fractal dimension, porosity, connectivity, and permeability of coal with temperature were discussed, and the best permeability of the coal was achieved at 200 °C. The connectivity and permeability were weakened with the further increase of temperature, and the structural changes had a close influence on the gas seepage pressure and seepage flow rate. The results of the study provide important engineering guidance for deepening fire prevention in coalfields.

Experimental investigation on high-temperature co-gasification and melting behavior of petrochemical sludge and bituminous coal in CO2 atmosphere

High-temperature co-gasification of petrochemical sludge (PS) and bituminous coal (BC) can melt heavy metals and fly ash in hazardous waste, decompose dioxins, and generate syngas, which can achieve clean disposal and high value resource utilization of wastes. In this investigation, the high-temperature co-gasification and ash melting experiments of PS mixed with BC were carried out in a high-temperature tube furnace under CO2 atmosphere. The effects of gasification temperature and blending ratios (PS:BC) on co-gasification characteristics and ash melting behavior were investigated. The synergistic effect of co-gasification of PS-BC was examined. The results show that the yield of syngas (CO + H2) was proportional to the temperature and the proportion of BC. As the temperature increased from 1100 °C to 1400 °C, the yield of syngas increased from 1.42 m3/kg to 1.54 m3/kg. At 1300 °C, as the blending ratio of PS:BC shifted from 1:0 to 0:1, the yield of syngas increased significantly from 0.49 m3/kg to 1.88 m3/kg. The most significant synergistic effect of PS-BC co-gasification was the enhanced CO yield. At a blending ratio of 1:1, the synergistic coefficient of CO yield reached a maximum of 1.31. As for the residues, with the increase of temperature and the proportion of BC, the ash melting got promoted. The leaching toxicity of heavy metals in the residues can meet the release standard (GB5805.3–2007), being safe for disposal.

Porous Electrode Optimization for PEMFCs Using 3D Printing Technology

Proton Exchange Membrane Fuel Cells (PEMFCs) represent a class of fuel cells that transform the chemical energy of fuels, ideally hydrogen and oxygen, into electrical power. Utilized in diverse applications, PEMFCs power vehicles and supply backup energy to buildings. The core of a PEMFC is the membrane electrode assembly (MEA), composed of a polymer electrolyte membrane, an anode, and a cathode. Oxygen, protons, and electrons merge at the cathode, forming water. One challenge PEMFCs face is water-induced cathode flooding at low temperatures, a consequence of the electrochemical reaction's water accumulation. This reduces the oxygen supply, potentially leading to decreased cell performance or even failure. This issue can have substantial undesired consequences, as PEMFCs depend on oxygen availability at the cathode to generate electricity.Gas Diffusion Layers (GDLs) serve as critical PEMFC components, providing porous structures that facilitate reactant access to the catalyst layer and enabling electron flow through the external circuit. GDLs also offer structural support and promote reactant distribution across the membrane surface. Water accumulation in the cathode may cause pore clogging within the GDL, restricting reactant flow, and reducing cell performance. Additionally, water build-up increases pressure drop across the GDL, hindering reactant access to the catalyst layer and diminishing fuel cell efficiency.Three-dimensional (3D) printing has emerged as a potential technique for fabricating GDLs in PEMFCs. 3D printing enables the creation of GDLs with ordered pore size structures, offering a more uniform surface than traditional GDLs with randomly oriented fibres. This uniformity enhances reactant distribution across the membrane surface and mitigates water accumulation risks. In addition, to prevent cathode flooding, 3D printed GDLs are immersed in PTFE solution to increase hydrophobicity.This talk delves into the creation and evaluation of 3D printed carbonized GDLs for PEMFC implementation. A desktop 3D printer constructed a polymer framework, which was subsequently carbonized in a high-temperature tube furnace. Isothermal thermogravimetric analysis (TGA) tests were performed to identify weight change across a temperature range of 30-900 °C under an N2 atmosphere, optimizing the carbonization step to reduce structural distortion and increase electrical conductivity.The 3D printed GDLs displayed pore size diameters spanning 80 to 120 μm and fibre radii of 20-30 μm. The 3D printing technique produced GDLs characterized by a consistent, planar structure without blocked pores that are normally caused by excess resin residue. Electrical conductivity assessments were conducted on the carbonized specimens, and tensile and compression tests measured their mechanical properties.GDLs possessing minimal pore sizes and thicknesses were integrated into membrane electrode assemblies (MEAs) and examined in low-temperature PEMFCs. Diverse spraying methodologies were investigated, involving either the catalyst being sprayed onto the 3D printed GDL or the membrane receiving a catalyst coating. Commercial MEAs, comprising Nafion membranes and platinum electrodes, acted as benchmarks for MEAs featuring 3D printed GDLs. Furthermore, the current challenges facing 3D printed GDLs, including material selection, production consistency, compatibility with other PEMFC components, costs, and scaling up are highlighted in the talk.These findings underscore the promise of 3D printed carbonized GDLs in boosting PEMFC performance, showing their potential as a cost-effective and proficient substitute for conventional carbon paper based GDLs. Figure 1

