scholarly journals Small Alcohols as Surfactants and Hydrate Promotors

Fluids ◽  
2021 ◽  
Vol 6 (10) ◽  
pp. 345
Author(s):  
Bjørn Kvamme
Keyword(s):  
Kinetic Modelling ◽  
Hydrate Formation ◽  
Formation Enthalpy ◽  
Mineral Surfaces ◽  
Surface Charges ◽  
Surrounding Water ◽  
Mole Percent ◽  
Bottle Neck ◽  
Stability Limits

Many methods to produce hydrate reservoirs have been proposed in the last three decades. Thermal stimulation and injection of thermodynamic hydrate inhibitors are just two examples of methods which have seen reduced attention due to their high cost. However, different methods for producing hydrates are not evaluated thermodynamically prior to planning expensive experiments or pilot tests. This can be due to lack of a thermodynamic toolbox for the purpose. Another challenge is the lack of focus on the limitations of the hydrate phase transition itself. The interface between hydrate and liquid water is a kinetic bottle neck. Reducing pressure does not address this problem. An injection of CO2 will lead to the formation of a new CO2 hydrate. This hydrate formation is an efficient heat source for dissociating hydrate since heating breaks the hydrogen bonds, directly addressing the problem of nano scale kinetic limitation. Adding limited amounts of N2 increases the permeability of the injection gas. The addition of surfactant increases gas/water interface dynamics and promotes heterogeneous hydrate formation. In this work we demonstrate a residual thermodynamic scheme that allows thermodynamic analysis of different routes for hydrate formation and dissociation. We demonstrate that 20 moles per N2 added to the CO2 is thermodynamically feasible for generating a new hydrate into the pores. When N2 is added, the available hydrate formation enthalpy is reduced as compared to pure CO2, but is still considered sufficient. Up to 3 mole percent ethanol in the free pore water is also thermodynamically feasible. The addition of alcohol will not greatly disturb the ability to form new hydrate from the injection gas. Homogeneous hydrate formation from dissolved CH4 and/or CO2 is limited in amount and not important. However, the hydrate stability limits related to concentration of hydrate former in surrounding water are important. Mineral surfaces can act as hydrate promotors through direct adsorption, or adsorption in water that is structured by mineral surface charges. These aspects will be quantified in a follow-up paper, along with kinetic modelling based on thermodynamic modelling in this work.

scholarly journals Hydrate—A Mysterious Phase or Just Misunderstood?

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 880 ◽  
Author(s):  
Bjørn Kvamme ◽  
Jinzhou Zhao ◽  
Na Wei ◽  
Navid Saeidi
Keyword(s):  
Pure Water ◽  
Hydrate Formation ◽  
Free Water ◽  
Mineral Surfaces ◽  
Dual Roles ◽  
Hydrate Reservoir ◽  
Nucleation Sites ◽  
Stability Limits ◽  
Real Stability ◽  
Non Equilibrium

Hydrates that form during transport of hydrocarbons containing free water, or water dissolved in hydrocarbons, are generally not in thermodynamic equilibrium and depend on the concentration of all components in all phases. Temperature and pressure are normally the only variables used in hydrate analysis, even though hydrates will dissolve by contact with pure water and water which is under saturated with hydrate formers. Mineral surfaces (for example rust) play dual roles as hydrate inhibitors and hydrate nucleation sites. What appears to be mysterious, and often random, is actually the effects of hydrate non-equilibrium and competing hydrate formation and dissociation phase transitions. There is a need to move forward towards a more complete non-equilibrium way to approach hydrates in industrial settings. Similar challenges are related to natural gas hydrates in sediments. Hydrates dissociates worldwide due to seawater that leaks into hydrate filled sediments. Many of the global resources of methane hydrate reside in a stationary situation of hydrate dissociation from incoming water and formation of new hydrate from incoming hydrate formers from below. Understanding the dynamic situation of a real hydrate reservoir is critical for understanding the distribution characteristics of hydrates in the sediments. This knowledge is also critical for designing efficient hydrate production strategies. In order to facilitate the needed analysis we propose the use of residual thermodynamics for all phases, including all hydrate phases, so as to be able to analyze real stability limits and needed heat supply for hydrate production.

