Process for treating pulp mill condenstates using a hollow fiber contactor
First Claim
1. A method for removing off gas contaminants from an aqueous evaporation condensate pulp mill effluent stream, which aqueous evaporation condensate contains methanol and off gas contaminants selected from the group consisting of sulphur dioxide and total reduced sulphur (TRS) compounds comprising:
- providing a hollow fibre membrane contactor comprising a plurality of hollow fibres, each fibre having a hydrophobic membrane wall having first and second opposed sides;
flowing the aqueous evaporation condensate through said contactor, in contact with the first sides of the walls of the fibres; and
flowing an acceptor fluid through the contactor, in contact with the second sides of the walls of the fibres, allowing said off gas contaminants in said aqueous evaporation condensate to migrate through the membrane walls to said second sides of the walls of the fibres and extracting the undesirable compounds migrating through the membrane walls with said acceptor fluid, while leaving an aqueous methanol stream rich in the methanol of said condensate at said first sides of said walls;
said acceptor fluid being selected from a stripping gas or an aqueous alkaline solution.
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Accused Products
Abstract
A method and apparatus for the treatment of pulp mill condensates is described. A hollow fiber contactor, incorporating a hydrophobic membrane, was used to remove several undesirable compounds from pulp mill condensates. For example, TRS compounds and SO2 were efficiently stripped from kraft and sulphite mill evaporator condensates, respectively. Methanol was also removed from kraft mill condensates but at a lower efficiency than TRS. Furthermore, other undesirable compounds found in condensates of pulp mills that contribute to the BOD and COD loading to effluent treatment systems were also removed. These contactors are cost effective since air, vacuum or a suitable solvent or scrubbing solution can be used as the stripping medium to drive off through the membrane several undesirable compounds from the feed solution. The undesirable compounds removed can thus be burned in the recovery boiler, lime kiln or a dedicated boiler.
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Citations
11 Claims
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1. A method for removing off gas contaminants from an aqueous evaporation condensate pulp mill effluent stream, which aqueous evaporation condensate contains methanol and off gas contaminants selected from the group consisting of sulphur dioxide and total reduced sulphur (TRS) compounds comprising:
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providing a hollow fibre membrane contactor comprising a plurality of hollow fibres, each fibre having a hydrophobic membrane wall having first and second opposed sides; flowing the aqueous evaporation condensate through said contactor, in contact with the first sides of the walls of the fibres; and flowing an acceptor fluid through the contactor, in contact with the second sides of the walls of the fibres, allowing said off gas contaminants in said aqueous evaporation condensate to migrate through the membrane walls to said second sides of the walls of the fibres and extracting the undesirable compounds migrating through the membrane walls with said acceptor fluid, while leaving an aqueous methanol stream rich in the methanol of said condensate at said first sides of said walls;
said acceptor fluid being selected from a stripping gas or an aqueous alkaline solution. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification