熱能動(dòng)力工程專(zhuān)業(yè)英語(yǔ)課件part

1、2022/10/14Specialized English for Thermal Energy and Power Engineering熱能動(dòng)力工程專(zhuān)業(yè)英語(yǔ) 2022/10/14Chapter 2 Boiler鍋爐Boilers（鍋爐） use heat to convert water into steam for a variety of applications. Primary among these are electric power generation and industrial process heating. Steam has e a key resource be

2、cause of its wide availability, advantageous properties and non toxic nature. The steam flow rates and operating conditions can vary dramatically; from 1000lb/h (0.1kg/s) in one process use to more than 10 million lb/h (1260kg/s) in large electric power plant; from about 14.7 psi（ Poundspersquareinc

3、h ） (1 bar) and 212F in some heating applications to more than 4500 psi (310bar) and 1100 F (593) in advanced cycle power plant.2022/10/142.1 Introduction簡(jiǎn)介Modern boilers can be classified by various criteria. These include end use, firing method, operating pressure, fuel and circulation method.Util

4、ity boilers(電站鍋爐) are used primarily to generate electricity in large central power stations(電站). They are designed to optimize overall thermodynamic efficiency at the highest possible availability. A key characteristic of newer units is the use of a reheater(再熱器) section to increase overall cycle e

5、fficiency.2022/10/142.1 Introduction簡(jiǎn)介A variety of additional systems also produce steam for power and process applications. These systems usually take advantage of low cost or free fuels(燃料), a combination of power cycles and process, and recovery of waste heat in order to reduce overall costs, exa

6、mples of these include:Gas turbine combined cycle (CC，燃?xì)廨啓C(jī)聯(lián)合循環(huán)) uses advanced gas turbines with heat recovery steam generator(蒸汽發(fā)生器) as part of a base cycle to use waste heat recovery and increase thermal efficiency.Integrated Gasification Combined Cycle (IGCC，整體煤氣化聯(lián)合循環(huán)) adds a coal gasifier to the

7、CC to reduce fuel cost and minimize airborne emissions.2022/10/142.1 Introduction簡(jiǎn)介2022/10/142.1 Introduction簡(jiǎn)介Pressurized Fluidized-bed Combustion (PFBC) includes higher pressure combustion with gas cleaning and expansion of the combustion products through a gas turbine.增壓循環(huán)流化床燃燒（PFBC）：在更高壓力下燃燒，包括燃

8、氣凈化，以及燃燒產(chǎn)物膨脹并通過(guò)燃?xì)廨啓C(jī)做功。Blast furnace hood heat recovery generates steam using the waste heat from a blast furnace.高爐排煙熱量回收：利用高爐余熱產(chǎn)生蒸汽。Solar steam generator uses concentrators to collect and concentrate solar radiation and generate steam.太陽(yáng)能蒸汽發(fā)生器：利用集熱器收集太陽(yáng)輻射熱產(chǎn)生蒸汽。2022/10/142.3 Fuel and combustion燃料與燃燒

9、The fuels used in most boilers are coal, natural gas and oil. However, during the past few decades, nuclear energy has also begun to play a major role in at least the electric power generation area. Also, an increasing variety of biomass materials and process byproducts have e heat sources for steam

10、 generation. These include peat, wood and wood wasters, straw(麥稈), coffee ground, corn husks, coal mine wastes (culm)煤屑, waste heat from steelmaking furnaces and even solar energy.2022/10/142.3 Fuel and combustion燃料與燃燒The dominant fuel in modern U.S. central stations is coal. While natural gas or fu

11、el oil may be the fuel of choice for selected future fossil fuel power plants, coal expected to continue its dominant role in supplying energy to new, base power utility power station boilers.2022/10/142.3 Fuel and combustion燃料與燃燒A coal classification system is needed because coal is a heterogeneous

12、 substance with a wide range of composition and properties. The properties of a typical China coal are showed in table 2-1. Coals are typically calssified by rank(煤階). This indicates the progressive alteration in the coalification process from lignite(褐煤) to subbitiminous(貧煤), bituminous(煙煤) and ant

13、hracite coals(無(wú)煙煤). The rank indicates a coals geological history and characteristics.lignitebituminousanthracite2022/10/142.3 Fuel and combustion燃料與燃燒2022/10/142.3 Fuel and combustion燃料與燃燒The system used in the U.S. for classifying coal by rank was established by the American Society for Testing an

14、d Materials (ASTM，美國(guó)材料試驗(yàn)學(xué)會(huì)). ASTM classification is a system which uses the volatile matter（揮發(fā)分） and fixed carbon (FC) results from the proximate analysis and the heating value(熱值、發(fā)熱量) of the coal as ranking criteria. This system aids in identifying commercial uses of coals and provides basic inform

