Steam Atmosphere Research Articles

Catalytic Effects of Potassium Concentration on Steam Gasification of Biofuels Blended from Olive Mill Solid Wastes and Pine Sawdust for a Sustainable Energy of Syngas

The effect of potassium impregnation at different concentrations during gasification, under nitrogen/water steam atmosphere, of char produced via pyrolysis of olive mill residues blended or not with pine sawdust was investigated. Three concentrations (0.1 M, 0.5 M, and 1.5 M) of potassium carbonate solution (K2CO3) were selected to impregnate samples. First, four types of pellets were prepared; one using exhausted olive mill solid waste (G) noted (100G) and three using G blended with pine sawdust (S) in different percentages (50%S–50%G (50S50G); 60%S–40%G (60S40G); 80%S–20%G (80S20G)). Investigations showed that when isothermal temperature increases during the gasification conducted with two water steam percentages of 10% and 30%, the reactivity increases with potassium concentration up to 0.5 M, especially for 100G. Still, higher catalyst concentration (1.5 M) showed adverse effects attributable to silicon release and char pore fouling. Moreover, the effect of the steam concentration on the gasification reactivity was significant with the non-impregnated sample 100G. Finally, a kinetic study was carried out to determine the different kinetic parameters corresponding to the Arrhenius law.

CONTROL SYSTEM OF CATENARY CONTINOUS VULCANIZATION LINE FOR RUBBER CABLES

The paper presents the control system of a continuous vulcanization line for the production of cables and conductors with rubber insulation, where the vulcanization process takes place in water and steam (vapour) atmosphere. The control, monitoring and recording of relevant parameters of the whole technological process was carried out with help of PLC (Programmable Logic Controller) and HMI (Human Machine Interface) and KepwareEx server. The control system is used to generate control signals for the regulation of speed, tension force, extruder temperature, water level and steam pressure in the vulcanization tube according to the technological parameters of the line. The monitoring system enables visualization of all technological units of the line via the HMI screens. The parts and entirety of the line are represented by conveniently drawn symbols that change colour depending on the current state and display the variables relevant to the operation of this object. Through the use of the KepwareEx server and database, the values of the variables important for the operation of the plant are recorded in real time. The developed supervisory and control system allows easy operation and monitoring of all important parameters of the plant.

Influence of Y2O3 doping on the aging behavior and mechanical properties of ATZ ceramics

The aim of this study was to investigate the influence of the Y2O3 content on the mechanical properties and aging behavior of ATZ ceramic. For this purpose, an ATZ ceramic consisting of 80 wt% stabilized ZrO2 and 20 wt% Al2O3 with varying Y2O3 stabilizer content between 2 and 3 mol% was prepared. The samples were analyzed regarding their sintered density, grain size, hardness and fracture toughness. The results show an increase in fracture toughness and a decrease in hardness with decreasing Y2O3 content. In addition, the aging stability was assessed by analyzing the phase composition determined by X-ray diffraction after aging the samples for up to 150 hours in steam atmosphere at 134 °C and 2 bar. The aging stability decreases with decreasing stabilizer content. Nevertheless, by producing a very fine-grained material, high aging stability can be achieved despite reduced Y2O3 content.

