Atmospheric emissions estimation of Hg, As, and Se from coal-fired power plants in China, 2007
雾霾英语PPT
Pollution control of sulfur oxides
yellowish gray
<80%
1km-10km
Haze do we more harm than fogfog for and its contains How do distinguish with haze? PM2.5
Haze
SO + N&O +PM2.5
Human Hair
What is PM
Environmental protection policies
December 2012
Ministry of environmental protection in December 5th announced the first comprehensive air pollution prevention and control planning
Form of sulfur in coal
Burning release heat, known as volatile sulfur
Does not participate in the combustion, is a part of the ash
General, the sulfur content of coal is
Average annual concentration
10%
10%
7%
5%
Environmental protection policies
“Double ten double eight”
Newly added
Causes of hazy weather
The main reason for the formation of smog is PM2.5 concentration is too high, in addition to meteorological factors, the fundamental reason is the huge amount of pollutant emissions. SO2, NOx, Industrial Dust, VOCs are the main pollutants affecting the PM2.5 concentration In 2012，the total discharge of major pollutants in the 30 air. In 2012, the total discharge of these four pollutants 25 are as follows, in which, the total emissions of coal-fired 20 power plants accounted for nearly 50%.
煤的化验方法
2.2.22
煤样混合
Sample mixing
把煤样混合均匀的过程
2.2.23
煤样缩分
Sample division
按规定把一部分煤样留下来，其余部分弃掉以减少煤样数量的过程
2.2.24
堆锥四分法
Coning andquarterirg
把煤样堆成一个圆锥体，再压成厚度均匀的圆饼，并分成四个相等的扇形，取其中两个相对的扇形部分作为煤样的方法
真相对密度
True relative density
在20Oc时煤（不包括煤的孔隙）的质量与同体积水的质量之比
TDR
真比重
2.3.24
视相对密度
APPARENT RELATIVE DENSITY
在20OC时煤（包括煤的孔隙）的质量与同体积水的质量之比
ARD
视比重、
容重
2.3.25
散密度
BULKDENS-ITY
煤中有害元素
Harmful elements in coal
煤中存在的、对任何生态有害的元素，通常指煤中砷、氟、氯、磷、硫、镉、汞、硌、铍、砣、铅等元素
2.3.32
煤中微量元素
Trace elements in coal
在煤中以微量存在的元素如锗、镓、铀、钍、铍、镉、铬、铜、锰、镍、铅、锌等元素
2.3.33
Qgr,v
2.3.29
恒容低位发热量
Net calor ific value at constant tvolu me
煤的恒容高位发热量减去煤样中水和燃烧时生成的水的蒸发潜热后的热值
Qnet,v
2.3.30
元素分析
Ultimate analysis
Alja-Safe 纯洁的膜矿硫砂自由奥尔加胶的产品介绍说明书
Alja-Safe®Crystalline Silica-Free Alginate PRODUCT OVERVIEWSafe to use Alja-Safe® is the world’s first and only for making single-use molds of the face, hands and other body parts. It captures detail better than other alginates, giving you a more accurate reproduction of your original.Alja-Safe® is easy to use and cures quickly. It reproduces fine detail and makes an excellent temporary mold – good for one or two reproductions of any body part. You can then cast plaster, Matrix® NEO® (polymer modified gypsum) or Smooth-Cast® 300Q small before going on to larger models. You’ll gain a lot of experience with a small test.Applying A Release Agent – Alja-Safe® will not stick to most surfaces. When making a mold of the head, a release preparation is recommended to prevent mechanical lock to the hair. CHOLESTEROL Brand Hair Conditioner (available at most pharmacies) can be applied to hair-covered areas prior to applying Alja-Safe®. It can be washed out of the hair easily after use.Because no two applications are quite the same, a small test application to determine suitability for your project is recommended if performance of this material is in question.MEASURING, WATER QUALITY & WATER TEMPERATURE...Measuring – Alja-Safe® is mixed 1 part water to 1 part powder by volume (1 cup + 1 cup, for example). You can vary the water level somewhat to change consistency of the mixture. Less water will make Alja-Safe® thicker. More water will make the mixture thinner and easier to pour. Be careful …too much water will may result in the mixture not curing.Water Quality – Water that has a high mineral content (calcium, phosphate, etc.) may cause any alginate to become “lumpy” or not set properly. A small-scale test is recommended prior to mixing large amounts.Temperature Of The Water - At 80° F / 27° C, Alja-Safe® will have a working time of 8 minutes and a demold time of 10 minutes. Warmer water will cause the material to cure faster (less working time). Colder water will give a longer working time and slower demold time. For best results, sift Alja-Safe® powder into water and mix as directed.Mix Ratio: 1 Part Warm Water (80° F / 27° C)* to 1 Part Alja-Safe Powder By Volume (or 5 parts water to 1 part Alja-Safe by weight)Specific Volume, cu. in./lb.: 26Pot Life: 8 minutes (ASTM D-2471)Cure time: 10 minutes Color: Light Purple102309 - JRAlja-Safe® can be poured around an object or applied to vertical surfaces. - Once mixed, Alja-Safe® can be poured around the hand, foot, fingers or other model in a fixed position inside a container. Suspend the model just above the bottom of the container and have at least ½” (1.27 cm) space between the * This guide is offered as a reference tool only. It is an estimation and actual amounts needed will vary from individual to individual. End User assumes full responsibility for own calculations of material needed.Safety First!CAUTION: Do not inhale dust. In case of eye contact, flush thoroughly with water. Children should not use this product without adult supervision.The International Agency For Research on Cancer (IARC), which is part of the World Health Organization, has rated free crystalline silica a “Group 1” carcinogen, known to cause cancer. Alja-Safe® alginate does not contain free crystalline silica. Read the Technical Bulletin and MSDS Call Us Anytime With Questions About Your Application.Toll-free: (800) 762-0744 Fax: (610) 252-6200The new is loaded with information about mold making, casting and more.HYDROCAL® PlasterWhite Gypsum CementPRODUCT OVERVIEWHYDROCAL® White Gypsum Cement is an easy to use, high strength, bright white casting plaster that can be used for a variety of arts and crafts applications. Do not apply this product to the skin.HYDROCAL® White Gypsum Cement when fully cured can be easily painted, sanded and machined. TECHNICAL OVERVIEWMixing Ratio: 1 Part Warm Water (70º to 100º F / 21º to 38º C) To 2 Parts Gypsum Cement by Volume.(100 Parts Gypsum Cement To 45 Parts Water by weight)Working Time:* 8 minutes Demold Time:* 3-4 hours (depending on mass) *Note: Working time and demold time can vary depending upon water temperature. Cooler water will give a longer working time and extend the demold time.PreparationGypsum powder is moisture sensitive and will absorb atmospheric moisture. Unused plaster should be stored in a dry environment in sealed containers. Materials should be stored and used in a warm environment(72° F / 23° C). This product has a limited shelf life and should be used as soon as possible. Mixing should be done in a well ventilated area. Wear eye protection, dust mask, latex or vinyl gloves and long sleeve garments to minimize skin contact.Measuring Mixing Pouring Curing Temperature Measuring . . .Gypsum is measured 1 Part Warm Water (70º to 100º F / 21º to 38º C) to 2 Parts Gypsum Cement by Volume (100 Parts Gypsum Cement To 45 Parts Water by weight). Working time and demold time can vary depending upon water temperature. Cooler water will give a longer working time and extend the demold time.Soaking . . .For best results, add powder to water by sprinkling or sifting it slowly and evenly onto the surface of the water. Do not add water to powder, as this may prevent a thorough and uniform mix. Let soak for 2 minutes. Gypsum Cement should be fully dispersed in the water prior to mixing.Mixing . . .Mix either by hand or with hand drill and mixing blade set on a slow speed. Mix for a minimum of 4 minutes to a creamy consistency. Mechanically mixed slurries produce a more uniform casting with optimal strength. Pouring . . .To prevent air entrapment and provide a uniform smooth surface, carefully pour mixture into a single spot at the lowest point of the mold and let the mixture seek its level. The mold may have to be rotated several times during the pour to eliminate air bubble entrapment. When the mixture levels off at the top of the mold, vibrate or gently tap the mold to break any remaining air bubbles.Curing . . .The gypsum cement will green cure in approximately 3 hours depending on size, temperature, water concentration and mold configuration. Thin, small areas will take longer to cure than larger, thick areas. If concerned about the strength of the casting for demolding, allow an addition 1 to 2 hours before removing from the mold. Temperature . . .Materials should be stored and used in a warm environment (72° F / 23° C). Working time and demold time can vary depending upon the water, mold and room temperature. Cooler temperatures will give a longer working time and extend the demold time. Optimal water temperature is 70º to 100º F / 21º to 38º C, optimal room temperature is 72ºF / 21ºC. Do Not Use Hot Water (in excess of 100ºF / 38◦C).If sanding or machining finished plaster, wear NIOSH approved respirator to avoid breathing plaster dust.Call Us Anytime With Questions About Your ApplicationToll-Free: (800) 762-0744 Fax: (610) 252-6200120320-JR Visit Us At Our Website: Safety First! Safety First! Safety First!