Gas Ratio Research Articles

Photocatalytic Activity of ZnO/Ag Nanoparticles Fabricated by a Spray Pyrolysis Method with Different O2:N2 Carrier Gas Ratios and Ag Contents

Wastewaters of the textile industry, e.g., those generated in Gresik, Indonesia, are a possible threat to the environment and should be treated before disposal. Photodegradation is a more promising method to overcome this problem than conventional methods such as biodegradation. ZnO is widely used for photodegradation due to its unique physical and chemical properties and stability. In this study, Ag was loaded onto ZnO, which is non-toxic and inexpensive, can improve the electron–hole separation, and has a significant catalytic potential. Pristine ZnO and ZnO-Ag nanoparticles were fabricated by an ultrasonic spray pyrolysis system at different Ag contents (1, 5, and 10 wt%). The carrier gas ratio (O2:N2) was also changed (1:0, 1:2, 1:1, 2:1, and 0:1) to examine its effects on the nanoparticle characteristics. The nanoparticle characteristics were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer, Emmett, and Teller (BET) specific surface area. The results were interpreted in relation to photodegradation under UV light irradiation. An increase in the ZnO-Ag activity compared with pristine ZnO was observed at a carrier gas ratio of 0:1 with reaction rate constants of 0.0059 and 0.0025 min−1, respectively.

The Comparison of Biotreatment and Chemical Treatment for Odor Control during Kitchen Waste Aerobic Composting

Odor ΨΩγemission has become mathvariant="normal" mathvariant="sans-serif-bold-italic" an important issue in kitchen waste management. Ammonia and hydrogen sulfide are the two most important odor sources as they contribute malodor and can cause health problems. As biotreatment and chemical treatment are two majorly applied technologies for odor control, in this study, they were used to remove ammonia and hydrogen sulfide and the performance of each process was compared. It was found that chemical absorption could efficiently eliminate both ammonia and hydrogenmathvariant="script" sulfide, and the removal efficiencies of ammonia and hydrogen sulfide highly depended on the pH of the adsorbent, contacting time, and gas and solution ratio (G/S). The ammonia-removal efficiency reached 100% within less than 2 s at G/S 600 and pH 0.1. The complete removal of hydrogen sulfide was achieved within 2 s at G/S 4000 and pH 13. Biotrickling filter showed better ability for hydrogen sulfide removal and the removal efficiency was 91.9%; however, the ammonia removal was only 73.5%. It suggests that chemical adsorption is more efficient compared to biotreatment for removing ammonia and hydrogen sulfide. In the combination of the two processes, biotrickling filter followed by chemical adsorption, the final concentrations of ammonia and hydrogen sulfide could meet the Level 1 standard of Emission Standards for Odor Pollution (China). The study provides a potential approach for odor control during kitchen waste aerobic composting.

Vertical sidewall of silicon nitride mask and smooth surface of etched-silicon simultaneously obtained using CHF3/O2 inductively coupled plasma

Silicon nitride (SiNx) has been playing a vital role in the fabrication of micro- and nano-scale structures in numerous applications for several decades. Optimal etch recipes and a mechanistic understanding of the SiNx plasma-etching process are necessary for its adoption as a hard mask. We present a systematic investigation on SiNx films and underlying silicon (Si) plasma etching via an inductively coupled plasma (ICP) system using a CHF3/O2 mixture. Effects of ICP power, RF power, CHF3 flow rate on SiNx etching rate, CHF3/O2 gas ratio on SiNx sidewall profile, Si surface roughness, and SiNx/Si etching selectivity have been methodically investigated. We paid particular attention to studying the effect of O2 concentration on SiNx and Si etching mechanisms. It was found that SiNx sidewall profile, Si surface roughness, and SiNx/Si etching selectivity depend strongly on the O2 concentration. A nearly vertical SiNx sidewall of 89°, a low Si surface roughness of 0.2 nm, and a high SiNx/Si etching selectivity of 2 were simultaneously achieved by adjusting O2 concentration to 10% with CHF3+O2 total flow rate of 50 sccm. Finally, the composition of the residue on the surface of the processed sample was examined by X-ray photoelectron spectroscopy (XPS).

