Nonlinear model predictive control of a biofuel fermentation process

• US 8,571,690 B2
• Filed: 10/30/2007
• Issued: 10/29/2013
• Est. Priority Date: 10/31/2006
• Status: Active Grant

• Current Assignee: Rockwell Automation Technologies Incorporated (Rockwell Automation, Inc.)
• Original Assignee: Rockwell Automation Technologies Incorporated (Rockwell Automation, Inc.)
• Inventors: Bartee, James F., Macharia, Maina A., Noll, Patrick D., Tay, Michael E.
• Primary Examiner(s): HARWARD, SOREN T
• Application Number:
  US11/927,960
• Publication Number:
  US 20080167852A1
• Time in Patent Office: 2,191 Days
• Field of Search: 700/28, 700/299, 703/11
• US Class Current: 700/28
• CPC Class Codes: C12M 41/12 of temperature controlling the temperature of chemical or physical processes B01J19/0013, heating or cooling apparatus for laboratory use B01L7/00
• CPC Class Codes: C12M 41/44 of volume or liquid level
• CPC Class Codes: C12M 41/46 of cellular or enzymatic activity or functionality, e.g. cell viability
• CPC Class Codes: C12M 41/48 Automatic or computerized control automatic analysis G01N35/00
• CPC Class Codes: C12M 45/09 by enzymatic treatment
• CPC Class Codes: C12P 7/06 Ethanol, i.e. non-beverage
• CPC Class Codes: G05B 13/04 involving the use of models or simulators
• CPC Class Codes: G05B 13/048 using a predictor
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel

Abstract

A system and method are provided for managing batch fermentation in a biofuel production process. A nonlinear control model of yeast growth and fermentable sugar concentration for biofuel (e.g., fuel ethanol) production in a batch fermentation process (pure and/or fed-batch fermentation) of a biofuel production process is provided. Process information for the batch fermentation process is received, and the nonlinear control model executed using the process information as input to determine values of one or more fermentation process variables for the batch fermentation process, e.g., fermentation temperature and/or enzyme flow, for substantially maximizing yeast growth and achieving target fermentable sugar concentrations. The batch fermentation process is then controlled in accordance with the determined values for the one or more fermentation process variables to substantially maximize yeast growth and achieve target fermentable sugar concentrations, where substantially maximizing yeast growth and achieving target fermentable sugar concentrations substantially maximizes biofuel production in the batch fermentation process.

Claims

1. A method for managing a batch fermentation process in a biofuel production process, comprising:

providing a nonlinear control model of yeast growth and fermentable sugar concentration for biofuel production in a batch fermentation process of a biofuel production process, wherein yeast growth is a function of a cooler return temperature of a fermenter, metabolic heat generation in the fermenter, and a volumetric change in a fermentation tank;

receiving process information for the batch fermentation process, wherein the process information includes the fermenter cooler return temperature;

executing the nonlinear control model of yeast growth and fermentable sugar concentration using the process information as input, thereby determining target values of one or more fermentation process variables and an optimal batch temperature trajectory during filling of the fermentation tank that substantially maximizes yeast growth and achieves target fermentable sugar concentrations, wherein the one or more target values comprise a mash flow rate or a yeast addition rate; and

controlling the mash flow rate or the yeast addition rate during filling of the fermentation tank in accordance with the determined target values for the one or more fermentation process variables and the optimal batch temperature trajectory.

2. The method of claim 1, wherein the nonlinear control model comprises a physics-based model including equations for the volumetric change in the fermentation tank, a yeast activation rate, a yeast growth rate, the yeast death rate, a fermentable sugar conversion rate, a dextrin conversion rate, a biofuel production rate, or an enzyme addition rate.

3. The method of claim 1, further comprising:

specifying an objective function, wherein the objective function specifies the target fermentable sugar concentrations;

wherein said executing the nonlinear control model of yeast growth and fermentable sugar concentration comprises;

an optimizer executing the nonlinear control model of yeast growth and fermentable sugar concentration in an iterative manner to solve the objective function, thereby determining the values for the one or more fermentation process variables.

4. The method of claim 1, wherein the process information further comprises one or more of:

measured attributes of the batch fermentation process;

laboratory data;

or

predicted values for unmeasured attributes of the batch fermentation process computed by one or more predictive models.

5. The method of claim 1, wherein the nonlinear control model of yeast growth and fermentable sugar concentration comprises:

a nonlinear control model of yeast growth and fermentable sugar concentration as a function of fermentation temperature and enzyme concentration; and

a nonlinear control model of temperature and enzyme concentration as a function of fermenter cooler return temperature and enzyme flow.

6. The method of claim 5, wherein said executing the nonlinear control model of yeast growth and fermentable sugar concentration comprises:

executing the nonlinear control model of yeast growth and fermentable sugar concentration as a function of fermentation temperature and starch-converting enzyme concentration using the process information as input, thereby determining values of temperature and starch-converting enzyme concentration for the batch fermentation process that substantially maximize yeast growth and achieve the target fermentable sugar concentration; and

executing the nonlinear control model of temperature and starch-converting enzyme concentration using the process information as input, thereby determining the values for the fermenter cooler return temperature and starch-converting enzyme flow that achieve the determined values of temperature and starch-converting enzyme concentration in the batch fermentation process.

7. The method of claim 1, wherein the batch fermentation process comprises a fed-batch process.

8. The method of claim 1, wherein the batch fermentation process comprises a pure batch process.

9. The method of claim 1, further comprising:

performing said receiving process information, said executing the nonlinear control model of yeast growth and fermentable sugar concentration, and said controlling the mash flow rate or the yeast addition rate in an iterative manner to produce the biofuel in a substantially optimal manner.

