Total Site Heat Integration of the Coal-Based Synthetic Natural Gas Process

Abstract

China is now boosting coal-based synthetic natural gas (SNG) process for clean energy supply. However, recent studies show that the plantwide energy efficiency is at a low level. One of the reasons is that the Total Site Heat system has not been well integrated. In this work, we develop detail models for the complete flowsheet. Total Site Heat Analysis method is introduced to diagnose and analyse the low energy efficiency. Studies reveal that the low temperature waste heat recovery and heat integration between coal gasification unit and water gas shift unit can provide considerable energy savings. Total Site Profile is constructed to obtain the maximum heat recovery and cogeneration potential at the Total Site level. Site utility system with minimum fuel coal consumption is designed based on mathematical optimization. The results show that the energy conversion efficiency of integrated process improves from 55.6 % to 57.9 %. The production cost will reduce 3.6 % from 1.65 CNY/Nm³ to 1.59 CNY/Nm³ without additional investment, which can bring extra 240 M CNY profits for the enterprise.