Energy analysis and process simulation for the energy efficiency improvement of existing chemical plants

In recent years, energy efficiency has been one of the topics of major concern from a worldwide perspective as clearly stated by the International Energy Agency (IEA,2021). The energy waste reduction not only improves the process performances from an economic perspective but reduces as well the equivalent CO2 emissions. This research work is the product of a collaboration between the SIBUR petrochemical company and the Tomsk and Milan Polytechnic Universities during the Process Operations Management program aiming at the training of the personnel and at the troubleshooting practical problems of the petrochemical industry. SIBUR is a petrochemical company with a unique business model focused on the integrated operation of two main segments, namely fuel and raw materials and petrochemistry. Inefficient use and big losses of steam/condensate, obsolete equipment are the main reasons for the development of energy efficient strategies. Different sites need identification of real technical problems and process drawbacks by application of novel approaches and local methods. This work deals then with the analysis of light hydrocarbon unit with the purpose of reducing energy consumption and solving operational problems. Structuring and analysis of information on the consumption and distribution of steam and condensate at the operated unit were performed. Main drawbacks were detected and technical measures for a more efficient redistribution/involvement of steam in production processes were proposed. Process simulation of light hydrocarbon unit with the related utility streams and equipment was performed via Aspen HYSYS. Revamping of existing heat exchanger network and application of extra units for better heat recovery and most efficient utility use were proposed according to established energy optimization methodologies. The results were then validated by a detailed design of the additional heat exchangers and consequent simulation of the optimized process scheme. As a result, the formation of secondary boiling steam in tanks and associated losses into the environment was reduced by 100 %; the electricity consumption for chillers was decreased by 20%; steam consumption was cut by 64% on the heater; debottlenecking allows to increase the yield of current units and improve plant efficiency; reduction of inefficient use of steam at steam header by 71%. The equipment design and the updated economic assessment were performed as well and resulted in substantial savings for the company. Moreover, according with established indicators, an additional environmental analysis was carried out and showed relevant CO2 emissions reduction corresponding to the methane not used for combustion thanks to the energy recovery.In conclusion, the detailed energy analysis and process simulation of the existing plants allowed not only for a considerably higher profitability of the process in general but also for a higher sustainability in agreement with the world guidelines concerning the environmental impact of the industry.