Gas Contact Research Articles

Operational aspects of the desulfurization process of energy gases mimics in biotrickling filters

Biological removal of reduced sulfur compounds in energy-rich gases is an increasingly adopted alternative to conventional physicochemical processes, because of economical and environmental benefits. A lab-scale biotrickling filter reactor for the treatment of high-H 2S-loaded gases was developed and previously proven to effectively treat H 2S concentrations up to 12,000 ppm v at gas contact times between 167 and 180 s. In the present work, a detailed study on selected operational aspects affecting this system was carried out with the objective to optimize performance. The start-up phase was studied at an inlet H 2S concentration of 1000 ppm v (loading of 28 g H 2S m −3 h −1) and inoculation with sludge from a municipal wastewater treatment plant. After reactor startup, the inlet H 2S concentration was doubled and the influence of different key process parameters was tested. Results showed that there was a significant reduction of the removal efficiency at gas contact times below 120 s. Also, mass transfer was found to be the main factor limiting H 2S elimination, whereas performance was not influenced by the bacterial colonization of the packed column after the initial startup. The effect of gas supply shutdowns for up to 5 days was shown to be irrelevant on process performance if the trickling liquid recirculation was kept on. Also, the trickling liquid velocity was investigated and found to influence sulfate production through a better use of the supplied dissolved oxygen. Finally, short-term pH changes revealed that the system was quite insensitive to a pH drop, but was markedly affected by a pH increase, affecting both the biological activity and the removal of H 2S. Altogether, the results presented and discussed herein provide new insight and operational data on H 2S removal from energy gases in biotrickling filters.

Wettability and Its Effects on Oil Recovery in Fractured and Conventional Reservoirs

Wettability, as the tendency of a reservoir rock surface to preferentially contact a particular fluid in a multiphase fluid system (Agbalaka et al., 2008), is determined by complex interface boundary conditions acting within the pore scale of porous media. Capillary pressure and relative permeability can be changed quite substantially from a wetting to a non-wetting phase, with subsequent influences on transition zone height, water–oil contacts, and residual oil saturation (Cockcroft et al., 1989). Wettability has a dominant effect on interface movement and associated displacement of different phases within porous media. For example, during tertiary miscible injection for a water-invaded oil column (double displacement process), gas and oil direct contact can be prevented by water surrounding residual oil due to wettability effects (water shielding phenomenon). Therefore, understanding formation wettability and its management is crucial for optimizing oil recovery. The wettability concept and its effect on multiphase flow within conventional and naturally fractured reservoirs (NFRs) is discussed here with some case studies.

Temperature Dependence of the Universal Contact Parameter in a Unitary Fermi Gas

The contact I, introduced by Tan, has emerged as a key parameter characterizing universal properties of strongly interacting Fermi gases. For ultracold Fermi gases near a Feshbach resonance, the contact depends upon two quantities: the interaction parameter 1/(k(F)a), where k(F) is the Fermi wave vector and a is the s-wave scattering length, and the temperature T/T(F), where T(F) is the Fermi temperature. We present the first measurements of the temperature dependence of the contact in a unitary Fermi gas using Bragg spectroscopy. The contact is seen to follow the predicted decay with temperature and shows how pair-correlations at high momentum persist well above the superfluid transition temperature.

Oil property changes during the waterflooding for reservoirs with condensate gas cap

Abstract Zanarol Oilfield is a giant carbonate reservoir with condensate cap, weakly volatile oil, and bioclastic limestone of low porosity and permeability. During the waterflooding stage, formation pressure decreased step by step resulting from the former depleting development and the strong heterogeneity of carbonate reservoirs. The gas cap spread outwards with the formation pressure dropping, causing gas breakthrough in production wells near the oil and gas contact, GOR increased and oil density decreased. In the internal oil region far from the oil-gas contact, the dropping reservoir pressure led to dissolved gas separating out from oil, making crude oil change to black oil from weak volatile oil. With the separated solution gas, the oil density, produced gas oil ratio and oil viscosity increased, the oil well productivity decreased, all these make waterflooding more difficult. The main method for improving development response is to keep formation pressure and improve the utilization factor of water injection.

