Vegetable oils and fats determine the texture, the look, the smell and the taste of many foods. They also protect the skin as cosmetics and transport the healing power of drugs in ointments and essences. Also in technology, oils and fats from oilseeds – rapeseed, soya beans and sunflower seeds play an important role. They can be processed among other things for pollution-free coolants for use in metalworking and for biodegradable lubricants and hydraulic oils. The oils and fats processing industry is continually looking for more efficient processes, quality and cost reasons. Maximum oil yield, minimum oil losses and energy savings are the relevant outcomes. Health aspects come into play: Only precise and sensitive processing (refining, hydrogenation) ensures that no unwanted reaction products occur.
Pumps are needed in all process steps of the refining of vegetable oils and vegetable fats
At the primary level, this includes the individual process steps of refining, as well as providing process water, cooling water and the treatment/disposal of waste water. The primary challenge in the primary area are temperatures of up to 280 °C, pressures between a vacuum to 80 bar, the mostly high viscosity of the medium and the solids still present in the crude oil. The use of solvents (hexane, acetone) and aggressive acids and alkalis also demands special constructive solutions in terms of materials technology.
In practice this means:
- Pumps installed in plants for the refining of vegetable oils and vegetable fats must be made of abrasion-resistant materials.
- Mechanical shaft seals are mostly implemented as SiC/SiC single seals; often tandem or back-to-back implementations are also required.
- Pumps designed for solvent extraction must be Atex compliant. Leak-proof pumps (canned rotor pumps and magnetic drive system pumps) are gaining importance.
- For the oils are quite aggressive the elastomers used must be of high quality (in most cases: Viton).
Classical single-volute pumps are used and even multi-stage high-pressure pumps if the solids content is not too high.
Grundfos has developed its single-stage volute casing pumps in long-coupled, or close-coupled construction NK(E) and NB(E) – the ‘E’ stands for the variable speed execution – for applications with high performance requirements for flow and head. For many particularly demanding applications (such as handling oils and greases at high temperatures), the variants NKG(E) and NBG(E) have been designed according to chemical standard DIN EN 22858. These pumps are characterised by a more robust design, including such features as reinforced bearings for longer life. In addition, DIN EN 22858 specifies greater inlet and pressure side connections for a corresponding operating point – leading to lower speeds on the suction nozzle and consequently the required inlet pressure is lowered (lower NPSH value). Atex versions are also available.
The operator can order NKG(E) pumps with double seals because of the generous space in the bearing housing, the double seals in tandem construction are also a highlight. These tandem seals prove themselves in difficult media that crystallises for example, or has a tendency to adhere. Double seals are also the technique of choice in conveying plant oils at high temperatures.