Lube-Tech Conclusions
Due to a number of factors ranging from a fire incident to the need to cut biobased grease manufacturing cost to better compete in the marketplace, several improvements have been introduced. These have now been fully incorporated in a new capacity expansion project as presented. The first improvement has been in the heating process using microwaves. The process has been well covered in earlier publications in this journal. Simply put, microwaves at 915 MHZ are applied directly to the product being heated resulting in molecular magnetic excitation due the interaction of the magnetic fields of microwaves and the product molecules. Since the amount of microwave power can be modulated infinitely, a temperature sensor is used to form a closed loop. In this way, the product can be heated to the desired temperature and maintained at that temperature accurately by modulating the microwave power. This accuracy removes the problems of overshooting the heating or delays due to slower heating.
The second improvement was made in the cooling process for grease. Relative to solids, water is slow in absorbing heat or in releasing heat. The use of water as a cooling medium has been known for centuries and the technology has matured in many industrial processes. Grease is a poor conductor of heat and the use of jacketed vessels for heating (using heat transfer oil or steam) and for cooling using towers or chilled water requires jacketed vessels and expensive scrape surface mixing mechanisms. The heat or the cold from the inside walls of the vessel has to be transferred to the entire body of the grease. To do this, layers of grease that are exposed to the inside walls of the jacketed vessel are wiped off by scraping blades of a mixer to be replaced by other layers. This process is inefficient and expensive.
An alternative cooling concept was introduced that uses re-useable solid metallic objects (in this case
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.146 page 5
steel balls) to remove the heat from the grease quickly and eliminate the need for chilled water. Preliminary work with this waterless cooling method has shown promise and currently two fully operational reactors are using the waterless cooling system post reaction. Further documentation of the results of this technology is on-going.
Finally, it was observed that grease as a semi-solid product would likely be better mixed in paddle blenders instead of the commonly used vertical mix tanks. Since usually minute amounts of additives are added to the grease, effective mixing becomes critical especially if the grease is shear-sensitive. When adding colourants and additives, typically mixing is combined with pump circulation. The pumping and extensive mixing requires time and energy and, in some cases, causes shear thinning of the grease.
Paddle blenders are gentler on the grease and due to their design can impart more effective mixing especially when small amounts of additives are to be mixed in a large volume of grease. A fully operational grease manufacturing plant that incorporates the improvements explained in this paper is to start production in June 2023.
While each of the above concepts have been used and tested in experimental production settings, full implementation is expected to yield the same results. The overall impact of these modifications will be the start of a truly sustainable manufacturing process where new ideas are tested for a change in the conventional practices.
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LUBE MAGAZINE NO.175 JUNE 2023
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