Selection of the Optimal Granulation Mode for Superphosphate
Abstract Generated abstract
This study examines optimization of dish granulation conditions for superphosphate, addressing the low industrial yield of standard 1 to 5 mm granules. Using production samples from the Dzhambul superphosphate plant, the authors tested granulation on a 1 m dish granulator while varying dish inclination, rotational speed, moisture addition, and binder solution. The best mode identified was a 45 degree dish inclination, 0.8 m/min peripheral speed, and 7 minute granulation time, with moisture added to the optimal pelletizing level. Under these conditions, use of a 5% sulfite-alcohol stillage solution increased the standard fraction yield to 89% and improved dry granule strength compared with water moistening and plant production data.
Full Text
SELECTION OF THE OPTIMAL GRANULATION MODE FOR SUPERPHOSPHATE
V. M. Vityugin, T. G. Leont’eva, N. S. Shimitova, N. P. Kolosova
(Presented by the scientific seminar of the Department of General Chemical Technology)
According to technical requirements, the sizes of standard granules must be in the range from 1 to 5 mm. In fact, at operating plants the yield of this fraction is only about 40%. An increase in the yield of the standard fraction is possible through optimization of the rolling process conditions.
In the present study, production samples of superphosphate from the Dzhambul superphosphate plant were used. Granulation was carried out on a dish granulator 1 m in diameter, with the dish inclination angle from 20 to 50°, and with a peripheral rotational speed of the dish from 0.5 to 1 m/min.
The best results were obtained when rolling superphosphate on a dish granulator with a bowl inclination angle of 45° and a rotational speed of 0.8 m/min, with a granulation duration of 7 min. The superphosphate was moistened directly on the granulator by means of a nozzle. The amount of moisture introduced strictly corresponded to the optimal working moisture content for pelletizing [1]. The results of the studies are given in Table 1.
Table 1
Properties of the granulate
| Yield of fraction, % | Yield of fraction, % | Yield of fraction, % | Crushing strength, g/granule | Crushing strength, g/granule | Number of drops from a height of 1 m | Number of drops from a height of 1 m | |
|---|---|---|---|---|---|---|---|
| +5 mm | +5–1 | −1 | wet | dry | wet | dry | |
| 1. Moistening with water | 24 | 67 | 9 | 340 | 1400 | 40 | more than 80 |
| 2. Moistening with 5% solution of SSB | 10 | 89 | 1 | 360 | 2250 | 70 | more than 80 |
| 3. Production data | 45 | 40 | 15 | — | 1200 | — | more than 80 |
Wet granules have low mechanical strength and do not withstand transportation. After drying the granules to a residual moisture content of 3–4%, their strength increases noticeably. An even greater increase in the mechanical strength of granules is achieved when the superphosphate is moistened with a five-percent solution of sulfite-alcohol stillage.
LITERATURE
- V. M. Vityugin, A. S. Bogma, P. N. Dokuchaev. Calculation of the optimal moisture content of disperse materials before granulation. Izvestiya vuzov, “Chernaya metallurgiya,” No. 8, 1969.