Abstract
Multipurpose reactors are very common in the specialty chemicals and pharmaceutical industries. Since these reactors often are designed to work under pressure, they must be equipped with an adequately sized emergency relief system (ERS). Due to the multipurpose character, the sizing of the ERS cannot be performed for a specific chemical reaction, but the design must be sufficient to cope with potentially very different reactions and different processing conditions. Hence it became a common practice to design the emergency pressure relief systems based on a credible physical scenario: in many cases, this is maximal heating applied on a volatile solvent. Maximum heating applied to a reactor results in very different flow behavior in the reactor compared to a chemical reaction, which results in a different mass flow rate to be discharged. The physical properties of a reaction mass may also be very different from a pure solvent as used in the design procedure, which results in a different discharge capacity. Thus the transfer of the design based on a physical scenario to a chemical scenario must be undertaken with care. A procedure allowing verification that the capacity developed for a physical scenario can be used for a chemical scenario and under which restrictions this transfer is valid was developed. The limitations are shown in the frame of a sensitivity analysis, allowing the identification of the critical parameters in the design. In every case, the behavior of a chemical reaction to be performed in a given reactor must be characterized with regard to its behavior under pressure relief conditions. This often involves an experimental study using different calorimetric techniques as adiabatic calorimetry, reaction calorimetry and Calvet calorimetry. Additionally, a simplified procedure based on past experience with the performance of the reaction at plant scale, but avoiding the calorimetric study is shown.
