Enriched Air Research Articles

Combustion analysis of a light duty diesel engine using oxygen-enriched and humidified combustion air

The present work presents the results of 3D CFD combustion simulations of a current production 4-cylinder turbocharged Diesel engine using oxygen-enriched and humidified combustion air. Enriched Air (EA) is supposed to be produced by desorption from water, exploiting the different Henry constants of N2 and O2. Simulation results show that EA permits to increase the engine thermal efficiency (up to 10%) and drastically reduces soot emissions but increases in-cylinder peak pressure and NOx emissions. Combustion air humidification helps to reduce NOx increment, without losing the advantage in terms of thermal efficiency and in soot reduction, even if NOx emissions cannot be reported to the base case values.

Characterization of laminar premixed flame firing biomass derived syngas with oxygen enriched air

Characterization of laminar premixed flame firing biomass derived syngas with oxygen enriched air

A Comparative study of cyanobacteria and microalgae for biofuel production

The use of algae for producing biofuel is expected to play a critical role as an alternative energy source in the near future, particularly in light of depleting fossil fuel reserves and the adverse environmental impact on fossil fuels.This study discusses the production of biofuel from cyanobacteria and microalgae by various processes. Microalgae and cyanobacteria can produce high amount of lipids and that is the sole reason for they being identified as a potential biodiesel feedstock. They also have the ability to fix CO2 and have rapid growth rates. It is observed that algae can be converted to oily substances that grows in Carbon-dioxide enriched air. It also can contribute to solve major problems of air pollution resulting from CO2 evolution This experiment is undertaken to know the proper trans-esterification, amount of biodiesel production (ester) from cyanobacteria and microalgae species. In this experiment, common species such as Cyanobacterium aponinum and Spirogyra sp. are used to compare the amount of biodiesel production. It is observed that C.aponinum can produce high amount of algal oil and biodiesel (ester) than Spirogyra sp. However, biomass when calculated was found to be higher in C.aponinum compared to Spirogyra sp. The paper indicates that biodiesel can be produced from both the species with C.aponinum being a better one.

INORGANIC CARBON ACQUISITION BY Gracilaria edulis AND ITS EFFECT ON GROWTH

The utilization of inorganic carbon by the red macroalgae, Gracilaria edulis (G. edulis) was investigated in this study. G. edulis were grown in brackish water aerated with varying concentration of carbon dioxide - 350 ppm (actual atmospheric carbon dioxide, CO2), 700 ppm and 1400 ppm CO2 gas. Higher growth rate was observed in culture medium aerated with 1400 ppm CO2 and the lowest growth rate was observed at actual atmospheric carbon concentration. Besides that, significant pH drift was observed in the culture medium with and without enriched carbon dioxide. In the control flask, the pH was higher with a mean of 8.65 0.14, and it greatly differed with carbon dioxide enriched air that exhibited lower pH of a 0.8 unit difference. Photosynthetic rate increased with an increment of inorganic carbon concentration and the highest oxygen evolution were 45 mol g-1FW h-1 and 35 mol g-1FW h-1 at 1400 ppm and 350 ppm, respectively. Therefore, elevated concentration of CO2 significantly decreased the pH of the medium, enhanced growth of macroalgae and evolved more O2.

ESTIMATION OF REDUCTION OF NITROGEN OXIDES IN COMBINED STEAM AND GAS POWER PLANTS

The characteristic of the united power system of Ukraine, based on thermal, nuclear and hydro power plants, as well as on alternative and renewable sources, is carried out. The structure of power system potential indicates a lack of maneuver capacity, some plants are of low mobility. Thermal power is in critical condition due to expired service time of the main technological equipment, additionally, it is a huge source of emissions of harmful substances into the environment. An attempt to use them to cover peak loads only worsens their critical state.It is suggested to restore thermal power on the basis of combined steam and gas power plants. Moreover, for operation of gas section it is necessary to use working substance, which is formed in an additional furnace by heating the compressed air with heat from combustion of some part of coal flow, which subsequently enters the main furnace. The steam and gas generation branches are parallel connected, which extends the range of power change (increasing its maneuverability.) Gas generation increases mobility (rate of power change). For combustion of organic fuel, oxygen enriched atmospheric air is fed, and a nitrogen-based fraction can form a working substance for gas generation. With such an organization of combustion the coefficient of excess air can be ignored, which enables to reduce the volume of flue gases. The membrane separation of atmospheric air into fractions - one en-riched with oxygen, and another with nitrogen, improves the environmentalperformance of a power plant, while increasing its power and economic indices. On the example of the boiler unit TP-92 the basic parameters of a power plant are checked by a calculation method. It is confirmed that the proposed technical solutions point to the correctness and validity of the assumptions. Analysis of the existing technical level of scientific research increases confidence in perspective of the selected direction.

