A study of CO2 capture in advanced IGCC systems by ammonia scrubbing

AbstractThis paper deals with post-combustion CO2 capture by aqueous ammonia in air-blown gasification-based combined cycles and follows previous authors’ investigations of CO2 capture by MEA scrubbing. Based on the calculations, CO2 capture seems to be more penalizing when realized by chilled ammonia instead of MEA. As a matter of fact, chilling down to 7°C both the exhaust gas and the ammonia solution results in significant power consumption of chillers, which is only partly balanced by the lower consumption for CO2 compression and lower steam extraction from the bottoming cycle compared to the MEA case. Cases with cooled instead of chilled ammonia are investigated as well. In particular, raising the process temperature up to 20°C seems to be an interesting solution, since temperature control in the absorber can be realized by passing the aqueous ammonia solution through an heat exchanger, using ambient-temperature water as refrigerant medium and removing the chillers from the system

A comprehensive modeling of the hybrid temperature electric swing adsorption process for CO 2 capture

Adsorption technologies provide high selectivity and low energy consumption making this technique very attractive to be employed in post-combustion carbon capture. In this publication, a material made of activated carbon and zeolite 13X is considered for a hybrid process termed Temperature Electric Swing Adsorption (T/ESA). This hybrid T/ESA can work as a traditional Temperature Swing Adsorption (TSA) heated by hot gas, but can also increase the temperature of the adsorbent very fast by Joule effect as long as the activated carbon provides a continuous conductive matrix for electricity. This paper discusses a detailed modeling of the T/ESA process when applied to three cases. The first case is the simulation of the T/ESA process with exhaust with 12% of CO2 concentration, which has been chosen to validate the model against literature results. The second and third case studies consider the T/ESA application in a natural gas combined cycle (NGCC) traditional power plant, and in a NGCC plant with exhaust gas recycle (EGR). These cases were selected to investigate the adsorption technology at low CO2 concentration and quantify the benefit of the EGR for carbon capture applications. Starting from an NGCC overall electric efficiency of 58.3% LHV based, the efficiency of the NGCC with T/ESA technology reduces to 35.3% while with EGR is 38.9% against the 49.9% with the MEA absorption plant. The same results are confirmed by the SPECCA index 13.05 MJLHV/kgCO2 to 9.64 MJLHV/kgCO2 against the reference of 3.36 MJLHV/kgCO2. The energy penalty of the T/ESA is significant because of electric consumptions required for the heating and fast cooling of the adsorbent

Emergency transapical mitral valve-in-valve implantation for bioprosthesis failure: Transapical implantation of an Edwards Sapien-XT in a dysfunctional mitral bioprosthesis in a critical patient

Background: Valve-in-Valve (VIV) Transcatheter Aortic Valve Replacement (TAVR) is now the treatment of choice in high-surgical-risk patients with failing aortic bioprosthesis. Although less performed, VIV-Transcatheter Mitral Valve Replacement (TMVR) is a valid treatment option for selected high-risk patients with degenerated mitral bioprostheses. Several cases of elective ViV- TAVR and -TMVR have been reported but only few were performed in critical hemodynamic conditions. Case presentation: We report the case of a patient underwent balloon-expandable transapical mitral valve-in-valve implantation in an emergency setting due to a severe stenosis of a bioprosthesis in mitral position. The procedure was successfully performed, with no residual mitral regurgitation or paravalvular leaks, and uneventful. Conclusion: Transcatheter transapical mitral valve-in-valve implantation could represent a feasible and effective strategy even in critical setting

Abnormal DNA Methylation Induced by Hyperglycemia Reduces CXCR 4 Gene Expression in CD 34+ Stem Cells

Background CD 34+ stem/progenitor cells are involved in vascular homeostasis and in neovascularization of ischemic tissues. The number of circulating CD 34+ stem cells is a predictive biomarker of adverse cardiovascular outcomes in diabetic patients. Here, we provide evidence that hyperglycemia can be "memorized" by the stem cells through epigenetic changes that contribute to onset and maintenance of their dysfunction in diabetes mellitus. Methods and Results Cord-blood-derived CD 34+ stem cells exposed to high glucose displayed increased reactive oxygen species production, overexpression of p66shc gene, and downregulation of antioxidant genes catalase and manganese superoxide dismutase when compared with normoglycemic cells. This altered oxidative state was associated with impaired migration ability toward stromal-cell-derived factor 1 alpha and reduced protein and mRNA expression of the C-X-C chemokine receptor type 4 ( CXCR 4) receptor. The methylation analysis by bisulfite Sanger sequencing of the CXCR 4 promoter revealed a significant increase in DNA methylation density in high-glucose CD 34+ stem cells that negatively correlated with mRNA expression (Pearson r=-0.76; P=0.004). Consistently, we found, by chromatin immunoprecipitation assay, a more transcriptionally inactive chromatin conformation and reduced RNA polymerase II engagement on the CXCR 4 promoter. Notably, alteration of CXCR 4 DNA methylation, as well as transcriptional and functional defects, persisted in high-glucose CD 34+ stem cells despite recovery in normoglycemic conditions. Importantly, such an epigenetic modification was thoroughly confirmed in bone marrow CD 34+ stem cells isolated from sternal biopsies of diabetic patients undergoing coronary bypass surgery. Conclusions CD 34+ stem cells "memorize" the hyperglycemic environment in the form of epigenetic modifications that collude to alter CXCR 4 receptor expression and migration