Mathematical Modeling and Robust Multi-Objective Optimization of the Two-Dimensional Benzene Alkylation Reactor with Dry Gas

The benzene alkylation reactor using the dry gas is the most significant equipment in the ethylbenzene manufacturing process. In this paper, a two-dimensional homogeneous model is developed for steady state simulation of the industrial multi-stage catalytic reactor for ethylbenzene. The model validation on a practical benzene alkylation reactor shows the model is accurate and can calculate the hot spot temperatures. The composition of dry gas from upstream process varies with the operating conditions, which can cause unexpected hot spots in the reactor and catalyst deactivation. Considering the uncertainty in dry gas composition, a robust multi-objective optimization framework is proposed: first, the back-off in constraints is introduced to the multi-objective optimization problem to hedge against the worst case; then the optimal operating point can be selected using the multi-criteria decision-making. The reactor optimization objectives are maximizing selectivity of ethylene and conversion of ethylbenzene, and the distribution ratios of dry gas are defined as decision variables. Results of robust multi-objective optimization show the selectivity and conversion at the optimal operating point are 90.88% (decreased by 0.24% compared to the practical condition) and 99.94% (increased by 0.72%). Importantly, the proportion of violations of the hot spot constraints decreases from 13.7% of the traditional method to 3.8% by applying the proposed robust multi-objective optimization method.

Study on the mass transfer of SO2 in ammonia-based desulfurization process

The coal hydrogen production process requires high-temperature steam as a reactant. Coal-fired boilers are usually used to provide high-temperature steam. The ammonia-based desulphurization process is an effective technology to remove SO2 in the coal-fired flue gas. However, the mass transfer coefficient of SO2 in such an engineered process is not readily available in the literature. In this paper, experiments were carried out to investigate the mass transfer process of SO2 absorption. Combing calculating the air and liquid contact area of the droplet and liquid membrane on the tower wall, the mass transfer coefficient contain parameters pH, gas flue rate and liquid to gas ratio was proposed. The comparison results show that the calculated SO2 mass transfer rate agrees well with the measured data. The relative error of the calculated and experimental values was less than ±20%. This proposed mass transfer coefficient appears to be beneficial for the design and operation of ammonia-based desulfurization FGD system.

Machine Learning-Assisted Prediction of Oil Production and CO2 Storage Effect in CO2-Water-Alternating-Gas Injection (CO2-WAG)

In recent years, CO2 flooding has emerged as an efficient method for improving oil recovery. It also has the advantage of storing CO2 underground. As one of the promising types of CO2 enhanced oil recovery (CO2-EOR), CO2 water-alternating-gas injection (CO2-WAG) can suppress CO2 fingering and early breakthrough problems that occur during oil recovery by CO2 flooding. However, the evaluation of CO2-WAG is strongly dependent on the injection parameters, which in turn renders numerical simulations computationally expensive. So, in this work, machine learning is used to help predict how well CO2-WAG will work when different injection parameters are used. A total of 216 models were built by using CMG numerical simulation software to represent CO2-WAG development scenarios of various injection parameters where 70% of them were used as training sets and 30% as testing sets. A random forest regression algorithm was used to predict CO2-WAG performance in terms of oil production, CO2 storage amount, and CO2 storage efficiency. The CO2-WAG period, CO2 injection rate, and water–gas ratio were chosen as the three main characteristics of injection parameters. The prediction results showed that the predicted value of the test set was very close to the true value. The average absolute prediction deviations of cumulative oil production, CO2 storage amount, and CO2 storage efficiency were 1.10%, 3.04%, and 2.24%, respectively. Furthermore, it only takes about 10 s to predict the results of all 216 scenarios by using machine learning methods, while the CMG simulation method spends about 108 min. It demonstrated that the proposed machine-learning method can rapidly predict CO2-WAG performance with high accuracy and high computational efficiency under conditions of various injection parameters. This work gives more insights into the optimization of the injection parameters for CO2-EOR.

