Journal of Food Engineering 43 (2000) 75±82www.elsevier.com/locate/jfoodeng Development of a small capacity double stage compression screw press for oil expression Jaswant Singh a, P.C. Bargale b,* b a Indian Institute of Sugarcane Research (ICAR), Dilsukha, Lucknow 226 002, UP, India Central Institute of Agricultural Engineering, Nabi Bagh, Berasia Road, Bhopal 462 038, MP, India Received 11 December 1998; accepted 7 September 1999 Abstract Mechanical pressing of oilseeds is the most widely used method for oil expression in the world. However, the mechanical oil expellers (screw presses) employed for this purpose leave about 8±14% of the expressible oil in the deoiled cake, so that a large quantity of edible oil is not available for human consumption. To improve the eciency of oil recovery, a modi®ed oil expeller was designed and developed based on a novel principle of single feed double stage compression. An evaluation of the performance of the developed expeller with moisture conditioned rapeseed samples indicated that in two passes it recovered over 90% of the available oil at a moisture content of 7.5% (w.b.). This is in contrast to normally required 3±5 passes in conventional oil expellers for an oil recovery of about 80%. The throughput capacity of the expeller was 25 kg/h while its eective capacity (two passes) was found to be 15 kg/h. The maximum barrel temperature was 70.3°C which assured production of a good quality oil, and the deoiled cake and the speci®c energy requirement was 0.05 kWh/kg of feed for the optimized pressing conditions. An economic analysis indicated that the developed screw press could pro®tably be used for small-scale processing of rapeseed in rural areas of India. Ó 2000 Elsevier Science Ltd. All rights reserved. 1. Introduction Mechanical pressing is the most popular method of oil separation from vegetable oilseeds in the world (Mrema & McNulty, 1985). In India, nearly 90% of the total 24 million tonnes of produced oilseeds are crushed using this method. The main reason for popularity of mechanical oil expellers in India as well as in other developing countries is that these equipments are simple and sturdy in construction, can easily be maintained and operated by semi-skilled supervisors, can be adapted quickly for processing of dierent kinds of oilseeds, and the oil expulsion process is continuous with product obtained within a few minutes of start of the processing operation. The safety and simplicity of the whole process is advantageous over the more ecient solvent extraction equipment. Furthermore, unlike the solvent extraction method, mechanical presses yield a chemicalfree protein rich meal. Screw presses are available in the * Corresponding author. Correspondence address: 133, Malviya Nagar, Bhopal 462 003, MP, India. Tel.: +91-755-547283; fax: +91755-547482. E-mail address:
[email protected] (P.C. Bargale). capacities from 40 to 1000 kg/h. The smaller capacity presses have socio-economic signi®cance as they provide a value addition at cottage level with gainful employment. However, the mechanical screw presses (oil expellers) are relatively inecient, leaving about 8±14% of the available oil in the cake (Srikantha, 1980). Thus, a large quantity of precious edible oil (about 0.6 million tonnes) worth Rs. 2:4 Â 109 (US$57 million) annually remains in the deoiled cake. An improvement in the mechanical extraction equipment and techniques through proper conditioning can raise oil recovery from 73% to 80% for rapeseed and groundnut (peanut) and from 60% to 65% for cotton seeds (Pathak, Singh, Singh & Verma, 1988). Thus, in order to reduce the demand and supply gap of vegetable oils in developing countries, there is a need to develop more ecient mechanical screw presses. Considerable eorts have been made in the past to improve the oil extraction eciency of screw presses. Most of them have focused on optimization of process variables such as applied pressure, pressing temperature and moisture conditioning of the fed samples (Ohlson, 1992). Various physical (e.g. dehulling, cracking, size reduction), thermal (e.g. preheating, dry extrusion), 0260-8774/00/$ - see front matter Ó 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 2 6 0 - 8 7 7 4 ( 9 9 ) 0 0 1 3 4 - X Oilseed medium is fed continuously into the screw press.2. Isobe. 2. Sosulski & Shook. 1988) . 