1、布袋除尘英文文献pdf#布袋除尘英文文献.pdf#LT#94 M. Saleem, G. Krammer / Powder Technology 173 （2007） 93106#direction blow the cake off the bag surface, which is collected in the dust hopper located at the bottom of the filter housing. As soon as the cake is removed, the P is reduced and filtration continues for anot
2、her filtration cycle.#The JP cleaning process may be divided into three phases:# （a） acceleration of the filter medium towards outside, （b） deceleration of the filter medium once it reaches a circular shape and （c） acceleration of the filter medium inwards towards the cage after completion of the cl
3、eaning cycle and after the decay of the cleaning pulse in the bag interior. The dust cake on the surface of the bag is broken by the inflation of the filter element. The acceleration from a concave to a convex shape with sudden impact mechanically ejects the dust together with particles that have pe
4、netrated the felt. The flowing air following the pressure pulse flushes out the dust assisting cake removal 1. The reverse flow, in addition to acceleration, is reported necessary for cake detachment in 2. The cake removal is improved at higher cake load in acceleration tests 3. In practice a fracti
5、on of filtration area is exposed to jet pulses and possibly only a fraction of the cake is removed from the jet pulsed area 4 resulting in a non-uniform cake distribution called patchy cleaning. Non-uniform filter cake distribution on the bag surface is a natural outcome of patchy cleaning and posse
6、sses many consequences like different residence times of the cakes on the bag surface 5, distribution of gas velocities across the filter surface as a result of the cake height distribution 6, different cake characteristics depending on different formation conditions 7, and as a consequence more fre
7、quent bag cleaning is required.#Various theoretical and experimental studies are reported in literature to provide understanding of underlying process of cake formation and detachment which affect the P. The P is related to the operating parameters using regression analysis 1#in one approach. Mostly
8、, the#P within the filter media （ Pm）#and the P within the cake （#Pc）, are taken additive based on#the assumption that the resistances contributed by the filter media and the cake act in series as reported in 1,5 for example. Filtration process is simulated using one dimensional model in 8 from its
9、start-up, where a uniform cake is assumed to form on a clean filter medium. At the end, JP removes a part of the cake leaving a thin dust layer behind on the filter surface. The second cycle starts with two model areas, one with the cake and one regenerated and containing a thin dust layer. A Darcy
10、equation represents each model area but pressure drop is the same across both areas. The fact that only a fraction of total area may be subjected to jet pulses is not considered by 8. Therefore, the characteristic property of cake detachment, a fraction of cake of certain thickness removed on jet pu
11、lsing, is not determined. The model presented in 9 deals with the case of filtration at constant pressure drop. It also does not distinguish between the fractions of the filter area that is subjected to jet pulses. A model considering the fractional area subjected to jet pulses is used for predictin
12、g operating points from specific cake detachment experiments 10. The model parameters are estimated from the linear part of the pressure drop curve ignoring the steep rise of the pressure drop curve. The cake formation on non-uniformly covered filters may#influence the cake detachment due to highly
13、non uniform gas velocities, though the overall gas flow remains constant. Therefore ignoring the cake formation may lead to erroneous results. Other models describing filter cake additionally consider cohesive stresses between single patches of filter cakes. However, the three dimensional structural
14、 information of the filter cake needed by these sophisticated approaches is not easily available 11,12. The size and thickness of single patch in conjunction with the length of boundary to the neighbouring patches are decisive for plausibility of the assumption of rectilinear, parallel gas flow. The
15、 question whether the actual size of patches observed in filter experiments allows the assumption of rectilinear flow is not yet settled, although this assumption is often used for the reasons of simplicity. Transient growth of the filter cake is simulated using two-dimensional model in 13. Results
16、revealed that the pressure drop after a cleaning pulse with constant cake mass removed is higher or lower depending on whether the removed patches are larger or smaller respectively. In the fringe zone between thick and thin cakes, gas enters sideways increasing the permeability of the filter cake. However, discrepancies in the pressure drop curves are small and restricted to the first 10% of the filter cycle only. The Darcy#s law with consta