JWST/NIRISS Reveals the Water-rich “Steam World” Atmosphere of GJ 9827 d

With sizable volatile envelopes but smaller radii than the solar system ice giants, sub-Neptunes have been revealed as one of the most common types of planet in the galaxy. While the spectroscopic characterization of larger sub-Neptunes (2.5–4 R ⊕) has revealed hydrogen-dominated atmospheres, smaller sub-Neptunes (1.6–2.5 R ⊕) could either host thin, rapidly evaporating, hydrogen-rich atmospheres or be stable, metal-rich “water worlds” with high mean molecular weight atmospheres and a fundamentally different formation and evolutionary history. Here, we present the 0.6–2.8 μm JWST/NIRISS/SOSS transmission spectrum of GJ 9827 d, the smallest (1.98 R ⊕) warm (T eq,A=0.3 ∼ 620 K) sub-Neptune where atmospheric absorbers have been detected to date. Our two transit observations with NIRISS/SOSS, combined with the existing HST/WFC3 spectrum, enable us to break the clouds–metallicity degeneracy. We detect water in a highly metal-enriched “steam world” atmosphere (O/H of ∼4 by mass and H2O found to be the background gas with a volume mixing ratio of >31%). We further show that these results are robust to stellar contamination through the transit light source effect. We do not detect escaping metastable He, which, combined with previous nondetections of escaping He and H, supports the steam atmosphere scenario. In water-rich atmospheres, hydrogen loss driven by water photolysis happens predominantly in the ionized form, which eludes observational constraints. We also detect several flares in the NIRISS/SOSS light curves with far-UV energies of the order of 1030 erg, highlighting the active nature of the star. Further atmospheric characterization of GJ 9827 d probing carbon or sulfur species could reveal the origin of its high metal enrichment.

Dry reforming of toluene for syngas production over Ni-based perovskite-type oxides

Developing efficient Ni-based catalysts and understanding the mechanism of tar removal are crucial for upgrading biomass gasification technology. Literature has identified the superior performance of Ni-based catalysts in reforming tar model compounds like toluene under a steam atmosphere. In this work, we have synthesized La1-xCexNiO3 catalysts and examined their activity with benchmark A2BO4-type perovskites in dry reforming of toluene (DRT). Catalytic experiments revealed that La0.25Ce0.75NiO3 catalysts exhibited superior activity and stability regarding toluene conversion (85.4%) compared to La0.5Ce1.5NiO4. The structural study, conducted through various techniques, highlighted the easier reducibility of Ni from the ABO3 perovskite lattice, leaving higher oxygen vacancies, and higher basicity for reactant adsorption in DRT. Besides, in-situ DRIFTS experiments confirmed the *CHO-participated pathway of syngas generation from DRT. The findings suggested potential pathways for designing catalysts to support biomass gasification while contributing to global carbon reduction.

Oxidation Behavior of a Novel Nickel-Based Alloy in Air and Steam at 1273 K for the Oxygen–Hydrogen Combustion Chamber

AbstractAs part of advancing oxygen–hydrogen combustion power generation technology, a study was carried out to evaluate the oxidation behavior of a novel developed Ni–Cr–W alloy as the structural material candidate. Tungsten is utilized in the alloy as a solid solution-strengthened element and as an α2-W precipitate former. The examination involved exposing the developed alloy and commercial alloys, Hastelloy X and Nimonic 263, to air and steam environments at 1273 K. The results show a different oxidation behavior of the developed alloy. Considering the air oxidation kinetics, the performance of the developed alloy was on par with that of Hastelloy X and superior to Nimonic 263. A single outer chromia scale was established with an intergranular oxide. Whereas steam exposure resulted in the formation of outer and inner chromia scales with a deeper intergranular oxide penetration. Thicker chromia formation with a lower mass gain indicates the evaporation of chromia under a steam atmosphere.

Hydrogen-Rich Syngas Production from Waste Textile Gasification Coupling with Catalytic Reforming under Steam Atmosphere

Hydrogen-Rich Syngas Production from Waste Textile Gasification Coupling with Catalytic Reforming under Steam Atmosphere

Density functional theory and ReaxFF MD study on steam-induced nitrogen migration mechanism during char gasification

