Wet Air Research Articles

Performance evaluation of a wet air oxidation reactor with external circulation for high-chemical oxygen demand wastewater treatment

The presence of high-concentration organic contaminants in wastewater poses considerable risks to the health of both humans and ecosystems. Wet air oxidation (WAO) is an attractive treatment option, but current dilution and retreatment processes do not align with economic and environmental principles. Here we report an external circulation wet oxidation treatment process that utilizes oxidizing liquids to reduce feed concentration. By coupling energy consumption model with computational fluid dynamics model, we explore the optimal parameters for an industrial external circulation reactor. A 90 kt/a external circulation wastewater treatment system has been established, achieving a 21.6% increase in chemical oxygen demand (COD) removal efficiency and a 34.8% reduction in energy consumption. These findings provide a promising pathway for the efficient, low-energy treatment of high-concentration organic wastewater while minimizing freshwater resource consumption.

Synthesis of PbOx to graphite felt anodes to improve the electro-assisted catalytic wet air oxidation of oxygen species for efficient dye degradation

Electro-assisted catalytic wet air oxidation (ECWAO) is an environmentally-friendly pollutant removal process with energy-saving and mild reaction properties. However, it requires an electrode with high catalytic capacity and stability, and the catalytic mechanism behind the process still needs to be further clarified. Herein, we report a graphite felt (GF)-supported PbOx catalyst which can chemically adsorb oxygen and activate it into free radicals by an anodic electric field to promote wet air oxidation. XRD, SEM, EDS, XPS, BET and TG measurements indicated that PbO and PbO2 were successfully doped and loaded onto the GF, increasing the specific surface area and number of active sites. The best RhB degradation efficiencies achieved were 91.26 % over 15 min and 96.68 % over 90 min. The PbOx@C/GF maintained good catalytic performance over eight cycles in the pH range of 3–11 with negligible metal leaching. The RhB degradation pathway of RhB was analyzed through GC–MS results. A free radical quenching experiment, a contrast experiment, and an electrochemical test revealed the process of oxygen being adsorbed by Pb(II) and activated to degrade organic matter was revealed. Five kinds of dyes were degraded by the electrode via the ECWAO process, and the degradation rate reached over 93.7 % within 90 min. The degradation specific energy consumption (SEC) of probe pollutant RhB is 48.70 kW·h/kg-COD. The industrial practical dye wastewater COD removal rate was close to 100 %, and the SEC was 24.44 kW·h/kg-COD. Therefore, it can be concluded that a graphite felt (GF)-supported PbOx catalyst can act as an anode for ECWAO to chemically adsorb oxygen and activate it into free radicals using an anodic electric field to promote wet air oxidation.

Study on the heat and mass transfer characteristics of wet air and solution on the surface of corrugated packings at lower ambient pressure

Study on the heat and mass transfer characteristics of wet air and solution on the surface of corrugated packings at lower ambient pressure

Continuous wet air oxidation of aqueous phase from hydrothermal liquefaction of sewage sludge

The conversion of organic waste into advanced fuels through hydrothermal liquefaction (HTL) is a promising route. However, for the commercialisation of HTL technology, treatment and valorisation of the generated aqueous by-product are required for its economic viability. This study investigates subcritical non-catalytic continuous wet air oxidation (WAO) for the treatment of the aqueous phase from hydrothermal liquefaction (HTL-AP) of sewage sludge. A custom-made tubular reactor was used at temperatures and residence times similar to the HTL process (300–350 °C; 6–50 min), with excess air equivalent to 1.5–2 times the oxygen demand. The WAO process removed up to 95.3 % of the chemical oxygen demand and 91.8 % of the total organic carbon, generating volatile fatty acids, mainly acetic acid, as intermediary compounds from the oxidation reactions, and CO2 and H2O from the pollutant’s complete degradation. The process effectively eliminated almost all of the organonitrogen compounds, generating NH4+, which reached values of up to 97 % of the total nitrogen. Comprehensive molecular characterization performed by FT−Orbitrap MS analysis revealed that the main basic organonitrogen compounds in HTL-AP are distributed in the O1N1, N2, O1N2, N1 classes. For neutral to acidic organonitrogen species, O3N1 is the most representative chemical class. The energy consumption for heating the WAO reactor was up to 40 % lower using HTL-AP compared to blanks experiments. Despite good process water clean-up, autothermal operation was not achieved, and improvements in the reactor design are suggested.

