燃煤砷污染和抑制的研究进展

对煤燃烧过程中微量砷的污染和抑制的国内外研究现状进行了综述 .概述了煤燃烧过程中微量砷的排放对环境产生的危害 .分析了煤中砷在燃烧过程中不同温度下的转化形态 ,烟气中砷的主要存在形态 ,以及煤中砷在燃烧产物中的配置和主要影响因素 .给出了美国不同电站的燃煤锅炉、工业燃煤锅炉以及民用燃煤锅炉砷的排放因子 .探讨了不同吸附剂与含砷化合物的作用机理 ,以及减少燃煤过程中砷污染的可行性 .强调了加强煤燃烧过程中微量砷排放研究的重要性     

燃煤有机污染物生成排放特性与采样方法研究进展

煤燃烧过程在生成SO_2、NO_x和颗粒物等常规污染物的同时,还会产生有机污染物。我国燃煤电厂数量多,燃煤产生的非甲烷挥发性有机物(NMVOC)已经占到了人为源排放总量的1/3。然而,已有的针对有机污染物的研究主要关注的是工业源和室内环境中的挥发性有机物,对燃煤过程产生的有机污染物研究较少。由于煤的组分复杂,燃烧温度高、燃烧工况多变,且产生高尘高湿的烟气,这些特殊环境决定了煤燃烧过程有机污染物的生成排放特性及其采样方法与工业源有所不同。本文对原煤有机污染物的前体赋存形态、燃煤过程有机污染物的生成排放特性以及有机污染物的采样与分析方法进行了较全面的综述,并探讨了燃煤有机污染物相关研究的发展方向。     

燃煤电站锅炉掺氨燃烧与排放特性综述

近年来,氨作为一种无碳、富氢的燃料,多被用作内燃机、燃气轮机和其他工业用途的无碳燃料。为了降低燃煤电厂CO₂排放,燃煤掺氨燃烧受到广泛关注。介绍了现有燃煤电厂锅炉碳减排的途径,论述了氨煤掺烧研究的最新进展,分析了燃煤掺氨燃烧过程中可能存在的问题,揭示了燃煤掺氨燃烧特性与污染物排放规律。针对氨在燃煤锅炉中的燃烧特性与燃煤掺氨燃烧过程中高NO_x排放特性,在一台燃烧炉中实现了0～100%掺氨比例的燃煤掺氨燃烧试验,并将空气分级燃烧技术应用于燃煤掺氨燃烧,通过试验进一步研究了不同掺氨比例和分级工况(温度、掺氨位置)对燃煤掺氨燃烧产物的影响。燃煤锅炉提供的高水平预热条件及炉内高温热环境均有利于强化氨气燃烧,氨燃烧特性差不会成为制约其在燃煤锅炉掺烧的主要因素。通过调整燃煤混氨方式、优化空气分级燃烧工况可大幅降低NO_x排放浓度。延后燃尽风的通入位置,可延长还原区长度,有利于还原区NH₃与NO选择性非催化还原反应和煤热解产物(挥发分和焦炭)与NO异相和同相还原反应的进行,有效降低尾气NO浓度。根据试验煤种,空气分级...     

燃煤屯站锅炉控制NOx技木的探讨

分析了大容量燃煤电站锅炉NOx生成的机理和规律,阐述了锅炉低NOx燃烧、排放的技术特点,总结归纳了在煤燃烧过程中抑制NOx产生的手段。     

燃煤电站锅炉控制Nox技术的探讨

分析了大容量燃煤电站锅炉NOx生成的机理和规律,阐述了锅炉低NOx燃烧、排放的技术特点,总结归纳了在煤燃烧过程中抑制NOx产生的手段。     

用于混煤燃烧控制砷排放模型研究

混煤掺烧是控制燃煤砷排放的有效方式,但由于缺乏相关的配煤模型,限制了该技术的应用。根据燃煤过程中砷的挥发释放机制,提出一种采用砷的释放指数P表征煤燃烧过程砷的释放特性的配煤模型。该模型综合考虑煤的灰分、灰中主要矿物元素含量、各矿物元素对砷的固定系数以及煤中砷含量等因素。研究结果表明,随着煤灰固定系数由23.12增至50.90,煤灰的气相砷吸附量由3.39 mg/g增至6.14 mg/g;随着释放指数P增大,砷的固定率减小,且随着温度升高,两者相关性由900℃的0.67增至1 300℃的0.86。根据P值筛选煤种进行掺烧,当掺混煤种P值差异较大时,掺烧低P值煤种不仅可降低混煤中的砷含量,还能促进高P值煤的砷在灰中富集,促进率达77.14%;掺混煤种P值差异较小时,掺烧低P值煤种会促进砷的释放。本模型可较好地筛选煤种,为混煤掺烧控制砷等痕量元素的排放提供了新的思路。     

