Waste water treatment

Abstract

The present invention relates to a method for treating a waste water stream. Said waste water comprises hydrocarbons and oxygenates such as alcohols, aldehydes, ketones, carboxylic acids, and has a COD of up to 5 wt %. The invention relates to a distillation column for treating a waste water stream and a system for treating a waste water stream.

What is claimed is: 
     
         1 . A method for treating a waste water stream comprising hydrocarbons and oxygenates selected from the group consisting of alcohols, aldehydes, ketones, and combinations thereof and a COD of up to 5 wt %, said method comprising the following steps:
 providing continuously said waste water to a distillation column comprising one or more catalytic sections, wherein the one or more catalytic sections are provided with one or more acidic catalyst beds promoting acetalization of aldehydes and ketalization of ketones and etherification of alcohols;   operating said distillation column at a temperature allowing the simultaneous conversion and separation of oxygenates at a pressure ranging from vacuum conditions up to maximally (syngas pressure) 40 bar;   withdrawing from the distillation column a distillate product in vapor and/or liquid form and a bottom product; wherein the bottom product has a COD in the range of up to 1000 ppmwt.   
     
     
         2 . The method according to  claim 1 , wherein the bottom product has a COD of 100 ppmwt or less. 
     
     
         3 . The method according to  claim 1 , further comprising the step of withdrawing one or more liquid streams at one or more withdrawal locations from the column to perform phase splits and reinjection of separated phases into the distillation column. 
     
     
         4 . The method according to  claim 1 , further comprising: providing alcohol to the distillation column by:
 (i) adding said alcohol to the water stream; and/or   (ii) providing said alcohol to the catalytic sections (between catalyst beds); and/or   (iii) providing said alcohol under the catalytic bed.   
     
     
         5 . The method according  claim 4 , comprising one or more of the following steps of:
 withdrawing an alcohol-containing organic stream from an overhead condenser of the distillation column;   providing said alcohol-containing organic stream to a three phase gas/liquid/liquid separator to recover alcohol from said alcohol-containing organic stream; and   providing said recovered alcohol to the distillation column according to any one or more of steps (i)-(iii).   
     
     
         6 . The method according to  claim 4 , further comprising the steps of:
 reacting esters and other reaction products in the one or more liquid streams to alcohols and acids by adding water under catalytic hydrolysis conditions; and   subsequently recovering alcohols by distillation for recycle into the distillation column.   
     
     
         7 . The method according to  claim 4 , further comprising the steps of:
 providing the one or more liquid streams to a three phase gas/liquid/liquid separator downstream from an overhead condenser of the distillation column;   withdrawing an aqueous phase from the three phase gas/liquid/liquid separator; and   refluxing the aqueous phase to one or more locations within a rectification and stripping section of the distillation column.   
     
     
         8 . The method according to  claim 1 , wherein the acidic catalyst of the one or more catalytic beds is an acidic resin. 
     
     
         9 . The method according to  claim 1 , wherein the waste water stream comprises waste water obtained from a Fischer-Tropsch synthesis unit. 
     
     
         10 . The method according to  claim 1 , wherein
 said waste water is provided above the one or more catalytic sections;   said alcohol is provided to the distillation column in/or under the at least one catalytic section; and   the distillation column is operated at a temperature of at least 120° C.   
     
     
         11 . A distillation column for treating a waste water stream, comprising one or more catalytic sections, wherein the one or more catalytic sections are provided with one or more acidic catalyst beds promoting esterification of organic acids and alcohols, acetalization of aldehydes, ketalization of ketones, etherification of alcohols, and combinations thereof. 
     
     
         12 . The distillation column according to  claim 11 , wherein the catalyst is an acidic resin. 
     
     
         13 . The distillation column according to  claim 11 , wherein one or more of the catalytic sections are located above a stripping section applied for alcohol recovery and/or within a rectification section for distillate enrichment. 
     
     
         14 . The distillation column according to  claim 11 , wherein the column comprises one or more inlets for providing an alcohol containing liquid to the catalytic beds and/or underneath the catalytic section. 
     
     
         15 . The distillation column according to  claim 11 , wherein the one or more catalytic beds comprise structured elements and/or tray kind of devices providing (i) heat and mass transfer area/surface and (ii) holding gauze/mesh bags/boxes filled with catalyst particles. 
     
     
         16 . A system for treating a waste water stream comprising one or more distillation columns according to  claim 11 . 
     
     
         17 . The system according to  claim 16 , further comprising connected to the exit of the distillation column, (i) a one or two step condenser and reflux accumulator, including devices to perform three phase gas/liquid/liquid phase split, overhead system and (ii) a three phase gas/liquid/liquid phase split separator for column side draws. 
     
     
         18 . The system according to  claim 16 , comprising upstream of the one or more distillation columns means of removing hydrocarbons from the waste water stream. 
     
     
         19 . The method according to  claim 1 , wherein the COD is in a range of from 1.6 wt % to 2.0 wt %.