Mathematical model of multiphase flow propagation for the case of underwater pipeline damage

2019 ◽  
Vol 14 (2) ◽  
pp. 142-147
Author(s):  
S.R. Kildibaeva ◽  
E.T. Dalinskij ◽  
G.R. Kildibaeva
Keyword(s):  
Oil And Gas ◽  
Control Volume ◽  
Hydrate Formation ◽  
Initial Moment ◽  
Hydrate Shell ◽  
Surrounding Water ◽  
Vertical Coordinate ◽  
Associated Gas ◽  
First Case ◽  
Underwater Pipeline

The paper deals with the case of damage to the underwater pipeline through which oil and associated gas are transported. The process of oil and gas migration is described by the flow of a multiphase submerged jet. At the initial moment, the temperature of the incoming hydrocarbons, their initial velocity, the temperature of the surrounding water, the depth of the pipeline is known. The paper considers two cases of different initial parameters of hydrocarbon outflow from the pipeline. In the first case, the thermobaric environmental conditions correspond to the conditions of hydrate formation and stable existence. Such a case corresponds to the conditions of the hydrocarbons flow in the Gulf of Mexico. In the second case, hydrate is not formed. Such flows correspond to the cases of oil transportation through pipelines in the Baltic sea (for example, Nord stream–2). The process of hydrate formation will be characterized by the following dynamics of the bubble: first, it will be completely gas, then a hydrate shell (composite bubble) will begin to form on its surface, then the bubble will become completely hydrate, which will be the final stage. The integral Lagrangian control volume method will be considered for modeling the dynamics of hydrocarbon jet propagation. According to this method, the jet is considered as a sequence of elementary volumes. When modeling the jet flow, the laws of conservation of mass, momentum and energy for the components included in the control volume are taken into account. The equations are used taking into account the possible formation of hydrate. Thermophysical characteristics of hydrocarbons coming from the damaged pipeline for cases of deep-water and shallow-water pipeline laying are obtained. The trajectories of hydrocarbon migration, the dependence of the jet temperature and density on the vertical coordinate are analyzed.

scholarly journals Enthalpies of Hydrate Formation and Dissociation from Residual Thermodynamics

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4726 ◽  
Author(s):  
Solomon Aforkoghene Aromada ◽  
Bjørn Kvamme ◽  
Na Wei ◽  
Navid Saeidi
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Gas Hydrate ◽  
Hydration Number ◽  
Hydrate Formation ◽  
Formation Enthalpy ◽  
Hydrate Dissociation ◽  
Enthalpy Changes ◽  
Hydrate Phase ◽  
Temperature Equilibrium

We have proposed a consistent thermodynamic scheme for evaluation of enthalpy changes of hydrate phase transitions based on residual thermodynamics. This entails obtaining every hydrate property such as gas hydrate pressure-temperature equilibrium curves, change in free energy which is the thermodynamic driving force in kinetic theories, and of course, enthalpy changes of hydrate dissociation and formation. Enthalpy change of a hydrate phase transition is a vital property of gas hydrate. However, experimental data in literature lacks vital information required for proper understanding and interpretation, and indirect methods of obtaining this important hydrate property based on the Clapeyron and Clausius-Clapeyron equations also have some limitations. The Clausius-Clapeyron approach for example involves oversimplifications that make results obtained from it to be inconsistent and unreliable. We have used our proposed approach to evaluate consistent enthalpy changes of hydrate phase transitions as a function of temperature and pressure, and hydration number for CH4 and CO2. Several results in the literature of enthalpy changes of hydrate dissociation and formation from experiment, and Clapeyron and Clausius-Clapeyron approaches have been studied which show a considerable disagreement. We also present the implication of these enthalpy changes of hydrate phase transitions to environmentally friendly production of energy from naturally existing CH4 hydrate and simultaneously storing CO2 on a long-term basis as CO2 hydrate. We estimated enthalpy changes of hydrate phase transition for CO2 to be 10–11 kJ/mol of guest molecule greater than that of CH4 within a temperature range of 273–280 K. Therefore, the exothermic heat liberated when a CO2 hydrate is formed is greater or more than the endothermic heat needed for dissociation of the in-situ methane hydrate.

CO2 capture using the clathrate hydrate process employing cellulose foam as a porous media

2015 ◽  
Vol 93 (8) ◽  
pp. 808-814 ◽  
Author(s):  
Abhishek Nambiar ◽  
Ponnivalavan Babu ◽  
Praveen Linga
Keyword(s):  
Porous Media ◽  
Water Saturation ◽  
Kinetic Modelling ◽  
Fixed Bed ◽  
Hydrate Formation ◽  
Silica Sand ◽  
Operating Pressure ◽  
Avrami Model ◽  
Uptake Data ◽  
Water Saturated

A new biodegradable porous medium has been employed in this work for the hydrate-based gas separation (HBGS) process to capture carbon dioxide in a fixed bed column from a precombustion stream. Propane (2.5 mol%) was added as a promoter to reduce the operating pressure of the HBGS process. Experiments were conducted at 6 MPa and 274.2 K at different water saturation levels (50% and 100%) in a cellulose foam bed. It was found that a normalized rate of hydrate formation was more than double for 50% as compared to 100% water-saturated level. In addition, kinetic modelling of hydrate formation in porous media has been carried out using Avrami model by utilizing the experimental gas uptake data from current and published works. The Avrami model was found to fit the hydrate growth kinetics very well, up to 40 min of hydrate growth for different porous media like silica sand, polyurethane foam, and cellulose foam, and for different guest gas and gas mixtures.

