INTENSIFICATION OF DEWATERING OF FINELY GROUND IRON ORE MATERIALS

V. M. Vityugin, N. N. Yudin, E. N. Chulkova

(Presented by the scientific seminar of the Department of General Chemical Technology)

It was reported earlier that it is expedient to use microadditives of the reagent K-4 (the sodium salt of acrylonitrile acid) for vacuum filtration of finely dispersed magnetite concentrates of deep beneficiation. The present article sets forth the results of subsequent studies of this question, aimed at identifying certain technological features of the proposed measure.

As the object of study, aqueous suspensions of magnetite concentrate from the industrial pelletizing plant of the Sokolov–Sarbai Mining and Processing Combine, and aqueous solutions of reagent K-4 from the Chirchik Electrochemical Combine, were used. Filtration was carried out on a standard laboratory filtration unit consisting of a vacuum pump, a receiver with a vacuum gauge, a Büchner funnel, and a Bunsen flask. Industrial capron cloth, grade 56035, was used as the filter. The concentration of the solid phase in the initial suspension was 60%. The suspension was prepared with process water having a pH value of 8.1–8.3. The time of pulp agitation before filtration in most experiments was 1 min, and in one of the series it varied from 1 to 15 min. The consumption of reagent K-4 was varied within the range from 100 to 1000 g/ton of concentrate. All experiments were begun at a constant vacuum of 500 mm Hg. After removal of the bulk of the water, the vacuum in the system began to decrease. The time from the beginning of the experiment to this moment was taken as the main filtration time. The total filtration time was varied from 1 to 4 min. The averaged results of the experiments are given in Table 1.

Introducing reagent K-4 into the pulp being filtered reduces the main filtration time from 49 to 26 sec, respectively, at K-4 consumption from 0 to 1 kg per ton of concentrate. With an increase in K-4 consumption, especially in the interval from 0.5 to 1 kg/ton, the moisture content of the cake increases substantially, which is due to the structuring action of reagent K-4 in the sediment layer. Thus, increasing the consumption of reagent K-4 above 0.5 kg/ton is inexpedient. The results of experiments studying the influence of pulp agitation time on the effectiveness of K-4 action deserve special attention. A comparative evaluation of experiments 2, 12, and 14 with the introduction of a minimal K-4 additive indicates the importance of taking this operation into account when selecting the optimal technological filtration regime for magnetite suspensions using K-4. Increasing the agitation time of the suspension will make it possible to reduce the consumption of K-4 and decrease the moisture content

cake. In this respect, it is most rational to introduce K-4 into the magnetite suspension at the thickening stage. The effectiveness of such a measure lies in the fact that, owing to the exceptionally high coagulating ability of the K-4 reagent, it will be possible to sharply reduce concentrate losses during thickening. Special experiments have established that the clarification time of comparatively dilute suspensions in the presence of small additions of K-4 decreases sharply, while the purity of the clarified overflow practically does not differ from that of process water.

Table 1

Average laboratory data on filtration with K-4

This coagulation effect of K-4 additions is also manifested in the filtration process. Losses of the finely dispersed fraction in the filtrate without addition of K-4 amount to 1.8% or 3.59 g/l; with addition of K-4 in the amount of 400 g/tonne, they amount to 0.27% or 0.34 g/l, respectively.