Photo-EMF Sensitivity of Porous Silicon Thin Layer–Crystalline Silicon Heterojunction to Ammonia Adsorption

A new method of using photo-electromotive force in detecting gas and controlling sensitivity is proposed. Photo-electromotive force on the heterojunction between porous silicon thin layer and crystalline silicon wafer depends on the concentration of ammonia in the measurement chamber. A porous silicon thin layer was formed by electrochemical etching on p-type silicon wafer. A gas and light transparent electrical contact was manufactured to this porous layer. Photo-EMF sensitivity corresponding to ammonia concentration in the range from 10 ppm to 1,000 ppm can be maximized by controlling the intensity of illumination light.

Universal structure of a strongly interacting Fermi gas

This paper presents studies of the universal properties of strongly interacting Fermi gases using Bragg spectroscopy. We focus on pair-correlations, their relationship to the contact C introduced by Tan, and their dependence on both the momentum and temperature. We show that short-range pair correlations obey a universal law, first derived by Tan through measurements of the static structure factor, which displays a universal scaling with the ratio of the contact to the momentum C/q. Bragg spectroscopy of ultracold 6Li atoms is employed to measure the structure factor for a wide range of momenta and interaction strengths, providing broad confirmation of this universal law. We show that calibrating our Bragg spectra using the f-sum rule leads to a dramatic improvement in the accuracy of the structure factor measurement. We also measure the temperature dependence of the contact in a unitary gas and compare our results to calculations based on a virial expansion.

Momentum distribution and contact of the unitary Fermi gas

Momentum distribution and contact of the unitary Fermi gas

Sour compression process for the removal of SO and NO from oxyfuel-derived CO2

Abstract Coal-fired power stations under oxyfuel combustion produce a raw CO2 product which contains impurities such as water, oxygen, nitrogen and argon from excess oxygen and air leakages. There are also acid gases present, such as SO3, SO2, HCl and NOX produced as by-products of combustion. These acidic impurities will need to be removed from the CO2 stream before it is introduced into the pipeline to prevent corrosion and comply with possible regulations. There may also be stringent requirements on purity, particularly for applications such as enhanced oil recovery. A novel compression method of producing NOx-free, SO2free CO2 was proposed in GHGT-8 [1] , [2] , [3] , [4] , [5] , [6] where SO2 and NOx are removed as H2SO4 and HNO3respectively by compression and water contact of the flue gas. At GHGT-9, initial experimental results were presented using actual fluegas via a sidestream from Doosan Babcock’s 160 kW coal-fired oxyfuel rig, showing the feasibility of the process eliminating 99% SOx and 90% NOx compounds. In this paper, we report on the effects of pressure, temperature, residence time and presence of water in a laboratory scale apparatus using synthetic flue gas.

Thermal gap conductance at low contact pressures (

Thermal contact conductance (TCC) measurements are made on bare and gold plated (⩽0.5 μm) oxygen free high conductivity (OFHC) Cu and brass contacts in vacuum, nitrogen, and argon environments. It is observed that the TCC in gaseous environment is significantly higher than that in vacuum due to the enhanced thermal gap conductance. It is found that for a given contact load and gas pressure, the thermal gap conductance for bare OFHC Cu contacts is higher than that for gold plated contacts. It is due to the difference in the molecular weights of copper and gold, which influences the exchange of kinetic energy between the gas molecules and contact surfaces. Furthermore, the gap conductance is found to increase with increasing thickness of gold plating. Topography measurements and scanning electron microscopy (SEM) analysis of contact surfaces revealed that surfaces become smoother with increasing gold plating thickness, thus resulting in smaller gaps and consequently higher gap conductance.

