Comparison of OLI Studio: Analyser 9.2 and MultiScale Simulation Software for design of MEG Regeneration Units

Abstract

Mono-ethylene glycol (MEG) is a common thermodynamic hydrate inhibitor used in the production and transportation of oil and natural gas. MEG is usually recovered, regenerated in MEG regeneration and reclamation unit (MRU) and reused to minimize operation cost. However, systems containing MEG often contain high concentration of dissolved minerals and therefore may cause adverse scale. As scale is one of the biggest water-related problems, it needs to be predicted in advance to determine the best treatment strategy. Simulation software are used to ensure efficient salt removal in the MRU, and therefore prevent scale. Fjords Processing currently uses MultiScale for the design of MRU. However, this simulation software cannot be integrated with a mass and energy simulation software as OLI Studio. In this study, a comparison between OLI Studio and MultiScale™ software in the design of a MRU was done. Three sets of evaluations were made. The first set consisted of CO2 partitioning calculations at different pressure, temperature, CO2 concentration in the gas phase, alkalinity and MEG content. The second set was based on the reproduction of the experimental pH values measured by K. Sandengen in OLI Studio and in MultiScale™. These calculations were performed at 60 wt % MEG and 90 wt % MEG and at 25 ⁰C and 80 ⁰C. The third set of calculations consisted of a case study where typical MRU design calculations were made at different pressures, temperatures and MEG content. The results showed that the difference between OLI Studio and MultiScale increased with the increasing content of MEG and decreased with the increasing temperature. CO2 partitioning calculation showed a good correspondence between OLI Studio and MultiScale in the distribution of the species in water. For water-MEG solution, it was observed that OLI Studio predicted a slightly lower concentration of dissolved CO2 than MultiScale. This corresponded with the pH calculations as well because OLI Studio predicted a slightly lower pH than MultiScale. Case study calculations showed that pH difference between OLI Studio and MultiScale was higher than in other evaluations. This discrepancy must be due to difference between their scale prediction models. The difference between OLI Studio and MultiScale was insignificant for the calculations of the precipitation of CaCO3 at the evaluated conditions. On the other hand, the calculations of precipitation of Mg(OH)2 showed a notable difference between OLI Studio and MultiScale for solutions containing MEG. Based on the significant difference in the prediction of the precipitation of Mg(OH)2 and based on Fjords Processing experience in the design of MRU with MultiScale, the simulation software MultiScale seems to provide more reliable results than OLI Studio. Hence, further evaluation needs to be done before start using OLI Studio in the design of a MRU.