Inconsistent 3‐D Structures and Sources of Sulfate Ammonium and Nitrate Ammonium Aerosols During Cold Front Episodes

AbstractSince the distinct thermostability difference of sulfate ammonium and nitrate ammonium aerosols, their distributions, evolutions and sources could be unpredictable on a long‐range transport condition. Here, we highlighted the 3‐D structures and sources of SO42−, NO3− and NH4+ (SNA) during two cold front episodes in east China. Cold fronts effectively uplift and transport PM2.5 and its precursors from upstream sources to the Yangtze River Delta (YRD). Specifically, in the YRD, surface SO42− is mostly imported from the upstreams, accounting for ∼48%, significantly higher than the contribution from the YRD itself (∼29%). In contrast, NH4NO3 is thermally unstable and more easily lost in the warmer and lower boundary layer (BL) ahead of cold front. Consequently, only 20% of the total NO3− originates from upstreams, while the YRD contributes 28%. In the upper BL, the contribution of SO42− from upstreams remain high (∼49%), with only 18% originating from the YRD. However, due to the intense thermostability of NH4NO3 in colder and wetter air, the YRD’s contribution to NO3− is 27%, and upstreams contribute 20%. The physical processes exert relatively consistent effects on variations of PM2.5 and SNA concentrations. The aerosol chemical process (AERO) of (NH4)2SO4 consistently contributes positively throughout the entire BL. Conversely, the temperature‐sensitive NH4NO3 undergoes repeated dissociation/condensation and deposition, causing positive AERO contributions in upper BL and negative contributions in lower BL. Results indicate that one difference in physicochemical property of species could induce their distinct distributions and sources in large scale, and should be considered in regional air pollution control.

Increasing thermodynamic stability and electrochemical performance of IT-SOFC cathodes based on Ln2MO4 (Ln = La, Pr; M = Ni, Cu)

La2-xPrxNi1-yCuyO4+δ (x = 0.5, 1, 1.5, y = 0.4, 0.6, 0.8) were synthesized by a citrate-nitrate method and studied as cathode materials for IT-SOFCs by Electrochemical Impedance Spectroscopy (EIS) in symmetrical cells based on the Ce0.8Sm0.2O2-δ (SDC) and La28-zW4+zO54+1.5z (z = 0.85, LWO) electrolytes. Phase identification and crystal structure analysis by means of X-ray powder diffraction (XRPD) shows that solubility of copper y decreases with the increase in praseodymium content x due to increasing structural distortions. Thermodynamic stability of La2-xPrxNi1-yCuyO4+δ at intermediate temperatures in air tends to decrease with praseodymium doping level x and increases with copper substitution for nickel y. Oxides with x = 0.5 and 0.6≤y ≤ 0.8 are shown to be thermodynamically stable at 700 °C in air. Electrochemical performance of the La2-xPrxNi1-yCuyO4+δ electrodes improves with praseodymium and copper doping. The results of EIS measurements at different temperatures and oxygen partial pressures (P(O2)) reveal that the rate-determining step of the overall electrochemical process is charge transfer, which can be a combination of surface diffusion and bulk diffusion. EIS studies in dry and wet air indicate the presence of proton conduction in the studied electrodes. The area-specific resistances (ASRs) for La2-xPrxNi1-yCuyO4+δ with x = 0.5, y = 0.6 and y = 0.8 in contact with SDC are comparable with those reported for Pr2NiO4+δ and equal to 0.07 and 0.065 Ω cm2 at 800 °C.

