The invention relates to a method for operating an electrode equipment assembly of an electric arc furnace as defined in the preamble of independent claim 1.

The invention also relates to an electrode equipment assembly of an electric arc furnace as defined in the preamble of independent claim 14.

A majority of electrodes used in electric arc furnaces are self-baking electrodes, so called

Soderberg electrodes. A self-baking electrode in a DC electric arc furnace consists of an electrode casing extending from the top of the electrode to below the electrode contact shoes in the electric arc furnace, and of an electrode portion, which initially consists of a carbon based paste sections in the electrode casing and which is baked by electric current into an electrically conductive solid cylindrical form in the lower portion of the electrode casing. The carbon based paste sections are connected to each other to form the electrode portion by a male joint section at one end of a carbon based paste section and by female joint section at the opposite end of a carbon based paste section. Electrical current is connected between three-phase electrode tips, and an arc is formed between the electrodes will consume the baked electrode. The electrode is held in place by a slipping device, which allows controlled displacement of the electrode.

A slipping device generally consist of a upper gripping ring and of a lower gripping ting, which are sequentially opened and moved to extend the electrode as the tip of the electrode is consumed in use of the electric arc furnace. The upper gripping ring and the lower gripping ring are connected with hydraulic cylinders that enable relative movement between the upper gripping ring and the lower gripping ring. This action enables slipping of the electrode portion through of the electrode casing whilst always maintaining a positive grip on the casing.

A problem is however that the electrode portion is more fragile at the ends of the carbon based paste sections the electrode portion is assembled of because of the male joint section and correspondingly of the female joint section.

Objective of the invention

The object of the invention is to provide a method for operating an electrode equipment assembly of an electric arc furnace, an electrode equipment assembly of an electric arc furnace, and an electric arc furnace to solve the above-identified problem.

Short description of the invention

The method for operating an electrode equipment assembly of an electric arc furnace of the invention is characterized by the definitions of independent claim 1. Preferred embodiments of the method are defined in the dependent claims 2 to 13.

The electrode equipment assembly of an electric arc furnace of the invention is correspondingly characterized by the definitions of independent claim 14.

Preferred embodiments of the electrode equipment assembly are defined in the dependent claims 15 to 29.

List of figures

In the following the invention will described in more detail by referring to the figures, of which

Figure 1 shows in partly cut view part of an AC electric arc furnace,

Figure 2 shows a part of an electrode equipment assembly of an electric arc furnace, Figure 3 shows in partly cut view parts of a DC electric arc furnace

Figure 4 shows in side view an electrode equipment assembly in a first position,

Figure 5 shows in side view the electrode shown in figure 4 in a second position, Figure 6 shows in side view the electrode equipment assembly shown in figure 4 in a third position,

Figure 7 shows in side view the electrode equipment assembly shown in figure 4 in a fourth position,

Figure 8 shows in side view the electrode equipment assembly shown in figure 4 in a fifth position,

Figure 9 shows in side view the electrode equipment assembly of the AC electric arc furnace shown in figure 1 in a first position,

Figure 10 shows in side view the electrode equipment assembly of the AC electric arc furnace shown in figure 1 in a second position,

Figure 11 shows in side view the electrode equipment assembly of the AC electric arc furnace shown in figure 1 in a third position,

Figure 12 shows in side view the electrode equipment assembly of the AC electric arc furnace shown in figure 1 in a fourth position,

Figure 13 shows in side view the electrode equipment assembly of the AC electric arc furnace shown in figure 1 in a fifth position,

Figure 14 shows in side view the electrode equipment assembly of the AC electric arc furnace shown in figure 1 in a sixth position,

Figure 15 shows a detail of embodiment of an electrode equipment assembly, and

Figure 16 shows the electrode equipment assembly shown in figure 2 in side view.

Detailed description of the invention

First the method for operating an electrode equipment assembly 1 of an electric arc furnace 2 and some embodiments and variants of the method will be described in greater detail. The electrode equipment assembly 1 comprises an electrode portion 6, which comprises a carbon based paste rod 8 formed by carbon based paste sections 9 connected together by joint sections 10 at the ends of the carbon based paste sections 9 so that connection sections 11 are formed in the carbon based paste rod 8 at the joint sections 10.

The method comprises the following steps, which are not necessarily performed in the order presented here:

a first moving step for moving a first electrode portion gripping ring 13 with respect to the carbon based paste rod 8 into a first gripping position with first moving means 21,

a first gripping step for bringing first gripping means 12 of the first electrode portion gripping ring 13 into pressure contact with the carbon based paste rod 8 at said first gripping position,

a second moving step for moving the carbon based paste rod 8 with the first moving means 21, while the first gripping means 12 of the first electrode portion gripping ring 13 are in pressure contact with the carbon based paste rod 8 at said first gripping position

a first releasing step for releasing first gripping means 12 of the first electrode portion gripping ring 13 from pressure contact with the carbon based paste rod 8 at said first gripping position,

a third moving step for moving a second electrode portion gripping ring 15 and the carbon based paste rod 8 with respect to each other into a second gripping position,

a second gripping step for bringing second gripping means 14 of the second electrode portion gripping ring 15 into pressure contact with the carbon based paste rod 8 at said second gripping position, and

a second releasing step for releasing second gripping means 14 of the second electrode portion gripping ring 15 from pressure contact with the carbon based paste rod 8 at said second gripping position.

The method comprises providing a detection means 16 for detecting connection sections 11 in the carbon based paste rod 8. The detection means 16 can comprise a photocell device or a similar device capable of visually detecting connection sections 11.

The method comprises functionally connecting the detection means 16 with the first moving means 21.

The method comprises moving the first electrode portion gripping ring 13 in the first moving step with respect to the carbon based paste rod 8 with the first moving means 21 into a first gripping position, which is outside any connection sections 11.

The method comprises moving the second electrode portion gripping ring 15 and the carbon based paste rod 8 with respect to each other in the third moving step into a second gripping position, which is outside any connection sections 11.

The electrode equipment assembly 1 comprises preferably, but not necessarily, supporting means 7 configured to support the electrode portion 6 with respect to the electric arc furnace 2. The supporting means 7 may be configured to support the electrode portion 6 with respect to the electric arc furnace 2 at the electric arc furnace 2 and/or at a structure (not shown in the figures) that is not part of the electric arc furnace 2. The method can comprise moving the second electrode portion gripping ring 15 and the carbon based paste rod 8 with respect to each other into the second gripping position in the third moving step with the first moving means 21.

The method can comprise moving the second electrode portion gripping ring 15 and the carbon based paste rod 8 with respect to each other into the second gripping position in the third moving step with second moving means 22. In such case, the method comprises functionally connecting the detection means 16 with the second moving means 22. In such case the method comprises a fourth moving step for moving the carbon based paste rod 8 with the second moving means 22.

If the method comprises a first moving step and a third moving step, the method can comprise a first holding step for holding the carbon based paste rod 8 with the first gripping means 12 of the first electrode portion gripping ring 3, wherein the first holding step is performed between the first gripping step and the first releasing step, and a second holding step for holding the carbon based paste rod 8 with the second gripping means 14 of the second electrode portion gripping ring 15, wherein the second holding step is performed between the second gripping step and the second releasing step. If the method comprises such first holding step and such second holding step, the first moving step may be performed during the second holding step, and the third moving step may be performed during the first holding step.

If the method comprises a second moving step and a fourth moving step, the second moving step and the fourth moving step are preferably performed simultaneously and at equal speed and for an equal period of time so as not to break the carbon based paste rod 8.

In case the electric arc furnace 2 is an AC electric arc furnace, the electrode equipment assembly 1 comprises an electrode casing 3 having an upper end 4 and a lower end 5, and electrode contact shoes 28 surrounding the electrode casing 3. In such case the electrode portion 6 is arranged in the electrode casing 3 and extending from the lower end 5 of the electrode casing 3, as is shown for example in figures 4 to 16.

In case the electric arc furnace 2 is an AC electric arc furnace, the method can comprise: a fifth moving step for moving a first electrode casing gripping ring 18 with respect to the furnace space 26 of the electric arc furnace 2 into a third gripping position with third moving means 23,

a third gripping step for bringing third gripping means 17 of the first electrode casing gripping ring 18 into pressure contact with the electrode casing 3 at said third gripping position, a sixth moving step for moving the electrode casing 3 with the third moving means 23 with respect to a furnace space 26 of the electric arc furnace 2, while the third gripping means 17 of the first electrode casing gripping ring 18 are in pressure contact with the electrode casing 3 at said third gripping position,

a third releasing step for releasing the third gripping means 17 of the first electrode casing gripping ring 18 from pressure contact with the electrode casing 3 at said third gripping position,

a seventh moving step for moving a second electrode casing gripping ring 20 and the electrode casing 3 with respect to each other into a fourth gripping position,

a fourth gripping step for bringing third gripping means 19 of the second electrode casing gripping ring 20 into pressure contact with the electrode casing 3 at said fourth gripping position, and

a fourth releasing step for releasing the third gripping means 17 of the first electrode casing gripping ring 18 from pressure contact with the electrode casing 3 at said fourth gripping position.

