HYDRAULIC PRESSING OF OILSEEDS: EXPERIMENTAL LABORATORY STAND FOR DETERMINATION OF MATERIAL BALANCE

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1 HYDRAULIC PRESSING OF OILSEEDS: EXPERIMENTAL LABORATORY STAND FOR DETERMINATION OF MATERIAL BALANCE Ionescu M., Biris S., Voicu Gh., Paraschiv G., Ungureanu N, Dilea M., Vladut V., Matache M., Voicea I. Abstract: Vegetable oil, one of the most important component for both food and non-food industry, is contained by the oleaginous plants in seeds, pulp, stone fruits, in the tubers or sprouts. Depending on the nature of material and their oil content, various methods can be used for oil extraction from oleaginous material. One of the most usually method for oil extraction is the mechanical expression, also known as pressing. Pressing represents the operation which separates the oil from the oleaginous material (solid-liquid mixture), under the action of external forces, resulting crude oil and cake. The pressing process of oleaginous material occurs under the influence of compressive forces that arise in the equipment. The equipments used for mechanical oil extraction are the presses, which can be screw presses or hydraulic presses. In this paper are presented the results obtained from oilseeds pressing, using a hydraulic laboratory press. Based on the experiments, the material balance was made, taking into account the piston speed and its applied force, for both types of oilseeds used (sunflower seeds and rapeseeds). Key words: Vegetable oil, oilseeds, extraction, hydraulic pressing INTRODUCTION In plants, fatty matter is concentrated only in some parts such as seeds, fruits and tubers, stone fruits, sprouts, representing a reserve substance that the plant uses during its development as a source of energy. Although the oilseeds field is very wide, plants that can be used as raw material in vegetable oils industry are slightly because many of them have low oil content - being unprofitable, others with higher oil content present difficulties in oil extraction because of the special structure of the plant. [2] The request for the vegetable oil industry increases with increasing population through the discovery of new uses. Thus, to satisfy the vegetable oil demand, it is necessary that the oil extraction methods to be faster and more efficient. [1] Vegetable oils are used principally for food (mostly as shortening, margarines, and salad and cooking oils) and in the manufacture of soap and detergents, in paints and varnishes, and for a variety of other industrial items. [6] Currently, worldwide there are four basic methods for obtaining vegetable oil: chemical extraction (using solvent or enzymes), supercritical fluid extraction, steam distillation and mechanical extraction. Mechanical extraction and solvent extraction are the most commonly used methods for commercial oil extraction. Mechanical pressing is used for oil recovery up to 90-95%, while solvent extraction is capable of extracting 99%. [3] Taking into account the disadvantages presented by solvent extraction method, many of vegetable oil producers choose to utilize mechanical extraction, using the screw presses or hydraulic presses. Between these equipments, hydraulic press is common in small scale processors because it is less capital-intensive in terms of initial and maintenance costs. Hydraulic presses are now available in different versions, but their efficiency seldom exceeds 70%. [4] Expression is a unit operation in which a liquid is separated from a solid-liquid mixture or liquid bearing matrix by mechanical compression. Hydraulic expression involves application of pressure to the oleaginous material found in a cylindrical cage perforated laterally. The results consist of an axial compaction and a radial oil flow. The three distinct 276

2 phases (initial stage, dynamic stage and final stage) of hydraulic expression are presented in the following figure. [4] Figure 1. Phases of hydraulic expressions, [5] a initial stage; b dynamic stage; c consolidation stage (final stage). In the present paper there are presented the experiments conducted on a small capacity experimental stand for obtaining oil from oilseeds under hydraulic pressing. MATERIAL AND METHODS The experiments were conducted using whole sunflower seeds and rapeseeds, supplied by Giurgiu County, Romania. Before the experiments, both types of seeds were subjected to a selection process using a SS-02 seeds selector (provided by STIMEL Timisoara) with a capacity of 100 kg seeds/h, in order to separate the impurities from the seeds. Mechanical expression of oil from oilseeds was performed using an experimental stand for hydraulic expression. The experimental stand, presented in figure 2, was constructed using the pressing chamber of a PU-50 screw press (STIMEL Timisoara), which was fixed in vertical position. For oilseeds compression, a computer control electromechanical universal testing machine, model WDW-100, provided by Jinan Testing Equipment IE Corporation, was used. On the external side of the pressing chamber, a metal ring was fixed for oil collection. The oil collected in the metallic ring reach farther, through a metallic pipe, in a beaker. For the experiments were also used a KERN-EG electronic precision balance, with maximum capacity of 4200 g, to measure the weight of seeds, respectively oil and cake. The experiments were conducted at NATIONAL INSTITUTE OF RESEARCH - DEVELOPMENT FOR MACHINES AND INSTALLATIONS DESIGNED TO AGRICULTURE AND FOOD INDUSTRY INMA from Bucharest, Romania. For the experiments, 120 g of seeds was placed in the press chamber, after which the piston was lowered on top of the seeds. With the help of electromechanical universal testing machine, the piston starts compressing the sample seeds. For each type of seeds, four experiments were carried out varying the speed of the piston. The four values choose for piston speeds were: 2 mm/min, 4 mm/min, 8 mm/min and 12 mm/min, while the maximum load for piston was 7 tons for all the experiments. After the samples compression, the oil and the cake obtained were weighed in order to achieve the material balance. 277

