GB1410990A - Combustor and method of operating same - Google Patents

Abstract

1410990 Liquid or gaseous fuel combustion apparatus PHILLIPS PETROLEUM CO 15 Dec 1972 [15 Dec 1971 27 March 1972] 58138/72 Heading F4B [Also in Division F1] To reduce formation of pollutants, particularly nitrogen oxides, primary, secondary and tertiary air (or other oxidant) is introduced into a flame tube as three distinct streams, the tertiary stream being preheated by heat exchange with the flame tube wall in the region of the primary combustion zone. In one arrangement, Fig. 1, a flame tube 12 is mounted within outer casing 16 to define an annular chamber 18. Primary air from the latter flows through oblique passages 24 to mix in a swirl chamber 22 with high aromatic fuel supplied axially through duct 26. Secondary air is added to the burning mixture through circumferentially spaced ducts 36 leading to openings 34, the secondary air having passed through a region 19 of chamber 18 defined outwardly of a sleeve 30 surrounding the primary combustion zone. The annular space 18<SP>1</SP> between sleeve 30 and flame tube 12 contains circumferential or axial spaced fins 40, 42 to assist transfer of heat from the primary combustion zone to tertiary air flowing through space 18<SP>1</SP>. The tertiary air leaves the latter through gaps (45, Fig. 6, not shown) between ducts 36 and thence flows through openings 38 to mix with the combustion gases. In a modification, Fig. 14, sleeve 30 is not provided and the secondary air is supplied through ducts 36<SP>1</SP> which may be disposed outside casing 16<SP>1</SP>, as shown, or within the latter (Fig. 13, not shown). Ducts 36<SP>1</SP> may be connetted to a separate source of air and may include means for heating the secondary air passing therethrough to a temperature higher than that of the primary air. The primary combustion zone may operate fuel-rich whereas the secondary zone may be fuel lean. The relative volumes of the primary, secondary and tertiary airflows are substantially 1 : 1 : 2. Temperatures and other operating conditions are specified. Various modified ways of introducing the fuel and air into the upstream region of the primary combustion zone are described (Figs. 7 to 12 and 15 to 17, not shown). The gases leaving the flame tube may be used in a turbine, furnace or boiler.