1. Energy and the Environment Fall 2014 Instructor: Xiaodong Chu Email ： chuxd@sdu.edu.cn chuxd@sdu.edu.cn Office Tel.: 81696127, 13573122659

2. Fossil-Fueled Power Plants: Components Emission control Emission control ( 排放控制 ) – Nitrogen oxide control – Nitrogen oxide control ( 氮氧化物控制 ) nitrogen oxidesnitric oxide NOnitrogen dioxideNO 2 dimernitrogen trioxideNO 3 pentoxideN 2 O 5 nitrous oxide N 2 O The other major category of pollutants from fossil fuel combustion is nitrogen oxides ( 氮氧化物 ), called NO x, which includes nitric oxide NO ( 一氧化氮 ), nitrogen dioxide NO 2 ( 二氧化氮 ) (and its dimer ( 二聚体 ) N 2 O 4 ), nitrogen trioxide NO 3 ( 三氧 化氮 ), pentoxide N 2 O 5 ( 五氧化二氮 ), and nitrous oxide N 2 O ( 一氧化二氮 ) NO x usually implies the sum of NO and NO 2. pernicious pollutant respiratory tract irritant precursorto photo-oxidants ozone acid deposition NO x is a pernicious pollutant ( 有害污染物 ) because it is a respiratory tract irritant ( 呼吸道刺激源 ) and it is a precursor ( 前驱体 ) to photo-oxidants ( 光氧化剂 ), including ozone ( 臭氧 ) and acid deposition ( 酸沉降 ) fuel No x Coal and oil contain organic nitrogen in their molecular structure and when burnt, these fuels produce fuel No x ( 燃料型氮氧化物 ) thermal No x All fossil fuels produce thermal No x ( 热力型氮氧化物 ), resulting from the recombination of atmospheric nitrogen and oxygen under conditions of the high temperatures prevailing in the flame of fossil fuel combustion There are basically two approaches to reducing sulfur emissions: during and after combustion of the fossil fuel

3. Fossil-Fueled Power Plants: Components Emission control Emission control ( 排放控制 ) – Nitrogen oxide control – Nitrogen oxide control ( 氮氧化物控制 ) staged combustion During combustion, a low-NO x burner (LNB) employs a process called staged combustion ( 分级燃烧 ) NO x formation is a function of air-to-fuel ratio (by weight) in the flame

4. Fossil-Fueled Power Plants: Components Emission control Emission control ( 排放控制 ) – Nitrogen oxide control – Nitrogen oxide control ( 氮氧化物控制 ) annulus stoichiometric fuel-rich luminous flame Fuel (e.g., pulverized coal) and air is injected through the central annulus ( 环 )of the burner and the air/fuel ratio is less than stoichiometric ( 化学计量比 ), i.e., fuel-rich ( 富燃 ), which produces a luminous flame ( 发光火焰 ), with some of the pulverized coal left unburnt, but also with low NO x formation annuli fuel-lean Secondary and tertiary air arrives through outer annuli ( 环 ), creating an outer flame envelope that is fuel-lean ( 贫燃 ), where all the unburnt carbon burns up and less NO x is formed

5. Fossil-Fueled Power Plants: Components Emission control Emission control ( 排放控制 ) – Nitrogen oxide control – Nitrogen oxide control ( 氮氧化物控制 ) selective catalytic reduction ammonia urea catalytic reactor flue gas After combustion, in a selective catalytic reduction ( 选择性催化还原 ) process either ammonia ( 氨 ) or urea ( 尿素 ) is injected into a catalytic reactor ( 催化反应器 ) through which the flue gas ( 烟气 ) flows selective noncatalytic reduction In a 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

6. Fossil-Fueled Power Plants: Components

8. Emission control Emission 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 particles microns Particles larger than 1–2 microns ( 微米 ) in diameter are almost all captured by the particle removal system, either by an electrostatic precipitator or a fabric filter Smaller particles and vapors may escape through the smoke stack and pollute the environment Mercury selenium cadmium arsenisemivolatile Mercury ( 汞 ), selenium ( 硒 ), cadmium ( 镉 ), and arsenic ( 砷 ) are semivolatile ( 半 挥发性 ) toxic metals that escape through the smoke stack as vapors radon uranium Another problem associate in part may do with coal-fired power plants is radon ( 氡 ) emissions, which is a disintegration product of uranium ( 铀 ), the minerals of which may cling to the coal

9. Fossil-Fueled Power Plants: Components Waste disposal Waste 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 none fly ash scrubber sludge impenetrable material leaching – For some coals the fly ash ( 飞灰 ) and the 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 material ( 不透材料 ) so that leaching ( 浸出 )into the soil and groundwater is to be prevented

10. Fossil-Fueled Power Plants: Components

11. Pollutants emission

12. Fossil-Fueled Power Plants: Components Pollutants and pollution control in coal fire power plant

13. Fossil-Fueled Power Plants: Components Pollutants and pollution control in oil fire power plant

14. Fossil-Fueled Power Plants: Components Pollutants and pollution control in gas fire power plant

15. Fossil-Fueled Power Plants: Advanced Cycles Combined cycle Combined cycle ( 联合循环 )

16. 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 lighting – Coal can be gasified to low-, medium- and high-heating value syngas – For an IGCC plant, high-heating value syngas is preferred

17. Fossil-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 steam methane methanation – To increase the heating value, the carbon monoxide and hydrogen is passed over a catalyst at about 400 ◦ C to form principally methane ( 甲 烷 ), a process called methanation ( 甲烷化 ) water gas shift reaction – An alternative is the production of hydrogen in the water gas shift reaction ( 水煤气反应 )

18. 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 processing – The 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 separately – Whether or not a cogeneration system reduces the amount of fuel needed to supply the electricity and heat depends upon the details of the cogeneration system

19. Fossil-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 gas – Where 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 plant

20. Fossil-Fueled Power Plants: Advanced Cycles Fuel cell Fuel 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 environment – Its theoretical thermal efficiency in terms of electrical energy generated versus fuel chemical energy input can be close to 100% when producing a low output of power reforming of methane – Fuel cell hydrogen is usually generated by the reforming of methane ( 甲烷重整 )

21. Fossil-Fueled Power Plants