The Effect of Jatropha Fruits Moisture Content on Shelling Process by Compression Roller

Transcription

1 The Effect of Jatropha Fruits Moisture Content on Shelling Process by Compression Roller Bo Yuan Lim 1, Rosnah Shamsudin 1, Robiah Yunus 2 1 Department of Process and Food Engineering, Faculty of Engineering, Universiti Putra Malaysia, Serdang, Selangor, Malaysia 2 Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia, Serdang, Selangor, Malaysia Abstract Separation of Jatropha seeds from shells is important to achieve better oil yield in biodiesel production. The changes of fruits moisture content can change the fruits properties and affect performance of shelling machine. The motor driven compression roller was used to crack the fruits to detach the shells from seeds. The performance was evaluated at four different moisture contents (5.83%, 8.18%, 10.30% and 11.15%). Based on findings, the quantity of unshelled seeds increase with the increase of moisture content. Hence, the harvested fruits should be dried to loosen the shells before shelling process during seeds preparation stage to improve shelling efficiency. Keywords Jatropha, moisture content, shelling, compression roller 1. Introduction Jatropha curcas L. has been reported as one of the most promising biodiesel feedstock to deal with fossil fuel depletion issue. It is non-edible and well adapt to marginal land [1-3]. The mature fruits which is yellow brown in colour should be harvested due to their higher yield as compared to immature fruits [4]. The dried fruits are brittle and its colour is dark brown [5]. The fruits are composed of seeds and shells and each fruit contains 2-3 seeds. The weight of seeds is 60-65% of the total weight of the fruits and the weight of shells is 35-40% of the total weight of the fruits [6]. The seeds yield and oil yield can achieve 4 tonnes/ha and 1590kg/ha respectively [5, 7]. Figure 1: Jatropha whole fruits, seeds and shells Some reports mentioned that the oil yield can be improved with decorticated seeds [5]. This is due to the shells do not content any oil and can be the barrier to block the oil coming out from kernel inside during oil extraction process. Due to shells oil expeller has to exert more pressure for oil extraction which causes higher energy input and lower extraction efficiency [8]. Therefore, it is important to detach and remove the shells completely prior to oil extraction process in Jatropha biodiesel production. The shelling process can be done manually or mechanically. Mechanical process is preferred due to its higher production capacity and low labor cost. During shelling process, the fruits will be first cracked by applying slight pressure or friction to detach the shells from seeds prior to separation process. The shelling process has been done by compression roller, rotating shearing blade or rotating shearing cylinder [5, 9, 10].

2 There is the fact that the changes of moisture content can affect physical properties and mechanical properties of fruits. The affected parameters including fruits dimension, density, porosity, angle of repose as well as crushing strength [11, 12]. The previous studies for tung fruits and sunflower seeds revealed that the moisture content of fruits can affect efficiency of the equipment designed for this work [13, 14]. Therefore, we can have better performance of shelling equipment by inducing changes in fruits physical properties. The objective of study has been determined to investigate on how does moisture content affect the performance of compression roller in Jatropha shelling process. 2. Methodology 2.1 Design of Testing A motor driven compression roller (Diameter 59.50±0.05mm) was set up for performance testing. There were two rollers arranged in parallel. The rollers are made of mild steel and came with trading on surface as shown in Figure 2 to avoid fruits sliping during cracking process. The speed of rollers were measured by tachometer (DT-2230, Lutron, Taiwan) at 1125rpm and the clearance between the roller was 13mm. The dry fruits were loaded slowly and cracked by compression roller. The output was collected by container at the bottom. The output was then being loaded back to compression roller again to complete two level of cracking process. The steps were repeated with four different moisture contents which are 5.83%, 8.18%, 10.30% and 11.15%. Each test was replicated three times and 20 fruits loaded for each test. Figure 2: The configuration of compression roller 2.2 Sample Preparation The mature Jatropha fruits (dark brown color), which procured from UPM (Universiti Putra Malaysia) in March, 2013 were used for performance test. The fruits were checked manually to remove foreign matter and broken fruits. They were then dried under the sun for 2 days prior to performance testing. The initial moisture content was determined by standard hot air oven method. The sample was dried by oven (OF- 22GW, Jeio Tech, Korea) at 105±0.8 C for 24 hours [5].

