GB870553A - Pulverised fuel burner - Google Patents

Abstract

870,553. Pulverulent fuel burners. ORR & SEMBOWER Inc. Feb. 6, 1958 [Feb. 22, 1957], No. 6114/57. Class 75(1). [Also in Group XII] In a pulverized fuel burner the air required for the separate stages in the burning namely; ignition and distilling, the burning of the volatiles, and the burning of the coke particles, is supplied at spaced positions along the length of the combustion chamber and only in the proportion required for the corresponding stage at each position. Fuel with a proportion of the air required for complete combustion is fed into the combustion chamber to flow in a helical path and is met at a point along the chamber by further air introduced to flow in an oppositely rotating helix whereby the inert combustion products surrounding each coke particle are swept away for the coke particle to be completely burnt. When operating at a lower rate the fuel supply is reduced by reducing the speed of the fuel crusher or the opening of a fuel delivery valve but the air initially admitted with the fuel is kept constant, the later admitted air being reduced to the necessary amount but still entering the combustion chamber at the spaced points at the same velocity as before. The burner is shown bolted to a front plate 2 of a boiler 3 in line with a central fire tube having a refractory lining 27 at its entrance. The pulverized fuel with the proportionate amount of air for ignition and distilling is supplied through a conduit 16 and given a helical motion by vanes before passing to a flaring conical opening 5 into the combustion chamber formed by a refractory cylinder 1 and end plate 4. The further air is supplied by a conduit 8 past a control damper 9 into a chamber 7 formed by a metal cylinder 6 spaced from and surrounding the refractory cylinder 1. The further air enters the combustion chamber through forwardly directed ports 10 tangentially inclined to impose a helical movement to the air as it enters at the spaced locations A, B, C, D along the combustion chamber. Between locations A and B the volatiles are burnt and at B the ports 11 are oppositely tangentially directed so as to give an oppositely directed helical flow whereby the coke particles are stripped of their surrounding body of combustion products and the completion of combustion is effected as the fuel passes the further locations C, D. Ignition of the pulverized fuel on starting up the burner is by an electrically ignited gas flame the gas being supplied by a tube 19 having an outwardly flaring conical discharge member 20 and associated end disc 23 which gives a divergent gas flame of greater angle than the entering fuel/air flow from the conical opening 5. The gas is ignited by a spark between relatively adjustable electrodes 24, 25 and first heats up the refractory lining 1 until thermostats on the surface allow the pulverized fuel to be supplied. When working at reduced rates the further air is reduced by shutting an appropriate number of the ports 10, 11 but the entering air for the helical flows is kept always at the full velocity. The ports 10, 11 are controlled by an appropriately ported cylinder B movable around the outside of the refractory lining 1 by being linked with the damper 9 in the additional air supply line 8. The divergence angle of the fuel/air leaving the conical flaring member 5 is regulated by' axially adjusting the gas supply pipe 19 to alter the position of the conical flaring member 20 relative to the member 5. A photo-electric cell may be provided to shut down the burner if the flame fails.