PROCEEDINGS
OF THE TOMSK POLYTECHNIC INSTITUTE
NAMED AFTER S. M. KIROV, HOLDER OF THE ORDER OF THE OCTOBER REVOLUTION
AND THE ORDER OF THE RED BANNER OF LABOR

Volume 215
1974

METHOD FOR CALCULATING THE OPTIMUM MOISTURE CONTENT FOR GRANULATION OF DISPERSE MATERIALS

V. M. VITYUGIN, A. S. BOGMA, P. N. DOKUCHAEV

(Presented by the scientific seminar of the Department of OChT)

The rate of the process of granulation of disperse materials and the strength of raw aggregates are determined, as is known, by the surface properties of the materials and by the technological factors of the process. It is expedient to evaluate the totality of the surface properties of disperse materials by a single index of granulatability.

The granulatability may be evaluated, with accuracy sufficient for practice, by complex parameters: the maximum, molecular, and capillary moisture capacities. The value of the maximum molecular moisture capacity \((W_{\text{MMV}})\) rather fully reflects the nature and surface properties of the material, characterizing the energy state of the material being aggregated, while the capillary moisture capacity \((W_{\text{KV}})\) characterizes the structural state of the system being aggregated. It has been proposed to determine the quantitative expression of the granulatability index of disperse materials \((K)\) from the following equation [1]:

\[ K=\frac{W_{\text{MMV}}}{W_{\text{KV}}-W_{\text{MMV}}}. \tag{1} \]

Under real conditions, the technological parameters of the process exert a substantial influence on the granulation process. Analysis of the regularities of wet aggregation shows that the basic condition for carrying out the granulation process is that there must be a strict correspondence between the optimum moisture content of the charge and its moisture capacity. In the best case, the optimum moisture content \((W_{\text{OPT}})\) is equal to the maximum molecular moisture capacity, i.e.

\[ W_{\text{OPT}}=W_{\text{MMV}} \]

However, such a relationship between moisture content and moisture capacity is valid only for materials with a granulatability index \(K=1\).

In the general case, the relationship between the moisture content and the moisture capacity of the material being aggregated may be represented by the following equation proposed by us:

\[ W_{\text{OPT}}=\frac{W_{\text{MMV}}}{K}. \tag{3} \]

It follows from equation (3) that for materials with a definite degree of granulatability, when \(K\) is constant, \(W_{\text{OPT}}\) is determined by \(W_{\text{MMV}}\). \(W_{\text{MMV}}\) is an additive quantity; consequently, for bringing into cor-

correspondence of the working moisture content and moisture capacity to the base material; when the value of its ballability index is below unity, additives with an increased value of moisture capacity must be introduced. To calculate the required amount of additive \((x_1)\), the following equation, derived from the preceding ones, is proposed:

\[ x_1=\frac{100(K\cdot W_{\mathrm{opt}}-W_{\mathrm{mmv}})} {W_{\mathrm{mmv\,add}}-W_{\mathrm{mmv}}}\ \% . \tag{4} \]

When the ballability index of the base material is greater than unity, less moisture-capacious materials must be added in an amount \((x_2)\), determined by the formula:

\[ x_2=\frac{100(K\cdot W_{\mathrm{opt}}-W_{\mathrm{mmv}})} {W_{\mathrm{mmv}}-W_{\mathrm{mmv\,add}}}. \tag{5} \]

In equations (4 and 5), \(W_{\mathrm{mmv\,add}}\) is the maximum molecular moisture capacity of the additives, and \(W_{\mathrm{mmv}}\) is the maximum molecular moisture capacity of the base material.

The results of investigations on balling the charges of the Sokolovsko-Sarbaiskii Mining and Beneficiation Combine fully confirmed the possibility of practical use of the proposed equations. Swelling bentonites were used as moisture-capacious additives in this case.

REFERENCES

1. V. M. Vityugin, A. S. Bogma. Assessment of the ballability of fine-grained materials. Izvestiya vuzov. Chernaya metallurgiya, No. 4, 1969.