3 The following equation was used for initial moisture content calculation: Wi Wf MCi x100% (1) W i Where MC i W i W f = Initial moisture content wet basis (% w.b.) = Initial weight of sample (g) = Final weight of sample (g) The initial moisture content of fruits was 5.83% w.b. After that, the moisture content of fruits was raise by rewetting technique [11]. The quantity of water needed to add was calculated based on following equation: Q W ( M f M i ) 100 M f (2) Where: Q Wi Mi Mf = Mass of water added (g) = Initial mass of the sample (g) = Initial moisture content of the sample (% w.b.) = Final moisture content of the sample (% w.b.) The calculated quantity of distilled water was added to the fruits and throughly mixed. The sample was placed in fully sealed polyethylene bags and stored in cooled incubator (TD-1600, Protech, Malaysia) at 5±0.2 C for a week. The required quantity of samples were warmed up to room temperature for about 2h before the moisture content checking and testing. The moisture contents obtained were 8.18% w.b., 10.30% w.b. and 11.15% w.b. 2.3 Performance Evaluation The shelling efficiency of compression roller was calculated based on following equation: U 1 x100% (3) T Where η U T = Shelling efficiency = Total weight of unshelled fruits and partially shelled fruits = Total weight of loaded fruits The cracking efficiency was calculated based on the effectiveness of compression roller to detach shells from seeds. 3. Results and Discussion Based on Figure 3, if referring to single level cracking process the shelling efficiency decreases (from 82.90% to 64.77%) with increase of moisture content (from 5.83% w.b. to 11.15% w.b.). The results are similar for double level cracking process. The efficiency decreases from 89.48% to 74.68%. The similar decreasing trend in shelling efficiency has been reported for tung fruits and sunflower seeds as well [13, 14]. Besides that, an earlier paper also reported high moisture content can lower shelling efficiency of the Jatropha decorticator with rotating blade [5]. The author reported the low moisture content fruits are more brittle, less elastic and easy damaged by mechanical force.

4 High moistured fruits tend to be soft and elastic result in more cracking energy loss in the form of elastic potential energy during shelling process. The other reason was probably due to the cohesion of water in the fruits. The cohesive force between the water molecules in high moistured fruits causes the shells and seeds tend to stick to each other during cracking process. Thus, wet fruits normally required smaller roller clearance which can provide bigger compression displacement and higher cracking energy to detach the shells. Besides that, there is comparison of performance between double level cracking and single level cracking in Figure 3. The overall results show that the efficiencies were higher for those samples which undergo two times of compression. The improvement of efficiencies were from 6.58% to 10.91% throughout different moisture contents. This is due to the fact that more cracking energy was needed by second level of roller. Some fruits, which escaped from first level roller without being shelled, would be cracked and shelled at second level roller. Thus, this can be the alternative solution to improve efficiency apart from reducing roller clearance. The other interesting thing was that the shelling efficiency dropped down to the smallest value of 6.58% at the minimum moisture content. This indicates the second level roller played less important role due to the fact that most of shells were already detached in first level roller. Thus, this proves that the shells can be detached easily from low moisture content fruits. Figure 3: Shelling efficiency under different moisture content (Data are mean values ± standard deviation) 4. Conclusions The study shows that shelling efficiency of the simple, low cost and constant speed compression roller can be improved by controling the fruits properties without fruits size sorting process. The conclusions are based on the investigating the moisture content ranging from 5.83% w.b. to % w.b. The shelling efficiency of compression roller can be increased by reducing Jatropha fruits moisture content due to the fact that the shells of low moisture content fruits can be detached easily. Therefore, the drying process should be carried out to reduce water content of fruits before loading the fruits to shelling equipment during production. The improvement of shelling efficiency ensures lesser shells sticking together with seeds and thus improves subsequent separation process during seeds preparation stage. The production time can be reduced as well due to less work required to clean out retained shells matter after separation process. The future research should study about the relationship between roller clearance and shelling efficiency to find out optimal design for compression roller. The research on mechanized separation process should be carried out as well to achieve shells-free seeds recovery to further improve biodiesel feedstock quality. Acknowledgement The authors are grateful to the Prototype Research Grant Scheme (PRGS) from Universiti Putra Malaysia (Reference No: UPM/700-2/1/PRGS/ ) for the financial support.

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