| OCR Text |
Show This method is applicable where more rJian one burner like shown in Fig-13 are provided and the boilers are place close eath other, and is a little more advantageous Fi*'1* Example of water tube boiler with two burners to the generation of Co or s soot because the mixing of fuel and air is better than that by two stage combustion. With gas combustion, the problem of CO or soot generation is less than that with oil combustion. As an example of operation with city gas, Fig-14 shows the data of NOx by Off-Stoichiometric combustion with double shell type water tube 45 T/h boiler (two burners) in which the lower burner is set for the fuel(city gas) rich and the upper one for the air rich. The problem for the practice of Off-Stoichiometric combus tion includes the followings (1) The number of burners is multiple and the burners are placed close to each other. (2) Allowance for fuel supply pressure and combustion air supply pressure (3) Balance between stoichiometric ratio and generation of soot. (4) Longer flame load reduction (rate down) (5) Safety for sudden change of load at strting and study on generation of unburnt substance. uut Fig--14 NOx suppression data by . Off-stoichiometric combustiio n oGaa quantlty:5,750 - 5,800 aVhr Looper .-Inside 10, out side 5 for both upper arid lower burners . o Gaa quanclcy:S,700 to S,750 mJ/hr Inside 5.6 and outside 5.1 for upper burner,Inside 3.1 and outside 3.0 for lower burner 50 45 46 44 42 40 Fuel gaa flow race (upper part coabuaclon/cocal coabuaclon)Z 8 - 18 - |
