大气复习题 电子版

1、1. FGD is Flue Gas Desulfurization.2. EGR is Exhaust Gas Recycle.3. ESPs is Electrostatic Precipitators.4. ODP is ozone depletion potential.5. VOCs is volatile organic compounds.6. Some of the most important air pollutions are secondary pollutants, formed in the atmosphere from primary pollutant pre

2、cursors.7. Before 1960, our principal concern about air pollution effects was with property damage. Since 1960, we have been concerned primarily with human health.8. Air pollution: is the presence of man-made harmful materials in the air, in quantities large enough to produce harmful effects.9. Glob

3、al warming (greenhouse effect): Humana are putting gaseous materials into the atmosphere that may cause the earths average temperature to rise.10. The overall air pollution problem takes the following form: emission transport, dilution, and modification in the atmosphere effects on people, property,

4、 and the environment. 11. The basic problems in ambient monitoring and source testing are the collection of a representative sample and the correct analysis of that sample. The collection of a representative sample is the harder part.12. The two meteorological parameters of greatest interest to air

5、pollution engineers are the atmosphere stability and the wind speed.13. In general, stable atmospheres and low wind speeds lead to the highest ground-level pollution concentration.14. Pollutant concentration models are based on known emission rates and meteorology.15. Gaussian plume models are widel

6、y used for point sources.16. If we have an air pollution problem how do we solve it? There are three control options available.(1) Improve dispersion: tall stacks, intermittent control schemes, relocate the plant;(2) Reduce emission by process change, pollution prevention;(3) Use a downstream pollut

7、ion control device.17. “3T” are time, temperature and turbulence.18. If one is face with an air pollution problem, the alternatives for alleviating it are improved dispersion, process change, or downstream control devices.19. In current U.S. law and practice the first choice is process change; the s

8、econd is a downstream control device; and only if these, taken together, cannot meet the applicable standard may improved dispersion be used.20. If the pollutant is valuable itself or as a fuel, and if its concentration is high enough, the best control solution may be to recover the pollutant or use

9、 it as a fuel.21. In most calculations, the penetration is a more convenient measure of control equipment performance than is the control efficiency.22. Most air pollutants are the direct and indirect result of combustion or processes using combustion.23. All pollution control devices that teat gase

10、s with even trace amounts of SO2 must be protected against acid dew point corrosion.24. Catalysts are widely used in air pollution control. The catalyst support in the form of a honeycomb is most widely used because its pressure drop is less than that of alternative forms.25. The particles of air po

11、llution interest are mostly in the size range 0.1to 10.26. Particles smaller than about 2 are rarely produced by mechanical means; they are primarily produced by condensation or chemical reaction of gases or vapors.27. These small particles behave quite differently from the particles with which we a

12、re familiar, like sand and gravel. Their high surface area per unit mass makes them adhere to one another if they are brought into contact.28. Because particles of air pollution interest are rarely present in the air or in a gas stream as a uniform particle size set, we normally have to deal with th

13、e distribution of particle size.29. The fine particles in the atmosphere are largely secondary particles, formed in the atmosphere from gaseous precursors. Most of the coarser particles in the atmosphere are primary particles, which enter the atmosphere as particles.30. Gravity settling chambers, cy

14、clones, and ESPs work by driving the particles to a solid wall where they form agglomerates that can be collected.31. Filters and scrubbers divided the flow. They have different design equations from wall collection devices and from each other.32. Surface filters are used to collect most of the part

15、icles in a heavily laden gas stream. Depth filters are mostly used for the final cleanup of air or gas that must be very clean or for fine liquid drops.33. To collect small particles, a scrubber must have a very large relative velocity between the gas being cleaned and the liquid drops. For this rea

16、son co-flow scrubbers are most often used. The venture scrubber is the most widely used type of co-flow scrubber.34. The VOCs control alternatives are prevention, concentration and recovery, or oxidation.35. What are the development problems with limestone scrubbers?(1)corrosion; (2)solids depositio

