Simulation studies of the existing cogeneration system and alternative conceptions to improve the energy efficiency for an ethylene petrochemical plant

Abstract

Energy efficiency is relevant for the competitiveness and growth of global industries. In this way, simulation studies aiming to increase energy efficiency can be useful for both retrofitting and greenfield projects. Few ethylene process licensors hold the technologies; however, they present different proposals for projects with varying energy efficiency and integration degrees. In the present work, simulation studies of the cogeneration system of a petrochemical plant located in Brazil were performed in order to identify alternative configurations to increase the electricity production without affecting the heat supply to meet the process thermal demand. The cogeneration system of the analyzed plant includes an electric energy conversion system composed of turbo-generators, back-pressure and extraction/condensing steam turbines driving electricity generators, compressors and pumps, and heat exchangers. The simulation studies were performed using the HYSYS software to simulate design conditions and validate the model with the actual plant's experimental measurements. New cogeneration configurations were proposed in subsequent simulations, aiming at increasing electricity generation. In addition, exergetic efficiency and environmental analysis of the simulated configurations and an economic estimate for the most efficient proposal were performed. The results showed that the best alternative improved the electricity generation, increased the energy utilization factor by up to 16.2%, reduced greenhouse gas emissions by 22.8%, increased global exergetic efficiency by 28.9% and decreased the steam production and cold utility consumption of the cogeneration system compared to the design conditions.