| OCR Text |
Show corner of the reactor is clearly evident in all three reactor maps. Second, there appears to be a zone of intense reaction which extends out of the primary jet, and curves along the boundary of the recirculation zone outward to the reactor shell. This zone is illustrated Dy tne dashed lines in Figure 5. A wall attachment point along tne outer wall seems to exist at about 30-35 cm. The flow in the remaining aft part of the reactor seems to show little change with only slight reductions in CQ2 and slight increases in CO and H2 as the water gas shift and char oxidation reactions take place. It has been postulated that coal basically reacts in two phases. The first, pyrolylis or devolatilization phase, takes place very rapidly. The second phase consists of the heterogeneous reaction of the remaining char with the C02 and steam, the oxygen having already reacted with the gaseous devolatilization products. The pyrolysis reactions are known to be very rapid (14) while the heterogeneous reactions are known to be relatively slow (14,15). The three maps shown in Figure 5 tena to support these postulates. A zone of very rapid reaction is observed where as much as 60-80% of the coal reaction has taken place. This is followed by a zone where the remaining reactions proceed very slowly. A similar set of maps for the principal sulfur pollutants (H2S, SO, and COS) is shown in Figure 6. These maps show the same recirculation zone and very intense reaction zone shown in Figure 5. Some very interesting observations can be made. Very high levels of S02, like C02 in Figure 5, are observed in the intense, oxygen-rich flame region. All of the 02 was introduced along with the coal in the primary stream. Tne levels of S02 then decrease and levels of the more fuel-rich species, h2S, CS2, and COS, are formed. It was expected, based on equilibrium calculations and complete carbon consumption, that no significant amounts of S02 would be present at the reactor exit for the overall fuel-rich operating conditions of the reactor (02/Coal = 0.912; steam/coal = 0.271). Nevertheless, it is evident that, in the early regions of the reactor, S02 is the major sulfur pollutant formed. It is also evident, if sufficient residence time exists in an entrained reactor, that virtually all of the S02 would be reduced to H2S and other fuel-rich sulfur species. 6-17 |