The effect of the liquid physical properties on the wave frequency and wave velocity of co-current gas-liquid stratified two-phase flow in a horizontal pipe

The aim of the present study was to investigate the effect of the liquid physical properties on the liquid film thickness, wave frequency, and wave velocity in co-current gas-liquid stratified two-phase flow in a horizontal pipe. The present experimental study was conducted using an acrylic pipe with an inner diameter of 26 mm and a length of 9500 mm. The superficial velocity of liquid (JL) and gas (JG) were 0.02 m/s to 0.1 m/s and 4 m/s to 16 m/s, respectively. A highspeed video camera was used to take the visual data which is then processed by the developed image processing techniques to obtain the time series data of the liquid film thickness. The probability distribution function (PDF) and discrete wavelet transform (DWT) were used to analyze the time series of the liquid film thickness. In addition, the data were also analyzed using the power spectral density (PSD) in order to obtain the wave frequency and the wave velocity. Next, the experimental correlations to predict the wave frequency and the wave velocity were developed using the dimensional analysis. From the time series of the liquid film thickness, the effect of the viscosity and surface tension on the shifting of scale and frequency of the wavelet decomposition level, as well as the frequency and velocity of the waves were clarified. In addition, a correlation to predict the frequency and velocity of waves has been successfully developed, in which the Martinelli parameter, the ratio of gas and liquid Reynold numbers, and the Weber number play the important roles in the correlation.

Analysis of TihxOy Films Produced by Physical Vapor Deposition Method

For decades, partially oxidized hydrides were commonly considered as undesirably contaminated phases and were avoided by scientists. Nevertheless, more recently, it was realized that in some hydrides and oxides, partial substitution of dissimilar H− and O2− anions allows one to obtain unique optical and electrical properties that might have appealing applications in commercial products. It was determined that specific properties of so called oxyhydride materials strongly depend on the used synthesis methods; therefore, there is a great interest in exploring various variants of oxyhydride formation. In the current study, TiHxOy films were deposited by a reactive magnetron sputtering process in Ar-O2-H2 gas mixtures. Color, transparency and crystal phase composition of the films coherently reacted to the Ar:O2:H2 gas ratio. Namely, the rise in partial hydrogen pressure promoted the formation of anatase phase TiO2 structure and darkening of the films. Interestingly, this had only minimal impact on the band gap values, but had a relatively strong negative effect on the photocatalytic activity of the films. The unaccustomed results stressed the difference between the partially reduced TiO2 with a significant amount of oxygen vacancies and synthesized TiHxOy films where some O2− ions are implicitly substituted by H− ions.

Heteroepitaxial Growth of Vertically-Aligned GaN Single-Crystalline Microrod Arrays on Silicon Substrates.

The heteroepitaxial growth of vertically aligned gallium nitride (GaN) single-crystalline microrod arrays on silicon substrates was achieved with high reproducibility by using the plasma-enhanced chemical vapor deposition (PECVD) method in the furnace. By reducing the plasma power from 70 to 15 W, the crystal morphology of GaN varied from thin films to microrod arrays with the decreased V/III gas ratio. The growth of GaN crystals occurred in the vertical direction of the substrate and in the lateral direction of the growth axis via the self-catalytic vapor-liquid-solid mechanism (VLS mechanism) and the vapor-solid mechanism (VS mechanism), respectively, contributing to the formation of inverted hexagonal GaN cone microrods. Furthermore, the morphology of inverted hexagonal GaN cone microrods shows extremely small contact areas between the microrods and the substrate, suggesting the potential to solve the problems of stress accumulation and poor crystalline qualities of heteroepitaxy. With the raised growth temperature of GaN from 930 to 980 °C, the material quality was improved and the high crystalline qualities were obtained, owing to the successful surface migration of gallium atoms. However, the density of GaN microrods became lower with the increased growth temperature because the spatial temperature gradient was reduced and the evaporation of gallium was enhanced, leading to fewer gallium atoms precipitating and remaining on the substrate. The growth direction of vertically aligned GaN single-crystalline microrod arrays with the (002) crystal plane is along the [0001] orientation (c axis) and normal to the substrate surface, which may bring about many device applications in future studies.

