The Measurement Of Basic Flow Parameters In Gas Phase Ethylene Polymerization Fluidized Bed Reactor

Fluidized-bed reactor is widely used in gas phase polymerization of polyolefin. As an important component of fluidized bed, distributor maintains the stability of the fluidization process, influences the flow pattern and the quality of fluidization. So investigation on the basic properties infected by distributor in fluidized bed has been a hot theme for a long time. However, there is not an effective apparatus to measure the properties, including flow pattern, fluidizing quality or the 'dead' zone on the distributor. A novel technology was used by means of an acoustic emission (AE) sensor to investigate the mentioned properties in the fluidized bed in this work. The sensor was set on the reverse of the distributor and the wall of the fluidized bed to obtain the AE signals, which came from the collision and friction among the particles, the distributor and the chamber. A new distributor was proposed, which had an good impact on fluidization, especially the high anti-deposition quality. And all the distributors were researched by new means mentioned above. The innovation of this article can be summarized as following:1. A new gas-solid fluidized-bed distributor for polyethylene producing was proposed. The new distributor could efficiently eliminate dead-zone on the distributor, improve the fluidization quality, and make the production process more stable and flexible.2. By analyzing the signals from the distributor, it was found that the biggest mutation of the mean energy and standard deviation of AE signal was at the minimum fluidized velocity (U_mf) and the second mutation was at the minimum turbulent velocity (U_mt). And the energy ratio and deviation ratio were defined, which became the criterion of the minimum fluidized velocity and the minimum turbulent velocity.An energy distribution theory was presented based on regular evolvement of energy fraction of AE signals with fluidization velocity. Wavelet packet analysis andwave let method were used in processing the AE signals. Another new criterion of judging U_mf and U_mt was proposed based on the energy distribution theory.According to these new criterions, the U_mf was 0.08m/s, which was consistent with the consequence of the classical pressure methods.3. The flow pattern of fluidized bed was investigated by the acoustic emission measurement. The multi-circulation flow pattern was found when the new distributor and the Borstar distributor were installed in the fluidized bed. The single circulation flow patter was found when the other two distributors were installed.The quality of fluidization was investigated. By analyzing the AE signals getting from the wall of the fluidized bed, the new distributor and the Borstar distributor were found having better fluidizing qualities than other two.4. The dead zone distribution on the distributor was investigated by AE measurement. By analyzing the AE signals obtained from the reverse of the distributor, it was found that the energy difference was consistent with the result of the visual method. The criteria to identify the dead zone was that, when the mean energy value of the AE signal was 40% of the maximum value or even smaller, the corresponding area must be the dead zone.By using the novel tuyeres, the new distributor efficiently eliminated the dead zone. And it had much higher anti-deposition quality, which made the fluidization better than others.5. The jet distance of different tuyeres was investigated by visual method and AE measurement. According to this study, it was found that the acoustic signal measurement could be used in the jet distance measuring. The tuyere of the new distributor was found having a twice longer jet distance as the former ones. Meanwhile, the new tuyere could also bring a better anti-deposition quality to the distributor.The anti-leakage quality of the distributor was investigated. Comparing with theother three distributors, the new one had a better performance on this aspect.