Hybrid Screw Compressor Suitable for Offshore Vapor Recovery or Flare Gas Elimination Application

Abstract

1. ABSTRACT Environmental issues such as global warming are getting widespread international attention. Flare Gas Elimination projects and Flare Gas Recovery systems become more interest among oil and gas industries all over the world. Screw compressors are suitable for gas compressor applications that can recover flare gas or the hydrocarbon vapor instead of sending it to a flare line for offshore platforms or FPSOs (Floating Production, Storage, & Offloading). This type of compressor system provides Zero Flare Emission. Oil-free screw compressors have been used for process gas applications since the 1970's. Oil-flooded screw compressors have been used in many process gas related applications since the 1980's. Recently, both oil-free and oil-flooded screw compressors have been expanding into the process gas compression application industry. The oil-free screw compressor is popular for the offshore applications in recent market trends, and it has been used due to several advantages, good suitability and reliability in comparison to other types of compressors. Hybrid Screw Compressors have been developed by creating the best combination of advantages in the oil-free and the oilflooded screw compressor. Hybrid Screw Compressors have good features of compact and reliable designs, simple single skid arrangements. These features translate into benefits for the users such as lower installation costs, simple and easy start/stop operation, and suitable for long-term continuous operation. 2. INTRODUCTION The purpose of this paper is to present technical information and advantages in Hybrid Screw Compressors, and also show a comparison to the conventional type of Oil-free and Oil-flooded Screw Gas Compressors. In addition, the paper will explain what benefits the Hybrid Screw Compressor provides to vapor recovery and flare gas elimination applications in the offshore areas. 3. HISTORY Since the screw compressors have characteristics of both rotary (centrifugal) compressors and positive displacement compressors (reciprocating), screw machines found rapid acceptance in petrochemical and gas processing industries. In 1975, API 619 was introduced to specify a screw compressor. This first edition of API 619 looked only at oil-free screw compressors. During this period, the oil-free screw compressor was applied in many unique applications such as butadiene, styrene monomer recycle gas, linear alkyl benzene, soda ash, etc. Most of these applications are subject to dust, polymers, and liquids that are likely to be present in the gas stream. In many cases, water injection was used to control the compression process. In the 1980's, oil-flooded screw compressors started appearing in process gas applications. During the same period of time, cogeneration started to take off with gas turbines becoming necessary in more and more applications. Also, oil-flooded screw compressors were finding their way into light gases such as Helium and Hydrogen.