Method and a system for converting liquid products into free-flowing powders with pre-cooling

Abstract

The present invention relates to a method and a system for converting liquid products for the cheese making or casein producing industry into substantially free-flowing powdery products, by subjecting the liquid product to heating to a temperature above the crystallisation temperature of any component in the liquid product in a heat exchanger, flash separating volatile components from said heated liquid product to obtain a past concentrate, pre-cooling a fraction of said past concentrate, and drying said combination product. By the pre-cooling it is possible to create lactose crystals by an extremely rapid in-line pre-cooling without any significant increase in viscosity (which would lead to an un-pumpable paste). It is assumed that only a fraction of the paste gets into contact with the walls of the cooler causing a rapid formation of a high number of seed crystals. Further, it is assumed that the seed promote the formation of lactose crystals during the subsequent drying process.

1 . A method for converting a liquid product into substantially free-flowing powder,  
       said method comprising the steps of 
 heating the liquid product to a temperature above the crystallisation temperature of any component in the liquid product in a heat exchanger,  
 flash separating volatile components from said heated liquid product to obtain a paste concentrate,  
 pre-cooling a fraction of said paste concentrate, and  
 drying said combination product.  
 
     
     
         2 . The method according to  claim 1 , wherein the pre-cooling step is conducted by passing the paste concentrate through a cooled vessel having a vessel wall, whereby at most 50% of the paste concentrate is in contact with the vessel wall during passing.  
     
     
         3 . The method according to  claim 1  or  2 , wherein at most 50% of the paste concentrate is crystallised when entering the dryer.  
     
     
         4 . The method according to any one of the preceding claims  claim 1 , wherein the drying step is performed in a spray/fluid bed dryer to obtain a free-flowing powder.  
     
     
         5 . The method according to  claim 1 , wherein the liquid product is selected from acid whey, sweet whey, salt or demineralised whey, lactose, mother liquor from production of lactose and permeate from production of protein from milk or whey.  
     
     
         6 . The method according to  claim 1 , wherein the heat exchanger is a plate heat exchanger  
     
     
         7 . The method according to  claim 1 , wherein the liquid product comprises at least 50% of solid, preferably at least 60%, more preferably at least 70% of solid.  
     
     
         8 . The method according to  claim 1 , wherein the product temperature during the flash separation is in the range of 65-98° C., more preferably in the range of 70-96° C., even more preferably in the range of 80-96° C.  
     
     
         9 . The method according to  claim 1 , wherein at least 75% of the paste concentrate obtained is mixed with liquid product and recycled to the heat exchanger to be reheated and subjected to the flash separating step.  
     
     
         10 . The method according to  claim 1 , wherein at most 25% of said paste concentrate is pre-cooled.  
     
     
         11 . A system for concentrating a liquid product comprising means ( 2 ) for feeding a heat exchanger, a heat exchanger ( 3 ) and a separator vessel ( 5 ), a cooled vessel ( 18 ) and a pump ( 9 ), and a dryer, connected by suitable conduits.  
     
     
         12 . The system according to  claim 11 , wherein the heat exchanger ( 3 ) is a plate heat exchanger.  
     
     
         13 . The system according to  claim 11  wherein the separator vessel ( 5 ) is a flash separator.  
     
     
         14 . The system according to  claim 11 , further comprising a secondary conduit ( 7 ) extending in a closed loop connection from the separator vessel ( 5 ) to the heat exchanger ( 3 ).