Method for determining a lifting angle and method for positioning a grinding mill

Patent metadata

Field	Value
Publication number	US-11007535-B2
Application number	US-201715823685-A
Country	US
Kind code	B2
Filing date	Nov 28, 2017
Priority date	May 28, 2015
Publication date	May 18, 2021
Grant date	May 18, 2021

Abstract

The purpose of the invention to provide a method for determining a lifting angle of a charge inside a grinding mill at a specific point in time and a method for positioning a grinding mill which is more accurate. Method for determining a lifting angle of a charge inside a mill body of a grinding mill being rotatable through a drive train, the method comprises the following steps of rotating the mill body; determining a reference lifting angle and a corresponding reference driving torque of the drive train at a reference point in time; calculating a fill factor for the reference point in time based on the reference lifting angle and the reference driving torque; determining a driving torque of the drive train; and calculating the lifting angle based on the driving torque and the fill factor.

First claim

The invention claimed is:

1. A method for determining a lifting angle (α) of a charge inside a mill body of a grinding mill being rotatable through a drive train, wherein the method comprises the following steps:
a) rotating the mill body;
b) determining a reference lifting angle of the charge and a corresponding reference driving torque of the drive train at a reference point in time, wherein the reference point in time is a point in time where a first cascading of the charge occurs, and wherein determining said reference lifting angle comprises:
analyzing a driving torque as a function of a rotational angle (β) of the mill body, recognizing an angle at which an increase of the driving torque is smaller than a pre-defined increment, and approximating the reference lifting angle to be equal to said angle; or
analyzing the driving torque as a function of the rotational angle (β) of the mill body, identifying a start of oscillations of the driving torque, and approximating the reference lifting angle to be equal to an angle where the oscillations start;

c) calculating a fill factor (K) for the reference point in time based on the reference lifting angle of the charge and the reference driving torque determined according to b);
d) determining a current driving torque (M) of the drive train;
e) calculating the lifting angle (α) based on the current driving torque (M) and the fill factor (K); and
f) positioning the mill body in response to the calculated lifting angle (α).

2. The method according to claim 1 , wherein after the calculation of the fill factor (K) in step (c) the calculation of the lifting angle (α) through the steps (d) and (e) is performed online or in real-time after the reference point in time.

3. The method according to claim 1 , wherein the mill body rotates with a constant rotational speed.

4. The method according to claim 1 , wherein a change of volume of the charge over time is determined and taken into account for the calculation of the fill factor (K) in step (c) and/or for the calculation of the lifting angle (α) in step (e).

5. The method according to claim 4 , wherein the change of volume of the charge over time is determined using a measurement of a volume of a material input to the mill body and a measurement of a volume of a material output from the mill body.

6. The method according to claim 4 , wherein the change of volume of the charge over time is zero.

7. A method for positioning a mill body of a grinding mill at a given rotational angle (βg), the method comprises the following steps:
a) rotating the mill body to a rotational angle (β*);
b) calculating a corresponding lifting angle (α*) for a point in time when the mill body reaches the rotational angle (β*) using a method according to claim 1 ;
c) repeating steps (a) to (b) until the rotational angle (β*) minus the corresponding lifting angle (α*) is equal to the given rotational angle (βg);
d) setting the current driving torque (M) to zero after reaching the rotational angle (β*) that fulfils the condition of step (c).

8. A method for positioning a mill body of a grinding mill at a given rotational angle (β g ), the method comprises the following steps:
a) rotating the mill body to a rotational angle (β*);
b) calculating a corresponding lifting angle (α*) for a point in time when the mill body reaches the rotational angle (β*) using a method according to claim 1 ;
c) repeating steps (a) to (b) until the rotational angle (β*) minus the corresponding lifting angle (α*) is equal to the given rotational angle (β g );
d) rotating back the mill body using the drive train by the amount of the lifting angle (α*) after reaching the rotational angle (β*) that fulfils the condition of step (c).

9. The method according to claim 8 , wherein the drive train is torque controlled while rotating back the mill body and the drive train stops the rotation when the current driving torque (M) reaches zero.

10. The method according to claim 2 , wherein the mill body rotates with a constant rotational speed.

11. The method according to claim 2 , wherein a change of volume of the charge over time is determined and taken into account for the calculation of the fill factor (K) in step (c) and/or for the calculation of the lifting angle (α) in step (e).

12. The method according to claim 3 , wherein a change of volume of the charge over time is determined and taken into account for the calculation of the fill factor (K) in step (c) and/or for the calculation of the lifting angle (α) in step (e).

13. The method according to claim 5 , wherein the change of volume of the charge over time is zero.

14. The method according to claim 11 , wherein the change of volume of the charge over time is determined using a measurement of a volume of a material input to the mill body and a measurement of a volume of a material output from the mill body.

15. The method according to claim 12 , wherein the change of volume of the charge over time is determined using a measurement of a volume of a material input to the mill body and a measurement of a volume of a material output from the mill body.

16. A method for positioning a mill body of a grinding mill at a given rotational angle (βg), the grinding mill being rotatable through a drive train, the method comprising:
a) rotating the mill body;
b) determining a reference lifting angle of a charge inside the mill body and a corresponding reference driving torque of the drive train at a reference point in time, wherein the reference point in time is a point in time where a first cascading of the charge occurs, wherein determining said reference lifting angle comprises:
analyzing a driving torque as a function of a rotational angle (β) of the mill body, recognizing an angle at which an increase of the driving torque is smaller than a pre-defined increment, and approximating the reference lifting angle to be equal to said angle; or
analyzing the driving torque as a function of the rotational angle (β) of the mill body, identifying a start of oscillations of the driving torque, and approximating the reference lifting angle to be equal to an angle where the oscillations start;

c) calculating a fill factor (K) for the reference point in time based on the reference lifting angle of the charge and the reference driving torque determined according to b);
d) rotating the mill body to a rotational angle (β*);
e) calculating a corresponding lifting angle (α*) for a point in time when the mill body reaches the rotational angle (β*) using the following method:
e1) determining a current driving torque (M) of the drive train; and
e2) calculating the corresponding lifting angle (α*) based on the current driving torque (M) and the fill factor (K);

f) repeating steps (d) to (e) until the rotational angle (β*) minus the corresponding lifting angle (α*) is equal to the given rotational angle (βg); and
g) setting the current driving torque (M) to zero after reaching the rotational angle (β*) that fulfils the condition of step (f).

17. A method for positioning a mill body of a grinding mill at a given rotational angle (βg), the grinding mill being rotatable through a drive train, the method comprising:
a) rotating the mill body;
b) determining a reference lifting angle of a charge inside the mill body and a corresponding reference driving torque of the drive train at a reference point in time, wherein the reference point in time is a point in time where a first cascading of the charge occurs, wherein determining said reference lifting angle comprises:
analyzing a driving torque as a f

Assignees

• Abb Schweiz Ag

Inventors

• Pischtschan Martin

Classifications

• G05D3/12

  using feedback · CPC title

• B02C25/00

  Control arrangements specially adapted for crushing or disintegrating · CPC title

• B02C17/1805 Primary

  Monitoring devices for tumbling mills · CPC title

• G05D27/02

  characterised by the use of electric means · CPC title

• B02C17/1825

  Lifting devices (lifting devices associated with the lining for containers B02C17/22) · CPC title