Gas Stripping Research Articles

Ammonia Recovery from Organic Waste Digestate via Gas–Liquid Stripping: Application of the Factorial Design of Experiments and Comparison of the Influence of the Stripping Gas

The effects of temperature, pH, and gas-to-liquid-volume-ratio on ammonia recovery via gas–liquid stripping have been widely studied. However, there is a lack of a structured approach towards characterising the stripping process. Furthermore, limited information is available on the effect of the composition of the stripping gas on ammonia recovery. This study includes the application of a factorial design of experiments to ammonia stripping. The outcome is a mathematical relationship for ammonia recovery as a function of process conditions. The temperature was found to have the highest influence on ammonia recovery. With respect to the influence of the stripping gas, similar ammonia recoveries were reported when using air, CH4, and N2 (96, 92, and 95%, respectively). This was attributed to their similar influences on the pH of the digestate, and subsequently, on the free ammonia equilibrium. In addition, the presence of CO2 in the stripping gas had a critical effect on ammonia recovery due to its influence on the total ammonia equilibrium in the digestate. These results showed the possibility of using different stripping gases interchangeably to obtain similar ammonia recoveries, with a critical emphasis on their CO2 content.

The galaxy morphology–density relation in the EAGLE simulation

ABSTRACT The optical morphology of galaxies is strongly related to galactic environment, with the fraction of early-type galaxies increasing with local galaxy density. In this work, we present the first analysis of the galaxy morphology–density relation in a cosmological hydrodynamical simulation. We use a convolutional neural network, trained on observed galaxies, to perform visual morphological classification of galaxies with stellar masses $M_\ast \gt 10^{10} \, \rm {M}_{\odot }$ in the EAGLE simulation into elliptical, lenticular and late-type (spiral/irregular) classes. We find that EAGLE reproduces both the galaxy morphology–density and morphology–mass relations. Using the simulations, we find three key processes that result in the observed morphology–density relation: (i) transformation of disc-dominated galaxies from late-type (spiral) to lenticular galaxies through gas stripping in high-density environments, (ii) formation of lenticular galaxies by merger-induced black hole feedback in low-density environments, and (iii) an increasing fraction of high-mass galaxies, which are more often elliptical galaxies, at higher galactic densities.

Design and evaluation of ecological interface for Feedwater Deaerating Tank and Gas Stripper System based on cognitive work analysis

Abstract The investigation of nuclear power plants (NPPs) accidents in the past shows that most of the accidents mainly occur in unexpected events. In this study, in order to verify whether Ecological Interface Design (EID) improves the situational awareness of operators in NPPs, this paper first analyzes the system by using the first three stages of cognitive work analysis, and then applies EID to the operating interface of NPPs to develop an ecological interface. In order to make the test results more complete, an improved interface has also been developed. A process expert and six operators were invited to participate in our experiments to measure situational awareness. The results show that the situational awareness of ecological interfaces in unexpected events is significantly higher than that of traditional and advanced interfaces. The significance of this study is that EID, as a practical technology, can be widely used in operator control rooms to improve the ability of operators to solve unexpected events.

Optimization of 10Be measurements at the 6 MV AMS facility DREAMS

We investigated benefits from raising the ion beam energy during measurements of 10Be with Accelerator Mass Spectrometry (AMS) at the 6MV DREAMS (DREsden AMS) facility. Increasing the terminal voltage to ≥5MV hardly reduces the yield of the Be2+ charge state after the accelerator if one applies only a thin Ar gas stripper and makes use of an overpopulation of the 2+ charge state with respect to the expected equilibrium charge state yield. As a further stripping to the 4+ charge state is conducted in a degrader foil after the analysing magnet, it is desirable to hit the foil with the highest available velocity in order to have optimal stripping of Be2+ to the fully stripped ion. At DREAMS the 10Be yield can be improved by a factor of 1.36. Applying a terminal voltage of 5.8MV the transport efficiency of 10Be from the ion source to the detector is ca. 32.5%.

