is, respectively, 35 minutes for the radiation method, and about 10 minutes for the radiation method with a susceptor. In combined drying, the required time of thermal action on the articles being dried is 5–7 minutes.

Conclusions

1. A method has been studied for drying molded capillary-porous colloidal bodies using powdered alumina as a susceptor.

2. A scheme has been proposed for a combined drying method with a susceptor.

Literature

1. K. Laslone. Study of heat and mass transfer in drying processes with a susceptor. Author’s abstract of dissertation, Minsk, 1970.

2. A. M. Vasil’ev. Fundamentals of modern methods and techniques of laboratory determinations of the physical properties of soils. Moscow, 1955.

STUDY OF THE WATER-PHYSICAL PROPERTIES AND AGGLOMERABILITY OF CERTAIN POWDERED OXIDES

I. N. Lantsman, G. V. Kocherovskaya, N. F. Stas’, G. G. Savel’ev,
M. S. Lantsman, V. V. Nakhalov, V. M. Vitorgin

The practical use of oxide adsorbents for carbon dioxide /1/ without preliminary aggregation will apparently be difficult owing to their high dispersity and possible entrainment by the stream of purified gas. The most expedient method of aggregation of adsorbents is granulation, since in the process no disruption of the microstructure of the finely dispersed material occurs. In this connection, in parallel with studies of adsorption capacity, kinetics, and thermodynamics of adsorption /2, 3/, we have begun studies on granulation, primarily on determining the water-physical properties and agglomerability of oxides.

The efficiency of the granulation process for finely dispersed materials is determined by the nature of the material and the technological parameters of the process. The totality of the natural properties of materials may be most fully assessed by the agglomerability index, which is determined by the ratio /4/:

\[ K_{\mathrm{comp.}}=\frac{W_{\mathrm{MMB}}}{W_{\mathrm{MKB}}-W_{\mathrm{MKB}}} \tag{1} \]

where \(W_{\mathrm{MMB}}\) is the maximum molecular moisture capacity (%), characterizing the complex of surface properties of the dispersed material and the energy state of the system; \(W_{\mathrm{MKB}}\) is the maximum capillary moisture capacity (%), reflecting the structural state of the material being granulated. The agglomerability coefficient combines static parameters and makes it possible to judge the possibility of granulating the dispersed material under study and the need to introduce particular additives for the successful conduct of the granulation process.

However, in materials possessing internal porosity, a significant amount of water is immobilized, as a result of which the values of the maximum molecular moisture capacity are overestimated. Therefore, for sorbents it is necessary to assess agglomerability with a correction for maximum hygroscopicity \((W_{\mathrm{MG}})\):

\[ K_{\mathrm{comp.}}=\frac{W_{\mathrm{MMB}}-W_{\mathrm{MG}}}{W_{\mathrm{MKB}}-W_{\mathrm{MMB}}} \tag{2} \]

Analysis of the regularities of wet granulation of various dispersed materials has shown that the principal condition for the successful execution of the process is a strictly defined optimal value of the working moisture content of the material during granulation, which can be calculated from the formula:

\[ W_{\mathrm{opt.}}^{p}=W_{\mathrm{MKB}}-W_{\mathrm{NKB}} \tag{3} \]

The rate of growth of granules and the change in the rate of moisture propagation in the material during its compaction are determined from data on the kinetics of capillary impregnation, which for dispersed materials is satisfactorily described by the equation of B. V. Deryagin (7):

\[ V^{2}=K_{\mathrm{SKN}}\tau, \tag{4} \]

where \(V\) is the volume of absorbed water \((\mathrm{cm}^{3})\) over time \(\tau\) (s); \(K_{\mathrm{SKN}}\) is the coefficient of the rate of capillary saturation.

Aluminum oxide of grade “ch.”, magnesium oxide of grade “ch.d.a.”, and zinc oxide of grade “kh.ch.” were used as the objects of the study.

The maximum molecular moisture capacity was determined by the method of moisture-capacious media of A. F. Lebedev /6/; the moisture content after saturation was determined by the gravimetric method; the lowest capillary moisture capacity \((W_{\mathrm{NKV}})\) was determined from the kinetics of capillary saturation on diaphragms of the starting materials at different degrees of compaction /7/.

The experimental data and the values calculated from them for the agglomerability coefficient and the optimal working moisture content for granulation are given in Table 1.

Table 1

Water-physical properties and agglomerability
of the materials studied

Analysis of the data obtained showed that the materials studied have different agglomerability; the agglomerability coefficient for them lies in a wide concentration range from 0,02 to 0,83. All the oxides should be classified as weakly agglomerating materials; without the introduction of additives they do not granulate. Among the carbonates studied, ZnCO₃ has good agglomerability, while the carbonates of magnesium, beryllium, and copper are weakly agglomerating. Among the hydroxides, aluminum hydroxide is well agglomerating, the re-

are weakly lumping. A study of the kinetics of capillary saturation showed that the powdered oxides, hydroxides, and carbonates investigated have a high rate of moisture propagation in the material and high values of the working moisture content for granulation. It is probable that simple mechanical granulation of these materials will be difficult. It is necessary either to add plasticizing and compacting additives or to use other granulation methods, for example, the formation of pellets in an indifferent liquid or in a fluidized bed.

References

1. V. V. Nakhalov, N. F. Stas’, G. G. Savel’ev, A. S. Guzenberg, A. M. Ryabkin, T. S. Gorina. On the question of the adsorption of carbon dioxide by metal oxides. This collection.

2. N. F. Stas’, G. G. Savel’ev, V. V. Nakhalov, A. S. Guzenberg, A. M. Ryabkin. Thermodynamics of the chemisorption of carbon dioxide and water vapor by metal oxides. This collection.

3. V. V. Nakhalov, N. F. Stas’, G. G. Savel’ev. Investigation of the adsorption of carbon dioxide by aluminum oxide. This collection.

4. V. M. Vityugin, A. S. Bogma. Izvestiya vuzov, “Ferrous Metallurgy,” No. 4, 18, 1969.

5. V. M. Vityugin, A. S. Bogma, P. N. Dokuchaev. Izvestiya vuzov, “Ferrous Metallurgy,” No. 8, 42, 1969.

6. A. M. Vasil’ev. Fundamentals of Modern Methods and Techniques for Laboratory Determination of the Physical Properties of Soils. Moscow, Stroiizdat, 1953.

7. B. V. Deryagin, N. N. Zakhavaeva, M. V. Talaev. Instrument for Determining the Filtration Coefficient and Capillary Impregnation. Moscow, Nauka Publishing House, 1953.

ADHESIVE INTERACTION OF PARTICLES OF POLYDISPERSE MATERIAL IN WET AGGREGATION PROCESSES

V. M. Vityugin, E. N. Chulkova, I. N. Lantsman

In the practice of wet granulation, as a rule, polydisperse materials are used. In this case, the active role in the process of granule formation is played by the finest fraction, relatively small by weight, which is concentrated in the pore liquid. The coarser particles, forming the framework of the granule, mainly determine the density