Advanced Marine Antifouling Hydrogels Based on 7-Amino-4-methylcoumarin Fluorescence Driven by Rare-Earth Phosphorescence.

At present, there are very few reports on the combination of phosphorescence and fluorescence in the field of pollution prevention. A composite antibacterial agent was designed to store energy by using the phosphorescence effect of rare earth oxides, emit light at night, and stimulate 7-amino-4-methylcoumarin to produce fluorescence and prevent algae from adhering. When complexed with PVA, it exhibited excellent characteristics as an all-weather autocatalytic phosphorescence-fluorescence antifouling hydrogel. The rare earth phosphorescent powder was prepared in a high-temperature tube furnace, coated with SiO2 on the surface for waterproofing, and then grafted with 7-amino-4-methylcoumarin to obtain a composite antibacterial agent with a phosphorescence-fluorescence effect. The composite antibacterial agent was added with PVA to obtain a hydrogel, which exhibited bactericidal rates of more than 99.98% against both Gram-positive and Gram-negative bacteria after 48 h. The results of fluorescence staining showed that the coverage rate of dead bacteria reached 41.6% after 24 h. The tensile strength of the antifouling hydrogel is up to 1.49 MPa, which is strong enough for real marine environments. Moreover, the algae coverage area of the composite hydrogel under natural light was only 2.7%, representing a 10-fold reduction compared with the control. The antifouling hydrogel has good antipollution and algae suppression performance, which is due to the fact that the rare earth phosphorescent powder when exposed to sunlight can provide a light source to stimulate 7-amino-4-methylcoumarin fluorescence at night and thereby prevent algae adhesion. After testing in the marine field and the real sea test when wrapped in a fishing net, the excellent antifouling performance was demonstrated. The functional hydrogel has great application potential in the protection of seawater-exposed structures, such as bridges and bay ports.

Modification of Inclusions by Rare Earth Elements in a High-Strength Oil Casing Steel for Improved Sulfur Resistance

Steel casing pipes used in the construction of deep oil wells usually require both high strength and corrosion-resistant behavior. Due to the exploration of deep H2S-bearing oil reservoirs, sulfide stress cracking (SSC) is becoming an increasingly serious concern for casing steel. The nonmetallic inclusions in the steel are among the key reasons for its service failure. The rare earth element Ce can be used to modify the inclusions in casing steel and improve its SSC resistance. Here, taking C110 grade casing steel (the highest class currently in service) as the investigated object, the modification behavior of Ce inclusions in the steel and the effect of the addition of Ce in varying amounts (0.01, 0.024, and 0.042 wt.%) on the modified products were studied through high-temperature tube furnace experiments and thermodynamic calculations. The results showed that Ce had an obvious modification effect on the CaO·Al2O3 inclusions in casing steel, and the diffusion of dissolved Ce in the steel was the limiting step of the modification reaction. With the extension of reaction time, the sequence describing the modification of inclusions in the steel was determined as follows: CaO·Al2O3 → CeAlO3 → Ce2O3/Ce2O2S. The final stable product after modification depended on the amount of Ce added. With 0.01 wt.% Ce, the stable phase in molten steel was Ce2O3; on the other hand, upon adding ≥0.024 wt.% Ce, the stable phase became Ce2O2S. In addition, the thermodynamic stability of Ce2O3 decreased, and it was transformed into CeAlO3, Ce2O2S, Ce2S3, and CeS during solidification. On the basis of our results and the considerations for smooth casting, the addition of a proper amount of a rare earth element is suggested for industrial trials, following the achievement of a significant and surprising improvement in the qualified rate of SSC resistance for the final steel products. The relevant mechanism is also analyzed.

