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High pressure acid leaching

High pressure acid leaching

Interest in the hydrometallurgical treatment of nickel and cobalt-bearing ores has kept pace with demand for these commodities. Nickel laterite ore constitutes more than two thirds of the worlds known nickel resources and the production of nickel from sulphide ores is expected to slow in coming years. A major portion of the laterite reserves are not amenable to conventional pyrometallurgical treatment, which requires higher grades and larger power requirements. As such, High Pressure Acid Leaching (HPAL) is the preferred treatment option for laterite projects. The HCE can accommodate a simple amenability leach test, progressing to scoping studies on master composites, right through to bankable feasibility studies encompassing comprehensive leach optimisation, process validation and variability studies.

Autoclave Parr

Dedicated autoclave facility

In essence, HPAL involves sulphuric acid leaching of lateritic ores at temperatures above 240ºC, which can only be achieved at high pressures. The HCE has a dedicated fully equipped pressure leaching facility with a range of bench scale autoclaves including; 2 x 1 Gal Ti2 and 1 x 5 Gal Ti2, plus a 1 Gal Hastelloy batch autoclave.


A continuous submarine 6-compartment Ti. Gr. 7 autoclave 90L autoclave facility is available for circuit development and is one of the most advanced of its kind available at any independent testing facility globally. This HPAL Pilot Plant is Ti Gr.7 and has maximum operating temperature of 290ºC at 8500 kPa, variable retention: (60 – 120 min), with a single stage flash let-down system. The plant treats up to 30 kg/h solids and handles liquors with up to 70 g/L Cl- .


The integrated depth and breadth of the suite of technical services available to our experienced staff means that testwork is carried out efficiently and informed decisions can be made in a timely manner. We have access to expertise and developments at the cutting edge of metallurgical technology.


Many of the challenges involved with the design and operation of modern laterite processing plants have been overcome or at least are now better understood. Problems, such as the difficulties associated with ore variability, upgrading by beneficiation and pulp rheology, can be addressed by appropriate testwork and engineering solutions.


Following leaching, and solid/liquid separation, hydrometallurgical treatments are undertaken to generate an intermediate product, typically Mixed Ni-Co Hydroxide (MHP) or Mixed Ni-Co Sulphide (MSP). The basic steps in the HPAL – MHP and HPAL – MSP treatment processes are shown below:

 

 

 
 

 Note: There are a number of possible variations to these basic flowsheets.

 

 

 

The appeal of nickel laterite projects has paved the way for the development of new techniques to upgrade and recover metal values from lateritic ores. Processes such as acid heap leaching, saprolite neutralisation, and pyrometallurgical upgrading have become an important consideration for many existing and developing projects. Other more novel investigations have also gained attention such as the addition of sulphide material as a feed/reductant to HPAL circuits and the use of alternative lixiviants such as in the Direct Nickel (DNi) and Intec processes.

Don't see what you need or are unsure about some of the services and associated requirements?

We understand that metallurgical testwork is not a one size fits all or a pick off a menu proposition, and so we are happy to help walk you through the process. Or you might know exactly what you want and just need some clarifications.

No problem. Please contact us for further details.

Here are some frequently asked questions

  • How much sample mass do I need for a bench scale pressure leach program?

    This depends on the % solids selected, typically each 1 Gal leach will require between 0.5 kg to 1.0 kg of sample (DWE) ore and the extent of the program depends on the level of study being considered. For scoping tests, a matrix of approx. 3 to 9 leaches is typical.

  • What does DWE stand for when talking about sample masses?

    DWE refers to dry weight equivalent (DWE) and is typically quoted as the required sample mass without any moisture takin into consideration.

  • How are laterite samples dried?

    Care is taken to dry clayey samples as high temperatures can change the properties of some laterites which then impacts on its rheological properties.

  • Can batch autoclaves be sampled during leaching?

    Yes, ALS can offer a suite of kinetic samples typically taken at 5, 15, 30, 60 and 90 min intervals, however the maximum number depends on pulp density and starting mass.

  • Can I do my own testwork in ALS’s laboratory?

    Generally, no. Insurance and safety protocols typically prevent renting laboratory space and this is not part of ALS’s business model. Clients are able to visit and witness testwork but this is to observe only! Typically clients may attend on 24/7 piloting campaigns and interact with senior staff members for Technical interactions.

  • Can vendors attend the ALS lab to do associated testwork?

    Yes, Vendors often attend during specific bench and pilot scale testwork periods to conduct offline tests for filtration, flocculation and thickening on fresh samples from the testwork programs. This is common during 24/7 piloting campaigns.

  • Can my associates and I view the testwork at ALS’s laboratory?

    Yes, clients are always welcome to visit our facilities and observe samples or tests in progress. Inductions are required and other rules may apply to visitors.

  • Will ALS dispatch my samples to third parties?

    Yes, if a testwork program is in progress, ALS will happily dispatch testwork products and feed samples to vendors, third party laboratories, and customers as required. Fees apply.

  • Does ALS do bulk pilot testwork?

    Yes, piloting testwork follows a successful bench testwork program where the proposed process flowsheet has been selected. Continuous testwork will prove the viability of the selected flowsheet and confirm recycle streams and overall circuit kinetics which is not possible from only batch or bench scale tests.

  • Does ALS do design engineering and consulting?

    No, as it is not our core business and would put us in direct competition with many of our clients. We can, however, put you in contact with a range of reputable engineering providers and consultants.

Associated testwork services

Leach testwork rarely happens in isolation and typically many other processes are required pre and post leaching testwork, as follows: Atmospheric Leaching, Neutralisation, CCD and Solution Purification, Impurity Removal, Solvent Extraction, Electrowinning, Column Heap Leaching.


Others include: Sample Characterization, Mineralogy, rheology, solid liquid separation including flocculation and settling, Iron control chemistry, tailings management, materials of construction selection testwork (corrosion coupons) preliminary piloting and fully integrated piloting



Click on the above links or contact us for further information. We can integrate a full program for you if required.