Electrostatic Distribution in the Riser of the Multizone Circulating Fluidized Bed for Polypropylene

Abstract

This work investigates the electrostatic distribution in the riser of a multizone circulation fluidized bed for polypropylene by various electrostatic measurements. Results show all measured electrostatic parameters have a strong dependence on flow patterns with increasing bed height. They remain constant in dense-phase pneumatic transportation, while they decrease in fast fluidization. However, their polarities are different. The charge-to-mass ratio is negative under all conditions, but the negative electrostatic potential only appears in the lower part of the riser at lower gas velocities. Further signal source analysis shows that only contact electrostatic potential generated by charge transfer has a one-to-one correspondence with real charge on particles. In addition, compared to the induced potential, the contact potential in regions with higher solids concentration tends to be more negative under stronger effects of charge transfer, while in regions with lower solids concentration it tends to be more positive under strong effects of contact charging.

Electrostatic effects on hydrodynamics in the riser of the circulating fluidized bed for polypropylene

“…At the gas velocity of 6.99 m/s, there was a fully dilute‐phase region in the riser similar to the pneumatic conveying regime and the particle‐wall contact frequency was more uniform in the axial direction. This dependence between charge distribution and gas–solid flow regime was consistent with the previous research results of our team …”

“…Experiments were carried out at superficial gas velocities of 5.68 and 6.99 m/s, under which there were two types of gas–solid flow patterns and two types of charge distribution correspondingly in the riser according to our previous research . The experimental procedure could be divided into two parts: the fluidization with electrostatics and the fluidization after eliminating the electrostatics.…”

“…The particle characteristic velocities in Table 2 were all calculated from empirical formulas. 38 The LAA (Atmer 163) used in experiments is the synthetic ethoxylated amine with a density of 0.86 g/cm 3 relative humidity of 40-80%. It is worth noting that the humidity control method adopted in this work inhibited the influence of humidity of fluidizing gas on electrostatics to some extent.…”

“…To prevent a series of problems caused by electrostatics such as particle agglomeration, wall fouling, and even abnormal sparking, a large amount of liquid antistatic agent (LAA) is usually added during the operation of MZCR to eliminate electrostatics (real‐time electrostatic data of MZCR can be found in the Supporting Information). However, the current studies on electrostatics in MZCR or CFBs are still limited to the detection of electrostatic and the mechanism of electrostatic generation . So far, there has been limited progress in understanding the mechanism of electrostatics on hydrodynamics in CFBs and the addition of antistatic agents in CFBs is still an empirical behavior.…”

“…However, the current studies on electrostatics in MZCR or CFBs are still limited to the detection of electrostatic and the mechanism of electrostatic generation. 3 So far, there has been limited progress in understanding the mechanism of electrostatics on hydrodynamics in CFBs and the addition of antistatic agents in CFBs is still an empirical behavior.…”