Weak acid cation (WAC) resins are normally utilized for softening high TDS produced water. The main disadvantage of the WAC process is that the resins require regeneration with hydrochloric acid followed by sodium hydroxide. This is expensive and necessitates the utilization of exotic, corrosion resistant alloys for construction.

Strong acid cation (SAC) ion exchange processes employing only brine regeneration (i.e. no acid or caustic) are much simpler and less expensive, however the SAC process is normally restricted to low TDS (<3000 mg/L) waters. A new ion exchange softening flow-sheet that uses brine regeneration has been developed based upon the Recoflo short-bed ion exchange process. Recoflo makes it possible to use extremely high service flow rates through very short (15 cm) resin beds, while achieving low hardness leakages. The key to applying this to high TDS produced water is the use of high purity brine regenerant. A novel ion exchange process which employs only water for regeneration (i.e. no chemicals) has been developed for purifying the brine. This paper explains the rationale for the process using ion exchange equilibrium calculations and then shows pilot plant and field data.

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