天然气全氧燃烧尾气生活垃圾气化热力学分析

基于Aspen Plus模拟平台,运用吉布斯能最小化原理,以天然气全氧燃烧尾气（后续称为烟气）作为气化剂,选取反应温度和烟气流量与生活垃圾量比（E/M）作为影响因素,气化炉温度变化范围为400~1 500℃,E/M范围0~3.0,对几种典型生活垃圾（木屑、纸屑、塑料、橡胶和厨余）气化进行模拟计算。模拟结果表明,以烟气作为生活垃圾气化剂,可制备富氢产品气,产品气为中热值燃气。温度在800℃左右时,H2的体积分数达到峰值46.75%,反应温度大于800℃时,反应温度的增加对提升产品气的热值、CO的含量有一定作用,但H2的含量和产品气产率有所下降,反应温度过高增加气化的能源投入,反应温度应控制在800~1 000℃范围。高温烟气的过量导致产品气热值和品质下降,E/M宜控制在0.4~1.0区间范围。     

基于Aspen Plus的水泥窑协同处置市政污泥烟气排放特性分析及工艺优化

利用Aspen Plus软件建立了水泥窑协同处置市政污泥的工艺模型,定量分析污泥进料量和含水率对 日产万吨熟料的生产线中烟气排放规律、分解炉炉温及煤耗的影响.结果表明:含水率60％的污泥,进料量由1 t/h增加至20 t/h,出口烟气中NO、SO2浓度分别由205.5,26.5 mg/m3变化至56.7,26.8 mg/m3;进料量10 t/h的污泥,含水率由10％提高至90％,烟气中NO由136.5 mg/m3降低到133.1 mg/m3,后又提高至134.6 mg/m3,SO2从27.4 mg/m3降低到26.2 mg/m3.以50％含水率为分界线,高含水率污泥会降低分解炉温度并增加煤耗,低含水率污泥情况则相反.结合模拟结果提出,在维持分解炉温度880～905 ℃条件下,污泥含水率控制在45％～63％,可保证污泥进料量达到20t/h.该研究结果可为现行工艺优化方向提供参考.     

埋地储罐清洗无组织排放油气冷凝法净化工艺模拟分析

针对净化埋地储罐清洗无组织排放油气水蒸气和HC浓度高的特点,采用Aspen软件的Flash 2模拟了单组分和多组分有机废气的冷凝过程,研究了水蒸气含量、冷凝温度、有机物结构等因素对液相回收率的影响,并模拟计算了3级冷凝工艺的净化效率。结果表明:温度低于0 ℃时,气体中水蒸气浓度不影响液相水的冷凝效率;对于C6H14废气,冷凝温度和同分异构是影响有机组分回收效率的重要因素,正己烷的全回收温度(T99.5%)比2,2-二甲基丁烷高15 ℃,模拟结果计算正己烷的摩尔蒸发焓为34.758 kJ·mol-1,与理论值接近;当采用温度分别为0、-40和-75 ℃ 3级冷凝工艺时,液相HC回收率达到77.2%。     

Techno-Economic Study of CO2 Capture from an Existing Cement Plant Using MEA Scrubbing

Carbon dioxide is the major greenhouse gas responsible for global warming. Man-made CO₂ emissions contribute approximately 63% of greenhouse gases and the cement industry is responsible for approximately 5% of CO₂ emissions emitting nearly 900 kg of CO₂ per 1000 kg of cement. CO₂ from a cement plant was captured and purified to 98% using the monoethanolamine (MEA) based absorption process. The capture cost was $51 per tonne of CO₂ captured, representing approximately 90% of total cost. Steam was the main operating cost representing 39% of the total capture cost. Switching from coal to natural gas reduces CO₂ emissions by about 18%. At normal load, about 36 MW of waste heat is available for recovery to satisfy the parasitic heat requirements of MEA process; however, it is very difficult to recover.     