Impacts of elevated pCO2 on estuarine phytoplankton biomass and community structure in two biogeochemically distinct systems in Louisiana, USA

Ocean acidification has the potential to impact the ocean's biogeochemical cycles and food web dynamics, with phytoplankton in the distinctive position to profoundly influence both, as individual phytoplankton species play unique roles in energy flow and element cycling. Previous studies have focused on short-term exposure of monocultures to low pH, but do not reflect the competitive dynamics within natural phytoplankton communities. This study explores the use of experimental microcosms to expose phytoplankton assemblages to elevated pCO2 for an extended period of time. Phytoplankton communities were collected from two biogeochemically distinct Louisiana estuaries, Caillou Lake (CL) and Barataria Bay (BB), and cultured in lab for 16 weeks while bubbling CO2 enriched air corresponding to current (400 ppm) and future (1000 ppm) pCO2 levels. Results suggest that elevated pCO2 does not implicitly catalyze an increase in phytoplankton biomass (chlorophyll a). While pigment data showcased a parabolic trend and microscopic observations revealed a loss in species diversity within each major taxonomic class. By the end of the 16-week incubation, 10 out of the 12 cultures had a community structure analogous to that of the startup phytoplankton assemblage collected from the field. Natural phytoplankton assemblages exposed to elevated pCO2 experienced multiple transitional states over the course of a 16-week incubation, indicating that there is no deterministic successional pathway dictated by coastal acidification but community adaptation was observed.

Experimental investigation on effects of oxygen enriched air on performance, combustion and emission characteristics of a methanol fuelled spark ignition engine

The present experimental investigation deals with the study of the effect of oxygen enriched intake air on performance, emission and combustion characteristics of a methanol (M100) fuelled spark ignition engine. The oxygen in the intake air of the engine fuelled with methanol was enriched from 23% (by mass) with base oxygen to 26.5%, 38.7% and 60.4%. The brake thermal efficiency increased drastically with methanol with 38.7% and 60.4% enriched air by 9.9% and 20.5% respectively. The peak pressure and cumulative heat release with the highest enriched air (60.4%) are higher about 2 and 1.27 times than base oxygen percentage (23% by mass). The ignition delay and combustion duration decreased by 35.24% and 57.8% respectively. Carbon monoxide (CO) and hydrocarbon (HC) emissions with the highest enriched air decreased substantially by 48.59% and 30.9%. However, nitrogen oxides (NOx) emission increased drastically by 112.2% with 38.7% of oxygen but it decreased by 31.5% with 60.4% oxygen enriched air which is lower than base oxygen. A notable conclusion emerged from this study is that a methanol fuelled engine with the oxygen enriched air (60.4%) could emit very lower emissions (CO, HC, NOx) along with improved thermal efficiency compared to base oxygen (23% by mass).

CFD Steady Model Applied to a Biomass Boiler Operating in Air Enrichment Conditions

A numerical model is proposed to perform CFD simulations of biomass boilers working in different operating conditions and analyse the results with low computational effort. The model is based on steady fluxes that represent the biomass thermal conversion stages through the conservation of mass, energy, and chemical species in the packed bed region. The conversion reactions are combined with heat and mass transfer submodels that release the combustion products to the gas flow. The gas flow is calculated through classical finite volume techniques to model the transport and reaction phenomena. The overall process is calculated in a steady state with a fast, efficient, and reasonably accurate method, which allows the results to converge without long computation times. The modelling is applied to the simulation of a 30 kW domestic boiler, and the results are compared with experimental tests with reasonably good results for such a simple model. The model is also applied to study the effect of air enrichment in boiler performance and gas emissions. The boiler operation is simulated using different oxygen concentrations that range from 21% to 90% in the feeding air, and parameters such as the heat transferred, fume temperatures, and emissions of CO, CO2, and NOx are analysed. The results show that with a moderated air enrichment of 40% oxygen, the energy performance can be increased by 8%, CO emissions are noticeably reduced, and NOx remains practically stable.

