459 research outputs found

    Operating pressure dependence of the pressurized oxy-fuel combustion power cycle

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    Oxy-fuel combustion technology is an attractive option for capturing carbon dioxide (CO2) in power generation systems utilizing hydrocarbon fuels. However, conventional atmospheric oxy-fuel combustion systems require substantial parasitic energy in the compression step within the air separation unit (ASU), the flue gas recirculation system and the carbon dioxide purification and compression unit (CPU). Moreover, a large amount of flue gas latent enthalpy, which has high water concentration, is wasted. Both lower the overall cycle efficiency. Pressurized oxy-fuel combustion power cycles have been investigated as alternatives. Our previous study showed the importance of operating pressure for these cycles. In this paper, as the extended work of our previous study, we perform a pressure sensitivity analysis to determine the optimal combustor operating pressure for the pressurized oxy-fuel combustion power cycle. We calculate the energy requirements of the ASU and the CPU, which vary in opposite directions as the combustor operating pressure is increased. We also determine the pressure dependence of the water-condensing thermal energy recovery and its relation to the gross power output. The paper presents a detailed study on the variation of the thermal energy recovery rate, the overall compression power demand, the gross power output and the overall net efficiency.Aspen Technology, Inc.Thermoflow Inc.ENEL (Firm

    Coal-CO2 Slurry Feed for Pressurized Gasifiers: Slurry Preparation System Characterization and Economics

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    AbstractGasification-based plants with coal-CO2 slurry feed are predicted to be more efficient than those with coal-water slurry feed. This is particularly true for high moisture, low rank coal such as lignite. Nevertheless, preparation of the CO2 slurry is challenging and the losses associated with this process have not been accounted for in previous analyses. This work introduces the Phase Inversion-based Coal-CO2 Slurry (PHICCOS) feeding system, in which coal-CO2 slurry is prepared at ambient temperature via coal-water slurry. Steady-state process simulation is used to estimate the performance of the proposed slurry preparation and feeding system for bituminous coal and lignite. An Integrated Gasification Combined Cycle (IGCC) power plant with carbon capture is used here as a potential application, but this concept is applicable to any high-pressure coal feeding process. The economic attractiveness of the PHICCOS feeding system is assessed through calculation of its capital costs and resulting levelized cost of electricity, relative to competing commercial technologies. The findings of this work show that the PHICCOS feeding system offers a good tradeoff between overall process performance and costs. It is the most cost-effective method for feeding lignite and the second most attractive for bituminous coal, for which the competing technology is marginally cheaper. The PHICCOS feeding system is hence the only feeding system which is consistently cost-effective across the entire coal rank spectrum and is increasingly so for high-moisture and high-ash coal

    Access to Eye Care Before and After Vision Loss: A Qualitative Study Investigating Eye Care Among Persons Who Have Become Blind

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    Navigating access to eye care requires that patients recognize the need for screening and care, employ limited financial and social resources, manage complex health insurance policies, and access specialty clinical care. We investigated the experience of patients through the progression of vision loss to blindness, utilizing qualitative methods. We conducted structured telephone interviews with 28 persons with blindness throughout Oregon. Utilizing closed and open-ended questions, we explored patient experience on the events preceding avoidable blindness. Coding for emergent themes was conducted independently by two researchers using a constant comparative method. Participants described important barriers to accessing eye care: at the systems level, lack of access to providers and treatment; at the community level, available social support and services; and at the individual level, readiness to act and trust in providers. These findings suggest that important barriers to accessing preventive eye care, early diagnosis and treatment, vocational rehabilitation, and social services often occur at multiple levels. Access to eye care should be prioritized in efforts to reduce preventable visual impairment

    Can climate models capture the structure of extratropical cyclones?

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    Composites of wind speeds, equivalent potential temperature, mean sea level pressure, vertical velocity, and relative humidity have been produced for the 100 most intense extratropical cyclones in the Northern Hemisphere winter for the 40-yr ECMWF Re-Analysis (ERA-40) and the high resolution global environment model (HiGEM). Features of conceptual models of cyclone structure—the warm conveyor belt, cold conveyor belt, and dry intrusion—have been identified in the composites from ERA-40 and compared to HiGEM. Such features can be identified in the composite fields despite the smoothing that occurs in the compositing process. The surface features and the three-dimensional structure of the cyclones in HiGEM compare very well with those from ERA-40. The warm conveyor belt is identified in the temperature and wind fields as a mass of warm air undergoing moist isentropic uplift and is very similar in ERA-40 and HiGEM. The rate of ascent is lower in HiGEM, associated with a shallower slope of the moist isentropes in the warm sector. There are also differences in the relative humidity fields in the warm conveyor belt. In ERA-40, the high values of relative humidity are strongly associated with the moist isentropic uplift, whereas in HiGEM these are not so strongly associated. The cold conveyor belt is identified as rearward flowing air that undercuts the warm conveyor belt and produces a low-level jet, and is very similar in HiGEM and ERA-40. The dry intrusion is identified in the 500-hPa vertical velocity and relative humidity. The structure of the dry intrusion compares well between HiGEM and ERA-40 but the descent is weaker in HiGEM because of weaker along-isentrope flow behind the composite cyclone. HiGEM’s ability to represent the key features of extratropical cyclone structure can give confidence in future predictions from this model

    Analysis of oxy-fuel combustion power cycle utilizing a pressurized coal combustor

