IJETAE_0314_112

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 3, March 2014)

631

Design of Twin Screw Oil Expeller for Pongamia Pinnata SeedsAmruthraj M1, Bharath H B2, Kamini S3, Chethan H S4

1,2,3,4 Department of Mechanical Engineering, R V College of Engineering, Bangalore - 560059

Abstract — Biodiesel is obtained by processing edible and

non-edible oils. Due to the increase in demand for fuel and

stringent emission norms, biodiesel is preferred as it meets the

emission norms. To meet the exponentially growing demands

in developing countries, continuous production is required

which can be achieved by mechanical screw presses.

Currently, single screw press is being widely used for

extraction of oil. The problems associated with the single

screw expeller is that, it requires three or more passes to expel

oil from seeds, which increases the production time and are

also less efficient. In this paper, a counter rotating twin screwexpeller is designed for extraction of oil from the Pongamia

pinnata seeds. This paper focuses on comparison between the

twin screw and single screw press technology based on both

technical and economical appraisals, study is been carried out

on how twin screw technology is better compared to single

screw.

Keywords — biodiesel, Pongamia pinnata seeds, single screw

press, twin-screw expeller, oil extraction.

I. I NTRODUCTION

The Oil extraction technology has been in use for a very

long time in India and the techniques that are followed for

expelling oil are very laborious and relatively inefficient.There has not been any significant improvement in the oil

extraction processes and even today a century old

technology such as single screw press, ghani, hydraulic

presses1 are being used in various parts of the country.

Mechanical screw presses are ideally preferred for oil

extraction as they are economical and continuous

production can be achieved. Any improvement in the

technique of oil extraction tends to bridge the technological

gap and increase availability of feedstock for extraction of

oil.

Biodiesel is processed from edible, nonedible and animal

oils. In South India, Pongamia Pinnata seeds are available

in very large quantity and its trees do not require any extracare in growing them. It has been proved that the oil from

Pongamia pinnata seeds can be converted to biodiesel2. The

oil from Pongamia seeds is usually extracted using a single

screw press oil expeller. The process is inefficient and

requires a lot of labour as oil extraction takes place only

after three or more passes. In order to overcome the above

mentioned drawbacks and to meet the production rate of 80

– 100 kg/ hour, a twin screw oil expeller is designed.

Experiments have already been performed on twin screw

expeller for extracting oil from Jathropa3 and sunflower

seeds4,5. No such experiments have been conducted on

Pongamia Pinnata, hence this paper focuses on designing a

twin screw expeller for Pongamia Pinnata seeds

For the designs of twin screw expeller, single screw

expeller design plays an important role, as many

assumptions in the twin screw designs were made based on

the single screw expeller design keeping the technical and

economical feasibilities in consideration.The single screw expeller is as shown in figure 1. The

design of the single screw expeller consists of a forward

screw shaft (powered using 5hp motor) and housing.

1. The specifications of the shaft are

The shaft has a constant outer diameter, the inner/root

diameter increases as the thread progresses forward.

i. Outer diameter = 88 mm,

ii. Inner / root diameter = from 56 mm to 84 mm

iii. Length = 390 mm

iv. Length/diameter = 4.43

2.

The specifications of the housing are:Inside the housing, a pressure of 20MPa is developed,

the wall thickness of the barrel is 25.4mm and 24 square

bars are arranged over the inner circumference of the

barrel, this arrangement is made in order to expel the oil

through the gaps in between two adjacent blades when the

seeds are pressed at 20MPa pressure. Inner diameter = 90

mm, Figure 2 shows the pressing region and screw profile

of the shaft.

The expelling efficiency of this oil expeller is 50%. The

average oil content in Pongamia pinnata seeds is 35%6, the

yield efficiency of the expeller is 18%, and the cake

contains 8% of oil in it. The cake after the removal of oil

flows axially and comes out as shown in figure 3.It is found that the extraction of oil is maximum at 80

degree Celsius with an average of 8% moisture content in

the seeds7. Keeping the initial conditions of the seeds

constant the twin screw expeller i.e., two screw shafts, liner

and housing is designed.

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II.

DESIGN

The design consists of two screw shafts, liner andhousing.

1.

