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Show type of reactor considered in this study. It should be noted that Eq. (16) is valid only above a critical value of Uavr where the flow is fully turbulent. For the 15 test cases considered here, the gas residence times calculated from Eq. (2) and the particle residence times calculated from the computer simulations are compared in Fig. 5. There are large differences between the two especially at the longer gas residence times. An empirical curve fit of the data produced from the simulations of 15 test cases gave the following values for the constants in Eqs. (6 to 9) : A = 0.60, B = 1.49 x 10-5, p = 1.40, q = 2.5 (17) With these constants, Eq. (6) is plotted in Fig. 6 against the particle residence times predicted from the computer simulations with a confidence of ± 25% for a wide range of operating conditions. This figure shows that the new correlation (Eqs. 6-9) can be used to estimate the particle residence times using known quantities or quantities that can be readily calculated Vtith a confidence of ±25% for a wide range of operating conditions. 6.0 CONCLUSIONS The panicle residence times for an entrained flow gasifier for pulverized coal were calculated Vtith a two-dimensional computer code suitable for simulating gas flows with a dispersed and reacting particle phase. Particle residence times thus calculated were used to develop a correlation for predicting the particle residence times for the reactor. The correlation took into account the slip between the particle and gas-phase due to gravity, turbulent panicle dispersion, and the change of particle size during its residence in the reactor. These effects were readily calculated from known flow rates, reactor geometry, and operating conditions. The predictions were shown to have a ±25% confidence level over a wide range of operating conditions. Therefore, particle residence times in future tests can be estimated without the use of complex and time consuming calculations. Acknowledgements This work was sponsored by the U. S. DOE, Morgantown Energy Technology Center, under the Contract No. DE-AC21-85MC22137. The authors would like to thank Mr. L.A. Bissett for his reviewing of the manuscript and sharing information related to his experiments. -10- |