In situ growth of ZnO on carbon nanospheres and its properties in natural rubber

AbstractCarbon Nanospheres (CNs) are nano‐carbon materials. In order to expand their application fields, this study applies them to rubber fillers. In this study, CNs were prepared by vapor deposition method in a high temperature tube furnace. After acidification of CNs, ZnO was grown in situ on the surface of CNs. CNs@ZnO/NR composite was prepared by traditional mechanical blending method. The experimental results showed that the ZnO nanoparticles were adsorbed on the surface of CNs, resulting in a strong interfacial interaction with the CNs. In the composite material, the hybrid is uniformly dispersed in the rubber matrix under the influence of its own many factors, thereby improving the cross‐linking effect of the composite material. Compared with the ZnO/NR composite, the modulus at 100%, 200%, and 300% elongation of NR composites are increased by 40.3%, 30.6%, 23.3%, and 9.6% respectively, maintaining the elongation at break of the composites. At the same time, the rigidity of the composite material is increased, the cross‐linking efficiency is improved, and the crosslinking density of the composite material is greatly improved. Compared with ZnOC/NR composite, CNs@ZnO/NR composite maintained better wet‐skid properties. The CNs in the CNs@ZnO can inhibit the agglomeration of ZnO nanoparticles, which can better improve the vulcanization rate and crosslinking density, and is an efficient vulcanization activator. This study provides a simple synthetic route for ZnO nanofillers for the preparation of high‐performance natural rubber composites.

Research on the evolution of pore and fracture structures during spontaneous combustion of coal based on CT 3D reconstruction

To study the evolution law of the pore and fracture structures during the spontaneous combustion of coal, a self-built high-temperature tube furnace was used in the experiment to heat the coal samples at different temperatures and gas atmospheres. The coal samples were scanned by Xray-CT technology, and the three-dimensional (3D) pore structure and equivalent pore network model of coal samples were extracted by CT 3D reconstruction technology. In the process of heating at 25–200 °C, the porosity and fractal dimension were more significantly developed for coal samples heat-treated in an air atmosphere than those for the coal samples heat-treated in nitrogen atmosphere. The connectivity and permeability of coal samples were investigated, and it was found that the connectivity of pore and fracture structures of coal samples heated in the air atmosphere was better. However, the coal samples heated after nitrogen injection had weak connectivity and permeability. At this temperature stage, the nitrogen injection into the goaf will have a stronger inhibitory ability to develop coal sample pore and fracture structures and a more obvious weakening of the permeability. Therefore, oxygen circulation inside the coal sample may be suppressed, which is more conducive to preventing and controlling coal spontaneous combustion.

