Solvent Extraction

Mixer - Settler

The basic simplicity of the solvent extraction process is a particular attraction for its use in metallurgical process design. As is so often the case with fundamentally simple processes when they are applied to real life situations they have a habit of becoming far more complex. There is a wealth of knowledge and experience built from plant operations, research and metallurgical testwork available at AMMTEC. What then is necessary to investigate and prove up a solvent extraction mixer-settler process route?



Batch Testwork


Feedstock
  • metal content
  • pH
  • density
  • organic and inorganic impurities
  • total solids content
Selection of Extractant
  • equilibrium isotherms (McCabe Thiele Diagrams)
  • phase separation times
  • metal loading
  • rate of mass transfer
  • solvent pre-treatment or conditioning
Stripping investigation
  • equilibrium isotherms (McCabe Thiele Diagrams)
  • phase separation times
  • metal loading
  • rate of mass transfer

In general terms the use of McCabe Thiele Diagrams enables the metallurgist or engineer to calculate the number of stages required, or alternatively, to predict the performance of a given set of conditions. Phase separation times are critical as they have a direct bearing on the size of the settler required and on the overall process efficiency. Metal loading refers to the solvent phase and is a function of the solution properties, namely pH. Competing ions will also have an effect on the metal loading. The significance of the determination of loading is in the definition of optimum plant operating conditions in terms of inventory of organic, O/A ratio and recirculation rates. The rate of which the metal is transferred from one phase to another (kinetics) can be a significant factor in the design and operation of the plant, whether in extraction or in stripping.



Deep Mixer-Settler

AMMTEC has available a deep mixer-settler apparatus equipped with a number of mixers of various volumes and a series of movable baffles and liquid take-offs in the settler. The data obtained is used in the engineering design of the required settler area for plant sized solvent extraction equipment. This unit is available for the testing of Exxon Chemicals products. For non-Exxon products an alternative apparatus is available.



Pilot Plant Testwork

Whilst data from batch testwork is indispensable in the sense that it establishes whether the chemistry envisaged for the recovery process is sound or not it does not provide any indication as to long term effects that can appear industrially nor does it allow for any scale-up to be done. This kind of information can only be obtained through an adequate pilot plant programme. The pilot plant will also help visualise certain phenomena which could not be observed in batch testing. (eg crud)

AMMTEC's mixer-settler pilot plant is undoubtably one of the best plants available in the world today.

  • variable feed rates from nominally 6 to 60 litres per hour.
  • peristaltic pumps eliminating volume fluctuations observed with pulse pump mechanisms.
  • maximum of 36 mixer-settlers with variable configuration available
  • flexible on-line pH control
  • the use of recirculating jacketed water baths ensures precise temperature control
  • in-stream assaying facilities via a Perkin Elmer Optima ICPOES.
  • fully integrated electro-winning circuit

Data from in-stream ICP assaying is monitored through external data capture for selected elements, typically 10-15 depending on the composition of the feed stock, with data for all elements available to the client on disk for later detailed analysis. This data is supplied in a format stipulated by the client eg. excel etc.

The pilot plant has been designed as a transportable unit and is available for on-site testing. In this case the plant would be set up and operated by AMMTEC staff in conjunction with plant operational personnel.

This world class pilot plant facility which when coupled with our 40mm and 100mm BATEMAN Pulsed Columns confirms AMMTEC's commitment to remain at the forefront of solvent extraction technology.



Bateman Pulsed Column

AMMTEC has purchased two pilot scale BATEMAN Pulsed Columns and commissioning of these columns has now been completed. Rather than manufacture small, locally designed, untested columns BATEMAN was chosen as the supplier due to their ability to supply capital and operating costs, fabrication facilities, supply and construction, start-up, commissioning and process quarantees to our clients.



BATEMAN - A Name Synonymous With Pulsed Columns

The original Pulsed Column concept has been enhanced and developed by Bateman to overcome problems and difficulties in the operation of traditional liquid-liquid contacting systems such as mixer-settlers or continuous contact as in tray columns. Bateman developed this technology in excess of 15 years ago with the first commercial column being used in the fertiliser industry in Israel. The technology was further refined and in 1997 two BATEMAN Pulsed Columns were installed for uranium recovery at Western Mining Corporation's Olympic Dam in South Australia. A further ten BATEMAN columns have been commissioned at Olympic Dam. Considerable testwork is being planned in Western Australia by the nickel laterite producers.

