Method and system for controlling the temperature of ceramic elements in a supporting or wiping strip in a paper production facility, and supporting or wiping strip

Abstract

The temperature of the ceramic elements of a supporting or wiping strip that is assigned to a wire or a felt in a paper production facility, is controlled by guiding a cooling carrier medium or a heating carrier medium through the supporting or wiping strip. For that purpose, the supporting or wiping strip is formed with at least one channel, through which the carrier medium for heat or for cold is pumped.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a device for implementing a first method according to the invention;

FIG. 2 is a schematic illustration of a device for implementing a second method according to the invention;

FIG. 3 is a longitudinal section through a first embodiment of a supporting or wiping strip according to the invention;

FIG. 3A is a section taken along the section line III-III in FIG. 3;

FIG. 4 is a longtidudinal section of a second embodiment of a supporting or wiping strip according to the invention;

FIGS. 4A, 4B, 4C and 4D are sections taken along the line IV-IV in FIG. 4;

FIG. 5 is a longtidudinal section of a third embodiment of a supporting or wiping strip according to the invention;

FIG. 5A is a section taken along the line V-V in FIG. 5;

FIG. 6 is a longitudinal section of a fourth embodiment of a supporting or wiping strip according to the invention;

FIG. 7 is a longtidudinal section of a fifth embodiment of a supporting or wiping strip according to the invention;

FIGS. 7A, 7B, and 7C are sections taken along the line VII-VII in FIG. 7;

FIG. 8 is a longtidudinal section of a sixth embodiment of a supporting or wiping strip according to the invention;

FIGS. 8A and 8B are sections taken along the line VIII-VIII in FIG. 8;

FIG. 9 is a longtidudinal section of a seventh embodiment of a supporting or wiping strip according to the invention;

FIG. 9A is a section taken along the line IX-IX in FIG. 9;

FIG. 10 is a longtidudinal section of a fifth embodiment of a supporting or wiping strip according to the invention;

FIG. 10A is a section taken along the line X-X in FIG. 10; and

FIG. 10B is a section taken along the line XI-XI in FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the figures of the drawing in detail, the temperature control of a supporting or wiping strip 1 will first be explained with reference to FIG. 1. In this case, the supporting or wiping strip 1 comprises a carrier strip 1a having ceramic elements 1b fixed to the latter, the supporting or wiping strip 1 being formed with two channels 11 and 12. At one end of the supporting or wiping strip 1, the ends of the two channels 11 and 12 are adjoined by connecting pipes 13 and 14. At the other end of the supporting or wiping strip 1, the two channels 11 and 12 are connected to each other by way of a piece of pipe 15.

The connecting pipe 13 connects to an output line 23 from a mixing valve 2 to which a carrier medium for cold is fed via a first connecting line 21 and a carrier medium for heat is fed via a second connecting line 22. The connecting pipe 13 or the combination of the pipe 13 and the output line 23 may be referred to as a feed line. By means of a control device 20, the temperature of the carrier medium, or heat exchange medium, discharged by the mixing value 2 via the output line 23 is set to that temperature value which that supporting or wiping strip 1 in the system which is fed with carrier medium via the mixing valve 2 is intended to have.

During operation of the system for paper production, the temperature which a supporting or wiping strip 1 located in a specific region of the system is intended to have is defined. The mixing valve 2 is then set to this temperature. In this way, by means of the carrier medium supplied to the supporting or wiping strip 1 via the output line 23 from the mixing valve 2, this strip 1 is brought to the intended temperature. The carrier medium flowing away from the supporting or wiping strip 1 via the pipe 14 and heated or cooled by said strip is led away via a further line 24, either into a reservoir or into the sewer. The pipe 14 or the combination of the pipe 14 and the line 24 may be referred to as a return line.

Moreover, in the lines 23 and 24 temperature sensors 25 and 26 are provided, by means of which the temperatures of the carrier medium flowing through these lines are registered.

By means of this method, as a rule the temperature of the relevant supporting or wiping strip 1 can be brought close to the intended value.

According to the second method, explained with reference to FIG. 2, the supporting or wiping strip 1 is assigned an intrinsically closed circuit 3 for a carrier medium for heat or cold, wherein there are a reservoir 30 for the carrier medium, a delivery pump 4, a control valve 5, a heating device 6 and a cooling device 7. Also provided is a control unit 8, which is assigned two temperature sensors 81 and 82 located in the circuit 3 and which are used to control the delivery pump 4, the control valve 5, the heating device 6 and the cooling device 7.

