Diesel production in coal-based high-temperature Fischer–Tropsch plants using fixed bed dry bottom gasification technology

Abstract

Gas-to-liquids (GTL) and also coal-to-liquids (CTL) Fischer–Tropsch plants using high-temperature (entrained flow) gasification all face the same refining challenge, which is meeting the EN590 density specifications of 820kgm−3 at 15°C for the produced distillate. Fischer–Tropsch distillates can, however, be blended with high density distillates originating from sources such as crude oil, direct coal liquefaction or coal pyrolysis products, in an effort to conform to those diesel density requirements. Fixed bed dry bottom (FBDB) gasification technology can in combination with high-temperature Fischer–Tropsch (HTFT) synthesis provide a way to produce final on-specification CTL transportation fuels. Hydroprocessing FBDB gasification tar results in a distillate with high density whereas a hydrotreated HTFT distillate corresponds to a highly paraffinic product with high cetane number but low density. Both distillates can be blended to produce a market-ready final diesel which is of particular industrial importance for CTL applications in countries which have no oil but low-rank coals instead and viable options for carbon capture and storage (CCS).