Tubular Furnace Research Articles

Synthesis and characterization of Cu-sandwiched Sb2Se3 thin films and numerical simulation of p-Sb2Se3/n-ZnSe heterojunction solar cell

Sb2Se3 and Cu-sandwiched Sb2Se3 thin films were prepared by sequential evaporation of (Sb/Se) × 3 and [(Cu/(Sb/Se) × 3/Cu)] precursor stacks over the glass substrates in a high vacuum using electron beam (e-beam) evaporation followed by annealing in a tubular furnace at various temperatures in Ar atmosphere. The growth of Sb2Se3 and Cu-sandwiched Sb2Se3 films is studied by varying annealing temperature. The Sb2Se3 films grown without copper layers were peeled off from the glass substrates when annealed above 300 °C, whereas the Cu-sandwiched Sb2Se3 films were adherent to substrates up to 450 °C. The XRD of Cu-sandwiched Sb2Se3 films annealed at all temperatures confirms the Sb2Se3 formation with orthorhombic crystal structure. The Cu-sandwiched films annealed at ≤ 250 °C showed the preferred orientation along the (hk0) plane, whereas films annealed at ≥ 300 °C exhibited the (hk1) preferred orientation. The morphology of Cu-sandwiched Sb2Se3 films annealed at 450 °C showed compact and larger grains (∼0.8 μm) with a direct optical band gap of 1.04 eV. Hall effect measurement exhibited a p-type conductivity with a hole concentration of 3.1 × 1015 cm−3. The numerical simulation of the proposed Glass/Ni/p-Sb2Se3/n-ZnSe/ITO/Al heterojunction solar cell showed a power conversion efficiency of 21.51%.

Catalytic Pyrolysis of Sawdust with Desulfurized Fly Ash for Pyrolysis Gas Upgrading

In this study, the catalytic effects of desulfurized fly ash (DFA) on the gaseous products of sawdust (SD) pyrolysis were investigated in a tubular furnace. The results indicated that DFA catalyzed the process of SD decomposition to improve the hydrogen content and the calorific value of pyrolysis gas. As to its effect on pyrolysis products, DFA increased the non-oxide content of CH4, C3H4, and H2 in pyrolysis gas by 1.4-, 1.8-, and 2.3-fold, respectively. Meanwhile, the catalytic effect of DFA reduced the CO and CO2 yields during DFA/SD pyrolysis. Based on the model compound method, CaSO3 and Ca(OH)2 in DFA was proved to have quite different catalytic effects on pyrolysis gas components. Ca(OH)2 accelerated the formation of CH4 and H2 through the cracking of methoxyl during lignin and cellulose degradation, while CaSO3 favored the generation of CO and CO2 due to the carbonyl and carboxyl of lignin in SD. CaSO3 also catalyzed SD pyrolysis to promote the C3H4 yield in pyrolysis gas. Overall, the catalytic pyrolysis of SD with DFA yielded negative-carbon emission, which upgraded the quality of the pyrolysis gas.

Biodegradable methylcellulose biopolymer-derived activated porous carbon for dual energy application

Activated porous carbon was synthesized from methylcellulose biopolymer through a two-step mechanism involving H3PO4 as an activating agent and then thermally carbonized in a tubular furnace under an inert atmosphere at 850 °C. The product was next rinsed with strong HCl, neutralized with deionized water, and dried in an oven at 80 °C. Then, to fully understand the behavior of the activated porous carbon, it was characterized using techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), RAMAN spectroscopy, Brunauer–Emmett–Teller (BET), and thermal gravimetric analysis (TGA). Additionally, we have created dye-sensitive solar cells and an electric double-layer capacitor (EDLC) using this porous carbon produced from methylcellulose (DSSC). We used the above-mentioned prepared porous carbon for the electrode portion of the Electric Double-Layer Capacitor (EDLC) fabrication, and the maximized polymer electrolyte film made from the methyl cellulose (MC) biopolymer combined with 60 wt.% of 1-ethyl-3-methylimidazolium tricyanomethanide ionic liquid (IL), with a maximum conductivity of 1.93 × 10−2 S/cm, for the electrolyte. The fabricated EDLC device shows a specific capacitance of 60.8 F/gm at 5 mV/s scan rate which was confirmed by cyclovoltammetry and a low-frequency impedance plot in the CH electrochemical workstation. The DSSC device was fabricated using the same porous carbon as a material for the counter-electrode and the same composition polymer electrolyte that had been used in the EDLC as the electrolyte for the DSSC which yields an efficiency of 0.86%. The fill factor and other parameters were also calculated from the JV characteristics that had been characterized and obtained in the solar simulator.

