| OCR Text |
Show Table 1 Experimental conditions combustion rat io 25% 50% 100%(25 Mcal/Hr) oxygen ratio 1. 05 (primary oxygen~total oxygen = 0.1) steam ratio (volume) 8 = flow rate of s+ am~ flow rate of COG = 0% 75% 150% velocity of COG J Nm/s velocity of primary oxygen 20 Nm/s velocity of secondary oxygen 120 Nm/s velocity of steam 60 Nm/s diameter between 2nd 02 nozzle D=115mm composition of COG (%) HL 00 Go Go' Kcal Nm3 Nm 3 Nm3 H2 02 N2 CO2 CO CH4 C2He C2H4 Nm 3 Nm 3 Nm 3 Nm3 54.1 0.6 6.0 2.9 7.4 25.4 1.3 2.3 4318 0.924 1.623 0.489 HL: lower calorific value 00: stoichiometric amount of oxygen Go : theoretical amount of wet burnt gas Go' : theoretical amount of dry burnt gas Figure 4 and Figure 5 indicate mean temperature in the furnace and mean heat flux on the water pipes, respectively. Neither CO nor H2 was detected at the gas exit in any condition shown in the figures. To compare, a conventional air/COO burner with the same heat capacity, was tested. Figure 4 tells the oxygen/COO burner produces furnace temperature higher than the conventional one by 200 degrees. It is because the amount of heat loss to the exhaust gas is reduced owing to less volume of the flue gas in the system. Steam blowing decreases gas temperature, but the mean temperature in the case of ~= 1500/0 (volume flow rate of steam / volume flow rate of COO) steam blowing is still higher than that of the conventional system by over 100 degrees. Figure 5 tells the heat flux to the water in oxygen/COO system is 1.5 times as large as that of air/COO system Decrease in the heat flux to the water caused by steam blowing is relatively small compared with that of mean temperature, and it seems reasonable to suppose that the steam blowing in the furnace increases the emissivity of flue gas, preventing the heat flux from decreasing. Figure 6 indicates longitudinal distribution of temperature in the furnace. The temperature values are normalized by setting the each mean temperature to unity. The maximum temperature always appears I-2m apart from the burnef. Normalized temperature distribution in the furnace is less than 200/0, using oxygen/COG burner without steam blowing, almost the same as that of the air/COO burner. Additionally, with steam blowing, the maximum temperature decreases and a longer flame is produced, which result in the decrease of distribution down to 120/0. Figure 7 indicates NOx emissions in each system The values of NOx concentration are standardized at 110/0-02 condition. Using the oxygen/COO burner, approximately 300ppm NOx emission was detected at 1250°C without steam blowing, and 200ppm with steam blowing. The effect of steam blowing on NOx emission is not clear below I 100°C. The total mass of 200ppm NOx in the oxygen/COG burner flue gas is approximately equal to that of 60ppm in a conventional ai /Coo burner flue gas. |
