OCR Text |
Show gas analysis. Oxygen and carbon monoxide concentrations increased and carbon dioxide concentrations decreased signifying incomplete or sparce combustion. An investigation of the fuel feed indicated varying feed to the combustor resulting from bridging in the feed hoppers. The bridging was overcome by replacing the feed hopper with a larger diameter hopper and inducing an air stream at the hopper's throat. Results The analysis of the data indicated that the char exhibited excellent combustion and emission characteristics over a wide range of operating conditions. No unusual problems were observed in start-up transition, achieving target run conditions, or establishing stable operating (steady-state) conditions. In general, combustion efficiencies* of greater than 90 percent were achieved in all tests. Probably the most significant combustion-related result both observed and measured in the tests was the location of the main combustion zone. Indications from the combustor temperature distribution and observation of the bed top and freeboard areas confirmed that the major combustion zone occurred at or near the top of the bed and in the freeboard. Results indicated that temperature increased steadily from the grid plate to a point near the top of the expanded bed. The temperature decreased slightly from the bed top to a height of approximately 40 inches above the distributor plate, followed by a rapid decrease in temperatures above the 40-inch level (see Figure 3). Using the maximum temperature to indicate the major zone of combustion, the temperature distribution (Figure 3) shows this point to be at the top of the bed. In general, emission levels were well within Federal guidelines. The results were not surprising based upon the char's low sulfur and nitrogen content. Emission levels were monitored continuously by "Combustion efficiencies is synonymous with carbon combustion efficiency, , _. , carbon in ash defined as 1- r : carbon in 22-10 |