Dry Degumming and Bleaching

INTRODUCTION TO TECHNOLOGY

Among the various stages of refining of edible oils, special attention must be paid to two intermediate processes: Dry Degumming and Bleaching. The combination of which is part of the physical refining cycle of edible oils, and is essential to remove most of the impurities before moving on to the deodorizing step.

Each stage of refining acts on different substances in a different way: the processing changes, depending on the type of raw material. While bleaching is necessary for all types of oil, the preceding stage is different: dry degumming only concerns hard oils, while soft oils must first be subjected to neutralizing, to remove most of the phosphorus through  the use of phosphoric or citric acid.

Dry Degumming is a purification process that removes gums from edible oils, such as palm or coconut oils, through precipitation by acid conditioning and filtration.

Edible oils contain complex phosphoric compounds, known as phospholipids, commonly called gums. The reason why they need to be removed is that they have a significant emulsifying capacity. Therefore, if they were not removed, they would cause excessive darkening of the product during the deodorizing phase. This process is used for low-phosphatides oils that contain few phospholipids – therefore hard oils –  and makes them suitable to be used in preparing oils for the subsequent step of physical refining: bleaching.

Bleaching is essentially a filtering phase.

It is a treatment mainly intended to complete the removal of those substances that affect the colour of the oil, as well as impurities such as carotene, chlorophyll or PAH (Polycyclic aromatic Hydrocarbon).

Depending on the type of edible oil, there is a wide variety of absorbent materials that can be used during bleaching, including acid-activated bleaching earth, natural bleaching earth, activated carbon and synthetic silicates.

There are three bleaching methods : heat bleaching, chemical oxidation and adsorption.

Among these, the most effective and widely used for edible oils is adsorption, which is based on the absorption capabilities of bleaching agents such as bleaching earths that naturally possess a large surface area with a specific affinity for pigment molecules, removing them from the oil, without damaging its quality.

TECHNOLOGY ADVANTAGES

Dry degumming and bleaching are well-proven and cost-effective processes.

Bleaching is a real purification process of vegetable oils, which goes beyond simple decolorization, increasing their quality and chemical stability. These two characteristics contribute to enhancing the perception and appeal of the product to the end-user. Furthermore, the high reliability of the to processes, allows for of fully automated systems in which the steps are carried out in an unattended manner, with reduced requirements also in terms of service and maintenance.

The main advantages of the combined process can be summarized as follows:

• Reliable process
• Dispersion for acid by high shear
• Efficient Bleaching Earth Dispersion
• Better removal of traces of metal and impurities
• Effective in bleaching to achieve a brilliant appearance

Fully automated plant for easy operation and maintenance.

FURTHER ADVANTAGES OF CMB TECHNOLOGY

Where technologies and processes  are mature and widely used, the challenge is to be able to constantly optimize them, increasing the reliability, performance and efficiency of each phase.

For this reason, CMB constantly invests in R&D to offer its customers state-of-the-art solutions.

The key equipment of CMB is the dynamic mixer, degumming reactor and bleacher. The special design of this device provides a dynamic mix that alternates moments of intense and slower amalgamation. The intensive mixing of acid and oil allows to remove the phosphorus before bleaching. This alternation allows for a continuous mixing and agglomeration of the gums, managing to remove them in an even more accurately. Once the degumming has been completed, the bleaching process moves on to the adsorption. In this phase, the gum particles are transformed into a film that adheres on the surface of the adsorbent, which varies according to the type of oil.

One of the main challenges in which CMB demonstrates its engineering excellence, is to offer a product with the highest possible quality and the least physiological loss of oil during the process. All this is achieved by using reduced quantities of bleaching earths.

Top efficiency is made possible by the bleacher designed and developed by CMB. Bleaching efficiency depends largely on the interaction between vacuum, moisture and temperature. In our case a steam stripping is used to agitate and mix oil and bleaching earths. The process lasts just under an hour, and is followed by a filtering phase to remove the bleaching earths, before going to refining.

CMB’s ability to design and manufacture the plants’ equipment in its own in-house workshop is as fundamental as the careful selection of the best materials and stainless steels.

Furthermore, CMB’s global presence and constant proximity to Clients are tangible proof of the strength and reliability of a solid and constantly growing partner, able to offer a series of advantages that can be summarized as follows:

• Global presence to serve the Clients
• Very competitive investment cost
• Higher overall efficiency and improved yield
• Low chemical and utility consumptions
• Continuous improvement

Do not hesitate to contact CMB consultants for more information.

We will help you get the most out of your business!