Process and System for Controlling Temperature of a Circulating Foamed Fluid

Abstract

A method and system are disclosed for actively cooling a fluid, particularly a foamed fluid. The foamed fluid may comprise a foamed suspension of fibers that is used to form a web. The foamed suspension of fibers is fed around a recirculation loop and actively cooled using a heat exchanger.

1 - 21 . (canceled) 
     
     
         22 . A system for controlling a temperature of a foamed suspension of fibers for forming a web, the system comprising:
 a mixing tank for holding a foamed suspension of fibers, the foamed suspension of fibers comprising a mixture of a fiber furnish, a surfactant, and water;   a recirculation loop that circulates at least a portion of the foamed suspension of fibers from the mixing tank and back to the mixing tank, the recirculation loop maintaining the fibers in a foamed suspension; and   a heat exchanger positioned along the recirculation loop, the heat exchanger being configured to adjust a temperature of the at least a portion of the foamed suspension of fibers.   
     
     
         23 . A system as defined in  claim 22 , further comprising a web forming surface configured to receive the at least a portion of the foamed suspension of fibers from the mixing tank. 
     
     
         24 . A system as defined in  claim 22 , wherein the heat exchanger is in fluid communication with a cooling fluid supply for receiving a cooling fluid, and
 wherein the heat exchanger defines a first pathway and a second pathway, the at least a portion of the foamed suspension of fibers flow through the heat exchanger along the first pathway while the cooling fluid flows through the heat exchanger along the second pathway for cooling the at least a portion of the foamed suspension of fibers.   
     
     
         25 . A system as defined in  claim 24 , wherein the first pathway and the second pathway flow in a same direction or an opposite direction. 
     
     
         26 . A system as defined in  claim 24 , wherein the heat exchanger comprises a shell and tube heat exchanger, the first pathway being defined by at least one tube of the shell and tube heat exchanger, the second pathway being defined by a shell of the shell and tube heat exchanger, the shell at least partially surrounding the at least one tube. 
     
     
         27 . A system as defined in  claim 22 , further comprising:
 a temperature sensing device configured to generate temperature information indicative of the temperature of the at least a portion of the foamed suspension of fibers, and   a controller configured to receive the temperature information and to control the heat exchanger based on the temperature information generated by the temperature sensing device.   
     
     
         28 . A system as defined in  claim 26 , wherein the at least one tube has an outside diameter of from about 0.2 inches to about 0.8 inches. 
     
     
         29 . A system as defined in  claim 27 , wherein the controller is configured to control the heat exchanger to maintain the temperature of the at least a portion of the foamed suspension of fibers below 40° C. 
     
     
         30 . A process for controlling a temperature of a foamed suspension of fibers for forming a web comprising:
 holding a foamed suspension of fibers in a mixing tank, the foamed suspension of fibers comprising a mixture of a fiber furnish, a surfactant, and water;   flowing at least a portion of the foamed suspension of fibers through a recirculation loop that circulates the foamed suspension of fibers from the mixing tank and back to the mixing tank, the recirculation loop maintaining the fibers in a foamed suspension; and   actively cooling the at least the portion of foamed suspension of fibers flowing through the recirculation loop to maintain a temperature of the foamed suspension of fibers being below a preset temperature.   
     
     
         31 . A process as defined in  claim 30 , further comprising ejecting an amount the foamed suspension of fibers from the mixing tank onto a forming surface for producing a web. 
     
     
         32 . A process as defined in  claim 30 , wherein actively cooling the at least the portion of foamed suspension of fibers comprises actively cooling the at least the portion of foamed suspension of fibers by flowing the at least the portion of the foamed suspension of fibers through a heat exchanger, the heat exchanger being positioned along the recirculation loop. 
     
     
         33 . A process as defined in  claim 32 , wherein flowing the at least the portion of the foamed suspension of fibers through the heat exchanger includes flowing the at least the portion of the foamed suspension of fibers through at least one tube of the heat exchanger, the at least one tube being at least partially positioned inside of a shell, a cooling fluid flowing within the shell over the at least one tube. 
     
     
         34 . A process as defined in  claim 31 , further comprising flowing a water from a water supply and a surfactant from a surfactant supply into the mixing tank in conjunction with a fiber furnish as the at least a portion of the foamed suspension of fibers is deposited onto the forming surface in order to maintain a volume of the foamed suspension of fibers within the mixing tank during the process. 
     
     
         35 . A process as defined in  claim 33 , wherein the at least the portion of the foamed suspension of fibers and the cooling fluid flow in a same direction or an opposite direction. 
     
     
         36 . A process as defined in  claim 30 , wherein the preset temperature is less than about 55° C. 
     
     
         37 . A process as defined in  claim 30 , wherein the fiber furnish comprises cellulose fibers, synthetic fibers, or mixtures thereof. 
     
     
         38 . A process as defined in  claim 30 , wherein the surfactant comprises an alkyl polyglycoside, a sodium dodecyl sulfate, an ammonium lauryl sulfate, a fatty acid amine, an amine oxide, a fatty acid quaternary compound, an alkyl polyglycoside, or a lauryl sulfate. 
     
     
         39 . A process as defined in  claim 30 , wherein the fiber furnish contains synthetic polymer fibers combined with pulp fibers. 
     
     
         40 . A process as defined in  claim 30 , wherein the at least the portion of foamed suspension of fibers contains greater than about 20% air. 
     
     
         41 . A process as defined in  claim 30 , wherein actively cooling the at least the portion of foamed suspension of fibers comprises actively cooling the at least the portion of foamed suspension of fibers after the temperature achieves a cooling initiation temperature, the cooling initiation temperature being greater than about 30° C. 
     
     
         42 . A process as defined in  claim 30 , wherein actively cooling the at least the portion of foamed suspension of fibers comprises actively cooling the at least the portion of foamed suspension of fibers to cool the temperature of the at least the portion of foamed suspension of fibers flowing through the recirculation loop by at least 3° C.