Hybrid System – An Emerging Solution to Sour Gas Treatment
Authors: Parekh Siddharth 
Published: January 2020

Shifting project economics into positive territory is a challenge for every project, but especially so for sour to ultra-sour, unconventional, and remote natural gas reserves. The application of conventional technologies incurs significant capital investment and operating expenses, and complexities of operations can make projects economically inviable during the FEED stage. To improve the economics and potential of these projects, shifting our approach to more innovative solutions is essential.

There are multiple methods to treat natural gas containing high amounts of acid gases. These can be broadly categorized as absorption (chemical and physical solvents), adsorption, membranes, and cryogenic distillation.

The traditional acid gas treatment approach utilizes amine solvent-based systems to meet desired acid gas (CO2 and H2S) content in the treated gas. More than three decades ago, an alternative treatment method using a membranes system became viable. Since then, membrane systems have become the preferred choice for bulk acid gas removal. Combining membrane and amine solvent-based technologies and optimizing the integrated system offers an economically attractive alternative for acid gas treatment. The combination of acid gas removal technologies is termed hybrid acid gas treatment.

This paper will demonstrate a more cost-effective approach by using the combination of acid gas removal membrane systems and conventional solvent-based technologies. With this combination, membrane systems perform bulk separation of acid gases and reduce the acid gas load in the feed stream entering the amine system. An amine system will further remove acid gas to meet the final product specifications.

A case study of the deployment of the hybrid system for an enhanced oil recovery project will be covered. The comparative techno-commercial analysis for the hybrid and the amine solvent-based system will be explained using an example for an acid gas treatment plant. Along with the salient features and configuration of membrane systems, the advantages and disadvantages of membrane and amine solvent-based systems will be presented to evaluate the hybrid system design.

Gas processors have adopted Industry 4.0 technologies such as devices using an industrial internet of things (IIoT) and edge and cloud computing, improving the economics of the hybrid system. These technologies enable near real-time computational analysis and insights derived from operational data, which feeds into dynamic process simulators. Total network capacity – as limited by membrane throughput and bounded by the defined KPIs – is dynamically evaluated, allowing for adjustments in process design configuration based on any change in operating parameters and required outlet KPIs like higher natural gas liquid (NGL) recovery higher purity treated gas and higher acid gas recovery. The digital tools provide insights to drive optimization of regular income from operations while protecting the integrity of the process.

In summary, the hybrid system has substantial economic advantages compared to the conventional amine solvent-based approach alone. The system – if optimally designed, engineered, and operated – can leverage the benefits of both technologies while minimizing their limitations. Advancements in complementary digital solutions allow for subject matter expert insights and lessons learned from years of design and operational experience to be seamlessly integrated into operations to ensure integrity, reliability, and coherence of the process to new deployments.