Method for starting a grinding tube

Abstract

A method for starting a grinding tube with an assigned drive device, wherein during the operation of the grinding tube a grinding mode and a charge release mode can be set such that a particularly reliable monitoring of the state of charge located in the grinding tube is ensured, where the grinding tube is rotated and, at a first rotational angle, a first actual torque is detected, a setpoint torque is calculated for a second, relatively large rotational angle based on the first actual torque, an actually occurring, second actual torque is detected when the second rotational angle is reached, an investigation is performed to determine the difference of the second actual torque from the setpoint torque, and the charge release mode of the grinding tube is set when the second actual torque is within the threshold range, otherwise the grinding tube is operated in the grinding mode.

Claims

1. A method for starting a grinding tube from a standstill state of the grinding tube, said grinding tube including a drive apparatus, the method comprising: rotating the grinding tube and, at a first angle of rotation, acquiring a first actual torque; calculating, based on the acquired first actual torque, a target torque for a second, greater angle of rotation; acquiring an effective second actual torque when the second angle of rotation is reached; examining an extent by which the second actual torque deviates from the target torque and comparing the deviation to a predefined threshold range; setting a charge release mode of the grinding tube when the second actual torque lies within the threshold range; and operating the grinding tube in grinding mode when the second actual torque lies outside the threshold range.

2. The method as claimed in claim 1, wherein a sine of the first angle of rotation and the sine of the second angle of rotation comprising a ratio of the sine of the first angle of rotation to the sine of the second angle of rotation is utilized to calculate the target torque.

3. The method as claimed in claim 1, wherein a quotient is formed from the second actual torque and the target torque.

4. The method as claimed in claim 1, wherein the threshold range is defined by a value specified as a percentage or as a rational number.

5. The method as claimed in claim 4, wherein the threshold range is defined as a deviation of the second actual torque from the target torque by 15%.

6. The method as claimed in claim 4, wherein the threshold range is defined as a deviation of the second actual torque from the target torque by 10%.

7. The method as claimed in claim 4, wherein the threshold range is defined as a deviation of the second actual torque from the target torque by 5%.

8. The method as claimed in claim 1, wherein the first and the second angles of rotation lie below 90.

9. The method as claimed in claim 1, wherein the first and the second angles of rotation lie below 70.

10. A tube mill, comprising: a grinding tube; a drive apparatus; and a control apparatus for the drive apparatus of the grinding tube, the control apparatus comprising: a processor including memory; wherein the control apparatus, starting from a standstill state of the grinding tube, is configured to: cause the drive apparatus to rotate the grinding tube and, at a first angle of rotation, acquire a first actual torque; calculate, based on the acquired first actual torque, a target torque for a second, greater angle of rotation; acquire an effective second actual torque when the second angle of rotation is reached; examine an extent by which the second actual torque deviates from the target torque and compare the deviation to a predefined threshold range; set a charge release mode of the grinding tube when the second actual torque lies within the threshold range; and operate the grinding tube in grinding mode when the second actual torque lies outside the threshold range.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An exemplary embodiment of the invention will be described in greater detail with reference to the drawings, in which:

(2) FIG. 1 shows a schematic and greatly simplified diagram of a grinding tube in four different angles of rotation in accordance with the invention;

(3) FIG. 2 shows an evaluation of the torque of the grinding tube in accordance with FIG. 1 as a function of an angle of rotation; and

(4) FIG. 3 is a flowchart of the method in accordance with the invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

(5) The same reference characters have the same meaning in the figures.

(6) In FIG. 1, a grinding tube 2 of a tube mill not shown in more detail here is represented symbolically. Allocated to the grinding tube 2 is a drive apparatus 3 with a control apparatus 4 including a processor and memory, which actuates inter alia the starting of the grinding tube 2. The grinding tube 2 is charged with a grinding product 6, in particular ore, which is furthermore referred to as charge.

(7) The grinding tube 2 can be operated both in a grinding mode and also in a charge release mode. The grinding mode represents the normal operation of a tube mill, in which the grinding tube 2 is rotated in view of crushing or pulverizing the charge. The charge release mode is the operating state of the tube mill in which, if a frozen charge is detected, measures for removing the frozen charge from the interior wall of the grinding tube are initiated.

(8) In FIG. 1, a total of four states of the charge 6 of the grinding tube 2 are shown according to angle of rotation. Z.sub.1 represents a standstill state at 0, in which the charge 6 is evenly distributed on the bottom on the grinding tube 2. Z.sub.4 represents the position of the caked-on charge at an angle of rotation of approx. 70. Z.sub.2 and Z.sub.3 represent the caked-on charge 6 at two further angles of rotation .sub.1, .sub.2 between 0 and 70.

(9) Starting from the standstill state Z.sub.1, the operation of the tube mill is commenced and the grinding tube 2 is driven in the direction of rotation 10, in that it is rotated about a central axis A. At a first angle of rotation .sub.1, which is smaller than 90, for example at 45, a torque T of the drive apparatus 3 is measured. This point is represented by M1 in FIG. 1. At a second angle of rotation .sub.2, e.g. 60, the torque T is measured again at point M2. The measurements can also occur at other angles of rotation D between 0 and 90; only at least two measured values at two different angles of rotation are required.

(10) The evaluation of the measurements at the measurement points M1 and M2 is shown graphically in FIG. 2. In this context, the torque T of the drive apparatus 3 is plotted as a function of the angle of rotation D. V.sub.1 refers to the increase in the torque T with a frozen charge. V.sub.2 is the effective course of the torque T when starting the tube mill. M refers to the maximum torque that is occurring.

(11) Within region B, which is used in the prior art for monitoring the frozen charge, lies in the exemplary embodiment shown, a minimum deviation of the effective course V.sub.2 of the torque T from the maximum torque M. Here, the course V.sub.2 has no pronounced torque peaks. At this point, conventional monitoring systems would thus regularly initiate the charge release mode.

(12) In order to avoid this, the torque T at the measurement points M1 and M2 is determined at .sub.1 and .sub.2, respectively. With caked-on grinding product 6, the torque T largely increases according to a sine of the angle of rotation D, as evident from the course of V.sub.1. It is therefore possible to determine from the torque T1 at the first angle of rotation (measurement M1), using the relationship:
sin(.sub.1)/sin(.sub.2),Eq. 1
the theoretical target torque T.sub.2TARGET at the point in time M2 at angle of rotation .sub.2.

(13) The effective torque T.sub.2ACTUAL at the measurement point M2 at .sub.2 is additionally measured and compared with T.sub.2TARGET, by making use of a threshold range 8. In the exemplary illustrated embodiment, the threshold range is defined as 10%, i.e., it is examined whether T.sub.2ACTUAL deviates more than 10% from T.sub.2TARGET. If T.sub.2ACTUAL is more than 10% below T.sub.2TARGET or is equal to T.sub.2TARGET, it should be assumed that the material has come loose from the interior wall of the grinding tube 2 and the tube mill is continued to be operated without faults. Otherwise, for example, the charge release mode is set, in particular the tube mill is shut down or use is made of a controlled rattling or shaking of the grinding tube 2 by way of adapting the drive torque.

(14) To compare T.sub.2TARGET with T.sub.2ACTUAL, the threshold range 8 is stored in the controller 4 or use is made thereof on demand in a case-related manner. For the evaluation, in particular, the quotient of T.sub.2ACTUAL and T.sub.2TARGET is formed and this is compared with the threshold range 8. In the above exemplary embodiment, in which the deviation boundary is defined at 10%, the condition for initiating the charge release mode is fulfilled when
T.sub.2ACTUAL<T.sub.2TARGET0.9. Eq. 2
As
T.sub.2TARGET=T.sub.1(sin((.sub.1)/sin(.sub.2)), Eq. 3
the following applies:
T.sub.2ACTUAL<T.sub.1(sin(.sub.1)/sin(.sub.2))0.9. Eq. 4

(15) With the angles of rotation .sub.1=45 and .sub.2=60 used in accordance with FIG. 1, the condition for the charge release mode can thus be expressed mathematically by:
T.sub.2ACTUAL<T.sub.11.1. Eq. 5

(16) If T.sub.2ACTUAL is equal to or greater than T.sub.2TARGET by 10%, however, then the normal grinding mode is continued.

(17) FIG. 3 is a flowchart of the method for starting a grinding tube 2 with an allocated drive apparatus 3, where a grinding mode and a charge release mode of during operation of the grinding tube 2 can be set. Starting from a standstill state of the grinding tube 2 the method comprises rotating the grinding tube 2 and, at a first angle of rotation .sub.1, acquiring a first actual torque T.sub.1, as indicated in step 310.

(18) Next, a target torque T.sub.2TARGET for a second, greater angle of rotation .sub.2 is calculated based on the acquired first actual torque T.sub.1, as indicated in step 320.

(19) Next, an effective second actual torque T.sub.2ACTUAL is acquired when the second angle of rotation .sub.2 is reached, as indicated in step 330.

(20) Next, examining an extent by which the second actual torque T.sub.2ACTUAL deviates from the target torque T.sub.2TARGET is examined while being aided by a predefined threshold range 8, as indicated in step 340.

(21) Next, a charge release mode of the grinding tube 2 is set when the second actual torque T.sub.2ACTUAL lies within the threshold range 8, as indicated in step 350.

(22) Next, the grinding tube 2 in grinding mode is operated when the second actual torque T.sub.2ACTUAL lies outside the threshold range 8, as indicated in step 360.

(23) Thus, while there have been shown, described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.