天然气发电与燃煤电厂污染控制

本文分析了上海市能源结构和电力构成，介绍了国外电力发展趋势，并结合西气东输工程，提出天然气再燃解决燃煤电厂污染的优化方案，同时对上海市电力发展和能源政策研究提出了若干建议。     

煤燃烧污染与控制技术的分析研究

煤炭是一种重要的能源,煤燃烧引发的技术和环境问题是全世界共同面临的难题.煤燃烧机理、煤燃烧过程中污染物的形成、排放和抑制规律、新型煤燃烧技术和低费用的污染控制技术等是煤燃烧领域重点研究的内容.针对煤燃烧对大气的污染现状及污染控制技术进行了分析,并提出了污染控制的研究方向.     

燃煤时的烟尘及其控制

燃煤时产生的烟尘是我国主要的大气污染源之一。虽然通过立法和技术改造,烟尘的排放已大大减少,但由于民用灶、工业锅炉和炉窑数量太大,所以燃煤烟尘对大气的污染在有些地区,特别是工业较为集中的地区和城市还相当严重。山西省环保局曾对全省大气污染状况作过一次全面的调查,发现全年大气污染物的排放总量达240万吨,其中烟尘量为49.6万吨。工业过程产生的烟尘占78.02％,城市生活占21.09％,而且这些烟尘主要来自燃煤。 燃煤时产生的烟尘粒径大多在70μm以内,它们随烟气飘移一段有限的距离后便会沉降,因此,燃煤烟尘对环境的污染主要局限于当地。它将引起呼吸道疾病、肺癌和氟中毒。在某     

燃煤火力发电厂生产过程中主要污染识别与控制措施

为了降低燃煤火力发电过程对环境的污染,以燃煤火力发电厂的生产过程为例,探讨燃煤火力发电厂生产过程中的主要污染来源,着重从气体污染控制、水体污染控制以及噪声污染控制的角度,列举能够应用于污染物控制的技术措施,为燃煤火力发电厂污染控制工作的开展提供参考,提升火力发电的环保效益。     

我国煤烟型污染防治策略研究

煤烟型污染防治对于我国经济社会可持续协调发展具有重要意义。煤的化学属性决定了其在燃烧过程中会形成不同的硫、氮污染产物及烟尘和微量重金属的排放,而我国煤炭清洁高效利用程度不高又催生了煤烟型污染。煤烟型污染防治技术可分为广义和狭义两类。广义来讲,包含燃用前处理、燃用中处理、煤转化和燃用后处理4类技术,实质上构成了洁净煤技术体系,是在煤炭开发利用的全产业链实现清洁化,目前在我国仍属于开发应用的初级阶段;而狭义仅是指燃用后处理技术,我国当前更需要优先考虑存量煤烟型污染源的防治,因此需加快推进燃用后处理技术的应用。污染防治必须变"被动应对"为"主动根治",形成"深化防控,加大治理,防治结合,以治为主"的"主动型"防治总体思路。建议进一步完善以区域联防联控为重点的污染防治管理职能,加强国家环境污染防治战略与规划顶层设计,构建完备严格的法规体系,加快推进煤炭能源产业政策调整优化,建立健全多样化的金融财税扶持政策体系,推进环保技术创新与人才开发,重建已损害或退化的生态系统,提高全民环保意识。     

清洁能源与保护环境

能源是国民经济的命脉 ,在工业建设和人民生活中起着至关重要的作用。太原市煤炭资源丰富 ,但由于过去不合理的工业结构 ,煤炭直接消耗量大 ,造成了太原市典型的严重煤烟型污染。要进一步发展经济、保护环境 ,太原市必须大力推广使用清洁能源 ,加强洁净煤等技术的研究与应用     

The development of pollution control technology in coal combustion in China

The recent development of coal combustion pollution control technologies in China, including desulphurization, denitrification, particulate matters and heavy metals emission control technologies, have been reviewed. The development histories and the advantages of China’s self-developed technologies have been introduced in detail. The key points of future research and development in coal combustion pollution control, e.g., combined emission control and CO₂ emission control technologies, have also been discussed.     