Abundance measurements of Titan’s stratospheric HCN, HC3N, C3H4, and CH3CN from ALMA observations

Previous investigations have employed more than 100 close observations of Titan by the Cassini orbiter to elucidate connections between the production and distribution of Titan’s vast, organic-rich chemical inventory and its atmospheric dynamics. However, as Titan transitions into northern summer, the lack of incoming data from the Cassini orbiter presents a potential barrier to the continued study of seasonal changes in Titan’s atmosphere. In our previous work (Thelen et al., 2018), we demonstrated that the Atacama Large Millimeter/submillimeter Array (ALMA) is well suited for measurements of Titan’s atmosphere in the stratosphere and lower mesosphere (∼100−500 km) through the use of spatially resolved (beam sizes < 1′′) flux calibration observations of Titan. Here, we derive vertical abundance profiles of four of Titan’s trace atmospheric species from the same 3 independent spatial regions across Titan’s disk during the same epoch (2012–2015): HCN, HC3N, C3H4, and CH3CN. We find that Titan’s minor constituents exhibit large latitudinal variations, with enhanced abundances at high latitudes compared to equatorial measurements; this includes CH3CN, which eluded previous detection by Cassini in the stratosphere, and thus spatially resolved abundance measurements were unattainable. Even over the short 3-year period, vertical profiles and integrated emission maps of these molecules allow us to observe temporal changes in Titan’s atmospheric circulation during northern spring. Our derived abundance profiles are comparable to contemporary measurements from Cassini infrared observations, and we find additional evidence for subsidence of enriched air onto Titan’s south pole during this time period. Continued observations of Titan with ALMA beyond the summer solstice will enable further study of how Titan’s atmospheric composition and dynamics respond to seasonal changes.

The Efficiency of the Countercurrent Blowdown in the Membrane-Sorption System with Three Adsorbers

Hybrid membrane-sorption systems are used to solve the problems of the gas mixtures separation, as air enrichment with oxygen or compressed air drying. Investigation of the waste flow of the PSA stage showed that the flow contains a significant amount of the target component. Thus, it is possible to increase the efficiency of the plant without additional energy costs by implementing a scheme, in which waste flow is used for expulsion. Considered scheme with the sorbent regeneration by the method of blowdown is applicable for various gas mixtures separation, in which it is necessary to separate out the low-sorption component. A demanded application of this scheme can be the solution of the air drying problem.

Empirical Model of Operating Temperature and Pressure Effect towards Pure and Binary O&lt;sub&gt;2&lt;/sub&gt;/ N&lt;sub&gt;2&lt;/sub&gt; Gas Permeability in Polysulfone Membrane

Oxygen (O2) enriched air combustion via adaption of polymeric membranes has been proposed to be a feasible alternative to increase combustion proficiency while minimizing the emission of greenhouse gases into the atmosphere. Nonetheless, majority of techno-economic assessment on the O2 enriched combustion evolving membrane separation process are confined to assumption of constant membrane permeance. In reality, it is well known that membrane permeance is highly dependent upon the temperature and pressure to which it is operated. Therefore, in this work, an empirical model, which includes the effect of temperature and pressure to permeance, has been evaluated based on own experimental work using polysulfone membrane. The empirical model has been further validated with published experimental results. It is found that the model is able to provide an excellent characterization of the membrane permeance across a wide range of operating conditions for both pure and binary gas with determination coefficient of minimally 0.99.

