GB1036559A - Production of sodium hydroxide - Google Patents

Abstract

Sodium hydroxide is produced from sea water using a resin-transferring ion exchange apparatus comprising a liquid-passing vessel, a regenerating vessel and a water-washing vessel. Sea water is fed into the liquid-passing vessel charged with ion exchange resin in the OH-form to give sodium hydroxide solution and ion exchange resin converted to the Cl-form. This resin is transferred to the regenerating vessel and contacted in countercurrent with a slurry of calcium hydroxide, the treated liquid being removed from the top of the regenerating vessel. The resin regenerated to the OH-form is passed to the water-washing vessel, washed with water and recycled to the liquid-passing vessel. The regenerating vessel may be provided with a stirrer revolving around a shaft suspended from the top of the vessel; alternatively, the regenerating vessel may be of the movable bed type with an inlet and an outlet for liquid at its lower portion and a resin reservoir connected through a check valve to its upper portion, the resin in the Cl-form being passed into the vessel through the upper portion, the slurry of calcium hydroxide being fed into the centre portion, water being fed through the lower portion, and treated liquid being withdrawn from the top of the vessel, the resin thus being regenerated by counter-current contact with the slurry. The resin in the Cl-form is preferably passed into the vessel intermittently at times when no water is being fed to the vessel. By reacting the sodium hydroxide produced above with sea water, the latter may be purified by removal of the magnesium ions as magnesium hydroxide, the calcium ions being removed as calcium carbonate, for example by treating the sea water with carbon dioxide or sodium carbonate, and the sulphate ions being removed, for example, by means of a weakly basic anion exchange resin in the Cl-form as described in Specification 1,036,560.ALSO:A resin-transferring ion exchange apparatus comprising a liquid-passing vessel, a regenerating vessel and a water-washing vessel is used in a process for producing sodium hydroxide from sea water. Sea water is fed into the liquid-passing vessel charged with ion exchange resin in the OH-form to give sodium hydroxide solution and ion exchange resin converted to the C1-form. This resin is transferred to the regenerating vessel and contacted in countercurrent with a slurry of calcium hydroxide the treated liquid being removed from the top of the regenerating vessel. The resin regenerated to the OH-form is passed to the waterwashing vessel, washed with water and recycled to the liquid-passing vessel. The regenerating vessel may be provided with a stirrer revolving around a shaft suspended from the top of the vessel; alternatively, the regenerating vessel may be of the movable bed type with an inlet and an outlet for liquid at its lower portion and a resin reservoir connected through a check valve to its upper portion, the resin in the C1-form being passed into the vessel through the upper portion, the slurry of calcium hydroxide being fed into the centre portion, water being fed through the lower portion, and treated liquid being withdrawn from the top of the vessel, the resin thus being regenerated by countercurrent contact with the slurry. The resin in the C1-form is preferably passed into the vessel intermittently at times when no water is being fed to the vessel.