ABSTRACT
Screw presses – their construction, design aspects and methods, and operation practices – are covered in this chapter. A brief history of various stages in the development of screw presses will help readers build appreciation of the features of modern presses. Technology of pressing of various oilseeds is discussed, with specific operation steps and parameters. The differences in operation steps, and in the quality of presscake, for different oilseeds, are discussed in relation with seed structure and composition, specifically the protein content.
Design philosophy of screw presses has been explained on the basis of a simple theory of uni-directional pressing. Theoretical design methods based on the first principles of material flow, as also empirical methods based on principles derived from the theoretical models are discussed. These methods will be of direct benefit to machine manufacturers in developing countries. Also, the discussion of design aspects will be of help to plant engineers in press maintenance and trouble-shooting. Discussion of operation issues and control schemes will be of help to oil mill operator to optimise the operation of presses and the entire oil mill.
An innovative design concept for a future press, which may enable recovery of more oil, without high electric energy inputs, is discussed based on the theory of ‘undrained compression’. Such a design may allow the development of ‘full press’ machines, which may reduce oil-in-cake below 4%, thereby overcoming the need for further solvent extraction.
