Regeneration Section of CO2 Capture Plant by MEA Scrubbing with a Rate-Based Model

CO2 capture from exhaust gas of power plants, natural gas and refinery gas can be successfully achieved by chemical absorption with alkanolamines. CO2 capture from exhaust gas is often obtained by absorption with monoethanolamine (MEA) which is the most frequently used solvent for this purpose. Thermodynamics, kinetics and mass transfer influence the chemical absorption process. Acidic gases and amines are weak electrolytes, which partially dissociate in the aqueous phase: the high non-ideality of the liquid phase must be properly taken into account, by employing a γ/φ method. Kinetics and mass transfer can be described using two different approaches: the “equilibrium-based stage efficiency” model or the “rate-based” one. ASPEN Plus® uses the rate-based model, but the prediction of mass transfer coefficients is based on the film theory by Lewis and Whitman, while other theories can more conveniently be used, i.e. the Eddy Diffusivity theory. Since ASPEN Plus® simulator is suitable to be user customized, it has been chosen as framework for the model proposed in this work, that was validated by comparing simulation results with experimental data of a pilot plant for the purification of exhaust gas from power plant by means of MEA washing

Regeneration section of CO2 capture plant by MEA scrubbing with a rate-based model

CO2 capture from exhaust gas of power plants, natural gas and refinery gas can be successfully achieved by chemical absorption with alkanolamines. CO2 capture from exhaust gas is often obtained by absorption with monoethanolamine (MEA) which is the most frequently used solvent for this purpose. Our paper focuses on the regeneration section, where the amine solution is separated from the absorbed CO2 and recirculated to the absorber. Since regeneration is obtained in a stripper or a distillation column, it is the most energy demanding unit of the plant, so a careful modeling is required. Thermodynamics, kinetics and mass transfer influence the chemical absorption process. Acidic gases and amines are weak electrolytes, which partially dissociate in the aqueous phase: the high non-ideality of the liquid phase must be properly taken into account, by employing a γ/φ method. Kinetics and mass transfer can be described using two different approaches: the “equilibrium-based stage efficiency” model or the “rate-based” one. ASPEN Plus® uses the rate-based model, but the prediction of mass transfer coefficients is based on the film theory by Lewis and Whitman, while other theories can more conveniently be used, i.e. the Eddy Diffusivity theory. Since ASPEN Plus® simulator is suitable to be user customized, it has been chosen as framework for the model proposed in this work, that was validated by comparing simulation results with experimental data of a pilot plant for the purification of exhaust gas from power plant

Sustainable combined production of hydrogen and energy from biomass in malaysia

This work relates to a comparison between process solutions for the production of H2 and the coproduction of H2 and energy by means of a zero emission biomass integrated gasification and a combined cycle (BIGCC) power plant. The energy production is 10 MWe, in agreement with the Small Renewable Energy Power Plant (SREP) Program, promoted by the Government of Malaysia. H2 is obtained by supercritical water gasification (SCWG), a technology of interest for the processing of biomass with high moisture content. An economic analysis has been carried out in order to demonstrate the feasibility of the process solutions and to compare their convenience. The feedstock is 280,000 t/y of Empty Fruit Bunch (EFB), a biomass obtained in the Palm Oil Industry. The location of the site is Teluk Intak District in the State of Perak (Malaysia). The processes are designed with Aspen Plus® V7.2. The aim of this work is to develop detailed process flow diagrams for the supercritical water gasification technology in order to study and compare the convenience and the sustainability of different scenarios that can be adopted in an industrial context. The processes have been developed to reach zero emissions and zero wastes. CO2 and solid residuals are recycled inside the palm oil lifecycle. A cost analysis has been performed to find out the convenience of the proposed solutions

ERK-1 MAP kinase prevents TNF-induced apoptosis through bad phosphorylation and inhibition of bax translocation in HeLa cells

Extracellular signal-regulated kinase (ERK) 1/2 signaling is involved in tumor cell survival through the regulation of Bcl-2 family members. To explore this further and to demonstrate the central role of the mitochondria in the ERK1/2 pathway we used the HeLa cellular model where apoptosis was induced by tumor necrosis factor (TNF) and cycloheximide (CHX). We show that HeLa cells overexpressing ERK-1 displayed resistance to TNF and CHX. HeLa cells overexpressing a kinase-deficient form of ERK-1 (K71R) were more sensitive to TNF and CHX. In the ERK-1 cells, Bad was phosphorylated during TNF + CHX treatment. In the HeLa wt cells and in the K71R clones TNF and CHX decreased Bad phosphorylation. ERK-1 cells treated with TNF and CHX did not release cytochrome c from the mitochondria. By contrast, HeLa wt and K71R clones released cytochrome c. Bax did not translocate to the mitochondria in ERK-1 cells treated with TNF + CHX. Conversely, HeLa wt and K71R clones accumulated Bax in the mitochondria. In the HeLa wt cells and in both ERK-1 transfectants Bid was cleaved and accumulated in the mitochondria. The caspase-8 inhibitor IETD-FMK and the mitochondrial membrane permeabilization inhibitor bongkrekic acid (BK), partially prevented cell death by TNF + CHX. Anisomycin, a c-Jun N-terminal kinases activator, increased TNF-killing. The ERK-1 cells were resistant to TNF and anisomycin, whereas K71R clones resulted more sensitive. Our study demonstrates that in HeLa cells the ERK-1 kinase prevents TNF + CHX apoptosis by regulating the intrinsic mitochondrial pathway through different mechanisms. Inhibition of the intrinsic pathway is sufficient to almost completely prevent cell death. © 2009 Wiley-Liss, Inc

