Technoeconomic analysis and feasibility of co-solvent mixtures in the liquid-liquid extraction of aromatics

It is desired to improve the efficiency of liquid-liquid extraction processes in the fuel industry by reducing energy consumption and operational costs as well as reducing risk to health, safety and the environment. Co-solvent mixtures for extraction consisting of butane-1,4-diol, propane-1,2,3-triol (glycerol), and 2-methylpentane-2,4-diol (hexylene glycol) were assessed in terms of capital costs, operating costs and total annual costs relative to a baseline process that is employed for the liquid-liquid extraction of toluene from n-heptane. Commercial solvents such as sulfolane, morpholine-4-carbaldehyde (NFM), and dimethyl sulfoxide (DMSO) were used for the baseline processes that were simulated in ASPEN Plus V10. The capital costs ranged between 5.8–6.2 million US dollars, while the energy intensity ranged between 1000 - 1400 kJ/kg. The total annual costs for all solvents studied varied between 2.4 - 2.6 million dollars. The results highlighted that these co-solvent mixtures may offer some benefits in terms of total annual cost when the impact of solvent choice is holistically considered.