A bottom-up method to construct Ru-doped FeP nanosheets on foam iron with ultra-high activity for hydrogen evolution reaction

As a clean, high calorific value and renewable energy, hydrogen is considered to be an ideal green energy to replace traditional fossil energy. Among various methods for preparing hydrogen, electrolytic water hydrogen evolution has attracted the attention of researchers because of its high efficiency, easy separation of products and green and pollution-free advantages. In this experiment, starting from the porous foam iron, Fe2O3 nanosheets are obtained by anodic oxidation, and then the material is phosphated by in-situ phosphating in a tubular furnace to obtain FeP nanosheets. Finally, the Ru dopants are deposited into the lattice of FeP nanosheets by electrodeposition to obtain the Ru-doped FeP nanosheets. Through the characterization of morphology and the test of electrocatalytic hydrogen evolution performance, the Ru-doped FeP nanosheets show ultra-high electrochemical hydrogen evolution activity and have regular nanosheets array structure.

Alumina/molybdenum nanocomposites obtained by colloidal synthesis and spark plasma sintering

Alumina/molybdenum nanocomposites were prepared by colloidal synthesis from alumina powder and molybdenum (V) chloride using ethanol as dispersion medium. Modified alumina was calcined at 450 °C in air atmosphere to remove chlorides, and then treated in a tubular furnace at 850 °C under Ar/H2 to reduce the MoO3 formed in the previous stage and obtain Al2O3 with molybdenum nanoparticles on the surface. Three different molybdenum contents were proposed (1, 5 and 10 wt % Mo), and pure alumina was used as reference, that were sintered by spark plasma sintering (SPS) under vacuum atmosphere at 1400 °C for 3 min with an applied pressure of 80 MPa. Composites were characterized by microstructure, hardness, toughness, and three-point bending test. The presence of molybdenum nanoparticles resulted in a fine-grained structure promoted by the presence of molybdenum at grain boundaries and triple points, as well as by the utilization of the SPS equipment. Hardness is at least a 20% greater and fracture toughness 30% larger in the composites than in the monolithic alumina.

Effect of calcium hydroxide on the characteristics of volatile organic compounds emission during sewage sludge incineration

AbstractEmission of volatile organic compounds (VOCs) during sludge incineration was explored after the addition of calcium hydroxide (Ca [OH]2), and the effects of incineration temperature, sludge particle size, and moisture content were investigated in a lab‐scale tubular furnace. Further, the contribution of the emission of VOCs in ozone formation potential (OFP) without Ca (OH)2 was calculated. The results indicated that incineration temperature in the range of 550–950°C can inhibit the emission of VOCs, with concentrations of the emissions varying from 3076.91 to 1277.11 μg/m3. Ca (OH)2 content had pronounced effects on the emission of VOCs during sludge incineration. The emission concentration of the VOCs decreased from 2421.16 to 1226.68 μg/m3 with Ca (OH)2 content increasing from 0 to 0.8 g. Sludge particle size and moisture content had little effects on the total amount of emitted VOCs during sludge incineration. Meanwhile, the contribution of the components of VOCs from sludge incineration in OFP was analyzed, which exhibited a decreasing trend: aromatic compounds > other substances > alkanes and olefins > chlorinated organic compounds. Aromatic compounds displayed the highest contribution rate at 92.72% because of the high concentration of benzene (1033.43 μg/m3). Our study provided theoretical data and a strong evidence of reduction in the emission of VOCs, OFP, and environmental regulation during sludge incineration.

