Technical, economic, and environmental assessment of flare gas recovery system: a case study

ABSTRACT

Concerns over the environmental impacts of GHG emissions have led refineries to deploy different FGR methods, most of which requiring new equipment and costly design and construction. In this research, we study three main methods of FGR to reduce energy consumption and control environmental pollution by the use of an environmental flow diagram and HYSYS, Thermo flow and aspen software. Three main scenarios are investigated for FGR with a technical and economic assessment of energy consumption and total flare gas flow is 4.5 MMSCFD in a gas field in southern Iran. The first scenario is pressurizing and injecting flare gas into oil wells, the second is producing electricity and injecting surplus flare gas into oil wells, and the third is producing power by using a combined heat and power system (CHP) and an internal combustion engine. Flare gas pressurizing and injection to oil wells with an internal investment rate of 171% and a payback period of 1.02 years is one of the best methods to reduce gas flare. In addition, all soil, air, and water pollution quantities are investigated together. After determining environmental indicators and collecting data an Environmental Flow Diagram (EFD) is developed to illustrate contamination sources and points and the relationship of units with respect to environmental issues. In these fields, the amount of CO₂, CO, NO_X in the furnaces, dehumidifier and flare were decreased by 100%, 100%, and about 57% using EFD and according to the results for the collection of associate gases, respectively.

Abbreviations and symbols EFD: environmental flow diagram; GTE: gas to ethylene; PFD: process flow diagram; IRR: internal rate of return; RES: reference energy system; LPG: liquefy petroleum gas; FGR: flare gas recovery; CHP: combined heat and power; GHG: greenhouse gas; NPV: net present value; UGS: underground gas storage; PBP: payback period; GTL: gas to liquid: RVP: reid vapor pressure; APG: associated petroleum gas; BOD: biochemical oxygen demand; MCDM: multiple criteria decision-making; COD: chemical oxygen demand; GTG: gas turbine generator; EOR: enhanced oil recovery; MMSCFD: million standard cubic feet per day; CO_2: carbon dioxide; CO: carbon monoxide; MW: megawatt; kWh: kilowatt-hour; barg: gauge pressure; kW: kilowatt; MMm^3: million cubic meter.

KEYWORDS:

• Flare gas
• energy recovery
• environmental pollution
• environmental flow diagram
• combined heat and power