∆WARNING! When mixed with water this material hardens and becomes VERY HOT – sometimes quickly.DO NOT attempt to make a cast enclosing any part of the body using this material. Failure to follow these instructions can cause severe burns that may require surgical removal of affected tissue or amputation of limb.KEEP OUT OF REACH OF CHILDREN WARNING: INJURIOUS TO EYES. CAUSES SKIN IRRITATION. Contains Portland Cement. Avoid contact with eyes and skin. Do not take internally. Avoid breathing dust. Contact with wet cement can cause severe irritation or chemical burns to the eyes and skin. Wear safety glasses and gloves.FIRST AID: For eye contact, flush with water for 15 minutes and get immediate medical attention. For skin contact, wash thoroughly with soap and water. If irritation persists, get medical attention. If ingested, do not induce vomiting. Drink 2 -3 glasses of water and get immediate medical attention.Product Safety information: (800) 507-8899. Keep Out Of Reach Of Children.The material safety data sheet (MSDS) for this product should be read before using and is included in this kit. All gypsum products are safe to use if directions are read and followed carefully.NOTICE - We shall not be liable for incidental or consequential damages, directly or indirectly sustained, nor for any loss caused by application of this product not in accordance with current printed instructions or for other than the intended use. The information contained in this bulletin is considered accurate. However, no warranty is expressed or implied regarding the accuracy of the data, the results to be obtained from the use thereof, or than any such use will not infringe a copyright or patent. User shall determine suitability of the product for the intended application and assume all associated risks and liability.HYDROCAL® Brand White Gypsum Cement is a product of United States Gypsum Company. For more information contact United States Gypsum Company, Industrial Gypsum Division, 125 South Franklin Street, Chicago, IL 60606-4678.Telephone: 800-487-4431 or 312-606-5380.Website: Product Safety information: USA 800-507-8899.Important: The information contained in this bulletin is considered accurate. However, no warranty is expressed or implied regarding the accuracy of the data, the results to be obtained from the use thereof, or that any such use will not infringe upon a patent. User shall determine the suitability of the product for the intended application and assume all risk and liability whatsoever in connection therewith.。
煤粉燃烧过程中NOx排放的数值模拟资料精
万千瓦 增加了 3000 万千瓦 按照国务院的要求 “十五”后三年 每年要新增
装机 2500 万千瓦 其中约 60 ~70 1500 — 1750 万千瓦 以上为火电机组
煤粉的燃烧将会产生大量的粉尘 SO2 和氮氧化物等有害污染物 其中燃煤 排放的 NOx 占总氮氧化物排放的 67 长期以来 我国对 NOx 污染问题的重视
旋风炉
1000~1500mg/N m3
燃油炉
600~1400mg/N m3
2002 年 1 月 30 日国务院第 54 次常务会议通过了新的收费制度 排污费 征收使用管理条例 2003 年 7 月 1 日起连同 排污费征收标准管理办法 简 称 收费标准 等配套规章一起施行 收费标准 的实行对火电行业形成了较 大的压力 排污收费标准规定 每排放 １ｋｇ 的 ＮＯｘ 收费 ０．６３ 元 上海市电站总 装机容量 ９６１２ＭＷ 大部分为燃煤机组 燃煤锅炉造成了严重的环境污染 如 １９９８
II
上海交通大学硕士学位论文
NUMERICAL SIMULATION ON NOx EMISSIONS IN COAL COMBUSTION PROCESS
ABSTRACT
Pollutants from coal combustion are a major environmental problem since they produce large amount of dust, sulfur dioxide and nitrogen oxides. The formation of nitrogen oxide (NOx) in combustion system is a significant pollutant in the environment, and the control of NOx emissions is a world-wide concern as the utilization of fossil fuel continues to increase. A lot of researches on the control of nitrogen oxides has been done, however, so far many real flames still cannot be described and calculated precisely due to the complex interaction between reaction and diffusion occurring in coal combustion. So it is always important to develop the theoretical and experimental studies for the combustion.
核设施气态流出物的环境γ吸收剂量计算及实验验证
第31卷第1期原子能科学技术V o l.31,N o.1 1997年1月A tom ic Energy Science and T echno logy Jan.1997核设施气态流出物的环境Χ吸收剂量计算及实验验证肖雪夫(中国原子能科学研究院保健物理部,北京,102413)采用有限烟云大气扩散模式,计算了中国原子能科学研究院的2座核反应堆烟囱排放的放射性气态流出物在核反应堆附近产生的附加吸收剂量。
对1990—1992年间3年的实验测量结果逐年进行了比较,其偏差均在62%以内。
关键词 有限烟云 大气扩散 Χ吸收剂量率 气态流出物核设施的气态流出物排入环境后所造成的附加吸收剂量是环境监测与保护等管理部门极为关切的数据之一。
本工作采用有限烟云大气扩散模式,对中国原子能科学研究院内2座研究堆的气态流出物高架排放在环境空气中产生的附加Χ吸收剂量率进行计算。
在与计算中相应的空间位置点上,将采用高气压电离室吸收剂量率连续监测仪进行长期的连续测量,并对2种方法得到的结果进行比较和讨论。
1 简况中国原子能科学研究院地处距北京市中心约40km的房山区境内,其地理座标为东经116°28′,北纬39°48′。
该地区属大陆性季风气候,冬季干旱多偏北风,夏季温湿以偏南风为主,春季多风沙,一年四季昼夜温差变化较大。
本地区的年均气温、风速、湿度、降水量分布及风玫瑰图等气候特征参见文献[1]。
实验测量点布置在中国原子能科学研究院院内一幢高14m的4层楼顶上,测点M与1号反应堆烟囱(高44m)水平距离为360m,与2号反应堆烟囱(高60m)水平距离为310m,其相对位置示于图1。
2 计算方法对于烟云或地面沉积物这一类扩展源,空气中某点的Χ吸收剂量与几百米内的放射性物质的分布有关。
对于尺度小于Χ辐射平均自由程的烟云,在计算某点的Χ吸收剂量时,必须考虑来自烟云各组成部分的辐射。
鉴于本工作实验测量点距烟云排放点较近,计算中采用有限烟云模式。
有机朗肯循环直接蒸发器的发展
INL/CON-10-19324PREPRINT Development of a Direct Evaporator for the Organic Rankine Cycle 2011 TMS Annual MeetingDonna GuillenHelge KlockowMatthew LeharSebastian FreundJennifer JacksonFebruary 2011This is a preprint of a paper intended for publication in a journal or proceedings. Since changes may be made before publication, thispreprint should not be cited or reproduced without permission of the author. This document was prepared as an account of worksponsored by an agency of the United States Government. Neitherthe United States Government nor any agency thereof, or any oftheir employees, makes any warranty, expressed or implied, orassumes any legal liability or responsibility for any third party’s use,or the results of such use, of any information, apparatus, product or process disclosed in this report, or represents that its use by suchthird party would not infringe privately owned rights. The viewsexpressed in this paper are not necessarily those of the UnitedStates Government or the sponsoring agency.DEVELOPMENT OF A DIRECT EVAPORATORFOR THE ORGANIC RANKINE CYCLEDonna Guillen1, Helge Klockow2, Matthew Lehar3, Sebastian Freund3 and Jennifer Jackson2 1Idaho National Laboratory, Idaho Falls, ID 83406 USA2General Electric Co., One Research Circle, Niskayuna, NY USA3General Electric Co., Freisinger Landstrasse 50, D-85748 Garching b. Muenchen, Germany Keywords: Organic Rankine Cycle, direct evaporator, waste heat recoveryAbstractResearch and development is currently underway to design an Organic Rankine Cycle (ORC) system with the evaporator placed directly in the hot exhaust stream produced by a gas turbine (GT). ORCs can be used to generate electricity from heat that would otherwise be wasted, thus producing carbon-free energy. In conventional ORC configurations, an intermediate oil loop is used to separate the hot gas from the flammable working fluid. The goal of this research effort is to improve cycle efficiency and cost by eliminating the pumps, heat exchangers and all other added cost and complexity of the additional heat transfer loop by developing an evaporator that resides in the waste heat stream. Direct evaporation – although simpler and less expensive to implement than indirect evaporation of the working fluid – has historically been avoided due to a number of technical challenges imposed by the limitations of the working fluid. The high temperature of the hot exhaust gas may cause decomposition of the organic working fluid and safety is a major concern due to the high flammability of some of these working fluids. The research team has addressed these challenges and developed a new direct evaporator design that can reduce the ORC system cost by up to 15%, enabling the rapid adoption of ORCs for waste heat recovery. The ORC system is intended to integrate with the GT either as a retrofit or to be marketed as a single package, thus maintaining the manufacturer’s warranty.IntroductionWaste heat from turbines and engines used in industrial applications along with waste heat from industrial processes are exceptionally abundant sources of energy. If even a fraction of this waste heat could be economically converted to useful electricity, it would have a tangible and very positive impact on the economic health, energy consumption, and carbon emissions in the U.S. manufacturing sector. Land-based gas turbines are used in a broad range of applications to produce both shaft and electrical power. Most commonly known for generating electricity either as peaking units or as base load units, they are also used to directly drive pumps, compressors or other machinery requiring shaft power. Simple cycle gas turbines have the advantage of a short startup time relative to coal-fired and nuclear units, however, they incur a significant penalty on their efficiency. Large frame gas turbines usually are combined with bottoming steam-based Rankine cycles to increase the overall efficiency of the system and thereby improve their cost performance. Small-frame gas turbines with exhaust temperatures around 500°C could in principle benefit from steam bottoming cycles, but rarely use them in practice because of the high capital cost of the steam system. Particularly for base load small frame gas turbines, akin to those used in pipeline applications, an increase in efficiency is highly desirable.The following sub-sections of this paper describe issues pertinent to the selection of an ORC working fluid, along with thermodynamic and design considerations of the direct evaporator. The FMEA (Failure Modes & Effect Analysis) and HAZOP (Hazards & Operability Analysis) safety studies performed to mitigate risks are described, followed by a discussion of the flammability analysis of the direct evaporator. Due to the proprietary nature of the design, no details will be disclosed relative to the actual working fluid selected or the design details of the direct evaporator. Rather, the methodology used to develop the ORC direct evaporator design will be discussed.The Organic Rankine CycleThe ORC is a vapor power cycle that operates using the same principles as the steam Rankine cycle, except that a fluid with a lower boiling point (and higher molecular mass) is used. An organic working fluid is evaporated, instead of boiling water to create steam, to run through a turbine to generate electricity. This enables the operation of the cycle at a much lower temperatures than a steam Rankine cycle. Thus, the ORC can utilize the energy from low temperature waste heat sources to produce electricity.The Rankine cycle is comprised of four main components: evaporator or boiler, turbine or expander, condenser and pump. Depending on the working fluid, a recuperator may be advantageous, depending on the residual enthalpy of the fluid as it exits the expander. In ORC systems the heat source is coupled to the boiler to evaporate the working fluid before it is expanded in the turbine. ORCs are a viable option to recover the exhaust waste heat, using the ambient air as a heat sink. Typically, the heat of the exhaust stream is transferred indirectly to the ORC by means of an intermediate thermal oil loop. The direct evaporator eliminates the need for an oil loop by transferring heat to the working fluid with just one heat exchanger unit placed directly in the exhaust gas stream. Figure 1 compares the indirect vs. direct evaporation arrangement.