Preparation and properties of conductive Ti4O7 surface coating for Ti bipolar plates of proton exchange membrane fuel cells

Focusing on the special electrical conductivity and corrosion resistance of Ti 4 O 7 , this work proposes for the first time to reduce TiO 2 film grown in situ on Ti substrate in a high-temperature tube furnace by using Ti/TiO 2 mixed powder as reducing agent to obtain Ti 4 O 7 surface coating. By characterization, the surface of the coated sample is identified as a Ti 4 O 7 coating, with a partially unconverted TiO 2 present at the interface between the Ti substrate and the Ti 4 O 7 surface coating. The electrochemical, water contact angle and surface contact resistance tests show that the Ti 4 O 7 surface coating provides superior protection to the Ti bipolar plate in the simulated proton exchange membrane fuel cell cathode environment, and simultaneously improving the electrical conductivity and water contact angle of the sample. • A novel preparation method of Ti 4 O 7 coating is proposed. • Uniform and dense Ti 4 O 7 coating on Ti substrate is obtained in a short time. • Ti 4 O 7 coating maintains excellent corrosion resistance in simulate PEMFC cathode environment . • The Ti 4 O 7 coating exhibits high conductivity and hydrophobicity.

Effect of high-temperature environment of mine goaf on pore and fracture of coal

To study the evolution law of pores and fractures in the process of injecting nitrogen to prevent and extinguish fire in the goaf of coal mines. With the help of a self-built high-temperature tube furnace, the coal samples were processed under different temperatures and gas atmospheres. Through comprehensive use of electron microscope scanning, low temperature nitrogen adsorption, and 13C NMR, the pores and fractures development rules of coal before and after heat treatment were researched. The coal samples heated in nitrogen atmosphere produced many strip-shaped fractures and coal debris, while the coal samples heated in air atmosphere produced many pores and an evident melting phenomenon. In addition, the proportion of carboxyl groups in coal samples heated in nitrogen atmosphere was always greater than that of the coal heated in air atmosphere. The pore specific surface area and volume of coal samples heated under air atmosphere increased significantly, while the degree of development was significantly reduced in nitrogen atmosphere. Thereby weakening the coal-oxygen reaction to a certain extent and inhibiting the generation of harmful gases (CO, CH4, etc.), which is conducive to preventing coal spontaneous combustion disasters.

Optical absorption tomography for temperature and H2O concentration imaging by a compact photoelectric detecting system combined with twice adaptive algebraic algorithm

Tunable diode laser absorption spectroscopy is a robust method for simultaneous measurements of temperature and gas species. Different from commercial detectors integrated with photodiode receivers and amplifiers as the detecting system, a custom-made photoelectric detecting system comprised of Ge detectors and separated amplifiers was designed. First, Ge detectors received optical power from laser beams and then converted it into electrical current signals. The trans-impedance amplifiers were used to convert the current signals to voltage signals. The second stage amplifiers further amplified the voltage signals. All amplifiers that integrated the electronic circuits were packed in a portable case. Finally, the amplified voltage signals were received by data acquisition card. In this way, detectors could be arranged more compact and are easier to facilitate expandability. In addition, absorption data were reconstructed using twice adaptive algebraic reconstruction technique (AART) algorithm. During the reconstruction, after obtaining the temperature distribution through AART algorithm, AART algorithm was adopted for the second time for H2O concentration distribution. This system was validated with measurements of one-dimensional average temperature in a high temperature tube furnace and the system combined with twice adaptive algebraic algorithm demonstrated in a square flow field containing McKenna burners for simultaneous measurements of temperature and H2O distribution. The results indicated the viability and potential of this system combined with twice adaptive algebraic algorithm for sensitive temperature and H2O distribution tomography.

Study on Final Equilibrium State and Process of CO2 Reacting with Fe–C Melt

Abstract To study the final equilibrium state and process of CO2 injecting into the Fe–C melt with different initial carbon contents, a model was established based on the method of minimization of Gibbs free energy and the corresponding experiments were carried out in a high-temperature tube furnace. When CO2 is continuously injected into the Fe–C melt at 1873 K, the final equilibrium state of the system is such that the carbon and oxygen contents in the melt are 0.1977 and 0.0115 wt pct, respectively, and the volume ratio of CO in the gas phase is 85.75 vol pct. When the initial a [O] × a [C] in the melt is greater than those in equilibrium with CO under 0.8575 atm, the CO2 gas removes carbon from the melt. On the contrary, the role of CO2 gas is to add carbon and oxygen to the melt. At the same time, the variation of carbon and oxygen with time obtained by experiments was different from the theoretical calculation at extremely low carbon content, which requires further study.