Monitoring of Various Minerals of Flash Furnace Charge and their Impacts on Furnace Operation

One of the most common copper concentrate smelting furnaces is Flash smelting furnace which smelts over the half of the world’s copper concentrates. The copper concentrate, air or oxygen enriched air and auxiliary fuel oil are charged into this furnace. Due to pyrolysis of copper concentrate, and reaction the decomposed products with oxygen intake, a large amount of heat release that causes the melting of copper concentrate. Since the copper concentrate, contains various minerals, and each of their reactions with atmospheric oxygen in the furnace creates certain conditions; by varying the percentage of minerals in the concentrate charged into the furnace, many problems are raised. In order to fix the problems, and also recognizing the proper actions at the time of changing minerals; within 6 months, inlet concentrate were mineralogically and chemically analyzed and the effect of concentrate minerals on-air and fuel consumption as well as the dust production were studied and The most appropriate concentrate which creates the best conditions in the Khatoon Abad Flash Furnace is obtained.

A study of continuous rotation modes of detonation in an annular chamber with constant or increasing section

The detonation regime is an alternative to the conventional constant-pressure combustion mode typically used for propulsive systems because of its higher thermal efficiency and temperature and pressure of products, and shorter characteristic combustion time and length. The classic implementation is the rotating detonation engine, with the combustion chamber consisting of the annular space between a center-body and an outer cylindrical wall. This experimental study focuses on the effects of the chamber inner geometry, the total mass flow rate, and the detonation cell width on the conditions for detonation rotation. Cylindrical and conical center-bodies with several lengths and half-apex angles are considered to approach the hollow configuration of the RDE chamber. The cell width is varied by testing with mixtures of ethylene and enriched air, with several equivalence ratios and nitrogen dilutions. The combustion modes and the detonation velocities and pressures are characterized by analyzing pressure signals and high-speed camera visualizations. Three detonation regimes are identified, characterized by one or two fronts propagating in the same or opposite directions. Decreasing the center-body length and increasing the half-apex angle increases the measured detonation velocity and pressure. Velocities range between 53 and 89% of the Chapman–Jouguet value, and the pressure reaches about 11 bar. For the conditions tested, higher detonation velocity and pressure are obtained for the conical center-body configuration. Our interpretation is that center-bodies that are too long, or channels that are too narrow, hinder the exhaust of the burned gas. As a result, the proportion of products in the unburned gas mixture ahead of the detonation wave (consisting of fresh and burned gas) increases, resulting in a decrease in the magnitude of the detonation properties.

Elevated CO2 and Temperature Effect on Essential Oil Content and Composition of Valeriana jatamansi Jones. with Organic Manure Application in a Western Himalayan Region

:Valeriana jatamansi is an important Himalayan medicinal and aromatic herb. An experiment was conducted to study the effect of environmental conditions and vermicompost at free air CO2 enrichment (FACE) and free air temperature increase (FATI) facilities of CSIR-Institute of Himalayan Bioresource Technology, Palampur, India during 2013-2015. Experiment comprised of six treatments with two factors, viz., three levels of environmental conditions viz., ambient conditions (390 μmol mol-1), elevated CO2 (550±50 μmol mol-1) and elevated temperature (2.5±0.5°C above ambient) and two levels of vermicompost (control and with vermicompost). Experiments were laid out in completely randomized design (CRD) with five replications. Essential oil was obtained from rhizomes and roots of V. jatamansi after 12 months of exposure to elevated CO2 and temperature by hydrodistillation in a Clevenger type apparatus for 6 h. Elevated CO2 enhanced the essential oil content by 17.7 % and elevated temperature decreased by 4.3 % as compared to ambient conditions. Essential oil composition was significantly affected by different treatments. Patchouli alcohol, bornyl acetate, β-patchoulene, germacrene D, monoterpene hydrocarbons and oxygenated sesquiterpenes were significantly higher in FACE and FATI as compared to ambient. Vermicompost application increased trans-β-guaiene, globulol, β-patchoulene, camphene, germacrene D and bornyl acetate content. These results indicate that elevated CO2 jatamansi. and temperature alters essential oil content and composition of V.

