OCR Text |
Show Through visual observation and in-flame measurements of gas composition, and temperature as well as solid sampling, it was intended to develop a "picture" of the combustion process in a blast furnace raceway, and to indicate to what extent that process could be influenced through the variation of these parameters. In order to correlate the results of this trial with existing blast furnace injection experience, heavy fuel oil was also used as an injectent. Also for that purpose the coal presently being used in the blast furnaces situated in the Armco steelworks [~3J was selected as one of the test coals. EXPERIMENTAL ARRANGEMENTS The proximate and ultimate analysis of the four coals are shown in table 1. The numbers are reported on a dry (df) and dry-ash free basis. Also in this table more complete information about the four test coals can be found. The composition of the coal after devolatilization is shown as weight percentages of the original coal (fixed elements). The ash composition, the petrographic analysis, calorific value and other coal properties giving information about the rank and plasticity can also be found in table 1. The particle size distributions for the four pulverized coals as measured by a wet sieve technique are shown at the bottom of table 1. A full-scale blow pipe and water cooled tuyere, 6 inch exit diameter, were used for these trials (fig. 6). A blow pipe previously used for oil injection on a blast furnace was obtained and modified for coal injection. At three axial locations an arrangement was made so that either a 16 mm or 32 mm diameter coal lance could be inserted to variable depths inside the blow pipe. All injectors, including the oil lance, were at an angle of 18°C with respect to the axis of the blow pipe. The injection of heavy fuel oil was performed at the standard position, resulting in the tip of the oil lance being located at the center of the inlet to the tuyere. The oil lance had an exit diameter of 10 mm. The blast mixture exited from the tuyere into the IFRF furnace nr. 1, which has a square cross-section of 4 m2 and a length of 6.25 m. The furnace is refractory lined with wall temperatures typically 1100°C during the execution of the trial. The furnace was operated at near ambient pressure. 10-4 |