Torrefaction characteristics of cellulose loaded with boric acid

To explore the catalytic effect of boric acid on biomass, cellulose loaded with boric acid was roasted by a tubular furnace. The gaseous products were adsorbed by activated carbon and then analyzed by GC-MS. Boric acid was shown to improve the selectivity of the product levoglucosenone (LGO). The effects of the parameters such as boric acid loading, nitrogen flow, and temperature on the torrefaction behavior of cellulose were investigated. In the studied temperature range of 240–420 °C, the yield of LGO first increases and then decreases. In addition, its yield increases directly with increasing nitrogen flow rate. The results show that the highest LGO yield of 6.64% (analytical value) can be obtained under 10% (w/w) boric acid loading, 380 °C and nitrogen flow rate of 65 ml/min conditions.

Effect of temperature, oxygen concentration, and CaO addition on SO2 and NOx emissions during oxygen-fuel combustion of municipal sludge

Oxygen-fuel combustion is an effective and promising method of steadily minimizing municipal sludge volume at the same time exploiting available heat and falling emissions. The effects of temperature, oxygen concentration, and CaO addition on SO2 and NOx emissions from municipal sludge combustion in CO2/O2 atmosphere were systematically explored via a lab-scale electrically heated tubular furnace in this work. The results show that the minimum average emissions of both SO2 and NOx were observed at 800 °C. Compared with air, all oxygen-fuel atmospheres reduced SO2 emission, and a salient effect was observed with 30% of oxygen concentration. In contrast, the inhibition of NOx emission was inconspicuous and exacerbated in some cases. With a lower oxygen concentration (21%), CaO evidently reduced SO2 emission and 8 wt% addition performed the best. The removal efficiency of NO by CaO addition was poor and only exhibited slight inhibition with 5 wt% addition.

Europium(III)-Doped Gadolinium(III) Complex for High-Sensitivity Temperature Sensing in the Physiological Range.

A new Eu3+-doped Gd3+ complex of formula [Eu0.0135Gd0.9865(pta)3me-phen] was synthesized and structurally characterized (Hpta = benzoyltrifluoroacetone, me-phen = 5-methyl-1,10-phenanthroline). The photoluminescence study revealed that when the compound was excited at RT, under a 457 nm continuous laser, the material exhibited high luminescence due to the antenna effect of the ligands, as well as a good balance between the phosphorescence from the spin-forbidden triplet (from the organic ligands), and the characteristic lanthanide f-f transitions. The ratio between the previous emissions drastically changed when the sample was heated up to 62 °C inside a tubular furnace. This ratio was investigated using the luminescence intensity ratio method, to analyze the capabilities of the sample as a temperature sensor. The relative sensitivity reached a maximum of 11.4 °C-1 %, maintaining a detection limit below 0.15 °C for the whole temperature range.

Co-combustion of sewage sludge and Zhundong coal: Effects of combustion conditions on gaseous pollutant emission and ash properties

The combustion of sewage sludge (SS) generates large amounts of NOx and SOx, while that of alkali and alkaline earth metal-rich coals produces slagging-prone ash. To determine whether these problems can be mitigated through the co-combustion of SS and coal, we examined the effects of SS and Zhundong coal co-combustion in a horizontal tubular furnace on the emission of NOx and SOx, analyzing the micromorphology, composition, and pore structure of the produced ash. Sludge content was inversely correlated with SO2 emission but had little effect on NOx emission. A high sludge content promoted the fusion of ash particles, whose size was positively correlated with combustion temperature. Na/Ca-feldspar miscibility led to the fusion of ash particles, facilitating the production of magnesia-iron spinel and complex phosphates to alleviate slagging. The specific surface area of ash was negatively correlated with temperature and was the largest at a sludge content of 20 wt%. The fractal dimensions calculated to examine pore structure complexity and pore surface roughness revealed that the latter parameter was inversely correlated with temperature. A reaction temperature of 900 °C and sludge content of 20 wt% were optimal conditions for gaseous pollutant emissions and ash agglomeration behaviors during co-combustion. Thus, this study provides a theoretical basis for controlling the operation of coal/SS co-fired power plants in terms of pollutant emission, combustion efficiency, and ash slagging.