scholarly journals Incidence and Diversity of Microorganisms within the Walls of an Active Deep-Sea Sulfide Chimney

2003 ◽  
Vol 69 (6) ◽  
pp. 3580-3592 ◽  
Author(s):  
Matthew O. Schrenk ◽  
Deborah S. Kelley ◽  
John R. Delaney ◽  
John A. Baross
Keyword(s):  
Community Analysis ◽  
Epifluorescence Microscopy ◽  
Rrna Gene ◽  
Mineral Surfaces ◽  
Group I ◽  
Juan De Fuca ◽  
Abundance And Diversity ◽  
Insight Into ◽  
Direct Microscopic Observation

ABSTRACT A large, intact sulfide chimney, designated Finn, was recovered from the Mothra Vent Field on the Juan de Fuca Ridge in 1998. Finn was venting 302�C fluids on the seafloor and contained complex mineralogical zones surrounding a large open central conduit. Examination of microorganisms within these zones, followed by community analysis with oligonucleotide probes, showed that there were variations in the abundance and diversity of eubacteria and archaea from the exterior to the interior of the chimney. The microbial abundance based upon epifluorescence microscopy and quantitative fatty acid analyses varied from >108 cells/g of sulfide 2 to 10 cm within the chimney wall to <105 cells/g in interior zones. Direct microscopic observation indicated that microorganisms were attached to mineral surfaces throughout the structure. Whole-cell hybridization results revealed that there was a transition from a mixed community of eubacteria and archaea near the cool exterior of the chimney to primarily archaea near the warm interior. Archaeal diversity was examined in three zones of Finn by cloning and sequencing of the 16S rRNA gene. The majority of sequences from the exterior of the chimney were related to marine group I of the Crenarchaeota and uncultured Euryarchaeota from benthic marine environments. In contrast, clone libraries from interior regions of the chimney contained sequences closely related to methanogens, Thermococcales, and Archaeoglobales, in addition to uncultured crenarchaeal phylotypes obtained from deep subsurface sites. These observations of microbial communities within an active hydrothermal chimney provide insight into the microbial ecology within such structures and may facilitate follow-up exploration into expanding the known upper temperature limits of life.

scholarly journals Stages in the Dynamics of Hydrate Formation and Consequences for Design of Experiments for Hydrate Formation in Sediments

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3399 ◽  
Author(s):  
Bjørn Kvamme ◽  
Richard B. Coffin ◽  
Jinzhou Zhao ◽  
Na Wei ◽  
Shouwei Zhou ◽  
...  
Keyword(s):  
Natural Gas ◽  
Mass Transport ◽  
Liquid Water ◽  
Transport Model ◽  
Hydrate Formation ◽  
Mineral Surfaces ◽  
Geological Time ◽  
Hydrate Reservoir ◽  
Hydrate Saturation ◽  
Mass Transport Model

Natural gas hydrates in sediments can never reach thermodynamic equilibrium. Every section of any hydrate-filled reservoir is unique and resides in a stationary balance that depends on many factors. Fluxes of hydrocarbons from below support formation of new hydrate, and inflow of water through fracture systems leads to hydrate dissociation. Mineral/fluid/hydrate interaction and geochemistry are some of the many other factors that determine local hydrate saturation in the pores. Even when using real sediments from coring it is impossible to reproduce in the laboratory a natural gas hydrate reservoir which has developed over geological time-scales. In this work we discuss the various stages of hydrate formation, with a focus on dynamic rate limiting processes which can lead to trapped pockets of gas and trapped liquid water inside hydrate. Heterogeneous hydrate nucleation on the interface between liquid water and the phase containing the hydrate former rapidly leads to mass transport limiting films of hydrate. These hydrate films can delay the onset of massive, and visible, hydrate growth by several hours. Heat transport in systems of liquid water and hydrate is orders of magnitude faster than mass transport. We demonstrate that a simple mass transport model is able to predict induction times for selective available experimental data for CO2 hydrate formation and CH4 hydrate formation. Another route to hydrate nucleation is towards mineral surfaces. CH4 cannot adsorb directly but can get trapped in water structures as a secondary adsorption. H2S has a significant dipole moment and can adsorb directly on mineral surfaces. The quadropole-moment in CO2 also plays a significant role in adsorption on minerals. Hydrate that nucleates toward minerals cannot stick to the mineral surfaces so the role of these nucleation sites is to produce hydrate cores for further growth elsewhere in the system. Various ways to overcome these obstacles and create realistic hydrate saturation in laboratory sediment are also discussed.

scholarly journals Association of mprF mutations with cross-resistance to daptomycin and vancomycin in methicillin-resistant Staphylococcus aureus (MRSA)

