546 research outputs found
Emission Minimization of a Two-Stage Sour Water Stripping Unit Using Surrogate Models for Improving Heat Duty Control
Sour water are aqueous waste streams from oil refining operations, heavily contaminated with hydrogen sulfide and ammonia, which need to be stripped before reuse or disposal, avoiding damages to process and environment. Two-stage sour water stripper units are the most common technology to treat sour water for hydrogen sulfide and ammonia
separation to produce reusable water and send these species respectively to Claus and ammonia plants. The first stage of a two-stage sour water unit is responsible for properly splitting hydrogen sulfide and ammonia. This work uses surrogate models to predict the limiting point of hydrogen sulfide separation in the first stage of a sour water unit,
allowing more efficient heat duty control strategies to achieve the difficult split of hydrogen sulfide and ammonia and simultaneously lowering heat consumption. Failure of compliance to this limit results in unspecified stripped gas from the first stage, impeding it to directed to Claus plant, entailing loss of sulfur production and higher load of pollutant emissions from flared gases. Therefore, a precise surrogate predictor was developed to dynamically define a quasi-optimum set-point to the controller of the first stage reboiler duty based on dynamic disturbances – the first stage input factors to the surrogate model, such as hydrogen sulfide and ammonia contents of the sour water. The new control policy outperformed the traditional first stage ratio control in terms of stripped gas composition and plant stability
Environmental Performance of a Solid Waste Monetization Process Applied to a Coal-Fired Power Plant with Semi-Dry Flue Gas Desulfurization
Mixing of semi-dry flue gas desulfurization solids and fly-ash from coal-fired power plants results in a solid waste contaminated by calcium sulfite. Therefore, it becomes useless for industry and is often landfilled. To support decision-making on process configurations to monetize this solid residue a gate-to-gate life cycle assessment was performed, considering three scenarios: BASE case – standard 360 MW power plant,
CASE I – base plant adopting dry thermal oxidation treatment of spray dryer solids, CASE II ‒ bypass of desulfurization system. Cases I and II allow commercialization of the solid residue as class C fly-ash. Evaluated alternatives were compared based on quantitative potential environmental impacts, using United States Environmental Protection Agency waste reduction algorithm. Based on the results, the BASE case was more aggressive to the environment, due to solid waste production. CASE II increased photochemical oxidation and acidification potentials. CASE I was the more environmentally friendly but demands additional capital and operational expenditure
IPC02-27145 A TIME SERIES APPROACH FOR PIPE NETWORK SIMULATION
ABSTRACT We applied time series predicting tools for the simulation of the temporal behavior of large pipeline networks submitted to timely changing inputs. The inputs may consist of a set of specified flow rates at client or supply nodes, while the outputs are another set of nodal pressures and internal flow rates. According to the topology, size, age and history of the network, the continuous generation of phenomenological dynamic simulations may be impossible, imprecise or numerically expensive, demanding thus alternative approaches. Our methodology is particularly oriented to this kind of demand. From recorded network past data covering relevant history of inputs and selected outputs, ARX-MIMO predictors are built with identification methods and launched for continuous estimation of the network outputs one time step ahead. Results are precise enough for engineering, training and monitoring applications
A Monte Carlo Methodology for Environmental Assessment Applied toOffshore Processing of Natural Gas with High Carbon Dioxide Content
Offshore production of oil and natural gas with high carbon dioxide content and high gas-to-oil ratio entail stringent processing conditions that require innovations and first-of-a-kind designs, which bear uncertainties derived from the scarcity of commercial-scale projects, hindering to move along technology learning curves. Consequently, unpredicted scenarios and unachieved specifications cause economic and
environmental losses. Such uncertainties force offshore plants to be designed under stochastic factors seeking best statistical performance. The Monte Carlo Method is suitable to such finality. This work proposes a computer-aided engineering framework ‘MCAnalysis’ automatically applying a probabilistic environmental assessment of offshore gas processing. ‘MCAnalysis’ integrates HYSYS simulator with ‘Waste
Reduction Algorithm’ to assess potential environmental impacts, whose most relevant categories were identified via Principal Component Analysis. An offshore plant processing natural gas with high carbon dioxide content was submitted to probabilistic raw gas flow rate under two scenarios of carbon dioxide content. The higher carbon dioxide content scenario presented the highest probabilistic potential environmental impacts, being the atmospheric category the most relevant
Physical and chemical properties, pectinases activity, and cell wall pectin of Acidulus, Momordica, Inodorus and Cantalupensis melons with different ripening degree at harvest
The objective of the present study was to evaluate the physical and chemical changes, pectinases activity, and cell wall pectin in melon varieties Acidulus (access 16), Momordica (access 2), Inodorus (cv. ‘Iracema’) and Cantalupensis (cv. ‘Olympic’), in the relation of ripening degree at harvest. Melon fruits were planted and evaluated with different ripening degree at harvest, from 15 to 35 days after anthesis (DAA). The fruits, arranged in a completely randomized design, had been evaluated on the harvest days to physical and chemical characteristics. We evaluate pectin methylesterase, polygalacturonase, beta-galactosidase, and pectin contents (water-soluble, chelate soluble, and sodium carbonate soluble). The ideal harvest for each melon was, 35 days after anthesis for cv ‘Iracema’, 30 days after anthesis for cv. ‘Olympic’, 30 days after anthesis for access 16, and 20 days after anthesis for access 2. High pulp firmness of access 16 is associated with the high levels of sodium carbonate soluble pectin and low levels of polygalacturonase and beta-galactosidase activity. Momordica melon fruit cracking is related to the high levels of pectinases activity, as well as pectin degradation
