OCR Text |
Show The boilers of about 120,000 units currently installed at various places in Japan can be classified into a number of different types as shown in Fig-3. Taking a fire tube boiler, for instance, the type has been changed from induced draft-*- 3 path forward flow - 4 path forward flow -*• 2 path reverse (return combustion) -*» 2 path forward flow, and to 1 path forward flow. (See Fig-4.) The shape of combustion chamber and the thermal load are also diversified. Low NOx arrangement is necessary not only for the boilers newly installed but also -for the oxisting boilers. Accordingly, the arrangement shall be advanced in the manner appropriate to respective boilers, in other words, while ensuring the original performance of each boiler. From the view point, different types of low NOx burners are developed to suit for each condition of representative combustion chambers as one of the most important measures for low NOx arrangement. The software technic for installation and operation control of low NOx burner has also been advanced considerably. Fig ."3" NumBer ot "boilers installed bv_type "and capacity Fig. 3 Number of boilers installed by type and capacity £9 ^2 Tvoe Center forward flow com-hncr- f nn path' 1 Deflec- . tion for--1 ward flotpat Combustion StL ch pach i TvPe 3 path t P*rh U-shape J path fire tube forward flow com-ipath^,flth butlon enter re turn com-bution Deflection return com-butlon combustion 8 iL„_ jt m M ^ i Total 55,046 Water tube type Forced circulation type Horizontal fire tube type Locomotive type Hot water boiler Cornish type £1 Coast iron combination . Once through type Fire_tube type J Lancashire type Locomotive type Vertical type Ship boiler JLJ] JLLLB a u S i UM O -. B-* < o o o o o o o o o at w ai at v i S i S $ & - 8 - |