Syngas composition and ash characteristics of corn straw under a CO2 atmosphere

Corn straw is one of the most common materials utilized as biomass. The effects of temperature and residence time on the syngas composition and ash characteristics of corn straw prepared in a CO2 atmosphere in a tubular furnace were studied. The results showed that CO was the dominant component of the syngas. With increasing temperature, the volume fraction of CO first decreased and then increased. When the temperature increased to 800 °C, CH4, CnHm and H2 participated in the gas-phase reaction, which promoted the generation of CO. At high temperature, longer residence times before the corn straw reacted completely resulted in greater CO production. Analysis of the ash characteristics showed that the higher the temperature and the longer the residence time were, the lower the ash mass. When the temperature was below 800 °C, the inorganic crystals in the residual ash were KCl and SiO2. When the temperature increased to 800 °C, the inorganic materials in the ash melted and slagged, resulting in low-melting-point salts such as CaMgSi2O3 and KAlSi3O8. The presence of carbon residue hindered the slagging of ash. At 800 °C, ash with a high K content exhibited obvious melting, while ash with a high Al content remained solid. With increasing temperature, the characteristic melting temperatures of ash also increased.

Evaluation of flue gas emission factor and toxicity of the PM-bounded PAH from lab-scale waste combustion

Atmospheric particulate matter (PM) has a significant threat not only to human health but also to our environment. In Hungary, 54% of PM10 comes from residential combustion, which also includes the practice of household waste burning. Therefore, this work aims to investigate the quality of combustion through the flue gas concentrations (CO, CO2, O2) and to identify and evaluate the negative impacts of PM and PAHs generated during controlled lab-scale combustion of different mixed wastes (cardboard and glossy paper, polypropylene and polyethylene terephthalate, polyester and cotton). Mixed wastes were burnt in a lab-scale tubular furnace at different temperatures with 180 dm3/h air flow rate. Chemical analyses were coupled with ecotoxicological tests using the bioluminescent bacterium Vibrio fischeri. Ecotoxicity was expressed as toxic unit (TU) values, toxic equivalent factors (TEF) were also presented. During the combustion same amount of O2 enters the reaction, but a different amount CO2 is generated due to the C content of the sample. The waste with highest C-content related to the highest CO2 emission. Increasing the combustion temperature produces more PM-bound PAHs, which remains the same composition in the case of plastic and textile groups. The TU of solid contaminants decreases with increasing combustion temperature and increases with the minerals which are left behind in the water from the solid contaminants.

Optimum temperature, time and atmosphere of precursor pyrolysis for synthesis of B4C ceramics

In this paper, the variables of the pyrolysis operation such as temperature, time, and atmosphere were studied and optimized. At first, the effect of increasing pyrolysis time at lower temperatures was investigated to understand the mutual influence of pyrolysis time and temperature in enhancing the efficiency of B4C synthesis. Then, three pyrolysis atmospheres were selected to find the optimal conditions: burial method in box furnace (air), pyrolysis in tubular furnace (argon), and pyrolysis in box furnace (air). The pyrolyzed powders were finally located inside the tubular furnace at 1500 °C for 4 h under argon atmosphere to synthesize B4C ceramics. X-ray diffractometry (XRD) was employed to determine the optimal processing conditions. The temperature of 600 °C and the holding time of 2 h were selected as the optimal pyrolysis conditions. Meanwhile, the burial method was chosen as the best atmosphere despite having a higher percentage of impurity because of the much lower cost compared to the argon atmosphere.

Synthesis of an Aluminum Alloy Metal Matrix Composite Using Powder Metallurgy: Role of Sintering Parameters

Powder metallurgy-based metal matrix composites (MMCs) are widely chosen and used for the development of components in the fields spanning aerospace, automotive and even electronic components. Engineered MMCs are known to offer a high strength-to-weight (σ/ρ) ratio. In this research study, we synthesized cylindrical sintered samples of a ceramic particle-reinforced aluminum metal matrix using the technique of powder metallurgy. The samples for the purpose of testing, examination and analysis were made by mixing aluminum powder with powders of silicon carbide and aluminum oxide or alumina. Four varieties of aluminum composite were synthesized for a different volume percent of the ceramic particle reinforcement. The hybrid composite contained 2 vol.% and 7 vol.% of silicon carbide and 3 vol.% and 8 vol.% of alumina with aluminum as the chosen metal matrix. Homogeneous mixtures of the chosen powders were prepared using conventional ball milling. The homogeneous powder mixture was then cold compacted and subsequently sintered in a tubular furnace in an atmosphere of argon gas. Five different sintering conditions (combinations of temperature and sintering time) were chosen for the purpose of this study. The density and hardness of each sintered specimen were carefully evaluated. Cold compression tests were carried out for the purpose of determining the compressive strength of the engineered MMC. The sintered density and hardness of the aluminum MMCs varied with the addition of ceramic particle reinforcements. An increase in the volume fraction of the alumina particles to the Al/SiC mixture reduced the density, hardness and compressive strength. The sintering condition was optimized for the aluminum MMCs based on the hardness, densification parameter and cold compressive strength. The proposed powder metallurgy-based route for the fabrication of the aluminum matrix composite revealed a noticeable improvement in the physical and mechanical properties when compared one-on-one with commercially pure aluminum.

