Thermo–Economical Evaluation of Producing Liquefied Natural Gas and Natural Gas Liquids from Flare Gases

Ehsan Barekat-Rezaei, Mahmood Farzaneh-Gord, Alireza Arjomand, Mohsen Jannatabadi, Mohammad Hossein Ahmadi and Wei-Mon Yan
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Ehsan Barekat-Rezaei: Faculty of Mechanical Engineering, Shahrood University of Technology, Shahrood 3619995161, Iran
Mahmood Farzaneh-Gord: Faculty of Engineering, Mechanical Engineering Department, Ferdowsi University of Mashhad, Mashhad 9177948974, Iran
Alireza Arjomand: Faculty of Chemical and Materials Engineering, Shahrood University of Technology, Shahrood 3619995161, Iran
Mohsen Jannatabadi: Minoodasht Branch, Islamic Azad University, Minoodasht 49816-36497, Iran
Mohammad Hossein Ahmadi: Faculty of Mechanical Engineering, Shahrood University of Technology, Shahrood 3619995161, Iran
Wei-Mon Yan: Department of Energy and Refrigerating Air-Conditioning Engineering, National Taipei University of Technology, Taipei 10608, Taiwan

Energies, 2018, vol. 11, issue 7, 1-17

Abstract: In many industrial plants including petrochemicals and refineries, raw hydrocarbons (mostly flammable gas) are released during unplanned operations. These flammable gases (usually called flare gases) are sent to a combustor and the process is called flaring. Flaring wastes energy and produces environmental pollution. Consequently, recovering the flare gases is an important subject in these industries. In this work, an economical and technical analysis is presented for the production of valuable products, namely, liquefied natural gas and natural gas liquids from flare gas. The flare gas of Fajr Jam refinery, a refinery located in the south part of Iran, is selected as a case study. One of the issues in recovering flare gases is the nonconstant flow rate of these gases. For this reason, an auxiliary natural gas flow rate is employed to have a constant feed for the flare recovery process. The Poly Refrigerant Integrated Cycle Operations (PRICO) refrigeration cycle is employed for producing liquefied natural gas and natural gas liquids. In the PRICO cycle, the mixed refrigerant is used as the working fluid. The other issue is the existence of H 2 S in the flare gases. The main idea is that the flare gas components, including H 2 S, have different boiling points and it is possible to separate them. Consequently, flare gases are separated into several parts during a number of successive cooling and heating stages and passing through phase separators. It is shown that the proposed flare gas recovery process prevents burning of 12 million cubic meters of the gases with valuable hydrocarbons, which is almost 70% of the current flare gases. Furthermore, about 11,000 tons of liquefied natural gas and 1230 tons of natural gas liquids are produced in a year. Finally, the economic evaluation shows a payback period of about 1.6 years.

Keywords: flare recovery; PRICO cycle; mixed refrigerant; payback period (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2018
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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