Liquid-Redox Process Used for Sulfur Removal on an FPSO

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper 2019-1016 OMC, “Sulfur Removal on an FPSO: A Liquid-Redox-Process Case Study,” by William I. Echt, Merichem, prepared for the 2019 Offshore Mediterranean Conference and Exhibition, Ravenna, Italy, 27-29 March. The paper has not been peer reviewed. Eni began producing oil reserves from the Aquila reservoir in the Adriatic Sea soon after its discovery in the early 1980s. As primary production decreased, a decision was made to begin enhanced recovery with artificial gas lift. With the play in deep water (815 m) and 46 km off the southern coast of Italy, a floating production, storage, and offloading (FPSO) vessel was needed. After a 5-year run, the Firenze halted operations in 2018 because of low oil production. The complete paper examines the decision to use hydrogen-sulfide- (H2S) removal technology, the cost of operation, and the unit’s availability over its lifetime. Introduction As the industry searches for reserves in ever-deeper formations, the requirement of contending with sulfur increases. Several H2S-removal technologies are available, including nonregenerative liquid scavengers (triazine-based), nonregenerative solid-bed absorbents, and the regenerative liquid-reduction/oxidation (redox) process. These technologies remove sulfur from associated gas streams and do not release them to the environment. The nonregenerative technologies are often referred to as scavengers. Process Evaluation During the initial design phase, several H2S-removal technologies were evaluated per the following criteria: Turndown capability H2S-removal efficiency Degree of operator involvement required Maintenance requirement and waste material produced Proven reliability in marine conditions The evaluation led to the selection of the liquid-redox process after it received the highest marks in four of the five criteria. Both liquid and solid H2S scavengers were considered as alternatives to the liquid-redox process for this installation. The considerations for each criterion are detailed in the complete paper.