共查询到20条相似文献,搜索用时 296 毫秒
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选取一种典型的生物质样品(木屑),将木屑与褐煤分别以15∶85、30∶70、50∶50的质量比例混合.采用热重分析法,在某一特定升温速率下,对各种混合物样品进行热解实验,探讨了单独木屑与褐煤热解特性的差异以及它们共热解时对褐煤热解过程的影响.实验研究表明,木屑与褐煤的热解特性差异较大,木屑的热解温度低,热解反应速度较快,褐煤的热解温度高,热解速度相对较慢.木屑与褐煤共热解特性并不是单独褐煤和单独木屑的简单叠加,而且木屑与褐煤混合热解过程的放热量和木屑的混合比例关系较大. 相似文献
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在高温管式电加热炉上进行大豆秆与3种煤掺混燃烧试验,掺混比例为95∶5、90∶10、85∶15,试验温度为1250℃。采集不同燃烧过程飞灰样品,对飞灰汞含量进行测定。计算燃料单位发热量汞含量及单位发热量汞排放(称为折算汞含量与折算汞排放)。研究结果表明:随大豆秆比例的增加,掺混燃料的汞灰比无显著变化,但氯汞比增加十分显著;1号煤掺混大豆秆后Hgp含量及Hgp比率均表现为增加趋势,但2号煤、3号煤情况却不相同;随大豆秆掺混比的增加,3种煤与大豆秆掺混燃料的折算汞含量均呈下降趋势,但折算气态汞生成并不一定下降。 相似文献
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生物质与煤掺烧燃烧特性的实验研究 总被引:2,自引:0,他引:2
利用热重分析仪,在不同条件下,对单一生物质、煤及其混合物的燃烧特性进行分析,研究了木屑、稻壳、稻草及耒阳白沙煤的着火温度、燃烧最大速率温度和燃烬温度等燃烧特性参数。实验结果表明,生物质的着火温度比白沙煤低,生物质在燃烧过程中有两个明显的失重阶段,而煤只有一个明显的失重阶段。通过掺烧可以使生物质与煤的混合物着火温度降低,着火时间缩短,延长了整个燃烧的温度区间,使煤能更好地燃尽,使燃料的燃烧特性得到了优化。随着生物质掺混比例的提高,掺混样品着火点温度降低得更加明显;且生物质颗粒尺寸由R90变为R200时,同样的掺混比例下,尺寸R200的掺混样品着火温度更低。 相似文献
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为解决陆地生物质资源短缺,开发水生生物质有效替代部分陆地生物质迫在眉睫。通过热重法研究玉米秸秆和海藻共同热解的特性,重点考察掺混比例和升温速率的影响,并对混合样品的热力学特性和动力学特性进行分析。结果显示,热解分为干燥、挥发分析出及焦炭热解三个阶段。掺配后的混合样品最终失重率与最大失重速率均小于纯秸秆与纯海藻。随着海藻掺配比例的增加,可燃性指数Ca先增大后减小,燃尽特性指数K递减,热解特性指数S先增大后减小。不同升温速率工况下,在热解区间(200~600℃),随着升温速率的升高,样品的热重曲线右移,失重率越来越大,最大失重速率先减小后增大,30℃/min时最小。Ca在递减,K、S呈增加趋势。动力学研究结果表明,不同掺配比例工况下,混合样品存在明显的协同作用,降低了共热解所需活化能。在不同升温速率工况下,升温速率越大,所需要的活化能越小,样品越容易发生热解。 相似文献
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在自行设计搭建的气化实验装置上进行不同制焦条件下稻焦-大同烟煤焦的混合焦样气化特性实验。对比不同工况下气化特性曲线发现:在本实验工况下,稻-煤焦样经机械掺混后的气化特性优于相同工况下浸渍混合后的气化特性;混合后制焦所得焦样气化特性优于先制焦后混合处理所得焦样的气化特性;煤和稻焦热解温度对混焦的气化特性影响不同,热解温度对生物质焦以及随后气化特性的影响大于对煤焦的影响;无论是稻焦还是煤焦,热解时间对混焦的气化特性影响均不明显。通过上述热解条件对稻-煤气化特性的影响,为煤与生物质共气化的工业应用提供指导。 相似文献
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采用微机差热天平对稻壳、花生壳、小麦秸秆及其1:1混合样品的热解过程进行研究,并采用FWO法计算共热解反应的活化能。结果表明不同种类生物质共热解与单独热解存在相似性,可以分为干燥脱水、预热解、挥发分大量析出和残余物缓慢分解共4个阶段;3种混合样品热解的着火温度均低于单独热解时的平均值,稻壳与麦秆、花生壳与麦秆混合样品的失重率大于任意组分单独热解的平均值,活化能小于单独热解的平均值,而稻壳与花生壳混合样品的失重率小于单独热解的平均值,活化能大于单独热解时的平均值;不同种类生物质共热解过程具有明显的协同效应,且共热解的协同效应表现为两种生物质联合作用的结果,与掺混比例不存在线性叠加关系。 相似文献
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采用热重分析和色谱、质谱偶联技术,对玉米秆与三种不同变质程度的煤混合热解中产生的H2S气体进行了在线检测,研究生物质对不同煤种热解析出H2S气体的影响.研究表明:生物质与不同变质程度的煤的混合热解过程中H2S析出有着相似的规律,即生物质的加入使煤析出H2S提前,且随着生物质比例的增加,H2S在更低的温度下有较大的析出速度.生物质与煤共热解时,在380℃以前析出的H2S的浓度和析出量都比煤单独热解时的高,且随着生物质加入比例的增加而增加,这是生物质加氢作用的影响.且随着煤中含氢量的增加,生物质对煤热解过程的加氢作用表现得越不明显.生物质与不同变质程度的煤的混合热解过程中H2S析出规律是生物质加氢作用和矿物质固硫作用的综合结果. 相似文献
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Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden. 相似文献
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《热能动力工程》2014,(5)
正1 ABSTRACT To reduce the effect of global warming on our climate,the levels of CO2emissions should be reduced.One way to do this is to increase the efficiency of electricity production from fossil fuels.This will in turn reduce the amount of CO2emissions for a given power output.Using US practice for efficiency calculations,then a move from a typical US plant running at 37%efficiency to a 760℃/38.5 MPa(1 400/5 580 psi)plant running at 48%efficiency would reduce CO2emissions by 170kg/MW.hr or 25%. 相似文献