3 Figure 2. Experimental hydraulic expression stand RESULTS AND DISCUSSION Table 1 presents the material balance (oil, cake, losses) obtained from the experiments, for both seeds type and the four piston s speed. The dependence between the stroke and the load of piston are represented in the following graphs. First graph is traced using the data obtained from the universal testing machine software for the experiments conducted with rapeseeds, for all the four pistons speed, while the second graph represents the same dependence for the sunflower seeds. Seeds Rapeseed Sunflower Table 1. Material balance of 120g seeds hydraulic compression Piston speed Oil [g] Cake [g] Losses [g] [mm/min]

4 Figure 3. Dependence between stroke and load piston In the figure 4 is presented the influence of piston speed on the efficiency of expression process. It can be observed that, for both seeds type, the increasing of piston speed from 2 mm/min at 12 mm/min conduces to a decrease of oil extracted quantity. Thus, the residual oil in the cake increases. The explication for this tendency is that oil extraction efficiency is influenced by the time of pressing, the oil needing enough time to drain the oleaginous material during the pressing process. Figure 4. Influence of piston speed on the efficiency of extraction process 279

5 CONCLUSIONS AND FUTURE WORK Many researches focused on the hydraulic pressing, one of the most utilized methods of oil extraction, in order to improve the extraction efficiency. Hydraulic extraction is influenced from various parameters, as it results from the researches, one of the most important being the pressing time. This work shows the influence of piston speed on the efficiency of hydraulic extraction method, in the case of rapeseeds and sunflower seeds. Thus, an increasing of speed piston, meaning a decreasing of pressing time, involves a decreasing of oil extracted, which is equivalent with the increasing of residual oil in the cake. It is necessary that the pressing time to be not small, so that the oil has enough time to cross the oleaginous material and be evacuated. REFERENCES [1]. Alonge A.F., A.M. Olaniyan, K. Oje and C.O. Agbaje, Effects of dilution ratio, water temperature and pressing time on oil yield from groundnut oil expression, Journal of Food Science and Technology, vol. 40, no.6, [2]. Banu C., Manualul inginerului din industria alimentară, vol. I and II, Editura Tehnică, București. [3]. Karaj S. and Muller J., 2009, Optimization of mechanical extraction of Jatropha curcas seeds, Landtechnik 64, no. 3, pp [4]. Owolarafe O.K., A.S. Osunleke and B.E. Oyebamiji, 2007, Effect of hydraulic press parameters on crude palm oil yield, International Agrophysics, vol. 21, pp [5]. Owolarafe O.K. et all, 2008, Mathematical modeling and simulation of the hydraulic expression of oil from oil palm fruit, Biosystems Engineering 101, [6]. ABOUT THE AUTHORS Ionescu M., Biris S., Voicu Gh., Paraschiv G., Ungureanu N, Dilea M. - Politehnica University of Bucharest, Spl. Independentei, nr.313, sect.6, Bucharest, Romania. maneamaryana@yahoo.com, biris.sorinstefan@gmail.com, ghvoicu_2005@yahoo.com, paraschiv2005@yahoo.com, nicoletaung@yahoo.com, mirela_dilea@yahoo.com Vladut V., Matache M., Voicea I. - National Institute of Research - Development for Machines and Installations Designed to Agriculture and Food Industry INMA, ROMANIA, 6 Ion Ionescu de la Brad, Blv, sector 1, Bucharest 71592, OP 18, valentin_vladut@yahoo.com, voicea_iulian@yahoo.com. 280