2 shows the material ¯ow through a small section of the worm channel (Vadke. 1. globoids and nucleus. the problem of the requirement of an excessive number of passes remains. Bargale & Shukla. These are surrounded by a tough membrane called cell wall (Fig. 2. Ohlson. speci®c theoretical considerations for screw press designs have not been applied. blanching. Williams. Such oil ¯ow. P. Wulfson & Irudayaraj. 1976. According to Ward (1976). For this reason. in the form of oil globules. These eorts have helped to increase oil recovery levels for various oilseeds from 50% to 80%. Singh.76 J. where it is compressed under high pressure (4±35 MPa) which ruptures the cell walls so that the oil globules can escape. The objective of the work presented in this paper was to develop an ecient modi®ed oil expeller based on a conceptual design. 1983. Attempts to improve upon existing screw presses by developing a suitable and ecient oil expression device have remained isolated. Singh. is present in the cells of the oilseed at dierent locations along with other constituents such as proteins. This pressure causes ¯ow of oil in the radial direction through the oil±solid matrix and oil ¯ows out through the barrel slits. ¯aking) and chemical (enzymatic hydrolysis) pretreatments have been considered (Tindale & Hass. 1976. and is exerted by the shaft. 3). Bargale / Journal of Food Engineering 43 (2000) 75±82 hydrothermal (e. In addition.g. 2.C. steaming. the maximum radial pressure is generated at the feed end and the axial pressure follows a similar trend (Fig. Singh. This pressure is generated due to volumetric compression along the screw barrel. 1988). Ford. Ward (1976) and Singh. 1). This results in increased speci®c energy consumption and wear and tear of the equipment. Sosulski & Shook. Bargale. 1990). and forces oil through the slits provided along the barrel length. Wei & Wei. 1995. energy and labour. Bargale and Shukla (1990) have discussed in detail the various components of screw presses. their functions and some design criteria.1. Uemura and Noguchi (1992) developed a screw press based on twinscrews and reported an oil recovery of over 93% from untreated. hot water soaking. 1988). the theory of Newtonian ¯uid ¯ow in an extruder. Zuber. The developed unit was tested with rapeseed which is the second largest produced oilseed of India with a production of 6. Mostly.5 million tonnes. The compressed solids are simultaneously discharged through a choke provided at the end of the barrel. 1976. Bredeson. Yeh. of these expellers (Tindale & Hill-Hass. However. the cage bar of an expeller is not continuous and radial ¯ow of oil takes place as the material moves forward in the barrel.7 million tonnes and the third largest produced oilseed in the world with an annual production of 30. it is subjected to a radial pressure. Fig. dehulled sun¯ower seed. Fig. 1987. Stainsby. The design was conceived based on the experience of investigators while testing several of the existing local as well as imported oil expellers. Nelson. 1992. Wijeratne. 1999). 1983. Contrary to the ¯ow of material in the extruder. Theoretical considerations 2. Design considerations The literature reveals that screw presses designs and modi®cations have largely come from screw press manufacturers who have used their experience in design Fig. Thus. the analysis and design of an expeller becomes complicated. Micro-section of rapeseed (Singh. Flow of material through a section of worm channel (Vadke. Sosulski. Ward. choking and jamming of the operating screw are generally encountered leading to excessive heating and burning of the cake and oil and thus loss of quality. As the mixture of the oil and solids passes through several such sections. Khan & Hanna. wherein pressure is built-up continuously along the barrel length. Principles of screw press operation The oil. has been adopted. while the secondary section consisted of only two of these sections. most mechanical screw presses require 3±5 passes to attain an oil recovery of 80% or more (depending on the oilseed. to avoid increased choking and jamming because of provided additional length. in turn. (i) a primary section and (ii) the secondary section (Figs. it was divided into two sections. namely the ram section and the plug section. The pressure development and the expression of oil starts at the beginning of the ram section. 