The development of analytical methods for predicting the strength characteristics of pellets produced by the compaction of fine-grained materials remains a significant and relevant area. To advance ...this area, the mechanisms of phase interactions in bulk media were analyzed. The analysis was then used to develop local models of adhesion processes for two basic particle interaction schemes: ‘particle + particle’ and ‘particle + liquid phase + particle’. For each local model, the types, nature, and combination of adhesion processes that occurred simultaneously were theoretically established, and the factors and indicators that determined the occurrence and intensity of adhesive bonding were justified. The experimental studies conducted in the laboratory premises of the Nekrasov Iron and Steel Institute of the National Academy of Sciences of Ukraine were analyzed to evaluate the nature and extent of influence exerted by the selected factors, determining the adhesion processes, on changes in the strength characteristics of compacts. Considering the results obtained and the analytical dependences established for the ‘particle + particle’ interaction scheme, a method for predicting the strength characteristics of pellets produced from fine-grained materials with zero moisture was developed. This paper justifies the methodological conditions for experiments intended to create strong bonds within the compacts under the ‘particle + liquid phase + particle’ interaction scheme, taking into account the mechanical, physical, and physicochemical interaction processes between individual particles of the pelletized material and between the charge components (liquid phase). A generalized analysis of the experimental findings was carried out to estimate the range of potential adhesion processes inherent in the ‘particle + liquid phase + particle’ interaction scheme, identify their manifestation, study the nature of their interaction, and evaluate the effect of introducing the liquid phase into the pelletized charge, considering the applied compaction pressures. The collected array of experimental data will enable a detailed cross-correlation analysis to determine the influence of various factors on the adhesion processes and the formation of strong bonds within the compacts. The analysis will also help establish the dependence of strength characteristics of compacts on integral indicators contributing to the formation of adhesive bonds and describe the dependence by analytical methods. The results will be used to develop a method to determine the moisture content in the charge required to produce compacts with maximum strength from materials that belong to the first of the four groups of systematization. The classification of materials into specific groups of systematization is determined by their pycnometric density.
We consider a parabolic equation in one spatial variable with Dini continuous coefficients. For this equation, the existence of a classical fundamental solution is proved and estimates are given. The ...condition on the nature of the continuity of the leading coefficient of the equation for the existence of a fundamental solution is sharp.
Researchers of the Nekrasov Iron & Steel Institute, National Academy of Sciences of Ukraine, conduct studies aimed at developing analytical methods for predicting the strength characteristics of ...pellets. These studies use analyses of phase interaction mechanisms within free-flowing media to develop theoretical ideas on the formation of strong bonds in the pellets through adhesion. This led to the establishment of local models of adhesion processes for two basic particle interaction schemes: ‘particle + particle’ and ‘particle + liquid phase + particle’. Experimental studies undertaken in laboratory premises of the Nekrasov Iron & Steel Institute for the ‘particle + particle’ interaction scheme provided the foundation for a method to determine the strength characteristics of pellets made from fine-grained materials with zero moisture at compaction pressures ranging from 50 to 220 MPa. The first part of the paper justified methodological prerequisites for experiments to study strong bonds within the compacts for the ‘particle + liquid phase + particle’ interaction scheme. The methodological prerequisites accounted for the mechanical, physical, and physicochemical interactions, both between individual particles of the pelletized material and between the charge components (liquid phase). A generalized analysis of the experimental findings allowed evaluating a range of potential adhesion processes for the ‘particle + liquid phase + particle’ interaction scheme, pinpointing their manifestation, examining their nature, and assessing the effect of a liquid phase introduced into the pelletized charge, considering the compaction pressures applied. This paper focuses on experimental findings for the ‘particle + liquid phase + particle’ interaction scheme, establishing analytical relationships between the strength characteristics of pellets and integral indicators of the adhesive bond mechanism in this interaction scheme (in particular, relationship between the bulk density (ρ
0
) and moisture content (W
m
) for materials in the first group of systematization). Additionally, an analytical relationship between the compaction factor for compacts produced at a pressure (P) of 220 MPa (K
comp220
), considering their loosening, and the bulk density of materials (ρ
0
) in the first group of systematization was established for the first time. Analysis of the findings led to a hypothesis suggesting that the amount of the liquid phase (in particular, water) introduced into the material should be balanced by its potential displacement during compaction to achieve maximum compact strength. Based on the hypothesis, a novel equation was derived to calculate the amount of liquid binder (water) to promote the most favorable conditions for the adhesion processes, thereby imparting the maximum strength to compacts from materials in the first group of systematization. A comparative analysis between the experimental findings and calculations confirmed that the equation was accurate. Consequently, an analytical method was proposed to determine the moisture content needed in the charge to produce compacts with maximum strength from materials in the first group of systematization (ρ
pycn
≥ 4.64 × × 10
–3
).
