Analysis of the Temperature Distribution on the Surface of Saddle-Shaped Briquettes Consolidated in the Roller Press

Abstract

The unit pressure in the fine-grained material consolidation process in the roller press can reach over hundred MPa and is a parameter which results, among other things, from the properties of the consolidated material and the compaction unit geometry. Its value changes depending on the place on the molding surface. Generating different pressure on the surface of briquettes makes their compaction different. One’s own and other researchers’ experience shows that, in the case of exerting high pressure on the merged fine-grained material, the higher unit pressure exerted on the material, the higher temperature of the consolidated material is. The temperature distribution on the surface of the briquettes can testify the locally exerted pressure on the briquette. The stress distribution in the briquetting material is still a subject of research. The article includes thermography studies of the briquetting process of four material mixtures. Thermal images of briquettes were taken immediately after they left the compaction zone as well as forming rollers. The obtained thermograms and temperature variability at characteristic points of the surface of briquettes were analyzed. The correlation between the temperature distribution and the stress distribution in the briquettes was determined.

Modelling of the Fine-Grained Materials Briquetting Process in a Roller Press with the Discrete Element Method

“…The average stress values are 36÷40 MPa, where the minimum value is determined for the circumferential speed of the rollers of 0.2 m/s ( Figure 12 ). These results align with the experiments presented in [ 53 , 54 ], which demonstrated higher pressures and greater density of saddle-shaped briquettes in their upper part.…”

“… A general correlation between pressure distribution, porosity, and temperature distribution: ( a ) pressure distribution—DEM; ( b ) map of the porosity distribution on the copper briquette cross-section [ 53 ]; ( c ) the thermographic image of the briquette after briquetting [ 54 ]. …”

The Use of Thermography to Determine the Compaction of a Saddle-Shaped Briquette Produced in an Innovative Roller Press Compaction Unit

“…It was possible to transfer the briquette to the plywood pad directly after it was removed from the compaction unit, while maintaining precise control of the briquette topbottom, front-back orientation due to the low peripheral speed of the rollers (0.02 m/s). The tests of briquetting with the higher peripheral speed were unsuccessful due to the lack of possibility of controlled catching of the briquettes in the right orientation [47,48]. The images of the briquettes were captured in such a way that their 'top' (Fig.…”

“…The results presented in this article are a continuation of previous research published in the literature that present a simultaneous study of the temperature distribution and the compacting pressures in various compacting units of the roller press.". In previous works, the temperature distributions on the surface of classic saddle-shaped [47] and pillow-shaped briquettes [48] were presented. The tests presented in this article were carried out on four different mixtures of fine-grained materials in the innovative roller press compaction unit described by the PL 222229 B1 patent [49], in which the saddle-shaped cavities are distributed along the forming rollers.…”

Experimental Investigation on the Effect of Dry Ice Compression on the Poisson Ratio

“…Examples of the use of pelletizers in worm and roller technology include, among others, the compaction of wood sawdust, bronze and other metals, and swarf [23]. Roller machines cause a noticeable and uneven increase in the temperature value on the briquette surface [24], which is not desirable in the case of dry ice, for which an increase in the ambient temperature means an increase in the intensity of the sublimation process. In the case of dry ice, the only option is to produce pellets using reciprocating machines.…”