CO2 reactivity of briquettes derived from discard inertinite-rich Highveld coal using lignosulphonate and resin as binders

Abstract

South African collieries generate approximately 31 Mt of fine and ultrafine coal annually, with the majority of the ultrafine fraction discarded in slurry ponds and underground workings. Use can be made of this energy source through briquetting, thereby alleviating the handling problems associated with fine coal. Briquettes of inertinite-rich high-ash coal when combined lignosulphonate and resin have shown promising mechanical strength, therefore requiring reactivity analysis. In this study, chars derived from lump coal, binderless briquettes, and lignosulphonate-and resin-bound briquettes were subjected to CO 2 gasification at 875, 900, 925, 950, and 1000°C. Binder addition brought about no distinct difference in char reactivity. The briquetted chars showed approximately double the reactivity of lump coal chars. The increase in micropore surface area derived during the devolatilization process is postulated to be the major contributor to the increased reactivity of the briquettes. No significant differences were observed between the activation energy of the lump coal and manufactured briquettes, with values ranging between 222-229 kJ/mole. Industrial implementation of fine coal briquetting in South Africa will result not only in an increase in coal resources, but also reduce environmental concerns linked to fine coal discards.

Catalytic Effect of Reactive Extraneous Mineral Composites on Char and Tar Distribution during Pyrolysis of Highveld Partially Oxidized Fine-Coal Reject and Its Beneficiated Residues

“…Mechanized mining, handling, and processing of South African (SA) run-of-mine (ROM) coals, raw coals which are extracted and transported directly from the collieries, produce more than 60 million tonnes of partially oxidized fine-coal rejects (FCRs) annually, which are unsuitable for utilization in some thermochemical processes due to their fine nature. – As a result, about 1 billion tonnes of FCRs containing sulfur-bearing mineral-matter (MM) (>1%) have been disposed of in slurry ponds and stockpiles in the country. These FCRs contain ultrafine particles (<250 μm) and coarser fine-coal particles (250–1000 μm) which are amenable to spontaneous combustion resulting in SO 2 , particulate matter (PM), nitrogen oxides (NOx), and CO 2 gas emissions during storage in stockpiles and slime dams. – This literature – reports that FCRs have chemical properties similar to coals utilized in boilers and gasifiers (i.e., feed-coals) but are classified as high-ash coals. The term “high-ash coals” refers to coals which are produced from SA collieries comprising a percentage ash yield (AY) greater than 30%.…”