3 and 4). It is de®ned as the ratio of volume of material displaced per revolution of the shaft at the feed section to the volume displaced at the choke section (see Fig. This was necessary in order to accommodate the ®ve proposed sections.C. 4. the following assumptions are made for design of screw press: · The maceration of oilseed mass is complete in the feed section. a compression ratio of 10:1 is normally used for groundnut compared to a theoretically calculated ratio of 4. (11) choke mechanism. 1988). Bargale / Journal of Food Engineering 43 (2000) 75±82 77 Fig. The primary section was further divided into three sub-sections namely (a) feed section (b) ram section and (c) plug section. · The temperature of oilseed mass remains constant in the ram section (while in reality. (6) barrel. In principle. (2) speed reduction unit. (8) oil collection tray. for the same oil recovery. pretreatment. the number of passes could be reduced in half. (1) hopper. To accommodate this concept.0 (Singh & Agarwal. Further. the temperature increases along the ram section due to shearing action of the shaft). an increase in the length of the screw was necessary. changes the ¯ow rate of mixture inside the barrel in the axial direction. Singh. As for extruder design. Illustration of principle of single-feed double stage compression used in the developed screw press.3. Design of the developed oil expeller The expeller developed in the present study is a prototype design based on the principle of single-feed double stage compression. (4) cake collecting tray. (3) frame. The compression ratio of the screw/worm is therefore one of the most important criteria in¯uencing the performance of a screw press. (5) worm-shaft. (9) clearance adjustment. · No pressure development would take place in the feed section. while the screw length was increased. (7) spacers. P. 2.J. This compression was achieved through increasing the root diameter of the worm while the pitch and helix angle of the screw and the barrel diameter were kept constant. (10) electric motor. for a theoretical overall eective compression ratio of 15:1 in one pass. 3).3:1. 3. It was hypothesized that this would facilitate pressing of the fed oilseed twice rather than once prior to its exit from the barrel. Hence. Fig. applied pressure. Hence. compression ratios higher than the theoretical compression ratios of high oil content seeds are used to compensate for slip and rotation of meal with respect to the shaft. leaving a homogeneous mixture of oil and solids in the ram section. a compression ratio of 5:1 was used for the primary section and a ratio of 3:1 for the secondary section. 3 shows the volume change pattern as well as the theoretical variation of the Fig. instead of a single stage compression ratio of 10:1 typical of conventional screw presses. Semi-sectional view of the screw press (oil expeller) developed based on the concept of single feed double stage compression. Since in practice. pressing temperature and pressing time). Expellers work on the principle of a pressure dierential applied to the incoming oilseeds versus that applied to the discharge material. viz. . In practice. the compression ratio of the worm con®guration was changed such that it was reduced to almost half. For example. it was considered worthwhile to design a screw con®guration with an additional intermediate choke. which remains however. the material in the primary plug section moves forward to the secondary section where it enters the ram section directly.0 200. Other components included thrust bearings.6 kW/3Ph/1440 rpm). 9% and 11% ( 0. The developed screw press consisted of a screw. The barrel was made up of a number of single circular mild steel plates joined together using two hollow mild steel rods which went through these plates.0 298.1.. 7%. 0. kg/h Eective capacity. mm Length of the secondary plug section. 4). Bargale / Journal of Food Engineering 43 (2000) 75±82 radial and axial pressures in various sections of the developed screw press (based on Ward.0 15.0 50.0 48.e. a clearance in the range of 0. To provide a consistent uniform feeding in the screw press. and oil and cake pan. mm Outer diameter of the screw.4. mm Length of the ram section.0 96. The power transmission system consisted of a motor (5. Cleaned rapeseeds were sprinkled with a predetermined quantity of water so that the moisture contents of the samples were approximately 5%.0 203. 