The formation of nitrogen-containing species during char gasification is crucial for emission of nitrogenous pollutants. In this work, the detailed nitrogen migration mechanism during char gasification is studied. Density functional theory (DFT) coupled with ReaxFF MD methods are used to conduct an in-depth analysis on the intrinsic reaction mechanism during Char(N) and steam interaction. DFT results show that orbital electrons of carbon atoms on char surface are driven towards nitrogen atoms by nitrogen functional groups. The electron density of adjacent carbon atoms is weakened, which has a positive charge. Orbital electron properties show that the band energy gaps of three Char(N) models are 3.063 eV, 1.092 eV and 3.328 eV, indicating the reactivity order for three Char(N) models is as follows: Char(N)-2＞Char(N)-1＞Char(N)-3. DFT calculation indicates that the interaction between Char(N) and steam reduces unsaturated carbon atoms and lower the char decomposition activity, which will inhibit the yield of HCN. In contrast, through hydrogen transfer reactions, nitrogen atoms are easily combined with hydrogen atoms, which is more conducive to the formation of ammonia. ReaxFF MD modeling proves that HCN is the main product for Char(N) decomposition under inert atmosphere. Under steam atmosphere, nitrogen atoms in char are more likely to be converted into amino products. The induction of steam provides a large number of active hydrogen radicals, which is able to attack the nitrogen atoms of char and form N–H bonds, thus promoting the formation of ammonia.

Effects of steam feeding on microwave heating of cellulose with magnetite used as susceptor

Microwave heating (MWH) of lignocellulosic biomass with susceptors has attracted attention for H2 production. In this study, H2 is produced from cellulose via MWH at 800 °C in a steam atmosphere with magnetite used as the susceptor. The effects of steam feeding and MWH on the product yields are experimentally investigated in comparison with conventional heating (CH). The H2 and CO2 yields are increased by steam feeding for both MWH and CH because the water–gas shift reaction occurs. Without steam feeding, MWH enhances H2 and CO production, thereby increasing the maximum energy efficiency. With steam feeding, the steam gasification of C is more predominant for CH than for MWH as the reduction in the C content in the char of CH is higher than that of MWH. MWH reduces the formation of secondary char, and it is therefore expected to overcome issues such as the clogging or blockage of gas lines.

Extraction of Essential Oil from Moringa Oleifera Leaves Using Steam Distillation and Soxhlet Extraction Method

Essential oil is one of Indonesia's agro-industrial export commodities, one of which is essential oil from Moringa oleifera leaves. This study aims to study the results of the yield and analyze the essential oil content of Moringa oleifera leaves using the steam distillation method and Soxhlet extraction using ethanol and isopropyl alcohol as a solvent. The fresh feed was either directly extracted or pre-treated using an oven and then followed by several stages of extraction. The pre-treatment of fresh feed was carried out in the oven at 70°C for 1 hour. Atmospheric steam distillation was carried out at 100°C for 6 hours using 500 ml of distilled water. In the case of soxhlet extraction, the temperature was set at the boiling point of the solvent for 6 hours. Once soxhlet extraction was complete, the essential oil was separated from the solvent by distillation. After various extraction processes, the essential oils were analyzed for their compound content using GC-MS. Based on the results of the study, the highest yield of 29.04% was obtained from the treated feed using two stages of soxhlet extraction variable with ethanol as solvent.

Multiplicative effects of co-incineration of sewage sludge and wasted oyster shells in air, CO2, and steam atmospheres on P speciation and bioavailability and metal ecotoxicity

The study was aimed at the reutilization of oyster shells (OS) as a calcium-based additive to turn sewage sludge ash into phosphate fertilizer, employing the oxygen-enriched combustion technology. This process transformed all non-apatite inorganic phosphorus into apatite phosphorus with the incorporation of a 7.5% Ca-based additive. OS demonstrated comparable effectiveness to CaO in catalyzing this transformation in the oxygen-steam atmosphere. The amount of OS added and the atmosphere type significantly influenced the P bioavailability of sewage sludge ash. The oxygen-steam atmosphere, with its increased water vapor concentration, facilitated the decomposition of CaCO3 and initiated reactions with calcium phosphate to form hydroxyapatite, thus substantially enhancing P bioavailability. The oxygen-steam atmosphere increased not only metal volatilization but also the ecological toxicity of residual metals, particularly Pb, mainly in the form of F2. Excessive OS addition appeared to elevate the toxicity of Cr. Therefore, additional strategies for metal removal or passivation are needed to improve the safety of sewage sludge ash with high metal content.

