The effect of using a co-solvent in the extraction process on the performance and quality of the obtained raffinates

During the investigations solvent refining tests were conducted using co-solvents of different concentration as well as carrying out a reference process without a co-solvent. The laboratory stand used for modelling the technological process allowed to carry out the solvent refining continuously, simulating a production process in the petroleum rafinery lube oil plant. The feed stock used in the investigation was fraction obtained during petroleum vacuum distillation serving to produce a base oil. The investigation of the solvent extraction process was conducted using formamide as a co-solvent in the amount of 10% (m/m) and 15% (m/m). In addition, the extraction process without formamide was carried out as a reference process when comparing both the yield of the obtained raffinates and quality of the products received when a co-solvent was applied. In all the solvent refining tests the same technological parameters were applied. Basic physico-chemical properties of the produced raffinates were determined. It was found that despite using the same technological parameters in the extraction processes, changing only the proportion of co-solvent from 0 to 10% (m/m), raffinates of different yield and quality were obtained. The lowest yield was observed during the process in which only furfural was applied, i.e. in the reference process for those with the use of a co-solvent, and during that process a raffinate of 49.7% (m/m) yield was obtained. The highest raffinate yield - 72.2% (m/m) was obtained in the process with 10% (m/m) of formamide. In the process with 5% (m/m) of a co-solvent a raffinate of 62.5% (m/m) yield was obtained. When comparing the performances obtained, it can be stated that an addition of a co-solvent in the proportion of 5% (m/m) will cause 12.8% (m/m) increase in the amount of the raffinate obtained, and 10% (m/m) addition of a co-solvent will bring 22.5% (m/m) increase of the refining process yield. This increase in the raffinate output leaded to with the lowering of its quality in regard to all the investigated parameters.