Apparatus for optimizing multiunit processing systems

• US 3,891,836 A
• Filed: 03/25/1974
• Issued: 06/24/1975
• Est. Priority Date: 04/21/1972
• Status: Expired due to Term

• Current Assignee: Wooyoung Lee
• Original Assignee: Wooyoung Lee
• Inventors: Lee, Wooyoung
• Primary Examiner(s): Ruggiero, Joseph F.
• Application Number:
  US05/454,620
• Time in Patent Office: 456 Days
• Field of Search: 235/150.1,151,151.1,151.12 444/1
• US Class Current: 700/3
• 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: G05B 13/021 in which a variable is automatically adjusted to optimise the performance

Abstract

A processing system comprising a plurality of individual units is optimized by first estimating the yields of the individual units at a standard set of operating conditions and then establishing optimum flow rates using a linear programming model or similar mathematical tehniques. Individual units are then controlled and locally optimized consistent with a sensitivity analysis which is performed by treating a proposed change in operating conditions of an individual unit as a disturbance in the unit yield column of the linear programming model. The overall system may then be optimized for the changes in operating conditions by determining and establishing new flow rates. The steps of changing operating conditions and establishing new flow rates may be repeated until the sensitivity analysis reveals that any further change in operating conditions will not further improve the profit of the overall system.

Claims

1. Apparatus for controlling the operation of a processing system including a plurality of individual processing units supplied by a plurality of feed streams of materials being transformed by the units into a plurality of product streams flowing from the units, the product yield and the product cost or profit for each unit being dependent upon the operating conditions of the unit, said apparatus comprising:

feed stream computer means for generating initial feed stream signals representing the initial feed stream flow rates for a given yield and cost at each of the units under a given set of operating conditions so as to maximize the profitability of the overall system;

feed stream control means coupled to said feed stream computer means for controlling the feed stream flow rates in response to said initial feed stream signals;

unit yield and cost computer means for repeatedly and continuously generating new yield and cost signals representing new yields and costs at one of the units corresponding to an increase in the profitability of the overall system;

unit control means coupled to said unit yield and cost computer means for controlling the operating conditions at said one of said units in response to said new yield and cost signals; and

another feed stream computer means coupled to said unit yield and cost computer means for repeatedly and continuously generating new feed stream signals representing new feed stream flow rates in response to said new yield and cost signals;

said other feed stream computer means being coupled to said feed stream control means for controlling the feed stream flow rates in response to said new feed stream signals.

2. The apparatus of claim 1 wherein said feed stream computer means and said other feed stream computer means comprise an overall system computer and said yield and cost computer means comprises a local computer located at said one unit and remote from said system computer, said system including means for transmitting said new yield and cost signals from said local computer to said system computer.

3. The apparatus of claim 1 wherein said feed stream computer means comprises an overall system computer and said yield and cost computer means and said new feed stream computer means comprises a local computer located at said one unit and remote from said system computer, said apparatus including means for transmitting said new feed stream signals from said local computer to said system computer.

4. The apparatus of claim 1 wherein said feed stream computer means, said new feed stream computer means and said yield and cost computer means comprises an overall system computer, said apparatus comprising means for transmitting said new yield and cost signals from said system computer to said unit control means.

5. The apparatus of claim 1 wherein said feed stream computer means includes means for computing the initial feed stream flow rates in accordance with the linear program model having an overall system objective function of maximizing the profitability Z c1x1 + . . . . cnxn subject to p1x1 + . . . . pnxn Q xi >

or = 0 for all i where pj

6. The apparatus of claim 5 wherein said unit yield and cost computer means includes means for automatically computing a local objective function for said one unit, said local objective function defining changes in product yield and product cost or profit for increasing the profitability of the overall system.

7. The apparatus of claim 6 wherein said means for automatically computing the local objective function computes the local objective function fm ( Delta cm - pi * Delta pm) >

0 where Delta cm is the change in the marginal profit coefficient for the mth unit, Delta pm is the change in the mth yield column for the mth unit and pi * are the simplex multipliers (c1 ...cn) Beta * at the previous operating conditions where Beta * is the inverse of the basis matrix in (p1...pn).

8. The apparatus of claim 7 wherein said other feed stream computer means includes means for computing said new feed stream flow rates

9. An apparatus for controlling the operation of a processing system including a plurality of individual processing units supplied by a plurality of feed streams of materials being transformed by the units into a plurality of product streams flowing from the units, a plurality of local control means associated respectively with the units, each of the local control means including condition control means responsive to condition control signals generated by the local control means for controlling the operating of each unit, and central control means including flow rate control means associated with each of the feed streams and responsive to flow rate control signals generated by the central control means, the product yield and the product cost or profit of each unit being dependent upon the operating conditions of each unit, said apparatus comprising:

means for automatically computing the initial feed stream flow rates for a given product yield and a given product cost at each of the units so as to maximize the profitability of the overall system, said central control means generating initial flow rate control signals in response to the computed initial feed stream flow rates and applying the initial flow rate control signals to the flow rate control means to establish the initial feed stream flow rates;

means for substantially continuously and automatically computing a new product yield and new product cost or profit for at least one of the units corresponding to an increase in the profitability of the overall system, said local control means associated with said one unit substantially continuously generating new condition control signals corresponding to the new computed product yield and the new product cost or profit and applying the new condition control signals to the condition control means associated with said one unit to establish new operating conditions; and

means for substantially continuously and automatically computing new feed stream flow rates for all of the feed streams in response to the new product yield and the new product cost or profit for said one unit so as to maximize the profitability of the overall system, said central control means substantially continuously generating new flow control signals representing new feed stream flow rates and applying the new flow rate signals to the flow rate control means of the feed streams to establish the new feed stream flow rates.

