The structure formation mechanism in wet coal fines briquetting with an active binder

Abstract

This paper presents the results of studies of the structure formation mechanism for briquettes made from coal fines (sludge, coal dust, and fines), with the use of powdered technical lignosulfonate (100 % Na base) as the binder. It has been established that, when briquetting fine coal fines with active finely-dispersed binders in an air-dry state, the structure formation mechanism of the briquette does not fully align with any of the existing hypotheses. As a result of the research, a theoretical substantiation is proposed for the hypothesis of wet coal sludge briquetting with the use of active finelydispersed binders in an air-dry state. It has been shown that the walls of capillaries and pores in the central part of the briquette experience precipitation from the fluid systems, dissolved by internal moisture, and of coarse particles and a certain amount of the binder entrained in the fluid. Further, a lean fluid advances to the surface of the briquette, consisting mainly of moisture and an excess amount of the active binder, dissolved in it. In the near-surface compacted area of the briquette, the binder is adsorbed on coal particles and the moisture released in the process of thermal destruction and adsorption evaporates. The practical use of the concepts obtained allows controlling the structure formation processes to improve strength without increasing the binder content through layer-by-layer reinforcement of the briquette mass with a closed surface, which significantly improves the process results.