Enriched Air Research Articles

Lab-scale validation and parametric numerical investigation on hydrogen production in a porous media as a byproduct of in-situ combustion

A numerical 1D model was developed and validated using the measured data on a porous tube lab experiment for hydrogen generation as an in-situ combustion (ISC) byproduct, and a detailed parametric numerical study was performed. This work explores the impacts of various water injection parameters on the generation of hydrogen, the oil recovery factor (ORF), and carbon monoxide using a thorough parametric analysis. The methodology included simulating the injection of mutually enriched air and water into the combustion tube, focusing on parameters such as water temperature, quality, and flow rates. Key findings reveal that the oxygen ratio in the oxidizer substantially influences hydrogen production and ORF, with hydrogen generation increasing from 1.65 × 103 cm3 to 3.0 × 103 cm3, which is around 82 % when the oxygen percentage is raised from 50 % to 95 %. The results showed that employing wet combustion instead of dry combustion increased the hydrogen production rate by roughly four times. Variable water temperature has insignificant impacts on the hydrogen production rate and ORF. Increasing the steam quality has an opposed effect on the hydrogen generation rate. Additionally, escalating the injected water flow rate from 3000 cm³/day to 15000 cm³/day boosts hydrogen production from 10000 cm³ to 53400 cm³, respectively.

The enrichment and separation of lanthanides ions from wastewater using solvent sublation coupled with high speed countercurrent chromatography

Rare earth elements are non-renewable resources. During their processing, a lot of wastewater are produced, which poses a danger to human beings and the environment. Herein, the enrichment method of solvent sublation for La (III), Ce (III), Gd (III) and Er (III) was designed and established. Enrichment parameters pH, flotation time, extractant concentration and air flow rate were optimized. The result showed that the highest recovery of La (III) reached up to 92.33 % under the optimized conditions of pH 8, 10 min of flotation time, 0.15 mol L-1 of the extractant 2-ethylhexyl phosphate acid-2-ethylhexyl ester and 30 mL min−1 of air flow rate. The light rare earth element Ce (III) and heavy rare earth elements Gd (III) and Er (III) were also examined and obtained with maximum recovery. The stability of the extractant complexation with rare earth ions and the mechanism of competitive extraction were studied by density functional theory calculations. The extraction ability was following sequence of La (III) < Ce (III) < Gd (III) < Er (III). The enrichment of rare earth elements from real water samples was investigated and obtained result was consistent with the experiment result of synthetic solutions. The established high speed countercurrent chromatography method was used to successfully separate La (III), Ce (III), Gd (III) and Er (III) from the solution of rare earth ions enriched by solvent sublation.

Microglial reactivity in brainstem chemosensory nuclei in response to hypercapnia.

Microglia, the resident immune cells of the CNS, surveil, detect, and respond to various extracellular signals. Depending on the nature of these signals, an integrative microglial response can be triggered, resulting in a phenotypic transformation. Here, we evaluate whether hypercapnia modifies microglia phenotype in brainstem respiratory-related nuclei. Adult C57BL/6 inbred mice were exposed to 10% CO2 enriched air (hypercapnia), or pure air (control), for 10 or 30min and immediately processed for immunohistochemistry to detect the ubiquitous microglia marker, ionized calcium binding adaptor molecule 1 (Iba1). Hypercapnia for thirty, but not 10min reduced the Iba1 labeling percent coverage in the ventral respiratory column (VRC), raphe nucleus (RN), and nucleus tractus solitarius (NTS) and the number of primary branches in VRC. The morphological changes persisted, at least, for 60min breathing air after the hypercapnic challenge. No significant changes were observed in Iba1+ cells in the spinal trigeminal nucleus (Sp5) and the hippocampus. In CF-1 outbred mice, 10% CO2 followed by 60min of breathing air, resulted in the reduction of Iba1 labeling percent coverage and the number and length of primary branches in VRC, RN, and NTS. No morphological change was observed in Iba1+ cells in Sp5 and hippocampus. Double immunofluorescence revealed that prolonged hypercapnia increased the expression of CD86, an inflammatory marker for reactive state microglia, in Iba1+ cells in VRC, RN, and NTS, but not in Sp5 and hippocampus in CF-1 mice. By contrast, the expression of CD206, a marker of regulatory state microglia, persisted unmodified. In brainstem, but not in hippocampal microglia cultures, hypercapnia increased the level of IL1β, but not that of TGFβ measured by ELISA. Our results show that microglia from respiratory-related chemosensory nuclei, are reactive to prolonged hypercapnia acquiring an inflammatory-like phenotype.

