(117a) Study on the Integrated Chilling Train and Mixed Refrigerant System for An Ethylene Plant

Study on the Integrated Chilling Train and Mixed Refrigerant System

for An Ethylene Plant

Karthik Krishnadevarajan, Jian Zhang, Qiang Xu and Kuyen Li

Dan F. Smith Department of Chemical Engineering

Lamar University, Beaumont, TX 77710, USA

Abstract

Refrigeration is one of the most important and crucial process in chilling train of ethylene plants. There are different ways to provide refrigeration for the process. The latest trend is to use a mixed refrigerant system (MRS) which has at least three components for the refrigeration task.  An MRS provides a continuum of temperatures change with smaller temperature differences during the heat exchange process than the single or cascade refrigerant system.  This leads to a lower energy loss in MRS and some other advantages than the traditional cascade refrigerant systems.  On the other hand, chilling train in ethylene plants contains a series of multiple heat exchangers and flash drums to separate hydrogen and methane gas from cracked gas and to liquefy the C2 and heavier components.  It handles process streams whose temperatures vary from 40 to -160 ^oC, which requires significant amount of cooling duty.  Obviously, the chilling train and mixed refrigerant systems should be integrated for study in terms of energy saving and system operational performance improvement.  The present work deals with combining chilling train and mixed refrigerant system for an ethylene plant.  Both process models are developed by ASPEN Plus.  Based on the rigorous simulation model, the conceptual optimal design and operational optimization for improving the integrated system has been conducted.