绿色能源与环境保护Lecture+2

1、1Pollution from Coal UtilizationPollution from Coal UtilizationLimin Chen（陈礼敏）Tel:E-mail:Office: B4-5052 Introduction Coal formation Coal classification Coal extraction Utilization Pollution from coal “Clean coal” technologies SummaryMain Contents345Coal formationCoal, a fossil fuel, is the largest

2、source of energy for the generation of electricity worldwide, as well as one of the largest worldwideanthropogenic sources of carbon dioxide emissions. Gross carbondioxide emissions from coal usage are slightly more than thosefrom petroleum and about double the amount from natural gas.Coal begins as

3、 layers of plant matter accumulate at the bottom of abody of water. For the process to continue the plant matter must beprotected from biodegradation and oxidization, usually by mud oracidic water. The wide shallow seas of the Carboniferous periodprovided such conditions. This trapped atmospheric ca

4、rbon in theground in immense peat bogs that eventually were covered overand deeply buried by sediments under which they metamorphosedinto coal. Over time, the chemical and physical properties of theplant remains (believed to mainly have been fern-like speciesantedating more modern plant and tree spe

5、cies) were changed bygeological action to create a solid material.6Coal FormationCoal formation relies on three factors:“(1) initiation, maintenance, and repetition of environments that favor large-scale accumulation and preservation of vegetal sediment; “(2) conditions within this depositional envi

6、ronment that favor biological degradation and alteration of the vegetal sediment to peat peatification; and “(3) geochemical processes that induce chemical coalification of the peat to higher-rank coal.”DiCiccio, 1996 Sediment burial, subsidence of peat bogs Completely cuts off contact with atmosphe

7、ric oxygen Overburden: compaction and subsidence Increase pressure, temperature7煤的生成过程 煤主要是远古时代的高等植物在地壳运动中被深埋在地下或水中，其残体在缺氧条件下被厌氧细菌生化降解，纤维素、木质素、蛋白质等被分解并聚缩，形成胶体状的腐殖酸。 其余具有抗腐能力的部分如树脂、角质、孢子等保留原有形态分散在腐殖酸中，逐步变成含水很多、黑褐色的泥炭。这是成煤的第一阶段泥炭化阶段。 经过漫长的地质年代，泥炭在地热和泥沙覆盖层不断增厚或地壳下沉而受压增大的作用下，泥炭层被压实、失水，其化学性质和成分发生变化。泥炭的密度

8、和碳含量相对增加，腐殖酸、水分、氧、氢和甲烷等挥发物逐渐减少。随着泥炭的质变由浅到深，依次形成不同种类的褐煤、烟煤、无烟煤等。这是成煤的第二阶段煤化阶段。8石油的生成过程 石油的生成过程与煤相似。它的形成物质主要是低等动、植物遗体中的脂肪、蛋白质和碳水化合物。 这些有机物质的沉积物在地壳长期缓慢下降中不断增厚，或在深水中被沉积保存。同样经历了缺氧或强还原环境中的细菌分解阶段和温度、压力增加条件下的转化阶段，碳和氢的含量富集，形成一种流动或半流动的粘稠性液体。 石油的生成条件要求较严格，沉积过程初期，温度和压力不够，不能生成石油。当沉积深度达到1 0004000m，温度达到6050时有机质生成大

9、量石油。若压力和温度进一步增加，有机质被热分解，如深度超过4000m，温度超过150200后几乎不能生成石油。9Petroleum & Natural Gas formation vs. Coal formation Not-so-well-understood differences in formation: Organic matter: Petroleum & Natural Gas: marine OM Coal: terrestrial OM Pressure Temperature Presence of solutions10Coal composition c

10、oal contained significant carbon, and smaller percentages of the elements hydrogen, oxygen, nitrogen, and sulfur. Inorganic compounds such as aluminum and silicon oxides constitute the ash.11The classification of coal Coal is not homogeneous it needs classification. Describes extent of geologic chan

11、ge and metamorphism since deposition as peat Low Rank High Rank parallels:Loss of recognizable plant remains (macerals)Dull shiny luster Increasing hardnessIncreasing Ash content12The classification of coalNameVolatiles %Carbon %Hydrogen %Oxygen %Sulfur %Heat content kJ/kgBraunkohle (Lignite)45-6560

12、-756.0-5.834-170.5-39.8132870Gasflammkohle (Gas flame coal)35-4082-855.8-5.69.8-7.3133910Gaskohle(Gas coal)28-3585-87.55.6-5.07.3-4.5134960Fettkohle(Fat coal)19-2887.5-89.55.0-4.54.5-3.2135380Esskohle(forge coal)14-1989.5-90.54.5-4.03.2-2.8191.53.752.5135300Percent by weightLignite 褐煤， Subbituminous

13、 亚烟煤， Bituminous 沥青煤，Flame coal烟煤，Gas flame coal亚烟煤，Gas coal气煤，Fat coal肥煤，forge coal锻造煤炭，Non bakeing coal贫煤，Anthracite无烟煤LigniteLigniteSubbituminousSubbituminousBituminousBituminousAnthraciteAnthracite13Coal Grade Describes size, appearance, weight, structure, cleanliness, heat value and burning cha