The functionality of the device is as follows:

By means of the delivery pump 4, carrier medium for heat or cold is guided via a line 31 to the control valve 5, from which it is conveyed either via a line 32 to the heating device 6 or via a line 34 to the cooling device 7. From the heating device 6 or from the cooling device 7, heated or cooled carrier medium passes via a line 33 or 35 and via the connecting pipe 13 into the channel 11 of the supporting or wiping strip 1 and, and via the piece of pipe 15, into the channel 12. The return flow of the carrier medium takes place via the pipe 14 and the line 36 to the delivery pump 4.

By means of the first temperature sensor 81, located in the line 35, a measurement of the temperature of the carrier medium flowing toward the supporting or wiping strip 1 is carried out and, by means of the temperature sensor 82 located in the line 36, a measurement of the temperature of the medium flowing away from the supporting or wiping strip 1 is carried out. The measured values output by the temperature sensors 81 and 82 are transmitted via control lines 83 and 84 to the control unit 8, from which, via control lines 85, 86, 87 and 88, the delivery pump 4, the control valve 5, the heating device 6 and the cooling device 7 are controlled.

As soon as it is established by the control unit 8 on the basis of the measured value output by the temperature sensor 82 that the temperature existing in the supporting strip 1 must be increased, the control valve 5 is changed to the effect that the carrier medium is fed by means of the delivery pump 4 to the heating device 6, wherein it is heated, whereupon it is led into the channel 11 via the connecting pipe 13. This procedure is maintained until the supporting or wiping strip 1 has the temperature required for the specific operating case. By contrast, if it is established by the control unit 8 that the temperature existing in the supporting or wiping strip 1 must be reduced, the control valve 5 is changed to the effect that the carrier medium is fed by means of the delivery pump 4 to the cooling device 7, wherein it is cooled, whereupon it is likewise led via the connecting pipe 13 into the channel 11.

This procedure is likewise maintained until the supporting or wiping strip 1 has the temperature required for the specific operating case.

Further control with regard to the heating or cooling of the supporting or wiping strip 1 can also be carried out by the output of the delivery pump 4 being raised or lowered by the control unit 8.

If, during the operation of a system for paper production, it is established by the control unit 8 assigned to the supporting or wiping strip 1 that this supporting or wiping strip 1 has a temperature that is too low or too high for the relevant operating case or that too rapid a change in the temperature of this supporting or wiping strip 1 is taking place, as a result of which in each case there is the risk of cracking or fracture of the ceramic elements 1b of this supporting or wiping strip 1, this supporting or wiping strip 1 is supplied with appropriately heated or cooled carrier medium, which means that the ceramic elements 1b are not subjected to any impermissible thermal loadings, so that damage caused by this is avoided.

By means of this second method, irrespective of the particular operating circumstances, largely accurate control of the temperature of the relevant supporting or wiping strip is carried out.

In FIGS. 3 and 3A, FIGS. 4 and 4A to 4D, FIGS. 5 and 5A, FIG. 6, FIGS. 7 and 7A to 7C, FIGS. 8 and 8A, 8B, FIGS. 9 and 9A, FIGS. 10, 10A and 10B, a variety of embodiments of supporting or wiping strips 1 are illustrated. They comprise carrier strips 1a with plates 1b of ceramic material fixed to the latter and which are formed with channels 11 and 12, which pass through these supporting or wiping strips 1 in their longitudinal direction. In this case, these channels can begin at one end of the supporting or wiping strips 1 and end at the other end of the strips 1. As an alternative to this, these channels can begin at one end of the supporting or wiping strips 1 and be led back to this end. Furthermore, these channels can pass through the ceramic plates 1b or be provided in the carrier strip 1a or be located between the ceramic plates 1b and the carrier strip 1a. Moreover, the channels can be formed with different cross sections.

Since the plates 1b of ceramic material have a very low thermal conductivity, the arrangement of the channels within the supporting or wiping strips and the formation of the cross section is of the utmost importance, in order to ensure that, by means of the carrier medium flowing through these, the intended temperature of the plates 1b of ceramic material is achieved in order to prevent them from being damaged by thermal stresses.

The carrier medium used for cold and for heat is in particular water.

Claims

1. A method for controlling a temperature of a ceramic element of a supporting or wiping strip assigned to a wire or a felt in a paper production facility, the method which comprises: providing the supporting or wiping strip with at least one channel; andguiding a carrier medium for heat or for cold through the at least one channel.

