CO2 capture from natural gas combined cycles by CO2 selective membranes

This paper performs a techno-economic analysis of natural gas-fired combined cycle (NGCC) power plants integrated with CO2 selective membranes for post-combustion CO2 capture. The configuration assessed is based on a two-membrane system: a CO2 capture membrane that separates the CO2 for final sequestration and a CO2 recycle membrane that selectively recycles CO2 to the gas turbine compressor inlet in order to increase the CO2 concentration in the gas turbine flue gas. Three different membrane technologies with different permeability and selectivity have been investigated. The mass and energy balances are calculated by integrating a power plant model, a membrane model and a CO2 purification unit model. An economic model is then used to estimate the cost of electricity and of CO2 avoided. A sensitivity analysis on the main process parameters and economic assumptions is also performed. It was found that a combination of a high permeability membrane with moderate selectivity as a recycle membrane and a very high selectivity membrane with high permeability used for the capture membrane resulted in the lowest CO2 avoided cost of 75 US$/tCO2. This plant features a feed pressure of 1.5 bar and a permeate pressure of 0.2 bar for the capture membrane. This result suggests that membrane systems can be competitive for CO2 capture from NGCC power plants when compared with MEA absorption. However, to achieve significant advantages with respect to benchmark MEA capture, better membrane permeability and lower costs are needed with respect to the state of the art technology. In addition, due to the selective recycle, the gas turbine operates with a working fluid highly enriched with CO2. This requires redesigning gas turbine components, which may represent a major challenge for commercial deployment

Placental thrombomodulin expression in recurrent miscarriage

<p>Abstract</p> <p>Background</p> <p>Early pregnancy loss can be associated with trophoblast insufficiency and coagulation defects. Thrombomodulin is an endothelial-associated anticoagulant protein involved in the control of hemostasis and inflammation at the vascular beds and it's also a cofactor of the protein C anticoagulant pathway.</p> <p>Discussion</p> <p>We evaluate the Thrombomodulin expression in placental tissue from spontaneous recurrent miscarriage and voluntary abortion as controls. Thrombomodulin mRNA was determined using real-time quantitative polymerase chain reaction. Reduced expression levels of thrombomodulin were found in recurrent miscarriage group compared to controls (1.82-fold of reduction), that corresponds to a reduction of 45% (from control group Delta CT) of thrombomodulin expression in spontaneous miscarriage group respect the control groups.</p> <p>Summary</p> <p>We cannot state at present the exact meaning of a reduced expression of Thrombomodulin in placental tissue. Further studies are needed to elucidate the biological pathway of this important factor in the physiopathology of the trophoblast and in reproductive biology.</p

Post-combustion CO2 capture from natural gas combined cycles by solvent supported membranes

AbstractAmong the CO2 separation technologies, CO2 membranes are currently receiving an increasing interest, largely thanks to the development of solvents such as ionic liquids and deep eutectic solvents, which are suitable for use in solvent supported membrane systems. The aim of this work is to perform a techno-economic analysis of a natural gas-fired combined cycle power plant integrating CO2 membranes. Such a configuration is based on a two-membrane system, the first one separating the CO2 for final sequestration, the second one used to generate a selective CO2-rich flue gas recycle. The techno-economic assessment uses three modelling tools: (i) process modelling of the complete power plant, performed with the in-house GS code and Aspen Plus, (ii) modelling of the membrane, performed with a finite difference method implemented in Matlab and (iii) economic modelling by a bottom-up approach. The final material balances show that using a moderate pressurization of the combined cycle flue gas results in the lowest energy loss and lowest capture cost

Techno-economic assessment of two novel feeding systems for a dry-feed gasifier in an IGCC plant with Pd-membranes for CO2 capture

This study focuses on the application of Pd-based membranes for CO[subscript 2] capture in coal fueled power plants. In particular, membranes are applied to Integrated Gasification Combined Cycle with two innovative feeding systems. In the first feeding system investigated, CO[subscript 2] is used both as fuel carrier and back-flushing gas for the candle filters, while in the second case N[subscript 2] is the fuel carrier, and CO[subscript 2] the back-flushing gas. The latter is investigated because current dry feed technology vents about half of the fuel carrier, which is detrimental for the CO[subscript 2] avoidance in the CO[subscript 2] case. The hydrogen separation is performed in membrane modules arranged in series; consistently with the IGCC plant layout, most of the hydrogen is separated at the pressure required to fuel the gas turbine. Furthermore, about 10% of the overall hydrogen permeated is separated at ambient pressure and used to post-fire the heat recovery steam generator. This layout significantly reduces membrane surface area while keeping low efficiency penalties. The resulting net electric efficiency is higher for both feeding systems, about 39%, compared to 36% of the reference Selexol-based capture plant. The CO[subscript 2] avoidance depends on the type of feeding system adopted, and its amount of vented gas; it ranges from 60% to 98%. From the economic point of view, membrane costs are significant and shares about 20% of the overall plant cost. This leads in the more optimistic case to a CO[subscript 2] avoidance cost of 35 €/t[subscript CO2], which is slightly lower than the reference case.Seventh Framework Programme (European Commission) (Grant agreement no. 241342

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

High fidelity model of the oxygen flux across ion transport membrane reactor: Mechanism characterization using experimental data

As a consequence of growing energy demand and expanded use of fossil fuels, CO2 level in the atmosphere has risen in the last couple of centuries. The principal effect of these anthropologic emissions of greenhouse gases is global warming. In the last years, there has been much effort on finding a long term solution to this problem, mostly based on clean power technologies. In order to reduce green-house gas emissions different technologies to capture CO2 are under investigation. One of the most promising technologies is oxy-combustion using ITM (ion transport membranes) used in air separation units or integrated directly in reactors. This work presents a model for the integration of dense oxygen membrane modules in air separation units. An axially resolved model for the distribution of oxygen concentration is developed, incorporating a model of the oxygen flux across membrane surface and its dependency on the local conditions, which satisfies the conservation equations of mass and energy. The oxygen flux model is based on accurate experimental measurements and incorporates the effects of chemistry at the surface and diffusion in the bulk material, as well as heat and mass transport on the feed and sweep side

Efficient low CO₂ emissions power generation by mixed conducting membranes

AbstractThis papers aims at the performance assessment of large scale, natural gas fired power plants where O2 and H2 sepa- ration membranes developed inside the DEMOYS project are implemented to make pre-combustion CO2 removal less energy demanding and more cost effective. Three different plant configurations are considered. Their heat and mass balance have been simulated and performance compared versus those achievable by equivalent plants based on commercially available technologies

Efficient low CO₂ emissions power generation by mixed conducting membranes

The integration of gas separation membranes in the energy sector has been actively investigated in the recent years because it has the potential to provide novel plant configurations that achieve improved performanceat lower investment costs than conventional designs. In particular, carbon capture is probably the most promising application of membranes in the energy sector. Therefore extensive research programsfinalized to CCS focused on different membrane technologies, able to permeate different chemical species,relying on different transport mechanisms and operating at different temperatures.DEMOYS (Dense Membranes for Efficient Oxygen and Hydrogen Separation) is a project co-financed by the European Commission run by a consortium, led by RSE, joining 15 partners from 6 Europeancountries. The project essentially aims at the development of thin mixed conducting membranes for O2