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Bleaching involves the use of bleaching earths orclays. The term itself is misleading as colour removal is not the most important purpose of the bleaching process.
Vegetable oils contain contaminates thatadversely affect the performance, appearance and taste of the oil. In order forit to be used in edible applications, the oil must meet high quality standardsthat require the removal of various impurities. It is used to decolorize purification in the field of animal andvegetable oil refining. It can take off the harmful pigments, phospholipids,cotton, acid, and so on in oil to make high-grade edible oil. And thedecolorant of edible oil grade is widely applicable to all kinds of vegetableoils, animal oil and mineral oil, such as soybean oil, rapeseed oil, peanutoil, cottonseed oil, sunflower oil, palm oil, coconut oil, castor oil, camelliaoil, corn germ oil, refined bran oil, sesame oil, safflower oil, and so on.
The bleaching process essentially removes somecolour from the oil; reduces how much chlorophyll and carotinoids the oilcontains; removes soap, gums and tracemetals; and decomposes oxidation products.
Bleaching is performed prior to other processing stepssuch as hydrogenation, refining or deodorisation. Suppliers of the clays say that bleaching earth will account for 4-10% of overall refining costs, depending on a variety of factorsincluding oil type, dosage, oil contaminant levels, specification and disposalcost.
What are bleaching earths?
Oils are bleached using a powdered, surfactant material. Simply put, the powderis mixed with water, and then added tothe oil where they absorb unwanted impurities before they are removed from theoil again, taking the impurities withthem.
Bleaching earths are generally composed of up tothree types of clay minerals: bentonite, attapulgite and sepiolite. The minerals act as absorbers with capacitybeing dependent on mineralogical structure and properties, such as surface area, particle size distribution, porosityand surface activity.
Bentonites are a soft stone with the capacity toabsorb substances dissolved in water and other liquids. The minerals have been formed over time due to the naturaladaptation of volcanic ash.
Dry bleaching vs wet bleaching
The two different methods utilising bleachingclays in the refining process are dry bleaching and wet bleaching. According to Alfa Laval, dry bleaching isthe traditional method used for bleaching oils and fats. It is most common inEurope and Asia, but is used worldwide.
The process first involves heating the oil, thenmixing it with bleaching earths or activated carbon (or a mix of both). Thisprocess takes place under vacuum â which prevents oxidation â and with asparging steam (the direct injectionof steam in order to heat the oil withvery high energy levels).
Because the bleaching takes place under vacuum ofabout 70 torr, the humidity of the oil is greatly reduced.
Following the bleaching process, the powder isremoved using pressure leaf filters and is collected in a buffer tank, which also operates under a vacuum.
Dry bleaching requires a much lower initialinvestment than wet bleaching. The operating costs are also significantly less due to the use of plate heat exchangers,which require lower consumption of utilities. The process is alsorelatively easy and straightforward and requires only minimumspace for set-up.
Wet bleaching, on the other hand, involves the addition of water in theprocess. Water makes bleaching earths work more efficiently, which means that less can be used, and oil losses arealso reduced. Wet bleaching is attractive due to the lower costs of the process itself, eventhough start-up costs are higher. Water is added in the form of a citric acidsolution, after the oil has been heated andbefore the bleaching earths are mixed in. The citric acid helps to bindtrace metals and decompose residualsoaps.
In the oil industry, it is used in thedecolouration and purification of oil, lubricant oil, grease, paraffin oil, gasoil, kerosene and other minerals as well as petroleum cracking.
In the food industry, it can be used as agent forclarifying wine and sugar, fruit juice, beer stabilization treatment, glycosylatedprocessing, and juice purification. It can save about 60% of the costs in sugardecolouration process. The colour of refined sugar, the content of reducingsugar, sulphite ions, chloride ion, protein calcium and magnesium ions, pHvalue and the temperature of the boil sugar have met current industrystandards. Filter cakes can be mixed in the animal feed, reducing environmentalpollution and utilizing resources comprehensively.
In the chemical industry, it is used as a catalyst, fillers,desiccants, adsorbents, and waste treatment flocculants.
- FOB Port
- Mundra / JNPT
- Payment Terms
- Letter of Credit at Sight (Sight L/C), Cash in Advance (CID), Cash Against Delivery (CAD)
- Supply Ability
- 1000 tons Per Month
- Delivery Time
- 15 Days
- Sample Available
- Sample Policy
- Free samples available with shipping and taxes paid by the buyer
- Main Export Market(s)
- Middle East, Western Europe, Australia, Asia
- Main Domestic Market
- All India