Patent GB-303422-A (GB)
Title: Improvements in or relating to the storage of powdered fuel and to the feeding of such fuel to the burners or injectors of furnaces
IPC: F23K3/00
Filed: 1927-06-25
Abstract: 303,422. Brand, J. J. C., and Laing, B. June 25, 1927. Pneumatic conveyers.-Relates to systems for feeding powdered fuel such as coal to the burner nozzles or injectors of a furnace, of the kind in which the fuel is fed through a pipe line from a source of supply such as a ship's bunker to a " ready-use " bin, whence it is withdrawn by a feeding device or distributor. According to the invention, provision is made for aerating or "fluffing-up" the powdered fuel within the ready-use bin, by means of air or inert gas, to cause it to flow more freely, and means are also provided for admitting a controlled volume of air to the fuel during or after its passage through the feeding device, as it passes from the bin to the burner nozzles or injectors. When the fuel is stored in powdered form in bunkers, before passing to the ready-use bin, provision may be made in addition, for "fluffing-up" the fuel in the bunkers. Two systems for use on board ships are described and shown. In the first, Fig. 1, lump coal is stored in bunkers 1 and is sucked through a pipe 3 from a feed hopper 2 into a closed hopper 4 arranged about a pulverizer 5. Suction is applied to the hopper 4 by means of a pipe 9 connected to a cyclone separator 8, which is in communication with a vacuum pump 6 through a pipe 7. By this means coal dust from the hopper 4 passes to the separator 8, whence it is periodically discharged through a valve 8<a> to the hopper 2. Coal is fed from the hopper 4 to the pulverizer 5 through a valve 11 or 12. Hot gases are drawn by the pulverizer fan from the funnel 19 through a ,pipe 20, which is fitted with an air. vent 21 to control the temperature. The use of such gases serves to dry the powdered fuel. Additional hot gases may be introduced at the delivery end of the pulverizer. A pipe 13 delivers the crushed coal to a cyclone separator 16, from which a branch pipe 15 returns surplus gas or fuel to the pulverizer; or gas may pass through a vent 18 to the atmosphere. The powdered coal passes from the separator 16 through a pipe 22 to a ready-use bin 23, which is provided with means (such as are subsequently described in connection with the second system) for "fluffing-up" the fuel in it as and when required. From the bin, the fuel is withdrawn by screw feeders 24 driven by a motor 26 and variable speed gear 25, the feeders supplying the fuel mixed with air through pipes 27 to burners 28 at the front of pre-furnaces 29. located in front of the existing combustion space of a boiler. A carburetter may be provided if necessary to mix the air and fuel thoroughly. The air for admixture with the fuel is drawn from heaters (not shown) by means of fans 32, and passes from a pipe 33 through branches 35 to the exit ends of the feeders 24. The system described above is shown as being arranged in duplicate, the section on the right half of Fig. 1 being taken on a plane behind that on which the section on the left is taken. The second system, in which coal already powdered is stored in the bunkers, is shown in Figs. 5 and 6. The fuel is preferably loaded into the bunkers, from a pulverizer on shore, by the method described in. Specification 301,413. To discharge the fuel into ready-use bins 23, pipes 42 are provided, extending along the length of each bunker 1, the pipes 42 communicating through branch pipes 43 with a pipe 42* connected to a suction fan 41. The fuel is sucked through openings in the pipes 42, controlled by valves 44, and is discharged by the ian through a pipe 46 into a cyclone separator 47, whence it passes to the bins 23. In the construction shown, air or inert gas passes from the separator down a pipe 39 which has branches 40 extending into the bunker. By this means, the gas is caused to " fluff up " the fuel so that it flows more freely through the pipe lines. Alternatively, the pipe 39 may be supplied with gas from a compressor, instead of from the separator 47. In this case, a pipe receiving hot air from the stokehold leads to the pipe 42. A screw feed device may be provided in the bunkers adjacent to the openings in the pipe 42. Air circulating through the casing of the auxiliary combustion chamber 50 is passed by means of a fan 51 through a pipe line 52, is circulated through a heater 31, and passed through a conduit 53 to a main 33. From this main, primary air passes through pipes 35 to the exit ends of screw feeders 24, discharging the fuel from the bins 23 through pipes 27 to the burners, while secondary air passes down pipes 55 to boxes 56 surrounding the burners. An opposing current of air passes down pipes 57 and enters the auxiliary combustion chamber. One or more pipes 58, Fig. 5, lead from the main 33 into the bins 23, to " fluff-up " the fuel therein when necessary.