58. Between the plates. This creates axial and thereby radial compression on the disintegrated oilseeds. thereby exposing a larger surface area to the pressure application in the forthcoming primary plug section (3). Experimental evaluation of screw press 3. Meanwhile.78 J. a higher quantity of oil was expressed and its quicker escape was necessary through wider spaced slits to avoid its accumulation and possibility of back-¯ow towards the feed section. Using this mechanism.1:1 4.5 59. mm Length of the primary section.0 area for these barrel plates facilitated faster dissipation of heat during operation of the screw press. Singh. The extracted oil ¯ows through slits provided in the barrel through shims in the primary plug section. rupturing the cell-walls. 96 and 115 rpm.6:1 .5 125. The backward movement of the worm (i. Major speci®cations of the developed screw press are given in Table 1. The calculations of quantity of water to be added were based on an initial moisture content of 6. In this section. water may be circulated through these rods to check the increasing barrel temperature during operation of the press. as oilseed is continuously fed through the feeder. Provision of a slightly larger Table 1 Speci®cations of the developed oil expeller Parameters Overall length of the screw. This provides an all-important breather to the material which then enters the secondary plug section and is compressed to the maximum pressure designed for the press before ®nally exiting from the expeller. mm Length of the secondary section. it is subjected to a gradually increasing pressure.3% 5:1 3:1 5. This second compression is more eective since the clearance between the barrel and screw can be reduced considerably with the help of the end cone clearance. involves no additional cost and energy and is the most widely used pretreatment for rapeseed.5%). 1976). kg/h Optimized screw speed. the end part of the worm is of conical form. The pressure in the primary plug section is generated due to restriction created by an intermediate choke. lower than that in the preceding primary plug section. mm Length of the feed section. To accomplish this. mm Outer diameter of the barrel.C.0 58. 3. variety ± Varuna). a regulatory feeder was provided.4 mm was attainable. 3) of the primary section of the screw (1). Pretreatment of moisture conditioning by instant water sprinkling was selected since this pretreatment is simplest to practice.025 mm thick spacers/shims were provided (1±5 in number) to facilitate the ¯ow of expressed oil during operation of the press. This was necessary due to maximum applied pressure in this section. mm Throughput capacity. and facilitating removal of oil from the oilseed.0 60. barrel (circular barrel rings inside which the screw rotates) and a cone mechanism for adjustment of clearance and regulation of pressure on fed oilseeds (Fig. This was driven through the gear reduction unit such that the feeder speed was synchronized with that of the screw press. P. Materials The developed screw press was tested for its performance with rapeseed (Brassica campestris L.8±0.4 25. movement towards the feed hopper) increases the clearance and thereby reduces the pressure on oilseed present inside while its forward movement does it otherwise. mm Inner diameter of the barrel. mm Length of the plug section. Operation mechanism As the oilseed fed through a regulated feeder enters into the feed section (refer to Fig. rpm (revolutions per minute) Compression ratio for Primary section Secondary section Length:Diameter (L:D) ratio Primary section Secondary section Overall Dimensions 561. 2.5:1 9. Using a pump. a gear reduction unit (25:1) and two four-step pulleys selected to provide four worm speeds of 29. it is conveyed to the ram section (2) where it disintegrates into small particles. A relatively large number of shims were provided in the plug section followed by the ram section. Performance of the developed screw press Table 2 summarizes the results of the performance of the developed screw press (oil expeller) with rapeseed samples at dierent moisture contents.3°C at a moisture content of 5.1°C. The maximum barrel temperature was 70. P. This was to ensure uniformity in oil recovery calculations from samples having dierent initial oil content because of dierent moisture