Patent GB-1113869-A (GB)
Title: Process for producing saturated sodium chloride brine
IPC: B01F1/00
Filed: 1965-10-13
Abstract: <PICT:1113869/C6-C7/1> In a continuous method of producing saturated sodium chloride brine for use in an electrolytic cell with a mercury cathode for the production of sodium hydroxide and chlorine, a source salt which is a particulate solid sodium chloride, containing calcium sulphate, e.g. mixed rock salt, is continuously introduced, e.g. at 10, into a first flowing unsaturated brine 12 in an amount greater than is required to saturate the flowing brine with sodium chloride; the flow of brine is maintained at such a rate as to entrain and carry along the source salt and all solids are extracted as a first slurry when the flowing brine reaches sodium chloride saturation but before any substantial amount of calcium sulphate goes into solution, e.g. at 16; the first slurry, 20, is introduced into a flowing solvent 22, (which is water or an unsaturated sodium chloride brine) and the flow of solvent is maintained at a rate to entrain and carry along the slurry so introduced; and all solids are extracted as a second slurry from the brine thus formed from the solvent and first slurry e.g. at 30, before any substantial amount of the calcium sulphate goes into solution.  The process is applied to the resaturation of a spent sodium chloride brine for recycling to the electrolytic cell.  The brine 12 obtained after extraction of the second slurry may be used as the first flowing unsaturated brine. The second slurry may be introduced into solvent (water or unsaturated brine) so as to entrain and carry along the second slurry and all solids may be extracted as a third slurry after at least some of the undissolved source sodium chloride has been leached from the second slurry but before any substantial amount of calcium sulphate has gone into solution.  The brine obtained after extraction of the second and third slurries may be used as the first flowing unsaturated brine, and mixed with the first slurry respectively.  In this embodiment fresh solvent (water or unsaturated brine) is introduced into the system and mixed with the third slurry, the insolubles and undissolved impurities, after a further separation, being passed to waste whilst the dilute brine is mixed with the second slurry.  In alternative embodiments (Figs. 4-6) the first flowing brine may be caused to flow in a plurality of parallel branches of a conduit system, the flow-rate being highest in the first branch and progressively lower in successive branches, source salt being introduced at a point in each branch and the slurry obtained after a separation in each branch being introduced into the branch which has the next lowest flow-rate, the flow-rate in each branch and the proportion of source salt added being such as to produce a saturated sodium chloride brine in each branch at a point of extraction of the slurry from said branch.ALSO:<FORM:1113869/C1/1> In a continuous method of producing saturated sodium chloride brine, a source salt which is a particulate solid sodium chloride, containing calcium sulphate e.g. mined rock salt, is continuously introduced, e.g. at 10, into a first flowing unsaturated brine 12 in an amount greater than is required to saturate the flowing brine with sodium chloride; the flow of brine is maintained at such a rate as to entrain and carry along the source salt and all solids are extracted as a first slurry when the flowing brine reaches sodium chloride saturation but before any substantial amount of calcium sulphate goes into solution, e.g. at 16; the first slurry, 20, is introduced into a flowing solvent 22 (which is water or an unsaturated sodium chloride brine) and the flow of solvent is maintained at a rate to entrain and carry along the slurry so introduced; and all solids are extracted as a second slurry from the brine thus formed from the solvent and first slurry, e.g. at 30, before any substantial amount of the calcium sulphate goes into solution.  The brine 12 obtained after extraction of the second slurry may be used as the first flowing unsaturated brine.  The second slurry may be introduced into solvent (water or unsaturated brine) so as to entrain and carry along the second slurry and all solids may be extracted as a third slurry after at least some of the undissolved source sodium chloride has been leached from the second slurry but before any substantial amount of calcium sulphate has gone into solution. The brine obtained after extraction of the second and third slurries may be used as the first flowing unsaturated brine and mixed with the first slurry respectively.  In this embodiment fresh solvent (water or unsaturated brine) is introduced into the system and mixed with the third slurry, the insolubles and undissolved impurities after a further separation being passed to waste whilst the dilute brine is mixed with the second slurry.  In alternative embodiments (Figs. 4-6, not shown) the first flowing unsaturated brine may be caused to flow in a plurality of parallel branches of a conduit system, the flow rate being highest in the first branch and progressively lower in successive branches, source salt being introduced at a point in each branch and the slurry obtained after a separation in each branch being introduced into the branch which has the next lowest flow rate, the flow rate in each branch and the proportion of source salt added being such as to produce a saturated sodium chloride brine in each branch at the point of extraction of the slurry from said branch.  A saturated sodium chloride brine containing under 2.0 grams per litre, of calcium sulphate may be obtained by the process.