Patent GB-746748-A (GB)
Title: Improvements in or relating to combustion apparatus
Inventor: ZOLLER RONALD ERNEST
IPC: F23C1/00
Filed: 1952-01-11
Abstract: 746,748. Pulverised-fuel burners. BABCOCK & WILCOX, Ltd. Jan. 12, 1953 [Jan. 11, 1952], No. 864/52. Class 75(1). [Also in Group XII] The invention resides in a furnace chamber and a method of controlling the temperature of vapour supplied by a tubulous vapour-generating and superheating unit having a furnace chamber including heat exchange surfaces and a gas pass communicating with the furnace chamber and containing a convection superheater. The furnace chamber of the invention comprises radiant heat exchange surfaces and flame producing burner means, the latter comprising a group of two or more burner elements arranged to discharge a combustible mixture of fuel and air and to produce a common flame having a burning core, further air discharge means being provided for supplying combustion air in the vicinity of the burner elements and means being provided for varying the direction of discharge of fuel and air from at least one of the burner elements so as to vary the ratio of air to fuel in the burner core whereby the flame length may be varied to achieve control of temperature variation along the gas now path within the combustion chamber ; or the furnace chamber comprises radiant heat exchange surfaces and pulverised fuel burner means directing a flame towards a molten slag pool associated with an outlet for molten slag, means being provided for effecting at low firing rates an extension of the flame to achieve control of temperature variation along the gas flow path and to promote the fluidity of the slag pool. The method of controlling the temperature of vapour, &c. comprises supplying burner means in the furnace chamber with air and fuel at rates suited to the load on the unit and regulating the length of the flame. In the construction shown in Fig. 5 four burners are mounted at the four corners of a rectangular part of the front wall 42 of a furnace and produce a common flame. Each burner comprises a pipe 43 supplied with pulverised fuel and primary air and pivotally mounted about an axis at its front end so that the four burners may be rocked from the parallel position shown, towards a line extending normally to the front wall 42 from a point centrally disposed of the four burners. The burner pipes extend through slots 77 in air registers 48 and through slots 74 in a secondary wind box 44 and are tilted simultaneously by a device comprising links 85 connecting the pipes to a nut 81 engaging a screw 82 rotated by a hand wheel 83 and rotatably supported and held against lengthwise movement at its forward end 84. The fuel/air ratio in the central part of the common flame increases as the axes of the pipes are caused to converge thus lengthening the flame. In a modification the air register of each burner is rigidly connected to its burner pipe 43 for movement therewith and is connected to the furnace wall by a ball and socket joint, the direction of the secondary air being thus varied with the direction of discharge of fuel and primary air. In a further modification the four burner pipes and their air registers are non-rotatably mounted to discharge parallel streams of fuel and air into the furnace and an impeller 58, Fig. 2, comprising spaced but overlapping conical rings and a closure member 70 closing the spaces between the rings over one quadrant only is positioned a short distance outside the discharge end of each burner pipe. The impellers are secured to rotabable shafts 56 extending through the burner pipes and provided with handwheels. When the impellers are positioned so that the blocked quadrants correspond with the outer parts of the common flame there results an insufficiency of air in the centre of the flame so that the flame is long. Fig. 9 indicates a vapour generating and, superheating unit comprising an upwardly extending pulverised fuel fired slag tap furnace chamber 100 having a lateral gas pass 101 leading from its upper end to a downwardly extending gas pass 102; a tubular convection superheater 103 being disposed in pass 101 and a further tubular convection superheater 104 and an economiser 105 being disposed in pass 102. A sideward extension 106 of the lower part of the furnace chamber provides an inclined arch wall 109 through which pulverised fuel burners 117 surrounded by a secondary air box 121 discharge fuel and primary air downwardly. The arch 109 and the upright side walls 110, 108 to which the arch is connected are lined with fluid cooled tubes. A slag discharge outlet 118 in the floor 111 of the furnace chamber communicates with a slag pit 119 containing water. Each burner 117 comprises twelve tubes 127 arranged in three groups 130a, 130b, 130c, Fig. 11, of four tubes, the discharge tips 112 of each group being arranged in a. row between pairs of adjacent fluid cooled tubes 115 lining the arch 109. The outlet ends 128b of the middle group 130b are secured to tip members 122b which are secured to the adjacent fluid cooled tubes 115 but the outlet ends 128a and 128c of the outer groups are joined to their tip members 122a, 122c by knuckle joints 132, Fig. 14, permitting angular displacement between the tubes and their tip members which are provided with pivot pins 133 fitting within slots 134 in blocks 135 attached to adjacent fluid cooled tubes 115. The inlet ends of the outer groups 130a, 130c are of rectangular section and have cylindrical surfaces 136 engaging complementary surfaces on a riffle 123 fed with fuel and primary air and subdivided by transverse bars 124 of upwardly tapering cross-section into a row of twelve side by side slots 125. The coacting surfaces of the ends of the tubes 127 and the riffle are held in contact by pairs of compression springs 140 compressed between the heads of studs 141 screwed to the riffle and lugs 142 on the tubes 127, the studs passing through the lugs with sufficient clearance to permit tipping of the tubes 127. The tubes of both outer groups 130a, 130c are moved simultaneously to vary the direction of discharge of fuel and air from their tip members by operating means positioned outside the secondary air box 121 and connected to a plate 143 having a slot 144 receiving the four tubes of the group. In operation the outer groups of tubes are inclined toward the middle group to starve of air the core of the common flame and thus to lengthen the flame to maintain a desired temperature of the products of combustion when they pass into the lateral gas pass and also to maintain a desired state of fluidity of the slag on the floor of the furnace chamber. In a modification the burner comprises three tubes discharging pulverised fuel and primary air to a furnace chamber, the outer pair of tubes being pivotally supported adjacent the furnace so that their inclinations to the middle tube can be varied to alter the flame length. Specifications 331,555, [Class 75(i)], and 433,834, [Group XII], are referred to.