GB1355054A - Industrial boilers - Google Patents

Abstract

1355054 Burning solid fuel and/or fluent fuel; burner controllers G W B BOILERS Ltd 21 Sept 1971 [22 Sept 1970] 44973/70 Headings F4B and F4T In a boiler furnace having a burner, a grate and means for feeding solid fuel to fall on to or towards the grate, the fuel feed and the burner are controllable so that in operation, the fuel feed or the burner can operate alone or both can operate together. A cylindrical combustion chamber with a burner at one end 26, is surrounded by a water jacket with two passes of smoke tubes 34, 36 leading to a chamber 37 having a grit arrestor 38 and flue 39. Solid fuel, such as wood waste, is fed from a hopper having an endless belt floor to a screw feeder to a pneumatic feeder connected to a conduit. From the conduit 11 wood waste passes to an inlet tube 12 leading through the boiler shell to a funnel shaped outlet 20 above a grate 25 in the combustion chamber. The tube 12 is surrounded by jacket 22 receiving pressure air from the conduit 11. Tangential inlets 21 at the top and bottom of the tube 22 ensure that the solid fuel is evenly distributed over the grate 25. Air from a blower is fed below the grate at A, and through a conduit 40 to the combustion chamber above the grate. Fuel residues from the grit arrester 38 are returned to the combustion chamber through the air conduit 40. Refracting rubble is supported in the grate 25 so that the wood waste forms a fluidized bed. The furnace is controlled by a system comprising two photoelectric cells, 45, 46, Fig. 3B, directed towards a flame in the combustion chamber, and towards the burner flame tube respectively. The detector 46 is shielded from the combustion chamber so that it gives an indication as to whether the burner is alight, regardless of whether wood is burning in the combustion chamber. These flame detector devices control the oil supply line 28. A programmed timer 49 controls both the wood and oil supply lines 11, 28. At start up, the timer control allows only oil to be fed to the furnace, after purging with air, and a first low rate of supply is maintained, subject to sensing of a flame by detectors 45 and 46. After a predetermined time, the oil supply is increased to that required for operation. After a further time interval, the oil supply is reduced and wood is fed to the furnace, the feeds being maintained while the flame is sensed by detectors 45, 46. The oil supply is then cut off under the control of the timer and the wood feed is increased and maintained while detector 45 senses a flame. A failure of sensors to detect either a wood flame alone, or both an oil or wood flame when required cuts off the appropriate feed lines, and returns the timer to the starting position to purge the furnace with air, and restart it.