Analysis of the process of structure formation due to briquetting of fine materials with participation of a liquid phase (water) and optimization of the process with the help of a mathematical model of formation of strength in artificial structures is of considerable practical interest. Experimental studies and computations are used for constructing two mathematical models of the strength of briquettes, which allow for the composite action of three factors, namely, the diameter of the particles of the material of the structure, its moisture content, and the proportion of the mechanisms of strength formation (capillary, molecular, and propping). The models are adequate for experimental data covering the range of particle sizes from~0.02 to 3 mm and the range of moisture contents from WMH to W MCM. The models make it possible to predict the strength of artificial structures, i.e., briquettes, depending on the particle size of the initial material and on its moisture content within the specified range of variation of initial data.Today briquetting as a method of agglomerating fine materials plays a noticeable role in various branches of industry. In order to analyze the process of structure formation from fine materials with participation of a liquid phase (water) and to optimize this process at commercial scale it is desirable to develop a mathematical model of formation of strength in artificial structures.The experience of designing nonlinear semi-empirical models shows that their application is limited by the accuracy of the mathematical description of the experimental base and frequently requires the use of specific constraints on the initial data.Assuming that the interaction of particles in a structure obeys potential "1 -3" [1], we will show the possibility of the use of a standard cubic equation for describing experimental data in the form of functions s max = f 1 (1/d p ) and s max = f 2 (W ), 2 where s is the ultimate compressive strength and d p and W are the diameter and the moisture content of the material, respectively. It can be seen from Fig. 1 that despite the high values of the correlation coefficients R (in the description of the experimental data used the quantity R varies from 0.679 to 0.980) curves 1 and 2 in Fig. 1a, b hardly reflect the essence of the phenomena. When the signs at the terms of the cubic equations are correct and correspond to the mechanisms of interaction of particles, the values of the ultimate compressive strength computed as a function of the quantity 1/d p can differ in some cases by a factor of 2 or more and the extreme values of the ultimate compressive strength of the structures can be mismatched with respect to the scales of 1/d p and W.In principle, a mathematical model can be constructed using two approaches, namely, -a formal approach with direct use of the discussed experimental functions s max = f 1 (1/d p ) and s max = f 2 (W ); an analysis of these functions made in [2] has already led to an incorrect conclusion that the mechanism of the interaction of particle...

On the basis of experimental data for briquetting of oxidized nickel ore with a clay component mathematical models have been developed taking account of all forms of particle interaction. These equations may be used in predicting the strength of artificial structures (briquettes) prepared from fine materials. The mathematical models developed connecting factors of processed material properties with compaction parameters promote to a considerable extent solutions for questions of controlling preparation of fine materials before the widespread method of caking, i.e. briquetting. Strength formation for artificial structures is a complex process whose control may be accomplished in different production stages.Currently briquetting, as a method for caking fine materials of different chemical and mineral compositions and the production of articles from them, is used as a weapon by many branches of industry, and mainly refractory, metallurgical, chemical, etc. Here, apart from chemical composition, the main property of a caked product and an article is strength. A particular role in creating the required strength of moist particle bonds in structures is an external compacting action realized in different technologies as a result of one-time compaction in the course of forming briquettes or as a result of dynamic treatment of already formed or forming granules and pellets.In soil mechanics [1] the compression curve, determining the nature of their compaction, is described approximately by the equation of a straight line e = e 0 -ms com ,where e and e 0 are current and initial porosity; s com is external compacting effect; m is material compressibility coefficient.In differential form Eq. (1) is precise and it is called the rule of soil compaction: de = -mds com .(2)During compaction of moist structures made from fine materials there is interest in relative strains d with compacting loads that exceed the structural compaction strength. In this case the connection between values of d and s com may be presented according to experimental data in the form of a power functionwhere a is coefficient of proportionality, in the simplest case a = b/E 0 , here b is side expansion coefficient; E 0 is linear strain modulus; n is a function nonlinearity parameter. However, with small changes in stresses applied to moist structures it is possible to use linear deformation theory for bodies, for which the value of n is assumed to equal one, then d = as com .(4)The principle of linear deformability, expressed by Eq. (4), is one of the main principles in contemporary soil mechanics [1].According to experimental data the connection between the external compaction load and the distance between the