Evaluating the carbon footprint of sulphur recovery unit: A comprehensive analysis

Desulphurising of oil based fuels and industrial gases is a widespread practice. The combustion process in the sulphur recovery unit (SRU) involves the reaction of H2S with oxygen to produce SO2, which is then converted to elemental sulphur through a series of catalytic reactions. Oxygen enrichment is a technique used to enhance the performance and efficiency of the SRU. By introducing a higher concentration of oxygen into the combustion process, the overall combustion reaction can be optimised, resulting in an increased sulphur recovery from sour gas and reduced emissions of sulphur compounds. The present study analyses the gate-to-gate comparative environmental impact of air versus oxygen enriched air used for combustion to recover 1.0 ton sulphur using GaBi software (8.5.0.79 version). The primary data was collected from the literature. The GaBi Indian extension database is used for the secondary data source. The results are reported using midpoint impact assessment methods CML 2001. The global warming potential for oxygen-enriched SRU is 232 kg CO2 eq. compared to 276 kg CO2 eq. for air enriched SRU. Similarly, the potential for abiotic depletion (elements + fossil), acidification, eutrophication, human toxicity, freshwater aquatic ecotoxicity, marine aquatic ecotoxicity, photochemical ozone creation and terrestric ecotoxicity are higher for air based SRU than oxygen-enriched SRU. The analysis concludes that oxygen enrichment technology is a highly effective way to reduce the environmental impact of the SRU.

Techno-economic analysis of carbon molecular sieve membranes to produce oxygen enrichment air

Oxygen Enriched Air (OEA) is essential for medical applications, metal production, chemical production, the petrochemical industry, and energy processes. In this work, carbon molecular sieve membranes (CMSM) and membrane systems are analyzed concerning their technical and economic feasibility to produce OEA for medical, post-combustion, and oxy-combustion applications. Process parameters, such as stage-cut, feed-to-permeate pressure ratio, membrane area, and the number of stages, were studied to assess the technical and economic feasibility of this technology. In this work, it was observed that for each membrane, there is a permeating oxygen concentration that minimizes the specific oxygen cost. The production of 56 tonO2·day−1 for a combustion enhancement process with a concentration of 72 % was obtained in a single-stage with a specific cost of 61.0 €·tonO2−1. A single-stage is also effective for producing OEA for medical applications (required concentration of 82 %) at a minimum separation cost of 45.8 €·tonO2−1. However, a two-stage system is required to produce OEA with a concentration higher than 95 % for oxy-combustion with an OEA production cost of 83.8 €·tonO2−1. These production costs are lower than those obtained with two different commercial membranes and are competitive with medium-scale cryogenic distillation and pressure swing adsorption processes.

A study on the laminar flame speed of ammonia-acetylene with enhanced oxygen content: Experimental and modeling investigation

The endeavor to decarbonize the maritime industry has spurred intensive exploration into ammonia as a potential solution, despite its inherent drawbacks such as low combustion speed and high ignition energy. Acknowledging the significance of employing a pilot fuel, a pivotal aspect in this context, the current work provides measurements on laminar flame speed (LFS) and Markstein length for ammonia/acetylene mixtures in enriched air (30 % O2) in a constant volume spherical chamber for the first time. With acetylene content ranging from 1 to 10 %—the conventional volume percentage as a pilot fuel—the research unveils compelling findings. The results show an expected increase in LFS with increasing acetylene content, but the Markstein length initially decreases followed by a modest increase, producing a clear plateau. To further bolster the investigation, a detailed assessment of recent kinetic mechanisms governing ammonia combustion, including the C2 sub-mechanism, is conducted. This study also includes the evaluation of the Zeldovich number, which is used for flame dynamics analysis, and the theoretical computation of Markstein length, which is then compared to experimental data.