An integrated experimental and numerical study of iron-coke briquettes' pyrolysis and reduction behaviour in an industrial-scale pyrolyser

Iron-coke is a promising raw material for ironmaking blast furnaces for reducing carbon consumption and can be produced by pyrolysers, but the present pyrolysis technologies should be improved to further lower energy consumption and CO2 emission. In this work, an integrated experimental and numerical study is conducted to investigate the pyrolysis and reduction behaviours of iron-coke briquettes in an industrial-scale gas heat carrier pyrolyser. A lab-scale two-stage tubular furnace is first employed to pyrolyze the briquette samples to obtain the recycled gas components. A DEM model is then used to simulate the packing status evolution of ellipsoidal iron-coke briquettes in the pyrolyser chamber. A CFD pyrolysis model is then used to study the pyrolysis and reduction behaviours of coke briquettes and then evaluate the impact of switching the carrier gas from traditional exhaust gas to recycled pyrolysis gas on the pyrolysis and reduction behaviours. The comprehensive in-furnace pyrolysis and reduction phenomena are illustrated. The simulation results also indicate that using the recycled gas as the gas heat carrier is beneficial to the pyrolysis efficiency and progress of ferric oxide reduction, compared to the exhaust gas. This study is useful for gas heat carrier pyrolyser design and optimisation for efficient iron-coke production.

Microplastics’ analysis in water: Easy handling of samples by a new Thermal Extraction Desorption-Gas Chromatography-Mass Spectrometry (TED-GC/MS) methodology

Thermal Extraction-Desorption (TED) using a thermobalance coupled to a gas chromatograph (GC) with mass spectrometer (MS) detector is an extended method for polymers identification in complex matrixes. A new TED-GC/MS method for microplastics identification is developed in this study, where the whole filter with solids collected from water is thermal treated in a furnace, instead of using a small portion in a Thermogravimetric analysis (TGA) device, avoiding sample handling. Pyrolyzing the whole filter in a tubular furnace has advantages with respect to the standard procedure of using a TGA with a small crucible in TED-GC/MS.The main advantage is the easy manipulation of the sample, since the filter does not have to be manipulated to extract the sample or cut some portions, avoiding sample losses during handling and ensuring that inhomogeneity on the filter surface is not a problem.Furthermore, there are no limitations on the weight of the sample beyond the adsorbent's ability to trap decomposition compounds without becoming saturated, so high intensity signals can be obtained in order to avoid confuse signals with noise, false negatives or values so close of the quantification limit.

Hydrogen reduction of low-grade banded iron ore

The current study investigates hydrogen reduction of low-grade iron ore (∼37 % Fe) containing dispersed bands of hematite and jasper/quartzite phases. Gaseous hydrogen reduction is carried out at isothermal conditions in a custom-made tubular furnace, followed by magnetic separation. The reduction temperature (300–600 °C), time (30–90 min), particle size (0.5–3.3 mm), and hydrogen flow rate (0.5–1.5 LPM) were optimized by statistical design of experiments to maximize the saturation magnetization, degree of reduction and metallization. Complete reduction of hematite was achieved in 2 h at 600 °C; however, the separation of quartz from reduced ferrite was inefficient evidenced by the lower saturation magnetization. The association of impurities with hematite does not affect the reduction rate; however, the trapped quartz particles in the reduced phases deteriorate the magnetic separation efficiency. Temperature and time synergize the reduction rate, improving reduction and metallization degree; meanwhile, flow rate and particle size have minimal effect. Reduction below 450 °C restricted the reduction to magnetite, and the optimal conditions; 600 °C, 60 min, 0.5 LPM H2, and 3.3 × 2 mm particle size yielded ferrite concentrate possessing saturation magnetization of 134.6 emu/g (68 % FeM) with 97.9 % DOR, 88.8 % DOM and 47.3 % yield. The reduction of hematite results in generation of micro cracks and porous morphology of the ferrite. Iron oxide reduction follows the Fe2O3 → Fe3O4 → Fe, evidenced by the absence of wustite (FeO) or fayalite (FeO.SiO2) phases in the product. The ferrite particles form a fused and porous layer trapping the silica particles.

