On-line Surface Area Measurement of Concentrated Slurries using low field spin-lattice relaxation NMR

A method for the rapid on-line determination of surface area and solids content in flowing concentrated slurries using low field NMR spin-lattice relaxation measurements has been developed and demonstrated. The relationship between flow and spin-lattice relaxation time (T₁) of protons in water at 20 MHz was examined using aqueous copper sulfate solutions. The ability to measure surface area and solids concentration in both stagnant (stopped flow) and flowing systems via NMR was demonstrated using several different concentrated aqueous titania and glass slurries (20 to 80 weight percent) for which the dried powder surface area was previously determined via nitrogen adsorption/BET analysis and the solids content determined gravimetrically. Surface areas were also calculated from particle size analysis and found to vary by up to an order of magnitude from the adsorption and NMR results.