OCR Text |
Show 15 The effects of pressure were not clear from the data collected; however, some trends were noted for Ole and temperature effects. Figures 5 and 6 illustrate the effect of Ole ratio on the abundance of As, ed, Se, and Hg in the assumed vapor phase at 1500° and l000°C initial gasification temperatures, respectively. The results indicate a general decrease in As, Cd, and Hg with increasing O/C ratio and a slight increase in Se with increasing Ole ratio. A possible explanation for these results is that more oxidized forms of As, Cd, and Hg are less volatile, whereas the oxided form or species of Se is more volatile. The lower volatility of reduced Se relative to the oxide form has been discussed by Dismukes (16). The effect of initial gasification temperature on the abundance of trace metals in the gas phase is depicted in Figure 7. At a constant pressure of 50 psi and an Ole ratio of 2.0, increasing the gas temperature causes the abundance of As, ed, Se, Hg, and Pb to increase. The effects of carbon burnout, which also tends toward greater values with increasing temperature, may be overshadowing '."Q.C..) 100 .oA EECsRdC CZ10462..CDR C,.) 80 Q) • Se 0 o Hg C,) .c..o. 60 ~ '+- 0 CD 40 C> .c..o. c CD (.) ~ 20 CD CL 0 0.5 1.0 1.5 2.0 OIC Ratio Figure 5. Trace metal distribution vs. Ole ratio for Illinois No.6. |