共查询到20条相似文献,搜索用时 46 毫秒
1.
2.
针对某燃煤电厂除尘器“电改袋”后运行中出现的设备阻力较高、滤袋破损、收尘灰斗灰量不均匀问题进行分析.采用数值模拟分析方法对除尘器内部的气流组织进行模拟试验研究,结合现场实际设备建立了物理模型,对除尘空间颗粒物沉积进行了理论分析,结果表明进入除尘器的颗粒物(200 μm以下)沉降速度低于1.5 m/s.把含尘气体近似为气相气流,采用Realizable κ-ε紊流模型进行该袋式除尘器除尘空间流场计算,结果表明除尘区中间气流平均上升速度达到1.0 m/s,在该上升气流作用下大部分颗粒物难以自然沉积是造成阻力增大的主要原因之一;采用长流程设计除尘空间会造成袋底下部空间的气流速度较大,前大后小,平均相差达到4倍左右,造成滤袋收尘量后移,它是造成滤袋破损和阻力升高的主要原因;各仓室流量分配相差11%~13%及各仓室滤袋流量分配不均容易造成局部滤袋破损几率增高. 相似文献
3.
结合某电厂“上大压小”改建工程中2台600 MW机组配套电袋除尘器的实际情况,分析了滤袋材料的选择原则及更换原因,论述了袋式除尘器滤袋材料对烟气的适应性,为燃煤电厂袋式除尘器滤袋材料的选择提供参考. 相似文献
4.
5.
郑州新力电力有限公司5号炉电除尘器2003年改造为袋式除尘器,该除尘器的滤袋突破传统4年的使用寿命,已达到6年运行使用时间,经检测滤袋预期使用寿命至少还有6个月以上。着重介绍了袋式除尘器的设计、制造、安装、运行及维护管理等方面的经验,并分析研究了滤袋长寿命的成因。 相似文献
6.
7.
8.
9.
10.
11.
《Spill Science & Technology Bulletin》1999,5(2):141-151
The burning rate of a slick of oil on a water bed is calculated by a simple expression derived from a one-dimensional heat conduction equation. Heat feedback from the flame to the surface is assumed to be a constant fraction of the total energy released by the combustion reaction. The constant fraction (χ) is named the burning efficiency and represents an important tool in assessing the potential of in situ burning as a counter-measure to an oil-spill. The total heat release, as a function of the pool diameter, is obtained from an existing correlation. It is assumed that radiative heat is absorbed close to the fuel surface, that conduction is the dominant mode of heat transfer in the liquid phase and that the fuel boiling temperature remains constant. By matching the characteristic thermal penetration length scale for the fuel/water system and an equivalent single layer system, a combined thermal diffusivity can be calculated and used to obtain an analytical solution for the burning rate. Theoretical expressions were correlated with crude oil and heating oil, for a number of pool diameters and initial fuel layer thickness. Experiments were also conducted with emulsified and weathered crude oil. The simple analytical expression describes well the effects of pool diameter and initial fuel layer thickness permitting a better observation of the effects of weathering, emulsification and net heat feedback to the fuel surface. Experiments showed that only a small fraction of the heat released by the flame is retained by the fuel layer and water bed (of the order of 1%). The effect of weathering on the burning rate decreases with the weathering period and that emulsification results in a linear decrease of the burning rate with water content. 相似文献
12.
The degradation of cellulose (a substantial component of low- and intermediate-level radioactive waste) under alkaline conditions
occurs via two main processes: a peeling-off reaction and a basecatalyzed cleavage of glycosidic bonds (hydrolysis). Both
processes show pseudo-first-order kinetics. At ambient temperature, the peeling-off process is the dominant degradation mechanism,
resulting in the formation of mainly isosaccharinic acid. The degradation depends strongly on the degree of polymerization
(DP) and on the number of reducing end groups present in cellulose. Beyond pH 12.5, the OH- concentration has only a minor effect on the degradation rate. It was estimated that under repository conditions (alkaline
environment, pH 13.3-12.5) about 10% of the cellulosic materials (average DP = 1000-2000) will degrade in the first stage
(up to 105 years) by the peeling-off reaction and will cause an ingrowth of isosaccharinic acid in the interstitial cement pore water.
