OCR Text |
Show generated when the air temperature increases. Low NOx combustion is realized when the flame cannot be held by using room temperature air, i.e., when the high temperature air is mixed with the fuel jet formed after the mixing with burned gas and then reacts. This combustion method is possible because high temperature air is used. LARGE SCALE EXPERIMENT As related with practical and measured NOx value in high temperature air combustion, many datas which cleared stably with no problem the representative 100ppm NOx regulation value (converted to 11% Oz) under high temperature air combustion using over 1,000'C pre heated air have been reported already. CORE FURNACECUNIT FURNACE)CONS I DERATION Furnace length is determined by heating capacity and fuel consumption unit, furnace width is determined by material's dimension, weaving, bending and distance pitch between materials. The maximum furnace width of conventional practical industrial furnace is 14m in walking beam furnace, then from the meterials arrangement it is about 12m or 10m. From the characteristics of regenerative burner which is placed opposite with pairing, half width of the above, namely, 7m, 6m or 5m are the fundamental unit furnace width. In the batch annealing furnace (BAF) and rotary furnace (ROF), there is a case of one coil or two coils piled up. The maximum coil width is 6.5 feet or 7 feet, then we may consider 2m height in one coil or 4m height in two coils piled up. The fundamental height of BAF and ROF is 2m. As related with burner size, there is burner tile size, for example, 1 million or 2 million kcal/hr's burner has a 800-1,000mm burner size and has a 1,000-1,500mm burner tile size. So, the fundamental burner size (diameter) or burner tile size is 1m. Burner pitch is considered 1.5m~2.0m from burner tile size and practical distance adopted in the already used regenerative industrial furnaces. Judging from above these matters, the fundamental dimension of unit furnace is concluded 2m length, 2m height and 7m width (or 5m width) and judging from more following matters, opposite or reciprocal arrangement of burners, upper and lower burner arrangement, and mutual interference between heating zones, the fundamental dimension of unit furnace in high performance industrial furnace is 4m length, 4m height and 7m width (or 5m width). If we consider the scale up from unit furnace results to practical furnace performance, we should reject changeable causes by scaling up, then we can conclude the above dimension. We show unit furnace dimension in Fig.7. According to the above reason, we made large scale experimental equipment (Fig.8) having following specification. furnace dimension : 2.0m widthX2.0m heightx 10.Om length fuel : COG (HI=4,340Kcal/Nm3(18.2MJ/Nm3)) combustion capacity : ISOXIO'Kcal/hrd .74MW) max.furnace temperature: 1,600'C(nor 1,400'c) heated material : thermal release cooling tube We adopted combustion capacity equivalent to practical furnace and the same calorific capacity of combustion chamber as practical furnace. Furnace's refractories are composed of ceramic fiber blocks. We have thermal release pipe and heat flux measurement equipment to measure heat transfer quantity and thermal release distribution. Furnace height is changeable to investigate optimal furnace shape. We can adopt distributed fuel and air injection separately. As related with burners, we can test the two type regenerative burners, that is, center gun type (case 2) and eccentric gun type (case 3) for distributed combustion, shown in Fig.9. Testing condition is as follows. - 5 - |