Hypoglycemic and anti-lipemic effects of the aqueous extract from Cissus sicyoides
BACKGROUND: Cissus sicyoides (Vitaceae) is a medicinal plant popularly known in Brazil as "cipó-pucá, anil-trepador, cortina, and insulina". The plant is used in several diseases, including rheumatism, epilepsy, stroke and also in the treatment of diabetes. In the present work, we studied the hypoglycemic and anti-lipemic effects of the aqueous extract prepared from fresh leaves of the plant (AECS), in the model of alloxan-induced diabetes in rats. In addition, hepatic enzyme levels were also determined. RESULTS: Results showed that the daily treatment of diabetic rats with AECS for 7 days (100 and 200 mg/kg, p.o.) significantly decreased blood glucose levels in 25 and 22% respectively, as compared to the same groups before AECS treatment. No significant changes were seen in control diabetic rats before (48 h after alloxan administration) and after distilled water treatment. While no changes were seen in total cholesterol levels, a significant decrease was observed in plasma triglyceride levels, in the alloxan-induced diabetic rats after AECS treatment with both doses, as compared to the same groups before treatment. Significant decreases in blood glucose (25%) and triglyceride levels (48%) were also observed in the alloxan-induced diabetic rats after 4 days treatment with AECS (200 mg/kg, p.o.). Aspartate (AST) and alanine (ALT) aminotransferases levels, in diabetic controls and AECS-treated rats, were in the range of reference values presented by normal rats. CONCLUSIONS: The results justify the popular use of C. sicyoides, pointing out to the potential benefit of the plant aqueous extract (AECS) in alternative medicine, in the treatment of type 2 diabetes mellitus
Community structure of shallow rocky shore fish in a tropical bay of the southwestern Atlantic
Os costões rochosos do Atlântico Sul Ocidental sustentam ricas comunidades de peixes recifais. Apesar disso, o conhecimento sobre essas comunidades em zonas tropicais continua escasso, especialmente no Brasil. No presente trabalho avaliamos parâmetros das comunidades de peixes recifais, tais como composição e estrutura trófica, além de sua interação com variáveis físicas e bióticas, em quatro costões rochosos tropicais na Baía de Todos os Santos, costa leste do Brasil. Durante seis meses 80 censos visuais foram realizados, nos quais 3.582 peixes pertencentes a 76 espécies foram registrados. Os peixes herbívoros territoriais e as algas filamentosas dominaram em todos os costões. A variação espacial na estrutura da comunidade de peixes esteve relacionada com a composição bêntica e profundidade. A elevada abundância observada de peixes herbívoros territoriais e invertívoros móveis pode ser devido à alta cobertura de algas filamentosas e à baixa profundidade e exposição às ondas. Além disso, esse padrão também pode ser explicado pela baixa densidade de herbívoros errantes e grandes carnívoros, provavelmente devido à intensa pressão da atividade pesqueira. Assim, novos estudos são necessários para avaliar o real estado de conservação destes ambientes, uma vez que estão localizados em posição singular na Baía de Todos os Santos, conectando recifes internos e externos da área.Southwestern Atlantic Ocean rocky shores sustain important reef fish communities. However, those communities in tropical regions are not well understood, especially in Brazil. In this present article we assess community parameters of reef fishes such as composition, trophic organization and their relationships with physical and biological factors on four tropical rocky shores in Todos os Santos Bay, southwestern Atlantic. During six months, a total of 80 visual censuses were performed, in which 3,582 fish belonging to 76 species were recorded. Territorial herbivorous fish and turf algae were dominant at all the sites. The spatial variability of fish community structure was related to the benthic cover composition and depth. The high abundance of territorial herbivores and mobile invertebrate feeders could be associated with high levels of turf cover, low wave exposure and shallow waters. Moreover, this fact could be a consequence of the low density of roving herbivores and large carnivores probably due to the pressure of intense fishing activity. Thus complementary studies are needed to evaluate the actual conservation status of these rocky shore reefs, singularly located habitats connecting inner and outer reefs in Todos os Santos Bay
On the behaviour of spin-orbit connection of exoplanets
Star-planet interactions play, among other things, a crucial role in
planetary orbital configurations by circularizing orbits, aligning the star and
planet spin and synchronizing stellar rotation with orbital motions. This is
especially true for innermost giant planets, which can be schematized as binary
systems with a very large mass ratio. Despite a few examples where spin-orbit
synchronization has been obtained, there is no demographic study on synchronous
regimes in those systems yet. Here we use a sample of 1,055 stars with
innermost planet companions to show the existence of three observational loci
of star-planet synchronization regimes. Two of them have dominant fractions of
subsynchronous and supersynchronous star-planet systems, and a third less
populated regime of potentially synchronized systems. No synchronous
star-planet system with a period higher than 40 days has been detected yet.
This landscape is different from eclipsing binary systems, most of which are
synchronized. We suggest that planets in a stable asynchronous spin state
belonging to star-planet systems in a supersynchronized regime offer the most
favourable conditions for habitability.Comment: 15 pages, 1 figure in main paper, 6 supplementary figures. Published
in Nature Astronomy, May 202
A complete model of the Plasmodium falciparum bifunctional enzyme dihydrofolate reductase-thymidylate synthase: a model to design new antimalarials
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