Concentrating acrylamide solutions

Claim 2

A process of concentrating aqueous acrylamide solution by flash evaporation of water therefrom while inhibiting polymerization of acrylamide, comprising the steps of a. flash-evaporating water from aqueous acrylamide feed solution having more than 50 percent by weight water in the total feed, by constantly introducing said feed solution into an evaporation chamber in which pressure has been reduced to a selected pressure in the range from about 60 to about 450 mm Hg and with at least a portion of said feed entering said chamber at temperature higher than the boiling point of said feed at the defined reduced pressure in said chamber, and b. constantly removing from said chamber to atmospheric pressure the liquid residue from said flash-evaporation at a rate sufficient to avoid accumulation of acrylamide solution in said chamber, and c. during said flash-evaporation in said chamber constantly washing the surfaces that contact acrylamide in said evaporation chamber, and d. as soon as said liquid residue from evaporation is removed to atmospheric pressure, restoring absorbed oxygen to saturation in said residue and, e. recycling part of said residue with oxygen restored to saturation therein to said evaporation chamber with the temperature of said recycled liquid below its atmospheric boiling point but above the existing boiling point of said liquid inside said chamber at the reduced pressure therein.

Claim 3

A PROCESS OF CONCENTRATING AQUEOUS ACRYLAMIDE SOLUTION BY FLASH EVAPORATION OF WATER THEREFROM WHILE INHIBITING POLYMERIZATION OF ACRYLAMIDE, COMPRISING THE STEPS OF A. FLASH-EVAPORATING WATER FROM AQUEOUS ACRYLAMIDE FEED SOLUTION HAVING MORE THAN 50 PERCENT BY WEIGHT WATER IN THE TOTAL FEED, BY CONSTANTLY INTRODUCING SAID FEED SOLUTION INTO AN EVAPORATION CHAMBER IN WHICH PRESSURE HAS BEEN REDUCED TO A SELECTED PRESSURE IN THE RANGE FROM ABOUT 60 TO LAABOUT 450 MM HG AND WITH AT LEAST A PORTION OF SAID FEED ENTERING SAID CHAMBER AT TEMPERATURE HIGHER THAN THE BOILING POINT OF SAID FEED AT THE DEFINED REDUCED PRESSURE IN SAID CHAMBER, AND B. CONSTANTLY REMOVING FROM SAID CHAMBER TO ATMOSPHERIC PRESSURE THE LIQUID RESIDUE FROM SAID FLASH-EVAPORATION AT A RATE SUFFICIENT TO AVOID ACCUMULATION OF ACRYLAMIDE SOLUTION IN SAID CHAMBER, AND C. DURING SAID FLASH-EVAPORATION IN SAID CHAMBER CONSTANTLY WASHING THE SURFACES THAT CONTACT ACRYLAMIDE IN SAID EVAPORATION CHAMBER, AND D. AS SOON AS SAID LIQUID RESIDUE FROM EVAPORATION IS REMOVED TO ATMOSPHERIC PRESSURE, RESTORING ABSORBED OXYGEN TO SATURATION IN SAID RESIDUE AND, E. RECYCLING PART OF SAID RESIDUE WITH OXYGEN RESTORED TO SATURATION THEREIN TO SAID EVAPORATION CHAMBER WITH THE TEMPERATURE OF SAID RECYCLED LIQUID BELOW ITS ATMOSPHERIC BOILING POINT BUT ABOVE THE EXISTING BOILING POINT OF SAID LIQUID INSIDE SAID CHAMBER AT THE REDUCED PRESSURE THEREIN.

Claim 4

A PROCESS OF CONCENTRATING AQUEOUS ACRYLAMIDE SOLUTION BY FLASH EVAPORATION OF WATER THEREFROM WHILE INHIBITING POLYMERIZATION OF ACRYLAMIDE, COMPRISING THE STEPS OF A. FLASH-EVAPORATING WATER FROM AQUEOUS ACRYLAMIDE FEED SOLUTION HAVING MORE THAN 50 PERCENT BY WEIGHT WATER IN THE TOTAL FEED, BY CONSTANTLY INTRODUCING SAID FEED SOLUTION INTO AN EVAPORATION CHAMBER IN WHICH PRESSURE HAS BEEN REDUCED TO A SELECTED PRESSURE IN THE RANGE FROM ABOUT 60 TO LAABOUT 450 MM HG AND WITH AT LEAST A PORTION OF SAID FEED ENTERING SAID CHAMBER AT TEMPERATURE HIGHER THAN THE BOILING POINT OF SAID FEED AT THE DEFINED REDUCED PRESSURE IN SAID CHAMBER, AND B. CONSTANTLY REMOVING FROM SAID CHAMBER TO ATMOSPHERIC PRESSURE THE LIQUID RESIDUE FROM SAID FLASH-EVAPORATION AT A RATE SUFFICIENT TO AVOID ACCUMULATION OF ACRYLAMIDE SOLUTION IN SAID CHAMBER, AND C. DURING SAID FLASH-EVAPORATION IN SAID CHAMBER CONSTANTLY WASHING THE SURFACES THAT CONTACT ACRYLAMIDE IN SAID EVAPORATION CHAMBER, AND D. AS SOON AS SAID LIQUID RESIDUE FROM EVAPORATION IS REMOVED TO ATMOSPHERIC PRESSURE, RESTORING ABSORBED OXYGEN TO SATURATION IN SAID RESIDUE AND, E. RECYCLING PART OF SAID RESIDUE WITH OXYGEN RESTORED TO SATURATION THEREIN TO SAID EVAPORATION CHAMBER WITH THE TEMPERATURE OF SAID RECYCLED LIQUID BELOW ITS ATMOSPHERIC BOILING POINT BUT ABOVE THE EXISTING BOILING POINT OF SAID LIQUID INSIDE SAID CHAMBER AT THE REDUCED PRESSURE THEREIN.

Claim 5

A process defined by claim 1 wherein the selected pressure in said evaporation chamber is about 70 mm Hg.

Claim 6

A process defined by claim 1 wherein liquid residue is removed from the bottom of the evaporation chamber to atmospheric pressure by means of a vertical barometric arm.