(a) (b) Figure 1. ORC with: (a) Indirect evaporation vs. (b) Direct evaporation.The efficiency of an ORC depends both on the initial temperature of the waste heat and the level of irreversibility introduced as that heat is transferred to the cycle fluid, then from the cycle fluid to the sink. Figure 2 compares the maximum attainable Carnot efficiency with that of anendoreversible process. The endoreversible process is a much more accurate measure of heat engine efficiency in that the two processes of heat transfer are not treated as reversible [1].An ambient air temperature of 18°C is used in the calculation. The Turbine Exhaust Gas (TEG) is available at temperatures between 400 and 550°C. However, the temperature to which the working fluid may be heated is limited by the chemical stability of the fluid. Although, in practice typical ORC efficiencies are around 10 to 20%, by integrating an ORC with a GT engine, total system efficiency can be increased by roughly 20% to 30%. Real-world GT efficiencies in the 25 MW power range of interest are between 35% and 40%, with 60-65% of fuel energy wasted as heat. If the ORC can harness 10% to 20% of the wasted heat energy (i.e., of the 65%), the total system efficiency increases to ~45%.Figure 2. Comparison of Carnot and endoreversible cycle efficiencies.The losses and productive output of the cycle can be represented graphically in an exergy diagram, in which the useful power output may be compared against the theoretical entitlement (shown in Figure 3 for an ORC heated by the exhaust stream from a GE PGT-25 gas turbine). A cycle that minimizes exergy destruction is sought.Figure 3. Exergy diagram for a PGT-25 gas turbine with ORC bottoming cycle.Working Fluid SelectionORC systems offer a wide range of parameters for optimization with the most obvious being the selection of working fluid. The working fluid selection dictates the operating pressures on the condenser and evaporator side, expander design, need for a recuperator, etc. The operating pressures are strongly dependent upon the available heat source and sink temperatures. For different combinations of heat source temperature range and heat sink temperature range, there would likely be a different optimal fluid. To simplify the optimization process, the initial down selection process focuses on cycle performance, with other considerations introduced later in the process.The selection of the optimal working fluid is the end result of a systematic comparison of over 40 different fluids on the basis of their suitability for use in an ORC cycle. Fluids were compared on the basis of chemical stability, flammability, toxicity, performance under the boundary conditions of the gas turbine exhaust application, and environmental risk in the event of a leak. Other considerations that factor into working fluid selection include corrosiveness and tendency to foul. Cost was not considered as a distinguishing factor among fluids, since the pressure level, component selection, operating temperature and other attributes, independently from fluid choice, most influence cost. The candidate fluids fall under five broad chemical groups:1. Simple aliphatic hydrocarbons, such as butane, pentane, and hexane – these chemicals areattractive because their near-ambient boiling points enable condensation near atmospheric pressure2. Fluorinated (or otherwise halogenated) hydrocarbons (including most refrigerants),attractive because of their efficient expansion behavior and lack of need for a recuperator3. Aldehydes & ketones – variations on simple hydrocarbons which can be chosen so as tocombine the benefits of hydrocarbons and refrigerants4. Silicones, with extremely high chemical stability at elevated temperatures to guaranteecontinued performance over the lifetime of the machinery5. Aromatic hydrocarbons, combining high stability with good expansion properties, butgenerally boiling well above ambient temperatures.Perfluorocarbons, chlorofluorocarbons and hydrochlorofluorocarbons have very attractive properties for the ORC, but unfortunately have an extremely high greenhouse warming potential and therefore were not considered. The down selection of working fluids was based primarily on performance in an ORC subject to the constraints identified above. Further selection was guided by consideration of the stability of the chemical at high temperature, health hazards, and potential to cause environmental harm. The qualities that tend to increase working fluid performance are as follows:x A high stability and critical point such that the fluid may be boiled at relatively high temperature, allowing the recovery as work of a relatively high fraction of the embodied heat energy (enthalpy) of the fluid. The use of fluid blends versus a single fluid presents concerns over unmixing.x Vertical to positive slope of the vapor curve on T-s diagram to eliminate need for superheating, increase efficiency and lower condenser cost. A tendency of the expanding vapor to remain close to saturation, without need for superheating. If the vapor is close to saturation as it is discharged from the turbine, its temperature will not differ greatly from the condensation temperature, and irreversible transfers of heat (within a recuperator) from the vapor to the cooler liquid returning from the pump will not be required. Any such irreversibility decreases cycle efficiency.x Sufficiently high volatility to boil at or above ambient temperature, meaning that the condenser can be operated at or above atmospheric pressure. A lower-than-atmospheric(i.e., vacuum) condenser is undesirable, since such systems incur additional cost andcomplexity to prevent in-leakage of ambient air. Fluids with low vapor pressures at ambient temperatures require the use of sub-atmospheric condensers or costly, cascaded cycles. Condensers that operate at pressures below atmospheric are unacceptable in ORCs because the ingress of air and moisture through unavoidable minute leaks catalyzes degradation reactions in the working fluid [2].Other desirable characteristics of the working fluid include:x High thermal conductivity in the vapor phase to maximize heat transferx High autoignition temperature, preferably above TEG temperaturex High specific heat ratiox Low environmental impact and toxicityx Low overall system pressure to reduce component costx Minimal reactivity with air or materials of constructionx Low flammability rating and transport hazard classx Low freezing point, as this affects operability in cold climates.Thermodynamic ConsiderationsThe performance of a particular working fluid, even once the source and sink temperatures for the ORC have been specified, is not uniquely determined. A principal variable strongly affecting performance is the pressure at which the working fluid boils. For each fluid, given a particularinitial heat source flow and temperature, the electrical output of the ORC will be maximized for a particular pressure level. Here, a single source and sink temperature are specified.To perform a comparison of fluids, the following five criteria were imposed on the computer simulations of ORC systems:1. Fixed initial heat source temperature2. Fixed log-mean temperature difference (LMTD), rather than fixed minimum temperaturedifference (the distinction is explained below), in evaporator and condenser3. Fixed expander technology and expander adiabatic efficiency4. Fixed pump efficiency5. Use of an additional fixed-LMTD heat exchanger (recuperator), if its inclusion would bebeneficial in the particular case, to transfer heat from the fluid vapor as it is discharged from the expander to the fluid in the liquid phase as it returns from the pump.By using the criterion of a fixed LMTD, rather than a fixed minimum temperature difference between the two flows in each heat exchanger, we eliminate one possible source of variability between fluids. Under given conditions of flow rate and flow inlet temperatures, the effectiveness of a heat exchanger is limited by the requirement that the temperature of the heated fluid may at no point exceed that of the cooled TEG. For this reason, strategies that guarantee more nearly parallel temperature profiles for the