Magnetic desulfurization of liquefied coals: Conceptual process design and cost estimation

Estimates of magnetic separation characteristics, conceptual process requirements, and capital costs for magnetic separation of mineral sulfur from liquid coal produced in a solvent refining process have been determined from preliminary empirical data obtained by Hydrocarbon Research, Incorporated, in a laboratory program sponsored by EPRI. The magnetic separator has been scaled to remove weakly magnetic sulfurous minerals from the process stream of a solvent refining plant fed by 9,072 metric tons (10,000 short tons) of raw coal per day whose product (moisture and ash-free solvent refined coal plus distillates plus undissolved carbon plus ash) meets point source sulfur emission standards for new installations burning coal. The conceptual installation, employing four batch type high-field high-gradient magnetic separators, each with 3.1 M³magnetized volume, packed to 94% void volume with fine stainless steel wool, and energized by a 2 T magnetic field, processes a stream of 315 liters/sec (5,000 gal/minute) reactor liquid effluent. The flow velocity through each unit is 1.8 cm/sec (27 GPM/ft²) with a 74% on line factor. The installation processes 3.31 million tons per year of raw coal, or 2.9 million tons per year of desulfurized product. Cost of installed magnets is estimated at $18 million and the add on processing costs associated with magnetic separation (including O&M) are estimated at $1.01 per ton of coal feed, $1.16 per ton of low sulfur product (4 cents per million Btu), and 33 cents per 1,000 liters of reactor effluent filtered ($1.27 per 1,000 gallons).