Combining pelletizing to cold pressing in the rapeseed crushing process improves energy balance and the meal and oil quality

Abstract

Cold‐pressing has well‐known adverse effects on solvent extraction performances from the resulting cakes. Here, we investigated the added value of an additional pelletizing step in a batch extractor (3.5 kg) to produce pellets with better physical quality (durability, wettability, and percolation speed) for hexane extraction and desolventization. We then led a second experiment in a pilot‐scale continuous belt extractor (250 kg/h) to evaluate the feasibility of the process and its impacts on mass balance, oil and meal quality, and energy consumption. Results showed that pelletizing cold‐pressed cakes enables suitable oil extraction and meal desolventization performances. Meal quality was preserved and press oil quality enhanced due to a very low phosphorus content (<10 ppm). The energy balance of cold‐pressing was compared to the regular process using the flaking‐cooking‐pressing preparation before solvent extraction on the basis of data obtained here or from industrial crushing plants. Results showed that cold‐pressing may lead to 69% energy savings in the preparation phase (40 vs. 131 kWh/t) and 32% energy savings at whole‐process level (192 vs. 283 kWh/t). The scheme also has benefits in terms of greenhouse gas emissions (36.8 vs. 58.5 kg CO2 t−1).Practical applications: Industrial rapeseed oil extraction currently relies on a two‐step process of preparation (conditioning, flaking, cooking, pressing) and solvent extraction (percolation, miscella distillation, meal desolventizing). Cooking and desolventizing are the biggest energy users in the process. Using cold‐pressing to remove the cooking step was identified as a simple and effective way to reduce whole‐process energy consumption. Our results show that pelletizing cold‐pressed cakes not only avoids the adverse effects of cold‐pressing on solvent extraction performances but can also lead to significant energy savings and better‐quality pressing oil.Cold Pressing used as an alternative to traditional preparation allows substantial energy savings.