Oil agglomeration as a pretreatment for coal liquefaction

Abstract Laboratory experiments demonstrated that a variety of distillate coal liquefaction recycle oils were satisfactory agents for cleaning Illinois no. 6 bituminous coal by oil agglomeration. Ash rejection up to 41% with 98% organic recovery was attained with conventionally cleaned coal, and ash rejection up to 67% with 90% organic recovery with run-of-mine coal. Agglomerates of > 1 mm average diameter were produced under a variety of conditions. Similar results were obtained in the scaled-up production of 268 kg of agglomerates. Oils with lower hydrogen aromaticities and higher hydrogen contents performed better than more aromatic oils. Fe, Ti and Mg were selectively enriched in the ash of the product coal, while Ca, Si, and Al were selectively rejected. The mineral pyrite was rejected only ≈ 30–40% as extensively as the bulk of the ashforming minerals. The coal cleaned by oil agglomeration performed similarly to the feed coal in batch donor liquefaction tests. In continuous hydroliquefaction tests, run-of-mine coal cleaned by oil agglomeration performed substantially better than coal cleaned to the same ash level by conventional means, because of the selective enrichment of catalytic iron minerals.