Exploration of optimal operating conditions for a natural gas combined-cycle power plant integrated with post-combustion CO2 capture using 2-amino-2-methyl-1-propanol/piperazine considering the propagation effect

Integrating post-combustion CO2 capture (PCC) into thermal power plants can reduce CO2 emissions but results in a significant decrease in net thermal efficiency. Optimizing PCC operating conditions, such as the ratio of the liquid flow rate to the gas flow rate (L/G) and stripper bottom temperature, reduces the net efficiency penalty. However, previous studies partially neglected the propagation effects of altered operating conditions on process performance, such as the effect of altered L/G and resultant change in fluid velocity on the heat transfer and pressure drop in the rich and lean solution heat exchanger. This study simulated amine-based PCC integrated into a natural gas combined cycle and explored optimal operating conditions comprehensively considering the propagation effects. The net efficiency penalty was minimized to 6.02%-pts. at a stripper bottom temperature of 130 °C and L/G of 0.82 for PCC operation with CO2 compression. Meanwhile, neglecting propagation effects of altered L/G led to underestimation of the efficiency penalty and erroneous determination of optimal operating conditions. The system evaluation methods suggested in this paper contribute to correctly optimizing PCC operating conditions and can be broadly applied to amine-based PCC studies employing novel amine solutions or process modifications.

Economic analysis of biobutanol recovery from the acetone-butanol-ethanol fermentation using molasses

Commercial production of biobutanol via acetone-butanol-ethanol (ABE) fermentation is challenged by the energy-intensive recovery of biobutanol from inherently diluted fermentation broth. Towards the solution of this problem, four combinations (scenarios) of separation techniques such as distillation, gas stripping (GS), liquid-liquid extraction (LLE), and pervaporation (PV) are investigated for the minimum unitary production cost of biobutanol. Cost components for the installation and operation of the plant are estimated using Matlab software and method given by Peters and Timmerhaus. Production costs with significant variables viz. biobutanol yield, price of molasses, and fermenter volume are individually estimated. Gas stripping followed by distillation is found as the most economical scenario with a unitary production cost of INR 74/kg. The optimum values of yield and fermenter volume are found as 0.4 kg ABE/kg sugars and 100 m3, respectively. The optimization of three major variables around the baseline values provides nearly 10% reductions in the cost with present fermentation technology. This economic analysis of biobutanol recovery certainly contributes to the commercial production of biobutanol from renewable raw materials. The economic feasibility of biodiesel production may offer better environment to the mankind.

The impact of the break-up of molecules in the stripper on the AMS performance

The break-up of molecules in the stripper of an AMS facility induces an energy and angular spread in the beam. This can cause beam losses, thereby reducing the performance of an AMS facility. With an appropriate design, these effects can be minimised and the efficiency enhanced. As an example, the break-up of BeO molecules is discussed here. First the basic physics is described and corresponding models and computer codes are explained. Then experimental data are shown and compared with the models. For gas stripping, beam profiles are available for small and large facilities. All show tails which can be attributed to the dissociation of the molecules. The size of the effect depends on various parameters such as beam energy, selected charge state, stripping gas type and ion optics. Foil stripping leads to energy distributions which are much wider, and show typically a double peak.

A single-stage accelerator mass spectrometer and its applications at Guangxi Normal University

GXNU-AMS, a compact 14C accelerator mass spectrometer jointly developed by the Guangxi Normal University and China Institute of Atomic Energy, was installed and commissioned in Guangxi Normal University in 2017. It is the first original single-stage AMS facility and one of the lowest designed energy AMS systems in China. Without the traditional mode of a SF6 pressure tank, the terminal of the system was designed as an open insulated high-voltage platform, which reduces the accelerator size to ∼2.5 m × 4.5 m. Helium gas stripping was used for eliminating the interference of molecular ions, and the maximum operating voltage is ∼200 kV. During several years of operation, its performance has been continuously improved and it has been applied in multidisciplinary fields. Currently, the measurement accuracy of the instrument is ∼0.6 % and the measurement sensitivity is 14C/12C ∼ 3 × 10−15 (equivalent to a 14C age of approximately 47,000 years.), which can meet the measurement requirements in the fields of life sciences and archaeology. In this study, the performance characteristics and operation of GXNU-AMS are discussed and several application studies being conducted by the GXNU-AMS group are presented.