Exploiting synergies between sustainable ammonia and nitric acid production: A techno-economic assessment

The decarbonization of the fertilizer industry is an important step towards a climate-neutral society. Nitric acid produced via the Ostwald process is a key precursor to nitrogen-based fertilizers, with the production of ammonia representing an important intermediate step. This work focuses on the search for synergies between the sustainable production of ammonia feedstocks – hydrogen and nitrogen – and nitric acid production in the Ostwald process: Oxygen a by-product of sustainable hydrogen and nitrogen production was considered for injection in the Ostwald process at 4 points. A techno-economic assessment was performed to identify the technical and economic potential of this air enrichment. In addition, the safety implications of applying a higher oxygen concentration in the ammonia combustion step of the Ostwald process was evaluated based on explosion limit simulations. The techno-economic assessment was based on a mono-pressure nitric acid plant with a plant capacity of 700t/d of pure nitric acid at a concentration of 60wt% in water. The investigations of injecting oxygen at four different points of the plant show that daily nitric acid production can be increased by 0.31% and final NOx concentration of the absorption column can be reduced by up to 43.6% by enriching the main air pipeline with oxygen. Optimal oxygen injection could reduce the capital costs by 0.41M€. Nevertheless, the operating costs dominated the final cash flow analysis with ammonia costs accounting for ca. 60% of the total operating costs. The CO2 price would need to increase to at least 233€/t to compensate for the higher green ammonia price and equalize the minimum selling price. As the oxygen injection at the main air line comes with safety risks due to the ammonia explosion limits, we evaluated the effect of O2-enrichment on the explosion limits of NH3-O2-N2 mixtures. The foreseen oxygen enrichment reduced the lower explosion limit only marginally. For a medium pressure plant at 5.8bar the lower explosion limit is reduced to 10.3% for the highest considered oxygen injection case, which is close to the applied ammonia concentration.

Trace elements and microbial community composition associated with airborne PM2.5 in wetlands: A case study in Tablas de Daimiel National Park

Tablas de Daimiel National Park (TDNP) is one of the most important wetlands in the Iberian Peninsula. Due to its location near various cities and new industries focused on agricultural waste revalorization, we investigated concurrently the concentrations of particulate matter 2.5 (PM2.5) mass, trace element composition, and associated microbial communities (bacteria and fungi) during a year-long study. The goal of this study was to explore the dependencies among these physicochemical and microbiological parameters on a seasonal time scale. Additionally, we assessed meteorological conditions and back trajectories to shed light on atmospheric mechanisms and sources related to these elements. We found the variability of PM2.5 to be influenced by local meteorological parameters. Through the analysis of crustal enrichment factors (EFs), bivariate correlations, and air mass patterns, we determined that soil resuspension was the primary contributor to elevated metal concentrations in PM2.5 within the park, followed by other minor sources, such as traffic emissions and Sahara dust intrusions. The measured metal levels were used to calculate the ecological risk in the area, resulting in a low ecological risk index (RI) of 52. Shifts in microbial community structure were observed to be mainly driven by changes in air temperature and Cu concentration. The results from this study contribute to a better understanding of the environmental dynamics in TDNP. Taken together, our findings will aid in the development of effective strategies for its conservation and management.

Application of the fermented broiler chickens manure under different aeration regimes during vermiculture cultivation

The growth of poultry population in Ukraine and in the world leads to a number of environmental problems such as concentration and accumulation of large masses of manure without litter and manure mixed with organic litter. A rational way to dispose poultry manure, including broiler chickens’ manure, is to produce vermicompost from it by growing there a hybrid of local red worm or Eisenia fetida. Unfermented broiler manure contains a high concentration of nitrogen-containing compounds, including ammonia, which has a negative effect on worms. Even at low ammonia concentrations in the organic biomass, the worms die. Traditional methods can take more than 17 months to compost broiler manure. One of the ways to speed up composting is to apply bioprocessing devices and aeration of the manure. The effectiveness of growing vermiculture on the fermented broiler manure with a biodegrader and different aeration regimes remains insufficiently studied. For the experimental cultivation of worms, we used the broiler chicken manure fermented for 160 days, which was enriched with air once every 10 days by mechanical mixing (control), 15 minutes a day using a compressor (I experimental group) and twice a day for 15 minutes using a compressor (II experimental group). The study determined the number of adult and immature worms, their weight, the number of cocoons and their weight. It has been experimentally found that fermented broiler chicken manure under different aeration regimes with litter as part of the vermiculture substrate has an effect on the reproduction and weight of worms and their cocoons. Growing worms on a substrate from fermented broiler chickens&amp;apos; litter with a daily one-time air enrichment with a compressor increases the number of mature worms by 15.7 % compared to the control group. The largest mass of mature worms was recorded in the first experimental group. It was proved that the use of fermented broiler manure with active aeration (experimental group I) as a substrate increased the number and weight of immature worms by 10.3 and 33.3 %, respectively, compared to the control. The largest number of cocoons has been found in the first experimental group.

