PURPOSE: To decrease the change of the concn. of a concd. liquid in a stage for changing the quantity of production and to stabilize the concn. of the concd. liquid of a liquid by adding the opening degree of a control valve meeting the set value of the vapor quantity of the heating steam to a control valve control system as a feedforward element.
CONSTITUTION: The control system has a feedback line 54 and a feedforward line 53 and makes the precedent operation of the control valve 55 by the feedforward compensation after the specified dead time according to the setting change of the quantity of the heating steam so that the flow rate of the line for the supply liquid and other liquid attains the value meeting the set value. The output An of a controller 56 for the flow rate, liquid level, concn., etc., of the feedback line sets the opening degree of the control valve 55 in the min. quantity of the production. The feedforward line is set with the quantity of the steam by a manual operation, etc., outputs a change rate 47 in accordance with the set value, and outputs the flow rate Bn by a ratio calculation after the dead time 58. The opening degree Cn is outputted according to the characteristic of the control valve in accordance with said flow rate.
TAKADA TOSHIHIRO
SETO TETSUHIKO
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