In case the electric arc furnace 2 is an AC electric arc furnace and in case the method comprises the steps described above, the method can comprise moving the second electrode casing gripping ring 20 and the electrode casing 3 with respect to each other in the seventh moving step into the fourth gripping position with the third moving means 23.

In case the electric arc furnace 2 is an AC electric arc furnace and in case the method comprises the steps described above, the method can comprise moving the second electrode casing gripping ring 20 and the electrode casing 3 with respect to each other in the seventh moving step into the fourth gripping position with a fourth moving means 24, and the method can comprise an eight moving step for moving the electrode casing 3 with the fourth moving means 24 with respect to the furnace space 26 of the electric arc furnace 2.

In case the electric arc furnace 2 is an AC electric arc furnace and in case the method comprises a fifth moving step and an seventh moving step as described above, the method can comprise a third holding step for holding the electrode casing 3 with the third gripping means 17 of the first electrode casing gripping ring 18, wherein the third holding step is performed between the third gripping step and the third releasing step, and a fourth holding step for holding the electrode casing 3 with the third gripping means 19 of the second electrode casing gripping ring 20, wherein the fourth holding step is performed between the fourth gripping step and the fourth releasing step. In such case the fifth moving step may be performed during the second holding step, and the seventh moving step may be performed during the first holding step.

In case the electric arc furnace 2 is an AC electric arc furnace and in case the method comprises a sixth moving step and an eight moving step as described above, the sixth moving step and the eight moving step are preferably, but not necessarily, simultaneously and at the same speed and for an equal period of time.

The method comprises preferably, but not necessarily, providing the carbon based paste sections 9 at the connection sections 11 with markings configured to co-operate with the detection means 16.

Next the electrode equipment assembly 1 of an electric arc furnace 2 and some embodiments and variants of the electrode equipment assembly 1 will be described in greater detail.

The electrode equipment assembly 1 comprises an electrode portion 6, which comprises a carbon based paste rod 8 formed by carbon based paste sections 9 connected together by joint sections 10 at the ends of the carbon based paste sections 9 so that connection sections 11 are formed in the carbon based paste rod 8 at the joint sections 10.

The electrode equipment assembly 1 comprises a first electrode portion gripping ring 13 comprising first gripping means 12, which can be forced into pressure contact with the carbon based paste rod 8 at first claiming positions and which can be released from pressure contact with the carbon based paste rod 8 at first claiming positions.

The electrode equipment assembly 1 comprises a second electrode portion gripping ring 15 comprising second gripping means 14, which can be forced into pressure contact with the carbon based paste rod 8 at second claiming positions and which can be released from pressure contact with the carbon based paste rod 8 at second claiming positions.

The electrode equipment assembly 1 comprises first moving means 21 configured to move the first electrode portion gripping ring 13 into first gripping positions selectively with respect to at least one of the electrode casing 3 and the second electrode portion gripping ring 15.

The electrode equipment assembly 1 comprises a detection means 16 for detecting connection sections 11 in the carbon based paste rod 8. The detection means 16 can comprise a photocell device or a similar device capable of visually detecting connection sections 11.

The detection means 16 are functionally connected to the first moving means 21 and the first moving means 21 are configured to move the first electrode portion gripping ring 13 into first gripping positions, which are outside any connection sections 11 in the carbon based paste rod 8.

The electrode equipment assembly 1 comprises preferably, but not necessarily, supporting means 7 configured to support the electrode portion 6 with respect to the electric arc furnace 2. The supporting means 7 may be configured to support the electrode portion 6 with respect to the electric arc furnace 2 at the electric arc furnace 2 and/or at a structure (not shown in the figures) that is not part of the electric arc furnace 2.

The first moving means 21 may be configured to move the carbon based paste rod 8 into said second claiming positions selectively with respect to at least one of the electrode casing 3 and the first electrode portion gripping ring 13.

