| OCR Text |
Show -7- For the mono-channel burner, the main variables studied were primary air percentage, injection velocity and momentum. For the multi-channel burners, additional parameters such as the air distribution between channels and the velocities of the axial and swirling air were studied. During the trials three fuels were used, high and medium volatile bituminous coals and petroleum coke, table 1. Input and flue gas concentrations were measured for a total of 161 flames, with detailed in-flame measurements of temperature and gas species for a number of selected flames. The temperatures of the walls were measured and heat flux to the wall determined by the take-up of heat in the external cooling water. Wall temperatures up to 17000 c (3090 0 F) were experienced. 3.1.1 CEMFLAM Resu1ts The results showed the following effects with respect to NOx formation: 1. The major effect on NOx emissions was the ignition distance; the greater the stand off of the flame from the burner, the higher the NOx emissions. 2. Fuel type had a strong effect on NOx with petroleum coke producing the highest emissions (because of a long ignition distance) and high volatile coal the lowest. 3. For any specific burner, increasing the burner momentum increased the NOx. 4. The mono-channel burner gave the highest NOx emissions and relatively longer ignition distance than the multichannel burners. 5. The geometry of the multi-channel burners had a significant effect on the NOx emissions. 6. Coal particle size affected NOx - generally coarser coal gave lower NOx values. 3.1.2 CEMFLAM Conclusions The principle conclusions were that the design criteria for a low NOx kiln burner for solid fuel should be: |
