Patent GB-986573-A (GB)
Title: Improvements in or relating to fuel burners
IPC: F23K5/00
Filed: 1961-07-12
Abstract: 986,573. Supplying fuel to burners. BABCOCK & WILCOX Ltd. July 12, 1961 [July 12, 1960], No. 25230/61. Heading F4T. In a burner having a plurality of gas nozzles G and a liquid fuel atomizer 11, means are provided for restricting simultaneously the gas supply to the nozzles and the liquid fuel supply to the atomizer 11. The burner can operate on gas only or on liquid fuel only or on both gas and liquid fuel and in all cases the burning rate is the same so that the same air supply can be used. The gas burner comprises eight nozzles 2, 6 distributed circularly and coaxially of a furnace firing port (not shown) and the liquid fuel atomizer 11 is disposed on the axis of the furnace port. (The drawing shows the atomizer at one side for clarity) Six of the gas nozzles are supplied from a manifold 1 and the other two nozzles 6 are supplied through a gas line 5. A shut-off valve 4 controls the gas supply to both the manifold 1 and the gas line 5, and a shut-off valve 10 controls the gas supply to the gas line 5 only. The liquid fuel atomizer is a return flow type; it is supplied by a pump 26, a supply main 13 and a line 12 having a shut-off valve 19. The return line 14 has a shut-off valve 20 and divides into a primary return line 15 having a shut-off valve 24 and leading to a primary return main 17, and a secondary return line 16 having a shut-off valve 25 and leading to a secondary return main 18. The pressure in the supply main 13 is maintained constant by a by-pass valve 27 automatically adjusted in dependence of the supply pressure. A load regulating valve 29 is disposed in the primary return main 17. The pressure in the secondary return main 18 is maintained at a value less than that in the primary return main by the automatic adjustment of a regulating valve 32 by a device 31 responsive to the difference in pressures in the two return flow mains. The two shut-off valves 19, 20 may be simultaneously opened or closed by a motor 21. The gas shut-off valve 10 and the primary and secondary liquid fuel shut-off valves 24, 25 are simultaneously operated by a coupling device 8 having two positions viz. a " single fuel " position in which the gas valve 10 and the primary liquid fuel shut-off valve 24 are open and the secondary liquid fuel shut-off valve 25 is closed and a " mixed fuel " position which reverses the three valves. In the " single fuel" position either the main gas shut-off valve 4 or the two liquid fuel shut-off valves 19, 20 are closed; in the first case liquid fuel only is burned at a high rate and the primary return line 15 is in operation and in the second case gas only is burned and all eight nozzles 2, 6 are supplied. In the " mixed fuel " position both gas and liquid fuel are burned, the gas being supplied to six nozzles 2 only and the liquid fuel being returned through the low pressure return line 16 so that less liquid fuel is burned. A plurality of burners may be arranged so that all the gas nozzles receive gas from a common main in which the pressure is variable and all the atomizers receive liquid fuel from the supply main 13. Some burners may burn gas only, some liquid fuel only and some both gas and liquid fuel. The burners burning liquid fuel only return fuel to the primary return main 17 and the burners burning both liquid fuel and gas return the liquid fuel to the secondary return main 18. The burners may be caused to assume gas firing one by one in a predetermined sequence according to a variable indicating gas availability or load and to relinquish gas firing in reverse sequence. In order to keep the liquid fuel circulating under all conditions the shut-off valve 19 to each burner as arranged to send back through a line 22 to the primary return main 17 a restricted flow of liquid fuel when it is closed and a fixed throttling device 30 connects the ends of the supply main 13 and the primary return main 17.