Patent ID: 7502667

Claim:
A method which may be used for operating a production plant, said method comprising: a) treating at least one gas mixture with at least one air separation unit, wherein said air separation unit is supplied with electricity; b) producing at least one fluid with said air separation unit; c) operating said air separation unit during at least one first period, when the cost of electricity is greater than a first predefined value; d) operating said air separation unit during at least one second period, wherein: 1) said cost is less than a second predefined value; and 2) said second value is less than or equal to said first value; e) storing at least part of said fluid during at least part of said second period, wherein: 1) said fluid is stored in at least one storage tank; and 2) said fluid is stored as either a liquid or a gas; f) delivering at least part of said fluid to a customer during at least part of said first period, wherein said fluid delivered is from said storage tank; g) producing at least one fluid with a first set of predefined characteristics, wherein: 1) said fluid with said first characteristics is produced by said air separation unit during at least part of said second period; 2) said first characteristics comprise: i) a first purity; ii) a first flow rate; iii) a first temperature; and iv) a first pressure; h) reducing the power consumption of said air separation unit to a reduced level, wherein: 1) said power consumption is reduced during part of said first period; and 2) said reduced level is less than the power consumption level during said second period; and i) producing at least one fluid with a second set of predefined characteristics, wherein: 1) said fluid with said second characteristics is produced by said air separation unit during at least part of said first period; and 2) said second characteristics comprise at least one member selected from the group consisting of: i) a second purity less than said first purity; ii) a second flow rate less than said first flow rate; iii) a second temperature less than said first temperature; and iv) a second pressure less than said first pressure; and 3) said fluid with said second characteristics is not delivered to said customer.