contents. This may be due to the plasticizing eect of water which decreases the frictional coecient of the material.1% to 11. Results are presented on a mass basis. one-half of the weight of the foots was added to the weight of the deoiled cake that exited from the cake outlet. it was found that the press capacity was relatively higher than that reported for shorter duration tests of about 2-h duration. The expressed oil was collected in measuring cylinders (resolution ± 1 ml).C. the experiment was started and pretreated rapeseed samples. Later.9 kg of feed/h for the second pass. the moisture content of each sample was determined by the standard hot air oven method (AACC. Singh.1% (w. column 9) was calculated as the ratio of quantity of the oil remaining in the cake (Table 2. de®ned for the purpose of this study as the ratio of amount of oil expressed to the amount of oil initially present in the pressed samples. Havells Electronics. Experimental procedure Prior to each experiment. The cake was collected in a weighing pan connected to a digital balance (resolution ± 0. 4. This may be due to reduction in loss of time for larger .2.).b. The collected oil also contained small fractions of solid particles (`foots') in suspension.b. Results and discussion 4. per kilogram of fed samples pressed at selected moisture contents. For the ®rst pass. The container was shaken at regular intervals to distribute moisture uniformly throughout the sample. New Delhi. The maximum oil recovery was obtained at a moisture content of 7.) measured in the raw rapeseed samples obtained from the Farm Section of the Central Institute of Agricultural Engineering. The soxhlet apparatus (Make ± Tecator. Smart. During the long-term tests of 16 h duration. pass-II) to the total weight of the sample after removal of net oil (column 7).b.8 mm while for the second pass it was reduced to 0. India). barrel temperature. The values of the throughput capacities at 7.1 g.2% of the available oil in the sample could be recovered (Table 2). 1995) were used for this purpose. for an overall effective capacity of 15 kg of feed/h in two passes. the clearance was set at 0.J. Omega Engineering Stamford. The speci®c energy consumption did not vary much with moisture contents with values from 0.4± 70. The residual oil content in the cake after the ®rst pass (Table 2. 30 Amp. The throughput and the eective capacity of the screw press were found to be the maximum for this moisture content. The feed rate to the screw press feed section was controlled and regulated through a feeder. Bargale / Journal of Food Engineering 43 (2000) 75±82 79 (w. In most of the cases. 3 Phase. 3.01 s. This may also be re¯ected in the recorded range of maximum barrel temperatures (61. Bhopal. A screw speed of 96 rpm was used based on the preliminary tests to ensure least choking/jamming of the screw press. USA). were fed to the screw press. For this purpose. in the batch sizes of 5 kg each. The quantity of foots was also minimum (22. Each experiment was replicated ®ve times. this quantity was added to the oil expressed from the oil outlet for the purpose of percent oil recovery.4°C at a moisture content of 11.1% (w. For removing moisture.1% and decreased to 61. Oil content of each of the sample was expressed on a moisture free basis. The developed screw press operated smoothly throughout these experiments without any observed choking or jamming. The measured values of maximum temperature recorded also decreased with increasing moisture contents from 5. packed in an air-tight metal container and stored for about 48 h for equilibration.b.) when a total of 90. 1995) prior to its feeding in the operating screw press by drying in an hot air oven at 105°C for 24 h. respectively. Sweden.048 to 0.4 mm. During the process of oil expression. column 4. the press was operated ®ve times continuously for 16 h duration to evaluate its suitability for longer durations without choking/jamming and excessive heating. Once this temperature was obtained. the screw press was warmed up to a temperature of about 50°C by processing raw rapeseed kernels. Model-1020) and the standard procedure (AACC. speci®c energy consumption and pressing time were measured using a digital temperature indicator (resolution ± 0.). LCD quartz watches. energy meter (Make ± HFD. samples were kept in an hot air oven at 40°C until the desired moisture was reached. The oil was allowed to settle for 24 h. CT.5% moisture content were 28.3°C) during the operation of the press. For long-term test. Initial oil content for the sample was determined using the laboratory scale solvent extraction method.4 g) at this moisture content. The water sprinkled samples were then thoroughly mixed manually. Hence. 