Caustic solution evaporation plant

Abstract

The invention relates to a caustic solution evaporation plant comprising a caustic solution feeding line, a first stage evaporator (EV-1101) receiving low concentrated caustic solution and operating at a reduced pressure of less than or equal to 0.15 bar, a second stage evaporator (EV-1201) receiving enriched caustic solution from the first evaporator (EV-1101) and operating at a reduced pressure of less than or equal to 0.5 bar, a third stage evaporator (EV-1301) receiving further enriched caustic solution from the second stage evaporator (EV-1201) and operating at a pressure of greater than or equal to 1.1 bar, a fourth stage evaporator (EV-1401) receiving further enriched caustic solution from the third evaporator (EV-1301) and operating under a pressure greater than 4.0 bar characterized in that the first stage evaporator (EV-1101) being heated by the vapours generated from the second stage evaporator (EV-1201), the second stage evaporator (EV-1201) being heated by the vapours generated from the third stage evaporator (EV-1301), the third stage evaporator (EV-1301) being heated by the vapours generated by the fourth stage evaporator (EV-1401), and the fourth stage evaporator (EV-1401) being heated by thermal oil, the thermal oil being circulated by a pump (P-6301) through an electric heater (H-6101) in a closed loop, a vapour condensate tank (T-7101) collecting vapour condensate from the first (EV-1101) second (EV-1201), and third stage evaporator (EV-1301), a water cooled surface condenser (C-7101) condensing vapour generated in the first stage evaporator (EV-1101), a pump (P7101) draining the vapour condensate tank (T-7101), and a product caustic solution exit line.

Dependencies are inferred from the claim text.