Thermal plasma assisted pyrolysis and gasification of RDF by utilizing sequestered CO2 as gasifying agent

A growing global population coupled with rising industrialization has led to an ever increasing energy demand, which in turn forced us to turn to fossils without sufficient consideration of the consequences. The most serious consequence, as is evident today, is the increase in CO2 levels responsible for adverse climate change, which compelled the United Nations to develop the Sustainable Energy Goal 13 (SDG-13), calling for immediate action to combat climate change and its effects. On the other hand, the increase in population has also resulted in a tremendous increase in waste generation, necessitating the need for safe and sustainable waste treatment. Over recent years, research has been concentrating on advanced thermal plasma technology to valorize diverse wastes into useful energy. The generated syngas can be utilized for energetic (such as heat and electricity) and chemical (such as methanol and dimethyl ether) end applications. The current investigation analyzes the viability of the thermal plasma system (a water-stabilized DC plasma torch) for the pyrolysis, partial pyrolysis, and gasification of refuse-derived fuel (RDF) coupled with the implementation of the CCUS concept using waste CO2 as a gasifying agent (which is planned to be separated from flue gas coming from waste combustion) and converting it into CO in the syngas through plasma valorization of RDF. A comparative evaluation of the attributes, impurities, and yield of syngas and the generation of solids (ash and char) is carried out along with the analysis of performance parameters for four different cases (with variable inputs of CO2, namely 173, 62, 26 and 0 L/m with gasification ratio ranging from 1.04 to 0.4). The syngas constituents are compared to the equilibrium compositions deduced by developing an equilibrium model in Aspen Plus (V 11.0) thermodynamic environment and are found to be close to the theoretical compositions. The highest gas yield is found for Case-I with 3.44 m3/kg due to the maximum carbon conversion, while the minimum gas yield is assessed as 1.60 m3/kg for Case-IV with high char production. Furthermore, H2 production was found to be almost the same for all cases (1.06–1.12 m3/kg of fuel). Furthermore, energetic efficiencies for all the four cases (63 %, 60 %, 62 % and 58 %) clearly reveal an encouraging energy balance. The theoretical maximum values of contaminants such as NH3, H2S, HCl, HF and HBr are calculated and a design of a syngas cleaning system is proposed. The promising results of the study can be considered a small but significant step towards SDG-13.

METHODOLOGY OF FACTOR ANALYSIS OF INCOME OF CITY GAS NETWORK ENTERPRISES

The article considers the method of calculating the influence of a number of factors on the change in income of enterprises of city gas networks. In the process of factor analysis of this indicator, it is recommended to use a number of economic-mathematical models containing factors that characterize the peculiarities of the production and operation process of enterprises of city gas networks. It is proposed to calculate the quantitative influence on the general change of this indicator of such important production and economic factors as the volume of natural gas obtained by the analyzed enterprise, the volume of gas supplied to the network, the volume of gas sold to consumers, the ratio of gas supply to the network, the sales ratio of gas to consumers, the average tariff of a unit of gas sold to consumers, the level of profitability of a unit of gas received, gas supplied to the network and gas sold to consumers. The positive aspect of this approach is that in the process of analytical calculations, indexes of factor indicators are used, and not their absolute values for the case when such data are not available. At the same time, when using this method, it is suggested to follow the rule in which the basic value of the analyzed income indicator is multiplied by the indices of the previous factors of the calculation formula and by the relative growth of the factor whose influence is calculated. To determine the absolute impact of these factors on the overall change in income, it is recommended to carry out a step-by-step factor analysis of this indicator, which is based on the method of chain substitutions. This methodical approach allows, depending on the available initial information and the purpose of the analysis, to calculate the impact on the change in income of a different number of factors (two, three, etc.). The given method of modeling and factor analysis of income makes it possible to decompose this indicator into a number of constituent parts, to present it in the form of multiplicative economic and mathematical models, to determine the absolute and relative influence of the most important factors on the overall change of this indicator for any period of time of the enterprise’s operation, to investigate the regularities of such impact, use the obtained analytical information to substantiate organizational and management decisions regarding further improvement of the efficiency of use of available resources. Keywords: methodology, analysis, income, model, simulation.