10. The apparatus of claim 9 wherein said means for automatically computing the new product yield And the new product cost or profit are located at the local control means associated with the unit;

said apparatus further comprising means for generating signals representing the new product yield and the new product cost or profit at the local control means; and

means for transmitting the signals representing the new product yield and the new product cost or profit to said central control means.

11. The apparatus of claim 9 further comprising:

means for substantially continuously and automatically computing local objective functions for each of the units at the local control means, said local objective functions defining changes in product yield and product cost or profit for increasing the profitability of the overall system;

said means for substantially continuously and automatically computing the new product yield and the new product cost or profit being located at the local control means and being responsive to and consistent with the local objective function of said one unit.

12. The apparatus of claim 11 wherein said means for automatically computing feed stream flow rates operates so as to satisfy and be consistent with a linear program model having an overall objective function of maximizing the profitability Z c1x1 + .... cnxn subject to p1x1 + .... pnxn Q xi >

or = 0 for all i where pj

13. The apparatus of claim 9 further comprising:

means for substantially continuously and automatically computing local objective functions for each of the units at the central control means, said local objective functions defining changes in product yield and product cost or profit for increasing the profitability of the overall system; and

said means for substantially continuously and automatically computing the new product yield and the new product cost or profit being located at the central control means and being responsive to and consistent with the signals representing the local objective function of said one unit

14. Apparatus for controlling a processing system including a plurality of individual processing units supplied by a plurality of feed streams of materials being transformed by the units into a pluraliTy of product streams flowing from the units, said system being characterized by a linear program model having an overall objective function of maximizing the profitability Z c1x1 + .... cnxn subject to p1x1 + .... pnxn Q where cj is the marginal profit coefficient of the coefficient jth unit, pj is a column vector of yield coefficients for the jth unit and the function of operating conditions of said jth unit, Q is a column vector of demand constraints on the product streams and xi is the flow rate of the ith feed stream, said system comprising:

unit control means for controlling the operating conditions of said individual units;

first computing means coupled to said unit control means for computing yield coefficients and profit or cost coefficients for each jth unit at a given set of operating conditions;

second computing means for computing the flow rate xi for each said ith stream so as to maximize the profitability Z for the computed yield coefficients and profit or cost coefficients for each said jth unit at said given set of operating conditions;

feed stream control means coupled to said second computing means for controlling the flow rate of materials in said feed streams; and

third computing means coupled to said first computing means for computing a new flow rate xi1 for each said ith feed streams so as to maximize the profitability Z for a change in operating conditions at the mth one of said units, said change in operating conditions being represented by a substituted vector column pm1 for said mth unit and a substituted cost coefficient cm1, said third computing means comprising;

first storage means for storing signals representing each flow rate xi* at a given set of operating conditions;

second storage means for storing signals representing the change in yield coefficients Delta pm and a change in cost coefficients Delta cm at said mth unit;

third storage means for storing signals representing the inverse basis matrix Beta * of the basis matrix Beta * of the vector columns pj* at the given set of operating conditions;

means coupled to said second storage means and said third storage means for generating signals representing s Beta * Delta pm; and

means coupled to said first storage means and said means for generating said s signals for generating signals representing

15. The apparatus of claim 14 further comprising fourth computing means coupled to said first computing means for determining the change in operating conditions for said mth unit so as to satisfy the local objective function fm cm -pi * pm thereby maximizing the overall profitability of the system.

16. Apparatus for controlling a processing system including a plurality of individual processing units supplied by a plurality of feed streams of materials being transformed by the units into a plurality of product streams flowing from the units, said system being characterized by a linear program model having an overall objective function of maximizinG profitability Z c1x1 + .... cnxn subject to p1x1 + .... pnxn Q where cj is the marginal profit coefficient of the jth unit, pj is a convector of yield coefficients for the jth unit and a function of operating conditions of said jth unit, Q is column vector of demand constraints on the product streams and xi is the flow rate of the ith feed stream, said apparatus comprising:

means for controlling the operating conditions at the local unit so as to correspond to column vectors pj for a given set of operating conditions at each unit;

means for controlling the feed stream flow rates xi to the local units so as to satisfy the overall objective function Z; and

means for computing the new feed stream flow rates xi1 to replace old feed stream flow rates x*i after a change in operating conditions at the mth unit resulting in the substitution of a new yield column vector pm1 for an old yield column vector pm1 and a new cost coefficient cm1 for an old cost coefficient c*m comprising;

first storage means for storing signals representing each flow rate x*i at a given set of operating conditions;

second storage means for storing signals representing the change in yield coefficients Delta pm and a change in cost coefficients Delta cm at said mth unit;

third storage means for storing signals representing the inverse basis matrix Beta * of the basis matrix Beta * of the vector columns p*j at said set of operating conditions;

means coupled to said second storage means and said third storage means for generating signals representing x Beta * Delta pm; and

means coupled to said first storage means and said means for generating said si signal for generating signals representing

17. The apparatus of claim 13 wherein said means for automatically computing feed stream flow rates operates so as to satisfy and be consistent with a linear program model having an overall objective function of maximizing the profitability Z c1x1 + .... cxn subject to p1x1 + .... pnxn Q xi >

or = 0 for all i where pj

18. The apparatus of claim 1 wherein said unit yield and cost computer means includes means for automatically computing a local objective function for said one unit, said local objective function defining changes in product yield and product cost or profit for increasing the profitability of the overall system.