Study Of The High-Density Circulating Fluidized Bed Pulsation Characteristics By Wavelet Theory

The fluid catalytic cracking, the integrated gasification combined cycle and other reaction process often need higher flux of particle and gas to satisfy the requirement of reaction productivity and thermal balance. The high-density circulating fluidized bed is considered the most potential reactor. The gas and solid two-phase characteristics in the high-density circulating fluidized bed, not only depends on the pressure of bed, the gas velocity, the circulating flow rate of particle and the gas-solid properties, but are affected by these influence factors such as the structural parameters (such as the diameter of bed, the height of bed and the structure of inlet and outlet) and so on. Pulsation is regard as one of the gas and solid two-phase characteristics in the bed, because the pulsation signal covers a lot of fluid dynamics behavior characteristics in the bed, and the used sensor accuracy is good, response frequency is high and operation range is wide.The study was conducted on the cold high-density circulating bed. It included the study of the pressure pulsation signal under different outlets structure and different operation conditions and the circulating flow rate pulsation signal under the same outlet structure and different operation conditions. The main bed diameter is0.205m and height is7m. The air was used as fluidized medium and the quartz sand was used as bed material in the laboratory bench. In the thesis, the signal analysis adopted wavelet analysis method, which respectively chose the best de-noising method for the pressure signal and the circulating flow rate signal. The de-noising signal adopted the wavelet packet energy spectrum analysis.Achievements of the thesis are:1. In the thesis, the impeller online measurement system of the circulating flow rate can change the sampling frequency according to the experimental requirement. The guide ring with grille is designed to improve the sensitivity and accuracy with the impeller measuring the circulating flow rate.2. In the thesis, improved the pressure sampling system and the flux of the main bed sampling system can change the sampling frequency according to the experimental requirement.3. Both the pressure pulsation and the circulating flow rate pulsation are low frequency pulsation. Both of their pulsation frequency ranges are0-12.5Hz.4. Under the same structure of outlet and superficial gas velocity, both the pressure pulsation frequency and pulsation amplitude improve while the circulating flow rate increases. Under the same circulating flow rate and superficial gas velocity, the pressure pulsation frequency and pulsation amplitude of the F-type mutation outlet are stronger than the C-type smooth outlet structure’s.5. Under the same superficial gas velocity, the constant inlet pressure and flux of the fluidization wind chamber and the constant inlet pressure of the loose wind chamber of the valve, the circulating flow rate frequency dosen’t almost change and pulsation amplitude improves with the flux of the loose wind chamber increasing. Under the same superficial gas velocity, the constant inlet pressure and flux of the loose wind chamber and the constant inlet pressure of the fluidization wind chamber of the valve, the circulating flow rat frequency dosen’t almost change and pulsation amplitude improves with the flux of the fluidization wind chamber increasing.6. Under both the inlet pressure of fluidization wind chamber and loose wind chamber of the valve are equal and maintain constant, one condition turns into another condition by only changing the fluidization flux and the condition turns into a third condition by only changing the same loose flux, the latter’s circulating flow rat pulsation amplitude is stronger than the former’s and pulsation frequency dosen’t almost change.