Perform a process alternatives evaluation for the purification of an existing normal hexane product stream to meet higher purity product specifications.
N-HEXANE PURIFICATION ALTERNATIVES EVALUATION STUDY
Process Engineering Associates, LLC (PROCESS) was contacted by a privately-owned operating company that produces specialty petrochemicals and conducts toll processing for major refining companies. Presently, the client’s main products are cyclopentane, normal and iso pentane, normal and iso hexane, and petroleum ether. The n-hexane currently sold has a minimum purity of 65-70%. PROCESS was hired to investigate technical alternatives for generating n-hexane that would have a minimum purity of 95%, with 98–99% purity desired if possible.
The 65–70% n-hexane stream that the client produced included various cyclic and branched isomers of hexane which represented impurities to be removed. The alternatives investigated for the purification of this mixture included molecular sieves, permeation, pervaporation, and distillation. It was determined by PROCESS that although all of these methods were, to some extent, technically capable of generating purified n-hexane, only distillation and molecular sieves appeared to offer commercially feasible methods.
PROCESS utilized its licensed commercial computer process simulation software to conduct simulations to determine the best method of generating the 95+% n-hexane by distilling the existing stream in the client’s plant. Four different distillation arrangements were examined to determine major operating characteristics (yield of purified n-hexane as well as utility requirements) depending on the hexane purity desired (95% or 99%) and whether the purified n-hexane would be removed as an overhead or bottoms product.
The study also determined that a proprietary molecular sieve (mol-sieve) process technology offered by a particular technology provider could be capable of generating the purity of n-hexane required. Specifically, this technology provider offers two process designs that are available either for purchase or licensing (for which exact financial requirements are unknown at the level of this study). Although the technology provider was not willing to divulge specific performance data, they claimed that either of their two process would likely result in a more favorable cost structure than distillation.
PROCESS issued a report which summarized the results of the study and the process simulation work. Should the client decide to continue the n-hexane purification study, this report will serve as a technical basis for a detailed distillation design.
- Specialty Hydrocarbons Production
- Process alternatives evaluation
- Light hydrocarbon distillation
- Licensed process technology screening