Patent ID: 11935665
Assignee: ELECTRICITE DE FRANCE
Field: Chemical engineering (Chemistry)
Classification: CPC G  B | IPC B  G

Claim 0:
1. A process for treating aqueous effluents comprising:
separating boric acid from aqueous effluents from a primary circuit of a nuclear power plant,
treating the aqueous effluents using a multi-stage assembly composed of multiple reverse osmosis modules, a general inlet, at least two general outlets, and multiple recycling lines,
wherein each of the multiple reverse osmosis modules comprises an inlet, an outlet, and a reverse osmosis membrane configured to let through a permeate which is less concentrated in the boric acid than an incoming liquid in the reverse osmosis membrane and to retain a retentate which is more concentrated in the boric acid than the incoming liquid, and wherein the multiple reverse osmosis modules are arranged in parallel and in series so as to define a one-way fluidic circuit from the general inlet to the at least two general outlets, and
wherein each of the multiple recycling lines fluidically connects the outlet of a first reverse osmosis module of the multiple reverse osmosis modules with:
the general inlet,
one of the at least two general outlets when the one-way fluidic circuit does not directly connect the outlet of the first reverse osmosis module to the one of the at least two general outlets, or
the inlet of a second reverse osmosis module of the multiple reverse osmosis modules when the one-way fluidic circuit does not directly connect the outlet of the first reverse osmosis module to the inlet of the second reverse osmosis module,

obtaining a boric acid fluid having a boric acid concentration between 6750 mgB/L and 8250 mgB/L at a first of the at least two general outlets in a boric acid enrichment zone of the multi-stage assembly, and
obtaining a purified fluid having a boric acid concentration comprised between 4.5 mgB/L and 5.5 mgB/L at a second of the at least two general outlets in a boric acid depletion zone of the multi-stage assembly,
wherein each of the boric acid enrichment zone and the boric acid depletion zone comprises one or more of the multiple reverse osmosis modules, and one or more stages in series, wherein each of the one or more stages consist of the one or more of the multiple reverse osmosis modules arranged in parallel,
the boric acid concentration in the boric acid enrichment zone is progressively increased so as to reach to a desired boric acid concentration,
the boric acid concentration in the boric acid depletion zone is progressively reduced so as to reach a required purified water concentration, and
the boric acid concentration is measured at selected points of the multi-stage assembly, and based on the result of the concentration measurements:
introducing a fraction of the boric acid fluid into an incoming fluid of the second reverse osmosis module through one of the multiple recycling lines,
introducing a fraction of the purified fluid into the incoming fluid of the second reverse osmosis module through one of the multiple recycling lines,
introducing into the boric acid fluid the retentate of the first reverse osmosis module through one of the multiple recycling lines, when the first reverse osmosis module is located in the boric acid enrichment zone, or
introducing into the purified fluid the permeate of the first reverse osmosis module through one of the recycling lines, when the first reverse osmosis module is located in the boric acid depletion zone.