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Countercurrent system cuts bleaching costs
... More bleaching earth saving can be expected from a counter-current bleaching process. The first real counter-current process was developed about 15 years ago by Ohmi Engineering [24]. The process features two bleaching reactors and two sets of filters. ...
In edible oil refining, the continuous effort to reduce overall production costs is mainly achieved by increasing plant capacities, installation of mono feedstock plants, and increasing the degree of automation. Over the years, more energy-efficient processes and technologies, resulting in a higher refined oil yield, have gradually been introduced. The growing importance of the (nutritional) oil quality and the sustainability aspect of the refining process itself are new challenges for oil processors. To reach these new objectives, “next-generation” oil refining process technologies have to be developed and implemented. This chapter gives an overview of some process improvements and new developments that have recently been introduced in the edible oil refining industry. Some potential new innovations which are currently not yet applied are also briefly discussed. The chapter discusses next-generation chemical refining with nanoneutralisation, enzymatic degumming, bleaching, and deodorisation. It also talks about short-path distillation, and supercritical processing.
... This allows a more efficient bleaching in the second stage. Even more efficient than the counter-current pre-filtration process is the Oehmi process [28] which guarantees savings up to 40%. This process features two bleachers and two sets of filters (Fig. 3). ...
Modification techniques like fractionation, interesterification (chemical or enzymatic) and hydrogenation allow proposing a large range of new fatty products. At a time when “trans” fatty acids are questioned, fractionation of fats and oils catches more and more interest; in this context, dry fractionation is by far the simplest and cheapest fractional crystallization technique (no chemicals, no effluent and no losses). The oil processing industry uses dry fractionation to extend the application of a whole variety of fatty matters as well as to replace, fully or partially, the chemical modifications. Due to the continuous developments of the dry fractionation process, a whole variety of products normally produced by solvent fractionation can now be obtained with a high degree of selectivity with dry fractionation. As the crystallization operates in the bulk, viscosity problems limit the degree of crystallization in one single step, and multi-step operations are currently used, giving rise to a wide range of fractions suitable for different applications. The secret is to combine proper crystal development with highly efficient separation by using membrane press filters allowing squeezing out the stearin cake for as much liquid occlusion (olein) as possible. The original booming of the dry fractionation process has helped mostly palm oil to conquer a strong position on the commodity market in one single stage; today, palm oil is without doubt the most widely fractionated oil. New demands for special cuts drifted the industry towards a more sophisticated approach: high-iodine value super and top oleins, palm red fractions (high carotene and tocopherol/tocotrienol contents) or solvent-free cocoa butter equivalents (palm mid fractions) are certainly what the future has in store.
... This allows a more efficient bleaching in the second stage. Even more efficient than the counter-current pre-filtration process is the Oehmi process [28] which guarantees savings up to 40%. This process features two bleachers and two sets of filters (Fig. 3). ...
Crude palm oil is rich in minor components that impart unique nutritional properties. The most relevant are tocopherols and tocotrienols (vitamin E) and carotenoids (α- and β-carotene). Palm oil is generally refined by the physical process, which is preferred over the chemical process since high acidity (up to 5%) can lead to excessive loss of neutral oil in the soapstock after alkali neutralization. The quality of the crude oil is to be considered as it can greatly affect the efficiency of the refining process and the quality of the end-products. The deterioration of bleachability index (DOBI) is a good indicator of the capability of palm oil to be successfully refined. Beside commodities, especially refined oils open a market for new high-quality products like golden palm oil, red palm oil, white soaps, fractionated products (CBE), etc. Optimization of the deodorization technology and of the process conditions for a maximal retention of natural characteristics without affecting the quality of the palm oil is an important challenge.
The amount of bleaching earth needed can be reduced by 55% if the grain size is <10 μM. The quality of the bleached and deodorized oil is better than that obtained with conventional bleaching earth. Hitherto, the use of finely grained bleaching earth has been prevented by the fact that fine-grained particles cannot be separated from the bleached oil at economically acceptable costs by conventional filtration techniques. The new process consists mainly of the use of an agglomerator in which the fine bleaching earth particles agglomerate to form larger, readily filterable particles for the formation of a dry filter cake in a conventional filter. The results have been verified on a semi-industrial scale.
Crude oils contain non-triacylglycerol components that must be partially or totally removed in order to become acceptable for human consumption. Crude oils are therefore submitted to several treatments, the objective being to remove the objectionable minor components with the least possible damage to the oil fraction and minimal losses of desirable constituents. There are two major processing methods known as chemical and physical refining. Palm oil is by far the most important fractionated oil in the world; crude, semi- and fully refined palm oil can be fractionated in multi-stage, giving access to several products for specific applications. Identically, palm kernel oil is a popular feedstock for the formulation of Cocoa Butter Substitutes (CBS) after fractionation and full hydrogenation. Recent developments in continuous dry fractionation have shown serious advantages when applied on palm oil.
