Hybrid solvent system design approach upgraded

Hybrid solvents, a mixture of aqueous amine solutions and a physical solvent, are frequently used for removal of mercaptan sulfur species and for the energy savings they offer over a conventional amine system. This paper presents BASFs cutting edge approach to these systems.

The design approach upgrade encompassed as a core element lab measurements investigating the gas solubility of CO2, H2S, mercaptans (methyl, ethyl, propyl), COS, CS2 and hydrocarbon components in the hybrid solvent. In open literature the data for hybrid solvents is scarce or not available. If any information is published, often only one solvent composition was investigated, whereas the impact of different concentrations of the physical solvent or different ratios between amine and physical solvent was not part of the research activity. Based on the lab test result comprising gas solubilities, physical properties, and reaction kinetics a rate-based simulation model was developed.

For model validation an extensive test program was performed in BASF’s pilot plant. There was a good match between the model and pilot plant data. Next the reengineered simulation model was compared to an industrial reference plant currently using BASFs hybrid solvent with good result.

Unwanted hydrocarbon coabsorption by the solvent is the traditional downside to any hybrid system. A comparison of field data and simulation results is presented for hydrocarbon coabsorption as well as a novel (patented) process configuration to minimize hydrocarbon in the acid gas.