Development and Assessment of Cracking and Sorting Processes of Palm Kernel Nut Machine

DOI: http://dx.doi.org/10.24018/ejers.2020.5.12.2258 Vol 5 | Issue 12 | December 2020 145 Abstract — This paper presents a research on the Development and Assessment of the cracking and sorting processes of palm kernels nuts in a mechanical cracking machine. The palm kernel oil is an important agricultural produce, it has a wide range of usage aside from cooking. In attempt to reduce energy exploitation, in conjunction with the regular high rate of demand for products been extracted from palm kernel nut, the need to improve on the manual method of cracking and sorting became eminent. The mechanical cracker was made up of two units: the cracking and sorting unit. Experimental studies of properties of machine components were considered with the purpose of avoiding fatigue failure and fracture on the palm nuts during the processing duration. The mechanical cracker was designed, fabricated and performance evaluation carried out using locally sourced materials. It was developed with a 5hp electric motor to drive the machine coupled with belts and pulleys. The average data assessment shows a 2.01% of un-cracked nuts, 2.36% of partially cracked nuts, 93.58% of un-cracked nut and 2.05% broken nuts. The cracking-sorting efficiency was estimated at 94% and throughput capacity was determined to be 80kg/h while the overall palm kernel recovery efficiency was 85%. These suggest that the machine is very suitable for separating the palm kernel nuts from the cracked shells clearly and completely.

I. INTRODUCTION 1 The palm kernel seed is the edible seed of the oil palm tree (Elaeis Guineensis) which originated from West Africa, it dates as far back as 5000 years and it can be used to obtain palm kernel oil which can be fractionated into liquid (olein), solid (stearin), and an intermediate fraction known as shortening. Palm fruit oil can be further broken down into diverse products such as vegetable oil, candles, soaps, ice cream, and as well as pharmaceuticals [1]. The three main varieties of palm tree are the Dura, Pisifera, and Tenera. The distinguishing feature of Dura is defined with thin epicarp, large nut and shell thickness of 2 to 5 mm. The Pisifera is in some cases referred to as shell-less variety while the Tenera is a combined form of Pisifera and Dura. The Tenera has medium size nuts, thick epicarp and shell thickness of 1.0-2.5 mm [2], [3]. Palm nut consists of the shell and the kernel; and are of economic importance [4], [5]. For some number of years, extraction of oil from oil seeds require a broad range of traditional and modern (mechanical and chemical) processes [14]. Separation of the oil from the palm kernel is a significant aspect of palm kernel processing. Although, the palm oil extraction process had undergone a lot of mechanical development, the palm kernel oil extraction process which starts with the separation of the palm nut from the fiber-base is still significantly less mechanized. Cracking palm nuts to release the kernel is therefore a critical step that affects the quality of oil [6]. The traditional cracking medium takes place in two forms, either by stone arrangements or by the use of mortar and pestle. This method of cracking and separating palm kernel nuts is time-consuming, low efficiency, labour intensive to meet high market demand and can cause serious and severe injuries to human beings. There are two mechanical actions used to crack palm kernel; shock caused by an impact against a hard object and the direct mechanical energy to crack, cut or shear through the shell [7]. The cracked nut mixture comprises of whole/broken kernels, shell particles, un-cracked nuts, fine particles and dust. The modern medium consists of the use of machines and equipment like the hammer mill, roller mill, centrifugal cracker, laser beam cracker, and many more that has a better advantage over the tradition medium.
Generally, there are two types of mechanical cracking machines; the simple nutcrackers and centrifugal impact crackers. In rollers type of centrifugal crackers, the nuts are cracked in between fluted rollers revolving in opposite directions. The clearance between the rollers is invariable but the nuts are of the different sizes, which makes the machine operates at reduced efficiency [8]. Due to the high level of demand for the products gotten from processed palm kernel nuts and the energy consumption rate, the need to improve on the local method of cracking gives way to the advance mechanism to ensure easy and fast access to the nut. The main purpose of this study is to produce an efficient palm kernel cracking and separating machine, then further carry out its performance evaluation.

II. METHODOLOGY
The palm kernel machine is made up of two units: the cracking and sorting unit. The essential design parameters considered include the size and strength of materials of individual machine components with the purpose of avoiding yielding and fatigue failure throughout the required duration of use of the machine.

Belt and Pulley Drive Mechanism
The palm kernel cracking and sorting machine requires two pulleys for operation: the first pulley is attached to the electric motor (driver) and the second pulley is attached to the shaft (driven) coupled with the hopper.
The transmitted speed was evaluated using the relationship given by [9]: where, 1 Nthe speed of the electric motor = 1725 rpm. 1 Ddiameter of the pulley connected to electric motor = 58 mm.

Power requirement to drive the machine
The power required to drive the machine can is determined from equation (2): where Vvelocity of the belt in (m/s).