Alternatively, the second moving means 22 may be configured to move the second electrode portion gripping ring 15 into said second gripping positions selectively with respect to at least one of the electrode casing 3 and the first electrode portion gripping ring 13. In this embodiment, the detection means 16 are functionally connected to the second moving means 22 and by the second moving means 22 are configured to move the second electrode portion gripping ring 15 into second gripping positions, which are outside any connection sections 11 in the carbon based paste rod 8.

In case the electrode equipment assembly 1 comprises a first moving means 21 and a second moving means 22 as described, the first moving means 21 are preferably, but not necessarily, configured to move the first electrode portion gripping ring 13 with respect to the second electrode portion gripping ring 15 when the second gripping means 14 of the second electrode portion gripping ring 15 are forced into pressure contact with the carbon based paste rod 8 and when the first gripping means 12 of the first electrode portion gripping ring 13 are released from pressure contact with the carbon based paste rod 8, and the second moving means 22 are preferably, but not necessarily, configured to move the second electrode portion gripping ring 15 with respect to the first electrode portion gripping ring 15 when the first gripping means 12 of the first electrode portion gripping ring 13 are forced into pressure contact with the carbon based paste rod 8 and when the second gripping means 14 of the second electrode portion gripping ring 15 are released from pressure contact with the carbon based paste rod 8.

In case the electrode equipment assembly 1 comprises a first moving means 21 and a second moving means 22 as described, the first moving means 21 and the second moving means 22 are preferably, but not necessarily, configured to together move the carbon based paste rod 8 with respect to the electrode casing 3 at a same speed and for an equal period of time when the first gripping means 12 of the first electrode portion gripping ring 13 are forced into pressure contact with the carbon based paste rod 8 and when the second gripping means 14 of the second electrode portion gripping ring 15 are forced into pressure contact with the carbon based paste rod 8.

In case the electric arc furnace 2 is an AC electric arc furnace, the electrode equipment assembly 1 comprises an electrode casing 3 having an upper end 4 and a lower end 5, and electrode contact shoes 28 surrounding the electrode casing 3, and the electrode portion 6 is arranged in the electrode casing 3 and extending from the lower end 5 of the electrode casing 3.

In case the electric arc furnace 2 is an AC electric arc furnace as described, the electrode equipment assembly 1 comprises preferably, but not necessarily:

a first electrode casing gripping ring 18 comprising third gripping means 17, which can be forced into pressure contact with the electrode casing 3 at third gripping positions and which can be released from pressure contact with the electrode casing 3 at third gripping positions, a second electrode casing gripping ring 20 comprising fourth gripping means 19, which can be forced into pressure contact with the electrode casing 3 at fourth gripping positions and which can be released from pressure contact with the electrode casing 3 at fourth gripping positions, and

third moving means 23 configured to move the first electrode casing gripping ring 18 into third gripping positions with respect to the a furnace space 26 of the electric arc furnace 2. If he electrode equipment assembly 1 comprises a first electrode casing gripping ring 18, a second electrode casing gripping ring 20, and third moving means 23 as described, the third moving means 23 may additionally be configured to move the electrode casing 3 with respect to the second electrode casing gripping ring 20 into said fourth gripping positions.

If the electrode equipment assembly 1 comprises a first electrode casing gripping ring 18, second electrode casing gripping ring 20, and third moving means 23 as described, the electrode equipment assembly 1 can comprise fourth moving means 24 configured to move the second electrode casing gripping ring 20 into said fourth gripping positions with respect to the a furnace space 26 of the electric arc furnace 2.

If the electrode equipment assembly 1 comprises third moving means 23 and a fourth moving means 24 as described, the fourth moving means 24 may be configured to move the second electrode casing gripping ring 20 with respect to the first electrode casing gripping ring 18 when the third gripping means 17 of the first electrode casing gripping ring 18 are forced into pressure contact with the electrode casing 3 and when the fourth gripping means 19 of the second electrode casing gripping ring 20 are released from pressure contact with the electrode casing 3, and the third moving means 23 may be configured to move the first electrode casing gripping ring 18 with respect to the second electrode casing gripping ring 20 when the fourth gripping means 19 of the second electrode casing gripping ring 20 are forced into pressure contact with the electrode casing 3 and when the third gripping means 17 of the first electrode casing gripping ring 18 are released from pressure contact with the electrode casing 3.