Gas accretion and ram pressure stripping of haloes in void walls

ABSTRACT We conduct hydrodynamical cosmological zoom simulations of 14 voids to study the ability of haloes to accrete gas at different locations throughout the voids at z = 0. Measuring the relative velocity of haloes with respect to their ambient gas, we find that one-tenth of the haloes are expected to be unable to accrete external gas due to its fast flow passed them (so called ‘fast flow haloes’). These are typically located near void walls. We determine that these haloes have recently crossed the void wall and are still moving away from it. Their motion counter to that of ambient gas falling towards the void wall results in fast flows that make external gas accretion very challenging, and often cause partial gas loss via the resultant ram pressures. Using an analytical approach, we model the impact of such ram pressures on the gas inside haloes of different masses. A halo’s external gas accretion is typically cut off, with partial stripping of halo gas. For masses below a few times 109 M⊙, their halo gas is heavily truncated but not completely stripped. We identify numerous examples of haloes with a clear jelly-fish like gas morphology, indicating their surrounding gas is being swept away, cutting them off from further external accretion. These results highlight how, even in the relatively low densities of void walls, a fraction of galaxies can interact with large-scale flows in a manner that has consequences for their gas content and ability to accrete gas.

Characterization of a low-pressure Micro-Megas-like gaseous detector with low energy x-ray sources

Within the family of the Micro Strip Gas Detectors (MSGD), the intrinsic characteristics of the bulk Micro-Megas (MM) device represent the most promising features for the construction of a new instrument to be operated as a TPC gas chamber in a low-pressure regime. In this study, we present the main properties of a low-pressure bulk MM detector in which the amplification gap was slightly increased to improve the gas gain. Two configurations have been deeply studied: the first one with a gap of 128μm and a second one with a 192μm gap, both filled and operated with a gas mixture (Ar-CO2) at pressures below 100 mbar. The dependence of the gain and the energy resolution on the amplification field, gas pressure and drift field have been evaluated. The reliability of the measured performance, combined with the simple and robust structure of the detector even with an increased length of amplification gap, make it an attractive choice for applications where the track length of low energy particles is detected by using a low-pressure filling gas.

Effects of different deodorization methods on the oxidation of sterol components in rice bran oil

Rice bran oil contains a significant quantity of phytosterols that have various active functions and are natural active substances beneficial to humans. It is well known that deodorization during refining affects the quality of rice bran oil. However, changes in phytosterols fraction caused by stripping with nitrogen compared to water vapor remain unexplored. We measured phytosterols in rice bran oil after deodorization with nitrogen and water vapor. The variations in sitosterol fraction, which accounts for the highest percentage of phytosterols in rice bran oil, were analyzed by Gas chromatography (GC), Fourier transform infrared spectrometer (FTIR), and Nuclear magnetic resonance (NMR). Results showed that using nitrogen as the stripping gas was more suitable for deodorization. It promoted the formation of phytosterol esters, reduced the production of phytosterol oxidation products and improved the oil quality. This study provides a theoretical basis for improving the industrial production quality of rice bran oil.

