(92c) Process Simulation Study of Sour Gas Sweetening Technologies for Distributed Resources

Gas desulfurization is a very important step in utilization of natural gas resources, not only in preventing the formation of SO₂ after combustion, but also in avoiding poisoning of catalysts. However, for most distributed gas wells, the sour gas is directly burned and emitted into the atmosphere, which is neither environmental friendly nor economic. The estimated amount of methane vented or flared from the oil and gas industry as well as from landfills in the U.S. in 2012 was 213 billion ft³ and 243 billion ft³, respectively [1]. It is urgently needed to identify a suitable desulfurization process that can be used in distributed gas wells. Due to the varying conditions of these types of wells, the process should be flexible, low cost and operable at small scales. There are numbers of gas sweetening processes, such as liquid phase oxidation process, absorption and catalytic conversion [2]. Unfortunately, most of these processes are either designed for large scale (Claus process) or have very high energy cost (Amine system). Some processes, such as LOCAT [3] and scavenger [4] have the potential to be built in a modularized unit and operated in remote gas-containing resources. IntraMicron, Inc., an Auburn University. spin-off and small business located in Auburn, AL, has developed a low-cost desulfurization technology called SourCat to sweeten sour gas resources [1], which has lower desulfurization cost than the previous mentioned two processes.

In this talk, three desulfurization processes are selected (LOCAT, SourCat and scavenger) and simulated at different conditions. Then, an economic analysis tool (ECON) is used to calculate capital and operating cost. Comparing with real data ($250-1000 per ST range, LOCAT) [3, 4], we will show that our simulation results are representative of the real cases. Based on this, we can calculate the desulfurization cost for each process at different conditions. According to preliminary results, the SourCat process will offer approximately a 53% savings per MSCF compared to the LOCAT desulfurization cost at 100 MSCFD and 500 ppm H2S. Finally, a desulfurization cost plot is generated to provide guidance with respect to the preferred operating conditions of these three processes. Furthermore, based on different scales, a comparison of Aspen Economic Analyzer and ECON is performed to verify that ECON shows preference for small scale plants and Aspen Economic Analyzer prefers large scale systems. Finally, a process synthesis and intensification framework is considered by combining these processes, which has the potential to operate at larger scale with lower desulfurization cost.

[1] https://www.aiche.org/resources/publications/cep/2017/january/catalyzin…

[2] Kohl A L, Nielsen R. Gas purification [M]. Elsevier, 1997.

[3] https://www.digitalrefining.com/article/1001502,Developments_in_H2S_scavenging.html#.XK-Eg5hKi72

[4] http://www.merichem.com/LO-CAT-Flexible-H2S-Removal-Process

[5] William Echt, “Liquid Redox Processes”, Laurance Reid Gas Conditioning Conference: Fundamentals of Low-tonnage Sulfur Removal and Recovery, Norman, Oklahoma, February 2017.

[6] Bob Veroba, P. Eng., Erik Stewart, “Fundamentals of Gas Treating”, Laurance Reid Gas Conditioning Conference, Norman, Oklahoma, February 2003.