热能与动力工程专业英语翻译ch02教案

热能与动力工程专业英语翻译ch02教案内容摘要：

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. 现在美国应用的煤分类标准是由美国材料试验学会（ ASTM）建立的。 其分类是通过煤的工业分析所确定的挥发分和固定碳的含量以及煤的发热量作为分类标准。 这套系统目的在于确定煤的商业使用价值，并提供关于煤燃烧特性的基本信息。 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. 燃烧系统 锅炉内化石燃料燃烧以产生蒸汽的技术已成熟多年。 然而，在过去的二十多年中，为了将大气排放和污染降到可行的最低程度，燃烧技术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 页 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. 油燃烧系统 所有的电站锅炉都燃用油，在燃煤锅炉中点燃煤粉，在煤进入炉膛之前加热炉膛并升压，而在燃油锅炉中则作为主要负荷燃料。 一般地，燃油都是粘度在 3500 sec 到 6500sec 的残渣燃料油。 为了有效的燃烧，这些油必须被 加热到 120~130℃并被良好地分散或雾化成很小的微滴。 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，要比一般的馏分油（柴油，汽油等）便宜，但又带来一些问题：酸性污染物和粉尘的排放。 酸性污染问题是由石油中的硫产生的，硫分的含量有时可高达 3%。 在 20 世纪 60 年代早期，人们对油燃烧器设计进行了深入研究和开发，目的在于解决燃油的排放问题。 由此诞生了一种油燃烧器 —— “标准燃烧器”，它可以在非常低的过量空气系数下减少碳排放。 为保证锅炉中每个燃烧器获得同样多的空气也做了大量的工作。 目前油燃烧过量空气系数运行水平为 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. 煤燃烧系统 煤燃烧器的发展模式同油燃烧器类似，而且重点放在准确控制每只燃烧器煤和油的供给量。 实际中所有的燃煤锅炉都是燃烧煤粉（由磨煤机生产），这些煤粉经过很好的粉碎，然后由空气流（一次风）送入燃烧器。 同以前相比，在流动平衡上的设计成果现在已能使锅炉在较低的过量空气水平下运行，并在不增加飞灰含碳量水平的情况下提高了总的效率。 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, 这样，结合低 NOx 燃烧器的开发，就使气体排放达到欧共体的标准，这也是两代锅炉转换（已完成）的主要目的，即设定 500MW 燃煤锅炉可能达到的NOx排放水平。 在第三代锅炉的设计中进行了进一步降低 NOx的 开拓 性试验。 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. 煤燃烧系统部件的布置必须根据经济因素和煤的性质来确定。 作为整个燃烧系统设计的性能参数，煤粉细度、 磨 煤机 出口温度 、 空煤比 等都必须达到要求。 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 燃烧系统 影响 NOx 生成的因素包括燃料含氮量 、 火焰峰值温度 、 火焰中的可用氧量以及气流在锅炉系统中的停留时间。 当煤进入炉膛其化学结构被破坏时，一些煤中的化合氮就作为挥发分被释放出来。 由大气中的氮生成的一氧化氮即“热力型 NOx”可以通过减少烟气在高温区域的停留时间而得到控制，这样就会控制燃烧阶段中可用氧量，最后生成的是无 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. 因为煤在燃烧区的燃烧需要一定的过量氧气以便使所有的碳燃尽，且不含氮的煤是难以获得的 ，因此 NOx 的减少必须依靠锅炉和燃烧器的设计来完成。 教材 28 页 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. 天然气燃烧系统 天然气曾经作为电厂主要燃料。 然而一些年来，没有太多的天然气可供电厂使用，并且人们没有正视这样的事实，即天然气作为一种优质燃料将会重新得到大量应用。 丙烷常常作为一种点火剂，广泛地应用于燃油锅炉和燃煤锅炉中的油燃烧器。 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。