High-temperature degradation behavior of PEO-coated ZIRLO alloy in N2 and N2+steam environments at 900 and 1000 °C

A compact oxide coating of ∼10 μm thick on ZIRLO alloy was fabricated by plasma electrolytic oxidation (PEO). The morphologies, compositions, phase constituents before and after exposures in N2 and N2+steam environments at 900 and 1000 °C were characterized. The PEO coating greatly enhanced the corrosion resistance of ZIRLO alloy in the N2+steam atmosphere at 900 and 1000 °C. The kinetic curves transformed from parabolic behavior for bare alloy and exponential behavior for PEO-coated alloy at pre-transition stage to linear at post-transition stage, due to the formation of ZrN and its re-oxidation.

Study of chlorine removal from shredder residue: Thermal dechlorination and water leaching

Shredder residue (SR) is an inevitable waste in the production of steel by scrap melting, and the presence of chlorine is the main responsible for its non-use of energy. This study aimed to remove chlorine from SR by thermal dechlorination and water leaching. Thermal dechlorination was first studied from a PVC sample to evaluate the optimum parameters of temperature, heating rate, residence time and atmosphere (N2 or steam). Under optimal conditions for PVC dechlorination, chlorine removals of 73.7 (N2) and 68.0% (steam) were achieved. Optimal parameters were applied to thermal dechlorination of a Brazilian SR with a chlorine content of 2.12 wt%. Reductions in chlorine content to 0.95 and 0.51 wt% were observed with N2 and steam atmospheres, respectively. In an additional evaluation (conducted also with the Brazilian SR and in order to investigate the reactor rotation effect), it was observed that the reactor rotation does not influence the release of chlorine during the thermal treatment but modifies the granulometry of the produced solid. Samples obtained from this test were subjected to a water leaching study to further reduce the chlorine content. The parameters studied were the type of water (tap and distilled), granulometry and carbonation (contact with CO2) in a total of five washing cycles. Carbonation and use of distilled water achieved the highest chlorine removal resulting in a reduction of chlorine content from 1.13 to 0.45 wt%. The obtained results show directions for chlorine removal aiming at the energetic use of shredder residue.

Effects of Al and Si elements on oxidation behavior in 1000–1200 °C steam for PEO/CrAlSi composite coating on Zr alloy

A PEO/CrAlSi composite coating of ~10 μm thick on Zr–2 alloy was prepared by duplex plasma electrolytic oxidation (PEO) and filtered cathode vacuum arc deposition (FCVAD) techniques. The high temperature steam oxidation behavior of bare and PEO/CrAlSi–coated Zr alloys was performed in 1000–1200 °C. Their morphologies, microstructures, compositions and phase components were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X–ray diffraction (XRD) and glow discharge optical emission spectrometer (GDOES). The effects of Al and Si elements on multilayers microstructure evolution of coated Zr–2 alloy at steam atmosphere were discussed. It was found that the composite coating significantly improved the high–temperature steam oxidation resistance of Zr–2 alloy. The mass gains of the PEO/CrAlSi–coated Zr–2 alloy after 3600 s exposure in 1000 °C, 1100 °C and 1200 °C steam were 28 %, 29 % and 44 % of the bare alloy. Through the oxidations, Al diffused both inward and outward to the substrate and the surface regions, respectively. Formation of a top oxide layer (Al2O3, Cr2O3) greatly suppressed the inward oxygen diffusion. The Si enrichment in the PEO interlayer formed a Zr2Si layer, which inhibited the Cr-Zr interdiffusion at 1000 °C and 1100 °C. At 1200 °C, the Zr2Si layer was oxidized and the CrZr2 phase was formed in the Zr alloy substrate especially at the β–Zr/α–Zr(O) interface.

