Experimental study on the role of moisture in the cold binderless briquetting of low-rank coal

Briquetting is needed to complete the upgrading process of low-rank coal, which commonly produces yield in a powder form. The process increases solid fuel's energy density, handling, and transportability. The binderless briquetting is frequently selected over the conventional briquetting process since it utilizes the coal substance to bind the particle such that the coal property as fuel is unaltered. Unfortunately, the mechanism of how the coal particles are bonded remains unclear. This research investigated the binderless briquetting process at room temperature (cold binderless briquetting), employing moisture content (MC) as a binding agent. Experimental results show that, during the compaction process, the moisture acts as lubricants and provides deformability in the coal particle, which eases the particle interlocking at a higher density. However, the change of moisture in the briquette after the compaction process could induce swelling and shrinkage in the particle, causing a discrepancy in the particle interlocking system and reducing the briquette strength. From the investigation, the cold binderless briquetting of LRC is recommended to be conducted at 2500 bar compaction and using coal particles with the initial MC of 10-20%. The prediction of briquette strength at different moisture content is also proposed in this paper.

Automated summary

Briquetting is necessary for upgrading low-rank coal, as it improves the energy density, handling, and transportability of solid fuel. This study investigated the binderless briquetting process at room temperature, and found that moisture acts as a lubricant during compaction, facilitating particle interlocking and increasing density. However, changes in moisture content after compaction can lead to swelling and shrinkage in the particles, resulting in decreased briquette strength.