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排序方式: 共有98条查询结果,搜索用时 15 毫秒
41.
Energy from Waste – Clean,efficient, renewable: Transitions in combustion efficiency and NOx control
M.H. Waldner R. Halter A. Sigg B. Brosch H.J. Gehrmann M. Keunecke 《Waste management (New York, N.Y.)》2013,33(2):317-326
Traditionally EfW (Energy from Waste) plants apply a reciprocating grate to combust waste fuel. An integrated steam generator recovers the heat of combustion and converts it to steam for use in a steam turbine/generator set. This is followed by an array of flue gas cleaning technologies to meet regulatory limitations.Modern combustion applies a two-step method using primary air to fuel the combustion process on the grate. This generates a complex mixture of pyrolysis gases, combustion gases and unused combustion air. The post-combustion step in the first pass of the boiler above the grate is intended to “clean up” this mixture by oxidizing unburned gases with secondary air.This paper describes modifications to the combustion process to minimize exhaust gas volumes and the generation of noxious gases and thus improving the overall thermal efficiency of the EfW plant. The resulting process can be coupled with an innovative SNCR (Selective Non-Catalytic Reduction) technology to form a clean and efficient solid waste combustion system.Measurements immediately above the grate show that gas compositions along the grate vary from 10% CO, 5% H2 and 0% O2 to essentially unused “pure” air, in good agreement with results from a mathematical model. Introducing these diverse gas compositions to the post combustion process will overwhelm its ability to process all these gas fractions in an optimal manner. Inserting an intermediate step aimed at homogenizing the mixture above the grate has shown to significantly improve the quality of combustion, allowing for optimized process parameters. These measures also resulted in reduced formation of NOx (nitrogenous oxides) due to a lower oxygen level at which the combustion process was run (2.6 vol% O2, wet instead of 6.0 vol% O2, wet).This reduction establishes optimal conditions for the DyNOR? (Dynamic NOx Reduction) NOx reduction process. This innovative SNCR technology is adapted to situations typically encountered in solid fuel combustion. DyNOR? measures temperature in small furnace segments and delivers the reducing reagent to the exact location where it is most effective. The DyNOR? distributor reacts precisely and dynamically to rapid changes in combustion conditions, resulting in very low NOx emissions from the stack. 相似文献
42.
Ambio - Gaps between public policy goals and the state of the environment are often significant. However, while goal failures in environmental governance are studied in a number of disciplines, the... 相似文献
43.
Mikael Hake 《Behavioral ecology and sociobiology》1996,39(2):71-76
Relationships between social status and levels of body reserves stored by members of greenfinch (Carduelis chloris) flocks in winter were investigated. In addition, the adjustment of reserves by birds of different rank to experimental changes
in food predictability and to changed weather conditions were examined. Birds with low social status carried overall larger
body reserves than high-ranked birds. The results of the experiments suggest that this was mainly because subordinates, due
to their low priority to food access, perceived future foraging success as less predictable than dominants. In response to
severe weather, which probably increased the risk of starvation for birds, dominants temporarily increased their reserves
more than subordinates. This response also indicated that birds with low social status carried larger reserves than high-ranked
birds, and demonstrated that dominants could increase food intake when there was a risk of energetic shortfall. The results
suggest that fattening strategies in greenfinches depend on social status. In winter, subordinates may be forced to carry
larger reserves than dominants to safeguard against social constraints in access to food during critical times. As body reserves
may be costly to carry and acquire, this should reduce the probability of surviving the winter for subordinates compared to
dominants.
Received: 2 March 1995/Accepted after revision: 13 April 1996 相似文献
44.
Several ecologically and commercially important fish species spend the winter in a state of minimum feeding activity and at
lower risk of predation. To enable this overwintering behaviour, energetic reserves are generated prior to winter to support
winter metabolism. Maintenance metabolism in fish scales with body size and increases with temperature, and the two factors
together determine a critical threshold size for passive overwintering below which the organism is unlikely to survive without
feeding. This is because the energetic cost of metabolism exceeds maximum energy reserves. In the present study, we estimated
the energetic cost of overwintering from a bioenergetic model. The model was parameterised using respirometry-based measurements
of standard metabolic rate in buried A. tobianus (a close relative to A. marinus) at temperatures from 5.3 to 18.3°C and validated with two independent long-term overwintering experiments. Maximum attainable
energy reserves were estimated from published data on A. marinus in the North Sea. The critical threshold size in terms of length (L
th) for A. marinus in the North Sea was estimated to be 9.5 cm. We then investigated two general predictions: (1) Fish smaller than L
th display winter feeding activity, and (2) size at maturation of iteroparous species is larger than L
th to ensure sufficient energy reserves to accommodate both the metabolic cost of passive overwintering and reproductive investments.
Both predictions were found to be consistent with data on size at maturation and total body energy in December and February. 相似文献
45.
