1Frohning, C. D.; Kolbel, H.; Ralek, M.; Rottig, W.; Schnur, F.; Schulz, H. I n "Chemierohstoffe aus Kohle"; Falbe, J., Ed.; 0. Thieme Verlag: Stuttgart, Huff, G. A. Chem. Eng. Sci. 198la, 36, 790. Satterfiekl, C. N.; Huff, G. A. Ind. Eng. Chem. Process Des. Dev. to be published, 1981b. Schlesinger, M.; Benson, H.; Murphy, E.; Storch, H. H. Ind. Eng. Chem. 1954, 46, 1322. Schumpe. A.; Serpemen, Y.; Deckwer, W.-D. Ger. Chem. Eng. 1979, 2 , 234, 267. Shah, Y. T.; Deckwer, W.-D. Chapter 6 in "Scaleup in the Chemical Process Industries"; Kabel, R.; Bisio, A., Ed.; Wiley: New York, to be published, 1982. Suganuma, T.; Yamanishi, T. Kagaku Kogaku 1966, 30, 1136. Szeri, A.; Shah, Y. T.; Madgavkar, A. Chem. Eng. Sci. 1976, 31, 225. Tareeff, M. ColloidJ. USSR 1940, 6 , 545; cited in Chem. Eng. 1957, 64(3), 273. Villadsen, J. V.; Michelsen, M. L. "Solution of Differential Equation Models by Polymonlal Approximation"; Prentice-Hall: Englewood Cliffs, N.J., 1978. Zaidi, A.; Louisi, A.; Ralek, M.; Deckwer, W.-D. Ger. Chem. Eng. 1979, 2 , 94.This paper discusses the linear and nonlinear stability analysis of a fixed bed catalytic reactor with heat exchange between the feed and product streams, with special emphasis on cases which are open loop unstable. Our approach, which uses classical frequency response techniques, contains the implicit assumption that the designer should evaluate the effect of the overall design on stability. The paper shows how at this stage, with only limited information about the process, he can determine the minimum information required for this evaluation. The method outlined clearly pinpoints where the stability problems exist because the effects of each unit operation on the system stability are evaluated independently.This work reports a kinetic study on the gasiflcation of Brazilian mineral coal with steam using a thermobalance.The coal is a high ash content (>50 wt %) subbituminous, run of mine coal (Charqueadas). Isothermal runs were made at temperatures between 800 and 1000 O C and at atmospheric pressure, using -14 +20 mesh Tyler size particles. The coal was devolatilized before the gasification. Initially, the influence of the particle size of coal and the flow of steam were studied in order to determine if diffusive effects are important. For certain conditions these effects are negligible and chemical reaction is the rate controlling step. The experimental results are well descrlbed by the unreacted core model above 850 O C and by the continuous model below this temperature. The gaseous products were determined at different times and temperatures and contained essentially H, , CO, and CO, .Comparison of the present results with other data published shows that this coal is highly reactive.
