Method in the bleaching of pulp and a device for the bleaching of pulp

• US 20030102094A1
• Filed: 10/21/2002
• Published: 06/05/2003
• Est. Priority Date: 05/05/2000
• Status: Abandoned Application

• Current Assignee: Upm-Kymmene Corporation
• Original Assignee: Upm-Kymmene Corporation
• Inventors: Tirri, Tapio, Dahl, Olli, Lehto, Jouko H., Tienvieri, Taisto
• Application Number:
  US10/274,786
• Publication Number:
  US 20030102094A1
• Time in Patent Office: Days
• US Class Current: 162/62
• CPC Class Codes: D21C 9/1052 Controlling the process
• CPC Class Codes: D21C 9/163 with peroxides

Abstract

Bleaching device for pulp includes a container to which a supply of pulp and bleaching chemicals containing peroxide as well as discharge of bleached pulp are connected. The device comprises an oxygen measuring device a temperature measuring device and/or a carbon monoxide measuring device, which are arranged to measure oxygen concentration, temperature and/or carbon monoxide concentration, respectively, from the contents of the container such as from the gas volume of the same, or from a substance flow coming from the container, such as gas flow. The measuring device is connected to a data processing unit which is coupled to a controller for automatic control of the process. The process is especially a high consistency pulp bleaching of mechanical pulp, in which the consistency of pulp in the reaction area is at least 25%, advantageously at least 30%.

Claims

1. A bleaching process for pulp comprising:

contacting cellulose-containing fibrous pulp with peroxide in a process area;

measuring oxygen concentration, temperature and/or carbon monoxide concentration in the process area; and

adjusting the bleaching process based on results from measuring oxygen concentration, temperature and/or carbon monoxide concentration.

2. The process according to claim 1, wherein that the oxygen concentration, temperature and/or carbon monoxide concentration is measured from a gas volume in a container containing the process area.

3. The process according to claim 2, wherein the oxygen concentration, temperature and/or carbon monoxide concentration is measured from an upper part of a bleaching tower in a process area

4. The process according to claim 2, wherein the oxygen concentration, temperature and/or carbon monoxide concentration is measured from a vent gas flow coming out of the bleaching tower.

5. The process according to claim 1 or 2, wherein the oxygen concentration is measured and the process is adjusted on the basis of the results obtained from this measurement.

6. The process according to claim 1 or 2, wherein the temperature and/or the carbon monoxide concentration is measured and the process is adjusted on the basis of the results obtained from this measurement.

7. The process according to claim 4, wherein the temperature is measured directly from the gas volume in the container containing the process area, from an upper part of the bleaching tower by means of a sensor placed therein, and the carbon monoxide concentration is measured from a vent gas flow coming out of the container.

8. The process according to claim 7, wherein the carbon monoxide concentration is measured from a vent gas flow from a bleaching sensor.

11. The process according to claim 1, wherein the oxygen concentration, temperature and/or the carbon monoxide concentration is monitored by means of a measurement conducted at intervals or continuously and the process is controlled automatically on the basis of the results.

12. The process according to claim 1, wherein a set value is defined for the oxygen concentration, and by means of this value a feedback control of the process is performed.

13. The process according to claim 11, wherein a set value of the oxygen concentration is a fixed maximum value, and the control is performed when this maximum value is exceeded.

14. The process according to claim 1, wherein a set value is defined for the temperature and/or carbon monoxide concentration, and by means of this value a feedback control of the process is performed.

15. The process according to claim 13, wherein that the set value of the temperature and/or the carbon monoxide concentration is a fixed maximum value, and the control is performed when this maximum value is exceeded.

16. The process according to claim 1, wherein the process is a high consistency pulp bleaching, in which the consistency of pulp in the reaction area is at least 25%.

17. The process according to claim 16, wherein the process is a high consistency pulp bleaching in which the consistency of pulp on the reaction area is at least 30%.

9. The process according to the results from measuring oxygen concentration, temperatuer and/or carbon monoxide concentration are utilized to control an alkali/peroxide ratio of the process area.

10. The process according to claim 9, wherein one of the amounts of alkali and peroxide is kept constant and the other is changed.

18. A bleaching device for pulp, comprising a container that includes a supply for pulp and bleaching chemicals containing peroxide, and a discharge for bleached pulp, wherein the bleaching device contains an oxygen measuring device, a temperature measuring device and/or a carbon monoxide measuring device, which is/are effective for measuring oxygen concentration, temperature and/or carbon monoxide concentration, respectively, from the contents of the container.

19. The bleaching device according to claim 18, wherein it comprises at least an oxygen measuring device.

20. The device according to claim 19, wherein the oxygen measuring device is arranged to measure the oxygen concentration from the gas volume of the container or from a gas flow coming from the container.

21. The bleaching device according to claim 18, wherein it comprises at least a temperature measuring device and/or a carbon monoxide measuring device.

22. The bleaching device according to claim 21, wherein the carbon monoxide measuring device is a measuring device connected to a gas flow coming out of the container.

23. The bleaching device according to claim 22, wherein the measuring device is a gas analyzer.

24. The bleaching device according to claim 22, further comprises a measuring device which is arranged to measure the concentration of a gas component other than carbon monoxide, from the contents of the container.

25. The bleaching device according to claim 24, wherein the measuring device is effective for measuring oxygen.

26. The device according to claim 25, wherein the measuring device is a gas analyzer, connected to the gas flow coming out of the container.

27. The bleaching device according to claim 26, wherein the gas analyzer is effective for measuring oxygen.

28. The device according to claim 18, wherein the oxygen measuring device, the temperature measuring device and/or the carbon monoxide measuring device is/are connected to a data processing unit (U) which is connected to a controller for automatic control of the process.

29. The device according to claim 28, wherein the device comprises both a temperature measuring device and a carbon monoxide measuring device.

30. The device according to claim 29, wherein the temperature measuring device is a temperature sensor placed in a gas volume of the container.