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

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.

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.