Physical Simulation of Powder Spraying at the Bottom of a Converter

Herein, a converter model is established to study the powder spraying process. The effects of powder spraying speed, solid–gas ratio, particle size, and powder spraying position on the distribution of powder in a molten bath and the molten iron splash on a liquid surface are quantitatively studied by using image technology. Increasing the carrier gas flow to 2 m3 h−1 can effectively promote the movement and mixing of the powder in the molten bath, but at the same time, this leads to a degree of splash of 50.61% above the molten bath. A similar situation occurs with increasing solid–gas ratio and decreasing particle size. However, as the powder injection position is gradually moved away from the center of the furnace bottom, the powder distribution before 3 s is more advantageous, and the degree of splash decreases from 25.39 to 12.40%.

In-situ cracking of oil into gas in reservoirs identified by fluid inclusion analysis: Theoretical model and case study

Natural gas formed by cracking of crude oil occurs in many basins globally. One of the key questions about such gas is whether it was produced in-situ—by cracking of crude oil in the reservoir itself—or whether it was generated elsewhere and accumulated in the reservoir subsequently. Fluid inclusions trapped in minerals can provide direct evidence regarding the genesis of natural gas, because these inclusions represent samples of the fluid present at the time of trapping, and/or resulting from subsequent modification of the trapped fluid. Here, we outline some theoretical aspects of the processes of cracking, trapping of fluid inclusions, and potential post-entrapment modifications, that lead to a model for identifying evidence for in-situ cracking of crude oil in reservoirs based on fluid inclusion assemblages (FIAs). This model divides the crude oil cracking process into three main stages, and considers the predicted evolution of fluids and possibility of forming FIAs. In the initial step, before cracking, only liquid oil and aqueous fluid are present in a reservoir, and two endmember types of inclusions may be formed. If cracking of crude oil occurs in the reservoir after these inclusions were trapped, then in-situ cracking of oil within the inclusions gives rise to systematic changes that can be interpreted through the lens of progressive thermal maturation, and hence provide direct evidence for cracking in the reservoir. In the second step, during cracking, the reservoir may host up to four fluid phases (residual oil, aqueous fluid, natural gas, and solid bitumen), and in theory as many as fourteen types fluid inclusions can be trapped; hence, complex FIAs comprising multiple fluid inclusion types can be considered evidence for trapping during in-situ cracking of crude oil in the reservoir. In the third and final step, after complete cracking, liquid oil has been exhausted and only natural gas, solid bitumen and aqueous fluid remain in the reservoir; at this stage, up to six fluid inclusion types can be trapped, which can be indicative of cracking. We applied this model to study the genesis of natural gas in the Sinian Dengying Formation reservoir of the Anyue Gas Field in the Sichuan Basin, southwest China. Six types of hydrocarbon-bearing primary fluid inclusions were observed in fluorite crystals formed during hydrocarbon accumulation. Notably, one type of inclusion showed consistent volumetric phase ratios of solid bitumen plus gas, suggesting that these inclusions originally captured crude oil, which subsequently underwent in-situ cracking in a closed system (within the inclusions) to generate fixed proportions of gas and solid bitumen. These FIAs are consistent with our model and suggest that the fluid inclusions trapped in fluorite can record the in-situ cracking of crude oil in the reservoir, and can therefore be used as direct evidence for the genesis of natural gas.