Protonic ceramics Ba5In2–xYxAl2ZrO13 with the perovskite-related hexagonal structure for solid oxide fuel cells: Synthesis, optical band gap and transport properties

The solid solution Ba5In2–xYxAl2ZrO13 (0 ≤ х≤0.50) with hexagonal structure (space group P63/mmc) was prepared by the solid-state reaction method. The effects of isovalent Y3+-substitution on the structure, hydration, bandgap and transport properties have been investigated. The introduction of yttrium was accompanied by lattice expansion, which led to an increase in the concentration of protons during hydration. The doping did not lead to a significant increase in oxygen-ion conductivity since there was no change in oxygen stoichiometry. At the same time, doping led to an increase in ionic transport numbers due to a decrease in hole conductivity. Proton conductivity contribution and the values of proton conductivity increase with the increase in yttrium concentration. The phases with yttrium content x > 0.2 were predominant proton conductors at the temperature below 600°С under wet air.

High-performance phosphorus-doped SrCo0·8Fe0·2O3-δ cathode for protonic ceramic fuel cells

Achieving high performance and stability in cathodes for the oxygen reduction reaction is crucial for the advancement of proton ceramic fuel cells (PCFCs). The introduction of non-metal doping method presents an opportunity to simultaneously optimize the perovskite structure and augment the activity and stability of the oxygen reduction reaction. Herein, we develop a phosphorus-doped SrCo0·8Fe0·15P0·05O3-δ (SCFP) cathode for PCFCs. The SCFP cathode shows a low area specific resistance of 0.24 Ω cm2 at 650 °C in wet air (5% H2O), which is smaller than that of the phosphorus-free SrCo0·8Fe0·2O3-δ (SCF) electrode (0.34 Ω cm2). The Ni–BaZr0.1Ce0·7Y0.1Yb0.1O3-δ (BZCYYb) anode-supported single cell with BZCYYb electrolyte and SCFP cathode exhibits a superior performance of 865 mW cm−2 at 650 °C under H2 atmosphere. This underscores the effectiveness of the phosphorus-doping strategy as a promising approach for advancing cathode development in PCFCs.

Prospects of industrial membrane concentrates: treatment of landfill leachates by coupling reverse osmosis and wet air oxidation.

Stabilized landfill leachates are characterized by a high chemical oxygen demand and limited biodegradability. This study investigates the removal of the organic fraction (chemical oxygen demand and total organic carbon) using a treatment approach that couples membrane processes and wet air oxidation (operating at 200-300 °C and 18 MPa). The aim is to address the challenges posed by landfill leachate membrane concentrates considering variations throughout the year across three different seasons. The efficiency of the treatment path was assessed through the removal of the chemical oxygen demand and total organic carbon, with additional insights provided by fluorescence spectroscopy to evaluate the degradation of the organic compounds' complexity. The most favorable results were achieved at the highest temperature (300 °C) with removals over 90% for total organic carbon and 87% for chemical oxygen demand, along with a complete elimination of fluorescence. The coupling of membrane processes and wet air oxidation has demonstrated its effectiveness in degrading the organic compounds of landfill leachates. The overall mass balance on the treatment path indicates the feasibility of discharging the treated effluent into the environment, meeting regulatory thresholds for total organic carbon and chemical oxygen concentrations.