warmed and cooled fluid within the exchanger can permit a lower overall LMTD than would be possible if the temperature profiles of either flow were strongly “kinked,” as when, at certain low pressures, the process of boiling at constant temperature absorbs roughly the same amount of heat as it took to steadily increase the temperature of the liquid phase from ambient level to the point of boiling. A lower overall LMTD implies lower irreversibility in the transfer of heat, and consequently a more efficient cycle. If the point of minimum approach (in a boiler, this generally occurs at the onset of boiling in the liquid) is the limiting factor in the design of the heat exchanger, strategies such as supercritical heating, or mixing two working fluids together to produce a binary fluid that boils at progressively increasing temperature, can alleviate the limitation and increase the cycle efficiency. But, if source temperatures are sufficiently high, and sink temperatures sufficiently low in relation to the cycle fluid temperature (conditions which hold for our own application), the point of minimum temperature approach will not limit the cycle performance, regardless of the strategy used (i.e., supercritical boiling, binary fluid mixtures). In this case, it is only the heat exchanger’s size that controls its effect on the cycle performance, and the implied size changes roughly in proportion to the LMTD of the exchanger. Since we wish to compare the different fluids on the basis of similar equipment size and cost, we have constrained LMTD to be constant across all fluid simulations in order to eliminate it as a source of performance variation. The difference in temperature between the two fluids at the point of closest temperature approach therefore varies slightly between different fluid trials. In practice, this “minimum 'T” will not measure less than a certain value, so if in any case the chosen LMTD would have forced a minimum 'T of less than 10°C, the LTMD was increased until a 10°C minimum 'T was reached. A 'T of 10°C at the pinch point is fairly typical for large industrial heat exchangers.Direct Evaporator DesignA successful design of the direct evaporator needs to satisfy the required duty, i.e., the amount of heat to be transferred per unit time given the inlet temperatures and mass flows, and meet certainconstrains specific to the working fluid and application. For extraction of heat from a low-pressure gas by a high-pressure fluid, finned-tube heat exchangers are employed because of their suitable characteristics of low pressure loss on the gas side along with high surface area ratio between the fins, where the heat transfer coefficient is low, and the tube inside, where the heat transfer coefficients of the fluid are typically about two orders of magnitude larger, leading to a high overall heat transfer coefficient with a relatively compact volume.Optimizing the heat exchanger design demands a compromise between size, i.e. capital-intensive heat exchange area, and tolerable pressure losses in each of the fluids streams. In this case, however, specific constraints require a distinctive approach in regard to dimensions, geometry and layout. The primary constraints imposed to the heat exchangers of the direct evaporator by the working fluid are:x Limiting working fluid maximum temperature to avoid excessive working fluid degradationx Ensuring safety in the event of working fluid leakx Observing fin surface temperature lower limitx Maintaining TEG temperature above dew point temperature for nitric acid formation (otherwise, can’t use carbon steel tubes).x Limiting backpressure from the ORC to within allowable limits to avoid choking the GT The most severe design constraint is the upper limit imposed upon fluid temperature above which decomposition is accelerated. As the highest fluid temperature is found in the boundary layer of the fluid close to the wall of an externally heated duct, the inside wall temperature of all heat exchanger pipes must remain below this temperature limit at all times. The thermal stability of the fluid determines the lifetime of the working fluid, affecting life-cycle cost, and has safety implications if undesirable chemical decomposition products are generated.The dehydrogenation reaction results in hydrogen evolution that, since hydrogen in non-condensable, dramatically reduces expansion pressure ratio, maximum output power and efficiency. Longer-chain hydrocarbons may form, which can leave a gummy or coke type of residue that is deleterious to system components (especially the pump and heat exchanger). Undesired reaction products, including non-condensables, should be periodically or continuously removed from the heat transfer loop. Avoiding oxygen ingress into some working fluid is critical, since experiments conducted at INL show that decomposition products (measured in solution) increase five-fold upon a bulk temperature increase from 300°C to 350°C, whereas solid product deposition is three times higher. Also, avoiding materials of construction or contaminants that contain catalysts that can promote working fluid degradation is recommended.Leak IgnitionPlacing a heat exchanger operating with a flammable hydrocarbon working fluid directly in the hot exhaust gas stream presents potential safety risks. In order to mitigate risks, FMEA and HAZOP safety studies were performed. The most serious risks anticipated from heating the working fluid in direct proximity to a hot gas turbine exhaust were examined. Potential causes of tube breaches that would initiate a leak include thermal fatigue, mechanical vibration, corrosion and manufacturing defects.1. Thermal FatigueFollowing a cold start of the direct evaporator, metal temperatures increase over a range of hundreds of degrees C. Differential thermal expansion in the various materials used in the construction of the evaporator can put large stresses on the material interfaces, especially on welded joints between the working fluid tubes and the frame. Over the life of the evaporator unit, repeated cycles of startup and shutdown can eventually aggravate small imperfections in the weld to open cracks through which working fluid under high pressure escapes from the tube into the hot TEG. A large leak would be noticed immediately from the measurable loss of working fluid, while the smallest leak could persist for weeks or months before it is recognized and repaired.2. Mechanical VibrationThe boiling process within the tubes, as well as the aerodynamic buffeting experienced by the tube banks during steady-state exhaust flow, contribute to vibration that can eventually fatigue and weaken the tube joints. Excessive strain of fatigued members could potentially open cracks in the tube material or welded joints, allowing a release of working fluid into the hot exhaust flow. This phenomena must be addressed during the design of the direct evaporator.3. CorrosionAlthough substantially depleted of oxygen, the residual oxygen content, as well as the water content, of the exhaust flow from the gas turbine have a non-negligible potential to corrode the carbon steel of the direct evaporator fluid tubes over time. The risk of corrosion is already significantly reduced by observing a minimum exhaust temperature to prevent so-called “acid gas” exhaust components from precipitating out of the gaseous phase and corroding metal surfaces. The concern arising from corrosion of the evaporator tubes is that it may ultimately open pinhole leaks in the tube wall, or simply weaken the wall sufficiently such that thermal or mechanical stresses could induce rupture. Routine inspection of all system components is recommended.4. Manufacturing DefectsDefects in the piping material or welded seams, if not discovered through pressure tests during commissioning, remain as potential nucleation points for cracks throughout the lifetime of the evaporator.Various more serious effects could result from leaks in any of the above scenarios, including ignition of the fluid causing hot spots and gradual weakening of the structure, as well as the possibility that leaks would feed larger cells of combustible gas, which could explode suddenly causing catastrophic failure. The estimated magnitude of these risks was necessarily quite provisional, as no research had yet been performed on the detailed mechanism for each of the failure mechanisms. However, reports on steam boiler technology provide examples of rupture mechanisms originating from corrosive interactions with the tube steel. For many boiler applications, leaks are described in the boiler literature as an inevitable symptom of ageing.As shown in Figure 4, oxygen, heat and fuel are the three elements necessary for a fire to occur. Autoignition occurs when sufficient self-heating by chemical reactions takes place to accelerate the rates of reactions to produce full-scale combustion. Combustion is the sequence of exothermic chemical reactions that occurs between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. Combustion feeds a fire with heat, enabling the process to continue. In the proposed ORC design, oxygen, heat (from the TEG) and fuel (i.e., the working fluid) are present creating the potential for a fire in the direct evaporator.Figure 4. Fire triangle (courtesy of Wikimedia Commons).The reaction rate depends on the mean species concentration of the