Steel slag filter design criteria for phosphorus removal from wastewater in decentralized applications

The objective of this project was to develop a novel phosphorus removal system using steel slag filters applicable in decentralized applications and to propose design criteria about maintenance needs. Slag exhaustion functions were measured on 2–3 mm, 3–5 mm, 5–10 mm and 16–23 mm slag. Three steel slag columns with particle size of 2–3 mm, 3–5 mm and 5–10 mm were fed with the effluent of an aerated lagoon during 589 days. A barrel reactor test was fed during 365 days with the effluent of an attached growth aerated biological reactor. The o-PO4 concentration at the effluent of the 2–3 mm and 3–5 mm columns and barrel reactor test was between 0.04 and 0.3 mg P/L. Particulate phosphorus, however, was removed by about 50%. The P-Hydroslag model implemented in PHREEQC was successfully calibrated with data from the column test, and validated with data from the barrel reactor test. The calibrated model was used to simulate long-term operation of a slag barrel reactor with two parallel streams of five replaceable steel slag barrels, with total hydraulic retention time of voids of 15 h. The system longevity was strongly influenced by the influent alkalinity. The simulated longevity was 7 years with an influent alkalinity of 50 mg CaCO3/L and 2 years with an influent of 210 mg CaCO3/L. The alkalinity of the steel slag filter influent was influenced by the type of aquifer supplying drinking water, the presence of nitrification activity and by the CO2 concentration in the enriched air of the upstream biological process. Simulated scenarios with partial barrel replacement (e. g. barrels 1 and 2 out of 5 replaced at frequency of 0.5, 1, 1.5, 2, 2.5, 3, 3.5 or 4 years) increased the system longevity up to 14 years while slightly increasing the number of barrels needed.

Carbon membranes for oxygen enriched air – Part I: Synthesis, performance and preventive regeneration

Abstract Chemisorption of oxygen on the active sites of carbon layers limits the use of carbon membranes in air separation application. A novel online electrical regeneration method was applied to prevent the active sites on carbon surface to be reacting with O2 while the membrane was in operation. This method reduced the aging effect and the membrane showed relative stable performance with only 20% loss in O2 permeability and 28% increase in O2/N2 selectivity, over the period of 135 days using various feeds containing H2S, n-Hexane and CO2-CH4 gas. The carbon membranes reported here were produced at the pilot-scale facility by the carbonization of regenerated cellulose under optimized conditions to achieve good air separation properties. The permeation properties of the membranes were tested by single gas separation experiments at 5 bar feed pressure (50 mbar permeate) and temperature range 20–68 °C. It was observed that O2 permeability is increasing exponentially with increase in operating temperature without significant loss in the O2/N2 selectivity. The O2 permeability of 10 Barrer (1 Barrer = 2.736E − 09 m3(STP)m/m2 bar h) with O2/N2 selectivity of 19 was achieved at 68 °C. Thermal (80 °C), chemical (propylene) and online-electrical (10 V DC) regeneration approaches were studied to lessen the aging effect on carbon membranes.

Experimental investigation on oxygen diluted partially premixed and oxygen enriched supplemental combustion for low emission

As one of the main sources of the air pollution, the NOx emission from combustion is difficult to avoid. In this research, a combustion method, named as Oxygen Diluted Partially Premixed and Oxygen Enriched Supplemental Combustion (ODPP/OESC) was proposed to reduce the NOx generation by adjusting the oxygen concentration. The relationships between the operating parameters were deduced. The effects of the ODPP/OESC on the NOx and CO emission were evaluated experimentally. Design of Experiments (DoE) was conducted to obtain the optimal operating parameters through the Response Surface Methodology (RSM). Further statistical analysis indicated that as the dominant operating parameter, the lower oxygen mole fraction of oxygen diluted air (Yod) resulted in lower NOx but higher CO emission. The Yod makes the most contribution to the NOx and CO emission, then the oxygen mole fraction of oxygen enriched air (Yoe) does, and the equivalence ratio of premixed gas (ERp) does the least. The regression analysis yielded two relationships between the NOx(CO), Yod, Yoe, and ERp. The optimal operating parameters were obtained by the RSM and verified experimentally. NOx and CO emission were 22.6 mg/m3 and 362 mg/m3 under the optimal condition, respectively. So the ODPP/OESC was promising and feasible for the low emission of the CH4/air combustion and the RSM can be used to control the combustion emissions.