Energy Saving Evaluation with Low Liquid to Gas Ratio Operation in HVAC&R System

Previous studies have been conducted by employing various methods to reduce the condenser water temperature, a crucial control variable to consider when attempting to improve the operational efficiency of a chiller. The existing literature dealing with the effects of low-condenser water temperatures is limited, as the cooling water flow rate is often considered the operating variable of the condenser loop. However, to produce additional low condenser water temperatures, the approach temperature of the cooling tower in the system must be reduced. To reduce the approach temperature, it is necessary to review the physical behavior and efficiency of the cooling tower according to the change in the liquid to gas ratio (LGR), which is dependent upon the condenser water flow rate and the cooling tower fan air flow rate within the condenser loop. However, this process has rarely been reviewed in previous studies. Therefore, this study developed a new cooling tower control algorithm from the LGR perspective, and the operational effectiveness was quantitatively reviewed using EnergyPlus. Compared to the conventional conditions, when the cooling tower operation algorithm for low-approach temperatures was applied, the annual energy saving was 27.0%, the average chiller COP was improved by 27.8%, and the average system COP was improved by 47.4%. Furthermore, even when the algorithm was not applied at the same condenser water set temperature, the annual energy saving was 15%. The average COP of the chiller and COP of the system is improved by 2% and 23.2%, respectively. These results indicated that when a cooling tower is operated with a low LGR, even under the same outdoor air and load conditions, the cooling system’s efficiency can be improved with a change in the control algorithm without installing additional high-efficiency equipment.

Combined cardiopulmonary test and exercise Doppler echocardiography in systemic sclerosis

Abstract Background Cardiopulmonary exercise test (CPET) and exercise Doppler echocardiography (EDE) may be useful for the early detection of pulmonary hypertension in systemic sclerosis (SSc) Aim To assess the feasibility of CPET and EDE in detecting early changes in gas exchange and/or pulmonary hemodynamics in SSc Methods From 2016 to 2021, we evaluated 19 SSc patients (Group 1, age = 52.58±11.27, women 17 (89.5%)), and age 32.10±6.67, men 17 (89.4%) matched healthy controls (Group 2). Simultaneous CPET and EDE were performed. With CPET, we assessed peak oxygen uptake (VO2), peak respiratory quotient (RQ), respiratory equivalent ratio for carbonic gas (VE/VCO2), and maximal respiratory equivalent divided by maximal ventilatory ventilation (V̇E Max/VVM). With EDE, we assessed tricuspid regurgitant velocity (TRV) jet and pulmonary flow acceleration time (ACT) to derive systolic pulmonary arterial pressure (SPAP). Results Exercise duration was similar in the 2 groups (Group 1 = 9.2±2.93 vs Group 2 = 10.14±1.78 minutes). Among CPET parameters, SSc patients showed lower peak VO2 (Group 1 = 1.23±0.55 vs Group 2 = 2.45±0.7, p<0.001), similar RQ (1.10±0.10 vs 1.17±0.09;. p=0.036), VE/VCO2 (Group 1 = 31.90±3.65 vs Group 2 = 23.79±2.64, p<0.001) and V̇E Max/VVM (Group 1 = 1.93±0.60 vs Group 2 = 1.76±0.36, p=NS). With EDE, feasibility at peak stress was low for TRV (Group 1 = 42% vs Group 2 = 58%, p=NS), moderate for ACT (Group 1 = 53% vs Group 2 = 78%, p=NS) and high when at least one was technically adequate (Group 1 = 73% vs Group 2 = 100%, p<0.001). Rest TRV (Group 1 = 2.48±0.14 vs Group 2 = 2.08±0.12 m/s, p=0.033) and ACT (Group 1 = 100.14±10.63 vs Group 2 = 108.86±6.38 ms, p=0.482) showed similar values in the 2 groups (será que ficou similar?). During stress, TRV increased more markedly in SSc (Group 1 = 3.33±0.32 vs Group 2 = 2.34±0.09 m/s, p=0.004) and ACT decreased (Group 1 = 81.9±6.54 vs 73.39±5.18 ms, p=0.304), with estimated peak SPAP higher in SSc (Group 1 = 53.34±7.88 vs Group 2 = 43.33±5.49, p<0.001): see figure. Conclusion CPET and EDE offer complementary information on gas exchange and pulmonary hemodynamics in SSc and can detect early alterations missed by resting assessment. The success rate of EDE increases significantly with the combination of TRV and ACT. Funding Acknowledgement Type of funding sources: None.

