Use of a fluidized bed for the energy-efficient pneumatic transport of fine dust
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Vol. 53, No. 5, January, 2013
USE OF A FLUIDIZED BED FOR THE ENERGY-EFFICIENT PNEUMATIC TRANSPORT OF FINE DUST S. Ya. Davydov1 Translated from Novye Ogneupory, No. 9, pp. 17 – 22, September, 2012.
Original article submitted February 9, 2012. This article presents characteristics of alumina dust, describes experimental process units, and reports results from experimental studies in which pseudo-fluidization is examined as a technology for the operation of an energy-saving vertical pneumatic conveyor with transverse drag devices installed over its height. The use of such a conveyor makes it possible to reduce the consumption of compressed air several-fold. Keywords: pneumatic conveyor, alumina dust, pseudo-fluidized bed, dispersing grates, porosity, air consumption.
Alumina dust is fine-grained in comparison to other materials. Results obtained from analyses of the granulometric composition of alumina-bearing materials were reported in [1 – 3]. It has been established that alumina dust of such coarseness (see Table 1 and Fig. 1) does not have a stable angle of repose and is not readily fluidized. It is not sufficiently friable and tends to cake. Thus, the fine dust captured by electrostatic precipitators can be regarded as a dispersed powder comprised of particles with limited mobility. Parameters of the Plitt approximation of the total-residue curve [1] were used to calculate the average size of particles d50 of polydisperse composition based on minimization of the squares of the differences between experimental and calculated values. It is apparent from Fig. 1 that the average size 1
of alumina dust is eight times smaller than the average size of coarse-grained alumina. The physico-mechanical characteristics of alumina dust are significantly different from those of alumina. Dust of such coarseness is an aerosol and is similar to nanopowders in terms of its properties. The dust is characterized by a tendency to undergo caking, and its particles have limited mobility. These characteristics account for the problems encountered in capturing alumina dust, removing it from hoppers, and its batching and transport.
TABLE 1. Granulometric Composition of Alumina Materials Alumina Serial particle no. diameter d, mm
Ural State Mining Institute, Ekaterinburg, Russia.
Fig. 1. Granulometric composition of alumina (¡, d50 = 51.2 mm) and alumina dust from electrostatic precipitators (l, d50 = 6.2 mm).
Alumina dust
content of total residues fractions t, % R, %
particle diameter d, mm
Total content of residues fractions t, % R, %
1
160
0.8
0.8
50
0.8
0.8
2
120
1.8
1.0
40
1.5
0.7
3
100
4.1
2.3
35
4.4
1.9
4
80
14.8
10.7
30
4.8
1.4
5
63
28.0
13.2
25
5.3
0.5
6
50
54.2
26.2
20
7.2
1.9
7
40
73.0
18.8
15
12.5
5.3
8
30
89.5
16.5
10
25.3
12.8
9
20
97.2
7.7
5
61.2
35.9
10
10
98.7
1.5
2
92.6
31.4
11
0
100.0
1.3
0
100.0
7.4
292 1083-4877/13/05305-0292 © 2013 Springer Science+Business Media New York
Use of a Fluidized Bed For the Energy-Efficient Pneumatic
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