Design of screw shaft:

The screw shaft is of increasing root/inner diameter,

decreasing pitch and a trapezoidal screw profile with a

buttress as shown in figure 2. These are incorporated in

order to increase the pressure of the seeds as the seeds

progress towards the crushing region. The seeds get

crushed at the mating region of the screws and the crushed

seeds get squeezed in the pressing region and the oil is

expelled.

The list of formulae and minimum calculations are

shown in table 1 below. The nomenclatures are shown intable 2.

Table 1

List of formulae and calculated values.

Sl

no.

Parameter Formulae Value

1 Power(P) -- 10hp or 7.5

kW

2 Torque (T) P= 2π NT/60000

And T=Fts*ds /2

715Nm

3 Pressure (p) From Reference 20MPa

4 Axial load on

one

thread(Fxs)8

Fxs = p*Lt*H 5200 –

10500 N

5 Tangential

Load on a

thread (Fts)8

Fts = Fxs[ l + πfds

]/[ πds-f l ]

3500 – 9200

N

6 Theoretical

Screw

Volume (Vs)

Vs = A*(l - H)

= 0.25π[ ds2 – d2

] (l - H)

1.14 E-4 m

7 Mass flow

rate (ṁ)

ṁ = Vs * n*ρ*Ψ 0.0303 kg/s

Specification of screw shafts are given below and the

draft of the shafts are as shown in figure 4.

i.

Outer diameter: 80 mm

ii.

Inner diameter: 40mm to 56 mmiii. Length of the shaft: 420mm

iv. Length/diameter: 5.25

Table 2

List of Nomenclature and values

PARAMETER VALUE

Speed (N) 100 rpm Crest Diameter(d

s) 0.080 m

Root diameter(d) 0.045 – 0.056 m Taper angle (α) 1.15 degrees Pitch Variation (l ) 2.5 mm/ pitch Thread height variation (H) 1 mm / pitch Number of turns (n) 7 Crushing head diameter 0.056 m Worm length (L

s ) 0.36 m

Crushing head length (Lc) 0.06 m

Total length ( L ) 0.52m Housing inner diameter (D

i) 0.082 m

Thickness of the housing (t) 0.025 m Density(ρ) 625kg/m

Filling Factor(Ψ) 0.3

Length if thread(Lt) 50mm – 38mm

2. Barrel design

The barrel houses a liner and two counter rotating shafts.

The counter rotating9 shafts helps in more pressure

development and more retention time. The seeds are fed to

the barrel through a hopper and these seeds are progressed

via counter rotating shafts towards the pressing region and

oil is expelled by the passage provided in the liner and

flows down due to gravity. Three ports are provided in the

barrel, one for air out, one for pressure relief and cleaning

and one for oil collection as shown in the figure 5.

Two barrel configurations are designed. Configuration 1

is designed for mass production at a lower cost.

Configuration 2 is designed for more flexibility and also for

research and development purpose using different seeds.

The specification of the barrel configuration1 is

mentioned below and the drafting is shown in figure 5.

i.

Length of the housing: 420 mm

ii.

Housing inner diameter: 84 mm

iii. Thickness of the barrel: 25.4 mm

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The specification of the barrel configuration 2 is as

mentioned below and the drafting is shown in figure 6.i.

Length of the barrel: 500 mm

ii.

Housing inner diameter: 84mm

iii.

Thickness of each plate: 10 mm

III.

A NALYSIS

To validate the designs provided in the previous

sections, analyses of the designs are performed. The

analyses of shaft, barrel designs along with liner design are

performed.

a) Shaft analysis

The expeller contains two counter rotating shafts and the

material used is mild steel. The loading and boundaryconditions on both the shafts are identical. Therefore,

analysis is performed on one shaft. The results obtained

from analysis of this shaft would be similar to that of the

other shaft and is as shown in figure 7. When the shafts

make one rotation, the seeds progress axially by one pitch

and also gets crushed to some extent. On continuous

rotation of the shafts, the seeds are transported from hopper

end to the crushing end. During this movement the seeds

exert axial and tangential forces on the shaft. As the seeds

progress, the clearance and the volume between the shaft

and barrel decreases, because of which the pressure

increases. The pressure reaches a maximum of 20 MPa at

the pressing region. All the loads that are developed areapplied on the shaft. The shaft is mounted on bearings. In

the analysis, the bearings are substituted by cylindrical

supports. The shaft is also subjected to a torque of 360 Nm.

b)

Barrel analysis

The barrel analysis includes barrel and liner. The

pressure of 20MPa is applied on the inner region of the

liner of the barrel assembly. The barrel is fixed on both the

end faces. The analyses of both the barrel configurations

are performed.

i.

