Boiler, and a silencer for a flue gas duct in a boiler

1. A boiler comprising:

a flue gas duct with a width W and a depth L;

heat exchanger pipes in the flue gas duct, for heating or preheating liquid, steam or air;

a first planar silencer plate substantially parallel to the flow direction of the flue gases, the first silencer plate comprising noise absorbing material, said first silencer plate being placed downstream of any of said heat exchanger pipes in the flow direction of the flue gases in said flue gas duct, and the distance d between said first silencer plate and said heat exchanger pipe being smaller than the width W of the flue gas duct or smaller than the depth L of the flue gas duct;

at least one noise absorbing wall, the wall comprising said first silencer plate, and the wall truncating the resonating area transverse to the flow direction of the flue gases in the flue gas duct;

a subfloor level for maintaining the silencer plate or the flue gas duct; and

a subfloor space left between the subfloor level and the silencer plate, wherein the silencer plate suppresses noise caused by turbulence of the flow of the flue gases.

2. The boiler according to claim 1 , wherein the silencer plates delimit a service aisle in a plane substantially transverse to the silencer plates, for maintaining the silencer, the silencer plate, or the flue gas duct, and the service aisle has access to the boundaries of the silencer and the silencer plates.

3. The boiler according to claim 1 , wherein said first silencer plate is placed downstream of a water preheating area and wherein said first silencer plate is placed upstream of a preheating area for incoming air.

4. A boiler comprising:

a flue gas duel with a width W and a depth L;

heat exchanger pipes in the flue gas duct, for heating or preheating liquid, steam or air;

a first planar silencer plate substantially parallel to the flow direction of the flue gases, the first silencer plate comprising noise absorbing material, said first silencer plate being placed downstream of any of said heat exchanger pipes in the flow direction of the flue gases in said flue gas duct, and the distance d between said first silencer plate and said heat exchanger pipe being smaller than the width W of the flue gas duct or smaller than the depth L of the flue gas duct;

at least one noise absorbing wall, the wall comprising said first silencer plate, and the wall truncating the resonating area transverse to the flow direction of the flue gases in the flue gas duct;

a second planar silencer plate substantially parallel to the flow direction of the flue gases, the second silencer plate comprising noise absorbing material; and

a second wall, which said second wall is substantially parallel to the first silencer plate and spaced at a distance from the first silencer plate in a direction substantially transverse to the flow direction of the flue gases, the second wall comprising said second silencer plate, wherein the silencer plate suppresses noise caused by turbulence of the flow of the flue gases.

5. The boiler according to claim 4 , wherein the silencer plates delimit a service aisle in a plane substantially transverse to the silencer plates, for maintaining the silencer, the silencer plate, or the flue gas duct.

6. The boiler according to claim 5 , wherein the service aisle has access to the boundaries of the silencer and the silencer plates.

7. The boiler according to claim 4 , further comprising a frame, said first silencer plate being placed in said frame for protecting the silencer plate from a dust removal device.

8. The boiler according to claim 4 , wherein said first silencer plate is placed upstream of a preheating area for incoming air.

9. The boiler according to claim 4 , wherein said first silencer plate is placed downstream of a water preheating area, and wherein said first silencer plate is placed upstream of a preheating area for incoming air.

10. The boiler according to claim 4 , wherein the silencer plate comprises

a noise absorbing core comprising noise absorbing material, such as soft mineral wool; and

a surface plate on its surface, for protecting the inner parts of the silencer plate, the surface plate comprising holes for transmitting sound.

11. The boiler according to claim 4 , further comprising a vibration preventing plate which is a planar plate substantially parallel to the flow direction of the flue gases, which vibration preventing plate is left between two heat exchanger pipes in a direction transverse to the flow direction of the flue gases, for diminishing resonance in the heat exchanger area of the flue gas duct.

12. A boiler comprising:

a flue gas duct with a width W and a depth L;

heat exchanger pipes in the flue gas duct, for heating or preheating liquid, steam or air; and

a first planar silencer plate substantially parallel to the flow direction of the flue gases, the first silencer plate comprising noise absorbing material, said first silencer plate being placed downstream of any of said heat exchanger pipes in the flow direction of the flue gases in said flue gas duct, and the distance d between said first silencer plate and said heat exchanger pipe being smaller than the width W of the flue gas duct or smaller than the depth L of the flue gas duct;

at least one noise absorbing wall, the wall comprising said first silencer plate, and the wall truncating the resonating area transverse to the flow direction of the flue gases in the flue gas duct; and

a second planar silencer plate substantially parallel to the flow direction of the flue gases, the second silencer plate comprising noise absorbing material, said second silencer plate being placed downstream of any of said heat exchanger pipes in the flow direction of the flue gases in said flue gas duct, and the second silencer plate is placed at an angle to the first silencer plate, wherein the width of the resonating area of the flue gas duct becomes narrower in two directions transverse to the flow direction of the flue gases,

wherein the silencer plate suppresses noise caused by turbulence of the flow of the flue gases.

13. The boiler according to claim 12 , wherein the second silencer plate is placed substantially transversely to said first silencer plate.

14. The boiler according to claim 12 , wherein the flue gas duct comprises:

two parallel side walls; and

a front wall and a rear wall substantially transverse to the side wall, in which boiler the silencer plates of the silencer are arranged in such a way that there is no transverse visual connection between the parallel side walls of the flue gas duct.

15. The boiler according to claim 14 , wherein the silencer plates of the silencer are arranged in such a way that there is no transverse visual connection between the parallel front wall and rear wall of the flue gas duct.

16. The boiler according to claim 12 , further comprising a frame, said first silencer plate being placed in said frame for protecting the silencer plate from a dust removal device.

17. The boiler according to claim 12 , wherein said first silencer plate is placed upstream of a preheating area for incoming air.

18. The boiler according to claim 12 , wherein said first silencer plate is placed downstream of a water preheating area and wherein said first silencer plate is placed upstream of a preheating area for incoming air.

19. The boiler according to claim 12 , wherein the silencer plate comprises:

a noise absorbing core comprising noise absorbing material, such as soft mineral wool; and

a surface plate on its surface, for protecting the inner parts of the silencer plate, the surface plate comprising holes for transmitting sound.

20. The boiler according to claim 12 , further comprising a vibration preventing plate which is a planar plate substantially parallel to the flow direction of the flue gases, which vibration preventing plate is left between two heat exchanger pipes in a direction transverse to the flow direction of the flue gases, for diminishing resonance in the heat exchanger area of the flue gas duct.