Application of the BISQ model to clay squirt flow in reservoir sandstones

An understanding of the variations of compressional wave velocity and attenuation in sandstones as a function of pore‐fluid properties is important for the identification and monitoring of hydrocarbon reservoirs. In order for seismic inversion to be well constrained a rock physics model that describes accurately the observed behavior is required; a number of such models have been proposed but have not been extensively tested against laboratory data. The unified Biot and squirt flow model was applied to data obtained from ultrasonic experiments conducted on a wide range of sandstone types when saturated with different pore fluids with viscosities ranging from 0.3 to 1000 cP. This model was seen to match well all the observed velocity and attenuation values as opposed to the Biot model, which was only successful for clean sandstones saturated with low viscosity fluids. This has led to the conclusion that a squirt flow mechanism is important at the grain scale. In addition, an increase in the dynamic uniaxial strain modulus of the dry frame with increasing pore‐fluid viscosity was observed. In the absence of free gas or grain contact microcracks (the laboratory data were collected at 60 MPa effective pressure), this can be linked to decreasing local flow and decreasing relaxation in the soft pore space of the sandstone, the extent of which is in turn connected to the clay content and pore structure of the sandstone. These results imply that at ultrasonic frequencies the squirt‐flow is due to the presence of clay.

The influence of gas shielding composition and contact tip to work distance in short circuit metal transfer of ferritic stainless steel

The shielding gas used in the MIG/MAG process affects not only the weld properties but also determines the form of the weld bead. Depending on the type of metal transfer, the shielding gas interacts to a greater or lesser extent on the electrode wire and weld bead, and may alter the mechanical properties of the weld bead. Another parameter that has a significant influence is the contact tip work piece distance. The objective of this work is to study the influence of the CTWD using various shielding gas mixtures (pure argon, and argon mixed with oxygen and carbon dioxide) on the average short circuit transfer period, the average welding current and the quality of a weld bead I ferritic stainless steel. The results show that the CTWD has a significant effect on the welding current, regardless of the type of shielding gas. The shielding gas significantly changes the amount of slag formed and the amount of splatter, changing the appearance of the weld bead with the increase of oxygen or carbon dioxide in argon.

Influence of sintering conditions on microstructure and oxygen permeation of Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3− δ (BSCF) oxygen transport membranes

Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3− δ (BSCF) exhibits high oxygen permeability, which is why it is being discussed for gas separation (oxygen transport membrane, OTM) in zero-emission power plants using oxyfuel technology when the membrane is operated in a clean environment, i.e. no flue gas contact. We investigate the influence of membrane processing on microstructure and oxygen permeation. Pure-phase BSCF powder is synthesized using a modified Pechini method. For comparison, commercially available powder is also used, synthesized by a solid-state reaction. Disk-shaped membranes of various microstructures, i.e. closed porosities and grain sizes, are prepared by uniaxial pressing and sintering of the powders processed in different ways. The powders and membranes are characterized by methods including BET, SEM, XRD, and DSC. The microstructures obtained by different sintering conditions are investigated by SEM and TEM. Sintering at 1150 °C leads to incongruent melting of BSCF indicated by DSC. The liquid phase appears at three-phase boundaries grain–grain–air and consists of nearly pure cobalt oxide with small impurities of barium and strontium detected by TEM/EDX analysis. Oxygen permeation of the membranes is measured in an air/Ar gradient depending on temperature and membrane microstructure. The closed porosity of different processed membranes is varied between 2 and 15% with uniform grain sizes in the range of approx. 10 μm. The average grain size is increased from 10 to 45 μm by increasing the sintering temperature. Neither porosity nor the grain size significantly influences the oxygen permeation rate of 1-mm-thick disks in the investigated parameter range.

Thin Film Solid Oxide Fuel Cells Deposited by Spray Pyrolysis

Two techniques of spray pyrolysis, namely, electrostatic and pneumatic spray deposition, were used to deposit samaria-doped ceria (SDC) electrolyte and lanthanum strontium cobalt ferrite (LSCF) cathode on cermet or metal supported anodes for solid oxide fuel cells (SOFCs) operated at reduced temperature. The deposition processes, the properties of the deposited films, and the electrochemical performances of the fabricated cells are reported in this paper. The deposited SDC electrolytes were dense and gas-tight, and had good adhesion to the underlying anodes. The deposited LSCF cathode had a preferred morphology to facilitate the transport of oxygen gas and effective contact with the electrolyte. Button cell testing indicated that the SOFCs with electrolyte or cathode deposited by spray pyrolysis had good electrochemical performance. This study demonstrated that spray pyrolysis is a cost-effective process for fabricating thin film SOFCs, especially metal supported SOFCs.

