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Objectives: We evaluated end-tidal CO2 (etCO2), which has been proposed to assess acute hemodynamic changes, to guide percutaneous edge-to-edge mitral valve repair (PMVR) with the MitraClip system., Methods: Thirty-nine patients (aged 78 ± 14 years) undergoing PMVR for moderate-to-severe mitral regurgitation (MR) of primary and secondary etiology were included. General anesthesia was maintained with sevoflurane and constant ventilation parameters to ensure stable etCO2 tension. MR grade was determined semiquantitatively by transesophageal echocardiography by 2 experienced operators blinded to etCO2 measurements. etCO2 levels were measured 3, 5, 10, and 15 min after final MitraClip placement., Results: Overall, etCO2 increased from 32.2 ± 1.7 before to 35.4 ± 3.0, 34.6 ± 2.6, and 34.2 ± 2.4 mm Hg 3, 5, and 10 min after implantation. A significant correlation was noted between the echocardiographic reduction in MR grade and the increase in etCO2. ANOVA for repeated measures confirmed a significant increase in etCO2 after clip implantation (corrected F = 20.0; p < 0.001) and revealed a significantly greater increase in etCO2 in patients with MR reduction ≥2 grades as compared to lesser MR reductions (F = 6.47; p = 0.015). Blood pressure changes did not correlate with the degree of MR reduction., Conclusions: We observed a close correlation between the reduction in MR grade during PMVR and etCO2, which might evolve as a useful parameter to complement treatment guidance during PMVR., (© 2017 S. Karger AG, Basel.)

An ab initio density functional theory (DFT) study with correction for dispersive interactions was performed to study the adsorption of N(2) and CO(2) inside an (8, 8) single-walled carbon nanotube. We find that the approach of combining DFT and van der Waals correction is very effective for describing the long-range interaction between N(2)/CO(2) and the carbon nanotube (CNT). Surprisingly, exohedral doping of an Fe atom onto the CNT surface will only affect the adsorption energy of the quadrupolar CO(2) molecule inside the CNT (20-30%), and not that of molecular N(2). Our results suggest the feasibility of enhancement of CO(2)/N(2) separation in CNT-based membranes by using exohedral doping of metal atoms.

High-quality nanometer thick ultramicroporous membranes were prepared from silica sol-gel processes and tested for the permeation of binary gas mixtures of He, H2, CO2, and CH4 across different temperature and partial pressure regimens. Pore size distribution by molecular probing showed that the majority of pore sizes had dimensions below 2.9 A. In 50:50 binary mixtures, the fluxes of gases increased as a function of temperature, indicating an activated transport mechanism. The ultramicroporous membranes showed high selectivities at 150 degrees C for He/CO2 (30), He/CH4 (93), H2/CO2 (10), and H2/CH4 (9) with lower selectivities for CO2/CH4 (5). High activation energies (Ea) were observed for the permeance of 50:50 binary mixtures containing He and H2 of 22.1-27.5 and 17.6-23.1 kJ.mol-1, respectively. The Ea for the permeance of the total mixture approached the Ea for the permeance of the molecule with the smaller kinetic diameter (He or H2).

Abstract: Calcium based sorbents are effective for CO2 capture. In this work, a modified grain size model has been developed to simulate the carbonation behavior of a calcium–magnesium based sorbent used for CO2 capture in the calcium looping process. The sorbent particle is comprised of CaO fine particles supported on porous magnesium oxide (MgO) (CGMG) framework. The model is based on the reversible reaction between CaO and CO2 and can predict the overall calcium oxide (CaO) conversion and temperature variation inside the sorbent particle under the calcium looping conditions. The overall conversion obtained by the model shows good agreement with experimental data. The effect of several parameters is also numerically analyzed on the dynamics of CaO conversion inside the particle. The conversion of CaO mainly depends on particle size, reaction temperature, CaO content and its porosity for this particular CGMG sorbent. The carbonation reaction does not generate a significant temperature increase inside the particle with a maximum increment of below 20K. Moreover, the CGMG particle carbonation shows a two stage control behavior while the heat transfer due to convection is significant. [Copyright &y& Elsevier]

