Patent ID: 7092893

Claim:
A method of controlling liquid production within a plurality of air separation plants situated at sites having different locations to produce and distribute liquid to a plurality of customers; said method comprising: obtaining demand data of liquid product demand and gaseous product demand for each of said customers over prespecified time intervals within a forecast period; inputting said demand data into a real time planing system programmed with model programs and a real time optimization program; said model programs including: plant model programs to calculate electrical power data needed for each of said air separation plants to produce gaseous and liquid product slates from said air separation plants and containing production constraints for each of said air separation plants that limit the production of gaseous and liquid products therefrom; power contract model programs responsive to the electrical power data to calculate cost data to produce the gaseous and liquid product slates for each of the air separation plants; and liquid distribution cost model programs containing cost shipment data referable to road shipping costs of liquid products from each of said sites to individual or groupings of said customers to calculate transportation costs to distribute the liquid products to each of said customers within the groupings of said customers; and liquid storage constraints for each of said sites; executing said model programs and said real time optimization program over said prespecified time intervals to obtain solutions from said real time optimization program through mixed integer nonlinear optimization of optimized gaseous and liquid product slates for each of said air separation plants for each of said prespecified time intervals over the forecast period in which a total of said cost of the electrical power and said liquid distribution costs over the forecast period are at a minimum while requirements for gaseous production are met as a hard constraint; and implementing said optimized gaseous and liquid product slates by controlling the air separation plants to produce gaseous and liquid products in accordance with the optimized gaseous and liquid product slates.