A Thermal-hydraulic assessment of condensing tube bank heat exchangers for heat and water recovery from flue gas

Condensing heat exchangers are capable of recovering a significant amount of latent heat at temperatures below 100 °C from the flue gas of combustion-based heating systems due to the presence of water vapor in their exhaust streams. However, the condensation of acids along with water vapor creates a highly-corrosive environment in these heat exchangers. As such, a large majority of these heat exchangers are made from corrosion-resistant alloys, such as stainless steel. Polymer-based materials are cost-effective and have great corrosion-resistant properties. Since the performance parameters of a heat and water recovery unit depend on the size and compactness of their heat exchangers, it is challenging to compare the overall performance of stainless-steel condensing heat exchangers with polymeric ones based on the data available in the literature. The main goal of the present study is to develop and assess the thermal–hydraulic performance of a proof-of-concept condensing heat exchanger made of fluorinated ethylene propylene compared to the same condensing heat exchanger made of stainless steel for heat and water recovery from flue gas. For this purpose, an in-depth parametric study is conducted experimentally to evaluate the water recovery efficiency, total heat recovery rate, and pressure drop in the flow paths. The results revealed that the water recovery efficiency of the unit with a specific size, declines when the mass flow rate of the gas increases, although it enhances the total heat recovery of the unit. Moreover, increasing the volumetric flow rate of the heat transfer fluid flow slightly increases the total heat recovery of the stainless-steel condensing heat exchanger, but has a negligible impact on the total heat recovery rate of the polymer-based heat exchanger. Increasing the humidity ratio of the flue gas or the inlet temperature of heat transfer fluid does not have any significant effect on the flue gas pressure drop. These findings are significantly important and novel as they unlock the potential of using polymer-based materials with thermally conductive additives for latent heat recovery from flue gas.

Design Optimization of Highly Efficient SOEC Co-Electrolysis Processes

High-temperature co-electrolysis of water and carbon dioxide using solid oxide electrolysis cells (SOECs) has attracted interest as an efficient synthesis gases production method. The SOECs and a fuel synthesis reactor are usually combined to produce hydrocarbon-rich fuel. In this study, we focused on investigating the effects of H2O/CO2 ratio of feed gas to the SOEC fuel electrode and gas and heat recycles on the fuel production efficiency were evaluated by mass and heat balance analysis. The results described that the amount of fuel production depended on the feed gas composition. In the case of increasing CO2 flow rate to the fuel electrode, the maximum amount of methane was produced and the efficiency of fuel production became 93.1% when the feed gas composition was controlled as H2O/CO2 = 4.32. These results indicate that the fuel production efficiency significantly depended on the operation condition of SOEC co-electrolysis and the system design.

Methanol from solid fuels: A cost-effective route to reduced emissions and enhanced energy security

Methanol (MeOH) is gaining increasing relevance as a future energy carrier. It can be produced through multiple avenues, including locally available solid fuels where the CO2 footprint of coal-derived MeOH can be strongly reduced through co-gasification with biomass and integration of CO2 capture and storage. This work presents a techno-economic assessment of five MeOH production processes from a 70/30 %w. coal/biomass blend under consistent cost assumptions of 2.5 €/GJ coal, 100 €/ton (6.1 €/GJ) biomass, 100 €/ton CO2 tax and 60 €/MWh carbon-free electricity. The reference plant configuration reached a levelized cost of MeOH (LCOM) of 285.5 €/ton, while the two advanced concepts with a more efficient gasification system reached costs of 245.0–255.0 €/ton. Two additional cases synergistically integrating PEM electrolysers to deliver H2 for improving the syngas H/C ratio and O2 for gasification reached higher LCOM of 363.0–448.8 €/ton due to the higher cost contribution of electricity. An unrealistically low price of 25.6–34.7 €/MWh for a steady-state supply of carbon-free electricity is required for these configurations to break even with the benchmark plant. Finally, MeOH from the best performing plant was shown to be cost-competitive with gasoline produced from 60 €/barrel oil, while total CO2 emissions (including combustion) were 56 % lower. Thus, MeOH from solid fuels offers a cost-effective solution to climate change and energy security in energy importing regions.