Ram pressure stripping and ISM disc truncation: prediction versus observation

ABSTRACT Ram pressure stripping (RPS) is known to be a key environmental effect that can remove interstellar gas from galaxies in a cluster. The RPS process is commonly described as a competition between the ram pressure by the intracluster medium and the anchoring pressure on the interstellar medium by the gravitational potential of a galaxy. However, the actual gas stripping process can be more complicated due to the complexity of gas physics such as compression and geometrical self-shielding as well as cooling and heating. In order to verify how well the observed signatures of the RPS process can be understood as simple momentum transfer, we compare the stripping radii of Virgo cluster galaxies in different stages of RPS measured from the H i observation with the predicted gas truncation radii for the given conditions. For the sample undergoing active RPS, we generally find good agreements between predictions and observations within a measurement uncertainty. On the other hand, galaxies likely in the early or later RPS stage and/or the ones with signs of environmental impacts other than RPS such as tidal interaction or starvation show some discrepancies. Our results imply that the conventional RPS relation works reasonably well in a broad sense when RPS is the most dominant process and the galaxy is located where the surrounding environment can be well defined. Otherwise, more careful inspections on the second mechanism and local environment are required to assess the impact of RPS on the target.

Produced Gas and Condensate Geochemistry of the Marcellus Formation in the Appalachian Basin: Insights into Petroleum Maturity, Migration, and Alteration in an Unconventional Shale Reservoir

The Middle Devonian Marcellus Formation of North America is the most prolific hydrocarbon play in the Appalachian basin, the second largest producer of natural gas in the United States, and one of the most productive gas fields in the world. Regional differences in Marcellus fluid chemistry reflect variations in thermal maturity, migration, and hydrocarbon alteration. These differences define specific wet gas/condensate and dry gas production in the basin. Marcellus gases co-produced with condensate in southwest Pennsylvania and northwest West Virginia are mixtures of residual primary-associated gases generated in the late oil window and postmature secondary hydrocarbons generated from oil cracking in the wet gas window. Correlation of API gravity and C7 expulsion temperatures, high heptane and isoheptane ratios, and the gas geochemical data confirm that the Marcellus condensates formed through oil cracking. Respective low toluene/nC7 and high nC7/methylcyclohexane ratios indicate selective depletion of low-boiling point aromatics and cyclic light saturates in all samples, suggesting that water washing and gas stripping altered the fluids. These alterations may be related to deep migration of hot basinal brines. Dry Marcellus gases produced in northeast Pennsylvania and northcentral West Virginia are mixtures of overmature methane largely cracked from refractory kerogen and ethane and propane cracked from light oil and wet gas. Carbon and hydrogen isotope distributions are interpreted to indicate (1) mixing of hydrocarbons of different thermal maturities, (2) high temperature Rayleigh fractionation of wet gas during redox reactions with transition metals and formation water, (3) isotope exchange between methane and water, and, possibly, (4) thermodynamic equilibrium conditions within the reservoirs. Evidence for thermodynamic equilibrium in the dry gases includes measured molecular proportions (C1/(C1 − C5) = 0.96 to 0.985) and δ13C1 values significantly greater than δ13CKEROGEN. Noble gas systematics support the interpretation of hydrocarbon–formation water interactions, constrain the high thermal maturity of the hydrocarbon fluids, and provide a method of quantifying gas retention versus expulsion in the reservoirs.

Anaerobic reactor with a phase separator for enhancing sulfide removal from wastewater by gas stripping

An internal phase-separated reactor (IPSR) was developed to remove sulfide from wastewater by gas stripping using biogas produced in the reactor itself. This reactor consisted of a first stage in an upper segment, a phase separator using a gas–liquid partitioning (GLP) valve, and a second stage in a lower segment. The IPSR is proposed as a new reactor structure. Reactors with and without GLP valves were operated in parallel at 35 °C. Synthetic wastewater with a sulfate concentration of 800 mg S/L was fed into the reactors at an organic loading rate of 10 kg COD/(m3 day). The IPSR removed more hydrogen sulfide than the control reactor because of the biogas supplied through the GLP valve. The reduction in the H2S in the IPSR was 39 % to 50 % more than that in the control reactor, and the IPSR reduced the sulfide concentration in the effluent by 19 % more than the control reactor.

