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流化床液体射流(文献)

Introduction

    Gas-liquid-solid fluidized beds are used in fluid cokers to convert a heavy hydrocarbon feed into lighter hydrocarbon components, gases, and coke [1,2]. The liquid hydrocarbon feed is introduced as a spray that wets hot solid bed particles. The solid bed particles provide a large surface area upon which rapid vaporization and chemical reactions take place because of high heat transfer rates. In such a process, the liquid to solids contacting and the resulting liquid film formation on particles is fundamental. For a given liquid feeding rate, a more uniform liquid to particle coverage results in a reduction in the film thickness leading to lower likelihood of agglomeration, higher heat transfer rates and increased product yields.
    The mechanism by which the liquid spreads over the particles' surfaces is collision between liquid spray droplets and bed particles, and between the wet bed particles themselves. More generally, collisions result in mass, momentum, and energy transfer between particles and cause a variety of associated physical effects. Momentum transfer results in the damping of relative motion between particles, which, in turn, reduces the collision frequency. In addition to spreading the liquid over the particles' surfaces, collisional mass transfer results in mixing of liquid residing on different particles and a tendency toward local uniformity of liquid chemical composition and liquid temperature on different particles.
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