| 摘要 |
PURPOSE:To improve the estimating accuracy of nitrogen concentration in material argon by a method wherein the discharge amount of product oxygen or material air amount is manipulated and the nitrogen concentration is continuously and automatically controlled to attain a preset value. CONSTITUTION:A relation between temperature and nitrogen concentration is previously obtained separately for each pressure value at each of specified steps in an upper part of an oxygen rectifying tower, the nitrogen concentration in material argon is obtained from the measured pressure and temperature and, according to the difference between an estimated value and a target value, the discharged amount of product oxygen and the amount of material air are manipulated, whereby the nitrogen concentration in the material argon is continuously controlled to attain the target value. Concerning the manipulation of the oxygen discharge amount and the material air amount, the manipulating amount is obtained by multiplying the deviation from the target control value and the value of state variable of an oxygen plant by the gain which has previously been obtained from input variables of the oxygen discharge amount and the material air amount and from a relation of response characteristics to the state variables of the oxygen plant such as the nitrogen concentration in the material argon and the temperature of the material air and the value thus obtained is continuously manipulated.
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