17、n, scaling and plugging; (3)entrainment separator plugging; (4)poor reagent utilization; (5)poor solid-liquid separation.36. SO2 emissions from human activities are mostly due to the combustion of sulfur-containing fossil fuels and the smelting of metal sulfide ores.37. What is the overall control s

18、trategy for SO2 emissions?(1) Convert the sulfur to CaSO4·2H2O and return it to the ground in some kind of landfill(2) Use CaSO4·2H2O to make wallboard.38. What is the most common approach for liquid or gaseous fuels containing reduced sulfur?The most common approach is to use catalytic pr

19、ocess to convert the contained sulfur to H2S, remove that by scrubbing the gas with a weakly alkaline solution, convert the H2S to elemental sulfur by the Claus process克劳斯二段脱硫法, and either sell that sulfur for sulfuric acid production or place it in a landfill.39. For metal sulfide ore smelting, whi

20、ch produces waste gases with 4 percent or more SO2, the common approach is to convert that SO2 to sulfuric acid.40. For coal used in a large power plant, the most common approach is to burn the coal and then treat the plants exhaust gas with limestone or lime in a forced-oxidation wet scrubber or a

21、spray dryer, to convert SO2 to CaSO4·2H2O, which will then go to a landfill or a wallboard plant.41. Combustion scientists classify the nitrogen oxides found in combustion gases as thermal, prompt, and fuel nitrogen oxides.42. The rate of conversion of NO to NO2 in flames is fairly slow, so tha

22、t most of the NOx in flames is NO. The proportion is typically 90 percent NO, 10 percent NO2.43. Global warming, destruction of the ozone layer, and acid rain are pollution problems that cannot dealt with mostly local regulations局部调节 used for other air pollutants. If action is to be taken, worldwide

23、 action is need.1Air pollution is the presence of man-made harmful materials in the air, in quantities Large enough to produce harmful effects.2A perfect air pollution philosophy and its implementing regulations are cost-effective, simple, enforceable, 灵活性 and 变革性 .3Generally there are two kinds of

24、air pollution measurements: ambient measurements and 污染源 measurements.4In stack sampling for particulatesbut not in any sampling for gasesone must maintain 等动力流速 into the sampling probe.5The horizontal movement of the atmosphere is driven mostly by uneven heating of the earths surface and modified b

25、y the effect of 地球的旋转 and the influence of the ground the sea.6Pollutant concentration models are based on known emission rates and 气象条件 .These models play a crucial role in the Air Quality Management type of air pollution control strategy currently used in the United States and much of the rest of

26、the world.7In air pollution control, we can indicate three logical approaches to improving dispersion:tall stacks, intermittent control schemes, 尾气处理 .8As shown in any fluid mechanics book there is an 最佳经济流速 for pumped fluid flows. This velocity minimizes the sum of pumping costs and the capital cha

27、rges for the equipments.9Consequently, any air pollution control device that treats a gas containing SO2 must either be made of corrosion-resistant materials, which are expensive, or be protected against 酸露点 corrosion.10Any two particles that have the same value of D will have the same Stokes stoppi

28、ng distance for any initial velocity (in air with the same viscosity).11The finest particles, with diameters 0.005 to 0.1, enter the atmosphere mostly by 热蒸汽冷凝 from combustion sources. Over time these smallest particles grow, mostly by agglomeration onto each other.12The first three types of control

29、 devices we considergravity settlers, 旋风分离室 , 静电除尘室 all function by driving the particles to a solid wall, where they adhere to each other form agglomerates that can be removed from the collection device and dispose of.13We may now state, as an approximate rule, that VOCs are those organic liquids o

30、r solids whose room temperature vapor pressures are greater than about 0.01psia and whose atmosphere boiling points are up to about 500F , which means most organic compounds with less than about 12 carbon atoms.14If possible, we prevent the formation of a VOC-containing air or gas stream, which we m