Mineral Industry
  • Copper
  • Uranium
  • Nickel/Cobalt
  • Vanadium
  • Other
Chemical Industry
  • Nitric Acid
  • Hydrochloric Acid
  • Phosphoric Acid
  • Inorganic Salts
  • Organic Purification
Pharmaceutical Industry
  • Recovery of active materials
  • Purification of vitamins
Environmental
  • Nitrate removal
  • Heavy metals removal
  • Effluent treatment
Petrolium Industry

Pulsed Columns - What are Their Advantages & How Do They Work?

The potential advantages of Pulsed Columns are as follows:

  • higher efficiencies
  • small column foot prints
  • insensitivity to solids (crud)
  • fully automated
  • low operating costs
  • maintenance free with no internal moving parts
  • safe with low environmental risk
  • high availability
  • low capital cost
  • continuous extraction, excellent if many stages are required
  • excellent entrainment separation

The BATEMAN Pulsed Columns are liquid-liquid (LLC) units which consist of two settlers (upper and lower). Mounted between the two settlers is a vertical cylindrical contacting section. This section is filled alternatively with disks doughnut-shaped baffles. The heavy (aqueous) phase enters through a disperser at the top of the contacting section, while the light (organic) phase enters through another disperser at the lower entrance of the contacting section. The light phase overflows from a weir in the upper settler and the heavy phase leaves from the bottom settler; both flow by gravity to their respective destinations. Level control is used to maintain the interface level in either the bottom or top settler depending on which phase is continuous. Energy for dispersion is provided by pulsing the column either pneumatically or mechanically. The pulsation is extremely important as it ensures:

  • optimum droplet size for optimum mass-transfer
  • hold-up of the dispersed
  • phase phase mixing
  • sufficient reaction time for the kinetics of the solvent extraction process

Pulsed Columns may be used for any, or all, of the following processes:

  • Extraction
  • Stripping
  • Scrubbing
  • Purification
  • Separation

Pilot plant trials are necessary to establish operating parameters and to obtain data for risk free scale-up. The diameter of the industrial sized column and the spacing between the discs and doughnuts are all calculated from the client's required flow-rates and the optimal design flux as determined experimentally during pilot plant tests. The height of the column is scaled-up from the experimental results and the equilibrium isotherm for the extracted species in the organic and aqueous phases. Scale-up from pilot plant runs using a 100mm diameter column is possible to full sized BATEMAN industrial columns up to 3.5 metres in diameter and 35 metres in height.



AMMTEC and Bateman Engineering Pty Ltd

Based on the superiority of the Bateman technology and levels of interpretation AMMTEC has purchased two pilot scale BATEMAN columns. The columns were manufactured by Bateman in Israel and imported into Australia. Training of AMMTEC's staff was carried out in Australia by senior Bateman Israel personnel. Bateman Engineering Pty Ltd have agreed to interpret the data generated from AMMTEC's pilot plant operations.



AMMTEC and the 40mm BATEMAN PILOT COLUMN

This column has four nominal 1 metre sections giving a total height of 6.5 metres with the number of theoretical stages being 3-5. Construction material is of glass enabling full observation of the phases. Feed rates of pregnant + organic of 30-60 litres per hour are typical.

AMMTEC are now able to offer our clients the possibility of running a full sized pilot column simultaneously with our mixer-settler pilot plant using the same feed solution. This enables direct comparisons between the two systems to be made. The pulsed column may also be integrated into the mixer-settler circuit to investigate specific applications eg. loading, stripping etc or alternatively may be run as a stand alone unit. All extractants, carriers and modifiers are supplied by the manufactures at no charge to our clients. Recycling of solvents is used as appropriate.



AMMTEC and the 100mm BATEMAN PILOT COLUMN

The column has 6 nominal 1 metre sections giving a total height of 8.8 metres with the number of theoretical stages being 4-8. Construction material is of glass/FRP/PVDF with observation of the phase interfaces being possible through the glass sections. A column of this size typically consumes 180-400 litres per hour of liquor and organics. It is for this reason that this column is designed to be transported to site. The column is a stand alone, self contained unit with the only impact on plant operations being the provision of assaying facilities as required. Data obtained from this unit can enable scale-up to full sized industrial BATEMAN columns to 3.5 metres in diameter and 35 metres in height and also makes possible the provision of capital costs, operating costs and process quarantees.

The BATEMAN Pulsed Columns when coupled with our world class mixer-settler piloting facilities confirms AMMTEC's commitment to remain at the forefront of solvent extraction technology.