The pelletizing of fine-grained mineral raw materials for ferrous metallurgy is studied. Relationships between the compressibility of metallurgical charges and the nature of the raw materials and ...process factors of the pelletizing process were studied in laboratory conditions. A new measure, such as the compressibility of ground materials, was introduced to quantify and compare compression performances. A mathematical description of the relationships between the compression coefficient and the following factors was formulated through nonlinear regression analysis and experiment design theory methods: the plasticizer content (varying from 0 to 50%), moisture content of the charge (from 0 to 10%), hardness of the particles according to the mineralogical scale (from 2 to 6 units), dynamic viscosity of the binder (from 1 to 657 mPa · sec), amount of the carbon-containing component (from 10 to 90%), and particle sizes of the iron- and carbon-containing components in the charge (from 1 to 4 mm). The compaction pressure range was limited to 220 MPa. Three mathematical models were developed to establish relationships between the charge compressibility and the specified factors as polynomial dependencies and as a Lorentz function. The quality of the models was verified using standard statistical indicators, including the Cochran and Fisher tests and the average relative error. Analysis of the models involved the solution of relevant optimization problems. Extremes of the functions for metallurgical charges were identified and process recommendations were made. The results have practical implications for improving the compressibility of charges from mineral raw materials and developing optimal pelletizing methods.
The mechanisms of phase interactions in granular media were studied to elaborate the results obtained previously at the Nekrasov Iron and Steel Institute of the National Academy of Sciences of ...Ukraine to establish analytical methods for predicting the strength acquired by compacts produced from fine-grained materials. This allowed the development of theoretical ideas on the adhesive bonds formed in pellets to propose local models of adhesive processes for two basic particle interaction schemes: ‘particle + particle’ and ‘particle + liquid phase + particle’. Types of adhesion processes occurring simultaneously, as well as their nature and combinations, were established for each local model. This provided grounds for selecting factors that governed the formation of adhesive bonds and indicators that determined the rate of their development. Experimental studies were conducted in laboratory facilities of the Nekrasov Iron and Steel Institute for assessing the nature and extent of influence exerted by the selected factors on the strength of compacts. The experimental results were used to establish analytical dependences to describe the strength as a function of integral indicators of adhesive bond formation, taking into account the pelletizing pressure. These dependencies underlay the proposed method for predicting the strength of pellets produced from fine-grained materials with zero moisture in the range of pelletizing pressures from 50 to 220 MPa. The proposed computational and analytical method allowed determining the strength of pellets with high accuracy. Thus, it can be successfully used to develop processes for the production of pellets and the development of compaction equipment. The proposed method may be developed further through the expansion of its capabilities by predicting the strength of compacts considering liquid bonding agents introduced into the starting charge.
—An experimental stand has been created to assess the characteristics of the electromagnetic field under which the current–voltage (
I
–
V
) characteristic of semiconductor elements change. The ...developed stand was used for a series of experiments on the effect of signals with different parameters on a KD520A diode in order to record changes in the slope of the diode’s
I
–
V
characteristic as an onset degradation feature of the
p
–
n
-junction. This is done by recording the amplitudes of higher harmonics under the action of microwave signals.
We consider a parabolic equation with Dini continuous coefficients in the case of many spatial variables The existence of a regular fundamental solution to this equation is proved, and estimates for ...the solution are obtained. These results imply that the Dini condition for the principal coefficients of the equation is sharp.
The linear regression analysis was used to perform a comparative assessment of the mathematical description of the experimental compaction curves by the new basic equation and the empirical ...compaction equations proposed by Balshin, Heckel, Kawakita, Panelli–Filho, and Ge. The studies were conducted on a specially compiled representative sample of the mining and metallurgical complex materials, divided into groups in accordance with the technological purpose in metallurgical redistribution. According to the results, the basic compaction equation developed by the authors is characterized by the best indicators of reliability and accuracy, and therefore it is preferable for determining the energy–power characteristics of the compaction process under a pressure of up to 220 MPa. The validity of the interpretation of the constant coefficients of the compaction equations was also evaluated.
An analytical method for preliminary assessment of the compactability of charges made from fine materials of the mining and smelting industry is developed. The method allows establishing the ...functional dependence of the density of a briquette on the applied pressure without experiments on the compression of a charge in special pressure equipment. The method involves the use of a new compaction model and the relationship between the compact density at a given pressure and the physical and mechanical properties of a charge (loose bulk density, tapped bulk density, true density of particles) for dry charges and charges mixed with water or liquid binder. The method can be used in briquette production when choosing processing modes and creating pressure equipment.
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