mixture and the local mean temperature. The concentration field and the progress of chemical reaction are affected by the topology of the turbulent flow field [3]. Ignition processes are usually very complex and involve many intricate physical and chemical steps [4]. These steps take a finite amount of time and the period between the start of injection and the start of combustion is referred to as ignition delay time. The ignition delay time is a latent period in the combustion process, during which the temperature remains nearly constant [5]. The delay time is comprised of a physical delay and a chemical delay component. The physical delay is due to the finite rate of mixing of injected working fluid with hot exhaust gas and is the time needed for the flammable gas mixture to reach the autoignition temperature. The chemical delay is due to pre-combustion reactions of the combustible gas mixture that lead to autoignition. In reality, both the physical and chemical processes are occurring simultaneously and cannot be decoupled. Therefore, the actual autoignition delay time in a flowing system is difficult to determine, as it will be affected by the [6]:· Time taken for fuel and TEG to mix,· Time for the fuel temperature to rise to that of the TEG, and· Chemical kinetic time for the autoignition reactions to initiate.Computational fluid dynamic (CFD) analyses were performed to assess the flammability of the selected working fluid in the hot exhaust gas stream stemming from a potential pinhole leak in the evaporator. The primary concern here is the potential for leaked working fluid to become trapped in the recirculation regions aft of the finned tubes. The stabilization of a flame in the eddy region behind a bluff body in a high velocity gas stream is a well known phenomenon used to anchor the flame in the combustors of jet engines [7]. A flame stabilized in this manner can spread throughout the entire flammable mixture. The residence time of gases in the recirculation zone behind a bluff body dictate whether the flame will propagate or extinguish. The scenario of concern is that fluid released a small leak in a finned tube could ignite, burn undetected for a long time, and potentially degrade surrounding materials or ignite secondary fires. A highlyconservative mixed-is-burned approach was implemented for the combustion. As a worst case scenario, the CFD analysis was performed assuming a zero ignition delay time wherein the working fluid burns as soon as it is released from the breached tube.SummaryA modification of the conventional ORC system using direct evaporation technology has been outlined. Issues surrounding the selection of an ORC working fluid have been outlined. The conditions and constraints imposed on the thermodynamic analysis and heat exchanger design have been discussed. Safety risks recognized during the FMEA/HAZOP are given, along with mitigation strategies. Leak ignition processes are identified and the methodology employed in the flammability analysis is provided.By identifying a safe means of detecting and handling leaks in general, all the particular leak scenarios, including corrosion, thermal or mechanical strain failure, can be simultaneously addressed. A safety mechanism that could anticipate and “disarm” leaks, allowing no opportunity for ignition or explosion, would conclusively mitigate all conceivable leak scenarios at once. In line with this approach, subsequent analyses and experiments have focused on setting safe limits on the range of velocities and temperature of hot exhaust within which no amount of leaked working fluid could ignite. Specifically, even at exhaust temperatures as high as 600°C and flow rates as low as one-third of the normal operating level, any leaked fluid would be expelled from the system before it had the chance to ignite. A prototype is being constructed for testing at GE GRC’s testbed located in Niskayuna, NY. During the prototype testing, leak tests are planned to confirm the retirement of fire risks, test detectors and safety chain under real-life conditions. Specific recommendations to minimize the potential for a deflagration in the direct evaporator unit include:1.Do not allow flammable/explosive concentrations of working fluid-TEG mixtures tostagnate. It is advisable to sweep such mixtures through the system. A minimum TEG velocity should be observed.2.Purge the oxygen out of the ORC with an inert gas upon system startup.3.Incorporate hydrocarbon sensors in appropriate locations to detect leaks. If a leak isdetected, a system to divert the hot gas to bypass stack should be activated and the working fluid system depressurized. Since the working fluid is heavier than air, any escaped liquid or vapor will tend to settle in low areas or travel some distance along the ground or surface towards ignition sources.The direct evaporator design shows promise for future ORC systems due to its simplicity and lower cost. Overall efficiency can be increased by eliminating the losses associated with the oil loop. The direct evaporator concept is probably best suited for lower temperature heat sources, where there is no need to protect the working fluid from overheating and autoignition is not a concern.AcknowledgmentsThis work was supported by the U.S. Department of Energy, Energy Efficiency & Renewable Energy, Industrial Technologies Program, under Contract #DE-PS36-08GO98014.。
土壤生态系统中黑碳研究的几个关键问题
关键词 ： 黑碳 ；生 物炭 ； 捕获 ；土壤有机碳 库 ；二氧化碳 ；温室气体 碳
中图分 类号 ：Ｘ７ ：Ｓ ５ ４ ７ １ １；Ｐ ６ 文献 标志码 ：Ａ 文章编号 ：１ ７ ．９ ６（ ０ ２）０ —１３０ ６ ４５ ０ ２ １ １０ ５ —６
。
水平？大气 Ｃ ２ Ｏ 浓度 的安全限值是多少？ 目 的 前 讨论和观点仍然存在分歧。如果将 ３ ０ 西 ５ ｘ０ 设定 １ 为大气 Ｃ ２ Ｏ 体积分数 的控制值 ，很显然 ，我们不 仅应该遏制持续增加的人为温室气体排放量 ，还 应该采取一些 有效 的措施减少 大气 中 Ｃ ２ Ｏ 的浓 度 ，既将大气 中的 Ｃ ２ Ｏ 捕获 、并促使碳元素重新 回归地球碳库 、实现碳元素的自然地质循环 。 如何将大气 Ｃ ２ Ｏ 进行捕集与封存是当前的一 个热点问题 ，黑碳这一物质形式有可能为这一 问 题的解决提供路径 。绿色植物通过光合作用吸收 同化大气 中的 Ｃ Ｏ 形成干物质 ，其中一部分 以能 量 、纤维等形式为人类所利用 ，另一部分干物质 则作 为农林业副产物而滞 留于环境 中。当这些副 产物以生物能源的形式被烧掉时 ，其中的碳仍 以 Ｃ ２ Ｏ 的形式返 回到大气中 ，但若通过无氧或低氧 炭化技术对废弃生物质材料进行热裂解 ，原生物
土壤 生态 系统 中黑碳研究 的几个关键 问题
胡 学玉 ，易卿 ， 禹红红
中国地质大学 （ 武汉 ）环境学院，武汉 ４０ ７ ３ ０４
摘要 ：因人类活动 的影 响 ，全球大气 Ｃ ２ Ｏ 浓度 自１５ 年 以来 呈现逐步上 升的趋势 。农 业生产活动 与气 候变化紧 密相 关 ，因 ７０ 土地利用 方式 的改变 以及 高度集 约化的粮食 、食 物生产等农 业活动都有 可能增加ｃ 等温室气体 的排放 。如何 遏制和减少 ０２
LOST IN THE HAZE雾霾英文简介
4
What can we do?
LOST IN THE HAZE
WHAT IS HAZE ?
LOST IN THE HAZE
WHAT CAN WE DO ?
Let’s talk about winds The haze weather is a pain that can breathe, but when cold snaps bring winds, haze and fog will be blown away. So maybe we need to expect the winds from the northern Eurasia.
LOST IN THE HAZE
WHAT CAUSE HAZE ?
Steelworks
LOST IN THE HAZE
WHAT CAUSE HAZE ?
Refineries
LOST IN THE HAZE
WHAT CAUSE HAZE ?
Heating
3
Damages
LOST IN THE HAZE
LOST IN THE HAZE
WHAT CAN WE DO ?
The adjustment of industrial structure.
The development of economy is no longer rely solely on manufacturing industry, vigorously develop the service industry and high-tech industry are the general trend. Reducing coal-fired power stations Develop new energy solar energy & nuclear energy Improve energy utilization rate
THU
2! 3 )2!煤中氟化淋滤新集分配挥发迁移浮沉洗选迁移气氛下煤燃烧产物的热力学分析李英杰，赵长遂，段伦博（东南大学洁净煤发电及燃烧技术教育部重点实验室，江苏南京!%""’#）摘要：利用4.567 689. 软件平台对2! 3 )2!气氛下煤的燃烧产物进行了热力学模拟计算，计算中对煤在2! 3 )2!气氛下和空气中的燃烧产物进行了对比，研究在2! 3 )2!气氛下燃烧温度、过量氧系数! 对煤燃烧产物的影响。
结果表明，煤在2! 3 )2!气氛下燃烧，形成的72! 量远低于空气气氛中的生成量；随温度和! 增大，72! 量增大；温度对.2!和.2&量的生成影响很小；当! : % 时，随! 增大.2!的量增大，当! ; %时，! 变化对.2!量影响不大；随! 增大，.2&有微量增长。
计算表明应用4.657 689. 模拟煤的富氧燃烧是可行的。
关键词：4.657 689.；2! 3 )2!气氛；燃煤过程；燃烧产物中图分类号：<=+&0 >0 文献标识码：4引言采用纯氧代替空气进行助燃的2! 3 )2!循环燃烧方式（富氧燃烧），是一种既能直接获得高浓度)2!，又能综合控制燃煤污染排放的新一代技术。
这种燃烧方式的主要特点是采用烟气再循环，以烟气中的)2!来替代空气中的氮气，与氧一同参与燃烧，这样能使排烟中的)2!浓度大为提高（’+? 以上），)2!无须分离即可利用和处理，从而有效降低)2!向大气的排放。
近年来，对于2! 3 )2!气氛下煤的燃烧特性、污染物释放特性及钙基固硫特性等已有一定量的报道［% @ +］。
本文采用了大型的反应流程模拟软件4.657689. 对煤在2! 3 )2!气氛下的燃烧过程进行模拟计算。
对于反应流程中的燃烧反应采用-ABBC 最小自由能热力学分析方法，在质量平衡、化学平衡以及能量平衡的基础上研究煤在2! 3 )2!气氛下的燃烧。
采用生命周期影响评价软件ReCiPe2016 研究煤矸石和煤燃烧时As 和Pb 排放的环境效应
Received :2020⁃09⁃11;Revised :2020⁃11⁃10 *Corresponding author.E⁃mail :wangbaofeng @ ,cfangqin @. The project was supported by the Foundation of NSFC⁃Shanxi Coal⁃based Low Carbon Joint Fund (U 1610254)and Natural Science Foundation of Shanxi Province (201901D 111006).