Odd–Even Effects in the Friction of Self-Assembled Monolayers of Phenyl-Terminated Alkanethiols in Contacts of Different Adhesion Strengths

We have studied the frictional properties of self-assembled monolayers (SAMs) of phenyl-terminated alkanethiols, C6H5(CH2) n SH (n = 13–16) on template-stripped gold. The friction force was measured with atomic force microscopy (AFM), and the magnitude of the adhesion was controlled by immersing the sliding contact in ethanol (giving low adhesion) or dry N2 gas (giving enhanced adhesion relative to ethanol). We observed a linear friction force as a function of load (F = μL) in the systems with low adhesion and a non-linear friction force when the adhesion was higher. The non-linear behavior in the adhesive systems appeared to be area-dependent (F = S c A) and was compared to contact areas calculated using the extended Thin-Coating Contact Mechanics (TCCM) model. In ethanol, the coefficient of friction μ was found to be systematically higher for odd values of n (i.e., for the monolayers in which the terminal phenyl group was oriented closer to the surface normal).

207 藻類利用によるCO2吸収システム開発(循環型廃棄物処理技術(2))

The recovery of carbon dioxide (CO_2) is one of the most important topics to improve global environments. The exhausted gases from power generator using petroleum and coal or incinerator include more than 10% of CO_2 which is excellent source for the multiplication of plants in which photosynthesis occurs with CO_2 and water. The higher the concentration of CO_2 is, the more the reaction rate gains. We have studied and found the species of green algae useful for recovery of CO_2 and the proper condition to best growth of the algae under the high concentration of CO_2 in a continuous flow water bath. However, the contact of solid (green algae) and gas (CO_2) is difficult to manage in the industrial scale. The whole system, the target and the technology will be presented.

Grafted Amine/CO2 Interactions in (Gas−)Liquid−Solid Adsorption/Absorption Equilibria

The effects associated with the presence of liquid water on the CO2 adsorption capacity by SBA-15 silica functionalized with aminopropyltrimethoxysilane (APS) and N-(2-aminoethyl)-3-(aminopropyl)trimethoxysilane (AEAPS) were examined to evaluate the potential of this mode of contact in gas−liquid−solid scrubbing operations for CO2 partial pressures typical of atmospheric postcombustion flue gases. The results were compared to the CO2 adsorption capacity of the grafted amines in moist and dry gas−solid conditions along with the CO2 absorption capacity in gas−liquid amine solution systems consisting of amines with almost identical structures. In these conditions, an estimation of CO2 physical adsorption was obtained through study of (bare) unmodified SBA-15. Furthermore, to assess the efficacy and long-term stability of the amine/SBA-15 association, grafted amines were subjected to up to eight successive immersion cycle tests (24 h each) in aqueous media. The recovered samples were characterized by X-ray di...

Drastic Solid‐State Fluorescence Enhancement Behaviour of Phenanthro[9,10‐d]imidazole‐Type Fluorescent Hosts upon Inclusion of Carboxylic Acids