15、ation regarding combustion characteristics.2022/10/142.3 Fuel and combustion燃料與燃燒Oil combustion systemsOil is burned in all utility boiler, in coal boiler to ignite the coal burners, to warm up the boiler and raise pressure before coal is admitted, and in oil fired boilers as the main load fuel. In

16、general, the oil is residual Fuel Oil of 3500 sec. to 6500 sec. viscosity. In order to burn effectively this oil must be heated to 120-130 and divided or atomized into very small droplets.2022/10/142.3 Fuel and combustion燃料與燃燒Coal combustion systemsCoal burners have been developed in a similar fashi

17、on to the oil burners, and considerable emphasis is placed upon feeding each burner with carefully regulated amounts of coal and oil. All coal fired boilers in the utility fire pulverized coal(PC，煤粉) (produced by milling) which is very finely divided coal carried to the burner on a stream of air (pr

18、imary air，一次風(fēng)). The design effort directed at flow equalization has produced boilers which can be operated at lower excess air levels than previously, and thus have increased overall efficiency without increasing unburned carbon levels in the ash.Pulverize : . 粉碎、破碎 2022/10/142.3 Fuel and combustion

19、燃料與燃燒This, when combined with the development of low NOx burners will result in reduced gaseous emission in line with EEC(European Economic community歐共體) directives and is the main objective of two boiler conversions (both complete) to establish the level to which NOx maybe reduced in the exhaust fr

20、om 500MW coal fired boilers. A NOx reduction development trial is proposed on a third boiler design.2022/10/142.3 Fuel and combustion燃料與燃燒The arrangement of coal-fired system components must be determined according to economic factors as well as the attributes of the coal. The performance in terms o

21、f product fineness, mill outlet temperature, and air-coal ratio(空煤比) must all be determined as part of overall combustion system design.煤燃燒系統(tǒng)部件的布置必須根據(jù)經(jīng)濟(jì)因素和煤的性質(zhì)來(lái)確定。作為整個(gè)燃燒系統(tǒng)設(shè)計(jì)的性能參數(shù)，煤粉細(xì)度、磨煤機(jī)出口溫度、空煤比等都必須達(dá)到要求。2022/10/142.3 Fuel and combustion燃料與燃燒Gas combustion systemsNatural gas has been fired at power

22、stations for main load purposes. However, gas has not been available to the utility for some years now and it is not envisaged that, as a premium fuel, it will ever be available again in any quantity.Propane（丙烷） is widely used in igniters for the oil burners in both main oil and coal fired boilers.2

23、022/10/142.3 Fuel and combustion燃料與燃燒 Fluidized-bed combustion（流化床燃燒）A variation on PC combustion is fluidized bed combustion in which coal is burned with air in a fluidised bed, typically a Circulating Fluidized-Bed (CFB). CFBs are best suited to low-cost waste fuels and low-quality or low heating

24、value coals. Crushed coal and lime stone are fed into the bed, where the lime stone(石灰石) undergoes calcination to produce lime (CaO， calcium oxide). The fluidized bed consist only of lime, with a few percent coal and recirculated coal char. The bed operates at significantly lower temperatures, about

25、 427(800F), which thermodynamically favors low NOx formation and SO2 capture by reaction with CaO to form CaSO4(calcium sulfate). 2022/10/142.3 Fuel and combustion燃料與燃燒 Fluidized-bed combustion1-Coal bunker 2-Limestone bunker 3-Coal crusher 4-CFB combustor 5-Cyclone 6-Convective pass 7-Air-Preheater

26、 8-Electrostatic Filter 9-Stack 13-Primary air 10-Fluided bed heat exchanger 11-Turbo-generator 12-district heating 14-Secondary air 15-Bottom ash 17-Blowers 16-Fluided bed heat exchanger air 18-Feed water 19-drum2022/10/142.4 Pulverizing System送粉系統(tǒng)The development and growth of coal pulverization cl

27、osely parallels the development of pulverized coal-firing technology. In order to achieve efficient combustion in the boiler furnace the coal leaving the burner must be sized so that it can burn rapidly and this means that it must be in the form of small particles(顆粒) that can quickly be heated up t

28、o ignition temperature(著火溫度) and get ready access to the combustion air. 2022/10/142.4 Pulverizing System送粉系統(tǒng)The job of the pulverizers(磨煤機(jī)) is to grind the feed coal down to a suitable size for the above purposes. Early systems used ball-and-tube pulverizers(筒式球磨機(jī)) to grind coal and holding bins to