本文的英文电子版由Elsevier 出版社在ScienceDirect 上出版(http :// /science /journal /18725813).Study on the environmental effects of heavy metals in coal gangue and coalcombustion by ReCiPe2016for life cycle impact assessmentPENG Hao ,WANG Bao⁃feng *,YANG Feng⁃ling ,CHENG Fang⁃qin *(Institute of Resources and Environmental Engineering ,Engineering Research Center of CO 2Emission Reduction and ResourceUtilization⁃Ministry of Education of the People′s Republic of China ,Shanxi University ,Taiyuan 030006,China )Abstract :During coal and coal gangue combustion ,many heavy metal pollutants are emitted and cause serious environmental problems.In this paper ,the environmental effect values of As and Pb emission during coal gangue and coal combustion in the 330MW pulverized coal boiler ,50kW circulated fluidized bed boiler and laboratory were calculated by ReCiPe 2016.The results show that when coal combustion in 330MW pulverized coal boiler ,the environment effect values of As for bottom slag ,fly ash and flue gas are 3.28×10-6,2.68×10-5and 3.89×10-3respectively ;while the environment effect value of Pb for bottom slag ,fly ash and flue gas are 8.57×10-6,6.00×10-5and 4.83×10-2,respectively.The environmental effects of As and Pb in bottom slag are lower than those in the fly ash ;and the environmental effects of As and Pb on air are higher than those on soil.Moreover ,when coal combustion in the 50kW circulated fluidized boiler ,the effect values of As and Pb in fly ash on environment are 3.26×10-5and 1.28×10-4;and the effect values of As and Pb in bottom slag are 1.16×10-6and 1.43×10-5respectively.The results also show that when coal gangue combustion in the laboratory ,the effect values of As and Pb emission increase with increasing of the temperature ;and the proportions of total environmental effects of As and Pb on air are higher than those on soil.Besides that ,this study also indicates that the effect of Pb emitted into environment is higher than that of As at the same conditions during coal combustion both in circulated fluidized boiler and pulverized coal boiler.The results may provide basic data for predicting the environmental effects of As and Pb during coal gangue combustion in circulating fluidized bed for life cycle impact assessment.Key words :coal gangue ;heavy metals ;combustion ;environmental effect CLC number :TK 16 Document code :A Combustion is one of the main ways to use coal gangue and coal effectively.Coal gangue and coal contain many kinds of heavy metals which can be emitted and cause serious environmental pollution during combustion.Therefore ,studying environmental effects of heavy metals during coal gangue and coal combustion is extremely important.The occurrence modes of heavy metals can influence the emission of them during combustion ,so it is necessary to know the occurrence modes of these heavy metals.Xie et al [1]showed that arsenic in coal from western Guizhou was mainly associated with minerals ,and there was an obvious positive correlation between the content of arsenic and pyrite sulfur in coal.Feng et al [2]showed that arsenic in raw coal from northeast of China was mainly in residual form and arsenic in fire coal was mainly in ion exchange state.For mercury ,Kolker et al [3]showed that mercury in bituminous coal was found mainly within Fe⁃sulfides ,whereas lower rank coal tended to have a higher proportion of organic⁃bound mercury.Feng et al [2]found that the forms of mercury in raw coal and fire coal were mainly inresidual form.Cao et al [4]showed that the occurrence mode of mercury in coal gangue was similar to the occurrence mode of arsenic in coal gangue which was mainly in sulfide⁃bound form ,and mercury and arsenic in this form accounted about 67.66%to 72.68%and 56.71%to 79.36%of total mercury and arsenic respectively.Zhou et al [5]showed that As in coal gangue was in the occurrence modes of Fe⁃Mn oxide binding state ,residual binding state and carbonate binding state.There are also many studies about emission characteristics of heavy metals.Zhou et al [6]showed that Ni ,Cu ,Zn ,Cd ,Sn ,Pb and As were vaporized at intermediate temperature and had high volatilize ratio ,while V ,Cr ,and Co were relatively non⁃volatile.Lu et al [7]showed that the release fraction of Zn was the largest ,followed by Pb and Cd ,and the release fraction of Cu ,Ni and Cr were the least at the same co⁃incineration condition.Zhang et al [8]showed that Hg ,As ,Be and Cd in coal gangue were highly volatilized during combustion.Liu et al [9]showed that with increasing of the temperature ,the volatilize rate of As in coal during oxy⁃fuel combustion was第48卷第11期2020年11月燃 料 化 学 学 报Journal of Fuel Chemistry and Technology Vol.48No.11Nov.2020also increasing.Besides that,Spörl et al[10]showed that the Hg2+/Hg tot ratios in the flue gas were higher during oxy⁃fuel combustion compared to air⁃firing. Chen et al[11]showed that wet flue gas desulfurization had good removal efficiency on Hg2+,which was exhausted to plaster and wastewater,and the proportion was0.15∶1.Wang et al[12]showed that during coal gangue combustion,V2O5was tested as the sorbent and was found to effectively oxide elemental mercury(Hg0).Ultrafine V2O5particles were formed during coal gangue combustion process and resulted in a high surface area aerosol which could effectively catalyze the oxidation of Hg0. Hoffart et al[13]showed that Hg removal rates of50% -70%were realized for the bituminous coal by pre⁃treating the coal prior to a wash with hot concentrated HCl.Marczak et al[14]showed that the efficiency of As removal for subbituminous coal ranged from 21.86%to90.80%depending on the sorbent used. Duan et al[15]showed that before combustion high uranium coal,Se,Hg and U could not be fully removed through stepped release flotation.Furthermore,Tian et al[16]showed that there were serious ecological environmental risks of heavy metals pollution in soil around coal gangue mountain in Liuzhi mining area.Finkelman[17]showed that selenium,arsenic,lead,tin,bismuth,fluorine and other elements condensed when the hot gaseous emissions came in contact with ambient air and formed mats of concentrated efflorescent minerals on the surface of the ground.Liu et al[18]showed that Se and As in coal were more likely to be released into water in combustion,whereas Hg and Be were less likely to be released into water.Furthermore,Kong et al[19]showed that heavy metals pollution of soil and vegetation in waste incineration plants increased. Heavy metals contents in soil and vegetation are much higher than those in the background value.Zhang et al[20]used two calculation methods to calculate capacity of heavy metals in the Beijing Rivers in Pearl River Valley and obtained natural environment capacity of Cd as24.8-26.3kg/d for about202km long river section.Moreover,there are many studies about the environmental effect by using ReCiPe2016. Literatures showed that ReCiPe2016including eighteen midpoint indicators and eight endpoint indicators were used to generate a full⁃fledged cradle⁃to⁃farm gate life cycle assessment of greenhouse tomatoes in a typical Albanian farm,while spatial differentiation and indicators were not covered by contemporary life cycle assessments.ReCiPe2016[21] also was used to estimate impacts hydropower plants in alpine and non⁃alpine areas of Europe by a systematic life cycle assessment approach.Huijbregts et al[22]implemented human health,ecosystem quality and resource scarcity as three areas of protection and determined three environmental indicators including human health,ecosystem and resources of horticultural crops by ReCiPe2016.From previous literatures we could know that ReCiPe2016is applicable to calculate the environmental impact factors to assessment environmental effects of heavy metals for life cycle assessment.With the widespread concern of environmental effects of heavy metals in the whole world,it is necessary to understand the environmental effect of heavy metals emission during coal combustion.This paper mainly studies the environmental effects of As and Pb during pulverized coal combustion in pulverized coal boiler and lignite in circulated fluidized bed boiler by using the software of ReCiPe2016.Besides that,the environmental effects of As and Pb during coal gangue combustion in laboratory also is studied by using the software of ReCiPe2016.The aim of this paper is to clarify the environmental effect of As and Pb in coal and coal gangue during combustion at different sized reactors, and provide basic data for predicting the environmental effects of As and Pb during coal gangue combustion in circulating fluidized bed for life cycle impact assessment.1摇Methodology and variable description Life cycle impact assessment translates emissions and resource extractions into a limited number of environmental impact scores by means of so⁃called characteristic factors.ReCiPe2016is a kind of life cycle impact assessment software.According to the previous literatures,it can be used to calculate the environmental impact factors[23]and the scope of life cycle assessment by ReCiPe2016also includes environmental effects of heavy metals on soil and air during coal combustion.The environmental effects of As and Pb emission during coal combustion in330MW pulverized coal boiler,50kW circulated fluidized bed boiler and in the tube furnace in laboratory was studied as follows: Firstly,according to the previous works[24-30], the contents of As and Pb in lignite and pulverized coal during combustion in the330MW pulverized coal boiler and50kW circulated fluidized bed boiler were listed.Then the releasing contents of As and Pb during combustion in the two boilers were calculated respectively.Finally the environmental effects of As and Pb for1kg fuel during combustion were looked3041第11期PENG Hao et al:Study on the environmental effects of heavy metals in coal gangue and coal combustion through according to ReCiPe 2016,and the environmental effects of As and Pb emission during combustion in the 330MW pulverized coal boiler ,50kW circulated fluidized bed boiler and coal gangue combustion in laboratory were calculated respectively.The effect value of As and Pb emitted into the environment during coal combustion in the 50kW circulated fluidized bed boiler and 330MW pulverized coal boiler can be calculated according to formula (1),and the effect value of As and Pb emitted into environment during coal gangue combustion in the laboratory was calculated according to formula (2):E 1=b f ×c ×RP ×b e ×10-5(1)E 2=b f ×c ×r ×b e ×10-5(2)where E 1is effect values of As and Pb emitted into environment during coal combustion in the 330MW pulverized coal boiler and 50kW circulated fluidized bed boiler ;E 2is effect values of As and Pb emitted into environment during coal gangue combustion in the laboratory ,1,4⁃DCB eq.