Abstract: Coal bed methane (CBM) recovery and CO2 sequestration into coal seams coupled with enhanced CBM recovery have been recognized as an economically effective and environmentally friendly technology to improve the utilization of coal reserves. However, implementation of CBM and CO2 enhanced CBM (CO2-ECBM) production involves complex deformation-flow interactions in the coal. These aspects and their fundamental understanding remain as major concerns for CBM/ECBM modeling. Increasing interest in CBM and potentially in CO2-ECBM technology requires accurate predictive modeling to minimize investment risks. This paper proposed a deformation-flow coupled model to address aspects of model improvement. This model was developed based on nonlinear elastic deformation mechanics and gas percolation theory and implemented using an established computer program named F-RFPA2D - 2D Flow-coupled Rock Failure Process Analysis code. The numerical simulations of this model were carried out according to a CO2 capture and sequestration (CCS) integrated underground coal gasification (UCG) process designed for Zhongliangshan coal mine in southwest China. The individual operations comprising (1) conventional CBM recovery and CO2 sequestration into coal and (2) the integrated operation of CBM recovery with CO2 enhancement were numerically investigated, respectively. The results show that CO2 sequestration into the coal bed promotes rapid transport of CBM towards the gas producer wells with a longer production period and can enhance coal bed methane recovery by up to 80% under the conditions of using this this study. [Copyright &y& Elsevier]

The article details a study which investigated the kinetics of binary gas displacement and Darcy flow in coal using Maxwell-Stefan (MS) diffusion theory. The study was conducted to understand the carbon dioxide (CO2)-sequestration enhanced coalbed methane (ECBM) recovery process. The bulk of coal used in the study was taken from a Bowen Basin coal mine located in Queensland. The study concluded that MS diffusion theory is best for describing diffusion of mixed gases in coals. Findings of the study are said to be of significance to modeling ternary gas mixtures in ECBM production.

CO2 sequestration in coal seams is a relatively new technique to simultaneously achieve enhanced coal bed methane production and reduced CO2 emission. In this article, we integrate understandings in individual research fields to provide improved insight into the nature of this complex process. Our current overall model constructed from a number of sub-models consists of mass transfer in four pore types, namely, fractures, micro-, meso-, and macro-pores, all having pore size dependent characteristics. Key parameters are estimated using well established methods from the general literature. Three mechanisms of coal swelling leading to permeability variations during adsorption are proposed based on molecular simulations. The macroscopic level model is validated using a true tri-axial stress coal permeameter, which provides previously unpublished, accurate dynamic measurements of systems properties in three orthogonal directions including changes to the coal matrix volume. The integrated model provides a more complete and flexible representation for this complex system. [ABSTRACT FROM AUTHOR]

Examines the membrane operating life under the cycling temperature operating conditions to verify the technology suitability for fuel cell applications. Overview of the gas permeation and separation experiments for both single-gas and synthetic reformate containing hydrogen, carbon dioxide, carbon monoxide and nitrogen; Selectivity of the membranes for gas mixtures; Number of layers and calcination procedure to coat the scaled-up tubes; Effect of temperature on selectivities.

