共查询到20条相似文献,搜索用时 62 毫秒
1.
介绍天然气冷凝式余热回收原理,分析天然气燃烧产物的组成,对排烟热损失、节能量、冷凝率进行了计算和分析。结果显示,烟气中可回收的蒸气潜热达到烟气低位热值的11.2%。排烟热损失随排烟温度的升高而增加,当排烟温度低于露点温度时,排烟热损失随排烟温度的升高急剧增加,水蒸气冷凝率随排烟温度的升高而降低。此外,对这种方法降低烟气中NOX排放的环保特性也进行了探讨。 相似文献
2.
3.
燃气锅炉排烟冷凝热回收技术 总被引:4,自引:2,他引:2
通过对天然气烟气特性的分析以及对冷凝式锅炉热效率的分析和计算得出,将烟气温度降低到露点温度以下对烟气进行余热回收有重要的实际意义;冷凝式换热器就是增设在天然气锅炉尾部的余热回收装置,可以将排烟中大量的能量加以回收利用,从而达到节能环保的效果.对几种不同结构型式的冷凝换热器的传热效果、烟气阻力以及腐蚀性等问题进行了定性对比,对各种排烟余热回收技术进行了综合探讨. 相似文献
4.
5.
6.
燃气锅炉排放的烟气中含有大量的水蒸气,因排烟温度未能降到露点以下而无法有效回收水蒸气的冷凝潜热。本文采用压缩式热泵与低温空预器相结合的方式深度回收燃气锅炉烟气余热,主要研究了在不同过量空气系数下供热回水流量和供热回水温度对排烟温度、余热回收效率、热泵机组制热性能系数及水蒸气冷凝率的影响。研究结果表明:在过量空气系数为1、供热回水流量为80 t/h条件下,热泵可将供热回水温度从50.0 ℃提升至65.1 ℃,其制热性能系数为4.25;空气进、出低温空预器的温度分别为-3.8 ℃和33.0 ℃,流量为15 360 m3/h时,排烟温度从90 ℃降至20 ℃,烟气余热回收效率达到14.8%;以29 MW的燃气锅炉为研究对象,按供热面积为5.2×105m2,供暖151天计算,烟气中回收的冷凝水量为8 000 t,占锅炉补水量的54.1%;该余热回收系统的投资回收期为2.1年,压缩式热泵烟气余热回收系统节能效果显著。 相似文献
7.
8.
天然气锅炉烟气余热回收能够显著提高锅炉的热效率,节省能源降低排放。对天然气锅炉的烟气进行了分析并对不同烟气排放温度的热效率进行了计算,指出烟气的露点温度会随着过量空气系数的增大而降低;烟气排放温度在60℃以下时热效率增长迅速。对常见的冷凝式和热管式天然气锅炉烟气余热回收技术进行了研究,并分析了其优缺点。 相似文献
9.
天然气等碳氢燃料燃烧后的烟气中合有大量水蒸气,将排烟温度降低到水蒸气冷凝温度以下可回收水蒸气的冷凝潜热,锅炉热效率按低位发热量计算可超过100%.热平衡计算结果显示可以用助燃空气回收烟气的冷凝潜热,但烟气进口温度有一个上限值.将蓄热式燃烧技术用于燃气锅炉,可将烟气温度降低到冷凝温度之下.换向周期越短热效率越高,换向周期20 s时热效率可达106.7%.通过空气分级燃烧可以使烟气中NOx排放水平降低到46 mg/m3 (6%O2)左右的水平,且烟气冷凝液可吸附烟气中约14.3%的NOx. 相似文献
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.
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
17.
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
18.
19.
20.
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