Integrated process design and safety analysis for caprolactam production via the cyclohexanone route: Oxime reactor balancing, beckmann rearrangement, and packed bed reactor mechanical engineering

This paper presents an integrated design and safety analysis for the production of caprolactam via the cyclohexanone route, focusing on the oximation and Beckmann rearrangement stages. The process begins with the continuous catalytic conversion of cyclohexanone into cyclohexanone oxime using hydroxylamine sulfate and aqueous ammonia, a highly exothermic reaction governed by first-order kinetics. We derive the reactor volume from the design equation for continuous flow systems, applying a twenty percent safety margin to accommodate operational variability. The rate constant is fixed at 0.096 per hour for the operating temperature range of 150–200 degrees Celsius. Following oximation, the oxime undergoes Beckmann rearrangement under strongly acidic conditions with oleum as the catalyst, effecting the ring expansion to caprolactam. A comprehensive energy balance is performed to quantify the total heat load, accounting for sensible heat changes and standard heats of formation relative to a datum temperature of twenty-five degrees Celsius; this calculation ensures that cooling systems are appropriately sized to manage the exothermic nature of the oximation step. The mechanical design of the packed bed reactor is addressed through thin-walled pressure vessel theory, with shell thickness computed using the standard formula that incorporates design pressure, inner diameter, allowable stress of stainless steel, and joint efficiency. Torispherical heads are selected for their favorable strength-to-weight characteristics, and their thickness is determined via a stress concentration factor. Structural integrity under wind and operational loads is evaluated through the design of lug supports, where the maximum compressive load on a single support is calculated from wind force, vessel height, ground clearance, number of supports, and total operating weight. The agitation system is sized using power number correlations for turbulent flow to ensure uniform mixing and heat transfer. The novelty of this work lies in the simultaneous treatment of material flow, thermal management, and mechanical integrity within a unified framework, thereby providing a robust methodology for process engineers. The significance of this integrated approach is that it reduces the risk of design oversights and enhances the reliability of caprolactam production facilities.