Ind. Eng. Chem. Res. 1988,27, 367-368
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CORRESPONDENCE Comments on “Comments on Recent Publications on ‘Minimum Fluidization Velocity at High Temperatures”’ Sir: We are happy to realize how much attention has been given to our work on incipient fluidization at high temperatures (Lucas et al., 1986). But, certainly, we are not that happy about certain comments by some investigators which seem to attribute as their own some of the original results of our investigations. To be specific, in a recent communication, Saxena and Mathur (1987) indicate that “...two recent i n d e p e n d e n t [italics are used for emphasis by present authors only] researchers (Lucas et al., 1986; Saxena et al., 1987,received for publication February 4,1986) have found that emf varies with temperature and have reported the same for sand beds of different sizes.” This statement is quite surprising since the same authors, in another article which was received for publication April 25,1985 (Mathur and Saxena, 1986), already mentioned the work by Lucas et al. (1986). We find hard to qualify as “independent” the results presented 10 months later from those quoted as already known. It is even more astonishing that reference to Lucas et al. (1986) (which had been already received for publication April 30, 1984) is made as a “private communication” and, as such, that we had never released a single preprint but the manuscript itself which was already submitted and not yet published. We are even more apalled to see that additional contributions of our work (Lucas et al., 1986)-which were also presented at the JournEes EuropEennes sur la Fluidisation (Lucas et al., 1983)-like our first attempt to explain the variation of emf with temperature in terms of the flow field configuration around the particle, have also been presented as theirs by these authors: In the last part of one of their recent communications (Mathur et al. (1986);received for publication March 10, 1986), they conclude “...As the Reynolds number is further increased, the separation point moves towards the downstream side of the particle equatorial plane, and the wake size decreases. This will reduce
the size of the wake and hence the magnitude of the inter-particle forces. As a result, emf increases ...” (there is an obvious printing error-which can be detected in Figure 7 of the same article-in the quoted paragraph where “decreases”appears instead of “increases”). Nevertheless, they do not mention that in our communication (Lucas et al., 1986) we stated “...Asthe Reynolds number is further increased, the separation point moves toward the rear of the particle (downstream), and the wake shrinks. Both friction and drag decrease, as well as the suction of the wake. Cohesive forces between particles will therefore decrease, and at incipient fluidization particles will rearrange themselves in a looser packing (higher emf).” Fluidization, like any other subject of research, offers an immense potential for creativeness, and we believe that it is with this approach that every researcher should work in an endeavour to achieve original results.
Literature Cited Lucas, A,; Arnaldos, J.; Casal, J.; Puigjaner, L. Communication presented at the JournCes EuropCennes sur la Fluidisation, Compiegne, France, 1983. Lucas, A.; Amaldos, J.; C a d , J.; Puigjaner, L. Chem. Eng. Commun. 1986,41, 121-132. Mathur, A.; Saxena, S. C. Powder Technol. 1986,45,281-289. Mathur, A.; Saxena, S. C.; Zhang, Z. F. Powder Technol. 1986,47, 241-256. Saxena, S. C.;Mathur, A. Znd. Eng. Chem. Res. 1987,26,859-860. Saxena, S.C.;Mathur, A.; Zhang, Z. F. AZChE J. 1987,33,5W502.
A. Lucas, J. Arnaldos J. Casal,* L. Puigjaner Chemical Engineering Department Uniuersitat Politecnica de Catalunya Diagonal 647 08028 Barcelona, Spain
Response to Comments on “Comments on Recent Publications on ‘Minimum Fluidization Velocity at High Temperatures’ ”
Sir: I am surprised and shocked to note the concern expressed by Lucus et al. in their preceding letter. Let me first put the true perspective of the research on the dependence of emf on temperature. Lucas et al., in their letter, give the impression that they were the first ones to propose it. Several years ago, Botterill and Teoman (1980) proposed it, and since then it has been confirmed by Botterill et al. (1982a,b). Lucas et al. might like to note the comments made by Saxena and Grewal(1981) when their work on the dependence of emf on temperature was begun. I feel that many others have made earlier similar comments, though somewhat implicitly in some cases, and these were referenced by Mathur and Saxena (1986a). I realize that the chronological development of any research topic cannot 0888-5885/88/2627-0367$01.50/0
be given in every article, but it has to be recognized if even an impression of claim to a scientific discovery is implied in an historical perspective. Lucas et al., in particular, seem to be concerned about the use of the word independent in relation to Saxena and Mathur’s (1987) reference to the works of Lucas et al. (1986) and Saxena et al. (1987). I do not see the basis of their objection. The works of Saxena et al. (1987) and Mathur et al. (1986) were conducted on separate equipment, in a different laboratory, and using different procedures from those of Lucas et al. (1986). This obviously makes them independent. Maybe Lucas et al. are confusing the meaning of independent with simultaneous in time. They should note that if our intention was to claim 0 1988 American Chemical Society