Coal combustion and its pollution control in China

Coal combustion will continue to be a major component of energy production in the foreseeable future, owing to its abundance in China. A primary challenge will be to seek ways to utilize the coal resources in an environmentally acceptable manner. This paper presents the coal combustion scenario and its related air pollution in China. Some commonly used technologies for removing the pollutants from coal combustion had been introduced after comparison of its utilization efficiency, engineering investment-, and operation expense. In order to cost-effectively reduce the pollutant emission, it is necessary to enhance the coal utilization efficiency by implementing large-scale advanced technologies and increasing the coal-washing rate. There is dire need for indigenously developed techniques for the pollution control to reduce the engineering cost. The development of low-cost, low water-consuming flue gas desulfurization technologies, low-cost technologies for reducing NO_x emission, and low-cost advanced technologies for inhalable particle emission control, must be predominantly paid attention.     

Preliminary study of trace element emissions and control during coal combustion

Hazardous trace element emissions have caused serious harm to human health in China. Several typical high-toxic trace element coals were collected from different districts and were used to investigate the emission characteristics of toxic trace elements (As, Se, Cr, Hg) and to explore preliminary control methods. Coal combustion tests were conducted in several bench-scale furnaces including drop tube furnace (DTF), circulating fluidized bed (CFB) combustion furnace, and fixed-bed combustion furnace. Calcium oxide was used to control the emission of arsenic and selenium. The granular activated carbons (AC) and activated-carbon fibers (ACF) were used to remove mercury in the flue gas from coal combustion. The chemical composition and trace element contents of ash and particulate matter (PM) were determined by X-ray fluorescence (XRF) spectrometry and inductively coupled plasma-atomic emission spectrometry (ICP-AES), respectively. The speciation and concentration of mercury were investigated using the Ontario-Hydro method. X-ray diffraction spectrometry (XRD) was used to determine the mineral composition of production during combustion experiments. With the addition of a calcium-based sorbent, arsenic concentration in PM₁ sharply decreased from 0.25–0.11 mg/m³. In fixed-bed combustion of coal, the retention rates of selenium volatiles were between 11.6% and 50.7% using lime. In the circulating fluidized-bed combustion of coal, the content of selenium in ash from the chimney was reduced to one-fourth of its original value and that in leaching water from the chimney decreased by two orders of magnitude using lime. Calcium-based sorbent is an effective additive to control the emission of As and Se during coal combustion. The emission of chromium is influenced by the occurrence mode of Cr in coal. Chromium emission in PM_2.5 during coal combustion is 55.5 and 34.7 μg/m³ for Shenbei coal and mixed Pingdingshan coal, respectively. The adsorptive capacity of granular activated carbon for Hg⁰ is significantly enhanced through ZnCl₂-impregnation. The activated carbon fibers showed decent efficiency in mercury adsorption, on which surface oxygen complex showed positive effects on mercury adsorption.     

浅论汽车尾气污染及控制治理

随着经济的发展,汽车数量与日俱增,汽车尾气排放的污染也越来越严重。叙述了汽车尾气的污染和危害,讨论了对其的控制和治理。     

煤燃烧过程中NOx的形成机理及控制技术(下)

通过对氮氧化物的生成机理分析,阐述了燃烧过程中控制NOx生成和降低排放量的原则,探讨了目前相关的低NOx燃烧技术.强调了在降低NOx的同时必须注意高效率,对低挥发份煤在采用分级燃烧情况下的高效低NOx燃烧措施进行了分析研究.     

Effects of pyrolyzed semi-char blend ratio on coal combustion and pollution emission in a 0.35 MW pulverized coal-fired furnace

The effects of blend ratio on combustion and pollution emission characteristics for co-combustion of Shenmu pyrolyzed semi-char (SC), i.e., residuals of the coal pyrolysis chemical processing, and Shenhua bituminous coal (SB) were investigated in a 0.35 MW pilot-scale pulverized coal-fired furnace. The gas temperature and concentrations of gaseous species (O₂, CO, CO₂, NO_x and HCN) were measured in the primary combustion zone at different blend ratios. It is found that the standoff distance of ignition changes monotonically from 132 to 384 mm with the increase in pyrolyzed semi-char blend ratio. The effects on the combustion characteristics may be neglected when the blend ratio is less than 30%. Above the 30% blend ratio, the increase in blend ratio postpones ignition in the primary stage and lowers the burnout rate. With the blend ratio increasing, NO_x emission at the furnace exit is smallest for the 30% blend ratio and highest for the 100% SC. The NO_x concentration was 425 mg/m³ at 6% O₂ and char burnout was 76.23% for the 45% blend ratio. The above results indicate that the change of standoff distance and NO_x emission were not obvious when the blend ratio of semi-char is less than 45%, and carbon burnout changed a little at all blend ratios. The goal of this study is to achieve blending combustion with a large proportion of semi-char without great changes in combustion characteristics. So, an SC blend ratio of no more than 45% can be suitable for the burning of semi-char.     

