OCR Text |
Show 5 Inside the furnace, these two streams first encounter a 30°, adiabatic quarl which is 0.425 m long. The gases then pass through a 0.782 m long, 0.826 m diameter, adiabatic, cylindrical section. These adiabatic sections (quarl and cylindrical sections) provide the necessary radiant heat feed-back to the coal particles on entering the furnace to devolatilize and burn. The gases then pass through a 4.22 m long, 0.984 m diameter cylindrical section before going through the 0.495 m diameter exit. This last cylindrical section consists of many "c" shaped sections through which a coolant flows. This "c" shaped section is shown schematically in Figure 1. The flow rate and temperature rise is recorded for each of these sections and thus acts as a calorimeter giving the axial variation of the total heat flux at the wall over the last 4.22 m of the furnace. The open part of the "c" forms an access slot along the last 4.22 m of the furnace. The intrusive probes are inserted into the furnace through this slot. As shown in Figure 1 both the adiabatic and cooled sections of the furnace have ports which allow for the insertion of probes to make measurements in the gas stream inside the furnace. An axial slot was cut in the adiabatic, cylindrical section to allow for probing in the near burner region at any axial location. The primary and secondary air is supplied from separate sources so that a varying demand on one will not have an effect on the supply for the other. The pressure inside the furnace is controlled by means of a forced draft fan. This ensures that there is no contamination of outside air in the furnace gases. The coal is pre-pulverised and fed to the furnace using a "KTron" feeder system shown schematically in Figure 3. The hopper holds about 100 kg. of coal which is brought to a venturi pick-up bucket via an auger feed mechanism. The weight of the coal in the hopper is monitored using load cells so that the auger can feed a constant mass flow rate of the coal to the furnace. |