In the second stage (105-106 years), alkaline hydrolysis will control the further degradation of the cellulose. The potential role of microorganisms in
the degradation of cellulose under alkaline conditions could not be evaluated. Proper assessment of the effect of cellulose
degradation on the mobilization of radionuclides basically requires knowing the concentration of isosaccharinic acid in the
pore water. This concentration, however, depends on several factors such as the stability of ISA under alkaline conditions,
sorption of ISA on cement, formation of sparingly soluble ISA-salts, etc. A discussion of all the relevant processes involved,
however, is far beyond the scope of the presented overview. 相似文献
13.
Deepak Srivastava 《Journal of Polymers and the Environment》2004,12(1):27-33
Six film samples of low-density polypropylene (LDPE)/linear LDPE (LLDPE)/high-density polypropylene (HDPE) with varying ratios of LDPE (20–45 ... wt%) and LLDPE (25–50 wt%) having a fixed amount of HDPE at 30 wt% were prepared by blown film extrusion technique. The samples were aged at four different temperatures, 55°, 70°, 85°, and 100°C, for four different time periods in the interval of between 150 hours and up to 600 hours. The change in the structure of various constituents and the formation of various oxygenated (peroxy and hydroperoxy) and unsaturated groups during thermo-oxidative degradation was discussed by infrared spectroscopy. The visiosity-average molecular weight was found to have decreased slowly in the initial aging hours and temperatures, whereas it decreased by 10% with its previous value tensile strength that is, 100°C when aged for 600 hours. The tensile strength of the sample first increased by 67% at 55°C and 89% at 70°C up to 450 hours, whereas the values increased by 52.5% at 85°C and 33.9% at 100°C when aged for 150 hours and then decreased. The percentage elongation at break increased by 2.7% at 55°C and 10.7% at 70°C for 150 and 300 hours of aging, respectively, whereas the percentage decreased when aged at 85°C and 100°C for up to 600 hours of aging. The values of gel content (percent) increased and initial degradation temperature decreased with aging time and temperature. 相似文献
14.
S. Urstadt J. Augusta R. -J. Müller W. -D. Deckwer 《Journal of Polymers and the Environment》1995,3(3):121-131
Establishing carbon balances has been proven to be an applicable and powerful tool in testing biodegradability of polymers. In controlled degradation tests at a 4-L scale with the model polymer poly(-hydroxybutyrate) (PHB), it was shown that the degree of degradation could not be determined with satisfactory accuracy from CO2 release alone. Instead, the course of degradation was characterized by means of establishing carbon balances for the degradation of PHB withAcidovorax facilis and a mixed culture derived from compost. Different analytical methods for determining the different carbon fractions were adapted to the particular test conditions and compared. Quantitative determination of biomass and residual polymer were the main problems in establishing carbon balances. Amounts of biomass derived from protein measurements depend strongly on assumptions of the protein content of the biomass. Selective oxidation of biomass with hypochlorite was used as alternative, but here problems arose from insoluble metabolic products. Determination of soluble components with the method of chemical oxygen demand (COD) also includes empirical assumptions but seems acceptable if the dissolved carbon fraction is in the range of some 10% total carbon. Results confirm both analytical assays and theoretical approaches, in ending up at values very close to 100%, within an acceptable standard deviation range under test conditions comparable to standard test practice.Paper presented at the Bio/Environmentally Degradable Polymer Society—Third National Meeting, June 6–8, 1994, Boston, Massachusetts. 相似文献
15.
16.