2. The method according to claim 1, which comprises providing a line leading to the at least one channel with a mixing valve connected to lines for conducting carrier media for heat and for cold, respectively, and setting a temperature at the mixing valve to a desired temperature of the supporting or wiping strip.

3. The method according to claim 1, which comprises measuring a temperature of the carrier medium with a temperature sensor disposed in a line leading away from the supporting or wiping strip.

4. The method according to claim 1, which comprises measuring a temperature of the carrier medium flowing toward the supporting or wiping strip with a temperature sensor disposed in a line leading to the channel in the supporting or wiping strip.

5. The method according to claim 3, which comprises controlling a temperature of the carrier medium flowing toward the supporting or wiping strip in dependence on the temperature of the carrier medium flowing away from the supporting or wiping strip.

6. The method according to claim 5, which comprises conveying the carrier medium by way of a delivery pump in a closed circuit.

7. The method according to claim 5, which comprises selectively guiding the carrier medium flowing away from the supporting or wiping strip via a heating device or via a cooling device and back to the supporting or wiping strip.

8. The method according to claim 7, which comprises controlling the heating device or the cooling device, respectively, in dependence on the temperature of the carrier medium flowing away from the supporting or wiping strip.

9. The method according to claim 7, which comprises controlling an output of a delivery pump conveying the carrier medium in dependence on the temperature of the carrier medium flowing away from the supporting or wiping strip.

10. The method according to claim 7, which comprises controlling an output of the heating device, an output of the cooling device, and an output of a delivery pump conveying the carrier medium in dependence on the temperature of the carrier medium flowing away from the supporting or wiping strip.

11. The method according to claim 1, which comprises continuously conducting the carrier medium through the supporting or wiping strip.

12. The method according to claim 1, wherein the supporting or wiping strip is formed with ceramic elements and the method comprises conducting the carrier medium continuously through the ceramic elements of the supporting or wiping strip.

13. In a paper production facility, a system for controlling a temperature of a ceramic element of a supporting or wiping strip assigned to a wire or a felt, the system comprising: the supporting or wiping strip having at least one channel formed therein;a feed line communicating with said at least one channel for conducting a carrier medium to the supporting or wiping strip; anda return line communicating with said at least one channel for conducting the carrier medium away from the supporting or wiping strip.

14. The system according to claim 13, which comprises a mixing valve communicating with said feed line for mixing a carrier medium for heat and a carrier medium for cold.

15. The system according to claim 14, which comprises a temperature sensor disposed in at least one of said feed line and/or said return line.

16. The system according to claim 13, which further comprises: a line system having connected therein a delivery pump for the carrier medium, a heating device for heating the carrier medium, and a cooling device for cooling the carrier medium;at least one temperature sensor disposed for determining a temperature of the carrier medium flowing away from the supporting or wiping strip; anda control unit configured to control at least one of said heating device, said cooling device, and said delivery pump.

17. The system according to claim 16, which further comprises at least one temperature sensor disposed to determine a temperature of the carrier medium being supplied to the supporting or wiping strip.

18. A supporting or wiping strip for the system according to claim 13, having at least one channel formed therein for conducting a carrier medium for heat or for cold therethrough.

19. The supporting or wiping strip according to claim 18, which comprises a plurality of ceramic elements defining a supporting surface of said supporting or wiping strip, and wherein said channel passes through said ceramic elements.

20. The supporting or wiping strip according to claim 18, which comprises a plurality of ceramic elements defining a supporting surface of said supporting or wiping strip and a carrier strip carrying said ceramic elements, and wherein said channel is formed between said ceramic elements and said carrier strip.

21. The supporting or wiping strip according to claim 18, wherein said supporting or wiping strip is formed with a first and and a second end, and said channel begins at said first end and terminates at said second end.

22. The supporting or wiping strip according to claim 18, wherein said supporting or wiping strip is formed with a longitudinal end, and said channel has a forward portion beginning at said end and a return portion guided back and terminating at said end.

23. The supporting or wiping strip according to claim 22, wherein said forward portion of said channel is connected to said return portion of said channel within the supporting or wiping strip.

24. The supporting or wiping strip according to claim 22, which comprises a piece of pipe disposed externally of the supporting or wiping strip for connecting said forward portion of said channel with said return portion of said channel.

25. The supporting or wiping strip according to claim 20, wherein said ceramic elements and said carrier strip are formed with at least one channel or with channel portions.