Controller and method for administering and providing on-line correction of a batch sterilization process

Abstract

The present invention comprises a batch sterilization system, a controller for use in the batch sterilization system, and a method performed by the controller. The system, controller, and method are used to administer and provide on-line correction of a batch sterilization process performed on a batch of containers. The controller compiles an actual retort time-temperature profile during the batch sterilization process from the actual retort temperatures sensed by a sensor. While this is occurring, the controller controls a batch sterilizer so as to administer an initial portion of the batch sterilization process before a temperature deviation has begun according to a scheduled time-temperature profile. This temperature deviation is between the actual retort time-temperature profile and the scheduled processing time-temperature profile. In response to the temperature deviation, the controller defines a re-scheduled remaining time-temperature profile for a remaining portion of the batch sterilization process that begins when the temperature deviation clears. This is done by simulating the batch sterilization process based on the actual retort time-temperature profile. During the temperature deviation, the controller controls the batch sterilizer so as to administer corrections to clear the temperature deviation between the actual retort and re-scheduled remaining time-temperature profiles. When the temperature deviation has finally cleared, the controller controls the batch sterilizer so as to administer the remaining portion of the batch sterilization process according to the re-scheduled remaining time-temperature profile.

What is claimed is:  
     
         1 . A batch sterilization system comprising: 
 a batch sterilizer to perform a batch sterilization process on a batch of containers;    a sensor to sense actual retort temperatures in the batch sterilizer during the batch sterilization process; and    a controller to: 
 compile an actual retort time-temperature profile during the batch sterilization process from the actual retort temperatures sensed by the sensor;  
 until a temperature deviation between the actual retort time-temperature profile and a scheduled time-temperature profile has begun, control the batch sterilizer so as to administer an initial portion of the batch sterilization process before the temperature deviation has begun according to the scheduled time-temperature profile;  
 in response to the temperature deviation, define a re-scheduled remaining time-temperature profile for a remaining portion of the batch sterilization process that begins when the temperature deviation has cleared by simulating the batch sterilization process based on the actual retort time-temperature profile;  
 during the temperature deviation, control the batch sterilizer so as to administer corrections to clear the temperature deviation between the actual retort and re-scheduled remaining processing time-temperature profiles;  
 when the temperature deviation has cleared, administer the remaining portion of the batch sterilization process according to the re-scheduled remaining time-temperature profile.  
   
     
     
         2 . The batch sterilization system of  claim 1  wherein the temperature deviation occurs during a processing phase of the batch sterilization process.  
     
     
         3 . The batch sterilization system of  claim 1  wherein the temperature deviation occurs during a come-up phase of the batch sterilization process.  
     
     
         4 . The batch sterilization system of  claim 2  wherein the controller defines the re-scheduled remaining time-temperature profile by: 
 computing a total lethality predicted to be delivered to the product cold spot over the batch sterilization process that (a) is based on the product cold spot time-temperature profile, and (b) satisfies a target lethality to be delivered to the product cold spot;  
 simulating the product cold spot time-temperature profile based on the actual retort temperature profile and the re-scheduled remaining time-temperature profile.  
 
     
     
         5 . The batch sterilization system of  claim 3  wherein the controller uses a finite difference simulation model to simulate the product cold spot time-temperature profile.  
     
     
         6 . The batch sterilization system of  claim 3  wherein the total lethality is the sum of (a) a lethality actually delivered over a first time interval from when the batch sterilization process begins to when the temperature deviation clears, and (b) a lethality predicted to be delivered over a second time interval from when the temperature deviation clears to when the batch sterilization process is predicted to end.  
     
     
         7 . The batch sterilization system of  claim 6  wherein: 
 the lethality actually delivered over the first time interval is based on the portion of the product cold spot time-temperature profile over the first time interval;  
 the portion of the product cold spot time-temperature profile over the first time interval is based on the portion of the actual retort temperature profile over a time interval from when the temperature deviation begins to when the temperature deviation clears.  
 
     
     
         8 . The batch sterilization system of  claim 6  wherein: 
 the heating lethality actually delivered over the first time interval is based on a portion of the product cold spot time-temperature profile over the first time interval;  
 the portion of the product cold spot time-temperature profile over the first time interval is based on the portion of the actual retort temperature profile over the first time interval.  
 
     
     
         9 . A method of administering and providing on-line correction of a batch sterilization process performed on a batch of containers, the method comprising the steps of: 
 compiling an actual retort time-temperature profile during the batch sterilization process from actual retort temperatures sensed during the batch sterilization process;    until a temperature deviation between the actual retort temperature profile and a scheduled time-temperature profile has begun, administering an initial portion of the batch sterilization process before the temperature deviation has begun according to the scheduled time-temperature profile;    in response to the temperature deviation, defining a re-scheduled remaining time-temperature profile for a remaining portion of the batch sterilization process that begins when the temperature deviation has cleared by simulating the batch sterilization process based on the actual retort time-temperature profile;    during the temperature deviation, administering corrections so that the temperature deviation will be cleared between the actual retort and re-scheduled remaining time-temperature profiles;    when the temperature deviation has cleared, administering the remaining portion of the batch sterilization process according to the re-scheduled remaining time-temperature profile.    
     