50 cps.056 kWh/kg of feed. half of the weight of the settled foots was found to be oil when separated in a centrifuge. These particles which are known as foots that had ¯owed out through the barrel slits along with the oil. Japan).5% (w. 60 rev/ kWh) and a digital stop watch (resolution ± 0. although speci®c energy consumption did decrease with increasing moisture content.2 kg of feed/h for ®rst pass and 23.1. Model-660. Make ± Avery. 022 0.2 356.4% (moisture free basis): Pretreatment ± moisture conditioning Initial quantity of oil in feed (moisture free basis) (g) Total recovery (oil + foots) (g) Foots after 24 h (g) Net oil recovery (total À half foots) (g) Net oil recovery (%) Residual oil content in cake (%) 392.3 105.033 0.3 354.3 54.5 328.6 66.1 I II 0.9 151.9 213.9 32.3 70.C.1 7.5 22.6 25.74 5.2 67.2 23.3 368.2 58.3 71.4 382. Bargale / Journal of Food Engineering 43 (2000) 75±82 Cumulative 2 À .80 Table 2 Performance of the developed screw press with rapeseed based on mass per kg of fed material:initial oil content of seed ± 41.5 24.6 70.4 66.4 24.1 2 I II ± 0.88 9.74 20.0 46.5 19.048 Press capacity (kg feed/h) Moisture content of the feed (% w. Singh.9 9.2 64.6 14.1 2 I II ± 0.5 2 I II ± 0.9 376.3 392.0 154.6 241.7 368.6 15.9 382.8 87.5 376.0 299.7 56.9 15.3 220.8 0.7 11.4 61.5 230.8 83.) Clearance (mm) 5.78 9.7 61.1 247.2 251.9 135.8 58.4 23.88 19.4 J.5 35.6 67.8 284.034 0.4 18.7 345.3 155.8 221.0 9.0 81.033 0.3 66.018 0.3 98.6 51.1 Cumulative 7.8 28.0 307.3 18.78 18.4 Cumulative 11.4 14.4 Maximum barrel temperature (o C) Speci®c energy consumption (kWh/kg feed) 0.030 0.8 0.7 11.8 250.6 14.0 77.6 26.5 56.b.9 61.019 0.015 0.9 103.4 Cumulative 9.8 0.9 22.6 85.2 54. P.7 41.9 13.0 25.8 17.051 0.056 0.3 48.049 0.8 0.) Pass (No.5 97.1 90.2 79.5 61.8 327.0 5. 000 (US$476) 272. yr Hours of operation per day Days of operation per yr Annual processing capacity for the raw material (rapeseed). man-hours of operation and the wear and tear of the barrel components when compared with operation of a conventional screw press under similar conditions of operation. labour wages per day (Rs. 7 per kg. Rs. P. Interest on cost of the machine @ 14% per annum Insurance @ 2. if operated as a small scale industry at the rural level in developing countries such as India.415) (US$8936) US$1.424 307. kg Revenue from sale of produced rapeseed oil @ Rs. 1976). This. 7. .343) (US$3072) (US$15.5% of the cost of the machines.800 kg Interest on cost of procured rapeseed @ 14% per annum Annual cost of storage/losses of rapeseed @ 10% of cost of rapeseed Annual variable cost Rs. considerably reduced energy losses. the insurance cost (2. Returns Average oil content of rapeseed. Bene®t-Cost-Ratio Return on Investment. per annum Housing @ 10% of the inital cost of machines per yr Annual ®xed cost. 7. kg Costs Fixed costs Machine depriciation (salvage value of @ 10% of initial cost). kg Annual production of deoiled cake produced per kg of rapeseed.224 (US$672) 20. ®lter press. Rs. Rs.400 129. In this analysis.00 is equivalent to approximately 42.432 518.00 per kg for 28. Man-days a Values 50. Variable costs Annual repair and maintenance cost @ 10% of machine cost.2.5% of the machine cost). This is important because barrel temperatures above 90°C have been reported to adversely aect the cake and oil quality (Ohlson.600 (US$4800) 28. Rs. Revenue from sale of deoiled cake @ Rs.00 per kWh . It is assumed that the miller would procure the rapeseed at the time of harvest at the lowest possible rate. but helped in eliminating the most prevalent problem namely choking/jamming found in oil expellers. Total annual revenue. kg of rapeseed per h Life of machine. Annual net pro®t from milling of rapeseed. Yr Employment generated. Economic feasibility of the developed press Table 3 presents a result of an economic feasibility analysis of the developed screw press. Rs.000 (US$1190) 15 10 8 240 28. Rs.400 (US$343) 2880(US$69) 201. 