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

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.

Simulation of the Production of Liquefied Petroleum Gas (Lpg) from Flare Gas System

“…With an annual profit of $95,182,350.60, the plant is considered profitable. When compared with result obtained by, the current plant is cheaper and more cost effective [8,[9][10][11][12][13][14][15][16][17][18][19][20][21][22].…”

Process Simulation and Integration of Natural Gas Condensate Recovery Using Ethane–Propane Refrigerant Mixture

“…Barakat-Rezaei et al [9] present an economic and technical analysis of producing valuable products from flare gas, namely liquefied natural gas and natural gas liquids. This research highlights the potential for utilizing flare gas as a valuable resource and demonstrates the economic and technical feasibility of producing LNG and NGL from this gas source.…”