552
Ind. Eng. Chem. Process Des. Dev. 1989, 22, 552
Hill. A. B.; McCormick, R. H.; Barton, P.; Fenske. M. R. AICM J . 1062, 8 , 681. KkffM, L. J. J . Chem. Doc. 1000, 8(3). 167. Mah, R. S. H. Clmpit. Chem. Eng. 1077, 1. 183. of the International SyrnposC Murthy, A. K. S.; Zudkevitch. 0. “Pr-ngs um on DlsMlatlon”; London, Apr 1979. Nelson, A. R. M.S. M,Unkerslty of Delaware, Newark, DE, June 1981. Sandler, S. I . ”Proceedkrgsof h NPL Conference on Chemical Thermodynamk Data on Fluids end FL*I Mlxhres: Thek ~stknatkn.corrdatkn and Use”; IPC Sclence and Technoloey Press: England, 1079; pp 79-86. Stocklng, M.; Erbar, J. H.; Maddox, R. N. Pet. Eng. 100, 52(4), C15. Strelch. M.; Kbtenmcher. H. "Proceedings of the 2nd IntcwnatknalConference on Phase Equ#lbria and Fluid Properties In the Chemical Industry”; Berlh, Mar 17-21, 1980; Knapp, H.; Sandler, S. I., Ed.; DECHEMA Frankfurt, 1980; p 863.
Van Wlnkle, M. ”Mstlylrtkn”; McGnwHIII: New York, 1967; pp 307-321. . &(a). 155. Wang, J. C.; M e , 0. E. h j d v x a ~ P r o c e s s1066, WIwiclms. C. C.; Albrlght, M. A. Hvaooarbon Rote#. 1070, 55(5). 115. Wilson, 0. M. J . Am. (%em. Soc. 1084, 86, 127. Yaws, C. L.; Patel, P. M.; Pttts, F. H.;Fang, C. 0. ~ o c a r b t mPIOcess. 1070, 58(2), 99. Zudkevltch, D. m f 6 o n procegs. 1076, 54(3), 97.
Department of Chemical Engineering University of belaware Newark, Delaware 19711
Andrew R. Nelson Jon E.Olson Stanley I. Sandler*
Received for review January 28, 1982 Accepted December 30,1982
CORRESPONDENCE Comments on “Kinetics of Coal Gaslflcatlon”
Sir: In a recent publication, Schmal et al. (1982)modeled the kinetics of coal gasification. They concluded that the experimental data can be adequately represented by both the continuous model and the shrinking core model with chemical reaction controlling. However, the basic assumption in the shrinking core model is that the chemical reaction step is fast. As Froment and Bischoff (1979) emphasize, “...the limiting case of chemical reaction rate controlling is not consistent with the concept of a shrinking core model with a single diffusivity throughout the particle: the existence of a sharp boundary implies transport by effective diffusion that is potentially slow with respect to the reaction”. It would have been more realistic if the
authors had considered both ash diffusion and chemical reaction rate to be controlling or used a more detailed model taking into account the structural changes in the solid (Szekely and Evans, 1970).
Literature Cited Froment, 0. F.; Blechoff, K. 6. “Chemical Reactor Anatysh and Design”, m y : New York, 1979. schmel, M.; Montelro, J. L. F.; Castellan, J. L. Ind. €4. (%em. frome Des. Dev. 1002, 21, 256. Szekely, J.; Evans, J. W. Chem. Eng. Sei. 1070, 25, 1091.
Department of Chemical Engineering Indian Institute of Technology Kanpur-208016, India
D.Kunzru
Response to Comments on “Kinetics of Coal Gaslflcation” Sir: The comments of Kunzru are pertinent, but as shown, the experimental data fit well the single skrinking core model. The diffusional effects should be important and are object of a new study. We published a paper including a more detailed reaction rate equation based on the Langmuir-Hinshelwood equation (Proceedings, In-
ternational Conference on Coal Science, DUsseldorf, Sept 1981,p 203). Corrdemcao dos B~~~~~~~ de Pos-Craduacao de Engenharia Universidade Federal do Rio de Janeiro Rio de Janeiro, Brazil
CORRECTION
Phase Equilibria for Aqueous Solutions of Ammonia and Carbon Dioxide, E. M. Paulikowski, J. Newman, and J. M . Prausnitz, Ind.Eng. C h m . Process Des. Dev.1982,21,764. Page 769. In Table VI, please note the following corrected expressions for binary interaction constants: Pij(NH,-NH,) = -0.0260 + 12.29/T /3ij(CO,-CO,) = -0.4922 + 149.2/T @ij(NH3-C0s2-)= 0.3238- 0.0008779.T 0196-4305/83/ 1122-0552$01.50/0
0 1983 Amerlcan Chemlcal Society
Martin Schmal
