preheater for combustion air, and a power plant

Abstract

A preheating device for combustion air in a boiler. First heat exchanger structures fitted in a flue gas duct heat primary air. A first air supply area in the wall of the flue gas duct supplies air to be heated to the first heat exchanger structures. Second heat exchanger structures fitted in a flue gas duct heat secondary air. A second air supply area in the wall of the flue gas duct supplies air to be heated to the second heat exchanger structures. The first air supply area is opposite the second air supply area. Also a power plant.

1 - 13 . (canceled) 
     
     
         14 . A preheating device for combustion air in a boiler, the device comprising:
 first heat exchanger structures fitted in a flue gas duct for heating primary air, the first heat exchanger structures comprising a set of heat exchanger pipes forming a primary air circulation for primary air flow;   second heat exchanger structures fitted in the flue gas duct for heating secondary air, the second heat exchanger structures comprising a set of heat exchanger pipes forming a secondary air circulation for secondary air flow;   an inlet of the first heat exchanger structure for supplying primary air to be heated to the primary air circulation; and   an inlet of the second heat exchanger structure for supplying secondary air to be heated to the secondary air circulation;   wherein the inlet of the first heat exchanger structure and the inlet of the second heat exchanger structure are placed substantially on a same level, the same level being substantially perpendicular to a central line of the flue gas duct.   
     
     
         15 . The preheating device according to  claim 14 , further comprising:
 a first air supply area in a wall of the flue gas duct for supplying air to be heated to the first heat exchanger structures, the first air supply area comprising the inlet of the first heat exchanger structure;   a second air supply area in the wall of the flue gas duct for supplying air to be heated to the second heat exchanger structures, the second air supply area comprising the inlet of the second heat exchanger structure; and   wherein the first air supply area is opposite the second air supply area.   
     
     
         16 . The preheating device according to  claim 15 , further comprising:
 deflecting structures for the air flow for changing the direction of the air flows of the heat exchangers, wherein the deflecting structures are arranged in a central area of the flue gas duct, and wherein the first heat exchanger structures and the second heat exchanger structures extend at the first air supply area and the second air supply area to the central area of the flue gas duct.   
     
     
         17 . The preheating device according to  claim 14 , wherein the first heat exchanger structures and the second heat exchanger structures are staggered. 
     
     
         18 . The preheating device according to  claim 14 , wherein the heat exchanger pipes are bent such that straight portions of the heat exchanger pipes are placed both parallel to the central line of the flue gas duct and perpendicular to the central line of the flue gas duct. 
     
     
         19 . The preheating device according to  claim 14 , wherein the flue gas duct is vertical, whereby the inlet of the first heat exchanger structure and the inlet of the second heat exchanger structure are located at a same height. 
     
     
         20 . A power plant, comprising:
 a boiler;   a flue gas duct to which flue gases exiting the boiler are led;   a preheating device for heating combustion air to be supplied into the boiler, the preheating device comprising:   first heat exchanger structures fitted in the flue gas duct for heating primary air, wherein the first heat exchanger structures comprise a set of heat exchanger pipes forming a primary air circulation for primary air flow,   second heat exchanger structures fitted in the flue gas duct for heating secondary air, wherein the second heat exchanger structures comprise a set of heat exchanger pipes forming a secondary air circulation for secondary air flow,   an inlet of the first heat exchanger structure, for supplying primary air to be heated to the primary air circulation, and   an inlet of the second heat exchanger structure, for supplying secondary air to be heated to the secondary air circulation,   wherein the inlet of the first heat exchanger structure and the inlet of the second heat exchanger structure are placed substantially on a same level, the same level being substantially perpendicular to a central line of the flue gas duct.   
     
     
         21 . The power plant according to  claim 20 , wherein the preheating device of the power plant further comprises:
 a first air supply area in a wall of the flue gas duct for supplying air to be heated to the first heat exchanger structures, the first air supply area comprising the inlet of the first heat exchanger structure;   a second air supply area in the wall of the flue gas duct for supplying air to be heated to the second heat exchanger structures, the second air supply area comprising the inlet of the second heat exchanger structure; and   wherein the first air supply area is opposite the second air supply area.   
     
     
         22 . The power plant according to  claim 20 , wherein the flue gas duct is vertical, whereby the inlet of the first heat exchanger structure and the inlet of the second heat exchanger structure are located at a same height. 
     
     
         23 . The power plant according to  claim 21 , wherein the first air supply area and the second air supply area are lowermost parts of the preheater placed in the flue gas duct. 
     
     
         24 . The power plant according to  claim 21 , wherein the first air supply area and the second air supply area are uppermost parts of the preheater placed in the flue gas duct. 
     
     
         25 . The power plant according to  claim 22 , wherein the flue gases from the boiler are introduced into the flue gas duct from an upper part of the flue gas duct and removed from a lower part. 
     
     
         26 . The power plant according to  claim 22 , wherein the flue gases from the boiler are introduced into the flue gas duct from a lower part of the flue gas duct and removed from an upper part.