Method for operation of a heating group subsystem, and heating group subsystem

Abstract

A method for operating a heating group subsystem of a machine for the production or treatment of a fibrous web. The heating group subsystem includes a first heating group and a last heating group and at least one additional heating group; in each case having at least one device that is heated with pressurized heating steam. Viewed in a direction of travel, the fibrous web is fed first through the first heating group, then through the at least one additional heating group, and thereafter through last heating group. The steam pressure of the heating steam of the at least one additional heating group is adjusted lower than the respective steam pressure of the heating steam of first heating group and of last heating group.

Claims

1. A method for operating a heating group subsystem in a machine for a production or treatment of a fibrous web, comprising: providing a first heating group including at least one first device that is heated with a pressurized heating steam, at least one additional heating group including at least one additional device that is heated with a pressurized heating steam, and a last heating group including at least one last device that is heated with a pressurized heating steam; feeding the fibrous web, when viewed in a direction of travel, first through the first heating group, then through said least one additional heating group and thereafter through the last heating group; and adjusting a steam pressure of said pressurized heating steam of said at least one additional heating group lower than a steam pressure of said pressurized heating steam of the first heating group and a steam pressure of said pressurized heating steam of said last heating group.

2. The method according to claim 1, further including a step of adjusting the steam pressure of the pressurized heating steam of the first heating group one of equal to or higher than the steam pressure of the pressurized heating steam of said last heating group.

3. The method according to claim 2, wherein the steam pressure of the pressurized heating steam of said at least one additional heating group is adjusted within a range between 50 kPa and 700 kPa.

4. The method according to claim 1, further including a step of feeding the respective pressurized heating steamafter flowing through the respective said at least one first device, said at least one additional device, and said at least one last deviceto a respective separator for respectively separating a condensate and an exhaust vapor, and in that the exhaust vapor of the first heating group and the exhaust vapor of said at least one additional heating group and the exhaust vapor of the last heating group are respectively fed to the respective pressurized heating steam of at least one of said at least one first device, said at least one additional device, and said at least one last device which is heated with the pressurized heating steam of said at least one additional heating group.

5. The method according to claim 4, wherein the exhaust vapor of said at least one additional heating group is fed via a thermocompressor to the pressurized heating steam of at least one of said at least one first device, said at least one additional device, and said at least one last device which is heated with pressurized heating steam of said at least one additional heating group.

6. The method according to claim 1, wherein the machine comprises one of a dryer section, a pre-dryer section, and an after-dryer section, and, viewed in a machine direction, the heating group subsystem is provided at one of a beginning of the dryer section, at a beginning of the pre-dryer section, and at a beginning of the after-dryer section.

7. The method according to claim 1, wherein said at least one first device, said at least one additional device, and said at least one last device are respectively in the form of at least one first drying cylinder, at least one additional drying cylinder, and at least one last drying cylinder.

8. A heating group subsystem for a machine for a production or treatment of a fibrous web, comprising: a first heating group including at least one first device that is heated with a pressurized heating steam; at least one additional heating group including at least one additional device that is heated with a pressurized heating steam; and a last heating group including at least one last device that is heated with a pressurized heating steam, wherein the fibrous webviewed in a machine directionis guided first through the first heating group, then through said at least one additional heating group, and thereafter through the last heating group such that a steam pressure of the pressurized heating steam of said at least one additional heating group is lower than a steam pressure of the pressurized heating steam of the first heating group and a steam pressure of the pressurized heating steam of the last heating group.

9. The heating group subsystem according to claim 8, wherein the steam pressure of the pressurized heating steam of the first heating group is one of equal to or higher than the steam pressure of the pressurized heating steam of the last heating group.

10. The heating group subsystem according to claim 8, further including a respective steam feed line, a respective discharge line, and a respective separator for each heating group, and thus, for each said at least one first device, said at least one additional device, and said at least one last device, respectively, and each said at least one device is connected via the respective steam feed lines with a first steam supply line, and that each said respective separator is allocated to each heating group for respectively separating a condensate and an exhaust vapor that is respectively connected via each said respective discharge line with said respective heating group and each respective device.

11. The heating group subsystem according to claim 10, wherein said separator of the first heating group and said separator of said at least one additional heating group and said separator of the last heating group are connected via a respective vapor line with a second steam supply line of the at least one additional heating group.

12. The heating group subsystem according to claim 11, wherein said vapor line for a vapor from said separator of said at least one additional heating group is connected via a thermo-compressor with said second steam supply line of said at least one additional heating group for a purpose of condensation, and wherein said thermo-compressor is connected with said first steam supply line.

