Effect of Fluidization Pressure on Electrostatic Charge Generation of Polyethylene Particles

Abstract

Electrostatic charge generation in gas−solid fluidized beds results in operational challenges in some industrial processes such as polyethylene production. Such reactors operate at elevated pressures, and thus, the aim of this work was to investigate fluidized bed electrification at pressurized conditions. The degrees of particles' charging and wall coating in a pressurized pilot-scale gas−solid fluidized bed of polyethylene resin was studied from atmospheric pressure to 2600 kPa (abs), while the gas bubble dynamics was concurrently measured by an optical fiber probe. The average gas bubble size was found to be larger at atmospheric condition along with the frequency of large bubbles, resulting in a larger degree of particle-wall contacts. The degree of fluidized bed wall coating increased with the increase of pressure. This finding was related to the decline in the gas bubble size and the increase in frequency of small bubbles found at elevated pressures, which promoted particle−particle contacts, and thus promoted bipolar charging. Bipolar charging was detected with particles that fouled on the column wall with small particles being negatively charged.

Influence of the Reynolds number from Reτ = 150 to 210 on size-dependent bipolar charging

“…Triboelectric charging causes a build-up of charge in particulate systems. In industrial environments, the excessive build-up causes unwanted agglomeration and wall-sheeting in the fluidized beds [1][2][3][4][5], pneumatic conveyors [6][7][8][9][10], or during powder handling in general [11]. This is an especially severe problem in the pharmaceutical industry [12][13][14][15] because the formulation of powders is strictly given and often cannot be changed to reduce the charging.…”

110th Anniversary: Effect of System Size on Boundary-Driven Contact Charging in Particulate Flows

“…Many of the prior studies have concentrated on how different particles charge in a given flow domain varies with operational conditions, − but charging of the same particles in different vessels has gained less attention. Hence, in this study we probe the effect of vessel size on the electrostatics while keeping the particle properties unchanged.…”