Unravelling the transport of moisture into the Saharan Air Layer using passive tracers and isotopes

AbstractThe subtropical free troposphere plays a critical role in the radiative balance of the Earth. However, the complex interactions controlling moisture in this sensitive region and, in particular, the relative importance of long‐range transport compared to lower‐tropospheric mixing, remain unclear. This study uses the regional COSMO model equipped with stable water isotopes and passive water tracers to quantify the contributions of different evaporative sources to the moisture and its stable isotope signals in the eastern subtropical North Atlantic free troposphere. In summer, this region is characterized by two alternating large‐scale circulation regimes: (i) dry, isotopically depleted air from the upper‐level extratropics, and (ii) humid, enriched air advected from Northern Africa within the Saharan Air Layer (SAL) consisting of a mixture of moisture of diverse origin (tropical and extratropical North Atlantic, Africa, Europe, the Mediterranean). This diversity of moisture sources in regime (ii) arises from the convergent inflow at low levels of air from different neighbouring regions into the Saharan heat low (SHL), where it is mixed and injected by convective plumes into the large‐scale flow aloft, and thereafter expelled to the North Atlantic within the SAL. Remarkably, this regime is associated with a large contribution of moisture that evaporated from the North Atlantic, which makes a detour through the SHL and eventually reaches the 850–550 hPa layer above the Canaries. Moisture transport from Europe via the SHL to the same layer leads to the strongest enrichment in heavy isotopes (δ2H correlates most strongly with this tracer). The vertical profiles over the North Atlantic show increased humidity and δ2H and reduced static stability in the 850–550 hPa layer, and smaller cloud fraction in the boundary layer in regime (ii) compared to regime (i), highlighting the key role of moisture transport through the SHL in modulating the radiative balance in this region.

Combination Effect of in-Situ Combustion and Exhaust Gases Recirculation on 1D Combustion Tube: Numerical Approach

ABSTRACT Despite the widespread use of renewable and green energy, the demand for fossil fuels is also rising due to increasing global energy demand. Therefore, unconventional solutions, with safe environmental impacts, are being pursued to solve this problem. Instead of getting rid of the exhaust gases in the surroundings, one solution might be to inject them with the oxidizer into the oil reservoir, to initiate an in-situ combustion (ISC) process to enhance oil recovery. A numerical study of a 1-D combustion tube has been conducted and validated to simulate the in-situ combustion process using enriched air as the oxidizer. The effects of injecting exhaust gases with the oxidizer are studied. Different ratios of oxygen to nitrogen are used in the enriched air as well as different ratios of exhaust gases. If enriched air which is mostly oxygen, i.e. 95% O2 +5%N2, is used, it is found that replacing 10% of the enriched air with exhaust gases can increase the oil recovery factor (ORF) from 94.7% to 94.9% and replacing 20% can improve oil recovery to 95.1%. For another enriched air, 60% O2 +30% N2, it is found that replacing portions of the enriched air with exhaust gases will reduce the oil recovery factor. In all previous cases, it was found that replacing the proportions of enriched air with exhaust gases reduces the amount of fuel burned and increases hydrogen production.