13. The heating group subsystem according to claim 10, wherein said first heating group further includes a first condensate line, and said at least one additional heating group further includes a second condensate line, and said first and second condensate lines are connected with said discharge line of said at least one additional device of said at least one additional heating group.

14. The heating group subsystem according to claim 11, wherein said vapor line of said first heating group comprises a backflow prevention device.

15. The heating group subsystem according to claim 14, wherein said backflow prevention device is in the form of a check valve.

16. The heating group subsystem according to claim 8, further including a vacuum separator which is connected via a vapor line with a thermocompressor, and a vapor of said vacuum separator is condensed by said thermocompressor and is fed to a steam supply line of said first heating group.

17. The heating group subsystem according to claim 8, wherein the machine comprises one of a dryer section, a pre-dryer section, and an after-dryer section, and, viewed in the machine direction, the heating group subsystem is provided at one of a beginning of the dryer section, at a beginning of the pre-dryer section, and at a beginning of the after-dryer section.

18. The heating group subsystem according to claim 8, wherein said at least one first device, said at least one additional device, and said at least one last device are respectively in the form of at least one first drying cylinder, at least one additional drying cylinder, and at least one last drying cylinder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

(2) FIG. 1a is a schematic illustration of a heating group subsystem known in the art;

(3) FIG. 1b illustrates the steam pressure of the heating steam of the individual heating groups known in the art;

(4) FIG. 2a is a schematic illustration of an embodiment of a heating group subsystem according to the present invention;

(5) FIG. 2b illustrates the steam pressure of the heating steam of the individual heating groups of a heating group subsystem according to the present invention; and

(6) FIG. 3 illustrates another embodiment of a heating group subsystem according to the present invention.

(7) Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

(8) FIGS. 1a-1b represent a heating group subsystem for a dryer section in a paper machine with dryer cylinders, according to the current state of the art, which is designed as a cascade heating system consisting of 3 heating groups HG1, HG2, HG3. The heating groups are heated with heating steam. Steam feed lines 3, 4, 5 are connected with a steam supply line 2. Steam supply lines 2 are supplied with heating steam by a steam supply system DV. In respect to the machine direction, heating groups HG1, HG2, HG3 are arranged one after another. Heating group HG1 thus forms the first heating group and supplies the first dryer cylinder with heating steam. Steam supply line 2 also supplies an after-dryer section NTP with steam. The volume of heating steam for each heating group is adjustable through valves. After the heating steam of one heating group HG1, HG2, HG3 has flowed through the dryer cylinders, the mixture of exhaust vapor and condensate is fed via discharge lines 6, 7, 8 to a respective separator S1, S2, S3 for separation of exhaust vapor and condensate. The respective condensate is discharged via condensate lines 9, 10, 11. The exhaust vapor of heating group HG3 is fed from separator 3 via vapor line 14 to steam feed line 4 of second heating group HG2. Accordingly, the exhaust vapor of heating group HG2 is fed from separator 2 via exhaust vapor line 13 to steam feed line 3 of first heating group HG1. In contrast, the exhaust vapor of heating group HG1 is fed from separator 1 via exhaust vapor line 12 to a condenser KS where it is condensed. The latent heat of the exhaust vapor of heating group HG1 is therefore not used directly for paper drying. As illustrated in FIG. 1b, steam pressure PD of the heating steam in heating groups HG1, HG2, HG3 is selected so that first heating group HG1 has the lowest steam pressure PD; that second heating group HG2 has the second lowest steam pressure PD and that the third heating group HG3 has the highest steam pressure PD.