Defect-induced improved structural and electrical properties of Gd-Sr co-doped ceria for solid oxide fuel cell applications

Compositions of Ce1-x-yGdxSryO2-δ (x = 0.1, 0.2, and y = 0.025, 0.05, 0.075) are prepared using the sol-gel auto combustion method. The as-prepared powders are calcined at 500 °C for 2 h, followed by pelletization and sintering at 1450 °C for 4 h. Phase identification, defect distribution, microstructural analysis, and conductivity are examined using X-ray diffraction, Raman spectroscopy, scanning electron microscopy and impedance spectroscopy, respectively. A single crystalline phase is formed, and the lattice parameter variation with dopant concentration exhibits anomalous behavior. All the samples show relative densities higher than 92 %. The partial liquid phase sintering is also observed. In co-doped samples, the doping of 10 % Gd with 2.5 % Sr exhibits the highest conductivity, i.e., 1.20 × 10−2 S cm−1 at 600 °C. The developed materials are used in anode-supported cell testing. It shows a maximum power density of 112.7 mW cm−2 and a current density of 288.7 mA cm−2 at 600 °C with wet hydrogen and air on the anode and cathode side, respectively.

Acetone-Treated Au Nanoparticles Supported on CeO2 for the Wet Air Oxidation of Dimethylformamide

Acetone-Treated Au Nanoparticles Supported on CeO₂ for the Wet Air Oxidation of Dimethylformamide

Assessment of Outdoor Thermal Comfort in a Hot Summer Region of Europe

Heat waves are increasingly frequent in Europe, especially in South European countries during the summer season. The intensity and frequency of these heat waves have increased significantly in recent years. Spain, as one of the southern European countries most affected by these recurring heat waves, particularly experiences this phenomenon in touristic cities such as Cordoba. The aim of this study was to perform an experimental assessment of outdoor thermal comfort in a typical three-hour tourist walkable path of the historical center of Cordoba. The experimental study was carried out in the three-hour period of higher temperatures from 16:30 to 19:30 h CEST (UTC+2) on a normal summer day (6 July 2023), a day with a heat wave (28 June 2023) and a day with a higher heat intensity, called a super heat wave (10 August 2023). Environmental conditions such as a radiant temperature, ambient temperature, wet bulb temperature, air velocity and relative humidity were measured at three different heights corresponding to 0.1 (ankles), 0.7 (abdomen) and 1.7 (head) m. The results show extremely high levels of heat stress in all bioclimatic indices throughout the route. Cumulative heat stress ranged from “very hot” conditions at the beginning of the route to becoming “highly sweltering” at the end of the route. The average temperature excess over the thermal comfort threshold was very high and increased with the heat intensity. In addition, a correlation analysis was carried out between the bioclimatic indices studied, with the UTCI index standing out for its strong correlation with other thermal comfort indices. The findings emphasize the need for interventions to improve the urban environment and promote better outdoor thermal comfort for city dwellers through measures such as green infrastructure, UHI mitigation and increasing public awareness.

Development of an optimal mechanism for a solar-air collector for drying thermolabile products

The article presents theoretical and experimental studies about the alternative construction of energy-efficient solar air collector that generates heat based on alternative energy sources for the drying process of agricultural products. In particular, the geographical latitude of the place (φ), the angle of elevation of the sun to the horizon (h°), the angle of deviation of the sun (δ), and τ the interrelationships between the sun’s hour angles (τ) were studied. The patterns of changes in the wet air and dry air parameters entering the solar air collector were analyzed. The mechanism of efficient use of the heat generated in the solar air collector was developed. The kinetics of the process of drying spices at low temperature was studied.B NNBB. 1

Performance evaluation of a passive air conditioning module integrating radiative sky cooling and indirect evaporative cooling

Amidst escalating global warming challenges, the demand for sustainable, carbon-free cooling technologies in buildings has become pressing. While radiative cooling (RC) and indirect evaporative cooling (IEC) are carbon–neutral, their efficacy is constrained by a limited cooling capacity. This study introduces an innovative passive air conditioning module that integrates RC and IEC to boost efficiency. The RC-IEC module unifies the air-conditioning process in both the RC and dry channels of the IEC unit, ensuring air cooling with a constant humidity ratio. A portion of the IEC dry channel outlet air is redirected to the wet channel to augment the efficiency of the IEC process. The outlet air from the wet channel is directed to the secondary RC air channel for cold energy recovery instead of being directly exhausted. The developed mathematical model, validated with experimental data, demonstrates that the RC-IEC system lowers the supply air temperature by 0.88 °C compared to the IEC-only system. This corresponds to an 11.91 % and 9.94 % improvement in dew-point effectiveness and cooling energy gain, respectively. A parametric study indicates the system's suitability for hot, arid climates, with optimal performance at a wet channel air mass fraction of 0.31. The analysis of the annual cooling performance of the RC-IEC system across diverse climates, spanning from Athens to Singapore, spotlights Dubai's system as the most efficient, achieving a remarkable annual gain of 1081.09 MJ. The study emphasizes the need for tailored strategies, such as advanced air dehumidification technologies, to optimize cooling in humid regions like Singapore.