Polymeric membranes for the oxygen enrichment of air in sulfur recovery units: Prevention of catalyst deactivation through BTX reduction

Polymeric membranes for the oxygen enrichment of air in sulfur recovery units: Prevention of catalyst deactivation through BTX reduction

Experimental study on tesla valve and bypass manifold to suppress feedback of rotating detonation engine fuel by kerosene

In this paper, the effects of the Tesla valve intake structure with or without bypass manifold on suppressing pressure feedback and combustion product backflow in rotating detonation engine fueled by kerosene and enriched air with 29% oxygen content are investigated, with the configuration of convergent–divergent intake without bypass manifold being used for comparison. The working range, detonation wave propagation characteristics, and propulsion performance for the three configurations are evaluated. It is found that the Tesla valve intake structure can effectively improve the suppression of pressure feedback and combustion product backflow through the diversion function of the Tesla valve bypass channel and that the addition of the bypass manifold further improves the suppression of pressure feedback. The Tesla valve intake with bypass manifold configuration has the best ability to suppress pressure feedback, with a minimum value of pressure feedback percentage of about 6.5% and a minimum value of air plenum pressure fluctuation percentage of about 6.7%. By comparison, the minimum value of pressure feedback percentage of the convergent–divergent intake without bypass manifold configuration is about 29.8%, and its minimum value of pressure feedback percentage is about 7.8%. The Tesla valve intake without bypass manifold configuration is most effective in suppressing combustion product backflow, with the effective inlet area ratio of about 95.7%. Under the same conditions, the minimum effective inlet area ratio of the convergent–divergent intake without bypass manifold configuration is about 90.2%. Ultimately, optimizing the engine structure leads to a broader working range and higher propulsion performance. The Tesla valve intake structure broadens the working range by suppressing the generation of the longitudinal pulsed detonation mode. When the bypass manifold is incorporated, some combustible reactants directly enter the rear of the combustion chamber from the head of the chamber, and the working range is reduced. Compared with the convergent–divergent intake without bypass manifold configuration, the working range of the Tesla valve intake with bypass manifold configuration is widened by 383.3%, and that of the without bypass manifold configuration by 700%. Both the Tesla valve intake and bypass manifold increase the strength of detonation waves and improve propulsion performance. The Tesla valve intake with bypass manifold configuration has the highest specific thrust, at about 90.1 N s3/(kg·m). This is increased by an average of 10% compared with the Tesla valve intake without bypass manifold configuration, and by an average of 30.1% compared with the convergent–divergent intake configuration.

Impact of nozzles on the wall-temperature in a valveless pulse detonation engine

As the increase of wall-temperature during the long-duration operation, pre-ignition of the fresh mixture in the filling process often occur in the detonation tube, resulting in the failure of operation. An experimental work has been conducted to investigate the impact of nozzle on the wall-temperature of the detonation tube. In the present study, kerosene and oxygen enriched air were employed in the experiments, and an internally grooved semi-circle spiral, instead of traditional Shchelkin spiral was utilized to facilitate the deflagration to detonation transition (DDT) process. The theoretical results showed that the temperature of fresh mixture increase along the detonation tube during the filling process, and it is likely to be ignited near the open end. It was observed from the experimental results that the convergent section and the divergent section of the exit nozzle has different influence on the wall-temperature. The convergent nozzle will not prevent the wrapping flame near the open end of the detonation tube, and lead to the increase of equilibrium wall-temperature. The nozzle with a diverging section will eliminate the occurrence of wrapping flame during the operation, and the wall temperature near the open end are dramatically decreased. In addition, smaller expansion ratio of the nozzle will lead to lower equilibrium wall-temperature.

A study on the effect of hydrogen enriched intake air on the characteristics of a diesel engine fueled with ethanol blended diesel

This work aims to replace conventional diesel fuel with low and no carbon fuels like ethanol and hydrogen to reduce the harmful emission that causes environmental degradation. Pursuant to this objective, this study investigated the performance, combustion, and emission characteristics of the diesel engine operated on dual fuel mode by ethanol-diesel blends with H2 enriched intake air at different engine loads with a constant engine speed of 1500 rpm. The results were compared to sole diesel operation with and without H2 enrichment. The ethanol/diesel was blended in v/v ratios of 5, 10, and 15% and tested in a diesel engine along with a 9 lpm H2 flow rate at the intake manifold. The results revealed that 10% ethanol with 9 lpm H2 combination gives the maximum brake thermal efficiency, which is 1% and 4.8% higher than diesel with and without H2 enrichment, respectively. The brake specific fuel consumption of the diesel-ethanol blends with H2 flow increased with increasing ethanol ratio in the blend. When the ethanol ratio increased from 5 to 10%, in-cylinder pressure and heat release rate were increased, whereas HC, CO, and NOx emissions were decreased. At maximum load, the CO and HC emission of 10% ethanol blend with 9 lpm H2 case decreased by about 50% and 28.7% compared to sole diesel. However, NOx emission of the same blend was 11.4% higher than diesel. From the results, the study concludes that 10% ethanol blended diesel with a 9 lpm H2 flow rate at the intake port is the best dual-fuel mode combination that gives the best engine characteristics with maximum diesel replacement.