(9) Referring now to FIG. 2a, there is shown a schematic illustration of an exemplary embodiment of a heating group subsystem according to the present invention for a dryer section in a paper machine with dryer cylinders, comprising 3 heating groups HG1, HG2, HG3. The heating groups are heated with heating steam. Steam feed lines 3, 4, 5 are connected with a steam supply line 2. Steam supply lines 2 are supplied with heating steam via a steam supply system DV. Heating groups HG1, HG2, HG3 are arranged one after the other in machine direction. Heating group HG1 thus represents the first heating group and supplies one or more first dryer cylinders with heating steam. Steam supply line 2 also supplies an after-dryer section NTP with steam. The steam pressure of the respective heating steam is independently adjustable for each heating group HG1, HG2, HG3 through valves. After the heating steam of a heating group HG1, HG2, HG3 has flowed through the dryer cylinder or cylinders, the mixture of exhaust vapor and condensate is fed through discharge lines 6, 7, 8 to a respective separator S1, S2, S3 for separation of exhaust vapor and condensate. The condensate of heating group 2 is fed via condensate line 10 to a condensate collection tank. The condensate of heating group 1 is fed from separator 1 via condensate line 9 to discharge line 7. Accordingly, the condensate of heating group 3 is fed from separator 3 via condensate line 11 also to discharge line 7 of heating group 2. The exhaust vapor of heating group HG3 is fed from separator 3 via exhaust vapor line 14 to steam feed line 4 of second heating group HG2 and is again used directly for paper drying. Accordingly, the exhaust vapor of heating group HG1 is fed from separator 1 via exhaust vapor line 12 to steam feed line 4 of second heating group HG2 and is again used directly for paper drying. In contrast, the exhaust vapor of heating group HG2 is returned through exhaust vapor line 13 via a thermo-compressor from separator 2 into steam feed line 4 of second heating group HG2 and is thus also used again directly for paper drying. Thermo-compressor 15 acts as a jet pump, wherein steam from steam supply line 2 is used as a propulsion jet. The pressure of the exhaust vapor from separator 2 of heating group HG2 is thereby brought at least to the pressure level of the heating steam in steam feed line 4. As shown in FIG. 2b, in contrast to the cascade system, steam pressure PD of the heating steam in heating groups HG1, HG2, HG3 is selected so that first heating group HG1 has the highest steam pressure PD; that second heating group HG2 has the lowest steam pressure PD and third heating group HG3 has a steam pressure PD between the steam pressure of first heating group HG1 and second heating group HG2.

(10) FIG. 3 illustrates further details of an embodiment of a heating group subsystem according to FIGS. 2a and 2b for a dryer section in a paper machine with dryer cylinders 1.1, 1.2, 1.3, 1.4, 2.1, 2.2, 3.1, 3.2 and including 3 heating groups HG1, HG2, HG3. The heating groups are heated with heating steam. Steam feed lines 3, 4, 5 are connected with a steam supply line 2. Steam supply lines 2 are supplied with heating steam from a steam supply system DV. First heating group HG1 comprises dryer cylinders 1,1, 1.2, 1.3, 1.4; second heating group HG2 comprises dryer cylinders 2.1, 2.2 and third heating group HG3 comprises dryer cylinders 3.1, 3.2. In respect to machine direction, heating groups HG1, HG2, HG3 are arranged one after another. Heating group HG1 thus represents the first heating group and supplies several first dryer cylinders 1.1, 1.2, 1.3, 1.4 with heating steam. Steam supply line 2 also supplies an after-dryer section NTP or another steam consuming device with steam. The steam pressure of the respective heating steam is independently adjustable for each heating group HG1, HG2, HG3 through valves. After the heating steam of a heating group HG1, HG2, HG3 has flowed through the dryer cylinder or cylinders, the mixture of exhaust vapor and condensate is fed through discharge lines 6, 7, 8 to a respective separator S1, S2, S3 for separation of exhaust vapor and condensate. The condensate of heating group 2 is fed through a condensate line 10 to a condensate collecting tank, whereby previously heat for the hood supply air HZL for the hood of the dryer section was removed. The condensate of heating group 1 is fed from separator 1 via condensate 9 to discharge line 7. Accordingly, condensate of heating group 3 is fed from separator 3 via condensate line 11 also to discharge line 7 of heating group 2. The exhaust vapor of heating group HG3 is fed from separator 3 via exhaust vapor line 14 to steam feed line 4 of second heating group HG2 and is again used directly for paper drying. Accordingly, the exhaust vapor of heating group HG1 is fed from separator 1 via exhaust vapor line 12 to steam feed line 4 of second heating group HG2 and is again used directly for paper drying. In contrast, the exhaust vapor of heating group HG2 is returned through exhaust vapor line 13 via a thermo-compressor 15 from separator 2 into steam feed line 4 of second heating group HG2 and is thus also used again directly for paper drying. Thermo-compressor 15 acts as a jet pump, wherein steam from steam supply line 2 is used as a propulsion jet. It is however also conceivable to supply thermo-compressor 15 with steam from another steam supply net, for example a steam supply net that has a higher steam pressure. The pressure of the exhaust vapor from separator 2 of heating group HG2 is thus brought at least to the pressure level of the heating steam in steam feed line 4. As shown in FIG. 2b, in contrast to the cascade system, steam pressure PD of the heating steam is selected in heating groups HG1 HG2, HG3 so that first heating group HG1 has the highest steam pressure PG; that second heating group HG2 has the lowest steam pressure PD and third heating group HG3 has a steam pressure PD between the steam pressure of first heating group HG1 and second heating group HG2.

