Lean Gas-Flare-Tip Technology Reduces Emissions in the Gulf of Thailand

Abstract

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 216098, “Revolutionizing Sustainability: Achieving Net-Zero Emissions With Lean Gas-Flare-Tip Technology Breakthrough in the Gulf of Thailand,” by Nunthachai Amarutanon, Boonyakorn Assavanives, and Kantkanit Watanakun, PTTEP, et al. The paper has not been peer reviewed. _ In the complete paper, the authors describe an extremely low-BTU (ELBTU) flare-tip technology designed to help the oil and gas industry achieve net-zero targets. The operator embarked on a joint research and development project to address the limitations of high-heating-value requirements by designing the technology. The prototype was proved to successfully combust lower-heating-value flare gas, significantly outperforming existing technologies. Introduction The joint research and development project began work in 2018. The development of the described technology began with a literature survey on lean-gas-combustion theory. The project included multiple iterations of prototype design, simulation, and testing, with various parameter adjustments to optimize performance while considering a thorough range of combustion criteria. The design was studied through computational fluid dynamics simulation and tested to determine its operating envelope. Confidence in the performance and mechanical integrity of the final design has been proved by a series of prototype tests. Theory and Definitions Requirements and general functions that had to be achieved by the technology, all of which are detailed in the complete paper, included the following: - Maintain flame stability - Minimize burnback - Minimize flame pulldown - Ensure mechanical integrity The design of the ELBTU flare tip, shown in Fig. 1, includes an assist fire around the tip-perimeter discharge and spokes that penetrate the flare-gas discharge. The assist fire is designed as a supplementary gas burner where assist gas and assist air are delivered. Jet pumps are used to supply assist air to the assist gas burner, minimizing the line size for the assist air. With this design, assist gas and assist air are well-mixed, producing stable combustion and providing heat to the flare gas. A top hat was introduced to mitigate wind impact, retard the mixing of ambient air, and increase the time the flare gas remains at elevated temperatures. These benefits allow combustion of the assist gas and subsequent mixing of combustion radicals with the flare gas without the involvement of wind. Two of the major components, the assist fire ring and the spokes, were borrowed from existing tip designs that have proved reliable over decades of operation. Prototype Testing The prototype test investigated flare-tip performance by varying vent-gas low heating value (LHV), vent-gas exit velocity, assist-air flow rate, and assist-gas flow rate (related to heat release) with and without a wind generator and with and without the top hat. The wind generator was an upgrade to the test facility. The wind generator created a crosswind across the tip of over 32 km/h. The performance envelope was generated based on the acceptable operating points regarding two performance aspects of the flame characteristics (stability and quality). After hundreds of tests, it was found that the ELBTU flare tip was able to combust a vent gas having an LHV as low as 110 BTU/scf with acceptable flame stability and flame quality. To ensure mechanical integrity, a crucial factor to ensure that the ELBTU flare tip will have an acceptable service life, internal and external parts of the prototype were thoroughly investigated before and after testing. It was concluded that the design has acceptable mechanical integrity for this application.