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“This joint study reveals that grease manufacturers can reduce their energy consumption by about 12 percent per unit weight of produced grease. However, a minimised soap content will also help to minimise the impact of price fluctuations of lithium hydroxide,” says Mehdi Fathi-Najafi, Senior Technical Advisor and Nynas Naphthenics’ grease specialist.
Aiming to find out if lubricating grease can be produced in a more efficient way, Mehdi Fathi-Najafi and his co-worker at Stratco decided to explore what impact the solvency power of the base oil would have on the energy consumption.
“It is well known that more efficient grease production can be obtained by employing a pressurised reactor in the “cooking stage” of the manufacturing process. However, the effect of the base oil on the efficiency of the grease production has never before been published to my knowledge,” he says.
Three conventional lithium greases with different base oil solvency were produced in Stratco’s pilot plant, a miniature version of the commercial scale Contactor reactors that have been used worldwide for decades. Batch sizes were kept at 30 kg, whilst all other process parameters were kept constant. The comparative study showed that naphthenic oils, such as NYNAS® T 110, offer advantages versus paraffinic SN525. T 110 based greases made in the Contactor reactor showed better optimisation than SN525 based greases due to the higher degree of base oil solvency.
“The soap content saving represents both a raw material cost saving for the manufacturer and a reduction in the demand for lithium. And the reduced energy during production represents both a utility cost saving for the manufacturer and a reduced demand on the electricity infrastructure,” concludes Mehdi Fathi-Najafi.
Typical characteristics of the greases and the energy consumption during their production.
A win-win scenario
If the energy saving of 2 kWh per 30 kg grease found in this study translates to the commercial scale, the total energy cost saving can be estimated as follows:
A medium-sized plant may produce 3,000 metric tons of conventional lithium grease on an annual basis. In Kansas City, USA, where several grease plants are located, electricity costs about 6.43 cent/kWh. That would enable a typical producer to make energy cost savings of almost 13,000 USD annually, and added to that is the extra cost saving due to better yields when using NYNAS T 110 instead of SN525.
Mehdi Fathi-Najafi is a Senior Technical Advisor and Group Specialist at Technical Development and Market Support, Nynas Naphthenics. He joined Nynas in 2008.