Predicting the Autoaccelerating Hydrogen Peroxide Decomposition Rate after Mixing with Sodium Hydroxide

Abstract

Due to the large amount of inherent chemical energy, implementation of hydrogen peroxide pulp bleaching requires a high level of safety design and process review. Even with safety controls, in-place accidents have occurred at kraft pulp bleaching facilities. Using a combination of experiments and chemical engineering analysis, we present a validated model of hydrogen peroxide decomposition under alkaline conditions that are typically found in kraft pulp bleaching processes. Using the model, we then calculated several characteristic parameters required to determine the criticality class and control system safety integrity level (SIL) for an industrial-scale bleaching process. When designed for 10 wt % hydrogen peroxide, pulp bleaching systems are inherently safe as long as it is used in a process with adequately sized pressure relief. Process designs using greater than 10 wt % hydrogen peroxide require controls with SIL 4, which is the highest level of control. This level is required for processes that present the most risk and have the most severe consequences. Regardless of the hydrogen peroxide concentration, processes without adequately sized pressure relief should never be considered safe. Finally, both the experimental and model results show the dramatic acceleration of hydrogen peroxide decomposition by iron. Because membrane-grade sodium hydroxide often has an order of magnitude lower concentration of iron than diaphragm-grade sodium hydroxide, choosing membrane-grade results in reduction in potential hazard.

Citation

Houtman, Carl; Hart, Peter. 2022. Predicting the Autoaccelerating Hydrogen Peroxide Decomposition Rate after Mixing with Sodium Hydroxide. Industrial & Engineering Chemistry Research. 61(34): 12473-12481. https://doi.org/10.1021/acs.iecr.2c01868.