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Batch Solvent Extraction and Desolventising Unit

The FT29 is a batch process unit suitable for teaching and research. Capable of a variety of solid/liquid extractions, it is particularly suitable for leaching edible oils from seeds and desolventising extracted solids and miscella.

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FT29 Batch Solvent Extraction and Desolventising Unit – Issue 4

The Armfield Batch Solvent Extraction and Desolventising Unit is a floor-standing, batch-process unit capable of carrying out a variety of solid/liquid extractions. It is particularly suitable for 'leaching' edible oils from oil-bearing seeds and desolventising both the extracted solids and the miscella.


  • Self-contained system
  • Floor standing
  • Single extraction/desolventiser vessel
  • Miscella tank
  • Tops condenser
  • Solvent/water recovery tank
  • All flameproof construction
  • ATEX approved


  • Operation of small-scale version of industrial processes
  • A wide variety of solid/liquid extractions may be processed
  • Small quantities (25kg) can be processed
  • Low disposal rates


All vessels, pipes, valves and fittings in contact with process materials are constructed in stainless steel with the exception of the borosilicate glass solvent condenser. The support framework is also stainless steel.

This vessel also incorporates a direct steam distribution pipe through which steam can be metered at a variable rate.

Vapour from the vessels, produced in the desolventising process, is directed by ducting to the solvent condenser, an inclined cylindrical tube containing a double coil through which cooling water is circulated. Condensate (usually a mixture of solvent and water) drains into the solvent water separator tank, which enables thorough separation of the solvent and water by a gravity process.

Note: Only hexane or solvents having a similar specific gravity can be effectively separated in this tank.

Solvent reclaimed from this vessel can then be recirculated by the solvent pump at a regulated rate through a variable-area flow meter. Excess water overflows to a waste water tank from where it can be disposed of on completion of the process. Operation at reduced system pressures are achieved by a PTFE diaphragm-type vacuum pump. The outlet of this pump is piped through a flame arrester to a suitable ventilation point.

Each vessel is equipped with suitable level/sight glasses so that the processes can be observed and monitored. Pressure and temperature gauges are supplied where necessary as are adequate sampling and drain valves.

Hexane is the most widely used solvent in the extraction process and due to the inflammable nature of this product, electrical equipment has been kept to a minimum. Where electrical equipment must be used, it is specified to the appropriate standards for safety.

The main processing vessels have been designed in accordance with the appropriate code of practice for welded pressure vessels.

Modes Of Operation

Extraction by recirculating miscella

This involves priming the miscella tank with clean solvent then pumping the solvent to the extractor where it percolates through the material bed and drains as miscella back into the tank for recirculation.

Extraction by washing with clean solvent

As miscella is formed, steam admitted to the miscella tank base causes solvent to evaporate. The vapour is condensed in the solvent condenser and returns to the separator tank from which it is pumped back to the extractor.

Desolventising extracted material

When the extraction is complete, the static hold-up of solvent remaining in the material must be removed and this is achieved using a combination of direct and indirect steam and vacuum. The solvent vaporises and is condensed along with the condensate. The mixture of solvent and water is separated in the solvent water separator tank. When the extracted material is free of solvent it is discharged through the door at the base of the extractor.

Desolventising miscella

Miscella is a mixture of the solvent and oil from the extraction material, which accumulates in the miscella tank during the process. The solvent and oil are separated in a similar method as for material desolventising using a combination of direct and indirect steam and vacuum.

A higher level of vacuum is required than for material desolventising in order to produce solvent-free oil.

Within each mode of operation, many operating parameters such as process temperature, solvent temperature, solvent flow rate, direct steam flow rate and system pressure can be adjusted to allow a high degree of experimentation.

Some examples of extractions possible using the FT29

Extraction material Extract Solvent
Oilseeds/presscakes Edible oil Hexane
Tree bark Tannin Water
Solanium (a grass) Steroid Dil. sulphuric acid
Pyrethrum flower Insecticide Hexane
Tea leaves Tea Water
Wheat germ Oil Hexane
Rice bran Oil Hexane
Poppy stalks Morphine Water
Flowers/fruits Essential oils Hexane
Liquorice roots Liquorice juice Water


  • Effect of degree of pretreatment of solid material on extraction efficiency
  • Effect of solvent type
  • Effect of solvent percolation rate
  • Effect of process temperature and pressure
  • Effect of extraction time and drain time
  • Method and degree of solvent recovery

Unit Specifications

Extractor vessel:

Volume: 100l
Batch capacity: 25kg based on density of 560 kg/m3
Direct steam: 0-7 kg/hr
Indirect steam: 0-3.5 bar

Miscella tank:

Volume: 30l
Minimum extract: 2l
Direct steam: 0-4 kg/hr
Indirect steam: 0-3.5 bar

Solvent condenser:

Condensing capacity: 2.5kW
Condensing area: 2.5m2
Cooling medium: Water
Cooling water flow range: 0-22 l/min

Solvent water separator tank:

Volume of separator section: 16l
Volume of solvent store section: 16l

Waste water tank:

Total volume: 15l

Vacuum pump:

Type: Double PTFE diaphragm
Drive: Flameproof AC motor
Operating pressure: 100 mbar (max)

Solvent pump:

Type: Gear
Drive: Flameproof AC motor
Solvent flow range: 0-8 l/min with bypass flow control


Electricity supply:
FT29-C: 415V 3ph 50Hz 0.6kW
FT29-D: 208V 3ph 60Hz 0.6kW
FT29-E: 380V 3ph 50Hz 0.6kW
FT29-F: 220V 3ph 60Hz 0.6kW
Cooling water:
25 l/min 3.0 bar min pressure 5.0 bar max pressure
Steam supply:
20 kg/hr 5.0 bar min pressure  

Shipping Specification

Volume: 5.8m3
Overall weight: 880kg

Overall Dimensions

Height: 1.75m
Width: 1.90m
Depth: 0.90m