Dissociation characteristics and anthropogenic emissions from the combustion of double gas hydrates

Gas hydrates are an alternative and environmentally friendly energy source increasingly in the focus of scientific attention. The physicochemical processes behind gas hydrate combustion are studied experimentally and numerically with a view to improving the combustion efficiency and reducing gas emissions. It is important to estimate the pollutant emission concentrations in the context of combustion conditions. The research deals with the dissociation and combustion behavior of double gas hydrates in a tubular muffle furnace. Gas hydrates of different composition are considered: methane, methane-ethane, methane-propane and methane-isopropanol. Double gas hydrates are characterized by more stable combustion compared to methane hydrate. It is also shown that the double gas hydrate dissociation rate increases by 15–30% with increasing temperature. Dissociation and combustion processes were also modeled as part of the research, accounting for phase transitions in a gas hydrate layer. According to the simulation results, the total dissociation rate of gas hydrate increases by 3 times with an about 2.5-times increase in the powder layer thickness. Our experiments also focused on the impact of furnace temperature and gas hydrate composition on concentrations of anthropogenic gas emissions. We have found that the presence of heavy hydrocarbons such as ethane, propane and isopropanol in double gas hydrates reduce unburned CH4 emissions by 60%. Also, an increase in the combustion efficiency of double gas hydrates, accompanied by a decrease in the concentrations of unburned CH4 and CO, affects the yield of CO2, which increased by 13–35%. When we increased the temperature in the furnace from 750 °C to 1050 °C, concentrations of nitrogen oxides and carbon dioxide increased by up to five times. Thus, the resulting correlations between the key parameters of these processes and a set of the main inputs illustrate the possibility to predict the optimal conditions for the combustion of gas hydrates.

Ru/MoO2 decorated on CNT networks as an efficient electrocatalyst for boosting hydrogen evolution reaction

Generally, electrochemical hydrogen evolution reaction (HER) is hampered by slow kinetics and low round-trip efficiency. Electrocatalysts with a hierarchical structure and large surface area are expected to overcome these problems. Herein, we prepared a Ru/MoO2/carbon nanotubes (RMC) hybrid with a hierarchical structure by a convenient solid-phase reaction (SPR) method, and studied the electrochemical activity for HER. After annealing as-prepared RuO2/MoO2/carbon nanotubes (ROMC) precursor in a tubular furnace under Ar atmosphere, RuO2 and MoS2 were in-situ transformed into Ru metal and MoO2 phase by the redox SPR. Through various tests, we have confirmed that the new formed Ru metal and MoO2 phase are combined and uniformly coated on the outer surface of CNTs. Interestingly, the RMC-500 exhibits the best HER performance with a low overpotential of 16 mV at l0 mA cm−2, small Tafel slope of 45 mV dec−1, higher electrochemical active surface area, and long-time durability in alkaline electrolyte.

Study on Decarburization Mechanism and Law of GCr15 Bearing Steel during Heat Treatment

In order to understand the effects of heating temperature and holding time on decarburization of GCr15 bearing steel, an experimental device for heat treatment of bearing steel was designed and the sample was heated and held by a tubular heating furnace. The microstructure and depth of decarburized layer of bearing steel under various working conditions were observed and measured by a metallographic microscope. The results show that the total decarburization depth increases with the increase of temperature; almost no decarburization occurred below 700°C; ferrite decarburization occurred at 750°C; partial decarburization began to occur at 820°C; after 900°C, the decarburization layer is mainly partial decarburization. When the heating temperature is below 1000°C, the depth of total decarburization layer increases slowly and increases rapidly after 1000°C. The total depth of decarburization layer is directly proportional to the square root of holding time. The relationship between the depth of the total decarburization layer of bearing steel and the heating temperature and holding time in the annealing process was obtained.