Juha Sipilä Pertti Auerkari Anna-Mari Heikkilä Risto Tuominen Iris Vela Jyrki Itkonen Mikael Rinne Kalevi Aaltonen 《Journal of Loss Prevention in the Process Industries》2012,25(3):617-622
While the self-heating and spontaneous combustion of coal is a known challenge at coal mines and storage sites, there are known methods for mitigating this challenge for typical open stockpile storage. However, closing the storage will reduce access for corrective action, and it is then important to manage the storage and its transport system with added attention without unduly adding cost or hindering availability. This paper aims to discuss the risk, prevention and extinguishing of fires in closed coal storage facilities, particularly in light of the experience with the Salmisaari underground rock storage facility in Finland. The observed autoignition events have indicated an array of contributing factors, some of which are unique to underground silo storage facilities. On the other hand, many features of the storage facilities can be compared with other extant closed storage systems. The factors affecting fire risk are described and the associated fault and event trees are outlined for autoignition at underground storage. Drawing upon the experiences with past events of self-heating and spontaneous combustion, recommendations are given on cost-effective preventive, corrective and other mitigating action for minimising fire risk and promoting storage availability. 相似文献
46.
Richard L. Andersson Michaela Salajkova Peter E. Mallon Lars A. Berglund Mikael S. Hedenqvist Richard T. Olsson 《Journal of Polymers and the Environment》2012,20(4):967-975
A template transfer method (TTM) and a fiber fixation technique were established for fiber handling and micro tensile stage mounting of aligned and non-aligned electrospun fiber mats. The custom-made template had been precut to be mounted on a variety of collectors, including a rapidly rotating collector used to align the fibers. The method eliminated need for direct physical interaction with the fiber mats before or during the tensile testing since the fiber mats were never directly clamped or removed from the original substrate. By using the TTM it was possible to measure the tensile properties of aligned poly(methyl methacrylate) (PMMA) fiber mats, which showed a 250?% increase in strength and 450?% increase in modulus as compared to a non-aligned system. The method was further evaluated for aligned PMMA fibers reinforced with cellulose (4 wt%) prepared as enzymatically derived nanofibrillated cellulose (NFC). These fibers showed an additional increase of 30?% in both tensile strength and modulus, resulting in a toughness increase of 25?%. The fracture interfaces of the PMMA?CNFC fibers showed a low amount of NFC pull-outs, indicating favorable phase compatibility. The presented fiber handling technique is universal and may be applied where conservative estimates of mechanical properties need to be assessed for very thin fibers. 相似文献
47.
Films of whey protein and chitosan acetic acid salt have lower oxygen permeability than, for example, ethylene-co-vinylalcohol under dry conditions, but water and water vapor seriously impair the gas barrier properties. To reduce the oxygen permeability at 90% relative humidity and the water-vapor transmission rate at 100% relative humidity, the films were coated with an alkyd, a beeswax compound, or a nitrocellulose lacquer. Permeability and transmission rate measurements were performed in accordance with standard methods and showed that the beeswax compound and the nitrocellulose were appropriate as water-vapor barriers. Overall migration to water was measured after 10 days exposure time, with the coated surface exposed to the water, showing that the alkyd-coated and the nitrocellulose-coated films were both below the safety limit for food contact. Water absorbency tests, performed by the Cobb method, showed that the films coated with the beeswax compound or with nitrocellulose lacquer exhibit lower absorbency than the alkyd-coated films. 相似文献
48.
The focus of this article is the Swedish experience of local governance and climate change, including mitigation and adaptation. The municipal response to these two challenges is set within a broader policy context that acknowledges Sweden as a pioneer in environmental governance, including its comparatively high ambitions with regard to the reduction of greenhouse ga emissions. Central-local relations in climate policy are analysed, and climate change mitigation and adaptation are exemplified by some snapshots of municipal initiatives, including the popular habit of networking between municipalities within as well as across national borders. In conclusion we briefly evaluate the Swedish local governance experience of climate change mitigation and adaptation to date as characterized by radical rhetoric and ambitious goals combined with a lot of promising initiatives, although still with fairly modest results in terms of tangible outcomes. Finally, we reflect upon what we consider to be the most important questions for future research on local governance and climate change. 相似文献
49.
50.
Lindahl P Maquet A Hult M Gasparro J Marissens G González de Orduña R 《Journal of environmental radioactivity》2011,102(2):163-169
The distribution of natural radionuclides was studied in winter wheat plants collected from three sites in Belgium during 2004-2007. Activity concentrations of 40K, 226Ra, 228Ra and 228Th in organically and conventionally grown wheat, and in the corresponding soil samples, were determined using ultra low-level gamma-ray spectrometry. The observed soil-to-wheat concentration ratios were calculated for the different parts of the wheat plant (root, stem and grain) in the two agricultural systems (organic and conventional). There were large variations in radionuclide activity concentrations between the sites and fields, but no significant difference between conventionally and organically grown wheat plants was observed. 相似文献