Soybean Oil Decolorization Process in Edible Oil Refinery

Soybean oil refining is a key link in the edible oil industry, and its quality is directly related to the quality of end products. This article focuses on the decolorization process in soybean oil refining, which is mainly divided into two directions: adsorption decolorization and thermal decolorization.

Soybean Oil Decolorization Process Guide
Soybean Oil Decolorization Process Guide

Through an in-depth introduction to the principles, influencing factors, process flow and key equipment, it is hoped to provide practical reference for the industry.

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3 Principles of Adsorption and Decolorization

Adsorption decolorization is one of the commonly used decolorization methods in soybean oil refining. This method uses the adsorbent to selectively adsorb the pigments in the oil, thereby removing the pigments in the oil. An in-depth understanding of this principle is the basis for the realization of efficient adsorption and decolorization processes.

1. Selective adsorption of adsorbents

In the process of adsorption and decolorization, adsorbents such as activated carbon and clay are usually used. These adsorbents have specific surface structures and chemical properties that allow them to selectively adsorb pigment molecules in oil. This selective adsorption is based on the comprehensive effect of factors such as affinity, electrostatic interaction, and spatial arrangement on the adsorbent surface.

2. Physical adsorption and chemical adsorption of pigments

There are two main forms of pigments in oils, namely dissolved state and suspended state. During the adsorption and decolorization process, the adsorbent can adsorb pigment molecules from the oil to its surface through physical adsorption and chemical adsorption.

  • Physical adsorption: refers to the adsorption of pigment molecules on the surface of the adsorbent through the pore structure or surface force of the adsorbent, similar to physical adsorption between molecules.

  • Chemical adsorption: refers to the chemical reaction between pigment molecules and the surface of the adsorbent to form compounds, which are fixed on the surface of the adsorbent. This adsorption method is stronger.

3. Desorption

When the adsorbent surface is saturated with a certain amount of pigment, the adsorbent needs to be desorbed, that is, the pigment adsorbed on the adsorbent surface is removed. The desorption process is usually carried out by steam or hot air to make the adsorbent regain its adsorption capacity.

During the adsorption and decolorization process, various parameters need to be optimized, including the type and amount of adsorbent, temperature, time, etc. By adjusting these parameters, the decolorization effect of different types of oils can be optimized.

Factors Affecting Soybean Oil Decolorization Process

Soybean Oil Decolorition with White Clay
Soybean Oil Decolorition with White Clay

The decolorization effect of soybean oil refining is affected by many factors, including the quality of crude oil, selection of decolorizing agent, operating conditions, etc. Detailed analysis of the impact of these factors on the decolorization effect will help optimize the production process and improve oil quality.

  • Crude Soya Oil quality

Pigment types and contents: The types and contents of pigments in different crude oils vary, which have a direct impact on the decolorization effect. High levels and strong pigments may require more depigmentation agents and more stringent operating conditions.

Impurity content: Impurities in crude oil (such as wax, colloid, etc.) may affect the effects of decolorizing agents and pigments, so the crude oil needs to be properly pretreated in advance.

  • Depigmentation Agent Selection

Activated carbon vs. clay: Activated carbon has a strong physical adsorption effect on pigments, while clay is more inclined to chemical adsorption. When selecting a decolorizing agent, crude oil characteristics and process requirements need to be considered, and experiments are often required to determine the most suitable decolorizing agent.

  • Operating Conditions

Temperature: The regulation of temperature can affect the adsorption speed and effect of the decolorizing agent on the pigment. Usually, a suitable decolorization temperature can improve the decolorization effect, but it is necessary to prevent the loss of oil quality caused by excessive temperature.

Time: The decolorization time is long enough to help the decolorizing agent fully interact with the pigment, but too long a time may increase the production cycle. There needs to be a balance between time and effect.

Stirring speed: Moderate stirring can promote the full mixing of the decolorizing agent and oil and improve the decolorizing effect.

  • physical state of oil

Grease viscosity: Grease with high viscosity may prevent the decolorizing agent from fully contacting the pigment, so the grease may need to be preheated to reduce the viscosity before decolorizing.

  • Reasonable design of operating process:

Selection of decolorization equipment: Different decolorization equipment may have certain differences in decolorization effects, so it is necessary to choose decolorization equipment that suits the process requirements.

Optimization of operating steps: including the dosing method, dosage, desorption conditions, etc. of decolorizing agent.

Adsorption and decolorization process

Soybean Oil Decolorizing Process Flow Chart
Soybean Oil Decolorizing Process Flow Chart

Detailed introduction to the process flow of adsorption and decolorization, including pretreatment, adsorption, filtration and other links. Emphasize the importance of each step and reasonable parameter settings.

Pretreatment: Including the removal of soluble impurities, moisture and acidity in soybean oil. The purpose of pretreatment is to improve the subsequent adsorption and decolorization effect.
Adsorption: Mix the selected decolorizing agent with the pretreated soybean oil and make it fully contact by stirring. Adsorbents adsorb pigments and other impurities.
Filtration: Separate the oil containing adsorbent and adsorbed matter through filtration equipment. The choice and effect of filtration directly affects the quality of the final product.

Design and optimization of adsorption towers

The design and process optimization of the adsorption tower have an important impact on the decolorization effect, mainly focusing on the following aspects:

  • Structural design: The structure of the adsorption tower should consider its internal fluid dynamics, such as tray design, packing selection, etc., to ensure that the adsorbent fully contacts the crude oil and improves the adsorption effect.

  • Mass transfer process: Optimize the mass transfer process and ensure the effective adsorption of pigments by the adsorbent by adjusting the air flow rate, liquid flow rate and other parameters in the tower to achieve the expected decolorization effect.

  • Temperature and pressure control: Ensure that decolorization is performed under appropriate temperature and pressure conditions to improve the activity of the adsorbent and decolorization efficiency.

Selection of filter equipment

Filtration equipment plays a key role in the decolorization process. Different types of equipment have their own advantages and disadvantages, and they need to be selected according to specific circumstances:

Plate and frame filter equipment: When using plate and frame filter equipment, the filtration speed can be controlled by adjusting the number and materials of filter plates, which is suitable for scenarios that require efficient separation.

Membrane filtration equipment

Membrane filtration equipment filters grease through microporous membranes, has higher filtration accuracy, and is suitable for situations where product quality requirements are high.

The selection of filtration equipment should consider the properties of the grease, production scale and subsequent process requirements to achieve economical, efficient and stable filtration effects.

Thermal decolorization method

Thermal decolorization is a decolorization method that dissociates pigment molecules through high temperature. Its principle, process and equipment characteristics are as follows:

  • Principle: By heating crude oil, the pigment molecules are dissociated to achieve the decolorization effect. High temperature can help remove pigments, but care must be taken not to reduce the quality of the oil.

  • Process: The heating temperature and holding time need to be precisely controlled to avoid quality changes in the grease. Usually used in combination with other depigmentation methods to achieve better depigmentation results.

  • Equipment features: The equipment needs to be able to provide precise temperature control. Common equipment includes heating tanks, heating refluxers, etc. The decolorization process in soybean oil refining is a key link to ensure oil quality. Adsorption decolorization and thermal decolorization are two commonly used technical means, each with its own advantages and disadvantages.

By having an in-depth understanding of the principles, process flows and key equipment of these technologies, we can better guide production practices and improve the decolorization effect and overall quality of oil products.

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