Method for the treatment of waste gas from a cellulose plant
View Patent ↗A process and a device for cleaning waste gas from pulp production, especially for cleaning waste gases from a bleaching reactor. Aerosols contained in the waste gas are removed and the gaseous impurities are scrubbed out of the waste gas by a scrubbing liquid.
1. A process comprising: bleaching pulp with a bleaching gas comprising ozone; withdrawing a waste gas containing aerosols from said bleaching step; passing said waste gas through a Venturi scrubber operated with scrubbing water so as to scrub out the aerosols contained in the waste gas; and passing the waste gas to a different scrubbing step so as to scrub out gaseous impurities from the waste gas by means of a scrubbing liquid ( 5 ).
2. A process according to claim 1 , wherein the nozzle cross section of the Venturi scrubber ( 4 ) is adjustable, and further comprising adjusting the nozzle cross section so as to match the amount of waste gas to be cleaned to the desired degree of cleaning.
3. A process according to claim 1 , wherein in said different scrubbing step, the gaseous impurities are scrubbed out in a scrubbing column ( 5 ).
4. A process according to claim 1 , wherein in said different scrubbing step, the gaseous impurities are scrubbed out in a packed column ( 5 ).
5. A process according to claim 1 , further comprising withdrawing some of the scrubbing liquid ( 10 ) from said further scrubbing step and passing said scrubbing liquid as scrubbing water to the Venturi scrubber ( 4 ).
6. A process comprising: bleaching pulp with a bleaching gas comprising ozone and chlorine dioxide; withdrawing a waste gas containing aerosols from said bleaching step; passing said waste gas through a Venturi scrubber operated with scrubbing water so as to scrub out the aerosols contained in the waste gas; and passing the waste gas to a different scrubbing step so as to scrub out gaseous impurities from the waste gas by means of a scrubbing liquid ( 5 ).
7. A process according to claim 6 , further comprising destroying the ozone in the resultant scrubbed waste gas.
8. A process according to claim 7 , wherein the ozone is catalytically ( 6 ) destroyed.
9. A process according to claim 1 , wherein pulp fibers in the waste gas are removed from the waste gas before the aerosols are removed.
10. A process according to claim 1 , wherein first the aerosols in the waste gas are removed, and then the gaseous impurities are scrubbed out of the waste gas by means of a scrubbing liquid.
11. A process according to claim 2 , further comprising withdrawing some of the scrubbing liquid ( 10 ) from said different scrubbing step and passing said scrubbing liquid as scrubbing water to the Venturi scrubber ( 4 ).
12. A process according to claim 3 , further comprising withdrawing some of the scrubbing liquid ( 10 ) from said different scrubbing step and passing said scrubbing liquid as scrubbing water to the Venturi scrubber ( 4 ).
13. A process according to claim 4 , further comprising withdrawing some of the scrubbing liquid ( 10 ) from said different scrubbing step and passing said scrubbing liquid as scrubbing water to the Venturi scrubber ( 4 ).
14. A process according to claim 10 , further comprising withdrawing some of the scrubbing liquid ( 10 ) from said different scrubbing step and passing said scrubbing liquid as scrubbing water to the Venturi scrubber ( 4 ).
15. A process according to claim 10 , wherein said further scrubbing step comprises scrubbing the gaseous impurities out in a scrubbing column ( 5 ).
16. A process according to claim 10 , wherein in said different scrubbing step, the gaseous impurities are scrubbed out in a packed column ( 5 ).
17. A process according to claim 15 , further comprising withdrawing some of the scrubbing liquid ( 10 ) from said different scrubbing step and passing said scrubbing liquid as scrubbing water to the Venturi scrubber ( 4 ).
18. A process according to claim 16 , further comprising withdrawing some of the scrubbing liquid ( 10 ) from said different scrubbing step and passing said scrubbing liquid as scrubbing water to the Venturi scrubber ( 4 ).
19. A process according to claim 18 , wherein the nozzle cross section of the Venturi scrubber ( 4 ) is adjustable and further comprising adjusting the nozzle cross section so as to match the amount of waste gas to be cleaned to the desired degree of cleaning.
20. A process according to claim 1 , wherein the gaseous impurities scrubbed out from the waste gas include chlorine and/or chlorine dioxide.
21. A process according to claim 1 , wherein the waste gas containing aerosols withdrawn from said bleaching step includes HCl, H 2 SO 4 and/or HNO 3 acids bonded to the aerosols.