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    Growing concerns over greenhouse gas emissions have driven extensive research into new power generation cycles that enable carbon dioxide capture and sequestration. In this regard, oxy-fuel combustion is a promising new technology in which fuels are burned in an environment of oxygen and recycled combustion gases. In this paper, an oxy-fuel combustion power cycle that utilizes a pressurized coal combustor is analyzed. We show that this approach recovers more thermal energy from the flue gases because the elevated flue gas pressure raises the dew point and the available latent enthalpy in the flue gases. The high-pressure water-condensing flue gas thermal energy recovery system reduces steam bleeding which is typically used in conventional steam cycles and enables the cycle to achieve higher efficiency. The pressurized combustion process provides the purification and compression unit with a concentrated carbon dioxide stream. For the purpose of our analysis, a flue gas purification and compression process including de-SO[subscript x], de-NO[subscript x], and low temperature flash unit is examined. We compare a case in which the combustor operates at 1.1 bars with a base case in which the combustor operates at 10 bars. Results show nearly 3% point increase in the net efficiency for the latter case.Aspen Technology, Inc.Thermoflow Inc

    Prospectus, October 28, 1974

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    NO TUITION HIKE, CANTEEN DISCUSSED AT BOARD MEETING; New Legislation On Students\u27 Rights and Privacy; Pre-registration Continues; Prospectus Gets Feedback On It\u27s Campus Coverage; giving up the franchise; make us a lab paper; The Short Circuit; The Kaleidoscope; Conscious Matter; A Column By And For Women; The Hocus Pocus Focus; Who Killed President Kennedy; P/C Debators Defeat U of I, Do Well At Bradley; Preparedness Program Gives Students A Chance; Child Rearing Course Here Winter Quarter; Spanish Visitors Entertain, Have Slide Show Here; Americaa\u27s \u27Holiday\u27 Really A Bad Time; Gimme That OId Time Religion; McGuinn Yawns Through Show At Ruby Gulch; Two-legged Amphibians Invade Parkland; Classified Ads; Fast Freddy\u27s Football Forecast; The History Of The Controversial Film - Salt Of The Earth ; Ski Club; S.W.A.M.P.https://spark.parkland.edu/prospectus_1974/1005/thumbnail.jp

    Nitrogen and phosphorus availability interact to modulate leaf trait scaling relationships across six plant functional types in a controlled-environment study

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    Nitrogen (N) and phosphorus (P) have key roles in leaf metabolism, resulting in a strong coupling of chemical composition traits to metabolic rates in field-based studies. However, in such studies, it is difficult to disentangle the effects of nutrient supply per se on trait-trait relationships. Our study assessed how high and low N (5 mM and 0.4 mM, respectively) and P (1 mM and 2 μM, respectively) supply in 37 species from six plant functional types (PTFs) affected photosynthesis (A) and respiration (R) (in darkness and light) in a controlled environment. Low P supply increased scaling exponents (slopes) of area-based log-log A-N or R-N relationships when N supply was not limiting, whereas there was no P effect under low N supply. By contrast, scaling exponents of A-P and R-P relationships were altered by P and N supply. Neither R : A nor light inhibition of leaf R was affected by nutrient supply. Light inhibition was 26% across nutrient treatments; herbaceous species exhibited a lower degree of light inhibition than woody species. Because N and P supply modulates leaf trait-trait relationships, the next generation of terrestrial biosphere models may need to consider how limitations in N and P availability affect trait-trait relationships when predicting carbon exchange

    Assessing the acute toxicity of insecticides to the buff-tailed bumblebee (Bombus terrestris audax)

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    The buff-tailed bumblebee, Bombus terrestris audax is an important pollinator within both landscape ecosystems and agricultural crops. During their lifetime bumblebees are regularly challenged by various environmental stressors including insecticides. Historically the honey bee (Apis mellifera spp.) has been used as an ‘indicator’ species for ‘standard’ ecotoxicological testing, but it has been suggested that it is not always a good proxy for other eusocial or solitary bees. To investigate this, the susceptibility of B. terrestris to selected pesticides within the neonicotinoid, pyrethroid and organophosphate classes was examined using acute insecticide bioassays. Acute oral and topical LD50 values for B. terrestris against these insecticides were broadly consistent with published results for A. mellifera. For the neonicotinoids, imidacloprid was highly toxic, but thiacloprid and acetamiprid were practically non-toxic. For pyrethroids, deltamethrin was highly toxic, but tau-fluvalinate only slightly toxic. For the organophosphates, chlorpyrifos was highly toxic, but coumaphos practically non-toxic. Bioassays using insecticides with common synergists enhanced the sensitivity of B. terrestris to several insecticides, suggesting detoxification enzymes may provide a level of protection against these compounds. The sensitivity of B. terrestris to compounds within three different insecticide classes is similar to that reported for honey bees, with marked variation in sensitivity to different insecticides within the same insecticide class observed in both species. This finding highlights the need to consider each compound within an insecticide class in isolation rather than extrapolating between different insecticides in the same class or sharing the same mode of action

    Post-inflationary thermalization with hadronization scenario

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    We study thermalization of the early Universe when the inflaton can decay into the Standard Model (SM) quarks and gluons, using QCD arguments. We describe the possible formation of the thermal plasma of soft gluons and quarks well before the completion of reheating. Relevant interaction rates of leading order processes and the corresponding thermalization time scale is presented. We discuss hadronization while thermalizing the decay products of the inflaton, when the reheat temperature of the Universe is below the QCD phase transition but above the temperature of the Big Bang nucleosynthesis.Comment: shortened version (8 pages), modified discussion of hadronization, conclusion unchanged, references adde
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