循环流化床锅炉燃烧固氟技术的应用研究

循环流化床锅炉是一种高效低污染的先进燃烧设备,应用广泛.但由于其具有煤种适用性广和燃烧稳定的特点,广泛用于燃烧劣质煤、石煤和煤矸石,因此,二氧化硫和氟化物排放污染控制问题不容忽视.75 t/h和200 t/h循环流化床燃烧固氟技术应用表明,流化床燃烧燃烧温度十分适合石灰石燃烧固硫固氟的要求,在循环流化床锅炉燃烧时添加石灰石可显著降低锅炉出口烟气中二氧化硫和氟化物的排放浓度及排放量,具有同时脱出二氧化硫和氟化物的作用,具有显著的经济效益、环境效益和社会效益.     

煤炭燃烧过程中大气污染物NO_X形成与转化研究进展

煤炭燃烧释放的烟气中氮氧化物(NO_X)是大气形成酸雨、光化学烟雾、雾霾的重要污染物,目前控制燃煤NO_X释放的常规方法是燃烧后烟气脱硝。鉴于大型燃煤锅炉烟气脱硝方法还存在脱硝效率低、运行成本高、氨逃逸、颗粒物产生(生成白色烟气),以及城镇、城乡结合部、农村居民燃煤以及小型工商业、设施农业散煤燃烧无组织排放、未设置脱硝设施等不足,研发燃煤过程中NO_X控制(燃煤过程中原位还原脱硝)对实现燃煤烟气直排NO_X浓度达标排放或间接降低NO_X浓度来减轻后续烟气脱硝负荷具有重要科学和应用价值。从燃煤过程中细分的低温热解和高温燃烧两个连续阶段产生的氮化物形态,NO_X的形成与转化及影响因素,过渡金属、碱土金属、碱金属等化合物对燃煤过程中原位还原脱硝的催化作用等方面,全面综述了煤炭燃烧过程中NO_X形成与转化规律,指出煤燃烧过程中通过热解降低NO_X前驱物含量耦合燃烧原位还原NO_X成N_2两个途径来控制燃煤NO_X释放,并强调通过引入添加剂促进NO_X催化还原成N_2来达到降低燃煤NO_X释放的思路,为煤炭燃烧过程中原位热解减少NO_X前驱物和燃烧脱硝的两步协同催化作用的科学研究及技术开发,最终降低燃煤NO_X释放提供理论和技术依据。     

煤燃烧过程中NOx的生成和还原

燃煤过程中ＮＯｘ 的排放是一个复杂的过程, 既包括ＮＯｘ 的生成过程又包括生成的ＮＯｘ 进行均相和多相还原反应． 简述了煤燃烧过程中ＮＯｘ 生成和还原的机理． 认为燃料氮是ＮＯｘ的主要来源,ＮＯｘ 的排放与煤阶、煤中氮含量以及温度等因素有关;ＮＯｘ 与半焦的多相反应是ＮＯｘ还原的主要原因, 其中包括ＮＯｘ 在半焦表面的化学吸附、表面络合物的生成以及产物的生成和脱附等过程     

循环流化床燃煤过程NOx和N2O产生-控制研究进展

循环流化床(CFB)燃烧技术因其燃料适应范围广、污染物排放低等优点,近几十年得到广泛应用. 随着当前环保要求的日益提高,CFB燃煤过程N2O排放浓度较高成为其应用的瓶颈问题. 因此系统总结CFB燃煤过程中NOx和N2O排放的研究现状对开发新型CFB燃煤技术具有重要意义. 本工作首先讨论了CFB燃煤过程中NOx和N2O的均相和异相反应机理,然后应用这些机理分析了床温、过剩空气系数、分级燃烧,以及煤种对CFB燃煤过程NOx和N2O排放的影响. 在此基础上,对常见的抑制NOx和N2O排放的工艺从机理角度进行了归纳总结. 最后,对2种本工作认为有应用前景的CFB燃煤减排NOx和N2O新技术?反向分级燃烧技术及CFB解耦燃烧技术进行了简要论述.     

