De Smet has supplied over 780 extractors.
The purpose of solvent extraction is to remove most of the oil contained in a seed. Extraction is conducted on prepared seeds or, generally in the case of high oil content seeds, the cakes yielded by the pre-presses. Solvent extraction consists of a sequence of four operations, i.e. :
- Physical removal of oil from the seed in the LM Extractor or in the Reflex Extractor.
- Desolventising-toasting of the de-oiled seed - i.e. meal - often combined with drying and cooling of the said meal.
- Distillation, to remove the solvent from the extracted oil.
- Recovery of solvent, which is reused again and again at extractor level.
Here is how the LM® works
Material enters through an inlet hopper and is soon saturated with miscella - extraction starts immediately after entry. After the initial saturation, the bed of material is continuously washed with counter-current stages of miscella.
Rakes at the surface of the material bed, along with an upward belt slope, maintain percolation and prevent miscella contamination.
Since the miscella has more contact time to penetrate the flake than in shallow bed designs, thicker flakes can be used to achieve desired residual oil.
Maximum Material - Miscella Contact
Contact time is the single most important factor for the efficient solvent extraction of vegetable oils.
To maximise contact time, the LM® ’s initial immersion sequence enables the oilseed material to be completely surrounded with miscella.
This is followed by a long percolation sequence to keep the miscella stages separated and extract the remaining oil.
The simplicity of the LM® extractor design delivers the reliability you need to gain the competitive edge.The LM® is the essence of reliability and simplicity – a rectangular housing enclosing a slow moving belt, driven by a single head shaft.
|Mechanical design advantages
Reinforced strength in construction with standard corrosion-resistant casing.
Pre-assembly for rapid and low cost installation requiring the minimum of site works.
Inclined bed ensures true counter-current operations under any conditions.
Stainless steel, self cleaning wedge bar or mesh screen for different rawmaterials.
Low maintenance and ease of operation emphasis.
- Exterior access to mechanical parts
- Improved, easely mounted drive/hollow shaft gearbox
- Special, long life conveyor chain.
Auto control with uniform discharge
The REFLEX® Extractor…..
Here is how the REFLEX® works
Material mixed with miscella is slurry-fed into the rotating baskets - Extraction starts immediately.
After the initial slurry feed, the bed of material is continuously washed with countercurrent stages of miscella. Totally sealed basket dividers ensure each miscella stage flows through the proper basket of material.
Totally sealed basket dividers allow the entire bed of material in the extraction zone to be thoroughly soaked in miscella. This minimizes inactive time between miscella stages and maximizes contact time. Since the miscella has more contact time to penetrate the flake than in shallow bed designs, thicker flakes can be used to achieve desired residual oil.
Maximum Material- Miscella Contact
Contact time is the single most important factor for the efficient solvent extraction of vegetable oils. To maximize contact time, the REFLEX’s sealed divider design enables the oilseed material to be completely surrounded with miscella from the time it enters the extractor until the extraction cycle is complete. Only a sealed divider design can do this.
Savings on Seed Preparation
The REFLEX® Extractor, with sealed divider design, accepts thicker flakes than shallow bed or conveyor designs when processing soybeans. Flakes at least 25% thicker can be processed.
This results in lower power and maintenance costs in seed preparation. The savings in seed preparation alone could easily
pay for the REFLEX ® over its life cycle.
|Mechanical design advantages
No internal drive chains ;
No induced vibration devices;
Fewer stage pumps to maintain;
No multiple drives to maintain;
No internal bearings to maintain;
No cell bottom doors to fail;
No internal cell bottom doors to clean.
The REFLEX® Extractor has patented screen technology at the base of the material bed to allow miscella to freely pass through while supporting the material above. The proprietary screen profile allows the screen to wear for many years with no change in slot width. The slot width allows optimum drainage without fine material plugging the slots. Solvent drainage remains constant over time because the baskets continuously move over the screen to keep it clean.
This design allows consistently low solvent carryover in spent material going to the desolventizer, thus saving steam energy. This design is a dramatic improvement over hinged bottom-type extractors where the material does not move with respect to the screen surface, causing frequent blinded screens and drainage problems.
Savings – Extractor Pumps
The REFLEX® uses fewer miscella stage pumps than shal-low bed designs.
Since the REFLEX® has the industry’s highest volume to surface area ratio, the miscella flow required to soak the material during the long contact time is minimized.
Savings – Extractor Drive
The REFLEX® uses 25-50% less horsepower than other designs, lowering your electric costs. This is possible because most of the material weight is picked up by the REFLEX® divider side walls which in turn transfer the load to the vertical rotating spindle. The spindle is supported directly by a bottom thrust bearing so even the largest model REFLEX® uses very little installed power.
|Retrofits for existingextractors
The Proven Solution:
SCBS (Stationary Cell Bottom Screen) for Rotocel extractor and RBBS (Rotating Basket Bottom Screen) for Stationary Basket extractors
Improved process Results
De Smet supplied over 700 Desolventising Toasters, Dryer Coolers, and DTDC.
Desolventiser Toaster Dryer Cooler
The desolventiser-toaster serves the purpose of removing the solvent from the meal, which can be directly used as an ingredient in animal feed compounds.
