Exergetic Evaluation of an Ethylene Refrigeration Cycle

Francisco Amaral,Alex Santos,Fernando Pessoa,Delano Santana,Ewerton Calixto

doi:10.3390/en13143753

Francisco Amaral, Alex Santos + Show 3 more

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https://doi.org/10.3390/en13143753

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Abstract

The production of light olefins by selective steam cracking is an energy-intensive process, and ethylene and propylene refrigeration cycles are key parts of it. The objective of this study was to identify opportunities for energy savings in an ethylene refrigeration cycle through an exergetic analysis. Two main causes of lower operational efficiency were identified: (1) Lower polytropic efficiency of the refrigerant compressor and (2) operating with the compressor mini-flow valve open to ensure reliability. The evaluation showed that the amount of irreversibilities generated by the cycle in operation is 22% higher than that predicted by the original design, which represents a 14% lower exergy efficiency. There is a potential savings of 0.20 MW in the cycle’s energy consumption with the implementation of the following improvements: recover refrigerant compressor efficiency by performing maintenance on the equipment and optimize the flow distribution between the recycle valve, the level control valve, and the temperature control valve.

Highlights

Selective cracking of hydrocarbons with steam, known as steam cracking (SC), is the main production route of ethylene and other light olefins, such as propylene and butadiene [1]
This study aims to identify opportunities for reducing the energy consumption of an ethylene refrigeration cycle of an existing petrochemical plant, through an exergetic evaluation
The methodology chapter is divided into four sections: a short presentation of the refrigeration systems applied in the olefins plants and the description of the ethylene refrigeration cycle that is the object of study; the simulations premises and the thermodynamic model used; the equations applied for the exergy analysis, and the methodological approach used for identifying the main energy gaps

Summary

Introduction

Selective cracking of hydrocarbons with steam, known as steam cracking (SC), is the main production route of ethylene and other light olefins, such as propylene and butadiene [1]. According to [5], a description of technologies and procedures is missing in most of the end-use models for industrial systems, including the lack of real operating data that addresses the challenges experienced by the several types of processes that require a high energy demand. This is a serious omission for energy analysts, once energy consumption is driven by the diffusion of various types of equipment and the performance, saturation, and utilization of those equipment has a profound effect on energy demand

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