Study of the Effect of Humic Acids and Insoluble Humates on the Compaction and Strengthening of Granules
Abstract Generated abstract
This study examines how humic acids and insoluble calcium, iron, and aluminum humates affect the agglomeration, compaction, and strength of marshallite granules. Humic substances prepared from peat were mixed directly with the material before granulation on a laboratory pan granulator, and the density and crushing strength of wet and dried granules were measured. The results indicate that these additives do not increase wet granule density or raw strength compared with water alone, and at higher concentrations can reduce compaction. Although drying improves strength, insoluble humates and humic acids are less effective binders than soluble sodium humates, making their direct use as plasticizing additives impractical.
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STUDY OF THE EFFECT OF HUMIC ACIDS AND INSOLUBLE HUMATES ON THE COMPACTION AND STRENGTHENING OF GRANULES
A. F. KARPOVICH, V. M. VITYUTIN
(Presented by the scientific seminar of the Department of General Chemical Technology)
The fine-grained material to be aggregated is a heterogeneous three-phase system, and the process of agglomeration is determined by the properties of these phases and by the nature of their interaction with one another. Both mixtures of materials and individual materials are subjected to granulation; their surface is not refined and is not free from adsorbed cations. The latter may enter into exchange reactions with cations located in the moist pore space. In the case where sodium humates are used as a binder, the formation of various insoluble humates in the granulated charge is not excluded.
In the present work we set ourselves the task of determining the effect of insoluble humates of calcium, iron, aluminum, and humic acids on the process of agglomeration of marshalite when they are introduced directly into the material being granulated.
The source for obtaining the humic substances was peat from the Vasyugan deposit in Tomsk Oblast. Humic acids were obtained by precipitating a sodium humate solution with 5% sulfuric acid. Calcium humates were obtained by the exchange reaction of sodium humate with calcium acetate. Aluminum humates were prepared by treating a sodium humate solution with aluminum chloride, and iron humates by the action of ferric chloride.
Granulation was carried out on a laboratory pan granulator with \(D = 300\) mm. Before granulation, the moisture content of the isolated humic acid or humates was determined in order to calculate their percentage share in the marshalite on an absolutely dry basis. A specified amount of humates or humic acids was thoroughly ground with the material; if necessary, water was added to the established granulation moisture content, equal to 15%. The density of the granules was determined by the paraffinization method. Drying was carried out at \(t = +100^\circ\text{C}\) for 2 hours. The crushing strength of the granules was determined. The experimental results are presented in Table 1.
The coagulation structure of humic acids and insoluble humates prevents their intensive adsorption on the surface of the particles of the material being granulated, which would ensure the effective manifestation of molecular forces, as occurs with solutions of sodium humates. The density of wet granules with insoluble humates and humic acid does not increase in comparison with the density of granules with water; at a high humate content, even decompaction of the granules occurs (see Table 1).
Table 1
Density and strength of wet marshallite granules with additions of humic acids and insoluble humates
| No. | Binder | Content, % of the initial marshallite charge | Granule density, g/cm³ | Granule strength, g granule |
|---|---|---|---|---|
| 1 | Water | — | 1.53 | 53.6 |
| 2 | Aluminum humates | 0.176 | 1.53 | 53.6 |
| 3 | Aluminum humates | 0.337 | 1.53 | 55.5 |
| 4 | Aluminum humates | 0.650 | 1.48 | 54.6 |
| 5 | Iron humates | 0.11 | 1.53 | 56.5 |
| 6 | Iron humates | 0.249 | 1.52 | 57.6 |
| 7 | Iron humates | 0.570 | 1.47 | 55.7 |
| 8 | Humic acid | 0.150 | 1.52 | 57.6 |
| 9 | Humic acid | 0.380 | 1.53 | 57.6 |
| 10 | Humic acid | 0.750 | 1.46 | 56.4 |
| 11 | Calcium humates | 0.268 | 1.53 | 57.5 |
| 12 | Calcium humates | 0.537 | 1.53 | 56.5 |
| 13 | Calcium humates | 0.798 | 1.49 | 56.3 |
The strength of raw granules with the addition of humic acids and humates and without addition (with water) is practically the same. After drying, humic acid and insoluble humates contribute to an increase in granule strength. However, soluble humates, at the same percentage of participation, provide greater granule strength than insoluble humates and humic acids. Evidently, the strength of granules upon addition of humates and humic acid depends to a greater degree on the type of cation. This conclusion agrees with the studies of P. V. Vershinin and D. G. Vilenskii [1, 2], which showed that the adhesion force of soil particles, depending on the absorbed cations, increases in the direction
\[ \mathrm{Al}^{\cdots} < \mathrm{H} < \mathrm{Ca} < \mathrm{Mg} < \mathrm{K} < \mathrm{NH}_4 < \mathrm{Na}. \]
Thus, the plastic properties of humic acids and insoluble humates do not manifest themselves in the process of marshallite granulation, and their binding properties are low in comparison with solutions of sodium humates. As a result, the direct use of humic acids and insoluble humates as plasticizing additives is inexpedient.
LITERATURE
- P. V. Vershinin. Formation of soil structure. Bulletin of Agricultural Science. Fertilizers, Agrotechnics, Soil Science, issue 1, 1941.
- D. G. Vilenskii. Soil Aggregation, Its Theory and Practical Application. Moscow–Leningrad, Publishing House of the Academy of Sciences of the USSR, 1945.