Study on the effect of pressure in humid air dehumidificationournal

In this paper, there are problems such as large energy consumption and complex system in the field of condensation dehumidification. It is found that increasing pressure can strengthen the effect of condensation dehumidification, simplify the system and reduce energy consumption. So this paper simulates the condensation and dehumidification process of humid air in horizontal pipe under positive pressure. The results show that the dehumidification capacity increases by 25%∼30% when the pressure increases by 100kPa on average. The increase of pressure has little effect on the heat transfer coefficient, but the increase of humidity increases the heat transfer coefficient more obvious. When the humidity of wet air increases by 20%, the heat transfer coefficient increases by 18% ∼ 33%. The dehumidification capacity and heat transfer coefficient increase with the increase of pipe diameter and fluid flow rate.

Analysis of Extreme Weather Causes of Flooding in Manado North Sulawesi

On January 27 and 28 2023, Manado City was hit by heavy rain which caused several areas to experience significant flooding. The high intensity of rain during that period reached extreme levels, resulting in the inundation of several areas and submerging hundreds of residents' houses in 22 villages or sub-districts and 7 sub-districts in Manado. In studying this event, this research investigates the factors that influence extreme weather in Manado, observing sea surface temperature data, streamlines, air observations, the Southern Oscillation Index (SOI), and the Indian Ocean Dipole (IOD). The analysis shows that the positive SOI and negative IOD phenomena significantly impact extreme weather in the region. Cumulonimbus (Cb) clouds drove the atmospheric conditions formed on January 27 and 28 2023 and air flows from the Indian Ocean which brought wet air masses into Indonesian territory. High sea surface temperatures, reaching 28-29°C, also play a role in the intensive growth of rain clouds. Based on atmospheric conditions seen from radiosonde observation data, the stability index value shows that unstable conditions trigger heavy rain which causes flooding

A fast ceramic mixed OH−/H+ ionic conductor for low temperature fuel cells

Low temperature ionic conducting materials such as OH− and H+ ionic conductors are important electrolytes for electrochemical devices. Here we show the discovery of mixed OH−/H+ conduction in ceramic materials. SrZr0.8Y0.2O3-δ exhibits a high ionic conductivity of approximately 0.01 S cm−1 at 90 °C in both water and wet air, which has been demonstrated by direct ammonia fuel cells. Neutron diffraction confirms the presence of OD bonds in the lattice of deuterated SrZr0.8Y0.2O3-δ. The OH− ionic conduction of CaZr0.8Y0.2O3-δ in water was demonstrated by electrolysis of both H218O and D2O. The ionic conductivity of CaZr0.8Y0.2O3-δ in 6 M KOH solution is around 0.1 S cm−1 at 90 °C, 100 times higher than that in pure water, indicating increased OH− ionic conductivity with a higher concentration of feed OH− ions. Density functional theory calculations suggest the diffusion of OH− ions relies on oxygen vacancies and temporarily formed hydrogen bonds. This opens a window to discovering new ceramic ionic conducting materials for near ambient temperature fuel cells, electrolysers and other electrochemical devices.

