外文翻译-洗涤系统概述.doc

1、Scrubber Systems Operation Review1 Introduction to Scrubbing Systems1.1 IntroductionScrubber systems are a diverse group of air pollution control devices that can be used to remove particles and/or gases from industrial exhaust streams. Traditionally, scrubbers have referred to pollution control dev

2、ices that used liquid to scrub unwanted pollutants from a gas stream. Recently, the term scrubber is also used to describe systems that inject a dry reagent or slurry into a dirty exhaust stream to scrub out acid gases. Scrubbers are one of the primary devices that control gaseous emissions, especia

3、lly acid gases.1.2 Wet ScrubbersWet scrubber is a term used to describe a variety of devices that use liquid to remove pollutants. In a wet scrubber, the dirty gas stream is brought into contact with the scrubbing liquid by spraying it with the liquid, by forcing it through a pool of liquid, or by s

4、ome other contact method. Of course the design of any air pollution control device (wet scrubbers are no exception) depends on the industrial process conditions and the nature of the air pollutants involved. Exhaust gas characteristics and dust properties, if particles are present, are of primary im

5、portance. Scrubbers can be designed to collect particulates and/or gaseous pollutants. Wet scrubbers remove particles by capturing them in liquid droplets. Wet scrubbers remove pollutant gases by dissolving or absorbing them into the liquid. Any droplets that are in the flue gas must then be separat

6、ed from the clean exhaust stream by means of another device referred to as a mist eliminator or entrainment separator (these terms are interchangeable). Also, the resultant scrubbing liquid must be treated prior to any ultimate discharge or reused in the plant.There are numerous configurations of sc

7、rubbers and scrubbing systems all designed to provide good contact between the liquid and dirty gas stream. Figures 1.1 and 1.2 show two examples of wet scrubber designs, including their mist eliminators. Figure 1.1 is a venture scrubber design. The mist eliminator for aventuri scrubber is often a s

8、eparate device called a cyclonic separator. Figure 1.2 has a tower design where the mist eliminator is built into the top of the structure. Figure 1.1 An example of a venturi scrubber designFigure1.2 An example of a tower scrubber designA wet scrubbers ability to collect small sized particulates is

9、often directly proportional to the power input into the scrubber. Low energy devices such as spray towers are used to collect particulate matter larger than 5 micrometers. To obtain high efficiency removal of 1 micrometer (or less) particles generally requires high energy devices such as venturis or

10、 augmented devices such as condensation scrubbers. Additionally, a properly designed and operated entrainment separator/mist eliminator is important to achieve high removal efficiencies: the greater the number of liquid droplets that are not captured by the mist eliminator the higher the potential e

11、mission levels.Wet scrubbers that remove gaseous pollutants are referred to as absorbers. Good gas-to -liquid contact is essential to obtain high removal efficiencies in absorbers. A number of wet scrubber designs are used to remove gaseous pollutants, with the packed tower and the plate tower being

12、 the most common.If the exhaust stream contains both particles and gases, wet scrubbers are generally the only single air pollution control device that can remove both types of pollutants. Wet scrubbers can achieve high removal efficiencies for either particles or gases and, in some instances, can a

13、chieve a high removal efficiency for both pollutants in the same system. However, in many cases, the best operating conditions for particle collection are the poorest for gas removal. In general, obtaining high simultaneous gas and particle removal efficiencies requires that one of them be easily co

14、llected (i.e., that the gases are very soluble in the liquid or that the particles are large and readily captured). For particulate control, wet scrubbers (also referred to as wet collectors) are evaluated against fabric filters and electrostatic precipitators (ESPs). Some advantages of wet scrubber

15、s over these devices are as follows:1)、Wet scrubbers have the ability to handle high temperatures and moisture.2)、 In wet scrubbers, flue gases are cooled, resulting in smaller overall size of equipment. 3)、Wet scrubbers can remove both gases and particles.4)、Wet scrubbers can neutralize corrosive g

16、ases.Some disadvantages of wet scrubbers include corrosion, the need for mist removal to obtain high efficiencies, the need for treatment or reuse of spent liquid, and reduced plume buoyancy. Table 1.1 summarizes these advantages and disadvantages. Wet scrubbers have been used in a variety of industries such as acid plants, fertilizer plants, steel mills, asphalt plants, and large power plants.Table1.1 Relative advantages and disadvantage