50 per kg. cost of oilseed at a rate of Rs.750 (US423) 5000 (US$119) 14. Besides this. 10 yr of press life with an annual maintenance cost at a rate of 10% of initial cost of the machine. 4. % Pay-Back Period.00 Indian Rupees. 30). Rs.104 (US$6479) 40 10. 30 per labour per day Cost of electrical energy @ Rs. 2.00 per kg and its storage and an averaged annual sale price of the produced oil and the deoiled cake were assumed Table 3 Economic feasibility analysis for the developed screw press for a small scale mechanical oil mill for rapeseed (based on costs in year 1998)a Operating parameters/costs Machine parameters Cost of machines (oil expeller.800 4500 (US$107) 7000 (US$167) 1250 (US$30) 5000 (US$119) 17. Eective capacity of oil expeller. Annual wages of two labours @ Rs.024 647.00 per kWh Cost of rapeseed @ Rs. store it until next season and express oil using the double stage compression screw press. Bargale / Journal of Food Engineering 43 (2000) 75±82 81 samples and an eective capacity of up to 20 kg of feed/h was observed. Rs. in turn. The expeller design exhibited additional bene®ts as follows: · A marginally reduced applied pressure which did not adversely aect the oil recovery rate.C. cost of the electricity as Rs. Rs.320 1.J. Singh. ®lter pump. Several other important assumptions included 240 number of days of operation per year with 8 h of press operation per day. % Annual production of rapeseed oil at 90% extraction eciency.23 146 0. interest on capital (14% per annum). · Elimination of choking/jamming reduced frictional heat so that the screw and the barrel temperature remained lower than the 90°C. 2. despite the longer barrel as well as duration of operations.368 18. prime mover).83 480 (US$12. Journal of Oilseeds Research. Pandey. Yeh. Processing eects on oil quality. G. (1988). Approved methods of the American association of cereal chemists (eighth ed. 53. Zuber. D. Uemura. Project planning. J. C. F. W. (1976). P. 76 (2). 1341± 1347... Agricultural Engineering Today. A. India: Central Institute of Agricultural Engineering. India: Central Institute of Agricultural Engineering. U.82 J. Isobe. A twin-screw press design for oil extraction of dehulled sun¯ower seeds. C.. 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Processing high oil content seeds in continuous screw presses. K.570 (US$ 8514) can be earned providing a Bene®t-Cost-Ratio of 1. Modern processing of rapeseed. based on the market values in India for these items. 69. 69. Y. Chouhan. Hence. R. W. 1991). M. (1992). 15 (1). Bhopal. S. A. Mechanical oil extraction. (1976). 495± 503. 261±264. Singh. Nelson. approach and issues. 223± 229. & Ojha. Stainsby. P. S. R. Srivastava. 6 (3). Chouhan. & Wei. F. MN: American Association of Cereal Chemists. the unit would generate an employment of 480 man-days at rural level. Journal of Agricultural Engineering Research. Singh. K. Kachru. D. Analysis indicated that a net annual pro®t of Rs... C. M. 53 (6).. the values of the revenue generated and the annually earned pro®t. 357. (1995). D. A search for an appropriate technology for village oil industry. Mini oil expellers: new direction to rural oil milling industry ± economic feasibility study. & Hanna. Tindale. Singh. Journal of the American Oil Chemists' Society. Ahamadabad. T. The data were analyzed following the standard formula and procedure for calculating the Bene®t-Cost-Ratio. & Shook. I. D. B. B.. implementation and evaluation. 65 (10). P. S. A. Bisht & Ojha. M.. (1979). 1610±1616. ®nancing. & Noguchi. Ohlson.. Singh.. I. Williams. F.. B. Srivastava. (1983). S. R. St. J. & McNulty. 211±213. (1983). P. S. Developments in screw pressing. AIDA: Lucknow (India) Publications. Srivastava. P. Mrema. M.83 yr.C. The values of these parameters used in economic analysis are given in Table 3. One hundred bankable post harvest equipments developed in India (pp. 265±270. B. Vadke. Ohlson.. Bisht. Ward. I.. P. (1985). Journal of Agricultural Engineering Research. 1979. & Agarwal. An analysis of an oil expeller expression. T. M. (1976). 71±76. Sosulski. W. Bargale / Journal of Food Engineering 43 (2000) 75±82 Khan.. A. R. Journal of the American Oil Chemists' Society. (1991). CMA Monograph No. L. 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In Proceedings of the national seminar on soybean processing and utilization in India (pp. Kachru. Sosulski. P. A. Bargale. Current equipment for mechanical oil extraction.