G‐C3N4 Coating Enhanced Cu@AC for Catalytic Wet Air Oxidation of Phenol under Mild Conditions

AbstractA Cu‐based supported catalyst with g‐C3N4 coating (Cu/g‐C3N4@AC) was prepared by facile in‐situ growth over activated carbon surface with urea and Cu(NO3)2, and the catalytic performance for wet air oxidation of phenolic wastewater was investigated. The effects of different reaction conditions (catalyst, temperature, pressure and pH) were examined. The results show that under the catalysis of Cu/g‐C3N4@AC phenol could be completely oxidized at 120 °C and 0.5 MPa O2 with COD removal of 92.6 % (from 4883 mg/L to 361 mg/L). TEM, BET, XRD, FTIR and XPS characterizations showed that g‐C3N4 coating could strengthen the metal surface interaction via the Cu−N−C bonds formation, thus suppressing the aggregation of the active components on the surface and mitigating the catalyst deactivation. Moreover, the interaction between the Cu species and the g‐C3N4 structure facilitates the electron transfer and thus significantly boost up the catalytic activity. These findings help explore efficient catalysts for the wastewater treatment via wet air oxidation under mild conditions.

Experimental Assessment of Different Air-Based Battery Thermal Management System for Lithium-Ion Battery Pack

<div>Lithium-ion (LI) batteries are widely used to power electric vehicles (EVs), owing to their high charge density, to minimize the environmental pollution caused by fossil fuel-based engines. It experiences an enormous amount of heat generation during charging and discharging cycles, which results in higher operating temperatures and thermal nonuniformity. This affects performance, useful battery life, and operating costs. This can be mitigated by an effective battery thermal management system (BTMS) to dissipate the heat there by safeguarding the battery from adverse thermal effects and ensuring high performance, safety, and longevity of the battery. This article presents a method to estimate the cooling requirement of a given battery pack using calorimetry and discusses the effect of airflow path, flow rate, and inlet air temperature on the thermal behavior of a 4S4P battery pack consisting of 18650 type lithium iron phosphate (LFP) cylindrical Li-ion cells each of 2.55 Ah capacity. In battery pack operation without a cooling system, it is found that the interior cells experience a 3°C higher cell temperature relative to the rest of the battery pack. The cooling performance of the different air BTMS, viz., natural convection cooling, single suction fan cooling, two-fan air cooling, centralized inlet air cooling, and wet jute-based single suction fan air cooling, is discussed. It is observed that the peak temperature rise of the cells in the battery pack was found to be the least in centralized inlet air cooling, unlike other cooling configurations. The wet jute-based single suction fan air cooling is superior by achieving the highest COP of 6, with an 8.9°C rise in battery pack peak temperature for a permissible peak discharge rate. It is observed that the temperature rise of the battery pack is profoundly influenced by the temperature of the inlet air compared to the flow rate.</div>

Simulating cumulus clouds based on self-organized criticality

Recently it was shown that self-organized criticality is an important component of the dynamics of cumulus clouds (Najafi et al., 2021). Here we introduce a new algorithm to simulate cumulus clouds in two-dimensional square lattices, based on two important facts: the cohesive energy of wet air parcels and a sand-pile-type diffusion of cloud segments. The latter is realized by considering the evaporation/condensation of air parcels in various regions of the cloud, which enables them to diffuse to the neighboring regions. The results stemming from this model are in excellent agreement with observations reported in the above-cited paper, in which the exponents were determined for two-dimensional earth-to-sky RGB cloud images. The exponents obtained at the lowest condensation level in our model are consistent with the exponents observed in nature. We find that the cloud fields obtained from our model are fractal, with the outer perimeter having a fractal dimension of Df=1.25±0.01. Furthermore, the distributions of the radius of gyration and the loop length follow a power-law function with exponents τr=2.3±0.1 and τl=2.1±0.1, respectively. The loop Green function is found to be logarithmic with the radius of gyration of the loops following the observational results. The winding angle statistic of the external perimeter of the cloud field is also analyzed, showing an exponent in agreement with the fractal dimension, which may serve as the conformal invariance of the system.