Opposed-flow combustion of pulverized coal

The possibility of achieving higher combustion intensity under conditions of stable burning by opposed-flow combustion is demonstrated in a series of experiments conducted in a furnace, provided for this purpose with an auxiliary combustion chamber. For this purpose measurements of temperature, pressure, gas composition, and velocity were carried out. Particle size distribution, ash, and volatile matter content were measured at the impingement point in order to determine locally the extent of the reaction and devolatilization. The results obtained regarding the burning of pulverized coal for the flow and temperature conditions actually existing in the combustion chamber were also analyzed computationally. The main advantages of the configuration investigated, in which secondary air is supplied in the final stage of the combustion process, are improved mixing of fuel and air and the ability to control the motion of the pulverized coal.     

Mercury emission control from coal combustion systems: A modified air preheater solution

Results are presented of pilot-plant testing of a new approach to resolve the mercury control problem primarily from coal combustors. Performed at the Western Research Institute’s facility in Laramie, Wyoming, the recorded data reflect the previous laboratory results that proved that untreated steel or platinum surfaces in a specific downstream temperature range can significantly convert gaseous atomic mercury to its water-soluble gaseous dichloride without a need for catalysis or amalgamation. This was confirmed by utilizing various steel inserts in a pilot-plant scale combustor fueled by a low-chlorine Powder River Basin coal. The results and mechanism help to explain why it is in full-scale combustors that large excesses of chlorine generally are necessary to convert their very low concentrations of mercury. These efforts have further validated the underlying predominance of mercury’s heterogeneous chemistry. Most importantly it has illustrated that the efficient laboratory proven mechanism extrapolates to the low mercury parts per billion by volume (ppbv) concentrations relevant to full-scale coal combustion. Depending on conditions, chlorine can become less controlling, removing the need for halogen addition or coal blending approaches as possible methods for mercury control. Additional testing now is establishing the exact surface area of the inserted thin metallic surfaces and the residence time required to attain specific conversion efficiencies. Optimal surface temperatures are about 230 ± 30 °C (450 ± 50 °F) for the conversion mechanism. As a result, this temperature region generally will occur in the location of air preheaters in many coal combustions. This also explains previous reports of mercury oxidation across these and other lower temperature devices. Suggestions now are made for modifying or retrofitting air preheater designs. This enhancement of what is mercury’s natural chemical mechanism now raises the possibility for a one-time modification of the combustion train to resolve this otherwise rather expensive problem.     

The effect of pressure on coal char combustion

A two-dimensional, two-phase combustion model of pulverized coal char at elevated pressures is presented in this paper. This is often encountered in furnaces used for power generation, industrial heating and steam production, and for conversion of solids to gas and liquid products. In pressurized circulating fluidized bed boilers, the effect of pressure on char combustion is significant. Of particular importance is to reveal the relative significance of the diffusion and chemical reaction, as controlling mechanisms, and to evaluate the effect of total pressure on the performance of the combustion chamber. The partial differential equations of conservation of mass, momentum and energy are solved taking into consideration turbulent flow, interphase mass- and heat-transfer, radiation and varying operational conditions (e.g. feed of coal and primary and secondary air). The equations are integrated with the finite volume method and are solved for the flow field, temperature field in the gaseous and solid phases and the concentration of reactants and products. The results show that both chemical reaction and diffusion mechanisms control the combustion at elevated pressure. Moreover, the effect of pressure on the reaction kinetics proves to be significant.     

煤气化置换燃烧分离CO2模拟分析与研究

基于Aspen plus软件,根据Gibbs自由能最小化原理对煤气化置换燃烧过程进行热力学平衡分析.对徐州烟煤以NiO作为载氧体,研究在常压时燃料反应器温度、水煤比对燃料反应器气体产率和载氧体循环倍率的影响.结果表明燃料反应器温度的降低有利于煤气化产物的氧化;水蒸气用量较少时可得到较高浓度的CO2燃料反应器温度的降低和水蒸气用量的减少将减少载氧体循环倍率.