Patent Document ID: 20140303792
Application ID: 14352656
Patent Flag: 0

Claim One:
1. A storage tank operation plan deriving system, comprising: storage means configured to accept respective inputs of tank initial state information containing initial storage quantity and initial storage heat quantity of liquefied natural gas of each of a plurality of storage tanks for storing the liquefied natural gas, reception plan information containing reception time, reception quantity and reception heat quantity of the liquefied natural gas in each of plural reception plans for the liquefied natural gas, and feed plan information containing feed plan quantity on a predetermined unit period basis in a feed plan for feeding the liquefied natural gas directly or after being vaporized from one or more discharge lines to feeding destinations assigned to each of the discharge lines, in a predetermined planning period, to save each information as input information, and to store a plurality of constraints on reception and storage of the liquefied natural gas into the storage tanks, and a plurality of constraints on discharge of the liquefied natural gas from the storage tanks to the discharge lines; and arithmetic processing means for finding a feasible solution for the storage tank operation plan problem at least on operations of reception and discharge of the liquefied natural gas configured as a mixed-integer non-linear programming problem by the input information and the constraints through computerized arithmetic processes, the arithmetic processing means including first processing means for solving a mixed-integer linear programming problem, and second processing means for solving a continuous non-linear programming problem, and being configured to execute, given the input information: a first solving process including conducting a first relaxing process on each of plural non-linear constraints containing a non-linear expression of the constraints, to replace the mixed-integer non-linear programming problem with a mixed-integer linear programming problem, and solving the mixed-integer linear programming problem by using the first processing means to derive at least provisional solutions or final solutions for a reception pattern that prescribes one or more of the storage tanks that are to be objectives of reception of the liquefied natural gas in each of the reception plans in the planning period, and a discharge pattern that prescribes the storage tank that is to discharge the liquefied natural gas corresponding to the feed plan quantity on the unit period basis, and a second solving process including conducting a second relaxing process on a plurality of discrete form constraints containing discrete variables of the constraints, to replace the mixed-integer non-linear programming problem with a continuous non-linear programming problem, and solving the continuous non-linear programming problem by using the second processing means to derive at least provisional solutions or final solutions for transitions of storage quantity and storage heat quantity of the liquefied natural gas for each of the storage tanks, two or more times, respectively, and in the first solving process of the second or later time, configured to execute the first relaxing process on at least part of the non-linear constraints by using provisional solutions for transitions of storage quantity and storage heat quantity of the liquefied natural gas derived in the preceding second solving process, and in the second solving process of the first or later time, configured to execute the second relaxing process on at least part of the discrete form constraints, by using the discrete variables derived in the preceding first solving process.