Lube-Tech
The third problem deals with mixing of the grease during cooling and during finishing processes. If the grease needs to remain in the mixing vessel for several hours to cool, then the grease yield is impacted. Finishing also requires the addition of small quantities of additives that may require extensive mixing to ensure the entire grease in a large vessel is uniformly additised. An example would be the addition of 400g of a liquid blue dye to change the colour of 5,000 Kg of grease in a vertical vessel. The amount of time in mixing and pump circulation required to effectively dye the entire volume of grease could add significant amount of time and cost. Importantly, some greases like the aluminium complex thickened grease are not shear stable. This means that often in the process of excess mixing for cooling or for additising, the grease shears down one to two grades, resulting in undue cost and waste.
In expanding a biobased grease manufacturing capacity, three approaches were introduced to not only address the observed shortcomings of the more conventional grease processing concepts; but also incorporate sustainability into the process. The first improvement is in the heating for reaction as follows.
1. An alternative method of heating Patterson Industries, a grease vessel manufacturing company in Canada has begun producing grease reaction vessels that use microwaves. The equipment includes one or two microwave transmitters (also called generators), waveguides that deliver the microwaves to the vessel, and a temperature sensor that creates a closed loop and adjusts the microwave power to the desired temperature. Microwave transmitters for processing grease or chemicals operate at 915MHZ and have a wavelength of 32.75 cm (12.9 inches). Microwave generators are normally 75KW or 100KW each and rather economical when compared to equivalent hot oil systems. The microwave-operated Patterson kettle has two new patented technologies that allow the kettle to be
30 LUBE MAGAZINE NO.175 JUNE 2023
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.146 page 2
used for manufacturing mineral-based grease as well as biobased grease (Figure 1). The laws of thermodynamics show that the amount of energy needed to react a certain volume of grease is the same regardless of the methods of heating. But, microwaves (radio waves at 915MHZ on the spectrum) are directly applied to the magnetic fields of materials being heated. Unlike heat transfer oil or steam heat, they do not require conversion of thermal energy to heated oil or steam, heat transfer lines, and heating of the walls of the vessels via vessel jackets, or similar equipment. The unfortunate grease manufacturing fire incidents at Environmental Lubricants Manufacturing in 2007 and Chemtool grease plant in 2021 (both in the Unites States) have shown the desirability of a safer approach to general industrial process heating and to the grease manufacturing processing in particular.
A paper presented at the NLGI Annual Meeting 2013, documented the time and energy savings of processing grease in the ranges of 40-50% total savings. Widespread use of this concept over time, will result in a more sustainable grease processing than the current technologies.
Figure 1: Patterson Kettle Microwave-Operated. courtesy of Patterson Industries Canada – division of All-Weld Company Limited
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