Enhanced control of a microwave heating system

Abstract

A method for controlling a microwave heating system is provided. The method may be used with a system having a liquid-filled microwave heating chamber and includes measuring the value of one or more microwave system parameters. Suitable parameters can include, for example, net microwave power discharged, the temperature of the liquid in the microwave chamber, the flow rate of liquid through the microwave chamber, and the speed of the conveyance system disposed within the microwave chamber. The measured value of the selected parameter is then compared to a target value for that parameter in order to determine a difference. Based on the difference, one or more actions can be taken in order to start, stop, or alter the operation of the microwave heating system.

1 . A continuous process for heating a plurality of articles in a microwave heating system, said process comprising:
 (a) passing said articles through a microwave chamber;   (b) introducing microwave energy into said microwave chamber via at least one microwave launcher;   (c) heating said articles in said microwave chamber using at least a portion of said microwave energy to provide heated articles, wherein said articles are submerged in a liquid medium during said heating; and   (d) subsequent to said heating, cooling said heated articles in a quench zone to provide cooled articles,   wherein said heating is sufficient to increase the minimum temperature of said articles to at least 80° C. in not more than 5 minutes and wherein said cooling is sufficient to reduce the temperature of said heated articles by at least 30° C. in not more than 6 minutes.   
     
     
         2 . The process of  claim 1 , wherein at least a portion of said heating of step (c) is carried out at a heating rate of at least 15° C. per minute (° C./min) and not more than 75° C./min. 
     
     
         3 . The process of  claim 1 , wherein said heating of step (c) is sufficient to increase the minimum temperature of said articles to at least 120° C. in not more than 5 minutes. 
     
     
         4 . The process of  claim 1 , wherein said heating of step (c) includes increasing the temperature of said articles by at least 30° C. and not more than 100° C. 
     
     
         5 . The process of  claim 1 , wherein the cooled articles have a temperature of not more than 50° C. 
     
     
         6 . The process of  claim 1 , wherein said cooling of step (d) includes reducing the temperature of said articles by at least 30° C. and not more than 100° C. 
     
     
         7 . The process of  claim 1 , wherein said microwave chamber comprises at least two individual microwave heating zones, and wherein each of said articles has an average residence time in each of said individual microwave heating zones of at least 2 seconds and not more than 1 minute. 
     
     
         8 . The process of  claim 1 , further comprising prior to said passing of step (a), thermalizing said articles in an upstream thermalization zone to provide thermalized articles and wherein said thermalized articles exiting said thermalization zone have a substantially uniform temperature. 
     
     
         9 . The process of  claim 8 , wherein said thermalization zone is at least partially filled with said liquid medium. 
     
     
         10 . The process of  claim 8 , wherein said substantially uniform temperature of said thermalized articles exiting said thermalization zone is in the range of from 20° C. to 70° C. 
     
     
         11 . The process of  claim 1 , wherein said liquid medium comprises water. 
     
     
         12 . The process of  claim 1 , wherein said heating of step (c) is performed at a pressure of at least 10 psig. 
     
     
         13 . The process of  claim 1 , wherein said introducing of step (b) includes introducing said microwave energy into said microwave chamber via at least one pair of opposed launchers disposed on generally opposite sides of said microwave chamber. 
     
     
         14 . The process of  claim 13 , wherein said pair of opposed launchers comprises a pair of oppositely facing launchers. 
     
     
         15 . The process of  claim 1 , wherein at least a portion of said microwave energy introduced into said microwave chamber is discharged at a launch tilt angle of at least 2°. 
     
     
         16 . The process of  claim 1 , wherein said articles comprise packages containing foodstuffs, medical fluids, or medical instruments. 
     
     
         17 . The process of  claim 1 , wherein said microwave heating system has an overall production rate of at least 10 packages per minute per convey line. 
     
     
         18 . A continuous process for heating a plurality of articles in a microwave heating system, said process comprising:
 (a) introducing microwave energy into a microwave heating chamber via at least two pairs of opposed microwave launchers, wherein said microwave heating chamber is at least partially filled with a liquid medium;   (b) transporting said articles through said microwave heating chamber using a convey system, wherein said transporting includes passing said articles through at least two individual microwave heating zones each defined between one of said pairs of opposed microwave launchers, wherein the residence time of said articles in each of said individual microwave heating zones is at least 2 seconds and not more than 1 minute;   (c) during said transporting, heating said articles using at least a portion of said microwave energy to provide heated articles, wherein said articles are submerged in said liquid medium during said heating, and wherein said heating is sufficient to increase the minimum temperature of said articles to at least 80° C.; and   (d) subsequent to said heating, cooling said heated articles in a quench zone to provide cooled articles, wherein said cooling is sufficient to reduce the temperature of said heated articles to not more than 50° C. in not more than 10 minutes.   
     
     
         19 . The process of  claim 18 , wherein said heating of step (c) is carried out for a time period of not more than 5 minutes. 
     
     
         20 . The process of  claim 19 , wherein said heating of step (c) is sufficient to increase the minimum temperature of said articles to at least 120° C. 
     
     
         21 . The process of  claim 18 , wherein said heating of step (c) is performed at a rate of at least 15° C./min and not more than 75° C./min. 
     
     
         22 . The process of  claim 18 , further comprising prior to said transporting of step (b), passing said articles through a thermalization zone to provide thermalized articles, wherein said thermalization zone is at least partially filled with said liquid medium, and wherein said articles exiting said thermalization zone have a substantially uniform temperature. 
     
     
         23 . The process of  claim 18 , wherein said cooling of step (d) is carried out for a time period of not more than 6 minutes. 
     
     
         24 . The process of  claim 18 , wherein said cooling of step (d) is sufficient to reduce the temperature of said heated articles by at least 30° C. 
     
     
         25 . The process of  claim 18 , wherein said liquid medium comprises water. 
     
     
         26 . The process of  claim 18 , wherein said heating of step (c) is performed at a pressure of at least 10 psig. 
     
     
         27 . The process of  claim 18 , wherein at least a portion of said microwave energy introduced into said microwave heating chamber is discharged at a launch tilt angle of at least 2°. 
     
     
         28 . The process of  claim 18 , wherein said articles comprise packages containing foodstuffs, medical fluids, or medical instruments. 
     
     
         29 . The process of  claim 18 , wherein said microwave heating system has an overall production rate of at least 10 packages per minute per convey line.