(1,4⁃DCB eq.is effect values of 1kg As and Pb emitted into soil and air.The effect value of As emitted into soil and air is 8.88and 3380259,respectively.The effect value of Pb emitted into soil and air is 9.77and 707927respectively );b f is fuel baseline ,kg ;c is the contents of As and Pb in coal and coal gangue ,g /kg ;RP is mass proportion of As and Pb from bottom slag ,fly ash and flue gas in circulated fluidized bed and pulverized coal boiler ,%;r is the volatilization rate of As and Pb during coal gangue combustion in the laboratory ,%;b e is environmental effect baseline ,1,4⁃DCB eq.By using ReCiPe 2016,the environmental effects of As and Pb emission during coal gangue and coal combustion in different scales of reactors can be calculated ,while the differences of the environmental effects of As and Pb emission during coal gangue and coal combustion at different operation conditions and different sized reactors cannot be determined.2 Result and discussion2.1 Emission characteristics of As and Pb during coal combustion in the 330MW pulverized coal boiler2.1.1 Content and relative mass distribution of As and Pb from the 330MW pulverized coal boilerAccording to the literature ,for the 330MW pulverized coal boiler ,the content of As and Pb in the pulverized coal is 3.84and 7.85mg /kg respectively [24].Table 1is the relative mass distribution of As and Pb from the 330MW pulverized coal boiler ,which is obtained from theprevious literature [24].According to these basic data ,the migration path of comparison of As and Pb and environmental effects of As and Pb emission during combustion coal gangue in the 330MW pulverized coal boiler was calculated.Table 1 Relative mass distribution of As and Pb from the330MW pulverized coal boiler Heavy metalDistribution w /%bottom slag fly ash flue gas As 9.6178.640.03Pb11.1878.040.87From Table 1,it can be seen that the relative proportions of As and Pb in fly ash are the highest and those in the flue gas are the lowest ,which imply that most of As and Pb are emitted into the fly ash during combustion.2.1.2 Environmental effects of As and Pb emission during coal combustion in the 330MW pulverized coal boilerTable 2shows environmental effects of As and Pb emission from various parts of the 330MW pulverized coal boiler [24].The environmental effects of As and Pb from bottom slag and fly ash on soil are only considered ,and the environmental effects of As and Pb from flue gas on air are considered.The environmental effect values are obtained according to the literature data by Hua et al [24].Table 2 Environmental effects of As and Pb emission duringcoal combustion in the 330MW pulverized coal boiler Ash location Environmental effect value(1,4⁃DCB eq.emitted to environment )As PbBottom slag 3.28×10-68.57×10-6Fly ash 2.68×10-56.00×10-5Flue gas3.89×10-34.83×10-2Table 2shows that in 330MW pulverized coal boiler the effect values for 1kg coal emitting As into environment from bottom slag ,fly ash and flue gas are 3.28´10-6,2.68´10-5and 3.89´10-3respectively ,and those for Pb from bottom slag ,fly ash and flue gas are 8.57´10-6,6.00´10-5and 4.83´10-2respectively.From the results it can be seen that the environment effect values of As and Pb from flue gas are the highest and those from bottom slag are the lowest.2.1.3 Migration path comparison of As and Pb during coal combustion in the 330MW pulverized coal boilerFigure 1is relative proportion of environmental4041 燃 料 化 学 学 报第48卷impacts of As and Pb emission from various parts of 330MW pulverized coal boiler equipped with an electrostatic precipitator combustion [24].Figure 1 Relative proportion of environmental effects of Asand Pb emission from various parts of 330MWpulverized coal combustionFigure 1shows that in 330MW pulverized coal boiler ,the relative proportion of environmental effects of As from bottom slag ,fly ash and flue gas are 0.08%,0.68%and 99.24%respectively ,and the relative proportion of environmental effects of Pb from bottom slag ,fly ash and flue gas are 0.02%,0.13%and 99.85%respectively.As is more enriched in fly ash and less enriched in bottom slag ,which is coinciding with the literature [25],and with the decreasing of the particle size of fly ash ,the concentration of As in fly ash is getting higher [26].The results also indicate that the most serious environmental effect of As and Pb emission is caused by flue gas ,and As and Pb in bottom ash cause less serious effect on environment.The reason maybe is that the occurrence mode of As in fly ash is different from that in bottom slag.As literatures report ,As in fly ash is mainly in residue state [27],while the occurrence mode of As in bottom slag is mainly in iron closed state [28].Therefore ,when combustion in 330MW coal pulverized boiler ,the effect value of As in fly ash emitting into environment is higher than that in the bottom slag.Besides ,the occurrence mode of Pb in fly ash also is different from that in bottom slag.The occurrence mode of Pb in fly ash is also mainly in residue state [29],while Pb in bottom slag is mainly in exchange state [29].Therefore ,the effect value of Pb in fly ash emitting into environment is higher than that in bottom slag.2.2 Emission characteristics of As and Pb during coal combustion in 50kW circulated fluidized bed boilerThe results of calculation value of environmental effects of As and Pb emission during coal combustionin 330MW pulverized coal boiler by ReCiPe 2016are consistent with the actual situation ,so we can infer that ReCiPe 2016is apt at analyzing the environmental effects of As and Pb during coal combustion ,and then we using it further calculate the environmental effects of As and Pb emission during lignite combustion in 50kW circulated fluidized bed boiler.2.2.1 Content and relative mass distribution of As and Pb from 50kW circulated fluidized bed boilerAccording to the literature ,the lignite was burned in a 50kW circulated fluidized bed boiler ,and the contents of As and Pb in lignite are 3.80mg /kg and 15.55mg /kg respectively [30].Table 3is the relative mass distribution of As and Pd in 50kW circulated fluidized bed boiler obtained from the literature by Zhao et al [26].The data are the basic data for comparison of As and Pb migration path and emission environmental effect during combustion.Table 3 Relative mass distribution rate of As and Pbfrom 50kW circulated fluidized bed boiler Heavy metalDistributian w /%bottom slag fly ash As 3.4496.56Pb9.3890.62From Table 3,we can see that the relative proportions of As and Pb in fly ash are higher than those in bottom slag.2.2.2 Environmental effects of As and Pb emission during lignite combustion in the 50kW circulated fluidized bed boilerTable 4is the environmental effects of As and Pb emission in bottom slag and fly ash on soil in 50kW circulated fluidized bed boiler [30],and the environmental effects value are calculated according to the data in literature [30].Table 4 Environmental effects of As and Pb emission during coal combustion in 50kW circulated fluidized bed boiler Ash location Environmental effect value (1,4⁃DCB eq.emitted to environment )As PbBottom slag 1.16´10-61.43´10-5Fly ash3.26´10-51.38×10-4Table 4shows that when combustion 1kg coal in 50kW circulated fluidized bed boiler ,the environmental effect values of As from bottom slag and fly ash are 1.16´10-6and 3.26´10-5respectively ,and the effect values of Pb from bottom slag and fly ash emitting into environment are 1.43´5041第11期PENG Hao et al:Study on the environmental effects of heavy metals in coal gangue and coal combustion10-5and1.38´10-4respectively.The environment effect values of As and Pb in fly ash are much higher than those in bottom slag.The reason also maybe that the occurrence modes of As and Pb in bottom slag and fly ash are different.Compared the environmental effect values of Pb in Table2and Table4,it can be seen that the environmental effect values of Pb during coal combustion in330MW pulverized coal boiler are lower than those in50kW circulated fluidized bed boiler.One of the reasons is maybe that Pb content in coal of330MW pulverized coal boiler is lower than that in the lignite burned in the50kW circulated fluidized bed boiler,and it also maybe is that 330MW pulverized coal boiler has devices to control heavy metals emission,while50kW circulated fluidized bed boiler does not have.2.3 Environmental effects of As and Pb emission during coal gangue combustion in laboratory2.3.1 Volatilization rates of As and Pb during coal gangue combustion in the laboratoryFor further understanding and prediction the environmental effect of coal gangue combustion in circulated fluidized bed boiler,the environmental effects of As and Pb emission during coal gangue combustion in laboratory is also studied by ReCiPe2016.Table5is the volatilization rates of As and Pb during coal gangue combustion at900and 1000℃in the laboratory,which is obtained from our previous work[31].Using these basic data,the environmental effects of As and Pb emission in the laboratory are calculated,and the migration path comparison of As and Pb during coal gangue combustion is also studied.Table5 Volatilization rates of As and Pb during coalgangue combustionHeavy metalVolatilization rate/% 900℃1000℃As94.6895.19Pb79.6881.43 