Control system and process for refining metals

Claim 1

A METHOD OF OPERATING A ROTARY REFINING FURNACE COMPRISING THE STEPS OF INTRODUCING A GAS BELOW THE LEVEL OF A MELT IN SAID FURNACE TO PRODUCE AN EXHAUST GAS OF A COMPOSITION WHICH CONSTITUTES AN OUTPUT VARIABLE SUBJECT TO PERIODIC FLUCTUATIONS, SAID OUTPUT VARIABLE RESPONDING WITH A PREDETERMINED TIME LAG TO CHANGES IN AN INPUT VARIABLE DEFINING THE DEPTH AT WHICH SAID GAS IS INTRODUCED INTO SAID MELT, MEASURING SAID OUTPUT VARIABLE DURING A FIRST FLUCTUATION PERIOD WITH SAID INPUT VARIABLE MAINTAINED CONSTANT, STORING THE SO MEASURED VALUES OF SAID OUTPUT VARIABLE FOR AN INTERVAL EQUAL TO ONE WHOLE FLUCTUATION PERIOD LESS THAN A TIME EQUAL TO SAID LAG, PRODUCING AT THE END OF SAID INTERVAL A DELAYED CONTROL SIGNAL FROM THE VALUES SO STORED, CHANGING SAID INPUT VARIABLE IN STEP WITH SAID CONTROL SIGNAL AND IN A SENSE COUNTERACTING SAID FLUCTUATIONS DURING A SECOND FLUCTUATION PERIOD, STORING DURING SAID SECOND PERIOD A FEEDBACK SIGNAL REPRESENTATIVE OF THE CHANGED VALUES OF SAID INPUT VARIABLE WHILE CONTINUING TO MEASURE SAID OUTPUT VARIABLE, STORING THE VALUES THEREOF FOR SAID INTERVAL AND PRODUCING THE DELAYED CONTROL SIGNAL THEREFROM, COMBINING DURING A THIRD FLUCTUATION PERIOD THE DELAYED CONTROL SIGNAL WITH THE FEEDBACK SIGNAL STORED FOR A WHOLE PERIOD, CHANGING SAID INPUT VARIABLE DURING SAID THIRD PERIOD IN STEP WITH THE COMBINED SIGNALS AND CONCURRENTLY STORING THE CHANGED VALUES OF SAID INPUT VARIABLE FOR ANOTHER WHOLE PERIOD, CONTINUING DURING SAID THIRD PERIOD TO MEASURE SAID OUTPUT VARIABLE, STORING THE VALUES THEREOF FOR SAID INTERVAL AND PRODUCING THE DELAYED CONTROL SIGNAL THEREFROM, AND PROCEEDING IN LIKE MANNER DURING SUBSEQUENT PERIODS, THEREBY ELIMINATING THE EFFECT OF SAID LAG.