Numerical Study On The Unsteady Flow Of The Two-stage Tandem Cyclone Separation In The FCC Regenerator

Characteristics of unsteady flow in the cyclone separator is that field changes continuously over time.While the swirl is spinning,the vortex core rotates at a certain frequency and amplitude,is called Processing vortex core phenomenon(Abbreviated as PVC).The precession of the vortex core causes a low-frequency high-amplitude pulsation of the flow field to form an exciting force acting on the housing of the separator to induce system vibration,which may cause mechanical failure.Two-stage series and multiple sets of parallel cyclone systems are used in the FCC regenerator.The PVC phenomenon of the first-stage cyclone separator and the secondary cyclone separator interacts with each other.Therefore,it is necessary to use the two-stage series cyclone system as the research object for unsteady flow analysis.If the catalyst particle concentration at the inlet of the first stage cyclone reaches 2kg/m3,the effect of solid phase particles on the PVC phenomenon cannot be ignored.In this paper,the numerical simulation method was used to study the unsteady flow the two-stage tandem cyclone sepatation.The main content and results of this paper are as followa:(1)The unsteady flow law of a two-stage series cyclone system is analyzed by taking the inlet velocity of 30m/s as an example.The pressure pulsation in the first stage cyclone is mainly based on the low frequency pulsation at the first main frequency(31.6 Hz).There are strong doubling frequency(63.2Hz)and tripling frequency(97.8Hz)components in the second stage cyclone.As the axial height decreases,the amplitude of the main frequency pulsation amplitude decreases continuously,and the amplitudes of both doubling and tripling frequency components remain unchanged.The swirl center swing in the same stage separator has a uniform period,and there is a phase difference between the different heights.(2)Inlet structure increases the asymmetry of the flow field so that both the flow field pulsation amplitude and the vortex core oscillation radius increase with height.The tangential exit structure of the first stage cyclone exacerbates the unstead y behavior of the flow field at the top of the first stage separator.Increase the swing radius of the Z=-100mm vortex core to142mm.The tangential velocity pulsation amplitude increased to 8.33 m/s and the pressure pulsation amplitude increased to 228.24 Pa.(3)Analysis of the influence of inlet velocity and exhaust pipe diameter on the unsteady state of flow field.The increase of the inlet velocity Vin causes the flow field pulsation frequency to rise steadily and the pulsation amplitude to increase.W hen the exhaust pipe diameter De increases from 0.4D to 0.6D,the frequency of the flow field pulsation decreases,and the pressure pulsation amplitude and the tangential velocity pulsation amplitude both increase first and then decrease,and reach the maximum at De=0.55D.(4)Analysis gas-solid two-phase unsteady numerical study of the system.It is found that when the solid phase concentration is 2kg/m~3,the solid phase particles will aggravate the instability of the flow field in the vertical direction,hinder the flow field from oscillating in the horizontal direction,and increase the pressure pulsation amplitude and decrease the tangential velocity pulsation amplitude,flow field pulsation frequency is slightly reduced when solid phase particles are added.(5)The accelerometer is used to measure the welded and fixed part of the refiner y industrial field regenerator and the cyclone system,and the obtained wall vibration frequency has a similar distribution with the simulated flow field pulsation frequency.