山东大学-能源与环境课件-08学习资料.ppt

山东大学-能源与环境课件-08Fossil-Fueled Power Plants:Components Emission controlEmission control (排放控制)Nitrogen oxide controlNitrogen oxide control(氮氧化物控制)During combustion,a low-NOx burner (LNB)employs a process called staged staged combustion combustion (分级燃烧)NOx formation is a function of air-to-fuel ratio(by weight)in the flameFossil-Fueled Power Plants:Components Emission controlEmission control (排放控制)Nitrogen oxide controlNitrogen oxide control(氮氧化物控制)Fuel(e.g.,pulverized coal)and air is injected through the central annulusannulus(环)of the burner and the air/fuel ratio is less than stoichiometric stoichiometric(化学计量比),i.e.,fuel-rich fuel-rich(富燃),which produces a luminous flame luminous flame(发光火焰),with some of the pulverized coal left unburnt,but also with low NOx formationSecondary and tertiary air arrives through outer annuliannuli(环),creating an outer flame envelope that is fuel-lean fuel-lean(贫燃),where all the unburnt carbon burns up and less NOx is formed Fossil-Fueled Power Plants:Components Emission controlEmission control (排放控制)Nitrogen oxide controlNitrogen oxide control(氮氧化物控制)After combustion,in a selective catalytic reduction selective catalytic reduction(选择性催化还原)process either ammonia ammonia(氨)or urea urea(尿素)is injected into a catalytic reactorcatalytic reactor (催化反应器)through which the flue gas flue gas(烟气)flows In a selective noncatalytic reduction selective noncatalytic reduction(选择性非催化还原),a reduction of NO can be accomplished at a higher temperature without a catalyst,where urea is used instead of ammonia Fossil-Fueled Power Plants:ComponentsFossil-Fueled Power Plants:ComponentsFossil-Fueled Power Plants:Components Emission controlEmission control(排放控制)Toxic emissions(毒性排放物)Coal and oil contain mineral matter that during the combustion process may produce toxic vapors and particlesParticles larger than 12 micronsmicrons(微米)in diameter are almost all captured by the particle removal system,either by an electrostatic precipitator or a fabric filterSmaller particles and vapors may escape through the smoke stack and pollute the environment Mercury Mercury(汞),selenium selenium(硒),cadmium cadmium(镉),and arseniarsenic(砷)are semivolatilesemivolatile (半挥发性)toxic metals that escape through the smoke stack as vaporsAnother problem associated in part may do with coal-fired power plants is radonradon(氡)emissions,which is a disintegration product of uranium uranium(铀),the minerals of which may cling to the coalFossil-Fueled Power Plants:Components Waste disposalWaste disposal(废物处理)Coal-fired power plants produce a significant amount of solid waste Oil-fired plants produce much less waste,and gas-fired plants produce practically noneFor some coals the fly ash fly ash(飞灰)and the scrubber sludge scrubber sludge(污泥)may contain toxic organic and inorganic compounds,for which the waste needs to be disposed of in a secure landfill and the landfill must be lined,with impenetrable materialimpenetrable material(不透材料)so that leachingleaching(浸出)into the soil and groundwater is to be preventedFossil-Fueled Power Plants:ComponentsFossil-Fueled Power Plants:Components Pollutants emissionFossil-Fueled Power Plants:ComponentsPollutants and pollution control in coal fire power plantFossil-Fueled Power Plants:ComponentsPollutants and pollution control in oil fire power plantFossil-Fueled Power Plants:ComponentsPollutants and pollution control in gas fire power plantFossil-Fueled Power Plants:Components Flare stack in gas fire power plantFossil-Fueled Power Plants:Advanced Cycles Combined cycle Combined cycle(联合循环)Fossil-Fueled Power Plants:Advanced Cycles Coal gasification combined cycle Coal gasification combined cycle(煤气化联合循环)A power plant using coal gasification and combined cycle is called an integrated gasification combined cycle plant(IGCC)Various coal gasification methods were developed already in the nineteenth century for providing piped gas for home heating,cooking,and lightingCoal can be gasified to low-,medium-and high-heating value syngasFor an IGCC plant,high-heating value syngas is preferredFossil-Fueled Power Plants:Advanced Cycles Coal gasification combined cycle Coal gasification combined cycle(煤气化联合循环)The crushed coal is fed to a retort,where,in the presence of catalysts,it is exposed to pure oxygen and steamTo increase the heating value,the carbon monoxide and hydrogen is passed over a catalyst at about 400 C to form principally methane methane(甲烷),a process called methanation methanation(甲烷化)An alternative is the production of hydrogen in the water gas shift water gas shift reactionreaction(水煤气反应)Fossil-Fueled Power Plants:Advanced Cycles Cogeneration Cogeneration(热电联产)Cogeneration is applied to systems that provide both electrical power and useful heat from the burning of fuel In industrial or commercial installations the heat may be used for space heating or material processingThe incentive for cogeneration is primarily financial in that the cost of supplying electricity and heat via a cogeneration scheme might be less than supplying them separatelyWhether or not a cogeneration system reduces the amount of fuel needed to supply the electricity and heat depends upon the details of the cogeneration systemFossil-Fueled Power Plants:Advanced Cycles Cogeneration Cogeneration(热电联产)When a heat engine drives an electric generator to produce electricity,it also provides a stream of hot exhaust gasWhere the exhaust gas is warm enough to be used for process or space heat,some of the exhaust gas enthalpy may be extracted to satisfy the heat requirement in a cogeneration plantFossil-Fueled Power Plants:Advanced Cycles Fuel cellFuel cell(燃料电池)In a fuel cell,some of the chemical energy of the fuel is directly converted into electrical energy,with the rest appearing as heat rejected to the environmentIts theoretical thermal efficiency in terms of electrical energy generated versus fuel chemical energy input can be close to high value when producing a low output of powerFuel cell hydrogen is usually generated by the reforming of methane reforming of methane(甲烷重整)Fossil-Fueled Power Plants此课件下载可自行编辑修改，仅供参考！此课件下载可自行编辑修改，仅供参考！感谢您的支持，我们努力做得更好！谢谢感谢您的支持，我们努力做得更好！谢谢