US 4,034,803 A · Corrosion resistant tubular air preheater

Abstract

A corrosion resistant tubular air preheater in which combustion air is heated by heat transfer from flue gases from a furnace. The heat exchanger is of a longitudinal type having a central enclosure of rectangular cross-section in which a plurality of tubular heat transfer elements are mounted. Surrounding the central enclosure is an outer plenum. Cold combustion air enters at the bottom of the outer plenum and circulates around and up the plenum to a series of openings on top of the heat transfer elements. The partially heated combustion air then passes downwardly through metal tubes in the heat transfer elements and then passes outwardly to the furnace. The minimum temperature in metal structure enclosing the combustion gases is controlled by two means. One is the use of insulation in selected areas to limit heat transfer rate to cold air impinging upon metal surfaces. The second method is by control of cold air flow incidence on or along heat transfer surfaces so as to minimize rapid heat transfer from any metal surface, which might chill the surface below the dew point.

Claims10

Dependent claims

A corrosion resistant tubular air preheater for transfer of heat from hot flue gases carrying corrosive vapors, without condensing said corrosive vapors, comprising:

a. an inner vertical cylindrical metal conduit or wall, for the upward flow of hot flue gas;
b. an outer vertical cylindrical metal wall of the same cross-section shape as said inner wall spaced outwardly from said inner wall forming an annular air inlet plenum;
c. a plurality of heat transfer elements and surfaces, including elements of narrow cross-section and including a plurality of vertical thin wall metal tubes connected between upper and lower plena;
d. said heat transfer elements inserted inside said inner wall with said upper plena connected to the top of said inlet plenum through said inner wall to an outlet plenum surrounding said inner wall below said inlet plenum;
e. inlet air conduit means connected to the bottom of said inlet plenum;
f. outlet air conduit means connected to said outlet plenum;
g. bypass means to control the flow velocity of cold air through said air preheater;
and
h. thermal insulation covering selected portions of the heat transfer surfaces where condensation and corrosion is likely to occur;
whereby the cooling of said flue gases below the dew point of said corrosive vapors in the presence of water vapor is prevented.

7 more elements

Dependencies are inferred from the claim text.

Corrosion resistant tubular air preheater

Life of this patent

Corrosion resistant tubular air preheater

Life of this patent

Abstract

Claims10