Microalgal CO2 capture at extreme pH values

Although algae are often grown at pH values between 6 and 8, shifting to more alkali or acidic conditions may benefit CO2 delivery to algal cultures. To assess the impact of culture pH on growth rate and uptake of CO2, we grew three relatively fast growing acidophilic (Coccomyxa sp., Euglena mutabilis and Euglena gracilis) and three alkaliphilic (Thalassiosira pseudonana, Phaeodactylum tricornutum, Chlamydomonas sp.) algal species at pH values near neutral and near the extreme of their growth range. All six species showed similar growth and CO2 uptake ability at extreme as at neutral pH values. Cultures of the alkaliphilic species captured a higher proportion of CO2 from the gas stream than the acidophilic species; removing 50 to 65% of CO2 from air compared to only 38% removed by acidophilic species (or 10–24% from CO2 enriched air). Alkaliphilic species did not become carbon limited when fed CO2 at the concentration provided by air (0.04% CO2), but produced less biomass and captured less total CO2 (0.06 to 0.08 g CO2 per day) than the acidophilic species (0.6–0.8 g CO2 day−1) which required CO2 enriched air to avoid carbon limitation. Bicarbonate feeding reduced the loss of CO2 to the environment, compared to feeding gaseous CO2, but with a potential cost in reduced specific growth rate or biomass production.

Draining Water from Aircraft Fuel Using Nitrogen Enriched Air

This paper concerns a computational study of the process of removing water from an aircraft’s fuel tank by pumping nitrogen enriched air (NEA) from the bottom of the tank. This is an important procedure for the smooth, efficient, and safe operation of the aircraft’s engine. Due to the low partial pressure of water in the pumped NEA, it absorbs water from the fuel. The water-laden bubbles enter the ullage, the empty space above the fuel, and escape into the environment. The effects of the number of NEA inlets and the NEA mass flow rate on the timescale of the NEA pumping were investigated using Computational Fluid Dynamics. The results reveal that the absorption of water by the NEA bubbles is low and is not affected by the number of the inlets used. Yet, the water content in the fuel decreases fast during the procedure, which is the desired outcome. We show that this is due to the relatively dry NEA entering the ullage and displacing the moist air, thus reducing the partial pressure of water at the fuel/ullage interface. This shift from equilibrium conditions forces water to evaporate from the fuel’s entire surface. Furthermore, the amount of water migrating from the fuel directly into the ullage is significantly greater than that absorbed by the rising bubbles. In turn, the rate of decrease of the water content in the ullage is determined by the total NEA mass flow rate and this is the dominant contributor to the draining time, with the number of NEA nozzles playing a minor role. We confirmed this by pumping NEA directly into the ullage, where we observe a significant decrease of water even when the NEA is not pumped through the fuel. We also show that doubling the mass flow rate halves the draining time. When considering the capability of most modern aircraft to pump NEA through the fuel as part of their inerting system, the proposed method for removing water is particularly attractive, requiring very little (if at all) design modification.

Production and application of O2 enriched air produced by fresh and salt water desorption in chemical plants

Oxygen enriched air intensifies oxidation processes since smaller reactors reach the same conversion of typical unit operations that employ simple air as reactant. However, the cost to produce pure oxygen or oxygen enriched air with traditional methods, i.e. cryogenic separation or membrane technologies, may be unaffordable. Here, we propose a new continuous technology for gas mixture separation, focusing on the production of oxygen enriched air as a case study. This operation is an absorption-desorption process that takes advantage of the higher oxygen solubility in water compared to nitrogen. In a pressurized solubilisation tank, water absorbs air. Subsequently, reducing pressure desorbs oxygen enriched air. PRO/II 9.3 (Simsci-Scheider Electrics) simulated, optimized, and calculated the capital and operative expenses of this technology. Moreover, we tested for the first time salt water instead of distilled water as appealing possibility for chemical plant near sea and ocean. We varied the inlet water flowrate between 5 and 15 m3/h. The optimum operative absortion unit pressure is 15–35 barg. After degassing, water may be recycled. With salt water, the extracted quantity of enriched air decreases compared with the desorption from fresh water (20% less), while the concentration of oxygen is independent from the salt concentration. The cost of enriched air at the optimum condition is 2–3.35 EUR/Nm3.