A desolventiser-toaster consists of a vertical stack of several cylindrical gas-tight pans, each having a steam-heated bottom. In the top trays, solvent is evaporated by simple heating in dry atmosphere. Live steam injection is used in the lower compartments and removes most of the residual solvent from the meal.
The meal is generally dried and cooled in additional pans located below those used for desolventising.
The de-oiled meal from the solvent extractor contains from 20 to 45 % solvent by weight depending on the material. The meal must be desolventized, then dried and cooled.
The De Smet Desolventizer-Toaster is a vertical vessel containing stages capable of pre-desolventizing, desolventizing, toasting and stripping the meal. It is often combined with the meal Dryer-Cooler in one vessel known as DTDC.
In the pre-desolventizing section, hexane is evaporated by indirect heating via heated trays. In the desolventizing section, most of the hexane is evaporated while condensing live steam.
Toasting and stripping
In the toasting and stripping section a combination of indirect and live steam is used to strip the remaining hexane while at the same time toasting the meal.
Optimal use of steam
In the drying section, hot air, steam heated in an air-heater, is blown through the meal, whereas ambient air is blown or pulled through the meal for cooling. Direct steam is introduced into the spent meal via a sparging tray at the bottom of the DT. The steam rises upward through several layers of meal supported by trays in a counter-current manner as the meal flows downward from tray to tray.
As it rises up through the meal, the steam provides specific heat and a carrier gas to strip final traces of solvent from the meal.
In the uppermost counter-current tray, the steam condenses into the meal, providing its latent heat to vaporize a solvent-water azeo-trope, and to heat the meal from about 65 °C to above 100 °C, 3 kg of condensing steam heat up about 100 kg of meal.
The amount of live steam that is condensed is directly proportional to the amount of solvent in the meal, one kg of condensing water vapor evaporating between 6 and 7 kg of hexane.
The purpose of the pre-desolventizing section (PD) is to evaporate a quantity of hexane before the meal enters in contact with live steam so as to reduce the meal moisture. The saving in meal drying requirement induces a saving in steam consumption, and also in fan power.
Great care in design
De Smet takes great care in designing and sizing the equipment so as to minimize the steam and power consumed by the DTDC complex, that consumes about 75% of the steam and of the power of the total solvent plant.
Oilseed processors are faced today with an increasing pressure to reduce solvent losses, because of environmental, health, and safety concerns.
Simply increasing steam flow in the DT to reduce solvent loss causes elevated vapor temperature and wastes steam.
Increasing toasting and stripping
time is not a good solution either because of its impact on meal quality. The challenge faced by De Smet as DT designer is to make better use of the toasting time to improve stripping of the residual solvent from the meal, without increasing energy consumption.
Patented slotted-screen trays
The answer adopted by De Smet is to replace the traditional counter-current decks with hollow stay-bolts with slotted-screen counter-current trays. The design is patented since 1999, with De Smet having exclusive rights to the patent.
High quality meal
De Smet now offers to the oilseed industry DTs that are designed smaller in diameter with more counter-current trays. This permits to increase the steam density in the lower part of the DT without wasting energy and allows the meal to be more effectively stripped of solvent in the normal toasting time.
By maintaining toasting time, the DT can also continue to provide good quality meal that has not been over-processed.This inno-vation in desolventizing provides new opportunity for satisfying both environmental and meal quality needs.
|Advantages of the Dimax slotted screen
Material flow has become quite smooth above the counter-current trays, indicating more even steam distribu-tion through the material bed.
Solvent loss is low: solvent in the meal remained at about 200-300 ppm with the original steam density and can be reduced by increasing steam density. Meal agglomeration into “water balls” reduced in half.
Water balls are one source of solvent loss.
Steam consumption down slightly as vapor temperature is allowed to drop.
Power consumption down: electrical power consumption for stirrer arms has dropped 15-20%.
De Smet supplied over 600 complete distillations.
Desmet Ballestra Hytech® Distillation
For the plant design and optimization, De Smet is using process simulation and special CAD tools. A unique computerised model is able to simulate all the plant and provides accurate component characterization, thermodynamic and physical properties prediction and liquid-liquid-vapor phase equilibria rigorous calculations.
The equipment performance prediction takes into account different internals and arrangements and calculates pressure drop, heat and mass transfer, efficiency, etc.
Tailor made solutions
The model allows a rigorous simulation for different operating conditions in function of summer/winter and required safety contingencies.
This dynamic design allows De Smet to provide tailor made solutions to fit customer needs and optimized design with different specifications of cooling water temperature, miscella concentration and DT vapour flow and temperature.
Solvent Recovery Unit
Minimum number of equipment : optimized layout and simplified operation
Only one equipment for each purpose
More efficient equipment, implying the requirement of less severe operating conditions in terms of temperatures and vacuum conditions in the stripper and dryer, preserving the quality of the vegetable oil.
Optimized overall steam consumptions, avoiding consecutive heating and cooling of miscella or oil.
Minimized solvent losses in air, oil and water even for start-up and shutdown conditions.
Control philosophy for minimum operating assistance thanks to the necessary control loops avoiding manual adjustments.
The air entrained into the extractor by the pores of the raw material must necessarily be eliminated, but this operation also entrains some hexane. To minimise this loss, hexane is recovered in an absorption column that uses mineral oil (sometimes vegetable oil).