关键词: 沸腾床, 返混, 固含率, 停留时间分布, 带回流的多釜串联模型, 数值模拟, 实验验证

Abstract:

The liquid backmixing characteristics were investigated experimentally using pulse tracing technique in an ebullated bed reactor of 7.2 m in height and 0.3 m in diameter. Air and water were used as the gas and liquid phases, respectively. The superficial gas velocity ranged from 0.26 to 12.97 cm·s^-1, while the liquid velocity was fixed at 0.86 cm·s^-1. The particles of aluminum oxide with an average diameter of 0.4 mm were used as the solid phase. All experiments were carried out under the solids holdup from 0 to 42.9%(vol). The results showed that each response curve demonstrated obvious long tail phenomenon, which implied that there existed evident liquid backmixing in the ebullated bed reactor at different operating conditions. A tanks-in-series with backflow model was adopted to interpret the response data, which showed an excellent agreement between the prediction and experimental data. It also indicated that the number of stages N was 8, while the backmixing coefficient k varied between 1.320 and 4.218. Most of the variances of the predicted model were within +18% of their corresponding experimental values.

Key words: ebullated bed reactor, backmixing, solid holdup, residence time distribution, tanks-in-series with backflow model, numerical simulation, experimental validation