綠色能源與環(huán)境保護Lecture+2

1、1Pollution from Coal UtilizationPollution from Coal UtilizationLimin Chen（陳禮敏）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煤的生成過程 煤主要是遠古時代的高等植物在地殼運動中被深埋在地下或水中，其殘體在缺氧條件下被厭氧細(xì)菌生化降解，纖維素、木質(zhì)素、蛋白質(zhì)等被分解并聚縮，形成膠體狀的腐殖酸。 其余具有抗腐能力的部分如樹脂、角質(zhì)、孢子等保留原有形態(tài)分散在腐殖酸中，逐步變成含水很多、黑褐色的泥炭。這是成煤的第一階段泥炭化階段。 經(jīng)過漫長的地質(zhì)年代，泥炭在地?zé)岷湍嗌掣采w層不斷增厚或地殼下沉而受壓增大的作用下，泥炭層被壓實、失水，其化學(xué)性質(zhì)和成分發(fā)生變化。泥炭的密度

8、和碳含量相對增加，腐殖酸、水分、氧、氫和甲烷等揮發(fā)物逐漸減少。隨著泥炭的質(zhì)變由淺到深，依次形成不同種類的褐煤、煙煤、無煙煤等。這是成煤的第二階段煤化階段。8石油的生成過程 石油的生成過程與煤相似。它的形成物質(zhì)主要是低等動、植物遺體中的脂肪、蛋白質(zhì)和碳水化合物。 這些有機物質(zhì)的沉積物在地殼長期緩慢下降中不斷增厚，或在深水中被沉積保存。同樣經(jīng)歷了缺氧或強還原環(huán)境中的細(xì)菌分解階段和溫度、壓力增加條件下的轉(zhuǎn)化階段，碳和氫的含量富集，形成一種流動或半流動的粘稠性液體。 石油的生成條件要求較嚴(yán)格，沉積過程初期，溫度和壓力不夠，不能生成石油。當(dāng)沉積深度達到1 0004000m，溫度達到6050時有機質(zhì)生成大

9、量石油。若壓力和溫度進一步增加，有機質(zhì)被熱分解，如深度超過4000m，溫度超過150200后幾乎不能生成石油。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、 亞煙煤， Bituminous 瀝青煤，F(xiàn)lame coal煙煤，Gas flame coal亞煙煤，Gas coal氣煤，F(xiàn)at coal肥煤，forge coal鍛造煤炭，Non bakeing coal貧煤，Anthracite無煙煤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立井開采20Longwall Mining長壁開采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煙氣脫硫產(chǎn)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新的分類國家標(biāo)準(zhǔn)對各類煤的若干

42、特征 1、無煙煤（WY） 揮發(fā)分低，固定碳高，比重大，純煤真比重最高可達1.90，燃點高，燃燒時不冒煙。對這類煤，可分為：01號為老年無煙煤；02號為典型無煙煤；03號為年輕無煙煤，無煙煤主要是民用和制造合成氨的造氣原料，低灰、低硫和可磨性好的無煙煤不僅可以做高爐噴吹及燒結(jié)鐵礦石用的燃料，而且還可以制造各種碳素材料，如碳電極、陽極糊和活性碳的原料，某些優(yōu)質(zhì)無煙煤制成航空用型煤還可用于飛機發(fā)動機和車輛馬達的保溫。（能源經(jīng)理人） 2、貧煤（PM） 變質(zhì)程度最高的一種煙煤，不粘結(jié)或微弱粘結(jié)，在層狀煉焦?fàn)t中不結(jié)焦，燃燒時火焰短，耐燒，主要是發(fā)電燃料，也可作民用和工業(yè)鍋爐的摻燒煤。 3、貧瘦煤（PS） 粘結(jié)性較弱的高變質(zhì)、低揮發(fā)分煙煤，結(jié)焦性比典型瘦煤差，單獨煉焦時，生成的焦粉甚少。如在煉焦配煤中配入一定比例的這種煤，也能起到瘦化作用，這種煤也可作發(fā)電、民用及鍋爐燃料。 50 4、瘦煤（SM） 低揮發(fā)分的中等粘結(jié)性的煉焦用煤。焦化過程中能產(chǎn)生相當(dāng)數(shù)量的焦質(zhì)體。單獨煉焦時，能得到塊度大、裂紋少、抗碎強度高的焦煤，但這種焦碳的耐磨強度稍差，但2煉焦配煤使用，效果較好。這種煤也可作發(fā)電和一般鍋爐等燃料，也可供鐵路機車摻燒使用。 5焦煤