What is the working principle of crude palm kernel oil expeller?

The crude palm kernel oil expeller, often simply called an oil expeller or screw oil expeller, is a fundamental machine in the palm kernel oil industry. Its primary function is to mechanically extract oil from the solid, dried kernels of the oil palm fruit (Elaeis guineensis). The core principle is straightforward: it's a continuous, high-pressure mechanical expeller. It uses immense and increasing physical force to squeeze oil from the pre-treated palm kernels, cleanly separating it from the solid residue, all without chemicals.

The entire process can be broken down into the following key stages and components.

1. Key Components of the Crude Palm Kernel Oil Expeller

To understand the working principle, you must first be familiar with the main parts of the crude palm kernel oil expeller:

The main parts of the crude palm kernel oil expeller

(1) Feed Hopper: The entry point for the prepared palm kernels.

(2) Main Driving System: A powerful electric motor that provides the energy to turn the screw.

(3) Screw Shaft: The heart of the crude palm kernel oil expeller. Located at the center, it's a robust, tapered shaft with spiral flights that conveys and compresses the palm kernels.

(4) Barrel Cage (Cylinder): The cylindrical enclosure that houses the screw. It is made of steel bars with minimal gaps between them, allowing oil to seep out while retaining the solids.

(5) Cake Outlet & Choke Mechanism: The exit point for the solid residue. An adjustable cone at the end regulates the pressure inside the crude palm kernel oil expeller.

(6) Oil Collection Tray: Located beneath the barrel cage to collect the seeping oil.

2. The Step-by-Step Working Principle

The operation of the crude palm kernel oil expeller is a continuous process of feeding, pressing, and separation.

(1) Pre-Treatment of the Palm Kernels (Essential Preparation)

To maximize oil yield in the expeller, palm kernels must undergo two essential pretreatment stages. First, they are crushed to break down their cellular structure, which creates a larger surface area for more efficient oil release. Subsequently, the crushed kernels are conditioned through heating. This critical step reduces the oil's viscosity for easier flow, coagulates proteins, and optimizes moisture content to generate the ideal friction and pressure within the crude palm kernel oil expeller.

Palm kernel pretreatment equipment

(2) Feeding and Conveying

The conditioned palm kernels are continuously fed into the crude palm kernel oil expeller's feed hopper. They are then drawn into the main pressing chamber, where the rotating screw conveys it forward.

(3) Pressing, Extraction and Filtration (The Core Action)

The core extraction process inside the crude palm kernel oil expeller can be broken down into a sequence of critical steps:

Conveyance & Compression: A heavy, tapered screw shaft rotates inside a barrel, moving the kernels forward. The progressively reducing volume and increasing diameter of the screw flights force the material into a tighter space, building immense mechanical pressure.

Heat Generation & Oil Liberation: The tremendous pressure and internal resistance generate significant frictional heat (90-120°C). This heat reduces the oil's viscosity, working in synergy with the mechanical pressure to rupture the oil cells and force the oil out of the solid matrix.

Filtration & Separation: The expelled liquid oil, carrying some fine solids, is forced through the narrow gaps between the steel bars. These gaps act as a filter, allowing the oil to pass through while retaining the bulk solid matter inside the barrel. The collected crude oil then flows out for further purification.

(4) Discharge of Palm Kernel Cake (PKC)

The remaining solid material, now compressed into a hard, dry Palm Kernel Cake (PKC), continues to be pushed forward by the screw. At the end of the barrel, it encounters the choke mechanism. By adjusting this choke, the operator can control the back-pressure inside the press. A tighter choke increases pressure, leading to higher oil yield but a drier cake, and vice-versa. The final palm kernel cake is discharged continuously from the cake outlet.

3. Characteristics of the Output

(1) Crude Palm Kernel Oil (CPKO): The oil obtained is dark and requires further refining (degumming, deacidification, decolorization, deodorization) before it is edible. It has a different fatty acid profile (higher in lauric acid) than palm oil, making it valuable for soaps, cosmetics, and specialty fats.

Crude palm kernel oil

(2) Palm Kernel Cake (PKC): The solid residue is a valuable byproduct used as a high-fiber, high-protein ingredient in animal feed.

In summary, the crude palm kernel oil expeller is the core equipment of your palm kernel oil processing production line. It efficiently releases the maximum value of palm kernels through a purely mechanized process. Its robust and durable design ensures continuous operation and high oil yield. To learn more about how our durable and efficient crude palm kernel oil expeller can optimize your production, we sincerely invite you to contact Henan Glory. Our experts are ready to provide you with customized solutions and detailed equipment specifications.