熱能與動力工程專業英語翻譯ch02教案(編輯修改稿)

　

【文章內容簡介】 ican Society for Testing and Materials (ASTM). ASTM classification is a system which uses the volatile matter and fixed carbon (FC) results from the proximate analysis and the heating value of the coal as ranking criteria. This system aids in identifying mercial uses of coals and provides basic information regarding bustion characteristics. 現在美國應用的煤分類標準是由美國材料試驗學會（ ASTM）建立的。其分類是通過煤的工業分析所確定的揮發分和固定碳的含量以及煤的發熱量作為分類標準。這套系統目的在于確定煤的商業使用價值，并提供關于煤燃燒特性的基本信息。 Combustion systems 299 The bustion of fossil fuels within a boiler for steam raising purposes has been practised for many years. However, within the past two decades bustion techniques have been considerably refined in order to reduce atmospheric emissions and pollution to practicable minimum. 燃燒系統 鍋爐內化石燃料燃燒以產生蒸汽的技術已成熟多年。然而，在過去的二十多年中，為了將大氣排放和污染降到可行的最低程度，燃燒技術得到了很大程度的提高。 Oil bustion systems Oil 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 教材 27 頁 fuel. In 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 120130℃ and divided or atomized into very small droplets. 油燃燒系統 所有的電站鍋爐都燃用油，在燃煤鍋爐中點燃煤粉，在煤進入爐膛之前加熱爐膛并升壓，而在燃油鍋爐中則作為主要負荷燃料。一般地，燃油都是粘度在 3500 sec 到 6500sec 的殘渣燃料油。為了有效的燃燒，這些油必須被 加熱到 120~130℃并被良好地分散或霧化成很小的微滴。 The use of this oil, cheaper than normal distillate (diesel/gas oil etc.) causes problems, amongst them, acid smuts and dust emissions. The smut problem is caused by the sulfur content of the oil, which may be up to 3%. In the early 1960s the utility undertook an intensive development program on oil burner design, which was aimed at removing the problems of oil fired emissions. This resulted in an oil burner, “the Standard Burner” which reduced emissions of carbon at very low excess air levels. Considerable work was also done in order to ensure that burner in a boiler received the same amount of air, and the current operating level for excess air in an oil fired unit is 2%. 燃用渣油，要比一般的餾分油（柴油，汽油等）便宜，但又帶來一些問題：酸性污染物和粉塵的排放。酸性污染問題是由石油中的硫產生的，硫分的含量有時可高達 3%。在 20 世紀 60 年代早期，人們對油燃燒器設計進行了深入研究和開發，目的在于解決燃油的排放問題。由此誕生了一種油燃燒器 —— “標準燃燒器”，它可以在非常低的過量空氣系數下減少碳排放。為保證鍋爐中每個燃燒器獲得同樣多的空氣也做了大量的工作。目前油燃燒過量空氣系數運行水平為 2%。 2910 Coal bustion systems Coal burners have been developed in a similar fashion 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 (produced by milling) which is very finely divided coal carried to the burner on a stream of air (primary air). 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. 煤燃燒系統 煤燃燒器的發展模式同油燃燒器類似，而且重點放在準確控制每只燃燒器煤和油的供給量。實際中所有的燃煤鍋爐都是燃燒煤粉（由磨煤機生產），這些煤粉經過很好的粉碎，然后由空氣流（一次風）送入燃燒器。同以前相比，在流動平衡上的設計成果現在已能使鍋爐在較低的過量空氣水平下運行，并在不增加飛灰含碳量水平的情況下提高了總的效率。 This, when bined with the development of low NOx burners will result in reduced gaseous emission in line with EEC directives and is the main objective of two boiler conversions (both plete) to establish the level to which NOx maybe reduced in the exhaust from 500MW coal fired boilers. A NOx reduction development trial is proposed on a third boiler design, 這樣，結合低 NOx 燃燒器的開發，就使氣體排放達到歐共體的標準，這也是兩代鍋爐轉換（已完成）的主要目的，即設定 500MW 燃煤鍋爐可能達到的NOx排放水平。在第三代鍋爐的設計中進行了進一步降低 NOx的 開拓 性試驗。 The arrangement of coalfired system ponents must be determined according to economic factors as well as the attributes of the coal. The performance in terms of product fineness, mill outlet temperature, and aircoal ratio must all be determined as part of overall bustion system design. 煤燃燒系統部件的布置必須根據經濟因素和煤的性質來確定。作為整個燃燒系統設計的性能參數，煤粉細度、 磨 煤機 出口溫度 、 空煤比 等都必須達到要求。 Low NOx bustion systems The factors affecting NOx are the proportion of nitrogen chemically bined with the fuel, peak flame temperature, the available oxygen in the flame and the residence time of the gases within the system. Some of the coal bound nitrogen is released as volatiles as the chemical structure of the coal breaks down on entering the furnace. Nitric oxide produced from atmospheric nitrogen as “thermal NOx” can be 2911 limited by minimizing residence times at high temperature, which limiting the amount of oxygen available to the fuel during the bustion stage results in the production of harmless nitrogen rather than NOx. 低 NOX 燃燒系統 影響 NOx 生成的因素包括燃料含氮量 、 火焰峰值溫度 、 火焰中的可用氧量以及氣流在鍋爐系統中的停留時間。當煤進入爐膛其化學結構被破壞時，一些煤中的化合氮就作為揮發分被釋放出來。由大氣中的氮生成的一氧化氮即“熱力型 NOx”可以通過減少煙氣在高溫區域的停留時間而得到控制，這樣就會控制燃燒階段中可用氧量，最后生成的是無 害氮而不是NOx。 Since coal firing requires some excess oxygen in the bustion zone to achieve total carbon burnout and nitrogen free coal is unavailable, NOx reduction has to be performed by boiler and burner design. 因為煤在燃燒區的燃燒需要一定的過量氧氣以便使所有的碳燃盡，且不含氮的煤是難以獲得的 ，因此 NOx 的減少必須依靠鍋爐和燃燒器的設計來完成。 教材 28 頁 Gas bustion systems Natural gas has been fired at power 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 is widely used in igniters for the oil burners in both main oil and coal fired boilers. 天然氣燃燒系統 天然氣曾經作為電廠主要燃料。然而一些年來，沒有太多的天然氣可供電廠使用，并且人們沒有正視這樣的事實，即天然氣作為一種優質燃料將會重新得到大量應用。 丙烷常常作為一種點火劑，廣泛地應用于燃油鍋爐和燃煤鍋爐中的油燃燒器。 Fluidizedbed bustion A variation on PC bustion is fluidized bed bustion in which coal is burned with air in a fluid bed, typically a circulating fluidized bed (CFB). CFBs are best suited to lowcost waste fuels and lowquality or low heating value coals. Cr