OCR Text |
Show (2) Transformation of Fuel-N content to N2. NOx The Fuel-N of refuse is considered to be transformed to N2 and NOx in the furnace by the .echanism shown in Fig. 1-2. It can be seen from the figure that the transformation ratio of Fuel-N to NOx is controlled lower when the 02 concentration is lower in the furnace. (3) AMount of air From itme (2) above. it is necessary to maintain 02 concentration in the furnace lower in order to control generation of Fuel-NOx. As a result that we studied a influence of the under-grate air by the same experimental device of item (I) above, the under-grate air does not affect the volume of NOx generated in the refuse layer much. NOx at the outlet of the furnace increases rapidly as the air blown into the refuse layer is increased, that is, increase in 02 concentration in the combustion gas. (Refer to Fig. 1-3) The reduction gas components (CO, C11 4 , 112 ••• ) generated in the refuse layer increase as the air flow volume is increased. (Refer to Fig. 1-4) This may be considpred due to the f8ct that by increasing air flow volume the drying of the refuse was accelerated. 2) Principle of NOx control The principle of NOx control is as shown below: (1) Generate as much reduction gas as possible in the drying zone. (2) Lower 02 concentration in the combustion chamber, so as to avoid the combustion of reduction gas generated in the combustion space above the refuse layer as much as possible. (3) Let the reduction gas from the combustion chamber go through the process of after burning, namely, two-stage combustion in the after burning chamber where it is not affected by flames in the combustion chamber, while making it sufficient to serve self-denitration. 3 |