The production of high quality food oils in a cost-efficient and also sustainable way requires a new refining approach and “next generation” oil refining processes are developed to meet the new refining standards. Nano-neutralization was recently successfully introduced in chemical refining as first industrial application of the nano-reactor® technology. Proven advantages include significant lower chemicals consumption and a higher refined oil yield. A better understanding of the working principle will definitively result in more applications in edible oil processing. Enzymatic degumming was (re-)discovered as efficient degumming technique making not only degummed oils suitable for physical refining giving but also giving a higher yield. Bleaching is gradually converted from a single stage “bleaching” into a multi-stage adsorptive purification process in which a wide range of unwanted components (soaps, phospholipids, oxidation products, trace metals, contaminants, etc.) are removed prior to deodorization. This is achieved by a more systematic use of more efficient adsorbents (bleaching earths, silica hydrogels, and activated carbon). Recent trends and developments in deodorization include more efficient heat recovery, improved stripping tray design and integration of packed column strippers, reducing heat load by application of dual temperature deodorizers and low pressure (ice condensing) vacuum systems and reducing oil losses and increasing the value of the deodorizer distillate by improved (dual) vapor scrubbers. Other technologies like short path distillation and supercritical CO2 technology have also been investigated but are not (yet) broadly applied because of too high operating cost. Although there is the growing importance of oil quality and sustainable processing, potential cost saving and/or oil yield increase remain the prime parameters for the implementation of a new process.
The adsorption isotherms of β-carotene on attapulgite and sepiolite were measured in the presence of 1,3-diglyceride in n-hexane to elucidate the relative inhibitory power of the diglycerides, hydroxyl group, carbon number, and double bond for
adsorption bleaching. The adsorption mode of β-carotene was the Langmuir type. The inhibition of β-carotene adsorption may
be caused by the polarity of diglycerides and the formation of diglyceride micelles. The relative inhibitory power of 1,3-diolein,
1,3-distearin, and 1,3-dipalmitin toward β-carotene adsorption was 1.49, 1.40, and 0.99, respectively. Therefore, the relative
inhibitory power due to the hydroxyl group and increase in the carbon atom of the fatty acid in glyceride was 0.41–0.49.
In edible oil refining, the various processes in current use lead to different by-products and/or waste products and they may also cause some form of pollution. The processes are reviewed in this paper and current or possible means of disposal of these by-products/waste products are discussed to highlight the areas requiring most attention. These areas turn out to be gum disposal when the degumming operation is carried out at a stand-alone refinery, and soapstock effluent resulting from the alkali refining process. Other waste products and pollution sources are found to be unimportant or manageable. Accordingly, a major step forward in pollution abatement in seed oil refining can be achieved by making two changes. The first one entails carrying out the degumming operation at the oil mill rather than at the refinery. This should be done in such a way that the degummed oil is amenable to physical refining. The acid refining process is recommended for this degumming step and consequently, acid refined oil with appropriate quality guarantees will then become the article of trade. The second one involves a switch from alkali refining crude or waterdegummed oil to the physical refining of acid refined oil. For this latter step, a counter-current process is recommended because of its low stripping steam requirement. Dry condensation of the distillate will further alleviate pollution problems associated with deodorization and physical refining. Finally, some processes, that may contribute to pollution control but that still require development, are mentioned.
Almost all fats and oils are subjected to so-called bleaching during processing. Originally bleaching was only used to reduce the colour. Today, however, the bleaching step is used mainly to remove or convert undesired by-products to harmless ones from fats and oils. This will guarantee that such compounds do not interfere with the processing and that the requirements for human food are being met.
Alcohols, polyethyleneglycols, supercritical fluids, and some of their mixtures have been investigated as to their usefulness to purify animal fats and vegetable oils by extraction. The main impurities are free fatty acids. Phase equilibrium was measured as function of temperature and pressure. As primary substances abattoir fat and palm oil were used. Carbon dioxide, dimethylether, and mixtures thereof, likewise methanol and ethanol were tested as extractants for free fatty acids by counter-current extraction in a pilot plant including a high-pressure column and by cross-flow extraction on laboratory scale. With experiments and process simulations including the recovery of the extractants the deacidification of animal fats and vegetable oils was found to be possible. Polyethyleneglycols extract carotenes together with free fatty acids. With the physical refining methods investigated, the formation of waste materials was avoided.
Summary The Votator continuous countercurrent vacuum bleaching system has been described and compared with older methods of bleaching.
Data have been presented, comparing the performance of batch open kettle-, batch vacuum-, and continuous countercurrent vacuum-bleaching
systems. These data indicate that the vacuum methods of bleaching result in a superior quality bleached oil with the use of
less adsorbent. They also prove the value of countercurrent contacting of oil and adsorbent as practiced in the Votator system.
The economic aspects of bleaching have been discussed, proving that the continuous countercurrent vacuum-bleaching system,
due to its automatic operation, compactness, and savings in adsorbent operates at a considerably lower cost than either batch
method. Data have been offered to show the qualitative advantages of vacuum-bleached oils over atmospheric-bleached oils.
The so-called press effect is widely credited with enhancing the overall efficiency of bleaching clays in commercial operations.
Laboratory bleaches are generally done with one use of bleaching clay, while plant operations often include a process in which
spent clay in a filter press acts as a fixed bed to remove additional impurities from slurry-treated oil. In this study, the
press effect is simulated in the laboratory by measuring the influence of a progres-sively-built filter cake on concentrations
of carotenes and chlorophyll in successive batches of slurry-contacted oils. The oil used was canola; the clay tested was
a commercially available acid-activated clay classified to two different average particle sizes. Conditions were chosen to
simulate those used in commercial operations. Better total bleaching was seen from the first batch to the last as filter cake
was built up. In addition, a significant particle size effect was seen.