14、racteristics. A: Superior 16% ash14Coal Extraction Open Pit Mining Most minerals are extracted this way For near-surface ore bodies Series of benches are cut15Surface Mining16Underground Mining Used when ore is far below surface Features: Vertical shaft or inclined passageway Drifts and crosscuts cr

15、eated to expose face Broken rock hauled from face and up to the surface17Underground Mining: Drift斜坑采煤18Underground Mining: Slope俯斜式采煤19Underground Mining: Shaft立井开采20Longwall Mining长壁开采21Social Effects Mine disasters Roof falls, moving coal, explosions and other (as of 1928 they were: 60%, 20%, 10%

16、, and 10% respectively). Rock dusting, inspection of hazardous sites,n good lighting, screening and moving parts of n machinery, marked safety exits, and employ a trained crew and hospital room in the mine.22232425Other Uses of Coal Today Gasification or Hydroliquefaction: blasting coal with steam t

17、o produce Carbon Monoxide and Hydrogen gas.The Pion Pine plant near Reno, Nevada. Converts Coal into Hydrogen gas.Advantages of Coal Burning Power Plants Safe burning High Efficiency (Work Output/Work Input)26Other Uses of Coal Today Paper, brick, limestone, and cement industries. Residential Heatin

18、g Coal furnaces have been replaced by oil or gas furnaces or by electric heat pumps. Less than one percent of the coal produced in the U.S. today is used for heating.27Miscellaneous Products Made from Coal Today Carbolic acid Fire Proofing Food Preservatives Billiard Balls Medicines Perfumes Baking

19、Powder Rubber cement fertilizer Paint pigments Sulfur TNT explosive Linoleum28Coal Combustion Products烟气脱硫产物29Coal Combustion Product UsesFly Ash: concrete, structural fill, and waste stabilizationBottom Ash: structural fill, snow and ice control, road bases, and concrete. FGD Material: wallboard ma

20、nufacture Boiler Slag: 煤渣 blasting grit and roofing applications Hungry Horse Dam in Montana was built between 1948 and 1953 with concrete containing 120,000 metric tons of fly ash. 30The Benefits of Using Coal Combustion Products Environmental and economic benefits. Reduced mining costs, disposal c

21、osts, landfill space usage. In concrete: reduction of Carbon Dioxide emissions by substituting ash for Portland cement. Mines: Injection of CCPs in abandoned mines controls subsidence and lessens acid mine drainage31Air Quality Effects of coal combustion on air Sulfur Dioxide - acid rain Flyash - pa

22、rticulate matter pollution Clean Air Act of 1970 National Ambient Air Quality Standards (NAAQS) 3 Ways to Control Pollutants Pre-Combustion Removal Post-Combustion Removal Use of Low Sulfur Coal32Air Quality:Sulfur Content of CoalsRankLow: 0-1%Med.: 1-3%High: 3+%Anthracite97.12.8-Bituminous29.826.84

23、3.4Subbituminous99.60.4-Lignite90.79.3-All Ranks65.015.020.033Water Quality Acid Mine Drainage34Water Quality Sedimentation Control Clean Water Act NPDES required for mining operations Cleanup Calcium Carbonate added to some water bodies to raise pH. 35Federal Environmental Laws National Environment

24、al Policy Act Federal Land Policy and Management Act Clean Air Act Federal Water Pollution Control Act Safe Drinking Water Act Comprehensive Environmental Response, Compensation and Liability Act Many others36What is “clean coal”? Coal is a highly polluting energy source. From mine to sky, it contam

25、inates every step of the way. From acid drainage from coal mines polluting rivers and streams, to the release of cancer-causing dioxins and other toxins when it is burned, as well as pollution-forming gases and fine particulates that wreak havoc on human health, coal is a dirty business. It is a maj

26、or contributor to climate change the biggest environmental threat we face. It is the most carbon-intensive fossil fuel, emitting 72% more carbon dioxide (the main driver of climate change) per unit of energy than gas. Mercury is a particular problem. According to the United Nations Environment rogra

27、mme (UNEP), mercury and its compounds are highly toxic and pose a global environmental threat to humans and wildlife.2 Coal-fired power and heat production are the largest single source of atmospheric mercury emissions.3 There are no commercially availabletechnologies to prevent mercury emissions fr

28、om coal-fired power plants. “Clean coal” is the industrys attempt to “clean up” its dirty image the industrys greenwash buzzword. It is not a new type of coal. “Clean coal” technology (CCT) refers to technologies intended to reduce pollution. But no coal-fired power plants are truly clean.37“Clean C

29、oal” Technologies “Clean coal” technologies fall into four main categories coal washing, pollution controls for existing plants, efficient combustion technologies and experimental carbon capture and storage.1) Coal washing Lowers the level of sulphur and minerals in the coal. Coal is not generally w

