Binderless briquetting technology for lignite briquettes: a review

Briquetting process offers unique advantages such as uniformity in briquette size and shape, easy storage and transportation, thanks to the influence of binders which ensures good bonding and combustion performance. Recently, much has been discussed about the briquettes-binders system and the influence of binders on the resulting physical and combustion properties of briquettes. However, the present knowledge is insufficient on the binderless briquetting technology which is commonly used for producing lignite briquettes, as well as the resulting properties and beneficial effects when compared to briquettes produced with binders. The present review discusses the binderless briquetting technology in detail and its influence on the combustion and mechanical properties of the lignite briquettes. To a large extent, some properties of the lignite like hardness, surface structure, plasticity and elasticity can influence the binderless briquetting process. Reducing the plasticity or increasing the elasticity of lignite is advantageous to binderless briquetting. The various forms/theorems of binderless technology including capillary, adhesion, bituminous and humic acid, colloidal, denser water and cation membrane theorems were discussed. Under binderless briquetting system, the influence of briquetting parameters (temperature and pressure) and lignite coal properties (particle size distribution, moisture content, and hydrogen bonding) on briquette strength was extensively analyzed and discussed. This review study is concluded by presenting a comprehensive overview on the bonding mechanisms and several points of interest for future studies as regards the binderless technology for producing lignite briquettes.