Process for controlling microbial growth

Abstract

The invention relates to a process for controlling microbial growth in a production line for cellulosic products with the aid of gases. The invention also relates to the use of gases such as carbon dioxide, nitrogen, argon and/or non-naturally occurring mixtures thereof for controlling microbial growth. In the process an aqueous material containing water and suspended pulp fibers and/or additives therefor is treated with the gaseous inhibitor to significantly retard or inhibit the growth of microorganisms therein. An oxygen rich gas may be introduced in addition to the inhibitor of the invention.

1 . A process for controlling microbial growth in a production line for cellulosic products comprising 
 providing an aqueous material containing water and suspended pulp fibers and/or additives therefor,    maintaining said aqueous material under conditions susceptible to microbial growth,    providing a gaseous microbe inhibitor selected from carbon dioxide, nitrogen, noble gases and a non-natural mixtures containing the same,    introducing said gaseous microbe inhibitor to said aqueous material in an amount sufficient for said microbe inhibitor to significantly retard or inhibit the growth of micro-organisms therein.    
     
     
         2 . A process according to  claim 1 , wherein said aqueous material is maintained in a storage vessel and said gaseous microbe inhibitor is introduced prior to and/or during said storage.  
     
     
         3 . A process according to  claim 1  or  2 , wherein said gaseous microbe inhibitor consists essentially of carbon dioxide, nitrogen or one or more noble gases.  
     
     
         4 . A process according to  claim 1  or  2 , wherein said noble gas is selected from helium, neon, argon, krypton, xenon and radon.  
     
     
         5 . A process according to  claim 1  or  2 , wherein said gaseous microbe inhibitor is a mixture of carbon dioxide and nitrogen, preferably in a ratio of 10-90% carbon dioxide and 90-10% nitrogen.  
     
     
         6 . A process according to  claim 1  or  2 , wherein said gaseous microbe inhibitor additionally contains oxygen.  
     
     
         7 . A process according to  claim 5 , wherein said gaseous microbe inhibitor comprises a combination of carbon dioxide and oxygen, preferably in a ratio of 10-90% carbon dioxide and 90-10% oxygen.  
     
     
         8 . A process according to  claim 1 , wherein said gaseous microbe inhibitor comprises a combination of carbon dioxide, nitrogen, noble gases and oxygen containing at least 10% carbon dioxide.  
     
     
         9 . A process according to any one of  claims 1  to  8 , wherein said gaseous microbe inhibitor is introduced into a liquid flow of said material prior to said storage.  
     
     
         10 . A process according to any one of  claims 1  to  8 , wherein said gaseous microbe inhibitor is introduced into a storage tank containing said aqueous material.  
     
     
         11 . A process according to any one of  claims 1  to  8 , wherein said gaseous microbe inhibitor is introduced into a diluent for said material.  
     
     
         12 . A process according to any one of  claims 1  to  11 , wherein said microorganisms comprise bacteria, fungi and/or algae.  
     
     
         13 . A process according to  claim 1 , wherein said gaseous microbe inhibitor, consisting essentially of carbon dioxide, nitrogen, argon gases or mixtures thereof, is introduced into a liquid flow entering a storage tank for said aqueous material or into said storage tank itself.  
     
     
         14 . A process according to  claim 13 , wherein said introduction of gaseous microbe inhibitor is followed by and/or preceded by an introduction of an oxygen containing gas into said storage tank or into a liquid flow entering said storage tank.  
     
     
         15 . A process according to  claim 14 , wherein said introduction of gaseous microbe inhibitor and said introduction of an oxygen containing gas are repeated in an alternating manner during storage of said aqueous material.  
     
     
         16 . A process according to any one of  claims 1  to  15 , wherein said aqueous material is a pulp suspension located in a pulp storage tower, a stock chest, a broke tower or the like storage tank.  
     
     
         17 . A process according to any one of  claims 1  to  15 , wherein said aqueous material is stock in the stock preparation of a paper making system.  
     
     
         18 . A process according to any one of  claims 1  to  15 , wherein said aqueous material is white water in a papermachine, preferably white water in a white water tank of the long circulation.  
     
     
         19 . A process according to any one of  claims 1  to  15 , wherein said aqueous material is a slurry of an additive chemical such as starch, coating, pigment, filler, or the like.  
     
     
         20 . A process according to any one of  claims 1  to  19 , wherein said production line for cellulosic products comprises a line for the production of pulp, paper, board or the like.  
     
     
         21 . A process according to  claim 20 , wherein said production line comprises the reprocessing of recovered paper and/or broke.  
     
     
         22 . A process according to  claim 20  or  21 , wherein said production line has a substantially closed water system.  
     
     
         23 . A process according to any one of  claims 1  to  22 , wherein said aqueous material treated with said gaseous microbe inhibitor is processed into a cellulosic product such as pulp, paper, board or the like.  
     
     
         24 . Use of carbon dioxide, nitrogen or a noble gas alone or in a non-natural gas mixture as a gaseous microbe inhibitor for controlling microbial growth in an aqueous material containing water as well as suspended pulp fibers and/or additives therefor, which material is processed and/or stored in a production line for cellulosic products.  
     
     
         25 . The use according to  claim 24 , wherein said gaseous microbe inhibitor consists of essentially carbon dioxide.  
     
     
         26 . The use according to  claim 25 , wherein carbon dioxide and oxygen are used in combination or as alternating feeds to said material.  
     
     
         27 . The use according to any one of  claims 24  to  26  in the production of paper in a production line having a substantially closed water system and comprising the reprocessing of recovered paper.