Methods, systems, and articles for controlling a fluid blending system

• US 7,188,637 B2
• Filed: 04/30/2004
• Issued: 03/13/2007
• Est. Priority Date: 05/01/2003
• Status: Active Grant

• Current Assignee: Aspentech Corporation
• Original Assignee: Aspen Technology Inc (Emerson Electric Company)
• Inventors: Dreyer, Rudolf Petri, Kotze, Gerhardus Dirk
• Primary Examiner(s): Hepperle; Stephen M.
• Application Number:
  US10/837,510
• Publication Number:
  US 20040221889A1
• Time in Patent Office: 1,047 Days
• Field of Search: 137/6, 137/93, 137/88
• US Class Current: 137/6
• CPC Class Codes: G05D 11/139 by measuring a value related to the quantity of the individual components and sensing at least one property of the mixture
• CPC Class Codes: Y10T 137/0346 Controlled by heat of combustion of mixture
• CPC Class Codes: Y10T 137/2499 Mixture condition maintaining or sensing

Abstract

Described herein are methods, systems, and articles that are useful for controlling a fluid blending system, such as a fluid utility system. The methods, systems, and articles of this invention allow for the control of both a quantity metric (e.g., pressure) of the blended fluid the fluid blending system as well as at least one quality metric of a blended fluid in a fluid blending system. For example, the methods, systems, and articles of this invention provide for the simultaneous control of both the pressure and quality of fuel gas within a fuel gas header system.

Claims

1. A method of controlling a fluid blending system, wherein the fluid blending system distributes a blended fluid, comprising the step of nearly simultaneously controlling both a quantity metric and a quality metric of the blended fluid within the fluid blending system using a non-linear fluid blending model.

58. The method of claim 1, wherein the non-linear model uses flow rate and quality metric data to calculate the quality of the blended fluid and flow rate data to calculate imbalance in the flow rates of the supply and consumption streams.

2. A method of controlling a fluid blending system, wherein the fluid blending system includes at least one fluid supply stream directing a fluid into the fluid blending system, at least one consumption stream directing a blended fluid out of the fluid blending system, the method comprising the steps of:

a) determining at least one quality metric of a fluid in the supply stream and at least one flow rate of fluid in a supply or consumption stream;

b) using a non-linear model to determine a quality metric of the blended fluid in the system and flow rate imbalances; and

c) using at least one manipulated variable to simultaneously control at least one quantity metric and at least one quality metric of the blended fluid, thereby controlling the fluid blending system.

3. The method of claim 2, wherein the quality metric of fluid in the supply stream is determined using first principle calculations or an empirical model.

4. The method of claim 2, wherein the non-linear model is based upon rigorous equations, an empirical model, or a Bounded Derivative Network.

5. The method of claim 2, wherein the non-linear model is embedded in a non-linear model predictive controller.

6. The method of claim 2, wherein the non-linear model is used to adapt steady state gains of a linear model predictive controller.

7. The method of claim 2, wherein the non-linear model is a non-linear fluid blending model or a non-linear furnace model.

8. The method of claim 2, wherein the non-linear model includes at least one variable gain that can be a negative value, a positive value, or zero.

9. The method of claim 8, wherein the gain varies linearly with variations in a quality metric of a fluid in the supply stream.

10. The method of claim 2, wherein the non-linear model includes at least two independent feed forward variables for every supply stream.

11. The method of claim 2, wherein the non-linear model uses a determined flow rate and quality metric for each supply stream as input variables.

12. The method of claim 2, wherein the quality metric of at least one supply stream is determined by assigning the quality metric a nominal quality value.

13. The method of claim 2, further including a step of creating the manipulated variable or a controlled variable, thereby providing a number of degrees of freedom sufficient for controlling the fluid blending system.

14. The method of claim 13, wherein the manipulated variable or controlled variable is created by controlling a flow rate of a supply or consumption stream.

15. The method of claim 2, wherein the non-linear model is calculated using blending rule calculations.

16. The method of claim 2, wherein the fluid blending system is a steam distribution system, a hydrogen distribution system, a refinery fuel blending system, or a fluid utility distribution system.

17. The method of claim 16, wherein the fluid blending system is a fluid utility distribution system and the blended fluid includes fuel gas.

18. The method of claim 17, wherein the quality metric of fluid in a supply stream is determined using first principle calculations or an empirical model.

19. The method of claim 17, wherein the non-linear model is based upon rigorous equations, an empirical model, or a Bounded Derivative Network.

20. The method of claim 17, wherein the non-linear model is embedded in a non-linear model predictive controller.

21. The method of claim 17, wherein the non-linear model is used to adapt steady state gains of a linear model predictive controller.

22. The method of claim 17, wherein the non-linear model is a non-linear fluid blending model or a non-linear furnace model.

23. The method of claim 17, wherein the non-linear model includes at least one variable gain that can be a negative value, a positive value, or zero.

24. The method of claim 23, wherein the gain varies linearly with variations in a quality metric of a fluid in the supply stream.

25. The method of claim 17, wherein the non-linear model includes at least two independent feed forward variables for every supply stream.

26. The method of claim 17, wherein the non-linear model uses a determined flow rates and quality metric for each supply stream as input variables.

27. The method of claim 17, wherein the quality metric of at least one supply stream is determined by assigning the quality metric a nominal quality value.

