Method and apparatus for reduction of contaminants in evaporator distillate

A method for producing high purity distillate from a produced water stream in hydrocarbon production operations, comprising:

• (a) feeding a produced water stream to an evaporator;
• (b) heating the produced water in said evaporator to produce a contaminated steam stream having (i) volatile silica and (ii) entrained water droplets therein, said entrained water droplets comprising solutes therein;
• (c) cleaning said contaminated steam stream to produce a high purity water vapor stream, by
• (1) passing said contaminated steam stream through an upflow chevron mist eliminator to remove ninety five percent (95%) or more of said entrained water droplets and producing an intermediate purity water vapor stream,
• (2) scrubbing said intermediate purity water vapor stream by passage through a continuous spray system, said continuous spray system comprising emission of fine droplets of dilute caustic solution into said intermediate purity water vapor stream, said fine droplets of dilute caustic solution configured for mass transfer contact with said intermediate purity water vapor stream to remove volatile silica from said intermediate purity water vapor stream, to produce a partially decontaminated steam stream having residual entrained mist particles therein,
• (3) removing said residual entrained mist particles from said intermediate purity water vapor stream by passing said partially decontaminated steam stream through an upflow mesh pad mist eliminator to produce a high purity water vapor stream;
• (d) condensing said high purity water vapor stream to produce said high purity distillate.

An apparatus for producing high purity water vapor stream from a produced water stream resulting from hydrocarbon production operations, said produced water stream comprising water, silica compounds, and volatile organics, said apparatus comprising:

• (a) a vertical tube, falling film evaporator system for evaporating said produced water stream and generating therefrom a contaminated steam stream having therein (i) entrained water droplets having solutes therein, volatile silica compounds, and volatile organic compounds, said vertical tube, falling film evaporator system comprising an evaporator body having a vertical condenser with an outer wall and a sump with an inner wall;
• (b) a caustic mixing system, said caustic mixing system configured to mix concentrated caustic with water to provide a dilute caustic solution;
• (c) a contaminant reduction system, said contaminant reduction system located in an annular space between said outer wall of said condenser and said inner wall of said sump, said multi-pass mist eliminator system comprising
• (1) an upflow first mist eliminator portion, said upflow first mist eliminator portion configured for removing said entrained water droplets to produce an intermediate purity water vapor stream,
• (2) a continuous spray system, said continuous spray system located above said upflow first mist eliminator portion, said continuous spray system configured to continuously provide droplets of said dilute caustic solution in a selected spray configuration for mass transfer contact with said intermediate purity water vapor stream to remove said volatile silica compounds and said volatile organic compounds therefrom, and to produce a partially decontaminated steam stream having residual mist particles therein,
• (3) an upflow second mist eliminator portion, said upflow second mist eliminator portion located vertically above said continuous spray system, said upflow second mist eliminator portion sized and shaped to remove said entrained mist particles from said partially decontaminated steam stream, to produce said high purity water vapor stream.