The Effect of Boron Addition on the corrosion behavior of Ni Cr Modental alloy prepared by powder metallurgy.

The powder metallurgy (PM) method was used to create the alloy. The sintering process was carried out in an inert high-temperature tube furnace in the presence of inert gas at a temperature of 1000 ° C for 8 hours (Argon). In this article, the effect of (B) at three wt.% (0.4,0.8,1.2) on the corrosion rate, hardness, and microstructure of alloys was examined. X-ray diffraction (XRD), open circuit potential, electrochemical tests (Tafel extrapolation method), and Macro hardness Brinell were used to study the effect of adding (B) in various amounts to alloys. Saliva was utilized as the corrosion solution for the testing. The inclusion of the alloy element (B) increased hardness and a decrease in particle size, as seen by the microstructures. Furthermore, the corrosion resistance of the master alloy improved next the addition, as shown by Corrosion potential has increased while corrosion current densities have decreased. The corrosion rate for A, A1, A2 and A3 was 14.50, 7.42, 2.03and 2.77 (mpy) respectively.

Promotional effect of silica on the combustion of nano-sized aluminum powder in carbon dioxide

This paper presents how the combustion performance of nano-sized aluminum (nAl) powder in carbon dioxide are affected by silica. The ignition and combustion performance of nAl powder with silica addition were studied by a high-temperature tube furnace. An s-type thermocouple and a high-speed motion acquisition instrument were performed to evaluate the ignition temperature, maximum combustion temperature, maximum change of rate of temperature, and combustion propagation speed. The combustion efficiency and combustion products were measured and analyzed by a gas-volumetric method and an X-ray diffraction. The results show that silica added into nAl powder can enhance its maximum combustion temperature and maximum change of rate of temperature, while its ignition temperature increases slightly. The nAl powders with addition of 6.00 wt.% and 12.00 wt.% silica present high combustion propagation speeds, especially for the latter, it has high combustion efficiency. The effect mechanism of silica on the combustion of nAl powder in carbon dioxide was discussed.

An Experimental Study on the Melting Solidification of Municipal Solid Waste Incineration Fly Ash

Melting solidification experiments of municipal solid waste incineration (MSWI) fly ash were carried out in a high-temperature tube furnace device. An ash fusion temperature (AFT) test, atomic absorption spectroscopy (AAS), scanning electron microscope (SEM), and X-ray diffraction (XRD) were applied in order to gain insight into the ash fusibility, the transformation during the melting process, and the leaching behavior of heavy metals in slag. The results showed that oxide minerals transformed into gehlenite as temperature increased. When the temperature increased to 1300 °C, 89 °C higher than the flow temperature (FT), all of the crystals transformed into molten slag. When the heating temperatures were higher than the FT, the volatilization of the Pb, Cd, Zn, and Cu decreased, which may have been influenced by the formation of liquid slag. In addition, the formation of liquid slag at a high temperature also improved the stability of heavy metals in heated slag.

Experimental Study on the Catalytic Reduction of NOX by Fe and Ce During the Coke Combustion Process

NOX emissions during the combustion of coal would cause serious pollution to the atmosphere. It is particularly important to reduce NOX pollution during the combustion process by replacing loose coal with clean coke. The use of clean coke for civil is one of the main ways to reduce NOX emissions, which is mainly formed by the mixed dry distillation of metal additives and coal. The coke samples with different proportions of metal additives were prepared by physical mixing method, and the NOX emission law of clean coke at different temperatures was studied in a high-temperature tube furnace reactor. The results show that the addition of Fe alone has a significant effect on the control of NOX emissions, and the co-doping with Ce can further promote the reduction of NOX, so as to achieve the final low emission of NOX. While the reaction temperature is 1000 ℃ and the addition ratio is 2:1, the NOX reduction rate is 73%. It has important practical value and scientific significance for the clean utilization of coal and the treatment of NOX in the atmosphere.

