CHEMICAL PROCESSING SYSTEM

• US 20100088075A1
• Filed: 02/26/2008
• Published: 04/08/2010
• Est. Priority Date: 03/09/2007
• Status: Active Grant

• Current Assignee: HRD Corporation, Process Asset Integration & Management Ltd
• Original Assignee: University of Manchester
• Inventors: Zhang, Nan, Yin, Qiying
• Granted Patent: US 8,346,519 B2
• Time in Patent Office: Days
• US Class Current: 703/2
• CPC Class Codes: B01J 19/0033 Optimalisation processes, i.e. processes with adaptive control systems adaptive control systems per se G05B13/00
• CPC Class Codes: B01J 2219/00243 Mathematical modelling

Abstract

A method of optimising apparatus utilised within a processing system includes defining a system model indicative of a predetermined range of apparatus options within a processing system, constraints indicative of feasible interconnections between each apparatus, and parameters indicative of performance criteria associated with each apparatus. The system model is analysed with respect to predetermined criteria to determine a preferred arrangement of apparatus within the processing system. A parameter relating to at least one apparatus is indicative of the availability and/or the reliability of the apparatus expressed as a function of time.

Claims

1. A method of optimising apparatus utilised within a processing system, comprising:

defining a system model indicative of a predetermined range of apparatus options within a processing system, constraints indicative of feasible interconnections between each apparatus, and parameters indicative of performance criteria associated with each apparatus;

analysing the system model with respect to predetermined criteria to determine a preferred arrangement of apparatus within the processing system,

wherein at least one parameter relating to at least one of said apparatus is indicative of at least one of the availability and reliability of the related apparatus expressed as a function of time.

2. A method as claimed in claim 1, wherein said step of analysing the structure with respect to predetermined criteria comprising minimising or maximising the value of a predetermined function.

3. A method as claimed in claim 1, wherein parameters indicative of both the availability and reliability are expressed as a function of time.

4. A method as claimed in claim 1, wherein said at least one parameter indicative of at least one of availability and reliability is expressed as a function of preventive maintenance.

5. A method as claimed in claim 4, wherein said parameter indicative of the availability of the apparatus is expressed as a function of the time taken to perform preventive maintenance.

6. A method as claimed in claim 4, wherein said step of analysing the system model with respect to predetermined criteria to determine a preferred arrangement of apparatus within the processing system comprises determining a preferred value of preventive maintenance interval for at least some of the apparatus in the preferred arrangement.

7. A method as claimed in claim 4, further comprising:

(a) assuming an initial value for a variable indicative of the interval of preventive maintenance of said at least one apparatus;

(b) determining values of parameters indicative of at least one of the availability and reliability of apparatus based upon the initial value of the interval of preventive maintenance;

(c) performing the step of analysing the system model with respect to predetermined criteria, and determining a preferred value for the maintenance interval from that step;

(d) if the determined preferred value for the maintenance interval is outside a predetermined range from the initial value of the maintenance interval, repeating steps (b) to (d) using a new initial value for the preventive maintenance interval, until the determined preferred value is within a predetermined range of the initial value.

8. A method as claimed in claim 1, wherein said predetermined criteria includes minimisation of the capital investment in manufacturing the arrangement of apparatus within the processing system and the operation cost of the apparatus within the processing system throughout the anticipated life of the preferred arrangement of apparatus.

9. A method as claimed in claim 1, further comprising analysing the performance criteria of real apparatus to determine said parameters indicative of performance criteria.

10. A method as claimed in claim 1, wherein the parameter indicative of the reliability of an apparatus is expressed as a function of a time-dependent distribution.

11. A method as claimed in claim 1, wherein the reliability R_sys(t) of an arrangement of apparatus is expressed by the function

$R_{\mathrm{sys}}$

( t ) = exp 

[ - ( t θ

) β

] , θ

>

0 , β

>

0 , t ≥

0

where t is time, and θ and

β

are Weibull distribution parameters.

12. A method as claimed in claim 1, wherein the parameter indicative of the reliability of an arrangement of apparatus comprising at least two apparatus is expressed as a function of a time-dependent distribution.

13. A method as claimed in claim 1, wherein the availability A_a,sys of an arrangement of apparatus is determined by

$A_{a,\mathrm{sys}}=\frac{t_d}{t_d+{\mathrm{MTTR}}_{\mathrm{sys}}·}$

( - ln 

( R sys 

( t d ) ) + MTPM sys ·

t d / T PM , sys

where MTTR_sys is the Mean Time To Repair the arrangement, MTPM_sys is the Mean Time To Perform Preventive Maintenance of the arrangement, R_sys is the arrangement reliability, t_d is the arrangement life cycle and T_PM,sys is the preventive maintenance interval of the arrangement.

14. A method as claimed in claim 1, wherein the availability A_a,sys of an arrangement of apparatus is determined by

$A_{a,\mathrm{sys}}=\frac{t_d}{t_d+{\mathrm{MTTR}}_{\mathrm{sys}}·}$

t d / θ





Γ



( 1 + 1 β

) + MTPM sys ·

t d / T PM , sys

where MTTR_sys is the Mean Time To Repair the arrangement, θ and

β

are Weibull parameters for the arrangement and MTPM_sys is the Mean Time To Perform Preventive Maintenance of the arrangement, t_d is the arrangement life cycle and T_PM,sys is the preventive maintenance interval of the arrangement.

15. A method as claimed in claim 13, wherein the parameter T_PM,sys is a variable optimised within the analysing step.

16. A method as claimed in claim 1, wherein the availability of an arrangement of apparatus comprising at least two apparatus able to operate in i operational modes within the processing system is defined as the Process System Availability PSA,

$P$



S 



A = Real 



Throughput Ideal 



Throughput = ∑

i 

A i 

x i

where

A_i=Availability of the arrangement of apparatus in operation mode i

x_i=Ratio of actual to maximum capacity of arrangement in mode i.

17. A method as claimed in claim 1, wherein at least one of the availability and reliability functions are linearised functions.

18. A method as claimed in claim 1, wherein said system model is one of a superstructure optimization or a stochastic optimization model.

19. A method as claimed in claim 1, further comprising the step of manufacturing the determined preferred arrangement of apparatus.

20. A method as claimed in claim 19, when dependent upon claim 6 or any claim dependent thereto, further comprising the step of performing preventive maintenance upon the manufactured arrangement of apparatus in accordance with the determined preferred value of preventive maintenance.

21. A carrier medium carrying computable readable code configured to cause a computer to carry out a method according claim 1.

22. A design for apparatus utilising a processing system, the design being determined by performing the method as claimed in claim 1.

23. A processing system including the preferred arrangement of apparatus as determined using the method of claim 1.

24. A processing system as claimed in claim 23, wherein the processing system is a chemical plant.