Numerical simulation of the influence of different oxygen concentration on the combustion characteristics of double tangential boiler at low load

In order to cope with the demand for deep peak regulation of high-parameter coal-fired units, this paper uses numerical simulation methods to systematically explore the influence of different secondary wind oxygen enrichment concentrations on the combustion performance and characteristics of singlefurnace double-cut round boilers during low-load operation, so as to provide theoretical support for the actual operation of power plants. The results are as follows: (1) The use of oxygen enriched secondary air combustion during low-load operation of the boiler can improve the overall temperature of the main combustion zone of the furnace and the local temperature of the burner nozzle section, and enhance the combustion stability of pulverized coal in the furnace. (2) When the secondary air oxygen concentration is 35% and 40%, the overall temperature of the main combustion area of the boiler increases the most obviously, and the combustion is the most stable. (3) Oxygen-enriched combustion effectively reduced the NOx emission concentration in the furnace, and the overall trend of NOx emission decreases first and then increases with the increasing trend of secondary air oxygen concentration.

TEMPERATURE AND MICROBIOLOGICAL PARAMETERS OF POULTRY MANURE UNDER DIFFERENT FERMENTATION MODES

To meet food needs both in Ukraine and globally, the production of affordable and relatively cheap poultry meat will increase. At the same time, the problem of increasing poultry waste accumulation, including manure with and without bedding, is becoming more acute. Large volumes of broiler manure in limited areas due to different storage conditions have a negative impact on the environment. The study of the conditions and modes of composting broiler manure as an effective way of its utilisation is of scientific and economic importance. The aim of the study is to determine the temperature and microbiological parameters of broiler manure composting using different modes of its aeration. To achieve this goal, fresh broiler manure was composted in the conditions of the scientific and educational research centre of the Bila Tserkva National Agrarian University using a mixture of biodestructors and different aeration regimes. In the control group, the piles were formed on a concrete platform without the use of a tubular frame of the barbital type, and aeration was carried out by mechanical mixing of broiler manure once every 10 days. In the experimental groups, piles of broiler manure were formed on tubular frames through which air was injected by a compressor. In the first experimental group, air injection was carried out for 15 minutes in the first half of the day. In the second experimental group, air was injected into the broiler manure twice for 15 minutes in the morning and in the evening. It was experimentally established that the composting temperature of broiler manure depended on the intensity of aeration of the latter. With daily aeration twice a day, the temperature of the manure biomass (6th day of composting) was the highest and exceeded the control values by 87.8 %. In experimental groups I and II, with one and two daily enrichment of broiler manure, the period of fermentation in the thermophilic mode was the same. Comparing the groups where poultry manure was enriched once and twice a day, it was found that double aeration did not lead to a statistically significant increase in the temperature of composted biomass. It was proved that active air enrichment of poultry manure (experimental group II) increased the QMAFAnM index and the number of Bacillus spp. bacteria by 7.6 and 24.0%, respectively, compared to the control group. The study of a number of chemical parameters of broiler chickens' manure composted by the accelerated method under different aeration regimes is promising.

