Methods of Making Purified Water from the Fischer-Tropsch Process

Abstract

The Fischer-Tropsch (FT) process creates significant amounts of water. This FT produced water contains significant amounts of organic impurities. The invention provides methods of treating FT produced water. Surprisingly, it was discovered that the FT produced water could be successfully treated in a membrane bioreactor (MBR) according to relatively simple and more efficient steps; for example, by adjusting the pH of the water in the range of 4.2 to 5.8 or treating the FT produced water in a stripper where the distillate product stream and a reflux stream returning to the stripper have the same composition. In a related aspect, water compositions are described.

1 - 26 . (canceled) 
     
     
         27 . A method of purifying water created via Fischer-Tropsch synthesis, comprising:
 providing a first volume of FT produced water having a COD of at least 4000;   passing the FT produced water into a stripper where the water is contacted with a vapor or gas that removes an organic fraction into an overhead stream ( 118 ) which is cooled to condense an overhead liquid stream; and   b) separating the overhead liquid stream into a distillate product stream ( 124 ) and a reflux stream ( 125 ) and the distillate product stream and the reflux stream have the same composition;   or condensing the effluent from the top of the stripper in a condenser ( 118 ) to form a liquid wherein the liquid phase condensed in the condenser is a single phase; and passing the bottoms liquid fraction ( 126 ) to further processing.   
     
     
         28 . The method of  claim 27  wherein the distillate product stream and the reflux stream have the same composition. 
     
     
         29 . The method of  claim 27 , wherein the products from the stripper are limited to a distillate product stream, a bottoms liquid fraction and, optionally, a vapor overhead fraction. 
     
     
         30 . The method of  claim 27  wherein the recovery of alcohols in the distillate product stream is greater than 90% (or greater than 95%) of the alcohols in the feed stream ( 112 ). 
     
     
         31 . The method of  claim 27  wherein the alcohol content in the bottoms liquid fractions is less than 100 ppm (or less than 50 ppm). 
     
     
         32 . The method of  claim 27  wherein the stripping is accomplished by the addition of live steam ( 116 ). 
     
     
         33 . The method of  claim 27  wherein the bottoms liquid in the stripper is indirectly heated with a reboiler. 
     
     
         34 . The method of  claim 27  comprising passing at least a portion of the bottoms liquid fraction ( 126 ) from the stripper to an MBR wherein microorganisms consume organics in the water, and removing a second volume of purified water from the MBR; wherein the second volume is at least 90% of the first volume and wherein the purified water has a COD of 50 mg/L or less, preferably 1 to 15 mg/L, or 5-15 mg/L. 
     
     
         35 . The method of  claim 34  wherein the process steps consist essentially of providing a first volume of FT produced water having a COD of at least 4000;
 passing the FT produced water into a stripper where the water is contacted with a vapor or gas that removes an organic fraction into an overhead stream ( 118 ) which is cooled to condense an overhead liquid stream; and 
 b) separating the overhead liquid stream into a distillate product stream ( 124 ) and a reflux stream ( 125 ) and the distillate product stream and the reflux stream have the same composition; 
 or condensing the effluent from the top of the stripper in a condenser ( 118 ) to form a liquid wherein the liquid phase condensed in the condenser is a single phase; and
 passing at least a portion of the bottoms liquid fraction ( 126 ) from the stripper to an MBR wherein microorganisms consume organics in the water, and removing a second volume of purified water from the MBR; wherein the second volume is at least 90% of the first volume and wherein the purified water has a COD of 50 mg/L or less, preferably 1 to 15 mg/L, or 5-15 mg/L. 
 
 
     
     
         36 . The method of  claim 27  where the FT produced water is made in a process comprising:
 passing syngas into a fixed bed, Co catalyst-containing FT reactor at a contact time in the range of 50-2,000 ms, preferably 100-500 ms, and a temperature in the range of 170-230 C (or 180-220 C; or 190-210 C). 
 
     
     
         37 . The method of  claim 36  where the fixed bed is operated isothermally, within a 5 C (or 2 C) temperature differential. 
     
     
         38 . The method of  claim 27  wherein the pH of the bottoms liquid fraction is adjusted to a pH in the range of 4.5 to 5.5 prior to addition to the MBR. 
     
     
         39 . The method of  claim 38  where pH is adjusted by addition of NaOH or KOH. 
     
     
         40 . The method of  claim 27  wherein a nutrient mix comprising: N, Mo, Cu, Co, Ni, Mn, Zn, Fe, P, Mg, K, S, and Ca is added to the MBR. 
     
     
         41 . The method of  claim 27  wherein purified water is removed from the MBR in a pH range of 6.5 to 8.0 
     
     
         42 . The method of  claim 27  wherein the first volume of FT produced water comprises one or any combination of the following characteristics: an alcohol to acid molar ratio of at least 15:1, or at least 25:1, or in the range of 15:1 to 200:1, or 25 to 250, or 25 to 200; or 25 to 100; or 30 to 70; and/or where the combined mass of methanol and ethanol comprises at least 70%, or at least 80%, or in the range of 70 or 75 to about 90% of the total mass of C1 to C10 mono-hydroxy alcohols; or where the combined mass of methanol and ethanol comprises at least 50%, or at least 60%, or in the range of 60 or 65 to about 85% or 90% of the total mass of the following: acetone, methyl ethyl ketone, diethyl ketone, benzene, toluene, xylenes, styrene, acetaldehyde, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexonoic acid, methanol, ethanol, propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, and n-decanol; or where the combined mass of methanol, ethanol and propanol comprises at least 55%, or at least 65%, or in the range of 70 or 75 to about 85% or about 90% of the total mass of the following: acetone, methyl ethyl ketone, diethyl ketone, benzene, toluene, xylenes, styrene, acetaldehyde, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexonoic acid, methanol, ethanol, propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, and n-decanol.