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分别在五种不同条件下进行了沼气产气对比试验。试验条件分别为:干牛粪,温度为20℃,排气方式分别为持续排气、间歇排气(每天排气4次);干牛粪,温度为35℃,排气方式分别为持续排气、间歇排气;干牛粪与小麦秸秆按质量比1∶1配比的混合物,温度为35℃,排气方式为间歇排气。将原料装入100 L自动生物发酵罐中,并控制发酵温度和压力,检测发酵过程中沼气的日产气量、料液pH及产气中甲烷体积分数。结果发现,在间歇排气条件下,干牛粪与小麦秸秆混合物与相同质量的干牛粪相比总产气量提高约20%,但日产气量降低,产气周期延长近40%。相同质量的干牛粪,在35℃时发酵与在20℃时发酵相比总产气量提高约35%,高峰产气速度提高约1倍;持续排气相比于间歇排气,日产气量提高约1倍,但甲烷平均体积分数降低约10%。 相似文献
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温度和pH值对餐厨垃圾和牛粪混合厌氧发酵的影响 总被引:1,自引:0,他引:1
通过序批式厌氧发酵,以产气量、产甲烷量、厌氧发酵过程中pH值以及有机物降解程度为指标,研究了不同温度、不同初始pH值对餐厨垃圾和牛粪混合厌氧发酵的影响。试验结果表明,温度为50℃时,厌氧发酵效果最佳,其单位产气量(以VS计)为722.98 mL/g,甲烷体积分数最高达62.73%.,有机物去除率为67.5%;初始pH值为7时,厌氧发酵效果最佳,其单位产气量(以VS计)为618.23 mL/g,甲烷体积分数最高达62.4%,有机物去除率为66%。 相似文献
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将本实验室一组稳定的低温兼性厌氧纤维素降解菌系X1接种到水稻秸秆和牛粪混合沼气发酵底物中,研究其在20℃低温沼气发酵过程中对产酸、产气的影响。结果表明,底物降解时主要产生乙酸、丙酸和丁酸,使pH值下降,处理组处理12 d时乙酸、总挥发性脂肪酸及甲烷含量分别为1.22,2.23 g/L和37.50%,对照组分别为0.47,0.81 g/L和28.50%。处理12 d后随着乙酸含量的逐渐下降,甲烷含量明显提高,15 d为50.20%,24 d达到67.60%,而对照仅为35%和43.30%;总产气量处理较对照提高76.81%。由此可见,菌系X1降解纤维素类物质时为甲烷合成提供了较多的前体物质,有效地提高了甲烷含量和产气量,使产气启动期提前。 相似文献
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在温度(55±1℃)和总挥发性固体浓度(2%)为固定参数,碳氮比(C/N)为可变参数的条件下,研究了构树和牛粪、餐厨垃圾、水稻秸秆分别进行混合发酵的产气性能。研究结果表明:与单一发酵相比,混合发酵均能提高甲烷产量,当构树与餐厨垃圾混合物的C/N为20时,可获得最高的累积产甲烷量(411.71 mL/g),比构树和餐厨垃圾单独发酵时的累积产甲烷量分别提高了45.45%和12.61%;构树与餐厨垃圾、牛粪、水稻秸秆进行混合发酵时,原料之间均存在协同作用,其中,构树与水稻秸秆在C/N为15的条件下进行混合发酵时,协同指数最高,为18.69%;构树与不同废弃物的混合厌氧发酵过程符合修正Gompertz方程(R~20.97),可用该拟合方程模拟混合厌氧发酵过程。 相似文献
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《可再生能源》2013,(11)
试验研究了沼液和NaOH用于药渣堆沤预处理对发酵过程的影响,以及接种量、pH值对于产气量的影响。结果表明:药渣经过沼液堆沤预处理后即可在较短的时间内高效发酵产沼气,发酵高峰为第210天,此阶段产气为总产气量的95%以上;以秸秆沼液预处理后的药渣产气量最高,为11 940 mL,原料产气率为54.4L/kg干药渣。药渣发酵过程中无需添加畜禽粪便调节碳氮比,秸秆沼液中驯化富集的利于秸秆类物质分解的微生物可大大提高药渣的降解率。NaOH预处理可显著提高药渣的产气潜力,发酵持久且总产气量高。以质量分数5%的NaOH预处理10 d,原料(干药渣)产气率达196.8 L/kg。 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