| OCR Text |
Show of the cone by using a factor L, representing the nose length of the concentrator. Coals were ground and sieved to be 80% passing through 200 mesh. The mechanism of the condensation process is as follows. Coal particles are carried to the concentrator by the primary air around the plug pulled backward at the high load condition , flowing inside and outside the cylinder, with no condensation occurred. At the condition of under 43 % load, the plug will be pushed in the cylinder and coal particles and primary air flow only outside the cylinder and coal particles go straight through the outer surface of the cone because of the force of inertia, whereas the primary air stream turns into the inside of the cone. Fig.6 shows the relationship between the coal concentration, (C/A) and the radial distance at the outlet of the coal burner. The upper figure shows the concentration map measured for the standard model of concentrator. The hatched area shows the region of the outer flow path of the cone and the parameter is the axial distance from the burner outlet. It is seen that the value of CIA greater than 0.2 was obtained at the dimensionless axial distance, r/R equal to 0.06. However, the coal concentration was diluted immediately outside of the burner outlet by the interaction of the inner flow. That is, the velocity gap caused the mixture of the lean and dense flows immediately outside the burner outlet. Therefore, the distribution of the coal concentration is like a Gaussian type at Z/R greater than 1.2. The lower figure is the coal concentration map for the concentrator with a longer nose than the standard. At Z/R equal to 0.06, a relatively high concentration area (C/A>0.2) is more remarkable than the upper figure. This is because the mixing of the lean and dense flows was reduced by the nose of the concentrator. In other words, the enlargement of the nose is effective to reduce the interference of the two phase jets at the outlet of the coal burner. LARGE SCALE EXAMINATIONS 1.Single Burner Test by using Small Scale Test Facility Fig.7 shows the cross section of the single burner test rig we used. The inner furnace shape is 0.6 m square and 5 m long, and total heat input is 300,000 kcal/h (equivalent to 50 kg/h coal feed rate). Combustion air was compressed by FDF ( Force Draft Fan), pre-heated and carried to the burner inlet. Coal particles were stored in the two bins and carried to the burner inlet at a desired coal feed rate. The two different flows were individually drawn into the outer and inner flow paths of the cone, therefore the CIA in the outer path was known to clarify the minimum coal concentration for the stable ignition in relation to the air flow rate. We used typical three burners, one conventional type and two new types we designed. Fig.8 shows the 02 concentration near the burner outlet in the 4 |