石化企业中间罐区VOCs治理工艺选择与流程优化

石化企业中间罐区VOCs排放量较大,多采用吸收、冷凝、膜分离及其组合工艺进行处理。本文采用AspenPlus软件分别对高、中、低浓度中间罐区VOCs废气应用上述3种工艺及其工艺组合的处理效果进行模拟计算。结果表明:中间罐区的VOCs经过不同组合的二级处理后,尾气VOCs质量浓度约为9~50g/m^3,后续仍需采用深度处理工艺以满足新的国家及地方污染物排放标准要求;同时,对比3种工艺能耗情况,冷凝法最低,膜分离法次之,吸收法最高,约为冷凝法能耗的5~10倍。以上模拟计算结果与实际工况数据基本符合,证明采用AspenPlus软件进行石化企业中间罐区VOCs治理工艺选择与流程优化是可行的,具有一定的参考价值。     

DNA damage in Populus tremuloides clones exposed to elevated O3

The effects of elevated concentrations of atmospheric tropospheric ozone (O₃) on DNA damage in five trembling aspen (Populus tremuloides Michx.) clones growing in a free-air enrichment experiment in the presence and absence of elevated concentrations of carbon dioxide (CO₂) were examined. Growing season mean hourly O₃ concentrations were 36.3 and 47.3 ppb for ambient and elevated O₃ plots, respectively. The 4th highest daily maximum 8-h ambient and elevated O₃ concentrations were 79 and 89 ppb, respectively. Elevated CO₂ averaged 524 ppm (+150 ppm) over the growing season. Exposure to O₃ and CO₂ in combination with O₃ increased DNA damage levels above background as measured by the comet assay. Ozone-tolerant clones 271 and 8L showed the highest levels of DNA damage under elevated O₃ compared with ambient air; whereas less tolerant clone 216 and sensitive clones 42E and 259 had comparably lower levels of DNA damage with no significant differences between elevated O₃ and ambient air. Clone 8L was demonstrated to have the highest level of excision DNA repair. In addition, clone 271 had the highest level of oxidative damage as measured by lipid peroxidation. The results suggest that variation in cellular responses to DNA damage between aspen clones may contribute to O₃ tolerance or sensitivity.     

燃煤烟气碳捕集模拟及节能优化

在某电厂建设了一套万吨级有机胺法碳捕集装置,采用新型复合胺吸收剂;设计工况下,烟气流量5877 Nm³/h,吸收剂循环流量37500 kg/h,捕集效率可达97%以上,CO₂产量≥1.39 t/h,再生能耗较传统MEA （单乙醇胺）降低约23%左右。依据工程设计参数建立了碳捕集系统模型,所建立的模型结果关键参数与工程实测值相对误差不超过3%;在原模型基础上,设计了含有富液分流、级间冷却和MVR闪蒸节能工艺的碳捕集系统,考察了富液分流率、级间冷却率和闪蒸真空度等关键工艺参数对碳捕集系统能耗和效益的影响。结果表明：MVR技术可降低15.45%的捕集能耗,节能效果最佳,富液分流和级间冷却节能效果在2%~4.5%。在得到各节能技术最优操作参数后,进一步考察了不同组合节能工艺的节能效果,发现级间冷却+MVR闪蒸技术节能效果最好,富液分流+MVR闪蒸技术居中,级间冷却+富液分流节能效果最小。研究结果可为燃煤电厂烟气碳捕集项目的工艺系统设计、节能降耗及运行提供一定参考。     

基于Aspen Plus的生物质燃烧NOx生成模拟

利用Aspen Plus软件平台建立了生物质燃烧模型,对燃烧中NOx的生成进行了模拟计算,计算结果与已有文献的试验结果较好地相符.在此基础上,研究了燃烧温度和过量空气系数对生物质燃烧NOx生成的影响规律.结果表明,生物质燃烧过程中NOx的生成量随温度和过量空气系数的增长而快速增长;应用Aspen Plus模拟生物质燃烧具有一定的可行性,而且其模型参数设置较为灵活,能够对多种生物质的燃烧进行热力学分析,可为生物质清洁燃烧技术提供有益参考.     

Differential response of aspen and birch trees to heat stress under elevated carbon dioxide

The effect of high temperature on photosynthesis of isoprene-emitting (aspen) and non-isoprene-emitting (birch) trees were measured under elevated CO₂ and ambient conditions. Aspen trees tolerated heat better than birch trees and elevated CO₂ protected photosynthesis of both species against moderate heat stress. Elevated CO₂ increased carboxylation capacity, photosynthetic electron transport capacity, and triose phosphate use in both birch and aspen trees. High temperature (36-39 °C) decreased all of these parameters in birch regardless of CO₂ treatment, but only photosynthetic electron transport and triose phosphate use at ambient CO₂ were reduced in aspen. Among the two aspen clones tested, 271 showed higher thermotolerance than 42E possibly because of the higher isoprene-emission, especially under elevated CO₂. Our results indicate that isoprene-emitting trees may have a competitive advantage over non-isoprene emitting ones as temperatures rise, indicating that biological diversity may be affected in some ecosystems because of heat tolerance mechanisms.