Shale - water - CO 2 reactions may occur during CO 2 geological storage, enhanced gas recovery, enhanced oil recovery, or supercritical CO 2 fracturing. Shale-acid reactions occur during fracturing or acid stimulation. The mobilisation of metals from these processes can be an environmental concern if production water leaks or is released at surface. In addition, reactions may cause changes at the pore scale and affect gas or fluid flow. Three gas shales from the Australian Cooper Basin REM sequence were characterised for metals in minerals by synchrotron X-ray fluorescence microscopy. Metals including Zn, As, Ni, Cr were hosted in sphalerite associated with organic matter, Pb was in pyrite cement, and Mn was hosted in siderite. The shales were separately reacted with brine and supercritical CO 2 , with CO 2 -SO 2 , with dilute HCl, or with N 2 at 100 °C and 20 MPa in batch reactors. The solution pH decreased during mineral reactions releasing metals to solution with the general concentrations from reaction with HCl > CO 2 -SO 2 > CO 2 > N 2 and brine. Of the total available Pb, As, Li, and Zn in the shales, from 0 to 17%, 0.3 to 23%, 3 to 13%, and 0.4 to 28% was released to solution respectively. Corrosion of siderite and ankerite was observed after the CO 2 reactions, with precipitation of Fe-oxides. After CO 2 -SO 2 reaction siderite and ankerite were dissolved with pyrite, barite, and Fe-rich precipitates. HCl reactions resulted in complete dissolution of carbonates, with dissolution pits and no mineral precipitation observed. The changes to the fractions of gas accessible mesopores were characterised by small angle neutron scattering (SANS). The Epsilon Formation had the greatest fraction of open accessible pores in the SANS range of 10 to 150 nm, followed by the Murteree and Roseneath shale samples. After CO 2 or CO 2 -SO 2 reactions a small decrease in pore accessibility was more pronounced in the Murteree and Roseneath shales, consistent with mineral precipitation. HCl reaction resulted in opening of pores at 150 nm and closing of the smallest measured pores at 10 nm. Metals were mobilised from siderite, ankerite and sulphide minerals mainly, and were dependent on the mineral and metal content but also on the injected gas stream or fluid composition. CO 2 based fluids may result in cleaner flow back water, than HCl based fluids. Geochemical reactions during CO 2 storage or acid treatment in reactive shales cause pore changes that can affect gas migration. Mineral precipitation during CO 2 and CO 2 -SO 2 reactions can result in favourable self-sealing. [Display omitted] • Cooper Basin REM shales reacted with dilute HCl or supercritical CO 2 or CO 2 - SO 2. • XFM: As, Ni in sulphides in organic matter pores. Pb in pyrite cements. Mn, Cr in siderite. • Siderite/ankerite dissolved with HCl; or corroded with CO 2 and Fe-oxides formed. • Concentrations of metals released to solution HCl > CO 2 -SO 2 > CO 2 > N 2 and brine. • Fraction of CD 4 accessible mesopores increased on HCl reaction, decreased with CO 2. [ABSTRACT FROM AUTHOR]

During geological CO 2 storage traditionally CO 2 is injected subsurface into a high permeability reservoir capped by a low permeability seal to trap the buoyant supercritical plume. Wastewater from oil and gas production is also currently disposed of by subsurface injection into suitable reservoirs, most notably in the USA and Canada. Injection of CO 2 dissolved in water may both increase storage security by reducing vertical migration and enhancing dissolution and mineral trapping. There is potential for surface dissolution of CO 2 into wastewater that is already being stored subsurface. CO 2 -water-rock reactions in different sandstone or limestone reservoir rocks with either saline coal production water or low salinity water were geochemically modelled. The geochemical potential for mineral trapping of CO 2 , and associated changes to pH for potential reservoirs is compared. For a mineralogically clean quartz-rich saline sandstone reservoir only 0.18 and 0.20 kg/m3 CO 2 was mineral trapped as ankerite and calcite over 30 or 1000 years. Feldspars, clays and carbonate minerals were converted to kaolinite, calcite, ankerite and smectites, as pH increased to 5.65. The specific silicate minerals present controlled mineral trapping potential e.g. with an Fe-rich chlorite present rather than a clinochlore chlorite 6.3 and 6.8 kg/m3 CO 2 was trapped at 30 and 1000 years respectively as siderite and ankerite. Dissolution trapping dominated in the low salinity or limestone reservoirs with minor mineral trapping. The presence of small amounts of SO 2 or H 2 S in the CO 2 stream resulted in dissolved S sequestered as elemental S, pyrite, barite, and anhydrite. The effects of low CO 2 content or potential reservoir cooling induced by injection fluids were also investigated. The low pH of the injection fluid could potentially corrode legacy wellbores, one solution is a form of amendment such as liming to neutralise pH. [Display omitted] • Large volumes of production water are reinjected dissolved CO 2 could be co-injected. • Reservoir rock reactivity to CO 2 dissolved in production water compared. • Precipitation of smectite, kaolinite, ankerite, siderite, dawsonite in sandstones. • With H 2 S or SO 4 present S, pyrite, barite, and anhydrite precipitate trapping S. • Low pH injection fluid could be amended with liming to avoid wellbore corrosion. [ABSTRACT FROM AUTHOR]

