(57a) Accurate Modelling of Acid Gas Cleaning Processes

The process of removing acid gas content, such as H2S, CO2, Mercaptans, COS, and CS2, from natural gas has several business challenges, the most important of which is meeting safety and environmental regulations. H2S is toxic and SO2 emissions into the atmosphere can lead to acid rain once the product is consumed.  In the presence of water, acid gases form acids that could corrode equipment and cause pipeline failures. Reducing the CO2 content in the gas not only prevents damage to equipment, but also improves the heating value.  Additional challenges include the increasing demand for the products, varying acid gas content in the feed, and performance degradation of the acid gas cleaning process over time.

Accurate modeling can offer valuable insight into understanding the intricacies and trade-offs involved in a process plant.  Process simulators with strong acid gas cleaning modeling capabilities such as Aspen HYSYS, can accurately predict performance helping users to meet sales gas regulations, ensure product quality, and identify process bottlenecks and creep capacity. In addition to modeling acid gas cleaning processes, Organizations can also save time and money by optimizing the entire gas plant with a simulator capable of modeling acid gas cleaning, dehydration, NGL recovery, heat exchangers, and more.

This paper discusses Acid Gas Cleaning and its ability to model processes using chemical solvents, such as amines, and physical solvents, such as DEPG. While modeling acid gas cleaning processes, it is important to account for the kinetic reaction rates and the mass transfer resistance. The mass transfer resistance is the rate-limiting step at the vapor-liquid interface, and simulating this effect results in superior modeling accuracy.  Another effect that must be captured in the model is the performance degradation from the presence of Heat Stable Salts.

The paper also details commercial case studies using Aspen HYSYS Acid Gas Cleaning, and the model validation work completed. Best practices will be shared on how companies have leveraged the power of this technology to improve their operations.