An Alternative Approach to Improve the Butanol Production Efficiency from Sweet Sorghum Stem Juice Using Immobilized Cells Combined with an In Situ Gas Stripping System

The effects of the nitrogen source and buffers used in butanol production with Clostridium beijerinckii TISTR 1461 from sweet sorghum stem juice (SSJ) containing 60 g/L of total sugar were first studied in this paper. Among the various nitrogen sources (dried spent yeast, urea, ammonium acetate, ammonium sulfate), urea was found to be the most suitable for butanol production. SSJ supplemented with urea (0.64 g/L) and cocktail buffers (KH2PO4, 0.5 g/L; K2HPO4, 0.5 g/L; ammonium acetate, 2.2 g/L) gave the highest butanol concentration (PB, 10.13 g/L). Then, the capability of immobilized C. beijerinckii TISTR 1461 cells for butanol fermentation was investigated. Two residual waste materials were examined as immobilized cell carriers. Bamboo chopstick pieces were more appropriate as carriers for cell immobilization than cigarette filter tips. The PB value of the immobilized cells on the bamboo chopstick pieces was ~13% higher than that on the cigarette filter tips. Using the response surface methodology (RSM), 1.9 cm bamboo chopstick pieces with a carrier loading of 1:32 (w/v) were the optimum conditions for cell immobilization for butanol production. Under these conditions, the PB value was 11.62 g/L. To improve the butanol production efficiency, a gas stripping system (GS) was connected to the fermenter. It was found that the PB (14.02 g/L) and butanol productivity (QB, 0.29 g/L·h) values improved by ~21% compared to butanol fermentation using no gas stripping.

Cluster environment quenches the star formation of low-mass satellite galaxies from the inside-out

ABSTRACT Environment plays a critical role in the star formation history of galaxies. Tidal and hydrodynamical stripping, prominent in cluster environment, can remove the peripheral gas of galaxies and star formation may thus be environmentally suppressed from the outside-in. We revisit the environmental dependence of the radial gradient of specific star formation rate (sSFR) profile. We probe the radial gradient by using the archival spectral indices D4000n and HδA measured from SDSS fibre spectra, to indicate central sSFR and the total sSFR from fitting the spectral energy distribution. Despite the low spatial resolution, the wealth of SDSS data allows to disentangle the dependences on stellar mass, sSFR, and environment. We find that low-mass satellite galaxies in the mass range $9\lt \mathrm{log}\, \mathcal {M}_{\star }/\mathcal {M}_{\odot }\lt 9.8$ on average quench in more inside-out pattern compared to isolated galaxies matched in mass, sSFR, and fibre coverage. This environmental effect is particularly strong for galaxies below the star formation main sequence, and peaks for those in the core of massive clusters where the phase-space diagram reveals clear links between the inside-out quenching and orbital properties. Our results suggest that both tidal and hydrodynamical interactions in cluster environment suppress the star formation of satellites mainly from the inside-out. As accreted gas of low angular momentum from hot gas haloes is an important source for replenishing central gas reservoir, we discuss how gas stripping in clusters may lead to starvation and cause inside-out quenching when the outer star-forming discs are not significantly affected.

Influence of Carbon Dioxide in Stripping Gas on Ammonia Removal

Influence of Carbon Dioxide in Stripping Gas on Ammonia Removal

An orbital perspective on the starvation, stripping, and quenching of satellite galaxies in the eagle simulations