Impact of Fractional Flow Reserve Derived from Coronary Computed Tomography Angiography on Heart Team Treatment Decision-Making in Patients with Multivessel Coronary Artery Disease: Insights from the SYNTAX III REVOLUTION Trial

Background: Fractional flow reserve (FFR) is a reliable tool for the functional assessment of coronary stenoses. FFR computed tomography (CT) derived (FFRCT) has shown to be accurate, but its clinical usefulness in patients with complex coronary artery disease remains to be investigated. The present study sought to determine the impact of FFRCT on heart team's treatment decision-making and selection of vessels for revascularization in patients with 3-vessel coronary artery disease. Methods: The trial was an international, multicenter study randomizing 2 heart teams to make a treatment decision between percutaneous coronary interventions and coronary artery bypass grafting using either coronary computed tomography angiography or conventional angiography. The heart teams received the FFRCT and had to make a treatment decision and planning integrating the functional component of the stenoses. Each heart team calculated the anatomic SYNTAX score, the noninvasive functional SYNTAX score and subsequently integrated the clinical information to compute the SYNTAX score III providing a treatment recommendation, that is, coronary artery bypass grafting, percutaneous coronary intervention, or equipoise coronary artery bypass grafting-percutaneous coronary intervention. The primary objective was to determine the proportion of patients in whom FFRCT changed the treatment decision and planning. Results: Overall, 223 patients were included. Coronary computed tomography angiography assessment was feasible in 99% of the patients and FFRCT analysis in 88%. FFRCT was available for 1030 lesions (mean FFRCT value 0.64\ub113). A treatment recommendation of coronary artery bypass grafting was made in 24% of the patients with coronary computed tomography angiography with FFRCT. The addition of FFRCT changed the treatment decision in 7% of the patients and modified selection of vessels for revascularization in 12%. With conventional angiography as reference, FFRCT assessment resulted in reclassification of 14% of patients from intermediate and high to low SYNTAX score tertile. Conclusions: In patients with 3-vessel coronary artery disease, a noninvasive physiology assessment using FFRCT changed heart team's treatment decision-making and procedural planning in one-fifth of the patients

Techno-economic assessment of the FReSMe technology for CO2 emissions mitigation and methanol production from steel plants

The iron and steel industry accounts for 6 % of the global CO2 emissions and it is one of the main hard-to-abate sectors that must be un-locked to reach climate neutrality in the coming decades. The objective of this work is to assess the economics of the FReSMe (From Residual Steel gases to Methanol) process for reducing the carbon footprint of conventional steel plants based on the Blast Furnace route. This reduction is achieved by capturing and converting part of the steel plants residual gases into methanol. The process includes the Sorption Enhanced Water Gas Shift (SEWGS) technology to treat the residual gases separating the CO2 and producing a H2-rich stream. The latter can be recirculated back to the steel plant to cover part of its primary energy demand or reacted together with part of the separated CO2 to synthetize methanol. The CO2 excess can be used for underground storage. Four different process configurations with different methanol production capacities are investigated. Costs and performances of each configuration are assessed and compared to two reference cases. Results show that the FReSMe process allows to avoid around the 60 % of the overall steel plant CO2 emissions, while the reference plant with post-combustion capture in the power section only 18 %. The cost of CO2 avoided is in the range 40.6 €/tCO2 – 46.2 €/tCO2. When no carbon tax is considered, the optimal methanol production capacity results 600 t/day with a Levelized Cost of Hot Rolled Coil of around 520 €/tHRC, 9.4 % higher than in the base case (476 €/tHRC). With a carbon tax rate above 40.6 €/tCO2, the optimal configuration has a methanol production capacity of 300 t/day and it ensures higher emissions reduction and lower costs than conventional post-combustion carbon capture systems