28. The method of claim 17, further including a step of creating the manipulated variable or a controlled variable, thereby providing a number of degrees of freedom sufficient for controlling the fluid blending system.

29. The method of claim 28, wherein the manipulated variable or control variable is created by controlling a flow rate of a supply or consumption stream.

30. The method of claim 28, wherein the manipulated variable or control variable is created by controlling a distribution of fuel gas between more than one fuel gas header system.

31. The method of claim 17, wherein the non-linear model is calculated using blending rule calculations.

32. A computer program product, comprising:

a) a computer usable medium; and

b) a set of computer program instructions embodied on the computer useable medium for controlling a fluid blending system, wherein the fluid blending system using a non-linear fluid blending model distributes a fluid, comprising the step of nearly simultaneously controlling both a quantity metric and a quality metric of the fluid of the fluid blending system.

33. The computer program of claim 32, wherein at least some portion of the computer program instructions include instructions to request data or request instructions over a telecommunications network.

34. The computer program of claim 32, wherein at least some portion of the computer program is transmitted over a global network.

35. The computer program of claim 32, wherein the computer usable medium includes a removable storage medium.

36. The computer program of claim 35, wherein the removable storage medium includes any of a CD-ROM, a DVD-ROM, a diskette, and a tape.

59. The computer program product of claim 32, wherein the non-linear model uses flow rate and quality metric data to calculate the quality of the blended fluid and flow rate data to calculate imbalance in the flow rates of the supply and consumption streams.

37. A computer system to control a fluid blending system, the computer system comprising:

a) a data transfer means for transferring data among components of a computer; and

b) a controller coupled to receive input from the data transfer means, wherein the controller nearly simultaneously controls both a quantity metric and a quality metric of a blended fluid that is distributed through the fluid blending system using a non-linear fluid blending model.

38. The computer system of claim 37, wherein the controller includes:

i) a controller means for calculating a control signal based upon a flow rate and a quality metric for at least one supply or consumption stream, wherein implementation of the control signal results in the blended fluid having an acceptable quality metric and the fluid blending system having an acceptable amount of blended fluid; and

ii) a flow manipulation means in communication with the controller means, wherein the flow manipulation means implements the control signals of the controller means.

60. The computer system of claim 37, wherein the non-linear model uses flow rate and quality metric data to calculate the quality of the blended fluid and flow rate data to calculate imbalance in the flow rates of the supply and consumption streams.

39. A control system that simultaneously controls a quantity metric and a quality metric of a fluid in a fluid blending system, wherein the fluid blending system includes at least one fluid supply stream entering the fluid blending system, at least one means for blending the fluid, and at least one blended fluid consumption stream leaving the fluid blending system, the control system comprising:

a) a controller means for calculating a control signal based upon a flow rate and a quality metric for at least one supply or consumption stream using a non-linear fluid blending model, wherein implementation of the control signal results in the blended fluid having an acceptable quality metric and an acceptable quantity metric; and

b) a flow manipulation means in communication with the controller means, wherein the flow manipulation means implements the control signals of the controller means.

40. The control system of claim 39, further including a quality determination means in communication with the controller means, wherein the quality determination means determines at least one quality metric of a fluid in at least one supply stream.

41. The control system of claim 40, wherein the quality determination means determines the quality metric using first principle calculations or an empirical model.

42. The control system of claim 40, wherein the quality determination means includes at least one online hardware analyzer.

43. The control system of claim 39, wherein the non-linear fluid blending model uses flow rate and quality metric data to calculate the quality of the blended fluid and flow rate data to calculate imbalance in the flow rates of the supply and consumption streams.

44. The control system of claim 43, wherein the non-linear fluid blending model is based upon rigorous equations or an empirical model.

45. The control system of claim 44, wherein the non-linear fluid blending model is based upon a Bounded Derivative Network.

46. The control system of claim 43, wherein the non-linear fluid blending model is embedded in a non-linear model predictive controller.

47. The control system of claim 43, wherein the non-linear fluid blending model is used to adapt steady state gains of a linear model predictive controller.

48. The control system of claim 39, wherein the blended fluid includes fuel gas and the fluid blending system is a fuel gas distribution system.

49. The control system of claim 39, wherein the blended fluid includes steam and the fluid blending system is a steam distribution system.

50. The control system of claim 39, wherein the blended fluid includes hydrogen and the fluid blending system is a hydrogen distribution system.

51. The control system of claim 39, wherein the blended fluid includes gasoline, diesel, or fuel oil and the fluid blending system is a refinery fuel blender.

52. The control system of claim 48, wherein the quality metric is a calorific value.

53. The control system of claim 48, wherein the flow manipulation means includes a non-linear furnace model that calculates fuel gas consumption and furnace coil outlet temperature based on fuel gas quality, burner counts, and fuel gas and alternative fuel flow controller set points.

54. The control system of claim 53, wherein the non-linear furnace model is based on rigorous equations or an empirical model.

55. The control system of claim 54, wherein the non-linear furnace model is based upon a Bounded Derivative Network.

56. The control system of claim 54, wherein the non-linear furnace model is embedded directly into anon-linear model predictive controller.

57. The control system of claim 54, wherein the non-linear furnace model is used to adapt steady state gains of a linear model predictive controller.