Bleachers
Bleaching is a very important processing step in both chemical and physical refining of all kinds of vegetable oils and fats.
In this step, phospholipids and metals are further removed from the oil by contacting them with adsorbents (mostly bleaching earths, but can be combined with other adsorbents like silica, active carbon, etc.). Before the actual bleaching step, in the case of physical refining, an acid conditioning step with acid is often used to improve the adsorbability and removal of phosphatides, metals, and soaps. Such a bleaching plant is often referred to as a dry pretreatment.
During the bleaching step, coloring components are also removed and peroxides are broken down. Moreover, by using activated carbons, some unwanted contaminants (heavy PAH, dioxins, PCBs, etc.) can also be removed from the oil.
The bleaching step is very important for the final quality of the oil after deodorization (more in particular, it impacts the shelf life and oil stability, but also reduces color and contaminants, etc.).
Desmet has build up a large experience in designing bleachers and bleaching lines for all kind of applications – continuous, semi-continuous and batch operating plants in a very large capacity range (up to 3000 tpd). Specific for continuous bleaching plants Desmet has designed the ‘Sparbleach’ bleacher.
How does it work
A bleaching – dry pretreatment line is mostly composed of an acid conditioning section, followed by the bleaching and filtration section. After dosing bleaching earth (and other adsorbents if needed) into the oil, the slurry oil bleaching earth enters the bleacher. In the bleacher, the oil is dried and heated if required, and a uniform retention time is given for optimal performance of the adsorbents. After the bleacher, the oil is filtered over hermetic leaf filters, and from there the cleaned oil will be polished and sent to further refining steps. The Desmet bleaching lines can be highly automated to increase safety and reduce manual interventions to a minimum – bleaching earth handling and dosing, filter operation, and spent earth handling can be fully automated.
The ‘Sparbleach’ bleacher is a continuous bleacher, operated under vacuum, where the oil is heated to final bleaching temperature (90-110°C) in the upper compartment with heating coils. Then the oil is overflowing to the lower compartment (bleaching compartment) where the oil is held for a uniform bleaching time (30 to 60 min), and from there the oil is pumped to the filtration stage for the removal of the spent bleaching earth.
Specific for the ‘Sparbleach’ bleacher is that the agitation is done by injection of sparge steam in the lower compartment. This allows good contact of the bleaching earth with the oil and hence also an optimal bleaching effect. The ‘Sparbleach’ bleacher is specifically designed for continuous refineries in a large capacity range (from 50 to 3000 tpd).
But besides that, Desmet has a large range of other types of bleachers for some specific applications: batch bleachers, mechanically stirred bleachers, and semi-continuous bleachers. The bleaching lines can be designed for continuous or frequent feedstock change, including heel volume filtration, etc. The design of the full bleaching lines can easily be adapted to the specific needs of the customer and the kind of operation.
Key advantages
Flexible design & big capacity range
Optimized standard configurations for all kinds of oils & fats