Abstract

This paper will discuss the use of simulation techniques, key performance indicators, ideal solvent selection, routine solvent analysis for optimal hygiene, and system performance to increase acid gas removal capacity while maintaining environmental compliance. Additionally, the paper will share real field experience and learnings from the implementation of these practices.

Introduction

Due to the rapid increase in global oil demand, pressure for greater production with fields containing heavier (higher density/more carbon rich) and more sour (high in sulfur) crude has increased. The average quality of crude oil (i.e. medium gravity, sour crude) dominates the oil production from the Middle East. For example, Saudi Arabia's response to the demand is the 900,000 barrel per day (bpd) mega project that will process heavy oil from the Manifa Field. The Field will support Saudi Arabia's plan to raise production capacity beyond the 12.5 million bpd from just above 11 million bpd today.

With the trend towards heavier and higher sulfur containing crudes, refineries are increasing processing capabilities which can include capital-intensive projects and additional energy consumption. Furthermore, in order to meet stringent regulations for ultralow sulfur fuels in the global market, refineries must increase processing capabilities to accommodate a heavier, sour crude slate. This includes upgrading hydro treating capacity to address the additional sulfur load and adding acid gas removal systems to treat the resulting H2S.

Often refineries design and operate acid gas removal systems with the sole objective of meeting permitted sulfur emission limits. MEA (monoethanolamine) and DEA (diethanolamine) are amine solvents commonly used for removal of H2S from sour gas streams. Refineries maintain low solvent concentrations to reduce degradation products and corrosion potential. Less amine in the system requires increased circulation rates and more aggressive stripping of the lean amine to meet stringent H2S and SO2 regulations. These practices result in excessive energy consumption and limited capacity.

Capacity upgrades have become a challenge for refineries already struggling with tightening margins. Thus, solutions to boost capacity should focus on minimal capital expenditures. Specific to gas treating systems, there are two ways to increase the treatment capacity and optimize energy consumption. Both require minimal capital investment. The first method involves upgrading the chemistry of the solvent to increase capacity and reduce required processing energy (i.e. reboiler duties). The second method requires an understanding of the system performance. With the use of mass and energy balances, a plan is developed to optimize appropriate operating conditions and key performance indicators to increase the treating capacity, while maintaining environmental performance.

This paper will discuss these two approaches in more detail, including the use of Dow proprietary simulators to determine optimum process conditions and the importance of continuous monitoring of process and solvent conditions. The paper will also share real field experience and learnings from actual implementation of these practices.

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