10. The method of claim 1, wherein the biofuel comprises ethanol, and wherein yeast growth is based on the following equation:

11. A computer-accessible memory medium configured for managing a batch fermentation process in a biofuel production process, wherein the memory medium stores:

a nonlinear control model of yeast growth and fermentable sugar concentration for biofuel production in a batch fermentation process of a biofuel production process, wherein yeast growth is a function of a cooler return temperature of a fermenter, metabolic heat generation in the fermenter, and a volumetric change in a fermentation tank; and

program instructions, executable to perform;

receiving process information for the batch fermentation process, wherein the process information includes the fermenter cooler return temperature;

executing the nonlinear control model of yeast growth and fermentable sugar concentration using the process information as input, thereby determining target values of one or more fermentation process variables and an optimal batch temperature trajectory during filling of the fermentation tank that substantially maximizes yeast growth and achieves target fermentable sugar concentrations, wherein the one or more target values comprise a mash flow rate or a yeast addition rate; and

controlling the mash flow rate or the yeast addition rate during filling of the fermentation tank in accordance with the determined target values for the one or more fermentation process variables and the optimal batch temperature trajectory.

12. The memory medium of claim 11, wherein the nonlinear control model comprises a physics-based model including equations for the volumetric change in the fermentation tank, a yeast activation rate, a yeast growth rate, the yeast death rate, a fermentable sugar conversion rate, a dextrin conversion rate, a biofuel production rate, or an enzyme addition rate.

13. The memory medium of claim 11, wherein the program instructions are further executable to perform:

receiving an objective function, wherein the objective function specifies the target fermentable sugar concentrations;

wherein said executing the nonlinear control model of yeast growth and fermentable sugar concentration comprises;

an optimizer executing the nonlinear control model of yeast growth and fermentable sugar concentration in an iterative manner to solve the objective function, thereby determining the values for the one or more fermentation process variables.

14. The memory medium of claim 11, wherein the process information further comprises one or more of:

measured attributes of the batch fermentation process;

laboratory data;

or

predicted values for unmeasured attributes of the batch fermentation process computed by one or more predictive models.

15. The memory medium of claim 11, wherein the nonlinear control model of yeast growth and fermentable sugar concentration comprises:

a nonlinear control model of yeast growth and fermentable sugar concentration as a function of fermentation temperature and enzyme concentration; and

a nonlinear control model of temperature and enzyme concentration as a function of fermenter cooler return temperature and enzyme flow.

16. The memory medium of claim 15, wherein said executing the nonlinear control model of yeast growth and fermentable sugar concentration comprises:

executing the nonlinear control model of yeast growth and fermentable sugar concentration as a function of fermentation temperature and starch-converting enzyme concentration using the process information as input, thereby determining values of temperature and starch-converting enzyme concentration for the batch fermentation process that substantially maximize yeast growth and achieve the target fermentable sugar concentration; and

executing the nonlinear control model of temperature and starch-converting enzyme concentration using the process information as input, thereby determining the values for the fermenter cooler return temperature and starch-converting enzyme flow that achieve the determined values of temperature and starch-converting enzyme concentration in the batch fermentation process.

17. The memory medium of claim 11, wherein the batch fermentation process comprises a fed-batch process.

18. The memory medium of claim 11, wherein the batch fermentation process comprises a pure batch process.

19. The memory medium of claim 11, wherein the program instructions are further executable to perform:

performing said receiving process information, said executing the nonlinear control model of yeast growth and fermentable sugar concentration, and said controlling the mash flow rate or the yeast addition rate in an iterative manner to produce the biofuel in a substantially optimal manner.

20. The memory medium of claim 11, wherein the biofuel comprises ethanol, and wherein yeast growth is based on the following equation:

21. A system for managing a batch fermentation process in a biofuel production process, comprising:

a processor; and

a memory medium coupled to the processor, wherein the memory medium stores;

a nonlinear control model of yeast growth and fermentable sugar concentration for biofuel production in a batch fermentation process of a biofuel production process, wherein yeast growth is a function of a cooler return temperature of a fermenter, metabolic heat generation in the fermenter, and a volumetric change in a fermentation tank; and

program instructions, executable by the processor to;

receive process information for the batch fermentation process, wherein the process information includes the fermenter cooler return temperature;

execute the nonlinear control model of yeast growth and fermentable sugar concentration using the process information as input, thereby determining target values of one or more fermentation process variables and an optimal batch temperature trajectory during filling of the fermentation tank that substantially maximizes yeast growth and achieves target fermentable sugar concentrations, wherein the one or more target values comprise a mash flow rate or a yeast addition rate; and

control the mash flow rate or the yeast addition rate during filling of the fermentation tank in accordance with the determined values for the one or more fermentation process variables and the optimal batch temperature trajectory.

22. The system of claim 21, wherein the program instructions are further executable to:

receive an objective function, wherein the objective function specifies the target fermentable sugar concentrations;

wherein said executing the nonlinear control model of yeast growth and fermentable sugar concentration comprises;

an optimizer executing the nonlinear control model of yeast growth and fermentable sugar concentration in an iterative manner to solve the objective function, thereby determining the values for the one or more fermentation process variables.

23. The system of claim 21, wherein the program instructions are further executable to:

perform said receiving process information, said executing the nonlinear control model of yeast growth and fermentable sugar concentration, and said controlling the mash flow rate or the yeast addition rate in an iterative manner to produce the biofuel in a substantially optimal manner.