Seasonal modeling analysis of nitrate formation pathways in Yangtze River Delta region, China

Abstract. Nitrate (NO3−) has been the dominant and the least reduced chemical component of fine particulate matter (PM2.5) since the stringent emission controls implemented in China in 2013. The formation pathways of NO3− vary seasonally and differ substantially in daytime vs. nighttime. They are affected by precursor emissions, atmospheric oxidation capacity, and meteorological conditions. Understanding NO3− formation pathways provides insights for the design of effective emission control strategies to mitigate NO3− pollution. In this study, the Community Multiscale Air Quality (CMAQ) model was applied to investigate the impact of regional transport, predominant physical processes, and different formation pathways to NO3− and total nitrate (TNO3, i.e., HNO3+ NO3−) production in the Yangtze River Delta (YRD) region during the four seasons of 2017. NO3-/PM2.5 and NO3-/TNO3 are the highest in the winter, reaching 21 % and 94 %, respectively. The adjusted gas ratio (adjGR = ([NH3]+ [NO3−])/([HNO3]+ [NO3−])) in the YRD is generally greater than 2 in the four seasons across most areas in the YRD, indicating that YRD is mostly in the NH3-rich regime and that NO3− is limited by HNO3 formation. Local emissions and regional transportation contribute to NO3− concentrations throughout the YRD region by 50 %–62 % and 38 %–50 %, respectively. The majority of the regional transport of NO3− concentrations is contributed by indirect transport (i.e., NO3− formed by transported precursors reacting with local precursors). Aerosol (AERO, including condensation, coagulation, new particle formation, and aerosol growth) processes are the dominant source of NO3− formation. In summer, NO3− formation is dominated by AERO and total transport (TRAN, sum of horizontal and vertical transport) processes. The OH + NO2 pathway contributes to 60 %–83 % of the TNO3 production, and the N2O5 heterogeneous (HET N2O5) pathway contributes to 10 %–36 % in the YRD region. HET N2O5 contribution becomes more important in cold seasons than warm seasons. Within the planetary boundary layer in Shanghai, the TNO3 production is dominated by the OH + NO2 pathway during the day (98 %) in the summer and spring and by the HET N2O5 pathway during the night (61 %) in the winter. Local contributions dominate the OH + NO2 pathway for TNO3 production during the day, while indirect transport dominates the HET N2O5 pathway at night.

On mechanisms influencing etching/polymerization balance in multi-component fluorocarbon gas mixtures

In this work, we performed both experimental and model-based study of plasma parameters, steady-state gas phase compositions and heterogeneous process kinetics in CF4 + C4F8 + Ar and CF4 + CHF3 + Ar gas mixtures under the condition of 13.56 MHz inductively-coupled plasma. As constant input parameters we used gas pressure (6 mTorr) and input power (700 W) while variable ones were fluorocarbon component ratios and bias power. It was found that the substitution of CF4 for any second fluorocarbon gas a) results in rather weak effects on electrons- and ions-related plasma characteristics (especially in the case of C4F8); and b) causes sufficient changes in kinetics of neutral species that accelerate the formation of polymerizing radicals and suppress the F atoms density (especially in the case of CHF3). The latter is due to the effective decay of F atoms in the CHFx + F → CFx + HF reaction family. On the contrary, the variation of bias power does not influence kinetics of plasma active species, but changes only the ion bombardment intensity (and thus, the ion-induced reaction kinetics) through the negative dc bias voltage. The phenomenological (based on the gas-phase-related tracing parameters) analysis of heterogeneous process kinetics indicated that the fluorocarbon gas ratio represents the more effective tool to adjust etching characteristics, polymerization rate and the fluorocarbon film thickness. The last two values were found to be always higher in C4F8 - containing plasmas.