Manuscript Title: Successful Implementation of Acid Gas Flare Recovery System
Authors: Allamaraju JagannathRao PrakashRao , Dutt Indrajit 
Published: November 2020

In line with the ADNOC HSE Policy, our goal is to minimize gas flaring to environment from Acid gas flare common for four plants as much as possible, using best available technologies.

The requirement is to recover the flare gases instead of being burnt in the Acid gas flare systems during normal plant operations and compress to the required pressure for injecting back into the processing facilities at the suction of Medium Pressure (MP) Compressors. Hydrocarbon liquids and sour water separated in the Acid gas flare recovery system (AGFRS) sent to existing sour water stripper.

The World Bank introduced the "Zero Routine Flaring by 2030" initiative, which serves as the foundation for our objectives to reduce acid gas flaring and recover flared gases. This is achieved by successful implementation of acid Gas Flare Recovery Systems in one of the existing ADNOC Gas Processing complexes.

This paper presents the stages involved and detailed design, i.e. Study, FEED and EPC.

The journey of implementing state of the art AGFRS commenced by conducting a thorough in-house study of all existing acid gas flare discharges from various operating plants in the complex, which were connected by a common acid gas flare system. After measurement and tally of flare flowrate during normal plant operations over a period, it was possible to forecast flow rates through the common acid gas flare header for various scenarios. The in-house study and analysis indicated potential recovery of approximately 1-3 MMSCFD of gas from existing operating plants.

This study prompted subsequent FEED and EPC detailed design phases, with HAZOP and SIL sessions to derive an inherently safe design to overcome implementation challenges. The project successfully commissioned in September 2014.The AGFR system found to be capable of operating at flowrates up to the design flowrate across the full range of molecular weights.The predicted recovery of acid gas was in the range of 1-3 MMSCFD. However, the actual average annual recovery of acid gas for a period of five years, after commissioning of the project, 2.5-3.27 MMSCFD for the period 2015-2019.Total Cost benefits for a period of five full years (Jan 2015 to Dec 2019) accumulate to US$ 14 MM (Basis: 2.61 US $/MMBTU, 1000 BTU/SCF).Total saving of CO2 emissions for a period of five full years (Jan 2015 to Dec 2019) accumulate to 325 KT(Basis: 140 billion cubic meters annually = 300 million Tonnes of CO2, 1MMSCFD= 22.14 KT of CO2/year).

The acid Gas Flare recovery unit has helped to achieve significant benefits by minimizing acid gas flaring to the environment and thereby reducing the carbon footprint in support of environmental norms, while still maintaining process safety for the existing plants.

The successful implementation of AGFRS is first of its kind within ADNOC Gas Processing. The project demonstrates tangible benefits to minimize continuous flaring with an operational record of accomplishment of nearly five continuous years.

The experience demonstrates that it offers reliable means to recover acid gases across a wide range of gas compositions without affecting the safety of the existing facilities and thus achieves 100% HSE, and increases profitability with a reduced environmental impact.