Length of Belt Required for Power Transmission
The length of the belt was determined from equation (4) [10]:

Angle of Contact between the Belt and Pulleys
The contact angle 12 and  for small and large pulley was estimated as follows: a. For the electric motor (driver) But, angle of wrap.

Belt Tension
The tension on the belt was determined using equation (5) [11].

Determination of the Torque in the Driven Pulley
The torque required in the driven pulley is determined from equation (7).
The total load to be supported by the shaft is. 1 2 1600.27

Determination of the hopper's Capacity
The hopper is another significant component of the palm kernel crushing and sorting machine as it is the region that houses the feed nut before crushing takes place. The shape, dimension and location of the hopper were chosen to ascertain the mass discharge of the nut.
The capacity of the hopper is calculated from equation 8: The volume of the hopper is estimated to be 3 0.0196 0.02m = .

Centrifugal Tension in the Belt and Equivalent Twisting Moment
The centrifugal tension was determined using equation 9: The selected rubberized class B type of V-belt has the following specification [11]: Density of the belt, The maximum tension of the belt is max.

N
The belt maximum speed is evaluated from max. max.

m s 3
Hence, The equivalent twisting moment is determined from:   The calculated diameter of the shaft is multiplied by a factor of four (4) to allow a variation in twisting moment and the effect of other straining actions [11].

The Design for Stiffness and Rigidity of a Shaft
The torsional deflection of a shaft was determined using equation (15).

Design of the Impeller
The optimum speed needed for crushing the nut is given by equation (18)  According to equation (22), the crushing force is now determined to be 47.86 N.

Throughput Capacity (TC) and Efficiency
The throughput capacity is the quantity of material moved or produced per unit time. That is, it is the measured processing speed of a machine expressed as total output in a unit period usually in hour under normal operating conditions. It can be measured as gravimetric or volumetric. The throughput and efficiency is estimated by (24) to (27) [12]. Thus,

III. RESULTS AND DISCUSSIONS
After fabrication, the results of the test analysis conducted on the palm kernel cracking and separating machine were presented in figure 1-5. The un-cracked nuts, partially cracked nuts, unbroken nuts, broken nuts and the through put of the nuts are in the following ranges of time: 7, 11, 21, 30, 39 and 47 sec. for cracking 29, 58, 85, 112, 145 and 170g respectively This trend is notified for the two types of nuts considered here namely; Dura and Tenera nut respectively. The cracking efficiency was estimated according to the number of absolutely peeled and sorted nuts per group of 100 nuts in accordance with the variation in feed rate and kernel size. Fig. 4 illustrates the percentage rate of the un-cracked nuts on the transient nuts per batch fed into the cracking chamber. In this case, it is observed that the un-cracked nut passes from a minimum value at the very beginning of the transient state towards a maximum value. Furthermore, the un-cracked nuts increase with the increases of the feed rate. The variation of the unbroken nuts with the number of nut fed into the cracking chamber per batch is shown in Fig. 5; the effect of increasing the nut into the cracking chamber decreases the rate of unbroken nuts. However, for high value of nuts fed into the cracking chamber, the low values of unbroken nut are being discharged from the outlet of the machine.   Fig. 6 shows the behaviour of percentage rate of broken nuts on the nuts per batch fed into the cracking chamber at different time. In this case, it can be noticed from figure 6 that as the nuts fed into the chamber increases in value at the initial state results to increases of the broken nuts value.
Thus, partially cracked nuts increase with the decreasing of the nut fed into the cracking chamber and vice versa in Fig. 7. The graph for the un-cracked nuts, unbroken nut, partially broken nuts, and broken nut for different values of number of feed rates parameters with time variation are illustrated in Fig. 8 of un-cracked nuts, 2.36% of partially cracked nuts, 93.58% of un-cracked nut and 2.05% broken nuts.    9 and 10 shows respectively, the through put versus the cracking time and the number of nut per batch. From these graphs we analyzed that the effect of increasing the values of through put is to increase the nuts profile taking into cognizance the variation of feed rate, and the cracking time thereby exhibiting an oscillatory behaviour before reaching a constant value in steady state. The throughput capacity was discovered to be 85.4kg/h. the entire kernel recovery, which was determined by means of unbroken palm kernels to give an efficiency of 94.5%.  IV. CONCLUSION The assessment of the developed cracking and sorting processor was successfully carried out with an overall palm kernel recovery efficiency of 85% and throughput of 80kg/h while the un-cracked nut increases with the increases of the feed rate. These metamorphoses in the production of palm kernel crackers with improved standard are a major plus to the agricultural production field of study. It was designed and fabricated using locally sourced, low cost and readily available materials which translates to affordability of machineries for the farmers. The results realised from the evaluation significantly shows that the machines are satisfactory for onward acceptance in the processing industries. In addition, it was developed considering maintainability; this makes it require little or no training for its operation and maintenance.