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Kanate Thitiananpakorn ◽  
Yoshifumi Aiba ◽  
Xin-Ee Tan ◽  
Shinya Watanabe ◽  
Kotaro Kiga ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Cross Resistance ◽  
Surface Charges ◽  
Genetic Determinants ◽  
Methicillin Resistant ◽  
Bacterial Surface ◽  
The Cross ◽  
Altered Gene ◽  
The Impact

Abstract We first reported a phenomenon of cross-resistance to vancomycin (VCM) and daptomycin (DAP) in methicillin-resistant Staphylococcus aureus (MRSA) in 2006, but mechanisms underlying the cross-resistance remain incompletely understood. Here, we present a follow-up study aimed to investigate genetic determinants associated with the cross-resistance. Using 12 sets of paired DAP susceptible (DAPS) and DAP non-susceptible (DAPR) MRSA isolates from 12 patients who had DAP therapy, we (i) assessed susceptibility to DAP and VCM, (ii) compared whole-genome sequences, (iii) identified mutations associated with cross-resistance to DAP and VCM, and (iv) investigated the impact of altered gene expression and metabolic pathway relevant to the cross-resistance. We found that all 12 DAPR strains exhibiting cross-resistance to DAP and VCM carried mutations in mprF, while one DAPR strain with reduced susceptibility to only DAP carried a lacF mutation. On the other hand, among the 32 vancomycin-intermediate S. aureus (VISA) strains isolated from patients treated with VCM, five out of the 18 strains showing cross-resistance to DAP and VCM carried a mprF mutation, while 14 strains resistant to only VCM had no mprF mutation. Moreover, substitution of mprF in a DAPS strain with mutated mprF resulted in cross-resistance and vice versa. The elevated lysyl-phosphatidylglycerol (L-PG) production, increased positive bacterial surface charges and activated cell wall (CW) synthetic pathways were commonly found in both clinical isolates and laboratory-developed mutants that carry mprF mutations. We conclude that mprF mutation is responsible for the cross-resistance of MRSA to DAP and VCM, and treatment with DAP is more likely to select for mprF-mediated cross-resistance than is with VCM.

scholarly journals Methane Hydrate Formation on Clay Mineral Surfaces: Thermodynamic Stability and Heterogeneous Nucleation Mechanisms

2015 ◽  
Author(s):  
Stephanie Teich-McGoldrick ◽  
David Blaine Hart ◽  
Margaret Ellen Gordon ◽  
Stephen P. Meserole ◽  
Mark A. Rodriguez ◽  
...  
Keyword(s):  
Clay Mineral ◽  
Thermodynamic Stability ◽  
Heterogeneous Nucleation ◽  
Methane Hydrate ◽  
Hydrate Formation ◽  
Mineral Surfaces ◽  
Nucleation Mechanisms

Therapy and prevention for mental health: What if mental diseases are mostly not brain disorders?

2019 ◽  
Vol 42 ◽  
Author(s):  
John P. A. Ioannidis
Keyword(s):  
Mental Health ◽  
Mental Disease ◽  
Brain Disorders ◽  
Social Stressors ◽  
Labor Education ◽  
Mental Diseases ◽  
Long Term Follow Up ◽  
Political Decisions

AbstractNeurobiology-based interventions for mental diseases and searches for useful biomarkers of treatment response have largely failed. Clinical trials should assess interventions related to environmental and social stressors, with long-term follow-up; social rather than biological endpoints; personalized outcomes; and suitable cluster, adaptive, and n-of-1 designs. Labor, education, financial, and other social/political decisions should be evaluated for their impacts on mental disease.

Brief summary of Kleť photographic search programme for minor planets

1999 ◽  
Vol 173 ◽  
pp. 189-192
Author(s):  
J. Tichá ◽  
M. Tichý ◽  
Z. Moravec
Keyword(s):  
Ccd Camera ◽  
Minor Planet ◽  
Minor Planets ◽  
Main Belt

AbstractA long-term photographic search programme for minor planets was begun at the Kleť Observatory at the end of seventies using a 0.63-m Maksutov telescope, but with insufficient respect for long-arc follow-up astrometry. More than two thousand provisional designations were given to new Kleť discoveries. Since 1993 targeted follow-up astrometry of Kleť candidates has been performed with a 0.57-m reflector equipped with a CCD camera, and reliable orbits for many previous Kleť discoveries have been determined. The photographic programme results in more than 350 numbered minor planets credited to Kleť, one of the world's most prolific discovery sites. Nearly 50 per cent of them were numbered as a consequence of CCD follow-up observations since 1994.This brief summary describes the results of this Kleť photographic minor planet survey between 1977 and 1996. The majority of the Kleť photographic discoveries are main belt asteroids, but two Amor type asteroids and one Trojan have been found.

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