(11) It is also possible to provide additional heating groups between first heating group HG1 and last heating group HG3, wherein these additional heating groups also have a steam pressure that is less than the steam pressure of first heating group HG1 and less than the steam pressure of the last heating group, which in this example is third heating group HG3. Condensate lines 9, 10, 11 and vapor lines 12, 13, 14 can then be connected consistent with the heating group subsystem illustrated in FIG. 3 with the steam feed lines or respectively the discharge lines of one of the at least one additional heating group or second heating group HG2.

(12) In the event of a web break in the paper machine, in other words in an event outside of normal operating procedure, valves and vapor lines 12, 13, 14 are provided as shown by arrows, in order to feed the vapors directly to a condenser KS. In addition, vapor lines 17 from other heating groups which are not illustrated in this embodiment, can be connected with this condenser. Condenser KS is connected with lines CW for supply and discharge of cooling water.

(13) Heating group subsystem 1 also includes a vacuum separator V into which the condensate lines from an after-dryer section NTP flow. From this, vacuum separator V produces exhaust vapor which is fed directly into condenser KS.

(14) The arrangement in FIG. 3 provides an optional thermo-compressor 16 with which it is possible to operate heating group subsystem 1 as a classic cascade heating systemfor example for production of certain paper types. Thermo-compressor 16 acts as a jet pump, wherein steam from steam supply line 2 is used as a propulsion jet. It is however also conceivable to supply thermo-compressor 16 with steam from another steam supply net, for example a steam supply net that has a higher steam pressure. In this caseviewed in machine directionfirst heating group HG1 of heating group subsystem 1 has the lowest steam pressure of heating steam of all heating groups HG2, HG3 of heating group subsystem 1; and second heating group HG2 of heating group subsystem 1 has the second lowest steam pressure and third heating group HG3 has the highest steam pressure of heating steam. This thermo-compressor 16 is connected with vapor line 18 and with steam supply line 2. In the case of cascade operation of heating group subsystem 1 it is thus possible to return the vapor occurring in separator Si and in vacuum separator V into steam feed line 3 of heating group HG1 and to use it directly for paper drying. For this case, vapor line 12 of first heating group HG1 comprises a check-valve 19 to prevent backflow of heating steam from steam feed line 4 via vapor line 12 into separator S1 of first heating group HG1, or into vacuum separator V.

(15) If heating group subsystem 1 is operated according to the invention and not in the cascade operational mode, thermo-compressor 16 may be taken out of operation. Thermo-compressor 16 can also be operated with steam from another steam net, for example a steam supply net that has a higher steam pressure. The pressure of the exhaust vapor from vacuum separator V can thus be brought at least to the pressure level of the heating steam in steam feed line 3 and can be used directly for paper drying.

(16) The valves in steam supply lines 3, 4, 5 are connected with pressure regulating systems PIC to regulate the steam pressure of the respective heating steam, and the valves for discharge lines 6, 7, 8 are coupled with pressure differential control systems PDIC. The valves in condensate lines 9, 10, 11 are equipped with level controllers LIC.

(17) While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

COMPONENT IDENTIFICATION

(18) 1 Heating group subsystem

(19) 2 Steam supply line

(20) 3 Steam feed line

(21) 4 Steam feed line

(22) 5 Steam feed line

(23) 6 Discharge line

(24) 7 Discharge line

(25) 8 Discharge line

(26) 9 Condensate line

(27) 10 Condensate line

(28) 11 Condensate line

(29) 12 Vapor line

(30) 13 Vapor line

(31) 14 Vapor line

(32) 15 Thermo-compressor

(33) 16 Thermo-compressor

(34) 17 Vapor line

(35) 18 Vapor line

(36) 19 Check valve

(37) DV Steam supply system

(38) NTP After-dryer section

(39) HG1 Heating group 1

(40) 1.1 Dryer cylinder

(41) 1.2 Dryer cylinder

(42) 1.3 Dryer cylinder

(43) 1.4 Dryer cylinder

(44) HG2 Heating group 2

(45) 2.1 Dryer cylinder

(46) 2.2 Dryer cylinder

(47) HG3 Heating group 3

(48) 3.1 Dryer cylinder

(49) 3.2 Dryer cylinder

(50) S1 Separator 1

(51) S2 Separator 2

(52) S3 Separator 3

(53) KS Condenser

(54) KSB Condenser collecting tank

(55) HZL Hood supply

(56) V Vacuum separator

(57) CW Cooling water