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Air Pollution Control Systems for Boiler and Incinerators Part 4

Tham khảo tài liệu 'air pollution control systems for boiler and incinerators part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | TM 5-815-1 AFR 19-6 CHAPTER 6 CYCLONES AND MULTICYCLONES 6-1. Cyclone The cyclone is a widely used type of particulate collection device in which dust-laden gas enters tangentially into a cylindrical or conical chamber and leaves through a central opening. The resulting vortex motion or spiraling gas flow pattern creates a strong centrifugal force field in which dust particles by virtue of their inertia separate from the carrier gas stream. They then migrate along the cyclone walls by gas flow and gravity and fall into a storage receiver. In a boiler or incinerator installation this particulate is composed of fly-ash and unburned combustibles such as wood char. Two widely used cyclones are illustrated in figure 6-1. 6-2. Cyclone types a. Cyclones are generally classified according to their gas inlet design and dust discharge design their gas handling capacity and collection efficiency and their arrangement. Figure 6-2 illustrates the various types of gas flow and dust discharge configurations employed in cyclone units. Cyclone classification is illustrated in table 6-1. b. Conventional cyclone. The most commonly used cyclone is the medium efficiency high gas throughput conventional cyclone. Typical dimensions are illustrated in figure 6-3. Cyclones of this type are used primarily to collect coarse particles when collection efficiency and space requirements are not a major consideration. Collection efficiency for conventional cyclones on 10 micron particles is generally 50 to 80 percent. c. High efficiency cyclone. When high collection efficiency 80-95 percent is a primary consideration in cyclone selection the high efficiency single cyclone is commonly used See figure 6-4 . A unit of this type is usually smaller in diameter than the conventional cyclone providing a greater separating force for the same inlet velocity and a shorter distance for the particle to migrate before reaching the cyclone walls. These units may be used singly or arranged in parallel or series