Phosphor thermometry at the surface of single reacting large-diameter spherical coke particles to characterise combustion for packed bed furnaces

Packed-bed furnaces fired with large-diameter coke are important in high-temperature material processing industries such as lime and iron production. The combustion conditions are complicated by the presence of an ash layer surrounding the coke particle that remains intact during passage through the furnace and alters oxygen diffusion and heat transfer to the reacting particle core. The objective of this study is to determine the surface temperature of this ash layer using lifetime-based phosphor thermometry during combustion of single spherical 38 mm diameter coke particles in a high temperature tube furnace. Time traces of the coke particle core temperature and mass conversion rate do not significantly differ between experiments performed with and without the phosphor layer, indicating that the presence of the phosphor particles does not alter the overall combustion behaviour. Surface temperatures of up to 950 °C are measured and correlated with the fuel mass conversion rate. When the coke particle starts to react the surface temperature is up to 100 °C higher than that of the core. As the reaction front progresses toward the centre, the core temperature exceeds the surface temperature by 200 °C due to the insulating effect of the ash layer. The surface temperature of the ash layer decreases with time due to the steadily decreasing fuel mass conversion rate. The method and results can be used to provide key validation data for shrinking-core combustion models, for example by constraining the unknown transport properties of the ash layer, thereby assisting the development of complete packed-bed furnace simulations for process optimisation.

Synthesis of Multiwalled Carbon Nanotubes on Stainless Steel by Atmospheric Pressure Microwave Plasma Chemical Vapor Deposition

In this paper, we synthesize carbon nanotubes (CNTs) by using atmospheric pressure microwave plasma chemical vapor deposition (AMPCVD). In AMPCVD, a coaxial plasma generator provides 200 W 2.45 GHz microwave plasma at atmospheric pressure to decompose the precursor. A high-temperature tube furnace provides a suitable growth temperature for the deposition of CNTs. Optical fiber spectroscopy was used to measure the compositions of the argon–ethanol–hydrogen plasma. A comparative experiment of ethanol precursor decomposition, with and without plasma, was carried out to measure the role of the microwave plasma, showing that the 200 W microwave plasma can decompose 99% of ethanol precursor at any furnace temperature. CNTs were prepared on a stainless steel substrate by using the technology to decompose ethanol with the plasma power of 200 W at the temperatures of 500, 600, 700, and 800 °C; CNT growth increases with the increase in temperature. Prepared CNTs, analyzed by SEM and HRTEM, were shown to be multiwalled and tangled with each other. The measurement of XPS and Raman spectroscopy indicates that many oxygenated functional groups have attached to the surface of the CNTs.

Highly Sensitive, Calibration-Free WM-DAS Method for Recovering Absorbance-Part II: Experimental Analysis.

Following the theoretical work in Part I, in this experimental study, the robustness, temporal resolution, and the narrow scan performance of the proposed wavelength modulation-direct absorption spectroscopy (WM-DAS) method are experimentally validated in a high-temperature tube furnace. The electromagnetic and other random-frequency noises can be effectively eliminated by extracting the characteristic spectra of the light intensity. The performance of WM-DAS with modulation frequencies from 0.1 to 100 kHz and scan indexes from 3.3 to 11.1 are also investigated at atmospheric pressure. The proposed method produces accurate line profile and high SNR over 500 consistently even with a weak absorption. As for real applications, the spectral line parameters of CO at 4300.6999 cm−1 including the collisional broadening, Dicke narrowing, and their dependence on temperature are measured. Furthermore, the high-speed measurement (1 ms) of the temperature and CO concentration of a McKenna flat flame are demonstrated.

Effects of the cooling rate on the crystallization behaviors of the CaO–Al2O3–B2O3–CaF2-based mold flux

The effects of the cooling rate on a new type CaO–Al2O3–B2O3–CaF2-based mold flux for high aluminum steel casting were investigated using CSLM and a high temperature tube furnace.