共查询到20条相似文献,搜索用时 78 毫秒
1.
切向燃烧的电站锅炉将水平浓淡低NO_x燃烧器与顶部燃尽风同时使用,即综合空气分级燃烧技术,可有效地降低NO_x排放。对350 MW电站锅炉数值计算结果表明:常规直流煤粉燃烧器改造成低NO_x燃烧器,可降低NO排放浓度7%;对于同一种燃烧器采用OFA可降低NO排放浓度9%;同时使用低NO_x燃烧器和OFA,可降低NO排放浓度18%。水平浓淡低NO_x燃烧器与周界风偏置等设计,在提高燃烧稳定性、预防炉壁结焦腐蚀等方面有诸多优点。对造成的飞灰含碳量增加,本文给出了合理的指导建议。 相似文献
2.
在设计热功率为1 MW的热态模化实验台上,研究了带有燃尽风的径向浓淡双调风旋流燃烧器的运行特点,得到燃尽风布置的相对位置、一次风率、内二次风率、外二次风率以及二次风旋流强度对NOx生成和飞灰含碳量的影响.结果表明:旋流对冲的煤粉浓淡燃烧配合采用燃尽风(OFA)空气分级燃烧技术,对降低NOx的生成和减少飞灰含碳量非常有益;只有合理地设计和布置OFA燃烧器,才能在降低NOx生成量的同时,尽量减少飞灰含碳量;增大一次风率时,NOx的生成量先增加后减少,而飞灰含碳量先减少后增加;增加内、外二次风的旋流强度,NOx的生成量不断提高,而飞灰含碳量则呈现降低趋势. 相似文献
3.
对一台660 MW旋流对冲锅炉在不同层燃烧器组合运行工况下进行了炉内流动、燃烧和NOx排放特性的数值模拟,模拟结果与试验值相对误差小于10%。模拟结果表明:额定负荷时,5层燃烧器运行,停前墙和停后墙同层燃烧器时NOx排放和飞灰含碳量基本相同;停上层燃烧器相比于停中层燃烧器,空气分级效果强化,煤粉颗停留时间增加,NOx和飞灰含碳量分别降低9.5%和9.8%,在锅炉实际运行过程中,停上层燃烧器更有利于降低NOx排放和提高燃烧效率。 相似文献
4.
为了控制NO_x排放,在3 100 t/h锅炉上进行了燃烧优化调整试验。通过调整二次风配风方式、主燃烧器上方的OFA风门开度、锅炉运行氧量、燃烧器与燃尽风摆角开度、燃尽风率和磨煤机的投运方式等因素,研究不同工况下炉膛出口NO_x浓度及锅炉热效率变化规律。试验表明:不同的配风方式下,束腰配风工况的锅炉热效率最高,炉膛出口NO_x排放量最低。主燃烧器上方的OFA风门开度在0%~25%之间变化时,炉膛出口NO_x浓度随着OFA风门开度的变大呈下降趋势;OFA风门开度在25%~100%之间变化时,炉膛出口NO_x浓度随着OFA风门开度的变大呈上升趋势;而OFA风门开度在0%~100%之间变化时,膛出口CO的浓度随着OFA风门开度的变大呈下降趋势。锅炉运行氧量变化对燃烧器区域火焰的平均温度影响较小,随着运行氧量的增加,锅炉热效率先升高后降低,而燃料型NO_x的生成量是随着运行氧量的增加而急剧增加的。在实际运行中,燃烧器的摆角向下倾斜,燃尽风的摆角向上倾斜能够延长火焰中心,防止主燃烧区局部高温发生,可以有效的抑制热力型NO_x的产生。在燃尽风率分别为10%、15%、20%和25%时,炉膛出口CO浓度和飞灰中的含碳量随着燃尽风率的升高而增加,炉膛出口NO_x浓度和锅炉热效率则随着燃尽风份额的增加而降低。 相似文献
5.
6.
采用现场试验研究和数值模拟的方法对布置前后墙对冲燃烧器的某600Mw超临界锅炉CO和NO,的排放特性进行了研究.结果表明:锅炉尾部烟气中CO质量浓度为500~2500mg/m3,当主燃烧区过量空气系数a,为0.86~0.90时,高于该锅炉低NO。排放的设计过量空气系数(0.80),对应的燃尽风占二次风的比例约为27%~32%,NOx排放质量浓度出现拐点;锅炉的NOx排放特性与HT—NR3燃烧器的低NOx设计有关,并与该锅炉的CO排放特性呈负相关关系;在负荷为600Mw和总风量一定的工况下,当燃尽风比例从32%提高至49%时,CO排放质量浓度显著下降,飞灰可燃物浓度降低,氧气量对CO和NOx排放的影响明显减弱,但NOx排放质量浓度升高,主燃烧区侧墙高温腐蚀的风险增大. 相似文献
7.
8.
基于现场燃烧调整试验方法,对某厂1台1000MW超超临界切圆燃烧锅炉NOx的排放特性及其影响因素进行了系统的分析。针对锅炉燃烧系统的运行特点,主要进行了氧量、负荷、燃尽风量(包括AA风和OFA风)、主燃烧区燃烧器风量和配风方式、磨煤机运行组合方式、燃烧器摆角、煤质等因素的试验研究。研究结果表明:对于具有先进低NOx燃烧系统的锅炉,其锅炉负荷、锅炉燃用的煤质、运行时氧量的变化和燃烧器喷口摆角及磨煤耗机组的运行方式都是锅炉NOx排放的影响因素,其中运行时氧量的变化对NOx排放影响最重,随着氧量的增加,锅炉NOx排放浓度呈线性增加。而在保持大量燃尽风实现空气分级燃烧的条件下,主燃烧区燃烧器风量和配风方式对NOx排放浓度的影响是微弱的。 相似文献
9.
10.
11.
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
12.
《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
13.
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
14.
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
15.
16.
17.
18.
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
19.
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
20.
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