Magnetic separation of solids from liquified coal

High gradient magnetic separation (HGMS) has been applied to the removal of ash-forming mineral matter and sulfur in the form of pyrites from solvent refined coal. These materials occur as suspended solids which are very finely divided in the product of a liquifaction pilot plant. The pyrites contain part of the total sulfur found in the coal. The rest is bound organically in the coal structure. Actual pilot plant process conditions are simulated in a continuous-flow high-pressure system which feeds the liquified coal at 500°F to a ferromagnetic matrix centered in the bore of a Bitter solenoid. Field values of up to 100 kOe have been used although lower fields would be dictated if conventional magnets are to be used commercially. Results indicate that the removal of ash and inorganic sulfur increase with magnetic field and decrease with flow rate. Typical results are shown in Fig. 1 where the percentage reduction in sulfur in the filtrate is plotted against H/v. H is the applied magnetic field in kOe and v is the flow velocity in cm/ min. This parameter is derived from the ratio of magnetic force to the viscous drag force of the carrier fluid. Data for use in pilot plant design have been collected.