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 H2S in the flare gases. The main idea is that the flare gas components, including H2S, 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.
Highlights
In recent years, the high emissions of greenhouse gases have caused environmental pollution and increased global concern
An fuel gas network (FGN) model was modified by Tahouni et al [15] and results indicated a 12% reduction in natural gas consumption compared to the nonintegrated flare gas stream case and a 27.7% reduction compared to the base case with no FGN
The total mass flow rate of Liquefied natural gas (LNG) and Natural gas liquids (NGLs) streams are selected as an objective function and constraints are the H2S amount in these streams, which should be less than 4 ppm
Summary
The high emissions of greenhouse gases have caused environmental pollution and increased global concern. Petrochemicals and refineries are the main energy consumers that have a great share of greenhouse gas emissions In these industries, large amounts of hydrocarbons are burned due to safety issues in the flares. Studies on design parameters of the flare gas recovery system (FGRS) by Enayati et al [4] was performed Their simulations were done in steady state and dynamic conditions in order to compare these two modes. Zolfaghari et al [13] presented three models for the utilization of flare gases and their optimal use These three ways included gas to liquid (GTL), gas turbines generation (GTG) and gas to ethylene (GTE). Integration and reuse of flared gases with fuel gas network (FGN) is an impressive method for reducing greenhouse gas (GHG) emissions in addition to saving energy in refineries. The flare recovery process is designed with three goals: separation of H2 S from gas flare, LNG, and NGL production
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