Ülis Sõukand Pille Kängsepp Rutt Kakum Toomas Tenno Lennart Mathiasson William Hogland 《Journal of Material Cycles and Waste Management》2010,12(1):57-65
The simultaneous adsorption of copper (Cu), cadmium (Cd), nickel (Ni), and lead (Pb) ions from spiked deionized water and
spiked leachate onto natural materials (peat A and B), by-product or waste materials (carbon-containing ash, paper pellets,
pine bark, and semi-coke), and synthetic materials (based on urea-formaldehyde resins, called blue and red adsorbents) or
mixtures thereof was investigated. The adsorbents that gave the highest metal removal efficiencies were peat A, a mixture
of peat B and carbon-containing ash, and a mixture of peat A and blue. At an initial concentration of 5 mg/l for each metal,
the removal of each species of metal ion from spiked water and spiked leachate solutions was very good (>90%) and good (>75%),
respectively. When the initial concentration of each metal in the solutions was twenty times higher (100 mg/l), there was
a noticeable decrease in the removal efficiency of Cu2+, Cd2+, and Ni2+, but not of Pb2+. Langmuir monolayer adsorption capacities, qm, on peat A were found to be 0.57, 0.37, and 0.36 mmol/g for Pb2+, Cd2+, and Ni2+, respectively. The order of metal adsorption capacity on peat A was the same in the case of competitive multimetal adsorption
conditions as it was for single-element adsorption, namely Pb2+ > Cd2+ ≥ Ni2+. The results show that peat alone (an inexpensive adsorbent) is a good adsorbent for heavy metal ions. 相似文献
17.
The effects of temperature on the release of chemical components of six solid organic materials under conditions of oversaturation were investigated in this paper. The six materials were peat moss (PM), weathered coals (WC), charred rice husks (CRH), sawdust (Sd), turfgrass clippings (TC), and chicken manure (CM). Significant differences were observed in the available nitrogen and phosphorus content of the aqueous extracts of organic materials at different temperatures. The available nitrogen content in aqueous extracts of PM and WC at 25 °C was higher than that registered at 15 °C and 35 °C. Available nitrogen content in the aqueous extracts of CRH, Sd, TC, and WC at 35 °C was higher than at 15 °C and 25 °C. The available phosphorus content in the aqueous extracts of organic materials at 35 °C was higher than that available at 15 °C and 25 °C, with the exception of Sd. In addition, the release of available phosphorus in the aqueous solution of organic materials at different temperatures varied constantly for 108 h. The release of potassium (K+) and sodium (Na+) ions in the aqueous extracts of organic materials was basically steady over time, with the exception of CM. High temperature (35 °C) may significantly hasten the release of K+ from organic substrates (except for WC) with low temperatures significantly inhibiting release of K+ in Sd and CRH. High temperatures (35 °C) might significantly facilitate the release of Na+ in CM and TC. However, no significant differences were manifested in the release of Na+ from organic substrates at different temperatures, with the exception of CM and TC. Moreover, no significant differences were observed in the release of calcium, magnesium and iron ions with time, nor were there any significant differences in the contents of iron ions in the aqueous extracts of organic materials at different temperatures. The results indicate that multiple mediums should be pretreated in water for a week before being used for planting. They should be used when all mineral elements of organic materials are steady and ignoring the effect of organic mediums. 相似文献
18.
The chemical recycling of poly(lactic acid) (PLA) to its monomer is crucial to reduce both the consumption of renewable resources for the monomer synthesis and the environmental impact related to its production and disposal. In particular, the production of lactic acid from PLA wastes, rather than from virgin raw materials, it is also possible to achieve considerable primary energy savings. The focus of this work is to analyse deeply the PLA hydrolytic decomposition by means of a kinetic model based on two reactions mechanism. To this end, new experimental data have been gathered in order to investigate a wider temperature range (from 140 to 180 °C) and to extend the water/PLA ratio up to 50 % of PLA by weight. The reported results clearly highlight that more than 95 % of PLA is hydrolyzed to water-soluble lactic acid within 120 min, when it is hydrolyzed within 160–180 °C. Furthermore, the kinetic constant is highly influenced by reaction temperature. The proposed “two reactions” kinetic mechanism complies satisfactorily with the experimental data under analysis. 相似文献
19.
Somani Mohit Datta Manoj Ramana G. V. Hölzle Ingo Sundaram Ravi Sreekrishnan T. R. 《Journal of Material Cycles and Waste Management》2022,24(5):1902-1912
Journal of Material Cycles and Waste Management - This study characterizes the municipal solid waste (MSW) accumulated for more than 25 years at Bhalswa dumpsite, Delhi, India. 50... 相似文献
20.