部分进口煤炭中氟元素的含量特征及赋存形态

为加强对进口高氟煤炭的管理,评价进口煤炭中氟元素的环境迁入风险,采用高温燃烧水解-氟离子选择电极法对唐山港口岸进口的225批煤炭中的氟含量进行了测定;用稳健统计描述了其整体含量水平,并根据我国煤炭行业分级标准及富集比进行了质量评价;用相关分析对氟的赋存形态进行了分析。结果表明:唐山港口进口煤炭中的氟含量可描述为(137±24)mg/kg;按我国煤炭行业标准进行质量分级评价,唐山港口进口的68%的朝鲜煤、62%的加拿大煤属于中氟煤,氟含量算术平均值高于中国煤、世界煤,其迁入风险值得关注;进口朝鲜煤中氟含量与灰分、全硫含量呈中度正相关、与磷含量呈微弱正相关,推断氟的赋存形态主要为无机硫结合态(硫化物和硫酸盐)和黏土矿物,少部分可能存在于磷酸盐类矿物及有机硫结合态中;进口澳大利亚煤中氟含量与灰分、全硫含量相关性不显著,与磷含量呈低度正相关,推断氟的赋存形态比较复杂,可能部分以磷酸盐结合态存在,赋存于氟磷灰石、磷铝钙石中;进口加拿大煤中氟含量与灰分、全硫含量相关性不显著,与磷含量的相关性系数为0.763,显著性水平为0.01,表明二者呈高度正相关,具有显著性,说明二者有很强的伴生关系,推断氟主要以磷酸盐结合态存在,赋存于氟磷灰石、磷铝钙石中。     

Volatilization behavior of fluorine in coal during fluidized-bed pyrolysis and CO2-gasification

The volatilization behavior of fluorine in five Chinese coals was investigated during fluidized-bed pyrolysis and CO₂-gasification at a temperature range of 500-900 °C. The effect of co-existed and added calcium on fluorine volatility during pyrolysis was also determined. With increasing pyrolysis temperature, the volatility of fluorine increases. However, the volatility is greatly dependent on the fluorine chemical forms occurred in coal. Except for Datong and Zhungeer coal, more than 65% of fluorine in other three coals occurs as the steady forms. Fluorapatite is not the major carrier of fluorine in the coals studied. Fluorine volatility is retarded by coexisting calcium during coal pyrolysis, indicating that at least part of the stable forms of fluorine in coal might occur as calcium fluoride or calcium fluoride with complex compounds which are stable even at high pyrolysis temperature. The addition of CaO and limestone can suppress the release of fluorine during pyrolysis. The effect of CaO is better than that of limestone. The volatility of fluorine of coal during CO₂-gasification depends on not only the occurrence mode of fluorine, but also the gasification reactivity of the coal. Compared with N₂ atmosphere, CO₂ is more favorable to the release of fluorine from coal.     

五彩湾煤中钠在燃烧过程中的迁移释放规律

采用不同萃取液对新疆准东高钠煤进行逐级萃取实验, 分析了煤中钠的存在形式。分别检测了不同温度下五彩湾煤原煤以及815℃下不同萃取方式处理的煤燃烧后煤灰中钠的含量, 研究了五彩湾煤燃烧过程中钠的迁移释放规律。并且对传统灰分分析方法和微波消解-电感耦合等离子体原子发射光谱仪分析法(微波消解-ICP-AES分析法)测量煤中钠含量进行了比较。实验结果表明, 新疆高钠煤中钠主要为水溶钠。五彩湾煤燃烧过程中, 钠的释放主要发生在815℃之前, 并且以水溶钠和有机钠的释放为主。不同存在形式的钠在燃烧中存在转化, 主要表现为水溶钠向不可溶钠的转化以及不可溶钠向有机钠的转化。通过比较, 微波消解-ICP-AES分析法对煤中钠含量的分析更准确。     

中国煤的燃烧和NOx排放特性研究

Seven Chinese coals ranking from anthracite to sub-bituminous from the Shanxi province were selected for study to forecast the combustion and NOx emission behavior.Three UK,one Indonesia and one South Africa coal was included in the study for reference.A flat flame-turbulent jet apparatus was employed to assess flame stability,ignition performance and NOx emission behavior for the initial stage of devolatilization and combustion. This apparatus can simulate particle heating rates,maximum temperatures and the influence of the turbulent fluid interactionson the fate of volatiles.To simulate processes occurring over longer residence time, additional devolatilization experiments were performed in a drop tube furnace.Char reactivity was studied through thermogravimetric analysis.Finally,fouling propensity was studied with the aid of a purpose-built laboratory combustor that enabled the characteristics of the ash deposit to be assessed empirically.The results show that Chinese coals do not appear to possess unusual features in respect of NOx formation,flame stability and ignition,char burnout and ash slagging.The range of coals available in China appears sufficiently broad that suits all requirements.In particular,Shenfu coal,with its initial fast devolatilization and nitrogen release rates and its low initial nitrogen content and high char reactivity,will perform well when fired in industrial boilers as far as NOx emission,flame stability and combustion efficiency are concerned.Pingshuo coal exhibits high char reactivity and an attractive slagging performance suggesting that this fuel represents a good compromise between NOx emission and overall plant efficiency.     