Ability to reduce iron with additional hydrogen introduced into the blast-furnace natural gas stream

Equations are obtained, calculations are made on them, and graphs of the temperature dependence of the extremely high degree of hydrogen utilization are presented, which characterize the reduction of iron under conditions when H2O moves from the zone of transformation of FeO into Fe to the zone of transformation of Fe3O4 into FeO and further from the zones of development of these two reactions to the zone of transformation Fe2O3 to Fe3O4 with decreasing amount of hydrogen. Under the blast furnace conditions, the limit value for the hydrogen use is 55&ndash;57 %. In the course of studies at a blast furnace with a useful volume of 1370 m3 at PJSC MMK, an increase in the ratio of the amounts of hydrogen supplied with natural gas and oxygen supplied with enriched air blast was accompanied by an increase in the degree of hydrogen use from 47.0 to 50.6 % and a decrease in specific coke consumption from 404.0 to 397.4 kg/t of pig iron. The ratio of specific consumption of coke and total hydrogen of natural gas in the form of hydrocarbons decreased from 1.41 to 1.29 kg/m3. In another series, a rational mode was revealed, characterized by an increased reactivity of coke and a reduced consumption of natural gas, the transition to which reduced the specific consumption of coke from 426.4 to 423.3 kg/t of pig iron. Under current conditions at PJSC MMK, a reduction in the specific consumption of coke by 50 kg/t of pig iron is possible with the consumption of additional hydrogen in the amount of 156 m3/t of pig iron by it introducing into the existing pipeline of natural gas.The article was prepared with the support of the grant of the President of the Russian&nbsp;Federation No. MD-1064.2022.4.

Light and carbon limited photosynthesis of Chlorella sorokiniana

Carbon dioxide (CO2) and light are essential for high photosynthetic rates of microalgal cultures. Microalgal photosynthetic behavior at low CO2 concentrations has not been revealed yet at the same level of detail as leaf photosynthesis. In the present study, we investigated the short-term photosynthetic response of suspended Chlorella sorokiniana to limiting light intensity and CO2 concentration. We used a novel CO2-based photosynthesis monitor originating from leaf research but equipped with an aquatic chamber sparged with CO2 enriched air. Photosynthesis was measured by employing a steady-state CO2 mass balance over the chamber. Light and carbon response curves were determined under constant pH, temperature, dissolved oxygen, light intensity or dissolved carbon dioxide. We determined the volumetric mass transfer coefficient of the aquatic chamber to accurately convert gaseous CO2 partial pressure into aqueous CO2 concentration to evaluate the CO2 response measurements.Light response measurements on dilute algal cultures revealed a high photosynthetic capacity on a time scale of minutes which by far exceeded the average CO2 uptake on a time scale of hours (cell growth). Light response measurements with dense and fully absorbing cultures provided accurate insight into the response of microalgal mass culture to changing incident irradiance, including the efficiency of photosynthesis of the algal culture as a whole. CO2 response measurements demonstrated severe CO2 limitation at dissolved CO2 levels of <20 μM giving a concrete target for optimization of CO2 supply in large-scale cultivation systems. Measurements at a background of either 21 % O2 (air) or 2 % O2 indicated the existence of photorespiration in Chlorella. Moreover, the magnitude of photorespiration first increased and then decreased again while reduced dissolved CO2 levels, indicating the activation of a carbon concentrating mechanism at low CO2. Simultaneous measurement of the quantum yield of PSII linear electron transport (ϕPSII) and CO2 uptake revealed the transition of CO2 limited photosynthesis towards light-limited photosynthesis.

Enhancement of efficiency and power output of hydrogen fuelled proton exchange membrane (PEM) fuel cell using oxygen enriched air

This paper deals with the effects of the oxygen-enriched air (up to 50% oxygen by mass) along with other operating parameters (hydrogen flow rate, temperature, and relative humidity) on the performance of hydrogen-fuelled proton exchange membrane (PEM) fuel cell. The active area of a fuel cell considered was 50 cm2 with three cells in series connections. The air was supplied with O2 enriched from 23% to 50% at the cathode. The voltage obtained with the respective enriched air was 2.52 and 2.80 V respectively. The optimum oxygen enrichment was found as 45%. The stack temperature plays a significant role on performance improvement and the optimum temperature was found as 50 °C. The voltage efficiency and power output were improved by 9% and 33% with 45% oxygen-enriched air. Electrochemical impedance spectroscopy was used to analyze the impedance behavior of the fuel cell with the variable current demand. The bode plot indicates current dominates voltage at low oxygen-enriched air (25%) and vice-versa at high-enriched air. The inductive effect was dominating at the low frequency and overtaken by the capacitive effects at the higher frequency. These results would be useful to develop a dedicated fuel cell with the oxygen-enriched air.