Mehdi Yosefinejad - Sharif university of technology, chemical engineering department, Azadi Ave.Tehran, Iran
Bahare Akbari - Iran university of science and technology, chemical engineering department, Tehran, Iran
Reza Jabari - Arya Sasol Polymer Company (ASPC), Asalouyeh-Boushehr, Iran
Jabbar Ghaffari - Amirkabir university of technology, Aerospace engineering department, Tehran, Iran
Saeid Alami milani - ESTORK industrial group technical service, Tehran, Iran
Mohsen Nazeri - Ilam petrochemical company (PGPIC), olefin plant, Ilam, Iran

Centrifugal compressors are employed in ethylene plants because they can handle very large volumes and are very robust, allowing for continuous operation in critical services. There are three main services where centrifugal compressors are utilized in ethylene plants: Cracked-gas compression, C۳ refrigeration and C۲ refrigeration. The names and process requirements of these compressors differ based on the process design. cracked-gas compressors (CGCs) are high-power compressors that draw gas from the cracking furnaces through the various quench coolers and separation sections of the plant, and pressurize the gas for further separation. CGCs are susceptible to fouling due to polymerization. The cracked gas contains trace amounts of compounds that can polymerize within the gas stream and stick to the flow path in the compressor. This fouling degrades the performance of the compressor, which reduces throughput or increases power consumption. There are two ways to deal with fouling: reduce the temperature to reduce the formation of fouling, or reduce the impact of fouling after it has formed. Although the configuration and refrigerant composition differ from plant to plant, all ethylene plants have two levels of refrigeration: C۳ refrigeration, which provides refrigeration duty around –۴۰°F using propane or propylene (or a mixture of the two), C۲ refrigeration, which provides refrigeration duty down to –۱۵۰°F using ethylene as a refrigerant (some process designs use a mixed-gas refrigerant for this service). Refrigeration compressors are multisectional machines with sideloads or extractions depending on the process design. Numerous mixed refrigerant cycles for separation systems of petrochemical industries were developed in the past several decades. mixed refrigerant cycles can improve thermodynamic performance of refrigeration systems in the case of using optimal working fluid mixture composition, optimal high and low operating pressures and optimal arrangement of the cycle components. The simulation results show that MRCs can improve the thermodynamic performance of refrigeration system in the case of using Optimal operating conditions and also proper arrangement of the cycle components (cycle configuration).

Cracked Gas Compressor, C۳ refrigeration and C۲ refrigeration, mixed refrigerant cycles (MRC)