Kobe Steel, Ltd.

Takeshi Iyoki

Takumi Mizokawa

Taichi Katsuki

Takaharu Goto

A method and apparatus for automatic change of operations in an air separation plant in increasing or decreasing the amounts of products. The present invention is characterized in that intended change values of the flow rate of feed air to be introduced into an air separation plant, the flow rate of liquid air recycled to an upper tower from a lower tower of a rectification column, the flow rate of recycled liquid nitrogen and the flow rate of an expansion turbine gas flowing in an expansion turbine are computed from the values of increased or decreased amounts of products. At the time of initiation of change of the flow rates, the ratio of the flow rate of feed air to the flow rate of the product is increased, and the flow rates of the feed air, recycled liquid air, recycled liquid nitrogen, expansion turbine gas and product are automatically changed to the intended values while gradually reducing the above ratio, and the period ranging from the point at which the intended values are attained to the point when the unstable operation state in the air separation plant is completed is set as the operation change-inhibiting period and the subsequent change of the flow rates is inhibited during this period.

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Kobe, Japan

Takeshi Iyoki