煤中微量元素氟测定方法的研究进展

介绍了煤中微量元素氟的各种间接和直接的测定方法 .间接方法 :碱熔 -比色 (或ISE)法 ;高频感应电炉 - ISE法 ;氧弹燃烧 - ISE法 ;高温水解 - ISE法等 .直接方法 :光谱分析法 ;质谱分析法 .并对各种方法的适用性、存在的问题及发展方向进行了比较和评述     

Submicron ash formation from coal combustion

In recent years, fine particles have been found to be the cause of various harmful effects on health, and many countries have imposed restrictions on emission of these particles. Fine ash particles are formed during coal combustion in power stations and, if not collected in the air pollution control devices, are emitted into the atmosphere. The fine ash particles can remain airborne for long periods and can result in deleterious health effects when inhaled and deposited in the lungs.Previous studies have shown that combustion of coals of different rank can result in differences in the amount and chemistry of the submicron ash particles. This study examines the variability occurring between the submicron ashes formed from coals of similar rank. Five Australian bituminous coals were burned in a laminar flow drop tube furnace in two different oxygen environments to determine the amount and composition of submicron ash formed. The experimental setup is described and the repeatability of the experiments is discussed. The variability in the submicron ash yield as a percentage of the total ash collected and the submicron ash composition are presented and discussed. This paper presents experimental results rather than a detailed discussion on its interpretation. However, the results indicate that the condensation of evaporated species is responsible for the formation of ash particles smaller than 0.3 μm.     

序批式生物反应器中自生动态膜的成分与结构分析

通过粒度分布仪、扫描电镜等对最佳工况条件下的序批式生物反应器中动态膜结构成分及过滤性能进行了测定分析,用能量色散X射线荧光法(EDX)分析了动态膜的元素组成,结果表明：动态膜中滤饼层质量为39.2g·m-2,其中胶体、挥发性悬浮颗粒物、无机物含量分别为5.7 g·m-2、 26.5g·m-2、 7.0 g·m-2;自生动态膜为多孔状结构,具有较高的孔隙率,可以清晰的观察到丝状菌夹杂在动态膜内,起到了骨架作用;动态膜内主要以70μm～130μm的颗粒为主;O、K、Na、Ca、P、S、Cl、Mg、Si等为动态膜成分的主要元素。     

Fine ash formation during combustion of pulverised coal-coal property impacts

In many countries, legislation has been enacted to set guidelines for ambient concentrations and to limit the emission of fine particulates with an aerodynamic diameter less than 10 μm (PM₁₀) and less than 2.5 μm (PM_2.5). Ash particles are formed during the combustion of coal in pf boilers and fine ash particulates may potentially pass collection devices. The ash size fractions of legislative interest formed during coal combustion are the result of several ash formation mechanisms; however, the contribution of each of the mechanisms to the fine ash remains unclear. This study provides insight into the mechanisms and coal characteristics responsible for the formation of fine ash. Five well characterized Australian bituminous coals have been burned in a laminar flow drop tube furnace in two oxygen environments to determine the amount and composition of the fine ash (PM₁₀, PM_2.5 and PM₁) formed. Coal characteristics have been identified that correlate with the formation of fine ash during coal combustion. The results indicate that coal selection based on (1) char characterization and (2) ash fusion temperature could play an important role in the minimization of the fine ash formed. The implications of these findings for coal selection for use in pf-fired boilers are discussed.     

Chemical forms of the fluorine and carbon in fly ashes recovered from electrostatic precipitators of pulverized coal-fired plants

The functionalities of the fluorine and carbon present in fly ashes formed in pulverized coal combustion have been studied with X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD) techniques. The ash samples include 20-130 μg/g-dry and 0.4-4.1 mass%-dry of fluorine and carbon elements, respectively, and these components are enriched at the outermost layer of the ash surface. The F consists of both inorganic and organic functionalities, and the proportion of the latter is as high as 84-98 mol%. The C has different types of surface oxygen species, such as carboxyl, lactone/acid anhydride and phenolic groups, and most of these groups decompose to CO₂ or CO up to 700 °C to yield carbon active sites. When the amount of the O-functional forms increases, the content of organic C-F forms tends to increase almost linearly. On the basis of the above results, it may be speculated as one possibility that the formation of covalent C-F bonds takes place mainly through secondary reactions between gaseous F-containing compounds (HF and/or F₂) in flue gas and carbon active sites produced below 700 °C downstream of coal-fired boilers.