30、ashed in New Zealand, although Solid Energy has a coal washing facility near its Spring Creek Mine. It is also trialling coal washing technologies using its high-sulphur Reefton coal .38“Clean Coal” Technologies2) Pollution Controls for Existing Power PlantsParticulate emissions can be reduced by El

31、ectrostatic Precipitators (ESPs) and fabric filters. ESPs are most widely used. Flue gases are passed between collecting plates. These attract particles using an electrical charge.NOX emissions can be reduced by Low-NOX Burners (LNB). These reduce the formation of NOX by controlling the flame temper

32、ature and the chemical environment in which the coal combusts. Selective Catalytic or Non-Catalytic Reduction (SCR/SNCR) are expensive and less widely used.SO2 emissions - can be reduced by Flue Gas Desulpurisation (FGD). Wet FGD, or wet scrubbing, is most common and absorbs SO2 using a sulphur abso

33、rbing chemical (sorbent), such as lime.Trace elements emissions these include mercury, cadmium and arsenic. Some emissions can be reduced by particulate controls, fluidised bed combustion and FGD equipment. Activated Carbon Injection is being trialled to remove mercury.39“Clean Coal” Technologies3)

34、Efficient Combustion TechnologiesSupercritical Pulverised Coal Combustion (PCC) - uses high pressures and temperatures. This can increase the thermal efficiency of the plant from 35% to 45%. This reduces emissions as less coal is used.Fluidised Bed Coal Combustion (FBC) - allows coal combustion at r

35、elatively low temperatures, which reduces NOX formation. A sorbent is used to absorb sulphur.Coal gasification - coal is reacted with steam and air or oxygen under high temperatures and pressures to form syngas (mostly carbon monoxide and hydrogen). Syngas can be burnt to produce electricity or proc

36、essed to produce fuels such as diesel oil. Integrated Coal Gasification Combined Cycle (IGCC) is the technology behind some experimental zero emission projects. It is considered the most suitable technology for possible carbon capture and storage but less reliable than other options. In IGCC a gas t

37、urbine burns syngas to produce electricity. Exhaust heat from the turbine is used to produce steam to power a steam turbine. Integrated Gasification Fuel Cells (IGFC) - a zero emission technology under development that does away with the steam cycle. It uses hydrogen from coal gasification in a soli

38、d fuel cell to produce electricity. 4041Supercritical Pulverised Coal Combustion (PCC)42Fluidised Bed Coal Combustion (FBC)43Integrated Coal Gasification Combined Cycle (IGCC)44Integrated Gasification Fuel Cells (IGFC)45“Clean Coal” Technologies4) Carbon capture and storageThere are currently no com

39、mercially available technologies to capture and store carbon. Such technology is very expensive and is unlikely to be available for at least 20-30 years.46Indirect coal to liquid47Summary “Clean coal” methods only move pollutants from one waste stream to another which are then still released into th

40、e environment. Any time coal is burnt, contaminants are released and they have to go somewhere. They can be released via the flu ash, the gaseous air emissions, water outflow or the ash left at the bottom after burning. Ultimately they still end up polluting the environment.48Questions What are the

41、differences between the pollution from oil utilization and coal utilization? Give an example on how to solve the pollution from coal utilization? Large amount of CO2 emission during fossil energy consumption, do you think what is the most effective way to solve this problem and why?49新的分类国家标准对各类煤的若干

42、特征 1、无烟煤（WY） 挥发分低，固定碳高，比重大，纯煤真比重最高可达1.90，燃点高，燃烧时不冒烟。对这类煤，可分为：01号为老年无烟煤；02号为典型无烟煤；03号为年轻无烟煤，无烟煤主要是民用和制造合成氨的造气原料，低灰、低硫和可磨性好的无烟煤不仅可以做高炉喷吹及烧结铁矿石用的燃料，而且还可以制造各种碳素材料，如碳电极、阳极糊和活性碳的原料，某些优质无烟煤制成航空用型煤还可用于飞机发动机和车辆马达的保温。（能源经理人） 2、贫煤（PM） 变质程度最高的一种烟煤，不粘结或微弱粘结，在层状炼焦炉中不结焦，燃烧时火焰短，耐烧，主要是发电燃料，也可作民用和工业锅炉的掺烧煤。 3、贫瘦煤（PS） 粘结性较弱的高变质、低挥发分烟煤，结焦性比典型瘦煤差，单独炼焦时，生成的焦粉甚少。如在炼焦配煤中配入一定比例的这种煤，也能起到瘦化作用，这种煤也可作发电、民用及锅炉燃料。 50 4、瘦煤（SM） 低挥发分的中等粘结性的炼焦用煤。焦化过程中能产生相当数量的焦质体。单独炼焦时，能得到块度大、裂纹少、抗碎强度高的焦煤，但这种焦碳的耐磨强度稍差，但2炼焦配煤使用，效果较好。这种煤也可作发电和一般锅炉等燃料，也可供铁路机车掺烧使用。 5焦煤