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Particle Control Technologies. Lecture notes adapted from Prof. Dr. Benoit Cushman-Roisin Thayer School of Engineering at Dartmouth. Design Criteria.
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Particle Control Technologies Lecture notes adapted from Prof. Dr. Benoit Cushman-Roisin Thayer School of Engineering at Dartmouth
Design Criteria • Partikül Giderim Yöntemlerinde bir gaz medyum için yer alan katı veya sıvı partiküllerin giderimine yönelik sistem tasarlanması söz konusudur. Partikül maddeye ve onu taşıyan gaz medyumuna ait tasarımda göz önünde bulundurulması gereken karekteristikler: • Boyut T,P,Q, • Kimyasal içerik Kimyasal İçerik • Direnç Basınç kaybı Partikül Kontrol Ünitesi
Collection Efficiency • Considering the wide range of size of particulates, efficiency will be different for each size. • The overall efficiency (h) can be calculated on a basis of total number (or mass) of particles • Generally regulations are written based on mass, and efficiencies are calculated on mass basis.
Collection Efficiency • Efficiencies calculated on mass basis: h: overall collection efficiency (fraction) Mi: total mass input rate (g/s or equivalent) Me: total mass emission rate (g/s or equivalent) Li: particulate loading in the inlet gas to the device (g/m3) Le:particulate loading in the exit gas stream, (g/m3)
Collection Efficiency • When the particulate size distribution is known, and the efficiency of the device is known as a function of particle size, the overall collection efficiency can be calculate: where hj: collection efficiency for the jth size mj: mass percent of particles in the jth size
Example • Example 3.1 from the book
Gravity Settler • Cyclones • ESP • Filters and Baghouses • Wet Scrubbers
Settling Chamber • Efficient for particles with diameter of 10-50 mm (depending on its density) • Velocity through chamber < 0.3-3 m/s (to prevent reentrainment) V H L
v H L Settling Chamber • Settling time < transit time through chamber • t = H/vt = L/v Settling chambers are cheap to build and operate but not preferred due to their large space requirement
Settling Chamber • Assuming unit density sphere at STP, vt and chamber Lw are tabulated below: Assumed flow rate Q = 150 m3/min
Settling Chamber • Baffled Settling Chamber • Large particles can not make sudden direction change and settle into dead space of chamber • Baffle chambers are used as precleaners
Cyclones • :
Cyclones • :
Collection Efficiency (i) increase Vt (expensive, since DPa Vt2, as we will see in the next slides
Pressure Drop K: a constant depends on cyclone configuration and operating conditions. Theoretically K can vary considerably but for air pollution work with standard tangential-entry cyclones values of K are in the range of 12 to 18 Cyclone pressure drops range from about 0.5 to 10 velocity heads (250 to 4000 Pa)
