Effects of preignition on pulverized-coal combustion. Seventh quarterly report, 1 April 1982-30 June 1982

Task 1, pore structure optimization, is complete. The results of Task 1 predict that high reactivity chars require high porosities and a higher concentration of large pores. The experimental studies of Task 2 illustrate the dependence of these quantities on heating rate and final temperature. The data obtained for Texas Lignite suggest that porosity (hence reactivity) is strongly dependent on the final pyrolysis temperature with the maximum porosity occurring at 1300 K. The data also indicate that to a lesser extent, the heating rate affects pore structure. Higher heating rates increase the relative number of large pores and thus can enhance reactivity by a factor of two. Hence, the optimum pore structure for char reactivity may be obtained by preparing char at 1300 K and high heating rates (> 1000 K/s). Such chars could be four times as reactive as chars prepared at 2000 K and 1 to 10 K/s. The theory of pore evolution is complete and was reported. Potential mechanisms of pore evolution have been identified and described. For the most part, all mechanisms lead to the preservation of the 1/r/sub p//sup 3/ distribution. This is the statistically derived pore distribution function which originally lead to the pore more » tree. Experimental studies conducted under Task 2 support this conclusion. The model for the bulk growth of existing pores is used to describe volatile transport through the pores. This model is reported in Section 4. The pore tree structure sufficiently resists the flux of volatiles such that very large internal pressures develop. These internal pressures provide a good environment for gas phase collisions and secondary chemistry. Secondary chemistry is assessed under Task 4 in Sec. 5. Preliminary results suggest vast potential for secondary chemical reactions. 16 figures, 2 tables. « less