Bath level set point control in an electrolytic cell and method of operating same

A circuit arrangement for controlling the concentration of a material in a molten salt bath in a process for providing molten metal by reduction of the material in the salt bath, the arrangement comprising

• means adapted to sense the height of the salt bath and to develop a signal representative thereof,
• means adapted to sense the density of the salt bath and to develop a signal representative thereof,
• means adapted to sense the volume of the molten metal and to develop a signal representative thereof, and
• a circuit means for receiving said signals and for receiving and storing an initial datum representing a predetermined, desired percent concentration of the material in the bath, said circuit means being further capable of calculating a bath level in response to said signals that will maintain the initial percent concentration of the material in the bath during the time molten metal is being produced and when the molten metal is removed from the bath.

A circuit arrangement for controlling the concentration of aluminum chloride in a molten salt bath of an electrolytic cell adapted to produce aluminum by reduction of the aluminum chloride, the arrangement comprising

• means adapted to sense the height of the molten salt bath in the cell and to develop a signal representative thereof,
• means adapted to sense the density of the molten salt in the cell and to develop a signal representative thereof,
• means adapted to sense the volume of the molten aluminum in the cell and to develop a signal representative thereof, and
• a circuit means for receiving said signals and for receiving and storing an initial datum representing a predetermined, desired percent concentration of the aluminum chloride in the salt bath, said circuit being further capable of calculating a salt bath level in response to said signals that will maintain the predetermined, desired concentration of aluminum chloride during the time the cell is producing aluminum and chlorine and when aluminum is removed from the cell.