US 4,303,205 A · Agitator mill and method of controlling the same

An agitator mill suitable for treating a liquid including material particles, the agitator mill comprising a milling vessel containing a plurality of freely movable milling bodies and having inlet and outlet means for said liquid, a controllable feed pump for supplying said liquid, a stirrer mechanism having a rotor located within the milling vessel, an electric stirrer motor for driving said stirrer mechanism and a cooling system for the throughflow of coolant to cool the liquid in said vessel, there being further provided a primary control circuit for controlling the stirrer motor current, said primary control circuit including means for comparing the actual value of said stirrer motor current with a desired value thereof and means for adjusting at least one of the speed of the feed pump and the number of milling bodies within the working volume of the milling vessel, whereby to readjust said actual value of the current to a value substantially equal to said desired value thereof, and a secondary control circuit for controlling the temperature of the liquid in the milling vessel, said secondary control circuit including a temperature controller for comparing the actual temperature of the liquid in the milling vessel with a desired temperature thereof and for adjusting said cooling system to increase the cooling when too high an actual temperature is present and to decrease the cooling when two low an actual temperature is present.

A method of controlling an agitator mill of the type used for treating a liquid including material particles and comprising a milling vessel having a working volume therein, said vessel containing a plurality of freely movable milling bodies, inlet and outlet means for admitting the liquid to and allowing the liquid to leave the milling vessel, a controllable feed pump for supplying the liquid, a stirrer mechanism located within the milling vessel, an electric stirrer motor for driving the stirrer mechanism, a cooling system for providing a throughflow of coolant, and a volume controller for varying the total volume of the milling vessel, said total volume being related directly to the number of milling bodies within the working volume of the milling vessel, the method comprising the following steps:

(a) monitoring the difference between the actual total volume and the desired total volume of the milling vessel and adjusting the volume controller in response to said monitored difference value whereby to hold the total volume of the milling vessel substantially constant,
(b) monitoring the difference between the actual and the desired values of said stirrer motor current and adjusting the throughput of the controllable pump in response to the difference between said actual and desired values of the stirrer motor current whereby to correct for deviations of said stirrer motor current to hold the stirrer motor current substantially constant,
(c) simultaneously monitoring the difference between the actual and desired values of the temperature in the milling vessel and adjusting the cooling of the milling vessel to hold the actual temperature substantially constant at said desired temperature and
(d) detecting when said actual temperature rises substantially above said desired temperature and, when such a condition occurs, overriding the adjustment made in (step b) to readjust the throughput of the pump and to restore said actual temperature to said desired temperature.

1 more element

A method of controlling an agitator mill of the type used for treating a liquid including material particles and comprising a milling vessel having a working volume therein, said vessel containing a plurality of freely movable milling bodies, inlet and outlet means for admitting the liquid to and allowing the liquid to leave the milling vessel, a controllable feed pump for supplying the liquid, a stirrer mechanism located within the milling vessel, an electric stirrer motor for driving the stirrer mechanism, a cooling system for providing a throughflow of coolant, and a volume controller for varying the total volume of the milling vessel, said total volume being related directly to the number of milling bodies within the working volume of the milling vessel, the method comprising the following steps:

(a) monitoring the difference between the actual throughput of the pump and the desired throughput of the pump and adjusting the throughput of the pump in response to said monitored difference to hold the throughput of the pump substantially constant,
(b) monitoring the difference between the actual and desired values of the stirrer motor current and adjusting the volume controller to correct for deviations of the actual stirrer motor current from the desired value,
(c) monitoring the difference between the actual and desired operating temperature of the mill and controlling the throughflow of coolant in response to said monitored difference whereby to hold the operating temperature of the mill substantially constant, and
(d) detecting when the actual operating temperature of the mill exceeds said desired operating temperature of the mill and overriding the signal from step (b) to adjust the volume controller to restore said actual temperature of said desired temperature.

1 more element

A method of controlling an agitator mill of the type used for treating a liquid including material particles and comprising a milling vessel having a working volume therein, said vessel containing a plurality of freely movable milling bodies, inlet and outlet means for admitting the liquid to and allowing the liquid to leave the milling vessel, a feed pump for supplying the liquid, a feed pump speed controller for controlling the flowrate of liquid, a stirrer mechanism located within the working volume of the milling vessel, an electric stirrer motor for driving the stirrer mechanism, a cooling system for providing a throughflow of coolant, and a volume controller for varying the total volume of the milling vessel, said total volume being related directly to the number of milling bodies within the working volume of the milling vessel, the method comprising the following steps:

(a) monitoring the difference between the actual and the desired values of the stirrer motor current,
(b) deriving a control signal related to the difference between the actual stirrer motor current and the desired value,
(c) passing said signal to the feed pump speed controller whereby to adjust the flowrate of the pump and to correct for deviations of said stirrer motor current from said desired value,
(d) monitoring the difference between the actual and desired total volume of the milling vessel and adjusting the volume controller to hold said total volume substantially constant,
(e) detecting when the value of the stirrer motor current substantially exceeds the desired value thereof,
(f) overriding the adjustment made in step (d) to increase the total volume and thus reduce the number of milling bodies in the working volume and thus to hold the stirrer motor current substantially constant when the condition in step (e) exists,
(g) monitoring the difference between the actual and desired values of the operating temperature of the mill and controlling the cooling of the milling vessel to hold the actual operating temperature of the mill substantially constant at said desired value,
(h) detecting when the actual operating temperature of the mill substantially exceeds the desired temperature and
(i) overriding the control signal derived from the stirrer motor current until said actual temperature is restored to said desired temperature.

6 more elements

Agitator mill and method of controlling the same

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Agitator mill and method of controlling the same

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Abstract

Claims31