29、 temporarily store the coal before firing. Evolution of the technology to eliminate the bins and direct fire the coal pneumatically transported（氣力輸運(yùn)） from the pulverizers required more responsive and reliable grinding equipment. Vertical air-swept pulverizers(中速磨煤機(jī)) met this need.2022/10/142.4 Pulve

30、rizing System送粉系統(tǒng)On pressurized pulverizing systems(正壓制粉系統(tǒng)) the primary air fan which provides the pulverized fuel transport medium is situated before the pulverizer and there handle clean air and is not subject to erosive wear as is an exhaust fan. This is the chief advantage of the pulverizing sys

31、tem, however the pulverizer does need sealing air which is usually provided by a separate fan at a pressure higher than that of the pulverizer interior.2022/10/142.4 Pulverizing System送粉系統(tǒng)A disadvantage of the pressure type pulverizer is that it must be absolutely air tight(不漏的) in order to avoid pu

32、lverised fuel leakage(泄漏) to the atmosphere. Conversely the standard of sealing on a suction pulverizer(負(fù)壓磨煤機(jī)) need not be so high, but it must not be allowed to deteriorate(惡化) too far as the inwards leakage, being cold air, will make it difficult to dry the wetter coals. This leakage air is also u

33、nmeasured as regards its quantity, and if excessive under certain conditions produces a high air/coal ratio which may be explosive should there be an ignition source.2022/10/142.4 Pulverizing System送粉系統(tǒng)Pulverizers are part of lager systems, normally classified as either direct-fired(直吹式) or storage(

34、中儲(chǔ)式，貯倉(cāng)式). In direct firing, coal leaving each mill goes directly to the combustion process. The air, evaporated moisture and the thermal energy which entered the mill, along with the ground coal, all e part of the combustion process. 2022/10/142.4 Pulverizing System送粉系統(tǒng)Storage systems separate the g

35、round coal from the air, evaporated moisture and the thermal energy prior to the combustion process. Stored ground coal is then injected with new transport air to the combustion process. Bin storage systems(倉(cāng)儲(chǔ)式制粉系統(tǒng)) are seldom used in steam generation today, but are still used with special technolog

36、ies such as coal gasification and blast furnace coal injection(高爐投煤). Of the 1000 or so MPS pulverizers in service in the U.S. more than 90% are used in direct-fired systems. 2022/10/142.4 Pulverizing System送粉系統(tǒng) The essential elements of a direct-fired system are: (1) A raw coal feeder(給煤機(jī)) that reg

37、ulates the coal flow from a silo or bunker to the pulverizer.(2) A heat source that preheat the primary air for coal drying.(3) A pulverizer (primary air) fan that is typically located ahead of the mill (pressurized mill) as a blower(鼓風(fēng)機(jī)), or after the mill (suction mill) as an exhauster(引風(fēng)機(jī)).(4) A

38、pulverizer, configured as either a pressurized or suction unit.(5) Piping that directs the coal and primary air from the pulverizer to the burners.(6) Burners which mix the coal and balance of combustion air.(7) Control and regulating devices.2022/10/142.5 System Arrangement and Key Components系統(tǒng)布置和主

39、要部件 Modern boilers are a complex configuration of thermal-hydarulic (steam and water) sections which preheat and evaporate water, and superheat steam. These surfaces(受熱面) are arranged， so that:1) the fuel can be burned completely and efficiently while minimizing emissions, 2) the steam is generated

40、at the required flow rate, pressure and temperature, and 3) the maximum amount of energy is recovered. 2022/10/142.5 System Arrangement and Key Components系統(tǒng)布置和主要部件A relatively simple coal-fired utility boiler is illustrated in Fig.2-4. the major components in the steam generating and heat recovery s

41、ystem include:(1) Furnace and convection pass(對(duì)流煙道)(2) Steam superheaters (primary and secondary)(3) Steam reheaters(4) Boiler or steam generating bank (industrial units only)(5) Economizer(6) Steam drum(7)Attemperator and steam temperature control system(8) Air heater2022/10/142.5 System Arrangemen

42、t and Key Components系統(tǒng)布置和主要部件2.5.1 Furnace（爐膛）The furnace is a large enclosed open space for fuel combustion and for cooling of the flue gas before it enters the convection pass. Excessive gas temperatures leaving the furnace and entering the tube bundles(管束) could cause particle accumulation on the

43、 tubes or excessive tube metal temperature. The specific geometry and dimensions of the furnace are highly influenced the fuel and type of combustion equipment. In this case, finely ground or pulverized coal is blown into the furnace where it burns in suspension. The products of combustion then rise through the upper furnace. The superheater, reheate