Inhibition strategies for phase separation of iron-based oxygen carriers in chemical looping gasification- enhanced oxygen transport efficiency through oxide-support interactions

Chemical looping gasification partially oxidizes biomass to obtain high-quality syngas using oxygen carriers, emerging as a potential method to cope with energy shortages. However, the oxygen carriers were susceptible to deactivation due to phase separation caused by different migration rates between atoms. In this work, the phase deviation of the oxygen carrier is inhibited by enhancing the lattice oxygen activity. Typically, the NiFe-based oxygen carriers were used as active sites and Ce atoms were introduced to change the lattice structure of the oxygen carriers. Calculated by density functional theory (DFT), Ce atoms formed a strong bonding interaction (Ni-O-Ce) with Ni atoms, causing lattice distortion of NiFe oxygen carriers that promote the formation of oxygen vacancies. Therefore, the syngas yields were increased from 537 ml/g (NF) to 633 ml/g (NF@0.5Ce) and 615 ml/g (NF@1.5Ce) in the N2 atmosphere. The syngas yields were increased from 895 to 1101 ml/g (NF@0.5Ce) and 1186 ml/g (NF@1.5Ce) with steam atmosphere. During the 20-cycle experiments, the phase separation of NiFe-based oxygen carriers was effectively suppressed by the intervention of Ce atoms. Therefore, it is a feasible option to induce lattice distortion of active grains by introducing inert elements to suppress phase separation.

Evaluation of Hydrothermally Treated Wood Fibre Performance in Cement Mortars

Biofibres’ wide application in mortar enhancement has thus far been restricted by factors related to their chemical composition and hygroscopic nature. Their hydrophilic behaviour increases the water demand of mortar mixtures and diminishes their affinity to the matrix, while further moisture-related fibre degradation issues may arise. Additionally, natural fibres seem to be susceptible to degradation caused by exposure to alkaline environmental conditions such as those experienced by cement mortars, restricting their utilisation in the construction industry. Therefore, the current study investigates the potential of fibre modification through treatments that would permanently alter their structure and chemical composition to improve their performance. In this study, wood fibres of black pine and beech species were exposed to mild thermal treatment (140 °C 2 h, under a steam atmosphere), characterised in terms of the physical and chemical properties and incorporated in cement mortars, applying the proportion of 1.5% v/v in the mortar, in order to assess their performance as reinforcement material. The mortars’ workability (at a fresh state) was examined, as well as other physical, hygroscopic, thermal, and mechanical characteristics of the mortars at the ages of 28, 90 and 365 days and weathering performance, by subjecting them to different artificial ageing environments (freeze–thaw cycles or outdoor exposure). The results revealed the beneficial role of the treated fibres in dimensional stability, flexural strength, thermal insulation properties and capillary absorption of the mortar specimens, especially during the ageing process, with the black pine fibres showing the greatest improvement. The hydrothermally treated wood fibres seem to help maintain the integrity of cement mortars under all ageing conditions, proving that they could provide low-cost and eco-friendly mortar enhancement pathways.

Mechanistic exploration of polytetrafluoroethylene thermal plasma gasification through multiscale simulation coupled with experimental validation

The ever-growing quantities of persistent Polytetrafluoroethylene (PTFE) wastes, along with consequential ecological and human health concerns, stimulate the need for alternative PTFE disposal method. The central research challenge lies in elucidating the decomposition mechanism of PTFE during high-temperature waste treatment. Here, we propose the PTFE microscopic thermal decomposition pathways by integrating plasma gasification experiments with multi-scale simulations strategies. Molecular dynamic simulations reveal a pyrolysis—oxidation & chain-shortening—deep defluorination (POCD) degradation pathway in an oxygen atmosphere, and an F abstraction—hydrolysis—deep defluorination (FHD) pathway in a steam atmosphere. Density functional theory computations demonstrate the vital roles of 1O2 and ·H radicals in the scission of PTFE carbon skeleton, validating the proposed pathways. Experimental results confirm the simulation results and show that up to 80.12% of gaseous fluorine can be recovered through plasma gasification within 5 min, under the optimized operating conditions determined through response surface methodology.