Hydrogen Liquefaction: a Systematic Approach to Its Thermodynamic Modeling

In the present work, a thermodynamic approach capable of describing the hydrogen behavior during its cooling and liquefaction is proposed both for the case of catalytic ortho to para conversion occurring inside dedicated reactors and for the case of continuous conversion inside heat exchangers where the catalyst is packed on the hydrogen side. The state-of-the-art Equation of State to describe the properties of normal-, para- and ortho-hydrogen is the Helmholtz free energy explicit equation. However, it can only describe pure components and not mixtures. The novelty of the proposed approach is that it is based on the widespread Peng Robinson Equation of State and that it allows to accurately describe the calorimetric and volumetric properties of the different forms of hydrogen and their mixtures. Furthermore, it can be easily implemented in the Aspen Plus® process simulator, resulting to be useful in view of design and optimization of the hydrogen liquefaction process

Design of the CO2 Removal Section for PSA Tail Gas Treatment in a Hydrogen Production Plant

CO2 capture, storage, and, recently, utilization (CCSU) is considered effective in achieving the target of 2°C established to reduce the gradual increase in global warming. In the literature, most of research has focused on the removal of carbon dioxide from power plants, particularly those fed with coal, which account for higher amounts of CO2 emissions if compared with those fed with natural gas. CCSU in other non-power sectors is still not fully considered, while its importance in mitigating the environmental impact of industrial activities is equivalent to that of power plants. In the field of hydrogen production, treatment of gaseous streams to remove carbon dioxide is performed for producing a stream of almost pure H2 starting from syngas and for reducing carbon dioxide emissions, so that CO2 removal units can be part of different sections of the plant. In this work, a state-of-the-art steam-methane-reforming (SMR) plant for the production of 100,000 Nm3/h of hydrogen has been considered. Hydrogen is produced from syngas by employing the pressure swing adsorption (PSA) technology, and the exiting tail gas is fed to the burners of the SMR unit, after removal of carbon dioxide. This work focuses on the design of the units for the treatment of the PSA tail gas by employing an aqueous solution of methyldiethanolamine (MDEA). Simulations have been performed with the commercial process simulator ASPEN Plus®, customized by the GASP group of Politecnico di Milano for best representing both the thermodynamics of the system and the mass transfer with reaction. For the scheme composed of the absorber and the regenerator, several column configurations have been considered, and the optimal solution, which minimizes the energy requirements of the plant, has been selected

Propionibacterium acnes bacteriophages display limited genetic diversity and broad killing activity against bacterial skin isolates.

UnlabelledInvestigation of the human microbiome has revealed diverse and complex microbial communities at distinct anatomic sites. The microbiome of the human sebaceous follicle provides a tractable model in which to study its dominant bacterial inhabitant, Propionibacterium acnes, which is thought to contribute to the pathogenesis of the human disease acne. To explore the diversity of the bacteriophages that infect P. acnes, 11 P. acnes phages were isolated from the sebaceous follicles of donors with healthy skin or acne and their genomes were sequenced. Comparative genomic analysis of the P. acnes phage population, which spans a 30-year temporal period and a broad geographic range, reveals striking similarity in terms of genome length, percent GC content, nucleotide identity (>85%), and gene content. This was unexpected, given the far-ranging diversity observed in virtually all other phage populations. Although the P. acnes phages display a broad host range against clinical isolates of P. acnes, two bacterial isolates were resistant to many of these phages. Moreover, the patterns of phage resistance correlate closely with the presence of clustered regularly interspaced short palindromic repeat elements in the bacteria that target a specific subset of phages, conferring a system of prokaryotic innate immunity. The limited diversity of the P. acnes bacteriophages, which may relate to the unique evolutionary constraints imposed by the lipid-rich anaerobic environment in which their bacterial hosts reside, points to the potential utility of phage-based antimicrobial therapy for acne.ImportancePropionibacterium acnes is a dominant member of the skin microflora and has also been implicated in the pathogenesis of acne; however, little is known about the bacteriophages that coexist with and infect this bacterium. Here we present the novel genome sequences of 11 P. acnes phages, thereby substantially increasing the amount of available genomic information about this phage population. Surprisingly, we find that, unlike other well-studied bacteriophages, P. acnes phages are highly homogeneous and show a striking lack of genetic diversity, which is perhaps related to their unique and restricted habitat. They also share a broad ability to kill clinical isolates of P. acnes; phage resistance is not prevalent, but when detected, it appears to be conferred by chromosomally encoded immunity elements within the host genome. We believe that these phages display numerous features that would make them ideal candidates for the development of a phage-based therapy for acne

New transgenic reporters identify somatosensory neuron subtypes in larval zebrafish

To analyze somatosensory neuron diversity in larval zebrafish, we identified several enhancers from the zebrafish and pufferfish genomes and used them to create five new reporter transgenes. Sequential deletions of three of these enhancers identified small sequence elements sufficient to drive expression in zebrafish trigeminal and Rohon-Beard (RB) neurons. One of these reporters, using the Fru.p2x3-2 enhancer, highlighted a somatosensory neuron subtype that expressed both the p2rx3a and pkcα genes. Comparison with a previously described trpA1b reporter revealed that it highlighted the same neurons as the Fru.p2x3-2 reporter. To determine whether neurons of this subtype possess characteristic peripheral branching morphologies or central axon projection patterns, we analyzed the morphology of single neurons. Surprisingly, although these analyses revealed diversity in peripheral axon branching and central axon projection, PKCα/p2rx3a/trpA1b-expressing RB cells did not possess obvious characteristic morphological features, suggesting that even within this molecularly defined subtype, individual neurons may possess distinct properties. The new transgenes created in this study will be powerful tools for further characterizing the molecular, morphological, and developmental diversity of larval somatosensory neurons