31、ust treat by some kind of tailpipe control device. The ways of doing this for VOCs are 使用替代品 , process modification, and leakage control.15The SO2 concentrations in off-gases from the smelting of metal sulfide ores depend on which process is used and vary with time within the batch smelting cycle. H

32、owever, they generally range 2%4% SO2. Such gases can be economically treated in plants that produced 硫酸 .16Combustion scientists classify the nitrogen oxides found in combustion gases as 热力型 , prompt, and fuel nitrogen oxides.一 Question and answer. (6 points per question, 24 points in all)1 Give th

33、e four ways to produce an inversion.、 自下而上的冷空气、 自上而下的热空气、 驱动一个冷空气层到暖空气层下面、 驱动一个暖空气层到冷空气层上面2Give the components of a typical pollution control system.污染物捕货设备、控制设备、气体推动器、对收集物质的再循和处理系统、烟囱。3Give the assumptions of Stocks law. 、流体是连续的、流动是层流状的、黏度符合牛顿粘性定律在公式中所有的平方项可以忽略4Give the development problems with fo

34、rced-oxidation limestone wet scrubber.、腐蚀、固体沉积 、雾沫分离器易堵塞、反应试剂利用不充分、固液分离率低四Calculation.（36 points in all）1A city has the following description: W=8km, L=20km, u=3m/s, H=800m. The upwind, or background, concentration of SO2 is b=3g/m3. The emission rate per unit area is q=6×10-6g/m3. What is the

35、concentration c of SO2 over the city? (7 points)2 Estimate the cut diameter for a cyclone with inlet width 0.7ft, Vc=58ft/s and N=5. (part=2500kg/m3,=1.8×10-5kg/m·s) (7 points)3A waste stream contains particles of three sizes: large, medium, and small. These are present in equal quantities

36、 by weight in the gas stream. We pass this gas stream through a collector that is 97 percent efficient on large particles, 68 percent efficient on medium particles, and 30 percent efficient on small particles. What is the overall weight percent efficiency of this collector? (7 points)4C2H6 is burned

37、 in air with 20 percent excess air and air moisture of 0.0124mol/mol dry air. What are the flow rate of combustion air and the composition and flow rate of the combustion products? (15 points)1The 固定盒子模型 and 高斯烟羽模型 of particles are used as a way of estimating the emissions of particles in plumes fro

38、m chimneys and other sources.2An air pollution control philosophy is a fundamental set of ideas about how one determines what constitutes an appropriately clean environment, appropriate cost, and appropriate 分配 of that cost.3Generally the ambient air sampler should be located at the place to which t

39、he public has 经常性出入 where the pollutant concentration is highest.4The Emission Factors compilations produced by the EPA allow us to estimate emissions from 现有的或新的污染源 quickly and cheaply. Often these compilations provide a practical substitute for emission measurements and a guide to the literature o

40、n testing of many kinds of sources.5The professional interest of air pollution control engineers in meteorology is mostly with 风速 and with 大气稳定性 .6All air pollutant concentration models are applied to one air pollutant at a time. Most models can be used for several different pollutants, but they mus

41、t be applied 各自独立 .7If we have an air pollution problem there are three control options available: 促进扩散, reduce emissions by process change, use a downstream pollution control device.8The designer of the whole air pollution control system would be expected to specify the gas flow rate, the concentra

42、tion and chemical nature of the pollutants in the gas, 去除反应机制 , and the disposal method for the collected pollutant.9If acid gases were not involved, the temperature requirement to avoid condensation would not be difficult. However, small amounts of acids, particularly sulfuric acid, can 升高 the dew

43、point dramatically.10Some authors use the term PM10 to refer to all particles smaller than 10 and PM2.5 to refer to those smaller than 3.5.11Filters and 洗涤器 do not drive the particles to wall, but rather divide the flow into smaller parts where they can collect the particles.12In U.S., more than 80%

44、 VOCs came from solvent usage, 运输 and storage of VOCs, and motor vehicles. 13Tanks containing liquid VOCs can emit VOC vapors because of filling and emptying activities as well as changes in temperature and atmospheric pressure. These emissions are called filling or displacement losses, emptying los

