TRICKLE-BED REACTORS.

Trickle-bed reactors can be defined as a fixed bed of catalyst particles, contacted by a gas-liquid, two-phase flow. The flow may be cocurrent (downflow or upflow) or countercurrent. In this article, cocurrent downflow is considered, which, because of its relatively lower pressure drop and the absence of flooding, is by far the most common mode of operation in industrial practice. Trickle-bed reactors are used primarily in the petroleum industry for hydrocracking, hydrodesulfurization, and hydrodenitrogenation. Many basic aspects of trickle-bed reactors are not yet fully understood, making design from fundamentals very difficult. The axial Peclet number in the trickling regime, which is in agreement with the experimental data, is relatively independent of the liquid flow rate.