If the electrode equipment assembly 1 comprises third moving means 23 and a fourth moving means 24 as described, the third moving means 23 and the fourth moving means 24 are preferably, but not necessarily, configured to together move the electrode casing 3 with respect to the furnace space 26 of the electric arc furnace 2 when the third gripping means 17 of the first electrode casing gripping ring 18 are forced into pressure contact with the electrode casing 3 and when the third gripping means 19 of the second electrode casing gripping ring 20 are forced into pressure contact with the electrode casing 3.

The carbon based paste sections 9 are preferably, but not necessarily, at the connection sections 11 provided with markings configured to co-operate with the detection means 16.

The second electrode portion gripping ring 15 and the first electrode casing gripping ring 18 can be arranged at a first frame means 29 that is movable arranged with respect to a second frame means 30 at which the first electrode portion gripping ring 13 and the second electrode casing gripping ring 20 are arranged, as is shown in figures 4 to 8. In figures 4 to 8, the second electrode portion gripping ring 15 is attached to the first frame means 29 by means of the second moving means 22 and the first electrode portion gripping ring 13 is attached to the second frame means 30 by means of the first moving means 21.

In the electrode equipment assembly 1 first electrode casing gripping ring 18 and the second electrode portion gripping ring 15 can be configured to move simultaneously.

In the electrode equipment assembly 1 the possible first electrode casing gripping ring 18 and the second electrode portion gripping ring 15 can be configured to move simultaneously by means of the possible second moving means 22.

In the electrode equipment assembly 1 the first electrode portion gripping ring 13 and the first moving means 21 can be configured to move simultaneously with the optional fourth moving means 24.

Next the function of the electrode equipment assembly shown in figures 4 to 8 will be described:

In figure 4 the second electrode portion gripping ring 15 is moved by the second moving means 21 into a second gripping position in a third moving step.

Figure 5 shows the situation after figure 4. Figure 5 shows the second moving step for moving the carbon based rod 8 with the first moving means 21 and the fourth moving step for moving the carbon based rod 8 with the second moving means 22, which second moving step and fourth moving step are in figure 5 performed simultaneously.

Figure 6 shows the situation after figure 5. In figure 6 the first portion gripping ring 13 is moved by the first moving means 21 into a first gripping position in a first moving step.

After the situation illustrated in figure 6, the steps shown in figures 4 and 5 can be repeated.

Figures 7 to 8 shows moving of the electrode casing 3.

In figure 7 the first electrode casing gripping ring 18 is moved in a fifth moving step by means of third moving means 23.

Figure 8 shows the situation after figure 7. In figure 8, the electrode casing 3 is moved together with the carbon based rod 8.

Next the function of the electrode equipment assembly shown in figures 9 to 14 will be described:

In figure 9 the second electrode portion gripping ring 15 is moved by the second moving means 22 into a second gripping position in a third moving step at the same time as the first gripping means 12 of the first electrode portion gripping ring 12 are in pressure contact with the carbon based paste rod 8 in a first gripping position.

Figure 10 shows the situation after figure 9. In figure 10 the second gripping means 14 of the second electrode portion gripping ring 15 are brought into pressure contact with the carbon based paste rod 8 a second gripping step in a second gripping position.

Figure 11 shows the situation after figure 10. In figure 11, the second moving step for moving the carbon based rod 8 with the first moving means 21 and the fourth moving step for moving the carbon based rod 8 with the second moving means 22 is performed simultaneously. After the situation illustrated in figure 11, the steps shown in figures 9 and 10 can be repeated.

Figures 12 to 14 shows moving of the electrode casing 3. In figure 12 the first electrode casing gripping ring 18 is moved with respect to the electrode casing 3 by means of third moving means 23 in a fifth moving step.

Figure 13 shows the situation after figure 12. In figure 13 a third gripping step is performed for binging third gripping means of the first electrode casing clamping ring 18 into pressure contact with the electrode casing 3 at a third gripping position.

Figure 14 shows the situation after figure 13. In figure 14 the electrode casing 3 is moved by moving the first electrode casing clamping ring 18 with the third moving means 23 to move the electrode casing 3.

It is apparent to a person skilled in the art that as technology advanced, the basic idea of the invention can be implemented in various ways. The invention and its embodiments presented in the description and in the figures are therefore not restricted to the above examples, but they may vary within the scope of the claims.