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The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°, −5°, +5°, +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods. 相似文献
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A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified. 相似文献
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As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied. 相似文献
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The physical aspects of the activation energy, in higher and high temperatures, of the metal creep process were examined. The research results of creep-rupture in a uniaxial stress state and the criterion of creep-rupture in biaxial stress states, at two temperatures, are then presented. For these studies creep-rupture, taking case iron as an example the energy and pseudoenergy activation was determined. For complex stress states the criterion of creep-rupture was taken to be Sdobyrev's, i.e. σred = σ1 β + (1 − β)σi, where: σ1-maximal principal stress, σi-stress intensity, β-material constant (at variable temperature β = β(T)). The methods of assessment of the material ageing grade are given in percentages of ageing of new material in the following mechanical properties: 1) creep strength in uniaxial stress state, 2) activation energy in uniaxial stress state, 3) criterion creep strength in complex stress states, 4) activation pseudoenergy in complex stress states. The methods 1) and 3) are the relatively simplest because they result from experimental investigations only at nominal temperature of the structure work, however, for methods 2) and 4) it is necessary to perform the experimental investigations at least at two temperatures. 相似文献
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Jaime Massanet-Nicolau Alan Guwy Richard Dinsdale Giuliano Premier Sandra Esteves 《International Journal of Hydrogen Energy》2010
Hydrogen was produced from primary sewage biosolids via mesophilic anaerobic fermentation in a continuously fed bioreactor. Prior to fermentation the sewage biosolids were heated to 70 °C for 1 h to inactivate methanogens and during fermentation a cellulose degrading enzyme was added to improve substrate availability. Hydraulic retention times (HRT) of 18, 24, 36 and 48 h were evaluated for the duration of hydrogen production. Without sparging a hydraulic retention time of 24 h resulted in the longest period of hydrogen production (3 days), during which a hydrogen yield of 21.9 L H2 kg−1 VS added to the bioreactor was achieved. Methods of preventing the decline of hydrogen production during continuous fermentation were evaluated. Of the techniques evaluated using nitrogen gas to sparge the bioreactor contents proved to be more effective than flushing just the headspace of the bioreactor. Sparging at 0.06 L L min−1 successfully prevented a decline in hydrogen production and resulted in a yield of 27.0 L H2 kg−1 VS added, over a period of greater than 12 days or 12 HRT. The use of sparging also delayed the build up of acetic acid in the bioreactor, suggesting that it serves to inhibit homoacetogenesis and thus maintain hydrogen production. 相似文献