Modelagem e simulação de reatores de PVC: aplicação ao dimensionamento de sistemas de alívio de pressão de emergência.

Abstract

The requirements for control in an industrial plant in a global point of view goes beyond simply keeping the desired process conditions and production rate. A capacity for emergency control is also required to mitigate the effects and avoid disatrous consequences. Last in order of demand there's the pressure emergency relief system. Its basic function is to direct process streams to a safe destination, condition or treatment avoiding rupture of the equipments. The design of relief systems, due to associated high risk and social responsability, has been improved over decades. A much used code is the API RP-520 "Sizing, Selection, and Instalation of Pressure-Relieving Devices in Refinerie". For two-phase relief the subject is still in development today, for example by Leung, Lenzing and Darby. To design a relief system capacity required for equipment safety, a model of the process at the emergency moment is necessary. A computer program for relief valve capacity design was developed for vinyl chloride polimerization reactors, coupling a kinetic model with a two-phase flow model. The kinetic model for homogeneous reactions in two phases in equilibrium is based on Xie et alli (Polymer, vol. 32, n° 3, pp. 537-557, 1991) and includes semibatch feed and temperature programing. The flow model used is the well established Omega Method. The model reproduces qualitatively the expected events. The use of the Mathcad platform including semibatch features and temperature programing easies its use in the industry for relief design, operations optimization and training.