Base oils used for drilling mud are well defined, low sulphur, low aromatics oils within the diesel range of distillation. Among the quality specifications for the base oil are density and flash point. In addition HSE requirements like low aromatics, BTEX and low sulphur applies.
 
Fingerprint
This Example with oil from a TCC^® site shows a GC MS profile of virgin base oil (top) and base oil recovered in the hammermill (bottom).
 
The recovered oil has the same fingerprint as virgin base oil. The recovered oil is directly re-usable as base oil in new mud.
 
The recovered oil is cleaned in several stages before it is discharged in two different fractions; the main fraction comes directly from the oil condenser and a small fraction is separated from the water which is evaporated in parallel with the oil.
 
BTEX
Despite the virgin base oil being low on BTEX GC analysis sometimes demonstrates small BTEX concentrations in the feed. In cases where the total BTEX is higher than spec one can separate it out by keeping the smallest fraction of recovered oil separate from the larger. BTEX will, if present, accumulate in the oil fractions separated from recovered water.
 
Flash point
Often a maximum flash point reduction is used as a quality assurance in thermal desorption of OBM drill cuttings, but if the flash point specified for virgin base oil in the MSDS is used as reference this may lead to misleading conclusions. It is important to compare flash point of the actual oil in cuttings and recovered oil. The TCC^® unit does not change flash point of oil.
 
Conclusions
The hammermill is used for recovery of high quality oil from OBM drill cuttings without degrading oil quality. In fact the thermal separation process can be used to raise the quality of oil compared to the actual feed to the unit by removing oil fractions outside of the virgin base oil specification. Compared to other drying methodologies TCC^® friction driers offer a gentle evaporation, low residence time in the reactor and low required process temperature. These, in addition to the homogenous mixing, are all factors that ensure the best possible oil recovery.