Abstract: Carbon dioxide capturing from the flue gas of power stations is an effective way to mitigate the global warming. In order to predict the performance from startup to stable operation in CO2 absorption process, a multi-field synergy model was developed based on CO2 capture process in a packed column by means of monoethanolamine (MEA). The model suggests that the integral diffusion–reaction coefficient plays an important role in the diffusion, fluid flow, heat transfer and chemical reaction processes. The influences of the fluid flow, heat transfer and chemical reaction can be justified using corresponding synergy numbers, quantifying multi-field interactive dynamic characteristics of the CO2 capture process. The simulation shows a good agreement compared with data in the literature. The results show that the packing Reynolds number can be used as a criterion to choose the proper packing. The less the Reynolds number is, the more efficient the reaction absorption is. The average synergy number Fdc would be decreased by 20% with 6K temperature drop and be descended by 7% with the 2.5% solvent weight percentage increment, which improved the efficiency of CO2 capture by about 5% and 14%, and lowered the energy consumption by about 5%. The average synergy number Fdh would be decreased by about 8% with the 0.062mol/molMEA lean solvent loading increment, which improved the efficiency by about 15% and lowered the energy consumption by 5%. After comparing with CMR-2, Raschig rings, Berl saddles and Pall rings, the 33% less average synergy number F df of the CMR-2 packing with about 5% drop in energy consumption yields the highest efficiency of 71%, which is 10% higher than that of the Berl saddle packing. The results indicate that the proposed multi-field synergy model is an effective way to intensify the capture process as a guideline with the priority of precision and simplicity. [Copyright &y& Elsevier]

Abstract: Coal fired power generation will continue to provide energy to the world for the foreseeable future. However, this energy use is a significant contributor to increased atmospheric CO2 concentration and, hence, global warming. Capture and disposal of CO2 has received increased R&D attention in the last decade as the technology promises to be the most cost effective for large scale reductions in CO2 emissions. This paper addresses CO2 transport via pipeline from capture site to disposal site, in terms of system optimization, energy efficiency and overall economics. Technically, CO2 can be transported through pipelines in the form of a gas, a supercritical fluid or in the subcooled liquid state. Operationally, most CO2 pipelines used for enhanced oil recovery transport CO2 as a supercritical fluid. In this paper, supercritical fluid and subcooled liquid transport are examined and compared, including their impacts on energy efficiency and cost. Using a commercially available process simulator, ASPEN PLUS 10.1, the results show that subcooled liquid transport maximizes the energy efficiency and minimizes the cost of CO2 transport over long distances under both isothermal and adiabatic conditions. Pipeline transport of subcooled liquid CO2 can be ideally used in areas of cold climate or by burying and insulating the pipeline. In very warm climates, periodic refrigeration to cool the CO2 below its critical point of 31.1°C, may prove economical. Simulations have been used to determine the maximum safe pipeline distances to subsequent booster stations as a function of inlet pressure, environmental temperature and ground level heat flux conditions. [Copyright &y& Elsevier]