     
         10 . The method of  claim 9  wherein the temperature deviation occurs during a processing phase of the batch sterilization process.  
     
     
         11 . The method of  claim 9  wherein the temperature deviation occurs during a come-up phase of the batch sterilization process.  
     
     
         12 . The method of  claim 9  wherein the step of defining the re-scheduled remaining time-temperature profile comprises the steps of: 
 computing a total lethality predicted to be delivered to the product cold spot over the batch sterilization process that (a) is based on a product cold spot time-temperature profile, and (b) satisfies a target lethality to be delivered to the product cold spot; and  
 simulating the product cold spot time-temperature profile based on the actual retort temperature profile and the re-scheduled remaining time-temperature profile.  
 
     
     
         13 . The method of  claim 12  wherein a finite difference simulation model is used in the step of simulating the product cold spot time-temperature profile.  
     
     
         14 . The method of  claim 12  wherein the total lethality is the sum of (a) a lethality actually delivered over a first time interval from when the batch sterilization process begins to when the temperature deviation clears, and (b) a lethality predicted to be delivered over a second time interval from when the temperature deviation clears to when the batch sterilization process is predicted to end.  
     
     
         15 . The method of  claim 14  wherein: 
 the lethality actually delivered over the first time interval is based on the portion of the product cold spot time-temperature profile over the first time interval;  
 the portion of the product cold spot time-temperature profile over the first time interval is based on the portion of the actual retort temperature profile over a time interval from when the temperature deviation begins to when the temperature deviation clears.  
 
     
     
         16 . The method of  claim 14  wherein: 
 the heating lethality actually delivered over the first time interval is based on a portion of the product cold spot time-temperature profile over the first time interval;  
 the portion of the product cold spot time-temperature profile over the first time interval is based on the portion of the actual retort temperature profile over the first time interval.  
 
     
     
         17 . A controller for use in a batch sterilization system, the batch sterilization system including a batch sterilizer to perform a batch sterilization process on a batch of containers and a sensor to sense actual retort temperatures in the batch sterilizer during the batch sterilization process, the controller comprising: 
 control circuitry to administer the batch sterilization process by controlling the batch sterilizer and measure the actual retort temperatures sensed by the sensor;    a memory to store a process control program and a temperature deviation program; and    a microprocessor coupled to the control circuitry and the memory to execute the process control and temperature deviation programs such that:    the process control program: 
 compiles an actual retort time-temperature profile during the batch sterilization process from the actual retort temperatures measured by the control circuitry;  
 until a temperature deviation between the actual retort time-temperature and a scheduled time-temperature profile has begun, causes the control circuitry to administer an initial portion of the batch sterilization process before the temperature deviation has begun according to the scheduled time-temperature profile;  
 during the temperature deviation, causes the control circuitry to administer corrections to clear the temperature deviation between the actual retort time-temperature profile and a re-scheduled remaining time-temperature profile for a remaining portion of the batch sterilization process that begins when the temperature deviation has cleared; and  
 when the temperature deviation has cleared, causes the control circuitry to administer the remaining portion of the batch sterilization process according to the re-scheduled remaining time-temperature profile; and  
   the temperature deviation program, in response to the temperature deviation, defines the re-scheduled remaining time-temperature profile by simulating the batch sterilization process based on the actual retort time-temperature profile.    
     
     
         18 . The controller of  claim 17  wherein the temperature deviation occurs during a processing phase of the batch sterilization process.  
     
     
         19 . The controller of  claim 17  wherein the temperature deviation occurs during a come-up phase of the batch sterilization process.  
     
     
         20 . The controller of  claim 17  wherein the temperature deviation program defines the re-scheduled remaining time-temperature profile by: 
 computing a total lethality predicted to be delivered to the product cold spot over the batch sterilization process that (a) is based on the product cold spot time-temperature profile, and (b) satisfies a target lethality to be delivered to the product cold spot;  
 simulating the product cold spot time-temperature profile based on the actual retort temperature profile and the re-scheduled remaining time-temperature profile.  
 
     
     
         21 . The controller of  claim 20  wherein the temperature deviation program uses a finite difference simulation model to simulate the product cold spot time-temperature profile.  
     
     
         22 . The controller of  claim 21  wherein the total lethality is the sum of (a) a lethality actually delivered over a first time interval from when the batch sterilization process begins to when the temperature deviation clears, and (b) a lethality predicted to be delivered over a second time interval from when the temperature deviation clears to when the batch sterilization process is predicted to end.  
     
     
         23 . The controller of  claim 22  wherein: 
 the lethality actually delivered over the first time interval is based on the portion of the product cold spot time-temperature profile over the first time interval;  
 the portion of the product cold spot time-temperature profile over the first time interval is based on the portion of the actual retort temperature profile over a time interval from when the temperature deviation begins to when the temperature deviation clears.  
 
     
     
         24 . The controller of  claim 22  wherein: 
 the lethality actually delivered over the first time interval is based on a portion of the product cold spot time-temperature profile over the first time interval;  
 the portion of the product cold spot time-temperature profile over the first time interval is based on the portion of the actual retort temperature profile over the first time interval.