Boiler for producing hot water or steam

Abstract

A boiler for producing hot water or steam, comprising a containment enclosure, which forms a heating chamber that contains water to be heated, and accommodating a firebox body, which forms internally a combustion chamber with a burner associated therewith which has a combustion head, accommodated in the combustion chamber, and a device for premixing air and gas which is connected to the combustion head. According to the invention, the premixing device comprises an air supply duct, which is connected to the combustion head, and a mixing tubular body, which is extended coaxially to the supply duct in order to create, between the internal lateral wall of the supply duct and the external surface of the sidewall of the mixing tubular body, an intake region which has a transverse air passage section that is narrower than the air passage section formed by the supply duct upstream of the mixing tubular body, along the air flow direction.

What is claimed is: 
     
         1 . A boiler for producing hot water or steam, comprising a containment enclosure, which forms a heating chamber that contains water to be heated, and accommodating a firebox body, which forms internally a combustion chamber with a burner associated therewith which has a combustion head, accommodated in said combustion chamber, and a device for premixing air and gas which is connected to said combustion head, wherein said premixing device comprises an air supply duct, which is connected to said combustion head, and a mixing tubular body, which is extended coaxially to said supply duct in order to create, between an internal lateral wall of said supply duct and an external surface of a sidewall of said mixing tubular body, an intake region which has a transverse air passage section that is narrower than the air passage section formed by said supply duct upstream of said mixing tubular body, along the air flow direction, said mixing tubular body having an internal cavity and being closed, at a first end that is directed against the air flow that arrives from said supply duct, by an ogive-shaped head and connected, at a second end, which lies opposite said first end, to a duct for supplying combustible gas, in the sidewall of said mixing tubular body there being at least one dispensing opening that is connected to said internal cavity of said mixing tubular body and to said intake region. 
     
     
         2 . The boiler according to  claim 1 , wherein in the sidewall of said mixing tubular body there is a plurality of dispensing openings distributed around the axis of said mixing tubular body. 
     
     
         3 . The boiler according to  claim 2 , wherein said dispensing openings have an elongated extension and are arranged so as to be inclined with a corresponding extension axis with respect to an axis of said mixing tubular body. 
     
     
         4 . The boiler according to  claim 1 , wherein said mixing tubular body has a diametrical space occupation that decreases progressively from said head toward said second end. 
     
     
         5 . The boiler according to  claim 2 , wherein said dispensing openings are arranged substantially in a point of said intake region that has an air passage section that is smaller than a remaining part of said intake region. 
     
     
         6 . The boiler according to  claim 1 , further comprising means adapted to place said combustion chamber in partial vacuum with respect to the external ambient pressure. 
     
     
         7 . The boiler according to  claim 6 , wherein said combustion chamber is connected to a plurality of heat exchange tubes, which are designed to be crossed by the combustion gases and lead into a combustion gas collection chamber, connected to a stack, said means adapted to place said combustion chamber in partial vacuum comprise at least one fan accommodated in said combustion gas collection chamber.