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- 1. Screw press and its performance Pragati Singham M.Tech (FPEM)
- 2. CONTENTS • • • • • • Introduction Types Construction & working Principle Performance(design) References
- 3. INTRODUCTION • It is the simplest machine for separation of solids and liquids. • It is a cage style press. • It is used for separation of – – Oils from various oilseeds – Fruit juices • Screw pressing is a continuous operation, hence these are also known as “expellers”
- 4. TYPES OF SCREW PRESS Horizontal screw press Huber inclined screw press
- 5. CONSTRUCTION & WORKING
- 6. PRINCIPLE • It works on the principle of ‘compression and shear’. Compression curve Compression ratio = volume displaced per revolution at the feed end volume displaced per revolution at discharge end
- 7. DESIGN OF SCREW PRESS • Diameter of shaft (ds) where, T = torque transmitted by shaft δ0 = yield stress • Load lifted by screw (We) where, Dm = mean thread diameter T = torque transmitted by shaft µ = coefficient of friction α = tapering angle θn = thread (lift) angle • Pressure developed by screw thread (Pr) where, Ap = pressing area h = screw depth at max. pressure area (discharge end) n = no. of threads Hall et al., 1961
- 8. Capacity (Qe) where, Ds = diameter of the screw thread ds = base diameter of the screw shaft Ps = screw pitch, Ns = rotational speed of the screw shaft φ = filling factor, ρ = bulk density Power requirement(Pe) where, Qv = volumetric capacity of the screw shaft ls = length of screw shaft g = acceleration due to gravity F = material factor Hall et al., 1961
- 9. PERFORMANCE OF SCREW PRESS • Design a screw press whose specifications areDs = 100 mm, Ns = 90.63 rpm, δ0 = 200 N/m2, µ = 0.15 , h = 5mm, ls = 500 mm , 1. ds = 50 mm, Φ = 0.8, T = 928.571 Nm, θn = 150, n = 9, g = 9.81 m/s, Diameter of shaft 2. Load lifted by screw (We) Ps = 50mm Ρ = 740kg/m3 Dm = 75 mm θ = 30 Qv = 1.281m3 / hr F = 0.4 = 16 x 928.571 = 44.407mm 0.27 x 3.14 x 200 = tan-1 (tan150 . Cos 30) =14.980
- 10. = 928.571 x 75/2 tan30 + 0.15 (1-0.15 tan 30 cos 14.980) =72.88KW Pressure developed by screw thread (Pr) = 3.14 x 75 x 9 x 5 = 72.88 x 1000 10602.88 Capacity (Qe) 740 = 10602.88 mm2 = 6.87 N/mm2 = 60 x 3.14/4 (100)2 - (50)2 x 50 x 90.63 x 0.8 x = 948.249 kg/hr Power requirement(Pe) = 4.5 x 1.281 x 500 x 740 x 9.81 x 0.4 = 8.369KW
- 11. YIELD , EFFICIENCY, EXTRACTION LOSS • Oil yield (OY) = • Oil efficiency (OE) = • Extraction loss (EL) = • • • • • • • • where, OE = % extraction efficiency OY = % oil yield EL = % extraction loss WOE = weights of oil extracted(g) WRC = residual cake (g) WFS = feed sample (g) x = oil content of seed in decimal.
- 12. 1. NUMERICAL • Soybean seeds contain 40% oil on weight basis and 4.2 g of oil is extracted by screw press from 100 g of soybean seeds. Calculate the oil efficiency of the soybean seeds. weight of soybean(WFS) Amt. of oil present(x) Amt. of oil extracted(WOE) Oil efficiency (Oy) = 100 g = 0.40 = 4.2 g = = 100 x 4.2 % 0.4 x 100 = 10.5 %
- 13. 2. NUMERICAL • Calculate the effectiveness of an screw press, which yields 3.7 kg oil containing 5% impurities from 100 kg mustard seeds. The oil content of the mustard seeds is 38%. Weight of mustard seeds Expected yield Oil extracted Effectiveness = 100kg = 38 kg = 3.7 – (3.7 of 5%) = 3.7- 0.185 = 3.515kg = calculated yield x 100 Expected yield = 3.515 x 100 38 = 9.25 %
- 14. REFERENCES • Deli, S., Farah Masturah, M., Tajul Aris, Y. and Wan Nadiah, W. A. The Effects of physical parameters of the screw press oil expeller on oil yield from Nigella sativa L seeds. International Food Research Journal 18(4): 1367-1373 (2011) • Hall, A. S., Holowenko, A. E., & Laughlin, H. G. (2002). Schaum’s outline series theory and problems of machine design. (1st ed.). New York: McGraw-Hill Companies, Inc., (Chapter 12). • Handbook of Food Processing Equipment by Geōrgios D. Sarabakos, Athanasios E. Kosaropoulos • http://www.reinartz.de/index.php?id=27&L=1 • http://www.fao.org/docrep/t0532e/t0532e04.ht m

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