ABSTRACT Using the eagle (Evolution and Assembly of GaLaxies and their Environments) suite of simulations, we demonstrate that both cold gas stripping and starvation of gas inflow play an important role in quenching satellite galaxies across a range of stellar and halo masses, M⋆ and M200. Quantifying the balance between gas inflows, outflows, and star formation rates, we show that even at z = 2, only $\approx 30{{\ \rm per\ cent}}$ of satellite galaxies are able to maintain equilibrium or grow their reservoir of cool gas – compared to $\approx 50{{\ \rm per\ cent}}$ of central galaxies at this redshift. We find that the number of orbits completed by a satellite on first-infall to a group environment is a very good predictor of its quenching, even more so than the time since infall. On average, we show that intermediate-mass satellites with M⋆ between will be quenched at $10^{9}\, {\rm M}_{\odot }\, {\rm and}\, 10^{10}\, {\rm M}_{\odot }$ first pericenter in massive group environments, $M_{200}\gt 10^{13.5}\, {\rm M}_{\odot }$; and will be quenched at second pericenter in less massive group environments, $M_{200}\lt 10^{13.5}\, {\rm M}_{\odot }$. On average, more massive satellites ($M_{\star }\gt 10^{10}\, {\rm M}_{\odot }$) experience longer depletion time-scales, being quenched between first and second pericenters in massive groups, while in smaller group environments, just $\approx 30{{\ \rm per\ cent}}$ will be quenched even after two orbits. Our results suggest that while starvation alone may be enough to slowly quench satellite galaxies, direct gas stripping, particularly at pericenters, is required to produce the short quenching time-scales exhibited in the simulation.

Novel approach to ammonia recovery from anaerobic digestion via side-stream stripping at multiple pH levels

Ammonia recovery from anaerobic digesters via side-stream stripping is a technique to recover nitrogen from manure wastes. This study demonstrated a novel approach to determining ammonia recovery to maintain total ammonia concentrations in the digester in the range of 1.7–2.1 gN/L. Increasing the pH during stripping from 8, 8.5 to 9.5 did not affect the stability of the digester. Methane yields of 60–80 mL/(gVS.d) and volatile fatty acid concentrations of 0–500 mg/L were reported throughout its operation. The low solubilisation increase upon recirculation of the digestate explained the lack of change in methane yields due to side-stream stripping. Increasing the pH during stripping also did not affect the digester's operating pH, which was attributed to the neutralising effect of biogas as stripping gas. Therefore, total ammonia concentrations in the digester can be controlled by determining the extent of ammonia recovery, and the pH during stripping can be increased without compromising the digester’s stability.

Discovery of a Cool, Metal-rich Gas Reservoir in the Outskirts of z ≈ 0.5 Clusters

We built the first-ever statistically significant sample of ≈80,000 background quasar–foreground cluster pairs to study the cool, metal-rich gas in the outskirts (>R 500) of z ≈ 0.5 clusters with a median mass of ≈1014.2 M ⊙. The sample was obtained by crossmatching the Sloan Digital Sky Survey (SDSS) cluster catalog of Wen & Han and the SDSS quasar catalog of Lyke et al. The median impact parameter (ρ cl) of the clusters from the quasar sightlines is 2.4 Mpc (median ρ cl/R 500 = 3.6). A strong Mg II, along with marginal Fe II, absorption is detected in the mean and median stacked spectra of the quasars with a total Mg II rest-frame equivalent width () of 0.034 ± 0.005 Å (7σ) and 0.010 ± 0.003 Å (3σ), respectively. The shows a declining trend with increasing ρ cl and ρ cl/R 500, but does not show any significant trend with mass (M 500) or redshift (z cl) within the small M 500 and z cl ranges probed here. The Mg II absorption signal and the trends persist even if we exclude the quasar–cluster pairs where the background quasars may be probing the circumgalactic medium of bright galaxies with impact parameters <300 kpc. The Mg II (and Fe II) absorption reported here is the first detection of its kind. It indicates the presence of a cool, metal-rich gas reservoir surrounding galaxy clusters out to several R 500. We suggest that the metal-rich gas in the cluster outskirts arise from stripped materials and that gas stripping may be important out to large clustocentric distances (>3R 500).