Table5shows volatilization rates of As and Pb during coal gangue combustion[31].When the combustion temperature increases from900to 1000℃,the volatilization rates of As and Pb are also increasing.2.3.2 Environmental effects of As,Pb emission during coal gangue combustion Figure2shows the result of environmental effects of As for1kg coal gangue emitting into environment(soil and air)during combustion in laboratory without pollution control device[31].Figure2 Effect value of As emitting into environment during coal gangue combustion in laboratoryFigure2shows that for1kg coal gangue combustion at900℃in the laboratory,the effect values of As emitting into ash and air are3.60´10-2 and13729respectively,and at1000℃,the effect values of As emitting into ash and air change slightly. The proportion of total environmental effect of As emitting into air is higher than that into ash.Arsenic has high volatilization rate,and As diffuses faster in the atmosphere than in the soil.The majority of As in coal gangue emits into air as aerosol during combustion,and the environmental effect on air is higher.Figure3is the result of environmental effects of Pb for1kg coal gangue emitting into environment (soil and air)during combustion in laboratory[31].Figure3 Effect value of Pb emitting into environmentduring coal gangue combustionFigure3shows that for1kg coal gangue combustion at900℃in laboratory,the effect values of Pb retaining in ash and emitting into air are1.46´10-3and1054,respectively.At1000℃,the effect value of Pb emitting into air is higher than that at6041 燃 料 化 学 学 报第48卷900℃,and the proportion of total environmental effect of Pb emitting into air is also higher than that into ash.The reason is just the same as that of arsenic mentioned above.2.3.3 Migration path comparison of As and Pb during coal gangue combustion in laboratoryTable 6and Table 7are proportions of total environmental effects of As and Pb on soil and air for coal gangue combustion in laboratory respectively [31].Here we assume that As and Pb in ashes mainly have effect on soil and As and Pb in atmosphere mainly have effect on air.Table 6 Proportion of total effect of combustion Asemission in laboratory Temperature /℃Combustion w /%into soilinto air9002.6221×10-499.999710002.6298×10-499.9997Table 7 Proportion of total effect of combustion Pbemission in laboratory Temperature /℃Combustion w /%into soilinto air9001.3784×10-299.986210001.3814×10-299.9861Table 6and Table 7show that for coal gangue combustion at 900and 1000℃in the laboratory ,proportion of total environmental effects of As and Pb emitting into air are 99.9997%and 99.9862%respectively ,which implies that during coal gangue combustion in laboratory ,the environmental effects of As and Pb on air are the highest and dominant ,which maybe is because that there are not pollutants controlling devices in the process.3 ConclusionsHigher contents of As and Pb lead to higher environmental effect values ,and the environmental effects of As and Pb on air are much higher than those on soil.The environmental effects of As and Pb in bottom slag are lower than those in fly ash on soil both for 330MW pulverized coal boiler and 50kW circulated fluidized bed coal boiler.The environmental effect values of Pb emitting into air increase with the increasing of temperature during coal gangue combustion ,and the proportion of total environmental effects of As and Pb on air are higher than those on soil.The environmental effect values of Pb are higher than those of As at the same conditions in circulated fluidized boiler and pulverized coal boiler.AcknowledgmentsThe authors thank Prof.Jun Nakatani ,Ryosuke Yokoi and Yuichi Moriguchi in the University of Tokyo for their help throughout the course of this 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slag[J].Nonferrous Met,2018.5:69-73.[29] CHEN Y,HE K.Analysis of chromium and lead in coal combustion[J].Mod Business Trade Ind,2007.6:178-179.[30] ZHAO S,DUAN Y,ZHOU Q,ZHANG J,DU H,TANG H,LV J.Experimental study on trace elements emission characteristics in coal⁃fired circulating fluidized bed[J].Proc CSEE,2017,37(1):193-199.[31] PENG H,WANG B,YANG F,CAO Y,CHENG F.Emission characteristics of heavy metal during combustion of coal gangue and coalslime[J].Clean Coal Technol,2019,25(5):118-124.采用生命周期影响评价软件ReCiPe2016研究煤矸石和煤燃烧时As和Pb排放的环境效应彭 皓,王宝凤*,杨凤玲,程芳琴*(山西大学资源与环境工程研究所,CO2减排与资源化利用教育部工程研究中心,山西太原 030006)摘 要:在煤和煤矸石燃烧的过程中,许多重金属污染物排放到大气中,从而造成严重的环境问题,因此研究煤燃烧过程中重金属排放的环境效应很有必要㊂本研究运用ReCiPe2016软件计算了煤矸石和煤在330MW煤粉炉㊁50kW循环流化床和实验室燃烧时As和Pb排放的环境影响值㊂结果表明当煤在330MW煤粉炉燃烧的时候,底渣㊁飞灰㊁烟气中的As排放对环境的影响值分别是3.28×10-6㊁2.68×10-5㊁3.89×10-3,底渣㊁飞灰㊁烟气中的Pb排放对环境的影响值分别是8.57×10-6㊁6.00×10-5㊁4.83×10-2㊂底渣中的As和Pb排放对环境的影响比飞灰中低;As和Pb排放到大气对环境的影响比排放到土壤高㊂另外,当煤在50kW循环流化床燃烧的时候,飞灰中的As和Pb排放对环境的影响值分别是3.26×10-5和1.28×10-4,底渣中的As和Pb排放对环境的影响值分别是1.16×10-6和1.43×10-5㊂本文的研究结果还表明当煤矸石在实验室燃烧的时候,随着燃烧温度的升高,As和Pb排放对环境的影响值升高㊂另外,As和Pb排放到大气对环境的影响占总环境的影响比例比排放到土壤高㊂此项研究还表明当煤在煤粉炉和循环流化床燃烧的时候,相同工况下Pb排放对环境的影响比As高㊂这项结果也为运用生命周期影响评价软件预测煤矸石在循环流化床燃烧As和Pb排放的环境影响提供基础数据㊂关键词:煤矸石;重金属;燃烧;环境效应中图分类号:TK16 文献标识码:A。
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ShortCommunicationAtmosphericemissionsestimationofHg,As,andSefromcoal-firedpowerplantsinChina,2007
HezhongTiana,⁎,YanWanga,ZhigangXueb,YipingQua,FaheChaib,JimingHaocaStateKeyJointLaboratoryofEnvironmentalSimulation&PollutionControl,SchoolofEnvironment,BeijingNormalUniversity,Beijing100875,China
bChineseResearchAcademyofEnvironmentalSciences,Beijing100012,China
cDepartmentofEnvironmentalScienceandEngineering,TsinghuaUniversity,Beijing100084,China
abstractarticleinfoArticlehistory:Received30August2010Receivedinrevisedform18April2011Accepted21April2011Availableonline31May2011
Keywords:EmissionHgAsSeEmissionfactorCoal-firedpowerplants
OverhalfofcoalinChinaisburneddirectlybypowerplants,becominganimportantsourceofhazardoustraceelementemissions,suchasmercury(Hg),arsenic(As),andselenium(Se),etc.Basedoncoalconsumptionbyeachpowerplant,emissionfactorsclassifiedbydifferentboilerpatternsandairpollutioncontroldevicesconfiguration,atmosphericemissionsofHg,As,andSefromcoal-firedpowerplantsinChinaareevaluated.ThenationaltotalemissionsofHg,As,andSefromcoal-firedpowerplantsin2007arecalculatedat132t,550t,and787t,respectively.Furthermore,accordingtothepercentageofcoalconsumedbyunitsequippedwithdifferenttypesofPMdevicesandFGDsystems,speciationofmercuryisestimatedasfollows:80.48tofHg,49.98tofHg2+,and1.89tofHgP,representing60.81%,37.76%,and1.43%ofthetotals,respectively.TheemissionsofHg,As,andSeinChina'seasternandcentralprovincesaremuchhigherthanthoseinthewest,exceptforprovincesinvolvedintheprogramofelectricitytransmissionfromwesttoeastChina,suchasSichuan,Guizhou,Yunnan,Shaanxi,etc.©2011ElsevierB.V.Allrightsreserved.
1.IntroductionThemajoruseofcoalisthegenerationofpowerthroughcombustion(Pavageauetal.,2002).Duringthecombustionprocess,significantamountsofvolatiletoxictraceelementssuchasmercury(Hg),arsenic(As),andselenium(Se)arereleasedanddistributedamongfluegasandflyash(Pavageauetal.,2002;Otero-Reyetal.,2003;Al-Abedetal.,2008).ThedangerouseffectsofHg,As,andSeontheenvironmentandpublichealthhavereceivedwiderangeofattentionthroughouttheworld(LenzandLens,2009;Dukeretal.,2005;Nelson,2007;WiedinmyerandFriedli,2007;ZhangandWong,2007).InChina,coalconstitutesabout70%ofthetotalprimaryenergyconsumption(YouandXu,2009).About55%ofthetotalcoalconsumedwasburneddirectlybypowerplantsin2007(NBS,NDRC,2009);anditispredictedthattheproportionwillincreaseto65%in2050(YouandXu,2009).Thus,coal-firedpowerplantshavebecomeonemainsourceofatmosphericconventionalairpollutantsemissions(PM,SO2,NOX),aswellashazardousairpollutantsemissions(Hg,As,andSe,etc.)inChina(WangandGao,2001;Wuetal.,2006;Streetsetal.,2005;Wangetal.,2008a).Inrecentyears,thereisawidespreadconcernoverthecontrolandreductionofatmosphericHgemissionsinChina(Wuetal.,2006;Streetsetal.,2005;FengandHong,1996;Wangetal.,2000;Jiangetal.,2005).Wuetal.(2006)estimatedthatmercuryemissionfromcoal-firedpowerplantsinChinaincreasedfrom63.4tto100.1twithanannualgrowthrateof5.9%during1995–2003.However,thecomprehensiveanddetailedstudiesonAsandSeemissionsarequitelimited.Wangetal.(2008a)estimatedthat442.31tofAswerereleasedfromcoalcombustionin1997,and76.9tofwhichwerefromcoal-firedpowerplants.Controlofhazardouselementsemissionsfromcoal-firedpowerplantsrequiresanunderstandingofthemannerinwhichtheyoccurincoal,theirbehaviorduringcombustion,theirabatementthroughvariousairpollutioncontroldevices(APCD),theirforminthestackgas,aswellasthefinalamountreleasedintotheatmosphere.Inthispaper,atmosphericemissionsofHg,As,andSefromcoal-firedpowerplantsinChinaundertheexistingparticulatematters(PM)andsulfurdioxides(SO2)controlconditionsareevaluatedanddiscussedindetail
byprovincesandregionsin2007.
2.MethodologyAtmosphericemissionsofHg,As,andSefromcoal-firedpowerplantsarecalculatedbycombiningthedetailedcoalconsumptiondata,elementcontentsincoal,andthespecificemissionfactorswhichareclassifiedbydifferentboilerpatternsandairpollutioncontrol
ScienceoftheTotalEnvironment409(2011)3078–3081⁎Correspondingauthorat:SchoolofEnvironment,BeijingNormalUniversity,No.19XinjiekouwaiStreet,Beijing100875,China.Tel./fax:+861058800176.E-mailaddress:hztian@bnu.edu.cn(H.Tian).
0048-9697/$–seefrontmatter©2011ElsevierB.V.Allrightsreserved.doi:10.1016/j.scitotenv.2011.04.039
ContentslistsavailableatScienceDirectScienceoftheTotalEnvironment
journalhomepage:www.elsevier.com/locate/scitotenv