Process selection criteria
Selection of the right process route for Full Pressing is based on several criteria, related to both the economics (CAPEX and OPEX analysis, products YIELDS) and the specificity of the products (CAKE and OIL).
The key market reason to select Hot Single stage full pressing is to produce, at lower operating cost, a high-quality cake, with high RUP (Rumen Undegradable Protein) content, especially suitable for cattle feeding. The RUP, or by-pass protein, are not digested by rumen bacteria and are, therefore, available for further digestion and absorption by the animal small intestine. It is of utmost importance for dairy cow milk productivity.
Other selection criteria are:
Oil Yield: due to cooking, material to be pressed is soft and liposome membrane are easily broken, hence releasing high amount of oil. This is the reason for high oil yield. Compared to Hot Double Stage Full Pressing, oil yield will be slightly less.
Oil Value: du to cooking, some nutritional components of the oil may be affected or degraded, just like in a refining process, making the oil value just as good as any solvent extracted oil. Compared to Cold Single Stage Full Pressing, oil value will be lower.
Cake PDI: PDI is affected by heat, therefore, the cooking step will reduce its value. Compared with Extrusion + Full Press, PDI will be lower.
OPEX Saving: due to cooking stage, the Hot Single Stage Full Pressing has a relatively high consumption of steam. It is however less energy demanding than Hot Double Stage Full Pressing, giving some OPEX savings based on steam and power consumption.
CAPEX Saving: compared to Hot Double Stage Full Pressing, the Hot Single Stage Full Pressing allows for CAPEX saving as far as process equipment is concerned. Moreover, the cost of installation is also lower because of its simpler design.
The seed from storage may contain up to 2% foreign material. The purpose of the cleaning process is to remove as much of foreign material as possible. An optional weighing process can be foreseen to get an accurate inventory of the material being sent through the seed preparation process.
Milling is aimed at reducing inlet raw material into smaller size particles. It is a necessary process step to increase the heat transfer rate in the subsequent Cooking process. Milling can be achieved in a hammer mill, or cracking rolls.
In some cases, the cracking rolls milling can be combined with dehulling system, generally aimed at increasing protein content on the press cake.
In addition to size reduction, milling can include flaking step to further improve heat transfer in the cooker and oil extraction in the press.
Cooking is a thermal process which heats the inlet material to approximately 100ºC (212ºF) and reduces its moisture to about 3%. It is aimed at turning hard and harsh cracks/flakes into soft and easy to squeeze material, and at same time, increase friction, thereby pressure, on the material inside the press resulting in oil extraction rate increase. DesmetBallestra offers full range of horizontal and vertical cookers design.
Full Pressing is the heart of the process. Properly prepared material is fed continuously into the screw press where cellular structure of the seed is severely distorted tearing open many of the cell walls. Most of the oil will be extracted while producing a discharge cake with both integrity of shape and porosity, ideal for downstream cake cooling. DesmetBallestra offers a full range of ROSEDOWNS screw presses for all kind of seeds, all capacities.
Cake cooling is requested to removing heat from the cake coming out from the press. It is achieved through convective and evaporative cooling via fully counter-current air flow through the cake layer. After the Cake Cooler, the cooled cake has a temperature within the range of 20 to 40°C (68 - 104ºF), and a moisture contains below 3%.
Oil clarification is a two-step process that separates solid matter from the oil removed during Pressing. The first separation step is by screening and the second separation step is by leaf filter filtration.