Analysis of Barrel Configuration 1.

As the barrel is meant to be used only for Pongamia

pinnata seeds and not much of flexibility is required. It ismanufactured using casting and is machined to the exact

accuracy, the two halves are joined using bind and then the

analysis is carried out by applying the pressure. The

analysis is as shown in figure 8

ii.

Analysis of Barrel configuration 2.

As the barrel is meant to be used for research purposeand the barrel is manufactured using the assemblage of

plates and are fastened together and will be placed on a

solid cast iron bed. The analysis was carried out similarly

to that of the barrel configuration 1. The results are shown

in figure 9.

IV.

R ESULTS

The results of the analysis shows that the twin screw

design is safe and the deformations are negligible when the

loads are applied, so in order to meet the growing demands

a twin screw expeller is feasible both economically and

technically by decreasing the overall cost of production and

by increasing the throughput rate of seeds.

V.

CONCLUSION

Twin screw expeller can be used for expelling oil from

Pongamia pinnata seeds. It can also achieve a throughput

rate of 80 – 100 kg/hour with single pass, unlike single

screw expeller which requires three or more passes.

Hence, twin screw expeller has more potential in oil

extraction process for nonedible oil extraction. Twin

screw expeller also overcomes the difficulties of single

screw expellers.

Acknowledgement

We would like to thank prof. Krupashankara Sethuram

and prof. Chandrakumar R for guiding and supporting us

throughout our work towards designing Twin Screw

Expeller. We would also like to thank KSBDB for

supporting us financially and we would like to thank all the

faculty of the Mechanical Department of R V college of

Engineering for supporting us during the work.

REFERENCES

[1]

Issac Bamgboye and A.O.D Adejumo, ― Development Of Sunflower

oil expeller ‖, Agricultural Engineering International, the CIGREJournal, Vol IX, September 2007.

[2]

Bobade S.N and Khyade V.B, ―Detail study on the Properties of

Pongamia Pinnata (Karanja) for the Production of Biofuel‖,

Research journal of chemical sciences, Vol 2(7), 16 – 20, July 2012.

[3]

Ph. Evon, I. Amalia Kartika, et al., ―Extraction of oil from jatrophaseeds using a twinscrew extruder: Feasibility study‖. Industrial

Crops and Products, vol. 47, 33-42, 2013.

[4]

Kartika I.A, et al., ―Twin-screw extruder for oil processing of

sunflower seeds: thermo-mechanical pressing and solvent extraction

in a single step‖ Industrial Crops and Products, Volume 32, Issue 3,

November 2010.

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[5]

Isobe S. et al., ―A new twin-screw press design for oil extraction of

dehulled sunflower seeds‖ National Food Research Institute, Japan,

Journal of the American Oil Chemists' Society, Volume 69, Number 9.

[6]

―Expellers in India and expelling operations‖, Department of science

and technology, Government of India, Vol. 1, June 2012.

[7]

Khan, L.M. and Hanna, M.A. Expression of Oil from Oilseeds-A

Review. J. agric. Engg Res. (1983) 28

[8]

Zhijun Zhong Theoretical and Experimental analysis of the

compaction process in a tapered screw press, 1991.

[9]

A. Shah and M. Gupta, ―Comparison of the flow in co-rotating andcounter-rotating twin screw Extruders‖ Mechanical Engineerings-

Engineering Mechanics Department Michigan Technological

University, Houghton, 2004

FIGURE 1: Single screw press expeller picture and draft

FIGURE 2: Pressing region (encircled) and buttress profile

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Figure 3: Indicating seed input, Oil output, Cake output

Figure 4: mating of Twin Screw shafts

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Figure 5: draft of burst view of the twin screw barrel of configuration 1 and legend

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Figure 6: 3D View Of Configuration 2 Barrel Fastened With Blades

Figure 6: Plate Profile Near The Pressing End

Figure 6: plate profile near hopper end

Figure 7: analysis of shaft

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Figure 8: analysis of barrel configuration 1Figure 9: analysis of barrel configuration 2

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IJETAE_0314_112