AbstractThe crystals of phenanthro[9,10‐d]imidazole‐type fluorescent host 1 exhibit drastic fluorescence enhancement behaviour with a redshift in the emission maximum upon enclathration of various carboxylic acids such as formic acid, acetic acid and propionic acid. The optical changes are greatly dependent on the identity of the enclathrated carboxylic acids. The fluorescent clathrate compounds are formed not only by cocrystallization from carboxylic acid solutions but also by solid (fluorescent host)–gas (carboxylic acid vapour) contact. Furthermore, when the acetic acid inclusion crystals are exposed to propionic acid vapour, acetic acid is gradually replaced by propionic acid. The guest exchange of the inclusion crystals was accompanied with colour and fluorescent intensity changes. The X‐ray structural analyses of the guest‐free and carboxylic acid inclusion compounds demonstrated that the destructions of the π–π interactions, and the intermolecular hydrogen bonds binding fluorophores were induced by the enclathrated carboxylic acid molecules. Moreover, the imidazole ring of the host is protonated by the enclathrated carboxylic acid proton. On the basis of the spectroscopic data and the crystal structures, the effects of the enclathrated carboxylic acid on the solid‐state photophysical properties of the clathrate compounds are discussed.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Surface characterization of poly(2,2,3,3,3-pentafluoropropyl methacrylate) by inverse gas chromatography and contact angle measurements

A fluorinated methacrylic homopolymer, poly(2,2,3,3,3-pentafluoropropyl methacrylate) (PPFPMA) was synthesized by a free radical polymerization reaction. The dispersive component of the surface energy ( γ s d ) of PPFPMA was determined by contact angle measurements and inverse gas chromatography (IGC). An extensive surface characterization was conducted by means of IGC. Surface characterization demonstrated that PPFPMA has low γ s d value, even at 35 °C and is a Lewis amphoteric polymer with predominantly basic character, as confirmed by the Lewis acidity and basicity constants K A and K B , respectively. The values of γ s d obtained by IGC are slightly higher than those obtained by the contact angle method. This trend can be attributed to the fact that IGC evaluates, primarily, high energy sites of a surface.

HHT analysis of electrostatic fluctuation signals in dense-phase pneumatic conveying of pulverized coal at high pressure

Particle charging generated by particle-wall, particle–particle and particle–gas contacts in pneumatic transport pipelines contain rich information on gas–solid flow hydrodynamics. In this paper, experiments were performed in a dense phase pneumatic conveying system, and electrostatic fluctuation signals were detected by a ring-shape electrostatic sensor that is based on electrostatic induction theory. Power spectrum analysis and Hilbert–Huang transform (HHT) were applied to the electrostatic fluctuations, namely outputs of the electrostatic sensor, to extract and characterize the intrinsic features of dense-phase gas–solid flow. Results show that the dominant peak of the power spectrum of the electrostatic fluctuations moves toward higher frequency with the increasing gas superficial velocity. The Hilbert–Huang transform reveals the non-linear and non-stationary intrinsic nature of the electrostatic fluctuations. By using the non-linear and non-stationary signal processing method (HHT), non-linear inter-modulation characteristics in the dense phase gas–solid flow were analyzed, and the relations between the energy distribution transmissions in intrinsic mode functions (IMFs) with different orders and the flow characterization of the dense phase gas–solid flow, was investigated as well, which can represent the behavior, stability and regime transitions of the gas–solid flow in the dense-phase pneumatic conveying system at high pressure.

Carbon dioxide treatment of low density sludge: a new remediation strategy for acidic mining lakes?

Acid mine drainage (AMD) is treated at several points in the Lausitz lignite mine district (Saxony, Germany) in treatment plants. The remaining alkaline low density sludge (LDS) was deposited in acidic mining lakes without having an impact on the lake water quality. Batch experiments show that alkalinity can be raised using LDS from acid mine drainage treatment plants together with CO2. Batch experiments were conducted using lake water and deposited LDS from the mining lake Spreetal-Nordost with varying concentrations of CO2. Also the duration of gas contact as well as the LDS–water ratio was changed in the batch experiments. The gas contact time and the partial pressure of CO2 are the relevant parameters controlling the alkalinity in the lake water at the end of the experiments. The Ca and Mg concentrations of the pore water are relevant for higher pH values. Therefore, dissolved CO2 can form bicarbonate or carbonate complexes, thus alkalinity rises. A second factor for alkalinity gain is the calcite content of the sludge, because CO2 triggers the dissolution of carbonates. Therefore, unused calcite in the sludge can raise the alkalinity more effectively by the application of carbon dioxide. Furthermore, it was shown that remobilization of trace elements will not affect the water quality.