45、es, and 呼吸损失 , or, collectively, working losses.14The sulfur-containing gas streams most often dealt with in industry belong to three categories 还原态硫 ，concentrated SO2 streams, and dilute SO2 streamseach with own control method. 15Most of the coal-burning electric power plants, the typical SO2 conte

46、nt of the exhaust gas is about 稀的 SO2. The most widely used procedure for controlling SO2 emissions from these sources is scrubbing with water containing finely ground 石灰石法 .16At high temperature 热力型 NO forms fairly quickly, but the times available for its formation are short enough that equilibrium

47、 may not be reached.一 Question and answer. (6 points per question, 24 points in all)1 Give the four philosophies of air pollution control.、排放标准、空气质量标准、排放税、费用效益原则2Give the condition of the peak temperature of open flames depending on.、燃料和氧化剂；、火焰温度；、空燃预混合程度；、空燃预加热的量3Give four wet approaches for removi

48、ng SO2 except forced-oxidation limestone wet scrubber.、湿式一次性法；、双碱法；干湿系统法；、再生系统法4 Give the assumption for the block flow model.、沉降室内气体平均流速等于；、气体中颗粒物速度的水平分量一直等于、颗粒物速度的垂直分量等于在重力作用下的终端速度、如果颗粒物一旦沉降到底就会滞留在哪里，不再进入沉降室。四Calculation.（36 points in all）1Estimate the plume rise for a 5-m diameter stack whose exi

49、t gas has velocity of 25m/s when the wind velocity is 4m/s, the pressure is 1atm, and the stack and surrounding temperature are 120 and 20, respectively. (7 points)2We wish to use three collectors in series. Each of the collectors has an efficiency of 96 percent. What is the overall efficiency of th

50、e group of three in series? (7 points)3Compute the terminal settling velocity in air of a sphere with diameter 2. (7 points) (g=9.81m/s2, part=2500kg/m3, fluid=1.15kg/m3, =1.8×10-5kg/m·s)4A “typical coal” has the following ultimate analysis by weight: H-4.0%; C-76.8%; N-1.3%; S-1.8%; O-7.6

51、%; ash-8.5%. It is burned with 20% excess air with humidity 0.0116mo/mol dry air, and combustion is complete. Determine the amount an composition of the gas produced. (15 points)1. FGD is 烟气脱硫 .2.The principal pollutants emitted from simple gasoline-powered IC engines are 一氧化碳、碳氢化合物、氮氧化合物 .3. In mos

52、t calculations, the 穿透率 is a more convenient measure of control equipment performance than is the control 去除率 .4. 过滤器 and 洗涤器 do not drive the particles to wall, but rather divide the flow into smaller parts where they can collect the particles.5. The two meteorological parameters of greatest intere

53、st to air pollution engineers are 风速 and 大气稳定性 .6. The SO2 concentrations in off-gases from the smelting of metal sulfide ores depend on which process is used and vary with time within the batch smelting cycle. However, they generally range 2%4% SO2. Such gases can be economically treated in plants

54、that produced 硫酸 .三、Answer in brief. (60 points in all)1. Please describe the factors to drive the horizontal movement of the atmosphere? (3 points)、赤道的加热和极地的冷却；地球自转作用；、陆地和海洋的影响。2. Please describe the ways to produce the temperature inversion? (4 points)自下而上的冷空气；自上而下的热空气；驱动一个暖气层到冷空气层上面；驱动一个冷空气层到暖气层下

55、面3. Please describe the basic Gaussian plume equation and fixed-box models. (4 points)、4. Please describe a typical pollution control system components. (5 points)污染物捕获器，控制设备、气体推动器、对物质的收集循环和处置系统，烟囱。5. Please describe the four-stroke of IC gasoline engine. (4 points)该发动机有四冲程：进气，压缩、动力、排气。动力来源于动力冲程，其他冲程都消耗动力。6. Please describe the mechanism of th