Intensification of the Dewatering Process of Fine-Grained Iron Ore Concentrates Using the K-4 Structure-Forming Agent
Abstract Generated abstract
This study examines the use of small additions of the K-4 structure-forming agent to improve vacuum filtration of fine-grained magnetite concentrates containing clay and slime fractions. Laboratory filtration tests on Sokolovsko-Sarbaiskie concentrate, conducted at constant vacuum with varying solid to liquid ratios and K-4 dosages, measured filtration time, volumetric filtration rate, and cake moisture. The results show that K-4 substantially accelerates filtration and can reduce cake moisture, with an indicated effective dosage range of about 300 to 500 g per ton of filtered concentrate. The proposed mechanism is coagulation of clay particles and formation of microaggregates with finely dispersed magnetite, producing a looser, more permeable cake and suggesting the reagent merits production-scale testing.
Full Text
Vol. 215 1974
INTENSIFICATION OF THE DEWATERING PROCESS OF FINE-GRAINED IRON-ORE CONCENTRATES USING MICROADDITIONS OF STRUCTURE-FORMING AGENT K-4
V. M. VITYUGIN, S. A. BABENKO, A. V. VOZNYAK
(Presented by the scientific seminar of the Department of CCT)
Deep beneficiation of iron ores is associated with significant overgrinding. In this process, the gangue components and, in particular, the clay constituents pass into the finest fraction, with grain sizes of the order of microns. During wet magnetic separation these clay constituents are not completely separated from the concentrate and, together with the concentrate pulp, enter dewatering. When the pulp is dewatered on vacuum filters, the open cross section of the filter cloth and of the concentrate cake decreases sharply because of deposition of the clay fraction. Swelling clay substances of the montmorillonite type have an especially noticeable effect on the filtration rate.
Under practical conditions this leads to an impermissible increase in cake moisture, or to a sharp decrease in the productivity of the vacuum filter. The negative effect of clay impurities, as well as of the finely dispersed slime fraction of the concentrate, can be substantially neutralized by adding small amounts of structure-forming agents to the pulp being filtered.
In the present work, the effect of additions of structure-forming agent K-4 on the filtration process of magnetite concentrate from the Sokolovsko-Sarbaiskie ores was investigated. Structure-forming agent K-4 is a product obtained by partial saponification of polyacrylonitrile [1] in an alkaline medium. In the work, a K-4 sample from the Chirchik Electrochemical Combine was used. The effect of K-4 additions was assessed by filtration time and by cake moisture. The experiments were carried out on a laboratory filtration unit at a constant vacuum (500 mm Hg). Filtration was performed through ash-free paper filters. The maximum filtration time was 2 min. The S:L ratio was varied from 1:1 to 1:4. The K-4 consumption was varied from 100 to 800 g/t of cake.
Additions of K-4, as can be seen from Table 1, sharply increase the filtration rate. At the same time, a decrease in cake moisture is observed. Thus, at a K-4 consumption of 400 g/t the moisture of the sediment is 12.1%, whereas without addition of the reagent the sediment moisture proved to be 19.3%; it is characteristic that the greatest reduction in moisture occurs at S:L = 1:4.
The filtration rate decreases somewhat with an increase in the K-4 addition, which is explained by the corresponding loosening of the sediment and an increase in its capillary moisture capacity.
Table 1
Effect of K-4 additions on filtration efficiency
| No. | S:L | K-4 consumption, g/t | Filtration time, sec | $W^{P}$, % | Volumetric filtration rate, cm³/sec |
|---|---|---|---|---|---|
| 1 | 1:1 | — | 75 | 11.5 | 1.77 |
| 2 | 1:1 | 200 | 32 | 13.8 | 4.05 |
| 3 | 1:2 | — | 93 | 19.3 | 1.95 |
| 4 | 1:2 | 400 | 55 | 12.1 | 3.41 |
| 5 | 1:4 | — | 120 | 15.3 | 1.60 |
| 6 | 1:4 | 800 | 65 | 10.6 | 3.00 |
The optimum value of the K-4 addition will evidently vary within the range of 300–500 g/t of filtered concentrate.
The action of K-4 is explained by coagulation of clay particles and, at the same time, by loosening of the cake on the filter as a result of the formation of microaggregates from finely dispersed magnetite particles. Visual observations showed that the volume of the iron-ore concentrate cake after its settling in the presence of K-4 is approximately 25% greater than when settling in distilled water.
The phenomenon of coagulation of clay impurities is also manifested very clearly during settling of the suspension. It is characteristic that when the suspension is settled in distilled water, a two-layer sediment is formed (concentrate at the bottom, clay particles on top), whereas when the suspension is settled in the presence of K-4, the upper clay layer is absent. In the latter case, the clay particles are coagulated on the surface of the magnetite particles and settle together with them.
The investigations carried out show that the use of the structure-forming agent K-4 should be tested under production conditions. The introduction of K-4 additives into the practice of dewatering iron-ore concentrates is distinguished by the fact that this type of structure-forming agent dissolves comparatively well in water, unlike polyacrylamide, and thus no additional capital expenditures will be required for its introduction.
REFERENCES
- S. Zainutdinov, K. S. Akhmetov. Production of an artificial structure-forming agent for the soils of Central Asia. Collection “Humic and Polymeric Preparations in Agriculture.” Publishing House of the Academy of Sciences of the Uzbek SSR, 1961.