GB728266A - Improvements in or relating to tubular furnaces for heating fluids - Google Patents

Abstract

<PICT:0728266/III/1> <PICT:0728266/III/2> The heating chamber of a tubular furnace, such as is used for heating petroleum hydrocarbons, comprises two side walls 1, 11 and two end walls 5, 51, and is divided into three zones, 7, 8, 9 by a central wall 4, which extends longitudinally through the chamber, and a cross wall 6 extending transversely from the central wall to one of the side walls. Two rows of burners 15, 151 direct flames and hot combustion gases upwardly against the opposite faces of the central wall, and heat it to a highly radiant condition. Different temperatures may be obtained within each of the zones 7, 8, 9 by controlling the various individual burners. A bank of horizontal tubes 17, joined by U-bends, is disposed in zone 7 along side wall 1; and independent banks of tubes 18, 19 are disposed in zones 8, 9 respectively. Above the upper ends of walls 4 and 6 is a tapering convection-radiation zone 10 which is in communication with all three combustion zones. Zone 10 has a bank of tubes 20 along sloping wall 11, another bank 201 along wall 111, and a central bank of tubes 21. The upper portion of the furnace is formed as a convection zone 12, containing a bank of tubes 22, which leads to a flue gas duct 14 and a stack (not shown). A plurality of spaced baffles 29 are placed at the lower end of duct 14 to control the flow of hot combustion gases through the upper part of the furnace. The baffles 29 may also be regulated to assist in controlling the draft from each of the combustion zones in the lower part of the furnace. The furnace may be used in a process for the catalytic reforming of naphtha, wherein the naphtha is required to pass through three reactors (not shown) containing catalyst in order to convert it into a high octane product. The naphtha is fed through line 23 into tubes of convection zone 12; it then passes through line 24 into the lowest tube of radiant bank 17; it flows up through the tubes of bank 17, then through tubes 20, 21, 201, and passes out of the furnace through line 25 which leads to the first catalytic reactor. The partially converted stream is then reheated by passing it through tube bank 18 in zone 8. The reheated naphtha leaves through line 26, and enters the second catalytic reactor. Upon leaving the latter, the naphtha enters tube bank 19, via line 27, wherein it is again re-heated. The reheated naphtha is then passed through line 28 to the third catalytic reactor. If desired, a furnace may be constructed having more than three combustion zones. Thus a second cross wall may be inserted on the left hand side of wall 4; or alternatively, there may be two or more cross walls on the same side of wall 4.