| 摘要 |
PURPOSE:To make it possible to drive this device in automatic mode and save manhour by determining the amount of circulating liquid nitrogen with calculation, controlling a control valve in conformity with the calculated value, carrying out feed forward control of the amount of circulating liquid nitrogen, and controlling the degree of purity of liquid air. CONSTITUTION:When converting to weight reduction operation, the amount of raw air to be supplied to a rectification lower tower 1 is reduced. Therefore, it is necessary to reduce the circulation liquid nitrogen to be supplied to a rectification upper tower 3 from the upper part and the middle part in order to keep constant the record purity of fluid. At that time, the amount of circulation nitrogen to the upper part is determined in such a manner that it may stay within a fixed range with the amount of product nitrogen while the amount of the circulation nitrogen to the internal part is determined in such a manner that the purity of liquid air may be kept constant. The amount thus determined is set to an inner part liquid nitrogen control valve 6 and an upper part liquid nitrogen control valve 8.
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