Devolatilization of extrasolar planetesimals by 60Fe and 26Al heating

ABSTRACT Whilst the formation of Solar system planets is constrained by meteoritic evidence, the geophysical history of low-mass exoplanets is much less clear. The bulk composition and climate states of rocky exoplanets may vary significantly based on the composition and properties of the planetesimals they form. An important factor influenced by planetesimal composition is water content, where the desiccation of accreting planetesimals impacts the final water content of the resultant planets. While the inner planets of the Solar system are comparatively water-poor, recent observational evidence from exoplanet bulk densities and planetary formation models suggests that rocky exoplanets engulfed by substantial layers of high-pressure ices or massive steam atmospheres could be widespread. Here, we quantify variations in planetesimal desiccation due to potential fractionation of the two short-lived radioisotopes 26Al and 60Fe relevant for internal heating on planetary formation time-scales. We focus on how order of magnitude variations in 60Fe can affect the water content of planetesimals, and how this may alter the formation of extrasolar ocean worlds. We find that heating by 26Al is the dominant cause of planetesimal heating in any Solar system analogue scenario, thus validating previous works focussing only on this radioisotope. However, 60Fe can become the primary heating source in the case of high levels of supernova enrichment in massive star-forming regions. These diverging scenarios can affect the formation pathways, bulk volatile budget, and climate diversity of low-mass exoplanets.

Characteristics of the steam degradation of poly(lactic acid) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

The introduction of biodegradable plastics is considered a practical approach to reducing plastic waste accumulation in the environment. Regardless of their biodegradability, plastics should be recycled to effectively utilize and circulate carbon as a resource. Herein, the use of pyrolysis was examined as a method for recycling two common biobased/biodegradable plastics: PLA and PHBH. The pyrolysis of PLA produced lactides (10.7 wt% at 400 °C), but the yield was decreased when the pyrolysis temperature was increased. The presence of steam promoted the hydrolysis of PLA: a steam concentration of 25 vol % increased, the production of lactides at 400 °C to 17.4 wt%. The pyrolysis of PHBH primarily yielded crotonic acid (30.1 wt% at 400 °C), and the yield increased with increasing pyrolysis temperature (71.8 wt% at 800 °C). Steam injection increased the hydrolysis of oligomers, resulting in a 76.1 wt% yield of crotonic acid at 600 °C with a steam concentration of 25 vol %. Thus, we determined that hydrolysis and pyrolysis progress simultaneously under a steam atmosphere, increasing the chemical feedstock recovery from PLA and PHBH. These findings may lead to the proposal of effective degradation methods for treating biobased/biodegradable plastic wastes and ways to maximize the conversion efficiency and target product yields.

Gasification Performance of Barley Straw Waste Blended with Lignite for Syngas Production under Steam or Carbon Dioxide Atmosphere

The gasification performance of lignite/barley straw mixtures for syngas production was investigated. The experiments were carried out under a steam or carbon dioxide atmosphere, in fixed-bed and thermogravimetric–mass spectrometry systems. The thermal behavior, reactivity, conversion, product gas composition, liquid and gaseous by-products and interactions between fuels were determined and correlated with the structural characteristics and inherent minerals in ashes, which were analyzed via mineralogical, chemical and fusibility tests. Devolatilization of the materials up to 600 °C resulted in the carbon enrichment of chars and a 30–90-fold increase in the specific surface area. Gaseous and liquid by-products with higher heating values of 5–7 MJ/m3 and 20–28 MJ/kg could offer valuable energy. Upon steam gasification up to 1000 °C, product gas was enriched in hydrogen and carbon monoxide. The syngas yield and heating value of the gas mixture were higher for barley straw fuel (0.77 m3/kg, 11.4 MJ/m3), which, when blended with the lignite, produced upgraded products. Upon carbon dioxide gasification up to 1000 °C, barley straw char exhibited a 3-times higher rate than the lignite, as well as higher conversion (94.5% vs. 62.9%) and a higher syngas yield (0.84 m3/kg vs. 0.55 m3/kg). Lignite/barley straw blends showed synergistic effects and presented higher gasification reactivity and conversion in comparison to lignite. The overall performance of lignite was improved with the steam reagent, while that of barley straw was improved with the carbon dioxide reagent.