This paper reviews recent results obtained in our laboratory and elsewhere which show the importance of particle size distribution (PSD) in fluidized beds. Fines content in itself, often used as a descriptor, is not a sufficient parameter to characterize the PSD effect. Broadening the PSD affects gas flow through the dense phase, produces smaller bubbles, leads to more particles in the dilute phase and causes earlier transition to the turbulent hydrodynamic regime of fluidization. Chemical conversion is therefore enhanced by broadening the PSD, and the enhancement increases when the bed operates in the turbulent regime.On examine dans cet article les resultats obtenus recemment dans notre laboratoire et dans d'autres laboratoires pour illustrer I'importance de la distribution de taille des particules (PSD) dans les lits fluidises. La teneur en fines, souvent utilisee comme descripteur, n'est pas en elle-m&me un parambtre suffisant pour caractkriser I'effet de la PSD. L'elargissement de la PSD influc sur I'Ccoulement dans la phase dense, produit des bulles plus petites, donne davantage de parlicules dans la phase diluee et entraine une transition plus rapide au regime hydrodynamique turbulent de la fluidisation. Ainsi, la conversion chimique est ameliorke par I'elargissement de la PSD, et cette amklioration augmente quand le lit fonctionne en rCgime turbulent.

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The characteristics of climatic change and river runoff, as well as the response of river runoff to climatic change in the northern Xinjiang are analyzed on the basis of the hydrological and meteorological data over the last 50 years by the methods of Mann-Kendall nonparametric test and the nonlinear regression model. The results show that: 1) The temperature and the precipitation increased significantly in the whole northern Xinjiang, but the precipitation displayed no obvious change, or even a decreasing trend in the northern mountainous area of the northern Xinjiang.2) River runoff varied in different regions in the northern Xinjiang. It significantly increased in the northern slope of the Tianshan Mountains and the north of the northern Xinjiang (p = 0.05), while slightly increased in the west of the northern Xinjiang. 3) North Atlantic Oscillation (NAO) affects river runoff by influencing temperature and precipitation. The NAO and precipitation had apparent significant correlations with the river runoff, but the temperature did not in the northern Xinjiang. Since the mid-1990s river runoff increase was mainly caused by the increasing temperature in the northern slope of the Tianshan Mountains and the north of the northern Xinjiang. Increased precipitation resulted in increased river runoff in the west of the northern Xinjiang.